CA1093043A - Track brake for railways - Google Patents
Track brake for railwaysInfo
- Publication number
- CA1093043A CA1093043A CA348,529A CA348529A CA1093043A CA 1093043 A CA1093043 A CA 1093043A CA 348529 A CA348529 A CA 348529A CA 1093043 A CA1093043 A CA 1093043A
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- CA
- Canada
- Prior art keywords
- brake
- track
- weighing
- tappet
- car
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
A TRACK BRAKE FOR RAILWAYS
ABSTRACT OF THE DISCLOSURE
The track brake is intended to limit the speed of rolling motion of a freight car according to the track gradient in a marshalling yard. Retarding means installed along a braking rail comprise a number of braking tappets each having a portion which projects above the braking rail in the rest position and each being applied in turn beneath each wheel of the car to be braked. The track brake comprises a motion con-verter constituted by a series of rockers each pivotally mounted on a pin connected to the braking rail. One portion of each rocker cooperates with a braking tappet and another portion of the rocker cooperates with a piston-rod of a substantially horizontal hydraulic brake cylinder.
ABSTRACT OF THE DISCLOSURE
The track brake is intended to limit the speed of rolling motion of a freight car according to the track gradient in a marshalling yard. Retarding means installed along a braking rail comprise a number of braking tappets each having a portion which projects above the braking rail in the rest position and each being applied in turn beneath each wheel of the car to be braked. The track brake comprises a motion con-verter constituted by a series of rockers each pivotally mounted on a pin connected to the braking rail. One portion of each rocker cooperates with a braking tappet and another portion of the rocker cooperates with a piston-rod of a substantially horizontal hydraulic brake cylinder.
Description
10~30~3 This is a division of my co-pending ~anadian Patent ApplicatiGn No. 292,484 filed December 6, 1977.
~ his invention relates to a railway track brake for limiting the speed of rolling motion of a freight car according to the gradient of a shunting track laid on crossties or sleepers having standardized spacing. The above-mentioned track brake comprises retarding means installed in the service position along one rail of the track in order to produce action successively on each wheel of the freight car.
The invention provides a railway track brake for limit-ing the speed of rolling motion of a freight car rolling along an inclined shunting track laid on crossties, the track brake being provided with retarding means to be installed in use along one rail of the track in order to co-act successively with each wheel on the corresponding side of the freight car, and a number of braking tappets each cooperating with a braking hy-draulic cylinder which is caused to operate by throttling of a fluid, said brake cylinders being connected to a regulator for controlling the flow of the throttled fluid by means of a throttling piston, said throttling piston being controlled by a weighing hydraulic cylinder provided with a piston connected to a weighing tappet, characterized in that means is provided - for detecting the freight-car speed, said detecting means comprising a flow-threshold closing means connected to by-pass the regulator in the discharge circuit of the brake cylinders, ; the closing means aforesaid being adapted to remain open in order to prevent throttling of the fluid below a predetermined value of flow of the fluid corresponding to a predetermined value of the freight-car speed, the flow-threshold closing means being actuated above said predetermined value of fluid flow in order to ensure throttling of said fluid flow by said ~0~30~3 regulator.
Further distinctive features and advantages of the invention will become apparent from the following description o~ a few embodiments which are presented hereinafter by way of example without any limitation being implied, reference being made to the accompanying drawings, wherein:
Figure 1 is a diagrammatic transverse sectional view of a track brake in accordance with the invention, this view being taken along line I-I of Figure 2;
Figure 2 is a plan view of the same track brake, this view being taken along line II-II of Figure l;
Figure 3 is an enlarged view of a portion of Figure 1 showing the braking rail and the vertical-motion tappet assoc-iated by the motion converter with the substantially horizontal hydraulic brake cylinder;
Figure 4 is an overhead plan view of the device shown in Figure 3, this view being taken along line IV-IV;
Figure 5 is a sectional view of Figure 3 along the line V-V and illustrates the vertical-motion weighing tappet of the track brake;
Figure 6, which is similar to Figure 5, illustrates a braking tappet of the track brake which is placéd after the weighing tappet;
Figure 7 is a general diagram of the hydraulic circuits .~ of the track brake shown in Figures 1 and 2;
Figure 8 is an enlarged diagrammatic view of the brake-application regulator and of the flow-threshold valve shown in Figure 7;
Figure 9, which is similar to Figure 8, shows dia-grammatically an alternative form of the brake-application regulator of the track brake in accordance with the invention, .
said regulator being provided with a pi.lot piston for control-ling the throttling piston;
Figure 10 is a diagram of an alternative form of the brake-application regulator of Figure 9, in which the threshold val.ve mounted as a by-pass is replaced ~y a controlled slide-valve;
Figure 11, which is similar to Figure 10, shows another mode of assembly of the controlled slide-valve which is mounted as a by-pass off the throttling piston;
Figure 12, which is similar to Figure 7, shows a further alternative form of the track brake in accordance with the invention and comprising an additional clearing tappet;
Figure 13, which is similar to Figure 9, illustrates the braking regulator which is associated with an automatic-clearing circuit having a calibrated-leakage orifice;
In the embodiment of Figures 1 to 8, the track brake 1 for railways is intended to limit the speed of rolling motion of a freight car (not shown) according to the gradient of a ; shunting track having two parallel rails 2 lai.d on standard-spacing crossties or sleepers 3. The track brake 1 comprises . retarding means described hereinafter which are installed in the service position along one rail 2 of the track in order to produce action successively on each wheel 4 of the freight car.
The track brake 1 constitutes a modular unit which is delimited diagrammatically by a chain-dotted line lA in Figure
~ his invention relates to a railway track brake for limiting the speed of rolling motion of a freight car according to the gradient of a shunting track laid on crossties or sleepers having standardized spacing. The above-mentioned track brake comprises retarding means installed in the service position along one rail of the track in order to produce action successively on each wheel of the freight car.
The invention provides a railway track brake for limit-ing the speed of rolling motion of a freight car rolling along an inclined shunting track laid on crossties, the track brake being provided with retarding means to be installed in use along one rail of the track in order to co-act successively with each wheel on the corresponding side of the freight car, and a number of braking tappets each cooperating with a braking hy-draulic cylinder which is caused to operate by throttling of a fluid, said brake cylinders being connected to a regulator for controlling the flow of the throttled fluid by means of a throttling piston, said throttling piston being controlled by a weighing hydraulic cylinder provided with a piston connected to a weighing tappet, characterized in that means is provided - for detecting the freight-car speed, said detecting means comprising a flow-threshold closing means connected to by-pass the regulator in the discharge circuit of the brake cylinders, ; the closing means aforesaid being adapted to remain open in order to prevent throttling of the fluid below a predetermined value of flow of the fluid corresponding to a predetermined value of the freight-car speed, the flow-threshold closing means being actuated above said predetermined value of fluid flow in order to ensure throttling of said fluid flow by said ~0~30~3 regulator.
Further distinctive features and advantages of the invention will become apparent from the following description o~ a few embodiments which are presented hereinafter by way of example without any limitation being implied, reference being made to the accompanying drawings, wherein:
Figure 1 is a diagrammatic transverse sectional view of a track brake in accordance with the invention, this view being taken along line I-I of Figure 2;
Figure 2 is a plan view of the same track brake, this view being taken along line II-II of Figure l;
Figure 3 is an enlarged view of a portion of Figure 1 showing the braking rail and the vertical-motion tappet assoc-iated by the motion converter with the substantially horizontal hydraulic brake cylinder;
Figure 4 is an overhead plan view of the device shown in Figure 3, this view being taken along line IV-IV;
Figure 5 is a sectional view of Figure 3 along the line V-V and illustrates the vertical-motion weighing tappet of the track brake;
Figure 6, which is similar to Figure 5, illustrates a braking tappet of the track brake which is placéd after the weighing tappet;
Figure 7 is a general diagram of the hydraulic circuits .~ of the track brake shown in Figures 1 and 2;
Figure 8 is an enlarged diagrammatic view of the brake-application regulator and of the flow-threshold valve shown in Figure 7;
Figure 9, which is similar to Figure 8, shows dia-grammatically an alternative form of the brake-application regulator of the track brake in accordance with the invention, .
said regulator being provided with a pi.lot piston for control-ling the throttling piston;
Figure 10 is a diagram of an alternative form of the brake-application regulator of Figure 9, in which the threshold val.ve mounted as a by-pass is replaced ~y a controlled slide-valve;
Figure 11, which is similar to Figure 10, shows another mode of assembly of the controlled slide-valve which is mounted as a by-pass off the throttling piston;
Figure 12, which is similar to Figure 7, shows a further alternative form of the track brake in accordance with the invention and comprising an additional clearing tappet;
Figure 13, which is similar to Figure 9, illustrates the braking regulator which is associated with an automatic-clearing circuit having a calibrated-leakage orifice;
In the embodiment of Figures 1 to 8, the track brake 1 for railways is intended to limit the speed of rolling motion of a freight car (not shown) according to the gradient of a ; shunting track having two parallel rails 2 lai.d on standard-spacing crossties or sleepers 3. The track brake 1 comprises . retarding means described hereinafter which are installed in the service position along one rail 2 of the track in order to produce action successively on each wheel 4 of the freight car.
The track brake 1 constitutes a modular unit which is delimited diagrammatically by a chain-dotted line lA in Figure
2. The modular unit of the track brake 1 is adapted to the spacing of the track crossties 3 and comprises at least one braking rail section 5 which is removably mounted in the service position in place of an ordinary rail section 2 of the track.
The retarding means described hereinafter are placed next to ; the braking rail section 5 over a limited length SL (Figures 2 and 7) which is shorter than the interval between the wheels 4 .
. ' 1093C~3 of one of the car bogies (not shown). By way of example, this interval is equal to 1.80 meter.
Preferably, the braking rail section 5 and the inter-mediate portion of the other rail 2 are both associated with a check-rail 5E in order to improve the guiding action ~09~043 of the car wheels 4 in the zone of action of the track brake 1 (as shown in Figs. 1 to 3).
As an advantageous feature which is illustrated in Fig. 2, the braking rail section 5 is provided at its two S end portions 5A, 5B with a profile, which is substantially identical with the profile of the ordinary rails 2 of the adjacent track in order to connect the braking rail section 5 to these latter, for example by means of bolted fishplates 5C. The zone 5D of the braking rail section which is located between the two above-mentioned end portions 5A, 5B is pro-vided in the upper portion thereof with a profile of reduced thickne,ss (as shown in Figs. 1 and 3) for the lateral mounting of a vertical-motion tappet 6. In the rest position shown in Figs. 3 and 5, said tappet has a portion which pro~ects above the level of the top face of the braking rall 5 in order to be applied successively beneath each freight-car wheel 4.
The retarding means of the track brake comprise a series of hydraulic cylinders 7A,,7B, 7C, etc. (as sh~wn in Fig. 2). There is slldably mounted within each cylinder . 7 a piston 8 ,(Fig. 3~ associated w1th a restoring spring 8A
which urges the piston 8 towards its rest position. Said piston has a rod 9 connected to a vertical-motion tappet 6A,-6B, 6C etc. by means of a motion converter 11 comprising a 25~ rocker llA mounted on a pivot-pin llB which is rigidly fixed . :
to the braking rail section 5 by means of a support structure as will be described hereinafter. The pivot-pin llB of each ; , rocker llA is secured to the structure aforesaid by means of a support bracket 11C (shown in Figs. 3 and 4), the axis , ~ 30 of said pivot-pin belng substantially horizontal and parallel to the braking rail section 5D. The rocker llA has 5 _ ' , a portion which cooperates with the vertical-motion tappet 6 and another portion which cooperates with the rod 9 of the piston 8 of the horizontal cylinder 7 which is oriented transversely with respect to the rail section 5.
The rocker llA is provided with a cup 12 on each of the aforesaid portions which cooperate with the tappet 6 and the piston-rod 9 (as shown in Figs. 3, 5, 6) in order to receive a substantially hemispherical face 13A of a half-ball joint component 13 which is concentric with the cup 12. A
substantially equatorial flat face 13B of each half-ball 13 forms a projection above the cup 12 in order to be applied against a corresponding flat face of the vertical-motion tappet 6 and against a flat face of the extremity of the piston-rod 9 respectively.
Thus, as will be explained hereinafter, the flat equatorial face 13B of each half-ball joint component 13 ls capable of slldlng freely against the opposlte flat face of the vertical-motion tappet 6 or of the extremity of the piston-rod 9 for the operation of the motion converter, taking into account the circular path followed by each cup 12. Preferably, an intermediate thrust member 9B is inter-posed between the extremity of the piston-rod 9 and the corresponding half-ball 13 (as shown in Figs. 3 and 4).
The half-ball 13 and the associated components of ~- 25 the motion converter 11 can be formed of all suitable materials. For example, the tappets 6 and thrust members 9A
are of steel as well as the rocker llA,and the half-ball 13 is of high-strength bronze. All the components can also be formed of steel and an anti-friction lining of bronze, for , 30 example (not shown) can be placed within the cups 12 of the rocker llA and on the flat faces of the tappets 6 and thrust ~; , -.
10~3043 members 9A which are associated with the half-balls 13.
By virtue of the arrangements and choice of materials indicated in the foregoing, the mechanisms of the track brake in accordance with the invention are capable of operating without lubrication.
In the direction of travel of the wheel 4 to be braked (arrow F of Figs. 2, 5, 6, 7), the first tappet 6A
is preferably a weighing tappet associated with a weighing hydraulic jack 7A as will be explained below. The weighing -tappet 6A has a convex top face 17A (as shown in Fig. 5)which forms in the rest position of the tappet a slight projection 17B above the level of the summit or top face of the braking rail 5D. For example, the height of projection 17B ls of the order of 10 mm.
15The vertical-motion tappets 6B, 6C, 6D, 6E whlch follow the weighlng tappet 6A are preferably braking tappets.
The profiled top portlon 17C of each tappet which projects above the braking rail 5D (as shown in Fig. 6) advantageously has a slope 17D in the intended direction of travel of the wheel 4 as indicated by the arrow F. The slope 17D ensures unlform downward displacement of the tappet 6 at the time of passage of the wheel 4 over a distance of tra~el correspond-~ ing to the height of projection 17E of the tappet 6 in the ;~ ~ rest position (as shown in Figs. 5 and 6), namely approximate-ly 50 mm, for example. As mentioned hereinafter, the uniform downward displacement of the tappet 6 prevents .
; dynamic pressure defects in the hydraulic brake circuits which will be described hereinafter.
The structure of the modular unit constituted by the track brake (shown in Figs. 1, 2, 4) comprises a bed-plate 18 formed for example of sheet steel having substantial .
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~093C~3 thickness and secured by means of ssrew-spikes 18A to the crossties 3A of that portion of the shunting track in which the brake unit is installed. The bed-plate 18 carries the braking rail section 5, the guides 16A of each vertical-motion tappet 6, the brackets llC for supporting the pivot-pin llB of the rocket llA of the motion converter and the associated hydraulic cylinders 7A, 7B, 7C, and so forth.
As shown in Figs. 1 to 4, the hydraulic cylinders 7 are substantially horizontal and mounted on a rear plate 18B, for example. Said rear plate is r1gidly fixed to the bed-plate 18 and forms together with this latter a casing which is closed by a detachable cover 18C in order to protect the brake components from dust and bad weather conditions.
In th~ embodiment which is described herein by way of example (with reference to Figs. 2, 7, 8),,the track brake 1 is constituted first by the weighing tappet 6A associated with the weighing hydraulic j,ack 7A, then by four braking , tappets 6B, 6C, 6D, 6E. These latter are each associated ', 20 with a brake cylinder 7B, 7C, 7D, 7E which operate~ by throt-, tling a suitable fluid such as a non-freezing mineral oil which is resistant to ageing. The track brake in accordance with the invention comprises means for adjusting the throt-. .
tling action of the fluid on demand, according to the weight ` 25 carried by each wheel 4. This weight is measured by means of , the weighing tappet 6A and the associated jack 7A.
Preferably, the adjusting means aforesaid comprlse ;'~as shown in Figs. 7 and 8~ a brake-application regulator 21 ' ~ ~having an opposing spring 22 associated with a weighing piston 22A which is controlled by the weighing tappets 6A.
Said tappet is placed before the first braking tappet 6B in : -~a-:: .
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'1093V43 the direction of travel of the cars indicated by the arrow F
and i5 associated with the weighing hydraulic cylinder 7A
which is similar, for example, to the brake cylinders 7B to 7E.
The brake-application regulator 21 is mounted in a hydraulic circuit 23 (Fig. 7) to which discharge pipes 23A
.of each brake cylinder 7B to 7E are connected in.parallel.
Throttling of the fluid discharged from the brake cylinders is carried out within the regulator 21 by means of a throttling piston 24 which is applied against its seating 24A by the weighing spring 22.
Check valves 25 æe mounted in the discharge pipe 7Alof the weighing hydraulic cylinder 7A and in the discharge pipes 23A of the brake cylinders 7B to 7E. All the cylinders mentloned above are connected directly to a common hydraulic reservoir 26 by means ~f a supply circuit 27. This latter is Il.' . ..
connected to each discharge pipe 7Al, 23A, by means of a : check valve 28 which operates in the direction opposite to : the discharge valve 25 of the same pipe.
Check valves 28 prevent the flow of the fluid which is forced back by the cylinders i when the pistons 8 ; are displaced do~lwards therein and compress the restoring . springs 8A. However, the valves 28 permit.the flow of fluid from the supply circuit 27 to the cylinders 7 when the pistons : ~ 25 8 are brought back to the rest position by the restoring i~ .
springs 8A as will be explained hereinafter.
he track brake can advantageously comprise means : for detecting the speed of the car wheel 4 combined with retardin~ means,in order to make these latter inoperative " ~ 30 below a predetermined value of speed of the wheel,in order to prevent excessive brake action on freight cars.
~: i ~: _g_ . . ~ .
In the embodiment which is illustrated diagrammatic-ally in Figs. 7 and 8, the means for detecting the speed of the wheel 4 comprise a flow-threshold valve 31 in which an obturator disc 31A is held at a distance from a valve-seat 31B by a spring 31C below a predetermined value o~ fluid flow corresponding to the rate of downward displacement of a braking tappet 6~ to 6E in respect of the aforementioned limiting speed of the wheel 4.
The threshold valve 31 is mounted as a by-pass off the brake-application regulator 21 in the discharge circuit 23 of the brake cylinders. In this manner, the fluid dis-charge from the brake cylinders 6B to 6E is subjected to the choking action of the throttling piston 24 within the regulator 21,only when the speed of the wheel 4 oversteps the limitlng value permltted by the track brake. A llmiting value of 0.8 m/sec is chosen by way of example.
Below the aforesald speed of the wheel, the threshold valve 31 remains open, thus making the throttling piston 24 inoperative and preventing brake action on the wheel 4.
The brake-application regulator 21 preferably ; comprises a clearing device for producing the expansion of the weighing spring 22 which has previously been compressed by the weighing tappet 6A. The device for clearing the weighing operation can be controlled by means of a clearing tappet 6F which is placed after the last braking tappet 6E
in the direction of travel of the wheel 4 as indicated by the arrow F in Fig. 7. The clearing tappet 6F is similar, for example, to the weighing tappet 6A (as shown in Figs. 5 and 7).
` In the embodiment which is illustrated by way of : ' .
--10- `
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example in Figs. 5 and 7, the clearing tappet 6F actuates a piston mounted within a hydraulic cylinder 7F which is similar for example to the weighing cylinder 7A. The clearing cyllnder 7F is connected by means of a clearing pipe 33 to a clearing relay 34 which controls a discharge valve 35 mounted in a pipe for connecting the chamber of the weighing piston 22A to the circuit 27 of the hydraulic reservoir 26.
In this manner, downward displacement of the clear-ing tappet 6F causes the disch æ ge of fluid from the chamber of the piston 22A,and expansion of the weighing spring 22 which has previously been compressed by the weighing tappet 6A.
As shown diagrammatically in Figs. 1 and 2, the brake-application regulator 21, the hydraulic reservoir 2~
and the different valves 25, 28, 35 of Fig. 7 can advantageous-ly be grouped together within a weatherproof caslng 37. Thedischarge pipes of the cylinder~ 7A to 7E converge towards the casing 37 and are protected outside this lattex by means of sheaths 38 such as metallic sheaths, for example.
Preferably, all similar components such as tappets 6, piston-rods 9, pistons 8, hydraulic cylinders 7 are interchangeable. The same applies to the various similar components of the motion converters of the successive track-brake elements, namely the rocker llA, the half-ball joint components 13, the horizontal thrust member 9A (as shown in Flgs. 2 to 6). As has been noted e æ lier, the mechanical components of the track brake in accordance with the inven-tion are capable of operating without any special lubrication, this being permitted by the choice of materials of associated ` ~ parts and by the degree of machining of these latter.
Operation of the track brake descrlbed in the fore-goLng with reference to figs. 1 to 7 w111 now be explained.
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The track brake which is mounted in the service position on the shuntlng track i5 assumed to be in the rest posi-tion corresponding to the diagrammatic figures 7 and 8. In particular, all the pipes of the different hydraulic circuits are assumed to be filled with fluid after air has been bled from said pipes by means of suitable orifices (not shown) located at a number of suitable points in the circuits.
When a wheel 4 of the car travelling in the direction of the arrow F (as shown in Figs. 5 and 7) reaches the convex top portion 17A of the weighing tappet 6A which forms a slight projection 17B above the braking rail 5D, the weighing tappet 6A is displaced downwards under the weight of the wheel 4. The tappet causes displacement of the rocker llA of the motion converter 11 and the piston-rod 9 (as shown ln Figs. 3 and 5). The piston 8 compresses the restoring sprlng 8A within the weighing cylinder 7A (Fig. 7) and dis-~ .r~
chargec the fluld from the cylinder. The fluid discharged from the weighing cylinder 7A via the pipe 7Al passes through the valve 25 and produces action within the regulator 21 on ~ 20 the weighing piston 22A, thus compressing the weighing spring -~ 22 to a predetermined extent which depends on the weight of the wheel 4. For a brief instant, said wheel is then in equilibrium on the weighing tappet 6A which in turn remains stationary.
Thus the downward displacement of the weighing piston 22A within the regulator 21 (as shown in Figs. 7 and 8) defines the downward travel of the con~-ex portion 17A of ¦ the weighing tappet 6A (shown in Fig. 5) with respect to its rest position. It has been noted that this rest position I ~ 30 projects upwards over a small distance to the level 17B which ! is equal to approximately 10 mm, for example, above the top .
1093(~43 level of the braking rail 5D.
By choosing the ratio of useful cross-sectional areas of the piston 8 of the weighing jack 22A of the regulator 21 (as shown n Figs. 7 and 8) as well as the characteristics of the restoring spring 8A and the weighing spring 22, steps are taken to ensure that the distance of upward projection 17B of the top face 17A of the weighing tappet 6A (shown in Fig. 5) still remains to a partial extent for weighing the maximum permissible weight of the wheel 4.
By way of example, this maximum weight is equal to 10 (metric) tons. A residual value of the order of 2 mm, for example, can be established by design so as to correspond to said maximum weight in the case of the distance of projection 17B
of the weighing tappet 6A above the braking rail 5D ~as shown in Fig. 5).
I( After the wheel 4 has passed over the weighing tappet 6A, the restoring spring 8 returns the tappet 6A to the rest position at a distance of projection of approximately 10 mr~t above the level of the top face o the braking rail 5D.
At the same time, the piston 8 draws a certain quantity of : fluid from the reservoir 26 via the supply circuit 27 and ~ the valve 28 of the weighing pipe 7Al. However, the weighing .: : valve 25 ensures that the piston 22A.is maintained stationary and that the weighing spring 22 is maintalned ln the com-pressed position, thus holding the throttling piston 24 against its seating 24A as a function of the welght of the : wheel 4 whLch is measured by the extent of downward displace-ment of the weighing tappet 6A.
As shown in Figs. 6 and 7, the wheel 4 then moves successlvely to each of the braking tappets 6B to 6E. The braking tappet such as 6B moves downwards at a substantially .~ ~
1093t~43 constant speed each time as a result of the uniform slope 17D
of its top face 17C which projects above the top face of the braking rail 5D (as shown in Fig. 6). The rocker llA of the motion converter then initiates compression of the restoring spring 8A of the corresponding brake cylinder 7B to 7E
(Fig. 7) and downward displacement of the piston 8 within the cylinder 7 (as shown in Figs. 3 and 7) at a uniform speed.
The fluid is thus discharged from the brake cylinder 7 without any irregularity of dynamic pressure within the brake-application pipe 23 which terminates in the regulator 21 andin the threshold valve 31 which is mounted as a by~pass.
If the speed of the wheel 4 (shown in Fig. 7) is over the minimum value which is permitted for the operation of the track brake and is equal to 0.8 m/sec, for example, the movable obturator 31A of the threshold valve 31 (shown ln Flg. 8) compresses the spring 31C under the action of the flow of fuel which is admitted through the brake-application pipe 23. The valve 31 closes, thus causing the entire quan'ity of fluid to pass through the brake-application regulator 21. In this latter, the 1uid 1s subjected to a choking action by the throttling piston 24, the pressure of application of said piston against its seating being dependent on the compression of the weighing spring 22. Thus the brake action transmitted to the wheel 4 as a result of resistance to downward displacement of each braking tappet 6B
to 6E is of greater or lesser intensity according to the weight measured by the weighing tappet 6A and resulting in compression of the weighing spring 22.
As long as the speed of the wheel 4 remains higher than the limiting speed permitted for the track brake 1, the obturator 31A of the threshold valve 31 is applied against ` -14-.,.. ~, . ~ . .. .
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1093(~43 its seating 31B by the flow of fluid which is discharged successively by each of the pipes 23A of the brake cylinders 7B to 7E. Thus the wheel 4 is subjected to brake action as long as the wheel speed exceeds the minimum value mentioned earlier, namely 0.8 m/sec, for example.
On the other hand, if the speed of the wheel 4 falls below the minimum value aîorementioned, for example before the wheel reaches the braking tappet 6E (shown in Fig. 7), said tappet becomes inoperative. -In fact, the rate of fluid flow within the threshold valve 31 is insufficient to apply the movable obturator 31A against the seating 32 and the valve 31 remains open. Under these conditions, the fluid discharged from the brake cylinder 7E can pass through the by-pass 31D instead of being subjected to the choking action produced by the throttllng piston 24 within the regulator 21.
By virtue of the aforementioned system for putting the regulator 21 out of circuit, steps are taken to prevent any reduction in speed of the wheel 4 below the limiting speeZ indicated earlier,in order to maintain uniform rolling motion of the car and a sufficiently high rate of classifica-tion yard operations.
The threshold valve 31-can advantageously comprise a regulating device or adjusting the compression of the spring 31C on demand,so as to correspond to the threshold flow rate of fluid in respect of the limiting speed of the wheel 4 - below which the brake action is intended to be inoperative.
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Adjustment of the spring 31 can take place, for example, by means of an external screw 31E as shown diagrammatically in Flg. 8.
When the wheel 4 reaches the clearing tappet 6F, discharge of the fluid from the cylinder 7F via the clearing .' pipe 33 (shown in Fig. 7) has the effect of actuating the clearing relay 34, thus in turn having the effect of opening the discharge valve 35. This permits discharge of the fluid from the chamber of the piston 22A towards the reservoir 26 and expansion o~ the weighlng spring 22. The regulator 21 is thus ready to receive from the weighing tappet 6A an indica-tion of the weight of the wheel which follows the first wheel 4. Since the tappets 6A to 6F are disposed along a limited length 5L (Figs. 2 and 7) which is shorter th~n the distance between the wheels 4 of the two axles of one bogie of the car, brake application on the second wheel of a bogie is not liable to be adversely affected by late clearing initiated by the first wheel. Moreover, the clearing tappet 6F makes all the braklng tappets 6E to 6B lnoperative in the case of the wheels of a train which i5 moved back along the shuting track in the direction opposlte to the arrow F (shown in Fig.7).
The track brake in accordance with the invention offers a number of advantages over brake systems of known types.
The design of the track brake in the form of a modular unit adapted to the spacing of the crossties of the classiflcation track permits economical industrial manufacture and easy erection of the brake unit. The bed-plate 18 (shown in Figs. l to 4) is advantageous in this respect since the j` 25 brake unit can be securely and conveniently fixed on the crossties of the track.
Since the braking rail section 5 has an upper profile of reduced thickness in that portion 5D which is located between the two end portions 5A, 5B, convenient lateral assembly of the tappet 6 opposite to the tires of the wheels 4 is accordingly permitted. It is thus possible ~ ~" _, to give the tappet 6 a sufficient width (as shown in Fig. 3) which is conducive to mechanical efficiency as well as endurance of the tappet over a long period of service.
By virtue of a profile which is identical with that of the ordinary rails 2 of the track, the two end portions 5A, 5B of the braking rail make it possible to connect the braking rail section 5 to the adjacent rail 2 in a convenient and secure manner, for example by means of ordinary fish-plates 5C (as shown in Fig. 2).
By arranging the weighing tappet 6A and the clearing tappet 6F over a limited length 5L which is shorter than the distance between the wheels of the two axles of one bogie, it is thus possible to prevent late passage of the first wheel over the clearing tappet 6F which would be liable to impair the brake action on the following wheel which has already engaged on the track brake 1. The horizontal arrangement makes it possible to give the desired dimensions to the cylinders 7A to 7F and especially to the braking cylinders 7B to 7E without having to form recesses in the track ballast which would have an adverse effect on the ease of installation of the brake unit.
.
The form of construction provided for the horseshoe tappet 6 (shown in Figs. 5 and 6) and for the rocker llA of the motion converter which is associated with each tappet and rigidly fixed on the bed-plate 18 (as shown in Fig. 3) makes it possible to endow the mechanical components of the brake unit with a high degree of strength and ruggedness in order to afford resistance to repeated impacts of the wheels 4 to be braked over a long pexiod of time.
The components aforesaid and the half-ball joint components 13 (shown in Figs. S and 6) which are associated :
i ~093043 with the vertical-motion tappets 6, with the rockers llA and with the thrust members 9A of the piston-rods 9 can be formed for example of treated steel, of special high-resilience cast-iron or of high-strength bronze. These materials make it possible to obtain an excellent state of surface which is conducive to mechanical efficiency of the motion converter of each element for weighing, braking or clearing the track brake. All these components and especially the removable half-balls 13 can readily be replaced.
The aforesaid state of surface ensures high smooth-ness of sliding motion of the substantially e~uatorial planes 13B of the half-balls 13 on the associated flat faces of the tappets 6 and thrust members 9A. The same applies to the sliding motion of the substantially hemispherical faces 13A
of the half-balls 13 within the cupq 12 of the rocker llA of each motion co~verter of the track brake. The choice of the materials constituting the moving parts and the machining of these latter thus make it possible to ensure operation of the frack bra~e without any particular lubrication.
The slope 17D of the projecting portion of each braking tappet such as the tappet. 6B (shown in FigO 6) ensures downward displacement of this la ter at a substantial-ly uniform speed at the time of passage of the wheel 4 (shown in Figs. 1, 6, 7) irrespective of the diameter "D" oi the wheel. This results in a uniform rate of flow of the fluid through each brake cylinder 7B to 7E at the time of passage of the wheel 4 to be braked. This accordingly prevents any irregularities of dynamic pressure of the fluid within the ` discharge pipes of the hydraulic cylinders which would be ; 30 liable to disturb the operation of the brake-application regulator 21 and the efficiency of thetrack brake.
~ ' . ' By employing a single regulator 21 for all the brake cylinders 7B to 7E, each cylinder is endowed economically with accurate regulating means for automatic brake application which is exactly adapted to the weight of each wheel by means of the weighing system which is controlled in dependence on the tappet 6A. By virtue of the clearing system controlled by the exit tappet 6F, th~ track brake is prepared to receive a fresh wheel each time in order to produce an accurate brake application on this latter.
The threshold valve 31 which is connected as a shunt off the regulator 21 makes it possible to conform to a bottom speed limit of the wheel 4 while preventing excessive brake action which would be liable to impair normal rolling motion of the car and to reduce the rate of classification operations. For example, by adopting a bottom speed limit in the vicinity of 0.8 m/sec, abnormal lmpact of cars is prevented without any need to resort to uneconomical reduction of spacing between track brake units.
As can readily be understood, the invention is not limited to the embodiment described in the foregoing by way of example,and a number of different alternative forms can accordingly be devised without thereby departing either from the scope or the spirit of the invention.
There is thus shown in Fig. 9 an alternative .~ ~
~ ~ 25 embodiment 41 of the brake-application regulator of the track .
brake unit in accordance with the invention. Said regulator comprises a fluid-throttling piston 42 associated with a throttling piston-seating 42A which is connected to the dis-charge circuit 23 of the brake cylinders. ~he throttling piston is subjected to the bearing pressure of an auxiliary spring 43 which is mounted within a bearing chamber 43A and .
~ ' .
.
1093~)~3 controlled in dependence on a weighing pilot piston 44 controlled by the pressure of the discharge pipe 7Al of the cylinder 7A which is associated with the weighing tappet 6A
(as shown in Fig. 6).
The weighing pilot piston 44 thus ensures compression of the opposing weighing spring 45 in order to determine the value of a leakage pressure of the bearing chamber 43A which is connected by means of an internal duct 46 to the discharge circuit 23 of the brake cylinders. The leakage pressure determined by the compression of the weighing spring 4S thus defines the value of hydraulic pressure within the chamber 43A
which is exerted on the rear face of the throttling piston 42 and maintained by the pressure of fluid within the brake pipe 23.
This mode of follow-up control of the regulator 41 makes it possible to improve the sensitivity and accuracy of the weighing system of the track brake in accordance with the invention since it is accordingly only necessary to apply a low pressure to the pilot piston 44 through the weighing pipe 7Al.
In accordance with another alternative embodiment (shown in Fig. 10), the regulator 41 which is similar to the ~ :
regulator of Fig. 9 is associated with a controlled slide-valve 47 which replaces the threshold valve 31. The controlled slide-valve 47 is mounted in a lateral pipe 47A
- which is connected to the brake pipe 23 through the internal duct 46 of the regulator. The slide-valve 47 is maintained in the rest position within a caslng by means of a spring 47B
~ in such a manner as to ensure that an annular chamber 47C of ;~ 30 the slide-valve accordingly puts the by-pass line 47A into communication with the pipe 27 of the hydraul1c reservoir 26.
~.
. -2a-:
- ' ` ` ' '' --' ' ' ' ''---- ' -` `` ` !.' - '~ ' : ' ' - ----_.___~.___.___ __.. -_ .` .. ' .. _ ~ ___ .__.__ __ ~_._ , ___._ _____ . _ . _ "",,j ., ._",.. _ . ..
A lateral branch pipe 48A is connected to the dis-charge pipe 48 of the throttling piston 42 upstream of an adjustable calibrated orifice 48B. As a function of the rate of flow of fluid through the calibrated orifice 48B at the moment of brake application, a predetermined pressure is thus generated within the branch pipe 48A which terminates in the casing of the slide-valve 47 in opposition to the spring 47B through a spring-loaded valve 48C having a calibrated orifice.
The velocity of the fluid which flows through the calibrated discharge orifice 48B (shown in Fig. 10) corre-sponds to the speed of the wheel 4 which passes over the braking tappets 6B to 6E (shown in Fig. 7). When the speed of the wheel exceeds a predetermined bottom limit such as 0.8 m/sec, for example, the pressure of the fluid of the lateral pipe 48A displaces the slide-valve 47, thus cutting-off the communication between the by-pass line 47A and the pipe 27 of the hydraulic reservoir. Thus the entire ~uantity of fluid discharged from the brake cylinders into the pipe 23 is subjected to the action of the throttling piston 42 when the speed of the wheel 4 (Fig. 7) exceeds the limit aforesaid.
~ here is shown in Fig. 11 a similar arrangement of the brake-application regulator 41 associated with a lateral slide-valve 47E which is connected in this instance upstream of the regulator before an adjustable calibrated orifice 48E.
This orifice which is located upstream of the regulator 41 is thus protected from any dynamic pressure disturbances resulting from the throttling piston 42 which would be liable to affect the calibrated orifice 48B of Fig. 10.
The arrangement shown in Fig. 11 accordingly ensures operation of the short-circuiting slide-valve 47E in ' both directions in a flexible and reliable manner. In th~
rest position (Fig. 11), the slide-valve 47E short-circuits the throttling piston 42 in the by-pass line 47F as long as the speed of the wheel 4 to be braked (Fig. 7) is below the predetermined value mentioned above. Should this not be the case, the slide-valve 47E is accordingly brought to the closed position (not shown) as a result of the dynamic pressure generated by the calibrated orifice 48E which causes the entire quantity of fluid discharged into the-brake pipe 23 to be subjected to the action of the throttling piston 42.
There is shown in Fig. 12 a further alternative embodiment of the track brake in accordance with the invention which is similar to the track brake shown in Fig. 7 but is provided with an additional clearing tappet 6G which is similar to the clearing tappet 6F already descrlbed. The additional clearing tappet 6G is associated with a hydraulic jack 7G which is similar to the jack 7F and mounted at the end opposite to the tapper 6F with respect to all the other tappets 6A to 6E. In the same manner as the hydraulic jack 7F, the jack 7G is connected by means of a pipe 33A to the clearing relay 34 which controls the discharge valve 35 of the weighing system of the regulator 21.
The additional clearing tappet 6G (shown in Fig. 12) is intended to ensure expansion of the weighing spring 22 after the passage of a train along the track in which the ; brake unit in accordance with the invention is installed, in ¦ the direction of the arrow Fl opposite to the direction of the arrow F of Fig. 7. A train which travels back along the track in the direction of the arrow Fl is not subjected to any braking action since each wheel 4 first actuates the clearing tappet 6F (Fig. 7) which ensures expansion of the I
, -22-`
.
1093C~43 1/
weighing spring 22. However, the last wheel 4A of the train produces action on the weighing tappet 6A and would thus leave the weighing spring 22 in the compressed state. The additional tappet 6G (shown in Fig. 12) has the effect of removing this disadvantage and of preparing precise adaptation of the track brake to the weight of a fresh wheel 4 to be braked in the direction of normal travel corresponding to the ~row F.
It is readily apparent that constructional arrange-ments are made to ensure that the overall length of all thetappets 6A to 6G which are disposed along the braking rail 5D
(as shown in Fig. 12) does not exceed the limitPd length 5L
as already defined in connection with Figs. 2 and 7. The length SL must be smaller than the distance between the wheels 4 of one bogie (not shown) of the frelght car to be braked.
This distance or wheel spacing is equal to 1.80 meter, for example.
In yet another alternative embodiment of the track brake in accordance with the invention, it is possible to dispense with the clearing tappet 6F (shown in Fig. 7) or the clearing tappets 6F and 6G (Fig. 12) as well as the asso-ciated hydraulic jacks 7F, 7G by means of an automatic time-controlled clearing circuit combined with the brake-applica-tion regulator such as the regulator 21 (shown in Figs. 7 and 8) or the regulator 41 (shown in Fig. 9). The afore-mentioned automatic clearing circuit is provlded by way of example with a calibrated leakage throat which permits within a pre-established time interval a discharge of fluid for ensuring application of the throttling piston 22A, 42 either directly (as shown in Figs. 7 and 8) or by means of the pilot piston 44 (as shown in Fig. 9).
' ~0!~3043 In the embodiment shown in Fig. 13 which corre-sponds to the case of the controlled regulator 41, the calibrated throat 50 is preferably adjustable and disposed li in a discharge pipe 50A which is connected at 50B to the weig-hing pipe 7Al between the check valve 25 and the constricted orifice or throat SO for putting the pilot piston 44 under pressure within the regulator 41.
~ As long as a discharge pressure of the weighing cylinder 7A is exerted, the low rate of flow of the leakag~
orifice 50 is insufficient to modify the compression of the opposing weighing spring 45 to any appreciable extent,thus deining the bearing pressure of the controlled throttling piston 42 as has been noted with reference to Fig. 9. On the other hand, as soon as the discharge pressure ls no longer exerted wlthln the weighlng plpe 7Al, the rate o flow through the constricted leakage orifice or throat 50 produces action so as to begin to reduce the compression of the opposing weighing spring 45.
In practice, the value of the caliber of the leakage throat 50 is chosen so as to ensure expansion of the opposing spring 45 from a value of compression corresponding to the maximum permissible weight in the case of a last car wheel, namely 10 (metric) tons for example, and at least down to a low value of compression correspondlng to the minimum weight which is possible for the first wheel of another car, namely 2 tons, for example. It is assumed that the second ` car immediately follows the first car, which represents for example a distance of only 2.44 meters between the wheels ` . .
considered. It is also assumed that the two cars travel at the maximum speed contemplated on the shunting track, I namely 1.50 m/sec, for example.
: - .
10~ 3 Taking into account the values indicated in the foregoing, it is possible to calculate the minimum time interval in which expansion of the opposing spring 45 should be capable o~ taking place and consequently to adjust the callber of the leakage throat 50. The time-controlled clearing circuit system also makes it possible to avoid the dead times related to the operation of the clearing system controlled by the exit tappet 6F which was described with reference to Fig. 7.
As a preferable feature shown in Fig. 13, the calibrated-leakage automatic clearing circuit associated with the regulator 41 further comprises an auxiliary pipe 50D
for putting the weighing circuit under pressure. The auxiliary pipe 50D connects the point 50B of the weighing pipe 7Al to the brake pipe 23 through a check valve 50E. In this manner, each pressure pulse transmitted to the brake pipe 23 by one of the successive braking tappets 7B to 7D
~Fig. 7) has the effect of compensating for the leakage produced by the throat 50. Substantially equivalent useful cross-sectional areas are chosen for the weighing cylinder 6A
and the brake cylinders 7B to 7E in order to return substan-tia}ly to the initial value of the weighing pressure of the ,~ ~ cylinder 7A at each operation of the brake cylinders 7B to ,~ 7E.
Thus the brake cylinders each come into action in turn after the weighing cylinder 7A in order to reproduce the braking pressure whlch has already been delivered by this ; ~ latter to the weighing pilot piston 44. 3y virtue of this complement æy function of the brake cylinders, it is possible to give a relatively large caliber to the leakage throat 50. This advantage is important in order to prevent 10~3043 any danger of irregular operation of the automatic clearing system since a throat of excessively small caliber is liable to be obstructed by impurities in suspension in the fluid~
As can readily be understood, an automatic clearing system which is similar to that of Fig. 13 can be associated with the direct-action regulator 21 of Figs. 7 and 8. In this case, the leakage pipe tnot shown) has an adjustable calibrated throat which is similar to the throat 50 and is located (as shown in Fig. 7) between the inlet of the weighing pipe 7Al within the regulator 21 and the reservoir pipe 27.
A number of other alternative embodiments of the track brake in accordance with the invention can also be contemplated. By way of example, it is clearly possible to form a modular braking unit comprising two braking rail sections ~not shown) which are placed side by side and are each similar to the braking rail section 5 of Fig. 2. An arrangement of this type will be adopted in particular for the purpose of reducing the length 5L of each track brake since the brake action is then doubled for the same length of brake unit.
Similarly, it is apparent that the track brake can ` comprise any number of-brake-application members such as the members associated with the cylinders 7B to 7E of Fig. 2.
~ The track brake can thus be constituted, for example, by six ;i 25 or eight brake-application members which make it possible to ~' obtain enhanced brake action in the case of members having the same power as those of Fig. 2. At the cost of an increase in length of the track brake 1, it will also be possible in this manner to reduce the energy absorbed by each member and to attenuate corresponding impacts or again to reduce the number of track brakes 1 to be installed in respect of a 1, : .
I
1093~43 given length of the shunting track. It is thus possible to achieve a most satisfactory compromise between the contradictory requirements of efficiency and endurance of the brake units and the desire to keep the cost price as low as possible in all automatic braking installations to be provided on the multiple tracks of a classification yard.
In Fig. 2, there is shown by way of example one embodiment of the track brake in accordance with the inven-tion which is mounted beforehand on special crossties 3A on which there have been fixed the bed-plate 18 together with the braking rail section 5D plus the two check-rails 5E. In order to position the complete track brake unit of Fig. 2, all the screw-spikes (not shown) are removed from the stand æd crossties of the track in that portion which is intended for the track brake 1. ~he two ordinary rails 2 are liftad in order to withdraw the standard crossties. One of the rails 2 is cut to the length which is necessary for mounting the braking rail section 5. The special crossties 3A of the track brake can then be introduced in the flat positlon beneath the intact rail 2, the rails 2 are lowered in order to fix the intact rail 2 on the crossties 3A and - the two end portions SA, 5B of the braking rail section are ~ ~ joined to the cut rail 2.
.
It is of course also possible to avoid part of the operations mentioned above if this is permitted by the strength of the ordinary crossties 3 of the shunting track. It is only necessary in this case to remove the screw-spikes from the ordinary rail 2 to be cut in order to place the braking rail section 5 in position. The bed-plate 18 is then placed on the ordinary crossties 3 of the shunting track ; after this operation, the two check-rails 5E
' .~
.
~093043 are also laid on the crossties, and the braking rail section 5 is joined to the cui rails 2.
The choice between the two modes of positioning of the track brake which may or may not be mounted beforehand on special crossties will depend in particular on the strength of the standard crossties of the classification track to be equipped.
In the different embodiments which have been described thus far, one of the important advantages of the track brake in accordance with the invention lies in the existence of means for clearing the weighing operation so as to permit reversal of at least one car along the track in the direction opposite to the normal direction of braking, without thereby producing any brake application and without any attendant danger of immediate or subsequent incidents.
As has already been noted, the above-mentioned clearing means are of the direct-control type in the case of the clearing tappets 6F, 6G (as shown in Figure 12) or of the automatic time-controlled operation type associated with the calibrated throat 50 (shown in Figure 13). Releasing of the opposing weighing spring 45 or 22 which is effected by means of these clearing means (Figures 9 to 13) makes it possible for a car to travel along the track in the direction opposite to the direction of normal braking without any brake application and without any ` troublescme occurrences.
The retarding means described hereinafter are placed next to ; the braking rail section 5 over a limited length SL (Figures 2 and 7) which is shorter than the interval between the wheels 4 .
. ' 1093C~3 of one of the car bogies (not shown). By way of example, this interval is equal to 1.80 meter.
Preferably, the braking rail section 5 and the inter-mediate portion of the other rail 2 are both associated with a check-rail 5E in order to improve the guiding action ~09~043 of the car wheels 4 in the zone of action of the track brake 1 (as shown in Figs. 1 to 3).
As an advantageous feature which is illustrated in Fig. 2, the braking rail section 5 is provided at its two S end portions 5A, 5B with a profile, which is substantially identical with the profile of the ordinary rails 2 of the adjacent track in order to connect the braking rail section 5 to these latter, for example by means of bolted fishplates 5C. The zone 5D of the braking rail section which is located between the two above-mentioned end portions 5A, 5B is pro-vided in the upper portion thereof with a profile of reduced thickne,ss (as shown in Figs. 1 and 3) for the lateral mounting of a vertical-motion tappet 6. In the rest position shown in Figs. 3 and 5, said tappet has a portion which pro~ects above the level of the top face of the braking rall 5 in order to be applied successively beneath each freight-car wheel 4.
The retarding means of the track brake comprise a series of hydraulic cylinders 7A,,7B, 7C, etc. (as sh~wn in Fig. 2). There is slldably mounted within each cylinder . 7 a piston 8 ,(Fig. 3~ associated w1th a restoring spring 8A
which urges the piston 8 towards its rest position. Said piston has a rod 9 connected to a vertical-motion tappet 6A,-6B, 6C etc. by means of a motion converter 11 comprising a 25~ rocker llA mounted on a pivot-pin llB which is rigidly fixed . :
to the braking rail section 5 by means of a support structure as will be described hereinafter. The pivot-pin llB of each ; , rocker llA is secured to the structure aforesaid by means of a support bracket 11C (shown in Figs. 3 and 4), the axis , ~ 30 of said pivot-pin belng substantially horizontal and parallel to the braking rail section 5D. The rocker llA has 5 _ ' , a portion which cooperates with the vertical-motion tappet 6 and another portion which cooperates with the rod 9 of the piston 8 of the horizontal cylinder 7 which is oriented transversely with respect to the rail section 5.
The rocker llA is provided with a cup 12 on each of the aforesaid portions which cooperate with the tappet 6 and the piston-rod 9 (as shown in Figs. 3, 5, 6) in order to receive a substantially hemispherical face 13A of a half-ball joint component 13 which is concentric with the cup 12. A
substantially equatorial flat face 13B of each half-ball 13 forms a projection above the cup 12 in order to be applied against a corresponding flat face of the vertical-motion tappet 6 and against a flat face of the extremity of the piston-rod 9 respectively.
Thus, as will be explained hereinafter, the flat equatorial face 13B of each half-ball joint component 13 ls capable of slldlng freely against the opposlte flat face of the vertical-motion tappet 6 or of the extremity of the piston-rod 9 for the operation of the motion converter, taking into account the circular path followed by each cup 12. Preferably, an intermediate thrust member 9B is inter-posed between the extremity of the piston-rod 9 and the corresponding half-ball 13 (as shown in Figs. 3 and 4).
The half-ball 13 and the associated components of ~- 25 the motion converter 11 can be formed of all suitable materials. For example, the tappets 6 and thrust members 9A
are of steel as well as the rocker llA,and the half-ball 13 is of high-strength bronze. All the components can also be formed of steel and an anti-friction lining of bronze, for , 30 example (not shown) can be placed within the cups 12 of the rocker llA and on the flat faces of the tappets 6 and thrust ~; , -.
10~3043 members 9A which are associated with the half-balls 13.
By virtue of the arrangements and choice of materials indicated in the foregoing, the mechanisms of the track brake in accordance with the invention are capable of operating without lubrication.
In the direction of travel of the wheel 4 to be braked (arrow F of Figs. 2, 5, 6, 7), the first tappet 6A
is preferably a weighing tappet associated with a weighing hydraulic jack 7A as will be explained below. The weighing -tappet 6A has a convex top face 17A (as shown in Fig. 5)which forms in the rest position of the tappet a slight projection 17B above the level of the summit or top face of the braking rail 5D. For example, the height of projection 17B ls of the order of 10 mm.
15The vertical-motion tappets 6B, 6C, 6D, 6E whlch follow the weighlng tappet 6A are preferably braking tappets.
The profiled top portlon 17C of each tappet which projects above the braking rail 5D (as shown in Fig. 6) advantageously has a slope 17D in the intended direction of travel of the wheel 4 as indicated by the arrow F. The slope 17D ensures unlform downward displacement of the tappet 6 at the time of passage of the wheel 4 over a distance of tra~el correspond-~ ing to the height of projection 17E of the tappet 6 in the ;~ ~ rest position (as shown in Figs. 5 and 6), namely approximate-ly 50 mm, for example. As mentioned hereinafter, the uniform downward displacement of the tappet 6 prevents .
; dynamic pressure defects in the hydraulic brake circuits which will be described hereinafter.
The structure of the modular unit constituted by the track brake (shown in Figs. 1, 2, 4) comprises a bed-plate 18 formed for example of sheet steel having substantial .
.
~' :~
~093C~3 thickness and secured by means of ssrew-spikes 18A to the crossties 3A of that portion of the shunting track in which the brake unit is installed. The bed-plate 18 carries the braking rail section 5, the guides 16A of each vertical-motion tappet 6, the brackets llC for supporting the pivot-pin llB of the rocket llA of the motion converter and the associated hydraulic cylinders 7A, 7B, 7C, and so forth.
As shown in Figs. 1 to 4, the hydraulic cylinders 7 are substantially horizontal and mounted on a rear plate 18B, for example. Said rear plate is r1gidly fixed to the bed-plate 18 and forms together with this latter a casing which is closed by a detachable cover 18C in order to protect the brake components from dust and bad weather conditions.
In th~ embodiment which is described herein by way of example (with reference to Figs. 2, 7, 8),,the track brake 1 is constituted first by the weighing tappet 6A associated with the weighing hydraulic j,ack 7A, then by four braking , tappets 6B, 6C, 6D, 6E. These latter are each associated ', 20 with a brake cylinder 7B, 7C, 7D, 7E which operate~ by throt-, tling a suitable fluid such as a non-freezing mineral oil which is resistant to ageing. The track brake in accordance with the invention comprises means for adjusting the throt-. .
tling action of the fluid on demand, according to the weight ` 25 carried by each wheel 4. This weight is measured by means of , the weighing tappet 6A and the associated jack 7A.
Preferably, the adjusting means aforesaid comprlse ;'~as shown in Figs. 7 and 8~ a brake-application regulator 21 ' ~ ~having an opposing spring 22 associated with a weighing piston 22A which is controlled by the weighing tappets 6A.
Said tappet is placed before the first braking tappet 6B in : -~a-:: .
:`:
'1093V43 the direction of travel of the cars indicated by the arrow F
and i5 associated with the weighing hydraulic cylinder 7A
which is similar, for example, to the brake cylinders 7B to 7E.
The brake-application regulator 21 is mounted in a hydraulic circuit 23 (Fig. 7) to which discharge pipes 23A
.of each brake cylinder 7B to 7E are connected in.parallel.
Throttling of the fluid discharged from the brake cylinders is carried out within the regulator 21 by means of a throttling piston 24 which is applied against its seating 24A by the weighing spring 22.
Check valves 25 æe mounted in the discharge pipe 7Alof the weighing hydraulic cylinder 7A and in the discharge pipes 23A of the brake cylinders 7B to 7E. All the cylinders mentloned above are connected directly to a common hydraulic reservoir 26 by means ~f a supply circuit 27. This latter is Il.' . ..
connected to each discharge pipe 7Al, 23A, by means of a : check valve 28 which operates in the direction opposite to : the discharge valve 25 of the same pipe.
Check valves 28 prevent the flow of the fluid which is forced back by the cylinders i when the pistons 8 ; are displaced do~lwards therein and compress the restoring . springs 8A. However, the valves 28 permit.the flow of fluid from the supply circuit 27 to the cylinders 7 when the pistons : ~ 25 8 are brought back to the rest position by the restoring i~ .
springs 8A as will be explained hereinafter.
he track brake can advantageously comprise means : for detecting the speed of the car wheel 4 combined with retardin~ means,in order to make these latter inoperative " ~ 30 below a predetermined value of speed of the wheel,in order to prevent excessive brake action on freight cars.
~: i ~: _g_ . . ~ .
In the embodiment which is illustrated diagrammatic-ally in Figs. 7 and 8, the means for detecting the speed of the wheel 4 comprise a flow-threshold valve 31 in which an obturator disc 31A is held at a distance from a valve-seat 31B by a spring 31C below a predetermined value o~ fluid flow corresponding to the rate of downward displacement of a braking tappet 6~ to 6E in respect of the aforementioned limiting speed of the wheel 4.
The threshold valve 31 is mounted as a by-pass off the brake-application regulator 21 in the discharge circuit 23 of the brake cylinders. In this manner, the fluid dis-charge from the brake cylinders 6B to 6E is subjected to the choking action of the throttling piston 24 within the regulator 21,only when the speed of the wheel 4 oversteps the limitlng value permltted by the track brake. A llmiting value of 0.8 m/sec is chosen by way of example.
Below the aforesald speed of the wheel, the threshold valve 31 remains open, thus making the throttling piston 24 inoperative and preventing brake action on the wheel 4.
The brake-application regulator 21 preferably ; comprises a clearing device for producing the expansion of the weighing spring 22 which has previously been compressed by the weighing tappet 6A. The device for clearing the weighing operation can be controlled by means of a clearing tappet 6F which is placed after the last braking tappet 6E
in the direction of travel of the wheel 4 as indicated by the arrow F in Fig. 7. The clearing tappet 6F is similar, for example, to the weighing tappet 6A (as shown in Figs. 5 and 7).
` In the embodiment which is illustrated by way of : ' .
--10- `
.
example in Figs. 5 and 7, the clearing tappet 6F actuates a piston mounted within a hydraulic cylinder 7F which is similar for example to the weighing cylinder 7A. The clearing cyllnder 7F is connected by means of a clearing pipe 33 to a clearing relay 34 which controls a discharge valve 35 mounted in a pipe for connecting the chamber of the weighing piston 22A to the circuit 27 of the hydraulic reservoir 26.
In this manner, downward displacement of the clear-ing tappet 6F causes the disch æ ge of fluid from the chamber of the piston 22A,and expansion of the weighing spring 22 which has previously been compressed by the weighing tappet 6A.
As shown diagrammatically in Figs. 1 and 2, the brake-application regulator 21, the hydraulic reservoir 2~
and the different valves 25, 28, 35 of Fig. 7 can advantageous-ly be grouped together within a weatherproof caslng 37. Thedischarge pipes of the cylinder~ 7A to 7E converge towards the casing 37 and are protected outside this lattex by means of sheaths 38 such as metallic sheaths, for example.
Preferably, all similar components such as tappets 6, piston-rods 9, pistons 8, hydraulic cylinders 7 are interchangeable. The same applies to the various similar components of the motion converters of the successive track-brake elements, namely the rocker llA, the half-ball joint components 13, the horizontal thrust member 9A (as shown in Flgs. 2 to 6). As has been noted e æ lier, the mechanical components of the track brake in accordance with the inven-tion are capable of operating without any special lubrication, this being permitted by the choice of materials of associated ` ~ parts and by the degree of machining of these latter.
Operation of the track brake descrlbed in the fore-goLng with reference to figs. 1 to 7 w111 now be explained.
.
~"., `-11-, `'`
:
.. . . ...
The track brake which is mounted in the service position on the shuntlng track i5 assumed to be in the rest posi-tion corresponding to the diagrammatic figures 7 and 8. In particular, all the pipes of the different hydraulic circuits are assumed to be filled with fluid after air has been bled from said pipes by means of suitable orifices (not shown) located at a number of suitable points in the circuits.
When a wheel 4 of the car travelling in the direction of the arrow F (as shown in Figs. 5 and 7) reaches the convex top portion 17A of the weighing tappet 6A which forms a slight projection 17B above the braking rail 5D, the weighing tappet 6A is displaced downwards under the weight of the wheel 4. The tappet causes displacement of the rocker llA of the motion converter 11 and the piston-rod 9 (as shown ln Figs. 3 and 5). The piston 8 compresses the restoring sprlng 8A within the weighing cylinder 7A (Fig. 7) and dis-~ .r~
chargec the fluld from the cylinder. The fluid discharged from the weighing cylinder 7A via the pipe 7Al passes through the valve 25 and produces action within the regulator 21 on ~ 20 the weighing piston 22A, thus compressing the weighing spring -~ 22 to a predetermined extent which depends on the weight of the wheel 4. For a brief instant, said wheel is then in equilibrium on the weighing tappet 6A which in turn remains stationary.
Thus the downward displacement of the weighing piston 22A within the regulator 21 (as shown in Figs. 7 and 8) defines the downward travel of the con~-ex portion 17A of ¦ the weighing tappet 6A (shown in Fig. 5) with respect to its rest position. It has been noted that this rest position I ~ 30 projects upwards over a small distance to the level 17B which ! is equal to approximately 10 mm, for example, above the top .
1093(~43 level of the braking rail 5D.
By choosing the ratio of useful cross-sectional areas of the piston 8 of the weighing jack 22A of the regulator 21 (as shown n Figs. 7 and 8) as well as the characteristics of the restoring spring 8A and the weighing spring 22, steps are taken to ensure that the distance of upward projection 17B of the top face 17A of the weighing tappet 6A (shown in Fig. 5) still remains to a partial extent for weighing the maximum permissible weight of the wheel 4.
By way of example, this maximum weight is equal to 10 (metric) tons. A residual value of the order of 2 mm, for example, can be established by design so as to correspond to said maximum weight in the case of the distance of projection 17B
of the weighing tappet 6A above the braking rail 5D ~as shown in Fig. 5).
I( After the wheel 4 has passed over the weighing tappet 6A, the restoring spring 8 returns the tappet 6A to the rest position at a distance of projection of approximately 10 mr~t above the level of the top face o the braking rail 5D.
At the same time, the piston 8 draws a certain quantity of : fluid from the reservoir 26 via the supply circuit 27 and ~ the valve 28 of the weighing pipe 7Al. However, the weighing .: : valve 25 ensures that the piston 22A.is maintained stationary and that the weighing spring 22 is maintalned ln the com-pressed position, thus holding the throttling piston 24 against its seating 24A as a function of the welght of the : wheel 4 whLch is measured by the extent of downward displace-ment of the weighing tappet 6A.
As shown in Figs. 6 and 7, the wheel 4 then moves successlvely to each of the braking tappets 6B to 6E. The braking tappet such as 6B moves downwards at a substantially .~ ~
1093t~43 constant speed each time as a result of the uniform slope 17D
of its top face 17C which projects above the top face of the braking rail 5D (as shown in Fig. 6). The rocker llA of the motion converter then initiates compression of the restoring spring 8A of the corresponding brake cylinder 7B to 7E
(Fig. 7) and downward displacement of the piston 8 within the cylinder 7 (as shown in Figs. 3 and 7) at a uniform speed.
The fluid is thus discharged from the brake cylinder 7 without any irregularity of dynamic pressure within the brake-application pipe 23 which terminates in the regulator 21 andin the threshold valve 31 which is mounted as a by~pass.
If the speed of the wheel 4 (shown in Fig. 7) is over the minimum value which is permitted for the operation of the track brake and is equal to 0.8 m/sec, for example, the movable obturator 31A of the threshold valve 31 (shown ln Flg. 8) compresses the spring 31C under the action of the flow of fuel which is admitted through the brake-application pipe 23. The valve 31 closes, thus causing the entire quan'ity of fluid to pass through the brake-application regulator 21. In this latter, the 1uid 1s subjected to a choking action by the throttling piston 24, the pressure of application of said piston against its seating being dependent on the compression of the weighing spring 22. Thus the brake action transmitted to the wheel 4 as a result of resistance to downward displacement of each braking tappet 6B
to 6E is of greater or lesser intensity according to the weight measured by the weighing tappet 6A and resulting in compression of the weighing spring 22.
As long as the speed of the wheel 4 remains higher than the limiting speed permitted for the track brake 1, the obturator 31A of the threshold valve 31 is applied against ` -14-.,.. ~, . ~ . .. .
.
1093(~43 its seating 31B by the flow of fluid which is discharged successively by each of the pipes 23A of the brake cylinders 7B to 7E. Thus the wheel 4 is subjected to brake action as long as the wheel speed exceeds the minimum value mentioned earlier, namely 0.8 m/sec, for example.
On the other hand, if the speed of the wheel 4 falls below the minimum value aîorementioned, for example before the wheel reaches the braking tappet 6E (shown in Fig. 7), said tappet becomes inoperative. -In fact, the rate of fluid flow within the threshold valve 31 is insufficient to apply the movable obturator 31A against the seating 32 and the valve 31 remains open. Under these conditions, the fluid discharged from the brake cylinder 7E can pass through the by-pass 31D instead of being subjected to the choking action produced by the throttllng piston 24 within the regulator 21.
By virtue of the aforementioned system for putting the regulator 21 out of circuit, steps are taken to prevent any reduction in speed of the wheel 4 below the limiting speeZ indicated earlier,in order to maintain uniform rolling motion of the car and a sufficiently high rate of classifica-tion yard operations.
The threshold valve 31-can advantageously comprise a regulating device or adjusting the compression of the spring 31C on demand,so as to correspond to the threshold flow rate of fluid in respect of the limiting speed of the wheel 4 - below which the brake action is intended to be inoperative.
.
Adjustment of the spring 31 can take place, for example, by means of an external screw 31E as shown diagrammatically in Flg. 8.
When the wheel 4 reaches the clearing tappet 6F, discharge of the fluid from the cylinder 7F via the clearing .' pipe 33 (shown in Fig. 7) has the effect of actuating the clearing relay 34, thus in turn having the effect of opening the discharge valve 35. This permits discharge of the fluid from the chamber of the piston 22A towards the reservoir 26 and expansion o~ the weighlng spring 22. The regulator 21 is thus ready to receive from the weighing tappet 6A an indica-tion of the weight of the wheel which follows the first wheel 4. Since the tappets 6A to 6F are disposed along a limited length 5L (Figs. 2 and 7) which is shorter th~n the distance between the wheels 4 of the two axles of one bogie of the car, brake application on the second wheel of a bogie is not liable to be adversely affected by late clearing initiated by the first wheel. Moreover, the clearing tappet 6F makes all the braklng tappets 6E to 6B lnoperative in the case of the wheels of a train which i5 moved back along the shuting track in the direction opposlte to the arrow F (shown in Fig.7).
The track brake in accordance with the invention offers a number of advantages over brake systems of known types.
The design of the track brake in the form of a modular unit adapted to the spacing of the crossties of the classiflcation track permits economical industrial manufacture and easy erection of the brake unit. The bed-plate 18 (shown in Figs. l to 4) is advantageous in this respect since the j` 25 brake unit can be securely and conveniently fixed on the crossties of the track.
Since the braking rail section 5 has an upper profile of reduced thickness in that portion 5D which is located between the two end portions 5A, 5B, convenient lateral assembly of the tappet 6 opposite to the tires of the wheels 4 is accordingly permitted. It is thus possible ~ ~" _, to give the tappet 6 a sufficient width (as shown in Fig. 3) which is conducive to mechanical efficiency as well as endurance of the tappet over a long period of service.
By virtue of a profile which is identical with that of the ordinary rails 2 of the track, the two end portions 5A, 5B of the braking rail make it possible to connect the braking rail section 5 to the adjacent rail 2 in a convenient and secure manner, for example by means of ordinary fish-plates 5C (as shown in Fig. 2).
By arranging the weighing tappet 6A and the clearing tappet 6F over a limited length 5L which is shorter than the distance between the wheels of the two axles of one bogie, it is thus possible to prevent late passage of the first wheel over the clearing tappet 6F which would be liable to impair the brake action on the following wheel which has already engaged on the track brake 1. The horizontal arrangement makes it possible to give the desired dimensions to the cylinders 7A to 7F and especially to the braking cylinders 7B to 7E without having to form recesses in the track ballast which would have an adverse effect on the ease of installation of the brake unit.
.
The form of construction provided for the horseshoe tappet 6 (shown in Figs. 5 and 6) and for the rocker llA of the motion converter which is associated with each tappet and rigidly fixed on the bed-plate 18 (as shown in Fig. 3) makes it possible to endow the mechanical components of the brake unit with a high degree of strength and ruggedness in order to afford resistance to repeated impacts of the wheels 4 to be braked over a long pexiod of time.
The components aforesaid and the half-ball joint components 13 (shown in Figs. S and 6) which are associated :
i ~093043 with the vertical-motion tappets 6, with the rockers llA and with the thrust members 9A of the piston-rods 9 can be formed for example of treated steel, of special high-resilience cast-iron or of high-strength bronze. These materials make it possible to obtain an excellent state of surface which is conducive to mechanical efficiency of the motion converter of each element for weighing, braking or clearing the track brake. All these components and especially the removable half-balls 13 can readily be replaced.
The aforesaid state of surface ensures high smooth-ness of sliding motion of the substantially e~uatorial planes 13B of the half-balls 13 on the associated flat faces of the tappets 6 and thrust members 9A. The same applies to the sliding motion of the substantially hemispherical faces 13A
of the half-balls 13 within the cupq 12 of the rocker llA of each motion co~verter of the track brake. The choice of the materials constituting the moving parts and the machining of these latter thus make it possible to ensure operation of the frack bra~e without any particular lubrication.
The slope 17D of the projecting portion of each braking tappet such as the tappet. 6B (shown in FigO 6) ensures downward displacement of this la ter at a substantial-ly uniform speed at the time of passage of the wheel 4 (shown in Figs. 1, 6, 7) irrespective of the diameter "D" oi the wheel. This results in a uniform rate of flow of the fluid through each brake cylinder 7B to 7E at the time of passage of the wheel 4 to be braked. This accordingly prevents any irregularities of dynamic pressure of the fluid within the ` discharge pipes of the hydraulic cylinders which would be ; 30 liable to disturb the operation of the brake-application regulator 21 and the efficiency of thetrack brake.
~ ' . ' By employing a single regulator 21 for all the brake cylinders 7B to 7E, each cylinder is endowed economically with accurate regulating means for automatic brake application which is exactly adapted to the weight of each wheel by means of the weighing system which is controlled in dependence on the tappet 6A. By virtue of the clearing system controlled by the exit tappet 6F, th~ track brake is prepared to receive a fresh wheel each time in order to produce an accurate brake application on this latter.
The threshold valve 31 which is connected as a shunt off the regulator 21 makes it possible to conform to a bottom speed limit of the wheel 4 while preventing excessive brake action which would be liable to impair normal rolling motion of the car and to reduce the rate of classification operations. For example, by adopting a bottom speed limit in the vicinity of 0.8 m/sec, abnormal lmpact of cars is prevented without any need to resort to uneconomical reduction of spacing between track brake units.
As can readily be understood, the invention is not limited to the embodiment described in the foregoing by way of example,and a number of different alternative forms can accordingly be devised without thereby departing either from the scope or the spirit of the invention.
There is thus shown in Fig. 9 an alternative .~ ~
~ ~ 25 embodiment 41 of the brake-application regulator of the track .
brake unit in accordance with the invention. Said regulator comprises a fluid-throttling piston 42 associated with a throttling piston-seating 42A which is connected to the dis-charge circuit 23 of the brake cylinders. ~he throttling piston is subjected to the bearing pressure of an auxiliary spring 43 which is mounted within a bearing chamber 43A and .
~ ' .
.
1093~)~3 controlled in dependence on a weighing pilot piston 44 controlled by the pressure of the discharge pipe 7Al of the cylinder 7A which is associated with the weighing tappet 6A
(as shown in Fig. 6).
The weighing pilot piston 44 thus ensures compression of the opposing weighing spring 45 in order to determine the value of a leakage pressure of the bearing chamber 43A which is connected by means of an internal duct 46 to the discharge circuit 23 of the brake cylinders. The leakage pressure determined by the compression of the weighing spring 4S thus defines the value of hydraulic pressure within the chamber 43A
which is exerted on the rear face of the throttling piston 42 and maintained by the pressure of fluid within the brake pipe 23.
This mode of follow-up control of the regulator 41 makes it possible to improve the sensitivity and accuracy of the weighing system of the track brake in accordance with the invention since it is accordingly only necessary to apply a low pressure to the pilot piston 44 through the weighing pipe 7Al.
In accordance with another alternative embodiment (shown in Fig. 10), the regulator 41 which is similar to the ~ :
regulator of Fig. 9 is associated with a controlled slide-valve 47 which replaces the threshold valve 31. The controlled slide-valve 47 is mounted in a lateral pipe 47A
- which is connected to the brake pipe 23 through the internal duct 46 of the regulator. The slide-valve 47 is maintained in the rest position within a caslng by means of a spring 47B
~ in such a manner as to ensure that an annular chamber 47C of ;~ 30 the slide-valve accordingly puts the by-pass line 47A into communication with the pipe 27 of the hydraul1c reservoir 26.
~.
. -2a-:
- ' ` ` ' '' --' ' ' ' ''---- ' -` `` ` !.' - '~ ' : ' ' - ----_.___~.___.___ __.. -_ .` .. ' .. _ ~ ___ .__.__ __ ~_._ , ___._ _____ . _ . _ "",,j ., ._",.. _ . ..
A lateral branch pipe 48A is connected to the dis-charge pipe 48 of the throttling piston 42 upstream of an adjustable calibrated orifice 48B. As a function of the rate of flow of fluid through the calibrated orifice 48B at the moment of brake application, a predetermined pressure is thus generated within the branch pipe 48A which terminates in the casing of the slide-valve 47 in opposition to the spring 47B through a spring-loaded valve 48C having a calibrated orifice.
The velocity of the fluid which flows through the calibrated discharge orifice 48B (shown in Fig. 10) corre-sponds to the speed of the wheel 4 which passes over the braking tappets 6B to 6E (shown in Fig. 7). When the speed of the wheel exceeds a predetermined bottom limit such as 0.8 m/sec, for example, the pressure of the fluid of the lateral pipe 48A displaces the slide-valve 47, thus cutting-off the communication between the by-pass line 47A and the pipe 27 of the hydraulic reservoir. Thus the entire ~uantity of fluid discharged from the brake cylinders into the pipe 23 is subjected to the action of the throttling piston 42 when the speed of the wheel 4 (Fig. 7) exceeds the limit aforesaid.
~ here is shown in Fig. 11 a similar arrangement of the brake-application regulator 41 associated with a lateral slide-valve 47E which is connected in this instance upstream of the regulator before an adjustable calibrated orifice 48E.
This orifice which is located upstream of the regulator 41 is thus protected from any dynamic pressure disturbances resulting from the throttling piston 42 which would be liable to affect the calibrated orifice 48B of Fig. 10.
The arrangement shown in Fig. 11 accordingly ensures operation of the short-circuiting slide-valve 47E in ' both directions in a flexible and reliable manner. In th~
rest position (Fig. 11), the slide-valve 47E short-circuits the throttling piston 42 in the by-pass line 47F as long as the speed of the wheel 4 to be braked (Fig. 7) is below the predetermined value mentioned above. Should this not be the case, the slide-valve 47E is accordingly brought to the closed position (not shown) as a result of the dynamic pressure generated by the calibrated orifice 48E which causes the entire quantity of fluid discharged into the-brake pipe 23 to be subjected to the action of the throttling piston 42.
There is shown in Fig. 12 a further alternative embodiment of the track brake in accordance with the invention which is similar to the track brake shown in Fig. 7 but is provided with an additional clearing tappet 6G which is similar to the clearing tappet 6F already descrlbed. The additional clearing tappet 6G is associated with a hydraulic jack 7G which is similar to the jack 7F and mounted at the end opposite to the tapper 6F with respect to all the other tappets 6A to 6E. In the same manner as the hydraulic jack 7F, the jack 7G is connected by means of a pipe 33A to the clearing relay 34 which controls the discharge valve 35 of the weighing system of the regulator 21.
The additional clearing tappet 6G (shown in Fig. 12) is intended to ensure expansion of the weighing spring 22 after the passage of a train along the track in which the ; brake unit in accordance with the invention is installed, in ¦ the direction of the arrow Fl opposite to the direction of the arrow F of Fig. 7. A train which travels back along the track in the direction of the arrow Fl is not subjected to any braking action since each wheel 4 first actuates the clearing tappet 6F (Fig. 7) which ensures expansion of the I
, -22-`
.
1093C~43 1/
weighing spring 22. However, the last wheel 4A of the train produces action on the weighing tappet 6A and would thus leave the weighing spring 22 in the compressed state. The additional tappet 6G (shown in Fig. 12) has the effect of removing this disadvantage and of preparing precise adaptation of the track brake to the weight of a fresh wheel 4 to be braked in the direction of normal travel corresponding to the ~row F.
It is readily apparent that constructional arrange-ments are made to ensure that the overall length of all thetappets 6A to 6G which are disposed along the braking rail 5D
(as shown in Fig. 12) does not exceed the limitPd length 5L
as already defined in connection with Figs. 2 and 7. The length SL must be smaller than the distance between the wheels 4 of one bogie (not shown) of the frelght car to be braked.
This distance or wheel spacing is equal to 1.80 meter, for example.
In yet another alternative embodiment of the track brake in accordance with the invention, it is possible to dispense with the clearing tappet 6F (shown in Fig. 7) or the clearing tappets 6F and 6G (Fig. 12) as well as the asso-ciated hydraulic jacks 7F, 7G by means of an automatic time-controlled clearing circuit combined with the brake-applica-tion regulator such as the regulator 21 (shown in Figs. 7 and 8) or the regulator 41 (shown in Fig. 9). The afore-mentioned automatic clearing circuit is provlded by way of example with a calibrated leakage throat which permits within a pre-established time interval a discharge of fluid for ensuring application of the throttling piston 22A, 42 either directly (as shown in Figs. 7 and 8) or by means of the pilot piston 44 (as shown in Fig. 9).
' ~0!~3043 In the embodiment shown in Fig. 13 which corre-sponds to the case of the controlled regulator 41, the calibrated throat 50 is preferably adjustable and disposed li in a discharge pipe 50A which is connected at 50B to the weig-hing pipe 7Al between the check valve 25 and the constricted orifice or throat SO for putting the pilot piston 44 under pressure within the regulator 41.
~ As long as a discharge pressure of the weighing cylinder 7A is exerted, the low rate of flow of the leakag~
orifice 50 is insufficient to modify the compression of the opposing weighing spring 45 to any appreciable extent,thus deining the bearing pressure of the controlled throttling piston 42 as has been noted with reference to Fig. 9. On the other hand, as soon as the discharge pressure ls no longer exerted wlthln the weighlng plpe 7Al, the rate o flow through the constricted leakage orifice or throat 50 produces action so as to begin to reduce the compression of the opposing weighing spring 45.
In practice, the value of the caliber of the leakage throat 50 is chosen so as to ensure expansion of the opposing spring 45 from a value of compression corresponding to the maximum permissible weight in the case of a last car wheel, namely 10 (metric) tons for example, and at least down to a low value of compression correspondlng to the minimum weight which is possible for the first wheel of another car, namely 2 tons, for example. It is assumed that the second ` car immediately follows the first car, which represents for example a distance of only 2.44 meters between the wheels ` . .
considered. It is also assumed that the two cars travel at the maximum speed contemplated on the shunting track, I namely 1.50 m/sec, for example.
: - .
10~ 3 Taking into account the values indicated in the foregoing, it is possible to calculate the minimum time interval in which expansion of the opposing spring 45 should be capable o~ taking place and consequently to adjust the callber of the leakage throat 50. The time-controlled clearing circuit system also makes it possible to avoid the dead times related to the operation of the clearing system controlled by the exit tappet 6F which was described with reference to Fig. 7.
As a preferable feature shown in Fig. 13, the calibrated-leakage automatic clearing circuit associated with the regulator 41 further comprises an auxiliary pipe 50D
for putting the weighing circuit under pressure. The auxiliary pipe 50D connects the point 50B of the weighing pipe 7Al to the brake pipe 23 through a check valve 50E. In this manner, each pressure pulse transmitted to the brake pipe 23 by one of the successive braking tappets 7B to 7D
~Fig. 7) has the effect of compensating for the leakage produced by the throat 50. Substantially equivalent useful cross-sectional areas are chosen for the weighing cylinder 6A
and the brake cylinders 7B to 7E in order to return substan-tia}ly to the initial value of the weighing pressure of the ,~ ~ cylinder 7A at each operation of the brake cylinders 7B to ,~ 7E.
Thus the brake cylinders each come into action in turn after the weighing cylinder 7A in order to reproduce the braking pressure whlch has already been delivered by this ; ~ latter to the weighing pilot piston 44. 3y virtue of this complement æy function of the brake cylinders, it is possible to give a relatively large caliber to the leakage throat 50. This advantage is important in order to prevent 10~3043 any danger of irregular operation of the automatic clearing system since a throat of excessively small caliber is liable to be obstructed by impurities in suspension in the fluid~
As can readily be understood, an automatic clearing system which is similar to that of Fig. 13 can be associated with the direct-action regulator 21 of Figs. 7 and 8. In this case, the leakage pipe tnot shown) has an adjustable calibrated throat which is similar to the throat 50 and is located (as shown in Fig. 7) between the inlet of the weighing pipe 7Al within the regulator 21 and the reservoir pipe 27.
A number of other alternative embodiments of the track brake in accordance with the invention can also be contemplated. By way of example, it is clearly possible to form a modular braking unit comprising two braking rail sections ~not shown) which are placed side by side and are each similar to the braking rail section 5 of Fig. 2. An arrangement of this type will be adopted in particular for the purpose of reducing the length 5L of each track brake since the brake action is then doubled for the same length of brake unit.
Similarly, it is apparent that the track brake can ` comprise any number of-brake-application members such as the members associated with the cylinders 7B to 7E of Fig. 2.
~ The track brake can thus be constituted, for example, by six ;i 25 or eight brake-application members which make it possible to ~' obtain enhanced brake action in the case of members having the same power as those of Fig. 2. At the cost of an increase in length of the track brake 1, it will also be possible in this manner to reduce the energy absorbed by each member and to attenuate corresponding impacts or again to reduce the number of track brakes 1 to be installed in respect of a 1, : .
I
1093~43 given length of the shunting track. It is thus possible to achieve a most satisfactory compromise between the contradictory requirements of efficiency and endurance of the brake units and the desire to keep the cost price as low as possible in all automatic braking installations to be provided on the multiple tracks of a classification yard.
In Fig. 2, there is shown by way of example one embodiment of the track brake in accordance with the inven-tion which is mounted beforehand on special crossties 3A on which there have been fixed the bed-plate 18 together with the braking rail section 5D plus the two check-rails 5E. In order to position the complete track brake unit of Fig. 2, all the screw-spikes (not shown) are removed from the stand æd crossties of the track in that portion which is intended for the track brake 1. ~he two ordinary rails 2 are liftad in order to withdraw the standard crossties. One of the rails 2 is cut to the length which is necessary for mounting the braking rail section 5. The special crossties 3A of the track brake can then be introduced in the flat positlon beneath the intact rail 2, the rails 2 are lowered in order to fix the intact rail 2 on the crossties 3A and - the two end portions SA, 5B of the braking rail section are ~ ~ joined to the cut rail 2.
.
It is of course also possible to avoid part of the operations mentioned above if this is permitted by the strength of the ordinary crossties 3 of the shunting track. It is only necessary in this case to remove the screw-spikes from the ordinary rail 2 to be cut in order to place the braking rail section 5 in position. The bed-plate 18 is then placed on the ordinary crossties 3 of the shunting track ; after this operation, the two check-rails 5E
' .~
.
~093043 are also laid on the crossties, and the braking rail section 5 is joined to the cui rails 2.
The choice between the two modes of positioning of the track brake which may or may not be mounted beforehand on special crossties will depend in particular on the strength of the standard crossties of the classification track to be equipped.
In the different embodiments which have been described thus far, one of the important advantages of the track brake in accordance with the invention lies in the existence of means for clearing the weighing operation so as to permit reversal of at least one car along the track in the direction opposite to the normal direction of braking, without thereby producing any brake application and without any attendant danger of immediate or subsequent incidents.
As has already been noted, the above-mentioned clearing means are of the direct-control type in the case of the clearing tappets 6F, 6G (as shown in Figure 12) or of the automatic time-controlled operation type associated with the calibrated throat 50 (shown in Figure 13). Releasing of the opposing weighing spring 45 or 22 which is effected by means of these clearing means (Figures 9 to 13) makes it possible for a car to travel along the track in the direction opposite to the direction of normal braking without any brake application and without any ` troublescme occurrences.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A railway track brake for limiting the speed of rolling motion of a freight car rolling along an inclined shunting track laid on crossties, the track brake being provided with retard-ing means to be installed in use along one rail of the track in order to co-act successively with each wheel on the corres-ponding side of the freight car, and a number of braking tappets each cooperating with a braking hydraulic cylinder which is caused to operate by throttling of a fluid, said brake cylinders being connected to a regulator for controlling the flow of the throttled fluid by means of a throttling piston, said throttling piston being controlled by a weighing hydraulic cylinder provided with a piston connected to a weighing tappet, characterized in that means is provided for detecting the freight-car speed, said detecting means comprising a flow-threshold closing means connected to by-pass the regulator in the discharge circuit of the brake cylinders, the closing means aforesaid being adapted to remain open in order to prevent throttling of the fluid below a predetermined value of flow of the fluid corresponding to a predetermined value of the freight-car speed, the flow-threshold closing means being actuated above said predetermined value of fluid flow in order to ensure throttling of said fluid flow by said regulator.
2. A track brake in accordance with claim 1, wherein said flow-threshold closing means comprises a flow-threshold valve.
3. A track brake in accordance with claim 1, characterized in that the throttling piston of the regulator is controlled in dependence on a weighing pilot piston which is actuated by the weighing tappet to compress an opposing weighing spring in order to determine the value of a leakage pressure of a bearing chamber of the throttling piston, said chamber being connected to the discharge circuit of the brake cylinders.
4. A track brake in accordance with claim 3, characterized in that said flow-threshold closing means comprises a slide-valve actuated in response to the fluid pressure in the discharge circuit of the brake cylinders upstream said regulator.
5. A track brake in accordance with claim 3, characterized in that said flow threshold closing means comprises a slide-valve actuated in response to the fluid pressure in the discharge circuit of the brake cylinders downstream said regulator.
6. A track brake in accordance with any one of claims 3 to 5 comprising a clearing device for producing expansion of a spring opposed to the said throttling piston of said regulator, characterized in that the clearing device of the regulator is controlled by means of a clearing hydraulic cylinder fitted with a piston and with a piston-rod cooperating with a clearing tappet placed after the last braking tappet in the aforesaid direction of travel of the wheel to be braked.
7. A track brake in accordance with claim 3 comprising a brake application regulator which comprises a time-controlled clearing circuit having a calibrated leakage throat which permits discharge of the fluid pressure applied to the throttling piston during a predetermined time interval.
8. A track brake in accordance with claim 7, characterized in that the discharge aforesaid produces expansion of said opposing spring from a value of compression corresponding to the maximum weight permitted in respect of the last wheel of one freight-car to a low value of compression corresponding to the minimum possible weight in respect of the first wheel of another car which immediately follows the first car, the maximum travelling speed of the freight cars aforesaid being the maximum speed adopted in the marshalling yard, the aforesaid expansion of the said opposing spring being intended to take place within the time interval corresponding to the distance between the last wheel of the first car and the first wheel of a following car.
9. A track brake in accordance with claim 7 or claim 8, characterized in that the time-controlled clearing circuit with a calibrated leakage throat is connected to the discharge cir-cuit of at least part of the brake cylinders in order to re-produce within the clearing circuit the initial pressure of the weighing cylinder at the time of passage of the wheel to be braked on each of the corresponding braking tappets.
10. A track brake in accordance with claim 7 or claim 8 comprising reversal means whereby a car is permitted to travel back along the track in the direction opposite to the direction of normal braking without any brake application and without any danger of incidents, characterized in that the reversal means comprise a complementary clearing device for causing expansion of the opposing spring compressed by the weighing tappet after the car aforesaid has passed in the opposite direction.
11. A track brake in accordance with claim 7 or claim 8 comprising reversal means whereby a car is permitted to travel back along the track in the direction opposite to the direction of normal braking without any brake application and without any danger of incidents, characterized in that the reversal means comprise a complementary clearing device for causing expansion of the opposing spring compressed by the weighing tappet after the car aforesaid has passed in the opposite direction, wherein the clearing tappets and clearing hydraulic cylinders are respectively interchangeable with the braking tappets and with the braking hydraulic cylinders.
12. A track brake in accordance with claim 7 or claim 8 comprising reversal means whereby a car is permitted to travel back along the track in the direction opposite to the direction of normal braking without any brake application and without any danger of incidents, characterized in that the reversal means comprise a complementary clearing device for causing expansion of the opposing spring compressed by the weighing tappet after the car aforesaid has passed in the opposite direction, wherein the clearing tappets and clearing hydraulic cylinders are respectively interchangeable with the weighing tappet and with the weighing hydraulic cylinder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA348,529A CA1093043A (en) | 1976-12-16 | 1980-03-26 | Track brake for railways |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7637900A FR2374196A1 (en) | 1976-12-16 | 1976-12-16 | Rail brake for shunting yard - has motion transfer mechanism working between brake plungers and rods of hydraulic pistons acted on by return springs |
| FR7637900 | 1976-12-16 | ||
| FR7734629 | 1977-11-17 | ||
| FR7734629A FR2409180A2 (en) | 1977-11-17 | 1977-11-17 | Rail brake for shunting yard - has motion transfer mechanism working between brake plungers and rods of hydraulic pistons acted on by return springs |
| CA292,484A CA1089827A (en) | 1976-12-16 | 1977-12-06 | Track brake for railways |
| CA348,529A CA1093043A (en) | 1976-12-16 | 1980-03-26 | Track brake for railways |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093043A true CA1093043A (en) | 1981-01-06 |
Family
ID=27426042
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA348,529A Expired CA1093043A (en) | 1976-12-16 | 1980-03-26 | Track brake for railways |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1093043A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107914733A (en) * | 2017-11-11 | 2018-04-17 | 华强方特（芜湖）文化科技有限公司 | A kind of universal hinge product of railcar cuts the processing maintenance unit of knurl |
-
1980
- 1980-03-26 CA CA348,529A patent/CA1093043A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107914733A (en) * | 2017-11-11 | 2018-04-17 | 华强方特（芜湖）文化科技有限公司 | A kind of universal hinge product of railcar cuts the processing maintenance unit of knurl |
| CN107914733B (en) * | 2017-11-11 | 2024-05-10 | 华强方特（芜湖）文化科技有限公司 | Treatment and maintenance method for universal hinged accumulated and cut nubs of railway vehicle |
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