GB2123901A

GB2123901A - Reciprocating hydraulic equipment

Info

Publication number: GB2123901A
Application number: GB08220291A
Authority: GB
Inventors: George Clarence Hobson
Original assignee: FLOWLINE HYDRAULICS Ltd
Current assignee: FLOWLINE HYDRAULICS Ltd
Priority date: 1982-07-13
Filing date: 1982-07-13
Publication date: 1984-02-08
Also published as: GB2123901B

Abstract

A reciprocating hydraulic machine comprises a valve block (2) with a bore (3) in which slides a push/pull rod (5) having a spool (12) on the end (4) which is provided with two axially spaced detents (13A, 13B) alternately engaged by at least one spring-loaded catch (14) and having a slide valve (17) carried by the push/pull rod (5) and cooperating with two valve ports (24, 25) in the valve block (2) and connected to supply (S) and exhaust (E) respectively. A pressure fluid-operating pump and a reciprocating ram are described. <IMAGE>

Description

SPECIFICATION Reciprocating hydraulic equipment This invention relates to reciprocating hydraulic equipment, such as a pump, an intensifier or a ram, provided with a self-reversing mechanism for its piston.

An example of such equipment is described in U.K. Patent Specification 1 450 538 in which the self-reversing mechanism of a pressure fluidoperated pump comprises control valves actuated at or towards the end of each stroke of the piston by a toggle linkage rocked by a push/pull rod extending from the toggle linkage and passing into a blind bore in the piston, the end of the push/pull rod within the blind bore being provided with lateral projections or an enlargement slidable in the bore, and the open end of the bore being restricted, whereby rocking of the toggle linkage in one direction is caused by contact and movement of the enlargement by the restriction at the open end of the blind bore, and in the other direction rocking of the toggle linkage is caused by contact and movement of the enlargement by the inner end of the blind bore, with the valves disposed intermediate the piston and the toggle linkage in a valve block with a bore in which the push/pull rod sealingly slides, and with rocker arms for operation of the valves by the toggle linkage pivoted on the valve block intermediate the valves and the toggle linkage.

The equipment just described suffers from a number of disadvantages. Firstly, the valves have to be mounted transversely in the valve block and require a large number of seals. Secondly, the toggle linkage and rocker arms require a considerable number of accurately milled parts. And, lastly, although the push/pull rod is accommodated in the piston to avoid having the lost motion between the stroke of the piston and the throw of the toggle linkage adding greatly to the overall length of the equipment, the toggle linkage and rocker arms add appreciably to the bulk of that end of the equipment.

The object of the present invention is to provide reciprocating hydraulic equipment with a selfreversing mechanism avoiding the above disadvantages.

According to the present invention, reciprocating hydraulic equipment has a self-reversing mechanism for its piston comprising a valve block with a bore in which slides one end of a push/pull rod the other end of which extends into a blind bore in the piston and is provided within the blind bore with lateral projections or an enlargement slidable in the blind bore, the open end of the blind bore being restricted, a spool on the end of the push/pull rod within the valve bore and provided with two axially spaced detents, at least one catch in a transverse bore in the valve block and intersecting the valve bore, a spring urging the catch into engagement with one or other of the detents a slide valve carried by the push/pull rod and slidable in the valve bore, a porting groove round the slide valve, and two valve ports in the valve block alternately communicating with the groove in the slide valve when the catch is in engagement with the respective one or other of the detents in the spool, movement of the spool in one direction being caused by contact and movement of the lateral projections or enlargement on the push/pull rod by the restriction at the open end of the blind bore, and in the other direction by contact and movement of the end of the push/pull rod within the blind bore by the inner end of the blind bore. The detents are preferably grooves round the spool, and two spring-loaded catches are preferably provided in axially aligned opposed transverse bores.

Thus all the self-reversing mechanism is contained within the valve block and the piston, with only a simple turned spool and a simple turned slide valve required within the valve bore, and with simple sealed lateral bores for inlets and/or outlets to or from the valve ports in the valve block and simple sealed transverse bores for the catches.

The stroke of the slide valve need not be the same as the stroke of the spool (and the push/pull rod), the slide valve being slidable on the push/pull rod between the spool at one side and a stop on the push/pull rod at the other side, or as controlled by a stop pin projecting into the bore and engaging one or other of the sides of the porting groove.

The invention finds particular application in the mining industry where space is at a premium.

A pressure fluid-operated pump in accordance with the invention (which may serve as a hydraulic intensifier for testing hydraulic mine roof supports) has a differential piston the smaller diameter portion of which extends into a pump body, and has one valve port connected to supply (preferably via a filter and flow control valve) and also communicating by an external tube to a non-return inlet valve of the pump body, an outlet from which is likewise provided with a non-return valve, while the other valve port is connected to exhaust, and the porting groove in the slide valve communicates via clearance between the slide valve and the push/pull rod with the adjacent side of the larger diameter portion of the piston, whereby this is connected alternately by the slide valve to supply and exhaust respectively.

A reciprocating ram in accordance with the invention has the valve ports connected respectively to supply and exhaust, and has a hollow push/pull rod with pairs of cross-bores providing for communication between the side of the piston adjacent to the valve block and one or other of the ports in the valve block as determined by the position of the slide valve, the valve block being provided with a third port axially intermediate the first two ports and communicating by an external tube to the side of the piston remote from the valve block, whereby the respective sides of the piston are alternately connected to supply and exhaust respectively.

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a part-sectional elevation of a pressure fluid-operated pump in accordance with the invention; Figures 2 and 3 are transverse sections on the lines II - II and Ill - Ill respectively of Figure 1; Figure4is mainly a longitudinal section on the line IV - IV of Figure 1; Figure 5 is mainly a longitudinal section through a reciprocating ram in accordance with the invention; and Figure 6 is a fragmentary transverse section on the lineVI-VI of Figure 5.

The pressure fluid-operated pump of Figures 1 to 4 has a cylinder and differential piston unit 1 and a valve block 2 with a bore 3 in which slides one end 4 of a push/pull rod 5 the other end 6 of which extends into a blind bore 7 in the piston 8 and is provided within the blind bore with lateral projections 9 (formed by the ends of a cross-pin) slidable in the blind bore, the open end of the blind bore being restricted by an inward flange 10 of a larger diameter portion 11 of the piston.

A spool 12 on the end 4 of the push/pull rod is provided with two axially spaced detent grooves 13A, 13B round the spool, and two ball catches 14 are disposed in axially aligned opposed transverse bores 15 in the valve block 2 and intersecting the valve bore 3, with springs 16 urging the catches into engagement with one or other of the detent grooves in the spool.

A slide valve 17 is slidable on the push/pull rod 5 between the spool 12 and a stop pin 18 and is also slidable in the bore 3 between a stop pin 19 and a bush 20 retained in a counterbore of the bore 3 by a spring clip 21 in a groove in the counterbore. The slide valve 17 has a porting groove 22, which communicates via holes 23 and clearance between the slide valve and the push/pull rod 5, and also via clearance between the bush 20 and the push/pull rod, with the adjacent side of the larger diameter portion 11 of the piston 8.

Two valve ports 24,25 in the valve block 2 communicate alternately with the groove 22 in the slide valve when the catches 14 are in engagement with the respective detent groove 13A or 13B in the spool, movement of the spool from left to right (changing the catches 14 from the detent groove 13B to the detent groove 13A) being caused by contact and movement of the end 6 of the push/pull rod 5 by the inner end 26 of the blind bore 7 in the piston 8, and in the other direction (changing the catches 14 from groove 13A to groove 13B) by contact and movement of the lateral projections 9 on the inner end of the push/pull rod by the restriction 10 at the open end of the blind bore.

A smaller diameter portion 27 of the differential piston 8 extends into a pump body 28, and the valve port 25 is connected to supply S, via a filter 29 and a flow control valve 30, and also communicates by an external tube 31 to a non-return inlet valve 32 of the pump body, an outlet 33 of which is likewise provided with a non-return valve 34, while the port 24 is connected to exhaust E. A pressure gauge 35 is secured and sealed to a tapping point 36 of the pump body 28 to indicate the pumping pressure.

In the position shown in Figure 4the differential piston 8 is approaching the end of its stroke from left to right, the right hand side of the larger portion 11 being connected to exhaust E via the clearances between the push/pull rod 5 and the bush 21 and the slide valve 17, through the holes 23 to the porting groove 22 and through the port 24, thus allowing pressure fluid from supply S and connected via the filter 29 and flow control valve 30, and through the port 25, tube 31 and non-return valve 32 to the pump body 28 to push on the smaller diameter portion 27 of the differential piston.

The inner end 26 of the blind bore 7 has just made contact with the end 6 of the push/pull rod 5 and is about to push itto the right along with the spool 12, which will result in the catches 14 riding up out of the detent groove 13B and dropping into the detent groove 1 3A, which in turn causes the cross-pin 18 to move the slide valve to the right until stopped by the pin 19, when the porting groove 22 will be in communication with the valve port 25, whereby pressure fluid from supply will pass from the port 25 via the porting groove 22 and holes 23 and through the clearances between the push/pull rod 5 and the slide valve 17 and the bush 21 to the right hand side of the larger diameter portion 11 of the piston 8.

Although pressure fluid is still communicated (also from the port 25) via the tube 31 and inlet non-return valve 32 to the pump body 28, the force on the right hand side of the larger portion 11 of the piston greatly exceeds the force on the end of the smaller portion 27, and so the piston now moves to the left, the non-return valve 32 closes, and the smaller portion of the piston pushes a charge through the non-return valve 34 to the outlet 33.

Towards the end of the stroke of the piston 8 from right to left, the restriction 10 contacts the projections 9 on the push/pull rod 5 and moves it to the left along with the spool 12, which will result in the catches 14 riding up out of the detent groove 13A and dropping back into the detent groove 13B, bringing the mechanism back to the position shown in Figure 4, except that the piston will have only just started its stroke from left to right.

In the reciprocating ram of Figures 5 and 6 like numerals to those in Figures 1 to 4 represent like parts, but the piston 8 is not a differential piston, its smaller end 27 being a projecting end of a piston rod, and the restriction 10 at the open end of the blind bore 7 is a hollow plug screwed into the bore.

The valve ports 24, 25 are connected respectively to exhaust E and supply S, and the push/pull rod 5 is hollow, with pairs of cross-bores 37, 38 providing for communication between the side of the piston adjacent to the valve block and whichever of the ports 24,25 is not in communication with the groove 22 in the slide valve 7, which groove is wide enough to provide communication between one or other of the ports 24, 25 and a third port 39 axially intermediate the first two ports, and a stop pin 40 makes contact with one or other of the sides of the groove 22 to limit its movement in the bore 3, although the stroke of the spool 12 (with the push/pull rod 5) is different. The port 39 communicates by an external tube 41 with the side of the piston remote from the valve block 2, whereby that side of the piston is alternately connected to supply S and exhaust E as the other side (adjacent the valve block) is connected alternately to exhaust E and supply S respectively.

The inner end 6 of the push/pull rod 5 cooperates with the inner end 26 of the blind bore 7 at the end of the return stroke of the piston 8 of the ram (i.e., from left to right) to operate the self-reversing mechanism consisting of the spool 12, catches 14 and slide valve 17 in one direction in similar manner to that described with reference to Figures 1 to 4. This movement is about to start in Figure 5.

Likewise, the projections 9 at the inner end 6 of the push/pull rod 5 cooperate with the restriction 10 at the open end of the bore 7 at the end of the forward stroke of the piston 8 of the ram (i.e., from right to left) to operate the self-reversing mechanism in the opposite direction.

Claims

1. Reciprocating hydraulic equipment having a self-reversing mechanism for its piston comprising a valve block with a bore in which slides one end of a push/pull rod the other end of which extends into a blind bore in the piston and is provided within the blind bore with lateral projections or an enlargement slidable in the blind bore, the open end of the blind bore being restricted, a spool on the end of the push/pull rod within the valve bore and provided with two axially spaced detents, at least one catch in a transverse bore in the valve block and intersecting the valve bore, a spring urging the catch into engagement with one or other of the detents a slide valve carried by the push/pull rod and slidable in the valve bore, porting groove round the slide valve, and two valve ports in the valve block alternatively communicating with the groove in the slide valve when the catch is in engagement with the respective one or other of the detents in the spool, movement ofthe spool in one direction being caused by contact and movement of the lateral projections or enlargement on the push/pull rod by the restriction at the open end of the blind bore, and in the other direction by contact and movement of the inner end of the push/pull rod within the blind bore by the inner end of the blind bore.

2. Equipment as in Claim 1, wherein the detents are grooves round the spool.

3. Equipment as in Claim 2, wherein two springloaded catches are provided in axially aligned opposed transverse bores.

4. Equipment as in any one of the preceding Claims, wherein the slide valve is slidable on the push/pull rod between the spool at one side and a stop on the push/pull rod at the other side.

5. Equipment as in any one of Claims 1 to 4, wherein the slide valve is slidable on the push/pull rod as controlled by a stop pin projecting into the bore and engaging one or other of the sides of the porting groove.

6. A pressure fluid-operating pump as in any one of the preceding Claims having a differential piston the smaller diameter portion of which extends into a pump body, and having one valve port connected to supply (preferably via a filter and flow control valve) and also communicating by an external tube to a non-return inlet valve of the pump body, an outlet from which is likewise provided with a non-return valve, while the other valve port is connected to exhaust, and the porting groove in the slide valve communicates via clearance between the slide valve and the push/pull rod with the adjacent side of the larger diameter portion of the piston, whereby this is connected alternately by the slide valve to supply and exhaust respectively.

7. A reciprocating ram as in any one of Claims 1 to 5 having the valve ports connected respectively to supply and exhaust, and having hollow push/pull rod with pairs of cross-bores providing for communication between the side of the piston adjacent to the valve block as determined by the position of the slide valve, the valve block being provided with a third port axially intermediate the first two ports and communicating by an external tube to the side of the piston remote from the valve block, whereby the respective sides of the piston are alternately connected to supply and exhaust respectively.

8. A pressure fluid-operating pump substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

9. A reciprocating ram substantially as hereinbefore described with reference to Figures 5 and 6 of the accompanying drawings.