US2293071A - Multiple ram hydraulic jack - Google Patents

Description

Aug. 18, I942 o. MORGENSEN, JR

MULTIPLE RAM HYDRAULIC JACK Filed Aug. 3, 1940 4 Sheets-Sheet l vwm am t PM w, N m E. s. 7 PM. 0 M

O. MORGENSEN, JR

MULTIPLE RAM HYDRAULIC JACK Aug; 1 8, 1 942 4 Sheets-Sheet 2' Filed Aug. 3, 1940 I42 42 la 40 32 47- TOMA/5Y5 Aug. 18, 1942- o. MORGENSEN, JR

' MULTIPLE RAM HYDRAULIC JACK 4 Shets-Sheet 3 Filed Aug. 6, 1940 fi rm M m 4 Aug. 18, 1942.

o; MORGENSEN, JR 2,293,071 MULTIPLE RAM HYDRAULIC JACK I Filed Aug. 3, 1940 '4 Sheets-Shag: 4

FIG. 8.

/AIVENTOR 07- 7'0 MORGE/VSEM we.

Arrawvs rs Patented Aug. 18, 1942 MULTIPLE mu mm'me .mcx Otto Morgensen, Jr., Dayton, Ohio Application August a, 1940, Serial No. 35am Claims. (01.6042) I (oi-antes mice!- the m of M s, amended April :0, me; an o. G.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to hydraulic jacks and more particularly t jacks of this type having multiple rams for high lift use as in connection with aircraft maintenance.

In hydraulic jacks, it is necessary that provision be made for controlling the maximum fluid pressure as otherwise continued pumping of fluid to the jack would subjectthe Jack to structed,

internal pressures far in excess of the stresses for which the jack structure was designed with resultant destruction of the jack. Also even if the pressures did not reach destructive magnitude, the continued pumping of fluid to create pressures in excessof that required to support the load is inemcient and enervating of personnel.

This problem has presented no dimculty for covering by the ram in the extended position of a port to a conduit connecting the cylinder to the supply chamber, thereby relieving againstv further increase in pressure. Multiple r'am jacks do not readily lend themselvesto such a simple solution. Prior to applicant's invention, resort was generally had to one of the following two solutions: (1) The provision of a pressure relief valye in thehydraulic line from the pump to the cylinders in which the rams were disposed. (2) The limiting of the quantity of fluid available to an'amount not in excess of the volume of the cylinders and conduits when the rams are in the fully extended position;

- single ram Jacks, as provision is made for the un- However, these solutions have not been adequate in that if the relief valve were used, it was necessary to load'the valve for a maximum pressure corresponding to the maximum load for which the jack is designed. Because of this inherent limitation, it is obvious that whenever the jacks are used with loads lesser. than the maximum load for which it is designed, it is still possible and likely that the operator of the jack would consume unnecessary energy in pumping fluid into the jack under a greater pressure than that necessary to support the load since it would not be obvious when the extended position is reached. As a corollary of this defect, it will be obvious that if all the internal parts are subject to the maximum pressure for which thefliack is designed, without reference to theload being liftto provide a as to be efl'ective to unless the relief valve mechanism were so conat additional cost and complication, so as to provide a return conduit chamber. Whether or not the relief valve were provided with a ,return conduit to the supply chamber, it will be appreciated that if the-jack were subjected to the maximum load for which it isdesigned and were supporting this load in a static condition, then, ifjan additional load were applied as would easily occur when used with aircraft as when the wind or additional loading might cause the center of gravityof the plane to shift to aposition more closely to the jack, then fluid would be exhausted from the cylinders through the relief valve with each impulse of excessive load and the rams would settle corre- I spondlngly as the fluid is discharged.

- On the other hand,'the second solution heretoinders. Likewise, if the liquid in the supply chamher were to become depleted for any reason to such an extent that-there was an insuflicient quantity to fully fill all the cylinders, air would then be pumpedin the jack even before the fully extended position has been reached. The presence of 'air under compression in the cylinders containing the rams is objectionable for the reason that it produces a resiliency of "bounding action of the rams, tending to make the position of the supported load unstable. Air must be revmoved before satisfactory operation can be obtained.

Therefore, it is the purposeof my invention novel means for limiting the hydraulic pressure to which the Jack can be subjected in the fully extended position to an amount not in excess of the load. To do this, I have provided a buoyant operated check valve which is used in connection with the supply chamber so preventthe return of liquid to the supply chamber as long as it has liquid therein, but in'contrast with the usual spring ed, the abutment restraining the piston of the loaded or gravity actuated check valve, my novel valve does not prevent exhaust of air from the fluid would be lost through the relief valve whenever excessive pressures are applied to the fluid supply comprise a ground pump through the valve when the supply chamber is empty. with the use of my novel check valve, the disadvantages pointed out above are overcome.

It is a further object of my invention to provide a novel means for automatically adiusting to i the right amount, the quantity of fluid required by the Jack.

It is still another object of my invention to provide as an integral part of such a jack, retractable casters which are urged into operative position for the jack with a force suflicient to support the jack per se, but which are retractable under 'slightly greater load so as to enable substantially all the lift load imposed upon the jack to be taken by the base of the jack.

It is yetanother object of this invention to provide means for preventing the transmission of load through the piston to the jack structure in the maximum extended position of the jack, thereby permitting a reduction in weight of the materials used in its construction which would otherwise be required. This object is accomplished by my novel design in that the quantity of fluid that can be supplied to the' cylinders is limited and therefore the rams cannot be extended beyond the position corresponding to the total liquid supply. Consequently, the retaining abutment for the smallest inner ram need not be made as strong as the rest of the parts, thereby resulting in the saving of precious weight. It will be obvious, however, that the upper end of the smallest cylinder should be-constructed to act as a limiting means to prevent disassembly of the ram from the cylinder. These jacks being primarily designed for aircraft use, must often be transported in airplanes, and in fact are preferably carried as servicing equipment of each plane. Hence, the desirability of lightness and a high lift capacity per unit of weight.

Other objects and advantages of my invention will be apparent from the following description and accompanying drawings wherein like reference numerals indicate like parts throughout the several views.

Figure 1 is an elevation view of a jack embodying my invention. A

Figure 2 is a section view taken on the line 2--2 of Figure 1 showing the hydraulic mechanism.

Figure 3 is a section view taken on the line 33 of Figure 2.

Figure 4 is a section view taken on the line 4-4 of Figure 3, showing the'buoyant check valve in open position. I

Figure 5 is a view similar to Figure 4 showing the check valve in closed position.

Figure 6 shows a modification providing a shield for the buoyant operated check valve.

Figure '7 is'a section view taken on the line I-| of Figure 1.

Figures 8 and 9 are schematic drawings showing the operation of the check valve in the jack system.

Referring to the drawings, the jack, illustrated in collapsed position of the rams, will be seen to engaging base I0, base l2 for the hydraulic elements, detachably connected to the base It by means of stud bolts l4, an'external Y sleeve l6 which is secured in the base l2 and forms the outer wall for the liquid supply chamber, and a pump l8 .for providing the hydraulic pressure. Constructed in the base It are 3 housings 20 for receivingv casters 22. The caster housings 20 may be angularly spaced with respectto the center and venient manner, or preferably as the structure arrangement each other in any conas near 120 apart of the jack base It o will permit.

- of piston The hydraulic mechanism is best illustrated in Figures 2 and 3, wherein the sleeve l6 which constitutes the outer wall of the liquid supply chamber 24, is seen to engage in liquid seal fit in a groove or recess 26 in the base 12. provided with screw threads at its lower end engages complementary threads 30 in the base M. This sleeve constitutes the inner wall of the supply chamber and. also serves as the cylinder for receiving piston 32. Piston 32 is formed with a central downward extending portion 34 having a central bore-36 therein and exterior threads 38. A gland nut 40, having a transverse slot M for engagement by a spanner wrench, secures a sealing element", of leather or other suitable material, to the outer face of the piston. Piston 32 is further provided with an upwardly extending skirt portion 44 which has interior threads for receiving the threaded lower end of sleeve 46 which serves as the piston rod or ram for piston 32 and also serves as the cylinder for piston 46 disposed-therein. Similarly to piston 32, piston 48 is provided with a threaded downwardly extending central portion 50. To the lower face 48 is secured a leather sealing element 52 by means of gland nut 54. It should be understood that the downwardly extending portion 50 is constructed with respect to the gland nut 54 so that the gland nut 54 rests on the inner face of piston 32 supporting the portion 50 in spaced relation to piston 32, for a purpose which will be explained hereinafter. piston 48 is also provided with an upwardly extending skirt portion 56 having interior threads for receiving the lower threaded end of the sleeve 68 which serves as the connecting rod or ram for piston 48.

Now proceeding to the top part of Figure 2, it will be seen thatsleeve 28 is threaded at its upper end to engage a collar nut 60 having a recess 82 at itsouter perimeter forming a support for the sleeve l5 and a recess 64 at its inner upper corner for receiving packing gland 66. Before securing nut 60 to sleeve 28, there is first assembled a strong washer-like annular plate 68 which serves as a lower support for the packing gland 66, and as an intermediate abutment for the skirt portion 44 of piston 32 when the piston has been forced to its upper extreme position. The upper end of sleeve nut I0 which has an inner recess 12 for receiving packing gland 14. Just as in connection with nut 60, before assembling nut 10, a second w'asherlike annular plate 15 is first assembled for the purpose of a lower support for packing gland 14. It is desired to note in this connection that cap nut 10 does not need to be constructed as ruggedly or as strong as nut 60, since the hydraulic mechanism is so adjusted, as hereinafter described in the operation, that piston 48 will not transfer any hydraulic load to this cap nut in the extended position of piston 48. This nut and A sleeve 2Bv Similarly to piston 32,

46 is likewise threaded to receive cap turn interlorly threaded lngs made in base I2 and the open ends of the bores are then sealed by plugs 66, I8 and 96 respectively. Disposed in conduit 84 intermediate the pump l8 and the head of piston 32 is a conventional spring loaded check valve 92 for engaging a valve seat 94 to prevent return of -'fluid from the cylinder to the pump or to the supply chamber.

Intermediate conduit 80 and supply chamber 24 is my novel buoyant operated check valve 96.

Referring to Figures 4 and 5. the buoyant check I28. The float is held in fixed relation to ball-,

check H8 by means of bushing I2I having a flanged lower end I22 engaging the lower side of float H9 and having its upper end received in a washer I24 flush with the upper surface of the float. The washer, flange, and wire are then soldered together at I26. Adjustment of the distance between the floatand ball-check is made by resoldering in a different position.

Intermediate the float and the nut H4 is disposed a baffle plate I28 spaced from the base I2 by spacers I30 and secured to the base by studs I32. The baiiie plate has a central aperture I34 for receiving the wire I28. Secured tothe baille are upwardly projecting pin I36 which are adapted to be received in the registering bores of bushings in the float II9 for the float.

A needle valve I48 is provided to enable return of fluid from the cylinders to the supply chamber 24 through conduits I42 and I44 when it is desired to release the load supported by the jack or to return the pistons to a, lower position.

Collar nut 60 has a threaded bore I46 for adjustably receiving threaded tube I48 which thereso as to serve as guide pins by provides a, novel means for adjusting a predetermined liquid level in chamber 24. Tube I48 is fixedly secured by nut I50 and is provided with a cap I52 having an aperture I54 for providing access to the atmosphere. The tube J48 is effective to limit the level of liquid in chamber 24'to the position of its lower end, since the space in said chamber above the lower end of the tube has no vent, and therefore the trapped air prevents the filling of thechamber above this level.

The operation of the jack will ,best be understood with reference to the schematic showing in Figures 8 and 9 in collaboration-with the.

showing in Figure 2. The chamber 24 is filled with liquid to a predetermined level corresponding to the volume of liquid required to substantially fill the conduits and piston cylinders when with a quantity of liquid corresponding to the.

tion in conduit 86 which enables the atmospheric pressure on the liquid in chamber 24 to force the liquid past the ball-check H8 in opposition tothe buoyancy of float II9. Check valve 92 in the conduit 84.prevents,the return of fluid from the cylinder containing piston 32 in response to the suction. Check valve 92 likewise prevents the return of fluid from this cylinder in response to the pressures created in the cylinder by the load. Then, on the force-stroke of pump piston I68, ball-check II8 prevents the return of liquid to supply chamber 24 and check valve 92 yields to permit the displacement of the additional liquid into the cylinder under the head of piston 32. This process will be repeated with continued operation of the pump until the liquid in the sup ply chamber 24 has been exhausted, as shown in Figure 9. at which time the float II9 will no longer urge the ball-check II8 into engagement with the seat II1. Now piston I60 on its suction stroke will take air into conduit 68 and lower the level of liquid in chamber I62, in the schematic drawing. In Figure 3, conduit 60 is shown made relatively large to provide a volume corresponding to that of chamber I62 in the schematic drawing. It is preferred that conduit 88, either itself or in connection with a reserve chamber, should provide a volume greater than the displacement volume of the pump for a purpose described hereinafter. on the force stroke of the pump, ball-check valve II8 being inoperative due to the absence of liquid in chamber 24 permits the exhaust of air from conduit 88 or chamber I62 through bore II6 into chamber 24. It will be appreciated that ill e air being exhaustedthrough bore II6 by the action of the pump will have considerable velocity, and therefore will exert an aerodynamic pressure on float H9. The float being relatively light, will tend to rise under the pressure, urging the ballcheck II8 into seating engagement, and thereby prevent the exhaust of air or fluid through the bore II6. If this'were to occur, the desired ob- 'jective of the float-controlled check valve would be defeated. Therefore, provision is made to defleet the air stream around float I I9 and to avoid an aerodynamic pressure on the float, which is accomplished, as illustrated, by means of baille plate I28 disposed intermediate the float and the bore II6. Not only does the bafile plate prevent the action of an aerodynamic force on float II9, but it also creates a back pressure in the path of the air stream through bore II6 so that there is created a favorable pressure differential on the seating face I64 of ball-check II8 tending to urge ball-check II8 away from the seat by aerostatio pressure. By keeping valve 96 open at all times when chamber 24 is empty. it will be noted that air is thereby prevent d from passing through check valve 92 into the cylinders supporting the pistons.

Additional. means of preventing the aerodynamic forces from closing ball-check II8 when liquid is absent from chamber 24, is shown in der, a second check valve shield I'III enclosing ball-check H8 and having ports I12 in the side walls of said shield spaced so as to direct air being exhausted by the pump onto the convex seating surface I64 of the ballcheck thereby removing any aerodynamic force from the bottom surface I18 of the ball-check and directing the aerodynamic force on the upper surface so as to urge the ball-check away from its seat I". For purpose of assembly, the shield is preferably attached to nut II4-as by soldering or welding I18.

As above pointed out, conduit 80 is made sufflciently large to hold a volume at least equal to the displacement volume of pump I8 so that on the force-stroke of the pump, air only and no liquid will be forced through the bore I I8. This is to prevent a spraying of liquid through this bore which might result in emulsification of the oil being used.

With further reference to the operation of the multiple rams, liquid is first introduced into the cylinder containing piston head 32 through conduit 84. When the piston has raised slightly, liquid also passes through bore 36 into contact with piston head 48. The gland nut 54 secured to piston head 48 has one or more diametrical slots I80 across the-face thereof serving both to provide engagement for a spanner wrench and also to enable the liquid to flow into engagement with the entire head area of piston 48 to provide a sufiicient pressure-area product so that the inner ram will operate under load. Downwardly extending portion 50 of piston 48 being spaced from the inner face of piston 32, cooperates with the slots I80 to accomplish this latter function.

Referring to Figure 7, the caster 22 is seen to .for gauging the quantity of fluid which may be f put into said reservoir so that it will not exceedbe mounted on a shalt I80, slidably received in a bore I92 of housing 20. The caster is urged into engagement with the floor or ground by a spring I94 under a compression force slightly more than suflicient to support the weight of. the jack. Cotter pin I96 prevents displacement of the shaft I90 from its housing when the Jack is picked up oi! the floor or ground. It will thus be seen that if an appreciable load is placed upon the jack that the caster will retract within the housing 20 under the additional load, overcoming the compression force of the pring, and that substantialthe load imposed upon the jack will be taken by the base I0 and not by the casters.

While my invention has been illustrated and described herein and is primarily useful in conly all of nection with multiple ram jacks, it is to be understood that my novel check valve and other novel features are not to be limited to such application or to the specific forms and modiflcations'shown, but embrace such applications, variations and equivalents as are included in the appended claims.

I claim:

1. A hydraulic jackcomprising a hydraulic cylinder, a piston in said cylinder, mechanical stop means associated with said piston and cylinder for delimiting the maximum piston displacement, a liquid supply reservoir having its upper end closed, a vertically disposed flller tube in said closed end, adjustable up or down to delimit the maximum volume of fluid which may be placed in the supply reservoir to a volume which isno greater than the said maximum piston displacement, a pump for transferring liquid from said reservoir to said cylinder, a check valve biased for one-way flow from said pump to said cylinin the bottom of the tank in the pump suction passage, a float in the supply reservoir attached to said second valve urged upwardly by the liquid in said reservoir to resiliently constrain said second check valve for one-way flow from the reservoir to the pump, and gravity-actuated means on said secdnd valve to move said second valve to open two-way flow position when said reservoir is emptied of liquid and said float is thereby rendered ineflective.

2. The structure of claim 1 with a baille plate associated with said second check valve and with said float so positioned that air returning to said reservoir through the opening of said second check valve may not raise said float to close said second check valve.

3. In combination. a pump, a hydraulic fluid motor having a cylinder and an extensible piston therein, a closed reservoir for supplying fluid to said cylinder by means of said pump to extend said piston, means for limiting the extension of said piston in said cylinder, a valve intermediate the reservoir and the pump that is normally operative to prevent return of liquid to said reser- I the volume necessary to extend said piston to said limiting means, said gauging means comprising a tube extending through the top of said closed reservoir downwardly into said reservoir, with means to adjust said tube to vary the distance which it extends downwardly through said top.

4. The combination with a hydraulic jack having a cylinder with a piston movable therein, of mechanical abutments to limit movements of said piston from a maximum retracted to a maximum extended position, thereby delimiting the maximum volume which may be pumped into said cylinder, a liquid supply reservoir, a measuring device associated with said reservoir adapted to so gauge the amount of liquid which may be put into said reservoir as not to exceed said volume which may be pumped into said cylinder, a pump arranged to move said liquid from said reservoir to said cylinde and asuction valve for said pump having a float means which is associated with the liquid in said reservoir to resiliently hold the suction valve closed and gravity means to hold said suction valve open when said liquid is all out of said reservoir and said float means is thereby made ineffective.

5. In'combination, a pump, a'hydraulic fluid motor, a cylinder for said motor, a piston extensible in said cylinder, a closed reservoir for supplying fluid to said cylinder by means of said pump to extend said piston, a valve intermediate the reservoir and the pump that is normally operative to prevent return of liquid to said reservoir but having means for establishing two-way communication between said pump and said reservoir when said reservoir is emptied, and means for gauging the quantity of fluid which may be put into said reservoir so that, when the entire volume is pumped from the reservoir into the cylinder the piston will not be extended thereby beyond a predetermined safe limit, said gauging means comprising av tube extending through the .'top of said,closed reservoir downwardly into said OTTO MORGENSEN, J l.

Images