US2070935A - Variable ratio jack - Google Patents

Description

w. A. TRAUT VARIABLE RATIO JACK Filedvuarcn 2o, 1935 Feb. is, 1937.

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Feb. 16, 1937. w. A. TRAUT VARIABLE RATIO JACK Filed March 20, 1933 4 Sheets-Sheet 2 /60 [22 Z3 ya @6 6 60. POWER PMANTS.

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Feb. 16, 1937. w. A. TRAUT 2,070,935

VARIABLE RATIO JACA Filed March 20, 1933 I 4 Sheets-Sheet 4 60. PQWER I" ANTS..

Patented Feb. 16, 1937 UNITED STATES bcaitii mea PATENT OFFICE VARIABLE RATIO JACK William A. Traut, Milwaukee, Wis., assignor to Blackhawk Mfg. Co., Milwaukee, Wis., a corporation of Wisconsin Application March 20, 1933, Serial No. 661,767

31 Claims.

The present invention relates to jacks in general, and more particularly to hydraulic jacks. The invention is also applicable to lift apparatus such as are used on motor trucks, hoist trucks, or the like.

It is an object of the present invention to provide a jack ywherein the effective leverage between the handle and the load may be varied so that the effective leverage may be increased with increasing loads and decreased with decreasing loads. By this arrangement the force required to lift exceedingly heavy loads is not excessive, may even be made substantially the same as the force required to lift light loads and, in the case of light loads, the speed with which the load is raised is substantially increased.

It is a further object of the present invention to provide a jack wherein the change in leverage is effected automatically, as the operator manipulates the jack to raise the load.

'Ihe arrangement ris preferably set so that at the full capacity of the jack the force required will be the same as is common in jacks on the market, whereas at'lighter loads the force will remain substantially the same but the speed of lift will be proportionately increased.

It is a further object of the present invention to provide a jack that may be easily adjusted to vary the leverage to suit the requirements of the particular user. This determines the setting from which the automatic variation in leverage will take place.

It is a further object of the present invention to provide an improved base for lift jacks of the type used for jacking automobiles, to permit the jack to rock as the. angularity of the axle changes, and thus to maintain the center line of the lifting member of the jack at right angles to thek automobile axle.

It is a further object of the present invention to provide a jack which will be economical and sturdy in construction and emcient in operation.

The attainment of the above and further objects of the present invention will be apparent from the following specification, taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figure 1 is a top view of the jack mechanism, taken along the line I I of Figure 2;

Figure 2 is a longitudinal section taken along the line 2 2 of Figure 1;

Figure 3 is a sectional view taken substantially along the line 3 3 of Figure 2;

Figure `4 is a sectional view taken along the line 4 4 of Figure 2; l

Figure 5 is a sectional view taken along the line 5 5 of Figure 1;

Figure 6 is a sectional View taken along the line 6 6 of Figure 1;

Figure 7 is a, sectional view taken along the line I I of Figure 6;

Figure 8 is a sectional view taken along the line 8 8 of Figure 6;

Figure 9 is a view similar to Figure 2 and illustrating the movement o f the oating fulcrum when the jack is lifting a heavy load; v

Figure 10 illustrates the tilting action of my jack when provided with a rocking base;

Figure 11 is a fragmentary iront view of the jack of Figure 10; and

Figurev 12 is a fragmentary side view of the jack of Figure 10.

Referring now more particularly to the drawings, the jack comprises a casing I which constitutes an oil reservoir and within which the various operative parts are mounted. This includes a hydraulic cylinder 2 having a plunger or ram 3 therein and actuated by oil which is forced into the cylinder by a reciprocating pump 4 which has a pump plunger 5 that is connected by means of a variable linkwork to an actuator 6 comprising a shaft that is adapted to be oscillated in a manner to be more fully set forth as this description proceeds. The connection between the pump plunger 5 and the actuator 6 ls such that the pump stroke decreases as the load on the pump increases, despite a full movement of the actuator 6 and of the jack handle which operates the actuator. The pump 4 is provided with a port I0 that extends communication from the bottom of the pump cylinder to a valve chamber II. The valve chamber I I is provided with a suction valve I2 and a check valve I3, both/of which are ordinary ball valves. The suction valve controls communication between the valve chamber II and a port I4 which opens into another port I5 which, in turn, communicates with a chamber I6 through a filtering screen II. The chamber I6 opens directly into the casing I, which comprises, as previously stated, the oil reservoir. The screen II is held in place by a screw I 8 which extends into, and closes, a threaded opening at the bottom of the casing I.

The check valve I3 controls communication between the valve chamber I I and a port hole 20, which constitutes the delivery port of the pump. The port hole extends diagonally downward, as may be seen in Figure 7, to a cross port hole 2l that extends diagonally between the hydraulic cylinder 2 and a control chamber 22. The pressure Within the control chamber will therefore always be the same as the pressure in the hydraulic cylinder 2. The control chamber is sealed against the leakage of oil therefrom into the reservoir comprising the casing I, by a packing 23 which bears against a control plunger 24 and through which extends a control rod 25.

It is to be noted that the valve chamber II and the port I4 are formed in a block 26 that is integral with the casing I, comprising merely a rib-like projection from the wall of the casing I. This constitutes a compact and sturdy construction that is not likely to become broken.

Oil from the delivery port 20 enters the hydraulic cylinder 2 at the bottom thereof and. raises the plunger 3, which constitutes a ram. The upper end of the plunger extends through a. cap 30 which is threaded on the end of the cylinder 2 and provided with an opening 3| to permit communication between the oil reservoir of the casing `I and the space between the inside wall of the cylinder and the ram or plunger. 'Ihe cap 30 extends through a cover 32 that is centered on the casing I by pins in lugs 33 formed in the cover and cooperating with pin holes in similar lugs on the inside of the casing I. The cover 32 forms a liquid-tight seal with the casing I, to complete the casing, and is held in place by the cap 30 threaded on the cylinder 2. The cap 30 forms a liquid-tight seal with the cover 32. The top of the ram or plunger 3 extends through the cap 30, being suitably sealed against the escape of oil, as by means of a packing 34 and a plunger gland nut 35.

An internally threaded sleeve or cylinder 36 is suitably secured within the top end of the ram 3, and rests on a shoulder 31 in the ram. The sleeve or cylinder 36 is nonrotatable within the plunger 3. A work-performing member 40, in the form of a saddle, has a screw 4I formed at the bottom thereof and threaded into the sleeve or cylinder 36. By turning the member 40, the screw 4I thereof will advance it with respect to the ram or plunger 3, to raise the saddle 40 with respect to the base of the jack. This provides a hand-screw extension for the jack.

When the plunger is operated it forces oil into the cylinder 2, in the manner previously set forth, to raise the ram or plunger 3. To lower the load and the ram 3 there is provided a release valve 43 that controls communication between an outlet port 44 and the oil reservoir. The valve 43 comprises a rod that is controlled from the outside of the casing by a suitable handcontrolled screw 45 that threads into a release valve gland nut 46. A suitable packing 41 is provided for the valve rod 43. 1f the screw 45 is turned outwardly a small amount the valve 43 will be pushed open by the internal pressure within the cylinder 2. This permits the escape of fluid from the cylinder, under the weight of the ram 3 and such load as may be carried thereby.

An explanation will now be given of the manner of operating the pump 4. The actuator 6 comprises a shaft, suitably journaled, and extending outside of the housing. A suitable seal is provided for preventing the escape of fluid at the point where the actuator 6 extends outside of the housing. This seal comprises a packing 50 and an actuator packing gland nut 5I. A handle 52 is keyed to a squared-off portion of the shaft 6. It to be noted that only one end of the shaft extends into the reservoir POIGOn of the casing I. The other end of this shaft extends into a suitable bearing 53 held in a boss 54 formed at the bottom of the casing I, but not communicating with the interior thereof, as clearly illustrated in Figure A4. A portion of the shaft or actuator 6 that is within the casing has its sides slabbed off to provide flat seating surfaces for a. square collar 55 which carries a crank arm 56. An actuating push rod 51 is slotted at its lower end and provided with a pin 58 extending through the slot. The end of the crank 56 extends into the slot in the actuating push rod and bears against the pin 58which pin is, preferably, slabbed off at the point of engagement with the crank 56. The crank 56 comprises a lifting lever for the actuating push rod. The actuating push rod is guided in a collar 59 formed on the inner wall of the casing I. The actuating push rod has reciprocating motion within the collar, but is held against movement out of a vertical position. At its upper end the actuating push rod 51 is connected to a floating lever or beam 60 by means of a pin 60'. 'Ihe floating lever or beam 60 is pivoted to a link 6I by means of a pin 62, the link being, in turn, pivoted to a control lever 63 by means of a pin 64. It is to be noted that the pin 64 does not extend through the lever 60, but it does extend through the link 6I. At its opposite end the floating beam or lever 60 is connected to the pump plunger 5 by a pin and slot connection comprising a pin 65 and a slot 66. For this purpose the upper end of the plunger 5 is slabbed off to provide flat surfaces engaging the lever 60.

The control lever 63 is pivoted about a pin 10 that is threaded through the exterior wall of the casing I and is held, at its inner end, by a projection 1I extending upwardly from the bottom of the casing. The lever 63 is provided with a surface 13 that bears on a locking cam 14 pivoted on a pin 15 extending through the casing wall.

insofar as it is permitted to do so by the locking cam 14. At its lower end the control lever is provided with a stem 16 against which the control plunger 24 bears. The control rod 25 extends past the stem 16 and is connected to the cam 14 by a pin and slot connection comprising a pin 11 and a slot 18.

Ihe end of the control rod 25 that is within the control chamber 22 is threaded and'has a flanged sleeve threaded thereon. The flange of the sleeve comprises a seat for a control spring 8I thatv extends from the flange to the packing f 23 and is held under compression. The flanged sleeve 80 bears against a nut 82 which closes the end of the control chamber 22 and which, when tightened, acts to preload the spring BI, thereby determining the action of the control lever 63, as will be more fully set forth as this description proceeds. It is to be noted that the flange on the sleeve 80 does not form a liquid-tight'seal with the nut 82. Free fluid communication is permitted between the inner left-hand end of the sleeve 80 and the rest rof the chamber 22. The control rod 25 therefore comprises a piston which is biased by the spring 8l to the position shown in Figure 2, and which is urged to the right from the position shown in Figure 2 by the pressure within the control chamber 22.

An explanation will now be given of the mode of operation of the jack. Assume that the jack is lifting a light load. A removable extension handle is secured to the handle 52, in a well 50. POWER Pl ANTS.

known manner and, through this extension handie, the handle 52 is reciprocated to reciprocate the actuator 6. Downward movement of the handle 52 causes the crank arm 56 to raise the actuating push rod 51 which, in turn, causes the beam 60 to turn about the pin 62 andthe pin 64. At this time the pin 64 is held stationary by the control lever 63, which is locked by the locking cam 14. The beam or floating lever 6I) turns counter-clockwise about the pin 64, carrying with it links 6I which rotate slightly on pin 62 compensating between the straight vertical movement of push rod 51 and circular movement of beam 60 due to the pivot about pin 64. The net effect of the upward movement .of the actuating push rod 51 is to lower the pump plunger 5. This forces oil from the pump cylinder through the check valve I3, into the hydraulic cylinder 2, to raise the ram or plunger 3, thereby raising the saddle 40. At this time pressure is also applied to the control chamber 22, the pressure within said chamber being the same as the pressure within the hydraulic cylinder 2. If the load on the jack is comparatively small, as is assumed at the present, this pressure does not rise to a value sufficient to overcome the action of the spring 8|. Therefore, the control rod remains stationary, in the position shown in Figure 2. The locking cam 14 thus remains in the position shown, thereby maintaining the control lever 63 locked in position and maintaining the pivot 64 stationary. Elevation of the handle 52 from its lowermost position causes the crank arm 56 to move downwardly. This permits a downward movement of the actuating push rod 51, which movement takes place under the action of a follow-up spring 84 within the pump cylinder. During the upward movement of the pump plunger the check valve I3 is maintained closed and the suction valve I2 is opened, thereby drawing oil from the casing I into the pump cylinder. A continued reoiprocation of the handle 52 causes continued operation of the pump in the manner above set forth, to continue the raising of the ram to raise the load. The stroke of the pump plunger 5 during such operation is determined by the stroke of the handle 52. The lowering of the load may be brought about by opening the release valve 43, as previously set forth.

An explanation will now be given of the mode of operation of the jack when lifting heavy loads. As the handle 52 is forced downward to force the pump plunger 5 downward, pressure is applied to the control chamber 22 and to the hydraulic cylinder 2. The ram cannot rise until the pressure within the cylinder 2 is suiiicient to overcome the load on the ram. As the pressure in the cylinder 2 rises there isa corresponding rise in pressure within the control chamber 22. When this pressure exceeds the pressure for which the control spring 8| was set, the control rod 25 is pushed slowly to the right, as seen in Figure 2. This causes a counter-clockwise rotation of the cam 14 to permit a controlled counter-clockwise rotation of the control lever 63, always under the control of the locking cam 14. Immediately upon the movement of the cam 14 to such an extent as to permit movement of the control lever 63, the control plunger 24 within the control chamber 22, together with the pack- 13 of said lever always in engagement with the cam 14.r lThis produces a small counter-clockwise rotation of the control lever 63. As the pressure within the control chamber 22 continues to rise, there is a continued rotation of the locking cam 14 and a continued movement of the plunger 24, thereby resulting in a continued rotation of the control lever 63. This continues until equilibrium is reached between the pressure within the control chamber and the compression of 10 the spring 8I, or until the limit of motion is reached. This limit of motion is reached when the cam 14 is in the position illustrated in Figure 9. Itis to be noted that the control rod 25 moves a greater distance than the control plunger 24. 15 Therefore, the compression of the control spring 8I is continuously increased as the cam 14 is rotated counter-clockwise. Under medium loads equilibrium will be reached between the pressure in the control chamber 22 and the compression 20 of the control spring 8| before the cam 14 reaches its extreme position, the precise point at which equilibrium is reached being determined by the load on the ram, for any particular setting of the apparatus. As the control lever 63 rotates about 25 the pin 10, the pin 64 is shifted to shift the effective leverage between the actuating push rod 51 and the pump plunger 5. As may be seen from Figure 9, the stroke of the plunger 5, for a fixed stroke of the handle 52, decreases as the pin 64 is shifted to the left as seen in Figure 2. This means that for a fixed rate of movement of the handle 52 there is a variable rate o-f movement of the plunger 5, depending upon the position of the pin 64'. The variable rate of move- 5 ment of the plunger 5 causes a variation in the rate at which oil is forced into the cylinder 2. This variation is determined by the position of the pin 64, which is controlled by the pressure in the control chamber 22, which is in turn controlled by the load on the ram. The greater the load the greater will be the requisite pressure within the hydraulic cylinder 2, and the further will the` pin 64 be shifted leftward, and the greater will be the reduction in the rate of oil flow to the cylinder 2 for a fixed stroke of the handle 52.

The apparatus is so adjusted that for full capacity loads of the jack the pin 64 will be shifted to such a position that the rate of rise of the ram, and the corresponding force that must be applied to the handle 52, will besubstantially the same as in hydraulic rams now constructed. Therefore, at lower loads, the same rate of movement of the handle 52 will cause a faster move- 55 ment of the ram. The force that must be applied to the handle 52 at lower loads is substanti ally the same as the force that must be applied vat higher loads. but the rate of movement of the ram at lower loads is greater than at higher loads. This permits a faster operation at lower lo-ads than was heretofore possible. In Figure 2, I have illustrated the extreme positions of the floating lever or beam 60 when the ram is raising a comparatively light load. The movement of the pin 65 indicates the stroke of the pump plunger 5, whereas the`movement of the pin 6IJ' indicates the movement of the actuating push rod 51, which latter movement is always proportionate to the stroke of the handle. In Figure 9, I have shown the relative positions of the various parts duringv heavy lifting. Assuming the same length of stroke of the handle 52, the pin 60' moves between the same extreme limits in Figure 9 as in Figure 2. However, the pin 65 has 75 a. much shorter movement, indicating a much shorter stroke. I

From the above description it is apparent that the pin 64 comprises a oating pivot for the link 6|, the position of this pivot being determined automatically by the load being raised. This arrangement constitutes a floating power transmission mechanism between the actuating push rod 51 and the pump plunger. A variable ratio jack embodying a floating power transmision arrangement is, I believe, broadly new.

The anged sleeve 8|l'and the member 82A constitute means for adjusting the movement of the control lever 63. Adjustment of the flanged sleeve 80 on the control rod 25 produces not only an adjustment of the position of the cam 14, but also a variation of the compression of the control spring 8| as initially set. A variation in initial compression placed on the control spring 8| by the flanged sleeve 80 will produce a change in the pressures required to move the control rod 25. While it is true that an adjustment of the position o-f the anged sleeve 80 on the control rod 25 adjusts not only the tension of the control spring 8I, but also the position of the cam 14, it is apparent that the adjustment of this sleeve co-nnot be made without first removing the nut 82. The effect of this is that the flanged sleeve adjusts the tension that is placed on the spring 8| under no load, or under loads below that at which an automatic change in effective leverage is require-d, and then securing the nut 82 in place determines the zero position of the pin 64, that is, the effective leverage between the actuating push rod 51 and the pump plunger 5, under no load.

It is to be noted that my jack is quite compact and rugged in construction. All of the actuating links are within the housing 2, and therefore arev not subjected to possible damage.

It is also to be noted that the valve arrangement is such as to permit ready access to the valves for cleaning or regrinding, lwithout requiring the disassembly of the rest of the unit. The valve chamber is not in a position where it can be damaged, and it is an integral part of the casting comprising the -casing It is also to be noted that I have placed the pump within the casing I, rather than outside of it, and that the pump plunger is always within the casing. This not only prevents damage to the pump but also prevents contamination of the oil, which is bound to take place if the plunger 5 moves outside of the casing and is therefore subjected to the dirt and dust usually prevailing in the open atmosphere. Also, if the jack is left in such a position that the pump plunger 5 is substantially entirely outside of the pump cylinder, as indicated in Figure 2,

it is not likely. to become coated with soot or dust. and produce a consequent contamination of thel oil. e

In Figures 10, l1 and 12,Ihave illustrated a modified form of base for a jack such as is described above, and have illustrated the manner in which such a jack is used. This jack is provided witl'r a rocking base to permit tilting of the jack to maintain the work performing member or saddle 40 always in engagement with the axle of a vehicle being raised, and the ram of the jack always at right angles to such axle. 'I'he desirability of such an arrangement is illustrated in Figure 10. 'Ihis figure shows the position of the rear axle of an automobile when one wheel has been jacked up. At the commencement of the jacking action the axle was horizontal. In the position shown in Figure 10 the axlehas been tilted through an angle a. In order to avoid bending strain on the jack it is necessary that the jack be tilted throughV the same angle, in order that the plunger of the jack shall be at right angles to the axle. To accomplish this result I have provided this jack with a curved or rocking base 90. This base is curved along an arc of a comparatively large radius and is substantially flat at its mld portion 9|. From this flat mid-portion the bottom of the base curves upwardly as indicated at 92 and 93, the upwardly curved portions being corrugated to prevent side slippage. The flat portion 9| prevents undue rocking in the placing of the jack, or when the jack is not in use, the tipping of the same.

It is to be noted, in connection with Figure 10, that the jack rocks in a plane parallel with the plane of the axle that is being raised, rather than in a plane at right angles to the axle. In this respect my jack differs from rocking jacks of the type wherein the lifting of the axle is obtained by reason of the rocking of the jack. In such jacks the lifting action was obtained by placing the jack under the axle and at an angle to the vertical, and then moving the vehicle longitudinally to bring the jack into a vertical plane and thus raiseV the end of the axle. In such lifting apparatus the jack is subjected to a bending strain due to the change in angle, with the horizontal, of the axle as one end of the axle is being raised. In such jack the rocking is in a direction longitudinally of the vehicle and at right angles to the axle. Inmy jack the rocking is in the plane of the axle and at right angles to the longitudinal center line of the vehicle. It is also to be noted that in my jack the rocking is a result of the lifting action, not the cause thereof.

While I have herein shown preferred embodiments of my invention it is to be understood that the invention is not limited to the precise structures herein set forth, the same being merely illustrative of the principles of the invention.

What I consider new and desire to secure by Letters Patent is:

l. A pump including a pump plunger, a pivoted lever connected to said plunger for actuating the same, one end of said lever being movable between predetermined limits, and means operable during the actuation of the pump plunger by the lever for altering the effective leverage of the lever to alter the length of stroke of the pump plunger, said means including a movable member determining the effective leverage of the lever, a cam for locking the movable member in different positions determined by the position of the cam, means for moving the cam, and means for maintaining the movable member in a position fixed by the instantaneous position of the cam even during movement of the cam.

2. A portable lifting jack movable into a position adjacent an object to be lifted, said jack comprising a casing enclosing a pump and constituting the sump of the pump, a pump operating handle outside of the casing, means comprising a lever having a movable pivot intermediate its ends within the casing connecting the pump and the prising a hydraulic cylinder, a plunger movable therein, a pump for supplying pressure to said agg pgwifa Pinus.

cylinder, means for actuating said pump including a lever, a movable pivot for said lever intermediate the ends thereof, a fulcrum, means supporting said pivot for oscillation about said fulcrum during movement of said lever, and means for varying the pressure supplied by said pump per cycle of operation thereof comprising manual means for shifting said fulcrum, and means responsive to the pressure in said cylinder for moving said manual means to shift said fulcrum to thereby vary the oscillatory movement of said pivot.

4. A lifting jack having operating means comprising a hydraulic cylinder, a plunger movable therein, a pump for supplying pressure to said cylinder, means for actuating said pump including a lever, a moving pivot for said lever intermediate the ends thereof, a fulcrum, means supporting said pivot upon said fulcrum and providing for limited oscillating movement of said pivot thereabout upon rocking movement of said lever, and means for varying the pressure supplied by said pump per cycle of operation thereof comprising means responsive to the pressure in said cylinder for shifting said fulcrum, said last named meansvincluding adjustable means for maintaining said fulcrum in shifted position.

5. A jack comprising a closed iiuid reservoir, a hydraulic cylinder within the reservoir, plunger means movable in said cylinder, a ram extending outwardly of said reservoir and actuated by said plunger means, a pump within said reservoir for supplying fluid under pressure to and disposed exteriorly of said cylinder, means within said reservoir for actuating said pump including a lever pivoted intermediate its ends, a fulcrum member pivotally mounted within said reservoir adjacent the base of said cylinder and supporting the pivot of said lever, and means within said reservoir adjacent the base of said cylinder and responsive to pressure in said cylinder for shifting said fulcrum member in accordance with the load on said ram.

6. A jack comprising a closed fluid reservoir, a hydraulic cylinder within the reservoir, plunger means movable in said cylinder, a ram extending outwardly of said reservoir and actuated by said plunger means, a pump within said reservoir adjacent the base portion thereof and exteriorly of said hydraulic cylinder for supplying fluid under pressure to said cylinder, said pump extending upwardly within said reservoir alongside said cylinder, means within said reservoir for actuating said pump including a lever disposed adjacent the upper end of said cylinder, a fulcrum member extending upwardly alongside said cylinder and serving as a pivotal support for said lever, means within said reservoir responsive to pressure in said cylinder for shifting said fulcrum in accordance with the load on said ram, and means energized by the pressure in said cylinder for locking said fulcrum in position.

7. In combination, a pump, a lever for actuating the pump, operating means for actuating said lever, means for varying the eiective leverage between said operating means and said pump comprising means responsive to the pressure developed by said pump, a pivot for said lever shiftable during reciprocation of said operating means, a fulcrum connected to and defining the range of movement of said pivot, cam means controlled by said pressure responsive means for transmitting motion of saidv pressure responsive UUI UH llUUli means to said fulcrum, said cam actuating means including self-locking means for preventing reverse transmission of movement from said lever through said fulcrum to said pressure responsiveY means.

8. In combination, a pump, a reciprocal plunger, lever means between said pump and plunger for operating said pump upon reciprocation of said plunger, a floating pivot for said lever means intermediate the ends thereof and shifting back and forwardly through a limited arc during reciprocation of said plunger, a fulcrum defining the range of movement of said pivot with respect to said fulcrum during rocking movement of said lever'means, means for moving said fulcrum into position in accordance with the pressure to be delivered by said pump, and means responsive to the pressure delivered by said pump for varying the position of said fulcrum.

9. In a jack, the combination of a hydraulic cylinder, a lifting head actuated by the pressure in said cylinder and engageable under a load to be lifted, a pump for supplying pressure to said cylinder, a reciprocating plunger, a lever connecting said plunger to said pump, a pivot for said lever, means for applying a substantially constant reciprocating force to said plunger, a fulcrum lever, means connecting said pivot to said fulcrum lever, and means for varying the position of said fulcrum lever in accordance with the load on said lifting head to vary the rate of lift of said head while maintaining said reciprocation producing force substantially constant, said means comprising a lock for said fulcrum lever and means responsive to the pressure within said cylinder for releasing said lock to provide for changing the position of said fulcrum lever.

10. In combination, a hydraulic cylinder, a pump for supplying pressure to said cylinder, op-

erating means for said pump including a lever, a

shifting pivot moving in a limited arc during movement of said lever, a fulcrum for said pivot, manually controlled means for locking said fulcrum in predetermined position, and means responsive to the pressure in said cylinder for shifting said manually controlled means to effect shifting of said fulcrum for varying the arcuate movement of said pivot to thereby vary the driving ratio between said operating means and said pump.

11. In combination, a hydraulic cylinder, a pump for supplying pressure to said cylinder, operating means for said pump including a lever, a fulcrum for said lever, manually controlled means for locking said fulcrum in predetermined position, and means responsive to the pressure in said cylinder for shifting said manually controlled means to effect shifting movement of said fulcrum for varying the driving ratio between said operating'means and said pump, said manually controlled means locking said fulcrum in a position fixed by the instantaneous effective shifting thereof produced by said pressure responsive means.

l2. Operating means for a hydraulic jack comprising a pump, a plunger, a lever connecting said pump and plunger, a moving pivot for said lever intermediate the ends thereof, a fulcrum connected to and defining Ithe range of movement of' said pivot, and means responsive to the pressure produced by said pump to shift said fulcrum for varying the range of movement of said pivot to vary the driving ratio between said pump and plunger.

13. Operating means of the class described comprising a pair of spaced reciprocal plungers, a lever connecting the corresponding ends of said plungers, a pivot intermediate the ends of said lever, a fulcrum lever having link means pivotally mounted at' one end thereof and connected to said pivot for defining the range of movement of said pivot about said one end of the fulcrum lever during rocking movement of said first-named lever, and means at the opposite end of said fulcrum lever for shifting the range of movement of said pivot to vary the driving ratio between said plungers.

14. Operating means for a hydraulic jack comprising a pump member, a plunger member, a. lever therebetween having .a pin and slot connection with one of said members, a moving pivot for said lever, a fulcrum about which said pivot oscillates during operation of said lever, and means for sluiting said fulcrum to vary the driving ratio between said members.

15. In combination, in a jack of a size and weight capable of manual transportation and having a supporting base portion, a ram cylinder in said jack, a ram in said cylinder having a. work-engaging head, a liquid reservoir in said base, pump means for supplying liquid under pressure to said ram cylinder below said ram, said pump means including a lever, a fulcrum for said lever, and means extending outwardly of the base portion of said jack for rocking said lever about said fulcrum, means controlled by the back pressure produced by the work engaged by said ram head for moving said fulcrum to vary the rate of raising of said ram inversely to the back pressure produced while maintaining substantially constant the force necessary to rock said lever means, and locking means biased for movement to a position locking said fulcrum and also controlled by said back pressure for releasing said fulcrum.

16. In combination, in a jack of the class described, a ram cylinder, a ram therein adapted to engage an object to be lifted, a liquid reservoir, pump means including a pump piston, a lever for reciprocating said plunger, a fulcrum defining movement of said lever, a plunger engaging said lever, and means supported at the base of said jack and extending outwardly thereof for reciprocating said plunger to actuate said piston for drawing liquid from said reservoir and forcing it against the bottom of said ram, means responsive to the back pressure of said ram for shifting said fulcrum in accordance with the weight of the object being lifted to vary the rate of lift of said ram while maintaining the force necessary to effect reciprocation of said plunger substantially constant, and a member movable in response to said back pressure and serving as a shiftable abutment limiting the movement of said fulcrum under the force of said back pressure.

17. A jack comprising, in combination, a hydraulic cylinder, a plunger movable therein, a work performing member actuated by the plunger, a pump supplying pressure to the cylinder, means responsive to the pump pressure for varying the movement of the work performing member per cycle of operation of the pump, and means for locking said last named means in adjusted position.

18. A jack comprising, in combination, a hydraulic cylinder,v a plunger movable therein, a.

work performing member actuated by the plunger, a pump supplying pressure to the cylinder. means responsive to the pump pressure for varying the movement of the work performing member per cycle of operation of the pump, and releasable means also responsive to the pump pressure for locking said last named means in adjusted position.

19. A lifting jack comprising a casing including a base, pump mechanism supported on said base within the casing and including a reciprocatory plunger, a reciprocatory actuating member movably mounted within said casing exteriorly of said pump, a rocking lever operatively connecting said actuating member and said plunger, a shiftable fulcrum member supporting said rocking lever for pivotal movement and pivotally carried at its lower end on said base, and a pair of movable parts disposed on opposite sides of and in engagement with the lower end of said shiftable fulcrum member and controlled by the pressure developed by the pump for fixing the position of said fulcrum member in accordance with the load raised by the pump.

20. A lifting jack comprising a casing including a base, pump mechanism disposed within said casing and having a reciprocating plunger, a fulcrum member pivotally supported in said base, a rocking lever disposed within said casing and having a pivotal sliding connection with the pump plunger at one end, a reciprocatory pump actuating member pivotally connected with the other end of said rocking lever, pivot link means serving to connectsaid rocking lever with the upper end of said fulcrum member, said link means being subjected to tension stresses when said reciprocatory actuating member forces the pump plunger inwardly, and means actuated by the pressure developed by said pump for holding said fulcrum member in position.

2l. A hydraulic jack comprising a base vmeniber, a pump carried thereby and including a pump cylinder and a plunger movable therein, a ram cylinder and a ram therein carried by said base and subjectedto the pressure developed by said pump, means for operating said pump including a pivotally mounted lever operatively connected with said plunger, means for varying the effective leverage of said lever with respect to said pump plunger including a shiftably mounted fulcrum member carried by said base, a third cylinder carried by said base, a control plunger movable in said third cylinder and acting against said movable fulcrum member for shifting the same in one direction, a member irreversibly connected with said movable member and serving by its position to limit the movement of said movable fulcrum member in said one direction under the influence of the pressure developed by said pump, and means also subjected to the pressure developed by said pump for shifting the position of said irreversible member to provide for the pump pressure shifting the fulcrum member to vary the effective leverage of said lever.

22. In combination, a hydraulic cylinder, a

.pump for supplying pressure to said cylinder,

operating means for said pump including a lever, a shiftable fulcrum for said lever, means actuated by the pressure developed by said pump for locking said fulcrum in predetermined position, and means also responsive to the pressure developed by said pump for releasing the locking means and shifting said fulcrum to vary the 60. www ams.

driving ratio between said operating means and said pump.

23. In combination, a hydraulic cylinder, a pump for supplying pressure to said cylinder, operating means for said pump including means providing for a variation of the mechanical advantage at which said pump is operated and said last named means including a movable member, a shiftable part irreversibly connected with said movable member for moving the same in one direction and adapted in any one position to prevent the member from moving in the other direction, pressure actuated means acting against said movable member for moving the same in said other direction limited by the position of said shiftable part, spring means tending to move said shiftable part in a direction tending to move y the movable member in said one direction, and means associated with said spring means and said pressure actuated means and responsive to an increase in pressure thereon to move said shiftable part away from locking position to permit the pressure to act through said pressure actuated means and shift said movable part to another position.

24. A pump including a pump plunger, a pivoted lever connected to said plunger for actuating the same, means for altering the effective leverage of the lever to alter the length of stroke of the pump plunger, said means including a movable member determining the effective leverage of the lever, a movable cam member with which a portion of said movable member is adapted to be moved intoengagement, spring means biasing said cam member for movement in one direction, means responsive to the pressure developed by said pump for moving said cam in the other direction against the bias of said spring means, and means also responsive to the pressure developed by said pump for continually maintaining said portion of the movable member in contact with said cam member.

25. A hydraulic lock for holding a. movable part in adjusted position comprising a member irreversibly connected with said part to shift the same in one direction only, pressure responsive means for shifting said part in the other direction, and means responsive to a diminution `of pressure acting against said last mentioned pressure responsive means for causing said member to move said part in said one direction.

26. A hydraulic lock for a movable part comprising a cam member with which a portion of said movable part is adapted to be moved into engagement, spring means biasing said cam member for movement in one direction, means responsive to hydraulic pressure for moving said cam in the other direction, and means for holding said movable part in engagement with said cam member.

27. A hydraulic lock for a movable part comprising a cam member with which a portion of said movable part is adapted to be moved into engagement, spring means biasing said cam member for movement in one direction, means responsive to hydraulic pressure for moving said cam in the other direction, and means also responsive to hydraulic pressure for continually maintaining said portion of the movable part in contact with said cam member.

28. A hydraulic lock for a movable part comprising a cylinder having an apertured control plunger movable therein and adapted to engage the end of said movable part, a pivoted cam adapted to be engaged by the lower end for limiting the movement of said part in one direction under the iniluence of the pressure within said cylinder acting against said control plunger, a rod passing through the aperture of said control plunger and connected at its outer end to said cam member for changing the position of the latter, a member mounted within said third cylinder on the inner end of said rod, and a spring biased between said control plunger and said last named member, the pressure within said third cylinder acting to compress said spring and shift said pivoted cam member to provide for the pressure acting against said control plunger shifting said movable part, the compression of the spring and the engagement of the lower end of said part with said cam member serving to lock the movable part in a given position responsive to a given pressure within said cylinder.

29. A. hydraulic lock for holding a movable part in adjusted position, comprising a source of pressure, a member irreversibly connected with said part and adapted to shift the same in one! direction, means responsive to said pressure tending to move said part in the other direction and adapted to hold said part against said member so as to iix said part against movement, and means for moving said member to adjust the position of said part.

30. Means for adjusting the position of a' movable part, comprising pressure responsive means tending to shift said part in one direction, a member irreversibly connected with said part and arranged when moved in one direction to shift said part in opposition to said pressure responsive means and when moved in the other direction to provide for the movement of said part under the iniiuence of said pressure responsive means, and biased means diiferentialiy associated with said pressure responsive means for moving said member.

31. Means for holding a movable part in adjusted position comprising a member irreversibly connected with said part and adapted to hold said part against movement in one direction, pressure responsive means acting directly against said part and tending to shift the latter in said one other direction, and means responsive to an increase in the pressure acting against said means for shifting said member to provide for movement of said part in said one direction under the influence of said pressure responsive means.

WILLIAM A. TRAUT.

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