US3062500A - Jack - Google Patents

Description

Nov. 6, 1962 ARNES ETAL JACK A W m I. m I I l I I llm lll PW x 3 W 2 m 6 /m/m I 15W Filed Aug. 26, 1957 Nov. 6, 1962 ARNES ETAL JACK 6 Sheets-Sheet 2 Filed Aug. 26, 1957 Nov. 6, 1962 1.. ARNES EI'AL 0 JACK Filed Aug. 26, 1957 6 Sheets-Sheet 5 INVENTORS 7e A. 171v? Nov. 6, 1962 ARNES ETAL JACK 6 Sheets-Sheet 6 Filed Aug. 26, 1957 M m m f .m R m vw 2 7. Fr %5 i QMWM United States Patent Ofitice 3,6Z,5 Patented Nov. 6., 1362 JACK Lyle L. Arnes and Bernard J. Zimmerman, Racine, Wis,

assignors, by mesne assignments, to Walker Manufacturing Company, Racine, Wis, a corporation of Delaware Filed Aug. 26, 1957, Ser. No. 680,176 8 Claims. (Cl. 254-7) This invention relates to jacks, and more particularly to devices for lifting and lowering truck transmissions, differentials and similar loads.

The handling of heavy duty transmissions, torque converters, differentials and vehicle engine assemblies has presented many problems, both because of the great weight of such units and the confined space in which the mechanic must ordinarily work. These parts furthermore are usually asymmetrical both in shape and weight distribution, thus making it difiicult to grip the assembly properly.

It is an object of the present invention to provide a novel and improved jack which overcomes the shortcomings of previously known devices of this nature, and provides a construction by means of which one mechanic can easily and safely service truck transmissions or similar units in a fraction of the time previously required.

It is another object to provide an improved transmission jack of this nature which requires a minimum of effort during the raising and lowering operations and which will securely hold the load in all adjusted positions.

It is a further object to provide an improved jack of this character which may be easily adapted for various types of transmissions, torque converters, differentials or engine assemblies with a minimum of expense and effort.

It is also an object to provide an improved transmis sion jack of this nature which is readily maneuverable into various positions beneath and away from a vehicle, and in which the load-engaging means may be pitched or tilted to various angles in order to accommodate loads in accordance with their position on the vehicle.

It is another object to provide an improved transmission jack of the above nature which is of strong and durable construction but may be manufactured using conventional materials and with a minimum of labor expense.

Other objects, features and advantages of the present invention will become apparent from the subsequent description, taken in conjunction with the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view of the novel jack of this invention showing the jack in its raised position and with a transmission adapter mounted on the platform;

FIGURE 2 is a side elevational view of the jack without the adapter showing the parts in their lowered position;

FIGURE 3 is a top plan view of the jack with parts broken away and showing the frame configuration;

FIGURE 4 is a crosssectional view in elevation taken along the line 4-4 of FIGURE 2 and showing the lifting screw drive;

FIGURE 5 is a cross-sectional plan view taken along the line 5-5 of FIGURE 4 and showing the pawl and ratchet for holding the screw in position;

FIGURE 6 is a fragmentary cross-sectional view in elevation taken along the line 6-6 of FIGURE 4 and showing the manner in which the lifting yoke is connected to the traveling nut;

FIGURE 7 is an enlarged fragmentary side elevational -view of the head portion of the jack showing the pitch and tilt adjusting feature;

FIGURE 8 is a front elevational view of the structure shown in FIGURE 7, parts being sectioned for clarity;

FIGURE 9 is a side elevational view of the truck transmission adapter visible in FIGURE 1;

FIGURE 10 is a top plan view of the construction shown in FIGURE 9;

FIGURE 11 is an end elevation view of the truck transmission adapter;

FIGURE 12 is a perspective view of another adapter attachable to the jack and useful for handling differential units;

FIGURE 13 is a top plan view of the differential adapter; and

FIGURE 14 is an end elevational view of the adapter shown in FIGURES l2 and 13.

In general terms, the invention comprises an elongated base preferably constructed of tubular elements and supported by casters, the base being generally flat and having an upwardly extending portion at one end thereof. A pair of lifting beams and a pair of parallel links are pivoted to the base adjacent said upwardly extending portion and carry a lifting platform at the outer ends thereof in such a manner that translatory motion in an arcuate path will be imparted to the platform when the beams and links are rocked on their pivots. A lifting screw is rotatably and rockably supported by the upwardly extending portions of said base and passes through a traveling nut carried between said beams, a sidemounted rotatable handle being connected to the screw by bevel gearing. The screw is held in its adjusted position by a pawl and ratchet arrangement combined with frictional holding or braking means in such a manner that the platform may be raised or lowered simply by rotating the handle in opposite directions with a minimum of effort. The platform is capable of being pitched or tilted in either direction from a horizontal plane, and various adapters are provided which are mountable on the platform in order to permit the gripping of transmissions, differentials and similar units of various types.

Referring more particularly to the drawings, the jack is generally indicated at 21 and comprises a base generally indicated at 22, this base being preferably constructed of tubular steel elements as seen best in FIG- URE 1. More particularly, base 22 is fabricated with a pair of longitudinal members 23 portions of Which are in parallel relation, these members having outwardly flared portions 24 at one end which are inclined upwardly as seen in FIGURE 2. A tubular cross member 25 is secured to the outwardly flared ends 24 of longitudinal members 23 by bolts 26. Member 25 has a V-shaped central portion between members 23 and has projecting end portions 27 to which are secured a pair of caster wheels 28.

The opposite ends of longitudinal members 23 are bent upwardly in a looped manner, as best seen in FIGURE 2, to form a pair of upwardly extending parallel standards 29 which are roughly of inverted V-shape. The outer ends of looped portions 29 are welded to the main parallel portions of members 23, as seen in FIGURE 3, so that the standards formed by these looped portions are of extremely rigid construction. A lower cross pin 31 and an upper cross bolt 32 are secured between standards 29 as seen in FIGURES 2 and 3, thus holding the standards in rigid spaced relation, A pair of caster brackets 33 are secured to the outsides of members 23 at the juncture of the outer ends of looped portions 29 with the longitudinal frame members, and a pair of casters 34 are supported by these brackets, casters 34 being disposed somewhat inwardly of casters 28 with respect to the longitudinal axis of the unit.

A lifting linkage generally indicated at '35 is provided, this linkage comprising two pairs of beams 36 in spaced aceaaoo parallel relation. More specifically, beam 36 are pivotally supported at one end by pin 31, and are held in position by spacers 3'7 on this pin as well as a spacer 38 secured to intermediate portions of beams 36. The outer ends of beams 36 carry a pin 39 for supporting the jack lifting platform, as will be later described.

As best seen in FIGURES 3 and 4, a pair of pins 41 extend inwardly from intermediate portions of beams 36 between pin 31 and spacer 38, and these pins support a lifting yoke 42 for rocking movement between beams 36. A traveling nut 43 is carried by yoke 42, this nut preferably being an antifriction ball bearing nut of standard construction. As best seen in FIGURES 4 and 6, nut 43 is retained within a recess in yoke 42 and is prevented from movement away from the yoke by a retaining pin 44 carried by an ear 45 on yoke 42.

A lifting screw 46 is threadably disposed within nut 43 and is supported at its upper end by a yoke 47. This yoke is rockably supported between the upper ends of standards 29 by a pair of tubular pins 48 extending inwardly from the standards so that only axial forces are applied to the screw and has a central apertured portion 49 through which the smooth upper shank 51 of screw 46 extends. The upper end of yoke 47 is provided with a recess within which an antifriction thrust bearing 52 is disposed, a bushing 53 resting on the upper race of bearing 52. Shank 51 extends through bearing 52 and bushing 53 which is rotatably mounted on the shank, and a friction collar 54 is secured to the upper end of shank 51 by a pin 55. A ratchet 56 is rotatably mounted on shank 51 and is disposed between collar 54 and bushing 53. A cover 57 encloses these parts and is secured to the end of shank 51 by a nut 58.

As is best seen in FIGURE 5, a pair of pawls 59 and 61 are pivoted at 62 and 63 respectively to the upper end of yoke 47 within cover 57, and are urged toward ratchet 56 by a looped spring 63 secured to both pawls. The pawls are so positioned that they will alternately engage the teeth of ratchet 56 each time the five-toothed ratchet rotates one-tenth of a revolution in a clockwise direction as seen in FIGURE 5, and will prevent substantial counterclockwise rotation of the ratchet. With this construction, it will be seen that the frictional forces exerted by collar 54 on ratchet 56 when a load is placed on screw 46 will prevent the free rotation of screw 46 in a counterclockwise direction as seen in FIGURE 5. However, the application of an external rotative force through screw 46 will overcome this frictional resistance and cause rotation of the screw.

The means for actuating screw 46 comprises a handwheel 65 having a handle 66, this handwheel being secured to a shaft 67 rotatably mounted in a pin 48 carried by one standard 29. The inner end of shaft 67 is supported within a recess 68 in the inner portion of yoke 47. A bevel pinion 69 is secured to the inner end of shaft 67 and meshes with a bevel gear 71 secured to shank 51 of screw 46 below yoke 47. With this arrangement, as seen in FIGURE 4, rotation of hand-wheel 65 in either direction will cause corresponding rotation of screw 46. When this rotation is in a clockwise direction as seen in FIGURE 5, nut 43 will be lifted while the teeth of ratchet 56 ride past pawls 59 and 61. When the screw is rotated in a counterclockwise direction, ratchet 56 will be held stationary but collar 54 will frictionally slide on the ratchet, this rotation causing nut 43 to be lowered. The arrangement is preferably such that, with the parts properly lubricated, the effort required on handwheel 65 will be about the same for both raising and lowering the loaded jack.

The load-supporting means carried by the outer ends of beams 36 comprises a pitching carrier 72 and a tilting carrier 73 each of which is pivot-ally secured to beams 36 by means of pin 39, these two carriers being independently rotatable on this pin. As is best seen in FIGURES 7 and 8, pitching carrier 72 has a pair of downwardly projecting apertured ears 74 which are pivotally secured to a pair of parallel links 75, the lower ends of these links being pivoted at 76 to longitudinal frame members 23 adjacent pivot 31 of beams 36. As seen in FIG- URE 2, beams 36 and links 75, together with pitching carrier 72, constitute a parallelogram linkage so that the angular disposition of carrier 72 with respect to the ground will remain constant as the beams are raised and lowered.

Tilting carrier 73 is disposed above and in over-lapping relation with pitching carrier 72, and carries a transversely apertured pin 77 at the outer end thereof, the aperture of this pin receiving the reduced end of a pitch adjusting screw 78 carried by carrier 72, as seen in FIG- URES 7 and 8. More specifically, carrier 72 has a pair of car 79 between which is rockably supported a nut 80 carrying screw 78. A washer 81 and cross pin 82 are provided on screw 78 for preventing separation of carrier 73 from the screw. It will be noted that by rotating screw 78 in one direction tilting carrier 73 may be pitched in a clockwise direction as seen in FIGURE 7, whereas rotation of screw 78 in the opposite direction will cause carrier 73 to be pitched counterclockwise from the horizontal. Pin 77 will rotate slightly during this movement to compensate for the change in angularity of screw 78.

Tilting carrier 73 has a pair of cars 83 at one side thereof, these ears having apertures the common axis of which extends in the direction of the jack base. A platform 84, which also serves as an adapter base, is pivotally secured to carrier 73 by means of a pin 85 which extends through ears 83 and through a pair of ears 86 on platform 34. The opposite side of carrier 73 has an internally threaded boss 87 through which a tilt adjusting screw 88 extends. The end of this screw has a connection with platform 84 similar to that between screw 78 and carrier 73. Rotation of screw 88 in one direction will thus cause tilting of platform 84 in a counterclockwise direction as seen in FIGURE 8, whereas rotation of screw 88 in the opposite direction will cause clockwise tilting of platform 84. The range of both the pitch ing and tilting of platform 84 is preferably sufiicient to permit the jack to accommodate transmissions or other units in the various positions ordinarily required for assembly purposes.

Although platform 84 may at times be usable for direct engagement with certain types of loads, means are preferably provided for adapting the novel jack to handle transmissions and differentials such as are in common use in modern day trucks and other vehicles. A suitable adapter for truck transmissions (visible in FIG- URE l) is shown in detail in FIGURES 9, 10 and 11. The adapter, generally indicated at 89, is adapted to support a transmission such as is shown in dot-dash lines at 90 in the drawings. The adapter comprises a flat rectagula-r plate 91 securable to platform 84 by means of four bolts 92 which are threaded in apertures 93 in the corners of platform 84, these apertures being visible in FIGURE 3. Plate 91 is provided with two pairs of spaced parallel slots 94 extending transversely to the jack centerline, and three parallel longitudinal slots 95 adjacent one end of the plate, as seen in FIGURE 10. Two pairs of brackets 96 are disposed within slots 94, these brackets each having an integral pin 97 at its lower end engageable with the underside of plate 91 and a base 98 engageable with the upper surface of the plate. Each pair of brackets 96 is adjustable in a transverse direction within its corresponding pair of slots, and the upper ends of the brackets are provided with apertures 99, as best seen in FIGURES 9 and ll. A shaft 101 extends through the apertures in each pair of brackets, the shaft being pinned at 192 to one of the brackets and having a threaded portion 103 extending outwardly from the other bracket. A spacer 104 and a wing nut are mounted on the threaded end of each shaft 101, and by tightening the wing nut the upper ends of brackets 96 may be drawn toward each other, thus frictionally clamping each pair of brackets in their adjusted position within slots 94.

Each shaft 161 is adapted to carry a floating support 196 which is slidably and rotatably mounted thereon. The configuration of support 106 is best seen in FIGURE 11, the outer portion of the support having a concave serrated edge 107. The curvature of this edge is preferably such that it will readily engage the casing of transmission 96 or a similar unit, the two brackets 106 cradling the transmission between them.

The two outer slots 95 are adapted to adju'stably support a pair of posts 108 best seen in FIGURES 9 and 10, these posts being adapted to engage the other end of transmission 91) being cradled by supports 106. Posts 188 comprise threaded studs locked in place by nuts 109 in any desired longitudinal position and at any height within slots 95. For some transmissions, an additional cradle support may be necessary, and this support is indicated at 111, being carried by central slot 95. More specifically, support 111 comprises a somewhat V-shaped member having an upwardly facing concave serrated edge 112 interrupted by a central clearance recess 113. Support 111 is carried by a stud 114 lockable in any adjusted postion within central slot 95 by lock nuts 115. Cradle support 111 and posts 108 may be used alternatively or together as desired.

In order to hold down a transmission 90 being carried by adapter 89, a chain 116 is provided, one end of this chain being secured to a lateral edge of plate 91 by an S-hook 117. An eye bolt 118 engages the outer end or any desired intermediate link of chain 116, this bolt being securable to the opposite edge of plate 91 by a wing nut 119. The threaded length of bolt 118 is sufficient to permit proper tightening of chain 116 on transmission 90.

FIGURES 12, 13 and 14 illustrate a suitable form of a differential adapter for handling conventional types of truck differentials and similar units. The adapter is generally indicated at 121 and comprises a rectangular plate 122 securable to platform 84 by bolts 123. As seen in FIGURE 13, plate 122 is provided with a longitudinal slot 124 and a pair of aligned transverse slots 125. An L-shaped bracket 126 is securable in adjusted positions to slot 124 by means of a lock bolt 127. The legs of bracket 126 are of unequal length, and slots 128 and 129 are provided in these legs. The bracket may thus be fastened with either the long or the short leg overlying plate 122, and the upstanding leg may be located in a variety of positions. The outer ends of the legs of bracket 126 are provided with apertures 131 and 132 respectively so that the upstanding bracket leg may be secured to a differential casing.

Transverse slots 125 are provided with a pair of posts 133 securable in adjusted positions by means of lock nuts 134. These posts comprise threaded studs rotatable by wing nuts 135 and serve to support opposite sides of the differential casing indicated at 136, as seen in FIGURE l2.

Operation Assuming it is desired to replace a.- truck transmission which has been overhauled, jack 21 will first be placed in its lowered position by rotation of handwheel 65. This rotation will cause lead screw 46 to rotate through the intermediary of pinion 69 and gear 71, the rotation being counterclockwise as seen in FIGURE 5. During this rotation, ratchet 56 will be held stationary by one of the spring-urged pawls 59 and 61, but friction collar 54 will slide on the stationary ratchet due to the force being exerted on handwheel 65. Ball nut 43 will be lowered on screw 46, causing counterclockwise swinging of beams 36 and links 75 to their lower position as seen in FIG- URE 2. It should be noted that the flared configuration of base portions 24 and the V-shaped central portion of cross member 25 will permit the jack platform to be retracted considerably.

A transmission adapter 89 Will be mounted on platform 84 by means of bolts 92, and a transmission 90 placed thereon. In mounting the transmission on the adapter, brackets 96 will first be laterally adjusted and locked in place by tightening wing nuts 105, and floating supports 186 will be longitudinally adjusted on shafts 101 to properly accommodate the transmission casing. Posts 108 will likewise be properly adjusted in slots 95, and if necessary cradle 111 will be secured to plate 91. Chain 116 will be wrapped around the transmission casing to hold it in place, being secured in its tightened position by wing nut 119 and eye bolt 118.

After the transmission has been mounted on the jack, the jack will be wheeled under the truck and beneath its assembly position. At this time pitch adjusting screw 78 and tilt adjusting screw 88 may be rotated to adjust the transmission to a position parallel to that which it will occupy when it is assembled. Rotation of pitch adjusting screw 78 will cause tilting carrier 73 to be rocked about pivot 39, while rotation of tilt adjusting screw 88 will cause platform 84 to be rocked about its pivot on the tilting carrier.

After transmission has been properly adjusted in this manner, handwheel 65 will be rotated to raise the transmission. It should be noted that the location of the handwheel to one side of the jack is particularly convenient for working in a confined area such as that beneath a motor vehicle. As the handwheel is rotated, screw 46 will be rotated clockwise as seen in FIGURE 5, raising ball bearing nut 43 and causing beams 36 and links 75 to swing in parallelogram fashion about their respective pivots. Due to the frictional forces exerted by collar 54 on ratchet 56, the ratchet will rotate with shank 51, the thrust forces on the screw being transmitted through thrust bearing 52 and yoke 47 to standards 29. When the proper height has been reached, handwheel 65 will be released whereupon one of pawls 59 or 61 will engage ratchet 56. The frictional forces exerted by ratchet 56 on collar 54 will prevent rotation of screw 51, thus holding the load in place. Final tilt and pitch adjustments may be made at this time if desired, adjusting screws 78 and 88 being conveniently available to the operator from the same side as handwheel 65.

After transmission 90 has been assembled to the vehicle and disconnected from adapter 89, jack 21 may be lowered by reverse rotation of handwheel 65. During this rotation collar 54 will slide on ratchet 56 which is held stationary, and after platform 84 has reached its lower position the jack may be withdrawn from under the vehicle.

In removing a transmission from the vehicle, the above procedure will be reversed, with the jack first being raised, adapter 89 adjusted to the proper pitch and tilt positions, transmission 90 attached to the adapter and disconnected from the vehicle, and the jack lowered. Should it be desired to handle a differential assembly or similar unit, adapter 89 may be removed from platform 84 and adapter 121 mounted thereon. It will be apparent that other types of adapters could be provided in order to handle torque converters, engine assemblies or other units.

A novel jack has thus been provided which may safely and efficiently handle any type of heavy unit such as those mentioned above. It has been found that the use of a ball bearing nut together with the novel reversing arrangement results in an extremely low handle effort being required for raising or lowering, even under full loads. All controls may be easily reached by an operator at one side of the jack, and the load may be quickly and accurately adjusted to its proper angular position.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In a lifting jack, an elongated wheeled base, a standard extending upwardly from one end of said base, a thrust bearing supported by said standard, a lifting screw having an upper portion passing through said thrust bearing, a friction collar fixed to the upper end of said screw, a ratchet rotatably mounted on said screw between said collar and said thrust bearing, a pawl mounted on said standard and engageable with said ratchet to prevent rbtation thereof in one direction, a lifting beam pivoted at one end to said base, a traveling nut carried by said beam and receiving said screw, whereby a load exerted on said beam will cause said collar to frictionally engage said ratchet with sufiicient force as to prevent rotation of the screw when the ratchet is held stationary, and means for overcoming said frictional engagement and positively rotating said screw in either direction.

2. In a lifting jack, an elongated wheeled base, a pair of standards at one end of said base, a yoke rockably mounted between said standards, a thrust bearing carried by said yoke, a lifting screw having a smooth upper shank extending through said thrust bearing, a friction collar fixed to the upper end of said shank, a ratchet rotatably mounted between said collar and thrust bearing, whereby an axial load exerted on said shank will cause said collar to frictionally engage said ratchet, a pawl pivotally mounted on said yoke and engageable with said ratchet to prevent rotation thereof in one direction, a handle and shaft rotatably mounted on one side of one of said standards, gearing connecting said handle shaft with said screw, a pair of beams pivoted to said base adjacent said standards on a common axis, a traveling nut rockably mounted between said beams and receiving said screw, and load supporting means mounted on the outer end of said beams.

3. In a lifting jack, an elongated wheeled base, a pair of standards at one end of said base, a yoke rockably mounted between said standards, a thrust bearing carried by said yoke, a lifting screw having a smooth upper shank extending through said thrust bearing, a friction collar fixed to the upper end of said shank, a ratchet rotatably mounted between said collar and thrust bearing, whereby an axial load exerted on said shank will cause said collar to frictionally engage said ratchet, a pair of pawls pivoted to said yoke at opposite sides of said ratchet, spring means urging said pawls against said ratchet, the pawls being engageable alternately with the ratchet teeth to prevent movement thereof in one direction, a handle and shaft rotatably mounted on one side of one of said standards, gearing connecting said handle shaft with said screw, a pair of beams pivoted to said base adjacent said standards on a common axis, a traveling nut rockably mounted between said beams and receiving said screw, and means on the beams for engaging a load to be lifted.

4. In a lifting jack, an elongated wheeled base, a pair of standards at one end of said base, a yoke, a pair of pins rockably supporting said yoke between the upper ends of said standards, at least one of said pins being tubular, a thrust bearing carried by said yoke, a lifting screw having a smooth upper shank extending through said thrust bearing, a friction collar fixed to the upper end of said shank, a ratchet rotatably mounted between said collar and thrust bearing, whereby an axial load exerted on said shank will cause said collar to frictionally engage said ratchet, a pawl pivotally mounted on said yoke and engageable with said ratchet to prevent rotation thereof in one direction, a handle and shaft rotatably mounted on one side of one of said standards, said handle shaft passing through said tubular pin, a bevel pinion secured to said handle shaft, a bevel gear secured to said screw and meshing with said pinion, a pair of beams pivoted to said base adjacent said standards on a common axis, a traveling nut rockably mounted between said beams and receiving said screw, and a platform mounted on the outer end of said beams.

5. In a lifting jack, an enlongated base comprising a pair of tubular members having parallel portions adjacent one end of the base and flared portions adjacent the other end of the base, a tubular cross member connecting said flared ends, said cross member being V-shaped between said flared ends, a pair of casters carried by the outer ends of said cross member, a second pair of casters at said one end of the base, upwardly extending looped portions formed on said tubular members at said one end to define a pair of spaced standards, means securing said tubular members in spaced relation, a yoke rockably mounted between the upper ends of said standards, a lifting screw, a thrust bearing carried by said yoke and supporting the upper end of said screw, a handle rotatably mounted on the outside of one of said standards, gearing operably connecting said handle with said screw, a beam pivoted to said base adjacent said standards, a traveling nut rockably mounted on said beam and receiving said screw, and a lifting platform mounted on the outer end of said beam, said platform in its lower position being disposed between said flared base portions and within said V-shaped cross member portion.

6. In a lifting jack, an elongated base comprising a pair of tubular members having parallel portions adjacent one end and flared portions adjacent the other end thereof, upwardly looped portions on said tubular members adjacent said parallel portions, said looped portions forming a pair of spaced standards, a yoke rockably mounted between said standards, a thrust bearing carried by said yoke, a lifting screw having a shank portion passing through said thrust bearing, a friction collar secured to the upper end of said shank, a ratchet rotatably mounted on said shank between said collar and thrust bearing, a pawl pivoted on said yoke and engageable with said ratchet, a handle rotably mounted on one of said standards, bevel gearing connecting said handle with said screw to rotate said screw in either direction, a tubular cross member connecting the flared ends of said longitudinal members, caster wheels secured to the outer ends of said cross member, a second pair of caster wheels secured to said longitudinal members adjacent said standards, a pair of beams pivoted to said base adjacent said standards on a common axis, a pair of links pivoted to said base adjacent said beam pivot axis, and a carrier pivoted to the outer ends of said beams and links to maintain a parallelogram relation between the beams and links.

7. In a lifting jack, a tubular carriage comprising a pair of substantially parallel tubular elements extending longitudinally, each of said elements comprising a substantially horizontal portion flaring transversely outwardly at one end and a reversely bent portion forming an upright loop portion at the other end, the end of said loop portions forming a juncture with said horizontal portion, transverse struts between said upright loop portions rigidly securing the two elements together, a tubular transverse member rigidly secured to the flared ends of said elements projecting outwardly beyond the sides thereof, said outwardly projecting portions of said transverse member being provided with wheels, wheels provided on said elements at the junctures of the ends of said loop portions with said horizontal portions, and lifting means secured between and to said elements at the upright loop portions and extending toward the transverse member.

8. In a lifting jack, a frame, a lifting screw, a lifting nut operated by said screw, a load-supportable lifting member attached to said nut, means for rotating said screw in said nut to elevate and lower said lifting member, pawl and ratchet elements, a first of said elements being rotatably mounted on said screw, the second of said ele ments being secured to said frame, the elements coacting to permit relative rotation in only one direction, means on said frame rotatably supporting said first element, said last-mentioned means being disposed between said first element and said nut, whereby the portion of said screw between said first element and nut will be put in tension by a load on said lifting member, and a friction member fixed to said screw above said first element and frictionally connectable to said first element with a force proportional to the load supported by said lifting member.

References Cited in the file of this patent UNITED STATES PATENTS Whittaker July 14, 1868 Smythe Mar. 5, 1912 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION November 6, 1962 Patent No, 3,062,500

Lyle L Arnes et a1,

It is hereby certified that error appears in the above numbered patt the said Letters Patent should read as ent requiring correction and the corrected below.

"rectagular" read lines 54 and 55, for

"2,363,192" read Column 4,

column 10 line 4, for

- rectangular 2368 192 Signed and sealed this 6th day of August 1963,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Commissioner of Patents Attesting Officer

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