US2973184A

US2973184A - Hydraulic jack

Info

Publication number: US2973184A
Application number: US519884A
Authority: US
Inventors: Walter C Trautman; Lyle L Arnes; Bernard J Zimmerman
Original assignee: Walker Manufacturing Co
Current assignee: Walker Manufacturing Co
Priority date: 1955-07-05
Filing date: 1955-07-05
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28

Description

Feb. 28, 1961 w. c. TRAUTMAN ErAL 2,973,184

HYDRAULIC JACK Filed July 5, 1955 5 Sheets-Sheet 1 Feb. 28, 1961 w. c. TRAUTMAN l-:rAL 2,973,184

HYDRAULIC JACK INVEN ORS. Vlffr 6T 75'42'/ 77747:*

m, 7229 PM Ta WNF/5? Feb. 28, 1961 w. TRAUTMAN ETAL 2,973,184

HYDRAULIC JACK Filed July 5, 1955 5 Sheets-Sheet 3 Feb. 28, 1961 w. c. TRAUTMAN ErAL 2,973,184

y HYDRAULIC JACK Filed July 5, 1955 5 Sheets-Sheet 5 f/cf United States Patent() HYDRAULIC JACK Walter C. Trautman, Bridgeport, Conn., and Lyle L.

Arues and Bernard J. Zimmerman, Racine, Wis., assignors, by mesne assignments, to Walker Manufacturing Company, Racine, Wis., `a corporation of; Delaware Filed July 5, 1955, Ser. N0. 519,884 .13 Claims. (Cl. 254-2) This invention relates to portable lifting ldevices and more particularly to mobile hydraulic lifts.

The object of this invention is to improve the performance, and the operational convenience and safety of hydraulic lifts.

A feature of this invention is an improved hydraulic lift comprising a generally horizontally disposed lifting frame movably supported upon a columnar member by means of bearings so contoured as to align and guide the movement of the lifting frame.

Another feature of this invention is an improved enlarged triangular supporting base for a hydraulic lift coupled with means for immobilizing the base when the lift is in use.

vAnother feature of this invention is a hydraulic lift embodying laterally adjustable support members for accommodating the lift to diverse load configurations.

Another feature of this invention is an improved safety mechanism insuring that the lift will not be accidentally lowered, and a single knob for controlling both the lowering of the lift and the intentional disabling of the safety mechanism.

A further feature of this invention is an improved power unit for a hydraulic lift.

Another feature of this invention is an improved means for locking the actuating lever of a hydraulic lift.

rPhe manner of attainment of the foregoing object, the nature of the foregoing features, and other objects and features of the invention, will be perceived from the follownig detailed description of an embodiment of the invention when read with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a hydraulic lift embodying the principles of the invention, sho-wn supporting an appropriate load such as an automobile;

Fig. 2 is a side elevational View of the hydraulic lift shown in Fig. l, the lift being in its lowered position;

vFig. 3 is a front elevational view of the structure shown in Fig. 2;

Fig. 3A is a smaller sized, fragmentary View of a portion of the structure represented in Fig. 3, showing a different arrangement ofthe parts;

Fig. 4 is a sectional view taken substantially along the line 4 4 of Fig. 2;

Fig. 5 is a sectional view taken substantially along the line 5-5 of Fig. 3;

Fig. 6 is a sectional view taken substantially along the line 6--6 of Fig. 2;

Fig. 7 is a top plan view of the hydraulic power unit employed in the structure shown in Fig. 2 of the drawings;

Fig. 8 is a vertical section taken substantially along the line 8-8 of Fig. 7; l

Fig. 9 is a fragmentary sectional view taken substantially along the line 9 9 of Fig. 7;

Fig. 10 is a top plan view of the base portion of the hydraulic power unit shown in Fig. 7 of the drawings;

upon the under portion of that automobile in a kneeling or sitting position. In its preferred form, the hydraulic lift comprises a generally vertical columnar member 12 supported upon a base assembly 14. The base assembly 14 includes a pair-of wheels 1,6 and `a caster 18 by means of which the hydraulic lift may be readily transported. A generally horizontally disposed lifting frarne assembly 20 is slidably supported upon the columnar member 12 and is adapted to engage selected portions of the automobile or other load to be lifted. The lifting frame assembly 20 is elevated relative to` the columnar member 12 by a hydraulic power unit actuated by a lever 22, and is lowered under the control off a release lever 24.

As may best be seen in the detailed representations of Figs. 2 to 4, the columnar member 12 is tubular, and" generally square 'in cross section. A base plate 26 is `welded or otherwise afxed near the bottom of each side of the columnar member 12. While the portions of thebase plates 26 which are welded to the columnar member 12 abut the sides of that column and hence'are parallel with one another, the forward portions of the base plates 26 are tapered and diverge (Fig. 3) so as to form av broad, generally triangulark base for the hydraulic lift. The forwardmost ends of the base plates 26 are interjoined by an angle-iron cross member 2S one leg of which is engageable with the ground, in a manner hereinafter to be described.

When the hydraulic lift is not under load, it may be readily moved upon a three-point suspension comprising rear wheels 16 and front caster 18. Wheels 16 are held, by means of Washers 30 and retaining rings 32, upon an `axle 34. extending transversely of and engaging apertures in the rear portions of the base plates 26. It will be noted that the lower left-hand ends of the base plates 26 (Fig. 2) are cut off so ,that they will not strike the ground when the hydraulic lift is pivoted about the longitudinal axis of the axle 34 for rapid transport.

As may best be seenv in Figs. 2 and 13, the caster 18.`

is mounted by means of a swivel `assembly 36 upon a bracket 38, the lower end of which normally abuts oneI mem-ber 28 thereby to raise the base assembly 14 to the shown position. When the lift is placed under load, the crossmember 28 will be deflected downwardly relative to' the caster l18, with the springs 42 being compressed and the bracket 38 tilting about the line of engagement between its lowermost edge and the face of the cross mem-- ber 28. This permits the horizontal leg of the cross mem-.

ber 28 and the toe ends of the base plates 26 to engage the ground or floor upon which the hydraulic lift rests to form a firm, relatively immobile foundation. The hori-l zontal leg of the cross member 28 provides a large sur-v face to prevent the toe ends of the base plates 26 from'.v digging into the gravel or other soft surface upon whichl the hydraulic lift may occasion rest.

The lifting frame assembly 20 comprises a pair of beam supporting plates 46 lying in spaced parallelism with each other and with the sides of the columnar member 12. Plates 46, which may be interjoinedfor rigidity by a tie plate 48, are welded or otherwise attached to the central portion of a laterally extending substantially horizontal lifting beam 50 (Figs. 2 and 3). Since in normal use the applied load will be approximately centered upon the lifting beam 50, it may be relatively long, being shown to be considerably longer than the width of the base assembly 14 (Fig. 3).

A pair of saddles 52 is supported by the lifting beam 50 to serve as load bearing surfaces. Since the disclosed embodiment of the invention is shown to be used as a bumper jack yfor lifting automobiles, saddles 52 are ap 'propriately formed with an upper concave surface designed to properly engage the underside of automobile bumpers of various shapes. As shown, each saddle 52 is a strap-metal member reinforced with a gusset 54 and welded or otherwise ailixed to a saddle bracket 56. Each bracket 56 has surfaces bearing upon each of the four surfaces of the lifting beam 50 lso that the bracket is rigidly a'ixed to the beam in a lateral sense but each bracket 56 may be moved along the beam so that the spacing between the' saddles 52 may be adjujsted. A pin 58 is preferably laffixed near each end of the lifting beam 50 in a position to engage an edge surface of an individual one of the brackets 56 in order to degline an outermost limit position of movement of those brackets. If it is desired to move the saddles 52 closer to one another than is possible with the shown arrangement, the pins 58 may be removed and one or both of the saddle 52-bracket 56 weldments may be removed, reversed, and reinstalled upon the beam 50, in the fashion represented in the fragmentary view of Fig. 3A of the drawings.

The beam support plates 46 are supported upon the columnar member =12 through the medium of a pair of

rollers

60 and 62, as may 4best be seen in Figs. 2 and 4 of the drawings.

Rollers

60 and 62 are rotatably mounted upon laxles 64 engaging aligned apertures in the beam supporting plates 46 and non-rotatively retained therein by means including retaining rings 66. Roller 60, which engages the rear face of the columnar member 12, is positioned substantially above roller 62 which engages the front face of the columnar member l12, in order to establish a relatively large support moment.

To maintain the lateral relationship between the columnar member 12 and the beam support plates 46 near each end of each `of the rollers 460 and 62, the diameter is gradually and preferably arcu-ately increased to define guide llanges 68 (Fig. 4). These lguide anges 68 engage the corners of the columnar member 12, which are pref-V erably rounded, and therefore forces a-re exerted tending to maintain the beam support plates 46 exactly laterally centered uponthe columnar member 12 and preventing tilting of the lifting frame `assembly 20 even though the' load is not centered thereon.' The use of' contoured rollers of this. nature yavoids the necessity of employing additional lateral support rollers engaging the sidesl of the columnar member 12.

Forces causing the elevation or permitting the lowering of the lifting frame assembly 20 are exerted through a pair of tension links 70 (Figs. 2 to 6). Each tension link 70 is attached to an individual one of the beam support plates' 46 by means such as a bolt 72, a washer 73 (Fig. 4) being placed therebetween, and a cross head 74, to

which it is aixed by bolts 76, The generally horizontally disposed cross head 74 is radially apertured lto accept,`

and is pinned to, the upperV end of `a ram 78 (Fig. 3)Y which is the driving element of the hydraulic power unit hereinafter to be described. As a result of these relationships, vertical motion of the ram 78 in either direction will be communicated vi-a the cross head 74, bolts 76, tension links 70 and bolts 72 to the beam support plates 46 to correspondingly raise or lower the saddles 52 to move the load.

yUpward movement of the ram 78 by the hydraulic power unit is accompylished by pumping an actuatingA lever 22 (Figs l and 2). One end of lever 22 is insertable within the central bore 23 of a lever socket 80. A cross pin 82 (Fig. 2), near the end of the lever 22,

engages slots 84 formed in the sides of the central bore 23 of the socket 80, being initially assembled to the socket and lever 22 through the hole 83. The handle 22 may be inserted in the socket 80, in the position represented in Fig. 1 of the drawings, for operating the hydraulic lift, or m-ay be disengaged therefrom and moved to the substantiallyvertical position represented in Fig. 2 for transportation and storage of the lift. It will be noted that the left-hand ends (Fig. 2) ofthe slots 84 turn downwardly, permitting actuating lever 22 to be moved so that its longitudinal axis is substantially at right angles to the axis of the socket 80. This arrangement, either alone or coupled with the rotatability of socket 80 about pin 90, enables the grip 86 on the end of the actuating lever 22 to be inserted, when the lifting frame 20 is in its lowermost position, between the rear face of the columnar member 12 `and the inner face of a cross bar vS8 welded between the ends of the beam supporting plates 46. Cross bar 88 therefore serves not only as a rigidifying element for the supporting plates 46 but also retains the actuating lever 22 in the position shown in Fig. 2 so that the entire lift may be tilted about the longitudinal axis of the axle 34 for rapid transportation of the lift without the actuating lever 22 swinging down and striking the floor.

An end cap 91 is attached to the upper end of the columnar member 12 by screws 93. The lever socket 80 is pivotally mounted to the end cap `91 by means of a transversely extending, headed fulcrum pin 90 extending through aligned apertures in the end cap 91 and the socket A80, and being retained therein by means of a cotter pin 92.

In order that the repeated pivotal motion of the lever socket 80 about its fulcrum pin 90 may actuate the pump element of the hydraulic power unit, a pump link 94 is pivotally connected to the socket -80 by a pin 96 (Figs. 2 and 6) at a suitable distance from the fulcrum pin 90.

As may be seen in Figs. 2, 3, 5 and 6, a handle 100, circular cylindrical in form, extends transversely of the lift and through aligned apertures in the end cap 91 and the columnar member 12. A pair of safety dogs 102 is pinned to the lhandle 100, one safety dog 102 abutting each side of the end cap 91, thereby serving to prevent the handle from being moved in translation relative to the end cap 91, but permitting the handle 100 and the dogs 102 to be rotatable about the longitudinal axis of the handle 100. Y

,One of the two safety dogs 102 is provided with a laterally extending pin 104 (Figs. 5 and 6) passing through an arcuate aperture 106'in the end cap 91 (Fig. 5), which permits swinging of pin 104 about the axis of handle 100. Pin 104 is engaged by an essentially U- shaped dog release clip 108 (Figs. 5 and 6), the-ends of the legs of which are apertured to engage a release rod 110. Release rod 110 carries at its upper end the release knob 24, is pivotally mounted at its lower end in a manner hereinafter to be described, and extends through an elongated aperture 112 in the upper surface of the end cap '91. It will be noted that the release rod 110 is also rotatable about its longitudinal axis with respect to the clip 108 for a purpose hereinafter to be noted.

Release rod 110 is biased forwardly of the lift (to the right in Fig. 5) by means of a tension spring 113 engag ing the rod 110 and anchored to a pin` 114 attached to the end cap 91. As a consequence, the upper end' of one of the safety dogs 102 which is connected to the clip 108 is' forced into engagement with the rear edge (Fig. 2) of the 100 is rotatable and both safety dogs 102 are pinned thereto, the other safety dog 102 will also tbe forced into engagement with the rear edge of its associated tension link 70. When the tension links 70 are raised, dogs 102 will engage notches 118 spaced along that rear edge. As long as the safety dogs 102 are so engaged in any one of the notches 118, the tension links 70, and hence the lifting frame assembly 20, cannot Ibe lowered. It will be observed that even if the selected position of elevation is such that the safety dogs 102 press against the tension links 70 at a point intermediate a pair of the notches 118 and if by some inadvertence or malfunctioning the lifting frame assembly 20 started to descend, that downward motion would be terminated when the tension links 70 have fallen to a point at which one set of the notches 118 is aligned with and engaged by the safety dogs 102.

To permit intentional lowering of the tension links 70 and hence of the lifting frame assembly 20, the release rod 110 is pivoted to the left (Fig. 5) to move the clip 108 and the pin 104 to the left, to rotate the safety dogs 102 in a counterclockwise directionv against the resistance of spring 113 to disengage safety dogs 102 from the tension links 70. Lowering is then accomplished by rotating the release rod 110 about its longitudinal axis to control a release valve in the hydraulic power unit hereinafter to be described. It will be noted that if the hydraulic system fails, the force of engagement between the safety dogs 102 and the notches 118 is such, when the lift is under load, that the release rod 110 cannot be pivoted to the left.

As may best be seen in Figs. 2 and 4, the hydraulic power unit is mounted within the column 12, with a pair of cross pins 119 (Fig. 2) engaging aligned apertures in the column 12 and in flanges 123 (Figs. 2 and 8) on the base 142 of the power unit. The base 142 firmly engages at least two of the inner faces of the column 12 so as to insure proper positioning and alignment of the operating

members

78, 94 and 110 (Fig. 4) relative to the column 12. The hydraulic power unit is shown in top plan view in Fig. 7 of the drawings, with the ram 78, the pump link 94, and the release rod 110 being shown in section. The pump link 94 is joined to a pump 120 by a pump link connector 122 which is a tubular member attached to the pump link 94 by a pin 124 and attached to the pump 120 by a pin 126. It will be noted that the diameter of the stem of the pump 120 is smaller than the inner diameter of the pump link connector 122, and further, that the longitudinal axis of the pin 126 is parallel to the longitudinal axis of the pin 96 by means of which the pump link 94 is connected to the lever socket 80 (Fig. 2) to permit the pump link 94 and the pump link connector 122 to slightly rotate about the axis of pin 126 during the pumping action of the actuating lever 22.

An O ring 128 mounted upon the pump 120 and a U cup packing 130, retained upon the pump 120 by a retainer 132, eng-age the inner walls of the pump cylinder 134. The upper end of pump 120 is sealed to the cylinder 134 by a packing ring 136 and a cap 138.

The pump assembly 121 is screwed or otherwise attached in a pump cylinder bore 140 in the base 1412. Pump assembly 121 is adapted to force hydraulic fluid through orifices (hereinafter to be described) to drive the ram 78 upwardly (Fig. 8). The lower end of the ram 78 carries a heel plate 146 and a leather cup 148 held in place by a washer 150 and a nut 152 for establishing tight hydraulic engagement with the inner walls of the cylinder 154.

Cylinder 154 is threaded, at its lower end, into a ram cylinder bore 156 in the base 142, and, at its upper end, into a tank nut 158. The upper end of the cylinder bore is sealed by an assembly including a washer 160, packing 162 and a nut 164, the latter of which is screwed into the tank nut 158. An outer casing 166 overlies a shoulder on the base 142 and engages a portion ofthe outer surface of the tank nut 158. Casing 166 is coaxial with but spaced from the cylinder 154 so as to define an oil reser'-, voir 168 therebetween.

The path of fluid communication between the pump and the ram may best be understood vby viewing Fig. 8 in conjunction with Fig. 10, which represents a top view of the base 142, and Fig. 11, which represents `a sectional View through the ram cylinder bore `156 and the pump cylinder bore 140, as is indicated by the section line 11- 11 on Fig. 10. As is shown in those views, the pump cylinder bore is connected by a passageway 170 to a pasageway 172, the end of which is sealed by a plug 174 (Fig. 7) engaging a threaded bore 176 (Fig. ll). Passageway 172 is connected by a passage 178 to a chamber which in turn communicates via a chamber 182 with the ram cylinder bore 156. The tapered area intermediate the

chambers

180 and 182 constitutes a valve seat 184 adapted to accept a ball 186 (Fig. 8). Fluid forced by the pump assembly 121 through the passageways 170,

l

172 and 178 into the chamber 180 will displace the ball 186 upwardly to permit that fluid to llow into the chamber 182 and the bore 156, and hence to apply a force' against the ram 78 to drive that ram upwardly.

While ball 186 will leave its valve seat 184, its maximum upward motion is limited by a ball retainer 188 (Fig. 8). Ball retainer 188 is a spring member having one portion of generally circular configuration abutting a shoulder intermediate the chamber 182 and the ram cylinder bore 156 and tightly engaging the walls ofthat bore. A downwardly extending projection on the ball retainer 188 extends into spaced proximity to the ball 186, when that ball is in position on its valve seat 184, and is of a length selected to properly limit the upward motion of ball 186.

The bottom of chamber 180 is joined to a passageway 190, the tapered area therebetween serving as a valve seat 192 for another ball 194. Passageway 190 communicates with a passage 196 which extends upwardly through the base 142, as may be seen in Fig. l() of the drawings, and in the sectional View of Fig. 12. Passageway 196 terminates at the annular horizontal surface 198 which, as may be seen in Fig. 8 of the drawings, lies within the oil reservoir As is shown in Fig. 8, a compression spring 200 is placed intermediate the

balls

186 and 194. On the downward stroke of the pump 120, fluid is forced through the abovetraced path to move the ram 78 upwardly. The fluid pressure in chamber 180 (Fig. 8) tends to force the ball 194 into engagement with its valve seat 192 so that the bypass to the oil reservoir 168 is blocked at this time. At the upward stroke of the pump 120, the hydraulic fluid supporting the ram 78 is prevented from returning since ball 186 will, under this pressure, return to its valve seat 184. However, fluid in the oil reservoir 168 will llow, as a result of the pressure differentials established during the upward stroke of pump 120, through passageways 196 and to force the ball 194 ot of its valve seat 192, against the resistive force of the spring 200, thereby permitting the oil to pass into the chamber 180 and thence (Fig. 11) via

passageways

178, 172 and 170 into the pump cylinder bore 140 to refill the pump cylinder 134 preparatory to the next downward motion of the pump 120. In this fashion, the ram 78 is driven upwardly (Fig.

2), carrying therewith the cross head 74, the tension'links 70 and the lifting frame assembly 20.

In order to permit the lifting frame assembly 20 to be lowered as the result of its own weight coupled with the weight of any load it may be carrying, it is necessary to release the safety dogs 102 (Fig. 2) in the manner hereinbefore described, and to rotate the release rod 110. As may be seen in Fig. 9 of the drawings, release rod 110 is coupled to a release stem 204 by a connector 206. The inner diameter of connector 206 is sufliciently greater than the outer diameter of the release rod 110 and of the release stem 204 so that rod 110 can rotate about its pivot pin 208 relative to the connector 206 land so that the connector 206 can rotate about pivot pin 210 relative to the release stem 204 to permit rod 110 to be moved to release the safety dogs 102, as was previously described. The engagement between pins 208 and 210 and the connector 206 is sutliciently loose to permit rotation of release rod 110 in its tilted position. It will be observed that pins 208 and 210 may be perpendicular to one another to provide universal action, if desired.

Release stern 204 is provided with a seal ring 212 engaging the walls of a bore 214 (Figs. 9, l and l2) in the base 142. Stem 204 is integral with a valve portion 215 which is engageable with a valve seat 216 so as to selectively con-trol the flow of hydraulic fluid between

passageways

218 and 220, the latter of which is sealed at one end by a plug 222 engaging a bore 224.

As 'may best be seen in Figs. l() and l2, of the drawings, passageway 220 joins with passageway 196 and hence is connected directly to the oil reservoir 168 (Fig. 2), whereas passageway 218 is connected to the cylinder bore 156 and hence tothe cylinder 154. During the aforesaid pumping oper-ation whereby the ram 78 is raised, release valve 215 is in engagement with its valve seat 216. To permit the load to be lowered, hydraulic fluid rnust be permitted to drain from the portion of the cylinder 154 (Fig. 8) below the ram 78 back into the oil reservoir 168. Release rod 11G is therefore rotated to partially unscrew release stern 204 from the threaded bore 214 (Fig. 9) to disengage valve 215 from its valve seat 216. Hydraulic fluid may then travel from the cylinder 154 through the passageway 21.8 (Figs. l0 and l2), 4past the valve 215, and via the

passageways

220 and 196 to the oil reservoir 16S. Obviously, this flow of hydraulic uid is metered by the valve 215 so that the rate at which the load is permitted to descend may be precisely controlled.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulll the vobject above stated, it will be appreciated that the invention is susceptible to modication, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. In a portable lift, an upright body membena lifting frame mounted on said body member for vertical movement, a hydraulic power unit for controlling the movement of said lifting frame relative to said lbody member, latching means for locking said lifting frame against downward movement relative -to said body member, a manually operable release rod mounted for rotation upon its longitudinal axis and for independent rotation about a transverse axis, means responsive to rotation of said release rod about its longitudinal axis for controlling said power unit, and means responsive to pivoting of said release rod about its transverse axis for controlling said latching means.

2. ln a portable lift, an upright body member, a lifting frame movably mounted on said body member, a hydraulic power unit, a pair of vertical tension links connected to said lifting frame and movable by said hydraulic power unit, said links having a plurality of notches therein, latching means engageable with said notches, a manually operable release rod, means responsive to rotation of said release rod about its longitudinal axis for controlling said power unit, and means responsive to pivoting of said release rod about a transverse axis for controlling said latching means. Y

3. In a portable lift, a body member, a lifting frame movably mounted on said body member, a hydraulic power unit, a pair of tension links connected to said lifting frame and movable by said hydraulic power unit, said links having a .plurality of notches therein, latching means engageable with said notches, a release rod, means responsive to rotation of said release rod about its longitudinal axis for controlling said power unit, said release rod Abeing pivotable about a transverse axis, and a rigid clip interconnecting said release rod and said latching means for rotating said latching means out of ening frame movably supported on said columnar member,

a pair of vertical tension links extending generally parallel with said columnar member and on opposite sides thereof, means connecting one end of each of said tension links to said lifting frame, a cross head interconnecting the other ends of said tension links, means for moving said cross head relative to said columnar member, said links having a plurality of notches along one edge, a shaft mounted at the upper end of said columnar member and extending transversely thereto, a pair of safety dogs supported thereon and pivotable about the longitudinal axis thereof, means biasing said safety dogs into engagement with said one edge of said tension links, both dogs being so positioned as to prevent downward movement of said links when engaged in said notches, and means for selectively and simultaneously rotating said safety dogs out of engagement with said tension links.

5. In a portable lift, a base, a cylinder extending upwardly from said base, a piston and piston rod slidable within said cylinder, a cross head secured to the upper end of said piston rod, a pair of downwardly extending tension links secured at their upper ends to opposite sides of said cross head, a lifting frame assembly secured to the lower ends of said tension links and adapted to engage the underside of a load, a plurality of spaced notches along corresponding edges of vsaid tension links, a pair of safety dogs pivotally mounted adjacent said tension links on a common axis, resilient means urging said safety dogs into engagement with said notches, both dogs being so positioned as to prevent downward movement of said links when engaged in said notches, means for supplying hydraulic liuid pressure to said cylinder to raise said piston, means for releasing said iluid pressure from said cylinder to lower said piston, and means for simultaneously retracting said safety dogs from said notches independently of the release of said pressure.

6. In a portable lift, a vertically extending closed tubular columnar member, at least two portions of the inner surface of said member being planar, a hydraulic power unit iixedly mounted within said columnar member, said unit including a ram, a pump link and a release rod extending longitudinally of said member and a base supporting said ram, link and rod, a pair of faces on said base engaging said planar portions of the columnar member, and means for supporting said base in said member.

7. In a portable lift, a base, a columnar member mounted on said base in a substantially vertical position, a lifting frame movablysupported on said columnar member, a pair of vertical tension links extending generally parallel with said columnar member and on opposite sides thereof, means connecting one end of each of said tension links to said lifting frame, a cross head interconnecting the other ends of said tension links, means for moving said cross head relative to said columnar member, said links having a plurality of notches along one edge, a shaft mounted at the upper end of said columnar member and extending transversely thereto, a pair of safety dogs supported thereon and pivotable about the longitudinal axis thereof, means biasing said safety dogs into engagement with said one edge of said tension links, and means for selectively rotating said safety dogs out of engagement with said tension links.

8. In a portable lift, a base, a cylinder extending upwardly from said base, a piston and piston rod slidable within said cylinder, a cross head secured to the upper end of said piston rod, a pair of downwardly extending tension link-s secured at their upper ends to opposite sides of said cross head, a lifting frame assembly secured to the lower ends of said tension links and adapted to engage the underside of a load, a plurality of spaced notches along corresponding edges of said tension links, a pair of safety dogs pivotally mounted adjacent said tension links, resilient means urging said safety dogs into engagement with said notches, means for supplying hydraulic fluid pressure to said cylinder to raise said piston, means for releasing said uid pressure from said cylinder to lower said piston, and means for retracting said safety dogs from said notches independently of the release of said pressure.

9. In a portable lift, an upright body member, a lifting frame mounted on said body member for vertical movement, a hydraulic power unit for controlling the movement of said lifting frame relative to said body member, latching means for locking said lifting frame against downward movement relative to said body member, a release rod mounted for rotation upon its longitudinal axis and for independent rotation about a transverse axis, means responsive to rotation of said release rod about its longitudinal axis for controlling said power unit, and means responsive to pivoting of said release rod about its transverse axis for controlling said latching means.

10. In a portable lift, an upright body member, a lifting frame movably mounted on said body member, a hydraulic power unit, a pair of vertical tension links connected to said lifting frame and movable by said hydraulic power unit, said links having a plurality of notches therein, latching means engageable with said notches, a release rod, means responsive to rotation of said release rod about its longitudinal axis for controlling said power unit, and means responsive to pivoting of said release rod about a transverse axis for controlling said latching means.

1l. In a portable lift, a base, a columnar member mounted on said base in a subsetantially vertical position, a lifting frame movably supported on said columnar member, a pair of tension links extending generally parallel with said columnar member on opposite sides thereof, means connecting one end of each of said tension links to said lifting frame, a cross-head interconnecting the other ends of said tension links, means for moving said cross-head relative to said columnar member, a pair of safety dogs movably supported by said columnar member, and means carried by said links and engageable by said safety dogs to prevent movement of said lifting frame in at least one direction.

12. In a portable lift, a base, a columnar member mounted on said base in a substantially vertical position, a lifting frame movably supported on said columnar member, a pair of tension links extending generally parallel with said columnar member on opposite sides thereof, means connecting one end of each of said tension links to said lifting frame, a cross-head interconnecting the other ends of said tension links, means for moving said cross-head relative to said columnar member, a pair of safety dogs movably supported by said columnar member, means carried by said links and engageable by said safety dogs to prevent movement of said lifting frame in at least one direction, and means for selectively rotatiin'g said safety dogs out of engagement with said tension links.

13. In a portable lift, a base, a cylinder extending upwardly from said base, a piston and piston rod slidable within said cylinder, a cross-head secured to the upper end of said piston rod, a pair of downwardly extending tension links secured at their upper ends to opposite sides of said cross-head, a lifting frame assembly secured to the lower ends of said tension links and adapted to engage the underside of a load, a pair of safety dogs movably mounted adjacent said tension links, means carried by said tension links and engageable by said dogs to prevent movement of said lifting frame assembly at least in one direction, means for supplying hydraulic fluid pressure to said cylinder to raise said piston, means for releasing said fluid pressure from said cylinder to lower said piston, and means for retracting said safety dogs.

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Branick Sept. 10, 1957