US3520426A - Hydraulic endgate apparatus - Google Patents

Description

July 14, 1970 INVENTOR. WILLIAM L.HOSTETLER BY WEW ATTORNEY July 14, 1970 w. L. HOSTETLER HYDRAULIC ENDGATE APPARATUS I5 Sheets-Sheet :3

Filed Nov. 20, 1967 .IIIIIII FIG. 4

4 6 M 2 w G F 2 .ws 5 II I I.. 5 IIII I 0 II I o H 3 2 Ill m 1 5 b I HII In I'IIIIII F I I r l I 2 J J T P W m O mm I IIIII I 'IIII" I\\'E.\'TOR. WILLIAM L. HOST ETLER y 1970 w. L. HOSTETLER 3,520,426

HYDRAULIC ENDGATE APPARATUS Filed NOV. 20, 1967 3 Sheets-Sheet S INVEA I OR.

WILLIAM -L.HOSTETLER ATTORNEY United States Patent 3,520,426 HYDRAULIC ENDGATE APPARATUS William Lester Hostetler, 701 E. Mam,

Harper, Kans. 67058 Filed Nov. 20, 1967, Ser. No. 684,201 Int. Cl. B6011 1/46 US. Cl. 214-75 4 Claims ABSTRACT OF THE DISCLOSURE A hydraulically actuated lift unit wherein a vertical hydraulic cylinder is mounted for guided vertlcal movement relative to fixed supporting structure, the; piston rod associated with the cylinder extending downwardly therefrom and resting upon the support structure. Means is provided for guiding vertical movement of an elongated lift column, the latter having horizontally extending load carrying means at its lower end. A pulley is mounted on the exterior of the cylinder for rotation about a horlzontal axis, and a cable is entrained over the pulley and has depending ends secured to the column and the fixed supporting structure whereby vertical movement of the column is twice that of the cylinder. The relatively fixed piston rod has a passageway therethrough whereby hydraulic fluid can be introduced into the cylinder to force upward movement of the latter. A pair of such units can be mounted on a truck bed with the load carrying means being common to both units and pivotally mounted thereon to serve as an endgate.

The present invention relates to new and useful improvements in hydraulic lift apparatus, and while the improved apparatus of this invention may be employed in other applications, the invention is more particularly directed to new and useful improvements in hydraulically actuated endgate lift systems.

With greater specificity, the instant invention 'is directed to new and useful improvements in combined hydraulic loading devices and tail gates of vehicles, such as disclosed in the following US. patents to which reference may be made for the purpose of ascertaining some of the more recent historical background of the field of the present invention: 3,024,926, Nolden, Mar. 13, 1962; 3,035,720, Selzer, May 22, 1962; 2,277,529, Richter, May 24, 1942; 2,701,654, Williamsen, Feb. 8, 1955; 3,275,170, MacRae et al., Sept. 27, 1966.

Generally speaking, the subject invention has for its principal object the attainment of the objectives sought to be realized by the application of the principles disclosed in the patents listed above.

An important object of the present invention is to pr0- vide symmetrical hydraulic units that may be eflicaciously attached to the rear end portions of the side walls of con-- ventional pick-ups or light trucks, and to the endgates provided with such pick-ups or light trucks as original equipment, whereby the endgate can serve the dual functions of a vertically movable load carrying platform and as a pivotally closable endgate in the conventional manner.

Still another important object of the present invention is to provide hydraulic units of the character specified in the preceding paragraph which in the environment of their use will have a vertical height substantially less than the height of the spacing of the load carrying bed of the vehicle above the ground surface, and preferably such that the units will have a vertical height either equal to or only slightly exceeding height of conventional pickup truck side walls to which they are attached.

Another object of the present invention is to provide 3,520,426 Patented July 14, 1970 a construction such as to minimize friction so that the tail gate and connected parts of the lift structure may readily descend to their lowered position by their own Weight in the absence of any application of hydraulic fluid pressure.

Still another important object of the present invention is to provide apparatus of the character specified in the preceding paragraphs such that the extent of hydraulic lines is minimized, and such that the hydraulic lines can be fixed or at least be subjected to a minimal degree of movement during operation of the hydraulic apparatus.

The final objective of the invention to be specifically set forth is to provide a simplified hydraulic unit and wherein the hydraulic cylinder and piston means is simplified to minimize cost and which will be durable and reliable in operation and yet simple to assemble and disassemble should repair or replacement of parts become necessary.

A broad aspect of the invention having a wide field of different utilizations involves the provision of hydraulic lift apparatus comprising an upstanding member, hydraulically extensible means including a vertical cylinder having a rod downwardly extensible therefrom, said rod having a lower end portion bearing upon said member, said member and the cylinder being provided with coacting means for guiding vertical movement of the cylinder relative to the member, an elongated load support column depending from said member, said member and the column being provided with coacting means for guiding vertical movement of the column relative to the member, said column being provided adjacent its lower end with horizontally extending means adapted to carry a load disposed thereon, a pulley mounted on the exterior of the cylinder for rotation about a horizontal axis, an elongated flexible element entrained over the pulley and having first and second depending end portions respectively connected to the member and the column, and hydraulic fluid conduit means to enable the introduction of hydraulic fluid into the cylinder under pressure to extend the rod therefrom, said conduit means including the rod having a passageway therethrough.

Still another broad aspect of the invention has to do with hydraulic apparatus of the type including an elongated single acting hydraulic cylinder and piston means, wherein the cylinder has a closed end and the piston means is reciprocably and sealingly received in such cylinder, such piston means including a rod that is extensible from the other end of the cylinder, and has to do with the improvement comprising the piston means including the rod having a passageway means therethrough for conducting hydraulic fluid through the extensible rod into the cylinder intermediate the closed end of the latter and the piston means, a pulley mounted on the exterior of the cylinder for rotation in a plane parallel to the longitudinal extent of the cylinder and for movement therewith relative to the rod, an elongated flexible element entrained over the pulley and having first and second ends, and means for preventing relative movement of the rod and the first end of the flexible element, the arrangement being such that movement of the second end of the flexible element is in the same direction and double in amount that of the cylinder relative to the rod.

Another aspect of the invention has to do with the hydraulic cylinder and piston means, and involves an improvement wherein a sleeve is slidable on and embraces the rod, said sleeve being provided with inner and outer sealing means respectively in sealing engagement with the rod and the cylinder, said rod being provided with means for preventing withdrawal of the rod from the sleeve, and said cylinder being provided with means for preventing withdrawal of the sleeve from the cylinder.

A final important aspect of the invention resides in the provision of coacting latch means carried by the endgate and the hydraulic units, such latch means being responsive to lowering of the endgate when the endgate is in its vertical position to secure the endgate against pivotal movement and to secure the hydraulic units and the vehicle side walls against separating movement.

An important feature of the present invention resides in the piston rod being maintained relatively stationary while the hydraulic cylinder is guided for vertical reciprocation thereabove.

Still another important feature of the present invention resides in the mounting of a pulley on the exterior of the vertically movable hydraulic cylinder, such pulley having entrained thereover a flexible tension element, such tension element having its depending ends respectively held stationary and attached to the vertically movable lift column provided for the endgate.

Yet another important feature of the present invention resides in the provision of a sleeve movably disposed between the exterior of the piston rod and the interior of the hydraulic cylinder, such sleeve being provided with sealing means for respective sealing action with the piston rod in the interior of the cylinder. Closely related to this feature is the provision of a removable stop on the piston rod preventing withdrawal of the latter from the sleeve, and the additional provision of a removable stop in the hydraulic cylinder to prevent removal of the sleeve from the cylinder.

Another important feature of the present invention resides in the spacial relationship between the flexible element and the means for connecting the lift column to the endgate and for limiting pivotal movement of the latter whereby the application of lifting force by the flexible element is at a position spaced from the axis of the pivotal connection of the endgate.

Still another feature deemed to be of importance is the provision of the coacting latch means carried by the hydraulic units and the endgate such that lowering movement of the endgate such as to secure the latter against pivotal action also secures the hydraulic units as well as the vehicle side walls to which they are attached from spreading apart.

These and other important objects, aspects and features of the invention will become apparent during the ensuing description of a preferred embodiment of the invention, such description to be taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an isometric view of the present invention as applied to the endgate of a pick-up truck that is partially shown, the apparatus being illustrated with the endgate pivoted to a horizontal load supporting position and at a height disposed below the load carrying bed of the vehicle;

FIG. 2 is a side elevational view of one of the hydraulic lift units, such view being partially in vertical section;

FIG. 3 is a horizontal sectional view taken upon the plane of the section line 33 in FIG. 2;

FIG. 4 is a horizontal sectional view taken upon the plane of the section line 44 in FIG. 2;

FIG. 5 is an enlarged isometric view of the means carried at the lower end of the lift column, and illustrates particularly the pivot pin for the endgate, the stop provided for limiting pivotal movement of the endgate, and the attachment of one end of the flexible tension element to the stop;

FIG. 6 is a side elevational view of one of the hydraulic lift units and the endgate as viewed from the other hydraulic lift unit, the endgate being in closed position;

FIG. 7 is a view similar to that of FIG. 6; however, this view shows the endgate swung to its horizontal position;

FIG. 8 is a view similar to FIGS. 6 and 7, however, this view shows the endgate as being in its lowered position with a load resting thereon; and

FIG. 9 is a view similar to FIGS. 6 through 8; however, this view shows the endgate with a load thereon as being elevated to the level of the vehicle load carrying bed.

Reference is now directed to the accompanying drawings wherein like numerals designate like parts throughout the various views with the reference numeral 10 designating the rearmost portion only of a pick-up truck.

The vehicle or pick-up truck 10 includes a load bearing platform or bed of generally rectangular configuration 12, and in the conventional manner the vehicle or pick-up truck 10 includes upstanding side walls 14 and 16 disposed along the opposite sides of the horizontal load carrying bed 12. It will be understood, of course, that the vehicle 10 is conventional and includes rear drive wheels, dirigible front wheels, a prime mover and an operators cab, none of which are shown as they are well known, and a detailed description or illustration thereof would serve no useful purpose and tend to obscure the actual invention. It will be understood, of course, that the vehicle 10 does as is conventional include a source of electrical energy (battery and/0r generator or alternator) by means of which energization may be provided for the electric prime mover for a hydraulic pump, reservoir and valve unit designated generally at 18.

Excepting only the electrically driven hydraulic equipment designated generally at 18, the vehicle 10 as thus far described is entirely conventional and is such that the opening defined between the rearmost ends of the upstanding side walls 14 and 16 is closed by a pivotally mounted endgate.

In lieu of the conventional endgate provision for the truck or vehicle 10, which ordinarily is hingedly or pivotally connected directly to the vehicle 10 there is provided according to the present invention a specially mounted and movable endgate designated generally at 20, and such endgate 20 is provided with special mounting and lifting means as hereinafter described.

The special mounting and lifting means mentioned in the preceding paragraph comprises a pair of hydraulic lift units designated generally at 22 and 24. Since such hydraulic lift units 22 and 24 are symmetrical and constitute mirror images of each other, a detailed description of one of such hydraulic lift units 24 will sufiice for both.

The hydraulic lift unit 24 comprises a pair of upstanding tubular steel members 26 and 28 of rectangular cross section, the members 26 and 28 being vertically coextensive, and the former being substantially larger with respect to transverse dimensions. As best seen in FIGS. 3 and 4, the tubular members 26 and 28 are placed side-by-side and welded together at 30 so as to be rigid with respect to each other, and have their sides 34 and 36, respectively, coplanar, it being noted that the sides 34 and 36 face toward the other hydraulic lift unit 22. It will be noted that as mounted on the vehicle, the smaller upright tubular member 28 is forwardmost, and to the side of the tubular member 28 remote from the tubular member 26 there is secured a vertical length of angle iron 38, the arrangement being such that the angle iron 38 defines a forwardly extending flange 40 which is detachably secured by means of bolts or the like 42 to the inner side of the rearmost end portion of the side wall 16 of the vehicle 10. It will be noted when the hydraulic unit 24 inclusive of the angle iron 38 is provided for attachment to a vehicle 10, the appropriate holes must be provided in the truck wall 16 and in the flange 40 of the angle iron 38 can be positioned for securance by the bolts 42 in such a manner that the hydraulic lift unit 24 will occupy a proper position with respect to the truck bed 12 and the side wall 16, as will be evident to those skilled in the art. This point is deemed important as the most probable utility of the present invention will reside in providing hydraulic lift units according to the present invention for modification of extant pick-up trucks and the like. As will be appreciated, when hydraulic lift units of the character herein described are to be included as a part of integral original vehicle equipment, the hydraulic lift units may be directly welded to or otherwise fixedly secured to the frame and side walls of the vehicle. Whether made as an integral part of original vehicle structure or to constitute an attachment for extant vehicles, it will be understood that the hydraulic lift unit 24 and more specifically the upright tubular members 26 and 28 thereof are fixedly and immovably secured to the vehicle with respect to the bed 12 and the side wall 16.

The lowermost end of the upstanding tubular member 24 is closed by a horizontal base plate 44 welded thereto. Hydraulic cylinder and piston means designated generally at 46 are disposed within the tubular member 26, such means 46 comprising a hydraulic cylinder 48 vertically movable within the tubular member 26, such hydraulic cylinder 48 having a closed upper end 50 that is in turn provided with a removable vent plug 52 whereby air may be bled from the system. A hollow piston rod 54 is coaxially received within the cylinder 48 in spaced relation thereto and extends downwardly from the lower end of the cylinder. A metal sleeve 56 is slidably received within the cylinder 46, such sleeve 56 being slidable on the exterior of the hollow piston rod 54. Adjacent its lowermost end, the internal surface of the cylinder 48 is provided with an annular groove within which is positioned a removable metallic snap ring 58 which in its installed position prevents removal of the annular cylindrical sleeve 56 from the lower end of the cylinder 48 by engagement of the lower end of the sleeve 56 with the snap ring 58. In a similar manner, the external surface of the hollow piston rod 54 is provided with an annular groove within which is removably seated a metallic snap ring 60 which limits upward movement of the sleeve 56 upon engagement of the upper end of the sleeve 56 with the snap ring 60.

Fluid-tight seals are provided between the sleeve 56 and the external surface of the hollow piston rod 54 on one hand and between the exterior of the sleeve 56 and the internal surface of the cylinder 48. Such means for sealing may comprise one or more O-rings of neoprene or Teflon seated in annular external grooves in the sleeve 56 such as the O-ring 62 seated in an external groove in the sleeve 56, it being understood that the O-ring 62 make sliding and sealing contact with the internal surface of the cylinder 48. Such sealing means also comprises one or more O-rings seated in internal annular grooves in the interior of the sleeve 56 such as the O-ring 64 seated in an annular groove in the internal surface of the sleeve 56, it being understood that the O-ring 64 has sliding and sealing engagement with the external cylindrical surface of the hollow piston rod 54.

Conventional coupling means 66 are provided at the lower end of the hollow piston rod 54 for coupling the hollow interior of the piston rod 54 to a hydraulic fluid conduit 68. The connection coupling the hydraulic fluid line 68 to the interior of the hollow piston rod 54 extends through an opening 70 provided in the base plate 44, the arrangement being such that the lower end of the hollow piston rod 54 rests upon or is supported by the base plate 44. The opening 70 is sufficiently large to loosely receive the coupling means 66 therethrough, while the base plate 44 does not in itself constitute any part of structure confining the hydraulic fluid. It will be appreciated that the loose extension of the coupling means 66 through the opening 70 serves to limit any lateral movement of the lower end of the hollow piston rod 54.

As thus far described, it will be manifest that introduction of hydraulic fluid into the interior of the hollow cylinder 54 by way of the hydraulic fluid conduit 68 and the coupling means 66 will result in hydraulic fluid being displaced from the upper end of the hollow piston rod 54 into an annular space 72 intermediate the exterior of the piston rod 54 and the interior of the cylinder 48. Such fluid movement will, assuming that the sleeve 56 has already moved to its normal position such that its lower end bears against the snap ring 58, result in. upward movement of the hydraulic cylinder 48 relative to the piston rod 54. Since the lower end of the piston rod 54 bears against and is fixed with respect to the base plate 44, such upward movement of the hydraulic cylinder 48 is also upward relative to the fixed tubular members 26 and 28 and correspondingly also with respect to the vehicle 10. Such relative upward movement of the hydraulic cylinder 48 will continue upon continued introduction of hydraulic fluid under pressure until the upper end of the sleeve 56 engages the stop constituted by the snap ring 60, whereupon movement ceases provided that the hydraulic fluid pressure is not allowed to increase to such a level as to cause mechanical failure. It will be apparent to those skilled in the art that hydraulic pressure is maintained at levels less than that which would result in failure of the parts.

Assuming that the hydraulic cylinder 48 is disposed at its uppermost limited position or at some intermediate position, and that hydraulic fluid pressure within the hydraulic fluid line 68 is allowed to fall below a predetermined value, exertion of a predetermined downward force upon the hydraulic cylinder 48 will result in downward movement of the latter and return of hydraulic fluid from within the hydraulic cylinder 48 to the hydraulic line 68.

The tubular member 26 serves to guide vertical movement of the hydraulic cylinder 48 in a manner now to be described. Adjacent its upper end, the cylinder 48 has welded thereto a pair of divergent ears 76 and 78, such ears being arranged so that the outer extremities thereof are in sliding engagement with dihedral angles defined by the internal surface of the tubular member 26 as readily apparent in FIG. 3. Inspection of FIG. 3 will show that the guide means constituted of the tubular member 24 and the cars 76 and 78 are such that the hydraulic cylinder 48 is not only guided for vertical movement but is restrained against rotation about its axis.

It will also be noted that the guide means previously described results in the cylinder 48 being spaced from the side 34 of the tubular member 26. The side of the cylinder 48 spaced from the side 34 of the tubular member 26 is provided with an integral stub axle 80 welded thereto. A pulley 82 is journaled on the stub axle 80 so as to rotate about a horizontal axis. It will be noted that the axial extent of the pulley 80 is approximately that of the spacing of the exterior of the hydraulic cylinder 48 from the side 34 of the tubular member 26, whereby the tubular member 26 serves to retain the pulley 80 rotatably mounted on the cylinder 48, it being understood that the axial extent of the pulley 80 is such as to afford free running clearance therefor. It will be evident that the pulley 80 is positioned on the axle 80 prior to assembly of the cylinder '48 within the tubular member 26.

The pulley 82 is provided with a peripheral groove 84, and a flexible steel cable 86 is entrained over the top of the pulley 82 and is seated in the groove 84, such flexible cable 86 having one end fixedly secured to the base plate 44 by means of such end being welded or otherwise fixedly attached to a solid steel extension 88 that is externally threaded and which projects through a suitable opening in the base plate 44. A nut 98 is threaded upon the lower end of the steel extension 88 so as to bear against the underside of the base plate 44. The other depending end portion 92 of the cable 86 extends freely downwardly through an opening 94 in the base plate 44 for a purpose presently to be described.

A tubular steel lift column of rectangular transverse configuration is vertically reciprocable within the upstanding tubular member 28 and projects downwardly therefrom. The lift column 100 and the tubular member 28 are provided with coacting antifriction means comprising a steel roller 102 mounted for rotation about a steel pin "104 carried by the upper end portion of the lift column 100, said roller 102 being disposed to bear against the inner surface of the side of the tubular member 28 that abuts the tubular member 26 as clearly shown in FIG. 2. A pair of vertically spaced steel rollers 106 and 108 are mounted for free rotation on a pair of steel pins 110 and 112 extending between vertically spaced pairs of steel ears 114 and 116 welded to the forward exterior of the tubular member 28. The steel rollers 106 and 108 have peripheries that extend rearwardly through suitable openings 118 and 120 in the tubular member 28 to be disposed within the interior of the tubular member 28 and to establish rolling contact with the lift column 100.

On consideration of FIG. 2, it will be appreciated that the rolling engagement of the steel roller 102 against the rear interior of the tubular member 28 and the rolling engagement of the rollers 106 and 108 with the forward side of the lift column 100 is such that friction is minimized and direct engagement between the forward and rear sides of the column 100 with the interior of the tubular member 28 is prevented when the lift column 100 is subjected to a torque or couple tending to rotate the latter in a clockwise direction as viewed in FIG. 2. The advantage of such characteristic of the antifriction means described above will become evident shortly.

The lowermost end portion of the lift column or member 100 is provided with means for pivotally supporting one lower or forward end edge of an endgate and also for limiting pivotal movement of an endgate. Such means will be best appreciated upon inspection of FIGS. 2 and and comprises a heavy steel foot member 120 of generally rectangular configuration, such foot member 120 being generally horizontally disposed and of substantially uniform vertical thickness and including a forward portion 122 and a rear portion 124 that is slightly offset upwardly from the forward portion 122. The forward portion 122 of the foot 120 includes a lateral projection or protrusion 126 that at its outermost extremity is welded securely at 128 to the lower end of the lift column 100. The forward portion 124 of the foot 120 is provided with another lateral extension or protrusion 130 that parallels the extension 126, and the extension 130 is disposed directly below the opening 94 in the base plate 44. The end portion 92 of the steel cable 86 is vertical and in alignment with its position of engagement with the pulley 82, the opening 94, and the lateral extension 130 of the foot 120. The lower end extremity of the cable portion 92 is provided with means for detachable securance to the lateral extension 130 of the foot 120, such means comprising an externally threaded steel member 132 that is fixedly secured by any suitable means such as welding and/or being crimped about the cable portion 94, and the externally threaded member 132 has its externally threaded lower extent (which is reduced in diameter, not shown) extending through a suitable opening 134 provided in the foot extension 130. A nut 136 is tightly threaded upon the threaded extent of the member 132 so as to fix the lower end of the cable portion 92 to the foot 120. As in the case of the cable securing nut 90, the nut 136 can be employed in conjunction with a lock Washer, not shown, to prevent inadvertent disengagement. It will be appreciated by those skilled in the art that the foot extension 130 is clamped between the member 132 and the nut 136, and this is also true with respect to the base plate 44 being clamped between the nut 90 and the member 88.

A steel pivot or hinge pin 140 is fixedly secured to the lower end portion of the lift column 100 so as to project horizontally in spaced relation above the forward foot portion 122. Preferably, in the interests of strength, the hinge or pivot pin 140 extends into the support column 100 and is securely welded to the opposite sides of the tubular lift column 100 as indicated at 142 and 144 in FIG. 3.

The lower extents of the walls 34 and 36 of the tubular members 26 and 28 are respectively provided with elongated slots 146 and 148. The slot 146 is for the purpose of accommodating vertical reciprocating movement of the foot projection 130, it being noted that the slot 146 and the opening 94 in the base plate 44 permits or accommodates vertical movement of the foot projection 130 from a position spaced above the bottom of the tubular member 26 to a position spaced below the lower end of the tubular member 26 and below the base plate 44; this with the entirety of the foot excepting the lateral projections 126 and thereof being disposed externally of the tubular members 26 and 28.

In a similar manner the slot 148 in conjunction with an opening, not shown, in the base plate 44 corresponding generally to the previously described opening 94 accommodates vertical movement of both the hinge or pivot pin and the foot projection 126 for vertical reciprocation between positions disposed above the bottom of the tubular member 28 and below the base plate 44.

In order to further reinforce the foot 120 and the pivot pin 140 in relation to the lift column 100 and also in relation to the cable portion 94, a reinforcement plate or gusset-like member 150 is provided, the same being disposed parallel to and closely spaced to the exterior surfaces of the walls 34 and 36 with free running clearance therebetween, and having a lower edge securely welded at 152 to the upper surface of the foot member 120. The reinforcement member 150 has a height greater than the spacing of the pivot pin 140 above the foot 120 has an opening therethrough through which the pivot pin 140 extends, and the reinforcement member 150 is securely welded to the pivot pin 140 extending therethrough. It will be evident that by virtue of both the foot 120 and the pivot pin 140 being directly welded to the lift column 100 and by further virtue of the reinforcement plate 150 being in turn welded to both the foot 120 and the pivot pin 140 at a position spaced from the lift column 100, the entire structure shown in FIG. 5 of optimized strength with respect to the amount of material incorporated therein. This is especially true with respect to the foot 120 being unable to resist any bending moments applied thereto about any axis parallel to the pivot pin 140. Although the reinforcing plate 150 is shown as only extending along the forward portion 122 of the foot 120 to the region of the juncture of the forward and rear portions 122 and 124 thereof, it will be evident that the reinforcing plate 150 can be extended, if desired or deemed expedient, to the rearmost edge of the rear portion 124 of the foot 120. It has been found that such enlargement of the reinforcement plate 150 is unnecessary in connection with an actual working embodiment of the invention, inasmuch as the greatest bending moments occur at and immediately rearwardly of the vertical projection of the pivot pin 140 upon the foot 120.

A flat generally rectangular metallic closure is detachably secured to the top of the tubular members 26 and 28, the closure 160 being detachably secured by means of cap screws 162 that extend through suitable openings in the closure 160 for threaded engagement with lugs, not shown, that are welded within the upper ends of the tubular members 26 and 28, it being understood that such lugs have internally threaded openings for receiving the cap screws 162. It is to be noted also that the cap screw 162 associated with the tubular member 26 is disposed at the rear outer corner thereof (see FIG.

1) so that the lug associated therewith does not interfere with the insertion of or removal of the cylinder and piston means 46 through the upper end of the tubular member 26 when the closure 160 is removed.

It is pointed out that the closure 160 serves to give the unit 24 a finished and attractive appearance at its upper end, while additionally serving the utilitarian objectives of denying the ingress of foreign objects, precipitation and the like into the upper end of the unit 24, and,

of course, serves a safety function in denying entry of the inquisitive fingers of children and the like.

For a purpose presently to be explained, the upper end of the wall 36 of the tubular member 28 is provided with a slot 170 opening through the upper end thereof, and the cover 160 is provided with a notch 172 that is in registry with the slot 170.

As explained previously, the hydraulic lift unit 22 and its mounting means are identical to or more accurately constitute a mirror image of the hydraulic lift unit 24 and mounting means therefor described in detail above. The symmetrical hydraulic lift units 22 and 24 are mounted at the rearmost ends of the vehicle side walls 14 and 16, preferably with the uppermost extents of the hydraulic lift units 22 and 24 terminating at or very near the upper edges of the rearmost ends of the side walls 14 and 16. The hydraulic lift units 22 and 24 are mounted so that the foremost edges of the upstanding tubular members 28 are closely adjacent and preferably just rearwardly of the rearmost edge 180 of the vehicle load carrying bed 12. As thus far described, the hydraulic units 22 and 24 are contiguous to and attached to the side walls 14 and 16 so as to constitute virtually parts thereof that define the lateral vertical margins of the opening at the rear of the bed 12 between the side walls 14 and 16 through which cargo is normally passed through on loading and unloading the vehicle 10.

The endgate 20 corresponds generally to and indeed may be the endgate furnished as original equipment with the vehicle modified only to the extent hereinafter explained.

The spacing of the hydraulic lift units 22 and 24 is such that the lateral extent of the endgate portion 182 is only slightly less than the spacing of the reinforcing plates 150 of the hydraulic lift units 22 and 24. As in the case of conventional endgates, the endgate 20 is provided with cylindrical recesses constituting bearings, not shown, into which are received the pivot or hinge pins 140 of the hydraulic lift units 22 and 24, such pivotal connection between the hydraulic lift units and the endgate 20 being such that the endgate 20 is mounted for pivotal movement about an axis adjacent its lowermost or for- 'wardmost edge portion 182 when the endgate 20 is in its closing and opening positions, respectively.

As will be evident, the feet 120 of the units 22 and 24 constitute stops limiting pivotal motion of the endgate 20 to a horizontal position, and the endgate 20 is shown in such horizontal load carrying position in FIG. 1. A hydraulic line 190 is coupled to the hydraulic reservoir and pumping unit 18, and such hydraulic line 190 is coupled to the hydraulic lines 68 of the cylinder and piston means 46 of the units 22 and 24, such connection being through a suitable T-fitting or the like, not shown. The unit 18 is of conventional character and includes a control lever 192, which lever 192 is in one position allows free fluid communication between the hydraulic line 190 and the internal reservoir of the unit 18. The lever 192 may be swung to a second position such as to energize the electric motor driving the hydraulic pump 18 with the result that hydraulic fluid is driven under pressure through the hydraulic line 190 to the lines 68 of the hydraulic units 22 and 24. The feeding of hydraulic fluid under pressure from the unit 18 through the line 190 results in the cylinders 48 of the units 22 and 24 to be driven up wardly with equal force. This in turn results in upward movement of the pulleys 82 and a consequent raising of the feet 120 of the hydraulic lift units 22 and 24, with the result that the endgate 20 is raised hydraulically. Such raising of the endgate 20 hydraulically occurs whether the endgate 20 is in its horizontal load carrying position seated against the feet 120 or not, it being recalled that the pivot or hinge pins 140 are relatively fixed with re spect to the feet 120 as well as with respect to the lift columns 100.

When the lift unit 18 is de-energized by appropriate manipulation of the control lever 192, the weight of the vertical moving portions of the lift units 22 and 24 and particularly as augmented by the weight of the endgate 20 carried thereby is suflicient to force the cylinders 48 downwardly with the result that hydraulic fluid is caused to return to the combined reservoir and pump unit 18. Accordingly, assuming as an initial condition the endgate 20 to be in the position shown thereof in FIG. 1, the endgate 20 will descend gravitationally to the ground surface or until the feet rest upon the ground surface 194 as shown in FIG. 8. With the endgate 20 disposed in the position shown thereof in FIG. 8, a load can be placed thereon such as the crate 196 shown disposed thereon in FIG. 8. With a load placed on the endgate as shown in FIG. 8, the hydraulic pumping unit 18 can be actuated to raise the endgate to the level shown thereof in FIG. 9, that is a level such that the top of the endgate 20 is substantially coplanar with the upper surface of the truck bed 12, whereupon the load 196 can be conveniently moved from on the endgate 20 to a position resting upon the truck bed 12.

After the load 196 has been moved to rest upon the truck bed 12, the endgate 20 can be swung about the pivot pins to a vertical position, and then lowered or allowed to descend by gravity until the endgate 20 has become latched with respect to the hydraulic units 22 and 24 by means now to be described.

Such means for latching the endgate 20 comprises the previously described slot and the notch 172 and a pair of outwardly offset depending latch bars 198 fixedly secured to the opposite edges of the endgate adjacent the upper edge 2% of the latter. The latch bars 198 are in the form of inverted L-shaped elements formed of steel and are disposed in positions such as to move downwardly through the recesses 172 and through the slots 170 when the endgate 20 is lowered while in its vertical closing position. Engagements of the latch bars with the lower edge of the slots 170 limits downward movement of the endgate, prevents or restrains the endgate 20 from pivotal motion from its vertical closing position, and additionally, engagement portions of the walls 36 directly below the slots 120 between the depending parts of the latch bars and the outer edges 202 of the endgate 20 positively precludes any possibility of a spreading movement of the upper ends of the lift units 22 and 24 as well as of the side walls 14 and 16 of the vehicle to Which they are attached.

FIG. 6 illustrates the relationship of the endgate 20 to the hydraulic lift unit 24 when the endgate 20 is in its latched position.

Conversely, when the endgate 20 is in its closed position, the hydraulic unit 18 is actuated to raise the endgate 20 to an extent sufficient to clear the latch bars 198 through the upper ends of the slots 120 and the notches 172, whereupon the endgate 20 can be swung to its horizontal load carrying position opening the rear end of the vehicle. The endgate 20 can then be raised or allowed to descend by gravity to such position of height as may be desired.

The conventional combined hydraulic reservoir, hydraulic pump and electric driving motor unit 18 is such that the control lever 192 can occupy an intermediate neutral position, that is, a position intermediate that which deenergizes the electric motor and allows free fluid communication between the self-contained reservoir and the hydraulic line 190, and the position such that the electric motor is energized and hydraulic fluid pumped under pressure through the line to the hydraulic units 22 and 24. When the control lever 192 is in such intermediate neutral position internal valving serves to positively prevent any fluid to enter the unit 18 or leave the unit 18 through the hydraulic line 190. The conventional unit 18 has means assoicated with the control lever 192 such as yieldingly bias the control lever 192 into its intermediate neutral position. In other words, in the use of the conventiona1 unit 18, as will be well known to those conversant with the art, the control lever 192 will normally be in its neutral position, and the endgate 20 thereby positively prevented from either upward or downward movement. A control lever 192 must be manually held in either of its other positions so as to selectively force upward movement of the endgate 20 or to permit gravitational downward movement of the latter.

If deemed necessary or expedient, rotary gear motors or pumps of positive displacement characteristic can be disposed in the separate hydraulic lines 68- communicating with the separate hydraulic lift units 22 and 24, with such motors or pumps, not shown, coupled to a common shaft, whereby fluid flow into and from each of the cylinder and piston means 46 of the units 22 and 24 can be maintained identical. The exercise of this expedient, which has thus far not been found necessary in practice, will serve to assure that the positions of the feet 120 with respect to their respective units 22 and 24 will be maintained equal at all times, this without regard as to whether any load placed upon the endgate 20 is placed equidistant thereon from the hydraulic lift units 22 and 24.

It will be manifest to those active in the field that the subject invention is subject to numerous variations and departures from the illustrated and described embodiment thereof without departing from the actual spirit of the invention.

I claim:

1. In combination with a vehicle, an improved hydraulic lift assembly comprising a pair of symmetrical hydraulic lift units symmetrically fixed to the vehicle at spaced positions, each of said units comprising a vertical hydraulic actuator means, a vertically elongated gate actuation member, and first and second vertically extending guide means for respectively guiding vertical movement of the hydraulic actuator means and the gate actuating member, said first and second guide means comprising first and second tubular members, respectively, that are secured together in relatively fixed side-by-side relationship, said gate actuation member being disposed in the second tubular member for guided vertical movement, a foot member, each of said tubular guide members having a vertical slot therein extending upwardly from the lower end thereof, said foot member having first and second horizontal extensions slidingly receivable in the slots of the first and second tubular members respectively, with the second extension of the foot member being fixed to the lower end of the gate actuation member, said hydraulic actuator means comprising a pulley having a horizontal axis together with a hydraulically extensible cylinder and piston rod assembly by raising the pulley, the cylinder of said cylinder and rod assembly vertically movable in said first tubular member with means for rotatably mounting the pulley on the outside of the cylinder, and wherein the rod of said assembly extends downwardly from the cylinder with the lower end of the rod being fixed against movement relative to the first tubular member, and said rod being provided with passageway means for introducing a hydraulic fluid into the cylinder through the lower end of the rod, an elongated flexible element extending over the pulley and having depending first and second ends, said first end of the flexible element being fixed to the first extension of the foot member and the second end of the flexible element being fixed to the first tubular member, and a generally rectangular wall extending between and mounted on the foot members of said units.

2. The combination of claim 1, wherein said vehicle includes a bed for carrying cargo, said bed being provided with an upstanding wall extending about at least a portion of the periphery of the bed, said wall being interrupted between two spaced positions along its length to define an opening, with the hydraulic units being disposed on opposite sides of the opening in close proximity to the upstanding wall, said generally rectangular wall having a peripheral configuration approximating that of the opening and constituting a closure gate therefor, and means pivotally securing the closure gate to the foot members for swinging movement between a vertical opening-closing position and a horizontal load carrying position, whereby the closure gate may be selectively employed to close the opening and to serve as a load carrying platform.

3. The combination of claim 2, wherein the upper ends of the tubular members are substantially coterminous vertically with each other and with the upper edge of the upstanding wall.

4. The combination of claim 3, including coacting latch means carried by the tubular members of the hydraulic units and the closure gate to secure and support the latter in opening-closing position in response to a downward movement of the latter when in a vertical position.

References Cited UNITED STATES PATENTS 411,681 9/1889 Ridgway 212- 2,706,565 4/1955 Krasno 1879 2,915,144 12/1959 Olson 187-9 3,024,926 3/1962 Nolden.

3,127,956 3/1964 Hosbein et a1. 187-9 3,174,634 3/1965 Peck 21475 3,240,369 3/1966 Kappen.

GERALD M. FORLENZA, Primary Examiner R. B. JOHNSON, Assistant Examiner US. Cl. X.R. 1879

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