Patent Publication Number: US-3877590-A

Title: Lift gate assembly

Description:
United States Patent Brown Apr. 15, 1975 [54] LIFT GATE ASSEMBLY 3,715,046 2/1973 Marklund 214/670 [76] Inventor: Donald C. Brown, Box 194, Botkins,  
  Ohio 45 306 Primary ExaminerRobert J. Spar Assistant Examiner-Lawrence J. Oresky [22] Flledi 1974 Attorney, Agent, or Firm-Melville, Strasser, Foster &amp; 21 Appl. No.: 441,455 Hoffman Related US. Application Data [60] Continuation of Ser. No. 355,031, April 27, 1973, [57] ABSTRACT abandoned, which is a division of Ser. No. 167,976, A lift gate assembly for trucks and the like of the type 2, 1971 3,747,782- wherein the lift gate is movable between a position wherein it rests on the surface upon which the truck is H 214/75 187/9 standing and a position wherein the lift gate is level 187/95 with the top of the truck body. The assembly com- [5 Int. Cl. prises a frame having a pair of vertical members Field of Search 214/75 75 R, 75 joined by an upper crosstie member at the level of the 187/9, 95 top of the truck body and a lower crosstie member at the level of the truck bed. The vertical members each References Cited support a stationary channel, the lift gate is provided UNITED STATES PATENTS at its corners adjacent the truck body with means slid- 2,146,533 2/1939 Erickson 214/75 T ably joined to the Stationary Channels The lift gate is 2,405,054 7/1946 Pringle 214/75 T raised and lowered y means Of a P of chains pass- 2,70l,654 2/1955 Williamsen..... 214/75 T ing over sprockets mounted on a shaft at the top of 3,0 3, 3 3/1962 Phillips 5 T the frame. Driving means are provided for the shaft 3,l42,396 7/l964 Pauley et ah... 2l4/75 T and control means are provided for the driving means 3,252,545 5/1966 Quayle 187/9 3,282,449 11/1966 Buford 214/75 T 8 Claims, 14 Drawing Figures PATENTEUAFR 1 5192s SHEET 1 OF 7 PATBHEUAFM 1 5 m5 SHEEIMUF? sum 5 or 7 LIFT GATE ASSEMBLY This is a continuation of the copending application Ser. No. 355,031 filed Apr. 27, 1973 now abandoned in the name of the same inventor and entilled LIFT GATE ASSEMBLY which, in turn, was a divisional application of copending application Ser. No. 167,976, filed Aug. 2, 197 l in the name of the same inventor and entitled LIFT GATE ASSEMBLY, now U.S. Letters Pat. No. 3,747,782 issued July 24, 1973.  
 BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates to a chain driven lift gate assembly for a vehicle or the like, and more particularly to such an assembly wherein the lift gate is movable between a ground level position and a position level with the top of the vehicle body.  
 2. Description of the Prior Art In recent years, it has become increasingly important to provide trucks and similar vehicles with some form of lifting device. Prior art workers have taken a number of different approaches in providing such lifting devices. A common approach has involved the provision on a vehicle of the same general type of lifting means used by the typical warehouse lift truck. Another approach has been to provide a lifting floor section in association with the truck bed. Yet another common lifting means has been a power tail gate capable of moving between ground level and the level of the truck bed.  
  Generally, the prior art lifting means have involved expensive hydraulic cylinders, or chains or cables having a number of flights or a twisted path of travel. In some instances, prior art workers have used chains to function in part as racks, cut this has required very critical tolerances. Various screw means have also been used. but these also require critical tolerances and a numer of moving parts.  
  As a consquence, the provision of lifting means in association with a truck or the like has generally been expensive; has frequently required numerous moving parts; and has often been characterized by the location of much of the lifting mechanism below the body of the truck where it is exposed to moisture and dirt, wear, and possible damage. Finally, prior art lifting structure have generally been limited in their movement, usually being confined to movement between ground level and the level of the truck bed.  
  The lift gate assembly of the present invention is simple in construction; inexpensive to manufacture; and characterized by a minimum of moving parts. The present lift gate assembly involves a simple chain drive, using a pair of chains each having a single, straight flight.  
  The lift gate of the present invention is capable of moving from ground level to the level of the top of the truck body and hence is particularly adapted to any sort of vehicle wherein it is desired to lift the load to a position higher than the truck bed. Such a vehicle is shown, for example, in U.S. Letters Pat. No. 3,207,166. Finally, the lift gate assembly of the present invention is capable of being produced as a simple frame-like assembly which may readily be applied to any suitable type of vehicle.  
 SUMMARY OF THE INVENTION The lift gate assembly for trucks and the like comprises a rectangular frame to which a tail gate or lift gate is slidably mounted. The frame comprises a pair of spaced, vertical members joined by an upper horizontal frame member or crosstie at the top of the frame and a lower horizontal member or crosstie at the level of the truck bed. A stationary, vertical member of channel-shaped or C-shaped cross section is affixed to each of the vertical frame members.  
  In one embodiment, each of the stationary channelshaped members has slidably mounted thereon a movable member of channel-shaped or C-shaped cross section, by means of an intermediate roller-carrying member captively held in both the stationary and movable channel members. The lift gate is pivotally affixed to the movable channel members and is swingable between a horizontal position and a vertical position. By virtue of the stationary and movable channel members and their intermediate roller-carrying members, the lift gate is movable vertically between a position at ground level and a position at the level of the top of the vehicle body.  
  In a second embodiment, the stationary channelshaped members extend above the top of the vehicle body. Each stationary member has a roller-carrying element slidably mounted therein. The lift gate is pivotally affixed to the roller-carrying elements and is again movable between a position at a ground level and a position at the level of the top of the vehicle body.  
  Vertical movement of the lift gate in both embodiments is accomplished by means of a pair of chains one end of each of which is affixed to the lift gate. A rotatable shaft, bearing a pair of sprockets, is mounted at the upper end of the frame. Each of the chains passes over one of the sprockets. Driving means is provided for the shaft and control means is provided for the driving means. Operation of the control means will cause the lift gate to move upwardly or downwardly between its ground level and uppermost positions.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a truck provided with the lift gateassembly of the present invention.  
  FIG. 2 is a fragmentary perspective view illustrating rear side of the lift gate assembly. I  
  FIG. 3 is a fragmentary plan view of the lift gate assembly, with parts in cross section.  
  FIG. 4 is a fragmentary front elevational view of the assembly of the present invention, with parts in cross section.  
  FIG. 5 is a fragmentary elevational view of the structure of FIG. 4, as seen from the left of that Figure FIG. 6 is a side elevational view of the assembly of the present invention illustrating the lift gate in its lowermost position.  
  FIG. 7 is a fragmentary side elevational view similar to FIG. 6, but illustrating the lift gate in an intermediate position.  
  FIG. 8 is a fragmentary side elevational view similar to FIGS. 6 and 7, but illustrating the lift gate in its uppermost position.  
  FIG. 9 is a framentary, perspective, exploded view illustrating a pair of channel members and an intermediate roller-carrying member of the present invention.  
  FIGS. 10 and 11 are fragmentary plan views, partly in cross section, illustrating the lift gate control means of the present invention.  
  FIG. 12 is a fragmentary side elevational view of another embodiment of the assembly of the present invention illustrating the lift gate in its lowermost position.  
  FIG. 13 is a fragmentary side elevational view, similar to FIG. 12, but illustrating the lift gate in its uppermost position.  
  FIG. 14 is a cross sectional view taken along the section line 14-14 of FIG. 13.  
 BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS While the lift gate assemblies of the present invention may be assembled during the construction of the vehicle to which they are applied, they lend themselves well to assembly as unitary structures, in and of themselves, and may be applied as a unit to a vehicle under construction or an already existing vehicle. The type of vehicle to which a lift gate assembly of the present invention may be applied may be applied does not constitute a limitation on the invention. Nor are the assemblies necessarily limited to their application to a vehicle. For purposes of an exemplary showing, however, the assemblies will be illustrated as applied to a truck of the type shown in U.S. Letters Pat. No. 3,207,166.  
  In FIG. I, the truck is generally indicated at l, and a first embodiment of the lift gate assembly is generally indicated at 2. The truck is illustrated as having a body 3 with side walls 4 and 5, a top or roof 6 and a bottom or bed 7.  
  In general, the lift gate assembly comprises a lift gate 8 movably affixed to a rectangular frame. The rectangular frame comprises vertical frame members 9 and 10. The frame members 9 and 10 are joined at the upper ends by an upper crosstie or frame member 11 at the level of the top 6 of the vehicle body and a lower crosstie or frame member 12 located at the vehicle bed 7.  
  For a more detailed description of the assembly of the present invention, reference is made to FIGS. 2 through .9, wherein like parts have been given like index numerals. As is most clearly shown in FIG. 3, the vertical frame member 9 has a generally L-shaped cross section and comprises a rear wall portion 9a, a side wall portion 9b and a front wall portion 90. The frame member 9 extends from the vehicle top 6 to a point below the vehicle bed 7. The verticalframe member 10 is a mirror image of the frame member 9 and has a rear wall portion 10a, a side wall portion 10b and a front wall portion 10c (FIGS. 1 and 6). The upper cross tie 11 may have any suitable configuration. For purposes of an exemplary showing it is illustrated in FIGS. 4 and as having a rectangular cross section. The crosstie II is affixed to the rear wall portion 9a of the vertical frame member 9 by spacer means 110, so that the crosstie I1 is spaced slightly rearwardly of the rear wall portion 9a. It will be understood by one skilled in the art that the crosstie II is similarly affixed to the rear wall a of vertical frame member 10.  
  The lower crosstie 12 is shown in FIGS. 4 and 5 as being directly affixed to the rear wall portion 9a of the vertical frame member 9. It will be understood that it is similarly affixed to the rear wall portion 10a of the vertical frame member 10.  
  As is most clearly shown in FIGS. 3, 4 and 5, the forward facing surface of the rear wall portion 9a of the vertical frame member 9 carries a channel member 13.  
 The channel 13 is of C-shaped cross sectional configuration and extends substantially from the top to the bottom of the rear wall portion 9a.  
  As shown in FIGS. 3 through 5, the right rear corner of the tail gate 8 is affixed by pivot means 14 to a brace means 15. The brace means 15 is, in turn, affixed to a channel member 16 of C-shaped cross sectional configuration. The channel members 13 and 16 are substantially identical except that the channel member 16 is considerably shorter than the channel member 13. The longitudinal opening 13a of channel member I3 and the longitudinal opening of channel member 16 face each other. The&#39;channel member 13 and the channel member 16 are joined together by an intermediate roller-carrying member 17. I  
  The channel member 13 and 16 and the intermediate member 17 are most clearly shown in FIG. 9. It will be noted that at its upper end channel member 13 has a pair of stops l8 and 19. At the lower end of the channel member an additional pair of stops 20 and 21 are provided. In similar fashion, channel member 16 has a pair of stops 22 and 23 affixed to its upper end. At the lower end of this channel member there is located a similar pair of stops 24 and 25 (see FIG. 4). With respect to all of the pairs of stops 18-19, 20-21, 22-23 and 24-25 a single stop, rather than a pair of stops, could be provided. The purpose of these stops will be described hereinafter.  
  The intermediate member 17 comprises a rectangular plate having 8 pairs of slightly staggered rollers affixed thereto. The rollers of each pair are mounted on either side of the plate. Four of the roller pairs are indicated at 26-2611, 27-270, 28-280 and 29-29a. The remaining four roller pairs are indicated at 30-30:: through 33-33a, only one roller of each pair being visible in this Figure (see also FIG. 15). Finally, the intermediate member I7 is provided with a centrally located stop 34. A similar stop is located on the opposite side of the intermediate member and is shown at 35 in FIG. 3.  
  It is evident from FIGS. 3 and 7 that when the channel members 13 and 16 are joined together by the intermediate member 17, the roller pairs 26-26a, 27-270, 28-28a and 29-29a will be located within the channel member 16. Similarly, the roller pairs 30 through 33 will be located in the channel member 13. The stops 34 and 35 on the intermediate member will be located between channel members l3 and 16 and will be so positioned as to contact the stops on these channel members. Thus, channel members 13 and 16 are joined together by means of intermediate member 17, which is captively held in the channel members.  
  Turning to FIG. 6, 7 and 8, it will be noted that the rear wall portion 10a of the frame member 10 supports a channel member 36 equivalent to the channel member 13. The channel member 36 bears two pairs of stops, one stop of which is shown at 37 and one stop of which is shown at 38.  
  The other rear corner of the lift gate 8 is affixed by pivot means to a brace means 40. The pivot means 39 and brace means 40 are equivalent to the pivot means 14 and brace means 15 of FIGS. 4 and 5. The brace means 40 is affixed to a channel member 4] equivalent to channel member 16. As is the case with channel member 16, channel member 14 is provided with an upper pair of stops. one stop of which is shown at 42 and a lower pair of stops, one stop of which is shown at 43. Again the stops 37 and 38 on channel member 36 and the stops 42 and 43 on channel member 41 may be single stops, rather than pairs of stops, if desired.  
  An intermediate member 44 is illustrated in FIGS. 6 through 8 and is substantially identical to the intermediate member 17 of FIG. 7. The intermediate member 44 carries eight pairs of rollers and these roller pairs are indicated at 45-4511 through 52-5211. Finally, the intermediate member 44 is provided with a pair of centrally located diametrically opposed stops, one of which is shown at 53. The various roller pairs of the intermediate member 44 cooperate with the channel members 36 and 41 in the identical manner described with respect to FIG. 7. The stops on these channel members and on the intermediate member 44 also cooperate in the manner described.  
  From the above description it is evident that the lift gate 8 is pivotally affixed to channel members 16 and 41. These channel members are, in turn, movably affixed to channel members 13 and 36 via intermediate members 17 and 44, respectively. The stationary channel members 13 and 36 are, in turn, affixed to vertical frame members 9 and 10.  
  FIGS. 6. 7 and 8 illustrate the operation of channel members 36 and 41 and intermediate member 44 during movement of the lift gate 8. It will be understood that channel members 13 and 16 and intermediate member 17 cooperate in an identical manner. FIG. 6 illustrates the lift gate in its lowermost or ground level position. In this position, it will be noted that the stops 53 on intermediate member 44 have contacted the stops 38 on the stationary channel member 36. Thus, intermediate member 44 has reached the lowest position it can attain. The channel member 41, bearing the lift gate 8, has reached its lowermost position as deter mined by the abutment of its stops 42 and the stops 53 on the intermediate member 44. Since the intermediate member 44 is captively held both in channel member 36 and channel member 41, it will offer sufflcient support for the channel member 41 and the lift gate 8.  
  As will be evident from FIG. 6, if the lift gate 8 and the attached channel member 41 are caused to move upwardly. the lowermost stops 43 on the channel member 41 will ultimately contact the stops 53 on the intermediate member 44. By virtue of this, as the lift gate proceeds upwardly, the intermediate member 44 will be carried upwardly with it. This is illustrated in FIG. 7. wherein like parts have been given like index numerals.  
  In FIG. 8, the lift gate is illustrated in its uppermost position, wherein it is substantially level with the top 6 of the vehicle body 3. Again like parts have been given like index numerals. It will be noted that contact between the stops 43 on the channel member 41 and the stops 53 on the intermediate member 44 have caused the intermediate member to be carried upwardly to its uppermost position. This uppermost position is determined by the abutment of stops 53 on the intermediate member and stops 37 and on the channel member 36.  
  From the above description it will be evident that the intermediate member 44 is capatively held in the channel members 36 and 41 and that in all positions of the lift gate 8, at least two pairs of rollers on the intermediate member will be in each of the channel members 36 and 41.  
  The drive means for causing movement of the lift gate between its lowermost and uppermost positions is illustrated in FIGS. 4 and 5. A horizontally oriented shaft 54 is rotatively supported by conventional shaft hangers (not shown) affixed to the upper crosstie 11. At one end, the shaft carries a sprocket 55. The sprocket is, in turn, engaged by a roller chain 56. One end of the roller chain 56 is anchored to the lift gate, as at 57. The other end of the roller chain is provided with a weight 58 adapted to ride in a chain race channel 58a affixed to the rear wall portion 9a of the vertical frame member 9 (see also FIG. 3). It will be noted that the rear wall portion 9a of the vertical frame member 9 has a notch 59 therein, to provide clearance for the sprocket 55. A chain guard and guide 59a extends part way about sprocket 55 and partially into the chain race channel 58a. The chain guard may be supported from the upper cross tie 11 by brace means as shown in FIG.  
  It will be understood by one skilled in the art that the other end of the shaft 54 will carry a sprocket 55a identical to sprocket 55. That sprocket will, in turn, carry a roller chain 56a (similar to chain 56), one end of which is affixed to the opposite corner of the lift gate 8 and the other end of which is provided with a weight equivalent to weight 58 adapted to ride in a chain race channel equivalent to channel 58a and affixed to the rear wall portion of 10a of frame member 10.  
  From the above description it will be evident that as the shaft 54 (as seen in FIG. 5) is caused to rotate in a counter clockwise direction, the chain 56 and its counterpart 56a on the other side of the lift gate assembly will cause the lift gate to move upwardly. Similarly, rotation of the shaft 54 in a clockwise direction will cause the lift gate 8 to move downwardly. It will be noted in FIG. 5 that the portion of the chain 56 which performs the pulling action lies in a single, straight, vertical flight from the lift gate to the sprocket 55. The remainder of the chain will simply move downwardly from the sprocket 55 into the chain race channel 58a under the influence of weight 58. The same will be true of the chain 55a on the other side of the lift gate assembly.  
  The driving means for causing rotation of the shaft 54 does not consitute a limitation on the present invention. Any suitable prime mover may be used. For example, the prime mover may comprise an internal combustion engine, an electric motor or the like. A brake and sprocket assembly,,driven by an electric or a hydraulic motor may be used. For purposes of an exemplary showing, however, the shaft is illustrated in FIGS. 1 through 3 as being driven by a low-speed, hightorque, rotatory hydraulic power unit (generally indicated at 60) of any suitable and well known type. In an exemplary installation, the shaft may be provided with an appropriate gear and the hydraulic motor may be provided with a suitable worm. The hydraulic motor 60 is connected to a control valve 61 by hydraulic lines 62 and 63. The valve is, in turn, connected to a source of hydraulic fluid under pressure (not shown) by inputs and return lines 64 and 65. The valve 61 is affixed to the rear wall portion 9a of the vertical frame member 9 by suitable bracket means 66. Means are provided on the lift gate assembly of the present invention whereby the operator may stand on the lift gate and operate control valve 61 irrespective of the position of the lift gate. I  
 These means are most clearly shown in FIGS. 3 through 5. l0 and 11. An elongated, vertically oriented rail 67 is pivotally affixed to the inside surface of side wall portion 9c of the vertical frame member 9, as at 68 and 69. It will be noted from FIG. 3 that the rail 67 is of T- shaped cross sectional configuration with the leg of the T extending away from the inside surface of the wall portion 9b.  
  Affixed to the rear surface of the rail 67 there is a lever 70 which extends through a slot 71 (FIG. 4) in the side wall portion 9b of the vertical frame member 9. The lever 70 is pivotally affixed to a link 72 which, in turn, is affixed to the stem 66a of the valve 66. Thus, as the rail 67 is caused to pivot about its pivot points, the lever 70 will pivot with it and, through the agency of link 72, will cause the valve stem 66a to move inwardly or outwardly.  
  A short channel member 73 is hingedly affixed, as at 74 and 75 to hangers 76 and 77. The hangers 76 and 77 are, in turn, affixed to angle irons 76a and 77a welded to the movable channel means 16. The channel member 73 has an elongate opening 73a therein, so positioned as to receive the leg of the T rail 67. In addition, the channel member 73 carries a handle 78.  
  FIG. 10 illustrates the control mechanism in its normal position. In this position, no hydraulic fluid flows through valve 66 and the lift gate will be stationary is whatever position it was stopped. In FIG. 11, manipulation of the handle 78 has caused the channel member 73 to pivot in a clockwise direction about its pivot point 74. The interaction of the rail 67 and the channel member 73 has caused the attached lever 70 to pivot in a counter clockwise direction about the pivot points 68 and 69 (FIG. 4). This has, in turn, resulted in the link 72 moving the valve stem 66a to its intermost position. This. in turn, will result in the flow of hydraulic fluid through the valve 65 and the motor 60, causing rotation of the shaft in a given direction with resultant movement of the lift gate in the direction dictated by the shaft rotation. It will further be evident from FIG. 11 that counter clockwise rotation of the handle 78 and channel 73 about the pivot points 74 and 75 will cause clockwise rotation of the rail 67 and attached lever 70. This, in turn, will cause the valve stem 66a to assume its outermost position, via link 72. Again, hydraulic fluid will flow through valve 66 and hydraulic motor 60. The rotation of the motor 60 and shaft 54 will be in the opposite direction, however, resulting in the opposite movement of the lift gate 8.  
  As is most clearly shown in FIG. 10 and 11, that end of hanger 76 which passes through angle iron 76a is threaded and provided with nuts 76b and 76c on either side of the angle iron. It will be understood that the same is true with respect to hanger 77. In this way, the hangers 76 and 77 may be adjusted longitudinally so that the channel member 73 properly coacts with the T rail 67.  
  Finally, since the tail gate of the assembly of the present invention is capable of movement to a position level with the top of the vehicle I, it is within the scope of the present invention to provide a cover member for the shaft 54 to protect the operator as he steps from the tail gate 8 to the vehicle top 6. Such a cover member is shown in FIG. 1 and 2 at 79.  
  FIGS. 12, 13 and 14 illustrate another embodiment of the lift gate of the present invention. In this Figure, the side wall 5 and top 6 of the truck body 3 are shown, these index numerals correspond to those used in FIG. 1. The rear wall 9a of vertical frame member 9 is also shown (again see FIG. I) mounted on the rear wall 9a there is a vertically oriented, stationary channel 79 which is substantially identical to the channel member 13 of FIG. 3, except that it extends slightly above the top 6 of the vehicle body. Slidably mounted within the stationary channel 79 there is a roller bearing element 80 having a plurality of slightly staggered roller pairs mounted on either side near its rearward longitudinal edge. These rollers are indicated at 81-8la through 85-850. Near the bottom of the roller-carrying element 80, there is illustrated an angle iron 86. As is most clearly shown in FIG. 14, the angle iron 86 is affixed to a spacing block 87, which, in turn, is affixed to the roller-carrying element 80. The angle iron 86 has a perforation 88 therein on the rear side of the angle iron there is a cylindrical sleeve 89 which forms an extension of the perforation 88. The sleeve 89 is affixed both to the angle iron 86 and to a spacing block 90 which, in turn, is attached to the roller-carrying element 80.  
  The angle iron 86 and spacing block 87 and 90 serve as mounting means for the lift gate (not shown). The lift gate will be provided with an appropriate pivot pin to be received in perforation 88 and sleeve 89. Thus, the tail gate will be swingable from a vertical position when not in use to a horizontal position, it being maintained in the horizontal position by engagement with the horizontal flange portion of the angle iron 86.  
  FIG. 12 illustrates the lift gate mechanism in its lowermost position. The side of the roller-carrying element 80, opposite the side shown, is provided with a stop member 91 indicated in dotted lines. The lowermost end of the stationary channel 79 has a cooperating stop 92 (see FIGS. 12 and 14). The abutment of stop 91 against stop 92 determines the lowermost position of the assembly. It will be noted that in its lowermost position wheel pairs 81-810 and 82-820 are captively held in the stationary channel 79, providing sufficient support for the lift gate.  
  FIG. 13 is similar to FIG. 12 and like parts have been given like index numerals. FIG, 13 differs from FIG. 12 in that it shows the lift gate assembly in its uppermost position. In this position, the lift gate itself (not shown) will be substantially level with the top 6 of the vehicle body 3.  
  Near its upper end, the stationary channel 79 is provided with a stop 93. The uppermost position of the assembly is determined by the abutment of the stop 93 and the spacing bock 87. This is illustrated in FIG. 14.  
  It will be understood by one skilled in the art that in substantially all other respect the embodiment of FIGS. 12 through 14 is substantially identical to the previously described embodiment. The lift gate of the assembly of FIGS. 12 through 14 will be raised and lowered by means of roller chains passing over sprockets mounted on a shaft, as described with respect to FIGS. 4 and 5, for example. Again, the shaft will be rotated by a prime mover which may be of the type described with respect to FIG. 2. The hydraulic motor will be controlled by valve means of the type shown at 61, which valve means will be controlled by the same elements shown in FIGS. 10 and 11. As a consequence, the channel member 73, hangers 76 and 77 hanger mounts 76a and 77a and control handle 78 are all shown in FIGS. 12 and 13, like parts having been given like numerals. Again, the hangers 76 and 77 are longitudinally adjustable. The primary difference between the embodiment of FIGS. 12 through 14 and the previously described embodiment being that the movable channel member 16 has been eliminated and the rollercarrying element 80 has been substituted for the intermediate member l7 (see FIG. 9). As a consequence, the hanger mounted 76a and 77a are, in the embodiments shown in FIGS. 12 and 13, affixed directly to the roller-carrying element 80. Again it will be understood that an assembly of the type shown in FIGS. 12 and 13 will be provided at the other rear corner of the vehicle with the other corner of the lift gate pivotally affixed thereto.  
  Modifications may be made in the invention without departing from the spirit of it.  
  The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
  l. A lift gate assembly comprising a frame, said frame comprising a pair of vertical frame members in parallel spaced relationship, an upper crosstie and a lower crosstie joining said vertical frame members, each of said vertical frame members having a stationary vertically oriented channel member affixed thereto, said channel members being of C-Shaped cross-section, the longitudinal openings of which face in the same direction and away from said vertical frame members, rollercarrying units, each of said roller-carrying units comprising a vertically oriented, elongated, plate-like structure having longitudinal sides and forward and rearward edges, each of said units having a plurality of vertically aligned pairs of rollers adjacent said rearward edge thereof, the rollers of each pair being located on opposite sides of said unit, said rearward edges of each of said units extending within said longitudinal opening of one of said channel members, said roller pairs along said rearward edge of said unit being located in and rotatable in said channel member, each of said units being movable vertically with respect to its respective channel member between an upper position wherein a portion of said unitextends above said channel member and a lower position wherein a portion of said unit extends below said channel member, stop means operatively connected to said units and said channel members to cause each of said units to be captively held in and at all times having at least two roller pairs in its respective channel, a lift gate, said lift gate being affixed to the lower ends of said plate-like structures, means for vertically moving said units and&#39;lift gate between said upper and lower positions and means to control said moving means.  
  2&#39;. The structure claimed in claim 1 including a vehicle having a body, said body having a top, a bed, side walls, a forward end and a rearward end, said frame being affixed to said rearward end of said body, said lower position of said lift gate being a ground level position below said bed and said upper position of said lift gate being a position level with said body top.  
  3. The structure claimed in claim 1 wherein said lift gate is pivotally affixed to said plate-like structures and swingable between a horizontal position when in use and a vertical position when not in use.  
  4. The structure claimed in claim I wherein said means to move said units and said lift gate comprises a shaft rotatively mounted on said frame, a pair of sprocket non-rotatively affixed to said shaft near the ends thereof, a chain engaging each sprocket, one end of each chain being affixed to said lift gate, the other end of each chain being free and having a weight affixed thereto, motor means for rotating said shaft in either direction and means for controlling said motor means.  
  5. The structure claimed in claim 4 including a channel shaped chain race affixed to each of said vertical frame members, each of said chain races being configured to receive said free and weighted end of one of said chains.  
  6. The structure claimed in claim 4 wherein said motor means comprises a hydraulic motor, a source of hydraulic fluid under pressure connected to said motor, said control means for said motor comprising a valve means in said connection between said source of hydraulic fluid under pressure and said motor to start and stop flow of said fluid through said motor and to determine the direction of said flow, and manually operable control means for said valve, said control means being movable vertically with said lift gate.  
  7. The structure claimed in claim 1 wherein said lift gate is pivotally affixed to said roller-carrying units and swingable between a horizontal position when in use and a vertical position when not in use.  
  8. The structure claimed in claim 1 wherein said upper and lower positions of said units and said lift gate are determined by cooperating stop means on said units and their respective channel members.