Abstract:
A lift assembly that can be reversibly installed in the bed of a pick-up truck or other flat bed transport means. At least four telescoping support legs are disposed at the four corners of the truck bed and support the upper rails on which the load is placed. The support legs are made up of a series of nested threaded segments driven by a similarly threaded drive shaft. A reversible motor associated with each support leg enables the segments to rotate in a forward direction to raise the load and to rotate in the reverse direction to lower the load. The motors are activated simultaneously and powered by the truck battery. The raising and lowering motion is smooth and continuous and can be stopped at any desired height. The lift assembly enables the height of the load to be easily changed by one person without any disturbance or shifting of the load. Telescoping braces are available to stabilize the support legs when fully extended and protective sleeves can be used to eliminate damage to the mechanism from environmental contaminants.

Description:
FIELD OF THE INVENTION 
     The instant invention relates to a carrier rack lift assembly for use with pick-up trucks, flat bed trucks and trailers and more particularly to a lift assembly having telescoping support members that can be raised to any desired height within a specified range for supporting and maintaining a wide variety of loads. 
     BACKGROUND OF THE INVENTION 
     The well known truck racks are used to increase the usefulness of pick-up trucks, flat bed trucks and trailers. Many of the prior art racks must be permanently fastened to the truck bed and are available at one specific height. Some may be adjustable to two or three preset heights while a few may exhibit a wider range of adjustability. In most of the adjustable prior art racks, any change in the height of the rack must be accomplished when there is no load resting on the upper portion of the rack and require more than one person to effect the change. The prior art racks are, in actuality, merely support frames with limited versatility. They are not designed to be completely height adjustable nor are they designed for adjustability under heavy loads. Changes in height cannot be made by one person. None of the prior art rack assemblies are meant to secure the interior of the truck bed or to provide any other functions. 
     Hart, in U.S. Pat. No. 2,720,414, describes a rack that is made in sections and is mounted on the body of a pick-up truck. All four sides of the rack are horizontally adjustable to fit a variety of truck bed lengths. Each of the four vertical support posts have one height adjustable member which can raise the upper horizontal supports high enough so that long boards can be extended over the cab of the truck. Both horizontal and vertical adjustments are made possible with outer tubes having multiple openings along their open ends and inner tubes with one opening. The inner tubes are inserted into the outer tubes to the desired distance and secured in place with pins. A load being supported on the rack must be completely removed in order to alter its height and more than one person would be needed to accomplish this. The rack cannot be collapsed and, if not needed, the entire rack must be removed from the truck bed and stored elsewhere. 
     In U.S. Pat. No. 5,190,337, McDaniel discloses a collapsible rack for use within the bed of a pick-up truck. The rack has four vertical legs, each having two segments connected by a knuckle joint which enables the legs to be folded downward when the rack is not in use. The bottom segments are pivotally mounted to base plates anchored to the truck bed and which run along its horizontal axis. An angled brace extending from mid base plate to the top of each rear leg gives added support to the frame when elevated. There is a side rail on each side of the rack mounted at the top of each pair of legs. A frame extension extends from each side rail over the cab to support long loads. The entire frame collapses flat along the sides of the truck bed when not in use and the parts of the rack fit within channels in the side rails for protection from the elements. The rack can only be used in the one elevated orientation and is stored in the collapsed orientation which takes up space in the truck bed. 
     An adjustable rack is taught by Berkich in U.S. Pat. No. 5,476,301. The height of the four vertical supports can be adjusted by raising the upper segments having a series of apertures and securing their positions with pins or bolts through corresponding apertures in the lower segments. The height of each support must be adjusted individually making it difficult to do while a load is supported on the rack. There are extensions of upper side rails over the cab that can reach as far as the front bumper, as well as rearward extensions beyond the tailgate. When the vertical supports are in the lowermost positions they rest below the sides of the truck and a cover, cap or camper can be used within the truck bed. This rack is not practical if the height of the rack must be changed with any frequency or with a load in place. 
     James, in U.S. Pat. No. 5,628,540, discloses another pick-up truck utility rack. The four vertical supports of this rack are mounted on the upper surfaces of the sides of the truck bed. There is a panel attached to the two forward supports which is hinged to pivot downward to form a shelf with a brace to limit the movement to 90°. A movable lower rail is attached to the rear supports and can be lowered to the level of the shelf with which it forms a second level to support a load. An extension can be used over the cab so that long boards can be carried. The vertical supports are of fixed length and once set in place remain stationery. Any load placed at mid-level can only be of the dimensions of the truck bed. 
     A camper for mounting in the bed of a pick-up truck is taught by Eckman et al. in U.S. Pat. No. 3,743,345. The camper has four telescoping corner support posts, each formed in three tubular sections that are square in cross section and have multiple apertures long their lengths. The supports are raised to the desired height and each segment is secured with a pin that is kept in place by a spring detent. There is a wood reinforced plastic roof that may be used in a horizontal orientation or it may be raised from one side to provide a slanted roof. A notched slotted bracket with a sliding bolt is used to set the angle of the roof. The roof height may be set at many different levels due to the many apertures in the tubular segments, but each post must be set individually. Once the roof is in place, adjustment to a different height may require more than one person. Canvas side flaps form the vertical walls of the camper. Horizontal arms secured to the uppermost sections of the corner support posts may be used to extend the camper space and can be covered by the canvas flaps. The entire camper unit can be removed and used as a tent independent of the truck. The canvas flaps only provide shelter from the elements but do not secure the interior of the camper. There is no way to raise all of the posts at the same time. 
     A lumber rack-camper as taught by Ingram in U.S. Pat. No. 5,423,587 has a non-adjustable rack frame which can be reversibly attached to the sides of a pick-up truck. There is an over-cab extension for carrying long boards and several cross rafters are supported on the tops of the corner vertical supports and intermediate posts supported on side frame members. A flexible cover is placed over the rafters to enclose the camper. The front of the cover fits over the extension and is supported by angled braces to proved and an air dam so the truck can travel at highway speeds while the camper cover is in place. Each side panel of the cover can be rolled up or down independently, but they do not secure the interior compartment. The corner supports are not adjustable. 
     Modifications to the side walls of a pick-up truck to provide secure storage compartments are taught by Clare et al. in U.S. Pat. No. 6,033,002. The storage compartments are hidden and built into the side walls. They are accessed through top mounted doors. A carrier rack that can be collapsed into the truck bed is also disclosed. The rack has a swivel mounted cab extension that folds backward for storage. The four supports for the rack may have two or three nesting segments and are adjustable by means of apertures and pins. When collapsed into the truck bed the rack cannot be seen from the outside. All adjustments to the height of the rack must be made one support at a time and only the storage compartments hidden in the side walls provide any security. 
     Though the prior art describes a variety of carrier racks for use with pick-up trucks, none of the prior art patents disclose a carrier rack lift assembly that can be raised and set at any desired height. Those with a degree of adjustability are limited to being set at specific levels according to the apertures in the support segments. None of the adjustable prior art rack lift means can easily be manipulated by one person. None of the prior art patents disclose an electrically powered carrier rack lift assembly that can be adjusted at the press of a button and raised to any desired height. And none of the prior art patents teach a rack lift assembly whereby any adjustment in height can be made with a full load of cargo in place. There is a need for a carrier rack lift assembly that exhibits all of the above-mentioned features and that is practical for use with all pick-up and flat bed trucks and carriers. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention may provide a carrier rack lift assembly for use with pick-up trucks, flat bed trucks and trailers. The lift assembly of the instant invention may be reversibly secured to the truck bed such that it may be removed when not needed. The essence of the lift assembly may be the four electrically activated support posts which may be completely collapsible to a height of only 13 inches (33 cm) from the truck bed and may be telescoped upward to a height of 65 inches (165 cm) from the truck bed. The support posts may also be set at any desired height in between by merely pushing a button. A roof cover in the form of a traditional cap or other such cover may be used with the lift assembly, and side panels may be added to enclose an interior compartment to make it secure from inclement weather conditions and outside tampering. 
     It is an object of the present invention to provide a carrier rack lift assembly that can be set at any desired height without the incremental limitations requiring specific openings in the telescoping support posts. 
     It is another object of the present invention to provide a lift assembly that is reversibly attached to the truck bed such that it can be removed when not needed. 
     A further object of the present invention is to provide a lift assembly that is operated electrically so that it can be manipulated by the touch of a button. 
     A still further object of the present invention is to provide a lift assembly that can be operated by one person. 
     Another object of the present invention is to provide a lift assembly that is adjustable and permits the height to be changed with a full load of cargo in place. 
     A still further object of the present invention to provide a lift assembly that can support a variety of upper rail systems. 
     A further object of the present invention is to provide a lift assembly that can support and raise loads of considerable weight at the push of a button. 
     It is another object of the present invention to provide a lift assembly that can be electrically wired such that the telescoping support posts can be raised simultaneously or in any desired combination or sequence. 
     Another object of the present invention is to provide a lift assembly that can be used with conventional truck caps or other roof covers. 
     The present invention is a rack lift assembly, for use with pick-up trucks, flat bed trucks and trailers having a horizontal cargo bed, and being capable of raising and supporting an elevated utility rack. The rack assembly comprises at least four telescoping support legs, each situated at a corner of the cargo bed, and each of the support legs comprising a series of nested rotatable cylindrical segments, an outer first segment and at least one inner second segment, the first segment being smooth on its exterior surface and having at least two threads situated at the bottom of its interior surface, and the second segment being threaded on its exterior surface, having a stop means at the top of its exterior surface and a stop means at the bottom of its exterior surface, and having at least two threads situated at the bottom of its interior surface. The stop means is to prevent the segments from becoming dissociated. There is a canister for containment of the segments; a support frame to support the canister on the cargo bed; a drive shaft to rotate the segments, the drive shaft being positioned axially within the nested segments, being threaded for substantially the upper three fourths of its length, and having a stop means at its top and another stop means situated below the threads, the stop means for preventing the drive shaft from becoming dissociated from said segments. The threads on the segments and the drive shaft are of the same dimensions for cooperation therebetween. There is a means to rotate the drive shaft in a forward direction and in a reverse direction and a top cap to which the rack is affixed. When a utility rack is supported on the four support legs and the rotation means causes the drive shafts to be rotated in the forward direction the segments rotate in the forward direction and move upward such that the support legs telescope upward raising the utility rack, and when the rotation means causes the drive shaft to be rotated in the reverse direction the segments rotate in the reverse direction and are moved downward such that the support legs are collapsed and the utility rack is lowered. 
     The present invention is also a lift assembly for smoothly raising and lowering a load. The lift assembly comprises a series of nested rotatable cylindrical segments, an outer first segment being smooth on its exterior surface and having at least two threads situated at the bottom of its interior surface, at least one inner second segment being threaded on its exterior surface, having a collar about the top of its exterior surface and a collar about the bottom of its exterior surface and having at least two threads situated at the bottom of its interior surface. There is a canister for containment of the segments, a support frame to support the canister on a horizontal surface, a drive shaft to rotate said segments the drive shaft being positioned axially within the nested segments, being threaded for substantially the upper three fourths of its length, and having a first collar about its top and a second collar situated below the threads. The threads on the segments and the drive shaft being of the same dimensions for cooperation therebetween, and the collars on the segments and the drive shaft being capable of acting as stops to prevent said segments from becoming dissociated. There is a rotation means to rotate the drive shaft in a forward direction and in a reverse direction and a cylindrical top cap on which the load is supported. When the load is supported on the lift assembly and the rotation means causes the drive shaft to be rotated in the forward direction the segments rotate in the forward direction and move upward such that the lift assembly telescopes upward raising the load, and when the rotation means causes the drive shaft to be rotated in the reverse direction the segments rotate in the reverse direction and are moved downward such that the lift assembly is collapsed and the load is lowered. 
    
    
     Other features and advantages of the invention will be seen from the following description and drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a rear perspective view of a typical pick-up truck. 
     FIG. 2 is a rear perspective view of the pick-up truck with the rack of the instant invention raised to the level of the truck cab. 
     FIG. 3 is a rear perspective view of the pick-up truck with the rack raised to a level above the truck cab. 
     FIG. 4 is a rear perspective view of the pick-up truck with the rack raised to its full height and with side panels lowered to fully enclose the truck bed. 
     FIG. 5 is a rear view of the truck of FIG.  3 . 
     FIG. 6 a schematic cutaway view of the main components of the lifting mechanism; 
     FIGS. 7-A through  7 -F are schematic cutaway views of six of the threaded segments; 
     FIGS. 8-A through  8 -D are schematic cutaway scale views of the four innermost segments; 
     FIG. 9 is a schematic cutaway view of the outermost segment; 
     FIG. 10 is schematic cutaway view of the support frame; 
     FIG. 11 is top plan view of the support frame of FIG. 10; 
     FIG. 12 is a partial cutaway view of the canister; 
     FIG. 13 is a side view of the drive shaft; 
     FIG. 14-A is a side view of the large Browning pulley; 
     FIG. 14-B is a s sectional view through line B—B of FIG. 14-A; 
     FIG. 15 is a schematic cutaway view of the complete lifting mechanism; 
     FIG. 16 is top plan view of the complete lifting mechanism; 
     FIG. 17-A is a top plan view of the bearing plate; 
     FIG. 17-B is a sectional view through line B—B of FIG. 17-A; 
     FIG. 18-A is a side partial cutaway view of the complete lifting mechanism in the fully collapsed orientation; 
     FIG. 18-B is a side partial cutaway view of the complete lifting mechanism in the fully extended orientation; 
     FIG. 19 is a top plan view of the bed of a pick-up truck with the lifting mechanism in place; 
     FIG. 20 is partial perspective view of the lifting assembly and brace; 
     FIG. 21 is a perspective exploded view of the top cap and bearings; 
     FIG. 22 is a partial cutaway view of the top cap and bearings; 
     FIG. 23 is a bottom plan view of the top cap without the bearings; 
     FIG. 24 is a partial cutaway view of the left assembly and brace with the sleeves; 
     FIG. 25 is a perspective view of a segment of the brace; and 
     FIG. 26 is a perspective view of the lift assembly being used with a trailer. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The carrier rack lift assembly  30  of the instant invention may be collapsible to a height of only 13 inches (33 cm) and may telescope to a height of 65 inches (165 cm) from the supporting surface. The lift assembly  30  may be compatible for use with a typical pick-up truck  35  (FIG. 1) which may have a cab  31 , a flat truck bed  32 , side panels  33  and a tailgate  34 . The lift assembly  30  may just as easily be used with a flat bed truck (not illustrated) or trailer  82 . The lift assembly  30  may be raised or lowered to any desired level from the fully collapsed orientation to the fully extended orientation. When fully extended, the top of the lift assembly with accompanying cargo rails  36  may reach a height of six feet above the truck bed  32 . The fully collapsed lift assembly  30  may not be visible above the side panels  33  of the pick-up truck  35 . 
     The truck  35  with the lift assembly  30  partially extended so that it may be observed above the side panels  33  may be seen in FIG.  2 . At this level the upper rails  36  situated at the top of the lift assembly  30  may accommodate various loads as long as they do not extend more than a few inches beyond the longitudinal dimensions of the rails  36  to insure that the objects placed on the rails  36  cannot strike the rear window  37  of the cab  31 . The lift assembly  30  may be raised further to levels above the top of the cab  31 , as seen in FIGS. 3 and 5 to accommodate longer loads. The fully extended rack  30  may be seen in FIG.  4 . 
     The lift assembly  30  may consist of four telescoping support legs  38  which may form the supporting structure for the rails  36 . The support legs  38  may be raised or lowered by means of an electric motor  73  powered by the truck&#39;s battery pack (not illustrated). A manual raising means may also be used, but is not illustrated or described herein. 
     Each support leg  38  may be comprised of a series of nested segments. The number of segments may determine the height of the fully extended support leg  38 . In the preferred embodiment, for use in pick-up trucks, each support leg may consist of seven nested segments  40 - 46  and a central drive shaft  47  contained within a cylindrical canister  39 . See FIG.  15 . (FIG. 6 shows the major parts but only five segments.) The canister  39  may act as a housing for the segments of the support leg  38 . A support frame  48  (FIGS. 10 and 11) may surround substantially three fourths of the circumference of the bottom third of the canister  39  and may serve to support the canister above the truck bed  32  a sufficient distance to allow the necessary moving parts to function properly. There may be three evenly spaced flanges  49  welded to the outside surface of the support frame  48  along its bottom edge. A band  61  may extend from one vertical edge  62  to the other vertical edge  62  of the support frame  48  such that the bottom edge of the support frame  48  that makes contact with the truck bed  32  may form a complete circle and may provide maximum stability to the support leg  38 . The flanges  49  may have openings  50  to accommodate bolts (not shown) used to anchor the support legs  38  to the truck bed  32 . There may be three bolts  51  passing through openings in the wall of the support frame  48  above the flanges  49  which may secure the support frame  48  to the canister  39 . 
     The seven segments  40 - 46  of the support leg  38  may be cylindrical and successively and incrementally smaller in diameter and longer in length. The outermost segment  40  (FIG. 9) may be the largest in diameter and the shortest in length. The outermost segment  40  may have a smooth outer surface and a smooth inner surface except for the presence of three threads  52  situated at the bottom interior edge. The other six segments  41 - 46  (FIGS. 7-A through  7 -F) may each have threads  53  along their entire exterior surfaces and smooth interior surfaces with the same three threads  52  situated at the bottom interior edges. Each of the six segments  41 - 46  may also have a collar  54  around the top of the exterior surface and another collar  55  around the bottom of the exterior surface. FIGS. 8-A through  8 -D provide slightly different views of four of the segments  43 - 46 . 
     The drive shaft  47  (FIG. 13) may be axially situated within the innermost segment  46  and may be of solid construction with threads  56  along the upper ¾ of its exterior surface. There may be a collar  57  around the top of the drive shaft  47  and another collar  58  situated below the threads  56 . The lower ¼ of the drive shaft  59  may have a smooth surface and the lower one inch (2.54 cm) of the drive shaft  47  may have a slightly smaller diameter and may be fitted with a vertically mounted flat sided key seat  60 . 
     The threads on the inner and outer surfaces of all of the segments  40 - 46  and on the drive shaft  47  may all be 5 Acme threads. The collars  54 ,  55  on the outer surfaces of the segments  40 - 46  and the collars  57 ,  58  on the drive shaft  47  may all be welded to the segments  41 - 46  and drive shaft  47  and may be substantially ¼ inch (0.64 cm) wide and the depth of the threads ( 52 ,  53  and  56 ) which are all the same, as noted above. 
     The cylindrical canister  39  (FIG. 12) may have smooth interior and exterior surfaces and may have a horizontal bearing plate  63  welded to the interior of the canister  39  just above the bottom edge. There may be a central opening  64  in the bearing plate  63  through which the drive shaft  47  may pass, and four evenly spaced smaller openings  65 . (FIGS. 17-A and  17 -B) An upper bearing  67  may be mounted on top of the bearing plate  63  and a lower bearing  68  may be mounted on the underside of the bearing plate  63 . The upper bearing  67  and lower bearing  68  may be secured by bolts  69  passing through the small openings  65  in the bearing plate  63  and secured by nuts  70 . The two bearings may assist in the smooth rotation of the drive shaft  47 . There may be two mounting ferrules  66  welded to the exterior of the canister  39  just above the level of the bearing plate  63 . The two mounting ferrules  66  may be situated within, and in close proximity to, the vertical edges  62  of the support frame  48 . 
     The lower end of the drive shaft  47  may pass through the upper bearing  67 , the central opening  64  of the bearing plate  63  and extend below the lower bearing  68  to communicate with the central opening  72  of a large Browning pulley  71  which may be disposed below the lower bearing  68 . The large Browning pulley  71  may have a channel  73  through the core extending from the central opening  72  to the perimeter. This channel  73  may be dimensioned to accept the key seat  60  of the drive shaft  47  to insure that there may be no slippage when the drive shaft  47  is rotated by the turning of the pulley  71 , (FIGS. 14-A and  14 -B). 
     Referring to FIG. 15, the large Browning pulley  71  may be made to turn by a motor  74  contained within a motor housing  75  that may be integral with a motor mount  76 . The motor mount  76  may be secured to the support frame  48  by means of two long threaded studs  77  projecting from the ferrules  66  of the canister  39 . The studs  77  may be bent to conform to the angles necessary to enable them to communicate with channels in the motor mount  76 . Nuts  78  may be located on both sides of the motor mount  76  to hold it securely at a specific distance from the support frame  48 . The nuts  78  may also permit adjustment of the distance of the motor mount  76  to the support frame  48  as described below. 
     The drive shaft of the motor  74  may be joined to a small Browning pulley  79  by a coupling  80 . The small Browning pulley  79  may be rotated by the action of the motor  74  which may be powered by the truck battery (not illustrated). A Browning belt  81  may cooperate between the large Browning pulley  71  and the small Browning pulley  79  to rotate the drive shaft  47 . The sizes of the large Browning pulley  71  and small Browning pulley  79  may be chosen to provide a 3:1 ratio, but other sizes may be selected to provide different ratios. 
     The Browning belt  81  may easily be changed or adjusted by loosening the nuts  78  and moving the motor mount  76  as needed along the studs  77 . To change the belt  81 , the motor mount  76  may be moved toward the support frame  48 , the belt  81  loosened and removed and the new belt put in place. The motor mount  76  may thereafter be moved away from the support frame  48  until the new belt is taut and the nuts  78  are tightened. The adjustment of the distance of the motor mount  76  to the support frame  48  may determine the tension on the Browning belt  81 . 
     In addition to the drive shaft being rotated by Browning pulleys and a Browning belt, the rotation may also be accomplished using a chain and sprocket assembly as well as a straight gear drive assembly consisting of two main gears and an idler gear. Neither the chain and sprocket assembly nor the straight gear drive is illustrated herein. 
     The support leg  38  may be made to rise as follows: when the motor  74  is activated the small Browning pulley  79 , the Browning belt  81  and thereafter the large Browning pulley  71  may be caused to rotate and with them the drive shaft  47 ; as the drive shaft  47  rotates, all of the nested segments  40 - 46  may rotate with it. Once the drive shaft  47  and the segments  40 - 46  revolve any one of the segments may begin to crawl upward until the lower collar  55  of the rising segment contacts the upper collar  54  of the adjacent concentric segment and it can go no farther. As the segments continue to revolve another segment may begin to move upward with the collars acting as the stops. This action may continue until all of the segments have moved upward to their fullest height and the support leg  38  has reached its full extension. The segments in each leg may not necessarily move in the same sequence but since all of the threads are alike the tops of the support legs  38  may rise at the same rate. Reversing the motor may reverse the process. The motor  74  may be stopped at any point thus enabling the support leg  38  to be raised or lowered to any desired level. 
     Since the threads on the interior and exterior of all segments  40 - 46  and the drive shaft  47  are the same (Acme 5 threads), the fact that the segments may rise in different sequences in the various support legs  38  will not effect the height attained by each leg  38  as long as the motors for all four of the support legs  38  are activated at the same time. This may be accomplished by the manner of wiring the electrical system which may have all support legs  38  activated by the same switch. The lift assembly  30  may lift a wide variety of loads to any desired height and maintain the loads in the same degree of horizontal orientation. Once the support legs  38  have reached the desired height the switch may be released. The support legs  38  may remain quite stable and retain their load until the height of the support legs  38  is changed by again activating the switch. 
     FIG. 18-A shows the fully collapsed support leg  38 . Line A-B may represent the width of the base of the leg which may be only 5 inches (12.7 cm) and line C-D may represent the overall height of 13 inches (33 cm). The fully extended support leg  38  may be seen in FIG. 18-B wherein line E-F may represent the fully extended height of 65 inches (165 cm). 
     The pick-up truck bed  32  may accommodate four support legs  38 , located in each of the four corners as seen in FIGS. 5 and 19. When used in a flat bed truck or trailer  82  (FIG. 26) six or more support legs may be needed. 
     The dimensions of the essential parts used in the preferred embodiment may be seen in Table I. The nested segments may be made of steel that is 0.625 in (1.588 cm) in thickness. A one horsepower motor may be used, as well as motors providing up to four horsepower. The preferred embodiment may utilize a 1.5 horsepower, 12 volt, 20 amp motor as exemplified by model #540-927-OM manufactured by FASCO. Pulleys having ratios other than 3:1 may provide different rates of rotation of the segments. The three threads  52  on the inside of each segment occupy the bottom ⅝ inch (1.59 cm) of the interior surfaces. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Dimensions of Preferred Embodiment 
               
             
          
           
               
                 Part 
                 height (in) 
                 (cm) 
                 exterior diameter (in) 
                 (cm) 
               
               
                   
               
             
          
           
               
                 Canister 39 
                 9½ 
                 24.1 
                 5¾ 
                 14.6 
               
               
                 Segment 40 
                 7{fraction (9/16)} 
                 19.2 
                 4{fraction (5/16)} 
                 10.9 
               
               
                 Segment 41 
                 7{fraction (25/32)} 
                 19.8 
                 3{fraction (15/16)} 
                 10 
               
               
                 Segment 42 
                 8{fraction (1/32)} 
                 20.4 
                 3⅜ 
                 8.6 
               
               
                 Segment 43 
                 8{fraction (5/16)} 
                 21.1 
                 2{fraction (13/16)} 
                 7.1 
               
               
                 Segment 44 
                 8½ 
                 21.6 
                 2¼ 
                 5.7 
               
               
                 Segment 45 
                 8{fraction (13/16)} 
                 22.4 
                 1{fraction (11/16)} 
                 4.3 
               
               
                 Segment 46 
                 9  
                 22.9 
                 1⅛ 
                 2.9 
               
               
                 Drive Shaft 47 
                 12{fraction (31/32)}  
                 32.9 
                  ¾ 
                 1.9 
               
               
                 Support Frame 48 
                 5{fraction (9/16)} 
                 14.1 
                 5  
                 12.7 
               
               
                   
               
             
          
         
       
     
     The support legs  38  may require a top cap  83  that will not interfere with the rotation of the segments. The top cap  83  may be in the form of a short cylinder that fits over and rests on top of the largest or outside segment  40 . There may be a flat top  84  on the top cap  83  that may by unadorned or the flat top  84  may accommodate one or more lugs  85  or other connectors. There may be two 0.25 inch (0.63 cm) plate bearings  86  inside the top cap  83  such as D- 35  bearings manufactured by Union Bearings. The inside of the flat top  84  may contain a circular bearing locator  87  which may maintain the bearings  86  in the center of the top cap  83 . The thickness of the bearing locator  87  may be equal to the thickness of the two plate bearings  86 . The lower bearing may rest directly on the segments  40 - 46  and the two bearings  86  may rotate with the segments. The top cap  83  itself may not rotate so that upper rails  36  or other structures supported on the support legs  38  are not disturbed by the rotation of the segments. (See FIGS. 21,  22  and  23 ) 
     The extension of the support legs  38  to a height of 65 inches (165 cm) may produce a degree of flexibility or wobble that may not be desired. To prevent any such effects in the extended legs a simple brace  88  may be set adjacent to each of the support legs  38 . (FIG. 20) The braces  88  may be composed of a series of nested telescoping brace segments  89 . Each brace segment  89  may be made from square metal tubing and may have a vertical slot  90  in one side, a stop knob  91  below the slot  90  and a stop collar  92  around the upper rim. (FIG. 25) The stop knob  91  of each segment may fit into the slot  90  of the larger segment below and may maintain the alignment of the segments as they are telescoped upward. The stop collars  92  may prevent the segments from falling into one another. The brace  88  may be attached to the support leg  38  at its top and at the bottom. There may be a square cap  93  attached to the uppermost and segment  89  of the brace  88  instead of a stop collar  92 . A curved attaching member  94  welded or otherwise affixed to the square cap  93  and also welded to the top cap  83  of the support leg  38  provides the upper attachment and may enable the support brace  88  to be raised simultaneously with the support leg  38  providing the added stability to the extended support leg  38 . There may be another curved attaching member  96  welded or otherwise affixed to the canister  39  and the lowermost brace segment  97  to provide the lower attachment. 
     The support legs  38  and the support braces  88  may be subject to a variety of weather conditions, road chemicals, dirt and other corrosive materials which may interfere with their smooth operation. To protect these open systems from undesirable outside conditions, protective sleeves  95  may be placed around both of them. The protective sleeves  95  may consist of telescoping rubber or other flexible polymeric sleeves that are folded accordion-style when in the compressed orientation and which easily extend upward when the support leg  38  and brace  88  are raised. The bottom of the sleeve  95  for the support leg  38  may be attached to the support frame  48  or canister  39  and the top may be attached to the top cap  83  so it may be pulled upward as the top cap  83  rises. The sleeve  95  for the support brace  88  may be attached to the lowermost segment of the brace and the brace cap  93  and may be likewise pulled upward as the brace  88  is extended. (See FIG. 24) Such sleeves are manufactured by McMaster Carr # 9421K17 (support leg  38  cover) and #9421K14 (brace  88  cover). 
     One of the four support legs  38  of the instant invention may be placed at each of the four corners of the bed  32  of a pick-up truck as shown in FIG.  19 . The best positioning of support leg  38 , motor housing  75  and support brace  88  may be as illustrated. For larger pick-up trucks, flat bed trucks and trailers  82  more than four support legs  38  may be utilized. (FIG. 26) 
     The basic lift assembly of the instant invention may be constructed with a drive shaft, and one segment, but at least two segments are preferable and as many segments as are needed to reach the desired height and perform the desired function may be utilized. The heights and diameters of the segments may also be made to accommodate the needs of the user and are not confined to the dimensions exemplified herein. 
     The four unit lift assembly may be electrically wired to insure that all support legs are activated simultaneously so that the load resting on the upper rack may be raised horizontally and kept level. Other arrangements of the wiring system may permit the two front support legs to be raised with one activation and t h e rear support legs to be raised with a second activation. This system may provide a dumping function. Another arrangement may enable the two right legs to be raised together and the two left legs to be raised together providing for a slanted roof support. Other combination may also be accomplished according to the sequence in which the support legs are electrically activated. 
     The lift assembly of the instant invention may be used to raise and support a wide variety of rack systems as well as top caps, covers and any other units used with flat bed trucks. 
     The support leg unit may itself have many other applications in addition to the uses in pick-up trucks and other truck and trailer beds as described above. An individual unit may be used as a jack and has considerable lifting capacity. A single unit with a ⅝ inch (1.59 cm) drive shaft may have a one ton lifting capacity and a single unit with a ⅜ inch (0.95 cm) drive shaft may have a 500 lb lifting capacity. Units may be made to lift up to three tons. Two support legs may be used to lift heavy items such as boats. Multiple support legs may also be utilized as the supports for temporary structures or variable height enclosures. 
     While one embodiment of the present invention has been illustrated and described in detail, it is to be understood that this invention is not limited thereto and may be otherwise practiced within the scope of the following claims. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 SLOSS PARTS LIST 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 30 
                 LIFT ASSEMBLY 
               
               
                 31 
                 CAB 
               
               
                 32 
                 TRUCK BED 
               
               
                 33 
                 SIDE PANELS 
               
               
                 34 
                 TAILGATE 
               
               
                 35 
                 PICK-UP TRUCK 
               
               
                 36 
                 UPPER RAILS 
               
               
                 37 
                 REAR WINDOW OF CAB 
               
               
                 38 
                 SUPPORT LEG 
               
               
                 39 
                 CANISTER 
               
               
                 40 
                 SEGMENT-OUTER SMOOTH 
               
               
                 41 
                 SEGMENT 
               
               
                 42 
                 SEGMENT 
               
               
                 43 
                 SEGMENT 
               
               
                 44 
                 SEGMENT 
               
               
                 45 
                 SEGMENT 
               
               
                 46 
                 SEGMENT INNER SMALLEST 
               
               
                 47 
                 DRIVE SHAFT 
               
               
                 48 
                 SUPPORT FRAME 
               
               
                 49 
                 FLANGE ON SUPPORT FRAME 
               
               
                 50 
                 OPENING IN FLANGE 
               
               
                 51 
                 BOLT 
               
               
                 52 
                 3 THREADS 
               
               
                 53 
                 OUTER SURFACE THREADS 
               
               
                 54 
                 TOP COLLOAR 
               
               
                 55 
                 BOTTOM COLLAR 
               
               
                 56 
                 DRIVE SHAFT THREADS 
               
               
                 57 
                 UPPER COLLAR DRIVE SHAFT 
               
               
                 58 
                 LOWER CLOOAR DRIVE SHAFT 
               
               
                 59 
                 LOWER SMOOTH PORTION 
               
               
                 60 
                 KEYSEAT 
               
               
                 61 
                 SUPPORT BAND 
               
               
                 62 
                 EDGEPF SUPPORT FRAME 
               
               
                 63 
                 BEARING PLATE IN CANISTER 
               
               
                 64 
                 CENTRAL OPENING BEARING PL. 
               
               
                 65 
                 OPENINGS BEARING PLATE 
               
               
                 66 
                 MOUNTING FERRULE 
               
               
                 67 
                 UPPER BEARING 
               
               
                 68 
                 LOWER BEARING 
               
               
                 69 
                 BOLTS 
               
               
                 70 
                 NUTS 
               
               
                 71 
                 LARGE BROWNING PULLEY 
               
               
                 72 
                 CENTRAL OPENING IN PULLEY 
               
               
                 73 
                 CHANNEL IN PULLEY 
               
               
                 74 
                 MOTOR 
               
               
                 75 
                 MOTOR HOUSING 
               
               
                 76 
                 MOTOR MOUNT 
               
               
                 77 
                 THREADED STUDS 
               
               
                 78 
                 NUTS 
               
               
                 79 
                 SMALL BROWNING PULLEY 
               
               
                 80 
                 COUPLING 
               
               
                 81 
                 BELT 
               
               
                 82 
                 TRAILER 
               
               
                 83 
                 TOP CAP 
               
               
                 84 
                 TOP PLATE OF TOP CAP 
               
               
                 85 
                 LUGS ON TOP CAP 
               
               
                 86 
                 PLATE BEARINGS 
               
               
                 87 
                 BEARING LOCATOR 
               
               
                 88 
                 BRACE 
               
               
                 89 
                 BRACE SEGMENT 
               
               
                 90 
                 VERTICAL SLOT IN SEGMENT 
               
               
                 91 
                 STOP KNOB 
               
               
                 92 
                 STOP COLLAR 
               
               
                 93 
                 BRACE CAP 
               
               
                 94 
                 ATTACHING MEMBER FOR BRACE 
               
               
                 95 
                 PROTECTIVE SLEEVE 
               
               
                 96 
                 ATTACHING BOTTOM MEMBER 
               
               
                 97 
                 LOWERMOST SEGMENT