Abstract:
An apparatus for loading a camper-insert, or other large-volume load, onto the bed of a pickup truck comprises a stiff-leg frame for supporting the load from the ground, the frame preventing the load from applying weight to the tail end of the bed with damaging consequences while the load is being cantilevered into position over the frame by the draw of a winch and cable system. The apparatus uses at least one telescoping leg to lift the rear of the load as part of a novel hoist assembly, which dynamically braces the telescoping leg on a foot while providing minimal interference to nesting the camper-insert closely to the host surfaces.

Description:
[0001]    This is a U.S. Non-Provisional application. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to loading devices for trucks, and more particularly to a loading device for a camper insert or other large volume load. 
       BACKGROUND OF THE INVENTION 
       [0003]    Loading a truck bed, such as on a pickup truck, sometimes involves heavy or unwieldy lifting in a situation where mechanized equipment is unavailable for the task. Such a situation might occur in a home or field environment. Such a case can be made for snowmobiles, four-wheeled recreational vehicles, boats, game carcasses, or camper-inserts, to name a few objects which are too large or too heavy for manual manipulation. Another case can be made for aggregated loads, such as firewood, shingle bundles, building blocks, or soil, fertilizer, or salt in bags, where lifting individual pieces one-at-a-time would be inefficient. In all cases, it is useful to stage the load at ground level and use a portable device to lift and transfer the load onto the truck bed. 
         [0004]    A winch and cable system powered by a battery comprises an easily portable device to drag a load onto a truck bed. In U.S. Pat. No. 5,232,329 to Livingston, a snowmobile loaded onto a ground-level pallet is lifted by a winch at the end of a boom. The boom doubles as a platform which can be raised to lift the load and then lowered by hydraulic means to receive the load at an appropriate incline. The loaded platform is then further lowered into the truck bed. The platform and associated hydraulics, however, must be installed in the truck, rendering the bed thereby unusable for other purposes. 
         [0005]    In U.S. Pat. No. 3,894,643 to Wilson, a boat is hoisted onto the rear of a pickup truck by means of a winch tugging against a pair of articulating brace members, said members braced against both the rear of the truck and the ground to scissor the load thereby upwardly. During the lift, however, the forces of the weight of the boat and the downward pull of the winch cable are collectively applied to the tail, or rearward-most part, of the vehicle. At the tail, in such an extreme position, the forces are applied against the suspension and the frame with damaging leverage. Additionally, lateral forces from the brace members and from the winch act at different elevations on the truck, thereby creating a force couple on the truck and the attached scaffolding, which would add stress to the truck and cost in overdesigned structure. 
         [0006]    In U.S. Pat. No. 5,269,642 to Zoromski, a camper-insert with an integrated structure comprising a winch and cable system is elevated at one end to be partially supported by stiff legs. As the load is winched farther onto the stiff legs, the center of gravity shifts to tilt the structure against the tail of the pickup truck bed. Further movement pivots the load over the tail and into the bed while simultaneously lifting the stiff legs. In spite of the temporary supporting role of the stiff legs, they are ultimately rendered ineffective in preventing weight from being applied to the tail in a potentially damaging way. Furthermore, the structural elements for the pivot are integrated into the load and cause the camper to sit high in the bed. Lastly, the winch cables are dragged over the lower front chine of the camper and along the bottom creating both frictional resistance and wear on both the camper and the cables. 
         [0007]    The present invention provides novel solutions for loading a truck bed without the need to for structure permanently installed in the bed, without using the tail of the bed as a fulcrum edge, and in a way that minimizes any offsetting structure so that the load rides as nearly flush to the bed as possible. 
       SUMMARY OF THE INVENTION 
       [0008]    It is desirable, particularly in the case of a camper-insert or other large-volume load, to have the load nest as closely and as far forward as possible to the truck body. Intervening structures that tend to lift the load, or offset it rearwardly, elevate the center of gravity, change the tipping dynamics of the loaded vehicle, and place additional stresses on the suspension system. Therefore, the ideal loading apparatus should place as little as possible of the apparatus underneath the load on the truck bed. It is further desirable to have the apparatus capable of, and available to, opportunistically unload the truck. In short, the apparatus should travel in a disassembled configuration with the load. It is further desirable to avoid dynamically loading the tail end of the vehicle where leverage upon the suspension system can be damagingly applied. It is further desirable, for resale purposes, to make as few modifications to the camper-insert as possible. 
         [0009]    Because a camper-insert, or other large-volume load, typically has a length equal to, or greater than, the truck bed, the center of gravity of the load is thereby positioned rearwardly to such an extent that a very large pulling force is needed to cantilever the load over an elevated tipping point. Such a large force would have to be countered by the vehicle holding position under brake power and fraction, again applying stresses to the to vehicle&#39;s systems. By sequentially lifting the rear of the load, however, the force vectors can be kept more nearly horizontal and the extremes of the moment-arm forces thereby avoided. Therefore, it is desirable to lift the rear of such a load with a rotating beam based against a foot positioned forwardly on the ground and braced directly against the structure applying the force. 
         [0010]    It is accordingly an object of the present invention to use a stiff-leg structure bearing on the ground, and not on the truck, to lift and transport there over a camper-insert, or other large-volume load, until a gravity shift positions the load well into the bed. It is a further object to use a winch and cable system as a means for drawing the load forward. It is a further object to lift the rear of the load by swinging it over at least one telescopic beam pivoting on a ground-based foot placed intermediately between the stiff-leg structure and the rear. It is a further object to use triangular geometry for at least two telescopic beams to avoid diagonal bracing of the beams and more than a singular foot. It is a further object to brace the ground-based foot against the stiff-leg structure by using similar triangular geometry. It is a further object to move the similar triangular geometry in a pivot upon the foot from a ground position to an elevated tipping position, avoiding thereby a force couple applied to the stiff-leg structure. It is a further object to use another winch and cable system to withdraw the load from the truck bed and return it to the ground. It is a further object to cooperatively link the two winches to apply braking force for the descent of the load. It is a further object to remove all structure beneath and in front of the load, except that necessitated by certain clearances, so that the load rides as closely nested as possible. It is a further object to provide at least one wheel extending rearwardly from the camper-insert to facilitate movement of the load over the ground. It is a further object to allow the truck bed to move independently from the stiff-leg structure while recoiling from the deposit and withdrawal of the load burden. It is a further object to use rope, instead of wire cable, for the winch and cable systems to avoid safety hazards attendant to flexing wire. It is a further object to make the loading and unloading apparatuses portable with the load. It is a further object to hold down the load with a lief spring which allows the truck body to twist independently of load. 
         [0011]    These objects, and others to become hereinafter apparent, are embodied in an apparatus for loading a camper-insert onto a truck having a bed with an open end, comprising a stiff-leg frame for lifting and supporting the camper-insert from a ground surface immediately adjacent the open end. The stiff-leg frame is comprised of at least two vertical members joined substantially at the proximal ends thereof by a crossbar member while the distal ends thereof rest upon the ground surface. The crossbar member is positioned at substantially the elevation of the bed. The stiff-leg frame is horizontally stabilized by at least one connector hinge attached between the stiff-leg frame and the open end. The apparatus is further comprised of a foot resting on the ground surface medially beneath the camper-insert when the camper-insert is in position for loading at the back of the truck. The foot is braced against the stiff-leg frame. The apparatus is further comprised of at least one telescoping beam pivotally connected at its distal end to the rear of the camper-insert and pivotally connected at its proximal end to the foot. The telescoping beam swings in a vertical arc about its proximal end and collapses to a minimum radius of curvature equal to the height of the crossbar. The minimum radius of curvature occurs when the center of gravity of the load shifts forward of the stiff-leg frame. Lastly, the apparatus comprises a means for drawing the camper-insert over the frame and into the bed. Functionally, the front and rear of the camper-insert are sequentially lifted up and over the stiff-leg frame by the means for drawing and the at least one telescoping beam braced against the stiff-leg frame. Further, the weight of the camper-insert is substantially supported by the stiff-leg frame and not by the open end. Further, the horizontal thrust from cantilevering the camper-insert over the frame is transferred to the truck through the at least one connector hinge. Lastly, the camper-insert settles onto the truck bed with minimal offset to mating surfaces. 
         [0012]    In the preferred embodiment, the means for drawing comprises a first winch and cable system. The foot is braced by two struts in a V configuration with the vertex located at the foot. The at least one telescoping beam, in this case, is two telescoping beams in a V-configuration with the vertex located at the foot. The first winch and cable system comprises a first winch fixed to the stiff-leg frame. The first winch winds a first cable to effectively draw the camper-insert forward from a rear attachment point. 
         [0013]    In a particular preferred embodiment, the apparatus further comprises a hoist assembly. The hoist assembly includes the two struts and the two telescoping beams, the struts and beams hingingly attached at distal ends thereof to the foot. The hoist assembly is configured to raise the front of the camper and position proximal ends of the two struts substantially at the elevation of the cross bar when lifted by the first winch and cable system. The hoist assembly is capable of partial disassembly for stowage and transport purposes. 
         [0014]    In another particularity, the apparatus further comprises a means for withdrawing the camper-insert over the stiff-leg frame and out of the bed. The means for withdrawing the camper-insert comprises a second winch and cable system. The second winch and cable system comprises a second winch fixed to the stiff-leg frame. The second winch winds a second cable to effectively draw the camper-insert rearward from a front attachment point. 
         [0015]    As this is not intended to be an exhaustive recitation, other embodiments may be learned from practicing the invention or may otherwise become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood through the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
           [0017]      FIG. 1  is a perspective view of the apparatus of the present invention in position with the truck and with the load partially raised; 
           [0018]      FIG. 2  is an elevation view of the apparatus at the beginning of the loading sequence with the load on the ground; 
           [0019]      FIG. 3  is an elevation view of the apparatus with the front end of the load raised by the hoist assembly; 
           [0020]      FIG. 4  is an elevation view of the apparatus with the rear end of the load raised by the telescoping beams; 
           [0021]      FIG. 5  is an elevation view of the apparatus at the end of the loading sequence with the load in place in the truck bed; 
           [0022]      FIG. 6  is a perspective view of the bottom of the camper-insert with the platform and hoist assembly showing; 
           [0023]      FIG. 7  is the perspective view of  FIG. 5 ; 
           [0024]      FIG. 8  is the perspective view of  FIG. 7  with the hoist assembly and stiff-leg frame disassembled and stowed for travel; 
           [0025]      FIG. 9  is a perspective view of the stiff-leg frame showing the cabling; 
           [0026]      FIG. 10  is a perspective view of the hoist assembly showing the cabling; 
           [0027]      FIG. 11  is a partial perspective view of the truck bed showing the lief spring; 
           [0028]      FIG. 12  is the detail view of  FIG. 11  showing the lief spring zoomed in; 
           [0029]      FIG. 13  is a partial perspective view the open end of the truck showing the connector hinge and the mating sockets; and 
           [0030]      FIG. 14  is a partial perspective view of the platform under the camper-insert showing the bosses that connect with the lief spring. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    The component systems for an apparatus for loading  1  are best shown in  FIGS. 5 and 6 . In the preferred embodiment, a camper-insert  5  supported on a pallet  50  is loaded onto a truck  2  assisted by a stiff-leg frame  10 , a hoist assembly  20  and a means for drawing  30  the camper-insert  5  onto a bed  3  of the truck  2  ( FIG. 1 ). In an alternate embodiment of the apparatus  1 , any large-volume load  8  (not shown) can be loaded with the same system components. 
         [0032]    In the progression sequence of  FIGS. 2-5 , several stages of the loading process are illustrated. In  FIG. 2 , the camper-insert  5  is resting on a ground surface  9  in a ready position supported by the pallet  50  and the hoist assembly  20 . The stiff-leg frame  10  is hingeably attached to the open end  4  of the bed  3  by connector hinge  15  ( FIG. 13 ). 
         [0033]    In  FIG. 3 , the hoist assembly  20  is raised by the means for drawing  30  to interposition a male socket  28  of the hoist assembly  20  with a female socket  17  of the stiff-leg frame  10  ( FIG. 13 ). In this interposition, proximal ends  22  of struts  21  of the hoist assembly  20  are approximately in line with the means for drawing  30 . As a consequence, forces relating to bracing and drawing are essentially co-planar, and no couple force is set up. At the same time, the front  6  of camper-insert  5  is raised to clear the stiff-leg frame  10 . The camper-insert  5  is advanced over the ground surface  9  by wheels  51  peripherally attached to extended side rails  53  of the pallet  50 . 
         [0034]    In  FIG. 4 , the means for drawing  30  has collapsed telescoping beams  24  to a minimum radius of curvature  27 , where upon continued drawing raises the rear  7  of the camper-insert  5  to a position essentially level with the floor of the bed  3 . The telescoping beams  24  pivot over a foot  29  bearing upon the ground surface  9 , which is braced by the struts  21  through a linkage of male socket  28 , female socket  17  and connector hinge  15  to the truck  2 . At this point, the center of gravity (not shown) of the load is balanced such that continued forward movement is there after achieved on a level. 
         [0035]    In  FIG. 5 , the camper-insert  5  has been advanced into its nesting position in the bed  3 . The telescoping beams  24 , no longer bearing weight, have extended to follow the pallet  50  onto the bed  3 . In the transition from ground to bed, the weight burden of the camper-insert  5  shifted from the stiff-leg frame  10  to a lateral point on the bed  3  roughly equivalent to the rearward offset of the center of gravity, and, at no time, did the burden bear on the open end  4 . 
         [0036]    Referring to  FIG. 9 , the stiff-leg frame  10  is comprised of two vertical members  11  having distal ends  12  bearing on the ground surface  9 . The distal ends  12  may be made to be telescoping and adjustable by inserting pins. The vertical members  11  are spread apart roughly the width of the bed  3  and are joined by crossbar  14  at proximal ends  13  thereof to form a scaffold-like structure. Two rollers  18  are mounted on crossbar  14  in flanking positions to rotationally receive the side rails  53  of pallet  50 . The rollers  18 , in their level placement with the bed  3 , are defining for the height of the crossbar  14 . Two side guide rollers  19 , axially-mounted perpendicular to the crossbar, are placed just outboard of the rollers  18  to keep the load centered when transported there over. The two connector hinges  15  and the two female sockets  17  are also mounted in outboard positions. The two connector hinges  15  allow articulation of the bed  3  up and down, thereby to buffer the stiff-leg frame  10  from the reflex of the truck&#39;s suspension when burden is applied or lifted, while forming a rigid lateral bridge to withstand forward thrust during loading. The two female sockets  17  receive the male sockets  28  of the hoist assembly  20  and position the hoist assembly appropriately with respect to the stiff-leg frame  10 . 
         [0037]    The means for drawing  30  and the means for withdrawing  40  are both operationally based at the crossbar  14 . In alternate embodiments, the means for drawing and withdrawing might be a reversible screw-threaded rod or a hand-crank. In the preferred embodiment, the means for drawing  30  is a first winch and cable system  31  and the means for withdrawing  40  is a second winch and cable system  41 . Both a first winch  32  of the first winch and cable system  31  and a second winch  42  of the second winch and cable system  41  are suspended beneath the crossbar  14 . The first winch  32  winds a first cable  33 , on an integral drum, following a first cable circuit  35 , as shown among  FIGS. 6 ,  9  and  10 . The first cable circuit  35  passes at all turning points over sheaves  16  on the stiff-leg frame  10 , sheaves  59  on the hoist assembly  20  and sheaves  54  on the pallet  50 . The orientation of the first winch  32  and the first cable circuit  35  is such as to draw, in the winding mode, a rear attachment point  34  proximate the rear  7  of the camper-insert  5  forwardly. In the preferred embodiment, the first cable circuit doubles back to the crossbar  14  to give a two-to-one purchase, as shown; therefore, all sheaves on the first cable circuit are paired. Other configurations for applying mechanical leverage, such as, for example, a running block, are also comprehended by this invention. A second first winch  32  may be used in parallel to provide redundancy and additional power. 
         [0038]    In the preferred embodiment, the first winch  32  and the second winch  42  are electric motor driven. The electric motors may be powered by the truck&#39;s battery system and controlled through a control box  56 . Control box  56  may alternatively be another battery, or a combined battery and control installation. 
         [0039]    The second winch  42  winds a second cable  43  in a second cable circuit  45 , as shown in  FIGS. 9 and 10 . Second cable circuit  45  passes over another sheave  16  and connects to a front  6  of the camper-insert at a front attachment point  44  (not shown). The orientation of the second winch  42  and the second cable circuit  45 , essentially reversing the former&#39;s direction, is such as to draw the front  6  rearwardly in winding mode. When the second winch  42  is in winding mode, the first winch  32  is in unwinding mode, and visa versa. When the first winch  32  is unwinding, it free-wheels until the tipping point, where the center of gravity of the load shifts rearwardly of the stiff-leg frame  10 . Thereafter, the first winch  32  engages to provide a braking force for the gravity takeover of the load. The manner and method of this braking force for two winches acting in cooperation is fully disclosed in U.S. Patent Application Publication 2011/0110753, which is incorporated in entirety herein by reference. 
         [0040]    Referring to  FIG. 10 , the hoist assembly  20  is comprised of the struts  21 , the at least one telescoping beam  25 , the foot  29  and a spreader bar  55 . In the preferred embodiment, the at least one telescoping beam  25  is two telescoping beams  25  in a V-configuration with the vertex based on the foot  29 . The use of a V-, or triangular, configuration, as opposed to a rectangular one, for example, avoids the sway bracing necessary to keep the rectangular arms square. It also allows a singular foot to be used. Since the weighted foot  29  will necessarily be dragged with strong frictional resistance over the ground surface in the manipulation of the hoist assembly  20 , it is important to keep the contact area to a minimum. Each telescoping beam  25  is hingingly and rotationally, on orthogonal axes, attached to the foot  29  at a distal end  26  thereof, and hingingly and rotationally attached to the rearward part of the corresponding side rail  53 . Each telescoping beam  25  swings in a vertical arc over the distal end  26  to lift the camper-insert  5 . Each telescoping beam  25  collapses to a minimal radius of curvature  27  ( FIG. 4 ) and extends to accommodate the full range of position from load-on-the-ground to load-in-the-bed. The minimal radius of curvature  27  represents the zenith of the swing when the rear  7  reaches the elevation of the bed  3 . 
         [0041]    The two struts  21  brace the foot  29  against the truck  2 , as described above, and also form a V-configuration with the vertex positioned at the foot  29 . Each strut  21  is hingingly attached to the foot  29  at its distal end  23  and attached at the proximal end  22  in a flanking position to the spreader bar  57 . The spreader bar  57  spans the distance between the female sockets  17 . The male socket  28  is located at each end of the spreader bar  57  and offset there from by riser stub  57 . The sheaves  59  on the hoist assembly  20  corresponding to the sheaves  16  on the stiff-leg frame  10  are also offset from the spreader bar  57  by extender stubs  58 . The extender stubs  58  are positioned inboard of the stiff-leg frame sheaves  16 , and the hoist assembly sheaves  59  are offset bi-laterally there from to align with the first cable circuit  35 . The lengths of the riser stubs  57  and the extender stubs  58  and all offsets are configured to place the sheaves  59  in the forward shadow of the sheaves  16 . 
         [0042]    Starting from a position on the ground, the sheaves  59 , and the strut-end of the hoist assembly, are lifted by the first winch  32  operating in winding mode through the threading connection of the first cable circuit  35  to first mount and then pass over the sheaves  16 . The male sockets  28  are received in the female sockets  17  when the juxtaposition of the sheave pairs takes place. When the sockets become locked in the receiving position, the forward advancement of the hoist assembly  20  ceases and the struts  21  are elevated to brace against the stiff-leg frame  10 , and by linkage to the truck  2 , at a position which places the proximal ends  22  essentially co-planar with the draw of the winch. If the struts  21  were left to brace against the stiff-leg frame  10  from a ground position, or any other position in between, a force couple would have been set up to topple the stiff-leg frame. It should be noted that if the sheaves  59  were not located, as they are, on the rising hoist assembly  20 , they would necessarily have been located in a forward position on the camper or pallet where they would have added to the load offset. Where they are presently, in the shadow of the stiff-leg frame, they are out of the way and ready to be used again during unloading. 
         [0043]    Referring to  FIG. 6 , the pallet  50  is comprised of the parallel side rails  53 , which extend rearwardly from the rear  7  of the camper-insert  5 . Ideally, the extent of the side rails  53  is sufficient to make an angle of inclination with the ground surface  9  of 20 degrees or less. The side rails  53  are mounted beneath the camper on the periphery edges thereof and provide the slipping surfaces for the load. The side rails  53  are boxed in on the front by head rail  48  ( FIG. 14 ) and on the rear by tail rail  49 . Tail rail  49  extends beyond the side rails  53  on each side to receive the wheels  51 . Wheels  51  are mounted on collars  52 . Tail rail  49  is square in shape, and collars  52  have corresponding square apertures therein to enable the wheels  51  to be dismounted and rotated ninety degrees. Zero degrees is for loading while ninety degrees is for travel ( FIG. 8 ), or otherwise for boosting elevation. The sheaves  54  are attached to the tail rail  49  and define the rear attachment point  34 . The sheaves  54  are laterally positioned to feed in a direct line with the sheaves  59 ; otherwise, the first cable  33  would jump the sheave groove. 
         [0044]      FIGS. 7 and 8  illustrate the camper-insert  5  in receivership on the bed  3 .  FIG. 7  shows the apparatus  1  at its end-of-loading or beginning-of-unloading configuration.  FIG. 8  shows the apparatus  1  in its travel configuration with the distal ends  12  of the vertical members  11 , the struts  21 , the foot  29  and the telescoping beams  24  disassembled and stowed in interstitial spaces on the truck. The camper-insert  5  is resting on the side rails  53  in its nested position on the floor of the bed  3 . In the preferred embodiment, the side rails  53  are 1.5 inches in height and define a minimal vertical offset to the load. The offset is minimally sufficient, also, to channel the cables. Since the side rails  53  are attached to the camper-insert for most of the length, the bending moment of the 1.5 inch gauge is restricted to the relatively small extension at the tail; therefore, a relatively narrow gauge is justified. The offset would have been a minimum of 3.5 inches if the sheaves  59  were configured beneath the camper instead of on the hoist assembly. 
         [0045]    The front  6  of the camper-insert  5  is held down for travel purposes by a means for holding  60 . The means for holding  60  can be any cable, rope, guy or bracket attached between the bed and the camper. In the preferred embodiment, the means for holding  60  is comprised of a lief spring  61  mounted onto the bed at the bulkhead position, as shown in  FIGS. 11 and 12 . The attachment point is the center of lief spring  61 , which leaves lateral arms  62  thereof free to flex. The lateral arms  62  have bores  63  therein positioned at the ends to receive bosses  64  extending forwardly from the head rail  48  ( FIG. 13 ). The flexibility of the lateral arms  62  allows the camper-insert  5  to roll, and to some degree pitch, independently from the truck body. In this way, the vehicle&#39;s suspension system is augmented. In the preferred embodiment, the lief spring  61  is 3 to 4 inches wide and defines the lateral offset for the load. The offset also prevents the front  6  from jostling against the bulkhead of the truck during travel and replaces space that might otherwise be taken up with a “headache rack”. The pallet  50  may be used to support any large-volume load  8  in the operation of the apparatus for loading  1  without the camper-insert  5 ; but, in such a case, the gauge of the side rails would need to be increased accordingly. 
         [0046]    The apparatus for loading  1  can be fabricated from two inch, or greater, metal tubing or channel, the exception being the side rails  53  at 1.5 inches. Steel is preferred, particularly for the side rails, for strength reasons. Hinged and telescoping assemblies can be pinned for easy disassembly, and multiple pin holes can be added on telescoping parts for adjustability. Bushings may also be added to telescoping parts for smooth operation. Non-hinged, or non-telescoping, joints are preferably welded. The stiff-leg frame  10  is preferably rated for a four thousand pound payload. The foot  29  may be contoured on the leading edge to facilitate sliding. Wire cable is dangerous because of whip-lash in the event of fracture. Also, wire strands tend to become frayed when traversing sheaves and the needle-like broken ends present a handling hazard. In the preferred embodiment, low-elongation synthetic rope is preferred for the first cable  33  and the second cable  43 . Twisted rope comprised of Dacron® fiber is a suitable choice for a low-stretch option. Elasticized shock cord, or rubber surgical tubing, can be used to gather slack rope, or otherwise keep running sections in the correct circuits. Such components as sheaves, wheels, rollers and winches are commercially available as stock items, in most cases. The synthetic rope and the winches should be rated, at minimum, for a two thousand pound pull. 
         [0047]    It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the preceding description or illustrated in the drawings. For example, a three or four to one purchase can be used for mechanical leverage in the first cable circuit  35 . Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.