Self loading and unloading cargo deck for pick up trucks

The present invention comprises a support frame secured within the cargo box of a pick up truck. The frame supports a drive train comprising a differential driven by an motor. One differential shaft drives a first cable winch while the other shaft incorporates a clutch to drive a second and third winch either independantly from each other or in unison. A system of pulleys ensures that cable wind on the first and second winches is toward the front of the cargo box while on the third winch it is toward the rear. The cable ends are secured to a cargo platform. When the electric motor is engaged the first and second winches are rotated, in a counterclockwise direction which winds the cable into the winch body. The retracting cable first raises and then draws the platform onto the frame. During this process the third winch freewheels and releases cable as necessary. Unloading the platform requires that the clutch mechanism is engaged to couple the second and third winches together. The motor is reversed and the first, second, and third winches rotate in a clockwise direction. The third winch retracts cable while the first and second winches release cable. The retracting cable, draws the platform off the support frame and toward the rear of the cargo box. As the platform draws far enough rearward to tilt off the support frame, the clutch is disengaged and the third winch freewheels, leaving the platform to continue to lower under its own weight.

FIELD OF THE INVENTION 
This invention relates to the field of cargo carrying devices and systems 
for use in pick up trucks; specifically to a self loading and unloading 
cargo deck for such trucks. 
BACKGROUND DESCRIPTION OF KNOWN ART 
The utility of pick up trucks is well understood and appreciated by those 
who drive them. However, those who have used such trucks to carry bulky 
and heavy objects know well the problems associated with such activity. 
For example snowmobile enthusiasts often need to transport their sports 
vehicles to relatively remote locations where the use of such vehicles may 
be enjoyed without disturbing others. 
The sheer size and bulk of snowmobiles, renders their transportation via 
pick up trucks especially problematic. They are difficult to load and 
unload, especially in remote areas where help may not be readily 
available, and the restrictive configuration of a typical pick up truck 
cargo box can make transporting more than one vehicle impossible. 
It is not unusual to find a large variety of makeshift devices used to 
expand the cargo carrying capacity of pick ups; the most common being that 
of a rigid platform laid over the truck's cargo box sidewalls and held in 
place by whatever means available. Such platforms do, of course, permit 
more than one snowmobile to be carried but simply exacerbate the problem 
of loading and unloading those snowmobiles. 
Not surprisingly, inventors have developed several solutions to this 
problem ranging from simple ramps to complex side loading mechanisms 
whereby the cargo platform swings out over the side of the vehicle and is 
lowered to the ground. 
While certainly better than manhandling the machines off the cargo platform 
all such devices heretobefore known suffer from one or more shortcoming. 
For example the danger associated with the use of ramps is obvious; they 
must be carefully positioned and the tendency for the ramp to move while 
in use must be accommodated. Those mechanisms which attempt to automate 
the loading and unloading procedure generally employ linkages whereby the 
cargo platform becomes unsupported at one end and therefore must be 
overbuilt to withstand the cargo weight. In addition, some automated 
systems employ mechanisms which occupy the truck's cargo box almost to 
capacity thus leaving little room for cargo storage underneath the cargo 
platform. 
The present invention seeks to remedy many of the inherent difficulties 
associated with current loading/unloading methods and devices by providing 
a relatively simple, yet safe and reliable, alternative system. 
An embodiment of the present invention comprises a rigid support frame 
which fits inside the cargo box of a pick up truck. The frame is generally 
confined to the perimeter of the box, leaving the interior of the box free 
for storage of additional cargo. Two of the individual elements which 
comprise the frame overhang the cargo box sidewalls and serve as anchor 
points for tie down cables as well as convenient locations for marker 
lights. 
The frame supports a drive train assembly which comprises a differential 
unit driven indirectly via a pulley system by a direct current electric 
motor. One differential output shaft is directly coupled to a first wire 
cable winch for rotation thereof while the other differential output shaft 
is directly coupled to a second wire cable winch having first passed 
through a third cable winch with the third winch free to rotate about the 
differential output shaft. A conventional clutch mechanism interposed 
between the second and the third cable winch couples and decouples the 
second and third winch so that, when required the third winch may be 
directly driven in unison with the second winch. 
Cable from the first and second winches is routed via a pulley system such 
that as the cable is wound onto the winch cable movement is toward the 
front of the truck cargo box. Cable from the third winch is routed such 
that as the cable is wound onto the winch, cable movement will be in a 
direction toward the rear of the truck cargo box. 
The cable ends are secured to one end of a flat cargo platform. The other 
end of the platform incorporates a pair of freewheeling wheels which 
enable free movement of the platform along the ground. In operation, 
snowmobiles are loaded onto the cargo platform and secured thereon by 
conventional means. The electric motor is engaged such that the first and 
second winches are rotated via the differential in a counterclockwise 
direction which winds the cable into the winch body. The retracting cable 
first raises and then draws the platform onto a pair of guide pulleys 
located on the support frame and subsequently fully onto the frame. During 
this process the third winch is freewheeling and releasing cable as 
necessary. 
Unloading the platform requires that the clutch mechanism is engaged to 
couple the second and third winches together. The direction of rotation of 
the electric motor is reversed and the first, second, and third winches 
rotate in a clockwise direction. The third winch now begins to retract 
cable while the first and second winches release cable. As the third winch 
retracts cable, the platform is drawn off the support frame and toward the 
rear of the truck cargo box. As the platform draws far enough rearward to 
tilt off the support frame, the clutch is disengaged and the third winch 
again freewheels leaving the platform to continue to lower under its own 
weight controlled by the rate at which the cable is released from the 
first and second winches. 
OBJECTS AND ADVANTAGES 
From the foregoing it may be seen that the present invention is relatively 
simple in operation, yet offers several advantages not found in the known 
art. The support frame leaves the truck cargo box relatively free for 
additional storage. Loading and unloading the cargo platform is completely 
automatic and effortless from an operators standpoint. 
Other objects and advantages will become apparent upon consideration of the 
ensuing description and accompanying drawings. 
SUMMARY 
According to one aspect the present invention is an apparatus for raising a 
cargo deck from ground level to a position above ground level and for then 
returning the cargo deck to ground level.

DESCRIPTION OF THE PRESENT EMBODIMENT 
When used in the following description "distal end" or "distal" refers to 
that portion of a component nearest the cab area of a pick up truck. When 
used in the following description "proximate end" or "proximate" refers to 
that portion of a component nearest the tailgate area of a pick up truck. 
When used in the following description the terms "left" and "right" refer 
respectively to the driver's side and passenger's side of a pick up truck. 
When used in the following description the terms "bottom" and "top" refer 
respectively to a direction toward the floor of the cargo bay of a pickup 
truck and a direction away from the floor of the cargo bay. 
The present invention is comprised of a rigid and robust support frame 
generally designated by the numeral 10 in the drawings. The frame 10 
includes a left top side rail 14, a left bottom side rail 16 and a 
plurality of bracing elements therebetween;and, a right top side rail 18, 
a right bottom side rail 20, and a plurality of bracing elements 
therebetween. A bottom transverse element 22 and a first top transverse 
element 24 with a plurality of bracing elements therebetween connect the 
respective side rails at the distal end of the rails. A second top 
transverse element 26 connects the side rails at the proximate end. The 
support frame 10 thus has a generally rectangular shape and is dimensioned 
to fit within the confines of a pickup truck 12 cargo bay such that the 
top rails of the frame 10 are slightly above, the top edge of the pickup 
truck 12 cargo bay side walls. The first transverse top rail 24 and the 
second transverse top rail 26 are substantially equal in length to each 
other and greater in length than the width of the frame 10 so that the 
first transverse top rail 24 and the second transverse top rail 26 
overhang either side of the pickup truck 12 cargo bay side walls to 
provide means whereby the frame 10 may be firmly secured and levelled 
within the confines of the truck 12 cargo bay by attachment of suitable 
and conventional tie downs 28 between each of the ends of the first 24 and 
second 26 transverse elements and appropriate mounting points on the truck 
12 body. Each of the ends of the first transverse element 24 and the 
second transverse element 26 additionally may serve as a mounting surface 
for conventional marker lights (not shown). A pair of conventional pulleys 
30 and 30' are rotatably and vertically mounted to each of the distal ends 
of the left and right top side rails 14, 18. A pulley bar 32 having a 
circular cross section and having a pair of rotatable guide pulleys 34 and 
34' axially mounted to either end thereof is transversely mounted between 
the left top 14 and right top 18 side rails, proximate to the second top 
transverse element 26. A third top transverse element 36 is mounted 
between the left and right top side rails 16,18 intermediate the first top 
transverse element 24 and the second top transverse element 26 and 
functions as a mounting platform to accommodate placement of the drive 
assembly, generally designated by the numeral 38 in the drawings. 
Referring now to FIGS. 2 to 2B it will be seen that the drive assembly 38 
comprises a conventional differential drive unit 40 mounted to the 
underside of the third top transverse element 36 by any conventional and 
appropriate fastening means. The input shaft 42 of the differential 40 
faces toward the proximate end of the support frame 10 and may be driven 
in one direction by pulley means 44, which pulley means 44 is, in turn, 
driven by a reversible direct current electric motor (not shown). 
Reversing rotation of the motor (not shown) output drives the input shaft 
42 of the differential 40 in the opposite direction. 
One output shaft 46 of the differential is axially coupled to, and drives a 
right pull-on cable winch, rotating the winch 48 in unison with the output 
shaft 46. The other output shaft 50 of the differential 40 passes through 
an axial bore in a pull-off cable winch 52 and is free to rotate therein. 
After passing through the pull-off winch 52 the output shaft 50 of the 
differential 40 is axially coupled to, and drives a left pull-on cable 
winch 54 rotating the winch 54 in unison with the output shaft 50. A 
conventional clutch mechanism of the type having a first moveable element 
56 splined to the differential 40 output shaft 50 and slidably engageable 
with a second element 58 fixed to the end of the pull-off winch 52 is 
interposed between the pull-off winch 52 and the left pull-on winch 54 so 
that movement of the splined element 56 into engagement with the fixed 
element 58 couples the pull-on winch 54 to the pull-off winch 52, rotating 
both winches 52, 54 in unison. The clutch elements 56, 58 may be 
alternately engaged and disengaged by any conventional and appropriate 
means such as electric solenoid activation and/or mechanical linkages. 
The pull-on and pull-off cable winches 48, 54, 52 are comprised of a pair 
of circular end elements 58 and 58' with a spool element 60 integrally 
mounted therebetween, the assembly having an axial bore 62 therethrough 
for receipt of the differential 40 output shafts 46, 50. One end element 
58 further incorporates a second bore 64 therethrough to receive one end 
of a wire cable 66 therein; the cable 66 end secured in the bore 64 by any 
conventional and appropriate means such as a grub screw insertion 68. With 
one end of the wire cable 66 secured in the end element 58 bore 64, the 
cable 66 is wrapped on the spool 60 and the other end of the cable 66 
passed through an elongate opening 70 in a cylindrical shield 72, which 
shield 72 is then inserted over the end elements 58, 58' and spool 60, and 
attached by any conventional and appropriate means such as welded 
bracketing 74 to the third top transverse element 36 of the support frame 
10. 
Referring now to FIGS. 3 and 3A it will be seen that the present invention 
further includes a cargo deck, designated in the drawings as number 76, 
which deck 76 is comprised of a generally rectangular rigid platform 78 of 
dimensions approximating those of a pick up truck 12 cargo bay, and having 
a pair of opposing ground contacting freewheeling wheels 80 at the 
proximate end thereof. The deck 76 further includes, on its bottom 
surface, a pair of spaced apart and parallel, longitudinally mounted guide 
rails 82 and 82' of rectangular cross section and of a width and depth 
sufficient to form a clearance fit to the support frame 10 guide pulleys 
34 and 34' such that the guide rails 82 and 82' ride within the 
corresponding guide pulley 34 and 34' as the deck 76 is loaded onto the 
support frame 10. The deck 76 further includes a pair of cable mounting 
points 84', 84, to accommodate conventional mounting of the ends of the 
wire cable 66 from the left and right pull-on winches 48,54 and a third 
mounting point 86 to accommodate conventional mounting of the cable 66 end 
from the pull-off winch 52. 
Operation of the present invention will best be understood with reference 
to FIGS. 1 and 4 to 6A wherein it will be seen that the support frame 10 
of the present invention is first positioned within the cargo bay of a 
pick up truck 12, and secured and levelled therein by the attachment and 
adjustment of the tie down cables or chains 28 to appropriate positions on 
the truck 12 body. While the tension applied to the tie downs 28 may be 
accomplished by any conventional and suitable means, the present 
embodiment utilizes conventional turnbuckles 88 in series with the tie 
downs 28. The deck 76 is positioned on the ground behind the pickup truck 
12 with the wheels 80 of the deck 76 facing away from the rear of the 
truck 12. The wire cable 66 from the left pull-on winch 54 is threaded 
underneath the first top transverse element 24, over the left distal 
pulley 30, over the top surface of the left guide pulley 34 and secured by 
conventional means such as a "U" clamp to the left mounting point 84 of 
the deck 76. The wire cable 66 from the right pull-on winch 48 is threaded 
underneath the first top transverse element 24, over the right distal 
pulley 30', over the top surface of the right guide pulley 34' and secured 
by conventional means such as a "U" clamp to the right mounting point 84' 
of the deck 76. The wire cable 66 from the pull-off winch 52 is threaded 
underneath the guide pulley bar 32 and attached by conventional means such 
as a "U" clamp to the mounting point 86 of the deck 76. 
Electrical power is applied to the DC motor (not shown) such that the 
output shafts 46, 50 of the differential 40 rotate in a counterclockwise 
direction thus causing both pull-on winches to rotate in the same 
direction winding the wire cable 66 back onto their respective spools 60 
and, as a consequence raising the distal end of the deck 76 off the ground 
and toward the support frame 10 guide pulleys 34, 34'. As the deck 76 is 
raised to the height of the guide pulleys 34, 34' the bottom guide rails 
82 of the deck 76 contact the guide pulleys 34, 34' and the deck begins to 
settle on the left top side rail 16 and right top side rail 18 of the 
support frame 10. With continued movement of the deck 76 toward the front 
of the pick up truck 12, cable 66 begins to unwind from the freewheeling 
pull-off winch 52 and is looped over the guide pulley bar 32. Electrical 
power to the motor (not shown) is removed when the deck 76 has been drawn 
all the way to the front of the truck 12 cargo bay. 
The splined clutch element 56 is engaged with the fixed clutch element 58 
thus coupling the left pull-on winch 54 to the pull-off winch 52. Power to 
the motor (not shown) is reversed causing the output shafts 46, 50 of the 
differential 40 to rotate in a clockwise direction. The pull-off winch 52 
begins to wind the wire cable 66 onto the winch 52 spool 60 over the guide 
pulley bar 32, which bar 32 acts as a pulley wheel, drawing the deck 76 
away from the front of the truck 12 cargo bay. Concurrently, cable 66 
unwinds from the left and right pull-on winches 54,48. As the deck 76 
begins to tilt off the support frame 10 the splined clutch element 56 is 
disengaged from the fixed clutch element 58 permitting the pull-off winch 
52 to freewheel and allowing the full weight of the deck 76 to become 
supported by the cable 66 from the left and right pull-on winches 54, 48, 
which winches 54, 48 continue to unwind cable 66 thus gently lowering the 
deck 76 to the ground. It will be understood that as the distal end of the 
deck 76 is raised or lowered the deck rolls forward or backward on the 
deck 76 ground contacting wheels 80. 
While the above description contains many specificities, these should not 
be construed as limiting the scope of the invention but rather as an 
illustration of a present embodiment. It is apparent that the present 
embodiment admits of several variations and modifications without in any 
fashion detracting from the spirit of the invention. Thus the scope of the 
invention should be determined by the appended claims and their legal 
equivalents.