Truck freight loading and dock device

Wheeled elevator apparatus for use in loading and unloading freight into and out of a highway truck; the apparatus including a platform raised and lowered by hydraulic power engaging lever arms arranged in a parallelogram structure, drawbridge access ways from the platform to the truck bed and from the platform to the loading/unloading level, the access directions being perpendicular to each other, wheels for moving the apparatus from place to place, and jacks for securing the apparatus off its wheels.

TECHNICAL FIELD OF THE INVENTION 
This invention relates to a wheeled elevatable platform for use in loading 
and unloading freight into and from highway trucks to and from loading 
levels different from the level of the truck bed. 
BACKGROUND OF THE INVENTION 
Highway freight trucks are widely used throughout the world for 
transporting goods of all types from one place to another. Because the bed 
of the truck is so high above ground level, e.g., about four feet, it is a 
normal procedure to load and unload such trucks from a dock that is about 
the same height above ground level as the truck bed. The dock usually is 
part of a warehouse that can be locked to protect the goods waiting to be 
loaded onto a truck as well as the goods unloaded from a truck. It is not 
always feasible to have a freight loading dock as a part of a building and 
at the same level as the truckbed. Accordingly, other means have been 
developed for assistance in loading and unloading freight from such 
trucks. One such means is to employ a folding tailgate on the truck which 
can be raised or lowered like an elevator. Another means is to employ a 
movable platform that can be placed alongside a truck such that freight 
can be transferred from the truck to the platform or vice versa. The 
movable platform can then raise or lower the freight to whatever elevation 
is desired for another location or lowered to ground unloading the freight 
from the platform. I have developed and marketed for the last few years 
such a movable elevatable platform having two aligned access ramps on the 
front and back, respectively, of the platform. One ramp provides access 
from the platform to an unloading level, which may be at ground level or 
at any selected elevation up to the maximum height of about five feet. The 
loading/unloading travel of the freight handler is substantially a 
straight line from truck bed to platform to unloading level. While this 
straight line travel across the ramp is appropriate for most situations, 
there are many occasions where it would be desirable to travel from the 
truck to the platform and then turn right or left and move perpendicular 
to the previous travel direction to travel from the platform to the 
unloading level, or vice versa for loading. 
It is an object of this invention to provide a novel freight loading and 
unloading .elevator platform having the lifting arms in a parallelogram 
arrangement. It is another object of this invention to provide such a 
novel mobile freight loading elevator platform having two folding access 
ramps providing travel onto and off of the platform in directions 
perpendicular to each other. Still other objects will become apparent from 
the more detailed description which follows. 
BRIEF SUMMARY OF THE INVENTION 
This invention relates to a movable freight lifting elevator for use in 
loading and unloading highway trucks which comprises an elevatable 
rectangular platform mounted on a wheeled carriage having a plurality of 
jacks for selectively lifting the carriage off the carriage wheels to make 
it immovable, a hinged first drawbridge member that is pivotable from a 
vertical inoperable storage position to an operational horizontal bridge 
floor between said platform and the truck bed; a hinged second drawbridge 
member that is pivotable from a vertical inoperable storage position to an 
operational horizontal bridge floor between said platform and a 
loading/unloading floor, the direction of travel for loading and unloading 
over said first drawbridge member being perpendicular to the direction of 
travel for loading and unloading over said second drawbridge member. 
In preferred embodiments of this invention, the platform is elevated by 
hydraulic cylinder power applied to two pairs of parallel pivotable 
lifting arms, the lower one of each pair connected to each other by a 
torque tube; and the chassis of the elevator is a structural beam in the 
shape of a hollow rectangle extending around the perimeter of the platform 
except for an opening in that rectangle immediately below the access ramp 
leading from the platform to the loading level.

DETAILED DESCRIPTION OF THE INVENTION 
The features of the elevator of this invention are best understood by 
reference to the attached drawings. 
The elevator apparatus includes a carriage 10 mounted on wheels 16 and 17, 
so as to be movable over the ground or other generally horizontal floor, 
such as the loading level of a dock attached to a warehouse. Mounted on 
carriage 10 is a rectangular elevator platform 11 which can be raised or 
lowered while always remaining in a horizontal position. 
The basic lower portion of carriage 10 is a chassis 12, which is a 
plurality of structural beams arranged in a generally hollow rectangular 
shape around the perimeter of the rectangular platform 11. The structural 
beams in the rectangular shape are rear beam 13, front beam 14, and two 
side beams 15. Short side beam 15S is on the same side as ramp 24 and long 
side beam 15L is on the side opposite to ramp 24. There is a single 
interruption in the hollow rectangle where no structural beam exists. That 
is immediately under ramp 24, about which more will be described below. 
Chassis 12 functions as a support for a plurality of wheels 16 and 17 and a 
plurality of jacks 18. Preferably there are four wheels, two of which are 
rear wheels 16 and two of which are front wheels 17. The rear wheels 16 
are on the rear of the elevator apparatus, which is the end adjacent to 
the truck to be loaded or unloaded. Correspondingly, the front wheels 17 
are on the front of the elevator apparatus, which is the side farthest 
away from the truck. Generally rear wheels 16 are fixed direction wheels 
rolling lengthwise, that is in the direction toward the front or the rear 
of the elevator apparatus. Front wheels 17 are preferably mounted on 
swivels so as to turn in any direction of travel. Jacks 18 are preferably 
six in number, three of which are spaced along the long side of chassis 
12, i.e., the side opposite to ramp 24. Two of the jacks 18 are spaced 
along the short side of chassis 12, i.e., the same side as that occupied 
by ramp 24. One of jacks 18 is placed generally in the middle of the front 
side of chassis 12, i.e., about half way between front wheels 17. Jacks 18 
are shown as having screw thread shafts engaging a stationary nut fixture 
on chassis 12. Each jack 18 is manually operable by a suitable handle and 
is capable of elevating chassis 12 sufficiently to lift chassis 12 high 
enough that there is no contact between wheels 16 and 17 and the ground or 
floor the apparatus rolls over. By using a suitable combination of jacks 
18, the entire elevator apparatus can be stabilized, immobilized, and 
leveled. Shock absorbing pad 32 on the rear of chassis 12 projects 
rearwarldy sufficiently to be the first portion of the carriage 10 to 
contact the rear of the truck to be serviced thereby. 
On each lateral side of carriage 10 adjacent rear wheels 16 is a vertical 
superstructure 19 resting on chassis 12. Superstructure 19 is generally 
trapezoidal in shape and serves as a support for platform 11 and the 
levers and pivots employed in raising and lowering platform 11. The 
operations of raising and lowering platform 11 are based on two pairs of 
parallel arms 20 and 21 which are pivoted at their rear ends by pivot pins 
25 in a vertical beam of superstructure 19, and pivoted at their forward 
ends by pivot pins 26 in vertical beam 34 of platform 11. A line through 
pins 25 is parallel to a line through pins 26. Furthermore, the two arms 
21 are connected to each other by a torque tube 35 connecting arms 21 by a 
rigid torque tube concentric to lower pins 25, although the tube may be 
connected in other ways to both of arms 21 or both of arms 20. The 
arrangement of parallel arms 20 and 21 and their pivot locations produces 
the well known parallelogram structure which assures that platform 11 will 
remain horizontal at all elevation positions of arms 20 and 21. 
The power to move arms 20 and 21 and thereby elevate platform 11 is 
provided by one or more hydraulic cylinder means 27, preferably one on 
each side, respectively, of platform 11. The upper end of cylinder means 
27 is pivoted at pin 28, mounted in superstructure 19, while the lower end 
of cylinder means 27 is pivoted at pin 29 mounted in lower arm 21. Left 
and right arms 21 are connected together by torque tube 35 which 
synchronizes arms 21 and thereby maintains platform 11 level at all 
positions. 
The elevator apparatus of this invention has two access ramps 23 and 24 to 
provide access, respectively, between platform 11 and the truck bed, and 
platform 11 and the loading level. Each of ramps 23 and 24 is attached to 
an edge of platform 11 by a hinge such that each ramp may be pivoted to a 
vertical position for storage purposes and to a horizontal, or slightly 
below horizontal, position to function as an operational bridge from the 
platform 11 to the truck bed or the loading level. Ramps 23 and 24 are 
pivotable by hydraulic power or manual power as desired. It is a special 
feature of this invention that ramp 24, which provides a passageway 
between the platform 11 and the loading level, opens to the side of 
platform 11, either the right or left side. 
The elevator apparatus with a side opening ramp 24 has quite different 
stresses and balance problems than does the apparatus with a front opening 
ramp as is known in the prior art. In the latter case, the freight being 
loaded or unloaded moves in a relatively straight line over the center of 
platform 11 and balancing problems are not critical items to consider. In 
the case of the apparatus of this invention, however, the freight moving 
over side access ramp 24 tends to tip the apparatus in the direction of 
ramp 24, and places great stresses on the carriage 10 and chassis 12. The 
stress problems are met by employing larger beams in chassis 12, side 
superstructures 19, and associated portions of the apparatus. 
Reinforcement beam 33 on long side beam 15L is typical of such additional 
support. The structure of chassis 12 in the shape of a rectangle around 
the perimeter of platform 11 also helps to solve the balance problems. Of 
course, the structural beams in chassis 12 cannot be continuous because 
they must not interfere with the presence of ramp 24 in its extended 
horizontal position which is required for the smooth loading or unloading 
of freight with minimal inclination of the ramps. Therefore, there is a 
discontinuity 31 in the beams of chassis 12, and that discontinuity 31 is 
exactly where it would meet ramp 24. Under ramp 24 there is no chassis 12 
beam. The extension of front beam 14 of the rectangular chassis to the 
corner near ramp 24 helps to provide the necessary support and stability 
for the elevator apparatus. Other portions of chassis 12 and 
superstructures 19 are also made of beams of the necessary size to provide 
rigidity and support for the apparatus in its usage. 
Platform 11 is provided with a suitable railing structure 22 to keep people 
and freight from falling off the platform. As a part of the railing there 
are two vertical support beams (one on each side) which are large enough 
to provide seats for pivot pins 26. The control levers 30 for operating 
hydraulic cylinders 27 are preferably mounted on railing 22. 
The materials of construction for the apparatus of this invention may be 
any of several strong materials, e.g., metals, reinforced plastic, or 
wood; however, steel is preferred. 
While the invention has been described with respect to certain specific 
embodiments, it will be appreciated that many modifications and changes 
may be made by those skilled in the art without departing from the spirit 
of the invention. It is intended therefore, by the appended claims to 
cover all such modifications an changes as fall within the true spirit and 
scope of the invention.