1. Field of the Invention
The present invention relates to a chassis for a pickup truck or van having a vertically adjustable bed.
2. Background Art
Pickup trucks and vans have long been used as utility vehicles. One of the most common uses for such vehicles is the transportation of cargo. The cargo must be loaded onto and off of the vehicle bed. Loading, unloading and positioning cargo on the bed can be difficult especially when handling heavy or awkward cargo.
Several means have been used to solve loading, unloading and positioning problems. Examples of such means include:
1. Lift trucks; PA1 2. Ramps; PA1 3. Lifting tail gates; and PA1 4. Adjustable beds.
Each of these means is helpful. However, each has its own draw backs. For instance, lift trucks are not always available and can be awkward to use in the limited space of a vehicle bed. Ramps require space behind the vehicle. Vertically adjustable tail gates are limited in the size and weight of cargo they can handle and may require counter balancing.
There are two basic types of adjustable utility vehicle beds. The adjustable beds include pivoting beds and vertically adjustable beds.
Pivoting beds include a bed pivotally connected to a vehicle chassis above the rear axle. The front of the bed is releasably connected to the vehicle to maintain the bed in a substantially horizontal orientation. Loading is accomplished by releasing the front end of the bed allowing the bed to pivot until the back end contacts the surface on which the vehicle is resting. In that position the bed forms a ramp onto which the cargo may be rolled, pulled or pushed.
Even though pivoting beds reduce loading problems, there are some draw backs. For instance, loading large or heavy cargo can be dangerous when the center of gravity of the cargo moves past the bed pivot point. Positioning loads on the bed is also difficult because the loads have a tendency to slide when the bed is in the ramped loading position.
Vertically adjustable beds include a bed connected to the frame by rotatably connected linkages. That arrangement allows the bed to remain substantially horizontal when moved from a raised transporting position to a lowered loading position and back again. That feature solves the shifting and sliding problems of pivoting beds.
Even though the vertically adjustable bed reduces many of the cargo handling problems there are some draw backs. The back portion of the frame is U-shaped. Rear axles and lateral supports cannot be disposed underneath the frame because the bed could not be grounded. Overhead supports limit the height of the cargo that can be carried. Without some lateral means of support there is a problem with frame stability.
The description in the Background is meant to be illustrative rather than exhaustive. It is intended to identify problems associated with the present state of the art.