This invention relates to a wheelchair ramp for a minivan and, in particular, to a battery powered, folding ramp that is powered by a motor under the floor of the minivan.
It is known in the art to provide a ramp for enabling a person in a wheelchair to enter or leave a vehicle. Trucks, buses, and large vans have a high ground clearance and are typically provided with a lifting mechanism to augment a ramp, which would be too long or too steep otherwise. The ramp in such mechanisms merely provides a gradual transition from the ground to the height of a platform that is raised or lowered. A type of light truck known as a minivan has a lower ground clearance than larger vehicles. Thus, a ramp can be used without a lift and the ramp typically folds when stored.
In the prior art, minivans are typically provided with a battery powered, folding ramp having a motor located on one side of the sliding door adjacent the ramp. The motor is coupled to the ramp by gears or chain; e.g. see U.S. Pat. No. 5,871,329 (Tidrick et al.). The location for the motor reduces precious space within the cabin of the minivan and reduces the width of the ramp.
The Tidrick et al. patent also describes a mechanism for counterbalancing a folding ramp. Although the mechanism described works satisfactorily, the mechanism is mechanically complex and relatively expensive. Competing devices power the ramp down to the expected ground level, which may drive the ramp into the ground or stop the ramp just above ground level. On the one hand, such is necessary because the ground may be uneven or there may be a high curb, for example. On the other hand, an uncontrolled descent of a heavy metal ramp is undesirable.
In the prior art, it is generally assumed that a power failure occurs with a person in the minivan and that exiting the vehicle is all-important. Typically, a release mechanism is provided for extending the ramp after the door is opened. The ramp free-falls into an open position, creating a dangerous situation for someone standing near the open door. A folding metal ramp is heavy and cannot be handled by a person sitting in a wheelchair. Even for someone able to move about freely, a folding ramp may be difficult to handle and it is preferred that two people control the ramp.
In the event of a power failure, it is not simply a matter of extending the ramp manually. A manual release mechanism in the mechanical drive for the ramp must be re-set. This usually requires some re-assembly of the mechanical drive. Thus, for example, a power failure due to a blown fuse has the effect of stranding a wheelchair bound person or at least greatly delaying his travel while the system is restored to working order.
While there are many obvious solutions to the problem, such as a back-up power supply, one must realize that a ramp and a drive mechanism must fit an existing vehicle, i.e. a ramp is designed for the vehicle, not the other way around. A minivan is, by definition, a small van. Thus, most solutions to the problem are either too big, too expensive, or simply impractical. One wants to modify a minivan in a way that changes the finished appearance of the minivan as little as possible. Finding a location where a second battery, and the associated switching and charging apparatus, is both hidden and accessible is not easy in a minivan and is more difficult in a minivan that has already been heavily modified to accommodate a powered ramp. Similarly, any other solution to the problem must fit within commercially available vehicles without significantly affecting the space available for passengers or cargo.
In view of the foregoing, it is therefore an object of the invention to provide an electrically powered, folding ramp that has a controlled descent even when there is no electricity available.
Another object of the invention is to provide a compact drive mechanism for a folding ramp for a minivan, wherein the drive mechanism for the ramp is invisible from within the minivan.
A further object of the invention is to prevent a powered folding ramp from free-falling open in the event of a power failure.
Another object is to provide a controlled operation of a folding, powered ramp when power is interrupted.