Wheelchairs having various designs and configurations have been used over a period of many years to provide help and assistance to handicapped personnel. In many cases where the handicapped person has limited or no use of his or her legs such as paraplegics and quadriplegics, the sole means of individual transportation is through the use of a wheelchair.
Over the past recent years, the design of wheelchairs has become very complex and sophisticated as a result of efforts intended to help the person so that they acquire a higher degree of control over their position within the chair as well as their mobility. Thus, in recent history, powered wheelchairs have incorporated a number of various control and safety devices to assist handicapped individuals so that they can achieve independent operation and movement.
One of the major problems that has been encountered by a paralyzed person whether he or she is a paraplegic and quadriplegic is the necessity to shift or move the body weight with respect to the support provided by a chair, wheelchair, bed or similar device.
This periodic shifting of the weight of a person's body is essential to prevent the occasion of ulcers, infection and possibly gangrene. This is due to the fact that the continuous pressure of the body's weight on certain specific locations of the body such as that provided by the skeletal structure such as hips causes the supporting skin to lose circulation causing it to deteriorate and possibly die. For this reason, it is absolutely necessary that a periodic or intermittent shifting of the weight of the paralyzed person be provided to prevent this condition.
In the past, with respect to a wheelchair, it has been found that if the user is tilted onto his or her back approximately 45 to 60 degrees, this provides sufficient shift in the body weight to permit circulation in the essential skin areas. This complete shifting of the weight is required about every 20 minutes.
In some cases, a nurse or attendant stands behind the wheelchair and manually tilts it backwards and supports it for a sufficient length of time to provide the beneficial effect. On the other hand, it is much more desirable to provide a mechanism built into the chair to allow the patient to perform this function himself.
Up to the present, a number of attempts have been made to accommodate a wheelchair so that various arrangements of the seat, back and leg support can be changed, all with respect to each other. In other words, in some situations, the seat remains permanently positioned and the back is tilted backward while the leg support is pivoted upward. This allows the patient to be moved to a supine position. Many of these wheelchair mechanisms are quite complex and require extensive mechanical linkage and mechanism so as to move the individual components in proper relationship with each other.
An object of the present invention is to provide a wheelchair mechanism which can be used to modify or retrofit a new or existing wheelchair which will allow the patient to control the tilting of the chair seat and back to periodically relieve the pressure spots and eliminate the possibility of skin and tissue degeneration.
It is also another object to provide a simple mechanism whereby the chair with the seat and back rigidly connected move as a unit to prevent the pulling or shearing of the patient's skin and tissue during the body movement. This is especially important due to the fact that the handicapped person does not have any sensation or feel in the skin whereby a pulling condition on the skin can take place without the patient realizing it.
Another object of the present invention is to provide a kit or retrofit assembly whereby the unitary seat of the wheelchair can be tilted automatically by the patient a sufficient distance and yet allow the weight of the patient and the wheelchair to remain within the wheelbase of the chair to maintain stability and security even while the wheelchair is moved.