Motorized standing wheelchair

Details Motorized standing wheelchair Motorized standing wheelchair

1998-01-12

2001-05-15

Vanaman, Frank (Department: 3611)

Land vehicles

Wheeled

Extensible

C180S065100, C180S907000

Reexamination Certificate

active

06231067

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to wheelchairs, and in particular to standing wheelchairs in which the wheelchair is able to automatically move a user between seated and standing positions.
BACKGROUND OF THE INVENTION
Standing wheelchairs, including both motorized and non-motorized versions having many different designs, are known in the art. These known standing wheelchairs are generally designed with the center of mass in the center of the wheelchair while the user is in the seated position. As the user is moved into the standing position, he or she is moved toward the front of the wheelchair, thus changing the location of the center of mass. To counterbalance the weight of the user at the front of the wheelchair when in the standing position, many wheelchairs are designed with a large amount of weight in the rear to prevent tipping of the wheelchair. Other standing wheelchairs are designed so that when the user is in the standing position, the footrest portions of the wheelchair contact the ground and in this manner prevent tipping of the wheelchair. However, when the user is moved into the standing position at the front of the chair, most of the user's weight is located at the front of the wheelchair, resulting in a “tippy” feeling in which the user feels that the wheelchair is about to tip over. To a person with a disability who must rely upon the wheelchair for mobility and support, and who utilizes the standing capabilities of the wheelchair to lead a more productive and independent life, this “tippy” feeling is an extremely uncomfortable sensation and detracts from the user's ability to fully lead a productive and independent life.
A common problem with all standing wheelchairs is the occurrence of shear which is created while the lifting mechanism is in motion. Shear is due to the offset of the user's knee joint and the pivot point of the seat assembly, with the greater the distance between these two points, the greater the shear and the resulting amount of discomfort, often times causing skin abrasions. Over time, the resulting skin abrasions can ultimately lead to the development of pressure sores, which are a significant problem for many people with disabilities. Therefore, a standing wheelchair should reduce the distance between the user's knee joint and the pivot point of the seat of the wheelchair as much as possible, in order to reduce the amount of shear that is created during movements between the seated and standing positions.
Existing standing wheelchairs also position a user at an angle of up to 27 degrees from a fully vertical standing position. This compromised posture prevents the user from reaching objects positioned at a greater distance, by reducing the distance of the user's reach, thus decreasing the user's independence. A proper standing posture is also important for the health and lasting comfort of the user.
Further, people often shy away from users of wheelchairs since wheelchairs are in general unapproachable, intimidating, ugly and awkward, utilizing intricate and complicated mechanical parts and systems which give the wheelchair a distracting appearance. Therefore, a standing wheelchair that is visually appealing, and which eliminates, or hides from view, many of the intricate mechanical components would be beneficial.
A standing wheelchair should also be adjustable so as to be able to accommodate different users who are each sized differently. Further, as with most machines, a standing wheelchair should be simple in design with the minimum number of parts, so as to reduce assembly time and reduce the number of parts that could potentially break down, need maintenance or repair.
Therefore there exists a need for a standing wheelchair that reduces shear on the user when moving between the seated and standing positions, as well as reduces stress on the lower body of the user, improves the reaching capabilities of the user while providing lasting comfort to the user in the standing position, adjusts so as to accommodate different users, and is simple in design with a reduced number of parts and systems. In addition to the above requirements, the standing wheelchair should be designed so as to be aesthetically appealing.
SUMMARY OF THE INVENTION
Therefore the general purpose of the present invention is to provide a motorized standing wheelchair that reduces the distance between the pivot axis of the seat assembly and the user's knee joints, thereby reducing shear on the user, improves the reaching capability of the user while providing lasting comfort to the user, is adjustable to accommodate different users, is simple in design with a reduced number of parts, and has enhanced visual appeal.
A preferred embodiment of the standing wheelchair in accordance with the principles of the present invention includes a base frame, a pair of front driveable wheels connected to the front end of the frame, and at least one rear wheel connected to the rear end of the frame. A seat assembly is connected to the center of the front end of the frame and includes a seat portion that is pivotable between a generally horizontal, seated position and a raised, angled standing position. An actuator is connected between the front end of the seat assembly and the rear end of the seat portion to actuate the seat portion between the seated and standing positions. The seat assembly includes a stub pivot shaft located proximate the front center of the seat portion and spaced above the seat portion, to permit the pivoting movements of the seat portion. By utilizing a single, centrally located stub pivot shaft, the number of parts is reduced, thus simplifying the wheelchair and reducing the number of parts that could potentially wear and need replacement, as well as enhancing the appearance of the wheelchair. Further, by spacing the stub pivot shaft above the seat portion, the distance between the pivot axis and the user's knee joints is reduced, thereby reducing shear on the user.
The seat assembly includes a seat pivot connected to the seat portion adjacent the front center thereof and having a first end that extends vertically above the seat portion. The seat assembly further includes a pivot assembly connected to the front end of the base frame at the center thereof, with the pivot assembly having a pivot column that extends vertically above the seat portion and which is pivotally connected to the end of the seat pivot by the stub pivot shaft. In this manner, the stub pivot shaft is vertically raised above the seat portion such that when a user is positioned on the wheelchair, the stub pivot shaft is located generally between the legs of the user as well being located closer to the axis of the user's knee joints. As stated previously, this reduces the distance between the pivot axis of the seat assembly and the user's knee joints, thereby reducing shear on the user.
The actuator for the seat assembly is pivotally connected at one of its ends to the front end of the seat assembly via the pivot assembly and fixed at its opposite end to the rear of the seat portion. The actuator extends generally centrally along the seat assembly, with no other mechanical linkage connected between the frame and the seat portion. Since no other linkage is present, the visual appeal of the wheelchair is enhanced, as well as reducing the number of mechanical parts and simplifying the structure of the wheelchair. In addition, the seat portion includes a channel shaped seat support bar extending parallel with the actuator. When the actuator extends to pivot the seat portion to the standing position, the actuator is substantially received within the channel of the seat support bar, effectively hiding the actuator from view and further increasing the visual appearance of the wheelchair.
The standing wheelchair of the present invention further includes a back support assembly connected to the seat portion that automatically adjusts itself from a slightly rearwardly angled orientation relative to the ground at the seated position

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