Motorized chair base

Details Motorized chair base Motorized chair base

1998-10-06

2001-01-30

Dickson, Paul N. (Department: 3618)

Motor vehicles

Power

Electric

C180S907000, C280S304100

Reexamination Certificate

active

06179076

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a motorized base for a transportation device, such as a wheelchair, a stretcher, or the like.
BACKGROUND OF THE INVENTION
Traditionally, powered wheelchairs have two drive wheels at the rear and two castor wheel, at the front. These chairs drive like a car in that they pivot about the rear of the chair. Accordingly, such motorized wheelchairs are generally adapted for movement either along a straight line or along a steered curved arc, somewhat in the same manner as an automobile. They require a significant turning radius and, as with a car, many manoeuvres must be executed backwards. Further, these chairs tend to lose traction on downward slopes since the rear drive wheels tend to become unloaded.
If it is desired to realign the wheelchair, for movement from one fixed position in an entirely new direction, it is typically necessary to go through complex turning manoeuvres, somewhat similar to the three point turn utilized on occasion in operating an automobile. The manoeuvres require a significant amount of space and many tight spaces must be approached backwards in a manner similar to a car reversing into a parking spot. These complex manoeuvres are sometimes difficult for disabled persons to carry out.
There are some powered chairs where the powered drive wheels are at the front. However, these chairs also require a large turning radius and tend to lose traction when going uphill.
In addition, existing motorized wheelchairs frequently have difficulty in traversing uneven flooring or terrain or when travelling along an incline, such as a wheelchair ramp, and may lose traction
In U.S. Pat. No. 5,445,233, (Fornie et at.), the free running wheels were urged into contact with the ground via a spring mounted around the shaft. Accordingly, for example, if the wheelchair of Fernie et al were travelling in a forward direction and encountered uneven terrain, the front wheels could pivot upwardly or downwardly about the shaft while ensuring that the drive wheels remained in contact with the ground. The spring would continually urge the free running wheels into engagement with the ground to stabilize the wheelchair and thereby prevent the wheelchair from tipping over.
One disadvantage with this approach was that the free running wheels would rock forward to backward and/or side to side as a person sat down or stood up from the wheelchair. This produced a sensation that the wheelchair was unstable and would cause concern to a disabled person. This was undesirable as midwheel drive chairs are garnering a reputation as being unstable.
In order to enable the occupant of the chair to reach objects positioned on a low shelf or on the ground, the chair included a shaft having two telescoping sleeves. One of the sleeves was connected to the seat of the chair and the other was connected to the drive wheels. A motor was used to extend or retract one of the telescoping sleeves thus raising or lowering the seat of the chair. While this design achieved the goal of allowing a person to reach low lying objects, it has several disadvantages. First, it necessitated the use of complex gearing and a the incorporation of a further motor into the design of the wheelchair. This constituted additional parts which were subject to wear and tear and potential failure. Further, the parts substantially added to the cost of the wheelchair thereby restricting the ability of some disabled people to acquire the wheelchair.
SUMMARY OF THE PRESENT INVENTION
In accordance with this invention, there is provided a base for receiving a seat comprising:
(a) a longitudinally extending chassis having a front end, a rear end, a central portion positioned therebetween and opposed sides extending longitudinally between the front and rear ends;
(b) at least one drive wheel mounted below the central portion;
(c) a plurality of rotatably mounted wheels positioned around the chassis and mounted at a fixed distance below the chassis; and
(d) a biasing member associated with the at least one drive wheel to bias the at least one drive wheel to engage the surface on which the base is situated and reduce the weight supported by the rotatably mounted wheels whereby the rotatably mounted wheels support sufficient weight of the base and the unoccupied seat to define a stable platform.
In accordance with another embodiment of this invention, there is provided a motorized chair comprising
(a) a longitudinally extending chassis having a front end, a rear end, a central portion positioned therebetween, opposed sides extending longitudinally between the front and rear ends and a seat mounted thereon;
(b) at least one drive wheel mounted below the central portion;
(c) a plurality of rotatably mounted wheels positioned around the chassis, the plurality of rotatably mounted wheels including a pair of forward wheels; and,
(d) a biasing member to maintain contact between the at least one drive wheel and the surface on which the base is situated and, when a person of average weight is seated in the seat, the forward pair of rotatably mounted wheels support up to 25% of the weight of the occupied chair.
In one embodiment, the at least one drive wheel comprises two drive wheels, each of which is driven by a motor. The at least one drive wheel preferably supports a major proportion of the weight of the base and the unoccupied seat. The at least one drive wheel may support at least 75% of the weight of the base and the unoccupied seat, preferably more than 85%, more preferably more than 90% and, most preferably, about 95%.
In another embodiment, when a person is seated in a seat affixed to the base, the rotatably mounted wheels support a major proportion of the weight of the person, preferably, the weight of the person is evenly divided between each of the rotatably mounted wheels,
In another embodiment, the rotatably mounted wheels include a pair of forward wheels and, when a person of average weight is seated in a seat affixed to the base, the forward pair of rotatably mounted wheels support up to 25% of the weight of the occupied seat.
In accordance with another embodiment of this invention, there is provided a base for receiving a seat comprising:
(a) a longitudinally extending chassis having a front end, a rear end, a central portion positioned therebetween and opposed sides extending longitudinally between the front and rear ends;
(b) at least one drive wheel mounted on the central portion to engage the surface on which the base is positioned;
(c) a plurality of rotatably mounted wheels positioned around the chassis and mounted below the chassis to engage the surface on which the base is positioned; and,
(d) a forward compartment positioned adjacent the front end for receiving at least one battery and a rearward compartment positioned adjacent the rear end for receiving at least one battery.
The base may further comprise batteries positioned in the forward and rearward compartments with the weight of the batteries being essentially evenly divided between the forward and rearward compartments.
One advantage of the instant design is that it provides a stable low profile base for a chair, stretcher or the like. Accordingly, even though the base may be used in the construction of a midwheel drive chair, the base is stable not only when a user is entering or exiting the chair, but also while the chair is in operation over a variety of terrain. Further, the base maintains good stability and traction when travelling up or down a ramp. This is particularly important when traversing uneven terrain (such as a bumpy road), or going up or down an incline (such as a ramp into a house or a building, particularly where it is necessary to turn either to the left or to the right while proceeding up the ramp).
Further, given the low height of vans, it is particularly suitable for a person who has the ability to drive a motor vehicle as the wheelchair may easily enter, travel through and exit a van which has been adapted for a handicapped person.
More importantly, even with its low profile, the motorized chair base is

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