Suspension for central drive vehicle

Motor vehicles – Steering by driving – Independently operable drive motors

Reexamination Certificate

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Details

C180S024070, C180S055000, C180S065510, C180S065600, C180S907000, C280S124170, C280S124175, C267S041000

Reexamination Certificate

active

06341657

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to personal mobility vehicles and more particularly to an improved drive wheel suspension system for a central drive personal mobility vehicle.
2. Prior Art Statement
Persons with partial and total walking disabilities have traditionally relied upon wheelchairs for locomotion. Wheelchairs generally have relatively widely spaced wheels for lateral stability and to comfortably accommodate the occupant. Persons in wheelchairs can move with relative ease in places such as hospitals which are usually provided with extra wide doors and halls and inclined ramps between vertically displaced levels. However, private homes and work places are generally not planned specifically to accommodate wheelchairs.
While wheelchairs are generally resistant to lateral tipping, wheelchairs are often designed for tipping backwards so that an attendant pushing a patient in a wheelchair can tip the front wheels up to negotiate such obstacles as steps, thresholds, and the like. While such a configuration is useful when the wheelchair is pushed by an attendant, the design presents some hazards when the occupant of the wheelchair attempts to move the wheelchair up a ramp.
In order to overcome some of the problems associated with wheelchairs, the medical equipment industry has developed small personal mobility vehicles as an alternative to the conventional wheelchair. In general, rear wheel drive personal mobility vehicles have a pair of powered rear wheels and a steerable front wheel. The track of the powered rear wheels is generally narrower than a conventional wheelchair, while the wheel base is generally longer than a conventional wheelchair. The personal mobility vehicles are usually designed for a tight turning radius in order to be more maneuverable than a conventional wheelchair. Accordingly, rear wheel drive personal mobility vehicles may be used in places which are not specifically designed for conventional wheelchair use.
Among the most maneuverable personal mobility vehicles are central drive personal mobility vehicles. A central drive personal mobility vehicle has a right and a left drive wheel and a left and a right trailing wheel. The right and left drive wheels are located substantially below a seat of the central drive personal mobility vehicle enabling the central drive personal mobility vehicle to essentially turn around within the overall length of the central drive personal mobility vehicle.
Although the central drive personal mobility vehicles are the most maneuverable personal mobility vehicles, the central drive personal mobility vehicle have certain disadvantages over the rear wheel drive personal mobility vehicles.
Firstly, most operators perceive the central drive personal mobility vehicle to be less stable than the rear wheel drive personal mobility vehicle. This perceived instability of the central drive personal mobility vehicle by infirm or elderly operators limited the acceptance of the central drive personal mobility vehicle by the purchasing public.
Secondly, when the central drive personal mobility vehicle is decelerated, the central drive personal mobility vehicle tends to pitch forward about the right and left drive wheels. In order to increase stability and to reduce the pitch forward upon deceleration, the central drive personal mobility vehicles is provided with a left and a right leading wheel. The addition of the left and right leading wheels reduces but does not eliminate the above problems.
Thirdly, the central drive personal mobility vehicle is unable to adjust for different weight distributions of the different operators of the central drive personal mobility vehicle. The central drive personal mobility vehicle designed to provide stability for an operator with one weight distribution may be unstable for an operator with another weight distribution.
Many in the prior art have attempted to solve the above problems with varying degrees of success. The following United States Patents are representative of attempts of the prior art to eliminate the aforementioned problems and to provide a central drive personal mobility vehicle which satisfies the needs of the art.
U.S. Pat. No. 3,952,822 to Udden et al. discloses an electrically powered wheel-chair for indoor and outdoor use comprising a pair of rear main wheels which are non-pivotably connected with the framework of the chair. At least one of the wheels is driven by an electric motor. A steering wheel is rotatably connected with the framework of the wheelchair and is positioned in front of the main wheels. The steering wheel is asymmetrically located on one side of a longitudinal axis through the middle of the chair. A support wheel is positioned on the other side of the longitudinal axis relative to the steering wheel at such a level above a flat and horizontal ground surface that it will not touch this surface when the steering wheel directed straight ahead. The diameter of the support wheel is less than that of the steering wheel and the distance from the fore-most point of the steering wheel to a transverse axis through the centers of the main wheels is greater than the corresponding distance for the support wheel. To provide good stability the electric batteries are located in a case thus designed that the common center of gravity of the batteries will be located on the same side of the longitudinal axis of the chair as the steering wheel. The frame-work is equipped with two auxiliary support wheels on either side of the chair and rearwards the main wheels.
U.S. Pat. No. 3,953,054 to Udden et al. discloses a hand operated wheel-chair with a pair of main wheels rigidly connected with the framework of the chair, at least one of which is either motor or hand operated and at least one castor wheel being pivotally connected with the framework of the chair and at least one support wheel being rigidly connected with the framework. At least one castor wheel and support wheel are positioned on each side of a line extending between the support points of the main wheels and at a level above the ground surface to permit either the castor or the support wheels to be in contact with the ground surface depending on whether the vertical through the center of gravity is located on one or the other side of the line between the support points of the main wheels. The wheel-chair also comprises a seat, which is disposed substantially mid-way between the main wheels and is supported by a transverse portion of the framework extending between the main wheels and being provided with a seat support in the form of a central column, which includes spring members for the seat and means for adjusting the height of the seat.
U.S. Pat. No. 4,245,847 to Knott discloses a wheelchair suitable for invalids or geriatric patients has a chair or seat supported on independent forward and rearward castor frames pivotally connected together at a transverse axis to form a castor frame assembly. The chair is pivotally mounted on the forward and rearward castor frames so that in negotiating a step or other obstacle, the lifting movement of the occupant is divided into stages so that a pleasant or comfortable ride is obtained. The wheelchair may be folded into a collapsed condition with the chair itself located between the castor frames.
U.S. Pat. No. 4,310,167 to McLaurin discloses a center of gravity wheelchair with an articulated chassis front and rear caster wheels, in which the main wheels and front and rear caster wheels are arranged in a diamond pattern, and the main wheels and rear caster wheel are carried by a subframe to form a bogie system, with the seat and front caster wheel carried by a seat frame assembly articulated with respect to the subframe through a pivoted link arrangement, whereby the seat may be moved forward relative to the main wheels, with a spring and damper connected between the subframe and seat frame assembly to minimize the tendency for the front caster wheel to lift off the ground when the main wheels are strongly propelled and to provide a sho

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