Land vehicles – Wheeled – Extensible
Reexamination Certificate
1999-02-02
2001-08-28
Swann, J. J. (Department: 3611)
Land vehicles
Wheeled
Extensible
C180S209000, C180S011000
Reexamination Certificate
active
06279927
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a wheelchair comprising a body frame equipped with a pair of drive wheels, and caster wheels arranged to the front and rear of the drive wheels so as to allow the wheelchair to be turned while remaining at a stationary point, and in particular to such a wheelchair which can travel over stepped floor surfaces without causing discomfort to the user while allowing the diameter of the drive wheels to be minimized for maximum maneuverability.
BACKGROUND OF THE INVENTION
As the proportion of senior citizens in the entire population increases at a rapid rate in recent years, an increasingly large number of newly built houses are based on barrier-free design. According to the concept of barrier-free design, no step-like discontinuity exists between adjacent living spaces, and a home elevator is often installed so as to allow the occupant to move from one floor level to another without descending or ascending stairways.
Senior citizens may be mostly capable of walking short distances but are often unable to walk to remote destinations.
Under such circumstances, there have been a significant amount of demand for motor-powered wheelchairs for home use which are suitable for lightly disabled people such as senior citizens. More conventional and widely used motor-powered wheelchairs are designed for more highly disabled people, and are normally large in size and not very maneuverable.
Based on such a consideration, KK Unicam or one of the co-applicants of this application previously developed a wheelchair for home use which comprises a body frame equipped with a pair of drive wheels, and caster wheels arranged to the front and rear of the drive wheels so as to allow the wheelchair to be turned while remaining at a stationary point, and announced it in the Journal of the Japan Society of Orthotics & Prosthetics, Vol. 9, No. 2 (1993).
This wheelchair for home use is capable of turning at a stationary position and compact in size so that it can be turned in a tight space such as an elevator cage without being interfered by the walls of the elevator cage. Also, the diameter of the drive wheels is significantly reduced for a high maneuverability.
However, as this wheelchair for home use developed by KK Unicam or one of the co-applicants of this application is adapted to ride over a step by lifting the front caster wheels by making use of the rearward inertia force resulting from a sudden forward movement of the wheelchair, the following problems were found as the wheelchair rides over a stepped part of the floor.
(1) the user experiences some discomfort from the sudden acceleration of the wheelchair;
(2) the wheelchair must often come to a sudden stop after riding over a stepped part of the floor to avoid collision with wall surfaces, in particular in narrow passages: and
(3) a special mode of operation is required when riding over a stepped part of the floor which may not be easy to execute for a senior individual.
The present invention was made in view of such problems, and has its primary object to provide a wheelchair which can travel over stepped floor surfaces without causing discomfort to the user while allowing the diameter of the drive wheels to be minimized for maximum maneuverability.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a wheelchair comprising a pair of drive wheels mounted to a body frame and a front caster wheel and a rear caster wheel mounted to the body frame to the front and rear of the drive wheels so as to allow the wheelchair to turn at a stationary position, further comprising: a link member extending between the body frame and the drive wheels, and having one end pivotally connected to an upper part of the body frame and another end rotatably supporting the drive wheels; a rotary shaft of the drive wheels being placed behind a point of connection between the body frame and the link member at least before the front caster wheel abuts a stepped portion of a floor surface.
Thus, when the front caster wheel runs into a stepped portion of a floor surface as the wheelchair moves forward, the link member turns around the point of connection between the body frame and the link member so as to reduce the distance between the front caster wheel and the drive wheels while, at the same time, the front end of the body frame tilts upward around the rear caster wheel. The front caster wheel thereby lands on the upper surface of the step, and successfully rides over the step.
According to the first aspect of the present invention, the improved wheelchair may further comprise first spring means and second spring means disposed between the link member and the body frame, the first spring means applying a downward urging force to the link member, and the second spring means applying an upward urging force to the link member; the second spring means comprising a first bracket attached to the body frame so as to be moveable in a fore-and-aft direction, a second bracket attached to the link member, and a tension spring engaged between the two brackets, the tension spring having a stronger spring force than the first spring means, and normally maintaining the first bracket and the second bracket in a mutually abutting relationship; a length of the second spring means when the first second bracket and the second bracket are placed in a mutually abutting relationship being selected so as to coincide with a length thereof when the second bracket is located at a frontmost position with respect to the body frame, and the second spring means prevents the downward movement of the link member against the spring force of the first spring means with the drive wheels kept in contact with the floor surface.
Thus, the drive wheels can be firmly pressed onto the floor surface while, at the same time, avoiding the front casters from being excessively lifted from the floor surface.
According to a second aspect of the present invention, there is provided a wheelchair comprising a pair of drive wheels mounted to a body frame and a front caster wheel and a rear caster wheel mounted to the body frame to the front and rear of the drive wheels so as to allow the wheelchair to turn at a stationary position, further comprising: a first link member and a second link member extending between the body frame and the drive wheels, and having one end pivotally connected to an upper part of the body frame and another end rotatably supporting the drive wheels; a rotary shaft of the drive wheels being placed behind a point of connection between the body frame and the first link member at least before the front caster wheel abuts a stepped portion of a floor surface, and ahead of a point of connection between the body frame and the second link member at least before the rear caster wheel abuts a stepped portion of a floor surface; the first and second link members being switch over in such a manner that the first link member is selected when the wheelchair rides over a stepped portion of a floor surface as it moves forward, and the second link member is selected when the wheelchair rides over a stepped portion of a floor surface as it moves rearward.
Thus, the wheelchair is provided with the following features.
(1) When the front caster wheel runs into a stepped portion of a floor surface as the wheelchair moves forward, the first link member turns around the point of connection between the body frame and the first link member so as to reduce the distance between the front caster wheel and the drive wheels while, at the same time, the front end of the body frame tilts upward around the rear caster wheel. The front caster wheel thereby lands on the upper surface of the step, and successfully rides over the step.
(2) When the rear caster wheel runs into a stepped portion of a floor surface as the wheelchair moves backward, the second link member turns around the point of connection between the body frame and the second link member so as to reduce the distance between the rear caster wheel and the drive wheels while,
Nishihira Morikazu
Nishihira Tetsuya
Suzuki Masayoshi
Armstrong Westerman Hattori McLeland & Naughton LLP
Misawahomu Kabushiki Kaisha
Shriver II J. Allen
Swann J. J.
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