Wheelchair and method of operating same

A method of operating a wheelchair comprising a seat, front and rear pairs of laterally spaced carriers, a plurality of wheels on each carrier, drive means for driving at least some of said wheels, and control means for operating the drive means, wherein the control means includes a microprocessor, means for feeding instructions to said microprocessor for controlling the front and rear carriers and wheels and the configuration of the wheelchair, and a plurality of transducers for providing electrical signals to the microprocessor to enable the microprocessor to determine the angular positions of the front and rear carriers and the control means is operated to cause said drive means to define one of a plurality of alternative predetermined configurations of the wheelchair and set the carriers automatically in any one of said predetermined configurations, one of said configurations is a compact configuration, another of said predetermined configurations is an extended configuration, in the compact configuration with the wheelchair resting on a horizontal floor, at least one of said wheels on each of said front carriers engages the floor and intersects a vertical plane containing the centre of gravity of the wheelchair and, in the extended configuration of the wheelchair, with the wheelchair resting on the horizontal floor, the centre of gravity lies in a vertical plane spaced from all of said wheels on the front and rear carriers and in the extended configuration, the attitude of the seat of the wheelchair is not parallel to the floor, and wherein the wheelchair is turned in the compact configuration whilst a respective wheel on each of the front carriers is engaged with the ground and the perpendicular line through the centre of gravity of the wheelchair, including the occupant, is near to, but is to the rear of, a straight line joining the positions where said wheels engage the ground and the geometry of the wheelchair is then adjusted to move the perpendicular line through the centre of gravity rearwardly away from said straight line.

A wheelchair comprising a seat, front and rear pairs of laterally spaced carriers, a plurality of wheels on each carrier, drive means for driving at least some of said wheels, and control means for operating the drive means,

• wherein, the front carriers are mounted for turning relative to the seat about a front axis, the rear carriers are mounted for turning relative to the seat about a rear axis, the wheels on each front carrier are spaced apart around the front axis, the wheels on each rear carrier are spaced apart around the rear axis,
• wherein the drive means includes wheel-driving motor means for driving said at least some of the wheels independently of driving of the carriers, carrier-driving motor means for driving the carriers and pulse-supplying means for pulsing the wheel-driving motor means while the carrier-driving motor means drives the carriers continuously,
• wherein the drive means is operable in either selected one of two alternative modes, in the first of which modes rotation of the carriers is restrained and the wheel-driving motor means drives wheels on at least two of said carriers and in the second of which modes the carrier-driving motor means is operable to rotate all of the carriers about their respective axes and the pulse-supplying means and the wheel-driving motor means are operable concurrently to drive intermittently at least respective wheels on two of the carriers about the axis of those wheels whilst the carriers are rotated continuously, and
• wherein the drive means includes means defining a plurality of alternative predetermined configurations of the wheelchair and is arranged for setting the carriers automatically in any selected one of said predetermined configurations, one of said configurations is a compact configuration, another of said predetermined configuration is an extended configuration, in the compact configuration with the wheelchair resting on a horizontal floor, at least one of said wheels on each of said front carriers engages the floor and intersects a vertical plane containing the centre of gravity of the wheelchair and, in the extended configuration of the wheelchair, with the wheelchair resting on the horizontal floor, the centre of gravity lies in a vertical plane spaced from all of said wheels on the front and rear carriers, and the control means includes a microprocessor, means for feed instructions to said microprocessor for controlling the front and rear carriers and wheels, and the configuration of the wheelchair, and a plurality of transducers for providing to the microprocessor electrical signals to enable the microprocessor to determine the angular positions of the front and rear carriers.