Powered invalid-chairs

Claim 1

An invalid wheelchair comprising a frame, two relatively large ground wheels mounted on the frame and having a common axis of rotation, and at least one further ground wheel mounted on the frame, an electric motor mounted adjacent to each of said relatively large ground wheels, and a drive arrangement between each of said electric motors and its adjacent ground wheel, each drive arrangement comprising a pulley which is driven by the motor to rotate on an axis parallel to the axis of rotation of said relatively large ground wheel and which has a driving surface, the pulley being adapted to swing into and out of engagement with said inner driven surface with the driving surface of the pulley following an arc which cuts the driven surface of the wheel at an acute angle so that the driving pulley swings towards the wheel in the direction opposed to the direction of movement of the driven surface and drives itself into engagement with the driven surface, control means for said drive arrangement, in which said control means include first manually-operable means to swing said pulleys into and out of engagement with the driven surfaces of the wheels, first electric switch means to close when said pulleys are in engagement with the driven surfaces and to open when said pulleys are out of engagement with the driven surfaces, second manually-operable means which are operated by an attendant to swing said pulleys into and out of engagement with the driven surfaces, and second switch means connected in series with said first switch means and operated by the invalid to energise the two electric motors when said pulleys are in engagement with the driven surfaces, said second switch means being held closed when said second means are to be operated by the attendant.