Abstract: A wheelchair has two central wheels that can be separately driven by a motor. In order to allow the wheelchair to turn around in narrow spaces, the central wheels can be driven in opposite directions of rotation. When the wheelchair is turned around, the front wheels and rear wheels do not constitute a hindrance because they are kept at a distance from the ground by the swiveling wheel. All three wheels are coupled together on each side by a chain. When the front wheels run against an obstacle, the wheelchair climbs over the obstacle with the driven front wheels. This causes the fork of the swiveling wheel to swivel about the rotational axis in the direction of arrow, against the force of a spring, bringing the rear wheels in contact with the ground and also driving the wheelchair's rear wheels. This all-wheel drive allows the wheelchair to overcome relatively high obstacles both forwards and backwards, even when driving slowly and without losing its maneuverability.

Abstract: A wheelchair has two central wheels (15) which can be separately driven by a motor. In order to allow the wheelchair to turn around in narrow spaces, the central wheels (15) can be driven in opposite directions of rotation. When the wheelchair is turned around, the front wheels (17) and rear wheels (19) do not constitute a hindrance because they are kept at a distance from the ground (25) by the swivelling wheel (21). All three wheels (15, 17, 19) are coupled together on each side by a chain (27). When the front wheels run against an obstacle, the wheelchair climbs over the obstacle with the driven front wheels (17). This causes the fork (22) of the swivelling wheel (21) to swivel about the rotational axis (31) in the direction of arrow (33), against the force of a spring, bringing the rear wheels in contact with the ground and also driving the wheelchair's rear wheels.

Abstract: The head support unit may be attached by attachment means (13) to a chair, e.g. a wheel chair. A set screw (15) permits vertical adjustment. The head rest (19) may be horizontally moved by the user into the desired position. This movement takes place without a recognizable movement in vertical direction. The head rest (19) is carried by a slender lever parallelogram (18) which is operatively connected by a flexible Bowden-cable (21) to the motor (23) located at a distance on the chair. This flexible connection (21) permits not only to put the motor (23) at a suitable location away from the head of the user, but does also not hinder a vertical adjustment of the head rest (19) by means of the vertical support bar (11) and the set screw (15).