with wheels fitted object of the type that is designed to be operated by a walking person

摘要

A wheeled object or vehicle, such as a hospital bed (10) comprises a main chassis or frame (12) supported by a plurality of supporting wheels or rollers (11), which define the vertices of a polygonal supporting surface (21). The bed, which is usually moved by a walking person, is provided with at least one motor driven driving device (15), including at least one driving wheel or roller (18), positioned within said polygonal supporting surface. The driving device is rotatable about a substantially vertical axis (14) in relation to the chassis or frame so as to change the angular position of the driving wheel (18) in relation to the chassis or frame. Biasing means, such as a compression spring or a pneumatic or hydraulic cylinder (22, 34) is provided for biasing the driving device (15) in a direction away from the main chassis or frame (12) and towards the supporting surface (21). The biasing force is controlled such that the driving device (15) id kept in close non-skidding contact with the ground or floor surface (21) without lifting the supporting wheels (11) out or contact with the supporting surface.