US Patent 7223196 Gear motor with fail-safe device

The invention concerns a gear motor (1) with a fail-safe device (2) consisting of a housing (4), an electromotor (3), a reduction gear (5) with at least one planetary gear (6), an electromagnetic clutch (11) and an output gear shaft (13), wherein the planetary gear (6) has an internal gear. The internal gear is in mesh with at least one planetary wheel (8) and is fixed in its operation relative to the housing (4). The planetary gear comprises the electromagnetic clutch (11), a magnetically conductive armature and a magnetically conductive stator (21) in which an electromagnetic coil (15) is arranged. During the application of current to the electromagnetic coil (15) the internal gear (10) is secured against turning. The task of the invention is to provide for a reliable operation of the fail-safe device in a gear motor of such kind using less construction space and less number of components thus enabling simple assembly. This task is solved in accordance with the present invention by providing an internal gear (10) that acts as a magnet armature, is axially displaceable and whose geometric alignment is not determined by the housing (4) at least during a power-on and off condition of the electromagnetic clutch (11).