Power actuator for a machine element such as a clutch

Claim 1

A power actuator for a machine element such as a clutch, a variable speed change device or a brake, said power actuator comprising a housing, a motor-driven worm gear and an actuating shaft for controlling the operative condition of the machine element being arranged in said housing, motion transmitting means for transmitting rotary motion of said worm gear to said actuating shaft, said motion transmitting means including gear means rotatable inside said housing and meshing with said worm gear and a sector gear arranged inside said housing and fixed for angular movement with said actuating shaft, said gear means also meshing with said sector gear, a force moderating spring disposed inside and attached at one end to said housing, said force moderating spring also attached at an opposite end to a link, said link being connected to said gear means at a location beyond the rotational axis of the gear means relative to said sector gear, said gear means and said sector gear meshing at a location intermediate an attachment zone of said force moderating spring to said link and an attachment zone of said link to said gear means, the attachment of the spring to the housing being spaced from the actuator shaft, said moderating spring having an axis extending at an angle less than about 90° to a central radius of said sector gear, said axis of said force moderating spring lying in a plane generally perpendicular to said actuating shaft and containing said sector gear, said link extending alongside a portion of said sector gear for applying the spring force of said force moderating spring to said gear means.