Patent ID: 6822409
Filing Date: 2004-11-23
Classification: G05B,H02P

Abstract:
Positioning apparatus for driving a movable member from a first position to a second position where it stalls, the movable member having a bias urging the movable member to the first position and an electric drive member operable to drive the movable member through a connection against the force of the bias to the second position, the drive member exerting a force proportional to the electric current supplied to the drive member and wherein the current increases when the movable member stalls so as to produce an undesirable excessive force, comprising:a drive circuit having an output connected to the drive member and operable to supply current to the drive member to drive the movable member from the first position to the second position; and a current limiter connected to the drive circuit to detect the current supplied to the drive member, said current limiter operable to detect an increased current above a first level when the movable member initially stalls and to maintain the current level supplied to the drive member at a level no greater than the first level, wherein the first level is below that which would cause damage to the positioning apparatus if the first level of current were maintained indefinitely.