Electrically operated door actuator with adjustable safety torque - uses friction clutch carried between spring positioned plates with screw position adjustment to give adjustable limit torque on clutch

摘要

The door actuator incorporates a torque limiting transmission to safeguard against injury to personnel and to prevent damage when an obstruction is olaced in the door. The output shaft of the electric motor engages a friction clutch which transmits rotation to a threaded rod passing through a threaded block coupled to the door actuating linkage. Excess torque causes slippage at the clutch. The clutch is carried between two plates by ball bearings and the plates are held together by springs acting against an adjustable plate. The torque limit of the clutch is thus adjustable by modifying the spring force on it.