HYDRAULIC ACTUATOR FOR A VEHICLE BRAKE

摘要

A hydraulic actuator for a vehicle brake incorporates an automatic adjuster which includes a strut of variable length formed by members which are threadedly interengaged by way of non-reversible screw thread connection. The member is an adjuster shaft which forms a reversible screw thread connection with a drive ring arranged to control rotation of the adjuster shaft during brake application and release. The non-reversible thread is subject, during brake application, to an axial force which is the resultant of forces derived from the braking pressure applied to different areas defined respectively by a seal on the piston and a further seal on the adjuster shaft. This ensures that random rotation of the adjuster shaft during brake application is resisted without the necessity for the application of axial spring load.