Automatic slack adjuster with adjusting clutch in control train

An automatic slack adjuster for a vehicle brake, comprising:

• a housing configured for coupling to a brake actuator;
• a driving worm wheel supported by the housing and configured to engage a brake cam shaft of the vehicle brake;
• a driving worm screw supported by the housing and in mesh with the driving worm wheel, the driving worm screw configured to transfer a brake actuating force, imparted by the brake actuator to the housing, to the driving worm wheel and brake cam shaft;
• and,
• a wear adjustment mechanism including
• a reference arm assembly configured to be fixed against movement and including a control ring gear;
• a pinion gear in mesh with the control ring gear and configured for rotation about a rotational axis, the pinion gear defining a first angular drive face;
• a clutch ring disposed about the rotational axis and configured for rotation with the pinion gear, the clutch ring defining a second angular drive face disposed within a common plane with the first angular drive face of the pinion gear and spaced from the first angular drive face of the pinion gear by an angular gap corresponding to a predetermined clearance between a friction lining of the vehicle brake and a friction surface of the vehicle brake;
• a control worm screw disposed about the rotational axis;
• a wrap spring engaging surfaces of the clutch ring and control worm screw;
• and,
• a control worm wheel in mesh with the control worm screw and configured for rotation with the driving worm screw.