Automatic adjusting mechanism for a disc brake assembly having a

Abstract

A disc brake mechanism, including an integral mechanical parking brake assembly and having automatic wear adjustment features, is disclosed. The adjusting mechanism comprises an axial thrust screw having one end exposed to atmospheric pressure to create an axial hydraulic differential pressure acting thereacross. An adjusting nut is threadably received on the thrust screw and normally engages a hydraulic actuating piston such that the adjusting nut is free to rotate with respect to the thrust screw and piston. Hydraulic pressures acting upon the thrust screw create opposing forces, the resultant of which is applied to a resisting mechanical spring. So long as the hydraulic pressure is below a predetermined value, the resultant hydraulic force acting upon the thrust screw is insufficient to overcome the resisting spring force and the thrust screw remains stationary. As the hydraulic piston moves upon hydraulic actuation of the brake, the adjusting nut is biased to rotatingly advance relative to the thrust screw, thereby adjusting for friction pad wear. As hydraulic pressure increase above the predetermined value, the resultant hydraulic force acting upon the thrust screw is sufficient to overcome the resisting mechanical spring, and the thrust screw in combination with the adjusting nut translates toward the piston. This causes the adjusting nut to frictionally engage the piston preventing any further advance of the adjusting nut relative to the thrust screw, thereby ending the adjustment cycle.