Self-compensating device for a drum brake

Abstract

An improved self-compensating device for a drum brake of the type including a first member and a second member which together define a hydraulic chamber in a wheel cylinder, said first and second members being slidably but non-rotatably arranged relative to one another so that brake shoes are actuated by displacement of the members away from one another which is initiated by hydraulic pressure introduced into the hydraulic chamber. The self-compensation device is incorporated in the hydraulic chamber and has a function for inhibiting excessive compensation, essentially comprising an adjustment nut disposed in one of the first and second members so as not to be rotated relative to the latter and adapted to detachably abut against an abutment face formed on the one member, a spring means serving to urge the adjustment nut toward the abutment face, an adjustment rod threadably fitted through the adjustment nut, and a clutch member integrally secured to one end of the adjustment rod and rotatably supported in a clutch bore formed in the other member to cooperate with a clutching face formed on the other member. The clutch member is adapted to come the frictional contact with the clutching face when it is thrusted toward the latter by hgdraulic pressure in excess of a predetermined level in the hydraulic chamber and when it is thrusted toward the clutching face by means of a return spring for the brake shoes. At least one air storage is provided on the other member and/or the clutch member which is opened to a bag chamber as defined by those members and extends upward when the device is mounted in use. Further, a distance piece may be removably disposed in an abutment area between the anchor of the other member and the corresponding brake shoe.

Dependencies are inferred from the claim text.