Slack adjuster for a disc brake.

摘要

A slack adjuster is for a disc brake of the type which includes a disc mounted for rotation about an axle and a caliper brake having a housing (30) mounted on the axle in alignment with a friction surface ofthe disc. A braking piston (20) is mounted in the housing for axial movement toward and away from the friction surface of the disc. Brake actuation produces rotation of a powershaft (46) mountyed in the housing (30) which will in turn produce a corresponding axial movement of the braking piston (20) through a non-rotating powershaft nut (48). An adjusting sleeve (56) between the piston (20) and the powershaft nut (48) is threadably coupled to the piston and capable of rotation in a first direction relative thereto to adjust the axial position of the piston toward the disc. A clearance sensing ring (68) is mounted about the adjusting sleeve (56) for axial movement therewith and has an angled groove (72) in its outer surface for receipt therein of a cam pin (78) which is secured to the housing. The angled groove (72) has opposite parallel walls (74, 76) with an axial distance therebetween equal to an axial thickness of the pin plus a predetermined maximum distance corresponding to the desired running clearance for piston. Camming between the groove (72) and the pin (78) will cause rotation of the clearance sensing ring (68) in the first direction when the axial movement of the adjusting sleeve (56) toward the disc exceeds the predetermined maximum distance and in an opposite direction when the axial movement of the adjusting sleeve away from the disc exceeds the predetermined maximum distance. A clutch element (80) is mounted on the adjusting sleeve with the clearance sensing ring (68) mounted thereon to produce corresponding rotation of the adjusting sleeve (56 in the first direction until the piston (20) contacts the friction surface of the disc and to prevent corresponding rotation of the adjusting sleeve in the second direction.