Abstract: A mechanical disc brake comprising a caliper housing having a cylinder bore, with a piston slidably disposed therein which bears at one end against one of the friction pads. Mounted in the outer end of the cylinder bore is an end plate having a screw-threaded bore to receive a power screw. One end of the power screw extends outwardly beyond the end plate and has a lever fixed thereto, which is operated by an air cylinder or other power device. A radially extending head on the inner end of the power screw abuts against a thrust bearing on the end of an adjuster screw that is screw-threaded into the skirt of the piston. A spiral spring is attached at one end to the power screw and at the other end to the adjuster screw, and exerts torque on the adjuster screw tending to rotate the latter in the direction to advance the adjuster screw toward the power screw head whenever there is any axial clearance between the adjuster screw and the power screw. The piston is returned a predetermined small amount (0.010 to 0.

Abstract: A disc brake comprising: a caliper housing having axially aligned first and second cylinder bores; a first piston slidable within the first bore and bearing against one of the friction pads; a second piston slidable within the second bore and having an internally threaded tubular piston rod projecting into the first bore; a threaded clearance-takeup member screwed into the piston rod and having a head abutting against the bottom of the first piston; springs acting against one side of the second piston in the direction to apply the brakes; a hydraulic fluid connection for applying pressure fluid to the other side of the second piston so as to release the brake and compress the spring; and a torsion spring having one end connected through a housing to the second piston, and its other end connected to a tubular sleeve that is nonrotatably connected to the clearance-takeup member.