Disc brake caliper piston and housing retraction and knockback control mechanism

In a disc brake assembly having a caliper including a housing slidably mounted on a fixed mounting member, a first brake pad assembly mounted on said caliper housing and having a first friction surface positioned for engagement with one side of a disc to be braked, a hydraulically actuated piston mounted in a cylinder formed in said caliper housing, a second brake pad assembly mounted on said piston and having a second friction surface positioned for engagement with the other side of the disc to be braked, and a grip-and-slip retraction and knockback control mechanism, the improvement comprising the mechanism determining and controlling disc brake pad assembly retractive movements to establish zero drag between the brake pad assembly friction surfaces and the disc, said mechanism comprising in combination:

• a caliper housing grip-and-slip retraction and knockback control mechanism providing for a predetermined limited amount of caliper housing retraction sliding movement on said fixed mounting member during brake pad assembly retraction and acting during brake actuation when said amount of predetermined limited axial caliper housing movement is exceeded in the brake actuation direction to adjust the retracted position of said caliper housing relative to said fixed mounting member;
• and a piston grip-and-slip retraction and knockback control mechanism providing for a predetermined limited amount of axial retractive movement of said piston relative to said caliper housing during brake pad assembly retraction and acting during brake actuation when said amount of predetermined limited axial piston retractive movement is exceeded to adjust the retracted position of said piston relative to said caliper housing;
• the predetermined limited axial retractive movement of said piston in the caliper housing upon brake release being established by the sum of the total caliper housing movement relative to the fixed mounting member at full hydraulic pressure actuation of the disc brake assembly and the total second brake pad assembly friction surface movement relative to the disc at full hydraulic pressure actuation of the disc brake assembly;
• said total caliper housing movement relative to the fixed mounting member being the sum of caliper housing deflection at the first brake pad assembly friction surface when the brake is fully hydraulic pressure actuated and a preset required minimum gap running clearance between the first friction surface and the disc to be braked;
• said total second friction surface movement relative to the disc to be braked being determined by the sum of the caliper housing deflection at the second brake pad friction surface when the assembly is fully hydraulic pressure actuated and a preset minimum gap running clearance between said second friction surface and the disc to be braked.

In a sliding caliper disc brake assembly having at least one mounting bolt and a caliper slidably mounted on said bolt, said caliper including a caliper housing having one leg defining a cylinder, a piston reciprocably received in said cylinder and adapted to be actuated by hydraulic brake pressure to actuate the brake assembly, a first brake pad assembly mounted on said piston for movement therewith, said caliper housing having another leg having a second brake pad assembly mounted thereon for movement with said caliper housing, and a caliper housing bridge section joining said legs, said assembly being arranged to cooperate with a brake disc selectively engageable and disengageable by said brake pad assemblies for brake actuation and deactuation, said mounting bolt extending in an opening in said caliper housing to permit guided axial movement of said caliper housing relative to said mounting bolt and the disc to be braked, the improvement comprising:

• a disc brake caliper piston and housing retraction and knockback control arrangement assuring zero drag of the brake pad assemblies on the brake disc while the brake is not actuated, said control arrangement comprising:
• a piston retraction and knockback control mechanism including an annular recess in said caliper cylinder, a friction ring in said recess extending about and frictionally gripping said piston and capable of a predetermined limited axial movement within said recess relative to said caliper housing, a spring in said recess acting on said friction ring and continually urging said piston via said friction ring toward a retracted position of brake assembly deactuation, actuating movement of said piston in the brake actuating direction in response to hydraulic fluid pressure acting thereon within said cylinder carrying said friction ring axially to compress said spring, said piston when moving an axial distance greater than the predetermined amount of limited axial movement of said friction ring in said recess slipping in said friction ring so that said friction ring grips said piston at an axially changed position, said spring expanding axially upon piston deactuation to move said friction ring with said piston to an axially changed retracted position established by the amount of movement of said piston in said friction ring, the retractive clearance of said first brake pad assembly relative to the disc being established by the predetermined limited axial movement of the friction ring in the recess;
• a caliper housing retraction and knockback control mechanism including an annular recess formed in said caliper housing opening, a second friction ring in said recess extending about and frictionally gripping said mounting bolt and capable of a predetermined limited axial movement in said recess relative to said caliper housing, a second spring in said recess acting on said caliper housing and continually urging said caliper housing toward a retracted position corresponding to brake deactuation by reacting on said mounting bolt through said second friction ring, actuating movement of said caliper housing in the brake actuating direction in response to hydraulic brake fluid pressure in said cylinder acting on said piston and said housing compressing said second spring axially as said housing recess moves axially relative to said second friction ring, said housing when moving an axial distance greater than the predetermined amount of limited axial movement of said second friction ring in said recess causing said second friction ring to slip axially on said mounting bolt so that said second friction ring grips said mounting bolt at an axially changed position, said second spring expanding axially upon caliper housing deactuation to move said housing to an axially changed retracted position relative to said mounting bolt established by the amount of movement of said second friction ring on said mounting bolt, the retractive clearance of said second brake pad assembly relative to the disc being established by the predetermined limited axial movement of said second friction ring in said recess;
• the required amounts of the predetermined limited axial movements of said friction rings in said recesses being cooperatively established to assure that said piston is sufficiently retracted to have the brake pad assembly mounted thereon positioned to be disengaged from the brake disc upon brake deactuation and the brake pad assembly mounted on said caliper housing to be disengaged from the brake disc upon brake deactuation.