Disc brake having a piston retraction assembly

Abstract

A disc brake having a piston retraction assembly includes a caliper (12) receiving a piston (14) for biasing a friction pad (16) into engagement with a rotor (18). A recess (30) on the caliper receives the retraction assembly 32 and a boot assembly 34 cooperates with the retraction assembly (32) to limit movement of the latter with the piston (14). A resilient member (40) engages the boot assembly (34) to bias the piston (14) via friction ring (36) to return to its rest position.

I claim: 
     
       1. In a disc brake having a piston retraction assembly, a caliper defining a bore for receiving a piston to substantially form a pressure chamber, the pressure chamber receiving pressurized fluid during braking to move the piston relative to the caliper, the retraction assembly cooperating with the caliper and the piston to substantially control withdrawal for the piston relative to the caliper upon termination of braking and a boot assembly cooperating with the caliper and the piston to isolate a sliding interface therebetween from the environment, characterized by said caliper bore including a recess at the open end, said retraction assembly comprising a friction ring engaging said piston and a resilient member biasing said friction ring to a first position engaging said caliper, said friction ring and said resilient member being disposed within said recess and said boot assembly including a portion extending into said recess to engage said resilient member, said friction ring being movable to a second position in response to movement of said piston to also engage said boot assembly portion whereby said boot assembly portion limits movement for said friction ring, and said friction ring .[.being substantially L-shaped in cross section with an axially extending leg.]. forming a radial clearance with an axially extending wall of said recess. 
     
     
       2. The disc brake of claim 1 further characterized by .Iadd.said friction ring defining an axially extending leg and .Iaddend.said axially extending leg being engageable with said boot assembly in said second position. .Iadd.3. The disc brake of claim 1 in which said friction ring is substantially L-shaped in cross-section to define an inner recess for receiving said resilient member in said inner recess. .Iaddend. .Iadd.4. In a disc brake having a piston retraction assembly, a caliper defining a bore for receiving a piston to substantially form a pressure chamber, the pressure chamber receiving pressurized fluid during braking to move the piston in an applied direction relative to the caliper, the retraction assembly cooperating with the caliper and the piston to substantially control movement of the piston opposite to the applied direction upon termination of braking, the bore forming a cylindrical wall with a first recess at an open end of the bore for receiving the retraction assembly and a second recess adjacent the first recess but spaced therefrom for receiving a seal therein sealingly engaging the piston and the caliper to retain the fluid pressure in the pressure chamber, a boot assembly extending between the piston and the caliper first recess to protect an interface between the piston and the caliper, the boot assembly terminating in the first recess at an element extending transversely to the applied direction in the first recess and fixedly disposed therein, the retraction assembly including a friction ring spaced from the seal and also engaging the piston to move slightly therewith and a resilient member extending between the element and the friction ring, the element being fixedly disposed within the first recess to separate the boot assembly from the friction ring and resilient member, and the friction ring normally engaging a radial shoulder of the first recess in a rest position and remaining spaced from an axial wall of the first recess when moving slightly with the piston against the resilient member in order to avoid interference between the axial wall and the moving friction ring..Iaddend. .Iadd.5. The disc brake of claim 4 in which the friction ring is substantially L-shaped to define a radially inner recess for receiving the resilient member..Iaddend. .Iadd.6. In a disc brake having a piston retraction assembly, a caliper defining a bore for receiving a piston to substantially form a pressure chamber, the pressure chamber receiving pressurized fluid during braking to move the piston in an applied direction relative to the caliper, the retraction assembly cooperating with the caliper and the piston to control movement of the piston opposite to the applied direction upon termination of braking, the bore forming a cylindrical wall leading to a recess at an open end of the bore, the retraction assembly being disposed within the recess and including a friction ring engaging the piston and movable therewith, an element fixedly disposed within the recess relative to an axial wall of the recess, and a resilient member extending between the element and the friction ring to bias the latter into engagement with a radial shoulder formed by the recess, and the friction ring defines a clearance with the axial wall of the recess to remain spaced therefrom at all times in order to avoid interference between the moving friction ring and the axial wall..Iaddend.