Disc brake actuator

Claim 1

A disc brake actuator comprising: hydraulic pressure actuating means including a cylinder having a piston slidably movable therein and cooperating therewith to form a pressure chamber, mechanical actuating means including a rotatable plug extending into the pressure chamber through the base of the cylinder and having an arm on the outer plug end for rotating the plug and having an enlarged inner end providing a shoulder engaging the cylinder base interior wall, said plug inner end having internal high lead threads formed therein, a high lead screw having one end threadedly engaging said plug inner end high lead threads and the other end extending toward said piston and formed to provide a cam, a split multi-section spline plate having exterior spline teeth thereon and receiving said cam centrally thereof and having cooperative cam surfaces engaging said cam so that rotation of said cam in one direction will expand the multiple sections of said spline plate radially outward, said spline plate having spring means joining the spline plate multiple sections and urging them radially inward, and interior spline teeth on said piston accommodating said spline plate exterior teeth in meshing relation when said spline plate multiple sections are moved radially outward, and being disengaged when said cam is rotated in the other direction so that said spline plate multiple sections move radially inward, said cam being rotated in said one direction by rotary movement of said plug until said spline teeth are engaged, with further rotary movement of said plug in said one direction imparting linear motion to said piston through action of said screw threads to mechanically apply the disc brake.