Hydraulic disc brake actuator with a self-adjusting mechanism

Claim 2

An adjusting device for a hydraulically actuated brake having a pressure-responsive actuating piston in an open-ended cylinder, the piston being adapted to move a brake pad toward a rotating member to be braked, means for retracting the piston, a spindle threaded into the piston and spring biased toward an extended position in which the spindle abuts against the bottom of the cylinder to limit retraction of the piston, the threaded connection between the spindle and the piston having an axial clearance equal to the desired clearance between the brake and the rotating member in the released condition, characterized by hydraulically actuated locking means responsive to the hydraulic brake pressure for preventing rotation of the spindle when the brake pressure is applied to the piston.

Claim 3

An adjusting device as defined in claim 1, wherein said means for providing a restoring force biasing the piston towards the retracting position comprises a resilient annular sealing ring in an annular groove between the piston and the cylinder, the sealing ring being adapted to frictionally grip the piston and provide a restoring force for retracting the piston when the braking pressure is released.

Claim 4

An adjusting device for a pressure medium operated brake system having a slidable hollow actuating piston in an open-ended cylinder housing and including means for applying said pressure medium during braking in a manner so as to cause said piston to translate axially to apply the brake comprising the combination of: means providing a restoring force biasing the piston toward its retracted position; an externally threaded spindle disposed coaxially within said hollow piston, one end of the spindle adapted to abut against the end of the cylinder to limit retraction of the piston and the threads of said spindle engaging corresponding threads on an internal portion of said hollow piston forming a first thread engagement, said first thread engagement having predetermined axial play equal to the desired brake clearance in the released condition; torque means operatively connected to rotate said spindle in a direction so as to bias said first thread engagement at one extremity of said axial thread play whereby to make the full amount of said play available for said axial translation of said actuating piston during braking; and locking means responsive To the application of pressure to said pressure medium to prevent operation of said adjustment means during braking.

Claim 5

An adjusting device for a pressure medium operated brake system having a slidable hollow actuating piston in an open-ended cylinder housing and including means for applying said pressure medium during braking in a manner so as to cause said piston to translate axially to apply the brake comprising the combination of: means providing a restoring force biasing the piston toward its retracted position; an externally threaded spindle disposed coaxially within said hollow piston, one end of the spindle adapted to abut against the end of the cylinder to limit retraction of the piston and the threads of said spindle engaging corresponding threads on an internal portion of said hollow piston forming a first thread engagement, said first thread engagement having predetermined axial play equal to the desired brake clearance in the released condition; torque means operatively connected to rotate said spindle in a direction so as to bias said first thread engagement at one extremity of said axial thread play whereby to make the full amount of said play available for said axial translation of said actuating piston during braking; and locking means responsive To the application of pressure to said pressure medium to prevent operation of said adjustment means during braking.

Claim 6

The invention set forth in claim 3 in which said means connected to rotate said spindle comprises a circumferentially wound spring connected to exert a rotational force between said actuator piston and said spindle.

Claim 7

An adjusting device as defined in claim 3, wherein said means for providing a restoring force biasing the piston toward the retracted position comprises a resilient annular sealing ring in an annular groove between the piston and the cylinder, the sealing ring being adapted to frictionally grip the piston and provide a restoring force when the braking pressure is released.

Claim 8

An adjusting device as defined in claim 3, wherein said locking means comprises a locking piston slidable within said hollow-actuating piston, the locking piston having a threaded section engaging said spindle threads and being movable in response to a braking pressure to jam against the spindle threads and to prevent rotation of the spindle.

Claim 9

An adjusting device as defined in claim 6 including means for drawing the actuating piston into the cylinder comprising abutments on the spindle and cylinder limiting the movement of the spindle away from the end of the cylinder, and means for manually rotating the spindle in the direction opposite the adjusting direction whereby the piston may be retracted.

Claim 10

The invention set forth in claim 6 further defined in that a hollow bushing located coaxially with respect to said spindle and actuating cylinder and fixed through the end of said housing opposite said actuating piston, and said circumferentially wound spring is also wound to exert an axially directed force tending to keep said spindle axially fayed against the end of said bushing extending within said housing.

Claim 11

The invention set forth in claim 8 in which auxiliary means are included within said hollow bushing for manually turning said spindle in response to the rotational force of a handtool thereby to withdraw said actuating piston from its quiescent position.

Claim 12

The invention set forth in claim 9 in which said auxiliary means includes a floating intermediate piston within said hollow bushing with rotational and translational freedom, means for obturating the sliding surface between said floating piston and the inside wall of said bushing, means for making said floating piston responsive to rotation and translation within said bushing in response to the rotational and axial force of an applied handtool, screw means engaging said spindle in rotational security, and means for causing said floating piston to engage said screw means in rotational security in response to said applied handtool translational and rotational forces.