Patent ID: 7188710

Claim:
A hydraulic brake actuator for an automotive brake system comprising a rotor and brake pads adapted to engage the rotor for braking, said hydraulic brake actuator comprising: a housing defining a cavity having an open front end and a closed rear end; a hydraulic piston slidably received in said cavity and cooperating with the housing to define a hydraulic chamber, said piston being moveable along a piston axis in response to hydraulic pressure with said hydraulic chamber between an brake application position wherein the piston urges the brake pads to engage the rotor and a brake release position wherein the piston is withdrawn to disengage the brake pads from the rotor; a stationary wedge plate adjacent the closed rear end of the housing and having an inclined surface facing the hydraulic piston; a moveable wedge plate operatively coupled to the hydraulic piston for movement concurrently therewith and having an inclined surface facing the stationary wedge plate spaced apart therefrom; a wedge moveable along a wedge axis perpendicular to the piston axis between an advanced position and a withdrawn position, said wedge having a first inclined wedge surface adapted to engage the inclined surface of the moveable wedge plate when in the advanced position and a second inclined surface adapted to engage the inclined surface of the stationary plate when in the advanced position, said first inclined surface and said second inclined surface extending at an acute angle relative to the piston axis, said wedge comprising an end; and an electrical solenoid assembly comprising a plunger moveable in response to an applied electric field and adapted to move the wedge along the wedge axis between the withdrawn position and the advanced position; whereby when the hydraulic piston is in the brake application position, the electrical solenoid assembly is actuable to advance said wedge to said advanced position, whereupon said inclined wedge surface engages the inclined surface of the moveable wedge plate and said second inclined wedge surface engages the inclined surface of the stationary plate to prevent movement of the hydraulic piston to the brake release position; said hydraulic brake actuator further comprising a detent assembly that includes a detent positioned to engage the end of said wedge when said wedge is in the advanced position and retractable to release said wedge for return to said withdrawn position.