Actuator assemblies for hydraulic braking systems
First Claim
1. An actuator assembly for a vehicle hydraulic braking system comprising a housing, means defining at least one first chamber in said housing having a first inlet for connection to a fluid pressure source and an outlet for connection to a slave cylinder of a wheel brake, a piston assembly working in a first cylinder bore in said housing in communication with said chamber and movable between a first advanced position and a second retracted position, an actuator piston working in a second cylinder bore in said housing and normally acting on said piston assembly to urge said piston assembly into said first advanced position in which the effective volume of said first chamber is at a minimum value and said inlet and outlet connections are open, said actuator piston having a first area at an end of said actuator piston remote from said piston assembly and a second area opposed to said first area, a movable member .[.in said second cylinder bore.]. adjacent said first area of said actuator piston, a compression spring urging said movable member towards said actuator piston, means for applying hydraulic fluid under pressure, between said movable member and said first area of said actuator piston to urge said piston assembly into said first advanced position, and a second inlet connection in communication with said second cylinder bore through which hydraulic fluid under pressure is adapted to be admitted into said second bore when the deceleration of a braked wheel controlled by a supply of hydraulic fluid from said outlet exceeds a predetermined value, said supply of hydraulic fluid under pressure admitted to said second bore acting over said second area of said actuator piston to apply to said actuator piston a force to move said actuator piston in a direction away from said piston assembly and permit said piston assembly to be moved towards said second retracted position in which said first inlet connection is closed and the effective volume of said first chamber is increased to reduce pressure in a line between said outlet connection and said slave cylinder.
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Accused Products
Abstract
In an actuator assembly for an hydraulic braking system the effective volume of a chamber through which hydraulic fluid under pressure is supplied to a wheel brake is adapted to be varied between a minimum and a maximum value by movement of a piston assembly working in a bore in communication with the chamber. An actuator piston having first and second different faces of different areas normally holds the piston assembly in a position in which the effective volume of the chamber is at a minimum until equal hydraulic pressures are applied to the areas of the actuator piston to cause the actuator piston to retract and permit the piston assembly to be withdrawn whereby the effective volume of the chamber is increased.
31 Citations
16 Claims
- 1. An actuator assembly for a vehicle hydraulic braking system comprising a housing, means defining at least one first chamber in said housing having a first inlet for connection to a fluid pressure source and an outlet for connection to a slave cylinder of a wheel brake, a piston assembly working in a first cylinder bore in said housing in communication with said chamber and movable between a first advanced position and a second retracted position, an actuator piston working in a second cylinder bore in said housing and normally acting on said piston assembly to urge said piston assembly into said first advanced position in which the effective volume of said first chamber is at a minimum value and said inlet and outlet connections are open, said actuator piston having a first area at an end of said actuator piston remote from said piston assembly and a second area opposed to said first area, a movable member .[.in said second cylinder bore.]. adjacent said first area of said actuator piston, a compression spring urging said movable member towards said actuator piston, means for applying hydraulic fluid under pressure, between said movable member and said first area of said actuator piston to urge said piston assembly into said first advanced position, and a second inlet connection in communication with said second cylinder bore through which hydraulic fluid under pressure is adapted to be admitted into said second bore when the deceleration of a braked wheel controlled by a supply of hydraulic fluid from said outlet exceeds a predetermined value, said supply of hydraulic fluid under pressure admitted to said second bore acting over said second area of said actuator piston to apply to said actuator piston a force to move said actuator piston in a direction away from said piston assembly and permit said piston assembly to be moved towards said second retracted position in which said first inlet connection is closed and the effective volume of said first chamber is increased to reduce pressure in a line between said outlet connection and said slave cylinder.
Specification