Abstract: A master cylinder for a vehicle braking system comprises a body (2) with a bore (3) open at the rear end of the body, a reservoir (4), a transverse port (17) in the body opening into the bore (3) and positioned rearwardly of the reservoir, and a passageway defined between the exterior of the body (2) and a sleeve (22) mounted thereon to communicate the transverse port (17) with a chamber (7) of the reservoir. in different disclosed embodiments the sleeve may be integral with the housing of a booster assembled with the master cylinder and an element may be interposed between the sleeve and the master cylinder body and be provided with a tubular extension interconnecting the reservoir with the passageway.

Abstract: A pedal-operated booster incorporates a valve mechanism for controlling pressurization of a boost chamber. The valve mechanism comprises a pedal-operated piston and a pressure-responsive valve spool which is coupled to the piston for limited relative movement in a longitudinal direction within a working chamber in the piston. The spool is movable with the piston in an initial brake-applying direction in which the spool is operative to isolate the boost chamber from an exhaust port and the piston is operative to place an inlet port in communication with the working chamber. This causes the spool to move relatively away from the piston in response to pressure fluid in the working chamber which is admitted to the boost chamber.

Abstract: An hydraulic actuator comprises a first piston and a second piston both working in a bore in a housing and the actuator incorporates a pressure proportioning valve. The valve comprises a valve head for engagement with a seating, first and second stems projecting from the head and through the first piston in each of two opposite directions, each stem being of an area smaller than that of the head, a seal between the first stem and the first piston, a first spring acting between an abutment adjacent to the seal and a shoulder on the first stem to urge the head in a first direction away from the seating and into engagement with a stop, and a second spring acting on an enlargement on the second stem also to urge the head in the first direction and to augment the force in the first spring. The second piston is provided with a longitudinally extending recess into which the second stem and the second spring both project.

Abstract: A booster for a vehicle braking system has an input piston, a boost piston and an output piston working a bore, the boost piston being advanced in the bore in response to pressure fluid from a source pressurizing a boost chamber under control of a valve.The operation of the valve is dependent on the pressure in the system, and the valve has a valve mechanism working in a bore in the boost piston of which one part has a pressure-responsive face, the valve being operative, on initial movement of the input piston to cause pressurization of the braking system to the threshold level, and application of pressure fluid to the pressure-responsive face to move the part relative to the input piston to place the boost chamber in communication with the pressure source. Threshold pressurization of the braking system may be achieved by pressurization of the boost chamber, or an auxiliary chamber forward of the boost piston to a predetermined level.

Abstract: In a power braking system for a vehicle a supply of fluid from a power source is utilized to augment the output pressure to be supplied to a brake from a pedal-operated brake control valve assembly. The power source comprises a source of hydraulic fluid of a type different from that which is supplied to the brake from the control valve assembly, and the fluid under pressure from the pressure source is supplied to at least one pressure converter which is adapted to pressurize hydraulic fluid in a sub-system to augment the output pressure from the control valve assembly. The sub-system is provided with hydraulic fluid of a type different from that of the power source, and an hydraulic accumulator is incorporated in a line between the pressure converter and the control valve assembly.

Abstract: In a servo booster in which the rear part of the valve body is slidably guided in a guide in the rear end of the booster housing, the rear part and the guide have non-round cross-sections to prevent the valve body from turning relative to the housing. This is of particular benefit when a tie extends through the movable wall for transmitting braking reaction forces. Such a tie has to be sealed to the movable wall by a suitable seal, and any turning of the movable wall might damage the seal.The interior of the valve body is of circular cross-section so that, due to the non-round external shape, a radially thickened portion of the valve body is formed to carry a fluid conduit.

Abstract: In order to reduce the distortion of a servo booster housing in use the booster is provided with one or more ties which extend through the movable wall for transmitting reaction forces directly from the master cylinder housing to the vehicle bulkhead between which the booster is mounted. This enables a housing of lighter weight, such as a plastics housing, to be employed, and an overall saving in weight may be achieved. The front or rear housing wall, or both, is provided with a sleeve which encases part of the tie within the housing. The sleeve may perform various functions: it may be keyed to the tie to resist turning of the tie, it may be arranged to support a rolling diaphragm sealing the tie to the movable wall, and its free end may locate a peripheral bead on the rolling diaphragm.

Abstract: In order to reduce the distortion of a servo booster bousing in use the booster is provided with one or more ties which extend through the movable wall for transmitting reaction forces directly from the master cylinder housing to the vehicle bulkhead. This enables a housing of lighter weight to be employed, and an overall saving in weight to be achieved. A diaphragm support plate of the movable wall is sealed to the tie by a rolling diaphragm, and the support plate is provided with a tubular extension co-axial with the tie.

Abstract: In order to reduce the distortion of a servo booster housing in use the booster is provided with one or more force transmitting means which extend through the movable wall for transmitting reaction forces directly from the master cylinder housing to the vehicle bulkhead between which the booster is mounted. This enables a housing of lighter weight to be employed, and an overall saving in weight may be achieved.

Abstract: An hydraulic pressure converter comprises a differential piston which works in a stepped bore in a housing. A pressure space is defined in the housing at the end of a portion of the piston which is of smaller area so that reciprocation of the piston in the bore causes hydraulic fluid to be drawn into the pressure space through a first one-way valve and then pumped to an outlet through a second one-way valve. Reciprocation of the piston is accomplished by subjecting the piston to pressure from a pump to move the piston in a first direction away from a stop face and against the force in a compression spring so that hydraulic fluid is drawn into the pressure space. A valve assembly is operative to reduce the force urging the piston in the first direction when the displacement attains a predetermined value whereafter the spring is operative to urge the piston in a second opposite direction to force fluid to the outlet from the pressure space.

Abstract: In a tandem servo booster provided with a pair of ties extending through the housing and diaphragm assemblies for transmitting braking reaction forces from the master cylinder housing directly to the vehicle bulkhead, the ties are tubular and are provided with axially spaced ports to provide fluid communication between pairs of alternate booster chambers. In another construction both ties provide fluid communication between the same two booster chambers, and the other two chambers are connected together by a tubular member which is secured to the diaphragm support plate of the front diaphragm assembly and extends rearwardly through a partition wall of the housing positioned axially between the two diaphragm assemblies.