Abstract: A wear adjuster for an internal shoe drum brake of the kind having a strut extending between one shoe and a handbrake lever pivoted on the other shoe includes a spacer between the strut and the one shoe, a screwing mechanism for adjusting the spacing effect of the spacer having an actuating mechanism responsive to service operation of the brake. The brake shoe pull-off spring serves also as a biassing spring for the actuating mechanism.

Abstract: A vehicle brake booster comprises a brake master cylinder operable by a brake pedal, and a power valve including valve means operable by the brake pedal to admit fluid under pressure from a source to a boost piston for applying a boost force to the master cylinder and to apply a reaction force to the brake pedal, the valve means are movable against a spring by fluid under pressure from the source from an inactive position to an active position so long as fluid under pressure is available.

Abstract: An internal shoe drum brake having a pair of brake shoes mounted on a back plate with double ended expanders located one between each pair of adjacent ends of the shoes. The expander has a strut assembly slidable within itself so that when the expander is operated the strut assembly transmits braking loads from one shoe to the other so that the brake operates in a duo servo mode. With the expanders arranged to operate vertically the weight of the shoes and acts against the strut assembly. In order to support the upper brake shoe and prevent the shoes moving off-center a variable length support acts between the upper shoe and the wheel cylinder. The support has a spring therein so that the support can resiliently collapse when the sheos move during duo servo braking.

Abstract: A dual pressure modulating valve unit for a motor vehicle braking system has two identical valves arranged side-by-side in a common housing, each valve being for inclusion in separate sub-systems of a split braking system. The valves are of the pressure limiting or pressure reducing type wherein the pressure at which the valves start to reduce or limit the outlet pressure is determined by a biassing load on the valve plungers. The biassing loads are provided by a beam which normally divides the load of a single biassing spring equally between each plunger. In the event of a failure in one sub-system the plunger of the valve in the other sub-system receives the full load of the spring so that the pressure at which that valve starts to limit or reduce is substantially increased.

Abstract: This invention relates to an air powered braking system for a vehicle. The air pressure in the front and rear brake systems is regulated by a respective one of a pair of air pressure valves. The air valves are hydraulically controlled and each valve (16) and (26) is independently connected to a driver operable hydraulic master cylinder so that the air pressure in each of the front or rear systems is proportional to the hydraulic pressure generated at the master cylinder (11). A hydraulic reducing valve is interposed in the hydraulic circuit between the master cylinder and the rear brake system air valve and operation of the reducing valve reduces the hydraulic pressure to that air valve and hence reduces the air pressure to the rear brakes relative to the air pressure to the front brakes.

Abstract: A hydraulic reservoir and master cylinder assembly having a piston with a blind bore for receiving an input rod, the piston having a breather valve therein provided with opening means operated by an abutment projecting laterally into the master cylinder bore and which is received into a slot in the piston. In order that the abutment be as short as possible and therefore that the slot be as shallow as possible, the piston carries a pivoted lever extending transversely of the piston and which is engageable with the abutment to operate the breather valve.

Abstract: This invention relates to a method of placing an elastomeric annular piston seal beyond an irregularity in the wall of a bore without damaging the seal and also to apparatus having a piston seal so placed. The seal is fitted onto a smaller diameter portion of the piston than that on which the seal operates so that when the piston is inserted into the bore, the seal moves freely past and is placed beyond the irregularity. When the seal is beyond the irregularity it is moved from the smaller diameter portion onto its operable position by relative movement of the piston past an abutment which is encountered by the seal.Such a method of assembly is particularly useful for motor vehicle brake master cylinder failure warning switch assemblies.