GB1063078A - Improvements in or relating to brake operating structures - Google Patents

Abstract

1,063,078. Fluid-pressure brakes. NEWAY EQUIPMENT CO. April 2, 1964, No. 13625/64. Heading F2F. In a compressed-air braking system for a vehicle, a fail-safe combined service and parking brake actuator comprises a doubleacting cylinder 30 containing a diaphragm 40 attached to flange 54 of a cup-like piston 52 and to a sleeve 46, open to atmosphere, through which passes a rod 60 carrying the piston, so that the area exposed to air in chamber 48 is greater than that exposed to air in chamber 50, a spring assembly 82, 84, 86 disposed in the chamber 48 to urge the piston-diaphragm assembly in the brake-applying direction, and ports 68, 70 each of which can be selectively connected with either a common reservoir or atmosphere, whereby the actuator is adapted to be operated for a service application by applying pressure equally to both chambers 48, 50, the force resulting from the difference in effective areas on opposite sides of the diaphragm being augmented by the spring assembly. The preferred pneumatic circuit (Figs. 5-8, not shown) consists of a compressedair reservoir (76), a valve (78) operated by the brake pedal (P) and connecting the port 68 selectively with either the reservoir or atmosphere, and a valve (80) operated by the handbrake lever (L) and connecting port 70 selectively with either the reservoir or atmosphere. In the brakes-off condition (Fig. 5), valve (78) connects chamber (48) to atmosphere and valve (80) connects chamber (50) to the reservoir, the spring assembly (S) then being compressed. When the brake pedal is depressed (Fig. 6) both chambers (48) and (50) are connected to the reservoir so that the resultant force mentioned above plus the spring force move rod 60 to the right to apply the brake via a lever (26) and cam-shaft (22) journalled in an axle bracket (24) (Figs. land 2, not shown). If, instead, the handbrake lever is operated (Fig. 7, not shown), chambers (48) and (50) are both connected to atmosphere and the brake is applied by the spring-assembly alone. This is also the case if loss of pressure in the reservoir (76) becomes excessive (Fig. 8, not shown) in the unoperated positions of the pedal and handbrake lever. It is said that by this arrangement normal use of the brakes results in a minimal amount of air being lost from the system.