GB703784A - Improvements in or relating to disc brakes for road and other vehicles - Google Patents

Abstract

703,784. Disc brakes. GIRLING, Ltd. Aug. 21, 1952 [Aug. 21, 1951; Jan. 2, 1952], Nos. 19657/51 and 130/52. Class 103(1) In a vehicle disc brake of the type described in Specification 688,382 wherein friction pads 11 on both sides of the disc 10 are applied simultaneously by hydraulic pressure from a single common master cylinder or other actuator 18, a suitable restriction 20 is inserted in the pipe 17 leading directly from the master cylinder, the restriction having the effect of permitting free passage of fluid between the cylinders but of throttling back flow from the actuator cylinder to the master cylinders. The restriction 20 may in practice take the form of a non-return valve assembly providing a greater resistance to flow in one direction than the other. In the valve assembly shown in Fig. 2, the pipe line to the two actuators is connected at 31 and that to the master cylinder at 32. Pressure from the master cylinder thus initially acts on one face of a piston 34 and moves it to the left together with a valve sleeve 37 thus forcing liquid to the left thereof out through connection 31 to the actuator cylinders. Later, after there has been a build up of pressure behind the sleeve 37 sufficient to compress spring 39, the sleeve 37 is unseated from piston 34 and liquid may flow directly in accordance with the force applied to the pedal. On release of the brakes the return of liquid is limited by the possible rearward movement of the piston 34. If, however, there is a build up of pressure in the actuator cylinders to between 100 and 1000 lbs. per square inch due to temperature rise during a prolonged period of braking or other causes, this pressure may be relieved by raising a valve 42 against a strong spring 44. In one alternative assembly shown diagrammatically in Fig. 3, pressure from the master cylinder is applied to the smaller end of a stepped piston 52, liquid from the larger left hand end being forced through the line 53 to the brake cylinders. When the pressure reaches a certain value it may lift non-return valve 56 and act in the annular recess 61 of the piston to neutralize the differential action. Further application at higher supply pressure takes place past the non-return valve 55 through piston 52. When a negative pressure is left in the pipe leading to the master cylinders, liquid can flow from a reservoir past non- return valves 60 and 58. Other valve assemblies are also described. The invention is particularly applicable to disc brakes having pads in light rubbing contact with the disc as described in Specification 519,787.