Patent GB-1123271-A (GB)
Title: Improvements in or relating to power-assisted brake means
Inventor: FULMER KEITH HAROLD
IPC: B60T13/14
Filed: 1965-08-09
Abstract: 1,123,271. Hydraulic power brakes; indicating position of brake pedal. BENDIX CORP. 9 Aug., 1965, No. 34021/65. Headings F2E and F2F. In a power braking system for operating vehicle brakes, a power brake control device or apparatus 10 is provided between an hydraulic pressure source, in the form of an accumulator 16 supplied by a pump 14 from a fluid reservoir 12, and an hydraulic braking circuit, the power brake control device including a differential piston 38 which defines a pressure chamber 40 connected to the braking circuit and an internal inlet chamber 42 connected to the pressure source through a one-way valve whereby, upon actuation of a brake pedal lever 80, the brake control device urges fluid to flow from the pressure source to the braking circuit in the normal braking operation and, in the event of failure of the pressure source, the differential piston 38 of the brake control device is reciprocable to create an hydraulic pressure in the braking circuit. The power brake apparatus further comprises a pressure responsive movable device for moving the brake control device and the brake pedal lever in high or low positions according to the value of pressure from the source with respect to a predetermined value, an accumulator means being provided which includes a movable wall responsive to the differential pressure between the inlet chamber and the auxiliary supply of the pressure responsive movable device to prevent an excessive pressure in the inlet chamber upon movement of the movable device, a oneway check valve being provided between the inlet chamber and the auxiliary supply. In operation, when the brake pedal actuated rod 80 is actuated, a valve stem 70 raises a ball valve 50 from its valve seat 54 to allow fluid pressure within the chamber 42 supplied from the accumulator to flow into the chamber 40 and to the vehicle brakes. The pressure supplied to the chamber 42 enters through a passage 149 and will be directed to the chambers 148 and 186 to act on the valve spool 130 (Fig. 2) and on a poppet valve 200 (Fig. 3) to open the latter and allow fluid under pressure to pass via conduit 183 to the chamber 42. When the pressure acts on the valve spool 130, the spool is moved to unseat a ball 136 to open a chamber 150 to a reservoir capacity 28 via a cavity 128 and a plurality of radial passages 202 in the sleeve 140. The spool 130 is forced to close the radial passage 126 and open the passage 124 which then allows high pressure fluid to the chamber 150 and by means of a passage 104 to the portion 102 behind the piston 100. This action will force the piston 100 to move inwardly of the bore 36 to move the piston 38 inwardly also and lower the position of the brake pedal. Upon a failure of the braking system such as a failure of the inlet line, accumulator, or pump, the spool 130 will not be activated and the spring 110 will cause the piston 100 to assume the position shown in Fig. 2, whereby the brake pedal is in its uppermost position. The differential piston assembly is then reciprocable to create an hydraulic pressure in the braking circuit. Reference has been directed by the Comptroller to Specification 1,034,137.