GB580468A - Improvements in or relating to manual and booster actuated hydraulic systems, particularly hydraulic braking systems - Google Patents

Abstract

580,468. Brakes. BENDIX AVIATION CORPORATION. Oct. 3, 1944; No. 18939. Convention date, Oct. 4, 1943. [Class 103 (i)] In a hydraulic braking or like system wherein the pedal-produced pressure in a primary master cylinder 12, Fig. 1, controls the action of a booster 42 operating a secondary master cylinder 90, the pedal-produced pressure is communicated by thrust rods 40, 104 to the secondary master cylinder, the primary hydraulic system thus being isolated from the secondary system. The cylinder 12, which has a low displacement, is connected by a pipe 30 to a follow-up chamber 32 housing the small-diameter piston or rod 40. A branch pipe 34 leads to valve 36 which controls the operation of the vacuum or pressure booster. As shown, the space 60 is connected to the intake manifold 64 of the engine and the space 66 also is connected thereto by the pipe 70 and passage 68. The spaces 50, 52 behind the pistons 44, 46 are joined by a tube 48 and are connected by a pipe 56 to the control valve 36. The valve 36 comprises a small piston 72 responsive to pressure in the cylinder 72 and connected by a cage 74 to a diaphragm 78. Valves 80, 82, joined by a stem 84, seat respectively on a ring 79 carried by the diaphragm 78, and on a seat 86 on the valve casing. When the pedal 18 is depressed, the piston 72 moves the ring 79 against the valve 80, thus separating the pipe 56 from the vacuum pipe 70. Further movement of the piston 72 opens the valve 82 and connects the pipe 56 to atmosphere. The consequent movement of the booster pistons increases the volume of the chamber 32 and allows the differential pressures on the diaphragm 78 to move back the piston 72, the valve 36 being thus self-lapped. A valve 112 operates if the change in pressure in the chamber 50 lags excessively behind the change in pressure in the valve 36. In this event, the diaphragm 120 is moved by differential pressure to open the valve 116 and the chamber 50 is thus placed in direct communication with the atmosphere. The master cylinder 90 is provided with a check valve 96 which maintains a slight residual pressure in the brake cylinders. A passage 98 in the piston 92 and a port 100 permit compensating liquid to pass from the reservoir 102 to the cylinder 90 to make up loss, the passage being closed by a valve on the end of the rod 104 when the pedal is operated. In Fig. 5, the piston 40c, which is moved by pressure in the follow-up chamber 32c, actuates a slide valve 138 associated with ports 134, 136 on opposite sides of the booster piston 46c. Both sides of the piston are connected by the ports to the vacuum connection 132, but the movement of the valve 138 connects the left hand side ta atmosphere through the ports 142, 140, 136. The consequent movement of the piston 46c and the tube 144 brings the ports 134, 136 again into lapped position relatively to the valve 138. The piston 92c of the secondary master cylinder 90c is bored to receive the plunger 146 which is abutted by the piston 40c, "feel" being thus transmitted to the pedal. In modifications, the follow-up chamber 32 is in the bore of the secondary master cylinder, the piston of the secondary master cylinder separating the two hydraulic systems. The loss make-up is from the reservoir on the pedal cylinder and, in one case, a normally closed spring-pressed valve is opened to connect both systems to the reservoir, when the pedal,is released. In another case, a valve which is normally open to connect both systems to the reservoir, is closed by the pressure in the primary master cylinder when the pedal is actuated. Specification 550,450 is referred to.