GB589075A - Improvements in or relating to booster-operated hydraulic braking systems - Google Patents

Abstract

589,075. Brakes. BENDIX AVIATION CORPORATION. Feb. 28, 1944, No. 3685. Convention date, March 1, 1943. [Class 103 (i)] [Also in Group XXVI] In a braking system which is controlled by a pedal operated master-cylinder, the valve controlling the differential air pressure in the booster is itself controlled both by the opposed hydraulic pressures in the master cylinder and the booster-operated secondary master cylinder, and by the differential air pressure in the booster. As shown, pressure from the pedal operated master cylinder 12 is transmitted through the pipe 13 and ball valve 71 to the tube 73 and from there to the brake cylinders 14a. Brake slack is thus taken up quickly by the direct action of the pedal 11, after 'which the pedal-produced pressure causes the plunger 70 to slide against the spring 76, and close the vacuum-opening 58 in a flexible diaphragm 43. Further pressure on the pedal causes the diaphragm 43 to move against the spring 77 and open the air-valve 47, permitting the admission of air through the filter 45 and ports 57 in the plunger 70 to the back of the piston 24, both sides of which are normally subject to vacuum. When the air pressure rises and operates the piston 24 to boost the pressure in the auxiliary mastercylinder 27, to an extent corresponding to the degree of pedal operation, the diaphragm 43 is moved by the air pressure to close the air valve. Also the plunger 70 is maintained in equilibrium by the opposed forces of the pedal produced pressure, the pressure of the spring 76 and the power-produced hydraulic pressure acting on the step or shoulder of the plunger. A pin 66 keeps the check valve 71 open until the movement of the plunger 70 closes the vacuum valve. The seals between the cover 40 and the air valve 47, and between the valve and the plunger 70, consist of soft leathers 48, 54 secured in position by cupped spring washers 49, 55. Plugged opening 34 serves as a bleeder connection and a plugged opening 68 also serves as a bleeder connection, or it may be used as a brake line connection or to operate other controls. The vacuum cylinder 10 is closed by a cover 28 secured by screws 29 threaded into anchors 30 spot-welded or otherwise secured to the inside of the cylinder The cylinders 10 and 27 may be secured inside the shell, the unoccupied spaces in the shell being used as a vacuum or pressure reservoir. In a modification, the housing 60 for the plunger has a straight bore instead of a stepped bore, a floating cap being provided inside the bore to present a shoulder to the cup leather 62. The plunger 26 is not internally bored to transmit the pedal-produced pressure to the cylinder 27, but this pressure is transmitted by an external pipe leading from the opening 68. Compressed air may be used for the power application instead of vacuum, and the ball valve 71 may be replaced by any form of check valve.