GB1302907A - - Google Patents

Abstract

1302907 Brake boosters ROBERT BOSCH GmbH 17 March 1970 [18 March 1969] 12788/70 Heading F2F A pressure booster actuable via a ram 5 on a hydraulic master cylinder of a motor vehicle, comprises a plastics piston 3 reciprocable in a cylinder housing 1, 1<SP>1</SP> and a doubleseat follower valve 13, 14, 15 actuable to alter the pressure difference across the piston 3, one seat 14 of the valve being provided on a plunger 10 movable in the axial direction of the piston 3 and the other seal being formed by a shoulder 13 of the otherwise smooth inner bore of a tubular extension 9 of the piston 3 and a closure member 15 co-operable with the two valve seats 13, 14 being provided with a diaphragm 16 having an annular seal 17 abutting tightly against the inside wall of the extension 9. As shown in Fig. 1, the seal 17 is retained in position by an indentation 22 in a metal tube 18 in the tubular extension 9, and springs 21, 23 are provided, the spring 21 being held in a cup shaped metal reinforcement 151 of the closure member 15 and the spring 23 being positioned in the tube 18. The booster is shown in its unactuated conditions with chambers on either side of the piston 3 in communication and held at low pressure. To actuate the booster a rod 7 hinged to a brake pedal is moved to the left to thereby move plunger 10 and closure member 15 until closure member 15 abuts shoulder 13 and interrupts the connection between the chambers: further movement of the plunger 10 then lifts the seat 14 off the closure member 15 and air may then enter the chamber to the right of piston 3 and move the piston 3 in the direction of braking. As shown in Fig. 2 valve spring 33 is pressed against the inside wall of extension 9 and is retained between seal 34 and the peripheral edge of a metal disc 9<SP>1</SP> in the closure member 15. Fig. 3 (not shown) illustrates a form of annular seal (37) with a radially directed edge (38).