GB986175A - Improvements in master cylinders for hydraulic braking systems - Google Patents

Abstract

986,175. Hydraulic brakes. GIRLING Ltd. Jan. 20, 1964 [Feb. 10, 1963; Feb. 10, 1963], Nos. 1183/63 and 1184/63. Heading F2F. A master cylinder 10 in which axial movement of a piston 29 forces liquid under pressure from a space 39 to one or more slave cylinders (not shown) has a longitudinal passage 32 in the piston 29 connecting said space with a reservoir and providing a seating 33 for a movable rod 42 which advances axially to close the passage 32 and to move the piston 29 to apply pressure to the liquid in the space 39, the rod being withdrawn from the seating through a distance defined by a member 41 which has spaced surfaces to form stops for the piston and for the rod (at 46) respectively. The piston 29 is secondary to a main piston 12, pedal operated through a rod 14, which forces liquid from a space 16 by way of a union 17 to one slave cylinder operating one wheel brake whilst the pressure liquid from the space 39 goes by way of a union at 38 in the cylinder end plug 37 to other brake cylinders. The piston 12 has an extension 22 with an apertured flange 21 which opens a tipping valve 19 to replenish the space 16 when the brakes are off. The rod 42 extends from a floating plunger 23 in the full diameter bore of the cylinder, the space 25 in front of which is at all times connected to a reservoir 27. The seating 33 comprises a perforated rubber disc held in position in the piston 29 by a washer 34 and flanged cup 35. When the brakes are applied the piston 12 advances, closing the valve 19 and causing the plunger 23 to advance the rod into the passage 32. The rod engages the seating 33 and pushes the secondary piston 29 into the space 36 which is now cut off from the reservoir 27. On release of the brakes, coil springs positioned respectively between the flange 21 and the plunger 23, the plunger 23 and the member 41 and the piston 29; and the plug 37, cause the movable parts to return to their " at-rest " positions as shown in Fig. 1. Should a leak occur in the space 16, the plunger 23 will still be moved by the extension 22 of the piston 12. With a leak in the space 36 the rod and piston 29 will advance until the latter contacts the stop 37, after which the liquid in the space 16 will be subject to pressure as usual from the piston 12.