GB1254089A - Improvements in or relating to master cylinders for hydraulic brake systems - Google Patents

Abstract

1,254,089. Master cylinders; valves. FIAT S.p.A. 2 April, 1970 [3 April, 1969], No. 15567/70. Headings F2F and F2V. A master cylinder, for an automobile hydraulic brake system including a slave cylinder, comprises a cylinder 2, a control piston 4 at one end of, and slidable within, the cylinder in response to an external control and defining a compression chamber 3 between the piston and the other end of the cylinder, a brake fluid inlet 35 including a passageway 34 for supply brake fluid from a fluid reservoir to the chamber, and a valve 33a for controlling flow of brake fluid through the. passageway, the valve having a cylindrical guide section 33 for sliding movement in the passageway. There are also an outlet pipe connection 44 for feeding brake fluid from the chamber to the slave cylinder, a coaxial shaft 27 having one end connected to the piston for relative sliding movement therewith, the other end of the shaft carrying the valve, and biasing means, i.e. springs 42, 43 for returning the piston after operation thereof, the springs being adapted for operating the valve to control the flow of brake fluid through the inlet 35. At least one groove 39, formed in the guide section 38, extends longitudinally from the outer end of the valve, and an annular jointing ring 40 is disposed on a flange 32 of the guide section. The arrangement is such that, in operation, the piston is moved for sliding movement in the chamber by activation of the external control to urge the valve for sliding movement in the passageway 34 and against the biasing means whereby the ring 40 provides a fluid-tight seal between the passageway and chamber 3, the piston movement increasing the brake fluid supplied through the outlet pipe connection for actuation of the slave cylinder, and deactivation of the external control causing or allowing the biasing means to return the piston whereby the fluid-tight seal is broken to release the fluid pressure and to allow supply of fluid from the inlet to the chamber. As shown, the shaft 27 is connected to the piston by a retaining member 17. In a modification, there are two master cylinders in tandem controlling separate braking circuits and each piston includes a valve as shown in the figure; the valve 33a of the piston 4 moves in a bore in the other piston and communicates via an annular recess in the latter piston with a reservoir passage in the side wall of the cylinder.