The master cylinder for hydraulic brakes of motor vehicles with opposed pistons acting on the separate hydraulic circuits serving the front and rear brakes

摘要

635,901. Elastic valves. FIAT SOC. PER AZIONI. Oct. 3, 1946, No. 29549. Convention date, Sept. 21, 1942. [Class 135] [Also in Groups XXVI and XXXIV] In a hydraulic master cylinder for operating brakes, annular gaskets 16, 19, 22 of rubber or the like are adapted by the action of spring and hydraulic pressure produced by the piston, to be expanded radially to cut-off the connection of the reservoir to the pressure chamber or to prevent leakage past the piston. The master cylinder shown is divided by a slidable partition 8 into two pressure chambers 9, 9SP1/SP connected by ports 26, 26SP1/SP to separate brakes, the pressure being produced by simultaneous operation of pistons 2, 21. Gaskets 19, 22 of rubber or the like normally convex at the periphery and in contact with the cylinder wall are associated with the pistons 2, 21 and the partition 8. Other gaskets 16, disposed between tubular members 14, 15, are normally spaced from the cylinder wall so that the chambers 9, 91 communicate with reservoir ports 10, 101 through holes in flanges 23 of the members 14. Springs 17, 20 are seated on plates 18 and on shoulders formed in the members 14, 15. When the pistons 2, 21 are moved to apply the brakes, the hydraulic pressure in chambers 9, 91 rises due to the resistance to flow towards the reservoirs offered by the apertured flanges 23. The gaskets 16 are thus expanded radially to contact the cylinder wall and so to cut-off the chambers from the reservoirs, by axial and radial pressure due to the springs and the hydraulic pressure acting on the gaskets. The gaskets 19, 22 are tightly pressed against the cylinder wall for the same reason, so as to prevent leakage from and between the chambers 9, 9SP1/SP. Equalization of the pressure in the two chambers is effected by movement of the partition 8. The valve devices 16 are such as described in Specification 626,622. The Specification as open to inspection under Sect. 91 describes a modification, Fig. 4 (Cancelled), in which the valve device comprises a tubular member 30 which abuts on the gasket 29 of piston 28 and a sleeve 36 slidable on the member 30 and abutting on a gasket 42. Due to the springs 31, 33, the parts normally assume the position shown with the sleeve 36 against a stop 43 so that the reservoir is open to the cylinder through passages 39 in the sleeve. When the piston is moved to apply the brakes these passages are closed by the engagement of the shoulder 40 on the member 30 with a flange 41 on the member 36. The movement of the partition 27 in this form is limited by a pin-and-slot 11 which acts as a stop for the partition if the pressure fails in one pressure chamber. A further form is described which is similar to that of Fig. 2, except for the provision of the pin-and-slot device for the partition. This subject-matter does not appear in the Specification as accepted.