GB928984A - Hydraulic pressure generating devices, more particularly master cylinders for hydraulic transmission systems provided on motor vehicles - Google Patents

Abstract

928,984. Hydraulic master cylinders. FIAT S. p. A and P. S. BALDWIN. Jan. 9, 1962 [Jan. 11, 1961], No. 871/62. Class 103 (1). [Also in Groups XXIV and XXIX] In a master cylinder of an hydraulic brake mechanism or for operating friction clutches on motor vehicles, of the type in which the piston head is formed with an annular groove 3 defined by radial shoulders 7, 8 accommodating an annular packing 9 of resilient material acting as a valve controlling communication between the cylinder chamber 6 connected with utilizing circuits and a reservoir, a ring 11 made of substantially undeformable material is slidably mounted without circumferential clearance in the cylinder on the side of the packing 9 remote from the chamber 6. The packing 9 is accommodated in the groove 3 with an axial and radial clearance, the bottom of the groove 3 being connected through radial holes 4 with a front opening in the piston head to establish communication between the chamber and reservoir opening 12. The packing 9 prevents flow of liquid to the reservoir during the operative stroke of the piston. The ring 11 is rectangular in cross-section, the periphery of the shoulder 8 on which the ring bears during the operative piston stroke being formed with an annular step 10 the axial size of which substantially matches the thickness of the ring. On the return stroke of the piston 2, accomplished by the spring 13, free communication is afforded of the chamber 6 and opening 12 in the wall 1 of the cylinder. The piston 2 carries a rear seal 15 acted upon by a push-rod 16 in which a seat is formed for the rod 17 actuated by the brake pedal.