GB1481612A - Liquid pressure master cylinders - Google Patents

Abstract

1481612 Master cylinders AUTOMOTIVE PRODUCTS Ltd 7 April 1975 [5 April 1974 18 Dec 1974] 15278/74 and 54705/74 Heading F2F A master cylinder comprises a tube 10, whose bore constitutes the master cylinder bore, mounted in a moulded body 11 of plastics material, the latter being formed with a cavity, to receive the tube, closed at one end by a wall 12, one end of tube 10 engaging an abutment 13 provided on or supported by the wall and the tube being held against the abutment by an annular member 16 in the form of a slotted sleeve secured to the body 11 at the open end of the cavity. A packing ring 39 which is a close sliding fit in the tube 10 is fitted on a boss 38 of the piston 34 and seals against the bore by liquid pressure on movement of the piston and a spring 42 is mounted between the ring and an abutment plate 43. A valve lifting rod 46 is slidably mounted in the piston ends 35, 36 and in the retracted position of the piston lifts the ring 39 away from end 35 so as to provide communication between the pressure chamber and a space behind the piston and hence with the reservoir via notches or holes in the piston end members. When the piston is moved forwardly the rod 46 is free to move rearwardly so that ring 39 contacts the front face of the piston to close the notch or hole and permit a build-up of pressure in the working chamber, the ring 39 serving as a valve and obviating the necessity for a bleed hole in the cylinder wall. In a modification Fig. 6 the tube 10 is located within the body 11 by engagement with longitudinal ribs 66 and communicates with the reservoir via grooves 71. The piston 83 is engaged by a member 92 having a central opening through which passes a rod 98 having a plate 102 secured to its end which plate can engage a sealing ring 103 when the piston is retracted, the latter moving under a spring 104, when the piston is moved forwardly, to shut off connection between tube 10 and the reservoir.