GB564608A - Improvements in or relating to master cylinder units for liquid pressure controllingsystems - Google Patents

Abstract

564,608. Hydraulic master cylinders. AUTOMOTIVE PRODUCTS CO., Ltd., and CHOUINGS, L. C. Jan. 29, 1943, No. 1579. [Classes 69 (ii) and 135] [Also in Groups XXVI and XXXIV] The reservoir connections for hydraulic master cylinders for operating brakes, clutches, &c., comprise a port in the cylinder wall that is uncovered when the piston reaches the retracted position and a non-return valve which may be mounted on the piston or the cylinder and which permits flow to the cylinder during retraction. As shown in Fig. 1, the piston has front and rear heads 18, 20 to provide an annular space 29 connected by passages 28, 27 to the reservoir and carries a packing ring 30 comprising an outer ring of rubberised fabric, synthetic resin or other wearresistant material and an inner ring of soft rubber under compression. According to the Provisional Specification, the groove for the ring 30 is axially wider than. the ring so that it may expand axially and so that the pressure in the cylinder may act on its endface to increase the outward thrust on the fabric ring. The piston end formed of the ring 30 is of reduced diameter and has a cylindrical recess 33 for the end of the spring 16 and for an apertured disc 41 upon which bears a seating spring 40 for a conical non-return valve 37 seated in a recess in the piston-rod carrying a packing ring 39 of soft rubber. The valve 37 permits flow of liquid from the reservoir to the cylinder chamber 35 through the space 29 and passages 42. A port 34 opening into passage 27 is uncovered by the piston in the retracted position. A bleeder plug 43 and a pressure-retaining valve 15 are provided. The non-return valve may instead comprise a resilient cup-shaped member seated in a cylindrical cavity in the piston, the rim of the cup yielding to permit passage of liquid from passages leading to the base of the cup. In a further form, Fig. 4, the non-return valve comprises a cylindrical stem 48 carrying a conical soft-rubber head 53 seated in a corresponding-shaped cavity in the piston head 18, the parts being fluted as shown at 52, 52a for the passage of liquid from the space 29 through passages 42a. According to Fig. 5, the connection 56 to the pipe-lines is provided in the cylindrical wall of the cylinder and the non- return valve is a resilient cup-shaped member 60 seated against an apertured wall 61 that divides the cylinder chamber from a chamber 62 connected by passages 63, 64 to 27 to the reservoir.