GB626073A - Improvements in or relating to hydraulic master cylinders - Google Patents

Abstract

626,073. Master cylinders. COATALEN, L. Aug. 29, 1946, No. 26036. Convention date, Nov. 3, 1945. [Class 103 (i)] [Also in Group XXVI] A hydraulic master cylinder comprises a cylinder having a pressure outlet connection, a plunger slidable through two annular packings fitted within the cylinder, and a reservoir connection leading into a space between the packings, the plunger being formed with a longitudinal passage communicating at its rear end with said space and provided at its front end with a valve member which is closed to isolate the passage from the cylinder pressure space during the working stroke of the plunger. In one form, Fig. 1, a plunger 17, acted on by a return spring 33 is slidable in collars 6 and 11 located in a bore 3 of a cast cylinder 1 having a working chamber 2 communicating with an outlet port 30 through a delivery valve comprising a member 32 acted on by the spring 33 and formed with a number of holes 32a normally closed by a flexible cup 34. Sealing rings 8 and 12 of rubber or other elastic material are disposed in grooves of greater axial width in the collars 6 and 11, and further sealing rings 10 and 13 are provided between the collars and the bore 3. The collars are separated by a tube 15 and a washer 20 and are retained in position by a circlip 14. The retracted position of the plunger is determined by a circlip 18 which engages the washer, and in this position the chamber 2 is in communication with a liquid reservoir through grooves 21 in the plunger, holes 16 in the tube 15, a passage 5 and a pipe connection 4. The chamber 2 may also communicate with the reservoir through passages 22 and 25 in the plunger and a valve 26 normally held seated by a spring 27. Initial movement of the plunger causes the ends of the grooves 21 to overlap the collar 6, and pressure is then built up in the chamber 2 to deflect the cup 34 so that liquid flows through the outlet port. On the return movement of the plunger, the valve member 32 unseats to allow the return flow of liquid to the chamber 2. If the movement of the plunger is sufficiently rapid to locate a depression in the chamber 2, the valve i6 unseats to allow make-up liquid to flow from the reservoir. In a second form, Fig. 2, the grooves 21 are omitted, and the valve 26 is normally held open by a light spring 28a and seated by the pressure in the chamber 2 during the working stroke of the plunger. In a third form, Fig. 3, the valve 26 is normally held seated by a spring 27 but is fitted with a transverse member 38 which is engaged by a shoulder 39 on the cylinder to unseat the valve as the plunger reaches the retracted position.