GB521441A - Hydraulic brake - Google Patents

Abstract

521,441. Hydraulic brakes. BOLSEZIAN, G., Sept. 12, 1938, No. 26626. Convention date, Sept. 10, 1937. [Class 103 (i)] A master cylinder for hydraulic brake transmission comprises a valve 25 in the passage 4, 11 leading to the pipe lines and brake cylinders, this valve having a lost-motion coupling to a piston 7 subjected to the pressure in the brake cylinders and of greater area. than the valve and subjected also to the pressure of a spring 10 which is weaker than the brake return springs. Thus the valve 25 and piston 7 are raised when the main piston 5 is operated to apply the brakes and return after release of the brakes and the piston 7 then continues to exert a slight pressure in the pipe lines due to the spring 10. Small contractions of the liquid in the pipe lines are made up by movement of the piston 7 but further contractions after the piston has reached its stop 13<SP>1</SP> are compensated for by flow from the reservoir 2 through the port 3 and valve 25. The cylinder acts as a pump for filling the system, the valve 25 then serving as the outlet valve which during the return stroke of the main piston liquid is supplied to the cylinder from the reservoir through a port 20, grooves 21 in the piston and past the cup washer 41. In a modification the main piston is of the same diameter as the cylinder substantially throughout its length except for an annular groove adjacent the grooves 21. This annular groove connects with a rearwardly extending groove by which and an annular groove in the cylinder, the port 20 communicates with the grooves 21 in any position of the piston. The piston in this case has a cup washer at the rear as well as at the front end instead of the arrangement of fixed rubber washers 32, 33 and metal ring 31 shown in Fig. 2, In a further construction, the piston rod 18 passes through a single fixed rubber sealing disc and grooves such as 21 extend the whole length of the piston. A modified form of the valve 25 comprises a flexible bell-shaped member which seats at its edge around a port such as 4 the yielding of this valve member allowing the necessary lost-motion between the piston 7 and the valve. According to the Specification as open to inspection under Sect. 91 liquid is supplied from the reservoir to the cylinder during the return of the piston through a non-return valve, the grooves 21 being dispensed with and a liquid seal being provided for the piston by an annular groove in the cylinder communicating by a port with the reservoir. This subject-matter does not appear in the Specification as accepted.