Patent ID: 7073875

Claim:
A brake circuit comprising brake means connected with a master cylinder via a brake application line and a brake return line, the brake master cylinder having a first chamber in which brake fluid is pressurized on movement of a first piston in a brake applying direction by an operating means, the first chamber being connected via a first port and a non-return valve with the brake application line of the circuit, characterized in that the brake master cylinder further comprises a second chamber connected to the brake return line of the circuit via a second port and having a second piston, said second piston having an outer circumference and a seal mounted about the outer circumference for sealingly engaging a bore of the cylinder which defines said second chamber, said second piston being moveable by the brake operating means in brake applying and releasing directions, the second chamber also being connected to a reservoir via a third port when the second piston is in a fully released position, the second chamber being arranged to draw-in brake fluid from the brake return line on movement of the second piston in a brake releasing direction by the operating means and establishing a connection with the associated reservoir via the third port to allow escape of aerated fluid into the reservoir when the second piston is in the fully released position, providing an arrangement such that during each application and subsequent release of the brakes, a small volume of brake fluid is displaced from the first chamber into the brake application line and a small volume of fluid is drawn out of the brake return line into the second chamber thereby circulating brake fluid through the brake means.