Patent ID: 6192685
Filing Date: 2001-02-27
Classification: B60T

Abstract:
A master cylinder for a vehicle hydraulic braking installation, said installation comprising a service braking system using external energy, and an emergency braking system using muscle power for actuating wheel brake cylinders, said master cylinder being isolated from the wheel brake cylinders through at least one shut-off valve for service braking using external energy, said master cylinder being associated with a simulator simulating the brake actuation travel and comprising a simulator piston defining a simulation chamber which receives brake fluid from the brake master cylinder, an elastic simulator element for urging the simulator piston against the action of the pressure of the brake fluid in said simulation chamber, said master cylinder being of the tandem type and having a bore in which a primary piston and a secondary piston are mounted to respectively slide from respective positions of rest therein to delimit a primary working chamber and a secondary working chamber, characterized in that said simulation chamber has an inlet orifice opening into said bore, and in that means of selective communication connect said simulation chamber to said primary working chamber when said secondary piston is in said position of rest, and to isolate said simulation chamber from said primary working chamber when said secondary piston is moved away from said position of rest, said means of selective communication comprising a peripheral groove formed in said bore and a sealing element borne by said secondary piston and capable selectively of shutting off said bore some distance from said peripheral groove, said peripheral groove being arranged in said bore between said primary piston and said inlet orifice of said simulation chamber, and said sealing element being located selectively facing said peripheral groove when said secondary piston is in said position of rest.