Hydraulic master cylinder

Claim 1

In a hydraulic brake system for a motor vehicle having front and rear brakes, a master cylinder for actuating said brakes comprising: a hydraulic fluid reservoir having a first opening and a second opening along the bottom thereof; housing means having a bore therein, said bore having a first opening and a second opening along the top thereof corresponding to the first and second openings in said hydraulic fluid reservoir; piston means telescopically positioned to reciprocate within said bore, said piston means having a first piston which slides within a second piston, said first piston having an effective diameter substantially equal to said second piston, said first piston and said second piston dividing said bore into a first variable volume chamber and a second variable volume chamber independent of each other, said first variable volume chamber being connected to said front brakes and said second variable volume chamber being connected to said rear brakes; cage means secured to said first piston; first resilient means located between said cage means and said first piston means for urging said first piston away from said cage means for establishing the size of the first variable volume chamber; second resilient means located between said first and second pistons for establishing the size of said second variable volume chamber; return spring means located between the bottom of said bore and said cage means for urgIng the piston means against a stop in said bore; first valve means located in said first opening in said reservoir having a first stem extending into said first variable volume chamber, said first stem being adapted to engage said cage means permitting fluid in the reservoir unrestricted flow into said first variable volume chamber with the piston means against the stop; second valve means located in said second opening in said reservoir having a second stem extending into said second variable volume chamber, said second stem being adapted to engage said first piston permitting fluid in the reservoir unrestricted flow into the second variable volume chamber with the piston means against the stop; and actuation means for transferring an initial operational force on said second piston moving said first piston through said second resilient means by overcoming said return spring means to simultaneously close the first and second valve means to interrupt fluid communication between the reservoir and the first and second variable volume chambers, said actuation means upon intensifying the operational force moving the first piston in the first variable volume chamber to displace fluid to the front brake and develop a first fluid pressure, said first fluid pressure and further intensification of the operational force overcoming the second resilient means allowing the second piston to telescopically move within the first piston and develop a second fluid pressure in the second variable volume chamber for operating the rear brakes, said first and second fluid pressures being substantially equal since the effective diameter of the first and second pistons are substantially equal and thereby uniformly continue energization of said front and rear brakes in response to an effective intensified operational force from said actuation means.