Patent ID: 6845615

Claim:
A master cylinder having a housing with a first and second bore therein, said first and second bores supplying a same braking system with pressurized fluid to effect a brake application, said first bore retaining a first piston to define a first chamber; said second bore retaining a second piston to define a second chamber; said first and second pistons being connected to an input member to receive an actuation force to effect the brake application, said first piston being characterized by a first cylindrical member that is connected to second cylindrical member by a shaft, said shaft having a peripheral surface with an actuation ramp that terminates at an apex with a retraction ramp, said second piston engaging said connecting shaft, said second cylindrical member upon receipt of an actuation force moving said first cylindrical member in said first chamber through said shaft and moving said second piston through the engagement of said second piston with said actuation ramp to respectively and simultaneously communicate first and second volumes of fluid to said braking system until said engagement of said second piston reaches said apex and as a result a pre-determined volume of fluid has been displaced from said second chamber such that thereafter exclusive communication of fluid to the brake system occurs from said first chamber to said braking system to effect a brake application; said second piston's movement being controlled by the sequential engagement of said actuation ramp, apex, and retraction second ramp such that communication of fluid from said second chamber only occurs while said second piston engages said actuation ramp and termination of communication of fluid from said second chamber occurs once said second piston reaches the apex and the pressure in said second chamber is eliminated with the engagement of the second piston with the retraction ramp.