Master cylinder with resiliently separated primary and secondary pistons

Claim 1

A master cylinder for a hydraulic system, comprising: a housing having a blind bore therein; reservoir means for retaining a quantity of fluid for said hydraulic system; first piston means located in said blind bore to form a first variable volume chamber therein with the bottom of said blind bore, said first piston means having a first cylindrical projection extending from a forward face of a first solid plug, said cylindrical projection having a first rib located along the inner periphery on the end of the cylindrical projection away from the face, said first variable volume chamber being connected to a first segment of said hydraulic system; first sleeve means concentric to the cylindrical projection, said sleeve means having an outwardly extending flange on one end and a land on the other end, said land being concentrically located along a surface of said cylindrical projection; first spring means located between said forward face and flange for urging said land against said rib; first resilient means located between the first piston means and the bottom of said blind bore for biasing said first piston means away from the bottom of said blind bore; first passage means located in said housing for connecting said reservoir with said first variable volume chamber; first valve means located in said first passage means responsive to movement of said first piston means for controlling the flow of fluid from said reservoir to said first variable volume chamber; a second cylindrical projection extending from the forward face of a second solid plug, said second resilient means being retained by said second cylindrical projection, said cylindrical projection having a second rid along the outer periphery of the end away from the forward face; second sleeve means surrounding said second cylindrical projection having a body with a first guide surface which is concentric to the outer surface of the second cylindrical projection and a second guide surface which is concentric to said blind bore; second spring means located between the second forward face and second sleeve means for urging said first guide surface against said second rib; second piston means located in said blind bore adjacent said first piston means to form a second variable volume chamber therebetween, said second variable volume chamber being connected to a second segment of said hydraulic system; second resilient means located between said first and second piston means for biasing said second piston means away from the first piston means; second passage means located in said housing for connecting said reservoir with said second variable volume chamber; second valve means located in said second passage means respoNsive to movement of said second piston means for controlling the flow of fluid from said reservoir to said second variable volume chamber; actuator means for transmitting an initial force to overcome said second resilient means and permit said second piston means to move, said second piston means upon moving permitting said second valve means to independently close and prevent fluid flow transmission through said second passage means from said second variable volume chamber to said reservoir, said second piston means receiving further input force to create a primary fluid pressure in the second variable volume chamber, said primary fluid pressure being communicated to said second segment of the hydraulic system and said first piston means, said primary fluid pressure and said second piston means upon receiving an additional input force overcoming said first resilient means and permitting said first piston means to move, said first spring moving said flange out of disengagement with said first valve means upon initial movement of said first piston means; said second spring means moving said first guide surface out of disengagement with said second valve means upon initial movement of said second piston means, said second valve means closing independently to prevent fluid flow from the second variable volume chamber to the reservoir, said first guide surface being adapted to slide on the outer surface of the second cylindrical projection upon said second piston means engaging said first piston means; and said first valve means independently closing said first passage to prevent fluid flow from the first chamber to the reservoir, said second piston means upon receiving an additional input force moving said first piston means to create a secondary fluid pressure in the first variable volume chamber, said land of the first sleeve means sliding along the inner surface of the first cylindrical projection when said flange engages the bottom of the blind bore as the first piston means moves in response to said additional input force, said secondary fluid pressure in the first chamber being communicated to said first segment of the hydraulic system.