Dual ratio proportioning valve

Claim 2

A valve for proportioning fluid hydraulic pressure comprising a valve body having a hydraulic fluid inlet and outlet connected by a bore; a spool slidably disposed in said bore and movable between a first position adjacent said outlet and a second position adjacent said inlet; means on said spool for sealing said inlet from said outlet; first piston means on said spool and second piston means slidably disposed on said spool; said first piston means having a first cross-sectional area exposed to said outlet pressure and said second piston means having a larger cross-sectional area exposed to said outlet pressure than said first piston means; first biasing means to urge said first and second piston means together with said spool to said first position, said piston means having a combined cross-sectional area greater than the cross-sectional area of the portion of said spool exposed to inlet pressure whereby inlet pressure is communicated from said inlet to said outlet until a first predetermined inlet pressure is reached whereupon the imbalance of hydraulic forces of such pistons relative to the inlet end of said spool causes said spool to move against said first biasing means and seal said inlet from said outlet and thereafter proportion pressure from said inlet to said outlet at a first proportioning rate until a second predetermined higher inlet pressure is reached; and second biasing means urging said second piston into abutment with said First piston until said second predetermined inlet pressure is reached and the pressure at said outlet permits said second piston to overcome said second biasing means and separate said second piston from said first piston to establish a second proportioning rate at pressures in excess of said second predetermined inlet pressure, said second proportioning rate being established by the first piston crosssectional area and cross-sectional area of said spool exposed to inlet pressure.

Claim 3

A valve in accordance with claim 1 including poppet means between said inlet and said outlet, said poppet means operable to permit fluid flow from said outlet to said inlet upon a decrease of pressure at said inlet relative to said outlet.

Claim 4

A valve in accordance with claim 2 including a fluid passageway in said spool, said poppet means being positioned in said passageway.

Claim 5

A valve in accordance with claim 7 including stop means engageable by said second piston means upon said second hydraulic inlet pressure being reached, and seal means slidably disposed intermediate said first and second piston means.

Claim 6

A hydraulic brake system for automotive vehicles having disc brakes on one set of wheels and shoe brakes on a second set of wheels, a master cylinder and a proportioning valve intermediate said master cylinder and one of said sets of brakes; said proportioning valve comprising a valve body having a hydraulic fluid inlet connected to said master cylinder, and a hydraulic fluid outlet connected to said one of said sets of brakes, said outlet and inlet connected by a bore in said valve body; a spool slidably disposed in said bore and movable between a first position adjacent said outlet and a second position adjacent said inlet; means on said spool for sealing said inlet from said outlet; first piston means on said spool and second piston means slidably disposed on said spool; said first piston means having a first cross-sectional area exposed to said outlet pressure and said second piston means having a larger cross-sectional area exposed to said outlet pressure than said first piston means; first biasing means to urge said first and second piston means together with said spool to said first position, said piston means having a combined cross-sectional area greater than the cross-sectional area of the portion of said spool exposed to inlet pressure whereby inlet pressure is communicated from said inlet to said outlet until a first predetermined inlet pressure is reached whereupon the imbalance of hydraulic forces of said pistons relative to the inlet end of said spool causes said spool to move against said first biasing means and seal said inlet from said outlet and thereafter proportion pressure from said inlet to said outlet at a first proportioning rate until a second predetermined higher inlet pressure is reached; and second biasing means urging second piston into abutment with said first piston until said second predetermined inlet pressure is reached and the pressure at said outlet permits said second piston to overcome such second biasing means and separate said second piston from said first piston to establish a second proportioning rate at pressures in excess of said second predetermined inlet pressure, said second proportioning rate being established by said first piston cross-sectional area and the cross-sectional area of said spool exposed to inlet pressure.

Claim 7

A hydraulic brake system for automotive vehicles having disc brakes on one set of wheels and shoe brakes on a second set of wheels, a master cylinder and a proportioning valve intermediate said master cylinder and one of said sets of brakes; said proportioning valve comprising a valve body having a hydraulic fluid inlet connected to said master cylinder, and a hydraulic fluid outlet connected to said one of said sets of brakes, said outlet and inlet connected by a bore in said valve body; a spool slidably disposed in said bore and movable between a first position adjacent said outlet and a second position adjacent said inlet; means on said spool for sealing said inlet from said outlet; first piston means on said spool and second piston means slidably disposed on said spool; said first piston means having a first cross-sectional area exposed to said outlet pressure and said second piston means having a larger cross-sectional area exposed to said outlet pressure than said first piston means; first biasing means to urge said first and second piston means together with said spool to said first position, said piston means having a combined cross-sectional area greater than the cross-sectional area of the portion of said spool exposed to inlet pressure whereby inlet pressure is communicated from said inlet to said outlet until a first predetermined inlet pressure is reached whereupon the imbalance of hydraulic forces of said pistons relative to the inlet end of said spool causes said spool to move against said first biasing means and seal said inlet from said outlet and thereafter proportion pressure from said inlet to said outlet at a first proportioning rate until a second predetermined higher inlet pressure is reached; and second biasing means urging second piston into abutment with said first piston until said second predetermined inlet pressure is reached and the pressure at said outlet permits said second piston to overcome such second biasing means and separate said second piston from said first piston to establish a second proportioning rate at pressures in excess of said second predetermined inlet pressure, said second proportioning rate being established by said first piston cross-sectional area and the cross-sectional area of said spool exposed to inlet pressure.

Claim 8

A hydraulic brake system in accordance with claim 5 including passage means intermediate said inlet and said outlet means, and check means in said passage means whereby upon said hydraulic pressure at said outlet means being greater than said pressure at said inlet means, said check means will permit fluid flow from said one brake set to said master cylinder.

Claim 9

A hydraulic brake system in accordance with claim 5 wherein said master cylinder comprises a dual master cylinder, one of said master cylinders being connected to said proportioning valve and the other of said master cylinders being connected to said other set of brakes.