Hydraulic booster with pedal travel control

Claim 2

In a hydraulically operated booster brake mechanism adapted for actuating the brakes of a vehicle comprising; hydraulic fluid circuit including a source of hydraulic fluid pressure, a housing forming a large bore portion and a small bore portion in communication with said large bore portion, a power plunger movable in said large bore portion and forming a power chamber at one side thereof, an output plunger movable in said small bore portion and forming a fluid containing control cavity in said bore portions between said power plunger and said output plunger, control valve means between said source and said power chamber and operative to admit fluid pressure to said power cHamber or moving said power plunger, and control means responsive to equal pressure in said power chamber and said control cavity for maintaining the volume of fluid in said cavity constant during movement of said power plunger under the influence of pressure in said power chamber whereby movement of said power plunger in a brake applying direction results in greater movement of said output plunger.

Claim 3

The booster brake mechanism set forth in claim 1 in which said control means includes valve means communicating with said power chamber and with said control cavity, said valve means being closed when pressure in said power chamber and said control cavity are substantially equal.

Claim 4

The booster brake mechanism set forth in claim 1 in which said control means includes additional valve means communicating with said power chamber and said control cavity and responsive to pressures therein to remain closed when the pressures in said power chamber and control cavity are substantially equal and being responsive to pressure in said power chamber less than in said control cavity to open and exhaust fluid from said cavity for movement of said pistons as a unit in a brake applying direction and responsive to a pressure in said power chamber greater than in said control cavity to open and admit fluid to said cavity.

Claim 5

The booster brake mechanism set forth in claim 1 in which said control means includes passage means between said control cavity and said power chamber, and valve means in said passage means responsive to pressures in said power chamber and said control cavity to close said passage means when pressures are substantially equal and to open said passage means when pressures are unequal.

Claim 6

The booster brake mechanism set forth in claim 4 in which said valve means includes piston means movable in said passage means between a first and second position, and check valve means operatively associated with said piston means and normally closing said passage means when said piston means is in said first position and opening said passage means when said piston means moves to said second position.

Claim 7

The booster brake mechanism set forth in claim 5 in which said check valve means is responsive to a greater pressure in said power chamber than in said control cavity when said Piston means is in said first position to open said passage means.

Claim 8

In a booster brake mechanism having; a housing, power piston means in said housing movable between a brake released and a brake applying position a0d forming a power chamber at one side thereof, a hydraulic fluid circuit including a source of hydraulic fluid pressure, a control member movable by an operator, control valve means movable by said control member and operative to apply a pressure from said source to said power chamber to move said power piston means when pressure is available from said source, said control member being operatively connected with said piston means for moving the latter after the available pressure in said source has been utilized, said piston means including a power piston and an output piston movable relative to each other, said pistons forming a control cavity therebetween in said housing, said output piston being smaller than said power piston and being movable in response to pressure in said control cavity, control means including passage means communicating said control cavity with said circuit, and additional valve means disposed in said passage means and normally isolating said control cavity from said circuit when said piston means is moving in response to pressure from said source and being responsive to a pressure differential in said power chamber and in said control chamber to open said passage means upon movement of said power piston means when available pressure from said source has been utilized.

Claim 9

In a booster brake mechanism having; a housing, power piston means in said housing movable between a brake released and a brake applying position a0d forming a power chamber at one side thereof, a hydraulic fluid circuit including a source of hydraulic fluid pressure, a control member movable by an operator, control valve means movable by said control member and operative to apply a pressure from said source to said power chamber to move said power piston means when pressure is available from said source, said control member being operatively connected with said piston means for moving the latter after the available pressure in said source has been utilized, said piston means including a power piston and an output piston movable relative to each other, said pistons forming a control cavity therebetween in said housing, said output piston being smaller than said power piston and being movable in response to pressure in said control cavity, control means including passage means communicating said control cavity with said circuit, and additional valve means disposed in said passage means and normally isolating said control cavity from said circuit when said piston means is moving in response to pressure from said source and being responsive to a pressure differential in said power chamber and in said control chamber to open said passage means upon movement of said power piston means when available pressure from said source has been utilized.

Claim 10

The booster brake mechanism set forth in claim 7 in which said passage means communicates said control cavity and said power chamber.

Claim 11

The combination set forth in claim 7 wheRein said control means include a cylinder, a piston movable in said cylinder between first and second positions, said cylinder communicating with said control cavity at one side of said piston and with said power chamber at the other side of said piston, check valve means associated with said piston and normally being closed when said piston is in said first position and operative to open when said piston is in said second position to communicate said control cavity with said power chamber to exhaust fluid from said cavity for movement of said pistons as a unit.

Claim 12

The combination set forth in claim 9 in which said check valve means is supported by said piston and includes an element engageable with a wall of said cylinder to open said check valVe upon movement of said piston to said second position.

Claim 13

The combination set forth in claim 9 in which said check valve means is responsive to pressure in said power chamber greater than in said control cavity to open said check valve to admit fluid from said power chamber to said control cavity.