Brake booster

Claim 2

In a power boost mechanism: housing means defining a working chamber and a control chamber therewithin; a piston slidably mounted in said working chamber; valve means responsive to a fluid pressure level in said control chamber to shift from a released position venting said working chamber to communicate successively higher fluid pressure levels into said working chamber as said valve means is shifted from said released position; an output plunger operatively connected to said piston and slidably received within said control chamber; operator-actuated means including an input plunger slidably received within said control chamber, a fluid pressure level in said control chamber varying as a function of the displacement of said plungers within said control chamber; said input plunger having a greater transverse cross-sectional area than that of the output plunger, whereby the stroke of the output plunger, is proportionally more than the stroke of the input plunger; said input plunger being aligned with said output plunger, whereby upon failure of the fluid pressure level in said control chamber, the input plunger engages the output plunger to permit normal actuation of said piston.

Claim 3

The invention of claim 1; and conduit means within said housing means communicating said control chamber with said working chamber; said output plunger being slidably received in said conduit means.

Claim 4

The invention of claim 1: said houSing means defining a bore therewithin having an inlet port communicating said bore with a fluid pressure source, an outlet port, and a return port communicated to a fluid reservoir, and means communicating the bore to the working chamber; said valve means being a spool valve having a reaction surface on one end thereof, said reaction surface being exposed to the fluid pressure level in said control chamber to shift said spool valve to control communication between said ports and to said communicating means to develop fluid pressure in the working chamber when a brake application is effected; and resilient means yieldably urging said spool valve to a released position.

Claim 5

The invention of claim 3: said spool valve having a reaction area opposing said reaction surface said reaction area being communicated to said working pressure whereby the spool valve is shifted against the force of said resilient means when the fluid pressure level in the control chamber exceeds the fluid pressure level in the working chamber by an amount necessary to overcome said resilient means.

Claim 6

The invention of claim 4; and relief valve means communicating said control chamber with the working chamber when the pressure level in the control chamber exceeds the pressure level in the working chamber by a predetermined amount substantially higher than the pressure differential between the control and working chamber required to overcome said resilient means.

Claim 7

The invention of claim 1; and resilient means yieldably urging said output plunger into engagement with said input plunger and thereafter urging the input and output plungers as a unit toward a predetermined release position.

Claim 8

The invention of claim 6; and refill passage means communicating said working chamber with said control chamber when the input and output plungers are disposed in said predetermined release position, and refill passage valve means responsive to movement of said output away from said release position to close communication through said refill passage means.

Claim 9

The invention of claim 7; and conduit means between the working and control chambers slidably supporting said output plunger, said refill passage means being a flat on said output plunger cooperating with the wall of the conduit means to define said refill passage means, said refill passage valve means including a land on said output plunger cooperating with said conduit means to close communication through the refill passage means when the plungers are moved from their released positions.

Claim 10

The invention of claim 1: said housing means including a valve housing enclosing said valve means and a servomotor housing separate from said valve housing enclosing the piston and said plungers.

Claim 11

The invention of claim 1: said valve means being a spool valve defining a bore therewithin; said piston, said plungers, and said spool valve being coaxial, said output plunger being received within the bore defined by the spool valve.

Claim 12

In a power boost mechanism: housing means defining a working chamber and a control chamber therewithin; a piston slidably mounted in said working chamber; valve means responsive to a fluid pressure level in said control chamber to shift from a released position venting said working chamber to communicate successively higher fluid pressure levels into said working chamber as said valve means is shifted from said released position; an output plunger operatively connected to said piston and slidably received within said control chamber; operator-actuated means including an input plunger slidably received within said control chamber, a fluid pressure level in said control chamber varying as a function of the displacement of said plungers within said control chamber; said input plunger having a greater transverse cross-sectional area than that of the output plunger, whereby the stroke of the output plunger, is proportionally more than the stroke of thE input plunger; relief valve means responsive to the pressure differential between the control chamber and the working chamber to vent the control chamber when said pressure differential between the control and working chambers exceeds a predetermined amount.

Claim 13

In a power boost mechanism: housing means defining a working chamber and a control chamber therewithin; a piston slidably mounted in said working chamber; valve means responsive to a fluid pressure level in said control chamber to shift from a released position venting said working chamber to communicate successively higher fluid pressure levels into said working chamber as said valve means is shifted from said released position; an output plunger operatively connected to said piston and slidably received within said control chamber; operator-actuated means including an input plunger slidably received within said control chamber, a fluid pressure level in said control chamber varying as a function of the displacement of said plungers within said control chamber; said input plunger having a greater transverse cross-sectional area than that of the output plunger, whereby the stroke of the output plunger, is proportionally more than the stroke of thE input plunger; relief valve means responsive to the pressure differential between the control chamber and the working chamber to vent the control chamber when said pressure differential between the control and working chambers exceeds a predetermined amount.

Claim 14

In a power boost mechanism: housing means defining a working chamber and a control chamber therewithin; said chambers being filled with a fluid medium; a piston slidably mounted in said working chamber and having output plunger means movable with said piston and slidably received within said control chamber; operator-actuated means including input plunger means slidably received within said control chamber; and valve means responsive to actuation of said operator-actuated means to shift from a released position venting said working chamber to communicate successively higher fluid pressure levels into said chamber as said valve means is shifted from said released position; said input plunger means and said output plunger means cooperating with the fluid medium in said control chamber so that the stroke of the output plunger is proportionally more than the stroke of the input plunger means upon actuation of the booster by communication of successively higher fluid pressure levels into said working chamber, said input and output plunger means cooperating upon manual actuation of said power boost so that the strokes of the input and output plunger means are equal; said input plunger being aligned with said output plunger whereby upon failure of the fluid pressure level in said control chamber, the input plunger engages the output plunger to permit normal actuation of said piston.

Claim 15

In a power boost mechanism: housing means defining a working chamber and a control chamber therewithin; said chambers being filled with a fluid medium; a piston slidably mounted in said working chamber and having output plunger means movable with said piston and slidably received within said control chamber; operator-actuated means including input plunger means slidably received within said control chamber; and valve means responsive to actuation of said operator-actuated means to shift from a released position venting said working chamber to communicate successively higher fluid pressure levels into said chamber as said valve means is shifted from said released position; said input plunger means and said output plunger means cooperating with the fluid medium in said control chamber so that the stroke of the output plunger is proportionally more than the stroke of the input plunger means upon actuation of the booster by communication of successively higher fluid pressure levels into said working chamber, said input and output plunger means cooperating upon manual actuation of said power boost so that the strokes of the input and output plunger means are equal; said input plunger being aligned with said output plunger whereby upon failure of the fluid pressure level in said control chamber, the input plunger engages the output plunger to permit normal actuation of said piston.