Hydraulic lock for hydraulic ratio changer

Claim 2

In a power braking system having a servomotor through which a first operational force is supplied to a brake energizer from the simultaneous movement of a plurality of concentric pistons in response to an input force, means for permitting one of said pistons to supply an additive operational force to said brake energizer when one of the pistons moves independently of the other pistons, said means comprising: chamber means connected by a passage to receive an output signal from said brake energizer; valve means located in said passage for controlling the communication of said output signal to said chamber means; and actuator means connected to said one of said pistons and said valve means to prevent said output signal from being communicated to said chamber means upon independent movement of said one piston, said valve means retaining said output signal within said chamber means to hold the remaining pistons stationary in said bore while said input force is transmitted through said one of said pistons to establish an increased output signal.

Claim 3

In the power braking system, as recited in claim 1, wherein said valve means includes: stem means located in said passage and connected to said actuator means; and resilient means located in said passage for urging said stem means toward a seat to prevent said operational signal from being communicated through said passage upon said independent movement of said one piston.

Claim 4

In the power braking system, as recited in claim 2, wherein said actuator means includes: an annular projection attached to said one piston for engaging said stem means during said simultaneous movement of the plurality of pistons permIt said output signal to be freely communicated into to said chamber means.

Claim 5

In the power braking system, as recited in claim 3, wherein said chamber means includes: seal means associated with said remaining pistons for limiting the communication path for the increased output signal to said passage.

Claim 6

In the power braking system, as recited in claim 1, wherein said valve means includes: first stem means located in said passage and connected to said actuator means, said first stem means having a first face on one end thereof; and first resilient means being connected to said first stem means for urging said first face toward a first seat to prevent said output signal from being communicated to said chamber means upon independent movement of said one piston.

Claim 7

In the power braking system, as recited in claim 5, wherein said valve means further includes: second stem means located in said chamber means and a reservoir, said second stem means having a second face on the end thereof; and second resilient means being connected to said second stem means for urging said second face toward a second seat upon movement of said one piston to retain said increased output signal in said chamber means.

Claim 8

In a vehicle braking system having a servomotor with a pressure ratio changer which includes a first piston connected to a movable wall and a second piston slidably carried by the first piston and responsive to an input force from an operator to actuate a control for developing a first output force upon movement of the wall to supply the braking system with a first operational fluid force, locking means for permitting said first and second pistons to move simultaneously with the wall until a desired operational force exceeds the first output force and for allowing the second piston to move independently of the first piston and supply a second output force to develop an additive change in magnitude of said first operational fluid force, said locking means comprising: a housing having a bore therein connected to a reservoir and said braking system, said first and second pistons being located within said bore to form a pressurizing chamber therein, said first piston forming a locking chamber with the housing, said locking chamber being connected to said bore by a passage within said first piston; valve means connected to said passage for controlling the communication of said first operational fluid force to said locking chamber; and actuator means associated with said second piston and said valve means to prevent the additive change in operational fluid force from being communicated to said locking chamber upon independent movement of the second piston, said valve means retaining said first operational fluid force in the locking chamber to hold said first piston in a stationary position in said bore during said independent movement of the second piston.

Claim 9

In a vehicle braking system having a servomotor with a pressure ratio changer which includes a first piston connected to a movable wall and a second piston slidably carried by the first piston and responsive to an input force from an operator to actuate a control for developing a first output force upon movement of the wall to supply the braking system with a first operational fluid force, locking means for permitting said first and second pistons to move simultaneously with the wall until a desired operational force exceeds the first output force and for allowing the second piston to move independently of the first piston and supply a second output force to develop an additive change in magnitude of said first operational fluid force, said locking means comprising: a housing having a bore therein connected to a reservoir and said braking system, said first and second pistons being located within said bore to form a pressurizing chamber therein, said first piston forming a locking chamber with the housing, said locking chamber being connected to said bore by a passage within said first piston; valve means connected to said passage for controlling the communication of said first operational fluid force to said locking chamber; and actuator means associated with said second piston and said valve means to prevent the additive change in operational fluid force from being communicated to said locking chamber upon independent movement of the second piston, said valve means retaining said first operational fluid force in the locking chamber to hold said first piston in a stationary position in said bore during said independent movement of the second piston.

Claim 10

In the vehicle braking system, as recited in claim 7, wherein said valve means includes: first stem means located in said passage and connected to said actuator, said stem means having a face thereon; and first resilient means being connected to said first stem means for urging said face toward a seat to simultaneously close said passage upon independent movement of the second piston.

Claim 11

In the vehicle braking system, as recited in claim 8, wherein said valve means includes: second stem means located in an opening between said reservoir and the bore, said second stem means being connected to said actuator means, said second stem means having a face thereon; and second resilient means being connected to said second stem means for urging the face thereon toward a seat in the housing to interrupt communication between the reservoir and the bore and permit said operational fluid force to be developed within said bore upon independent movement of the second piston.

Claim 12

In the vehicle braking system, as recited in claim 8, wherein said valve means includes: second stem means located in an opening between said reservoir and the locking chamber, said second stem means having a face thereon, said second stem means being connected to said first piston; and second resilient means being connected to said second stem means for urging the face thereon toward a seat in the housing to prevent communication therebetween during the development of the operational fluid force.