Hydraulic brake booster with piston return device

Claim 2

A hydraulic boost device comprising: a housing having a bore therein: an inlet in the housing in communication with said bore and connectible to a fluid pressure source; a piston slidably positioned in said bore and at time subjected to said fluid pressure source; operator-operated means for controlling movement of said piston toward one end of said bore under the influence of fluid pressure, said means also including mechanism for controlling movement of said piston toward one end of said bore solely through manual effort; and piston return means urging said piston toward the other end of said bore at times when the inlet is subjected to a fluid pressure source, said piston return means becoming ineffective in urging said piston in the direction aforementioned upon failure of inlet fluid pressure to thereby enable the operator to manually move the piston more rapidly toward said one end of the bore; said piston return means including resilient means, and connecting means responsive to the fluid pressure level at said inlet for operably connecting said resilient means to said piston when the fluid pressure at said inlet exceeds a predetermined level, said connecting means disconnecting said resilient means from said piston upon failure of the inlet fluid pressure level.

Claim 3

A hydraulic boost device as in claim 1, characterized in that said operator-operated means includes valve means for communicating said inlet to the other end of said bore and push-through means for effectuating piston movement.

Claim 4

A hydraulic boost device as in claim 2, wherein said operator-operated means is located in said piston.

Claim 5

A hydraulic boost device as in claim 2, characterized in that said valve means and push-through means are coaxial with the piston.

Claim 6

A hydraulic boost device as in claim 1, wherein said piston is provided with a passage in communication with its respective ends, and a check valve in said passage to thereby facilitate piston movement toward said one end of the bore at times when said piston is moved manually solely by the operator.

Claim 7

A hydraulic boost device as in claim 1, wherein said piston is provided with a passage which communicates with the ends of said piston, and a check valve in said passage.

Claim 8

A hydraulic boost device comprising: a housing having a bore therein; an inlet in the housing in communication with said bore and connectible to a fluid pressure source; a piston slidably positioned in said bore and at times subjected to said fluid pressure source; operator-operated means for controlling movement of said piston toward one end of said bore under the influence of fluid pressure, said means also including mechanism for controlling movement of said piston toward one end of said bore solely through manual effort; and piston return means urging said piston toward the other end of said bore at times when the inlet is subjected to a fluid pressure source, said piston return means becoming ineffective in urging said piston in the direction of aforementioned upon failure of inlet fluid pressure to thereby enable the operator to manually move the piston more rapidly toward said one end of the bore; said piston return means comprising a movable land carried by said piston, said laNd being subject to fluid pressure at times, a return spring acting on said movable land in a direction opposing movement of the land by fluid pressure, a stop on said piston against which the fluid pressure urges said land, and a stop located within said bore against which said land is urged by the return spring.

Claim 9

A hydraulic boost device comprising: a housing having a bore therein; an inlet in the housing in communication with said bore and connectible to a fluid pressure source; a piston slidably positioned in said bore and at times subjected to said fluid pressure source; operator-operated means for controlling movement of said piston toward one end of said bore under the influence of fluid pressure, said means also including mechanism for controlling movement of said piston toward one end of said bore solely through manual effort; and piston return means urging said piston toward the other end of said bore at times when the inlet is subjected to a fluid pressure source, said piston return means becoming ineffective in urging said piston in the direction of aforementioned upon failure of inlet fluid pressure to thereby enable the operator to manually move the piston more rapidly toward said one end of the bore; said piston return means comprising a movable land carried by said piston, said laNd being subject to fluid pressure at times, a return spring acting on said movable land in a direction opposing movement of the land by fluid pressure, a stop on said piston against which the fluid pressure urges said land, and a stop located within said bore against which said land is urged by the return spring.

Claim 10

A hydraulic brake boost mechanism comprising: a housing with a bore therein; inlet and outlet ports in communication with said bore; a piston slidably positioned in said bore and dividing said bore into two chambers, located at the respective ends of said piston; operator-operated means including valve means for controlling communication of fluid pressure between said ports and the two chambers to cause piston movement, and further including push-through mechanism which effectuates move-ment of said piston manually upon failure of fluid pressure in one of said chambers; and means acting to resist movement of said piston under fluid pressure but ineffective to resist such movement upon failure of fluid pressure; said last-named means comprising a movable land mounted on the piston for movement relative thereto and forming therewith a cavity in communication with said inlet port, and resilient means acting on said movable land.

Claim 11

A hydraulic brake boost mechanism comprising: a housing with a bore therein; inlet and outlet ports in communication with said bore; a piston slidably positioned in said bore and dividing said bore into two chambers, located at the respective ends of said piston; operator-operated means including valve means for controlling communication of fluid pressure between said ports and the two chambers to cause piston movement, and further including push-through mechanism which effectuates move-ment of said piston manually upon failure of fluid pressure in one of said chambers; and means acting to resist movement of said piston under fluid pressure but ineffective to resist such movement upon failure of fluid pressure; said last-named means comprising a movable land mounted on the piston for movement relative thereto and forming therewith a cavity in communication with said inlet port, and resilient means acting on said movable land.

Claim 12

A hydraulic brake boost mechanism as in claim 8, wherein check valve means is utilized to control communication between said two chambers to facilitate piston movement during actuation of the push-through mechanism.

Claim 13

A hydraulic brake boost mechanism comprising: a housing with a bore therein; inlet and outlet ports in communication with said bore; a piston slidably positioned in said bore and dividing said bore into two chambers, located at the respective ends of said piston; operator-operated means including valve means for controlling communication of fluid pressure between said ports and the two chambers to cause piston movement, and further including push-through mechanism which effectuates movement of said piston manually upon failure of fluid pressure in one of said chambers; and means acting to resist movement of said piston under fluid pressure but ineffective to resist such movement upon failure of fluid pressure; said last-mentioned means including resilient means and connecting means responsive to the fluid pressure level at said inlet port for operably connecting said resilient means to said piston when the fluid pressure level at said inlet port exceeds a predetermined level, said connecting means disconnecting said resilient means from said piston upon failure of the fluid pressure level at said inlet port.

Claim 14

A hydraulic brake boost mechanism comprising: a housing with a bore therein; inlet and outlet ports in communication with said bore; a piston slidably positioned in said bore and dividing said bore into two chambers, located at the respective ends of said piston; operator-operated means including valve means for controlling communication of fluid pressure between said ports and the two chambers to cause piston movement, and further including push-through mechanism which effectuates movement of said piston manually upon failure of fluid pressure in one of said chambers; and means acting to resist movement of said piston under fluid pressure but ineffective to resist such movement upon failure of fluid pressure; said last-mentioned means including resilient means and connecting means responsive to the fluid pressure level at said inlet port for operably connecting said resilient means to said piston when the fluid pressure level at said inlet port exceeds a predetermined level, said connecting means disconnecting said resilient means from said piston upon failure of the fluid pressure level at said inlet port.