Brake warning switch

Claim 2

In a dual hydraulic system having first and second lines normally subject to substantially equal pressures, a sensing unit including a housing connected to said first and second lines to produce a signal responsive to a predetermined pressure differential between said lines, a pressure changing device in one of said lines, and said sensing unit including valve means operable responsive to said pressure differential to render said pressure changing device inoperable in said one line, the improvement comprising said valve means including a piston member axially movable in said housing responsive to said predetermined pressure differential and having a neutral position when said pressures are balanced, an insert member in said housing axially spaced from said piston member, an axially extending passage in said insert member, said insert member including an annular end face surrounding said passage, valve seat means carried by said piston member for engaging said annular end face for closing said axially extending passage when said piston member is in said neutral position and for moving away from said annular end face for opening said axially extending passage when said piston member is moved from said neutral position by said predetermined pressure differential, said opening of said passage by said movement of said valve seat means rendering said pressure changing device inoperable, resilient means for resiliently urging said valve seat means in a direction toward said annular end face, and said valve seat means being a poppet slidably disposed on said piston member and operatively connected to said resilient means for movement away from said annular end face against the urging of said resilient means when said piston member is in said neutral position.

Claim 3

A sensing unit as set forth in claim 1, wherein said piston member is slidably disposed within a bore in said housing, and said passage is in axially aligned relationship with said piston member.

Claim 4

A sensing unit as set forth in claim 2, wherein said insert member is fixedly disposed in said bore.

Claim 5

A combination hydraulic brake warning device for use in a dual brake system including a housing, an axial bore in said housing, piston means slidably mounted in said axial bore and making sealing engagement with the walls thereof, signal sensing means operable by movement of said piston means in said bore in either direction from a centered position, passage means at one end of said axial bore to admit fluid pressure to one end of said piston means from a first brake line, a first chamber at the other end of said piston means, an inlet to said first chamber connected to a second brake line whereby said piston means is normally held in a centered position by a balanced fluid pressure at said passage means and said first chamber, said first chamber having an outlet passage, a pressure changing valve having an inlet and an outlet, said valve inlet being connected to said first chamber outlet passage, a second chamber at the other end of said axial bore, an inlet port in said housing connecting said valve outlet to said second chamber, a bypass passage extending between said first chamber and said second chamber, an annular end face surrounding said bypass passage, a valve member operable to engage said annular end face to close said bypass passage, said valve member being slidably carried by said piston means so that said valve member engages said annular end face and continuously closes said bypass passage when said piston means is in said centered position and when said piston means is moved only a slight distance in either direction in said bore from said centered position, said valve member being moved away from said annular end face to open said bypass passage and establish direct fluid pressure communication between said first chamber and said second chamber when said piston means is moved a substantial distance in said bore in one direction from said centered position, and said valve member being resiliently urged in a direction toward said annular end face and being movable away from said annular end face to operate as a one-way check valve when said piston means is in said centered position to establish direct fluid communication from said second chamber to said first chamber through said bypass passage when the fluid pressure in said second chamber exceeds the fluid pressure in said first chamber.

Claim 6

A combination hydraulic brake warning device for use in a dual brake system including a housing, an axial bore in said housing, piston means slidably mounted in said axial bore and making sealing engagement with the walls thereof, signal sensing means operable by movement of said piston means in said bore in either direction from a centered position, passage means at one end of said axial bore to admit fluid pressure to one end of said piston means from a first brake line, a first chamber at the other end of said piston means, an inlet to said first chamber connected to a second brake line whereby said piston means is normally held in a centered position by a balanced fluid pressure at said passage means and said first chamber, said first chamber having an outlet passage, a pressure changing valve having an inlet and an outlet, said valve inlet being connected to said first chamber outlet passage, a second chamber at the other end of said axial bore, an inlet port in said housing connecting said valve outlet to said second chamber, a bypass passage extending between said first chamber and said second chamber, an annular end face surrounding said bypass passage, a valve member operable to engage said annular end face to close said bypass passage, said valve member being slidably carried by said piston means so that said valve member engages said annular end face and continuously closes said bypass passage when said piston means is in said centered position and when said piston means is moved only a slight distance in either direction in said bore from said centered position, said valve member being moved away from said annular end face to open said bypass passage and establish direct fluid pressure communication between said first chamber and said second chamber when said piston means is moved a substantial distance in said bore in one direction from said centered position, and said valve member being resiliently urged in a direction toward said annular end face and being movable away from said annular end face to operate as a one-way check valve when said piston means is in said centered position to establish direct fluid communication from said second chamber to said first chamber through said bypass passage when the fluid pressure in said second chamber exceeds the fluid pressure in said first chamber.

Claim 7

A sensing unit as set forth in claim 4, wherein said valve member is slidably disposed in a bore in said piston means, and a spring means acts between said piston means and said valve member to resiliently urge said valve member toward said bypass passage.

Claim 8

A sensing unit as set forth in claim 5, wherein said bypass passage is formed in an insert member disposed in said bore in axially aligned relationship with said piston means, said valve member is a poppet member, and said poppet member cooperates with said annular end face to close said bypass passage when said piston means is in said centered position.

Claim 9

A sensing unit as set forth in claim 6 including an outlet port in said housing connected to said second chamber and in axially aligned relationship with said axial bore, and said insert member includes a fitting portion cooperating with said outlet port to receive a suitable fitting for connection to the remainder of the brake system.

Claim 10

In a dual hydraulic system having first and second lines normally subject to substantially equal pressures, a sensing unit including a housing connected to said first and second lines to produce a signal responsive to a predetermined pressure differential between said lines, a pressure changing device in one of said lines, said pressure changing device having an inlet side and an outlet side, said pressure changing device including means for maintaining said outlet side pressure less than said inlet side pressure when said inlet side pressure increases above a predetermined pressure, and said sensing unit including valve means operable responsive to said pressure differential to render said pressure changing device inoperable in said one line, the improvement comprising said valve means including a piston member axially movable in said housing responsive to said predetermined pressure differential and having a neutral position when said pressures are balanced, an insert member in said housing axially spaced from said piston member, an axially extending passage in said insert member, an annular end face surrounding one end of said passage, valve seat means for engaging said annular end face for closing said passage when said piston member is in said neutral position and for moving away from said annular end face for opening said axially extending passage when said piston member is moved from said neutral position by said predetermined pressure differential, said valve seat means being a poppet, and resilient means urging said poppet toward said annular end face, said resilient means being operatively connected to said poppet to permit said poppet to be displaced against the biasing force of said resilient means away from said annular end face to open said passage without substantial movement of said piston member From said neutral position when said inlet side pressure decreases to a pressure below said outlet side pressure.

Claim 11

In a dual hydraulic system having first and second lines normally subject to substantially equal pressures, a sensing unit including a housing connected to said first and second lines to produce a signal responsive to a predetermined pressure differential between said lines, a pressure changing device in one of said lines, said pressure changing device having an inlet side and an outlet side, said pressure changing device including means for maintaining said outlet side pressure less than said inlet side pressure when said inlet side pressure increases above a predetermined pressure, and said sensing unit including valve means operable responsive to said pressure differential to render said pressure changing device inoperable in said one line, the improvement comprising said valve means including a piston member axially movable in said housing responsive to said predetermined pressure differential and having a neutral position when said pressures are balanced, an insert member in said housing axially spaced from said piston member, an axially extending passage in said insert member, an annular end face surrounding one end of said passage, valve seat means for engaging said annular end face for closing said passage when said piston member is in said neutral position and for moving away from said annular end face for opening said axially extending passage when said piston member is moved from said neutral position by said predetermined pressure differential, said valve seat means being a poppet, and resilient means urging said poppet toward said annular end face, said resilient means being operatively connected to said poppet to permit said poppet to be displaced against the biasing force of said resilient means away from said annular end face to open said passage without substantial movement of said piston member From said neutral position when said inlet side pressure decreases to a pressure below said outlet side pressure.

Claim 12

A sensing unit as defined in claim 8 wherein said poppet is carried on said piston member, and said passage extends axially in axially aligned relationship with said poppet.

Claim 13

A sensing unit as defined in claim 9 wherein said piston member is slidably disposed within a bore in said housing, and said insert member is fixedly disposed in said bore.