Brake warning switch requiring recentering pressure

Claim 2

A differentIal pressure sensing device comprising a housing, first and second fluid pressure receiving chambers each adapted to be connected to a separate source of fluid pressure, pressure responsive means in said housing, said pressure responsive means providing at said first chamber major and minor circular pressure reaction areas defined by major and minor piston diameters, a first annular sealing member sealing the periphery of the major circular reaction area of the major piston diameter, a second annular sealing member sealing the periphery of the minor circular reaction area of the minor piston diameter, said first and second sealing members each being independent in size relative to the respective piston diameter of the other, said pressure responsive means providing at said second chamber a pressure reaction area having a predetermined relation to the pressure reaction areas associated with the first chamber, said pressure responsive means being sensitive through said reaction areas to fluid pressures in said chambers, said pressure responsive means including means to actuate a signal detectable externally of said housing and operable when the pressure in said chambers change substantially from a normal relationship therebetween and to self-maintain said signal after the substantial change in pressure relationship is eliminated, said pressure responsive means including means to deactuate said signal, said signal deactuating means requiring predetermined reset pressures having magnitudes generally inversely proportional to the difference in size of the sealing diameters of said first and second sealing members supplied at said chambers.

Claim 3

In a brake failure warning device for use in a vehicle having dual fluid brake circuits including a housing, a pair of fluid pressure receiving chambers in said housing, means to connect each of the fluid circuits to one of said chambers, a passage in said housing extending between said chambers, a pair of coaxial pistons in said passage and communicating with a first one of said chambers, one of said pistons defining a circular major pressure reaction area and the other piston defining a minor circular pressure reaction area smaller than said major area, said pistons each defining a normally centered position in said housing, said major area piston being limited to axial movement from said centered position towards said first chamber and back to said centered position, said minor area piston being axially reciprocal towards and away from both of said chambers, piston means associated with a second one of said chambers causing pressure in the second chamber to force said pistons towards said first chamber upon loss of fluid pressure in said first chamber, means to sense movement of said pistons and produce a warning signal externally of said housing, renewal of pressure in said first chamber causing a return of said pistons away from said first chamber to said centered position, said piston means resisting return movement of said pistons from said first chamber towards said centered position, said piston means providing a pressure reaction area at said second chamber of a predetermined size in relation to the normal pressure in said second chamber such that the pressure-area product therein is not less than the product of said minor area and the normal pressure in said first chamber and is not greater than the product of the major area and the normal pressure in said first chamber, the improvement comprising separate sealing means associated with said major and minor area pistons including sealing ring means permitting selection of the size differential of said major and minor areas substantially independent of the configuration of said sealing ring means whereby said size differential may be selected sufficiently small to require substantial pressures to be introduced into said chambers before said pistons are caused to return to their centered condition from said first chamber.

Claim 4

In a brake failure warning device for use in a vehicle having dual fluid brake circuits including a housing, a pair of fluid pressure receiving chambers in said housing, means to connect each of the fluid circuits to one of said chambers, a passage in said housing extending between said chambers, a pair of coaxial pistons in said passage and communicating with a first one of said chambers, one of said pistons defining a circular major pressure reaction area and the other piston defining a minor circular pressure reaction area smaller than said major area, said pistons each defining a normally centered position in said housing, said major area piston being limited to axial movement from said centered position towards said first chamber and back to said centered position, said minor area piston being axially reciprocal towards and away from both of said chambers, piston means associated with a second one of said chambers causing pressure in the second chamber to force said pistons towards said first chamber upon loss of fluid pressure in said first chamber, means to sense movement of said pistons and produce a warning signal externally of said housing, renewal of pressure in said first chamber causing a return of said pistons away from said first chamber to said centered position, said piston means resisting return movement of said pistons from said first chamber towards said centered position, said piston means providing a pressure reaction area at said second chamber of a predetermined size in relation to the normal pressure in said second chamber such that the pressure-area product therein is not less than the product of said minor area and the normal pressure in said first chamber and is not greater than the product of the major area and the normal pressure in said first chamber, the improvement comprising separate sealing means associated with said major and minor area pistons including sealing ring means permitting selection of the size differential of said major and minor areas substantially independent of the configuration of said sealing ring means whereby said size differential may be selected sufficiently small to require substantial pressures to be introduced into said chambers before said pistons are caused to return to their centered condition from said first chamber.

Claim 5

A brake warning device as set forth in claim 2, wherein said sealing ring means is associated with said minor area piston and said ring means has an outer diameter equal to the diameter of said minor area.

Claim 6

A brake warning device as set forth in claim 3, wherein said sealing means includes a second sealing ring associated with said major area piston.

Claim 7

A brake warning device as set forth in claim 2, wherein said piston means associated with said second chamber provides a pressure reaction area having a size intermediate to that of said minor area and said major area.

Claim 8

A brake warning device as set forth in claim 2, wherein said piston means of said second chamber comprises a pair of coaxial pistons providing major and minor pressure reaction areas substantially the same in size as said major and minor areas associated with said first chamber.

Claim 9

A differential pressure sensing device comprising a housing, first and second fluid pressure receiving chambers each adapted to be connected to a separate source of fluid pressure, pressure responsive means in said housing, said pressure responsive means providing at said first chamber major and minor circular pressure reaction areas defined by major and minor piston diameters, first and second separate means for sealing said major and minor piston diameters respectively, said first and second means for sealing each being independent in size relative to the respective piston diameter of the other, said pressure responsive means providing at said second chamber a pressure reaction area having a predetermined relation to the pressure reaction areas associated with the first chamber, said pressure responsive means being sensitive through said reaction areas to fluid pressures in said chambers, said pressure responsive means including means to actuate a signal detectable externally of said housing and operable when the pressures in said chambers change substantially from a normal relationship therebetween and to self-maintain said signal after the substantial change in pressure relationship is eliminated, said pressure responsive means including means to deactuate said signal, said signal deactuating means requiring predetermined reset pressures having magnitudes generally inversely proportional to the difference in size of the sealing diameters of said first and second means for sealing supplied at said chambers.

Claim 10

A differential pressure sensing device comprising a housing, first and second fluid pressure receiving chambers each adapted to be connected to a separate source of fluid pressure, pressure responsive means in said housing, said pressure responsive means providing at said first chamber major and minor circular pressure reaction areas defined by major and minor piston diameters, first and second separate means for sealing said major and minor piston diameters respectively, said first and second means for sealing each being independent in size relative to the respective piston diameter of the other, said pressure responsive means providing at said second chamber a pressure reaction area having a predetermined relation to the pressure reaction areas associated with the first chamber, said pressure responsive means being sensitive through said reaction areas to fluid pressures in said chambers, said pressure responsive means including means to actuate a signal detectable externally of said housing and operable when the pressures in said chambers change substantially from a normal relationship therebetween and to self-maintain said signal after the substantial change in pressure relationship is eliminated, said pressure responsive means including means to deactuate said signal, said signal deactuating means requiring predetermined reset pressures having magnitudes generally inversely proportional to the difference in size of the sealing diameters of said first and second means for sealing supplied at said chambers.