Fluid pressure-operated braking systems for vehicles

Claim 2

A booster-assisted pressure-operated braking system comprising at least one actuator for applying a wheel brake, a booster incorporating a housing, a wall movable in said housing in response to differential fluid pressures applied to chambers in said housing on opposite sides of said movable wall to operate said actuator, a first supply of fluid under pressure, a second supply of fluid under pressure, a control valve assembly which is normally open to supply fluid under pressure from said first supply to a chamber in said housing on one side of said movable wall whereby said movable wall is moved in one direction to actuate said actuator, and deceleration responsive means responsive to the deceleration of a wheel braked by said wheel brake to apply to said control valve assembly, when the deceleration of the braked wheel exceeds a predetermined value, said second supply of fluid under pressure which is adapted to cause said control valve assembly to place the chamber on the opposite side of said movable wall in communication with said first supply of fluid under pressure whereby said movable wall is restored to a position in which the pressure applied to the booster is relieved.

Claim 3

A booster-assisted fluid pressure-operated braking system as claimed in Claim 1, wherein there is interposed between said first supply of fluid under pressure and said control valve assembly a restrictor valve assembly which is normally open to allow fluid under pressure to be supplied to said control valve assembly and means are incorporated for subjecting said restrictor valve assembly to said second supply of fluid under pressure, when the deceleration of said braked wheel exceeds said predetermined value whereby said restrictor valve assembly is operative to regulate communication between said supply of fluid under pressure and said control valve assembly.

Claim 4

A booster-assisted fluid pressure-operated braking system as claimed in claim 2, wherein said restrictor valve assembly is operative to restrict progressively communication between said supply of fluid under pressure and said control valve assembly simultaneously with closure of said control valve assembly, and said means comprise a passage connecting said control valve assembly to said restrictor valve assembly,

Claim 5

A booster-assisted fluid pressure-operated braking system as claimed in claim 2, wherein said restrictor valve is operative to restrict progressively communication between said supply of fluid under pressure and said control valve asseMbly after a predetermined delay following closure of said control valve assembly.

Claim 6

A booster-assisted fluid pressure-operated braking system as claimed in claim 1, wherein said deceleration responsive means comprise a sensor for sensing the deceleration of said braked wheel, a solenoid-operated trigger valve for closing said control valve assembly, and an electronic control module which receives signals from said sensor and which is operative to energise the solenoid of said trigger valve when the deceleration of said braked wheel exceeds said predetermined value.

Claim 7

A booster-assisted pressure-operated braking system comprising at least one actuator for applying a wheel brake, a booster incorporating a housing, a wall movable in said housing in response to differential fluid pressure applied to chambers in said housing on opposite sides of said movable wall to operate said actuator, a supply of fluid under pressure, a control valve assembly which is normally open to supply fluid under pressure from said supply to a chamber in said housing on one side of said movable wall whereby said movable wall is moved in one direction to actuate said actuator, and deceleration responsive means responsive to the deceleration of a wheel braked by said wheel brake to close said control valve when the deceleration of the braked wheel exceeds a predetermined value and to cause said control valve to place the chamber on the opposite side of said movable wall in communication with said supply of fluid under pressure, whereby said movable wall is restored to a position in which the pressure applied to the booster is relieved, wherein said control valve assembly comprises a housing having a first inlet passage connected to said supply of fluid under pressure, a first outlet passage connected to the chamber on the said one side of said movable wall, a second outlet passage connected to the chamber on the said opposite side of said movable wall, a first valve member in said housing for engagement with a first seating between said first inlet passage and said first outlet passage, a second valve member in said housing for alternative engagement with one of a pair of axially spaced second and third seatings located respectively between said first inlet passage and said first outlet passage, and between said first outlet passage and said second outlet passage, a coupling between said first and second valve members, spring means normally urging said first valve member away from said first seating and said second valve member into engagement with said second seating whereby said fluid from said supply is delivered to said chamber on said one side of said movable wall through said first inlet passage and said first outlet passage, a flexible diaphragm carrying said first valve member, a normally closed valve for controlling communication between said supply of fluid under pressure and a chamber in said housing on the side of said flexible diaphragm remote from said second valve member, and means for opening said valve when the deceleration of the braked wheel exceeds said predetermined value so that fluid from said supply of pressure fluid enters said chamber and acts on said diaphragm in opposition to said spring means to urge said first valve member into engagement with said first seating to cut-off communication between said first inlet passage and first outlet passage, and then urge said second valve member away from said second seating to place said first and second outlet passages in communication and equalise the pressure acting on opposite sides of said movable wall.

Claim 8

A booster-assisted pressure-operated braking system comprising at least one actuator for applying a wheel brake, a booster incorporating a housing, a wall movable in said housing in response to differential fluid pressure applied to chambers in said housing on opposite sides of said movable wall to operate said actuator, a supply of fluid under pressure, a control valve assembly which is normally open to supply fluid under pressure from said supply to a chamber in said housing on one side of said movable wall whereby said movable wall is moved in one direction to actuate said actuator, and deceleration responsive means responsive to the deceleration of a wheel braked by said wheel brake to close said control valve when the deceleration of the braked wheel exceeds a predetermined value and to cause said control valve to place the chamber on the opposite side of said movable wall in communication with said supply of fluid under pressure, whereby said movable wall is restored to a position in which the pressure applied to the booster is relieved, wherein said control valve assembly comprises a housing having a first inlet passage connected to said supply of fluid under pressure, a first outlet passage connected to the chamber on the said one side of said movable wall, a second outlet passage connected to the chamber on the said opposite side of said movable wall, a first valve member in said housing for engagement with a first seating between said first inlet passage and said first outlet passage, a second valve member in said housing for alternative engagement with one of a pair of axially spaced second and third seatings located respectively between said first inlet passage and said first outlet passage, and between said first outlet passage and said second outlet passage, a coupling between said first and second valve members, spring means normally urging said first valve member away from said first seating and said second valve member into engagement with said second seating whereby said fluid from said supply is delivered to said chamber on said one side of said movable wall through said first inlet passage and said first outlet passage, a flexible diaphragm carrying said first valve member, a normally closed valve for controlling communication between said supply of fluid under pressure and a chamber in said housing on the side of said flexible diaphragm remote from said second valve member, and means for opening said valve when the deceleration of the braked wheel exceeds said predetermined value so that fluid from said supply of pressure fluid enters said chamber and acts on said diaphragm in opposition to said spring means to urge said first valve member into engagement with said first seating to cut-off communication between said first inlet passage and first outlet passage, and then urge said second valve member away from said second seating to place said first and second outlet passages in communication and equalise the pressure acting on opposite sides of said movable wall.

Claim 9

A booster-assisted fluid pressure-operated braking system as claimed in claim 6, wherein said second valve member is mounted on an axial extension of said first valve member and is urged into engagmeent with an abutment on said extension by a first spring acting between said valve members, and a second spring acts between said extension and said housing to urge said first valve member away from said first seating and said second vaLve member into engagement with said second seating.

Claim 10

A booster-assisted fluid pressure-operated braking system as claimed in claim 6, wherein said valve comprises a first piston working in a bore connected at one end to said supply of fluid under pressure, and a spring normally urges said first piston into a closed position in which the inner end of said first piston engages with an annular seating in said bore, a radial passage in said wall of the housing on the side of the seating remote from said piston providing communication between said bore and said chamber,

Claim 11

A booster-assisted fluid pressure-operated braking system as claimed in claim 8, wherein a rod extending through said seating with which said first piston engages acts on said inner end of said piston, and wherein a solenoid-operated trigger valve, of which the solenoid is energised when the deceleration of said braked wheel exceeds a predetermined value, incorporates a core-piece coupled to said rod and adapted to be advanced to cause said first piston to move away from its seating when said solenoid is energised.

Claim 12

A booster-assisted fluid pressure-operated braking system as claimed in claim 9, wherein said annular seating is formed by one end of an annular shoulder located at an intermediate point in the length of said bore and a second piston working in the portion of said bore located between said shoulder and the free end of the bore remote from said end connected to said supply of fluid under pressure has an inner end for engagement with a seating defined by an opposite face of said shoulder, a spring acting on said first piston normally urging said second piston away from its seating so that said chamber above said diaphragm is in communication with atmosphere through said radial passage, and said second piston being urged into engagement with its seating when said solenoid is energised whereby said chamber is placed in communication with said supply of fluid under pressure.

Claim 13

A booster-assisted fluid pressure-operated braking system as claimed in claim 10, wherein each piston is of cup-shaped outline having a crown incorporating a passage which provides communication between portions of said bore at opposite ends of that piston at a position radially outwards from a radially innermost edge of said seating on said shoulder with which that piston is adapted to engage.

Claim 14

A booster-assisted fluid pressure-operated braking system as claimed in claim 6, wherein said first inlet passage is connected to said supply of fluid under pressure through a restrictor valve assembly adapted to regulate communication between said supply of fluid under pressure and said control valve assembly when said deceleration of said braked wheel exceeds said predetermined value.

Claim 15

A booster-assisted fluid pressure-operated braking system as claimed in claim 12, wherein said restrictor valve assembly comprises a housing having a first radial passage connected to said supply of fluid under pressure and a second radial passage communicating with said first radial passage through a longitudinally extending bore in said housing and connected to said first inlet passage of said control valve assembly, a piston rod working in the longitudinally extending bore being adapted to control communication between said first and second radial passages in response to changes in the pressure of fluid applied to said chamber in the control valve assembly above the diaphragm.

Claim 16

A booster-assisted fluid pressure-operated braking system as claimed in claim 13, wherein a portion at the end of said longitudinally extending bore remote from said radial passage is counterbored and a piston working in said counterbore and carried by said piston-rod is exposed to pressure in said control chamber to advance said piston-rod in said bore and regulate communication between said first and second radial passages, and normally a return spring acting between said piston and a shoulder at a step in diameter between said bore and said counteRbore is adapted to urge said piston in an opposite direction into a retracted position in which said radial passages are in free communication.

Claim 17

A booster-assisted fluid pressure-operated braking system as claimed in claim 13, wherein a normally closed valve is adapted to control communication between said chamber in said control valve assembly and said piston-rod, and said normally closed valve is adapted to open when the pressure in said control chamber exceeds a predetermined value.

Claim 18

A booster-assisted fluid pressure-operated braking system as claimed in claim 15, wherein said normally closed valve comprises a valve member guided in a valve guide for axial movement relative to a seating surrounding an inlet connected to said chamber in said control valve assembly, and a spring for normally urging said valve member into engagement with said seating, said valve guide incorporating a radial outlet passage having a restriction through which fluid under pressure can escape gradually from said restrictor valve assembly when said valve member is moved away from its seating.

Claim 19

A booster-assisted fluid pressure-operated braking system as claimed in claim 13, wherein said radial passages are spaced axially from each other along a length of said longitudinally extending bore and are separated at adjacent ends by a bore portion in which works a free end portion of said piston-rod.

Claim 20

A booster-assisted fluid pressure-operated braking system as claimed in claim 17, wherein said free end portion is reduced in diameter to provide communication between said radial passages when said piston-rod is in a normal retracted position, and a full diameter of said piston rod inwardly of said reduced diameter portion is adapted to enter said bore portion when said piston-rod is advanced in said longitudinally extending bore.