Hydraulic unit for a braking mechanism provided with an anti-locking system

Claim 1

Hydraulic unit for a braking mechanism having an anti-locking system for at least one wheel of a vehicle which is intended to ensure the pressure variations of a fluid in the brake operators receiving said fluid connected to said wheel both when locking is imminent and when the wheel regains its grip and which is constituted by a source of fluid under pressure controlled by the driver, by said brake operators, by a first pipe connected to the source of fluid under pressure, by a second pipe connected to the brake operators and by a third exhaust pipe, characterized in that a three-way valve having two stable positions controlled by a device detecting the dynamic state of the wheel is connected to the three said pipes and is able to connect the second pipe selectively to the first pipe and the third exhaust pipe, however, on the one hand, a distributor having two positions which is arranged in the second pipe, closes the latter in its second position as soon as the detection device registers an abnormal state of rotation of the wheel and remains in a cloed position as long as the value of the pressure of the fluid from said controlled source has not appreciably decreased and thereby opens the distributor thus allowing a substantially free passage of fluid in said first position and that, on the other hand, a first conduit is provided having a first flow-limiter in parallel flow relationship to said distributor, and in that said third pipe includes a first accumulator and a second flow-limiter, and in that a second conduit is provided in parallel flow relationship to said second flow limiter, said second pipe comprising a valve member constituted by a moving member of a second accumulator permanently connected to said second pipe between said distributor and the brake operators, said moving member being in its position opening said second conduit when the volume of said accumulator is minimal.