| 摘要 |
Hydraulic booster device comprising a body 10 having a bore 12 in which a first and a second piston means 18, 20 are slidably mounted, the first piston means 18 being displaceable under the effect of the actuation of a third piston 16 slidably mounted in the body 10, and the second piston means 20 being displaceable by way of a hydrostatic connection formed in a pressure chamber 22, defined between the first and the second piston means 18, 20, a respective valve means, 60, 100 in a respective hydraulic circuit between a pressurised fluid source 52, 96 and a respective brake circuit, 74, 110 being associated with each piston means 18, 20; and a third chamber 36 defined in the bore 12 between the first piston means 18 and the third piston 16, the said third chamber 36 being connected to a low pressure reservoir 25 by a passage in which a valve means 42 is mounted, characterised in that the device comprises a second valve means 112 in a second passage 130, 132 between the third chamber 36 and the reservoir 25 and sensitive to the pressure of the corresponding pressure source 52 in such a way that, in the event of a failure of this high pressure source, the second valve means 112 closes in order to isolate the third chamber 36 from the reservoir 25. <IMAGE>
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