| 摘要 |
Braking device comprising a master cylinder (2), a primary piston (3), a manual-control member (4), a booster (6) coupled to the manual-control member (4), and an emergency assist valve (VA) comprising a reaction piston (17) through which there passes a ratio control (24) having a head (25) located in a chamber (26) lying between the reaction piston (17) and a bushing (27) housed further forward in a bore (18) of the primary piston, this bushing (27) having an axial passage (28) in which there can slide a rapid piston (29), the rear end of which forms, with the head (25), a valve (36) capable of closing the inlet to a passage (30) in the rapid piston. The device comprises a means (E), consisting in the bushing (27) being mounted so that it can slide, for limiting the pressure difference between the chamber (26) and a zone (18a) of the bore situated forward of the bushing, to a value below the one which can cause the valve (36) to open.
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