| 摘要 |
PCT No. PCT/FR95/01327 Sec. 371 Date Nov. 13, 1995 Sec. 102(e) Date Nov. 13, 1995 PCT Filed Oct. 12, 1995 PCT Pub. No. WO96/17757 PCT Pub. Date Jun. 13, 1996A pneumatic brake booster (1) having a piston (5) which is responsive to first and second sources of air pressure. The booster (1) has a rigid casing (3) which is divided by a leaktight movable partition (4) into first (3a) and second (3b) chambers. The partition (4) including a pneumatic piston (5) which carries a control valve (7). A difference in pressure established between the first (3a) and second (3b) chambers causes the piston (5) to move within the casing (3). The inside (50) of the piston (5) is separated from the second source of air pressure by an impurities filter (14). A closing-off means (15,17) is located between an opening to the inside (50) of the piston (5) and the second source of air pressure to control an air inlet path which bypasses the impurities filter (14). An elastic means (18) acts on and opens the closing-off means (15,17) to allow the second source of air pressure to enter the inside (50) of the piston (5) when a difference between the air pressure on the inside (50) of the piston (5) and the second source of air pressure exceeds a given threshold. |
