| 摘要 |
<p>A plunger (21) movable in response to an input shaft (9) is slidably fitted in a hollow valve body (7) having a negative pressure passage (17) and a compressed air inlet port (19) through a pair of seal members (20a and 20b). Two valves 27 and 28 are associated with the plunger to successively introduce the air and compressed air into a working pressure chamber (4) of a pneumatic booster so as to output boosted thrust. The bore (9a) of the valve body has a uniform diameter, and the inner surface of the bore is provided with an annular groove (45) including the compressed air inlet port (19). When the plunger (21) is inserted into the valve body (7), the leading seal member (20a) is prevented from coming in contact with the compressed air inlet port (19) by the presence of the annular groove (45) . There is no difference in pressure bearing area between the two end portions of the plunger (21), which are forward and rearward of the compressed air inlet port (19), when compressed air is introduced. <IMAGE></p> |
