Device for rapidly building-up pressure in a device of a motor vehicle, said device being supplied with a pressure medium by means of a feed pump

An apparatus (1) for rapid pressure buildup in a motor vehicle reservoir-type injection system (common rail) (4) supplied with fuel by a high-pressure feed pump (2), the apparatus comprising a piston (40) defining a pressure chamber (44) communicating with the feed pump, said pressure chamber containing a spring element (50) prestressed counter to the piston, the piston being moveable counter to the force of the spring element (50) to enlarge the pressure chamber, a locking device (56, 64, 74) acting on and releasibly locking said piston in a locking position, assumed as a result of movement by pressure built up in said pressure chamber (44) by the feed pump (2), counter to the prestressing force of said spring element (50), means for unlocking said piston to permit movement of said piston by said spring element (50) to reduce the volume of the pressure chamber (44), said piston being guided longitudinally displaceably inside a closed cylinder (24), said pressure chamber (44) being formed between the piston (40) and a bottom wall (22) of said closed cylinder (24), said bottom wall being provided with a pressure connection connecting said pressure chamber (44) to a pressure conduit (10) affecting communication between the feed pump (2) and the common rail (4), wherein said locking device comprises two locking bolts (56), received in diametrically opposed receiving bores (56) in said closed cylinder wall (52), said locking bolts being movable between a first position protruding into the cylinder (24) in a direction transverse to the direction of motion of the piston (40) and a second position withdrawn from said cylinder, and spring means (64) biasing said locking bolts to said first position, said bolts being capable of being forced from said first to said second position by the motion of said piston (40) in a direction counter to the prestressing force of said spring element and, after said piston (40) has moved past the bolts and reached said first position, wherein the bolts positively engage and releasibly retain said piston (40) to retain said piston.