| 摘要 |
In the duct (5) carrying the fuel flow there is arranged a shaped piston (4) comprising an upper bellows (11) which engages with a central coaxial control stem (10). The piston is driven by an operator (2) whose intervention is conditioned by activation or not of an anti-theft device. With the operator (2) in neutral position or with the anti-theft turned on, the piston (4) closes the fuel passage port. With the operator in working position, i.e. with the anti-theft device excluded, it is extended, the piston rises and the passage port (7) opens. Under these conditions the pressure differential between upstream and downstream, apart from the direction of flow, arranges itself both in the direction of flow and upstream and downstream of the central zones delimited and separated by said upper bellows (11). The pressure differential arranges the central control stem (10) in a position of adherence with a ring of balls (9) which, thrust radially outward, are engaged in a peripheral seat (13). Said engagement prevents the piston (4) from returning to its neutral position even if the operator (2) should return inward because of, for example, breakage. The fuel flow continues thus for the entire period that the vehicle keeps the motor running, i.e. as long as the status of pressure head between upstream and downstream of the stem (10) prevails. Upon stopping of the motor, i.e. upon elimination of the pressure differential, the piston (4) is thrust into the closed position by a counteracting spring (6) which relaxes from its compressed condition. <IMAGE> |
