| 摘要 |
The device comprises a tube (1) in which are housed a push-button (2), a return spring (3) and sealing means (4). The tube (1) consists of four successive cylindrical portions (6, 7, 8, 9) of different diameter arranged in a staircase fashion. An annulus (5) is driven into the upper portion (6) corresponding to the head (2a) of the push-button (2). The annulus (5) has, at its upper end, an internal shoulder (5a) allowing for a circular passage whose wall (5b) is conical over its lower portion. The head (2a) in the rest position and under the action of the return spring (3) abuts against the conical wall of the annulus (5) by means of a conical surface (2b) thus forming a passage which is sealed at least against dust. The head (2a) of the push-button (2) has, in its lower portion, a shoulder (2c) intended, on the one hand, to form, together with the vertical wall (5c) and the shoulder (5a) of the annulus (5), the housing for a seal (4) and, on the other hand, to serve as a stop collaborating with an end-of-travel stop formed by the shoulder (10) between the second (7) and the third (8) cylindrical portions. <IMAGE>
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