| 摘要 |
<p>The stem (9) of the piston (7) has a series of impressions in indented (12) or relief form, permitting the tactile perception, even by persons without sight, of the position of the piston with respect to the cylinder; said impressions (12) being able to interact with one or more elastic tongues (16, 16A) formed in the stopper.</p> |
