| 摘要 |
<p>The device (1a) has a shoulder (2) provided between a cylindrical casing (11) i.e. tube body, and a threaded rod (8), where the shoulder has double walls that are upper wall (4a) and lower wall (4b). The shoulder has a cavity (10) formed between the walls, where opening of the cavity is closed by the casing. The upper wall has a portion in contact with outside and another portion covered by the casing. The lower wall is placed inside the device. The upper wall has another portion pierced by an orifice i.e. annular opening (6). Thickness of the shoulder ranges from 2.0 mm to 2.5 mm.</p> |
