| 摘要 |
A vibrator has (a) a housing including a wall forming a cavity, (b) a sleeve in the cavity, and (c) a piston received in the sleeve for reciprocating movement therein. In the improvement, the cavity has a boundary surface inside the housing and the vibrator includes an impact block interposed between the boundary surface and the sleeve. Such impact block is positionally retained in the cavity by the boundary surface and the sleeve.
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