The piston may be connected to the upper end of the connecting rod either directly (trunk piston type), or indirectly (crosshead type).

活塞与连杆上端的连接，既可以是直接连接(筒状活塞式)，也可以是间接连接(十字头式)。

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In crosshead-type engines, the piston fastens to a vertical piston rod whose lower end is attached to a sliding member called a crosshead, which slides up an down in guides.

在十字头型发动机中，活塞连接在一根垂直的活塞杆上，活塞杆的下端又连接在一个叫做十字头的滑动构件上，十字头在导轨中上下滑动。

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The vibration signals of reciprocating compressor are basically non-balanced from its configuration and work principle, such as the vibration signals of air-valve, crosshead and piston.

由压缩机的结构和工作原理可知，压缩机的振动信号基本上都是非平稳信号，如气阀，十字头、活塞等振动信号。

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