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)。
2
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.
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.