短语词组短語piston fastening bolt 活塞緊固螺釘piston retaining bolt 柱塞固定螺栓piston rod bolt 活塞杆螺拴articulation cylinder piston retaining bolt 鉸接油缸活塞固定螺栓piston junk ring bolt 活塞壓環螺釘piston -rod spool bolt 活塞杆接頭螺栓 返回 piston bolt