四曲柄压力机 four crank press

四弯曲柄轴 four throw crank shaft

等曲柄四连杆组 four-bar linkage equal crank ; equal crank linkage

平行曲柄四连杆组 parallel-crank-four-bar linkage ; four-bar linkage parallel crank

平行等曲柄四连杆组 parallel equal crank linkage