The action principle is as follows : When the valve body at around 2 pm between iron block, the spring plunger 12 13 stretch under left movements, the plunger cavity volume have increased LV cavity.

• 其动作原理如下：当泵阀体处于前后两挡铁之间时，柱塞12在弹簧13的弹力作用下向左运动，使柱塞腔的容积增大产生低压腔。