The expansion and contraction of the rope of the crane boom is the use of the principle of the hydraulic rod, the specific principle is as follows:
The work of the hydraulic rod mainly depends on the oil pressure, the clearance between the tappet body and the hundred seat hole, the clearance between the valve rod and the tappet post and the check ball valve in the tappet post. When the hydraulic tappet starts to work, because there is no oil pressure in the cavity, the stiffness plunger is at the very bottom, and the gap between the tappet and the valve is large, and the valve produces short-term abnormal sound.
With the operation of the engine, under the action of the oil pressure, the oil is filled in the plunger cavity in the tappet, the plunger goes down, the effective working length of the tappet increases, and the valve clearance decreases. Because the force generated by the plunger in the tappet is small, it can not generate the force to compress the valve spring, so when the clearance between the tappet and the valve is very small, the tappet hundred no longer moves.
At the same time, due to the role of the check ball valve in the tappet, the oil pressure in the plunger cavity can not be quickly discharged, so that the plunger remains in place and maintains the original length to form a rigid, thereby driving the valve to open. With the operation of the engine, the valve clearance remains a certain gap.