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5.1.4 Cut-off valve
The cut-off valve is mounted at the bottom of the cylinder (See Fig. 5-17) to prevent
the goods from falling suddenly when the high pressure pipe is broken. The oil from hoist
cylinder passes through the hole A on the outer circumference of the spool when
returning to oil tank, if flow rate of oil through the hole is less than the setting value of
the valve and the pressure difference before and after spool smaller than spring force, the
spool will not move at this time and slide valve does not work. If the flow rate through
the spool hole exceeds the setting value due to high pressure pipe cracking or other
reasons, the pressure difference before and after spool will be larger than the spring force
and move the spool to the left. In this way, hole A is closed, only small amount of oil
flows out from the small clearance of spool and valve bush and the goods descends
slowly.
When flow is lower than set value when flow is higher than set value
Figure 5-17 working principle of cut-off valve
5.1.5 Flow regulator valve
The flow regulator valve, located in the lift cylinder circuit to limit the descending
speed of loaded forks, has the construction as shown in Fig. 5-18.
When the lift spool is placed in the “lift” position, the oil from the control valve
flows through the oil chambers A and B, oil holes C, D, E and F, and the chamber G to
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