▲ Action of cut-off valve
There is a cut-off valve that operates when the high-pressure hose bursts for any
reason to prevent the load from dropping down abruptly at the bottom of the lift cylinder
(Fig. 7.5). The oil from the lift cylinder flows through small holes in the circumference of
the cut-off valve spool and produce a pressure difference between two chambers. As the
pressure difference is smaller than the spring force as result of passing the holes so that
the cut-off valve spool won’t move. If the high-pressure hose bursts, the pressure
difference will be big enough to overcome the spring force, causing the spool to move
until the holes on the circumference of the spool are blocked up and allowing only a small
amount of oil to flow through the holes at the spool end to let the forks descend at low
speed.
Fig.7-5 Action of cut-off valve
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