TM 9-3418-201-14&P
REVERSING VALVE CHOKES
On the main valve body are placed four choke plugs, two at each end, for the purpose of adjusting the ram
reversals at each end of its stroke. By means of these chokes the rate of deceleration at the end of the stroke may be
controlled. Likewise the rate of acceleration at the beginning of the stroke may be controlled.
These chokes are adjusted by experts at our factory to give the most suitable ram action under the conditions
existing here. No further adjustment should be necessary and the chokes should not be tampered with.
However, in rare cases, the conditions under which the machine must operate in a customer's plant may require a
slight readjustment of the chokes. If such a case arises no one except a thoroughly experienced mechanic should attempt
to change the setting.
The following is offered in explanation of the functioning of the choke plugs.
They operate on the principle of a needle valve for governing the rate at which oil may be discharged from the
space at the ends of the reversing valve spool, and therefore the speed at which the valve spool travels during the shifting
action. If the chokes are open too far the ram will reverse with a shock or bump at the end of the stroke; if closed too
much the ram will be sluggish in its action.
Chokes 3 and 4 control the reversal of the ram at the end of the cutting stroke and beginning of the return stroke.
Chokes 1 and 2 control the reversal at the end of the reverse stroke and beginning of the cutting stroke. When the correct
adjustment has been made the ram will have a snappy action but still without shock.
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