Lock Check Valve.

TM 5-3805-261-23-1

THEORY OF OPERATION - CONTINUED

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HYDRAULIC SYSTEM - CONTINUED

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e.

Lock Check Valve.

(1)

There is a lock check valve between the control valve and the hydraulic cylinder (or motor) in each of the

hydraulic systems. The purpose of each lock check valve is the same, but several designs are used because

of the different system requirements.

(2)

Lock check valves prevent hydraulic cylinder rods from drifting when the controls are in HOLD (neutral)

position, by locking the hydraulic pressure in against ball check valves. Outlet chokes in lock check valves

serve to slow down the hydraulic flow when needed. Relief valves serve to prevent overloading the sys-

tem.

(a) The circle drive and leaning wheel systems use lock check valves without chokes or relief valves.

(b) The centershift, articulation, and right hand lift systems use lock check valves with chokes and with-

out relief valves.

(c) The left hand lift system and the scarifier system use lock check valves with chokes and a relief valve.

(d) The tip and sideshift systems use lock check valves with relief valves but without chokes.

(e) When the control valve is in HOLD position, the oil in lines is stopped and the rod in the cylinder can-

not move. The springs and the oil in lines keep the balls on seats. Oil in the lines is at tank pressure.

PISTON

LINE TO CONTROL VALVE

CHOKE IN OUTLET

BALL

SEATS

LINE TO HEAD END

LINE TO ROD END

OF CYLINDER

397-049

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