PLATE 3376714 - Caterpillar

Illustration 1 g00829815
When the machine is equipped with a winch, the winch control valve is at the top of the valve stack. The winch control valve controls the operation of the winch motor. The control valve is equipped with these components: control valve spool (2), resolver (10), flow control valve (13) and load check valve (18) .The winch control valve is a spring centered valve. Control valve spool (2) is a closed center spool and a pilot operated spool with three positions: REEL IN, HOLD and REEL OUT. Spring (1) keeps the spool in HOLD position when the winch motor is not active. Movement of the spool is controlled by the pilot control system. The pilot control system connects the winch control lever to control valve spool (2) .Resolver (10) is a double check valve. Flow control valve (13) limits the maximum flow of oil to the winch motor. The functions of the resolver and of the control valve spool are described in the sections on positions of the control valve. The description of the function of load check valve (18) is in a separate section.Load Check Valve
Load check valve (18) prevents reverse oil flow in the winch motor, which can cause circuit drift or load loss. The load check valve does not open until pump oil pressure in chamber (16) becomes greater than the combined forces of the spring for the load check valve and of the oil pressure in passage (17) .HOLD Position
When all the control valve spools are in the HOLD position, pump oil fills the parallel oil passages of the control valves. The pump maintains oil pressure at 3000 kPa (435 psi). Passage (3), chamber (8), and resolver (10) are drained. Passages (4), (6) and (17) are blocked.REEL IN Position
When pilot control pressure causes control valve spool (2) to move to the REEL IN position, passage (3) is opened to passage (6). Winch oil from passage (6) flows through passage (3) to chamber (8). The oil functions as signal oil. Part of the signal oil flows to chamber (12) behind flow control valve (13). The signal oil opens flow control valve (13). The rest of the signal oil flows through resolver (10) to the inlet manifold.The increase of pump oil flow to inlet passage (14) flows through primary metering holes (15) into chamber (16). The pump oil opens load check valve (18). The oil flows through load check valve (18). Then, the oil flows through passage (17), around control valve spool (2), and through passage (6) to the winch motor. The winch then reels in the cable.Return oil from the winch motor flows through passage (4), around control valve spool (2), and through outlet passage (19) to the tank.REEL OUT Position
Illustration 2 g00825140
When pilot control pressure causes control valve spool (2) to move to the REEL OUT position, winch oil from passage (4) flows through passage (3) to chamber (8). The oil functions as signal oil. The signal oil opens resolver (10). The signal oil flows