TURBO GP 5389810 - Caterpillar

Illustration 1 g03113216
(1) Pilot oil port (2) Shims (3) Springs (4) Signal oil passage (5) Rod end (6) Head end (7) Makeup valve (8) Passage (9) Outlet to tank (10) Chamber (11) Pilot oil port (12) Resolver (13) Spring (14) Chamber (15) Inlet chamber (16) Flow control valve (17) Metering slot (18) Chamber (19) Load check valve (20) Passage (21) Outlet passage (22) Control valve spoolWhen the machine is equipped with a bulldozer and with a ripper, the ripper tip control valve is the fourth valve in the valve stack. The ripper tip control valve changes the angle of the ripper from the vertical toward the machine. The control valve is equipped with these components: makeup valve (7), resolver (12), flow control valve (16), load check valve (19) and valve spool (22) .The ripper tip control valve is a spring centered valve. Control valve spool (22) is a closed center spool and a pilot operated spool with three positions: TIP IN, HOLD and TIP OUT. Spring (3) keeps the valve spool in the HOLD position when the ripper tip control valve is not active. Movement of the spool is controlled by the pilot control system. The pilot control system connects the ripper control lever to valve spool (22) .Resolver (12) is a double check valve. Flow control valve (16) limits the maximum flow of oil to the tip circuit. The functions of the resolver and of the control valve spool are described in the sections on positions of the control valve. The descriptions of the function of load check valve (19) and of makeup valve (7) are in separate sections.Load Check Valve
Load check valve (19) prevents reverse oil flow in the ripper tip cylinders, which can cause cylinder drift. The load check valve does not open until pump oil pressure in chamber (15) overcomes the force of the spring for the load check valve and of the cylinder oil pressure in passage (20) .Makeup Valve
Makeup valve (7) is in the rod end of the tip circuit. The makeup valve opens when cylinder oil pressure in passage (5) drops below the return oil pressure in outlet passage (8). Makeup valve (7) adds return oil from outlet passage (8) to cylinder oil in passage (5). The additional oil prevents cavitation (vacuum) in the tip cylinders.HOLD Position
When the control valve spools are in the HOLD position, pump oil flows to the inlet passage of the control valve. Oil flows around flow control valve (16) and oil flows in primary metering slots (17). Since there is no oil in chamber (14) to move flow control valve (16) to the left, no oil flows through the metering slots to open load check valve (19). Pump oil then flows through the outlet passage to the next control valve.Since all the valve spools are in the HOLD position, pump oil fills the parallel oil passages of the control valves. Passage (4), chamber (10), and resolver (12) are drained. Passages (6), (8) and (20) are blocked.TIP