BARREL GP-PUMP 1646987 - Caterpillar

Illustration 1 g00487258
Bulldozer Lift Control Valve (Control Valve Spool in HOLD position) (1) Outlet passage to tank (2) Passage to rod end of lift cylinders (3) Outlet passage to tank (4) Passage to head end of lift cylinders (5) Makeup valve (6) Outlet to tank (7) Spring (8) Lever (9) Detents for the FLOAT position (10) Control valve spool (11) Passage for signal oil to next control valve (12) Passage for signal oil (13) Load check valve (14) Passage (15) Chamber (16) Flow control valve (17) Metering slots (18) Inlet passage for pump oil (19) Orifice (20) Spring (21) Passage (22) Chamber for signal oil (23) Shuttle valve (24) Passage for signal oil from tilt control valveThe bulldozer lift control valve is the second valve in the control valve stack. The valve is used to raise and the valve is used to lower the bulldozer blade. The control valve has the following components:control valve spool (10), shuttle valve (23), load check valve (13), makeup valve (5) and flow control valve (16) .Control valve spool (10) is a spring centered closed center manually operated spool. The control valve has the following four positions: RAISE, HOLD, LOWER and FLOAT. Spring (7) keeps the spool in the HOLD position when the bulldozer lift control valve is not active. Movement of the spool is controlled manually by the operator. A linkage connects the bulldozer control lever to lever (8). Lever (8) is connected to control valve spool (10) .Flow control valve (16) limits the pressure drop across the valve spool (10). This limits the forces on the control valve spool and this reduces operator lever efforts.Shuttle valve (23) is a double check valve that sends the highest signal oil pressure to the ripper control valve. More descriptions of the shuttle valve and the flow control valve are given. Also, descriptions of the control valve spool in different positions are given. Descriptions for load check valve (13) and makeup valve (5) are under separate topics.HOLD Position
When the control valve spool and all other implement valve spools are in the HOLD position, the pump oil flows to inlet passage (18), which is common in all the valve sections and the passage has no outlet. Oil then flows around the flow control valve. Also, the oil flows in metering slots (17) and the oil moves the flow control valve against spring (20). Since all the valve spools are in the HOLD position, pump oil fills the parallel oil passages of the control valves and the pump maintains the pressure at approximately 3600 kPa (520 psi). Now, passage (12), chamber (22), shuttle valve (23), passage (11) and passage (24) are drained. Oil in passages (14), (2) and (4) is blocked.LOWER position
When control valve spool (10) is moved to LOWER position, passage (21) is closed off from outlet passage (6). Cylinder oil from passage (4) flows through passage (12) to chamber (22). The oil becomes signal oil. Some of the signal oil flows through passage (21) and