ENGINE AR-BASIC 0R3959 - Caterpillar

Implement Control Valve
Control Valve And Linkage
(1) Main relief valve. (2) Return manifold. (3) Valve sections. (4) Inlet manifold.The implement control valve group consists of inlet manifold (4) with main relief valve (1); two identical valve sections (3) with four positions, PORT "A", HOLD, PORT "B", and FLOAT; and return manifold (2).PORT "A" and PORT "B" positions are both detented with an automatic pressure kickout to return the valve stem to HOLD when a cylinder has reached the end of its stroke. FLOAT position is detented, but does not have an automatic kickout. The valve stem must be returned to HOLD manually by the operator.The PORT "A" and PORT "B" outlets from each valve section are connected to quick couplers (disconnects) at the rear of the tractor.Both valve sections have a load check valve that prevents the implement from dropping when the valve is shifted from HOLD to PORT "A" or PORT "B" position and the pump pressure is less than the pressure in the implement cylinder.Operation of Control Valve In HOLD Position
Valve Section In HOLD Position
(1) Valve spool. (2) Port "A" passage. (5) Passage from pump. (6) Port "B" passage. (11) Passage from pump. (12) Passage to next valve section. (13) Passage from pump.The pump oil from the inlet manifold goes into passages (5), (11), and (13). Passage (5) is a common passage through both valve sections and has no outlet.Passages (11) and (13) do not go through the valve section. When valve spool (1) is in the HOLD position, the pump oil in passages (11) and (13) goes around valve spool (1) into passage (12). The oil in passage (12) goes into the next valve section. If this valve section is also in HOLD, the pump oil flows to the outlet manifold and back to tank.The HOLD position of valve spool (1) stops the oil in passages (2) and (6). With the oil in the lines to the implement cylinders stopped, the implement cylinders can not move. The implement will remain in the position where it was stopped until valve spool (1) is moved to PORT "A", PORT "B", or FLOAT position.Operation Of Control Valve In PORT "A" Position
Valve Section In Port "A" Position
(1) Valve spool. (2) Port "A" passage. (3) Passage. (4) Load check valve. (5) Passage from pump. (6) Port "B" passage. (7) Detent balls. (9) Return oil passage. (11) Passage from pump. (12) Passage to next valve section. (13) Passage from pump.When the control valve is shifted into the PORT "A" position, valve spool (1) blocks the flow of pump oil through passage (12). Pump oil can no longer go to tank. The pressure of pump oil in passages (5), (11) and (13) increases. Passages (11) and (13) are blocked by valve spool (1). When the pressure of the oil in passage (5) is equal to the pressure in PORT "A" passage (2) plus the force of the spring in load check valve (4), the load check valve opens allowing pump pressure into passage