HARNESS AS 7Y8112 - Caterpillar

Illustration 1 g00544662
Stick lowering control valve (1a) Spool (1b) Set screw (2) Relief valve (3) Retainer (4) Spring (5) Poppet (6) Spring (7) Valve pin (8) Tapered section of valve (9) Check valve (10) Ball (11) Seal nut (12) Cap (13) Screw (manual stick lowering) (14) Stop cover (15) Control piston (16) Spring (17) Shim (18) Sleeve (19) Rod (20) Tapered piston (21) Ball (22) Ball retainer (23) Valve body (24) Spring (25) Spring chamberSTICK EXTEND
As the joystick is moved to the STICK EXTEND position, pump oil flows from port (A) through port (B) after pushing on check valve (9). The control valve works as a standard check valve. When the joystick returns to the NEUTRAL position, the load will be held by all valve elements in a sealed condition. STICK RETRACT
Pilot pressure comes in the control valve through port (X). The pressure pushes piston (15) against spring (16). When pilot pressure increases, piston (15) pushes ball (10). Ball (10) then pushes pin (19). Pin (19) lifts poppet (5) off the seat. This allows spring chamber (25) to release pressure to the tank. Now, piston (20) can be pushed against spring force (24). Oil can flow from port (B) to port (A) through orifices of piston (20). Increased pilot pressure allows the opening between port (A) and port (B) to be increased.Note: Adjustable spool (1a) restricts the initial stroke of piston (20) .When pilot pressure is decreased, forces of springs (24) and (16) push the piston backward. Spring (4) closes poppet (5). Piston (20) comes back on the seat. This closes the opening between ports (A) and (B). Oil leaks between piston (20) and housing (23) refill chamber (25) with oil. This locks piston (20) on the seat and the stick lowering control valve is locked again.
Illustration 2 g00544663
Flow control valve (26) Nipple (27) Stop nut (28) Spring (29) Washer (30) BoltParallel Cylinders
If two cylinders are working in parallel mode, a flow control valve is installed in (M/R) port of the stick lowering control valve. The flow control valve restricts oil leakage if a connecting hose breaks.Normal Operation (Open Valve)
Spring (28) pushes washer (29) open. Stop nut (27) determines the length of bolt (30), which determines the amount of flow from port (B) to port (A) .Broken Line
A high flow from port (B) to port (A) raises the pressure in chamber (B). This pressure closes washer (29) against the seat and flow is restricted through orifice (D) .