PLATE 2900232 - Caterpillar

Float Operation
When the lift control lever is moved to FLOAT detent position, lift valve spool (23) moves into the detent in lift control valve (22). The signal oil passage drains around the lift valve spool. The signal oil at unloading valve (8) and margin stem (7) drains back to hydraulic tank (5) through shuttle valves (13) and (20). Implement pump section (3) unloads around unloading valve (8). The implement oil pressure is low.The head and rod ends of lift cylinders (21) are now open to the tank passages in the lift control valve. Outside forces on the bucket control the movement of the cylinder rods.The lift control lever must be manually moved out of the FLOAT detent position. There is no kickout for FLOAT position.Tilt Circuit
Tilt Back Operation
When the tilt control lever is moved to TILT BACK position, tilt valve spool (15) moves to TILT BACK position. Tilt cylinder oil (head end) oil goes through tilt valve spool (15) and divides. This oil is now signal oil. Some of this oil goes to the spring chamber of priority flow control valve (17). The valve moves toward the left. The remainder of the signal oil goes to shuttle valve (13), pushes the valve to the right and goes to unloading valve (8) and margin stem (7) of inlet valve group (1). Unloading valve (8) moves completely to the left and the implement oil pressure increases. Margin stem (7) is held to the left (does not move).The implement oil now goes through priority flow control valve (17) and opens load check valve (16). The oil goes around tilt valve spool (15) and out tilt control valve (14) to the head end of tilt cylinder (10). The cylinder rod extends. The Z-bar linkage causes the bucket to tilt back.The movement of the cylinder rod pushes the oil out of the rod end of tilt cylinder (10). This oil comes into tilt control valve (14) and goes around tilt valve spool (15). The oil goes through the common tank passages in the tilt control valve and inlet valve group (1) on its way back to oil filter (6) and hydraulic tank (5).When only part of the implement oil is needed, the pressure of the oil on the left end of margin stem (7) pushes the margin stem to the right inside of unloading valve (8). This lets implement oil, that is not needed, go through unloading valve (8) and back to the hydraulic tank. Margin stem (7) is now in its pressure compensation position. When all of the implement oil is needed in the implement hydraulic system, margin stem (7) is moved all the way to the left (it does not operate).There is a linkage detent in TILT BACK position when the bucket is between DUMP position and the correct angle to dig. This detent holds the tilt control lever [and tilt valve spool (15)] in TILT BACK position until the bucket