ROLLER 3151300 - Caterpillar

Illustration 1 g01147487
(1) Left main control valve. (2) Right main control valve. (3) Port for the right implement pump. (4) Port for the left implement pump. (5) Outlet to the head end of the tilt cylinder. (6) Outlet to the rod end of the tilt cylinder. (7) Line relief/makeup valve. (8) Makeup valve. (9) Makeup and vent valve. (10) Outlet to the rod end of the lift cylinder. (11) Outlet to the head end of the lift cylinder. (12) Load check valve.
Illustration 2 g01147557
(13) Port for the center implement pump. (14) Inlet for pilot oil.Main control valves (1) and (2) are open centered valves. The main control valves operate identically. The main control valves are constructed similarly except for valves (7) and (8). Main control valve (1) has line relief/makeup valves (7). Main control valve (2) has makeup valves (8). The main control valves are located below the front pump drive in the front of the machine.Main control valves (1) and (2) receive the same pilot signal from the pilot control valve. This means that pilot oil flows to both the main control valves simultaneously when a control lever is moved. The pilot oil from the pilot control valves flows through individual lines to the control valves. At the control valves, the lines form a tee. The lines then flow to each valve.The four implement pumps send oil to the main control valves. The output oil from the center tandem implement pump is sent to spools (21) of the main control valves. Oil from the center fixed implement pump enters the right main control valve through port (13). Oil from the center variable implement pump enters the left main control valve through port (13). Oil from the left implement pump enters control valve (1) through port (3). Oil from the right implement pump enters control valve (2) through port (4). The oil from the right implement pump combines with the oil from the fixed implement pump in a common passage in the right main control valve (2). Oil from the left implement pump combines with the oil from the variable implement pump.There is a line for pressure balance that connects the lift outlets of each main control valve bank. The rackback outlets and the dump outlets in each control valve bank also have a connecting line for pressure balance. The lines for pressure balance ensure that the oil pressure remains equal from the control valves to the respective cylinders.The four bucket operations are DUMP, RACKBACK, RAISE, and LOWER. The control valve functions similarly for the four separate bucket operations. Therefore, only the DUMP operation will be explained. Left control valve (1) and right control valve (2) operate similarly. Therefore, only the operation of left control valve (1) will be explained.
Illustration 3 g01147566
Main Control Valve in Hold (3) Port for the left implement pump. (15) Spool. (16) Passage. (17) Passage. (18) Passage. (19) Port to tank. (20) Spool for the lift circuit. (21) Spool for the tilt circuit.Each control valve contains two