GEAR-SUN 8P7887 - Caterpillar

Speed Change Valve
The speed change valve, in the circuit to the ejector cylinder, automatically changes the amount of oil to the head end of the ejector cylinder. The amount of oil control the speed of the rod as the oil moves the rod out of the cylinder. More oil moves the rod faster.
Speed Change Valve In Fast Position
(1) Valve spool. (2) Inlet for rod end of cylinder. (3) Outlet to tank. (4) Chamber for spring in valve spool. (5) Chamber for springs against stem. (6) Piston. (7) Passages. (8) Stem. (9) Piston. (10) Passage for head end of cylinder. (11) Passage.When the scraper bowl is empty and the ejector control lever is moved to the EJECT position, the pump oil flows through passage (10) to the head end of the ejector cylinder. The pump oil is also in passages (7) and (11). The spring in chamber (4) does not have as much force as the springs in chamber (5) and the pump oil in passages (7) moves piston (6). The piston moves valve spool (1) and the oil in chamber (4) flows through stem (8) into chamber (5) and then through outlet (3) to the tank. The position of valve spool (1) now lets the oil from the rod end of the cylinder go through inlet (2) around the valve spool and into passage (10) to the head end of the cylinder. The oil from the rod end is an addition to the pump oil to the head end of the cylinder and the greater amount of oil moves the piston and rod at a faster speed.
Speed Change Valve
(View is up, at the left side rear) (12) Line from rod end of cylinder to inlet (2). (13) Line between the head end of the cylinder and passage (10). (14) Line from outlet (3) to the control valve (tank). (15) Line from passage (10) to control valve.With the scraper bowl loaded and the ejector control lever in the EJECT position, the pump oil in passage (10) and in the head end of the ejector cylinder increases.
Speed Change Valve In Slow Position
(1) Valve spool. (2) Inlet for rod end of cylinder. (3) Outlet to tank. (4) Chamber for spring in valve spool. (5) Chamber for springs against stem. (6) Piston. (7) Passages. (8) Stem. (9) Piston. (10) Passage for head end of cylinder. (11) Passage.When the pump oil pressure in the head end of the cylinder is approximately 12 750 kPa (1850 psi), the oil in passage (11) to piston (9) moves the piston. The piston moves stem (8) to a position that allows the oil in passage (11) to flow through the stem into chamber (4). The pump oil in chamber (4) moves the position of valve spool (1). The oil in inlet (2) from the rod end of the cylinder now flows through grooves in valve spool (1) and flows through outlet (3) to the tank. With only pump oil available to the head end of the cylinder,