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| Illustration 1 | g00688986 |
Speed Change Valve in Fast Position (1) Valve spool (2) Inlet for rod end of ejector cylinder (3) Outlet to main control valve (4) Chamber for spring in valve spool (5) Chamber for springs against stem (6) Piston (7) Passages for pump oil (8) Stem (9) Piston (10) Passage for head end of ejector cylinder (11) Passage for pump oil | |
When the scraper bowl is empty and the ejector valve stem is moved to the EJECT position, 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 springs that are inside chamber (5) exert more force than the spring that is inside chamber (4). The pump oil that is in passages (7) will move piston (6). Piston (6) moves valve spool (1) and the oil in chamber (4) flows through stem (8) into chamber (5). This oil flows through outlet (3) to the main control valve then to the hydraulic tank. The position of valve spool (1) now allows oil to flow through inlet (2) from the rod end of the ejector cylinder. The oil then flows around valve spool (1) and into passage (10). This oil flows from passage (10) into the head end of the ejector cylinder. The oil from the rod end of the ejector cylinder is an addition to the pump oil to the head end of the ejector cylinder. The increased oil flow moves the ejector at a faster speed.
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| Illustration 2 | g00688989 |
Speed Change Valve (12) Line from rod end of ejector cylinder to inlet (2) (13) Line between the head end of ejector cylinder and passage (10) (14) Common oil line from outlet (3) to the main control valve | |
When the scraper bowl is loaded and the ejector valve stem is in the EJECT position, the pressure of the oil in passage (10) and the pressure of the oil in the head end of the ejector cylinder will increase.
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| Illustration 3 | g00688991 |
Speed Change Valve in Slow Position (1) Valve spool (2) Inlet for rod end of ejector cylinder (3) Outlet to main control valve (4) Chamber for spring in valve spool (5) Chamber for springs against stem (6) Piston (7) Passages for pump oil (8) Stem (9) Piston (10) Passage for head end of ejector cylinder (11) Passage for pump oil | |
The oil in passage (11) moves piston (9) when the oil pressure in the head end of the ejector cylinder increases to a set pressure. Piston (9) moves stem (8) upward to a position that allows the oil in passage (11) to flow through the stem into chamber (4). The pressure oil in chamber (4) moves valve spool (1) to the left.
The oil in inlet (2) from the rod end of the ejector cylinder flows through grooves that are in valve spool (1). This oil flows through outlet (3) to the main control valve then to the hydraulic tank. When only pump oil is available to the head end of the ejector cylinder, the ejector moves slowly.
As the ejector moves the load out of the scraper bowl, less oil pressure is required. When the oil pressure decreases to a set pressure, the springs in chamber (5) move stem (8). The stem moves to a position that allows the oil in chamber (4) to drain through stem (8) to chamber (5) and passage (3) to the main control valve and the hydraulic tank. With only spring force in chamber (4) on valve spool (1), the pump oil from passage (10) through passage (7) moves piston (6) and valve spool (1) to the right. Valve spool (1) is now in the position that allows the oil in passage (2) from the rod end of the ejector cylinder to flow into passage (10) and combine with the pump oil. As the pump oil and the pressure oil in passage (11) from the rod end of the ejector cylinder flows to the head end of the ejector cylinder, the ejector moves faster.