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| Illustration 1 | g00518546 |
Pump Compartment (1) Upper tandem implement pumps (2) Left tandem implement pumps (3) Lower tandem implement pumps | |
There are three tandem implement pumps on the machine. The tandem implement pumps are the upper tandem implement pumps (1), the left tandem implement pumps (2) and the lower tandem implement pumps (3). Each tandem implement pump is mounted to the pump drive which is driven by the engine. Each tandem implement pump consists of a front implement piston pump and a rear implement piston pump. Both the front implement piston pump and the rear implement piston pump are identical in operation. The implement piston pumps are variable displacement axial piston pumps. The implement piston pumps are connected in parallel. The implement piston pumps act as a single pump system.
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| Illustration 2 | g00805976 |
Implement Pumps (4) Rear pump (5) Front pump (6) Port (case drain) (7) Passage (outlet) (8) Load sensing pressure section (9) Port (load sensing signal pressure) (10) Port (power shift pressure) (11) Constant power regulator section (12) Implement pump regulator control valve (13) Passage (inlet) (14) Charge pump | |
Pump Operation
Each main pump has a charge pump (14). The charge pumps draw oil through inlet port (13). The charge pump supplies oil to the rotating group of front pump (5) or rear pump (4). Each front pump (5) or rear pump (4) delivers oil through outlet port (7) .
Each front pump (5) and rear pump (4) have implement pump regulator control valves (12) that are identical in construction and operation. Each implement pump regulator control valve (12) consists of a constant power regulator section (11) and a load sensing pressure section (8). Power shift pressure signal oil is directed to the constant power regulator section (11) through ports (10). Load sensing signal oil is directed to load sensing pressure section (8) through load sensing signal pressure ports (9) .
Each front pump (5) and rear pump (4) has a case drain port (6). Case drain port (6) returns oil that has leaked from sliding surfaces and clearances into the pumps. The oil is returned through the case drain filters to the hydraulic tank.
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| Illustration 3 | g00849926 |
Tandem implement pump (5) Front pump (12) Implement pump regulator control valve (13) Passage (inlet) (14) Charge pump impeller (15) Swashplate (16) Slipper pad (17) Retaining plate (18) Piston (19) Minimum angle stop screw (20) Barrel (21) Passage (22) Port plate (23) Maximum angle servo (24) Shaft (25) Maximum angle stop screw (26) Destroking rod (27) Destroke actuator piston (28) Coupling for the rear pump | |
Shaft (24) is coupled to the pump drive and splined to barrel (20). Shaft (24) is also fixed to charge pump impeller (14). When shaft (24) is driven by the engine, barrel (20), charge pump impeller (14), slipper pad (16), retaining plate (17), piston (18), and coupling (28) rotate. The other pump components are fastened to the pump housing or held by the pump housing. Rear pump (4) is mechanically connected to front pump (5) through coupling (28).
There are nine pistons (18) in the cylinder bores of barrel (20). Each piston (18) is connected to a slipper pad (16). Retaining plate (17) holds slipper pads (16) against the inclined surface of swashplate (15). When shaft (24) rotates, oil is drawn into the pump housing through inlet passage (13). The oil then flows through the passage of port plate (22) into passage (21). Each piston (18) and slipper pad (16) slides on the inclined surface of swashplate (15). As barrel (20) rotates, pistons (18) move in and out of the cylinders in barrel (20). Each piston draws oil in through passage (21) during the down stroke. Each piston expels oil during the up stroke.
Pump output oil flow is controlled by implement pump regulator control valve (12). During implement pump control valve operation, tank pressure or modulated pump discharge pressure acts on destroke actuator piston (27). When destroke actuator piston (27) moves to the left, rod (26) moves to the left. The movement of rod (26) to the left rotates swashplate (15) clockwise. Rotating swashplate (15) clockwise decreases the swashplate angle. Decreasing the angle of swashplate (15) destrokes the pump.
Destroke actuator piston (27) contains passages in order to provide a soft stop. When destroke actuator piston (27) is moved left, swashplate (15) approaches minimum displacement angle. As swashplate (15) approaches minimum displacement angle, the modulated pump discharge pressure begins to progressively bleed off through the passages. Progressively bleeding off the modulated pump discharge pressure softly stops swashplate (15) before the swashplate makes contact with the minimum angle stop screw (19). The minimum displacement angle is determined by the length of rod (26). The minimum angle stop screw (19) prevents excessive destroking of the pump. The minimum angle stop screw (19) does not determine the minimum displacement angle.