 | |
| Illustration 1 | g00627150 |
Pump Compartment (1) Pump discharge lines (2) Regulator control valve for the swing pump (3) High pressure cut adjustment screw (4) Horsepower control screw (5) Case drain line (6) Rear swing piston pump (7) Pump suction lines | |
 | |
| Illustration 2 | g00627151 |
Tandem Swing Pump (1) Pump discharge lines (2) Regulator control valve for the swing pump (3) High pressure cut adjustment screw (4) Horsepower control screw (5) Case drain line (6) Rear swing piston pump (8) Front swing piston pump (9) M1 test port | |
There are two swing piston pumps on the machine. The front swing piston pump (8) and the rear swing piston pump (6) are splined and bolted together in order to form one tandem swing pump. The tandem swing pump is mounted to the right side of the pump drive which is driven by the engine. Both the front swing piston pump (8) and the rear swing piston pump (6) are identical in operation. The swing piston pumps are variable displacement axial piston pumps. The swing piston pumps are connected in parallel. The swing piston pumps act as a single pump system.
The swing piston pumps have a torque control feature which limits the pump flow when the pump discharge pressure is too high.
 | |
| Illustration 3 | g00806068 |
Tandem Swing Pump (2) Regulator control valve for the swing pump (3) High pressure cut adjustment screw (4) Horsepower control screw (6) Rear swing piston pump (8) Front swing piston pump (9) M1 test port (10) Port (swing signal) (11) Positive flow control section (12) Port (case drain) (13) Port (discharge) (14) High pressure cutoff section (15) Shaft (16) Port (suction) (17) Constant horsepower control section (18) Charge pump (19) Minimum angle servo (20) Maximum angle servo | |
Pump Operation
Each main pump has a charge pump (18). The charge pumps draw oil through suction port (16). The charge pump supplies oil to the rotating group of front pump (8) or rear pump (6). Each front pump (8) or rear pump (6) delivers oil through discharge port (13) .
Each front pump (8) and rear pump (6) have regulator control valves (2) that are identical in construction and operation. Each regulator control valve (2) consists of a constant horsepower control section (17), a high pressure cutoff section (14) and a positive flow control section (11) .
Each front pump (8) and rear pump (6) has a case drain port (12). Case drain port (12) 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.
 | |
| Illustration 4 | g00627154 |
Front Swing Piston Pump (2) Regulator control valve for the swing pump (15) Shaft (20) Maximum angle servo (21) Swashplate (22) Slipper pad (23) Retaining plate (24) Piston (25) Minimum angle stop screw (26) Barrel (27) Passage (28) Port plate (29) Maximum angle stop screw (30) Destroke rod (31) Destroke actuator piston (32) Passage in piston (33) Impeller for the charge pump (34) Coupling for the rear pump | |
Shaft (15) is coupled to the pump drive and splined to barrel (26). Shaft (15) is also fixed to impeller (33). When shaft (15) is driven by the engine, barrel (26), impeller (33), slipper pad (22), retaining plate (23), piston (24), and coupling (34) rotate. The other pump components are fastened to the pump housing or held by the pump housing. Rear pump (6) is mechanically connected to front pump (8) through coupling (34).
There are nine pistons (24) in the cylinder bores of barrel (26). Each piston (24) is connected to a slipper pad (22). Retaining plate (23) holds slipper pads (22) against the inclined surface of swashplate (21). When shaft (15) rotates, oil is drawn into the pump housing through suction port (16). The oil then flows through the passage of port plate (29) into passage (27). Each piston (24) and slipper pad (22) slides on the inclined surface of swashplate (21). As barrel (26) rotates, pistons (24) move in and out of the cylinders in barrel (26). Each piston draws oil in through passage (27) during the down stroke. Each piston expels oil during the up stroke.
Pump output oil flow is controlled by the regulator control valve for swing pump (2). During regulator control valve operation, tank pressure or modulated pump discharge pressure acts on destroke actuator piston (31). When destroke actuator piston (31) moves to the left, rod (30) moves to the left. The movement of rod (30) to the left rotates swashplate (21) clockwise. Rotating swashplate (21) clockwise decreases the swashplate angle. Decreasing the angle of swashplate (21) destrokes the pump.
Destroke actuator piston (31) contains passages (32) in order to provide a soft stop. When destroke actuator piston (31) is moved left, swashplate (21) approaches minimum displacement angle. As swashplate (21) approaches minimum displacement angle the modulated pump discharge pressure begins to progressively bleed off through the passages (32). Progressively bleeding off the modulated pump discharge pressure softly stops swashplate (21) before the swashplate makes contact with the minimum angle stop screw (25). The minimum displacement angle is determined by the length of rod (30). The minimum angle stop screw (25) prevents excessive destroking of the pump. The minimum angle stop screw (25) does not determine the minimum displacement angle.