Grapple Open/Close Operation
 | |
| Illustration 1 | g00952542 |
(1) Pilot line (2) Solenoid valve (grapple control) (3) Pressure switch (4) Grapple cylinders (5) Pilot line (6) Pilot line (7) Line (8) Line (9) Pilot line (10) Control valve (grapple cylinders) (11) Center bypass passage (12) Load check valve (13) Main control valve (right) (14) Parallel feeder passage (15) Return passage (16) Line (17) Negative flow control line (18) Pilot line (19) Proportional reducing valve (negative flow control) (20) Negative flow control line (21) Pilot oil manifold (22) Left pump (23) Right pump (24) Pilot pump (25) Hydraulic tank | |
The oil delivery for the open/close operation is supplied by right pump (23) only.
The oil delivery from right pump (23) flows through line (16) and center bypass passage (11) in main control valve (13) to grapple control valve (10) .
When the hydraulic activation control lever is in the UNLOCKED position, the oil delivery from pilot pump (24) flows through pilot oil manifold (21) and pilot line (5) to solenoid valve (2). When the switch for the grapple is activated to the GRAPPLE OPEN position, pilot oil flows through solenoid valve (2), pilot line (1), and pilot line (9) to grapple control valve (10). The pilot oil pressure shifts the spool in the grapple control valve downward. The pilot oil on the other end of the spool in the grapple control valve flows through pilot line (6) and solenoid valve (2) to hydraulic tank (25) .
Since the spool in the grapple control valve is fully shifted, center bypass passage (11) is blocked. None of the oil delivery from the right pump flows to the negative flow control orifice and no negative flow control pressure is created in center bypass passage (11). Proportional reducing valve (19) is energized when solenoid valve (2) is activated. Pilot oil line (18) supplies pilot oil pressure to proportional reducing valve (19). The machine ECM controls proportional reducing valve (19) in order to control the negative flow control pressure to the drive and right pumps. The output flow rate of the pumps is adjusted. Oil flows through parallel feeder passage (14), load check valve (12), grapple control valve (10) and line (8) to the rod end of grapple cylinders (4) .
Reference: For more information concerning the negative flow control operation, refer to Systems Operation, "Negative Flow Control".
The return oil from grapple cylinders (4) flows through line (7), the passage in grapple control valve (10), and return passage (15) to hydraulic tank (25) .
The GRAPPLE CLOSE operation is similar to the GRAPPLE OPEN operation.
When the switch for the grapple cylinders is moved to the GRAPPLE CLOSE position, pilot oil flow from solenoid valve (2) flows through pilot line (6) to grapple control valve (10). The spool in grapple control valve (10) shifts upward. The oil delivery from the right pump now flows through line (7) to the grapple cylinders.
When the switch for the grapple cylinders is in the OFF position, the grapple control valve is maintained in the NEUTRAL position. The oil flow to the grapple cylinders is blocked.
Grapple Rotate
 | |
| Illustration 2 | g00936999 |
(26) Grapple rotate motor (27) Line (28) Line (29) Crossover relief valve (30) Relief valve (cushion) (31) Relief valve (cushion) (32) Line (33) Line (34) Crossover relief valve (rotate counterclockwise) (35) Crossover relief valve (rotate clockwise) (36) Orifice (37) Orifice (38) Check valve (39) Check valve (40) Passage (41) Passage (42) Spool (43) Spring (44) Spring (45) Control valve (grapple rotate) (46) Return line (47) Main relief valve (48) Supply line (49) Auxiliary pump (50) Hydraulic tank | |
The oil delivery for the grapple rotate circuit is supplied by auxiliary pump (49) .
The oil delivery from auxiliary pump (49) flows through line (48) to grapple control valve (45). When spool (42) is in the NEUTRAL position, oil flow is returned to hydraulic tank (50) .
Relief valve (47) maintains the circuit pressure when the rotate control valve is operated.
Crossover relief valve (29) is located in the lines to the grapple rotate motor in order to reduce pressure spikes in the rotate circuit.
When the switch for the grapple is activated to the GRAPPLE ROTATE COUNTERCLOCKWISE position, the solenoid valve shifts spool (42) in grapple control valve (45) against spring (44) .
When the spool in the grapple control valve is fully shifted, the oil delivery from the auxiliary pump flows through passage (41), check valve (39), line (33), relief valve (29), and line (28) to grapple rotate motor (26). The grapple will rotate counterclockwise.
The return oil from grapple rotate motor (26) flows through line (27), relief valve (29), line (32), orifice (36), passage (40), spool (42), and return line (45) to hydraulic tank (50). Orifice (36) will restrict the return oil flow in order to control the rotating speed of the grapple.
The GRAPPLE ROTATE CLOCKWISE operation is similar to the GRAPPLE ROTATE COUNTERCLOCKWISE operation.
When the switch for the GRAPPLE ROTATE CLOCKWISE operation is activated, the solenoid valve shifts spool (42) against the force of spring (43). The oil delivery from the auxiliary pump now flows through line (27) to the grapple rotate motor.
When the switch for the grapple rotate is in the OFF position, springs (42) and (43) maintain the spool in the grapple control valve in the NEUTRAL position. The oil flow from the grapple rotate motor is returned to the hydraulic tank.
Crossover Relief Valve (Grapple Rotate)
The crossover relief valves prevent cavitation in the grapple rotate motor. The crossover relief valves also prevent a shock load when the grapple rotate motor stops.
When the spool in the control valve shifts to the NEUTRAL position, oil flow to the grapple rotate motor is blocked. Pressure will increase in line (32) from the grapple rotate motor. This will cause the spool in relief valve (34) to shift against the spring. The passage in the relief valve will open. Oil will flow to line (33) until the pressure in the line (32) is less than the force of the spring in relief valve (34) .