BUCKET AR 5618146 - Caterpillar

Illustration 1 g00764692
Circuit for negative flow control (1) Center bypass passage (2) Center bypass passage (3) Return passage (4) Orifice (5) Relief valve (negative flow control) (6) Orifice (7) Relief valve (negative flow control) (8) Negative control line (9) Negative control line (10) Idler pump (11) Drive pump
Illustration 2 g00764706
(8) Negative control line (9) Negative control lineThe drive pump and the idler pump receive signal oil pressure from the center bypass passages of the main control valve. This signal oil pressure that is created in the center bypass passages of the main control valve is called negative flow control pressure. Negative flow control pressure flows to the regulators at the drive pump and the idler pump in order to control the output flow of the pumps. Negative flow control pressure is created during the following machine operating conditions.
All of the joysticks and travel levers/pedals are in the NEUTRAL position.
Any of the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position in order to perform a fine control operation.
A boom lower operation is performed alone.The right body of the control valve receives supply oil from the drive pump. Negative flow control pressure from the right body of the main control valve flows through negative flow control line (9) to the drive pump. The left body of the control valve receives supply oil from the idler pump. Negative flow control pressure from the left body of the main control valve flows through negative flow control line (8) to the idler pump. The negative flow control operation of the drive pump and the idler pump is identical.
Illustration 3 g00786405
Partial cross section of stick II control valve (relief valve for negative flow control) (2) Center bypass passage (4) Orifice (5) Relief valve (negative flow control) (9) Negative control line (12) Return passage (13) Body (14) Spring (15) Valve (16) PassageNegative flow control valve (5) consists of the following components: valve (15), spring (14) and body (13) When the oil flow in a center bypass passage suddenly changes and the oil pressure in passage (1) reaches the pressure setting of negative flow control valve (5), the negative flow control valve allows a portion of the oil to flow through valve (15) to return passage (12). This provides a cushion effect in order to prevent any pressure spikes to the pump regulator.When all of the control levers are in the NEUTRAL position, all of the oil from the drive pump flows through passage (1) to orifice (6). The oil flows through orifice (6) and through return passage (3) back to the hydraulic tank.Maximum negative flow control pressure (PN) develops in passage (1) and the pressure oil is directed to the drive pump. Now, the pump cylinder rotates to the minimum angle and the drive pump destrokes for minimum flow.
Illustration 4 g00786407
Bucket control valve (fine control operation) (2) Center bypass passage (17) Stem (18) Port (19) Passage (20) Parallel feeder passageWhen the control lever is moved partially for fine control, pilot pressure (P) starts to shift stem