Swing System Operation

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Swing System Operation

When the swing joystick is fully shifted, pilot oil from the swing joystick flows to the swing control valve to shift the control spool. The control valve shifts and blocks the oil in the center passage from flowing to the idler pump. The idler pump fully upstrokes.

Also, when the swing control valve shifts, pilot oil from the pilot manifold is blocked from flowing through the pilot logic network to the tank. The increased pilot pressure closes the implement pressure switch. The Machine ECM senses the switch is closed and energizes the swing brake solenoid.

The swing brake solenoid directs pilot oil to release the swing brake.

The load check valve unseats and supply oil from the pump is directed to the swing motor. The swing relief cushions the start of the swing motor. Return oil from the motor flows past the swing control valve to the tank.

Also, when the swing joystick is fully shifted, the swing pilot oil shifts the swing priority valve up. Oil flowing from the straight travel valve to the stick 1 valve is blocked at the swing priority valve.

In the illustration above, swing is the only circuit in operation.

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The swing priority valve provides a swing priority function over the STICK IN and STICK OUTfunctions when the swing function is activated at the same time as the stick function.

The swing pilot oil pressure from the swing pilot control valve directly corresponds to the amount of movement or position of the swing joystick. The swing pilot oil pressure from the pilot control valve acts on the swing priority valve. The reduced pilot pressure during a partial swing movement will not move the swing priority valve up.

If the stick 1 circuit is being operated at the same time as a partial swing, idler pump oil flows through the swing priority valve and is directed to the stick 1 control valve. The stick control valve directs oil to the stick cylinder.

The stick cylinder speed is determined by how far the stick spool shifts.

The stick 2 control valve also shifts for a full stick out. The stick 2 control valve is not affected by the variable swing priority valve.

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As the swing joystick is moved farther from the NEUTRALposition, the pilot oil pressure increases.

This gradual increase in pilot oil pressure causes the swing priority valve to shift up. Oil from the idler pump parallel passage is blocked at the swing priority valve. The stick 1 valve receives pump supply through only an orifice restriction which causes a lower flow to be sent to the stick functions.

Swing priority is controlled by the position of the swing joystick. Swing priority over the stick is hydraulically activated when the swing joystick reaches a certain position.

For STICKIN, only the stick 1 control valve shifts. Due to the regeneration valve (not shown), the STICK IN speed is not affected unless the stick has reached the vertical position and the stick unloading valve is open. Without swing priority, during a full STICKIN, the stick circuit would receive most if not all of the idler pump flow.

Since swing priority increases the swing acceleration whenever the stick is also used, swing priority is useful for loading operations. Swing priority is also useful for leveling operations and trenching operations when higher swing force is required.