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| Illustration 1 | g01279832 |
Partial hydraulic schematic for swing boom (1) Swing cylinder (2) Control valve for the swing boom (3) Center bypass passage (4) Load check valve (5) Main control valve (6) Swing pump (7) Pilot line (swing right) (8) Pilot line (swing left) (9) Solenoid valve group for boom swing (10) Pilot manifold | |
The swing boom is used to dig in locations that prevent the upper structure from swinging. The main components of the swing boom are listed below.
- Joystick slide control
- Solenoid valve group for boom swing
- Main control valve
- Control valve for the swing boom
- Swing boom cylinder
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| Illustration 2 | g01177991 |
Joystick slide control for swing boom (11) Left joystick (12) Joystick slide control for the boom swing | |
When the joystick slide control is moved from the center position, oil will be supplied to the hydraulic system of the swing boom.
Moving the joystick slide control to the left allows pump oil to flow to the head end of the swing boom cylinder. This causes the swing boom to swing left. Moving the joystick slide control to the right allows pump oil to flow to the rod end of the swing boom cylinder. This causes the swing boom to swing right.
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| Illustration 3 | g01178174 |
(1) Left Joystick (2) Joystick slide control for the boom swing (3) Solenoid for swing boom (4) Pilot in port (5) Port for boom left (6) Solenoid for swing boom (7) Tank port (8) Port for boom right | |
When joystick slide control (2) is depressed to the right, an electrical signal is sent to solenoid (6). The solenoid moves the hydraulic spool. When the spool shifts, the pilot oil is directed to the port for boom right (8) .
The oil leaves through port (8). The oil enters the control valve for the swing boom. The pilot oil then shifts the spool in the control valve for the swing boom.
The shifted spool allows pump oil to flow to the swing boom. The spool also forces the pilot oil at the front of the control valve for the swing boom to flow back to the pilot control valve and to port (5). The pilot oil pushes up on solenoid valve's stem. The stem compresses the spring. When the pressure is high enough, the stem moves up against the force of the spring. The pilot oil flows out of port (7) to the drain. When the pilot oil pressure decreases, the spring moves the stem downward, and passages close.
The same operation happens in reverse order when joystick slide control (2) is depressed to the left. The pilot oil flows from port (5) of the pilot control valve. The spool of the control valve for the swing boom shifts and the valve of the swing boom drains.
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| Illustration 4 | g01178349 |
Front lines of swing boom (1) Line (head end) (2) Main control valve (3) Line (rod end) (4) Cylinder (5) Swing boom | |
Swing Left
Supply oil flows from the main pump to the main control valve. When the activation switch is pressed to the RIGHT, an electrical signal is sent to the pilot solenoid valve. When the pilot solenoid valve shifts, pilot oil is directed to the boom swing control valve. The boom swing control valve shifts to the right. When the boom swing control valve shifts to the right, main pump oil is directed to the rod end of the cylinder through line (3). Return oil flows out of the rod end of the cylinder, through line (1), and back through the main control valve.
Swing Right
Supply oil flows from the main pump to the main control valve. When the activation switch is pressed to the LEFT, an electrical signal is sent to the pilot solenoid valve. When the pilot solenoid valve shifts, pilot oil is directed to the boom swing control valve. The boom swing control valve shifts to the left. When the boom swing control valve shifts to the left, main pump oil is directed to the head end of the cylinder through line (1). Return oil flows out of the head end of the cylinder, through line (3), and back through the main control valve.