The feed roller motors are mounted to the feed roller arms. The feed roller arm cylinders control the movement of the feed roller arms. The computer aided bucking system controls the flow of oil from the main control valve to the feed roller arm cylinder.
Note: The head end of the cylinders is mounted on the feed roller arms near the feed roller motors.
The speed of the feed roller arms is controlled by the oil flow to the feed roller arm cylinders from proportional solenoid valves. The computer aided bucking system controls the oil flow to the feed roller arm cylinders by controlling the movement of the proportional solenoid valves. The computer aided bucking system controls the movement of the proportional solenoid valves with a pulse width modulated signal.
When the feed roller arms are not being used, the proportional solenoid receives no signal from the computer aided bucking system. The valve spool remains in the NEUTRAL position. No oil will flow to the feed roller arm cylinders or from the feed roller arm cylinders.
When the valve spool is in the NEUTRAL position, there is no signal pressure from this section of the main control valve.
The line relief valves protect the feed roller arm cylinders and hydraulic oil lines from damage when the valve spool is in the NEUTRAL position. When an external load acts on a feed roller, the oil pressure in the circuit increases. When the pressure in the circuit exceeds the relief valve pressure setting, the relief valve opens. The oil in the circuit flows to the hydraulic oil tank on the machine through return line.
When the proportional solenoid receives a 13.5 to 18 V signal, the feed roller arms close. The solenoid causes the valve spool to move to the UP position.
Oil under pressure flows through the saw pressure relief valve to the valve spool. The saw pressure relief valve limits the maximum flow of oil to the feed roller arm cylinders. From the valve spool, the oil flows to the rod end of the feed roller arm cylinders. Oil from the head end of the feed roller arm cylinders returns to the main control valve. From the main control valve, the oil returns to the hydraulic oil tank through return line.
The saw pressure relief valve controls the pressure in the rod end of the feed roller arm cylinders. When the pressure in the rod end circuit exceeds the pressure setting of the relief valve, the valve opens. This function allows oil to return to the hydraulic tank. The pressure in the system is reduced.
The valve spool remains in the UP position while the tree is processed. With the valve spool in the UP position, the feed rollers keep pressure on the tree as the diameter of the tree changes.
The clamping pressure of the feed roller arms is controlled by the computer aided bucking system. The computer aided bucking system has a minimum setting and a maximum setting for the clamping pressure. 0 % equals the minimum pressure setting and 100% equals the maximum pressure setting. This setting control movement of the valve spool. The clamping pressure increases as the valve spool travels further in the UP position.
The maximum setting in the computer aided bucking system cannot override the maximum setting of the stroke limiter screws on the main control valve. The stroke limiter screws limit the travel distance of the valve spools. When the clamping pressure is correctly adjusted, the maximum pressure setting of the computer aided bucking system should equal the maximum pressure setting of the stroke limiter screws.
When the proportional solenoid receives a 6 to 10.5 V signal, the feed roller arms open. The solenoid causes the valve spool to move to the DOWN position.
Oil under pressure flows through the flow compensator valve to the valve spool. The flow compensator valve limits the maximum flow of oil to the feed roller arm cylinders. From the valve spool, the oil flows to the head end of the feed roller arm cylinders. Oil from the rod end of the feed roller arm cylinders returns to the main control valve. From the main control valve, the oil returns to the hydraulic oil tank through return line.
Pressurized oil is sent to the rod end of the measuring arm cylinder and the oil pump for the feed roller arms as the arms open. The oil causes the measuring arm to swing away from the log. The oil also causes the pivot pins to be lubricated.
The signal limiter valve controls the pressure in the head end of the feed roller arm cylinders. When the pressure in the head end circuit exceeds the pressure setting of the signal limiter valve, the valve opens. This function allows oil to return to the hydraulic tank. The pressure in the system is reduced. The resolver allows the signal limiter valves to be set at different pressures.