The saw motor is a bent axis type motor. Pressurized oil flows from the main control valve to the saw motor through the hydraulic oil lines. The oil then flows through the saw motor. This pressure causes the saw chain to rotate. Part of the oil then flows to the saw cylinder through hydraulic oil line for the cylinder. The remaining oil returns to the main control valve through the return line.
The saw cylinder controls the movement of the saw bar. Pressurized oil flows to the head end of the saw cylinder. The saw cylinder pushes the saw through a stroke. When pressurized oil flows to the head end of the saw cylinder, the saw bar returns to home position. When pressurized oil flows to the rod end of the saw cylinder, the saw bar feeds to the open position. The saw position sensors indicate the location of the saw bar.
When the saw is not operating, the valve spool is in the NEUTRAL position. No oil flows to the saw motor or the saw cylinder.
The saw pressure relief valve protects the saw cylinder and hydraulic oil lines from damage when the valve spool is in the NEUTRAL position. If the saw bar is prevented from retracting, the oil pressure in the circuit for the head end of the saw cylinder 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 the return line.
When the signal voltage is between 13.5 V and 18 V, the solenoid causes the valve spool to move to the UP position. This voltage causes the saw bar to extend.
Pressurized oil flows from the main control valve to the saw motor. The speed of the saw motor increases. The check valve allows oil from the saw motor to recirculate through the saw motor. The check valve protects the saw motor from cavitating when the saw is turned off.
Hydraulic oil flows to the head end of the saw cylinder. One orifice restricts a fixed flow of oil to the saw bar feed. The other orifice restricts an adjustable flow of oil to the saw return. The pressure is adjustable in order to meet the cutting conditions.
The saw bar position sensor sends an electrical signal to the computer aided bucking system as the saw bar swings. The signal indicates the amount of swing of the saw bar. The amount of swing of the saw bar is based on the diameter of the tree. When the position sensor determines that the saw bar has cut through the tree, the saw bar retracts.
When signal voltage is between 6 V and 10.5 V, the solenoid causes the valve spool to move to the DOWN position. This voltage causes the saw bar to retract.
Hydraulic oil flows to the rod end of the saw cylinder. Oil from the head end of the cylinder flows through the main control valve to the hydraulic oil tank on the machine.
When the saw bar is fully retracted and the saw bar home sensor senses the saw bar in the HOME position, the signal voltage to the solenoid is 12 V. A centering spring returns the valve spool to the NEUTRAL position.
The computer aided bucking system will not allow the tree to feed through the harvester head when the saw bar is in the CUT position. The saw bar home sensor sends a signal to the computer aided bucking system when the saw bar is fully retracted. The computer aided bucking system must receive the signal in order to continue feeding.
The saw motor is a bent axis type motor. The motor is also a piston type motor. The motor has a fixed displacement of oil per revolution.
The components of the motor that turn is the shaft, a retainer plate, the pistons, and the barrel. The parts that do not turn are the head, the case, and the port plate.
When the drive shaft turns, the drive shaft turns the saw chain.
Any internal leakage drains back to the hydraulic tank through the drain passage.
The saw bar home sensor signals the computer aided bucking system whether the saw bar is away or in the HOME position. When the pin for the rod end of the saw cylinder is sensed, a signal is sent to the computer aided bucking system. This signal is sent from the saw bar home sensor.
Before the harvester head fells a tree, the saw bar must be in the HOME position. Also, the computer aided bucking system must sense the saw bar in the HOME position.
The saw bar position sensor signals the position of the saw bar to the computer aided bucking system. The saw bar position sensor sends an ON pulse to the computer aided bucking system when the wheel is sensed. The saw bar position sensor sends an OFF pulse to the computer aided bucking system when the cam is not sensed. Each pulse represents a travel distance of the saw bar. The wheel on the saw bar has eight notches. These notches means that 16 pulses can be sent to the computer aided bucking system.
The computer aided bucking system uses the diameter of the tree and the species of tree to determine the travel distance of the saw bar. These parameters prevent the saw bar from jamming and increase the cutting efficiency.