Hydraulic system for a multi-process machine and a multi-process machine using it

A hydraulic system for a multi-process machine, the multi-process machine including a base machine, a boom assembly comprising at least one boom and a felling head for felling and further processing trees, the felling head being arranged to be suspended on said boom via a joint, said felling head including:

• a rotator for rotating the felling head,
• a suspension device, its actuator unit and a frame for the felling head, including log feeding equipment complete with hydraulic motors, and wherein the hydraulic system comprises:
• a hydraulic pump on the base machine,
• a dedicated valve assembly for supplying medium from the hydraulic pump to the felling head,
• a hydraulic pressure line and a return line led from the dedicated valve assembly of the base machine to the felling head, comprising separate valve channels on the pressure P side and the tank T side,
• at least one said hydraulic motor for operating the feed device,
• at least two pressure accumulators placed in the system for increasing the instantaneous output with said motor and each arranged with a different pre-charge pressure,
• a dedicated supply valve, a supply line (A/B) and a return line (B/A) arranged in the felling head, the dedicated supply valve connected to said hydraulic pressure line and the return line and actuating the supply line (A/B) for feeding medium to said hydraulic motor operating the feed device and the return line (B/A) for returning medium from the hydraulic motor operating the feed device, and
• the hydraulic system includes:
• a logic control for implementing pulse-operated use of the pressure accumulators mainly for sawing and log feeding including their auxiliary steps, wherein the pressure accumulators are used only for improving log feeding, and the hydraulic system providing a direct feeding line from the accumulators to the said hydraulic motor operating the feed device,
• a first auxiliary supply line from the pump to the pressure accumulators, a first end connected between the pump and the dedicated valve assembly, and being a straight line comprising only a first control valve, and
• a second auxiliary supply line as said direct feeding line led directly from the pressure accumulators to the forward side of the hydraulic motor operating the feed device and having a second control valve for supplying the pressure of the accumulator directly to the motor.