The Kato excavator arm cylinder is controlled by the spool 4 of the control valve (valve block A) and the spool 5 of the control valve (valve block B). When the arm spool is in neutral, the arm cylinder does not supply oil. When the arm control lever moves forward or backward, the arm extends or retracts. The supplementary valve and overload relief valve are installed at the two oil ports of the arm spool.
As shown in Figure 3-4, when operating the arm, the pressure oil of the pump A1 enters the arm cylinder through the arm I valve in the control valve (valve block B).
The pressure oil of the pump A2 merges with the pressure oil in the arm I through the control arm (valve block B) and then flows to the arm cylinder. The arm II is connected to the series oil circuit, but in the control valve a The side arm II is connected in parallel to make it easy to control when working at the same time.
When the arm is moved in all directions, the oil return at the top of the arm cylinder returns to the tank only through the arm I valve. In the fine-tuning control mode, the pilot pressure acting on the control valve (valve block B) is blocked by the solenoid valve block, only The pressure oil of the pump AI is supplied to the bottom end of the arm cylinder to make the operation easy.
(1) Arm recirculation circuit
The arm Ⅰ is equipped with a recirculation device, so that the oil returning from the top of the arm cylinder recirculates into the bottom.
(2) Arm balance valve
The top of the arm cylinder is equipped with a balancing valve. Under load conditions, the extension of the arm cylinder is reduced by limiting oil leakage.
