Hitachi Construction Machinery Co., Ltd.

Hitachi Construction Co., Ltd.

Kazuhiro Sunamura

Toichi Hirata

Osamu Tomikawa

Yusuke Kajita

Ei Takahashi

Shigehiro Yoshinaga

Hidefumi Takegahara

When an arm end exceeds a boundary line K,and enters a slowdown area R,a proportional solenoid pressure reducing valve,is operated to reduce a pilot pressure for slowing down a first boom cylinder,A, thereby slowing down an arm end speed. When the arm end exceeds a boundary line K,and enters a restoration area R,a restoration gain is calculated in control gain block,depending on an intrusion amount by which the arm end enters the restoration area, while a feedback gain is calculated depending on an arm end speed at that time on the basis of functions,and,In accordance with these gains, a second boom,is automatically dumped depending on the intrusion amount of the arm end into the restoration area and the arm end speed at that time so that the arm end is moved for return to the slowdown area. As a result, such work as requiring a work front to be moved toward the operator is continuously smoothly performed and working efficiency is improved.

Interference prevention system for two-piece boom type hydraulic excavator

To provide a burglarproof device for a hydraulic machine which has a high degree of security against burglary, ensures high safety, and can be simply installed in a location where the device is hard to find for burglars, a solenoid valve 23 of a burglarproof device 20 is installed in a pilot primary pressure line 3 between a pilot hydraulic pump 1 and a pilot valve device 4. Unless ten numeral keys 21a of a key input device 21 are depressed in the order of the password, an unlocking electronic circuit 22K does not generate an unlock signal and the solenoid valve 23 keeps the pilot primary pressure line 3 cut off. Therefore, a pilot primary pressure from the pilot hydraulic pump 1 is shut off and, even with a manual lever 4c of the pilot valve device 4 operated, no pilot secondary pressure is produced and a main control valve 6 is kept standstill. As a result, a hydraulic cylinder 8 is not operated and the hydraulic machine is unable to move.

Burglarproof device for hydraulic machine

Drive control system for hydraulic machine

A working machine such as a hydraulic excavator is provided with a working apparatus including a boom pivotally mounted on the body of the working apparatus and a boom-cylinder hydraulic system for the working apparatus. The hydraulic system includes an actuator for moving the boom up and down and a directional selecting valve. The directional selecting valve is arranged to effect selective switching of the feed of a pressurized working fluid to and the discharge of the working fluid from with respect to the rod-side and the bottom-side hydraulic chamber. The hydraulic system further includes a device for relieving the pressure of the bottom-side hydraulic chamber of the actuator. This relieving device is connected to the bottom-side hydraulic chamber of the actuator via a hydraulic circuit. When the pressure in the bottom-side hydraulic chamber changes from rise to fall, the pressure is released to a low-pressure side of the hydraulic circuit, thereby suppressing oscillation of the boom.

Anti-vibration apparatus in a hydraulic system for boom cylinder of

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Tsuchiura, Japan

Kazuhiro Sunamura