The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 27, 1997
Filed:
May. 22, 1996
Kazuhiro Sunamura, Tsuchiura, JP;
Osamu Tomikawa, Ibaraki-ken, JP;
Shigehiro Yoshinaga, Yokohama, JP;
Toichi Hirata, Ushiku, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
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.