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:
Jan. 27, 2004
Filed:
Jan. 17, 2002
Mitsuhisa Tougasaki, Ibaraki-ken, JP;
Yoshizumi Nishimura, Tsuchiura, JP;
Yusaku Nozawa, Ibaraki-ken, JP;
Kinya Takahashi, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A spool provided with a flange is inserted in a spool bore , and a pressing force of a spring is always applied through the flange to the spool at its one end in a second pressure chamber . A fluid groove is formed in an inner peripheral surface of the spool bore at a position near an abutment surface . A hydraulic fluid under the same pressure P as that in the second pressure chamber is introduced to the fluid groove through a fluid passage formed in a valve body . When the flange and the abutment surface are in contact with each other, the hydraulic fluid is allowed to enter the interface between them through the fluid groove . A rise of the cracking pressure, which occurs upon the flange coming into tightly close contact with the abutment surface, can be prevented without reducing the strength of the flange , and stable opening/closing characteristics of the spool can be achieved.