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:
Dec. 29, 1987
Filed:
Sep. 18, 1985
Kenji Takahashi, Abiko, JP;
Heikichi Kuwahara, Ibaraki, JP;
Takehiko Yanagida, Tsuchiura, JP;
Wataru Nakayama, Kashiwa, JP;
Kiyoshi Oizumi, Tsuchiura, JP;
Shigeo Sugimoto, Ibaraki, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi Cable, Ltd., Tokyo, JP;
Abstract
A heat transfer tube has at least a row of projections provided on its inner surface at regular intervals along a spiral curve thereof. The row of projections are formed by plastic deformation of part of the heat transfer tube, which is effected by pressing a rolling disc having projections against the outer surface of the heat transfer tube. The projections have smooth curved surfaces. The height of the projections ranges from 0.45 mm to 0.6 mm, their pitch along the spiral curve ranges from 3.5 mm to 5 mm, and their pitch in the axial direction ranges from 5 mm to 9 mm.