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:
Nov. 10, 2020
Filed:
Oct. 12, 2016
Ngk Spark Plug Co., Ltd., Aichi, JP;
Satoru Ochiai, Nagakute, JP;
NGK SPARK PLUG CO., LTD., Nagoya, JP;
Abstract
A multi-diameter tubular body is cold-forged by forming a large-diameter hole portion in a formed body having a preliminary hole through subjection of the preliminary hole to deep hole forming and by punching out the bottom surface of the large-diameter hole portion to thereby form a small-diameter hole portion. Since a punch having a central protrusion on its forward end surface is used, an internal flaw is generated by dead metal in the inner circumferential surface of a depression, formed by the protrusion, in the bottom surface of the large-diameter hole portion. An outside diameter of a protrusion of a deep hole forming punch is rendered smaller than an inside diameter of the small-diameter hole portion to be formed later by punching out the bottom surface of the large-diameter hole portion. As a result, the internal flaw is removed when the small-diameter hole portion is formed.