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:
Apr. 28, 1981
Filed:
Aug. 28, 1979
Applicant:
Inventors:
Isao Oda, Nagoya, JP;
Masayuki Kaneno, Tokoname, JP;
Assignee:
NGK Insulators, Ltd., Nagoya, JP;
Primary Examiner:
Int. Cl.
CPC ...
B29D / ;
U.S. Cl.
CPC ...
264 62 ; 264 65 ;
Abstract
A high pressure metal vapor lamp and a transparent polycrystalline alumina tube therefor have been disclosed. The average crystal grain size at ends of the tube is selectively made smaller than that of the middle portion of the tube so that the mechanical strength and the thermal shock resistance of the end portions are made higher than those in the middle portion. Accordingly, the tube hardly causes cracks by a thermal shock when the both ends of the tube are sealed and when the lamp using the tube is switched on and off. Whereas middle portion of the tube has an excellent transparency so that the lamp has a high luminance efficiency.