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. 03, 1994
Filed:
May. 29, 1992
Masatsugu Arai, Ibaraki, JP;
Akiomi Kohno, Ibaraki, JP;
Kazuaki Yokoi, Ibaraki, JP;
Yuuji Yoshitomi, Ibaraki, JP;
Yutaka Sakurai, Katsuta, JP;
Tamio Ishihara, Katsuta, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An electromagnetic flowmeter for measuring the flow rate of a fluid. The flowmeter has a measuring tube made of ceramics and defining a fluid passage therein for the fluid, electrodes having ends exposed to an interior of the measuring tube through holes which are formed in a wall of the measuring tube, a magnetic field generating device disposed around the electrodes, and a case encasing the measuring tube, the electrodes and the magnetic field generating means. A ratio t/R between a wall thickness t and a mean radius R of the measuring tube is determined such that stress generated in the measuring tube by the fluid in the measuring tube does not exceed the rupture stress of the measuring tube. The measuring tube can have flanges on both axial ends thereof, a radial height of the flange from an outer surface of the measuring tube is not greater than the wall thickness of the tube when the tube is made of Al.sub.2 O.sub.3 and not greater than a value three times as large as the tube wall thickness when the tube is made of Si.sub.3 N.sub.4. The electrodes may be made from Ni or an Ni alloy and are secured to the measuring tube by press-fitting into holes formed in the tube wall or by jointing. The electromagnetic flowmeter thus obtained exhibits high strength and reliability and high degree of gas-tightness in the tube portions around the electrodes.