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. 17, 1988
Filed:
Oct. 30, 1984
Philip S Carter, Palo Alto, CA (US);
Metcal, Inc., Menlo Park, CA (US);
Abstract
The impedance of an autoregulating heater is greatly increased by employing in one embodiment a return conductor in the form of a helix surrounded by and insulated from a magnetic conductor; the two conductors connected in series or as a transformer across an a.c. source whereby the current in the magnetic material is forced to follow a helical path. In a preferred embodiment, a multilayered coil is wrapped about and insulated from a magnetic sleeve disposed about a copper rod; the sleeve and rod forming the secondary of a transformer. The helical path of the current in the secondary plus the impedance transformation effect of the transformer greatly enhances the impedance of the load as presented to a current source. The winding is enclosed within another magnetic sleeve which provides another magnetic shield about the heater and if connected at one end to the inner magnetic layer increases the width to thickness ratio for purposes to be described.