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:
Jul. 20, 1982
Filed:
Nov. 19, 1980
Akira Yamamura, Framingham, MA (US);
Kuldip Raj, Merrimack, NH (US);
Ferrofluidics Corporation, Nashua, NH (US);
Abstract
A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal length at the one end, and which one end of each pole piece extends into a close, noncontacting relationship with the surface of the shaft, to form a small-gap width and a large-gap width between the one end of the pole piece and the surface of the shaft; and a ferrofluid in the small- and large-gap widths to form a ferrofluid O-ring seal at each gap width, whereby, during rotation of the shaft, the ferrofluid at the small-gap width evaporates and forms an air gap, while the ferrofluid at the large-gap width provides extended seal life.