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:
Sep. 12, 1989
Filed:
Nov. 04, 1988
Kuldip Raj, Merrimack, NH (US);
James Bonvouloir, Nashua, NH (US);
Ronald Moskowitz, Hollis, NH (US);
Frank Bloom, Windham, NH (US);
Ferrofluidics Corporation, Nashua, NH (US);
Abstract
A multi-stage ferrofluid seal incorporates a ferrofluid reservoir for extending seal life. The reservoir is located between seal stages and contains a quantity of ferrofluid sufficient to replace ferrofluid in the seal stages which is lost due to evaporation or contamination. The seal is designed to withstand a pressure drop between a high pressure area and a low pressure area and the location of the reservoir is selected so that the pressure capacity of the seal stages between the low pressure area and the reservoir is sufficient to withstand the entire pressure drop. The pressure capacity of the seal stages between the high pressure area and the reservoir is less than the entire pressure drop. Failure of the seal stages between the reservoir and low pressure area causes failure of the seal stages between the reservoir and the high pressure area. The total failure of all of the seal stages allows fluid to flow through the seal which fluid sweeps ferrofluid from the reservoir into the seal stages between the reservoir and low pressure area. This latter ferrofluid replenishes the ferrofluid in the failed seal stages and restores pressure capacity of the seal. A preferred embodiment is described which utilizes a single pole piece to define the seal stages and the reservoir.