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. 17, 1991
Filed:
Mar. 14, 1990
Domenico S Sarcia, Carlisle, MA (US);
Richard J Birch, Wellesley, MA (US);
Other;
Abstract
A method and apparatus for controlling the reciprocal movement of a free piston, gas-driven displacer in a cooling engine are disclosed. A bi-directional magnetic 'detent' is established for the displacer at both the top dead center and bottom dead center portions of the cooling cycle. Each bi-directional magnetic 'detent' provides a magnetic snubbing force to limit overshooting of the displacer in one direction and a magnetic retention force to hold the displacer from moving in the other direction until a pre-determined pressure differential is established across the displacer's drive piston. The magnetic 'detents' are formed by means of a three pole double magnet with a single core or alternatively, by a two pole single magnet with a double core. The magnetic snubbing and retention forces can be made equal or unequal in magnitude either through the selection of permanent magnet(s) or core configuration(s) or by controlling the field strength of electro-magnets.