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:
Oct. 21, 1997
Filed:
Jun. 21, 1996
Kenneth D Price, Long Beach, CA (US);
Hughes Electronics, Los Angeles, CA (US);
Abstract
A three state EM motor/damper used in a ground-based or space-based Stirling refrigerator expander mechanism provides multiple states of operation to obtain fail safe performance during assembly, launch (space based refrigerators), and operation. The device is attached to the expander's reciprocating displacer to enable actuation during assembly, provide maximum damping during launch, and provide attenuated damping to control displacer motion during operation as a refrigerator. The motor/damper is a linearly actuated 'voice coil' device employing a moving coil wound on an electrically conductive bobbin and oscillating within a permanent magnet/back iron field assembly. The electrically conductive bobbin internally generates and dissipates eddy currents when moved through the magnetic field. The bobbin acts as a coil of one turn, shorted to itself. This mechanism transforms kinetic energy to electrical energy, which then dissipates as heat. In this manner, mechanical energy is removed from the system. Operational states are obtained by switching the coil terminals at a multi-pole relay that alternately connects a voltage supply, a dead short, or a short through a ballast resistor. In the event of a switch open failure, fail safe performance during launch and operation is provided by the fixed, intrinsic damping of the coil bobbin.