Variable temperature magnetic damper

Abstract

A passive magnetic damper suitable for use as a vibration isolator coupled between two masses, one of which is subject to vibration. The damper includes at least two pairs of rare earth permanent magnets configured to provide a narrow, generally planar gap, and backing plates positioned to complete a magnetic circuit passing through the magnets and the gap. A flat conductor plate is positioned to be freely movable in the gap. Any time-varying force on the conductor plate results in the generation of eddy currents in the plate, and these in turn generate a mechanical force on the plate, which resists the time-varying force and produces a damping effect. With careful selection of materials for the magnets, the backing plates and the conductive plate, the damper is effective over a wide temperature range that includes cryogenic temperatures, and is operable over a wide range of damping levels.

1 . A magnetic damping mechanism for use over a wide temperature range that includes cryogenic temperatures, the damping mechanism comprising: 
 at least two pairs of permanent magnets positioned to define a generally planar gap in which a magnetic field is generated;    first and second backing plates of magnetic material positioned to complete a magnetic circuit through the magnets and the gap; and    a conductor plate of conductive but non-magnetic material positioned to move freely in the gap;    wherein vibratory movement of the conductor plate in the gap, relative to the magnets, generates eddy currents in the conductor plate, which result in generation of a damping force on the conductor plate, such that the damping force opposes and diminishes the vibratory force, whereby the damping mechanism acts as an isolator if coupled between two masses, one of which is subject to vibration;    and wherein the permanent magnets, the backing plates and conductor plate are of materials selected to provide reliable damping operation over a wide range of temperatures.    
     
     
         2 . A magnetic damping mechanism as defined in  claim 1 , and further comprising: 
 a housing of non-magnetic material, supporting the backing plates and the magnets in a unitary structure.    
     
     
         3 . A magnetic damping mechanism as defined in  claim 1 , wherein: 
 the conductor plate is of a material selected from the group consisting of copper, beryllium, and an alloy of copper and beryllium.    
     
     
         4 . A magnetic damping mechanism as defined in  claim 3 , wherein: 
 the alloy of copper and beryllium contains approximately 2% beryllium.    
     
     
         5 . A magnetic damping mechanism as defined in  claim 1 , wherein: 
 the magnets are of rare earth materials selected from the group consisting of neodymium iron boron (NdFeB) and samarium cobalt (SmCo).    
     
     
         6 . A magnetic damping mechanism as defined in  claim 1 , wherein: 
 the backing plates are of a material selected for its high magnetic saturation limit.    
     
     
         7 . A magnetic damping mechanism as defined in  claim 6 , wherein: 
 the backing plates are of a material selected from the group consisting of iron, silicon-iron alloys, and cobalt-iron alloys.    
     
     
         8 . A magnetic damping mechanism for use over a wide temperature range that includes cryogenic temperatures, the damping mechanism comprising: 
 at least two pairs of permanent rare earth magnets positioned to define a generally planar gap in which a magnetic field is generated, the magnet materials being selected from the group consisting of neodymium iron boron (NdFeB) and samarium cobalt (SmCo);    first and second backing plates of magnetic material positioned to complete a magnetic circuit through the magnets and the gap, the backing plate materials being selected from the group consisting of iron, silicon iron alloys, and cobalt-iron alloys; and    a conductor plate of conductive but non-magnetic material positioned to move freely in the gap, the conductor plate material being selected from the group consisting of copper, beryllium, and an alloy of copper and beryllium;    wherein vibratory movement of the conductor plate in the gap, relative to the magnets, generates eddy currents in the conductor plate, which result in generation of a damping force on the conductor plate, such that the damping force opposes and diminishes the vibratory force, whereby the damping mechanism acts as an isolator if coupled between two masses, one of which is subject to vibration.