[NM020ABQ], Technical Note, Thomas Alva Edison, November 26th, 1886


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[NM020ABQ], Technical Note, Thomas Alva Edison, November 26th, 1886

Editor's Notes

"Seeley-- The object of this invention is to increase the quantity of iron in the rotating armature of a dynamo machine or rotating converter and at the same time not increase the strength of the Focault currents in the iron-- Heretofore the Iron plates which make up the core have been separated by paper The invention consists in coating each plate by a varnish which will not shrink or crack at a high temperature & which shall be a good insulator of electricity and a good conductor of heat so as to allow the heat to be rapdily conducted to the surface-- After the plates have been stamped out & the burs taken off the are dipped in a hot solution of Asphalt or Asphaltene in Turpentine Benzol or other volitile solvent. The film dries almost instantly is exceedingly tough stands a high temperature & may be safely reduced to 1/3000 of an inch thick The plates are all assembled on the shaft and by means of bolts are gradually brought in intimate contact while the armature is in a hot chamber the heat serving to drive off all traces of the solvent used. The film left will sustain a heat of over 400 degrees Fahr without softening or running out of the plates & is sufficient tough to prevent any burrs from being forced through it, so as to make electrical contact with the adjacent plates-- almost all of the Bitumens or partially decomposed Resins in proper solvents will answer but I prefer ordinary Asphalt boiled to drive off some of its volitile constituents Claim The method of electrically insulating the iron armature plates of Dynamos by coating them with an insulating varnish The use of Asphalt in proper solvent. Heating armatures after assembled slightly etc [prob should not select but should use as annot to show how experiments on lamp filaments influenced this idea]




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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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