[PT032ABS1], Technical Note, Thomas Alva Edison, February 3rd, 1889


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[PT032ABS1], Technical Note, Thomas Alva Edison, February 3rd, 1889

Editor's Notes

Patent.## The object of this invention is to produce a strong cylinder or shell for phonograph records over the surface of which a thin coating of material to be recorded upon is placed. which shell shall have great strength and be capable of withstanding rough usage but which shall have a coefficient o expansion in near relation to the material placed on its surface to receive the record.## The material I use for this purpose is the stearates of the metals and their coefficient of expansion is very small compared to waxes parafine and like material. Hence I am enabled to use Hard Rubber or ebonite, sometimes called Vulcanized Rubber a commercial product of variable character consisting of Rubber or allied gums in combination with Sulphur-- The expansion of this material is very great so that it nearly approaches the expansion of hte stearates of the metals, hence the two can be used together. The veneer of Recording material may be put on by dipping hte Ebonite sheet in the molten liquid or it can be placed in a mould & poured around it in a molten state. The surface of the Ebonite should not be polished but made rough to cause adherence;## Afterward the surface is turned true & is ready for the phonograph The great value of the backing shell of Ebonite is that it has great strength with abnormal expansion it being unique in this respect. Hence Musical or other phonographic records or duplicate made on material with Ebonite backing may be handled and shipped without danger of breaking-- as Ebonite varies so much in composition the expansion of the stearate of a metal may be increased or diminished by using a little Oleate of a metal for instance if Mono Stearate of Soda is used the expansion may be increased by adding to it a small quantity of Oleate of Alumina the proportions must be determined experimentally to suit the particular Ebonite used--## Claim a phonogram blank of Hard Rubber Sometimes called Ebonite, Vulcanized rubber faced with phonographic Recording material## 2nd. Ebonite shell coated with a Recording substance of about the same coeff of expansion## 3rd Ebonite faced with a stearate of a metal.## Etc TAE




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