Edison, His Life and Inventions [86]
record required a very sharp cutting-tool, while satisfactory and repeated reproduction suggested the use of a stylus which would result in the minimum wear. After many experiments and the production of a number of types of machines, the present recorders and reproducers were evolved, the former consisting of a very small cylindrical gouging tool having a diameter of about forty thousandths of an inch, and the latter a ball or button-shaped stylus with a diameter of about thirty-five thousandths of an inch. By using an incisor of this sort, the record is formed of a series of connected gouges with rounded sides, varying in depth and width, and with which the reproducer automatically engages and maintains its engagement. Another difficulty encountered in the commercial development of the phonograph was the adjustment of the recording stylus so as to enter the wax-like surface to a very slight depth, and of the reproducer so as to engage exactly the record when formed. The earlier types of machines were provided with separate screws for effecting these adjustments; but considerable skill was required to obtain good results, and great difficulty was experienced in meeting the variations in the wax-like cylinders, due to the warping under atmospheric changes. Consequently, with the early types of commercial phonographs, it was first necessary to shave off the blank accurately before a record was formed thereon, in order that an absolutely true surface might be presented. To overcome these troubles, the very ingenious suggestion was then made and adopted, of connecting the recording and reproducing styluses to their respective diaphragms through the instrumentality of a compensating weight, which acted practically as a fixed support under the very rapid sound vibrations, but which yielded readily to distortions or variations in the wax-like cylinders. By reason of this improvement, it became possible to do away with all adjustments, the mass of the compensating weight causing the recorder to engage the blank automatically to the required depth, and to maintain the reproducing stylus always with the desired pressure on the record when formed. These automatic adjustments were maintained even though the blank or record might be so much out of true as an eighth of an inch, equal to more than two hundred times the maximum depth of the record groove.
Another improvement that followed along the lines adopted by Edison for the commercial development of the phonograph was making the recording and reproducing styluses of sapphire, an extremely hard, non-oxidizable jewel, so that those tiny instruments would always retain their true form and effectively resist wear. Of course, in this work many other things were done that may still be found on the perfected phonograph as it stands to-day, and many other suggestions were made which were contemporaneously adopted, but which were later abandoned. For the curious-minded, reference is made to the records in the Patent Office, which will show that up to 1893 Edison had obtained upward of sixty-five patents in this art, from which his line of thought can be very closely traced. The phonograph of to-day, except for the perfection of its mechanical features, in its beauty of manufacture and design, and in small details, may be considered identical with the machine of 1889, with the exception that with the latter the rotation of the record cylinder was effected by an electric motor.
Its essential use as then contemplated was as a substitute for stenographers, and the most extravagant fancies were indulged in as to utility in that field. To exploit the device commercially, the patents were sold to Philadelphia capitalists, who organized the North American Phonograph Company, through which leases for limited periods were granted to local companies doing business in special territories, gen- erally within the confines of a single State. Under that plan, resembling the methods of 1878, the machines and blank cylinders were manufactured by the Edison Phonograph Works, which still retains its factories
Another improvement that followed along the lines adopted by Edison for the commercial development of the phonograph was making the recording and reproducing styluses of sapphire, an extremely hard, non-oxidizable jewel, so that those tiny instruments would always retain their true form and effectively resist wear. Of course, in this work many other things were done that may still be found on the perfected phonograph as it stands to-day, and many other suggestions were made which were contemporaneously adopted, but which were later abandoned. For the curious-minded, reference is made to the records in the Patent Office, which will show that up to 1893 Edison had obtained upward of sixty-five patents in this art, from which his line of thought can be very closely traced. The phonograph of to-day, except for the perfection of its mechanical features, in its beauty of manufacture and design, and in small details, may be considered identical with the machine of 1889, with the exception that with the latter the rotation of the record cylinder was effected by an electric motor.
Its essential use as then contemplated was as a substitute for stenographers, and the most extravagant fancies were indulged in as to utility in that field. To exploit the device commercially, the patents were sold to Philadelphia capitalists, who organized the North American Phonograph Company, through which leases for limited periods were granted to local companies doing business in special territories, gen- erally within the confines of a single State. Under that plan, resembling the methods of 1878, the machines and blank cylinders were manufactured by the Edison Phonograph Works, which still retains its factories