VIII
THE EDISON PHONOGRAPH
Edison, His Life and Inventions, vol. 2 | ||
8.
VIII
THE EDISON PHONOGRAPH
THE first patent that was ever granted on a device for permanently recording the human voice and other sounds, and for reproducing the same audibly at any future time, was United States Patent No. 200,251, issued to Thomas A. Edison on February 19, 1878, the application having been filed December 24, 1877. It is worthy of note that no references whatever were cited against the application while under examination in the Patent Office. This invention therefore, marked the very beginning of an entirely new art, which, with the new industries attendant upon its development, has since grown to occupy a position of worldwide reputation.
That the invention was of a truly fundamental character is also evident from the fact that although all "talking-machines'' of to-day differ very widely in refinement from the first crude but successful phonograph of Edison, their performance is absolutely dependent upon the employment of the principles stated by him in his Patent No. 200,251. Quoting from the specification attached to this patent, we find that Edison said:
"The invention consists in arranging a plate, diaphragm or other flexible body capable of being vibrated by the human voice or other sounds, in conjunction with a material capable of registering the movements of such vibrating body by embossing or indenting or altering such material, in such a manner that such register marks will be sufficient to cause a second vibrating plate or body to be set in motion by them, and thus reproduce the motions of the first vibrating body.''
It will be at once obvious that these words describe perfectly the basic principle of every modern phonograph or
Edison's first model of the phonograph is shown in the following illustration.
It consisted of a metallic cylinder having a helical indenting
groove cut upon it from end to end. This cylinder was
mounted on a shaft supported on two standards. This
shaft at one end was fitted with a handle, by means of which
the cylinder was rotated. There were two diaphragms, one
on each side of the cylinder, one being for recording and the
other for reproducing speech or other sounds. Each diaphragm
had attached to it a needle. By means of the needle
attached to the recording diaphragm, indentations were
made in a sheet of tin-foil stretched over the peripheral surface
FIG. 1
[Description: Drawing of Edison's first model of the phonograph.]
Crude as this first model appears in comparison with machines of later development and refinement, it embodied their fundamental essentials, and was in fact a complete, practical phonograph from the first moment of its operation.
The next step toward the evolution of the improved phonograph
It will be noted that this was merely an elaborated form
of the first model, and embodied several mechanical
modifications, among which was the employment of only one
FIG. 2
[Description: Drawing of tin-foil machine.]
In operating the machine the recording diaphragm was advanced nearly to the cylinder, so that as the diaphragm was vibrated by the voice the needle would prick or indent a wave-like record in the tin-foil that was on the cylinder. The cylinder was constantly turned during the recording, and in turning, was simultaneously moved forward. Thus the record would be formed on the tin-foil in a continuous spiral line. To reproduce this record it was only necessary to again start at the beginning and cause the needle to retrace its path in the spiral line. The needle, in passing rapidly in contact with the recorded waves, was vibrated up and down, causing corresponding vibrations of the diaphragm. In this way sound-waves similar to those caused by the original sounds would be set up in the air, thus reproducing the original speech.
The modern phonograph operates in a precisely similar way, the only difference being in details of refinement. Instead
The cutting-tool and stylus are devices made of sapphire, a gem next in hardness to a diamond, and they have to be cut and formed to an exact nicety by means of diamond dust, most of the work being performed under high-powered microscopes. The minute proportions of these devices will be apparent by a glance at the accompanying illustrations, in which the object on the left represents a common pin, and the objects on the right the cutting-tool and reproducing stylus, all actual sizes.
In the next illustration (Fig. 4) there is
shown in the upper sketch, greatly magnified,
the cutting or recording tool in the
act of forming the record, being vibrated
rapidly by the diaphragm; and in the
lower sketch, similarly enlarged, a representation
of the stylus travelling over the
record thus made, in the act of effecting
a reproduction.
Fig. 3
[Description: Diagram of the minuteness of the cutting tool and stylus used for
phonograph.]
From the late summer of 1878 and to the fall of 1887
Edison was intensely busy on the electric light, electric railway,
and other problems, and virtually gave no attention to
the phonograph. Hence, just
prior to the latter-named period
the instrument was still
in its tin-foil age; but he
then began to devote serious
attention to the development
of an improved type that
should be of greater commercial
importance. The practical
results are too well known
to call for further comment.
That his efforts were not limited
in extent may be inferred
from the fact that since the fall of 1887 to the present
writing he has been granted in the United States one hundred
FIG. 4
[Description: Illustration of the cutting tool used to form a record,
magnified.]
Interesting as the numerous inventions are, it would be a work of supererogation to digest all these patents in the present pages, as they represent not only the inception but also the gradual development and growth of the wax-record type of phonograph from its infancy to the present perfected machine and records now so widely known all over the world. From among these many inventions, however, we will select two or three as examples of ingenuity and importance in their bearing upon present perfection of results.
FIG. 5
[Description: Diagram of phonograph.]
The function of the floating weight is to automatically keep
Some of Edison's most remarkable inventions are revealed in a number of interesting patents relating to the duplication of phonograph records. It would be obviously impossible, from a commercial standpoint, to obtain a musical record from a high-class artist and sell such an original to the public, as its cost might be from one hundred to several thousand dollars. Consequently, it is necessary to provide some way by which duplicates may be made cheaply enough to permit their purchase by the public at a reasonable price.
The making of a perfect original musical or other record is a matter of no small difficulty, as it requires special technical knowledge and skill gathered from many years of actual experience; but in the exact copying, or duplication, of such a record, with its many millions of microscopic waves and sub-waves, the difficulties are enormously increased. The duplicates must be microscopically identical with the original, they must be free from false vibrations or other defects, although both original and duplicates are of such easily defacable material as wax; and the process must be cheap and commercial not a scientific laboratory possibility.
For making duplicates it was obviously necessary to first secure a mold carrying the record in negative or reversed form. From this could be molded, or cast, positive copies which would be identical with the original. While the art of electroplating would naturally suggest itself as the means of making such a mold, an apparently insurmountable obstacle appeared on the very threshold. Wax, being a non-conductor, cannot be electroplated unless a conducting surface be first applied. The coatings ordinarily used in electro-deposition were entirely out of the question on account of coarseness, the deepest waves of the record being less than one-thousandth of an inch in depth, and many of them probably ten to one hundred times as shallow. Edison finally decided to apply a preliminary metallic coating of infinitesimal thinness, and accomplished this object by a remarkable process known as the vacuous deposit. With this he applied
The process consists in placing in a vacuum two leaves, or electrodes, of gold, and between them the original record. A constant discharge of electricity of high tension between the electrodes is effected by means of an induction-coil. The metal is vaporized by this discharge, and is carried by it directly toward and deposited upon the original record, thus forming the minute film of gold above mentioned. The record is constantly rotated until its entire surface is coated. A sectional diagram of the apparatus (Fig. 6.) will aid to a clearer understanding of this ingenious process.
After the gold film is formed in the manner described above, a heavy backing of baser metal is electroplated upon it, thus forming a substantial mold, from which the original record is extracted by breakage or shrinkage.
Duplicate records in any quantity may now be made from this mold by surrounding it with a cold-water jacket and dipping it in a molten wax-like material. This congeals on the record surface just as melted butter would collect on a cold knife, and when the mold is removed the surplus wax falls out, leaving a heavy deposit of the material which forms the duplicate record. Numerous ingenious inventions have been made by Edison providing for a variety of rapid and economical methods of duplication, including methods of shrinking a newly made copy to facilitate its quick removal from the mold; methods of reaming, of forming ribs on the interior, and for many other important and essential details, which limits of space will not permit of elaboration. Those mentioned above are but fair examples of the persistent and effective work he has done to bring the phonograph to its present state of perfection.
In perusing Chapter X of the foregoing narrative, the reader undoubtedly noted Edison's clear apprehension of the practical uses of the phonograph, as evidenced by his prophetic utterances in the article written by him for the North American Review in June, 1878. In view of the crudity of the instrument at that time, it must be acknowledged
FIG. 6
1, base: 2, vacuum chamber or jar; 3, pipe for creating
vacuum, 4, valve; 5, glass tubes which serve as arms for
supporting gold leaves (6); 7, conductors leading from
induction-coil (8), through glass tubes, and connecting with
gold leaves; 9, battery for coil; 10, spindle upon which
record holder (11) revolves; 12, record; 13, Iron or steel
armature carried by 11; 14, exterior magnet attached to
arm (15), and rotated by pulley (18) by means of belt
attached to motor.
[Description: Diagram of producing the process of applying metal to
the surface of a record.]
VIII
THE EDISON PHONOGRAPH
Edison, His Life and Inventions, vol. 2 | ||