Improvements in Phonographs.
Year: 1899

page_text: Improvements in Phonographs.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23, Southampton Buildings, in the
County of London, Patent Agent, do hereby declare the nature of this inven-
tion (a communication to me from Thomas Alva Edison, residing at Llewellyn
Park, Essex County, State of New Jersey, in the United States of America,
Inventor), and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:
The invention relates to improvements in phonographs and the object of
the invention is to produce a phonograph wherein the reproduction secured
may be improved both in loudness and in quality.
A phonograph record consists, as is well known, of a series of more or less
connected gouges, waves, or depressions all of less depth than width, and pre-
senting in cross section at any point an are depending in extent upon the depth
of cut of the recorder. A record of this character offers a large bearing surface
for the customary spherical reproducing device and causes the latter to track
automatically. It is well known that the imperfections in phonographic repro-
ductions are due in part to the fact that the spherical reproducer is not allowed
to engage all the portions of the record because some of the waves or gouges
thereof are of less length than width. The standard phonographs and allied
talking machines are provided with cylindrical phonograms in which a spiral
record groove will be formed, having a pitch of about four threads per linear
millimeter, and since the width of the space in which the record may be formed
is limited to 25 millimeters, a restriction is imposed upon the depth to which
it may be permissible to form the record in the blank, since if the waves or
depressions are cut to so great a depth that they lap over upon the adjacent
record, echoes will be formed in the reproduction which are objectionable.
With the present improvement the objection first stated is overcome by pro-
viding a reproducer which will automatically track the record groove and engage
all portions thereof even when the waves or depressions are greater in width
than in length, and the formation of echoes is overcome by allowing for the
making of a record of about three threads per millimetre, thus permitting the
use of more sensitive recording diaphragms.
In order that the invention may be better understood attention is directed to
the accompanying drawings forming a part of this specification and in which;
Fig. 1 is a sectional view taken lengthwise of the record groove illustrating
the manner of forming the record by means of a recorder having a circular
cutting edge, the parts being enlarged for the purpose of clearness.
Fig. 2, a plan view on an enlarged scale of a record groove produced by a
recorder having a curved cutting edge.
Fig. 3, a diagram showing a longitudinal section on an enlarged scale of a
portion of a record groove, showing at a, a spherical reproducer, engaging a
record wave of less length than width, and at 6, a reproducer engaging with a
record wave of a greater length than width.

page_text: Fig. 4 a section longitudinally of the record on an enlarged scale, showing
the improved reproducer engaging with the record wave of less length than
width.
Fig. 5 an enlarged section taken longitudinally of the record, showing the
improved reproducing device taken in the opposite direction of Fig. 4, and
illustrating in dotted lines the usual spherical reproducing device, whereby a
comparison of the two producers can be conveniently made.
Fig. 6, a section on the line 6-6 of Fig. 5.
Figs. 7 and 8, longitudinal sections showing modified forms of reproducing
devices, and
Figures 9 and 10 cross sections thereof.
Figure 11, a diagrammatic view showing a circular recording device in cross
section cutting a record in a phonograph blank, having a pitch of four threads
per linear millimeter.
Fig. 12. a corresponding view showing a circular recording device forming a
record having a pitch of three threads per linear millimeter."
In all of the above views corresponding parts are represented by the same
numerals of reference.
1 represents a phonograph blank which is made of the usual soap-like compo-
sition.
2, the recorder having a curved cutting edge.
3, the pivoted lever carrying the said recorder, and 4 the diaphragm connected
to the lever by a link 5, said diaphragm being preferably of as great sensitiveness
as possible.
With such a device the record will partake generally of the appearance shown
in Fig. 2, being composed of a series of more or less connected gouges, waves
or depressions of varying dimensions according to the amplitude or extent of
movement of the recording diaphragm and to the rapidity of vibration thereof.
Owing to the relatively great diameter of the recording edge to the depth of
cut all the depressions of which the record is formed are characterized by a
greater width than depth. Some of these waves, as for instance 5-5, are
greater in length than width, but others such as 6-6, are found in practice to
be of less length than width. The effect of an attempt to reproduce these
records with a spherical reproducer is shown in Fig. 3, wherein two spherical
reproducers 77 are shown. In the case of the waves which are of greater
length than width, the reproducers, as at b, would be free to engage the entire
length of the wave, but when the length of the wave is less than its width, the
spherical reproducers as shown at will not be allowed to enter the record
groove but will be arrested by the crests of the adjacent waves.
The reproducer in the latter case therefore does not accurately track the
record, and the reproducer diaphragm is not vibrated in accordance therewith.
Referring to Fig. 4, 8 represents the improved reproducer in its preferred
form, which may be connected directly to the diaphragm or to a lever 9, which
is connected to the diaphragm 10 by a link. The reproducer is preferably
cylindrical in form with its lower edge resting in the groove, the axis of the
cylinder being preferably inclined at an angle of about forty-five degrees from
the tangent of a cylindrical record or from the face of a flat record.
The reproducer may be inclined in the direction of movement of the blank,
as shown in Fig. 4, or against the movement of the record, as shown in Fig. 5.
The curve of the engaging edge of the reproducer, as shown at Fig. 6, is not
more than the curve of the cutting edge of the recording device 2, and it is
preferably slightly less than that curve, so that the reproducer can always be
free to track accurately in the groove.
The curve presented by the engaging edge of the reproducer longitudinally
of the wave, as shown in Fig. 5, is very much less than is presented by a spherical
reproducer as may be seen from an examination of this figure, hence a depres-
sion or wave which could not possibly be engaged by a spherical reproducer can

page_text: be accurately tracked by the improved reproducer. At the same time the
bearing surface of the reproducer device is almost as great as that which is pre-
sented by a spherical reproducer, so that there will not be any extensive wear.
It will be understood that instead of using a reproducer which is cylindrical in
form, any other form of reproducer may be employed presenting a curved sur-
face to the record, and with its longitudinal dimension contracted sufficiently
to allow it to enter to the full depth in the record groove even when the waves
are very short and deep, as for example the forms of reproducers shown in
Figs. 7 to 10 inclusive, which figures are self-explanatory.
Heretofore it has been the practice to make the recording device 2, with a
diameter ranging from 875 millimetres to 1 millimetre, as indicated at Fig. 11.
The vertical lines 11-11 in this figure illustrate the extent in width of the
available surface of the phonograph blank having a pitch of four threads per
millimetre. The recorder 2 in Fig. 11, it will be observed, has entered the blank
to an extent to occupy the entire distance between two of the lines 11-11, so
that the record which is being formed is of a maximum width, if the production
of echoes is to be avoided, as is desirable. Taking the depth indicated as a
maximum possible at the present time to secure in the art, it is the practice
to so adjust the recording device that it will normally engage or track the record
at about half this extent, so that in making a maximum vibration, over-lapping
will be avoided. It is difficult, however, to realize these ideal conditions, and
at the present time almost all records are partly characterized by the objec-
tionable overlapping referred to.
In order that the extent of the vibrations possible with a recording device
of the diameter indicated, working on a blank having a pitch of four threads
per millimeter, may be properly controlled, the diaphragm by which the
recorders are operated is made preferably relatively insensible, or else care is
taken not to impress upon it sounds of too much volume.
Referring to Fig. 12, the recording device 2, is represented as having a dia-
meter from 625 to 75 millimeters, and the record with which such a recorder
co-operates, is provided with a pitch of not more than three threads per milli-
meter, as indicated between the lines 12-12. Obviously the space allowed for
the formation of a record in this instance is considerably more than at the
present time, and since the diameter of the recorder is less, the entire space
to be occupied by the record can be utilized for the formation of indentations
of considerably greater amplitude than is now possible, and which record will
not be characterized by an objectionable overlapping upon the adjacent grooves.
By thus employing a phonograph having a pitch of not more than three
threads per millimeter, it becomes possible to make the records of much greater
amplitude, whereby loudness of the reproductions will be secured, while by
employing a reproducing device which will accurately track a record even when
it is characterized by the formation in part of waves or depressions having a
greater width than length, the quality of the reproduction will be correspondingly
increased.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, I declare that what
I claim is:-
1. The improved phonograph reproducing device having a form adapted to
enter and accurately track all the waves of which the record may be composed,
even when some of said waves are characterized by a greater width than length.
2. The improved reproducing device for use with a record formed of a series
of more or less connected gouges or waves, with rounded sides and bottom, some
of said waves being characterized, by a greater width than length, said repro-
ducing device having a curved bearing surface which engages the record groove
and being reduced in its longitudinal dimension.
3. The improved reproducing device for use with phonograph records, com-

page_text: posed of a series of more or less connected gouges or waves with rounded sides
and bottom, said reproducing device being cylindrical in form with a rounded
lower edge.
4. Arranging the pitch of a phonograph blank so that the spiral record groove
will be sufficiently curved to allow for the formation without overlapping, of
depressions or waves representing an abnormal amplitude.
5. A phonogram having a record formed thereon with a pitch of not more
than three threads per millimeter.
;
6. A curved recording device having a diameter of not less than 625 milli-
meters co-operating with a phonograph blank, the pitch of which is not more
than three threads per millimeter.
Dated this 17th day of October 1800
HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.