IMPROVEMENTS IN TELEPHONES
Year: 1879

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVEMENTS IN TELEPHONES." A communication from abroad by Francis
Blake, junior, of Weston, Massachusetts, United States of America.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at the
Office of the Commissioners of Patents on the 20th January 1879.
"
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. IMPROVEMENTS IN TELEPHONES." [A com-
munication from abroad by Francis Blake, junior, of Weston, Massachusetts,
United States of America.]
One part of the said improvements has reference to a method of holding the
diaphragm of a telephone so that it will be free to expand or contract without
altering its form.
Other parts of the said improvements relate to that form of transmitting-tele-
phones in which the undulations or variations in the strength of an electric current
necessary for reproducing sounds in a receiving instrument are produced by varying
the resistance of the circuit through changes of pressure between two electrodes of
the circuit. As heretofore constructed one of the electrodes is held in a fixed
position, while the other, being free to move to some extent, is pressed against it
with greater or less force by the vibrations of the diaphragm with which it is
connected. In using an instrument of this form it has been found necessary to
adjust the initial static pressure between its electrodes with great care and delicacy,
in order to secure such a variation of resistance between them under the vibrations of
the diaphragm as will enable the current to reproduce in a receiving instrument
the sounds which fall upon the transmitting instrument. When such an adjustment
has been secured it is easily disturbed by slight causes, such as a change in the
temperature of the instrument, or a trifling movement of some of its parts in relation
to other parts.
'
By this Invention the proper adjustment is easily secured, and is not liable to be
disturbed in the practical use of the instruments. I support both electrodes in
such a manner that they can move freely with the diaphragm. One of them may

page_text: be attached directly to and be supported by the diaphragm, but I prefer to support
it in contact with the diaphragm, but by an independent support.
The other electrode is so supported as to move freely, but is made so heavy or
is so weighted, that by its inertia it will offer a resistance to the slight and quick
vibrations of the diaphragm, which will give a varying pressure between the elec-
trodes, and a consequent change in the resistanco of the circuit. This second
electrode is so supported that the initial static pressure between the two will not
be sensibly affected by a change of temperature within the ordinary range of tem-
peratures to which such instruments are exposed. It is on the end of a spring
whose other end is connected to a lever by means of which the proper initial pres-
sure between the electrodes and against the diaphragm is obtained.
To secure contact between the electrodes independently of the pressure against
the diaphragm, I support the one next to the diaphragm upon a spring which
exerts its pressure against the opposite electrode.
I provide a box or casing in which the mechanism of the telephone embracing
my improvements is enclosed. This mechanism is for convenienco attached to the
cover or top of the said box.
the cover.
A metal ring or frame is used for holding the mechanism of the telephone to
On the inner surface of the said ring is a narrow ledge or lip on which
the disc or diaphragm is placed. This diaphragm is formed as usual of a thin iron
plate. A lining of paper or other suitable material is placed between it and the
ledge or lip, and it is held in place by two springs attached to the said metal rim
or ring with their free ends pressing upon the back of the diaphragm. Thin pads
of india rubber are placed between the ends of the springs and the diaphragın.
The centre of the ring and diaphragm is opposite an orifice in the cover through
which the sounds enter the instrument. On the other side of the diaphragm and at
its centre is placed one of the electrodes. It is a small metal bar, one end of which
rests against the said diaphragm. The other end is brought nearly to a point and is
in contact with the other electrode. I prefer to support it independently upon a
light spring, which tends to press it away from the diaphragm and towards the
opposite electrode. This method of supporting the electrode ensures its contact
with the other electrode under some circumstances, when otherwise they would be
liable to be separated and the circuit broken.
The other electrode is formed on a weighted spring supported on an adjusting
lever by which the tension of the spring is regulated. This spring must be
stronger than the spring which supports the first named electrode, and from its
greater strength it tends to keep the electrode in contact with the diaphragm. It
carries at its free end a weight, heavy enough to check very greatly the rate of
vibration of the spring. This weight may be of metal which may serve directly
as the electrode, but I have obtained better results by applying to it at the point
of contact with the other electrode a piece of gas-coke or a hard pressed block of
carbon. If the weight is a non conductor there must be a metallic conductor
between the carbon or other electrode used and the spring or some other part of
the circuit. The weight must be proportioned to the stiffness of the spring. The
adjusting lever, to an arm of which one end of the weighted spring is attached, is
connected at one end by a stiff spring to an ear on the aforesaid ring. The other
end rests upon an adjusting screw placed in another ear on the opposite side of the
said ring. The said spring tends to force the lever away from the diaphragm and
against the adjusting screw.
The part of the lever which comes in contact with the screw is inclined to the
axis of the screw. The outer end of the said screw extends into a hole through
the casing, and is fitted to receive a key by which it can be turned to adjust the
lever to a desired position. The changes in the pressure by turning the said screw
will be much less rapid than they would be if the electrode was acted upon directly
by the lover or the adjusting screw. Hence a proper adjustment of the initial
static pressure between the electrodes can be much more easily obtained through
the agency of the said weighted spring than without it.

page_text: The main object of my improvements will be obtained even when the one
electrode is attached directly to the diaphragm, but an additional improvement is
gained by supporting that electrode on the aforesaid light or independent spring
which keeps it in contact with the other electrode.
For convenience in construction when employing the independent spring for the
purpose stated, I attach it to the same arm of the adjusting lever to which the
weighted spring is attached, the two springs being separated by a piece of insu-
lating substance, but the said independent spring might be attached to any con-
venient portion of the instrument if properly insulated.
The wires for connecting this transmitting instrument with the receiving tele-
phone are connected with the primary circuit of an induction coil, in connection
with which are screw-cups leading to the battery and for connecting the line
wires with the secondary circuit of the coil.
The use of the induction coil is not essential, and the wires may go at once to
the receiving instrument.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Robert Lake in the Great Seal Patent Office on the 19th
July 1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN TELEPHONES."
A com-
munication from abroad by Francis Blake, junior, of Weston, Massachusetts,
United States of America.
One part of the said improvements has reference to a method of holding
the diaphragm of a telephone so that it will be free to expand or contract without
altering its form.
Other parts of the said improvements relate to that form of transmitting tele-
phones in which the undulations or variations in the strength of an electric current
necessary for reproducing sounds in a receiving instrument are produced by varying
the resistance of the circuit through changes of pressure between two electrodes of
the circuit. As heretofore constructed one of the electrodes in such instruments
is held in a fixed position, while the other being free to move to some extent is
constantly held in contact with such fixed electrode, and is pressed against it with
greater or less force by the vibrations of the diaphragm with which it is connected.
In using an instrument of this form it has been found necessary to adjust the
initial static pressure between its electrodes with great care and delicacy, in order
to secure such a variation of resistance between them under the vibrations of the
diaphragm as will enable the current to reproduce in a receiving instrument the
sounds which fall upon the transmitting instrument. When such an adjustment
has been secured it is easily disturbed by slight causes, such as a change in the

page_text: temperature of the instrument or a trifling movement of some of its parts in relation
to other parts.
By this Invention the proper adjustment is easily secured, and is not liable to
be disturbed in the practical use of the instruinents. I support both electrodes in
such a manner that they can move freely with the diaphragm. One of them may
be attached directly to and be supported by the diaphragm, although I prefer to
support it in contact with the diaphragm but by an independent support. The
other electrode is so supported as to move freely, but is made so heavy or is so
weighted that by its inertia it will offer a resistance to the slight and quick
vibrations of the diaphragm, which will give a varying pressure between the
electrodes and a consequent change in the resistance of the circuit. This second
electrode is so supported that the initial statio pressure between the two will not
be sensibly affected by a change of temperature within the ordinary range of
temperatures to which such instruments are exposed. It is placed on the end of a
spring whoso other end is connected to a lever, by means of which the proper
initial pressure between the electrodes and against the diaphragm is obtained.
To secure contact between the electrodes, independently of the pressure against
the diaphragm, I support the one next to the diaphragm upon a spring which
exerts its pressure against the opposite electrode.
Figure 1 is a plan of the mechanism attached to the top or cover of a box.
Figure 2 is a section of the said box and mechanism on the line x, x, Figure 1,
and showing one of the screw-cups for making connections with the exterior
circuits.
Figure 3 is a transverse section of the said box and mechanism on the line ¹, x²,
Figures 1 and 2, and showing the screw-cups for making connections with the
exterior circuits.
A represents the box or casing in which the mechanism of the telephone
embracing my improvements is enclosed. This mechanism is for convenience
attached to the cover or top A¹ of the said box.
B represents a metal ring or frame for holding the mechanism of the telephone.
It is screwed to the cover A', as shown, and has two ears B1, B. On the inner
Burface of the ring B is a narrow ledge or lip b, on which the disc or diaphragm C
is placed. This diaphragm is formed as usual of a thin iron plate. A lining of
paper or other suitable material is placed between it and the ledge or lip, and it is
held in place by two springs D, D, attached to the metal rim or ring B, with their
free ends pressing upon the back of the diaphragm near its centre so as to hold it
against the ledge. Thin pads of india-rubber a, a, are placed between the ends of
the springs and the diaphragm. By this method of holding the diaphragm in place
it is less liable to be distorted by a change of temperature than when held wholly
at its circumference. The centre of the ring and diaphragm is opposite the orifice E
in the cover A', through which the sounds enter the instrument. On the other
side of the diaphragm and at its centre is placed one of the electrodes. It is a
small metal bar e, one end of which rests against the said diaphragm. The other
end is brought nearly to a point and is in contact with the other electrode e'. It
is desirable that it should be formed of or plated with some metal like platinum or
nickel which is not easily corroded. It may be attached directly to the diaphragm,
but I prefer to support it independently, as shown, upon a light spring c, which
tends to press it away from the diaphragm and towards the opposite electrode e¹
This method of supporting the electrode e ensures its contact with the other
electrodo under some circumstances when otherwise they would be liable to be
separated and the circuit broken.
The electrode e' is formed on a weighted spring d, supported on an adjusting
lever F by which tho tension of the spring is regulated. This spring must be

page_text: stronger than the spring c which supports the electrodo e, and from its greater
strength it tends to keep the electrode e in contact with the diaphragm. It may
be made of a piece of a common watch spring, and carries at its free end a weight g
heavy enough to check very greatly the rate of vibration of the spring. This
weight may be of metal, which may serve directly as the electrode, but better
results are obtained by applying to it at the point of contact with the other.
electrode a piece of gas-coke, or a hard-pressed block of carbon h, such as is used
in electric lighting. The employment of the coke or carbon does not however
constitute a part of my Invention farther than it contributes a portion of the
weight carried by the spring. If the weight is a non-conductor there must be a
metallic conductor between the carbon or other electrode used and the spring or
some other part of the circuit. The weight must be proportioned to the stiffness of
the spring, a stiff spring requiring a heavier weight than a weaker one.
adjusting lever F, to an arm of which one end of the spring d is attached, is a stiff
bar connected at one end by a stiff spring to the ear B' of the ring B. The other
end rests upon an adjusting screw G, placed in the ear B on the opposite side of
the ring. The spring j tends to force the lever F away from the diaphragm and.
against the adjusting screw Q. The ear B³, supporting the adjusting screw G, is
drilled and slotted as shewn in Figures 1 and 2, to prevent the screw from wearing
loose.
The
The part of the lever F which comes in contact with the screw is inclined to the
axis of the screw, as shown, so that when the screw is forced inward it will press
the lever toward the diaphragm, and when it is withdrawn the lever will by the
tension of the spring ; be forced away from the diaphragm. The outer end of the
screw extends into a hole through the casing, and is fitted to receive a key by
which it can be turned to adjust the lover to a desired position.
The pressure between the two electrodes and against the diaphragm obviously
depends upon the position given to the adjusting lever by the adjusting screw G,
but it is obvious that as this pressure can be increased or diminished only by.
increasing or diminishing the tension of the spring d, the changes in the pressure
by turning the screw will be much less rapid than they would be if the electrode
were acted upon directly by the lever or the adjusting screw.
Hence a proper
adjustment of the initial static pressure between the electrodes can be much more
easily obtained through the agency of the spring d than without it. It will also
be seen that this pressure will not be sensibly offected by any slight change in the
position of the electrodes which might arise from the expansion or contraction of
any part of the apparatus under a change of temperature. On the other hand, it
will be seen that if the diaphragm is thrown into the rapid but slight vibrations
caused by sounds, the spring alone would yield to them so readily as to give but
little change of pressure between the electrodes within the range of the vibrations,
but by reason of the inertia of the weight the tendency of the spring to follow the
vibrations of the diaphragm will be checked, and a greater range of pressures
between the electrodes will be obtained. At the same time it will be readily seen
that the changes of pressure will be very different from what they would be if the
electrode were supported rigidly, and could not yield to the movements of the
diaphragm.
The main object of my improvements will he obtained even when the electrodo e
is attached directly to the diaphragm, but an additional improvement is gained by
supporting that electrode on the aforesaid light or independent spring, which keeps
it in contact with the electrode e', for it not unfrequently happens when the inter-
mediate electrode is attached directly to the diaphragm that a too rapid vibration
of the diaphragm, or some other disturbance in its vibrations, will throw the outer
electrode out of contact with the intermediate electrode, and thus break the circuit,
but in my construction such irregular vibrations of the diaphragm will separate the
diaphragm from the intermediate electrode e rather than separate the two electrodes
from each other, and the circuit will not be broken.
For convenience in construction when employing the independent spring c for

page_text: the purpose stated, I attach it to the same arm of the adjusting lever F, to which
the spring d is attached, the two springs being separated by a piece of insulating
substance r, but the spring c might be attached to any convenient portion of the
instrument if properly insulated.
The wires for connecting this transmitting instrument with the receiving telephone
are marked w and w¹. I have however shown them as connected with the primary
circuit of an induction coil I, in connection with which are the screw-cups 8, 8¹,
leading to the battery, while a³, 83, are screw-cups for connecting the line wires with
the secondary circuit of the coil I.
The use of the induction-coil is not essential, and the wires may go at once to
the receiving instrument. The wire wis connected directly with the spring-a mc
of the electrode e, as shown in Figure 2. The wire w' is connected with one of the
ears of the ring B, as shown in Figure 1, which is in metallic connection with the
electrode e¹, as shewn in Figure 2.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it under-
stood that I claim,―
First. The method herein described for holding the diaphragm of a telephone by
means of springs pressing against one of its surfaces.
Second. A spring forming or carrying one electrode of the circuit of a telephone,
and constantly pressing against the other electrode and diaphragm to maintain the
required initial pressure between the electrodes, and yield to the movements of the
diaphragm, substantially as above described.
Third. The adjusting lever for regulating the tension of the spring which carries
one of the electrodes, and the initial pressure between the two electrodes and against
the diaphragm, substantially as herein described.
Fourth. The combination of the two electrodes by means of springs acting against
each other, substantially as described, to maintain the electrodes in contact when
forced away from the diaphragm.
Fifth. The yielding weight connected with the moveable electrode e¹ to resist the
movement of the diaphragm, and modify by its inertia the variation of pressure
between the two electrodes, substantially as above described.
In witness whereof, I, the said William Robert Lake, havo hereunto set my
hand and seal, this Fifteenth day of July, in the year of our Lord One
thousand eight hundred and seventy-nine.
WM BORT LAKE
WM RORT LAKE
(L.C.)