Year: 1886

page_text: Date of Application, 14th Sept., 1886.
Complete Left, 10th June, 1887.
Complete Accepted, 12th July, 1887.
I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
Engineer, do hereby declare the nature of the said invention to be as follows :-
This invention relates to telephone receivers known as Electro-magnetic receivers.
In order to avoid the sounds which are emitted by a plate of iron when secured
around its edge and submitted to the action of a magnet, I use for an armature a short
thick piece of iron; this mass is secured to a very light, elastic support, in order that
the support may offer very little resistance to the attraction of the magnet. I use for
a tympan or sounding board a thin sheet of wood, cardboard, celluloid, glass, horn,
ivory, bone, cork, mica, vulcanite, brass or equivalent materials. It is found that when
the tympan is enclosed in a case or sounding box, the vibrations of the tympan produced
by the varying attractive force of the magnet, are injuriously affected. It is also found
that the passage of air waves through a tube are more or less injuriously affected by
the vibrations of the sides of the tube, therefore, the tympan is secured at its edge to a
rigid support attached to the magnet and there is no substance whatever between the
vibratory part of the tympan and the ear of the listener.
Sometimes a permanent magnet having a coil surrounding it from end to end, may
be used, and in order to increase the magnetic force of the pole of the magnet in front
of the armature, I place a mass of soft iron against the other pole of the magnet.
The armature is made of soft iron in the form of a short, thick mass of iron of
about the same diameter as the end of the magnet, and its length is about equal to its
diameter; this armature is attached to a thin piece of wood, whale-bone, vulcanite,
brass or equivalent material; the ends of this armature holder lie loosely in cavities
made in a support attached to the case of the magnet. On the opposite side of the
material supporting the armature, is a short spur against which is held a tympan of
wood, or equivalent material, clamped around its edge between two rings attached to

page_text: the case of the magnet; the tympan is protected from coming into contact with the
car, by a ring supported by several projections from the ring. The holder to which the
armature is attached may be a straight piece or may have the form of a cross, having
three or four armis, the ends of the arms of the cross may be curved so that they will
form, as it were, legs to support the armature, their ends to rest loosely in cavities
made in the ring attached to the case of the magnet.
In order to put the tympan out of condition to produce its particular scale of
harmonic sounds, I pierce it with holes, irregularly placed and outside the portion
thereof lying over the core of the magnet, thus leaving it. to reproduce the words of
the speaker without alteration in quality or tone or in any other respect.
The core of the magnet may be permanently magnetized and surrounded by a helix
or coils of the same.
In order to intensify the action of one end of the magnet, a mass of soft iron is
attached to the other pole thereof; opposite the other pole thereof is an armature in
the form of a short, thick piece of iron as aforesaid that is fastened to an elastic
support which is made as before stated, and sustains the armature in proximity to
the pole of the magnet, but the support is free to move as the armature is vibrated
by the vibrations in the magnetism.
At the other side of the armature support there is a projection that rests against the
tympan. This tympan will operate with the other parts heretofore named; when
made of any suitable material, but it is found that a veneer of Bird's Eye maple is the
best because it has no tone of its own when vibrating in consequence of the knotty
nature of the wood.
The edges of the tympan are clamped between rings so as to be properly held, and
one of these rings is formed upon or connected with the handle portion of the
instrument that is composed of a case surrounding the electro magnet. In the
casing below the ring several openings are made so that the air is not confined upon
either side of the tympan. One way of making such openings is to form the upper
part of the case with lugs or arms, the spaces between which form the openings when
the ring is in position.
The ring may be pressed against the side of the head and the ear, but I prefer to
uso projections that extend out from the ring and limit the approach of the instrument
to the ear.
The coil on the electro magnet may extend from end to end thereof..

page_text: I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
M.I.M.E. do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to telephone receivers known as Electro-magnetic receivers.
In order to avoid the sounds which are emitted by a plate of iron when secured
around its edge and submitted to the action of a magnet an armature is used consisting
of a short thick piece of iron; this armature is secured to a very light elastic
support in order that the support may offer very little resistance to the attraction of
the magnet. I use for a tympan or sounding board a thin sheet of wood card board
celluloid glass horn ivory bone cork mica vulcanite brass or equivalent materials. It
is found that when the tympan is enclosed in a case or sounding box the vibrations of
the tympan produced by the varying attractive force of the magnet are injuriously
affected. It is also found that air waves in passing through a tube are more or less
injuriously affected by the vibrations of the sides of the tube therefore the tympan is
secured at its edge to a rigid support attached to the magnet and there is no substance
whatever between the vibratory part of the tympan and the ear of the listener.
Sometimes a permanent magnet having a coil surrounding it from end to end may
be used and in order to increase the magnetic force of the pole of the magnet in front
of the armature a mass of soft iron is placed against the other pole of the magnet.
The armature is made of soft iron in the form of a short thick piece of iron of about
the same diameter as the end of the magnet and its length is about equal to its
diameter; this armature, is attached to a thin piece of wood whale-bone, vulcanite
brass or equivalent material; the ends of this armature holder lie loosely in cavities
made in a support attached to the case of the magnet. On the opposite side of
the material supporting the armature is a short spur against which is held a tympan
of wood or equivalent material clamped around its edge between two rings attached
to the case of the magnet; the tympan is protected from coming into contact with
the ear by a ring supported by several projections from the ring. The holder to
which the armature is attached may be a straight piece or may have the form of a
cross having three or four arms, the ends of the arms of the cross may be curved so
hat they will form as it were legs to support the armature their ends to rest loosely
n cavities made in the ring attached to the case of the magnet.

page_text: In order to put the tympan out of condition to produce its particular scale of
harmonic sounds it is pierced with holes located irregularly outside the portion thereof
lying over the core of the magnet thus leaving it to reproduce the words of the speaker
without alteration in quality or tone or in any other respect.
In the drawing Figure 1 is a longitudinal section of the telephone receiver ;
Figure 2 is a separate elevation and side view of the armature and support; Figure 3
is a detached edge view and side view section of the bird's eye maple tympan with holes
in it; Figure 4 is an end view of the instrument; Figure 5 is an edge view and
Figure 6 is a side view of the armature support in the form of a cross.
A represents the core of the magnet which core may be permanently magnetized
and surrounded by a helix B or coils of the same.
In order to intensify the action of one end of the magnet a mass of soft iron C
is attached to the other pole thereof; opposite the other pole thereof is an armature D
in the form of a short thick piece of iron as aforesaid that is fastened to an elastic
support E which is made as before stated and sustains the armature in proximity to
the pole of the magnet but the support is free to move as the armature is vibrated by
the vibrations in the magnetism.
At the other side of the armature support E there is a projection F that rests against
the tympan G.
This tympan will operate with the other parts heretofore named when made of any
suitable material but it is found that a veneer of bird's eye maple is the best because it
has no tone of its own when vibrating in consequence of the knotty nature of the wood.
This quality may be further increased by perforating it as previously described and
shown in Figures 3 and 4.
The edges of the tympan G are clamped between rings H I so as to be properly
held and one of these rings is formed upon or connected with the handle portion of
the instrument that is composed of a case surrounding the electro magnet. In the
casing below the ring H several openings O are made so that the air is not confined
upon either side of the tympan. One way of making such openings is to form the upper
part of the case with lugs or arms the spaces between which form the openings when
the ring H is in position.
The ring I may be pressed against the side of the head and the ear but it is
preferable to use projections L that extend out from the ring 1 and limit the approach
of the instrument to the ear.
The coil on the electro magnet may extend from end to end thereof.
Having now particularly described and ascertained the nature of the said invention
as communicated to me by my foreign correspondent and in what manner the same is
to be performed I declare that what I claim is:
-
1. The combination in a telephonic receiver with an electro magnet of an armature
consisting of a short thick piece of iron and a free elastic support for the same sub-
stantially as specified.
2. The combination in a telephonic receiver with an electro magnet having a mass
of soft iron attached to one of its poles of an armature in front of the other pole
consisting of a short thick piece of iron and a support to which the same is attached
substantially as specified.
3. The combination of an armature capable of inductive action with a permanent
magnet covered with a coil throughout its entire length having a mass of soft iron in
close contact with one end thereof substantially as specified.
4. The combination in a telephonic receiver of an armature consisting of a short
thick piece of iron and an elastic support to which the armature is attached and a
permanent magnet covered with a coil throughout its entire length and a mass of soft
iron in close contact with one end thereof substantially as set forth.
5. The combination with an electro magnet and armature composed of a short thick
piece of iron of a tympan formed of a thin plate of wood card-board vulcanite mica
brass or equivalent material substantially as set forth.

page_text: 6. In a telephone receiver the combination with a magnet and an armature of an
independent tympan having several holes pierced irregularly therethrough outside of
the portion thereof lying over the core of the magnet as and for the purposes set forth.
7. The combination in a telephone receiver having a magnet an armature and a
tympan of an open support for the armature and tympan so that the air is not confined
at either side of the tympan substantially as specified.
8. The combination with the magnet and armature in a telephonic receiver of a
tympan of bird's eye maple for the purposes set forth
9. The combination with a permanent magnet having coils around the end or ends
of said magnet of an armature consisting of a short thick piece of iron attached to a
free elastic support substantially as specified.