Year: 1886

page_text: I, HENRY EDMUNDS of 2 Victoria Mansions Victoria Street in the City of
Westminster Electrical Engineer do hereby declare the nature of this Invention
which has been communicated to me from abroad by Hy. S. Thornberry of Boston,
Massachusetts, United States of America 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 as far as the transmitter is concerned to that class of
telephone transmitters using a granular substance as the current varying medium
such as that known as the Hunning's transmitter and the Improvements relate to
the means by which the contact is maintained, between the complimentary fixed
Electrode, and the granular conducting material and to the form and to the
position of the complimentary electrode relative to the flexible Electrode.
There have until the present time been inherent defects contained in the
Hunning's class of transmitters, to remove which many attempts have been made.
All have hitherto failed; for the construction heretofore has been open to this
objection that in producing an active instrument, the efficiency of the transmitter
has been impaired.
One of the most prominent of these defects has been the liability of this.
transmitter to clog when in action and more especially when it is at rest by reason
of the mass of particles becoming homogeneous. This trouble is especially apparent
when the transmitter has been at rest over night. It is then necessary to loosen
the particles by knocking the instrument against the wall or otherwise. The
clogging action even occurs when the instrument is being used, so that it is found
necessary to shake it at intervals during a conversation to restore it to a working
condition.
The Hunning's transmitter is normally held at about forty five degrees from
perpendicular, when the powdered carbon by gravity falls between the diaphragm
and the brass plate forming the complimentary electrode and by each successive

page_text: vibration of the diaphragm becomes more and more homogeneous until the action
of the instrument is impaired; it then becomes necessary to shake it to restore its
function.
An object of this invention is to overcome the defects above named and so
produce a reliable and at the same time a first class talking instrument that
requires no attention on the part of the user to keep it in working order, a result
that has not been hitherto obtained.
To maintain a permanent contact with, and produce a continuous mechanical
disturbance of the particles, thereby maintaining the proper functions of the
transmitter is the object of this part of the present Invention. To secure these
results, the diaphragm is set in on a horizontal plane, a chamber being placed over
the diaphragm, the said Chamber being almost filled with a granular conducting
substance, (I prefer carbon,) and immersed in this granular substance is a compli-
mentary electrode, the face of which is partly spherical in shape or corresponds,
somewhat to a hemisphere and preferably has V shaped grooves cut around its
circumference, thereby exposing a large surface to contact with the granular
inaterial, thus reducing the resistance of the contact. To further increase the
surface contact the containing chamber is encased with a metal ring, the ring
being in metallic contact or connection with the complimentary electrode.
It will be readily seen this form of complimentary electrode allows of the free
movement of the granular material for on every successive upward motion of the
diaphragm the granular material is pushed against the face of the complimentary
electrode, and by reason of the convex shape of the contact moves off at an angle
corresponding to that surface, other particles coming in from the side of the
chamber on every reactionary motion of the flexible plate, to take the place of
those pushed, away. This action is used as a means for maintaining the instru-
ment in a good working condition. Good results are obtained by using three cells
of a Fuller battery or four of a Le Clanche battery in good condition These can
be replaced by a Gravity battery where heavy work is required, care being taken
to reduce the resistance of the Gravity cells. About six volts and four to six ohms
are good-relation between the electro motive force and internal resistance of the cells.
Having described in general terms the construction of the transmitter I will'
more particularly explain the same reference being made to the accompanying
drawings.
the same.
Figure 1 is a section of a transmitter constructed according to this invention in
which A. is the complimentary electrode. A¹ screw post terminal for the same.
A A V shaped grooves. B the containing chamber. B¹ flange on the face of
B B screw threaded portion of the chamber. C annular casing.
C' cap.
02 recess in the same. D flexible diaphragm. E containing case
threaded to receive the chamber B. E¹ mouth piece for the same preferably
of vulcanite E³ (preferably of metal) tube leading to the diaphragm. Ġ granular
material. H. H grooves for sealing the chamber hermetically. S¹ S₁ taper recess
to receive clamping screws. S. S. Numeral 7 indicates an opening in the cap C¹.
Figure 2 is a face view of the complimetary electrode. Figure 2 is a side view
of the same with parts cut away to shew the taper recess S₁ S¹. Figure 3 is an
inside view of the cap C and Figure 3* a sectional view of the same. Figure 4 is
an exterior view of the transmitter looking towards the mouth piece. Figure 5 is
an upper view of chamber B and Figure 6 is a lower face view of the same.
The numerals in Figures 2, 3, 5 and 6 indicate the corresponding parts in
Figure 1 where the same numerals are used as references.
In forming the chamber B it is preferred to extend the face towards the centre
in the form of a flange thus removing the diaphragm a little distance from the
annular ring casing C..
The opening on the face of the chamber it is preferred to have about one and
five sixteenths of an inch in diameter, and the diameter of the chamber proper
about one and seven sixteenths of an inch but of course we are not limited to these
or the following measurements.

page_text: The complimentary electrode at its greatest projection it is preferred to place
one sixteenth of an inch from the flexible electrode, and the depth of the ohamber
it is preferred to have one half an inch from the upper portion of the annular
casing to the diaphragm.
The cap it is preferred to have rest when screwed home on that portion of
the containing case E directly adjacent; forming metallic contact therewith.
The cap C has an opening of preferably about three quarters of an inch in the
centre as shown thus leaving the diaphragm exposed to the direct action of the air
waves.
The complimentary electrode as is seen by the drawings has the form nearly of
two cones, the one superimposed upon the other; the upper one having the slightly
larger diameter.
recessed with two
It will be seen the
The screws S S aro
The upper circumference of the complimentary electrode is
taper holes S¹ S₁ into which two screws are driven as shown.
taper holes are a little above the points of the screws S. S.
driven through the insulating chamber as shown and when driven home, clamp the
complimentary electrode firmly in place. When this has been done the chamber B
is filled by turning it face up and shaking gently until full, and any surplus is
then scraped off with a straight edge, taking out a very little if it does not talk
well. After filling, the platinum diaphragm is placed over the face of the
chamber B. The said diaphragm should not be thicker than five ten thousandths
of an inch. After screwing on the cap C¹ the chamber is screwed into the con-
taining case E until the cap C¹ makes contact with the case E; the case E forming
one terminal and the screw post A¹ the second terminal.
Where frequent handling occurs it is best to have cap C¹ without the recess C³
and in place of the extension thus formed to use a thin metal ring. This prevents
too harsh treatment of the flexible plate, by reason of the friction between it and
the
cap C¹.
It is preferred to cast the case E in one piece threading it as shown to receive
the mouth piece E¹.
The tube Es attracts the particles of moisture in the breadth, preventing them
from reaching the chamber.
The recess or groove H. H. it is preferred to fill with some expansive material
such as beeswax, or paraffine, thus sealing the chamber hermetically.
For purposes of adjustment to varying heights to suit different speakers and yet
retain the transmitter in a horizontal position, I may connect it to the support by
means of a parallel motion. Figure 7 represents this arrangement in side elevation.
The transmitter X is connected to the box Y by which it is supported by means of
rods connected at either end to the transmitter and the box by the centre
pins y. The full lines show one extreme position and the dotted lines the other
extreme position of the transmitter.
As to the receiver the object is to provide one which may be rendered more or
Jess sensitive so that it can be operated by heavier line currents whilst it will be
less affected by induction. For this purpose I provide the instrument with a
commutator or switch which can be adjusted so as to alter the resistance of the
coil. This may be effected by looping the wire of the coil and making a com-
mutator or switch to cut out or couple in multiple or series.
Having now described and particularly ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is-
1st In a telephone transmitter wherein a granular substance is employed as the
current varying medium, the combination of a horizontal flexible diaphragm
forming the primary electrode, a mass of finely divided conducting particles
resting thereon, and a rigidly fixed complimentary electrode immersed in the said
conducting particles substantially as and for the purpose herein before described.

page_text: 2nd In a telephone transmitter wherein a granular substance is employed as
the current varying medium, the combination of a flexible horizontal diaphragm
and a. rigidly fixed complimentary electrode, the mean plane surface of which lies
in a horizontal plane substantially as and for the purpose.herein before described..
3rd In a telephone transmitter wherein a granular substance is employed as the
current varying medium, the combination of a flexible horizontal diaphragm and a
complimentary electrode, the face of which is hemispherical substantially as and for
the purpose herein before described.
4th In a telephone transmitter wherein a granular substance is employed as the
current varying medium, a complimentary electrode having one or more lateral
V shaped grooves (as at A³ A³) around its circumference substantially as, and for
the purpose herein before described.
5th In a telephone transmitter wherein a granular substance is employed as the
current varying medium, a rigidly fixed complimentary electrode immersed in and
maintaining contact with the said granular material substantially as and for the
purpose herein before set forth.
6th In a telephone transmitter wherein a granular substance is employed as the
current varying medium a chamber B and an annular casing of metal C in metallic
contact with and forming a part of the complimentary electrode substantially as
and for the purpose hereinbefore set forth.
7th In a telephone transmitter wherein a granular substance is employed as the
current varying medium a complimentary electrode with recesses S S for the
purpose described. and screw post A¹ forming the terminal to the said electrode all
substantially as and for the purpose herein before set forth.
8th In a telephone transmitter an annular chamber of insulating material
recessed and threaded as shown in combination with the externally threaded
complimentary electrode and the screws S. S, all for the purpose and substantially
as herein before described.
9th In a telephone transmitter a cap with a central opening 7 and annular
recess C on its inner surface and threaded to screw onto the face of the chamber B
substantially as and for the purpose hereinbefore described.
10th In a telephone transmitter a metal case threaded substantially as shown, to
receive the annular chamber B; the said case forming one terminal electrode
substantially as herein before described.
11th In a telephone transmitter the combination of a mouth piece E' and tube E
formed and arranged substantially as and for the purpose hereinbefore described.
12th. In a telephone transmitter the means for sealing the chamber hermetically
substantially as and for the purpose hereinbefore described.
13th In combination with telephone transmitters the rods a jointed or centered
at their ends respectively to the transmitter and its support as hereinbefore
'described and illustrated in Figure 7 of the accompanying drawings.
14th In a telephonic receiver the combination of means whereby the resistance
of the coil can be varied as required substantially as hereinbefore described.
Dated this 00
of T1000'