IMPROVEMENTS IN ELECTRO TELEPHONIC INSTRUMENTS
Year: 1885

page_text: I SILVANUS PHILLIPS THOMPSON of University College Bristol Doctor of Science
and Professor of Experimental Physics do hereby declare the nature of said
Invention for "IMPROVEMENTS IN ELECTRO TELEPHONIC INSTRUMENTS" to be as
follows:-
The object of my Invention is to construct telephonic instruments very cheaply
and of great power and efficiency especially when used as Receivers although they
may be used as Transmitters if desired. According to my Invention I dispense
with the magnetic or mechanical restraint which has hitherto been put upon the
central portion of the diaphragms of these instruments and I cause the variations
in the current due to the sound waves to act upon moveable pieces forming part
of a circuit independently magnetized and attached to an elastic but stiff body or
spring of a non-magnetic material and carried in the box of the instrument by its
sides or ends so that its mid portion is not under either mechanical or magnetic
restraint The coil or coils of the instrument is or are situated in proximity to the
aforesaid moveable pieces which preferably take the form of two bent arms or
levers their outer ends being attached towards the opposite sides or ends of the
aforesaid elastic and stiff body or spring and their inner ends having a space
between them forming a slight break in the magnetic circuit the coil or coils
preferably surrounding these ends. When an instrument thus constructed is in
use as a Receiver the variations in the current due to sound waves and passing
in the coil or coils cause the moveable pieces of the magnetic circuit to act upon
the opposite outward parts of the elastic and stiff body or spring to which they
are attached whereby the central portion is vibrated or moved in such a manner as
to give good and clear articulation and great power in the instrument.
11002
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.,
Agent for the said Silvanus Phillips Thompson.

page_text: I SILVANUS PHILLIPS THOMPSON of University College Bristol Doctor of Science
and Professor of Experimental Physics 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:
The object of my invention is to construct telephonic instruments very cheaply
and of great power, and efficiency especially when used as receivers although they
may be used as transmitters if desired. According to my invention I am enabled
to dispense with the magnetic or mechanical restraint which has hitherto been put
upon the central portion of the diaphragms of these instruments and I cause the
variations in the current due to the sound waves to act upon moveable pieces
forming part of a circuit independently magnetised and attached to an elastic but
stiff body or spring of a non-magnetic material and carried in the box of the
instrument by its sides or ends so that its mid portion is not under either
mechanical or magnetic constraint. The coil or coils of the instrument is or are
situated in proximity to the aforesaid moveable pieces which preferably take
the form of two bent arms or levers, their outer ends being attached towards
the opposite sides or ends of the aforesaid elastic and stiff body or spring and
their inner ends having a space between them forming a slight break in the
magnetic circuit, the coil or coils preferably surrounding these ends which are in
proximity to one another. When an instrument thus constructed is in use as a
Receiver the variations in the current due to the action of the sound waves on
a suitable transmitting apparatus passing in the coil or coils cause the moveable
pieces of the magnetic circuit to move toward and from one another and these in
turn act upon the opposite outward parts of the elastic and stiff body or spring to
which they are attached whereby the central portion is vibrated or moved in such
a manner as to give good, clear and powerful articulation in the instrument.
In order that my Invention may be thoroughly understood I will now describe
manners in which it may be carried into practical effect reference being had to the
accompanying Drawings.
Figure 1 is a section of an instrument constructed according to my Invention.
Figures 2, 3 and 4 are similar views of modified forms, Figure 5 being a perspective
view of the arrangement shewn in Figure 4 but with the cover removed.
In the several Figures the parts are essentially the same and they are marked
with the same letters of reference A is the box or case of the instrument in which
is held the elastic or stiff body or spring B which may be of mica, ebonite, wood,
brass, or other non magnetic and elastic material. At or towards the sides or
edges of this spring piece B pieces C are attached, the said pieces forming part of
a magnetic circuit by reason of their being in proximity to the magnetized Bar D,
the said pieces C being preferably attached to the spring B, so that they can move
independently of the main body of the magnet D, to which also the spring B may
be attached as shewn. Around but preferably not touching the approximated ends
of the pieces C is fixed the coil E in connection with the external wires. The only
difference between the arrangements Figures 1 and 2 is that in Figure 2 the axis
I of the coil and the direction of the ends of the moveable pieces Care at right
angles to the position of those parts in the arrangements Figure 1. In figure 3
the moveable pieces are constituted by thin strips or additional pieces C³ fastened
by screws to the parts C, attached to the spring B instead of being formed by
continuations of the same piece as in figures 1 and 2. In figures 4 and 5 the main

page_text: body of the magnet D is arranged as a ring and it may be in halves separated by
an insulating space or substance the moveable pieces C being affixed to the spring
in proximity to the adjacent onds of like polarity as shewn clearly in Figure 5.
In all cases it will be seen that there is no mechanical or magnetic constraint
upon the central portion of the spring B and the said portion is therefore free to
act in the most beneficial manner in receiving or transmitting vibrations.
I do not limit myself to the precise mechanical arrangements shewn in the
examples given in the drawings as it is evident that they may be varied without
departing from the essential feature of my Invention. For example the magnetio
circuit pieces or any of them may be magnetized. by a coil or coils constituting
them an electro magnet instead of their being permanently magnetized as herein-
before described.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that
what I claim is
First. In electro telephonic receiving or transmitting instruments a non magnetic
elastic piece or spring (for receiving or transmitting vibrations) which is not
mechanically or magnetically constrained at its mid portion or region, but which
is attached at or towards its sides or edges to moveable magnetic attachments
or pieces forming portions of a magnetic circuit substantially as hereinbefore
described.
Second. In electro telephonic receiving or transmitting instruments the com-
bination of an unconstrained non-magnetic elastic piece or spring (for receiving
or transmitting vibrations,)-moveable magnetic attachments or pieces forming
portions of a magnetic circuit, and a surrounding coil or coils of wire, substan-
tially as herein before described and illustrated under several modifications in the
accompanying drawings.
Third. An electro telephonic instrument, capable of being used either as trans-
mitter or as receiver, in which there is a magnetic circuit having a gap or space
between portions of it so arranged that they can approach or recede from one
another, and in which there is a coil (or coils) so placed or disposed with respect
to the said gap or joint or the said magnetic circuit that when electric current
traverses the coil (or coils) it will vary the magnetic attraction between the
portions of the magnetic circuit and thereby cause mechanical vibrations to be
imparted to a diaphram or to a lamina or other body which is not necessarily
itself part of the magnetic circuit substantially as herein before described.
Fourth. In an electro telephonic instrument an elastic lamina or other flexible
body so arranged that its central part is under no magnetic or mechanical constraint
save such as is imparted laterally from its extremities or edges substantially as
described.
Fifth. In electro telephonic receiving or transmitting instruments of the kind
claimed by the preceding claiming clauses the arrangement of the main body or
core of the magnet as a ring or part or parts of a ring, situated in the upper
portion of the case, substantially as illustrated by figures 4 and 5 of the accom-
panying drawings.
Sixth. The arrangements and combinations of parts constituting the several
electro telephonic instruments herein before described and illustrated respectively
in Figure 1, Figure 2, Figure 3, and Figures 4 and 5 of the accompanying drawings.
Dated this 11th day of January 1886.