Improvements in or in connection with Magneto-electrical Telephones.
Year: 1894

page_text: Date of Application, 31st May, 1894-Accepted, 7th July, 1894
COMPLETE SPECIFICATION.
Improvements in or in connection with Magneto-electrical
Telephones.
I, MAX FRANK of 58' Hessstrasse Munchen, Bavaria, in the Empire of
Germany, Student of Mechanics, 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 present invention relates to telephones and has for its object to arrange
the magnetic circuit therein in such a manner as to prevent as much as possible
loss of energy or magnetic dissipation and to reduce resistance in the magnetic
circuit.
This is designed in order that the, telephone membrane (diaphragm) shall follow
the variations of the magnetic field as accurately and closely as possible so as to
obviate crackling in the telephone and thus combine intensity of sound with great
clearness in transmission.
The invention is illustrated in the accompanying drawings in which :-
Fig. 1 is a longitudinal section, and
Fig. a separate view of the membrane (diaphragm).
Fig. 3 shows the course of the lines of force in the improved instrument and
Figs. 4 and 5 show the course of the same in apparatus as heretofore constructed.
The improved telephone comprises a bar magnet AC screw threaded at its
upper end on which is screwed a piece of iron tube H. The latter may be replaced
by partially turning down the magnet.
The piece of tube H carries the induction coil I through which pass the induction
currents coming from the transmitting station.
B indicates the leading-in wires or conductors.
The bar magnet A C is fixed at its lower end in a wrought iron plate D which
while it is a good fit in the steel tube R is capable of shifting therein. A set
screw E serves to fix the plate D in a definite position pressed firmly against the
tube R.
A finer adjustment of the plate D and through it of the bar magnet may be
effected by means of the screws which works in the plate L (which latter is fixed
by screws L' to the tube R) and presses against the plate D. The diaphragm G
is fixed by screws to the flange F of the tube R and carries at its centre an iron
core K which is fastened by a screw and which projects into a hollow or recess
formed in the bar magnet A C in any suitable manner for instance by boring or by.
screwing a piece of tube thereon.
The core K has for its objects:
:-
1. To prevent as far as possible the magnetic dissipation at the passage of the
lines of force into the air.
2. To impart the desired direction to the lines of force that is to say at right
angles to the diaphragm.
3. To expose the membrane as much as possible to the action of the undulating
magnetic current and consequently to subject it to the undulations of the electric
current and to obviate crackling noise in the telephone and consequently to combine
intensity of sound with clearness in transmission.
On the flange F there is screwed the mouth piece S which is fastened by means
of screws a passing from underneath through the flange and the diaphragm.
In order to fasten the leading-in wires B to the wrought iron plate D but so as
to be insulated from the latter the wires B are led to studs u u which pass through
holes in the plate that have a greater diameter than the studs; the space thus

page_text: formed being filled up with washers of leather or rubber or other suitable
material so as to insulate the wires from the plate. The screws d with the nuts w
serve to fasten the pins u u to which the leading-in main wires or conductors N
are attached.
The holes abc Fig. 2 serve for the reception of the screws a.
Throughout the apparatus the magnetic flow is conveyed by iron parts with the
exception of the air space between K and A. This air space offers the main
resistance to the magnetic flow in the whole magnetic circuit and its variations
produce variations in the magnetic flow.
Figs. 4 and 5 show diagrammatically the magnetic circuit of telephones as usually
employed heretofore. The lines of force effective for the purposes of the apparatus
traverse an air space between 1 and 2, and 3 and 4. The remaining lines which
traverse an air space are lines of dissipation.
Fig. 3 show a diagrammatic view of the course of the lines of force in the
improved arrangement.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
:-
1. In telephones-the combination of an iron core such as K fixed in a suitable
manner to the diaphragm opposite to and acting in conjunction with a corre-
spondingly shaped recess suitably formed in the magnet for the purpose of rendering
the course of the lines of force as favorable as possible arranged and acting
substantially in the manner and for the purposes hereinbefore set forth.
2. The use of iron tubes in magneto-electrical telephones arranged combined
and acting substantially in the manner and for the purposes hereinbefore set
forth.
3. The improved arrangement and construction of magneto-electrical telephones
substantially as and for the purposes hereinbefore described and illustrated in the
drawings hereunto annexed.
Dated this 21st day of May 1804
TONGUE & BIRKBECK,
34, Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicant.