Improvements in Telephonic Receivers.
Year: 1896

page_text: Date of Application, 2nd May, 1896
Complete Specification Left, 2nd Feb., 1897-Accepted, 20th Mar., 1897
PROVISIONAL SPECIFICATION.
Improvements in Telephonic Receivers.
I, ALEXANDER MARR of 9 Repton Street, Manchester, in the County of
Lancaster, Electrical Engineer, do hereby declare the nature of this invention to
be as follows:-
This invention relates to that class of telephonic receivers in which there are
two parallel diaphragms between the poles of a permanent magnet of the horse-
shoe type, a short bar electro-magnet being arranged between the diaphragms and
included in the line or speaking circuit. Such instruments have been known since
May 1887 as Raverot and Combette's receivers but, as hitherto constructed, are
expensive to manufacture as compared with the ordinary receivers, are clumsy to
use, and in general are no more effective than a "Double-pole Bell" instrument.
By these improvements I reduce the cost of manufacture, make the instruments
handy and convenient in use, and increase their efficiency to a considerable
extent.
In a receiver constructed to embody these improvements the horse-shoe
permanent magnet has one of its limbs longer than the other, and the end of
this longer limb is bent or returned so that its pule overhangs or is in line with
the other limb. In the space between the two magnet poles is placed the casing
containing the short electro-magnet and the diaphragms.
The casing preferably consists of three parts, i.e. an inner part which contains
the electro-magnet and supports the two parallel diaphragms upon its opposite
faces, and two outer parts or covers which bold the diaphragms in place.
The inner part has preferably cast or fixed within it three or more radial wings
or projections between which the electro-magnet can be centred and held.
The two outer parts may be provided with pole pieces which come opposite to
the poles of the electro-magnet, and, when the covers are in place, make contact
magnetically with the poles of the permanent magnet. The inner face of each
part is slightly recessed to permit the free action of the contiguous diaphragm,
and this recess is caused to communicate by means of channels or the like with a
suitable external part of the casing which may be provided with an ear-piece.
The casing is fixed between the pole pieces of the permanent magnet so that the
axis of the electro-magnet is in a line joining the poles of the permanent magnet,
and may be adjusted by screws, packing pieces and the like.
I prefer to employ an electro magnet of special construction. In producing it
I take two similar perforated dises or washers of insulating material preferably,
such as vulcanised fibre, and arrange them at the proper distances apart and
co-axially in a divided holder, through which a core hole is formed. I then
insert soft iron core wires which extend through both discs. When a sufficiency
of the wires has been inserted, a tapered pin, preferably non-magnetic, is driven
down through their midst, and tightly binds them against the surrounding discs.
The bobbin thus formed, is removed from the holder, and then consists of two
flanges and a connecting magnetic core which may, if desired be covered with an
insulating material such as paraffined paper. The wire which is thereafter wound

page_text: upon the bobbin thus comes very closely to the core, and a current passing through
it produces a more energetic effect.
The space in the casing around the electro-magnet may be partly filled up
leaving a separate recess at the inner face of each diaphragm, and these recesses
may communicate by suitable channels or openings with the before mentioned
ear-piece or with a tube connected with a second ear-piece.
Improvements in Telephonic Receivers.
I, ALEXANDER MARK, of 9 Repton Street, Manchester, in the County of
Lancaster, Electrical Engineer, 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 that class of telephonic receivers in which there are
two parallel diaphragms between the poles of a permanent magnet of the horse
shoe type, a bar electro-magnet being arranged between the diaphragms and
included in the line or speaking circuit. Such instruments have been known
since May A.D. 1887 as "Raverot and Combette's receivers," but as hitherto
constructed, they are expensive to manufacture as compared with the ordinary
type of receiver: are clumsy to use and in general, are no more effective than a
"Double-pole Bell" instrument. By these improvements I reduce the cost of manu-
facture make the instruments more handy and convenient in use, aud increase
their efficiency to a considerable extent.
I will describe my said improvements with reference to the accompanying
drawings in which :-
Figure 1 represents a side view: Figure 2 a plan: Figure 3, a partial front view
of one of my new receivers.
Figure 4 shews an elevation of one of the casing covers viewed from the inside
of the instrument:
Figure 5, a vertical section of the instrument taken along the line x-y Figure 6,
the permanent maguet being omitted: and
Figure 6, a sectional plan along the line a-y, Figure 5.
In a receiver constructed to embody my improvements, the horse-shoe permanent
magnet A, has one of its limbs a¹ longer than the other a³, and the end of this
longer limb a is bent or returned so that its pole overhangs, or is in line with the
other limb a². In the space between the two magnet poles, there is arranged the
casing C, containing the short electro-magnet E, and the two diaphragms D D'.
The casing preferably consists of three parts, that is to say, an inner tubular part c
which contains the electro-magnet and also supports, upon its opposite faces, the
two diaphragms: and two outer parts or covers cc, which hold the diaphragms in
place.
The inner tubular part c, bas preferably cast or fixed within it, three or more
radial wings or projections R, between which the electro-magnet can be centred
and held. The two outer parts cc, may be provided with pole-pieces P P¹,
arranged opposite to the poles of the electro-magnet, and which, when the covers
are in place, make magnetic contact with the poles of the permanent magnet A.

page_text: The inner faces of c¹ and are respectively recessed as shewn by Figures 4 and 5,-
to permit the free action of the contiguous diaphragms, and these recesses are
caused to communicate by channels or passages such as F F, Figure 4, with the
external part of the casing which is provided with an ear-piece or ear-pieces such
as G, Figures 1, 2 and 3. This part of each cover is also by preference, recesse I
around its centre to a deeper extent, and this recess also communicates with the
ear-piece through a suitable passage such as F'.
The
The casing, with its accessories, is fixed between the pole-pieces of the permanent.
magnet, and may be adjusted by screws, packing pieces and the like.
instrument may be suspended by the screwed eye B, in the magnet A.
I prefer to employ an electro-magnet of special construction, Figure 5. In
producing it, I take two similar perforated dises or washers 1 1', constructed of
any suitable insulating material such as vulcanised fibre, and arrange them in a
longitudinally divided temporary holder which is adapted to receive the core and.
ends and to permit their removal therefrom when the two parts of the holder are
afterwards separated. As this holder is the exact equivalent of a "two-part "
mould for the electro-magnet bobbin, it need not be further described. The discs
having been arranged in the holder, I insert soft iron core wires which extend
through both discs. When sufficient wires have been inserted, a hollow or solid
taper pin J, is driven down through their midst, thus tightly binding them in place.
in the discs. The bobbin thus formed is removed from the temporary holder and
then consists of two flanges and a connecting magnetic core which may, if desired,.
be covered with an insulating material such as paraffined paper before winding..
The wire which is thereafter wound upon the core thus comes very closely to the
core, and a current passing through it produces a more energetic effect. It is an
advantage if one of the flanges 1, is made of a larger diameter than the other so
that it may be secured to the wings by screws S, passing through the edge of the
flange. The terminals T T are connected in the usual manner with the beginning.
and end of the electro-magnet coil, as indicated by Figure 6.
The space in the casing around the electro-magnet, may be partly filled up,.
leaving a separate recess at the inner face of each diaphragm, and these recesses
may communicate by suitable channels or openings with the ear-piece, but I do
not find that this gives sufficient advantage in practice to compensate for the
additional cost, and in some cases, it is positively disadvantageous. If the
space between the diaphragms is thus utilised, it is better to put it in com-
munication with a totally separate ear-piece, which may be used by a second
listener.
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 a telephonic receiver of the type set forth, a permanent magnet having.
one of its limbs longer than the other and returned so that the longer limb over-
hangs the shorter, constructed and arranged substantially as herein before described.
and as illustrated by the accompanying drawings.
2. In a telephonic receiver of the type set forth, arranging the ear piece or
ear pieces in communication with recesses or chambers on the outer faces of the
diaphragms, substantially as herein before described and as illustrated by the
accompanying drawings.
In a telephonic receiver, an electro-magnet consisting of two flanges, a wire core,
and a taper pin driven into the midst of the core, constructed substantially as
herein before described and as illustrated by the accompanying drawings.
A telephonic receiver consisting of a permanent magnet whereof one leg is bent
and overhangs the other: a casing between the permanent magnet poles: a short
electro-magnet in the casing with its core fin line between the magnet poles: two.
diaphragms two recesses or chambers on the outer faces of the diaphragms.

page_text: communicating with the ear-piece or ear-pieces: and pole-pieces between the
permanent and electro-magnet poles: constructed and arranged substantially as
herein before described and as illustrated by the accompanying drawings.
W. E. HEYS & SON,
Agents for the Applicant.