Year: 1886

page_text: I, NORMAN ALEXANDER TANNER of New Haven in the State of Connecticut,
one of the United States of America, Manufacturer, 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 provide an auxiliary mouth-piece for telephones;
and it consists in a novel combination of a sound chamber and funnel for focusing
the sound waves upon the diaphragm of a telephone transmitter and in a spring
clasp for attaching the device to the case of the transmitter.
In the accompanying drawings, Figure 1 is a perspective view of my improved
mouth-piece attached to a telephone transmitter, and Fig. 2 shows a vertical section
centrally through Fig. 1.
Referring to the drawings, a designates a hollow concave shell adapted to fit
over the orifice b in the front of the transmitter case c with its edge received in
the annular groove d surrounding the orifice.
A hollow frustum or conical funnel e is arranged, with its small end fitted into
and projecting within the concave shell; with its axis at right angles to the
transmitter front, and its sides substantially radial to the centre of the telephone
diaphragm f which is therefore nearly at the apex of the cone. The said hollow
frustum or conical funnel can also be made with slightly curved sides as represented
in the drawings lettered e¹, e³. The opening at the inner end of the funnel is left
sufficiently large to permit free egress of the sound waves, and the outer end of
the same is preferably made slightly bell-mouthed, as shown. The concave shell
is formed with a series of perforations or vents, g near its junction with the conical
funnel, and in order to conform to slight variations in the size of the annular
groove the edge of the shell is slitted, as shown. A spring hook or clamp h, is
fastened or soldered at its lower extremity upon the funnel near its smaller end
and extends upward through the concave shell near its edge. The spring is bent
around at its upper part to hook over the edge of the transmitter-cover with its
end inserted downward between the case and cover. The spring clamps the
mouth-piece firmly against the cover and holds it securely in place, but permits it
to be readily removed from the transmitter when desired. If the device is not held
firmly and flatly against the case, a rattling sound is produced while in use, and
the tones of the voice are thereby rendered indistinct.

page_text: In the application of this device the conical funnel directs and converges the
sound-waves upon the centre of the diaphragm and the concave shell serves as a
sound-chamber inclosing the orifice of the funnel. The funnel projects into the
sound chamber and extends nearly to the orifice in the transmitter cover, and the
walls of the sound-chamber prevent the divergence of sound-waves from the
orifice in the funnel. The perforations in the sound-chamber permit a circulation
and equilibrium between the interior of the chamber and the surrounding
atmosphere, thus allowing the escape of vapours from the breath, and preventing
air-compression within the shell while speaking, and thereby producing such an
economy of voice that even a whispered conversation may be carried on. It
is important that the funnel shall project within the shell, as shown, for other-
wise the sound-waves will not be converged upon the diaphragm with sufficient
intensity and effect.
It is evident that the slits in the edge of the concave shell may be omitted when
it is formed to accurately fit the annular groove around the orifice in the trans-
mitter case.
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 :-
1st. An auxiliary mouth-piece for telephones, consisting of a concave shell
adapted to fit over and around the orifice of the transmitter-case, a conical funnel
with or without slightly curved sides fitted into and extending into the shell
pearly to the orifice in the case, and a spring-clasp secured to the shell' and funnel,
and bent at its upper end to book over the transmitter-cover, substantially as and
for the purposes hereinbefore described, set forth, and illustrated in the drawings
annexed.
2nd. In an auxiliary mouth-piece for telephones, the combination of the conical
funnel.e, e, e the concave shell a, having perforations g, and slitted around its
edge, and the spring clasp, h, secured to the shell and funnel, and bent at it's upper
end to hook over the transmitter-cover, substantially as, and for the purposes
herein before described, set forth and illustrated in the drawings annexed.
Dated this twenty first day of September 1886.
J