An Improved Electro-magnetic Alarm or Call.
Year: 1892

page_text: Date of Application, 15th Nov., 1892
Complete Specification Left, 15th Aug., 1893-Accepted, 23rd Sept., 1893
PROVISIONAL SPECIFICATION.
An Improved Electro-magnetic Alarm or Call.
I, PARNELL RABBIDGE, of William Street, Double Bay, Sydney, in the Colony
of New South Wales, Electrician, do hereby declare the nature of this invention
to be as follows :—
This invention deals with that class of electro-magnetic alarms or calls, that are
commonly known as electric trumpets, wherein a diaphragm is caused to rapidly
vibrate, by means of an electro magnet that is provided with means, such as a
contact breaker, whereby the current may be rapidly interrupted.
It is usual in electric trumpets to make the diaphragm itself a contact breaker,
but this invention consists essentially in providing an independent contact breaker,
so as to leave the diaphragm perfectly free. To this end, the pole of the electro-
magnet is elongated, so as to leave room between the diaphragm and the coil of the
magnet for a metallic tongue or spring armature to vibrate transversely beneath
the diaphragm. This metallic tongue or spring armature constitutes the contact
breaker or current interrupter. The circuit is closed through a contact point
against which the spring armature impinges or abuts in the usual manner.
This invention has been specially designed for use with telephones, whereby the
receiver is adapted to act both as a receiver and as a call or alarm.
In the accompanying drawings:
Fig. 1 is a plan view of one form of improved electro magnetic alarm, designed
as a substitute for an electric bell. In this figure part of the diaphragm is broken
to exhibit the interior.
away
Fig. 2 is a vertical section of the same.
Fig. 3 is a modified form of spring armature or contact breaker.
Fig. 4 shews an adaptation of my invention to a telephone receiver, whereby the
diaphragm of the receiver is caused to act as the call or alarm.
Fig. 5 is a vertical section of the same.
A, is a circular box, that is preferably constructed of iron. A diaphragm B is
secured on the top edge of the box A by means of the screw cap b (or in any other
suitable manner) and forms metallic contact with the box. The box A contains
an electro-magnet C C¹, the core of which is secured to the bottom and forms
metallic contact with the box. By this arrangement the diaphragm B constitutes
a pole as well as an armature thus securing increased efficiency. The core C
projects from the bobbin of the solenoid C, thus leaving a space between the
bobbin C and the diaphragm B, sufficient to allow of the free reception of a
transverse spring armature or contact breaker D.
In Figs. 1, 2, 4 & 5, one end of the spring armature D is carried by an insulated
pillar D while the other end abuts or impinges against a contact point d.
When
a current passes through the solenoid C, the spring armature D is attracted towards
the periphery of the core C¹ and circuit is consequently broken at the central
point d, thus producing a rapid vibration of the armature D and corresponding
vibration of the diaphragm B.
In Fig. 3 the spring armature D is secured at each end to, and insulated from
the box A, the contact point d touching the armature at about its centre, the same
results being obtained. It is not necessary that the box A should be of iron, any
other suitable materials may be employed, such as wood, brass, &c. The shape
also may be altered so as to obtain the greater effect of resonance.
A horse shoe
electro magnet may also be employed with advantage instead of the single bar
core C. Figs. 3 & 4 shew a telephone receiver constructed on the same lines as
in Fig. 1. The necessary circuits are switched in and out by means of a gravity

page_text: switch X that closes the different circuits (receiver and alarm) according to the
position in which it is held or retained. In the drawing the alarm circuit is closed.
Any other suitable means to effect the switching in of the different circuits may be
adopted.
The following are the chief points of the invention.
a
1. In electro magnetic alarms or calls in which a sound is produced by
vibrating diaphragm operated by an electro-magnet, a spring armature or contact
breaker and contact point, secured within the case, the armature being actuated by
the lateral attraction of the electro magnetic core as herein specified.
2. The combination of a case, diaphragm, electro magnet, and spring armature
or contact breaker the spring armature being distinct from the diaphragm and
enclosed within the case as and for the purposes herein set forth.
3. An iron case, iron diaphragm, and electro-magnet all in magnetic contact,
whereby the diaphragm constitutes one pole of the magnet as well as an armature
in combination with a spring armature contact breaker that is enclosed within the
case as specified.
4. The combination of a telephone receiver, with a spring armature contact
-breaker that is contained within the receiver casing, whereby an interrupted current
is obtained and the diaphragm of the receiver is caused to act as an aların as
herein set forth.
Dated this 10th day of October 1892.
PARNELL RABBIDGE.
COMPLETE SPECIFICATION.
An Improved Electro-magnetic Alarm or Call.
I PARNELL RABBIDGE of William Street, Double Bay, Sydney in the Colony
of New South Wales, Electrician, 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 deals with that class of electro magnetic alarms or calls that are
commonly known as electric trumpets, wherein a diaphragm is caused to rapidly
vibrate by means of an electro-magnet that is provided with means, such as a
contact breaker, whereby the current may be rapidly interrupted.
It is usual, in electric trumpets, to make the diaphragm itself a contact breaker,
but this invention consists essentially in providing an independent contact breaker,
so as to leave the diaphragm perfectly free. To this end, the pole of the electro-
magnet is elongated so as to leave room between the diaphragm and the coil of the
magnet, for a metallic tongue or spring armature to vibrate transversely beneath
the diaphragm. This metallic tongue or spring armature constitutes the contact
breaker or current interrupter. The circuit is closed through a contact point,
against which the spring arinature impinges or abuts in the usual manner.
In the drawings left with my Provisional Specification,
Fig. 1 is a plan view of one form of improved electro magnetic alarm designed
as a substitute for an electric bell. In this figure, part of the diaphragm is broken
away, to exhibit the interior.
Fig. 2 is a vertical section of the same;
Fig. 3 is a modified form of spring armature or contact breaker.
Fig. 4 shows an adaptation of my invention to a telephone receiver, whereby the
diaphragm of the receiver is caused to act also as the call or alarm.
Fig. 5 is a vertical section of the same.
A is a circular box that is preferably constructed of iron. A diaphragm B is
secured on the top edge of the box A by means of the screw-cap b (or in any other
suitable manner), and forms metallic contact with the box. The box A contains
an electro magnet CC, the core of which is secured to the bottom, and forms
metallic contact with the box. By this arrangement, the diaphragm B constitutes

page_text: a pole as well as an armature, thus securing increased efficiency. The core C
projects from the bobbin of the solenoid C, thus leaving a space between the
bobbin C and the diaphragm B, sufficient to allow of the free reception of a
transverse spring armature or contact breaker D.
In Figs. 1, 2, 4, and 5, one end of the spring armature D is carried by an insulated
pillar D, while the other end abuts or impinges against a contact point d. When
a current passes through the solenoid C, the spring armature D is attracted
towards the periphery of the core C¹, and circuit is consequently broken at the
central point d, thus producing a rapid vibration of the armature D, and corre-
sponding vibration of the diaphragm B.
In Fig. 3, the spring armature D is secured, at each end, to, and insulated from,
the box A, the contact point d touching the armature at about its centre, the same
results being obtained. It is not necessary that the box A should be of iron; any
suitable materials may be employed, such as wood, brass, &c. The shape, also,
may be altered, so as to obtained greater effect of resonance. A horse-shoe electro-
magnet may also be employed with advantage, instead of the single bar core C¹.
Figs. 4 and 5 show a telephone receiver constructed on the same lines as in
Fig. 1. The necessary circuits are switched in and out by means of a gravity
switch X that closes the different circuits (receiver and alarm), according to the
position in which it is held or retained. In the drawing, the alarm circuit is
closed. Any other suitable means to effect the switching in of the different circuits
may be adopted.
In some cases, the vibrating armature may be shortened, the contact point d
being shifted inwards to permit of the same.
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 electro-maguetic alarms or calls in which a sound is produced by a
vibrating diaphragm operated by an electro-magnet, a light spring armature or
contact breaker and contact point secured within the case between the magnet and
the diaphragm, the spring arinature being actuated by the lateral attraction of the
electro-magnetic core, as herein specified.
2. An iron case, iron diaphragm, and electro-magnet, all in magnetic contact,
whereby the diaphragm constitutes one pole of the magnet, as well as an armature,
in combination with a spring armature contact breaker that is enclosed within the
case, as specified.
3. The combination of a telephone receiver with a light spring armature contact
breaker that is contained within the receiver casing, and between the magnet and
the diaphragm of the receiver, as and for the purpose herein set forth.
4. The construction and arrangement of apparatus substantially as herein shown
and described.
Dated this 15th day of Anouat 1893
NEWTON & SON,
Agents for the Applicant.