Improvements in or connected with Electro-magnetic Alarm Apparatus.
Year: 1892

page_text: Date of Application, 23rd Aug., 1892
Complete Specification Left, 21st Apr., 1893-Accepted, 27th May, 1893.
PROVISIONAL SPECIFICATION.
Improvements in or connected with Electro-magnetic Alarm
Apparatus.
I, BERTHOLD HOFFMANN, of 70 Alexanderstrasse, Berlin, in the Empire of
Germany, Manufacturer, do hereby declare the nature of this invention to be as
follows:-
The invention relates to improvements in electro-magnetic alarm apparatus by
enclosing the vibrating mechanism in an air and water tight chamber, so as to
protect it from the access thereto of water, dust, vapours, or other injurious
.matters.
The accompanying drawing gives an illustration of such an alarm, the
construction and operation of which are as follows:
The base plate G, Figure 1, is provided with an arm G¹ which carries the
bell W. The base plate G also carries the air and water tight box B, through
the cover of which pass the core ends of a pair of bobbins, their passage being
also made air and water tight. The conducting screws and are insulated and
also rendered air and water tight in the walls of the box B, and they are connected
on the inner side to the bobbins. Through the action of an electric current
passing through the bobbins, the armature A fixed to the flat spring, is attracted,
which causes the hammer or striker connected to it to strike against the bell W.
Another box C is fastened to the base plate G, which box C has in its cover C¹
an opening, which may be of either a circular or elliptical form, as represented at
Figure 1, or of a rectangular form as represented at Figure 2. This opening is
covered with an air and water tight elastic diaphragm M, which, when the apparatus
is at rest, is slightly pressed, inwards by means of an adjusting screw t carried by
the armature A.
In order to protect the diaphragm M, the screw t is made to bear against a
small metallic plate on the diaphragm M; a similar plate on the opposite or
interior side of the diaphragm is provided with an insulated pin o, which, when
the apparatus is at rest, presses the spring upwards.
The spring bears, by means of its contact spring p, against the spring z.
11
The complete contact make and break device, or vibrating mechanism, consisting
of the parts o, u, p and 2, is lodged within the air and water tight box C.
The insulated conducting screws & and s are made air and water tight in the
walls of the box C and are connected with the springs and . An electric
current coming from will pass along v, p, z, s2, 3, through the bobbins and sª
back to the negative pole.
The contact make and break device or vibrating mechanism acts in the following
manner.
The armature A with its adjusting screw is attracted by the bobbins, the
diaphragm M with the pin o, and consequently the spring with the contact
pin p, will follow in the same direction and thereby cause an interruption of the
current. The armature A will then spring back again and the contact between p.
and be renewed, when the armature A will be again attracted and the cycle of
operations repeated again and again.
=
Figure 2 represents the cover C' with a rectangular opening.
The chamber B containing the bobbins can by a coating, say of paraffin, for
instance, be made sufficiently secure.
Dated this 22nd dor of two 1202
DQ77
BERTHOLD HOFFMAN,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in or connected with Electro-magnetic Alarm
Apparatus.
I, BERTHOLD HOFFMANN of 70 Alexanderstrasse, Berlin in the Empire of
Germany, Manufacturer, do hereby declare the nature of my invention and in
what manner the same is to be performed to be particularly described and
ascertained in and by. the following statement :—
The invention relates to improvements in electro magnetic alarm apparatus by
enclosing the vibrating mechanism in an air and water tight chamber so as to
protect it from the access thereto of water, dust, vapours or other injurious
matters.
The drawing accompanying my Provisional Specification gives an illustration of
such an alarm the construction and operation of which are as follows.
The base plate G, Figure 1, is provided with an arm G which carries the
bell W. The base plate G also carries the air and water tight box B through
the cover of which pass the core-ends of a pair of bobbins, their passage being
also made air and water tight. The conducting screws 3 and s are insulated and
also rendered air and water tight in the walls of the box B and they are connected
ou the inner side to the bobbins. Through the action of an electric current
passing through the hobbins, the armature A, fixed to the flat spring f, is attracted
which causes the hammer or striker connected to it to strike against the bell W.
Another box C is fastened to the base plate G, which box C has in its cover O¹
an opening which may be of either a circular or elliptical form as represented at
Figure 1, or of a rectangular form as represented at Figure 2.
·
This opening is covered with an air and water tight elastic diaphragm M which
when the apparatus is at rest is slightly pressed inwards by means of an adjusting
screw carried by the armature A.
In order to protect the diaphragm M the screw t is made to bear against a
small metallic plate on the diaphragm M, a similar plate on the opposite or interior
side of the diaphragm is provided with an insulated pin o, which, when the apparatus
is at rest, presses the spring upwards.
The spring bears, by means of its contact spring p against the spring .
The complete contact make and break device, or vibrating, mechanism, consisting
of the parts o,, p and, is lodged within the air and water tight box C.
The insulated conducting screws s' and s² are made air and water tight in the
walls of the box C and are connected with the springs vand z.
An electric current coming from s¹ will pass along v, p, 2, s, så through the
bobbins and back to the negative pole.
The contact make and break device or vibrating mechanism acts in the following
manner.
The armature A with its adjusting screw is attracted by the bobbins, the
diaphragm M with the pin o and consequently the spring with the contact pin p
will follow in the same direction and thereby cause an interruption of the current.
The armature A will then spring back again and the contact between p and z be
renewed when the armature A will be again attracted and the cycle of operations
repeated again and again.
Figure 2 represents the cover C¹ with a rectangular opening.
The chamber B containing the bobbins can by a coating, say of paraffin for
instance be made sufficiently secure.
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
1: An electro magnetic alarm having the contact making and breaking device
enclosed in an air and water tight chamber which enables the alarm to be used in

page_text: any place without fear of the electric contacts becoming faulty through the
influence of the weather, water, dust or noxious vapours, substantially as herein
shown and described.
2 In electro-magnetic alarm apparatus the peculiar construction of protecting
casing for the contact making and breaking device substantially as herein shown
and described.
Dated April 21st 1893.
B. HOFFMANN,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.