Improvements in Alarm Devices.
Year: 1899

page_text: Date of Application, 6th May, 1899-Accepted, 1st July, 1899
COMPLETE SPECIFICATION.
Improvements in Alarm Devices.
I, LUDWIG SCHIFF, of 1, Bingerstrasse, Wilmersdorf, near Berlin, Empire of
Germany, Engineer, do hereby declare the nature of my said invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
The present invention relates to alarms and consists of novel means for pro-
ducing the alarm. According to the present improvement, the sound is produced
by means of a disc of sheet metal, stretched over a circular shoulder, formed on
a base plate, and retained in the bulged or stretched position by means of an
overlapping flange. A spring is soldered or otherwise fixed to the outer surface of
the said metal disc and the sound is produced by causing a rotary tooth or star
wheel to vibrate the end of the said spring. The tone of an alarm of the class
described may be varied by varying the tension of the disc.
In order to render the present specification more easily intelligible reference
is had to the accompanying drawing in which similar letters of reference denote
similar parts throughout the several views:-
Fig. 1 is a vertical section through the disc and base plate before the former
is stretched over the circular shoulder of the latter, Fig. 2 is a similar section
showing the metal disc properly stretched or bulged and secured in position by
means of the circular base plate flange, which is forced over the edge of the disc
and Fig. 3 is a plan of the finished alarm.
a
In carrying out the invention, the base plate 6 is provided with a circular
circular shoulder f over which the disc of
grooved, forming the
sheet metal is stretched. When the disc has been stretched and
secured in position the spring e is attached thereto and the sound is produced
by causing a tooth or star wheel to rotate against the free end of the said spring e.
The alarm is made by first placing the disc of sheet metal on the base plate, so
that its edges overlap the shoulder f and lie within the circular flange c, the
parts are then placed in a lathe and the edge of the disc a is depressed into the
grooved, stretching or bulging the disc over the shoulder or ridge f, the flange c
being simultaneously pressed down over the edge of the disc and serving to secure
the same in proper position.
The spring e may then be soldered or otherwise attached to the surface of the
disc..
If a rotary tooth or star wheel is caused to vibrate the free end of the disc the
alarm will be sounded and the tone of the same may be varied according to the
degree of tension to which the disc a is strained.
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
15:-
1: An alarmi device consisting of a base plate having a circular shoulder and
a sheet metal disc bulged or stretched over said shoulder, means for retaining the

page_text: disc in its bulged or stretched position and a spring attached to the said disc and
having free extending -end substantially as described.
2: In an alarm the combination of a base plate 6 having circular groove d
to form shoulder f and a standing circular flange c, a metal disc stretched over
said shoulder and retained in the stretched position by the said flange and a spring
attached to the face of said disc and having free projecting end in the manner and
for the purpose substantially as described.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and
25, Cross Street, Manchester, Agents.