A New or Improved Automatio Oircuit-closing Device for Electric Fire Alarms.
Year: 1891

page_text: Date of Application, 21st Oct., 1891-Accepted, 6th Feb., 1892
COMPLETE
SPECIFICATION.
A New or Improved Automatio Oircuit-closing Device for Electric
Fire Alarms.
A communication from abroad by the CоMPAÑIA ELECTRICISTA CONTRA
INCENDIOS, of Madrid, Spain.
I ERNEST JAMES ELKINGTON of Clifton Lodge, Dalston Lane, London N.E.
in the County of Middlesex, Gentleman, 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, as communicated to me, relates to a new or improved automatic
circuit closing device for electric fire alarms, whereby efficiency and cheapness of
construction are obtained.
The object of this invention is to produce a cheap and efficient device for
automatically closing the circuit of an electric fire alarm when a predetermined
temperature is suddenly attained that is to say a device which shall automatically
complete the electric circuit when the temperature suddenly rises to the point at
which the instrument is set to act but which shall not so complete the circuit
should the temperature rise gradually, as it may do under normal conditions, to the
said point.
The object of this invention having been indicated in general terms, its nature
and the manner in which it is to be or may be performed or carried into effect
will now be described; and for the purpose of such description reference will be made
to the accompanying sheet of drawings in which
Figure 1 is a front elevation, partly in section, and
Figure 2 a section on the line a-b of Figure 1.
In these figures A represents the base of the apparatus which may be made of
any convenient non-conducting material. Upon A is mounted the bridge piece C
formed of a solid piece of metal of considerable mass. His a thin perforated strip
of metal soldered at its two ends to C. M and N are the terminals for the connec-
tion of the conductors forming the circuit of the electric fire alarm. The
terminal N is in connection with C and the terminal M with a compressed
spring F. This spring is carried by A and bears against the contact-piece G
which, passing through the insulating sleeve Z into an orifice in the centre of C,
makes contact with the regulating contact screw K when the circuit is completed
as will now be described.
Let us assume that a fire has broken out in a chamber fitted with an electric
fire alarm embracing this invention. The sudden increase of temperature will tend
to produce expansion of both C and H, but the mass of H being small in com-
parison with that of C, H will expand much more rapidly than C. H being
fixed at both ends cannot expand longitudinally and will therefore commence to
sag. This sagging will however be taken up by the spring F in such manner
that G will be pressed towards K until contact between G and K will take
place on the temperature being reached for which K is adjusted.
On the other hand, if, instead of a fire breaking out, the temperature gradually
rises to this point, as may happen under normal conditions, the difference of
mass of H and C will not produce the effect mentioned, for C will have time
to expand in the same way as H, and G will not overtake K.
In practice it is found convenient to perforate H in order to diminish its
mass and to coat C with a layer of varnish to retard its absorption of heat.
A convenient metal of which to construct C and H is zinc on account of its
high coefficient of expansion, its lasting powers and the ease with which it can be
wrought.

page_text: Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what I
claim is.
1. The new or improved automatic circuit closing device for electric fire alarms
substantially as set forth.
2. In a circuit closing device for electric fire alarms the use of a perforated strip
of thin metal substantially as set forth.
1001
E. J. ELKINGTON.