Improvements in Thermometers for Closing Electric Circuits for Alarm and other Purposes.
Year: 1892

page_text: Date of Application, 3rd Nov., 1892-Accepted, 17th Dec.,
1892
COMPLETE SPECIFICATION.
Improvements in Thermometers for Closing Electric Circuits for
Alarm and other Purposes.
I, EDWARD WESTBROOKE of 185 Queen's Road Dalston, London, N.E.
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 has reference to improvements in thermometers of the kind in
which the attainment of a pre-determined maximum, or minimum temperature is
indicated by the closing, of an electric circuit caused by movement of mercury in a
bent tube, one end of which is open, and the other end of which is closed, and
contains a suitable fluid, such as alcohol.
In such a thermometer according to my invention the contact by which the
circuit is closed when the minimum temperature is attained, is made adjustable, so
that its position can be varied to suit different requirements.
In the accompanying drawing are two flexible wires or conductors (M, M'), that
are, when the thermometer is in use, connected with a source of electricity, and
with a suitable indicating device, such as an electric-bell. These wires are intro-
duced through the open end of the thermometer tube.
The one (M) which I hereinafter term the maximum wire I insert in the
tube (m) till it reaches a point corresponding to the degree of maximum tempera-
ture at which contact is required to be made; the other (M¹) which I distinguish
as the minimum wire, passes the first named, and enters the mercury (a) following
the course of the tube (m, m¹) till it arrives at a point above the mercury (a¹) in
the minimum arm (m') where it may be adjusted to suit any required degree of
minimum temperature.
The maximum wire (M) may be bare where it enters the tube (m), but the
minimum wire (M') should be properly insulated by any suitable insulating
material, (as for example silk), that will insulate a wire passing through mercury
and entering alcohol, or other fluid, forming the contents of the bulb (B) and a
portion of the tube (m³).
The end of each wire consists of an un-insulated point, preferably of fine
platinum wire (c, c²). A fixed contact (b) of platinum wire is fused (in the process
of manufacture) into the side of the glass tube of thermometer on the inside of
bend, so as to be in contact with the mercury (a, a¹) and in such a position as
to allow the minimum wire (M¹) to pass freely without short circuiting.
The free end of the contact (b) is in connection with a terminal, which I herein-
after term the line terminal (L). Although I place the platinum contact (1)
in, or about, the bend of the tube, it may be inserted in any other position where
it will always be in contact, or in electrical communication with the mercury (a, a').
To enable the position of the contact (c¹) to be adjusted to suit requirement, I
fix the minimum wire (M³) to which it is connected, in a suitable clamp, or
holder (N) by means of a screw, or other suitable fastening, in such a way, that it
can be readily loosened, when desired to enable the said wire to be forced further
into the thermometer tube, or to be partly withdrawn therefrom, as may be
required from time to time to vary the position of the contact (c¹).
The maximum wire (M) may advantageously be fixed in a similar manner by a
clamp, or holder (N) so that the position of the contact (c) carried by it can also
be varied as may be desired. By employing tubes of different lengths any desired
range of temperature may be indicated. As will be seen, the arrangement is such,
that an electrical circuit will be completed, or broken, between the line terminal (L)
and the maximum (M) or minimuin (M¹) wires by the movement of the mer-
cury (a, a¹) in either arm of the tube (m, m¹).

page_text: 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 :-
1st. A thermometer of the kind herein referred to, in which the insulated
contact, serving for the completion of an electric circuit, when a predetermined
minimum temperature is attained, is, made adjustable, substantially as herein
described.
2nd. My improved thermometer, constructed substantially as described and
shown.
1 L
1 1
1