AN IMPROVED AUTOMATIC ELECTRIC FIRE ALARM
Year: 1885

page_text: I ANDREW DALZIEL of 4 Reservoir Terrace, Pern Street Salford in the County
of Lancaster Electrician do hereby declare the nature of my invention for
"AN IMPROVED AUTOMATIC ELECTRIC FIRE ALARM" to be as follows:-
=
The object of this invention is to construct an automatic electric fire-aların
which shall sound an electric bell or alarm whenever the temperature of the room
or other place in which it is situated shall rise beyond any given point, the
apparatus being either made to sound the alarm at any fixed temperature or so
that it can be adjusted to work at any temperature desired.
Upon a board or other convenient base I fix an inverted glass syphon, one arm
of which is left open at the top and the other closed and formed with a bulb.
In the bend of the syphon I place a certain amount of mercury thereby
enclosing a quantity of air in the closed arm and bulb of the syphon. Through
the top of the bulb I pass a thin platinum wire and I fuze the glass round the
wire so as to make it airtight.
The lower end of this wire lies in the mercury in the bend of the syphon and
the upper end thereof is soldered or otherwise connected to one of the terminal
wires forming the electric circuit.
Inside the open arm of the syphon is suspended a copper or other metallic wire,
the lower end of which (when the temperature is normal) does not reach to the
surface of the mercury in the syphon, and the upper end of this wire is connected
with the other terminal for forming the electric circuit.
The terminals may be connected with any kind of electric bell, or with telephone
or telegraph wires according to the nature of the alarm desired to be given.
It will be evident that so long as the lower end of the suspended copper or other
metallic wire does not come into contact with the mercury the electric circuit is
interrupted and no alarm is given, but whenever the temperature rises beyond that
to which the alarm is set or constructed, the expansion of the air in the bulb and
the closed arm of the syphon will force the mercury downwards in that arm and
upwards in the other until it reaches the lower end of the suspended copper or
other metallic wire, when the electric circuit will be completed, and the alarm will
be given

page_text: When it is desirable that the instrument shall be made adjustable, so as to give
the alarm at any required temperature I attach the upper end of the suspended
copper or other metallic wire to a screwed rod, which passes through a milled nut
held between two brackets attached to an index plate. The upper end of the
screwed rod is provided with an index finger, working against a scale on the plate.
By turning the nut round by means of its milled edge the suspended wire is raised
or lowered and the finger indicates on the scale the temperature to which the
instrument is set. The index plate is made of metal and is connected to the
terminal by a wire, so as to complete the circuit as soon as the mercury rises into
contact with the suspended wire.

page_text: ANDREW DALZIEL of 4 Reservoir Terrace Pern Street Salford in the County
of Lancaster Electrician do hereby declare the nature of my Invention for
AN IMPROVED AUTOMATIC ELECTRIC FIRE ALARM" to be as follows :—
The object of this Invention is to construct an Automatic Electric Fire Alarm
which shall sound an Electric Bell or Alarm whenever the temperature of the
room or other place in which it is situated shall rise beyond any given point: the
apparatus being either made to sound the Alarm at any fixed temperature or so
that it can be adjusted to work at any temperature desired.
Upon a board or other convenient base I fix an inserted glass syphon one arm
of which is left open at the top and the other closed an i formed with a bulb.
In the bend of the syphon I place a certain amount of mercury thereby
enclosing a quantity of air in the enclosed arm and bulb of the syphon. Through
the top of the bulb I pass a thin platinum wire and I fuze the glass round the wire
so as to make it airtight.
The lower end of this wire lies in the mercury in the bend of the syphon and
the upper end thereof is soldered or otherwise connected to one of the terminal
wires forming the electric circuit.
Inside the open arm of the syphon is suspended a copper or other metallic wire
the lower end of which (when the temperature is normal) does not reach to the
surface of the mercury in the syphon and the upper end of this wire is connected
with the other terminal for forming the electric circuit.
The terminal may be connected with any kind of electric bell or with telephone
or telegraph wires according to the nature of the alarm desired to be given.
It will be evident that so long as the lower end of the suspended copper or
other metallic wire does not come into contact with the mercury the electric Alarm
is interrupted and no alarm is given but whenever the temperature rises beyond
that to which the Alarm is set or constructed, the expansion of the air in the bulb
and the closed arm of the syphon will force the mercury downwards in that arm
and upwards in the other until it reaches the lower end of the suspended copper or
other metallic wire when the electric circuit will be completed and the alarm will
be given. When it is desirable that the instrument shall be made adjustable so as
to give the alarm at any required temperature I attach the upper end of the
suspended copper or other metallic wire to a screwed rod which passes through a
milled nut held between two brackets attached to an index plate.
The upper end of the screwed rod is provided with an index finger working
against a scale on the plate.
By turning the nut round by means of its milled edge the suspended wire is
raised or lowered and the finger indicates on the scale the temperature to which

page_text: the instrument is set. The index plate is made of metal and is connected to the
terminal by a wire so as to complete the circuit as soon as the mercury rises into
contact with the suspended wire.
Having now described and ascertained the nature of my invention and the
manner in which the same is or may be performed I would observe in conclusion
that I do not limit myself to the precise details herein described as various
modifications may be made therein while retaining the essential features of my
Invention but what I claim as new and desire to be secured to me by the
herein before in part recited Letters Patent is an Automatic Electric Fire Alarm
substantially herein described.