IMPROVEMENTS IN AUTOMATIC FIRE ALARMS
Year: 1880

page_text: LETTERS PATENT to Robert Thomas Brown, of No. 6, Cicely Road, Hanover
Park, Peckham, in the County of Surrey, for an Invention of "IMPROVEMENTS
IN AUTOMATIC FIRE ALARMS." A communication from abroad by Frederick
Bogen, of Valparaiso, in the Republic of Chili.
PROVISIONAL SPECIFICATION left by the said Robert Thomas Brown at
the Office of the Commissioners of Patents on the 24th July 1880.
ROBERT THOMAS BROWN, of No. 6, Cicely Road, Hanover Park, Peckham, in the
County of Surrey. "IMPROVEMENTS IN AUTOMATIC FIRE ALARMS." [A com-
munication from abroad by Frederick Bogen, of Valparaiso, in the Republic of
Chili.]
This Invention has for its object improvements in automatic fire alarms. For
this purpose, together with other instruments, a "detector" is employed. It consists
of two straight compound blades, and each blade is composed of two strips of
different metals soldered together in such manner that when heated the compound
blade will become somewhat curved. These two blades are placed side by side, and
parallel the one to the other. At one end they are attached to insulated supports,
and at the other end one blade is provided with a contact screw, by which it makes
contact with an arm provided upon the other blade. Adjusting screws are also.
provided to press upon the blades near their attachments to the insulated supports
for the minute regulation of the contact between the blades at their other ends.
One of the compound blades is provided with a sheath of paper, but the other is left
The whole of these parts are contained within a cage, which serves to
protect them from mechanical injury. One or more of these detectors is placed in
each room or place where protection may be judged to be necessary, and each is
connected with a battery, so that an electric current continues to flow through the
detector so long as the two blades of the instrument continue in metallic contact.
In the circuit with each detector there is an electro magnet, which serves so to
increase the resistance of the circuit as to prevent undue waste in the battery, and
the magnet also serves to hold an armature off a contact point, against which it
rises when at any time the circuit is broken. The armature then closes the circuit
bare.

page_text: of an electric bell, this being the instrument by which the alarm is sounded. The
circuits for all the detectors are derived from one main battery, the current being
divided between them, and there is also one circuit in which there is no detector
but only an electro magnet. The parts are so adjusted that the armature of this
magnet will (as the power of the battery from long use decreases) fall away from
the magnet sooner than either of the other armatures, and when it does so, it moves
an indicator, and so indication is given that the battery requires charging.
When fire occurs the detector acts in either of two ways, according to the way
in which the fire operates upon it. If a sudden rise of temperature (even of a few
degrees) occurs, the bare blade of the detector is acted on more rapidly than the
blade which has the protecting sheath, and becoming more curved than the other
the contact between the blades ceases. On the other hand, if the rise in temperature
be very gradual, but extends beyond the range of natural temperatures, then both
blades move together with the very gradual rise of temperature, until one of the
blades come against a fixed stop in a prearranged position, and is so mechanically
stopped.
The other blade then continues to move, becoming more bent under the influence
of the increasing temperature until the contact between the blades is thus separated,
with the result that the alarm is caused to sound.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Robert Thomas Brown in the Great Seal Patent Office on the
22nd January 1881.
ROBERT THOMAS BROWN, of No. 6, Cicely Road, Hanover Park, Peckham, in the
County of Surrey. "IMPROVEMENTS IN AUTOMATIC FIRE ALARMS." A com-
munication from abroad by Frederick Bogen, of Valparaiso, in the Republic of
Chili.
This Invention has for its object improvements in automatic fire alarms. For
this purpose, together with other instruments, a "detector" is employed. A side
view of the detector is shown by Figure 1 of the annexed Drawing, and Figure 2
is a plan of the same. It consists of two straight compound blades a and b, and
each blade is composed of two strips of different metals soldered together in such
manner that when heated the compound blade will become somewhat curved.
These two blades are placed side by side, and parallel the one to the other. At one
end they are attached to insulated supports (upon which are the binding screws c, c,
for holding the ends of the circuit wires), and at the other end one blade is provided
with a contact screw a', by which it makes contact with an arm b' provided upon
the other blade. Adjusting screws d and d¹ are also provided to press upon the
blades near their attachments to the insulated supports for the minute regulation of
the contact between the blades at their other ends. One of the compound blades,
viz., a, is provided with a sheath of paper, but the other b is left bare. The whole
of these parts are contained within a cage e which serves to protect them from
mechanical injury. e' is a turn button for closing the end of the cage after the
instrument has been adjusted; e' is a stem on the side of the cage to enter a socket
conveniently placed to hold the instrument. One or more of these detectors is
placed in each room or place where protection may be judged to be necessary, and
each is connected with a battery so that an electric current continues to flow
through the detector so long as the two blades of the instrument continue in
metallic contact. In the circuit with each detector there is an electro magnet a,
Figure 3, which serves so to increase the resistance of the circuit as to prevent
undue waste in the battery, and the magnet also serves to hold an armature, and
when at any time the circuit is broken the movement of the armature closes the
circuit of an electric bell, this being the instrument by which the alarm is sounded.
The arrangement in connection with each electro magnet is as follows:-Between
the two parts of the magnet a a stationary horizontal rod 6 is fixed, and upon it a
tube c is able to turn; stops b', 6', on the rod prevent the tube moving longi-
tudinally; d is a disc with a notch in it on one side (see Figure 4); this disc is
soldered on the tube c, and when the armature is retained by the magnet a
pin on the armature enters the notch in the disc d; e is the armature; it is
carried at the end of a spring blade f which, when the circuit is broken, moves it
away from the magnet; g is a screw stop to limit the movement of the spring;
h is the pin on the armature which engages with the disc d. There is a hole e¹
(see Figure 5) in the armature by which the tube c passes through it; c' is an arm
on the tube c, and it carries a disc cx, which, acting as a weight, causes the tube to
turn when the pin h is withdrawn from the notch in the disc d on the armature
leaving the magnet. When in this way the tube c is allowed to turn the disc c*
falls on to a contact point (i, Figure 6) and closes the bell circuit.
The circuits for all the detectors are derived from one main battery, the current
being divided between them, and there is also one circuit in which there is no
detector but only an electro magnet. The parts are so adjusted that the armature
of this magnet will (as the power of the battery from long use decreases) fall away

page_text: from the magnet sooner than either of the other armatures, and when it does so it
moves an indicator, and so indication is given that the battery requires charging.
When fire occurs the detector acts in either of two ways, according to the way
in which the fire operates upon it. If a sudden rise of temperature (even a few
degrees) occurs, the bare blade of the detector is acted on more rapidly than the
blade which has the protecting sheath, and becoming more curved than the other,
the contact between the blades ceases. On the other hand, if the rise in temperature
be very gradual, but extends beyond the range of natural temperatures, then both
blades move together with the very gradual rise of temperature until one of the
blades, viz., a, comes against a fixed stop f, in. Figures 1 and 2, in a prearranged
position, and is so mechanically stopped. The other blade then continues to move,
becoming more bent under the influence of the increasing temperature, until the
contact between the blades is thus separated, with the result that the alarm is
caused to sound.
What I claim is the improvements in automatic fire alarms, substantially as
herein described.
In witness whereof, I, the said Robert Thomas Brown, have hereunto set my
hand and seal, this Twenty first day of January, in the year of our Lord
One thousand eight hundred and eighty onc.
ROBERT THOMAS BROWN. (L.S.)