An Improved Automatic Fire Alarm System.
Year: 1893

page_text: Date of Application, 21st Dec., 1893-Accepted, 14th Apr., 1894
COMPLETE SPECIFICATION.
An Improved Automatic Fire Alarm System.
We, HENRY STOPFORD TUNNARD, of Bilton Road, Rugby, in the County of
Warwick, Gentleman, and ARTHUR MAITLAND KEAYS, of Wandle Cottage,
Sutton, in the County of Surrey, Electrician, 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 :-
Our invention refers to An Improved Automatic Fire Alarm System, by which the
presence of a fire is audibly indicated, firstly, in the room or landing or immediate
locality in which the fire takes place, secondly, in the hall or central position
which is set apart conveniently for inspection by indicators which show the exact
spot or room in which the fire has broken out, thirdly, outside the house in a
convenient position, over the door or on a gate post or wherever desirable the
presence of a fire is audibly indicated by means of ringing a gong or its equivalent,
and fourthly, in the fire station itself the presence of the fire is audibly indicated
on a gong and visibly indicated by an indicator showing the street, or the street
and house if desired, in which the fire has broken out.
The essence of our invention to effect these results consists in the improved
form of thermostat, which gives a greater degree of sensitiveness than is generally
given by thermostats. It is obvious that the time interval of alarms between the
breaking out of the fire and its indication depends upon the degree of sensitiveness
of the thermostat; therefore, we rely largely as to the correct working of our
invention and the early intimation of the presence of a fire upon the thermostat
hereinafter described.
We will now proceed to describe our invention, reference being made to the
accompanying drawings, in which similar numbers refer to similar parts in the
several figures.
Figure 1 illustrates the gong, wire connections, and indicator in the fire station,
together with a suitable relay, battery and switch.
Figure 2 illustrates the apparatus fixed in the house itself; this consists of gongs
placed in any suitable positions in the various rooms or passages, the automatic
thermostats placed in suitable positions in each room (there may be one or any
number of thermostats in any one room or landing), the indicator placed in the
hall or other suitable position, together with a double pole relay and a battery,
and we also provide suitable testing switches for the purpose of ascertaining the
proper working of the various electrical circuits.
Figure 3 illustrates the gong and connections fixed outside the house in any
suitable position for giving intimation to a passer-by.
Figure 4 is a plan of a thermostat.
Figure 5 is an underneath view of the thermostat.
Figure 6 is a section of our improved thermostat, together with its supporting
base.
Figure 7 shows the arrangement of a testing switch with the cover removed.
Figure 8 shows the switch with the cover in position.
Figure 9 is a section of the switch with the cover on.
Figure 10 is an elevation of the switch key.
It is obvious that the action of the thermostat for working our invention
depends upon a rise of temperature.
With reference to Figure 1, is the indicator fixed in the fire station and is
provided with “drops" 2, 3, 4 and 5 (there may be any number of "drops
19

page_text: according to the requirements); this indicator is provided with any number of
terminal screws, corresponding with the number of "drops," and an additional
terminal for the return circuit is provided. A wire is connected from this terminal
to a switch 6 hereinafter described, the other terminal of the switch 6 is connected
by a wire 7 to a relay 8, the other end of relay 8 is connected by a wire 9 to one
pole of a battery 10, the other pole of battery 10 is connected by a wire 11 to
earth, from the centre of battery 10 a wire 12 is connected to one terminal of
the gong 13, the other terminal of the gong 13 is connected by a wire 14 to
the contact stop 15 of the relay 8, 16 is the armature of the relay 8 provided with
a suitable contact stop 17, the armature 16 is connected to the wire 9, the street
line wire 18 is connected to a suitable terminal 19 on the indicator 1, this terminal
being in connection with one of the indicator "drops," the other wire from the
indicator "drop" is taken to the return terminal 20 this return terminal being
common to all the "drops."
Referring to Figure 3, 21 is the gong or bell placed on the gate or any convenient
position outside the building, 22 and 23 are testing switches.
With reference to Figure 2, 24 is a double pole relay provided with two
armatures 25 and 26, also with two stop contacts 27 and 28, 29 is a testing switch,
30 is the main battery, 31 is the indicator placed in the hall or any convenient
position and is provided with any number of indicator "drops," one indicator
"drop" being provided for every room, landing or other place where one or more
thermostats are fixed. The indicator 31 is provided with a suitable number of
terminals, one for each indicator "drop," and one return terminal 32 which is
common to all the indicator "drops.' 33 are gongs placed in the rooms or
suitable positions in the house, 34 are circuit testing switches and 35 are
thermostats. The line wire 18 is connected to one terminal of the testing
switch 22, the other terminal of this switch is connected by means of a wire 36
to one terminal of the detector galvanometer 90, the other terminal is connected
to the armature 25, of relay 24, a wire 37 is taken from the stop contacts 27 of
relay 24 and goes to earth at 38. A wire 39 is taken from the centre of the
battery 30 to the switch 29, the other terminal of the switch 29 is connected to the
coil of relay 24 by means of a wire 40, the other end of the coil of relay 24 is
connected by means of a wire 41 to the return terminal 32 of indicator 31, wires 42
are led from the other terminals of the indicator 31 to each of the thermostats 35
that are situated in any position. The other terminal of each thermostat 35 is
connected to a common wire 53, this wire 53 may branch off into any number of
rooms, passages or floors in the building, the other end of the wire 53 is connected
to the terminal screw 43, this terminal screw 43 is in connection with one pole
of the battery 30. From the terminal screw 43 is led a wire 44 which is common
to one terminal of all the gongs 33, the other terminal of each of the gongs or
bells 33 is connected to a wire 45, the other end of the wire 45 is connected to
a terminal 46, a wire 47 from terminal 46 is led to one terminal of the switch 23,
the other terminal of the switch 23 is connected by a wire 48. to one terminal of
the gong 21, the other terminal of the gong 21 is connected by means of a
wire 49 to the terminal 43, the terminal 43 is connected to the battery 30. From
the terminal 46 is connected a wire 50 which is joined to the contact stop 28 of
the relay 24. The armature 26 of relay 24 is connected by means of a wire 51
to the battery 30 and one terminal of each of the testing switches 34 is connected
by means of a wire 52 to the wire 53, the other terminal of each of the testing
switches 34 _connected by means of a wire 54 to the wires 42.
Figures 4, 5 and 6 each illustrate different views of the thermostats 35. The
construction of our thermostat is as follows:-
We make in the tube of glass or other non-conducting material which contains
the mercury, a bulb 56 at one end, but instead of making the bore of the tube of
the same diameter from end to end we make the tube as of two parts, the first
part 57 having a bore of larger diameter than the second part 58; we blow an
expansion chamber 59 at the point of union of the two tubes 57 and 58 and another

page_text: expansion chamber 60 at the other end of the fine bore tube 58, we also provide a
small expansion chamber 61 at the point of union that the bulb 56 makes with the
tube of greater diameter 57; platiuum wires 62 and 63 are fused into the ends
of the thermostat; the wire 62 that is fused into the bulb 56 is always in contact
with the mercury, and the wire 63 that is fused into the expansion chamber 60 at
the end of the tube 58 having the smaller bore only makes contact with the
mercury when the latter expands and runs up, first into the tube of larger bore 57,
next into the expansion chamber 59 that separates the tube of larger bore from
that of the smaller, the mercury then enters the tube 58 of smaller bore and
traverses its entire length coming in contact with the platinum wire 63.
Referring to Figure 5, 64 and 65 are plates of conducting metal that are screwed
to the under side of the thermostat, 66, 67, 68 and 69 are holding down clips
screwed also to the hottom of the thermostat. The platinum wire 62 in Figure 4
makes electrical contact with the metal plate 64, the platinum wire 63 in Figure 4
makes electrical connection with the metal plate 65. The platinum wire 62 and 63
(Fig. 4) are carried through holes in the base of the thermostat, 70, (see Fig. 6).
With reference to Figure 6, the metal plates 64 and 65 make electrical contact
with the conducting plates 71 and 72. To the conducting plate 71 is connected
wire 42, to the conducting plate 72 is connected wire 53. 73 is an insulating
supporting base to which the metal conducting plates 71 and 72 are fixed; the
thermostat is fixed to the insulating base 73 by means of screws or other suitable
attachment to the clips 66, 67, 68 and 69. It is therefore obvious that if the
supporting base 73 be screwed to the wall or ceiling of a room, by means of
removing the screws that fix clips 66, 67, 68 and 69 to the supporting base the
thermostat can be removed for renewal or examination when necessary without
removing the supporting base 73.
Figures 7, 8, 9 and 10, show details of the testing switches, as for example say
switch 6 in Fig. 1.
The switches 29, 34 and 89 in Figure 2, also switches 22 and 23 in Figure 3, are
of similar construction.
The switches 6, 22, 23 and 29 are constructed to be normally closed, the
switches 34 and 89 are constructed to be normally open.
With reference to Figure 7, to an insulating base 74, which may be of wood,
slate, ebonite or other material, is pivotted a switch contact maker 75, this contact
maker consists of a strip or bar of conducting material, having two holes 76 and 77
pierced in it; this bar is pivotted at 78. Fixed to the base 74 are metallic contact
pieces 79 and 80.
With reference to Figure 8, which is a plan of the cover of the switch, 81 is a
cover of insulating material which screws on to the base 74, the cover 81 has a
slot 82 in the top.
Figure 9 is a cross section of Figure 7 with the cover 81 in position; 83 is a
spring see Figure 7 which tends to return the contact bar 75 to its normal position.
With reference to Figure 10, which represents the switch key by means of which
the switch is operated (this switch key is separate and independent of the body of
the switch), 84 is the handle of the key to which is attached a bar 85, fixed to the
bar 85 are pins 86 and 87. The action of this switch is as follows:-When the
switch key 84 is inserted in the slot 82 the pins 86 and 87 enter the holes 76 and 77,
if the handle 84 is now turned the bar 78 will break or make the contacts as the
case may be at 79 and 80. One wire is led from the contact strip 79 and another
wire is led from the contact strip 80; when the switch is operated the circuit
between 79 and 80 is either completed or else it is broken; the switches are con-
structed to effect both operations, that is to say, the circuit through the switches
may be normally made or normally broken as the case may be.
For the purpose of ascertaining the correct working of the circuits to the line
wire 18 we find it convenient to provide a detector galvanometer 91) inserted in the
circuit of wire 36 in Figure 2. It is obvious that when a current is sent along the
line wire to the fire engine station the needle of this galvanometer will be deflected,

page_text: and in the event of a break in the line wire to the fire engine station no deflection
will be visible on this galvanometer.
The operation of our invention is as follows:-
On a fire breaking out in any room, landing or place in which one or more
thermostats are fixed, on the temperature reaching a pre-determined limit the
thermostat in that particular place will come into action and will automatically
close the electric circuit. Take the case of a fire breaking out in the room
which is protected by, say thermostat 35" (see Fig. 2), on the thermostat coming
into action the current from battery 30 will flow to the terminal 43, wire 53,
thermostat 35*, to terminal 88, indicator 31 and passes round to the magnet of the
indicator "drop" which corresponds to thermostat 35, to terminal 32, the current
passes through wire 41, round the coil of relay 24, to wire 40, through switch 29
which is normally closed, to the wire 39 and back to the battery 30, relay 24 is
excited and attracts the armatures 25 and 26 simultaneously, the current from the
battery 30 now goes to terminal 43, wire 44, rings all the bells 33 and returns by
the wire 45 to terminal 46, through the wire 50 to the stop contact 28 of the
relay 24, to armature 26, to wire 51 and back to the battery 30. It will thus be
seen that when the switch 29 is closed, when the relay 24 is excited and the
armature 26 is in contact with the stop 28 the battery 30 rings the whole of the
bells 33 automatically. The switch 23 (refer to Figure 3) being normally closed,
the gong 21 which is placed outside the house is also rung automatically through
the medium of the wire 49, wire 48, passing through switch 23, wire 47 to
-terminal 46.
The operation of the circuit actuated by the armature 25 of relay 24 (sce
Fig. 2), is as follows:-
The armature 25 being in contact with the contact stop 27 the wire 37 is
.automatically put to earth at 38, the normal position of the switch 22 in Figure 3
is closed, the circuit of the line wire 18 to the fire engine station in Figure 1 is now
completed in the following manner:-The circuit from the battery 10 (refer to
Fig. 1) passes to the wire 11 and to earth, entering the earth terminal 38 in Figure 2,
the current passes to wire 37, to contact 27 of relay 24, to armature 25, wire 36,
through switch 22 which is normally closed, to the line wire 18, to the terminal 19
(Fig. 1) of the street indicator 1 in the fire engine station, the current passes round
the electro-magnet of the indicator drop to the terminal 20, through switch 6 which
is normally closed, to wire 7, round the coils of relay 8, to wire 9, to the other pole
of battery 10, the relay 8 is now excited and attracts its armature 16, the contact
stop 17 makes contact with the stop 15 and the current passes from the battery 10,
to wire 12, round the coils of the gong 13, to wire 14, stop 15, stop 17, armature 16,
wire 9, back to the battery 10. It will thus be seen that when the relay 24 in
Figure 2 is excited and armature 25 is automatically brought in contact with
stop 27, the indicator drop in indicator 1 at the fire engine station will indicate the
number of the street, or it may be the number of the house, in which the fire has
originated, and the relay 8 attracting its armature 16 and causing the stop 17 to
make contact with the stop 15 will automatically set ringing the gong 13. It will
thus be seen that on a thermostat coming into action in any one room of the house
-the indicator 31 will indicate by means of its "drop" the exact position in the house
in which the fire has broken out, the gongs 33 will be simultaneously rung in the
various parts of the house, the gong 21 will be simultaneously rung on the outside
of the house, and the gong 13 will be simultaneously rung in the fire engine
station, at the same time the indicator in the fire engine station will indicate the
. street or in some cases the number of the house to which the "call" has been made.
It is necessary that facilities should be provided for testing the circuits within
the house without at the same time calling up the fire engine station.
The facilities we provide for testing the efficiency and proper working of the
- electrical circuits throughout the system, are as follows:-
It is essential for the proper testing of any fire alarm system, that it shall be
. impossible for unauthorized persons to operate the testing switches; we therefore

page_text: provide switches of special construction, hereinabove described in Figures 7, 8, 9
and 10 for this purpose. One or more switch keys are provided (refer to Figure 10)
and are placed in the hands of responsible persons. The switches can only be
operated by means of this switch key. The normal positions of the various
switches are as follows:
In Figure 1 the switch 6 is normally closed, in Figure 2 the switch 29 is normally
closed, the switches 34 & 89 in Figure 2 are normally broken, the switches 22 and 23
in Figure 3 are normally closed.
Let us suppose that it is required to ascertain the correct working of the
circuits throughout the house, in Figure 2, the operation is as follows:-The
switch 22 in Figure 3 is first broken, this interrupts the circuit of the line wire 18
to the apparatus in the fire engine station, shown in Figure 1, now if the switch
key is inserted in any of the switches 34 and these circuits are in proper working
order the whole of the bells 33 throughout the house will be rung, together with
the bell 21 placed on the outside of the house. It is obvious that if the switch 23
is broken the bells 33 can be rung without ringing the bell 21. The switches 34 are
shown in the figure as controlling the thermostats in each separate floor, but it is
obvious that switches 34 may be provided to control every individual thermostat
rather than a series of thermostats as shown in Figure 2, in other words, it is
possible by providing a testing switch 34 to every thermostat fixed in the building
every circuit from that thermostat and every indicator "drop" together with the
circuits to every bell in the building can be readily tested and this with efficiency
without ringing up the fire station. When the testing has been completed the
switches 22 and 23 will be closed to their normal condition and the switches 34 will.
remain broken in their normal condition, and the line will again be restored to
working order.
In the event of the whole of the circuits in the house breaking down and
assuming that the line wire 37 remains in working order it is possible to
mechanically call the fire station up by operating the armature 25 of relay 24,
or a testing switch 89 can be provided for this purpose. The electrical connections
to the bells 33 together with the gong 21 are joined up in parallel so that if the
circuits are in complete order the whole of the bells will be rung simultaneously;
any one bell that failed to ring would indicate a break in the wires, either 44
or 45, that are in connection with that particular bell (see Fig. 2).
The fireman or other person in charge at the fire station, by opening the
switch 6 (Fig. 1) interrupts the circuit to the battery 10 together with the circuit
to the gong 13. If the switch 29 (refer to Fig. 2) be broken the whole of the
circuits through the relay 24 together with those to all the bells in Figures 2 and 3
will be interrupted and the bells if ringing will cease to ring.
We are aware that previous efforts have been made to effect partial results in
so called automatic fire alarm systems, we are further aware that audible and visual
signals have been given at fire stations for indicating the localities of fires, and
again that visual and audible indications have been given in a central position in a
building, such as the hall or watchman's room, for indicating the locality, and we
are further aware that substitutes for thermostats and thermostats have been used
in fire alarm systems, we therefore do not claim broadly any of these by themselves,
but what we do claim is :-
1. In automatic fire alarm systems, the combination of apparatus by which visual
and audible signals are given at the fire station, au audible signal outside the house
or building in which the fire is located, audible and visual signals inside the house
or building in any central position or pre-determined position, immediately upon
the outbreak of a fire and as soon as the thermostat is operated, all substantially as
described and illustrated in the drawings annexed.
2. In automatic fire alarm systems, providing an audible indication outside a bouse
or other building which audible signal is brought into action by the operation of

page_text: the thermostat acted upon by the fire inside the building, all substantially as
-described with reference to the drawings annexed.
3. In automatic fire alarm systems, our improved thermostat illustrated in
Figures 4, 5 and 6 of the drawings annexed, which on being operated by a rise of
temperature to a pre-determined point due to any cause whatsoever sets our
combination of signals in operation, substantially as illustrated and described.
4. In automatic fire alarm systems, the combination of our improved thermostat
with the various bells, indicators, wires, batteries, relays and switches, all
substantially as described and illustrated and for the purposes set forth.
5. In automatic fire alarm systems, the heroinbefore described testing switch
illustrated in Figures 7, 8, 9 and 10, in combination with the system as a whole
illustrated in Figures 1, 2 and 3 of the drawings annexed.
Dated this 21st day of December 1893.
JOHN P. O'DONNELL,
70 & 71, Palace Chambers, Bridge Street, Westminster, S.W.,
Agent for the said Applicants.