This document describes a patent application for a device that detects warm air or gas currents that may indicate conditions leading to a fire. The device contains a thermally sensitive element made of a wire with spaced lengths coated in a second metal. When heated gas or air penetrates the device's casing, it causes an electromagnetic force between the ends of the coated wire lengths. This EMF can be used to energize a relay and automatically trigger alarms or countermeasures, such as switching off a faulty amplifier and activating fire suppression, to respond to rising temperatures that may indicate a fire. The device was intended to provide early detection of rapid temperature increases to allow timely response to prevent fires from starting or spreading.

1. * GB780194 (A)
Description: GB780194 (A) ? 1957-07-31
Improvements in or relating to a device for detecting warm air or gas
Description of GB780194 (A)
PATENT SPECIFIATION
Inventor: -PETER MELBURN PUCILL.
Date ql,filing Complete Specification: April 27, 1955.
Applcationb Date: Mlay 11, 1954. No. 13760/54.
Complete Specification Published: Jouly 31, 1957.
7805194 Index at Acceptance:-Classes 37, K(1D6 2 5); and 118(1), D15.
International Classification:-008d. H011.
COMPLETE SPECIFICATION.
Improvements in or relating to a Device for Detecting Warm Air or Gas.
We, THE WALTER KIDDE COMPANY LIMITED, a British Company, of Lux Works,
Belvue Road, Northolt, Middlesex, do hereby declare the invention, for
which we pray that a patent may be granted to us, and the method by
which it is to be performed, to be particularly described in and by
the.
following statement: -
The present invention relates to a device for detecting the presence
of warm air or gas currents which may be associated with conditions
likely to lead to an outbreak of fire or other dangerous conditions.
The provision of equipment made in accordance with the invention
permits an alarm to be given and counter-measures to be taken to
prevent such outbreak or to obviate other dangerous conditions. The
counter-measures may be effected automatically by means which act in
response to a signal from the detecting equipment.
The present invention has been developed to provide a means for
detecting conditions of rapid temperature rise, such as are associated
with fire and, if desired, for automatically actuating apparatus
adapted to extinguish fire or to take other appropriate
counter-measures.
One application of equipment which incorporates the present invention
is concerned with the problem arising from the overheating and failure

2. of large size, unattended amplifiers. Amplifiers are frequently
installed in groups in a booth, one or more of the amplifiers being
employed only as stand-bys against the failure of one or more of the
other amplifiers. The present invention provides a thermally sensitive
device which enables incipient failure of an amplifier through
overheating to be detected and at the same time provides a means for
automatically switching such amplifier out and simultaneously
switching a stand-by amplifier in, to take the place of the failure.
Simultaneously means of preventing or checking fire in the defective
amplifier are brought into action automatically in response to the
device.
The detector device made in accordance with the present invention has
a thermally sensitive element comprising a wire having separate spaced
lengths thereof coated with a second metal, one end of each coated
portion being arranged in heat conductive relation with and
electrically insulated from a relatively large metallic mass and the
other end of each coated portion being exposed to the ambient
atmosphere.
The thermally sensitive element is preferably mounted in a casing into
which heated gas or air can penetrate. The apparatus used for
detecting overheating in an amplifier is housed in a holder which is
arranged directly over the amplifier in the path of the hot air
current which will rise from the amplifier in the event of it
overheating. The holder is made of insulating plastic material and the
top and bottom of the holder are open, a wire grille being provided to
protect the thermally sensitive element contained within. Hot air may
rise up into the holder through the open bottom s..o as to contact the
thermocouple system inside it.
One device made in accordance with the present invention is shown in
the accompanying drawings, in which:Figure 1 shows an underneath plan
view of the complete device with the bottom grille plate removed; and
Figure 2 is a section of the thermocouple system.
The thermocouple system consists of a coil of "Eureka" (Registered
Trade Mark) -ricS!CC, -, metal 1, which is partly plated with copper,
each convolution having two copper-plated portions 2 and two plain
portions 3. The material of the coil is essentially very light n gauge
narrow strip. The coil is substantially rectangular in shape and the
plating is applied at two diagonally opposite corners so that 'the
copper-plated portions 2 have ends 4 and 4' at approximately the
middle of each side of the coil. It is found that if the ends 4 and 4'
of a plated portion 2 are maintained at different temperatures, a
potential difference is developed between the two ends of the plated
portion.
The partially plate coil 1 is mounted in the holder 5 directly over

3. the bottom opening in the holder so as to be exposed to rising heated
air. The coil 1 is mounted on formers 6 made of insulating material
and constructed so as to space neighbouring convolutions of the coil
apart. The formers 6 are mounted on spacing bolts 7 which also serve
to clamp heavy metal blocks 8 and 9 against the formers and the coil
1. The cold junctions at the ends 41 are located so that they are in
heat conductive relation with the blocks 8, but they are electrically
insulated therefrom by a thin layer of lacquered paper 10.
When the air or gas temperature around the thermocouple coil 1 rises
with any rapidity, an e.m.f. is developed between the two ends of the
coil, because the junctions at the ends 41 in thermal contact with the
metal blocks 8 remain at a lower temperature than the junctions at the
ends 4 of the plated portions since it takes a little time for the
blocks 8 to warm up to the temperature of the surrounding air. The
resultant e.m.f. between the two ends of the plated portions are
additive since all are in the same direction. The resultant e.m.f.
between the two ends of the coil 1 is employed by connecting the
terminals 11 to a relay.
The whole thermally responsive portion of the device is held away from
contact with the surrounding holder 5 and is supported therein by
means of clips 12 which engage with the spacing bolts 7.
In the particular application of the invention to the fire protection
of amplifiers, the relay is employed to energise operator circuits
which respectively switch out the faulty amplifier and switch in a
stand-by amplifier and also which release CO. to the space around the
faulty amplifier so as to prevent fire.
The device may equally well be applied for general fire protection
purposes, as in the hold of a ship or in a warehouse or factory. Any
sudden rise in temperature will cause an e.m.f. to arise between the
ends of the coil I and the relay energised thereby may be employed to
actuate an alarm and/or to initiate counter-measures.
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