Improvements in Heat Indicators and Fire Alarms.
Year: 1890

page_text: Date of Application, 8th Oct., 1890
Complete Specification Left, 17th Apr., 1891-Accepted, 13th June, 1891
PROVISIONAL SPECIFICATION..
Improvements in Heat Indicators and Fire Alarms.
I SIDNEY STUART WALKER of Woodside Knowle in the County of Warwick
Mechanical Engineer do hereby declare the nature of this invention to be as
follows:-
My invention consists of the improvements hereinafter described in heat
indicators and fire alarms the action of which depends on the unequal expansion
and contraction produced in two metals or substances by an equal change of
temperature.
In constructing a heat indicator or fire alarm according to my invention I take
two thin strips of different metals or alloys preferably one of iron and the other
of brass the said strips being many times as long as they are broad. I solder or
braze the said strips together face to face so as to form a compound strip iron on
one side and brass on the other. 1 coil the said compound strip into a flat coil
preferably of several convolutions. I fix the inner end of the coil to the base or
foundation plate of the instrument and to the outer end of the coil I fix an index
finger or pointer the free end of which traverses a graduated arc. As the instrument
is exposed to a higher or lower temperature the coil expands or contracts and the
index finger indicates the temperature on the graduated arc. Instead of connecting
the index finger directly to the coil it may be fixed on an axis carrying a pinion
with which pinion a toothed quadrant engages. This quadrant is the long arm of
a lever on the short arm of which the end of the coil operates.
Instead of a coil a straight or curved compound strip of the kind described may
be employed and instead of fixing the inner end of the coil to the base and the
index finger to the outer end the reverse arrangement may be employed that is
the onter end of the coil may be fixed to the base plate and the index finger fixed
to the inner end of the coil.
The instrument described constitutes a heat indicator. It may be converted into
a heat indicator and fire alarm by the following additions. Near the graduated
are which the index finger traverses is a metallic stud which may be carried by a
disc and travel in a curvilinear path or may work on a screw and travel in a rectilinear
path. This stud by being moved in one or other direction can be brought opposite
that part of the graduated arc which indicates the temperature at which it is desired
that the alarm shall be brought into operation. When the temperature of the
apparatus is raised to the height indicated by the position of the stud the index
finger comes in contact with it. The apparatus is made part of an electric circuit
which is open so long as the index finger is not in contact with the stud but which
is closed by contact of the said finger with the stud. The closing of the electric
circuit is made to operate an alarmn in any of the various well known ways: The
temperature at which the electric circuit is closed and the alarm operated can be
varied at pleasure by changing the position of the stud. Instead of closing the
electric circuit by the index finger it may be closed by the quadrant or other
moving part of the instrument.
Dated the 8th day of October 1890.
W. T. WHITEMAN,
Agent for the Applicant.

page_text: COMPLETE
SPECIFICATION.
Improvements in Heat Indicators and Fire Alarms.
I SIDNEY STUART WALKER of Woodside, Knowle in the County of Warwick
Mechanical Engineer do hereby declare the nature of my invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
My invention consists of the improvements hereinafter described in heat
indicators and fire alarms the action of which depends on the unequal expansion
and contraction produced in two metals or substances by an equal change of
temperature.
In constructing a heat indicator or fire alarm according to my invention I take
two thin strips of different metals or alloys preferably one of iron and the other of
brass, the said strips being many times as long as they are broad. 1 solder or braze
the said strips together face to face so as to form a compound strip iron on one side
and brass on the other. I coil the said compound strip into a flat coil preferably
of several convolutions. I fix the inner end of the coil to the base or foundation
plate of the instrument and to the outer end of the coil I fix an index finger or
pointer the free end of which traverses a graduated are. As the instrument is
exposed to a higher or lower temperature the coil expands or contracts and the
index finger indicates the temperature on the graduated arc.
Instead of connecting
the index finger directly to the coil it may be fixed on an axis carrying a pinion
with which pinion a toothed quadrant engages. This quadrant is the long arm of
a lever on the short arm of which the end of the coil operates.
Instead of fixing the inner end of the coil to the base and the index finger to the
outer end the reverse arrangement may be employed, that is, the outer end of the
coil may be fixed to the base plate and the index finger fixed to the inner end of
the coil.
The instrument described constitutes a heat indicator. It may be converted into
a heat indicator and fire alarm by the following additions. Near the graduated
are which the index finger traverses is a metallic stud which may be carried
by a disc and travel in a curvilinear path or may work on a screw and travel in a
rectilinear path. This stud by being moved in one or other direction can be brought
opposite that part of the graduated are which indicates the temperature at which
it is desired that the alarm shall be brought into operation. When the temperature
of the apparatus is raised to the height indicated by the position of the stud the
index finger comes in contact with it. The apparatus is made part of an electric
circuit which is open so long as the index finger is not in contact with the stud but
which is closed by contact of the said finger with the stud. The closing of the
electric circuit is made to operate an alarm in any of the various well known ways.
The temperature at which the electric circuit is closed and the alarm operated can
be varied at pleasure by changing the position of the stud.
I will now describe with reference to the accompanying drawing the manner in
which my invention is to be performed.
Figure represents in front elevation and Figure 2 in cross section a heat
indicator constructed according to my invention suitable for attachment to the doors
of ovens and for other like purposes. The same letters of reference indicate the same
parts in both figures.
a is the foundation plate of the heat indicator and is the graduated dial or are
of the same; cis the flat coil of several convolutions made from a compound metallic
strip (see the enlarged view of Figure 6) of the kind hereinbefore described, for
opérating the index finger. The inner end of the flat coil e is fixed at d to the
foundation plate a and to the outer or free end of the coil the index finger or pointer e
is fixed the said index finger or pointer traversing the graduated are b. The
finger or pointer e is bent in the manner shown in Figure 2. As the instrument is

page_text: exposed to a higher or lower temperature the coil c expands or contracts and the
index finger or pointer e indicates the temperature on the graduated arch.
In fitting the heat indicator to an oven door (or other like door) it is placed at
the back thereof, the frame of the dial part projecting through the hole in the
door so as to present the dial to the front of the door and the foundation plate a is
fixed to the door by screws passed through holes in the lugs 7 g taking into holes
made in the door.
Any other convenient mode of fixing the heat indicator at the place where it is
required to be used may however be adopted.
the
Figure 3 represents in back elevation, Figure 4 in front elevation and Figure 5
in cross section a heat indicator in which the coil is made to operate the index
finger or pointer through gearing instead of being connected directly to the index
finger or pointer as first described: c is the flat coil made of a compound strip of
metal as before described its inner end being fixed to the block d on the case and
its outer end bearing against the arm on the axis of the toothed quadrant
said quadrant giving motion to the pinion with which it gears. On the axis of
the pinion is the index finger which traverses the dial m for indicating the
temperature. The return motion of the quadrant is effected and the arm h
preserved in contact with the outer end of the coil c on the contraction of the said
coil by the helical spring a connected to the toothed quadrant.
This heat indicator is fitted to an oven door (or other like door) in the manner
illustrated in Figure 5 where a portion of the oven door is marked p the case of
the heat indicator being passed from the front of the door through a hole therein
until the ring like collar q on the case bears against the door. A screw collar or
ring is then screwed-from the inside of the door upon the screwed projecting
parts of the case and made to bear against the inside of the door. The case
of the heat indicator is thus clamped to the door between the fixed and screwed
collars and r.
9
Figure 6 represents in front elevation (with a portion drawn to a larger scale)
and Figure 7 in cross section a combined heat indicator and fire alarm constructed
according to my invention; c is the flat coil made from a compound strip fixed to
the foundation plate a at d the free end of the said coil bearing directly upon the
lower arm of the toothed quadrant i gearing with the pinion on the axis of the
index finger traversing the graduated dial m.
The mechanism for converting the heat indicator into a fire alarm consists of
the adjustable metallic stud near the graduated dial m which dial the index
finger traverses. The dial m is made of china or earthenware or other insulating
material. By the traverse of the index finger to indicate the temperature it comes
in contact with the adjusted stud for putting the alarm into operation in the manner
hereinafter described. The metallic stud is carried by the disc turning in
electric contact with the metallic ring fixed to the non-metallic dial m the said
ring u being in electrical communication by the coiled spring with the insulated
terminal y of a voltaic battery or other source of electricity; y' is the other terminal
of the voltaic battery fixed to and in electric contact with the case of the
instrument.
.2
The metallic stud t is moved in one or other direction so as to bring it opposite
that part of the graduated dial m which indicates the temperature at which it is
desired that the alarm shall be brought into operation in the following way. The
face of the rotating disc carrying the metallic stud is made into teeth at t³ with
which teeth the pinion t gears the said pinion t being carried by an axis passing
to the outside of the case and being insulated from the case. By fitting a knob or
key on the end of the pinion axis the disc t2 can be rotated and the position of the
stud adjusted opposite the figure on the dial for the purpose hereinbefore
described. When the temperature of the apparatus is raised to the height indicated
by the position of the adjusted stud t the index finger / comes in contact with it and
closes the electric circuit through the disc 2 ring u spring and terminal y. The
closing of the electric circuit operates an alarm in the usual way.

page_text: When a graduated are is used in place of a circular dial the metallic stud
may be moved in a rectilinear path' instead of a circular path for adjusting its
position.
Instead of closing the electric circuit by the index finger coming in contact withi
the adjustable stud t it may be closed by the quadrant or other moving part of the
instrument the said quadrant' or other moving part being in electrical communication
with the insulated terminal y of the voltaic battery.
Having now particularly described and ascertained the nature of my invention
and the manner in which the same is to be performed I declare that I claim
as my invention of "Improvements in heat indicators and fire alarms" :-
First The combination with a heat indicator of a flat coil made of two thin
strips of dissimilar metals or alloys for operating the index finger or pointer of the
heat indicator one end of the coil being fixed and the other end of the coil being
connected directly to the index finger or acting through gearing upon the index
finger substantially as hereinbefore described and illustrated in the accompanying
drawing.
Secondly Converting heat indicators of the kinds referred to in Claim 1 into
fire alarms by the combination therewith of the parts hereinbefore described and
illustrated in the accompanying drawing.
Dated the Sixteenth day of April 1891.
SIDNEY STUART WALKER.