AN IMPROVED HEAT. INDICATOR
Year: 1859

page_text: LETTERS PATENT to Charles Neale May, of Devizes, in the County of
Wiltshire, Engineer, for the Invention of "AN IMPROVED HEAT.
INDICATOR."
Sealed the 7th June 1859, and dated the 18th January 1859..
PROVISIONAL SPECIFICATION left by the said Charles Neale May at the
Office of the Commissioners of Patents, with his Petition, on the
13th January 1859.
I, CHARLES NEALE MAY, of Devizes, in the County of Wiltshire, Engineer,
do hereby declare the nature of the said Invention for "AN IMPROVED HEAT
INDICATOR," to be as follows :-
This instrument, although applicable to various other purposes, has been con-
structed more particularly for shewing the heat of ovens for culinary operations."
It consists of an external face or dial, upon which are marked figures'
indicating the degree of heat to which the apparatus is exposed. Internally,
there is a semicircular compound bar of brass and steel, one end of which is
firmly secured to the frame or case of the apparatus, the other end, which is
free to move, presses upon the short end of a lever, the opposite end of which
carries a toothed segment gearing into a pinion on the axis of a hand or
pointer which traverses round the dial face; at ordinary temperatures this"
pointer stands at zero, but the action of heat upon the compound metal bar'

page_text: causes it to expand and press upon the lever, giving motion through the
toothed segment and pinion, to the pointer, which moves round the dial until
it points to a number that indicates the heat of the oven. By means of this
apparatus, therefore, the heat of an oven may be easily regulated, so as to be
suitable for the baking of meat, pastry, and other culinary operations.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Neale May in the Great Seal Patent Office on the
12th July 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
NEALE MAY, of Devizes, in the County of Wiltshire, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of January, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Charles Neale May, Her special licence that I, the said Charles Neale
May, my executors, administrators, and assigns, or such others as I, the said
Charles Neale May, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
éxercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "AN IM-
PROVED HEAT INDICATOR," upon the condition (amongst others). that I, the
said Charles Neale May, my executors or administrators,. by an instru-
ment in writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and in
what manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six.calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Charles Neale May, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
This instrument, although applicable to various other purposes, has been
constructed more particularly for shewing the heat of ovens for culinary
operations. It consists of an external face or dial, upon which are marked

page_text: figures indicating the degree of heat to which the apparatus is exposed.
Internally there is a semicircular compound bar of brass and steel, one end of
which is firmly secured to the frame or case of the apparatus, the other end
which is free to move, presses upon the short end of a lever, the opposite end
of which carries a toothed segment gearing into a pinion on the axis of a hand
or pointer which traverses round the dial face; at ordinary temperatures
this pointer stands at zero, but the action of heat upon the compound metal
bar causes it to expand and press upon the lever, giving motion through the
toothed segment and pinion to the pointer, which moves round the dial until
it points to a number that indicates the heat of the oven. By means of this
apparatus, therefore, the heat of an oven may be easily regulated, so as to be
suitable for the baking of meat, pastry, and other culinary operations."
And in order that the same may be more fully understood, reference is
had to the Drawings hereunto annexed, and to the letters and figures marked
thereon.
Figure 1 is a front view, and Figure 2 a back view (the outer case or
covering being removed) of a heat indicator constructed 'agreeably to this my
Invention. The front view, Figure 1, shews a dial face, on which are marked
a series of numbers corresponding to certain degrees of heat. In front of this
dial face there is a hand or pointer which moves round with increase of
temperature, thereby indicating the amount of heat to which the apparatus is
exposed. In Figure 2, A, A2, is a semicircular compound bar, composed of
two strips, one of brass and one of steel, one end of which is firmly secured to
a block of metal at A2; the other end of the bar presses against the short end
of a lever B, the outer end of which carries a toothed segment b, taking into
and turning a pinion on the axle of the hand or pointer shewn in Figure 1.
C is a spring pressing against the opposite side of the lever B, and keeping it
in contact with the compound bar A; D is a regulating screw. When
exposed to the action of heat, the unequal expansion of the two metals
increases the curvature of the bar A, causing it to press against the lever B,
and by means of the toothed segment and pinion to give motion to the band
or pointer, the amount of traverse of which indicates the degree of heat to
which the apparatus is exposed.
Although I prefer to use a compound metallic bar, a ring of single metal
of a L-section will answer the purpose almost as well as the compound bar.
I am aware that the unequal expansion of compound metal bars by heat has
been long known, and I lay no exclusive claim to that arrangement for
thermometric purposes; what I claim as new and constituting my Invention
is, the construction of an improved heat indicator for culinary and other

page_text: purposes, substantially as herein-before described and shewn in the ac
companying Drawings.
In witness whereof, I, the said Charles Neale May, have hereunto set
my hand and seal, this Thirteenth day of June, in the year of our
Lord One thousand eight hundred and fifty-nine.
Witness,
THO. JA. HEARD,
Justice of the Peace for the
Borough of Devizes.
CHAS. NEALE MAY. (L.S.)