AN IMPROVEMENT IN HEATING BAKERS' OVENS
Year: 1854

page_text: LETTERS PATENT to Alexander Hendry, of Port Glasgow, in the County
of Renfrew, Baker, for the Invention of "AN IMPROVEMENT IN HEATING
BAKERS' OVENS."
Sealed the 16th June 1854, and dated the 17th March 1854.
PROVISIONAL SPECIFICATION left by the said Alexander Hendry at the
Office of the Commissioners of Patents, with his l'etition, on the 17th
March 1854.
I, ALEXANDER HENDRY, of Port Glasgow, in the County of Renfrew, Baker,
do hereby declare the nature of the said Invention for "AN IMPROVEMENT
IN HEATING BAKERS' OVERS" to be as follows:-
Whereas the usual practice of heating bakers' ovens is to permit the flame
and smoke to fill the interior of the oven itself, the fuel being often put on the
grate through the same door by which the bread is put in. This practice pre-
vents the use of the oven while being beated, and causes dust and soot to be
left on the oven floor, all which must be removed previous to the bread being
placed thereon, and it also endangers the bread being injured by soot falling
from the roof. Instead of this plan, I heat the oven by carrying the flame,
smoke, heated air, or other hot products of combustion, within pipes, tubes, or
other suitable conductors, one or more times across the upper part of the
interior of the oven; and I find that by so doing not only do I get a better
heat, and the uninterrupted use of the oven, but I can, by the use of proper.
valves or dampers, sustain or regulate the heat while the bread is being baked,.
a circumstance I find of much importance. The inside of the oven can also:
be kept always perfectly clean, and the roof and sides may be whitewashed.
I

page_text: can also have gas constantly burning within the oven, and, by means of a ther-
mometer fixed in a suitable place, can at any time ascertain whether the proper
heat is maintained. I find that pipes of fire clay, of about 10 inches diameter,
suit the purpose very well, but I do not confine myself to any particular kind
or size of pipe. The pipes are fixed a short distance below the roof of the
oven, and are supported by having their ends and the elbows (or curved parts
at the turns) built into the sides or ends of the oven, and they may be also
suspended by metal rods from the roof itself; the ends and elbows (or turns
of the pipes) are furnished with small doors, by which the soot can be cleaned
out when required. In the Complete Specification a more particular de-
scription may be given, but the above description will enable persons skilled
in mechanics, or conversant with the construction & use of ovens, to see what
my improvement is, and how it may be carried out. I am aware that plans
have been tried to get rid of the dirt and smoke; for instance, the flame, &c.
has been carried in flues under the oven, over it, and round about it, but these
have not gone into general use, as either the proper heat is not obtained, or
the expense of fuel is too great. I do not therefore claim as my Invention
any other mode of heating ovens so as to keep them free from smoke, except
the one above described, namely, the placing of the pipes or other conductors
of the heat within the oven itself."
+
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alexander Hendry in the Great Seal Patent Office on the
11th September 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
HENDRY, of Port Glasgow, in the County of Renfrew, Baker, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of March, in the year of our Lord
One thousand eight hundred and fifty-four, in the seventeenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Alexander Hendry, Her special licence that I, the said Alexander Hen-
dry, my executors, administrators, and assigns, or such others as I, the said
Alexander Hendry, 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,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "AN IMPROVEMENT
IN HEATING BAKERS' OVENS," upon the condition (amongst others)..that. I, the

page_text: said Alexander Hendry, by an instrument in, writing under my hand and-seal,
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
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Alexander Hendry, do hereby declare
the nature of my 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, that is to say:-
My Invention consists in heating bakers? ovens by causing flame, heated-air,
or other hot products of combustion to pass through one or more pipes or
other suitable conductors placed within the oven to be heated. The pipes or
conductors may be of such length, diameter, and form; as are' best adapted to
the circumstances, and may be made of fire-clay, cast iron, or other suitable
material. They may be made to rest upon bearing-bars placed across the
oven, or upon the sides or ends of the oven itself, or they may be sus-
pended by metal: rods from its roof, or otherwise fixed in the interior of
the oven, taking care that sufficient space is left for the bread or other sub-
stance to be baked.. I find that a good effect is produced in an oven, having an
interior area of about eight or nine feet square, by laying a continuous series of
cylindrical fire-clay pipes, of about nine inches internal diameter, and about one
inch thick, with spigot and faucet or similar joints, upon three malleable iron
supporting bars, placed across the interior of the oven, and fixed into the sides
of it, so as to leave about eighteen inches of clear space above the sole or floor of
the oven upon which the bread is laid, the series of pipes being bent, and thus
made to traverse the interior of the oven four times, and to convey the flame,
heated air, and other products of combustion circuitously through the oven,
from a furnace at one side of the oven, to a flue or chimney at the other, by
which they escape into the air. It is better that the bends or turns of the
pipes should be curved or rounded, and not angular; and at the bends, and
elsewhere, if necessary, there may be small doors or apertures in the pipes,
which can be temporarily opened for the purpose of cleaning them. The heat
in the oven may be increased or diminished by wholly or partially closing or
opening a damper placed in or over the flue or chimney, and the use of the
damper may be regulated by means of a thermometer placed in the oven beside
or above the door or mouth.
The interior of an oven so heated is kept free of smoke, soot, and ashes;
the heat is quickly got up and easily maintained at the proper temperature;
there is a saving of fuel; the oven can be used continuously, without stopping

page_text: to re-heat it; a gas light may be kept burning within the oven, so as to guide
and facilitate the operations, and with a properly constructed furnace the
issue of smoke from the flue or chimney may be almost entirely avoided.
My improvement can be adapted to ovens now in use; for the present
"chauffer" or other furnace now used can be altered, so as to be fed from the
outside, and enclosed so that no smoke or flame can get into the oven; and the
pipes are then led from the furnace through the oven to the chimney, and are
easily fixed and supported, as already described, care being taken that sufficient
space is left between the sides of the oven and the ends of the pipe-bends to
allow for their insertion into and withdrawal from their sockets; and also that
the bends are not made too large to go into the door of the oven about to be
altered..
I am aware that ovens have been constructed and heated in various ways,
so as to keep the interior of the oven free from dirt and smoke; and I there-
fore do not claim as my Invention all methods of attaining that result; nor
do I confine myself to any particular kind or form of pipes or conductors;
but what I do claim as my Invention is, the heating of bakers' ovens, by
passing flame, heated air, and other hot products of combustion, through
one or more pipes, or other suitable conductors, placed within the oven
itself.
In witness whereof, I, the said Alexander Hendry, have hereunto set my
hand and seal, this Fifth day of September, in the year of our Lord
One thousand eight hundred and fifty-four.
ALEXR (L.S.) HENDRY.