IMPROVEMENTS IN OVENS
Year: 1878

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for the Invention of "IMPROVEMENTS IN
OVENS." A communication from abroad by Girolamo Taddei, of Paris, in the
Republic of France.
aled the 31st January 1879, and dated the 3rd August 1878.
PROVISIONAL SPECIFICATION filed by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 3rd August 1878.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN OVENS." A communication from abroad by
Girolamo Taddei, of Paris, in the Republic of France.
This Invention relates to the construction of portable and stationary ovens, with
continuous or an intermittent action applicable to baking bread or any other sub-
stances, as well as to the drying and heating of other substances, such, for example,
as cocoons of silk.
This improved apparatus, which is so constructed as to enable a uniform though
very elevated temperature to be obtained, is of a cylindrical form, and is provided
at the lower part with a furnace, from which the waste products of combustion pass
through a chimney situated at its upper part.
The casing of the apparatus is composed of 3 vertical cylinders, forming two
annular spaces between them, in which the products of combustion and heated air
are allowed to circulate without coming in contact; the products of combustion
escape through the chimney, whilst the hot air, on reaching the upper part of the
annular space, is directed downwards and passes through the inner cylinder to the
lower part, whence it finally escapes into the chimney through a tube situate in the
centre thereof. This tube, which is fitted so as to be capable of being rotated, has
attached thereto a number of discs, forming shelves upon which the substances or
articles to be baked or heated are placed, and a door is provided in the walls of the
cylinder to facilitate the introduction and removal of the articles.

page_text: The three cylinders forming the casing are closed at their upper ends by a conical
cover communicating with the chimney, whilst the said cylinders are connected at
their lower ends to the furnace. This furnace is covered by a solid plate of cast
iron, carrying the central moveable portion of the apparatus, which is supported on
pivots upon which it is capable of being rotated.
The rotatory motion is imparted to the apparatus by means of a crank handle
fitted on a horizontal shaft, carrying at one end a pinion in gear with a spur wheel
attached to the base of the rotating part of the apparatus.
The furnace is provided with a grate capable of burning all description of fuel, a
number of pipes being arranged at the upper part of the furnace, passing through
the covering plate herein-before referred to. These tubes are surrounded by the
products of combustion, which subsequently pass round the oven by circulating in
the annular space formed by the cylinders or casings, whence they are discharged
into the chimney.
The cast-iron covering plate and the vertical sides of the furnace are provided
with numerous webs, which together with the tubes form a heating apparatus with
multiple heating surfaces.
The air for effecting the baking of the substances placed in the oven enters the
apparatus through orifices arranged at the lower part of a casing, which is fitted
externally round the furnace, so as to form a chamber into which the air first enters,
then passing through the tubes, comes in contact with the metal bottom of the inner
cylinder.
The air, which thus becomes heated, then passes into the annular space formed
by the two inner cylinders of the oven, whence it passes into the interior of the
oven at different levels through openings provided in the inner cylinder, and circu-
lates among the substances placed upon the shelves; it then descends to the lower
part of the oven, to which it is drawn by the effect of the draft in the chimney,
into which it ultimately escapes through the central rotating tube herein-before
referred to.
The course of the heated gases, as well as that of the hot air, and the progress
of the cooking, are regulated by registers suitably arranged, and the apparatus is
protected from external cold by a casing of iron-conducting substance and by a
roof.
In order that the progress of the operation may be continually observed a pyro-
meter and a glazed spy hole are provided in the charging door.
The whole apparatus, that is to say, the cylindrical part and the furnace, is
supported by projections formed upon the sides of the furnace, and bolted firmly to
suitable supports which, when the apparatus is intended to be portable, are carried
on the axle of the wheels of the carriage.
It will be readily understood that by means of this arrangement an elevated and
very uniform temperature will be obtained inside the oven, which is indispensable
for successful baking.
If desired, two apparatus may be arranged on one carriage or platform, and when
the apparatus is portable, particularly when adapted for military purposes, the
chimney may be made capable of being lowered to facilitate the transport.
When the oven is stationary it may be constructed of iron, as herein-before
described, or of brickwork, or any suitable ceramic materials, and may be employed
not only for baking bread or other substances, but also for stoving silk cocoons or
other substances, and even for drying them; in this case, as in the arrangement
herein-before described, the introduction and withdrawal of the substances to be
treated may be effected with the greatest facility, and the operation may be carried
on in a continuous or intermittent manner, with a considerable saving of time
and fuel.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the 3rd
February 1879.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN OVENS." A communication from abroad by
Girolamo Taddei, of Paris, in the Republic of France.
The said Invention relates to the construction of portable or stationary ovens,
with continuous or intermittent action applicable to baking bread, as well as to the
drying and heating of other substances, and in particular of cocoons of silk.
By means of the said Invention a very elevated, and at the same time uniform
temperature is obtained; the heating is effected by means of air, which is itself
heated by the walls of the combustion chamber or furnace, and in the casing of the
oven, in which it is caused to circulate in proximity to the products of combustion,
which heat the upper and the central parts of the apparatus by direct action before
escaping into the chimney.
The substances to be baked or heated are arranged upon discs, forming shelves
capable of rotating around a vertical axis, so that all the contents of the oven may
be brought in succession opposite the door.
And in order that the said Invention may be fully understood, I shall now pro-
ceed more particularly to describe the same, and for that purpose shall refer to the
several Figures on the annexed Sheet of Drawings, the same letters of reference
indicating corresponding parts in all the Figures.
Figure 1 of the accompanying Drawings represents a side elevation of a portable
oven constructed according to the said Invention, mounted on two wheels.
Figure 2 is a plan, Figure 3 a transverse section, and Figure 4 a horizontal section
of the same, all corresponding to Figure 1.
The remaining Figures relate to modifications of the apparatus, and will be
herein-after particularly referred to.
Referring to Figures 1, 2, 3, and 4, the casing of the apparatus is composed of
three concentric cylinders A, B, and C, of sheet iron, forming two annular pas-
sages a, b, between them, and closed at their upper extremities by circular
plates D, E, F, which form two circular air spaces, communicating with the annular
passages a, b; a roof or cover ris also provided above the plates D, E, F. The
lower extremity of the inner cylinder A is closed by a circular plate G forming the
floor of the oven, and the lower extremity of the cylinder B is closed by a cast-
iron plate g forming the cover of a circular furnace H, whilst the lower extremity
of the external cylinder C is closed by a plate I surrounding the sides of the
furnace.
The plate g is provided with a boss, in the centre to which is secured a vertical
bar h, forming a pivot upon which the central movable part of the apparatus.is
supported, so as to be capable of rotating on its vertical axis. Rotary motion is
imparted. to this movable portion by means of a toothed wheel j in gear with a
pinion, the latter being mounted on an axis k¹, provided with a crank handle k³,
for the facility of turning the same.
The movable part of the apparatus is composed of three tubes d, d¹, d", forming
two annular passages L, L', between them; the external tube d¹¹ carries shelves m
upon which the substances to be baked are arranged. These shelves are each
composed of two circular discs of sheet iron, containing a sheet of air between
them.
The products of combustion from the furnace H surround a number of pipes t,
the upper extremities of which pass through the plate g, and communicate with the

page_text: .
space formed immediately underneath the floor of the oven, whilst their lower
extremities pass through the plate I, and communicate with an air space formed
round the furnace by an external casing o. After circulating among the pipes / the
products of combustion pass up the annular passage b, then into the space formed
between the plates E and F, and down the annular passage L, whence they pass
up the passage L', as indicated by the arrows, and escape through a chimney i,
which is hinged to enable it to be lowered when required, in order to facilitate the
transport.
.
The furnace, with its covering plate 9 and tubes t, which are provided with
numerous webs, constitutes a heating apparatus with multiple heating surfaces, and
serves to heat the air employed for the baking, which enters the apparatus through
orifices p at the lower part of the casing o. This air then passes through the
tubes t into the space under the floor of the oven, and enters the annular passage a
and the space between the plates D and E, whence it passes into the interior of the
oven through openings x, and circulates among the substances placed upon the
shelves; it then descends to the lower part of the oven under the action of the draft
caused by the products of combustion in the chimney, into which it ultimately
escapes through the central tube d. The passage of the products of combustion, as
well as of the heated air, is regulated by registers or dampers v and u, and a valve
is provided for the purpose of emptying the apparatus of hót air when required.
A pirometer and a glazed spy hole e are provided, in order to enable the progress
of the apparatus to be watched.
An external case or covering c of nonconducting materials serves to protect the
apparatus from external cold, and internal screens y are provided for the purpose of.
preventing any over-heating or burning of the substances in the lower part of the
oven, whilst external screens prevent any undue loss of heat by radiation at that
part of the apparatus, which is nearest the furnace.
When the oven is not portable, it may be constructed of brickwork and iron, or
of any other suitable materials.
Figures 5 and 6 are respectively an elevation and plan, representing an apparatus
constructed according to the said Invention, as herein-before described, mounted
upon four wheels with a movable fore carriage.
The arrangement will be understood without further description.
Figures 7 and 8 are respectively an elevation and plan of a modification of the
apparatus herein-before described.
In this case two cylindrical ovens constructed according to the said Invention
are employed, enclosed in one external case c' provided with one chimney i, and
heated by one and the same furnace.
Having now described and particularly ascertained the nature of the said Inven-
tion, and the manner in which the same is or may be used or carried into effect, I
would observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before in part recited
Letters Patent is,―
First. The general construction, arrangements, and combinations of parts forming
ovens applicable to the baking of bread or alimentary substances, and to the heating
or desiccation of substances, substantially as hercin-before described, and illustrated
by the accompanying Drawings.
Secondly. The peculiar arrangements of the casing, and the mode of circulating
the air and products of combustion in the apparatus, substantially as herein-before
described.
Thirdly. The system of furnace with webbed plate and tubes for heating the
apparatus, substantially as herein-before described.
Fourthly. The arrangement of the central part of the apparatus, forming the
shelves rotating upon a pivot, in combination with tubes, ensuring the regular
E

page_text: heating of the interior of the oven, and serving for the escape of the hot air and of
the products of combustion, substantially as herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this my Specifica-
tion set my hand and seal, this Thirty-first day of January, One thousand
eight hundred and seventy-nine.
J. HENRY JOHNSON. (L.S)