Improvements in Electrically Heated Ovens.
Year: 1893

page_text: Date of Application, 10th Nov., 1893
Complete Specification Left, 10th Aug., 1894-Accepted, 10th Nov., 1894
PROVISIONAL SPECIFICATION.
Improvements in Electrically Heated Ovens.
I, FRIEDRICH. WILHELM SCHINDLER, Manufacturer, of Kennelbach near
Bregenz, in the Austro-Hungarian Empire, do hereby declare the nature of this
invention to be as follows:-
Electrical baking ovens are usually constructed in such a manner, that the walls
of the oven (that is the body of the oven itself) are surrounded with a coil of
conducting wire, which during the passage of the electric current gives off its heat
to the body of the oven, which in its turn communicates its heat to the interior of
the oven.
This arrangement produced much waste of heat by radiation; it did
not provide for any means of regulating the application of heat and rendered
repairs difficult.
In order to avoid these defects, I provide the oven with two, three, or four
independent heating bodies, which may be made to slide into suitable guides formed on
In some cases a
the walls of the oven, at the bottom, at the top or at the sides.
single heating body, adapted to slide between guides, may be employed.
The oven is preferably of rectangular shape and closed on all sides, but provided
with a door, or with two doors situated on opposite sides, the front door serving the
usual purpose, while the back door chiefly serves to give access to the heating
bodies and to facilitate their manipulation. As a rule, two heating bodies suffice
for an oven, one at the bottom and one at the top, but in some cases there may
be only one heating body, or there may be heating bodies also at the right and left
wall. The heating bodies are adapted to slide between stationary guides, and each
is connected with the electric supply system or main wires independently of the
others, so that it may be supplied with current alone, or simultaneously with any
or all of the other heating bodies. For some purposes it is important, to vary the
heating effect of the different heating bodies, and especially of the upper one, which
effect attain by causing either the upper or the lower heating body, or both, to
approach the middle of the oven, or to recede from the same, more or less, as may
be required, thus regulating the clear height of the oven or the distance between
the upper and lower heating bodies. In most cases, it is sufficient to render the
upper heating body or plate adjustable, which may be done by arranging in the
oven several guides (or pairs of guides) one over the other, so that the heating
body may be introduced into a higher or a lower guide or pair of guides.
I prefer, however, to adjust the position of the beating bodies by means of a
mechanism, which may be set in action, while the heating bodies are hot.
In the case of an oven having an upper and a lower heating plate, the latter
may, for instance, rest on and between a pair of horizontal guides fixed to the
sides of the oven, while the upper body is fixed to the bottom of a horizontal iron
frame which is moveable up and down by means of a rack extending downward
from the end of the frame and moveable between a pair of vertical guides fixed to
the side wall of the oven. Into this rack gears a pinion actuated from outside by
means of a crank, in order to raise or lower the upper heating plate, which may be
retained at the required height by means of a ratchet wheel and pawl.
As an alternative, the upper heating plate may be suspended at the ends from a
pair of chains running over a pair of rollers, on the axles of which are mounted
tooth wheels or ratchet wheels. The latter are kept in position by a double pawl
fixed on a vertical pin, so that by lifting the latter the rollers are allowed to turn
and the chains to descend.

page_text: Other mechanism may, however, be adapted for adjusting the position of the
heating plates.
Dated this 10th day of November 1893.
FAIRFAX & WETTER,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electrically Heated Ovens...
I, FRIEDRICH WILHELM SCHINDLER, Manufacturer, of Kennelbach near
Bregenz, in the Austro-Hungarian Empire, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
Electric baking and roasting ovens are usually heated by surrounding or lining
the walls of the heating chamber with plates which can be raised to a high
temperature by means of a conducting wire embedded in enamel or other suitable
refractory material.
The present invention has for its object, to apply the heating plates or blocks in
a more advantageous manner, as regards economy of heat, facility of regulation and
facility of repair or exchange.
For this purpose I place the heating plates or blocks in the interior of the
heating chamber and attach or support them in such a manner, that their position
may be easily regulated according to requirements, and that the plates may be
readily drawn out and exchanged.
In the accompanying drawings;
Fig. 1 is a front elevation of an oven embodying my invention,
Fig. 2 is a side elevation of the same,
Fig. 3 a cross section showing the regulating mechanism applied to the upper
heating body,
Fig. 4 a plan of the upper heating plate and its regulating mechanism ;
Fig. 5 represents an electric oven partly in front elevation and partly in vertical
section, with another regulating mechanism;
Figs. 6 and 7 show on a larger scale the regulating mechanism indicated in
Fig. 5, Fig. 7 being a plan of Fig. 6.
Fig. 8 is a vertical section through the back door and the rear part of the
oven.
The oven chiefly comprises a casing a, preferably of rectangular shape and
closed on all sides, but provided with a door, or with two doors situated on opposite
sides, the front door serving the usual purpose, while the back door c chiefly
serves to give access to the heating bodies and to facilitate their manipulation. As
a rule, two heating bodies or plates suffice for a baking oven, one at the bottom and
one at the top, as represented by Figs. 3 and 5, but in some cases there may be
only one heating body (at the bottom), or there may be heating bodies also right
and left along the side walls or parallel to the same.
At those places, where a stationary heating. plate is to be inserted into the oven,
the latter is provided with guides, which correspond in size to the heating plate and
may be arranged in any suitable manner, for instance like those used in a chest of
drawers.
Each heating plate contains an electric conductor connected with the electric
supply system or main wires independently of the others, so that it may be supplied
with current alone, or simultaneously with any or all of the other heating plates,
and that the contents of the oven may therefore be heated from the bottom, or
from the top, or both. For some purposes it is important, to vary the heating
effect of the different heating plates, and especially of the upper one, which object

page_text: I attain by causing either the upper or the lower, heating plate, or both, to
approach the middle of the oven, or to recede from the same, more or less, as may
be required, thus regulating the distance between the upper and lower heating
plates. In most cases, it is sufficient to render the upper heating plate adjustable,
which may be done in various ways, for instance, by arranging in the oven several
horizontal guide ribs or rails (or pairs of guides) fixed to the side walls one over
the other, so that the heating body may be introduced into a higher or a lower guide
or pair of guides.
I prefer, however, to adjust the position of the heating plates by means of
a mechanism, which may be set in action from outside while the heating plates are
hot and without opening the oven.
In the case of an oven having an upper and a lower heating plate and f, the
latter may, for instance, rest on and between a pair of horizontal guides d fixed
to the sides of the oven, as illustrated by Figs. 1 to 4, while the upper body's is
fixed to the bottom of a horizontal iron frame it, which is moveable up and down
by means of a rack extending downward from the end of the frame and
moveable between a pair of vertical guides k fixed to one of the side walls of
the oven.
Into this rack gears a pinion n actuated from outside by means of
a crank, in order to raise or lower the upper heating plate, which may
then be retained at the required height by means of a ratchet wheel mounted on
the axle of the wheel n, and a pawl acting on the said wheel l.
The direction in which the crank I must be turned for raising the heating plate y
and also for lowering the same, is indicated by means of two arrows marked on the
side wall of the oven, as shown by Fig. 2.
Figs. 5 to 7 represent another construction of a baking oven with mechanism for
varying the position of the upper heating plate g. The latter is suspended at the ends
from a pair of chains m m running over a pair of rollers o o; on the axles of which
are mounted tooth wheels or ratchet wheels p p. The latter are kept in position by
a double pawl r fixed on a vertical pin g, so that by lifting the latter the rollers are
allowed to turn, and the chains to descend.
The pin g is surrounded by a helical spring, which tends to press the pin down-
ward, so as to prevent the accidental turning of the wheels p p.
From the rollers oo the chains m m pass upward, behind the pin q, as indicated in
Fig. 6 by dotted lines, and then to one of the sides of the oven.
The electric conductor which passes through the heating plate and heats the
same may extend to one side of the oven, and the oven may have a partition which
separates from the heating chamber a compartment for the said extended portion
of the electric conductor to permit access thereto without opening the oven.
The said partition may be divided into two or more parts, one of which is
moveable with the heating plate or heat body.
This construction is represented by Fig. 8, in which A indicates a metal plate
fixed to the sides of the oven, and A' another metal plate fixed to the upper
heating plate. The two plates A and A' form a vertical partition which divides
the baking space from a compartment formed at the back of the oven. s, and t
are two of the supply wires which pass through the said compartment and supply
current to the heating wires of the plates f and g.
Each heating plate ƒ and g may have one or several heating circuits fed by one
or more pairs of supply wires. Instead of extending the heat bodies into the outer
compartment as shown in Fig. 8, they may be completely enclosed in the baking
chamber, and only the supply wires or conductors caused to extend through the.
partition which is made of one plate fixed to the side of the oven.
The regulating appliances shown and described are only mentioned by way of
example, and I wish it to be understood, that I do not limit myself to any special
mechanism for raising and lowering a beating plate and then securing it in the
desired position, nor do I limit myself to any special shape and arrangement of the
heating plates and of the guides.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In electric ovens, the combination of a heating chamber containing a moveable
heating plate or plates adapted to be heated by electricity, with means for holding
the said plate at various distances from the centre of the heating chamber, substan-
tially as described and for the purpose specified.
2. In electric ovens, the combination of a heating chamber containing a moveable
heating plate or plates adapted to be heated by electricity, with means located
outside the heating chamber for varying the distance of the said plate or plates
from the centre of the said chamber, and then securing it or them in the required
position, while the oven is in use, substantially as described.
3. In electric ovens, a heating chamber containing a moveable beating plate or
several moveable heating plates independent of each other, the said plate or plates
being inserted and held between guides fixed to the walls of the chamber, and
connected with a suitable source of electricity, substantially as described and for
the purposes specified.
4. In an electric baking and roasting oven, a heat body contained in said oven
and provided with an electric conductor a portion of which extends to one side of
the oven, and a partition separating from the oven a compartment for said extended
portion of the electric conductor to permit access thereto without opening the
oven, substantially as and for the purposes described.
5. In an electric baking and roasting oven, the combination with a heat body in
the oven provided with an electric conductor extending to one side thereof, and a
divided partition separating the compartment containing said extended portion of
the electric conductor from the oven, one part of said partition being moveable
with the heat body, substantially as and for the purposes described.
Dated this 10th day of August 1894.
FAIRFAX & WETTER,
433, Strand, London, Agents.