Electrical Heating Appliances Formed of Artificial Stone.
Year: 1898

page_text: Date of Application, 24th Aug., 1898-Accepted, 3rd Dec., 1898
COMPLETE SPECIFICATION.
Electrical Heating Appliances Formed of Artificial Stone.
We, JOSEF FRANZ BACHMANN, Engineer, of VII Kaiserstrasse 81, ADOLF VOGT,
Engineer, of I Lothringerstrasse 5. CARL CAMILLE WEINER, Gentleman, of
I Elisabethstrasse 3, all of Vienna, Austria, ALBERT KÖNIG, Banker, of Budapest,
Hungary, DR. JOSEF KIRCHNER, Chemist, of I Elisabethstrasse 3, Vienna, and
DR. ALEXANDER JÖRG, of I Opernring 1, Vienna, Austria, Chemist, do hereby
declare the nature of this invention and in what manner the same is to be per-.
formed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to electrical heating apparatus constructed of an artificial
stone consisting of a moulded and burnt mixture of non-conducting bodies such
as clay, cement, porcelain, with conducting bodies such as carbon, metal, etc. or
any other electrical resistance material may be used whose properties allow of
its being applied in the construction of the apparatus hereinafter described.
Examples of such compositions are to be found in the material manufactured
according to the invention claimed in our previous Patent No. 15238 of 1897
and Adolf Vogt's Application for Letters Patent No. 18156 dated August 23rd
1898. This artificial stone can have imparted to it a substantially constant
resistance through a considerable range of temperature, or one that increases
or decreases with the temperature, in a required manner within certain limits;
it is therefore particularly adapted to the manufacture of electrical heating
apparatus, such as stoves, cooking stoves, boilers, baking dishes, cooking utensils,
hot plates or rechauds, soldering irons, heaters for curling tongs and flat irons,
smelting furnaces and crucibles, electrically heated floors, ceilings, walls, etc. in
which the electrical currents are converted into heat, and thus utilised.
Apparatus constructed of such artificial stone are divided into those which
serve for the heating of a metal from within outwards, such as soldering irons,
flat irons, ironing rollers, and singeing apparatus, and into apparatus for cooking,
baking, and heating purposes generally.
The accompanying drawing shews in Figs. to 21 a number of such electrical
heating apparatus.
Figs. 1, 2 and 3, shew soldering irons the metal body f of which is heated
from within outwards by an inserted rod shaped resistance body a.
The body a can be insulated from the iron f by means of an insulating
material, by air insulation, by a glazing or by enamelling or advantageously
by the process hereinafter described which is particularly suitable for crucibles
and smelting furnaces. The insulation by means of glazing or enamelling is
done in precisely the ordinary way that any one conversant with the art would
adopt. In the case of enamelling, the choice of enamel will be determined by
the nature of the metal to be enamelled. In the case of glazing, the body a
may be glazed in the manner in which pottery is glazed. According to the
special method referred to above the body is constructed with a slightly lower
resistance than that which it is required to have in use, it is then provided with

page_text: contacts, and on being included in an electric circuit it is raised to about a white
heat. By this means the graphite burns out of the surface of the body a, and
this is consequently provided with an insulating coating which is however porous;
it is. then covered with a paste of the non-conducting component of the resistance
material (e.g. alumina), with water, or is dipped into a solution of a salt of such
non-conducting component (e.g. "aluminium nitrate or sulphate) which on heating
is converted into oxide. By either of these modes repeated if necessary, the pores
of the surface become filled up with an insulating material.
The point or end of the body a which is in contact with the soldering iron fis
galvanised or made of metal for determining the path of the current. The
body may also be made with different specific resistances in its different parts,
in order to produce the greatest heat development at the proper place.
One of the contact wires is connected to the resistance body a by means of
a screw, while the other one is led away from the soldering iron. In place of
this second wire the metal tube b can be advantageously used as conductor
(Figs. 1 and 2) which passes up to the handle. If at the same time the length
through which the current passes to be capable of regulation this can be
effected as shewn at Fig. 3, by means of an adjustable screw h, screwed into a
boring in the resistance body. The screw his traversed by the major part of
the current and so by screwing the screw in or out, the length of the resistance
body traversed by the current is altered, and hence the heat developed can be
regulated.
Fig. 4 shews a flat iron the metal body f of which has a hollow for the recep-
tion of the tubular resistance or heating body a.
The latter is connected at its
two ends with insulated conducting wires b (in a similar manner to Fig. 3)
which are led to contacts.
The insulating layer can either be provided on the surface of the heating
body a or on the inner surface of the metal body f.
The property of the material of such heating bodies, that it can be glazed
after the application thereto of the contacts, and the specific resistance be made
of any desired degree, facilitates a simple and cheap manufacture of heating
devices, cooking utensils, etc. having a high degree of efficacy.
Figs. 5 to 10 shew heating or rechaud plates.
The contact wires b, b₁₂ are arranged in circular grooves i of the heating
body a, in which they are secured by means of a conducting cement (Fig. 9).
The body which is glazed after the insertion of the wires, is arranged, as shewn
at Fig. 5, for switching the current for producing different heating effects. The
current can either pass from wire to the wires and 2, whereby the greatest
heating effect is obtained, or it can pass from 6 to only one of the two wires b
or 2 whereby a fractional degree of heat will be produced corresponding to the
distance between the respective wires, or it can pass from 6 to 62, in which
case the heating effect will be a minimum. The plate a is suitably mounted,
with handles and is provided with a three-pole plug contact; it may however
bo arranged with only two or more than three poles.
The rechaud shewn at Fig. is intended in particular for heating pots, and
can be made of any desired height, so that the pot is enclosed to a greater or less
extent of its height. The heating body a is formed with a lateral slot for the
passage of the handle.
The practically non-conducting lower part or foot a* contains the binding
posts for the contact wires b, b'.
The rechaud shewn in plan and side view at Figs. 7 and 8 is constructed
wholly of resistance material a, which has the form of a disc bent downwards
at the periphery and provided with a handle the disc having concentric wires b, b¹
imbedded in it in the described manner, and connected with the lateral contact
pins.
Fig. 10 shews another form of rechaud in which the heating body a consists
of a plate galvanised on both sides, which is introduced from below into a

page_text: casing k, and is held by means of a setting screw a, pressing against a spring i
and screwing through the bearer m.
Between the spring and screw is inserted an insulating plate o, and the
current, which is led to the under side of the rechaud plate
passes through
this to the upper galvanised surface and into the casing, or if this be insulated
from the rechaud plate, into the second contact wire attached to the latter.
The resistance material provided with inserted contact wires can also be made
in the form of rings or plates for the manufacture of ring or plate heating or
boiling apparatus, which are provided with feet and handles (Figs. 11, 12, 13)
or in the form of tubes as apparatus for heating liquids by circulation (Figs. 14,
15) or heaters for curling tongs (Fig. 16) in which latter case the heating body
can be enclosed and be provided with a contact device which effects the putting
in circuit of the apparatus on the insertion of the curling tongs.
The electrical resistance material with imbedded contact wires may also be
made into the form of cooking vessels, such as shewn at Fig. 17, which vessel
is arranged for change of the current, and whose circular contact wires imbedded
in the bottom and the sides, are led insulated into the non-conducting handle
and into the sides of the vessel and are connected to the contact pins on the
handle.
For imbedding the wire in an insulated manner, the grooves in the heating
hody are lined at those points where the wires are to be insulated, with a pre-
viously burnt and then ground non-conductor, the wire is then introduced and
is covered with a paste of the same non-conductor, after which the groove is
closed by a paste of the same composition as the material of the heating body.
The prepared vessel is then completely glazed before the introduction of the
contact pins, and as in using the vessel the material in the same that is to be
heated is only separated from the heating body by the thin layer of glazing,
a very effectual heating action will be produced.
The vessel can also be galvanised internally and externally, so that the current
will pass from the one metal surface to the other.
The one metal surface can also be made of several separate parts, in order
to be able to heat particular parts. Fig. 18 shews a contact device suitable for
such galvanised vessels. It is provided with spring contacts which on fitting the
device upon the edge of the vessel a are applied against the metal coating on
both sides thereof.
The contacts can also be fixed, or be made as plug contacts.
In the same way as the cooking vessels, may of course be constructed roasting
and baking pans and other vessels serving for heating substances; also heating
stoves for rooms, smelting furnaces and crucibles.
Fig. 19 shews an electrically heated room stove which may be glazed and
provided with any desired number of contacts as also with a commutator for
regulating the heat.
Fig. 20 shews a smelting furnace in vertical section, the heating body a of
which can also be built up of conducting slabs in which contact rings of a good
conductor are imbedded. The insulation on the inner and outer surface is
effected in the previously described manner, and the heating body is provided
with an insulating casing p.
Fig. 21 shews a section of a smelting crucible, which is in like manner insu-
lated on the inner surface and provided with an outer casing to protect it from
loss of heat, this being made of a refractory non-conductor, such as fireclay, or
the casing may be made with an enclosed air space.
In the same way wholly or partially heatable floors, walls, and the like may
be constructed, as also heating bodies suitable for various industrial purposes,
such as laundries, drying rooms &c.
For special purposes, in particular if a very high temperature be required on
the outer surface of the body, the material can also be made of a mixture of
metal and an insulating body.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1. Apparatus for converting electricity into useful heat for the purpose of
heating a metal body from within outwards, consisting of a resistance body a of
rod or tubular form, which is introduced into the metal body f, such resistance
body being made of a mixture of non-conducting and conducting materials
formed into an artificial stone, and being insulated by means of an insulating
coating, a glazing or air insulation, or by first heating the body to a high degree
by an electric current so as to burn out the conducting material from the surface
of a porous heating body, and then soaking it in a liquid insulating material,
substantially as described with reference to Figs. 2 to 5.
2. Apparatus for heating, cooking, baking and smelting purposes made of
artificial stone of the herein described nature, the heating surfaces of which are
formed with grooves in which are imbedded contact wires band which are then
glazed and are galvanized on the outer side or on both sides, the outer side
being provided with a metal covering and if required enclosed in a casing pro-
tecting against loss of heat, substantially as described.
3. The heating, cooking, baking and smelting apparatus herein described.
Dated this 24th day of August 1898.
ABEL & IMRAY,
Agents for the Applicants.