Improvements in Electro-heating Apparatus.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Electro-heating Apparatus.
1. CHARLES EDWIN CARPENTER, of the City of Minneapolis, County of Hennepin,
and State of Minnesota, United States of America, Electrician 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 :-
This invention relates to improvements in electro-heating apparatus, in which,
heretofore, a carbon resistance has been employed for heating the body by which it
is enclosed. This method however, is objectionable not only because of the great
expense involved in the use of the carbon resistance, but also because of the liability
to short circuiting, the inequality in the distribution of heat, and the constant danger
of fracture thereof, due to concussions to which the body is subjected, especially if
of a movable form, such as a sad iron, foot rest, or other form of device to which
electro-heating apparatus is attached, as a result of which the utensil would imme-
diately become useless, and require complete disconnection and the substitution of a
new resistance, thereby involving both time and expense.
The object of this invention is to utilize, economically the heating effects produced
by passing a current of electricity through a conductor of high resistance and small
capacity, for the purpose of heating stoves, laundry machinery, flat irons and similar
utensils by producing heat in, and confining it to such part or parts only of the utensil
as is desirable.
Another object is to prevent the heat thus developed from being transmitted, either
by conduction or radiation, to other parts of the same body, or to other bodies than
those it is desired to heat, and to combine in the maximum degree in an electro
heating apparatus, cheapness, durability, compactness and simplicity of construction.
A further object is to have a metallic resistance, and of such character that it may
not only be readily and quickly attached to and detached from the utensil but may
be conformed to any desired configuration of surface to be heated, and so arranged
as to operate directly upon, and uniformly heat all parts of the surface.
And finally, to dispense with the necessity for chambering or grooving the body of
the utensil for reception of the resistance, which has heretofore been found necessary
by reason of the peculiar character of the resistance employed, as a result of which
the utensil cannot be heated uniformly throughout, or near the edges thereof; and
to have a resistance of such a character that no chambering is required and which
cannot be fractured when once in its operative position.
These objects are attained by the devices illustrated in the accompanying drawing
in which
Figure 1, represents a plan view of a cooking stove embodying my invention.
Figure 2, a similar view showing the top or heating plates of the stove removed,
more clearly disclosing the arrangement and disposition of the resistance to the e
said plates..
Figure 3 an enlarged transverse section on the line 3, 3, of Figure 1.**
Figure 4, illustrates the application of my invention to a laundry or other heating

page_text: And Figure 5, its application to a sad iron.
Similar letters of reference indicate the same parts in the several figures of the
drawings.
My invention broadly consists in interposing between the surface plate to be
heated, and the body supporting the same, a reflex metallic resistance, between
which and the surface to be heated, lies an electric insulator, and between which
and the body lies an electric insulating non-conducting heat material for confining
the heat to the surface plate.
This general construction is applicable to numerous forms of apparatus and
utensils, regardless of their shape or contour, and, I have therefore illustrated in
the drawings only the more common forms of utensil for which my invention
is especially adapted and which are sufficient to disclose the adaptability thereof to
various uses.
Referring now in general terms to the construction common to all of the forms
illustrated in the drawings let A represent the main body, whether stove, roller or
sad iron, or any other desirable form of utensil, and B the surface plate to be
heated secured together by means of screws, C or in any other well known and
convenient manner, between which are interposed, first a sheet of asbestos cloth or
card board, D or any other suitable electric insulating non-heat-conducting substance
lying next to the body of the utensil, to the opposite or outer surface of which is
secured the metallic resistance E consisting of wire, of a refractory character
reflexed back and forth over the surface of the asbestos sheet as illustrated in
Figure 2 and preferably secured thereto by any convenient form of fastening, such
as sewing with an asbestos thread, staples and numerous other devices well known in
the arts.
This metallic resistance is separated from the surface to be heated by another
sheet F of substantially the same size and contour as the sheet D, composed of some
electrical insulating substance which is non-combustible, and of just sufficient thick-
ness to prevent the wires, or other material used as a resistance, from coming into
contact with the surface plate to be heated, such for instance, as very thin asbestos
paper mica, or any other material that fulfills the above requirements it being under-
stood that this sheet F, while a non-conductor of electricity, should be a fairly good
conductor of heat, while the sheet D, on the contrary, should be not only an electric
insulator, but a non-conductor of heat, for which reason I prefer that the sheet D
should be of thick asbestos and the sheet F of thin mica.
The body A, is preferably recessed immediately back of the insulating sheet D, to
any desired depth leaving only thin walls around the sides thereof, which recess is
filled with a packing G of asbestos felt, mineral, wool or some other substance which
is a non conductor of heat, and which in conjunction with the asbestos sheet D laying
behind the resistance wires, acts as an insulator for the heat evolved from the
resistance and almost perfectly confines the heat to the surface-plates preventing it
from being wasted in the atmosphere, or being conducted to bodies other than those
it is desired to heat, and from the construction described, it will readily be seen,
that while the dissipation of beat by radiation is prevented by this layer and packing
of asbestos or other non-conducting material, its transmission and conduction and
dissipation is likewise almost wholly prevented, by reason of the only metallic
connection between the heated surface-plate and the body of the utensil, being the
screws or other devices by which they are united together, the asbestos and mica
layers interposing there between at all points.
The use of a wire of a refractory metal as the heat generating resistance, is
prefered, because a large amount of wire can be applied so as to almost completely
cover a surface without any part of the wire coming into contact with any other
adjacent part of the same, or other wire, and being reflexed prevents self induction
when used with. an alternating current, besides which it is well known that the
resistance to the passage through metallic wires of electric currents increases with the
increase of temperature and decreases with a corresponding decrease of temperature,
which principle is of a special benefit in an electro-heating apparatus, such as I

page_text: have described by rendering the utensil self adapting to the various conditions to
which it is subjected.
A further and equally important advantage in the use of a metallic resistance is its
cheapness, and the readiness with which it may be shaped to conform to any surface,
or to any contiguration upon a surface; which may he desirable.
Referring now more particularly to the specific applications of my invention
illustrated in the drawings I will first describe the detailed construction of a stove
embodying my invention, illustrated in Figures 1, 2 and 3.
In this as in all other special appliances, the common features exist, namely, the
body A surface-plate B the resistance E, the electric insulating, but non-heat-
conducting sheet D, and the electric insulating sheet F, between the resistance and the
surface plate; but in this construction the surface plate is preferably divided into a
series of sections H, the meeting edges of which are beveled so as to reduce the area
of the metallic contracting surfaces to the minimum and thus correspondingly reduce
the conduction of heat from section to section, and each of which may be heated
independently of the other or while the others are in a warm or cold condition. Or,
if desired, the sections H, may be subdivided into smaller sections I, each of which
is likewise arranged to be heated independently of the other and having the same
Still further
general rectangular shape, but of less dimensions than sections H.
divisions of the sections may be made by the employment of the circular detached
plates J, fitting within corresponding openings in the main plate and sustained therein
by radial lugs or projections K resting upon and corresponding with recesses in the
main plate or in any other convenient manner.
Each of the sections H, 1 and J, has a resistance or resistances, connected with
the source of electrical energy, independently of all of the other sections, one form of
disposing of the resistance and their connection with the line-wires L, M. being
illustrated in the diagram view of Fig. 2.
For instance, the section H, is provided with two independent resistances, but
both connected with the same source of supply, the resistance being thus arranged
in multiple are, and although separate, operate simultaneously to uniformly heat the
entire plate.
In the plates I, the resistances are shown as connected in independent series for
each plate, while in the circular plates J, two are shown as provided with independent.
resistances, similar to the plate H, and the other with the resistances, in series
similar to those of the plates I.
The resistance of these sections may be controlled by a switch-board of any. desirable
form, such as is well known in the art to which this invention appertains, for
connecting all of the resistances of the section, either in series or multiple are and
for cutting out one or more of the sections, while the remainder are in operation.
or, if desired, all of the resistances of all of the sections may be thrown into a single
series, or any other desired combination, for producing a desired result, such as
the warming of all of the plates, or regulating the temperature thereof to any desired
degree.
Referring now to the heating roller illustrated in Fig. 4, the electro heating
apparatus is identical in every respect with that of the stove illustrated in Figs. 1, 2,
and 3, in so far as relates to the arrangement of the heating surface-plate body and
the insulating materials thereof, as well as the disposition of the resistance wires
between the insulating sheets, the only difference being in the manner of disposing
of the terminals of the resistance and line wires which, in this case, must be adapted
to make constant contact between a moving and a stationary surface, which, however,
may be readily accomplished by having the terminals suitably insulated, and
connected respectively with the insulated metallic rings O, P, mounted upon the
hub or the roller, against which bear metallic brushes Q. R, with which connect the
terininals L, M, of the line-circuit, from the source of electrical energy.
The general contour of this roller, while cylindrical, and differing materially from
the flat surface of the stove, may be beated in exactly the same manner,
the resistance

page_text: wires being reflexed over the surface thereof, just as in the case of the stove, and
by reason of their flexibility, readily conform to the contour of the roller, without
affecting its function as a resistance in the least degree.
So also with the flat-iron illustrated in Fig. 5, are the principal elements of my
invention disposed and arranged in substantially the same manner, as in the construc
tions previously described, the surface-plate thereof, however, being continuous as
best adapted to the work to be performed, and the resistance being reflexed, and
arranged in a suitable manner to cover substantially all of the surface-plate,
not withstanding its irregular contour.
In this case the terminals of the resistance pass upwardly through the body of
the iron to binding posts S, mounted upon an insulating block attached to the iron,
with which engages a metallic spring coupling T, of any desired form, to which
the terminals of the line circuit are attached this coupling serving as a means for
readily detaching the iron from the line wire, and thereby cutting it out of the
circuit.
The shell or body of the various devices to which my invention is applied, is of
just sufficient thickness to withstand mechanical injury, and still form a rigid
structure, the corners, ends or any intermediate portions thereof, being made some-
what thicker than the other portions of the shell, to accomodate the screws which
fasten to it the removable heating surface-plate.
By the employment of a reflexed wire resistance, as described, the heat may be
directed to and confined at the very edges of the surface-plate to be heated, thus
making all portions thereof of a uniform temperature; and when the resistance is
fastened to the detachable sheet or card, a further advantage is gained by the readi-
ness with which the resistance may be changed to suit any voltage of current by
simply taking out one card with its wires, and substituting another with more or
less resistance as required, which is of especial importance where it becomes necessary
to change the source of electrical energy, for in all other devices of this class, so far
as I am aware, the utensil would have to be changed or reconstructed with every
material change in the electrical pressure.
An apparatus constructed in accordance with my invention combines in the
maximum degree cheapness, durability and simplicity, possessing all of the advantages
and none of the disadvantages common to electric heating apparatus, as heretofore
employed, besides having advantages possessed by no other electric heating apparatus,
all as fully herein before set forth.
Having described my invention, what I claim and desire to secure by Letters
Patent is
First. In an electro-beating apparatus, the combination with the body and the
heating surface-plate thereof, of an electrical resistance lying between said body
and plate, a layer of electrical insulating material between said resistance and the
plate, and a layer of electrical insulating non-heat-conducting material between said
resistance and the body, substantially as described.
Second. In an electro-heating apparatus, the combination with the body and the
heating surface-plate thereof, of an electrical resistance consisting of a reflexed
refractory wire lying between said plate and body, a layer of electrical insulating
material between said resistance and plate, and a layer of electrical insulating, but
non-heat-conducting material between said resistance and the body, substantially as
described.
Third. In an electro-heating apparatus, the combination with the body recessed on
the outer face thereof, and the heating surface plate covering said recess, of a packing
of incombustible non-heat-conducting material filling said recess, an electrical
resistance lying between said body and plate, a layer of electrical insulating but non-
heat-conducting material interposed between said resistance and the body, and a layer
of electrical insulating material interposed between said resistance and the heating.
plate, substantially as described.

page_text: Fourth. In an electro-heating apparatus, the combination with the body, and the
removable heating surface-plate, of a detachable layer of electrical insulating and non-
heat-conducting material between said body and plate, an electrical resistance consisting
of a refractory reflexed wire attached to, and removable with. said layer, and a layer
of electrical insulating material between said resistance and the removable heating-
plate substantially as described.
Fifth. In an electro-heating apparatus, the combination with the body and the
sectional heating surface-plate thereof, of a series of independent electrical
resistances, underlying the sections of said plates, a layer of electrical insulating
material between said resistances and the plate, and a layer of electrical insulating
non-heat conducting material between said resistances and the body, substantially as
described.
Sixth. In an electro-heating apparatus, the combination with the body, and the
sectional heating surface-plate thereof, of one or more electrical resistances, under-
lying each section of said plate, a layer of electrical insulating material between said
resistances and the plate, and a layer of electrical insulating non-heat-conducting
material between said resistances and the body, substantially as described.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.