Improvements in Electro Magnetically Heated Receptacles and Articles.
Year: 1893

page_text: Date of Application, 10th Jan., 1893-Accepted, 1st Apr., 1893
COMPLETE SPECIFICATION.
Improvements in Electro Magnetically Heated Receptacles and
Articles.
I WILLIS MITCHELL Electrician of Malden, in the County of Middlesex and
State of Massachusetts, United States of North America, do hereby declare the
nature of my 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 has for its chief object to utilize more perfectly in electrical
heaters for household and other uses the heat derived from magnetic lag or
hysteresis in addition to the heat derived from resistance, the magnetism being
generated in the body of a receptacle or utensil or in a part thereof composed of
magnetic metal. To this end, I provide the bottom or body of a receptacle with
projecting studs or cores to which heaters including wire helices in electric circuit
are applied, the studs and preferably also the body of the vessel being of magnetic
metal. I sometimes make use of the same principle and construction, with the
necessary difference of form in flat plates capable of use as a frying pan or gridiron
and in other culinary article not intended to contain but to support.
In the accompanying drawings,
Figure 1 represents in vertical section a coffee pot embodying my invention;
Figure 2 represents in detail perspective the bottom part thereof and heaters,
also suitable to other vessels and articles;
Figure 3 represents in perspective one half of a melting pot or glue pot,
sectioned through the middle to show the studs and heating devices j
Figure 4 represents a similar view of a modified form of the same;
Figure 5 represents a side elevation of a frying pan constructed according to my
invention;
Figure 6 represents a plan of the same; and
Figure 7 represents a detail view, on a larger scale, of one of the heaters
employed.
A designates projecting studs of magnetic metal on a body preferably of the
same having a wire B, which forms part of an electric circuit, wound in helices
about each of them. As shown in Figure 7, the said wire is wound about
successive concentric cylinders C of asbestos or other insulating material, which
keep the successive concentric helices of each heater apart. The winding is at
about the interval of five times the width of the wire; that is, each winding of
the wire is in a space about ten times its own breadth. This is found to give
results in the way of heating beyond those obtained by resistance, independent of
the magnetic material used. Each stud A has therefore a tubular or hollow
cylindrical heater fitted on it consisting of alternating helices of wire and
cylindrical asbestos partitions with a metal cap or casing. The wire B runs from
heater to heater connecting all.
Very often as shown in Figure 1 the studs are formed only on the bottom of a
receptacle or article, the said bottom being made concave as at d to leave room for
them. The plate or body D of metal on which they are formed need not include
the whole article, but may as in this instance, be merely the said bottom, the
remainder of the vessel or article being of non magnetic metal. As shown in
Figure 4 the said studs are formed on the bottom of a melting pot or glue pot E
which is integral and of magnetic material. The studs and heaters are hidden
and protected by a supporting casing F on which the said pot rests.
Figure 3 shows the sides as well as the bottom of the pot provided with such
studs and their heaters and enclosed in a supporting casing F.. A horizontal
flange on the upper edge or rim of the said pot rests on the upper edge of the

page_text: said casing and the pot is supported thereby. The studs at the bottom might be
entirely dispensed with, and those at the sides may be used either alone or with
the bottom ones on receptacles or articles of varying shapes and for many
purposes..
When a frying-pan or similar article is made according to my invention the
studs are formed on the under side thereof and the body is simply a flat plate G of
magnetic metal.
Whatever the shape or function of the vessel or article the operation is the
same. When the electric current passes through the wire B the studs A and
the magnetic plate or body to which they are attached are heated partly by the
resistance of the wire, partly by the induction between adjacent coils of the wire,
partly by some not fully understood effect of the especial method of winding, but
also largely by the heat due to the magnetic lag or hysteresis. This heat is
communicated to the remainder of the receptacle or article when that is not all of
magnetic metal.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1st. A receptacle consisting of a hollow body of magnetic material provided
with studs and having electrical heaters applied thereto in such manner as to
magnetize it for the purpose set forth.
2nd. A receptacle or article consisting of a body having studs of magnetic
material formed thereon, in combination with wire helices which are in electric
.circuit and magnetize the said studs for the purpose set forth.
3rd. In a receptacle or article, a body of magnetic material having studs of the
same material, in combination with electric heaters fitted on the said studs, each
heater consisting of a series of continuous wire helices and alternating cylindrical
partitions substantially as set forth.
4th. A hollow receptacle having its bottom formed of a plate or body of
magnetic metal provided with studs of the same, in combination with a wire
wound about the said studs and forming part of an electric circuit, the said wire
serving to magnetize the said studs and body or plate and thereby heat the same
beyond the heat due to resistance, substantially as set forth.
5th. A receptacle having its bottom composed of magnetic metal, concave and
provided with studs of the same material, in combination with electrical heaters
which include wire helices, and are fitted on the said studs for the purpose set
forth.
6th. A receptacle consisting of a hollow shell of magnetic material provided
with cores in combination with an electric conductor applied thereto so as to
magnetize the said cores and an exterior shell or casing substantially as set
forth.
7th. A receptacle consisting of a hollow body provided with magnetic cores or
studs in combination with an electric conductor applied to the said cores or studs
to magnetize the same for the purpose set forth.
Dated this Sixth day of December 1892.
WILLIS MITCHELL.