Improvements in Insulating and Supporting Electric Wires Intended to Act as Electrical Resistances, applicable as Radiators of Heat for Cooking, Warming, and other Purposes.
Year: 1896

page_text: Date of Application, 10th July, 1896
Complete Specification Left, 10th Apr., 1897-Accepted, 15th May, 189?
PROVISIONAL SPECIFICATION.
Improvements in Insulating and Supporting Electric Wires
Intended to Act as Electrical Resistances, applicable as
Radiators of Heat for Cooking, Warming, and other
Purposes.
We, ROOKES EVELYN BELL CROMPTON and EDMUND JOHN Fox, Engineers, both
of Mansion House Buildings in the City of London do hereby declare the nature
of tbis invention to be as follows:-
Our improvements relate to the manufacture of electrical heating and cooking
apparatus and more particularly to the methods by which electrical conductors are
attached to metallic or other surfaces by means of non-conducting materials having
a high electrical resistance.
Hitherto such electrical conductors have been attached to the surfaces intended
to be heated by means of vitreous enamels, applied and fused to the surface in
the form of successive layers of enamel, as described by one of us in Patent
No. 17,091 of 1892. In the place of the first coating or supporting enamel described
in the above patent, we apply first to the surface of the metallic or other plate what.
we bereafter for convenience call cement ground. This cement consists of various
forms of alumina or china clays worked into a paste with silicate of soda and
applied to the surface of the plate as a wash either in one or several successive layers.
The cement covered plate can then be enamelled by the process described by one
of us in Patent No. 17,091 of 1892, & the wires embedded in the enamel in the
usual manner.
We find that by covering the plates with this cement ground & enamelling
thereon, the wires cannot sink through to the metal plate, & consequently we avoid
all liability of breakdown due to this cause during manufacture.
In some cases however, we apply this cement to the plates, as described above.
& apply, and embed the electrical conductor in the cement itself. The cement
ground can be afterwards dried, stoved, & if necessary fired at a high temperature.
It however, differs from enamel, in that when stoved, it is of a somewhat porous
nature, & requires, to make it useful for our purpose, to have applied to its outer
surface a partial coating of enamel, fased, & vitrified in the usual manner.
We find this combination of cement ground afterwards made water & air tight
by means of enamel used on its surface, to offer considerable facilities in manu-
facture & easier to accommodate to the varying rate of expansion of the materials
employed, so as to avoid subsequent cracking when the apparatus is in use.
Although we prefer glutinous matter, such as above described for the cement
groundwork, yet we do not bind ourselves to use such materials, but can in some
cases, employ materials, consisting chiefly of silica, or other earths, which can be
made into a paste, & afterwards stoved, & fired, & which, when finished,
leaves our wire embedded in the porous material, requiring a subsequent coating
of enamel to make it useful for our purpose.
We do not confine ourselves to this use of this cement ground applied to the
metallic surfaces, but in some cases we make the whole of the heating portion of

page_text: the apparatus up with some cement groundwork, embed the wire into it,. & eventually
coat it with the enamel.
Dated the 10th day of July 1896.
ROOKES EVELYN BELL CROMPTON.
EDMUND JOHN FOX.
..Win. Brookes & Son,
55 & 56 Chancery Lane, London, Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Insulating and Supporting Electric Wires
Intended to Act as Electrical Resistances, applicable as
4.1
Radiators of Heat for Cooking, Warming, and other
Purposes...
We, ROOKES EVELYN BELL CROMPTON and EDMUND JOHN Fox, Engineers,
both of Mansion House Buildings, in the City of London, 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 :-
Our improvements in insulating and supporting electric wires intended to act as
electrical resistances applicable as radiators of heat, relate to the manufacture of
electrical heating and cooking apparatus and for other purposes and more particu-
larly to the methods by which electrical conductors are attached to metallic, or
other surfaces, by means of non-conducting materials, having a high electrical
resistance.
Hitherto such electrical conductors have been attached to the surfaces intended
to be heated by means of vitreous enamels-applied and fused to the surface in the
form of successive layers of enamels-as described by one of us in the specification
of Patent No. 17,091 of A.D. 1892..
In place of the first coating or supporting enamel described in the above patent
_we apply first to the surface of the metallic or other plate-what we hereafter
for convenience call. "cement ground.""
This cement ground we apply to the metallic or other plate in the form of a
wash or of a paste. The metallic conductors and successive layers of enamel being
then applied on the top of this in the same way as described by one of us in the
patent above referred to.
The chief difference and improvement on the invention described in the specification
of Patent No. 17,091 of 1892, which constitutes part of the present invention,
consists in interposing between the metal conductors and the metal supporting plate
a layer of cement ground which we find considerably increases the insulation
résistance between the resistance wires and metal plate, and also prevents the
resistance wire from sinking through, and coming in contact with the metal plate
and thus forming an earth during manufacture."
In some cases instead of applying the cement ground direct to the metal sup-
porting plate we prefer first to cover the metal supporting plate with a thin layer
of enamel and then on the top of this applying the layer of cement ground thus
sandwiching layer of cement ground between the two layers of enamel.
We find that we can use various forms of alumina or china clays worked into a paste
with silicate of soda or other suitable substance for our purpose.
One mixture which we find answers our purpose very well, consists in a paint
made by mixing equal parts of oxide of iron and lava (commercially known as
"volcanic cement") with a solution of silicate of sodium, diluted with ten times its
volume of water.

page_text: This paint we can apply as described above either for painting over the surfaces of
metal plates or tubes-or as a non-conducting layer interposed between two successive
layers of enamel, but we do not confine ourselves to the use of the above materials.
In some cases however we apply the cement to the plates, as described above, and
apply and embed the electrical conductor in the cement itself.
The cement ground can be afterwards dried-stoved-and if necessary fired at a
high temperature.
It differs however from enamel-in that when stoved it is of a somewhat por.us
nature, and requires to make it useful for our purpose, to have applied to its outer
surface a partial coating of enamel, fused and vitrified in the usual manner.
We find this combination of cement ground afterwards made water and air-tight
by means of enamel used on its surface, to offer considerable facilities in manufacture,
and easier in some cases to accommodate to the varying rate of expansion of the
materials employed, so as to avoid subsequent cracking when the apparatus is in use.
Although we prefer glutinous matter, such as above described, for the cement
groundwork, yet we do not bind ourselves to use such materials, but can in some-
cases employ materials, consisting chiefly of silica, or other earths, which can be
made into a paste, and afterwards stoved and fired.
The essential property of the cement, paste or paint, used as ground work being
that it should be a good non-conductor of electricity, and that it should not soften
at temperatures below those that the enamels fuse at.
We do not confine ourselves to this use of the cement ground applied to the
metallic surfaces, but in some cases we make the whole of the heating portion of
the apparatus up with such ground cement groundwork, embed the wire in it,.
and eventually coat it with the enamel.
Hitherto in order to prevent the resistance wires from sinking through to the
metal supporting plate, an enamel of higher fusing point has been used under the
wire than that used to cover it.
In the present invention however, a layer of a non-conducting infusible substance
is, interposed between the wire and the metal supporting plate which we find offers.
sufficient resistance to the wires, tending, due to their gravity to sink down, to.
prevent their coming into contact with the metal plate.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what we
elaim is-
In the manufacture of means or apparatus for use as electrical resistances;.
applicable as radiators of heat for cooking, warming and other purposes :-
1. The use of a cement, or clay, capable of withstanding high temperatures
without softening-and a good non-conductor of electricity-consisting of various
forms of alumina, or china clays, interposed between the resistance wires and metal
supporting plate, either direct on the metal supporting plate itself, or between two
layers of enamel.
2. The use of enamel for covering over and making water and gas-tight-a
cement or clay in which the electrical resistance wire has been embedded.
Dated the 0th day of 'A 1807
W.M., BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for the Applicants.