Improvements in Insulating and Supporting Electric Wires Intended to Act as Resistances, applicable as Radiators of Heat for Cooking, Warming, and other Purposes.
Year: 1892

page_text: Date of Application, 24th Sept., 1892
Complete Specification Left, 24th July, 1893-Accepted, 26th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements in Insulating and Supporting Electric Wires Intended
to Act as Resistances, applicable as Radiators of Heat for Cooking,
Warming, and other Purposes.
We ROOKES EVELYN BELL CROMPTON Engineer, and HERBERT JOHN
DOWSING, Engineer, both of Mansion House Buildings, in the City of London, do
hereby declare the nature of this invention to be as follows:-
In using conducting wires embedded in enamel as a means of usefully producing
heat by electricity we sometimes find it convenient to vary the amount of heat to
be applied to the surface of the enamel or supporting plate and for this purpose
instead of applying the conducting wire in the form of a single circuit we apply
two or more circuits arranged electrically parallel to one another with a commutating
device or switch so that each of these parallel circuits may be successively switched
into circuit and thus the amount of electrical energy traversing the apparatus
regulated at will.
The wire used in the parallel circuits need not be of the same electrical resistance
but if in any one of the circuits it is found advisable to use wire or strip of greater
cross section and consequently of greater useful surface its resistance must be such
that the current passed through it from a source having a constant E.M.F. at the
terminals of the apparatus may not raise its temperature to a greater degree than
that of the other wires in parallel circuit with it but of different resistances so as
to avoid the effects of unequal heating and consequently unequal expansion and
liability to crack the enamel. In all such parallel circuits therefore we so proportion
them that the eventual temperature reached under working conditions at the surface
of the conductors will be the same. In large apparatus such as that used for the
heating of ovens each of the parallel circuits may be enamelled separately to its
own support so as to avoid as far as possible the bad results of accidental difference
in the resistances but in smaller apparatus where it is necessary to embed the
several circuits on to one support it is desirable that close attention be paid to
ensure the equality of heat above mentioned.
In certain cases more particularly where electric heating has to be applied to
kettles or pans or other apparatus either of a complicated form or of a highly
ornamental character we find it advantageous to make our metallic support to
which the electric conductor is enamelled separate from the vessel which is to
contain the liquid and attach it to it either by a soldered joint using solder which
will run at a temperature far lower than that at which the more fusible part of the
enamel can be damaged or by a flange joint using bolts or screws or any of the
well known meaus usually employed to make such water tight joints. In making
electrical cooking apparatus for stewing, baking or in fact for any operation which
requires heating to be carried on for a considerable period and which would thus
render the use of electrical energy costly we combine with our electric heating
apparatus carefully arranged methods of coating all surfaces of the apparatus
which are not intended to usefully radiate heat with non-conducting substances in a
manner well understood so as to prevent loss of heat. For instance in ovens to be
heated electrically we make the whole of the external casing of two thicknesses of
metal and pack the whole of this space full of silicate or slag wool or asbestos
waste, or any of the other efficient but inodorous non-conducting compositions may
be used.
Dated the 24th day of Sentember 1892.

page_text: COMPLETE SPECIFICATION.
Improvements in Insulating and Supporting Electric Wires Intended
to Act as Resistances, applicable as Radiators of Heat for Cooking,
Warming, and other Purposes.
We ROOKES EVELYN BELL CROMPTON, Engineer, and HERBERT JOHN
DOWSING, Engineer, 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:-
In using conducting wires embedded in enamel in the manner described in respect
of the Complete Specification of application for Letters Patent No. 17091 of even
date herewith as a means of usefully producing heat by electricity we sometimes
find it convenient to vary the amount of heat to be applied to the surface of the
enamel or supporting plate and for this purpose instead of applying the conducting
wire in the form of a single circuit we apply two or more circuits arranged
electrically parallel to one another with a commutating device or switch so that
each of these parallel circuits may be successively alternatively or otherwise
switched into circuit and thus the amount of electrical energy traversing the
apparatus regulated at will. The wire or equivalent resistance used in the parallel
circuits need not be of the same electrical resistance but if in any one of the
circuits it is found adviseable to use wire or strip of greater cross section and
consequently of greater useful surface its resistance must be such that the current
passed through it from a source of energy having a constant. E.M.F. at the
terminals of the apparatus may not raise its temperature to a greater degree than
that of the other wires in parallel circuit with it but of different resistances so as
to avoid the effects of unequal heating and consequently unequal expansion and
liability to crack the enamel. In all such parallel circuits therefore we so
proportion them that the eventual temperature reached under working conditions
at the surface of the conductors will be the same.
Fig. 1 shews a part of a heating plate in underside view 1, 2, 3, 4 being separate
or independent parallel circuits, each circuit is attached to a terminal as 5, 6, 7 or 8.
9, 10, 11 and 12 indicate switches of ordinary and suitable character for switching
one or more of these circuits into connection with wire 13. In large apparatus
such as that used for the heating of ovens each of the parallel circuits may be
enamelled separately to its own support so as to avoid as far as possible the bad
results of accidental difference in the resistances but in smaller apparatus where it
is necessary to embed the several circuits on to one support it is desirable that close
attention be paid to ensure the equality of heat above mentioned.
Fig. 2 illustrates this construction 1, 2 being circuits and the separate strips of
enamel and 6 the base plate on which they are applied.
In certain cases more particularly where clectric heating has to be applied to
kettles or pans or other apparatus either of a complicated form or of a highly
ornamental character we find it advantageous to make our metallic or other
rigid support to which the electric conductor is enamelled separate from the
vessel which is to contain the liquid and attach it to the ornate or other
valuable vessel in some cases by a soldered joint using solder which will run
at a temperature sufficiently low (say lower than that at which the more
fusible part of the enamel can be damaged) in order to allow of the heating
plate becoming detached from the vessel to be protected in case of overheating
or we connect the heater by a flange joint using bolts or screws or any of the
well known means usually employed to make such connection between the heater
and the heated vessel as shall ensure good heating surface contact.
Fig. 3 shews the underside of a cooking pan a with heater the enamelled
heater with helical circuit 6* bedded and covered therein.

page_text: which the electric conductors are enamelled in the manner herein before set forth,
separate from the vessels which are to contain the liquid or matter to be heated and
to attach it by a soldered joint composed of solder fusible at a temperature
sufficiently below the fusing point of the most sensitive portion of the enamel,
substantially as set forth.
7. The methods of attachment between metallic supports, used in the application
of electric heating to kettles, pans or other apparatus of complicated or highly
ornate character and the vessels which actually contain the liquid substantially as
and for the purposes set forth.
Dated the 22nd day of July 1893.
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for the Applicants.

page_text: Fig. 4 is a vertical section thereof 62, 62 are terminals.
Fig. 5 shews a convenient method of effecting such connection a shews the
bottom of the vessel b the enamelled heater ca casing to hold up the heater
acted by a screw d passing through the casing c into a piece of metal formed
on or attached to the wall or bottom of the vessel.
In making electrical cooking apparatus for stewing, baking or in fact for any
operation which requires heating to be carried on for a considerable period and
which would thus render the use of electrical energy costly we combine with
our electric heating apparatus carefully arranged methods of coating all surfaces
of the apparatus which are not intended to usefully radiate heat with non-
conducting substances adapted to prevent such radiation in a manner well
understood and thereby prevent loss of heat. For instance in ovens to be heated
electrically we make the whole of the external casing of two thicknesses of
metal and pack the whole of this space full of silicate or slag wool or asbestos
waste, or any of the other efficient but inodorous non-conducting compositions
may be used.
Fig. 6 shews a part of such double walls with intervening packing.
Fig. 7, shews to a smaller scale an exterior of such an oven, part of one side
wall a
being broken away to shew the non-conducting filling a between the said
inner and outer skins.
The whole, or substantially the whole of the interior walls of this oven may be
lined with plates having enamelled surfaces imprisoning the resistances or circuits
in their enamelled substance and constructed and arranged substantially as described
in respect of Fig. 1 or Fig. 2 and of these paris, or the whole may be thrown into
circuit at one time according to the heat being required, generally or locally as in
browning portions of food in culinary operations.
It is necessary to enlarge or provide an enlargement of the ends of the
resistances or circuits as at 2 Figs. 1, 2, 3 and 4 and in order to avoid burning or
injury to the small section circuits &* a portion of the enlarged area of the circuit
wire adjacent to the wire itself is embedded in and covered by the insulating
enamel b¹.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The method of arranging and combining the resistances with enamelled heating
plates of the character described, so that the amount of heat employed may be
varied to the requirements of the case substantially as set forth and shewn with
reference to Fig. 1.
2. The method of constructing enamel heating surfaces of the character
described with separate parts having independent resistances as and for the
purpose set forth.
3. The combination or arrangement of a composite enamelled heating plate of
the character described with a vessel or body to be heated substantially as set forth
and illustrated by the drawings.
4. An electrically heated culinary oven or other like electrically heated heating
chamber the arrangement and use of parts constructed substantially as and for the
purpose set forth.
5. In apparatus for use in electric heating, cooking or analogous purposes the
arrangement or combination and application of wire or strip conductors of the
electrical energy embedded in the enamel attaching them to the metal plates used
to develop and apply the heat, in two or more circuits arranged electrically parallel
to one another with commutating devices or switches so that the amount of electrical
energy traversing the conductors may be regulated by selection of the conductor or
conductors employed substantially as set forth.
6. In the application of electrical heating means to kettles, pans, or other
analogous culinary or heating apparatus the employment of metallic supports to