Improved Means for Electrically Heating Ovens, Hot Chambers, Rooms, and the like.
Year: 1898

page_text: Date of Application, 6th Dec., 1898
Complete Specification Left, 31st Aug., 1899-Accepted, 21st Oct.,
1899
PROVISIONAL SPECIFICATION.
Improved Means for Electrically Heating Ovens, Hot Chambers,
Rooms, and the like.
We, FRANK CHRISTY and LEONARD FELL CHRISTY, Electrical Engineers, both
of Broomfield Road Works, Chelmsford, in the County of Essex, do hereby
declare the nature of this invention to be as follows:--
Our invention relates more particularly to improved means for electrically
heating ovens, hot chambers, radiators, and also other rooms or articles, one of
the advantages of the invention being that the heat can be easily and quickly
controlled.
In applying our invention, for example to an oven, we usually employ several
heaters at the top and several at the bottom, and each may be controlled by a
separate switch. The heater consists of a frame of thin perforated sheet metal
covered entirely or partly with asbestos, mica, enamel, or other suitable insulating
and heat-resisting material, over which we wind a wire or strip of high electric
resistance. The heat of the oven is usually controlled by switching on or off
We may
a larger or smaller number of heaters, or by other well known means.
also apply an automatic method of regulating or controlling the heat of the oven,
chamber, or the like either directly by means of the expansion of metal wires,
rods or strips, or the expansion of liquids, air or gases causing the electrical
heating current to be varied by suitable devices, or indirectly by means of a
relay or similar contrivance, as for instance the rise of electrical resistance in a
conductor when the surrounding space rises in temperature may be utilised to
actuate a relay which can vary the electrical heating current.
The frame of the heaters may be made of slate or porcelain or any other suit-
able material, insted of metal, is so desired.
We do not confine our invention, however, to the use of several heaters at
the top and bottom of the oven or chamber, as the several heaters can be replaced
by one large heater if desirable. We also sometimes put a heater or heaters
at the sides or between the shelves or in the interior portion of the oven, chamber,
or place to be heated, instead of or in addition to the top and bottom heaters.
To get as much length of heating wire as possible on each heater we use a
triangular or square in preference to circular form, and the frame or tube is
preferably perforated or slotted for the double purpose of storing as little heat
as possible in the mass of the heater, thus enabling the heat of the oven to be
attained or altered more quickly, and also sometimes for allowing air circulation
through and around the frame or conductors.
The electrical connection to the heaters is made by means of metal fastenings
of suitable shape such as a hinged or like clamp or wedge, so that by loosening
the fastenings the heaters can be easily taken out and renewed, such renewal
being necessary at intervals owing to the oxidation of the heating wire, one of
our objects being to make this renewal cheap and easy..
The switches or other devices for turning the electric current on or off, or for
regulating the same are preferably fixed on or near the oven, chamber, or the like,

page_text: which may also be provided with a heat indicating device but these switches or
other devices may be at any reasonable distance from the oven or chamber, and
the heat indicating device may be of an electrical or optical character and so
arranged that the temperature may be ascertained at any suitable distance.
Dated the 6th day of December 1808
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent,
For the Applicants.
Improved Means for Electrically Heating Ovens, Hot Châmbers,
Rooms, and the like.
We, FRANK CHRISTY and LEONARD FELL CHRISTY, Electrical Engineers, both
of Broomfield Road Works, Chelmsford, in the County of Essex, 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:
Our invention relates more particularly to improved means for electrically
heating ovens, hot chambers, radiators, and also other rooms or articles, one of
the advantages of the invention being that the heat can be easily and quickly
controlled.
In applying our invention, for example to an oven, we usually employ several
heaters at the top and several at the bottom, and each may be controlled by a
separate switch. The heater consists of a frame of thin perforated sheet metal
covered entirely or partly with asbestos, mica, enamel, or other suitable insulating
and heat-resisting material, over which we wind a wire or strip of high electric
resistance. The heat of the oven is usually controlled by switching on or off
a larger or smaller number of heaters, or by other well known means.
We may
also apply an automatic method of regulating or controlling the heat of the oven,
chamber, or the like either directly by means of the expansion of metal wires,
rods or strips, or the expansion of liquids, air or gases causing the electrical
heating current to be varied by suitable devices, or indirectly by means of a
relay or similar contrivance, as for instance the rise of electrical resistance in a
conductor when the surrounding space rises in temperature may be utilized to
actuate a relay which can vary the electrical heating current.
The frame of the heaters may be made of slate or porcelain or any other suit-
able material, instead of metal if so desired.
We do not confine our invention, however, to the use of several heaters at
the top and bottom of the oven or chamber, as the several heaters can be replaced
by one large heater if desirable. We also sometimes put a heater or heaters
at the sides or between the shelves or in the interior portion of the oven, chamber,
or place to be heated, instead of or in addition to the top and bottom heaters.
To get as much length of heating wire as possible on each heater we use a
triangular or square in preference to circular form, and the frame or tube is
preferably perforated or slotted for the double purpose of storing as little heat
as possible in the mass of the heater, thus enabling the heat of the oven to be
attained or altered more quickly, and also sometimes for allowing air circulation
through and around the frame or conductors.
The electrical connection to the heaters is made by means of metal fastenings
of suitable shape such as a hinged or like clamp or wedge, so that by loosening

page_text: the fastenings the heaters can be easily taken out and renewed, such renewal
being necessary at intervals owing to the oxidation of the heating wire, one of
our objects being to make this renewal cheap and easy.
The switches or other devices for turning the electric current on or off, or for
regulating the same are preferably fixed on or near the oven, chamber, or the like,
which may also be provided with a heat indicating device but these switches or
other devices may be at any reasonable distance from the oven or chamber, and
the heat indicating device may be of an electrical or optical character and so
arranged that the temperature may be ascertained at any suitable distance.
In order that the invention may be clearly understood reference is made to the
accompanying drawings in which
Fig. 1 is side sectional elevation of a small oven provided with only three
heaters.
Fig. 2 is a front elevation of same.
Fig. 3 is a cross sectional view of a heater drawn on a larger scale.
Fig. 4 is a side eleration partly in section of such heater.
Fig. 5 is a side elevation of part of the oven grate or grid taken on line z z of
Fig. 6, and
Fig. 6 is a cross sectional view of such grate or grid.
In such drawings the oven 1 is of ordinary construction and carries three
heaters 2 and a suitable grate or grid 3. The heaters are open at the ends
and are made of perforated metal or gauze 4 covered with asbestos or suitable
covering 5 upon which is wound the resistance wire 6 the size and length of which
is of course proportioned to the current to be employed and the heat it is desired
to generate. The ends of wires 6 are held in place by clamps 7 the lower portions
of which carry the terminals 8 and are also employed with suitable insulating
pieces 9 for securing the heater to the oven. When it is desired to renew a
heater all that is necessary is to loosen the two clamps, remove the old and
substitute the new heater and retighten the clamps. Among the advantages of
this form of heater is that the heat is rapidly given off from the fully exposed
resistance wire, the direct and secondary radiation and air currents generated by
same take off the heat almost as rapidly as it is formed and by tests we find
that the wire temperature need rarely exceed that of the oven by over 10 degrees.
As the resistance wires are fully exposed it is of course necessary to prevent
gravy or other substances falling on them and for this purpose we prefer the
form of grate or grid illustrated which consists of a sheet of metal stamped
with rows of holes 10 and bent up or corrugated so as to bring the holes in the
sides of the corrugations as shown in Figs. 1, 2, 5 and 6.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is:-
1. The improved electric heater substantially as described.
2. In electrically heated ovens in which the improved electric heater is em-
ployed protecting such heater by means of a grate or grid substantially as
described.
Doted this 21st day of droust 1899
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent,
For the Applicant.