Improved Manufacture of Electrical Heating Appliances of High Electrical Resistance Capable of Sustaining High Temperatures.
Year: 1899

page_text: Date of Application, 7th Nov., 1899
Complete Specification Left, 4th Aug., 1900-Accepted, 8th Sept., 1900
Improved Manufacture of Electrical Heating Appliances of High
Electrical Resistance Capable of Sustaining High Temperatures.
I, ADOLF VOGT, of 82, Victoria Street, Westminster, in the County of London,
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to a manufacture of electric heating appliances of
high electrical resistance which shall be capable of producing and sustaining
very high temperatures during long continued use, and which are mainly
composed of a mixture of a non-conducting substance and a metal conductor.
As non conductor there may be used for this purpose kaolin, alumina, talc,
quartz, and the like, also all very difficultly reducible or fusible metallic oxides,
such as aluminium oxide and the so called rare earths, the essential charac-
teristic of the material employed or of some part thereof being that when heated
to a high degree it shall become fritted slagged, or more or less vitrified so
as to form a hard dense body.
The metals employed as the conducting material are nickel, cobalt, wolfram,
and the like.
For forming the heating bodies of a mixture of such materials it is indis-
pensably necessary, to first reduce them to an exceedingly fine state of sub-
division and then to mix them intimately together and form the mixture into
a paste or dough by the addition of water or other liquid. From this dough,
which can be worked like potters clay, the heating bodies can be moulded of
any desired configuration, or the plastic compound can be pressed in moulds,
such pressure being only effected in order to insure perfectly uniform dimen-
sions when the heating bodies are to be manufactured on a large scale. After
moulding, the heating bodies are dried, and they are then heated in an almos-
phere of hydrogen gas, at first only to such a temperature that the
more or less oxidised metal particles shall be completely reduced, for example
when nickel is used as the metal, the temperature would be about 400° C.
When such reduction of the more or less oxidised metal has been completely
effected by this means (such oxidation will mainly occur on the surface of the
particles); the mass while still surrounded by hydrogen gas is heated to so
high a degree that it becomes fritted or slagged that is to say more or less
vitrified, forming a dense hard body.
The temperature employed should about equal the welding heat of the métal
constituent, but should not exceed this.
In the above process special care has to be taken that the metal is kept.
as free as possible from contact with carbon, as otherwise the bodies produced,
when subject to frequent use, are liable to become of increased resistance, the
metal becoming brittle and of reduced conducting power.
The subjecting the resistance bodies first to a comparatively low tempera-
ture in an atmosphere of hydrogen, and then to a high temperature while still
surrounded by hydrogen instead of subjecting them at once to a high tempera-
ture while surrounded by carbon powder, as was heretofore done, constitutes

page_text: the essential and important feature of the present invention, in as much as the
metal employed boing unavoidably more or less oxidised, it is necessary to
effect its complete reduction by means of the hydrogen gas before the non-con-
ducting constituent has been made to assume the dense fritted or vitrified con-
dition by the application of a high heat, as if the still oxidised particles become
reduced, and consequently shrink in volume after the non-conducting consti-
tuent has assumed the said hard condition, it can no longer shrink to a corre-
sponding extent and as a consequence the metal particles would not be in such
relative positions in the mass as would enable them to afford the requisite
conducting power for giving the body the exact degree of resistance required,
that is to say, the resistance would be too high and unreliable and conse
quently the body practically usoless.
Electrical heating bodies manufactured according to the above described in-
vention are particularly applicable with advantage for effecting the preliminary
heating of second class conductors, also for lighting cigars and pipes, for heat-
ing branding dies, and a variety of similar purposes.
Dated this 7th day of November 1899.
ABEL & IMRAY,
Agents for the Applicant.
Improved Manufacture of Electrical Heating Appliances of High
Electrical Resistance Capable of Sustaining High Temperatures.
I, ADOLF VOGT, of 82, Victoria Street, Westminster, in the County of London,
Engineer, 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 a manufacture of electric heating appliances of
high electrical resistance which shall be capable of producing and sustaining
very high temperatures during long continued use, and which are mainly
composed of a mixture of a non-conducting substance and a metal conductor.
As non-conductor there may be used for this purpose kaolin, alumina, talc,
quartz, and the like, also all very difficultly reducible or fusible metallic oxides,
such as aluminium oxide and the so called rare earths, the essential charac-
teristic of the material employed or of some part thereof being that when heated
to a high degree it shall become fritted, slagged, or more or less vitrified so
as to form a hard dense body.
The metals employed as the conducting material are nickel, cobalt, wolfram,
and the like.
For forming the heating bodies of a mixture of such materials it is indis-
pensably necessary, to first reduce them to an exceedingly fine state of sub-
division and then to mix them intimately together and form the mixture into
a 'paste or dough by the addition of water or other liquid. From this dough,
which can be worked like potters clay, the heating bodies can be moulded of
any desired configuration, or the plastic compound can be pressed in moulda,
such pressure being only effected in order to insure perfectly uniform dimen-
sions when the heating bodies are to be manufactured on a large scale. After
moulding, the heating bodies are dried, and they are then heated in an atmos-
phere of hydrogen gas, at first only to such a temperature that the
more or less oxidised metal particles shall be completely reduced, for example
when nickel is used as the metal, the temperature would be about 400° C.

page_text: When such reduction of the more or less oxidised metal has been completely
effected by this means (such oxidation will mainly occur on the surface of the
particles); the mass while still surrounded by hydrogen gas is heated to so
high a degree that it becomes fritted or slagged that is to say more or less
vitrified, forming a dense hard body.
The temperature employed should about equal the welding heat of the metal
constituent, but should not oxceed this.
In the above process special care has to be taken that the metal is kept
as free as possible from contact with carbon, as otherwise the bodies produced,
when subject to frequent use, aro liable to become of increased resistance, the
metal becoming brittle and of reduced conducting power.
The subjecting the resistance bodies first to a comparatively low tempera-
ture in an atmosphere of hydrogen, and then to a high temperature while still
surrounded by hydrogen instead of subjecting them at once to a high tempera-
ture while surrounded by carbon powder, us was heretofore done, constitutes
the essential and important feature of the present invention, in as much as the
metal employed being unavoidably more or less oxidised, it is necessary to
effect its complete reduction by means of the hydrogen gas before the non-con-
ducting constituent has been made to assume the dense fritted or vitrified con-
dition by the application of a high heat, as if the still oxidised particles become
reduced, and consequently shrink in volume after the non-conducting consti-
tuent has assumed the said hard condition, this can no longer shrink to a corre-
sponding extent and as a consequence the metal particles would not be in such
relative positions in the mass as would enable them to afford the requisito
conducting power for giving the body the exact degree of resistance required,
that is to say, the resistance would be too high and unreliable and conse-
quently the body practically useless.
By means of the above described process, which only relates to the use of
metals as the conductor in the heating body, the above mentioned disadvantages
of the existing manufactures of such bodies are entirely obviated, and an essen-
tially improved product is obtained. This results, as above stated, essentially
in first subjecting the compound, while surrounded by an atmosphere of hydrogen
to only such a comparatively low temperature as is sufficient to reduce all the
oxidised metallic particles thereof to the metallic condition, and in then raising
the body to such a high temperature that the non-conducting constituents of
the body, while being burnt or baked, are caused to shrink and assume a
dense fritted or more or less vitrified condition. By this process alone is it
possible to produce electrical heating bodies that shall have, and maintain for a
long time the desired degree of resistance and consequently of heating power.
Electrical heating bodies manufactured according to the above described in-
vention are particularly applicable with advantage for effecting the preliminary
heating of second class conductors also for lighting cigars and pipes, for heat-
ing branding dies, and a variety of similar purposes.
It is not intended to claim generally either the use of hydrogen gas as the
reducing gas in the manufacture of electrical resistance bodies, nor the use of
nickel as the metallic constituent of such bodies, as I am aware that these have
been proposed separately in the manufacture of glow lamp filaments and the
like, but not in combination and in the manner herein described.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. Process for the manufacture of electrical heating appliances capable of
sustaining high temperatures for a long time which consists in first subjecting
a compound composed of a mixture of a finely divided metal such as nickel
and a non-conducting material such as kaolin or equivalent material to only
such a temperature in reducing atmosphere as to cause all the oxidised metal

page_text: particles to be reduced thereby to the metallic state, and then heating the
compound to about the welding temperature of the metal, whereby the non-
conducting particles of the compound are caused to assume a fritted or more
or less vitreous, hard, dense condition, the reducing agent employed for this
purpose being hydrogen, under careful avoidance of carbon, substantially as
and for the purposes described.
2. An electric heating appliance composed of a mixture of a metallic conductor
such as nickel and a non-conductor such as kaolin, which is brought into a hard
fritted or more or less vitreous condition, by first. being heated only to the reduc-
ing temperature of the metallic constituent so as to effect the complete reduction
thereof, and then being heated to the welding temperature of the motal, so as
to become fritted, or more or less vitrified, substantially as described.
Dated this 4th day of August 1900
ABEL & IMRAY,
Agents for the Applicant.