Improvements in Incandescent Bodies for Incandescent Electric Lamps and in the Process of Manufacturing the same.
Year: 1898

page_text: Date of Application, 17th Sept.,
1898
Complete Specification Left, 1st Mar., 1899-Accepted, 6th May, 1899
Improvements in Incandescent Bodies for Incandescent Electric
Lamps and in the Process of Manufacturing the same.
I, CARL KELLNER, of Vienna and Hallein, Austria, Doctor of Philosophy, do
hereby declare the nature of this invention to be as follows:-
-
In the heretofore used incandescent bodies (carbon filaments) of electric incan-
descent lamps, only a small part of the energy supplied in the form of electricity
is converted into light, the greater portion being lost in the form of heat, for the
reason that the filament, which is made of amorphous carbon, must not be heated
to an intense white heat, as it would then be quickly destroyed, the conversion
of the amorphous carbon into graphite of increased density, which takes place
at white heat, altering the molecular grain of the filament. I have found that this
alteration also takes place in the ordinary incandescent lamp, but in a gradual
manner, the filament which is converted by the ordinary glowing partly into a
graphite-like modification of carbon, being converted by the continued use of the
lamp into denser graphite, with the result that the filament breaks. Many
attempts have been made to discover a better and more durable incandescent
body for incandescent electric lamps, and it has been recognized that only those
bodies that fuse with the most difficulty are capable of being used.
No practical result however has heretofore been obtained, because either too
good conductors of electricity have been tried, in which the resistance necessary
for producing white heat cannot be reached, or because in incandescent bodies
which are made of mixtures of conductors and non-conductors (or conduciors of
the second class) binding or fusing agents have been employed which in use have
been continuously altered by the electric current, or, finally, because the bodies,
in order to effect their object, have first had to be heated in a tedious manner to
that temperature at which they become conducting.
Incandescent bodies according to the present invention allow of the conversion
into light of the greatest portion of the electric energy supplied, it being possible
to raise them by the electric current to the brightest white heat without their
becoming damaged.
These incandescent bodies consist of infusible metals which are not very good
conductors of electricity and which have a high capacity for emitting light, such
as thorium, or of almost infusible metals such as titanium (in the form of pure
titanium or nitride of titanium) chromium, wolfram, or alloys of such metals
(which incandescent bodies are oxidized at their surface); or of mixtures of
almost infusible metals or alloys of the same, or of graphite of the kind which
offers the very greatest resistance to conversion into graphite-acid, by potassium
chlorate and nitric acid (graphite of high density up to 2.25 specific gravity),
with metallic oxides that are infusible or are fusible with difficulty and capable
of emitting light, such as thorium oxide with or without an addition of cerium
oxide.
Incandescent bodies of the kind referred to have the advantage (since they possess

page_text: a relatively small conductivity) that they can be made in convenient dimensions
which will not break too easily. The manufacture of incandescent bodies is
effected according to this invention by moulding the metals of the kind referred
to, or the mixtures of the metals fusible with difficulty, or alloys, or graphite of
the kind stated, with metallic oxides fusible with difficulty and capable of emitting
light, in a state of fine powder without the addition of a binding or fusing agent,
into solid bodies under high pressure. For this purpose, the dry powder is placed
in a press mould and by means of a suitably formed plunger, a considerable
pressure (up to 20,000 kilos. per square centimetre) is exerted upon it. When
the bodies are made of thorium metal, or of metals fusible with difficulty such as
titanium, chromium, wolfram, or alloys of such metals alone, they are oxidized
at their surface by being made to glow in the air, by immersion in an oxidizing
liquid, or by being inserted as an anode in an electric circuit by means of which
an electrolyte is split up and of which oxygen is an anion, or by any other suit-
able means.
The thin layer of oxide adheres so firmly to the metal that it is not damaged
when the incandescent body is used. When the incandescent body is to consist
of a mixture of graphite of high density with metallic oxides, it may also be
made by moulding and pressing a mixture consisting of powdered metallic oxides
capable of emitting light and of a small addition of cellulose swelled up in
chloride of zinc. After glowing, the body is subjected in a vacuum, or
neutral gas such as nitrogen, to a current of high potential for the purpose of
converting the amorphous carbon into graphite of high density before the incan-
descent body is put into use.
in a
Crumbling of the body during the conversion into graphite of the carbon is
not to be feared, because the small portions of the latter (at most five per cent.)
are surrounded by the particles of metallic oxide.
In order to avoid damaging by excessive heating, the incandescent bodies of
the kind described at those parts to which the current is applied to them when
in use, viz.; The places of contact, it is advisable to strengthen them at such parts,
that is to say to make them larger, and to mould the leading-in wires into the
mass of the incandescent bodies when the latter are being moulded, or to melt
the said wires into the said strengthened portions by means of the electric are.
Dated this 17th day of September 1898.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
Improvements in Incandescent Bodies for Incandescent Electric
Lamps and in the Process of Manufacturing the same.
I, CARL KELLNER, of Vienna and Hallein, Austria, Doctor of Philosophy, 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 follow-
ing statement:-
The
In the heretofore used incandescent bodies (carbon filaments) of electric incan-
descent lamps, only a small part of the energy supplied in the form of electricity
is converted into light, the greater portion being lost in the form of heat.
cause of this is that such filaments, which are made of amorphous carbon, cannot
be heated to an intense white heat, as they would then be quickly destroyed,
the conversion of the amorphous carbon into graphite of increased density, which

page_text: takes place at white heat, altering the molecular structure of the filaments. I
have found that this alteration also takes place in the ordinary use of incandescent
lamps, but in a gradual manner, the filament, which is converted by the ordinary
glowing partly into a graphite-like modification of carbon, being converted by
the continued use of the lamp into denser graphite, with the result that the
filament breaks.
Many attempts have been made to discover a better and more durable incan-
descent body for incandescent electric lamps, and it has been recognized that
only those bodies that fuse with the most difficulty are suitable for the purpose.
No satisfactory practical result, however, has heretofore been obtained, because
either too good conductors of electricity have been tried, in which the resistance
necessary for producing white heat cannot be reached; or because in incandescent
bodies which are made of mixtures of conductors and non-conductors (or con-
ductors of the second class), binding or fusing agents have been employed which
in use have been continuously altered by the electric current; or, finally, because
the bodies, in order to effect their object, have first had to be heated in a tedious
manner to that temperature at which they become conducting.
Incandescent bodies according to the present invention enable the greatest
portion of the electric energy supplied to be converted into light, because they
can be raised by the electric current to the brightest white heat without becoming
deteriorated.
These incandescent bodies consist of infusible metals which are not very good
conductors of electricity and which have a high capacity for emitting light,
such as thorium, or of almost infusible metals such as titanium (in the form of
pure titanium or nitride of titanium), chromium, or wolfram, or alloys of such
metals, incandescent bodies made of these infusible or almost infusible metals or
alloys being oxidized at their surfaces; or of mixtures of (a) almost infusible
metals or alloys of the same, or (b) graphite of the kind which offers the very
greatest resistance to conversion into graphite-acid by potassium chlorate and
nitric acid (graphite of high density up to 2.25 specific gravity), with metallic
oxides that are infusible or are fusible with difficulty and capable of emitting light,
such as thorium oxide with or without an addition of eerium oxide.
Incandescent bodies of the kind referred to have the advantage (since they possess
a relatively small conductivity) that they can be made in convenient dimensions
without being liable to break too easily.
The manufacture of incandescent bodies is effected according to this invention
by moulding the metals of the kind referred to or the mixtures of the difficultly
fusible metals or alloys or graphite of the kind stated, with metallic oxides
fusible with difficulty and capable of emitting light, in a state of fine powder and
without the addition of a binding or fusing agent, into solid bodies under high
pressure. For this purpose, the dry powder is placed in a press mould and by
means of a suitably formed plunger, à considerable pressure (up to 20,000 kilo-
grammes per square centimetre) is exerted upon it.
When the bodies are made of thorium metal or of metals fusible with difficulty
such as titanium, chromium, or wolfram, or alloys of such metals alone, they
are oxidized at their surfaces in a suitable manner, as by being made to glow in
the air by passing an electric current through them, by immersion in an oxidizing
liquid, or by being inserted as an anode in an electric circuit which decomposes
an electrolyte of which oxygen is the anion. The thin layer of oxide adheres
so firmly to the metal that it is not damaged when the incandescent body is used.
When the incandescent body is to consist of a mixture of graphite of high
density with metallic oxides, it may be made by moulding and pressing a mixture
consisting of powdered metallic oxides capable of emitting light and of a small
addition of cellulose made to swell up by soaking in chloride of zinc.
After glowing, by passing an electric current through the filament, in a vacuum,
or in a neutral gas such as nitrogen, the body is subjected in the said vacuum or
eutral gas to a current of high potential for the purpose of converting the

page_text: amorphous carbon into graphite of high density before the incandescent body
is put into use. Disintegration of the body during the conversion of the carbon
into graphite is not to be feared, because the small quantity of the latter (at most
five per cent.) is enclosed by the particles of metallic oxide.
In order to prevent the incandescent bodies of the kind described from being
damaged, when in use, by excessive heating at the parts where the current is sup-
plied to them, riz. at the places of contact, it is advisable to strengthen them
at such parts that is to say to make them thicker and to mould the leading-in
wires into the mass of the incandescent bodies when the latter are being moulded,
or to fuse the said wires into the said strengthened parts by means of the electric
are.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. Incandescent bodies for incandescent electric lamps, composed of infusible
metals or metals fusible with difficulty which are not good conductors of electricity
and which have a high capacity for emitting light at white heat, such as thorium,
or titanium, chromium, or wolfram, or alloys of such metals, the said incandescent
bodies being oxidized on their surfaces.
2. Incandescent bodies for incandescent electric lamps, composed of mixtures
of metals fusible with difficulty, or alloys of the same, or of graphite of high
density, with metallic oxides which are either infusible or fusible with difficulty
and have the capacity of emitting light, such as thorium oxide, with or without
the addition of cerium oxide.
3. The manufacture of incandescent bodies according to the preceding claims,
by pressing the powdered metals or the powdered mixtures therein referred to,
under high pressure and without the addition of a binding or fusing agent, into
the form of solid bodies.
4. The manufacture of incandescent bodies according to Claim 2, by pressing
a mixture of powdered metallic oxides which are either infusible or fusible with
difficulty and are of high light-emitting power, with a small addition of cellulose
made to swell up by soaking in chloride of zinc, and converting the amorphous
carbon into graphite of high density by passing a current of high potential
through the body in a vacuum or in a neutral gas such as nitrogen.
5. The production of a layer of oxide on the surface of incandescent bodies
according to Claim 1, by glowing them in the air, placing them in an oxidizing
liquid, or inserting them as an anode in an electric circuit by which an electrolyte
is decomposed and gives up oxygen as an anion.
6. For the purpose of obviating damage to incandescent bodies according to
Claims 1 and 2, by excessive heating at the places of contact, fusing the leading-
in wires into the strengthened or thickened ends of the incandescent bodies by
means of the electric arc.
Dotod his 1ut dow of Warah 1900
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.