DIE DI MUITIVATION Improvements in and relating to Incandescent Bodies for Electric Incandescent Lamps.
Year: 1899

page_text: Date of Application, 13th Mar., 1899--Accepted, 10th Mar., 1900
CUAL DIE DI MUITIVATION
Improvements in and relating to Incandescent Bodies for Electric
Incandescent Lamps.
A communication from abroad by ORLANDO M. THOWLESS, of Newark, New
Jersey, U.S.A., Inventor.
I, WILLIAM LLOYD WISE, of 46, Lincoln's Tun Fields, in the County of London,
Consulting Engineer and Chartered Patent Agent, 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 improvements in incandescent bodies for electric
incandescent lamps, in which a thin strip or filament of highly resisting material
is caused to glow or incandesce by reason of the heat developed when a current
of electricity is forced through said filament.
Hitherto such filaments have been made of solid strips of carbon or other highly
resistant materials, and in some lamps metallic filaments have been used. Hollow
carbon tube filaments have also been employed. These lamps have, however,
generally been of low efficiency, and in most instances short lived.
The object of this invention is to furnish a filament which while being cheaply
constructed, is very efficient, that is requiring few watts of energy per candle
power, and is more durable than any other with which I am acquainted.
The globe, the sealing, the exhaustion, the leading-in wires are the same as
are generally employed in lamps of the incandescent class, and require no further
description. To carry this invention. into effect, I can proceed in various ways,
which I will now describe.
The accompanying drawing shows the general plan of my incandescing body in
its various forms. The filament is shown partly in section and partly in elevation.
Figure 1 shows the filament having an internal or basic filament; Figure 2, a
hollow non-conducting base, without the internal filament, and Figure 3 shows
the non-conducting base as solid. Referring to Fig. 1, A, represents a filament
composed of the internal filament B, non-conducting base C, and the coating
or deposited surface D. Fig. 2 shows a filament A' composed of the hollow non-
conducting base C₁, and, the light-giving coating D¹. Figure 3, shows the fila-
ment A, composed of the solid non-conducting base, C2, coated by the light-giving
surface, D.
I take an ordinary incandescent lamp filament, or a metallic composition wire,
and cover it with a non-conducting substance. For the basic filament I prefer
to take a combination of carbon and alumina, carbon and iron, carbon and
manganese, carbon and tungsten, or a metal or metallic compound or oxide having
the property of forming conductors. For the basic filament silk, cotton, bamboo-fibre,
or other similar material is to be soaked in a solution composed of sulphate or some
other salt of aluminium or sulphate or other salt of iron, or salt of manganese, or salt
of tungsten and after such soaking the material is removed from the solution
and dried. It is then wound upon carbon blocks 'and packed in graphite and
carbonized by the well known method of heating in a covered crucible. Upon
"

page_text: being removed therefrom it will be found that the material so formed will be in
filamentary form and be composed of carbon and alumina, or carbon and iron,
or some other compound with carbon, dependent upon the nature of the solution
in which the original material was soaked.
Or a mixture may be made of carbon-forming materials and a metal, or a
metallic compound or oxide and the mixture forced through small dies into the
necessary form and then carbonized as above.
33
One method of producing the non-conducting covering on the basic filament
is to take, say, a cotton braid, soak it in a proper salt, for instance, nitrate of
alumina, and apply it to the above mentioned filament. The filament thus covered
is submitted to a high degree of heat, electric or other, and the result is the
destruction of the cotton covering, leaving a filament covered with a so-called
non-conducting material. The word "non-conducting" is used in this
specification in its usual electrical meaning, that is, a comparatively poor con-
ductor. In order to deposit upon the non-conducting covering a layer of con-
ducting material, the filament is then subjected to the process known in the art
as flashing." This is done by placing the filament thus prepared in the flashing
jar, or apparatus, and exhausting the air from the same. When the air in the
apparatus has reached the required degree of exhaustion, the air-pump is shut off,
and the flashing apparatus is filled with a hydrocarbon or other suitable gas.
electric current is then sent through the filament and the same is raised to a
high degree of temperature, when the carbon from the gas begins to deposit upon
the filament, and this operation is continued until the desired homogeneity and the
Icquired resistance of the filament is required. After this has been accomplished,
the original or basic filament or substratum may either be removed by pulling
it out, or chemically, or by burning it out with a heavy current, or by any other
of the well known methods. This removing of the substratum is not however
absolutely necessary, as it may remain and assist in giving rigidity to the filament.
Of course, the flashing operation can also be performed by immersing the
filament in a heavy hydro-carbon oil, and heating it by means of an electric
current.
"
An
There are other methods, besides using cotton braid saturated with the appro-
priate salt, by which I may secure the non-conducting material upon which the
conducting surface is deposited or coated. For instance, I may make a paste of
the non-conducting material and apply it to the basic filament, by means of a
brush, or I may apply it chemically, or by electric or igneous fusion, or otherwise.
The conducting envelope of the filament may be simply drawn on over the non-
conducting basic filament, like a hood, and be mechanically and electrically inde-
pendent of the non-conducting portion, the latter serving merely to give shape
and stability to the light giving portion. In this construction, the materials for
the light giving portion, the non-conducting basic filament and the method of
their treatment remain the same.
As materials for forming the non-conducting portion of the filament, I have
tried and recommend the nitrate, the sulphate, the chloride, and the silicate of
alumina, magnesia and other similar substances, whose salts when properly treated
form a high resistance material. There are certain substances that I can use,
which under the combined reducing effect of heat and carbon, may form carbides,
which although comparatively poor conductors, would still be better conductors
than some of the materials mentioned for the non-conducting covering. Such
carbide-forming substances are, for instance, zirconium, thorium, calcium, silicon
and others. Although these carbides would not be so efficient as the layer of non-
conducting material mentioned above, yet in some cases, they may answer the
purpose of the non-conducting covering...
Carbide forming substances, viz. zirconium, etc. are used in connection with
hydro-carbon vapors in the well known "flashing" operation and form carbides.
They are produced by heating vapors of the haloid salts of one of these metals
in a chamber free from air and by causing the vapor to enter the flashing jar

page_text: which has previously been exhausted of air, as much as is desirable, and at the
same time a small amount of hydro-carbon vapor is allowed to enter. A good
illustration of this can be shown by heating to about 50° Centigrade a quantity
of silicon chloride (Si Cl) and then passing the vapor formed into the flashing
jar, at the same time admitting hydrocarbon vapor, the two vapors will mix, so
that a carbonized filament being enclosed in the jar, and being raised to a high
state of incandescence, the carbon and silicon will be deposited together upon the
filament in the form of a carbide, having the well defined colors of carbide of
silicon (known in commerce as carborundum).
Instead of using deposited carbon as the light-giving material, I may deposit
other substances answering the same purpose, for instance, metallic deposits,
as metallic zirconium, niobium, molybdenum or silicon. Also, besides carbides
mentioned above, some metallic oxides, as well as other materials that form con-
ductors and are capable of being deposited or coated on the non-conducting base.
For metallic deposits the same method of heating the haloid salts is adopted
but hydrogen gas is admitted with the metallic vapor instead of hydrocarbon
vapor.
As I have said above, it is not necessary to remove the basic filament, but when
it is left in order to give stability to the filament, it does not form the light
giving portion of the filament, the electrical connection being made to the material
deposited or coated upon the non-conducting portion of the filament.
In order to prepare the non-conducting base for receiving the carbon deposit
in the flashing jar, when no internal filament is employed, I proceed as follows:-
I pour oil of rosemary on dry chloride of platinum in a porcelain dish and knead
it until all parts of it are well moistened: I then rub this up with five times its
weight of oil of lavender and allow it to stand a short time in order to clear.
The filamentary strips are thinly coated with the above preparation, and after-
wards heated in a muffle or over a Bunsen burner. This gives a coating of
platinum to the surface of the filament which can then be placed in the hydro-
carbon flashing jar and carbon deposited thereon to the proper thickness.
For high voltage lamps, in which a very high resistance is necessary. I may
employ for the light giving portion (deposited or coated) a conducting substance
combined or mixed with a non-conducting or poorly conducting one. For instance,
a proper mixture of carbon and magnesia, or of carbon and a carbide may be
deposited or coated upon the non-conducting portion of the filament, and serve
as the light-giving substance.
This invention is not limited in its scope to a strip or filamentary form, but
may be applied to filaments of any desired shape or size. For instance, the
filaments may have the form of a mantle or hood, such as is usual in the Welsbach
or Auer gas burner, or it may be button shaped, or in the form of a thin ribbon.
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. A filament for incandescent or glow lamps composed of an internal basic
filament or strip covered with a layer of non-conducting material and a light-giving
surface deposited thereon.
2. A filament for an incandescent lamp composed of a basic non-conducting
filament having a loosely fitting conducting covering, designed to serve as the
light-giving portion of the filament.
3. The method of making filaments for incandescent lamps, which consists
in properly preparing the surface of an internal non-conducting core, solid or
hollow, for receiving a layer of electrically deposited carbon, and then submitting
the filament so prepared to the action of the flashing or other similar process.
4. A filament for incandescent lamps, consisting of a hollow tube or cylinder
of non-conducting substance covered with a layer of conducting material.
5. A filament for incandescent lamps, composed of a hollow internal filament

page_text: or strip, a coating of non-conducting substance and a layer thereon of conducting
material.
6. A filament for incandescent lamps composed of a properly prepared non-
conducting base, and having for its light-giving portion a composite material com-
1-osed of a mixture of conducting and poorly conducting substances.
7. A filament for incandescent lamps, composed of an internal filament, a layer
of non-conducting substance and a covering of composite conducting material.
S. A filament for incandescent lamps, composed of a hollow non-conducting base
covered with a layer of composite material formed of a mixture of conducting and
non-conducting substances.
9. The method of making filaments of incandescent lamps which consists in
enclosing a carbonised filament in a flashing jar into which hydrocarbon vapor
and the vapor of the haloid salt of a carbide forming substance are forced, flashing
said filament and causing the carbon and the carbide forming substance to com-
bine together and become deposited in the form of a carbide upon the filament.
10. A filament for incandescent lamps having a properly prepared internal non-
conducting base, upon which is deposited or coated a light-giving portion of
metallic carbide.
11. A filament for incandescent lamps, having a properly prepared internal non-
conducting core, and whose light-giving portion is composed of conducting metallic
oxides.
12. The method of making filaments for incandescent lamps, which consists in
treating a chloride of platinum with proper essential oils, applying the resultant
compound to a non-conducting basic filament, heating the filament thus covered,
and subjecting the filament thus formed to the action of an electric current in the
presence of a hydrocarbon gas or liquid.
Dotod the 19th day of Mal 1900
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.