Improvements in Forming Filaments or the like for Incandescence or Glow Electric Lamps,
Year: 1898

page_text: Improvements in Forming Filaments or the like for Incandescence or
Glow Electric Lamps,
I, HUGO HIRST, of Nos. 69-71-88-92, Queen Victoria Street, in the City
and County of London, Electrical Engineer, do hereby declare the nature of
this invention to be as follows:--
My invention relates to improvements in forming filaments or the equivalents
thereof in incandescence or glow electric lamps in which said filaments are
practically non conductora when cold, but when heated externally, become incan-
descent and are maintained in this state by the passage of the electric-current.
The composition of such filaments are usually the metallic oxides known gener-
ally as rare earths," such as zirconium oxide ZrO, or magnesium oxide MgO,
and the object of my invention is to dispense with the squirting of a paste into
a. die as heretofore employed in making such filaments.
"
In carrying my invention into effect I take cotton thread, or like vegetable
fibre, either twisted, plaited or woven to form a temporary support for the fila-
ment to be constructed. Two platinum or other wires are suitably attached to
each end to serve the purpose of leading in wires when the filament is made
and in position, said wires being held apart during the process of formation by
a glass or other insulator.
A solution of the soluble salts, before referred to, such as Zr O₂-; Si O, Zr O₂-;
MgO; or other suitable metallic salts are arranged so that the thread or fibre
with its two wires may be dipped therein and thus saturated, or said solution
may be painted thereon. The thread or fibre is then dried and heated to the
point of destruction, thus driving off the acid radicle of the salt or salts leaving
a pure oxide filament between the two wires which are again dipped or saturated
with the solution, dried and heated, and this process is repeated until the
requisite thickness, density and carrying capacity is attained.
In practice I prefer to use 6 parts of zirconium nitrate ZrNO, and 1 part of
yttrium nitrate YttNO, dissolved in water to form a solution for the aforesaid
process, and the filament may be exposed before drying to ammonia vapor which
reduces the nitrates or like salts to hydrated oxides.
I may use insoluble salts of the carths or metals aforesaid, by grinding, them
firmly in water which is rendered slightly glutinous, and dipping or painting
the filament upon its destructible framework of fibre as aforesaid.
I may also make the filaments in lengths, cutting off where required and
attaching to the leading in wires after finishing.
1000

page_text: Improvements in Forming Filaments or the like for Incandescence or
Glow Electric Lamps.
I, HUGO HIRST, of Nos. 69, 71, 88, 92, Queen Victoria Street, in the City and
County of London, Electrical 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:-
My invention relates to improvements in forming filaments or the equivalent
thereof in incandescence or glow electric lamps in which said filaments are
practically nonconductors when cold, but when heated from an external source
become conductive and are raised to incandescence, or a high degree of luminosity
by the passage of the electric current when in that condition.
"E
The composition of such filaments are usually the metallic oxides known as
rare earths" such as zirconium oxide ZrO, or magnesium oxide MgO, and
the object of my invention is to dispense with the operation of squirting a paste
into a die or matrix as heretofore employed in making such filaments.
In carrying my invention into effect I take cotton thread or like vegetable or
animal fibre either twisted, plaited or woven to form a temporary support for
the filament to be constructed. Two platinum or other wires are suitably attached
to each end and to serve the purpose of leading in wires when the filament is
made and in position, said wires being held apart during the process of formation
by glass or other insulation, said wires or the like having loops at the ends
thereof which clip the ends of the thread fibre, or texture forming the temporary
base of the filament to be constructed or any other method of attachment may
be adopted that affords a firm adjustment and a good electrical connection.
A saturated solution of the soluble salts of Zio, or MgO is prepared, and
the thread, fibre or texture inumersed therein, the connecting wires being also
immersed so that the deposition of the solution may cover the point of junction
or said solution may be painted thereon. The filament so constructed is then
dried and gradually raised to a high temperature, which destroys the acid radical
of the metallic salts forming the saturated solution, and a filament composed of
the oxide or oxides is left, in the form of a shell. This filament is again dipped
into the solution and dried, and again subjected to a high temperature, and the
process may be repeated until the substance of said filament has acquired the
requisite density and conductivity when heated in the ordinary process of use,
such heating being preliminary and temporary applied by a separate function or
the like.
The preferable salts forming the saturated solution are nitrate of zirconium
ZrNO, six parts, and nitrate of yttrium Ytt NO, one part, but this proportion
may be varied and the soluble salts of thorium or other rare earths or the oxides
thereof may be used, which are refractory under extremely high temperature,
either singly or in combination.
In some cases before finally drying the filament I may expose it to ammonia
gas NH, which reduces the nitrates to hydrated oxides.
When a cotton or like vegetable fibre core is used in combination with the
soluble salts aforesaid, the core becomes a porous filament at first, but repeated
dippings and heatings will tend to reduce the porosity and make it more dense.
But with a core of organic material such as horsehair or felted hair fabric cellu-
loid or the like, the material forming the core may be destroyed by the heating
process leaving the conductor in the form of a shell of which the core of organic
material is the matrix.

page_text: I may, instead of using the soluble salts use the oxides or insoluble salts, in
which case they are finely ground or pulverized in water in which a small pro-
portion of glutinous material is dissolved, rendering the mixture of a cream like
consistency in which the fibrous or organic base of the filament is dipped, dried
and heated as hereinbefore described, to the attainment of the required density
and thickness.
Instead of at once forming the filaments between the conducting wires, I may
make a length, and cut out the required portions and fix to the conducting wires
in the ordinary manner.
Having now particularly described and ascertained the nature of my said
invention and the manner in which the same is to be performed, I declare that
what I claim is :-
First. The formation of a filament for incandescence or glow electric lamps
in which exterior or primary heating is applied to render said filament con-
ductive, by using a base or core of organic matter such as fibre or texture, and
dipping into a solution of the soluble salts of magnesium zirconium yttrium
thorium, singly or in combination or the soluble salts of such metallic oxides
which are refractory at extremely high temperature, and subsequently heating as
herein described.
Second. The use of a core or matrix of vegetable or animal matter which is
surrounded by repeated dippings, by a coating of the soluble salts of the rare
earths, or the metallic oxides which are sufficiently refractory at high tempera-
ture, in combination with a heating process which may destroy said core and
also the acid radical, leaving a shell or an incorporated residue of the core sub-
stantially as herein described.
Third. In combination with the process referred to in the preceding claims
and described in the specification the process of subjecting the prepared filament
to ammonia gas to reduce the soluble salts of the metallic oxides of the rare
earths to the hydrated oxides substantially as herein described.
Fourth. In forming a filament for incandescence or glow electric lamps, the
use of the insoluble salts or oxides of the rare earths which are refractory under
extremely high temperature, by grinding and pulverizing in water and a glutinous
or binding vehicle into which the filament is dipped and heated as aforesaid.
Dated this 16th day of August 1899
FREDK. WALKER,
73, St. Stephen's Road, Upton Park, London, E.C.,
Agent for the Applicant.