Incandescence Body for Electrical Glow Lamps, and Process of Manufacture of the said Body.
Year: 1896

page_text: Date of Application, 22nd Aug., 1896-Accepted; 3rd Oct., 1898
COMPLETE SPECIFICATION.
Incandescence Body for Electrical Glow Lamps, and Process of
Manufacture of the said Body.
We, JOSEF FRANZ BACHMANN, of VII Kaiserstrasse 81, Vienna, Engineer,
ADOLF VOGT, of V Zentagasse 41, Vienna, Engineer, CARL CAMILLO WEINER,
of I Elisabethstrasse 3, Vienna, Proprietor of a Traffic Office, Dr. Josne
KIRCHNER of 1 Elisabethstrasse 3, Vienna, Gentleman, and ALBERT KÖNIG of
I Elisabethstrasse 3, Vienna, Gontlenian, do hereby declare the nature of this inven-
tion 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 an incandescence body for electrical glow lamps which
is characterized by the fact that its specific electrical resistanco is considerably
greater than that of the carbon filaments employed hitherto, so that an
incandescence body of that kind can be subjected to a more powerful action
than these said filaments, and therefore a glow lamp provided with said body will
consume considerably less current than the ordinary electrical glow lamps having
the same "life."
This advantage as compared with the known incandescence bodies is obtained
by making the light-emitting body of a mixture or chemical combination of a
conducting substance with refractory non-conductors, in the forin of hollow bodies
whose length and thickness are only slightly different from each other, that is to
say, are as equal to each other as possible; and the connection with the contacts
(supply wires) is effected by means of contact pieces (eo called centre contacts) of
low resistance.
As the conductor we employ carbon, such as in the form of graphite, whilst as
non-conductors we employ refractory metallic oxides (oxides of magnesium, calcium,
chromium) also silicic acid or alumina.
The incandescence body is preferably made in the form of hollow spheres, hollow
ellipsoids or short hollow cylinders, or portions of tubes, or generally speaking, in
the shapes of such bodies whose length and mean dinmeter are but slightly
different from each other, and which, as they are made hollow, obviate the
occurrence of different degrees of strain in the various parts of the incandescence
body which would cause breakage of the same.
In making incandescence bodies of such kind the conductors and non-conductors
are intimately mixed together in the form of a fine powder, in proportions depending
upon the voltage for which the lamp is designed, and also upon the form to be
given to the incandescence body.
To this mixturo there is then added a liquid binding agent such as gum, tar,
syrup, pure water or a dilute solution of sugar, and the whole is then kneaded in
kneading machines (and heated during the mixing operation if necessary) into a
stiff dough-like mass.
This mass is compressed in moulds under strong pressure to form the above
mentioned hollow bodies; it may also be heated whilst in the mould.
Finally the incandescenco bodies are at this stage raised to glow heat in a
crucible; the duration of the heating process being made such that the incandescenco
bodies acquire the desired specifio electrical resistance in addition to suitable
strength and capability of withstanding high temperatures, this having to be
determined by experiment according to the nature of the materials contained in the
mixture and to the proportions thereof employed.

page_text: We will proceed to describe by way of example the manufacture of an
incandescence body of this kind for an illuminating power of 60 standard candles
and a potential of 100 volts.
This incandescence body consists of one part by volume of soot or pure retort
carbon and four parts by volume of magnesia. These two materials are reduced
to powder, intimately mixed together, first in the dry state, and then in a kneading
machine with heat and an addition of boiling coal tar. The mass thus produced
is placed whilst hot in a heated press and is pressed into the shape of say tubes of
3 millimetres in diameter.
The portions of tube cut into suitable lengths and after having hardened in tho
air, are embedded in graphite in a crucible and are briskly heated to glowing
for approximately 48 hours in a gas blowpipe flame or preferably in an electric
furnace.
The incandescence body produced in this manner is then provided with contacts
in the way hereinafter described, unless this has been done prior to the glowing
process, but in this case the said glowing must not be effected in an electric
furnace.
The platinum or nickel wires which are employed for leading in the current, are
connected with the incandescence body by means of small short tubes which are
composed of a mass possessing the smallest possible resistance, such as of carbon
tbese being burnt after having been moulded into shape, and then inserted into the
unburnt incandescence body, and are then glowed together with the latter.
These middle contacts become only moderately warm when the lamp is worked
at its normal power.
lucandescence bodies made in the form of hollow spheres or hollow ellipsoids are
connected to the platinum wires in a similar manner, care being always taken that the
air contained in said bollow bodies is removed at the exhausting of the glass casing
or hulb in which the incandescence body has been inserted, for which purpose a
emall hole is formed in the shell of the incandescence body or of the middle
contacts.
As the variations in the total resistance and of the superficial area or surface of
such incandescence bodies, resulting from evaporation or volatilization of the
carbon are but slight, the brightness of the lamp will vary only to an unappreciable
extent during a long period of burning of the lamp.
These carbon bodies may, similarly to those of the ordinary glow lamps, be
provided with a deposit of carbon for the purpose of varying the resistanco and
also of rendering their surface more smooth.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. Incandescence bodies of high specific resistance for electrical glow lamps,
consisting of mixtures or compounds of graphite or retort carbon and non con-
ducting refractory metallic oxides (oxide of magnesium, calcium, or of chromium)
or silicic acid, or alumina, the said mixtures or compounds being compressed in the
form of hollow bodies of as far as possible equal height and thickness, and
subjected to glow heat, substantially as described.
2. For the purpose of connecting the incandescence bodies such as are specified
in the first claim, with the conducting wires, the combination therewith of niddle
contacts having the smallest possible resistance (in contradistinction to the
incandescence bodies) consisting of small tubes of carbon inserted in said bodies
and suitably formed to receive the ends of the wires.
3. The process for the manufacture of the incandescence bodies specified in the
first claim, consisting in mixing a conducting material such as carbou, with one or
more non-conducting materials such as retractory metallic oxides, in the state of
powder, first in the dry state, and then with the addition of a binding agent, into
a stiff dough-like mass, which is tben pressed so as to form the hollow bodies

page_text: above mentioned the said mixing and pressing being effected under heating if
required, substantially as described.
Dated thin ond das of Amount 1900
ABEL & IMRAY,
Agents for the Applicants.