IMPROVEMENTS IN AND RELATING TO THE MANUFACTURE OF INCANDESCENCE ELECTRIC LAMPS
Year: 1884

page_text: I, HUGH WATT, Managing Director, of The Maxim-Weston Electric Company
Limited, 32 Queen Victoria Street, in the County of Middlesex, do hereby declare
the nature of my invention for "IMPROVEMENTS IN AND RELATING TO THE
MANUFACTURE OF INCANDESCENCE ELECTRIC LAMPS," to be as follows:-
This invention relates to the manufacture of incandescence electric lamps and
to apparatus therefor, and comprises various improvements as hereinafter set forth.
In making the filainents according to the said invention, I take a suitable
quantity of gun-cotton and dissolve it in a solution of camphor, or otherwise
reduce it to the condition of celluloid; it then has the appearance of a cake of
light-coloured glue. This cake is then split by means of a suitable tool into thin
sheets, which are treated with sulphide of ammonium, so as to produce a pure non-
structural substance, which I term "tamadine." This substance is rolled into very
thin sheets, and stamped or formed by means of dies into the wavy shape of the
ordinary Weston filament, flat end pieces being provided having apertures for
attachment to the wire terminals of the lamp. A large number of the pieces thus
formed are placed between sheets of paper and packed with powdered plumbago
in nickel boxes, which are heated in a small furnace for an hour or two and then
slowly cooled.
The filament thus produced can be easily bent, but it is brittle. It is now pinched
or held at its ends between two clamps connected with a source of electricity. The
said clamps are arranged within a glass receiver resting upon india-rubber or other
suitable material and the said receiver is exhausted of air. Vapour of gasoline at
a low pressure is then admitted into the said receiver and a current of electricity
is passed through the filament to cause a deposit of carbon upon it. The object of
this treatment is to bring the filament down to the standard resistance. To ensure
the accomplishment of this object, the ends of the support are connected to a high
resistance galvanometer in order to measure the electromotive force, and resistances
in the battery-circuit are altered by hand so as to keep this electromotive force
Prine 61

page_text: constant. As carbon is deposited upon the said filament, the resistance of the
latter diminishes and the current increases until it attains sufficient strength to
release a catch by means of an electro-magnet, and thus cut off the current. By
these means every lamp has the same electro-motive force and the same current.
The filament is now screwed into the lamp-terminals, which are embedded in a
piece of glass tubing. This is accomplished by means of minute screws and nuts,
say, about the size of the head of an ordinary pin. The glass log-pieces are now
fitted into the bulb, and the tube is connected by means of a blow-pipe to the
edges of the bulb.
The bulb has an exhausting tube attached to it, and the next process is to
withdraw the air; for this purpose I prefer to employ an improved air-pump or
apparatus hereinafter described, that is to say, I employ a common mechanical
pump for directly effecting the preliminary exhausting, and indirectly effecting
the final exhausting with no more manual labour than the turning of a stop-cock..
A mercury pump is used to exhaust ten lamps, and a large number of the said
mercury pumps are worked by the mechanical pump. There is a large reservoir for
mercury, from the bottom of which a tube extends to the lamps, and another tube
extends to a second and lower reservoir. From the top of the first reservoir a tube
passes through a bent capillary tube to a glass bulb, and thence to the mechanical
air-pump. A three-way cock connects the lower reservoir eitlier with the mechanical
air-pump, or with the external atmosphere. When it is connected with the external
atmosphere, mercury rises in the first reservoir and in the tube connected to the
lamps, but is prevented from rising in the latter by a cylindrical glass float, whose
ground upper surface is conical and acts as a valve to close the passage through
the tube. But mercury rises in the main reservoir and, passing finally out of the
top thereof, passes through the capillary tube and into the bulb. The second
reservoir is then connected with the air-pump by turning the stop-cock, and tho
Inercury falls from the first reservoir, but cannot escape rapidly.from the bulb
through the capillary tube. Thus a vacuum is formed in the main reservoir, the
valve in the passage to the lamps opens and the air in the lamps expands into the
reservoir. This process is ropeated by turning the stop-cock, until in about an
hour and a half the lamps are sufficiently exhausted. During this time, the lamps
are made highly incandescent by a current of electricity. Finally the exhausting
tubes are closed by the blow-pipe, the ends cut off, and the lamps are practically
complete. A cork is now put into the tube which holds the legs, in order to retain
the wires in place. Litharge cement is poured in, a brass collar being placed
around the glass tube to hold the cement. A wooden plug is laid on the top of
the cement. One wire is connected to a central pin, and the other to a flat brass
ring. The plug is held in place by pinching the brass collar. There are two studs
on the brass collar which fit into a bayonet-joint on the socket, to which the
leading wires for the current are attached. The socket has a central spring which
makes contact with tho pin on the lamp, and a spiral flat spring which makes
contact with the flat ring of the lamp. And there is a switch attached to the
socket by which the current can be sent through the lamp or cut off.

page_text: Incandescence Electric Lamps.
I, HUGH WATT, Managing Director of the Maxim-Weston Electric Company,
Limited, 32 Queen Victoria Street, in the County of Middlesex, do hereby declare
the nature of my invention for "IMPROVEMENTS IN AND RELATING TO THE
MANUFACTURE OF INCANDESCENCE ELECTRIC LAMPS" 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 the manufacture of incandescence electric lamps and
comprises various improvements hereinafter described.
An important feature of the said invention is the treatment of celluloid or
collodion with sulphide of ammonium or other chemically equivalent agent, in
order to produce a non-structural substance, which I term "tamadine."
The said invention, moreover, comprises the manufacture of filaments or
conductors by cutting this substance into thin strips and imparting the desired
shape thereto and then packing tho said strips in a muffle with flaky plumbago,
as hereinafter described.
In making the filaments or conductors, according to the present invention, I, in
some cases, take a suitable quantity of gun-cotton and dissolve it in a solution of
camphor, or otherwise reduce it to the condition of celluloid. It then has tho
appearance of a cake of light colored gluc. This cake is split by means of a suitable
tool into thin strips, which are subsequently treated with sulphide of ammonium.
In other cases, I first convert a suitable quantity of cellulose, that is to say,
cotton, linen, or paper, by any of the well known processes into pyroxyline. This
substance, after being washed and dried, I dissolve with a mixture of ether and
alcohol to convert it into collodion, or with naphtha, nitro-benzol, or camphor
(either alone or in combination with other solvents) to produce celluloid. From
either of these compounds I produce the pure amorphous cellulose by making it.
into sheets or other forms and immersing the same in a bath of ammonium
sulphide, protochloride of iron, or other chemically equivalent agent, the effect of
which is to deprive the collodion or celluloid of its nitrous principles and to reduce
it to its original chemical condition as cellulose, but cellulose without fibre or
definite structure.
To produce carbon filaments or conductors from the substance obtained as abovo
described, I cut or stamp therefrom blanks of the desired shape, and then carbonize
the said blanks in a close retort or muffic.
When, however, I employ reducing agents into whose composition sulphur enters,
which agents I have found it very desirable to use, great difficulty is experienced
in obtaining a material free from traces of sulphur, which, though not chemically
combined with the cellulose, impairs by its presence the quality of the carbon
residue produced by destructive distillation. In order, therefore, to free the
cellulose from all traces of sulphur, I immerse it, previous to its carbonization, in
some solvent of sulphur, such as bisulphide of carbon, turpentine, chloroform, or
caprylic alcohol,

page_text: L
The carbon prepared from cellulose thus treated is.of very superior quality and
is well adapted for use in incandescence electric lamps. The solvents of sulphur
can be applied either to the sheets of collulose or to the blanks after they are cut
therefrom. Moreover the blanks may be cut from the material either before or
after it has been reduced as above described, the said blanks, in the former case,
being afterwards immersed in the reducing agent.
To enable filaments or conductors of considerable length to be used in globes of
small size, I prefer to make the filaments or conductors of spiral form. But I can
attain the same result by making them zigzag or of other suitable shape. For this
purpose I cut strips or blanks from the sheets of amorphous cellulose or the like,
and bend them to the shape required for the completed carbon filament or
conductor. In this condition the said blanks are exposed to a moderately high
temperature, that is to say, to a temperature, just sufficient to set their shape.
They are then placed in a muflic or retort and carbonized.
In order to impart the spiral form to the blanks, I prefer to wind them upon
mandrils of any suitable material, and secure their ends by means of clamps, and
then expose them, while thus secured, to a temperature sufficiently high to fix
their shape, so that, when removed from the mandrils they will retain such shape.
A small quantity of flaky plumbago is then placed in the bottom of a common
muffle and upon this layer of plumbago a number of the spiral blanks are laid.
The said spiral blanks are then buried or packed in flaky plumbago and a cover
is placed over them which is supported so as not to press upon or compact the
plumbago. Another layer of plumbago and spiral blanks may be placed above the
first layer, and so on, if desired. The muffle with its contents is then placed in a
carbonizing furnace and exposed to the requisite heat until the said spiral blanks
are carbonized.
It is known. that, during carbonization, a considerable shrinkage of the blanks
takes place. I have found that, by employing flaky plumbago, this shrinkage is
permitted to take place properly, that is to say, in such a manner that the con-
ductors do not come from the muffle broken or distorted in shape and unfit for
use, as when powdered carbon is employed. The conductors contract or shrink
evenly and retain their original form.
In the accompanying drawing, I have shown simple and convenient means for
making the said filaments or conductors.
Figure 1 is a side elevation of a mandril or bar, with a blank wound thereon.
Figure 2 is a sectional view of a muffle illustrating the method of packing the
spiral blanks.
A is the said mandril or bar, B is the blank which is wound spirally thereon,
CC are clamps to hold the ends of the blank in place.
D is the muffle or box. E is the first or lower layer of plumbago with blanks
buried therein. F, F are carbon or metal bars upon which a cover G of metal or
carbon is laid. E¹ is the next layer of plumbago which is similar to the first layer.
More of these layers may be used when the depth of the muffle admits thereof.
It is obvious that this method is applicable to the manufacture of any conductors
of irregular shape, such as those having the form of loops, rings, or the like.
The filament. thus produced can be easily bent, but it is brittle. It is now
pinched or held at its ends between two clamps connected with a source of
electricity. The said clamps are arranged, within a glass receiver resting upon
india-rubber or other suitable material, and the said receiver is exhausted of air.
Vapour of gasoline at a low temperature is then admitted into the said receiver
and a current of electricity is passed through the filament to cause a deposit of
carbon thereon. The object of this treatment is to bring the filament down to the
standard resistance. To ensure the accomplishment of this object, the ends of the
support are connected to a high resistance galvanometer in order to measure the
electromotive force; and resistances in the battery-circuit are altered by hand so
as to keep this electromotive force constant. As carbon is deposited upon the said
filament, the resistance of the latter diminishes and the current increases until it
-
-
-

page_text: attains sufficient strength to release a catch by means of an electro-magnet, and
thus cut off the current. By these means, every lamp has the same electromotive
force and the same current. The filaments or conductors may, however, be other-
wise treated for this purpose.
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
First. In the manufacture of carbon filaments or conductors for incandescence
electric lamps, the treatment of celluloid or collodion with sulphide of ammonium
or an equivalent reducing agent, as, and for the purpose, above specified.
Second. The improved method or process which consists in first treating collodion
or celluloid with ammonium sulphide or other reducing agent containing sulphur,
and then removing the traces of sulphur by means of a suitable solvent, as, and for
the purpose, set forth.
Third. The improved method or process which consists in winding the strips or
blanks upon mandrils, baking them to set or fix their shape, and then carbonizing
them, substantially as, and for the purpose, set forth.
Fourth. The improvement in the manufacture of carbon filaments or conductors
for incandescence electric lamps, which consists in packing strips or blanks of the
desired shape in a muffle with flaky plumbago; and carbonizing them, substantially
as above set forth.