Year: 1886

page_text: Date of Application, 22nd Nov., 1886.
Complete Left, 20th Aug., 1887.
Complete Accepted, 27th Sept., 1887.
the nature of this invention to be as follows:
My invention relates to the mounting of the filaments or illuminating conductors,
and to the exhausting and sealing of the lamps.
When the filaments have been joined to the platinum wires in the usual manner I
place them with the "mounts" or junctions resting upon or adjacent to one or more
refractory conductors within a case that can be closed airtight, and having withdrawn
the air and admitted a suitable gas I electrically heat the conductors, and thereby heat
the mounts of the filaments to any required degree. By this process the occluded
gases and vapours are expelled and the carbonization of the mounts completed.
For the purpose of exhausting I enclose one or more lamps in a case or chamber
from which the air can be withdrawn, and to which a gas may be admitted and
maintained at a low pressure, and I increase or regulate the temperature to any degree
by means of conductors electrically heated or by other suitable means, while I maintain
the dessicating agents, and the pump, or the mercury circulating in the pump at a low
tenperature by refrigerators.
When the required degree of vacuum has been attained I hermetically seal the lamp
while "running" by means of a refractory conductor electrically heated to a high
temperature.
When it is required that the residual atmosphere in the lamp shall be a gas such as
nitrogen or hydrogen that will not actively combine with the substance of the filament,
I dry the gas at a reduced pressure and low temperature, and may then pass it through
electrically heated metallic septa, or ignited tubes, before introducing it to the lamps
prior to or during the final stages of exhaustion.
When a number of mercurial pumps are joined to a common mercury supply and
return system, I unite the parts of the system, and connect the pumps to the system,
by inverted syphons or tubes of a length greater than the height of the barometric
column so that the mercury-acting as a valve-will prevent the accidental admission
of air to the system.
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page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Incandescent Electric Lamps.
I, WILLIAM MAXWELL, of 34 Claybrook Road, Fulham, S.W. 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 the mounting of the filaments or illuminating conductors of
incandescent electric lumps and to the exhausting and sealing of the lamps.
+6
When the filaments or illuminating conductors have been joined to the leading
wires in the usual manner I electrically bake or carbonize the junctions or mounts
in vacuo or in a gas such as coal gas or nitrogen at a reduced pressure using for this
purpose a modification of the Electric Furnace described in my Specification No.
12117 of 1886. The filaments may be placed with the junctions or mounts resting
upon or adjacent to the refractory conductor described in the said Specification or the
conductor may be placed between the mounts. The case or furnace having been
closed airtight and a suitable gas flowing through, preferably at a reduced pressure,
the conductor is electrically heated and thereby the mounts are gradually brought to
a sufficiently high temperature to complete the carbonization while the gases and
vapours given off during the process are withdrawn by an airpump or other means
of exhaust.
For the purpose of exhausting lamps I place one or more lamps within an air-tight
case or receiver, which may be heated by an electrical conductor in its interior or by
the circulation of heated fluid through a double casing as described in the Specification
No. 13485 of 1885 or otherwise. I then exhaust the case and the lamps, and, when
the desired degree of vacuum has been attained, I seal the lamps by fusing their stems
or exhaust tubes by means of a refractory conductor electrically heated.
The case may be an ordinary glass receiver clamped upon a metal base, with a
packing ring interposed to ensure a tight joint, the leading electric conductors passing
airtight and insulated through the base; or the case may be made of iron or other
opaque material with suitable sightholes. The conductor employed for sealing may
be of carbon or other suitable refractory material placed close beside or around
that part of the stem which is to be sealed.
I sometimes construct the base of the receiver with a hollow or well therein, in the
centre of which 1 insert a narrow tube that projects upwards into the stem of the
lamp, and is continued downwards through the base to the mercurial pump. By
admitting mercury to the well, a hydraulic joint may be formed between the case and
the lamp at the close of the preliminary exhaustion, the lamp alone being finally
exhausted to a high degree by the mercurial pump.
I maintain the temperature of the dessicating agents and of the mercury low and
constant by enclosing each pump or a number of pumps within a refrigerator, or I
cause the mercury to circulate through a cooling tube or chamber in its passage to or
from the pump. By exhausting the lamps within receivers they can be evenly heated

page_text: to the high temperature required for the removal of gaseous films from the interior,
without danger of collapse, and by maintaining the dessicating agents and the mercury
at a low temperature, the transference of the gaseous fluids and the absorption of the
moisture are facilitated, while the use of electrically heated conductors to seal the lamps
without disturbing the cases which enclose them allows the most favourable conditions
to be maintained until the operation is completed.
It is desirable that the residual atmosphere within the lamp should be incapable of
combining injuriously with the substance of the illuminating conductor, or of
blackening the interior of the glass; for the purpose of avoiding such combination or
blackening, gases such as nitrogen and hydrogen have been used, but the methods
hitherto used for purifying the gas from oxygen and moisture before introducing it to
the lamps have not yielded satisfactory results.
To attain the requisite purity I first exhaust the vessels or tubes containing the
purifying and dessicating agents while keeping them at as high a temperature as they
will safely bear, and when by this means occluded gases and adherent films have been
removed and the vessels and their connections are proved to be tight, I bring them to
a low temperature by refrigeration and allow the gas to circulate through at a
reduced pressure into a dry exhausted receiver which may be made of metal.
From the receiver or holder the gas is drawn to supply the lamps when required
and may preferably pass through a heated tube containing a metal or other substance
which combines with oxygen and retains it.
When hydrogen is employed, its final purification may be effected by a metal
septum consisting of a tube of metal such as platinum or steel which is porous to
hydrogen when heated. The tube may be placed within a closed case and heated
electrically, or the containing case may be strongly heated. The gas having been
admitted to the case or the tube and the tube being brought to a red heat, the
hydrogen passes through the metal of the tube leaving the impurities behind.
Between the gas holder and the lamps I insert inverted syphons, or tubes arranged
to act as such syphons. These are preferably made of fine steel tubes, the height of
the arm which is connected to the holder affording when filled with mercury a colunin
sufficient to counterbalance the greatest difference of pressure that can exist between
the gas and the atmosphere. The arm towards the lamp may be of any convenient
length and is provided with an enlargement or bulb at the bottom into which the first
arm enters. The bulb being partially filled with pure mercury, the gas flowing from
the holder to the lamp bubbles up through it but should the lamp or its connections
break during the process the mercury will ascend the tube next the holder, and thus
form a seal preventing admission of air.
For exhausting incandescent electric lamps it is advantageous to connect a number
of mercurial pumps to a common mercury supply and return system which is kept
under exhaust.
In the Specification No. 13571 of 1885 the construction of such an exhaust-
ing system is described in which the several parts are connected by valves.
According to my present improvement, I connect the parts of such apparatus
without using mechanical valves, and so simplify the construction and improve the
action.
. Instead of short connections and valves I employ tubes arranged as inverted
syphons with vertical limbs of a length greater than the mercurial barometric column,
so that mercury will always remain in the bend of the syphon and thus act as a seal
to exclude the air from the exhausted portion of the system. When two or a number
of pumps are thus joined to a common mercury system, one or several may be
removed or replaced, or may be accidentally broken without interfering with the
action of the others.
The parts of the mercury raising apparatus are similarly connected, the syphons or
bent tubes returning the mercury to the vessels at the point of highest level, or
preferably the syphons are prolonged within the vessels by flexible caoutchouc tubes
which float and deliver the inflowing mercury gently upon the surface of that
within the vessels. As the open ends of these floating tubes are not immersed the

page_text: mercury cannot return when the flow ceases
admitted to the lower vessel.
or when the air is periodically
The accompanying drawing is a vertical section shewing a convenient form of
apparatus for exhausting an incandescent electric lamp while its bulb is electrically
heated, and for sealing its stem within the airtight casing. On a packing ring on
a metal base B is placed an inverted vase A of glass, or it might be of metal pro-
vided with suitable sight holes. The bulb D to be exhausted is suspended from a
plug of insulating material at the top of the vase by wires W which are in
electrical connection with the carbon filament C within the bulb D, and is steadied
by an insulated cross bar K. The stem tube S of the bulb extends through a hole in
a slab E of refractory conducting material such as carbon, and down into a well F
formed in the base B. This well F communicates by a pipe G with an exhausting
pump. A pipe T extends up within the stem tube S from an air tight chamber
L which contains material for drying the air, and which is connected by a pipe H
with an exhausting pump. Any suitable exhausting pumps may be connected with
G and H during the first part of the exhausting process, but when the pressure
within the vase and the bulb is much reduced, the pipe H should be connected to a
pump of the Sprengel kind. In the well F is a quantity of mercury which if the
pressure in the vase A exceeds that in the bulb D, rises in S and forms a seal
preventing passage of air into the bulb. To the base B are attached two pairs of
insulated connecting posts M and N, and O and P. By the posts M N a current of
electricity is transmitted through a wire coil R surrounding the bulb D. This coil
being heated by the current heats the bulb during exhaustion. By the other posts
OP, when the exhaustion is completed, a current is transmitted through the slab E
heating it and heating that part of the stem S to which the slab E is adjacent and
causing the glass of the stem to collapse and seal itself. Although I have shewn in
the drawing only one lamp operated on, it is obvious that, by employing a base B
and vase A of larger size, several lamps might be accommodated within the vase
and treated at the same time.
Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed, I declare that what I claim is :-
1. In the manufacture of incandescent electric lamps, baking or carbonizing the
mounts of the filaments or the junctions of the illuminating conductors with the
leading wires, by heat imparted to them from an adjacent electrically heated con-
ductor within a closed case, substantially as described.
2. Exhausting incandescent electric lamps within airtight cases or receivers, and
sealing their stems by the heat of an adjacent electrically heated conductor, substan-
tially as described.
3. For maintaining low and constant the temperature of the mercurial apparatus
used for exhausting electric lamps, causing the mercury to circulate through a
refrigerating tube or chamber.
4. Connecting the parts of mercurial exhausting apparatus for electric lamps by
inverted syphons or their equivalents wherein mercury acts as a seal to prevent
admission of air.
5. The herein described method of purifying at a reduced pressure and regulated
temperature gaseous fluid to charge an electric lamp and of introducing it to the lamp
through an inverted syphon or its equivalent in which mercury forms a seal against
admission of air.
DL: 20th 1.... Ր Ant 1007