IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS
Year: 1884

page_text: COME LEIE
DIECIFICATION.
I, WILLIAM PHILLIPS THOMPSON Fel. Inst. P. A. of the Agency for Foreign
Patent Solicitors 6, Lord Street, Liverpool, in the County of Lancaster and
323, High Holborn, in the County of Middlesex, Civil Engineer do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN INCANDESCENT 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 class of electric lamps in which the conducting
strip, wire or filament of carbon, hydro-carbon or other suitable refractory
substance, is enclosed within a transparent air-tight globe or chamber from which
the air is exhausted and which may or may not be filled with a non-oxydizing gas
or vapor.
In the construction of enclosing globes or chambers for incandescent lights, it is
desirable that the globe itself should be so formed that it will not be liable to crack
or break when unevenly heated by the current employed for rendering the filament
incandescent; that it should be of uniform thickness and offer as little opportunity
as possible for the formation of rings or shadows by refraction; and that the entire
process of shaping, exhausting and sealing the globe or vacuum chamber should be
simple and effective.
For this purpose it is desirable that the several elements comprised in the lamp,
namely the globe the incandescing filament its supporting conductors and the.
supporting cup, in connection with which the completed lamp is to be employed,
should be each adapted in form and construction to the other parts. In setting
forth this Invention therefore, a complete description will be given of the process of
forming and manufacturing all these several parts of the lamp, together with the
description of the formation of the globe and process of exhausting and closing
the sainc.
The globe is constructed of a single piece of glass which is preferably blown into
a mould, whereby all the lamps are rendered uniform in size; and, contrary to the
usual custom, they are formed entirely spherical and with a smooth surface at the
lower end, that is to say, opposite to the neck, where it is usually customary to

page_text: form a slight projection for the purpose of attaching a tube and exhausting the air
after the conductors have been secured in place. This is rendered unnecessary for
the reason that, by this Invention, the globe is exhausted and closed at the end at
or near which the conductors enter.
The neck of the globe is afterward narrowed or diminished in size and it is cut
or broken off, by a suitable tool, near the bulb or globe. The conducting filament,
which will be hereinafter described, is then inserted within the globe and the
conducting wires leading to the same, are suspended across the edge of the neck of
the globe. By means of a blow-pipe, the glass is then heated about the conducting
wires, which are preferably of platinum. The wires, by reason of their own weight
sink into the glass as it becomes softened, and the glass closes above them. If
however this action should not take place quickly enough, a little particle of glass
is fused upon the exposed platinum wire resting on the globe, for the purpose
of holding the conductors and the filament firmly during the subsequent
manipulations.
The portion of the neck, which was at first cut off, is then placed against the
neck from which it was removed and the two are welded together by means of a
blow-pipe, the two parts occupying the same relative positions as those they
originally held. A platinum or other suitable metallic stopper is then inserted
within the neck formed of the two sections which have been thus welded together
into a whole tube, and the tube is then preferably drawn to a diameter that will
prevent the stopper from falling out, or it may be curved to an angle for the samo
purpose. The air is then exhausted from the globe and the glass is softened
around the stopper at the lowest possible temperature, and caused to be compressed
against the same. While the surrounding atmosphere is compressing the softened
glass around the pin or stopper, tho glass neck elongated, to still further ensure
the close fitting of the pin to the neck of the tube which joins the lamp to the
air-pump.
In the sides of the neck there are preferably formed slight depressions which
afford points for the holder to grasp the lamp and retain it in its proper position.
The neck of the globe or chamber is however preferably otherwise straight.
The form of carbon which it is preferable to employ in this globe consists of a
carbonized filament formed in the shape of two incomplete circles having preferably
slightly different diameters and united with each other by a curved continuation
of the filament. The circles of different diameters serve a special purpose in
preventing a continued movement of the filament when the lamp is jarred, by
breaking up the variations into ones of smaller amplitude. The form of the
filament is also of especial advantage for producing and radiating as equal an
amount of light as possible from a given length of conductor, and that too within
as small an area of containing globe as possible.
The supporting conducting wires for the filament are united thereto by means of
a peculiar form of clamp which is formed at the end of each wire. This clamp is
made by forming an enlargement at one end and then causing the enlargement to
be flattened into a disc. The discs are doubled preferably in the axis of the wire,
so that two lips are formed which are intended to receive the filament between
them. The lips are then together bent out laterally, so that they project from the
wire at right angles. One of these conducting wires is applied to each extremity
of the filament and they are preferably so arranged that the lips of the clamps are
turned in toward each other, so as to make use of the resilience of the carbon loop
in case of a defective clamping.
For the purpose of handling the delicate filaments with facility in introducing
the ends into the clamps and for rendering the connection between the end of the
filament and supporting conductors as perfect as possible, the ends of the filament
are preferably coated with metal by electrolysis before they are applied to the
clamps. The metallic coatings may then be forcibly brought into intimate contact
with the clamps by crushing the ends of the filament contained therein. They
may afterward be soldered to the clamps if it is desired.

page_text: A suitable bridge-piece of glass preferably unites the supporting conductors with
each other, for the purpose of stiffening the same and preventing the filament from
being displaced.
The operation of coating the ends of the filament with copper or other metal as
well as the details of the construction of the lamp and holder, will be described in
connection with the accompanying Drawings, in which Figure 1 illustrates a
complete lamp together with its holder. Figure 2 is a side view of the incandescing
filament. Figures 3 and 4 and 5 illustrate the mould employed for carbonizing the
filament and the method of removing the filament therefrom. Figures 6 and 7
illustrate the apparatus employed for coating the ends of the filament. Figures S, 9,
10 and 11 illustrate the construction of and the method of manufacturing the
supporting conductors. Figure 12, illustrate the form of the globe before the
filament has been inserted, and Figure 13 illustrates the method of inserting
the conducting wires after the section of the neck of the globe has been removed.
Figures 14 and 15 illustrate the process of closing the globe. Figures 16 and 17
illustrate certain details in the form and construction of the holder.
Referring to Figures 1, 2, 3 and 4, a description will first be given of the
incandescing filament and the process of forming and manufacturing the same.
The filament H is constructed from a single piece of cane, bamboo, parchmentized
paper, thread woody fibre or other suitable carbonaceous material, by being
subjected in a suitable mould, to a very high temperature.
The form of the
filament which is preferred, may be described as a long loop bent upon itself, so as
to form two incomplete circles, the one of which h¹, is preferably of greater diameter
than the other 2. The curved end 3 of the loop unites the two incomplete circles
with each other and is at right angles to them.
It may here be observed that an especial advantage is derived from having the
two circles of the loop of different diameters, namely that is neither circle intercepts
the path of the other when the lamp is viewed from one side but the light emitted
from each circle is radiated independently of the other.
Such a filament is preferably formed by means of a mould of the character
illustrated in Figures 3 and 4. This mould which is preferably formed of nickel
or some form of iron, steel or carbon or hydro-carbon consists of an outer case H¹
and an inner section H². This case H' has a central bore h* of greater diameter at
one extremity h³ than at the other ho. Within the bore h' it is designed that the
section H2, constituting a stopper or a plug shall be inserted. The section H* of
the mould, tapers at the same angle as the bore of the portion H¹.
The two conical contact-surfaces of the sections H¹ and H2 are ground smooth
for the purpose of making the joint as perfect as possible.
Upon the surface of the section H2 there are cut two spiral grooves and kª
joined at their inner ends, as shown at 3, by a curved continuation of the grooves.
The portion of the mould is preferably cut under slightly for the purpose of
preventing the filament from slipping out of the groove. The spiral grooves,
starting from the portion ³, pass outward toward the respective ends of the
section H2 of the moulds. It is not essential however, that the grooves should in
all instances be spiral as they may be made parallel. It is designed that the
filament to be carbonized shall be laid in this groove being wound about the
plug H. The plug or section H2 is then inserted within the section H and driven
tightly into place. The mould is then placed in a suitable kiln with the smaller
end of the taper bore downward, and while in the kiln it is subjected to a sufficient
heat to effect the carbonization of the filament.
It is essential that the mould should be perfectly tight during the process of
carbonization and this is one of the objects of tapering the bore . It is evident,
that during the process of heating the mould, the outer section H will expand
causing the diameter of the bore to increase. The section H2, however, may
thereupon drop further into the section H¹ and continue to keep the joint between
the two tight. The section H afterward, as it becomes thoroughly heated, expands

page_text: still more and binds tightly against the inner surface of the bore. The plug H³ is
made hollow so that the heat of the kiln may enter the same and more quickly
penetrate the filament which is now being carbonized.
The filament after it has been placed in the groove of the mould may with
advantage be covered and held in position by means of a thread wound about the
same and covering it more or less. Such a thread not only serves to hold the
filament in position but also serves to prevent the filament from being converted
into carbonic oxide or carbonic acid gas in the event that any oxygen should be
present.
In Figure 5 there is illustrated a mould especially adapted to permit such a
thread to be applied. In this mould grooves are made for two filaments and
instead of being spiral in form, they are made in the form of complete circles the
grooves, and ³, being respectively intended to receive the two limbs of the
filament, while the portion serves to connect the same.
At points 7 and 8 slight depressions are made for the purpose of permitting the
thread to pass across the filament.
It is well-known that during the process of carbonizing, the filaments shrink a
considerable portion of their lengths. It is desirable that they should be maintained
under tension throughout their lengths during the time such shrinkage takes
place. The pressure of the filament against the sides of the groove in which it is
placed secure precisely this result and a tension is placed upon the same throughout
its length, although a similar result could be obtained by fastening the end or ends
of the filament before and during carbonization.
It may be found desirable in some instances to cover the filament, after it has
been placed in the mould with carbonaceous material for the purpose of more
thoroughly protecting it from any oxygen which may gain access thereto. This
may be accomplished by covering the filament as already stated with a thread
wrapped about in the groove, or coating it with some substance easily applied and
melted or distilled away like wax or paraffine.
In practice it is found that when the moulds are of iron more or less of the
carbon of the filament will enter into the iron forming steel throughout the
immediate surfaces of the grooves. For the purpose of avoiding such destruction
of the filaments, the moulds may be made of carbon, or of some other metal than
iron or nickle but it is preferred to make them of iron and to electro-plate or
otherwise coat the surfaces of the grooves with nickel. This may be readily
accomplished by any of the well-known methods of electro-plating or surface
coating.
It is necessary to provide some means for removing the filament from the mould
after it has been completely carbonized without doing injury to it. When it is
desired to remove the filament after carbonizing, the mould is dropped over a rod m,
shown in Figure 4, which is approximately the size of the interior bore of the
plug H. The rod is cool and has therefore, the effect of cooling the interior of
the moulds more rapidly than the exterior, and thus to produce a consequent
contraction of the interior section H2. The rod m extends from a base m¹ and is
constructed with a screw-thread m² upon the rod designed to receive a suitable
nut m³. This nut is employed to press against a flanged washer m which is
placed upon the rod after the mould has been placed in position. The flange m³ of
the washer rests against the upper end of the mould section H¹. By turning the
nut m³ downward the washer presses the outer section H₁ of the mould downward
causing it to slip by the section H2 the lower end of which is engaged by an
annular shoulder m° formed at the base of the rod m. A slight movement of the
outer section H¹ at once separates the two sections of the mould and the section H³
containing the carbonized filament may then be readily removed from the outer
section without bringing the filament into contact therewith, being guided by the
rod m. The filament is then removed from the mould it being sufficiently flexible
to allow of its being bent or sprung outward.

page_text: It is desirable that the niament should be subjected to as high a temperature as
possible before it is finally placed in the lamp for the higher the temperature to
which it is exposed, the more hard tough and firm will it become. The temperature
to which the filament may be exposed while in the moulds is limited to the
capacity of the moulds to resist the heat and not themselves become melted.
When therefore, the filaments are removed from the moulds, it is preferable to
pack them in loose carbon powder, and while thus packed they may be subjected
to as high temperature as may be desired. The carbon powder may for convenience
be contained in boxes or crucibles made of carbon, clay or other refractory
material, and a large number may be treated in the same bath. They will be
found to retain their shapes during this treatment and when removed from the
carbon powder will be found to be exceedingly hard and tough.
The surrounding carbon powder prevents also the access of air to the filaments
both during the process of heating and during the time the filaments are being
cooled.
The core or plug H2 may be placed in the bath of powdered carbon when the
filament is first applied; the filaments being held in place by the threads, in which
case the section H₁ of the mould would be dispensed with. When the core is to be
used in this manner it may with advantage be of carbon or other refractory
material, though it is not necessary that it should be.
The next step in the process of manufacture is that of electro-plating the ends of
the filainent. The metal which it is usually preferable to employ for this purpose
is copper but other metals may be employed. For this purpose an apparatus of
the character illustrated in Figures 6 and is employed. This apparatus consists
of a clamp N, having its ends split or cut apart, as shown at n¹ and n², and
provided with set screws n³ n³. The ends of the filament are respectively placed
in the ends n¹ and n³ of the clamp and securely held in position by means of the
clamping or set screws n³. The entire clamp is thus suspended in any suitable
manner with the ends in an electro-plating-bath, as shown at O, the curved or
bent portion of the filament extending outside of the bath, as shown in the
Drawing.
Any suitable process of electro-plating may then be employed. In the Drawing
I have shown a battery having one pole connected with the clamp N by a wire or
supporting rod and the other with a copper electrode o. Owing to the form of the
contact which exists between the metallic suspending clamp N and the ends of the
filament, only a short time is required to completely coat the ends of the filament
with copper. After this is accomplished the filament may be removed from the
bath and may be very conveniently handled by taking hold of the copper-plated
ends. The ends will bear a very considerable pressure when thus coated, whereas
they are very easily fractured when not so coated. The portions of the filament
which were held by the clamps may, if it is so desired, be cut off, the filament
having in the first place been made of such length as to allow of such portions
being removed.
By so cutting off the ends of the filament the extremities are left bare, that is to
say, not covered by the metal. This is of especial advantage because during the
process of curling the filament the fluids contained therein tend to be driven and to
collect at the cooler portions that is to say near the ends which are in contact with
the support. Now if the ends were completely covered the fluids would be
confined in the carbon surrounded by the metal but the extremities being open
they readily escape therethrough.
The next step in the process of manufacturing the lamp consists in clamping the
ends of the electrodes into the supporting conductors for the same. Each of these
conductors is made in a manner which will be described in connection with Figures
8, 9 10 and 11. At the end of a piece of platinum wire F, there is fused a globule
or ball f. This ball is either hammered or compressed into a flat disc. The two
halves of the disc are bent toward each other in the manner shown in Figure 10,
along the line of the wire F, and they are then bent over as shown in Figure 11.

page_text: The two semicircular sections or lips are then clasped upon the metal coated end of
the filament to which it is applied and, if it is so desired, they may be soldered
thereto in any convenient manner.
The two conducting wires are secured to each other by means of a bridge f2 of
glass. This bridge consists merely of a small section of glass tube having the
conducting wires inserted through it and let into its respective sides by softening
the glass or by moulding the glass about the wires. The bridge-piece may be
applied either before or after the filament has been clamped to the wires.
The filament and the conducting wires, having been prepared in this manner,
they are placed within the globe. The diameter however of the curve of the
filament is preferably made somewhat greater than the diameter of the opening
into the globe, for the purpose of giving to the lamp a capacity for giving light
as great as possible and for rendering the size of the globe as small as possible,
relatively to the length of the filament. It is therefore necessary to first insert
the loop h³ of the filament, into the globe and to spring the entire filament in by
slightly bending the double loop during the process. When however the loop is
once within the globe it resumes its normal shape and form.
Referring now to the form and method of constructing the vacuum chamber and
of closing the same A represents a cylindrical glass tube at the end of which is a
bulb B which is preferably formed by blowing into a suitable mould. The bulb B
is made of the size which it is desired that the lamp shall have. Instead of
blowing it in a mould, however, it may be blown directly on the punty from the
metal in the glass makers crucible, or from a tube of any diameter. The globe, it
will be particularly noticed, is thus formed without any projection at the side
opposite the tube A but with an entirely smooth surface. The tube or neck is
then narrowed toward the contraction where it is to be finally closed.
The globe is placed in a lathe and a portion of the neck or tube A is cut off at a
point on the curved part which is of less diaincter than the neck as indicated,
along the line xx in Figure 12, leaving a short neck, about one half of an inch
in length. Before the section of the neck is cut off however, a mark is preferably
put upon
the same to indicate the positions which the two pieces originally
occupied, so that the portion a¹ of the neck or tube can be re-applied to the
portion a after the filament and conductors have been inserted in the globe B.
The carbon filament, the form and manufacture of which has already been
described, is then inserted within the bulb or globe B, the portion ³ being first
inserted through the neck a and the filament being then bent in such a manner
as to allow its entire length to be pushed forward into the interior of the globe.
The flexibility of the filament will permit this to be accomplished although it
would not be possible to bend the two sides of the curved filament toward each
other sufficiently to permit the filament to be inserted in a flattened form. This
method of insertion is also applicable to other forms of filaments. After tho
filament is within the globe it will immediately resume its previous form.
After the filament H is placed within the globe the conducting wires F, F which
sustain the same, are caused to rest across the edge of the neck a of the globe B,
in the manner indicated in Figure 13 and the latter is, by means of a blow-pipe
or in any other suitable manner, heated sufficiently to soften the glass around the
conducting wires and to allow them to sink by their own weight into the edge of
the neck, forming slight depressions. The glass, however, will close over the
conductors thus completely embedding them in the neck of the globe and securing
a tight joint, or a small piece of glass may be added to each conductor for that
purpose, if necessary.
The next step in the process consists in replacing the section a¹ of the tube A
upon the neck a of the globe. The marks which were applied before the section
was cut off or removed, serve to guide the workmen in replacing the latter in the
precise position which it at first occupied. By means of a blow-pipe or in any
other suitable manner, the two portions of the glass are then welded together
along the line x¹ x¹ as shown in Figure 14, and the lamp resumes its former shape,

page_text: the filament H and the conductors F having been inserted. It will be understood
moreover that the two portions of the globe are entirely homogeneous and that
the disadvantage of having glass of different thicknesses or different qualities in
the lamp is entirely avoided.
A platinum stopper d, having at one and a loop or head e, is then inserted within
the narrowed opening of the globe or neck and the tube is narrowed sufficiently to
prevent this stopper from falling out. The lamp is then applied to an air-pump,
by means of which the air is exhausted from the chamber.
When the vacuum has been formed in the chamber B, the neck of the globe is
closed about the platinum stopper d, thus forming a tight joint. It is not found
necessary, in so closing the globe, to form a temporary sealing at some distanco
below the point where the globe is permanently closed as is usually customary in
other forms of lamp, but the lamp may be closed once for all while still upon the
air-pump; and it may further be observed, that since the point of closing is at the
end of the globe which enters the holder, it may be made at such a distance from
the globe as may be desired, whereas, in a lamp which is sealed at the other
extremity of the globe, it is necessary to form the final seal as close to the globe
as possible. For convenience however in shaping the glass around the pin it may
in some instances, be preferred to first seal the lamp at a second lower contraction
to permit of the final closing to be done at the glass blowers table instead of on
the pump.
After the lamp has been closed the neck formed or extending below the point of
closure may be readily broken off or removed. The unnecessary portion of the
platinum stopper may by means of any suitable tools then be cut off and ground
down even with the glass tube; or the neck may be drawn down to a beak and
then only the stopper is required to be cut off.
It is well-known that platinum when cooled sends out gases which are occluded
in the metal while it is heated, and for the purpose of preventing such gases from
escaping from the stopper into the glass of the tube, it is advisable to conduct
the process of closing the glass around the stopper at as low a temperature as
possible or it may sometimes be preferred to coat the latter with a thin film of
glass preparatory to inserting it within the globe. By reason of this film of
glass, gases would not be given off which were occluded before the closing of the
globe.
The glass as it is closed about the stopper enters the pores at the surface of the
platinum stopper and forms a tight joint without forming any chemical union
therewith.
Such a film of glass is preferably applied by first inserting the platinum wire
into a tightly fitting glass tube, then placing the same in a suitable chamber and
exhausting the air therefrom. While thus in a vacuum the platinum wire is
heated to incandescence. The gases are thus driven out from the platinum and
the glass then enters the pores of the platinum by reason of the capillary attraction
and in this manner a very close mechanical contact is formed between the two
materials. The vacuum chamber may, if it is so desired, be allowed to suddenly
fill with air while the platinum is still beated and the glass will then be brought
under a pressure which insures that it will penetrate the pores of the platinum.
Not only may the platinum stopper be thus treated, but the conductors leading
to the filament may also be treated in the same manner.
The platinum stopper may instead of being cut-off at the end of the beak, be
allowed to protrude, and then it may be bent into a loop as shown in Figure 15
for the purpose of affording a convenient means of hanging the lamp.
It is desired also to call attention to the fact that the stopper may be placed at
the end of the lamp opposite the neck the usual projection being formed at that
end, for the purpose.
It remains now to describe the holder which it is preferable to employ for
sustaining the lamp in position. Such a holder is illustrated in Figures 1, 16 and
17. Referring to those Figures, R represents a suitable calyx of the proper, size

page_text: for receiving the neck B¹ of the lamp. In this calyx the neck is designed to fit
and to be held securely by means of suitable lugs which are designed to enter
depressions 2 formed in the sides of the neck of the lamp. These depressions are
formed while the shank about the lamp is still softened by heat.
Soldered to the ends of the supporting conductors F are suitable conducting
wires 8 and 82 which extend to the lower end of the supporting calyx R, and
through these conductors it is designed that the connections of the lamp shall be
completed. For this purpose a plug or nut S¹ is inserted at the lower extremity
of the calyx R and either screwed into the same or tightly fastened, in any
suitable manner. In the lower ends of the nut or plug there is set a ring t¹ of
conducting material surrounding a disc t2 of like material. The disc and ring
are insulated from each other, the nut itself being of insulating material. The
conductor s¹ is soldered to the ring t', while the conductor 82 is united with the
disc t³. The ring and the disc both preferably project a slight distance beyond
the face of the nut.
A second nut S is designed to be applied to the extremity of the calyx R and
this nut is provided with a ring t³ and dise t' similar to the parts t¹ and t. The
second nut S, by being screwed into the case or calyx R, brings the two rings
against each other and likewise the two discs thus making two perfect electrical
connections. The ring t³ and the disc t' are respectively provided with conductors 83
and 8, which are connected with the connecting wires of the system in which the
lamp is to be employed so that either by screwing the calyx upon the neck or the
latter into the calyx the lamp will be placed in circuit.
It is understood that suitable circuit interrupting devices may be applied to the
supporting calyx as desired. Instead of two of the depressions and lugs formed
in the neck of the lamp for securing the calyx, any number may be employed, and
they may be extended throughout the length of the neck, if so desired, for the
purpose of preventing the lamp from being turned when in position, or the side of
the neck may be flattened if it is found desirable.
Having thus described the nature of this Invention and the manner in which it
is to be performed, as communicated to me by my foreign correspondent I would
have it understood that I claim :
1. In an incandescent electric lamp the combination, substantially as hereinbefore
set forth, of a transparent chamber having its neck formed of two sections of
homogeneous glass cut apart and welded together, with the metallic conductors
leading through the joint thus formed, and a metallic stopper at or near the end of
the neck around which the glass of the neck is closed.
2. In an incandescent electric lamp, an enclosing globe for the filament having
its neck formed from two sections of the same piece of transparent material, which
have been cut apart for the insertion of metallic conductors and replaced after such
conductors have been inserted.
3. In an incandescent electric lamp, the combination substantially as herein before
set forth of an enclosing chamber for the filament, conductors leading through the
wall of the chamber and a stopper of platinum closing the evacuating opening of
the chamber.
4. In an incandescent electric lamp, a glass enclosing chamber for the filament
formed in two sections which have been welded together, and conductors leading to
the filament which are embedded in the glass of one of the sections, substantially
as described.
5. In an incandescent electric lamp, a glass enclosing chamber for the filament
formed in two sections which have been sealed or welded together under the
influence of heat, and conductors leading through the walls of one section which
conductors have been sunk into the edge of that section under the influence of heat,
substantially as described.
6. In an incandescent electric lamp, a platinum conductor passing through the wall
of the enclosing chamber, which conductor has been coated with a film of glass by
being heated in vacuum while surrounded by glass, substantially as described.

page_text: 7. In an incandescent electric lamp, a metallic wire passing through the wall of
the enclosing chamber and having a loop formed at its outer end, substantially as
described.
8. In an incandescent electric lamp, the combination of a transparent vacuum
chamber, formed of two parts united by a sealed joint, and metallic conductors
entering the chamber at or within said joint.
9. In an incandescent electric lamp, an air-tight joint formed by sealing or fusing
together the parallel surfaces of an upper and lower cylinder, with metallic
conductors between them.
10. A filament for incandescent electric lamps formed in the shape of two
incomplete circles united with each other, substantially as described.
11. A filament for incandescent electric lamps consisting of two approximately
parallel curved portions united at corresponding ends and supported at their free
ends, substantially as described.
12. A filament for incandescent electric lamps consisting of a loop of incandescing
material bent so as to form two curves, substantially as described.
13. A carbon filament for incandescent electric lamps having its respective ends
coated with metal by electro-deposition, substantially as described.
14. A carbon filament for incandescent electric lamps, having its outer extremities
covered with a metal which has been applied by clectro-deposition and its ends
bare, substantially as described.
15. The herein before described method of introducing within a globe a curved
filament having a greater diameter than the opening through which it is to be
inserted, which consists in placing one end of such filament or a loop of the same
within said opening and temporarily bending the same as may be necessary to
force the entire filament through the opening.
16. The herein before described method of introducing a curved incandescent
filament within a globe having an aperture of less diameter than the diameter of
the curve of the filament, which consists in first inserting one end of the curve
through the opening and causing the entire filament to enter thereafter.
17. An incandescent electric lamp having a filament formed in a curve of greater
diameter than the diameter of the opening through which it was inserted.
18. The hereinbefore described method of treating carbon filaments for
incandescent electric lamps which consists in first shaping and carbonizing them in
moulds and subsequently subjecting them to heat in a bath of powdered carbon or
hydro-carbon substantially as described.
19. A cylindrical filament carbonizing mould having grooves formed in its outer
surface for receiving the limbs of the filament, in combination with means
substantially such as described for covering said grooves.
20. A filament carbonizing inould consisting of a core having grooves formed in
its outer surface for receiving the filaments, and a tubular enclosing case for
said core.
21. A filament carbonizing mould consisting of a core having the shape of a
frustrum of a cone and having grooves formed in its surface for receiving the
filaments, and an enclosing case for the same having a bore conforming to the outer
surface of the core, substantially as described.
22. A filament carbonizing mould consisting of a core having grooves formed in
its outer surface for receiving the filaments which grooves are electro-plated with
nickel or other similar metal, and an enclosing case for said core.
23. The combination, substantially as herein before set forth, with an incandescent
electric lamp, of a holder which holder consists of an outer shell surrounding the
neck of the lamp having at one extremity two insulated contact-points or plates
which are designed to be respectively connected with conductors leading to the
two ends of the lamp filament, which points or plates are respectively a central
conducting surface and a conducting ring surrounding the same, and two
corresponding insulated contact-points or plates which are designed to bo

page_text: respectively connected with the two portions of the main conductor and means
substantially such as described for placing the last named contact-plate in contact
with the first named plates respectively.
WP. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Agents for the Applicant.