Improvements in the Manufacture of Electric Incandescence or Glow-lamps.
Year: 1891

page_text: Date of Application, 18th July, 1891-Accepted, 12th Sept., 1891
Improvements in the Manufacture of Electric Incandescence
or Glow-lamps.
We, PAUL SCHARF, Engineer & Inventor, and RUDOLF LATZKO, Manu-
facturer, both of Vienna, in the Empire of Austria, 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 :—
This invention relates to a simple and inexpensive process of making electric
incandescence or glow-lamps and has for its chief object to provide a substitute for
the use of platinum for the leads employed therein.
Hitherto platinum wires or strips have been the only practical means of leading
in the electric current through the glass envelope to the conductor to be rendered
incandescent. This use of platinum adds considerably to the cost of production of
the lamps, and numerous attempts have been made to find a less expensive practical
substitute but these attempts have hitherto failed owing to one or more of the
following causes :—
.
Firstly the co-efficient of expansion of the substitute for platinum has not been
of equal or nearly equal value to that of the glass or other envelope into which the
substitute has been sealed and it has consequently been impossible to produce a
vacuum-tight joint;
Secondly because the substitutes became oxidized when heated to the necessary
degree to make a joint with the glass or other envelopes and consequently the joint
has not been vacuum-tight;
Thirdly because the temperature necessary was sufficient to melt or destroy the
substitute for platinum.
Our invention has none of the above defects, and consists in using leading-in
conductors of the common metals, such as copper, iron, etc., instead of platinum
without sacrificing any of the practical advantages which have hitherto been
considered peculiar to the use of that metal.
We will now proceed to describe our invention with reference to the accom-
panying drawing, forming part of this Specification, wherein Figures 1 and 3 shew
finished lamps and Figures 2 and 4 shew various glass-blower's methods of
introducing the mounted carbons into the bulbs and forming the holes or tubes for
the leading-in wires. Figure 5 shews in section on an enlarged scale details of the
junction of the metallic conductor with the glass tube through which it is led, the
joint being made by soldering. Figures 6 and 7 shew in section on an enlarged
scale details of the joint made by the use of a metallic cap which forms one of the
lamp electrodes.
We first make two small openings in the glass bulb for the leading-in wires, as
shown at a Figure 3, and we preferably fuse on at the openings in the glass bulb
two small glass-tubes, as shown by bb Figures 1 and 2, the mounted carbons being
introduced at the opposite end of the bulb by the opening or neck (shewn in
Figure 2) which is afterwards finished off by the glass-blower, as shewn in
Figures 1 and 3. On the edges and surfaces immediately around and adjacent to
any of these various forms of openings, we apply an intimately-adherent coating of
a noble metal (as described below) and to this coating of noble metal we then join
the metallic conductors or leading-in wires of common metals to which the carbon
conductors or filaments have been previously affixed. To make this junction
between the two metals, we employ the ordinary operation of soldering and for this
purpose we use a soft solder having tin as one of its constituents, or we employ the
electrolytic method for obtaining the junction, or we employ a combination of these
two methods. We apply the noble metal in the form of a metallic powder or

page_text: as a chemical combination and in either case in admixture either with an oil
(i.e. camomile oil, turpentine, etc.,) or a resinous body such as canada-balsam,
copaiva-balsam, resin oil, or any other which will form a thick liquid or paste with
and act as a vehicle for the noble metal or its compound of such a nature that it is
completely volatilizable by the application of heat leaving only the noble metal
remaining in intimate contact or incorporated with the glass. We prefer to use
silver, platinum, or gold, in the form of a metallic powder or precipitate.as
generally used for decorating porcelain, in order to obtain a denser and more
intimate junction of both the noble metal to the glass and (because of greater
thickness of the solder to the noble metal than is possible when using any
chemical combination of the noble metals, such as nitrates, chlorides, etc.
prefer, and obtain the best results with, silver but do not restrict ourselves to it
exclusively.
We
We add to the silver or other metal or compound thereof a small amount of
canada balsam or copaiva balsam or any of the other matters aforesaid but
preferably the first two and this mixture we reduce to the finest possible state in a
muller. When reduced to the consistency and fineness of a thick cream we
carefully apply the mixture to the surface of the glass around the openings or at
the ends of the tubes in or on the lamp bulb by means of a small brush or pencil or
by dipping the surfaces to be coated into the mixture. In Figures 5, 6, and 7, this
coating of noble metal is indicated by the dark portion c. The coating thus
applied to the glass is now carefully dried and is gradually heated to a temperature
sufficiently high to drive off the balsam or other vehicle and at the same time
sufficient to obtain an intimate adhesion or incorporation of the silver or other
metal to or with the glass (i.e. to burn it into the glass). We find that with too
high a temperature or by too long an application of heat, the metallic deposit is
rendered nodulous or non-continuous; we also find that too low a temperature
gives a non-adherent coat or deposit, and also that a good coat or deposit is more
readily obtained by revolving or moving the glass in the flame or other source of
heat. If by one application a successful result be not obtained, then one or more
successive coats may be applied as may be necessary but each coat must have been
previously well burnt on to the glass before applying a fresh coat. This part of
the operation can, with very little practice, be quickly and successfully performed.
The glass around the openings being thus prepared, they are ready for the insertion
of the leading-in wires.
We would here point out that the carbon conductors or filaments may by our
invention be directly mounted on or attached to their metallic supports which we
form out of iron or copper wire or of wire of any other suitable common metal and
of a sufficient length to reach from the carbon conductor or filament in one
continuous piece through the glass bulb to the outer electrode or terminal of the
lamp, as shewn in Figure 5 which represents the outer electrodes of a fitting such
as is used for bayonet holders (the outer brass ring (d) shewn in this figure being
attached to the glass by any insulating cement such as plaster of paris) whilst in
Figures 6 and 7 the iron or copper leading-in wires are soldered each to a small
metallic cap e. By using continuous metallic conductors, we avoid the usual and
more costly operations of making the leading-in conductors of two or three
separate parts, one of which parts having to pass through the glass bulb has
always been made of platinum.
The carbons or filaments having been previously affixed to the metallic con-
ductors in the usual manner, we introduce the mounted carbons into the glass bulb
and the metallic conductors on which the filaments are mounted are now inserted.
in the aforesaid holes or glass tubes (of which the surrounding surfaces have been
coated with a noble metal as above described) and the wires are adjusted therein.
so that the filaments are centred in the bulb in the usual manner (as shewn in
Figure 1) after which the neck at which the filament was introduced is drawn off
by a glass-blower and a small exhausting tube attached. We now proceed to join
the conductor of common metal to the aforesaid coating of noble metal c and for.

page_text: this purpose we use either the ordinary method of soldering with a tin-solder or
we use an electrolytic deposit of copper iron, silver, etc., by either of which methods
we can make a good and efficient vacuum tight joint between the two said metallic
surfaces. We obtain the cheapest and most efficient results by soldering with a
tin-solder applied by means of a soldering bit with the aid of a soldering fluid or
flux in the well known manner.
We would point out that the best way is to apply the soldering-bit (having the
melted tin-solder adherent to it) to the openings or ends of the glass-tubes 6 by
one or more touches of short duration as the quicker the coating of solder is
obtained the better is the result. By very little practice this operation can also be
quickly and successfully performed and a perfectly secure and vacuum-tight
junction made between the metal of the conductor and the metallic coating
incorporated with the glass.
In Figure 5, ff are the conducting wires, c the coating of the glass, and g is the
tin solder joining the coated surfaces to the conducting wires.
Another method is to use small metallic caps e of copper etc., (already mentioned)
which can be closed or can preferably have a small hole or opening for the better
insertion of the leading-in wires, as shewn by h Figure 6, these caps eventually
constituting the electrodes of the finished lamps. When using a metallic cap we
prefer to join it first on to the metallically-coated surface of the glass by the
soldering method and by using the same precautions and operations as already
described. Or the metallic cap may be attached to the coated surface of the glass
by an electrolytic deposit. These metallic caps e having been slipped over the
ends of the projecting glass tubes which have previously received an intimately
adherent coat of a noble metal (in the manner previously described) they are
attached thereto by solder or an electrolytic deposit and the conducting wires f of
copper, iron, etc., are inserted through the small holes hand in some cases cut off
short, as shewn in Figure 7, or they can be left longer for attachment to other
fittings. The wire fis in all cases finally soldered to the metallic cap e by the use
of a tin-solder in the usual manner.
We wish it to be understood that we do not confine ourselves to the particular
methods of introducing the mounted carbons or filaments into the glass bulbs as
here described, for any of the other well-known glass-blower's methods are equally
applicable to the invention. For instance, the leading-in wires can be first fixed
by the methods just described to the neck portion made separate from the bulb and
then the filament can be introduced into the bulb and this neck portion finally
sealed on to the lamp bulb so as to form a neck or elongation of the same, as
shewn in Figure 4. Various methods of manipulating the glass and the joint in
the same will suggest themselves as being the best or equally applicable according
to the particular purpose for which the lamp is to be used and the variety of
fitting it has to be adapted to. The dimensions of the filaments and bulbs will
also vary according to the particular method employed.
Having now particularly described and ascertained the nature of the said inver-
tion and in what manner the same is to be performed, we declare that what we
claim is:
1st. In electric glow lamps, the method of attaching the leading-in conductors
of common metal to the glass envelope by first affixing a coating of a noble metal
on that part of the glass through which the conductors are to pass and then joining
the leading-in wires to the said coating of noble metal by means of a solder,
essentially in the manner set forth.
2nd. In electric glow lamps, the method of joining the leading in conductors
of common metal to the coating of noble metal on the glass envelope by means of
an electrolytic deposit, substantially as described.
3rd. In electric glow lamps, the combination of small glass tubes affixed to the
glass bulb through which tubes the metallic conductors are led and to the outer
ends of which tubes is attached a coating of noble metal to which the leading-in

page_text: conductors are attached, as set forth in Claims 1 and 2 substantially as and for the
purpose described.
4th. In electric glow lamps, the combination of small glass tubes affixed to the
glass-bulb through which tubes the metallic conductors are led and to the outer
ends of which tubes is attached a coating of noble metal to which the leading in 4
conductors are attached by first attaching small metallic caps to the ends of these
glass tubes the edges of which have been previously covered with noble metal and
then by affixing by solder or electrolytic deposit, the outer ends of the leading-in
wires to these metallic caps, substantially as and for the purpose set forth.
11
0 T1 1001
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P. SCHARF.
R. LATZKO.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.