CARBONS FOR ELECTRIC LAMPS
Year: 1885

page_text: I, JAMES SWINBURNE, of 9 Manor Rd., Brockley in the County of Kent,
electrician, do hereby declare the nature of my invention for CARBONS FOR
ELECTRIC LAMPS to be as follows:-
For glow lamps of very high resistance long thin carbons are necessary, and
these are difficult to handle. It has been proposed, not, perhaps, in connection with
high resistance lamps, to put several filaments in one globe. This, in the case of
very fine filaments is troublesome, because there are more joints to make, & because
it is more difficult to make two filaments uniform. According to my invention a
long filament may be made with a loop or loops, & the loop or loops held by
supports, being shortcircuited in hydrocarbon or similar gas if necessary. Thus
to make a 200 volt 16 candle-power lamp a filament which would make two
100 volt 8 candle-power lamps may be made with a double loop. The ends may
be electrically joined to the leading in wires, and the bottom of the loop, which
will probably be between the leading-in wires, may be fastened to a third support.
The part of the loop touching the support may be thickened by shortcircuiting so
as not to be hot when the lamp is in use. By these means a lamp having the
advantages of a multiple filament lamp may be made with one continuous filament
instead of two or several joined together. The shortcircuited part may be electro-
plated to reduce its resistance or to fix it to the support. Instead of shortcircuiting,
a cement may be applied.

page_text: I, JAMES SWINBURNE of 3 Fairfield Villas Chelmsford in the County of Essex,
Electrician, do hereby declare the nature of my invention for IMPROVEMENTS IN
FILAMENTS FOR ELECTRIC GLOW LAMPS. and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
When it is desired to make an incandescent lamp of high electromotive force,
a long thin filament with the necessary radiating surface has to be used; and in
lamps as at present generally constructed a limit to the length and thinness of the
filament is soon reached, for the filament, if made too thin bends about too easily
and is easily broken by any jars or shocks.. Thus if a filament of about the specific
resistance & strength of those generally in use be made of the right length and
surface to give, say, twenty candle power at eighty watls and a hundred & twenty
volts it will be about as long & thin as can well be used.
My invention has for its object the use of longer and thinner filaments, so that a
higher electromotive force may be available. Thus a filament to give ten candles
at 100 volts is now not difficult to make, and as it is shorter than the 100 volt
20 candle filament above mentioned, it does not bend about so easily though it is
thinner. If two such filaments be put in one lamp, & connected in series, a
200 volt 20 candle lamp is obtained. This method of making high resistance
lamps is, I think already known; but has some great disadvantages. It is difficult
to mount two separate filaments so as to get them set truly, and the labour is as
great as in mounting two filaments for separate lamps. It is also difficult to get
two filaments, separately made, sufficiently carefully adjusted as to their resistances,
and it is expensive to adjust two filaments for each lamp.
According to my invention one long filament is used, and it is supported at the
point where the two filaments above described would be joined.
Thus in fig. 1a a is the filament, which is cut from a continuous piece shewn in
fig. 3.
The lower end of the loop c is thickened by being electrically heated in,
say, coal gas. It is rigidly held by a little loop e sealed into the glass stem d.
The ends of the filament are connected to the leading in wires bb as usual. The
filament can be flashed before the loop c is thickened or after, & may be finally
adjusted after mounting if desired. Fig. 2 shews a lamp with a 3 loop filament
and two thickened loops. The wires e e should hold the loop firmly. Fig. 3 shews
some of the filament when made in long pieces before being cut up.
The same method of supporting long filaments is applicable when the filament is
made in the form of a helix; &, in fact, the filament may have any suitable form.

page_text: Having now particularly described & ascertained the nature of my said Inveu-
tion, and in what manner the same is to be performed I declare that what
I claim is:
1. A long thin filament for an incandescent lamp supported at an intermediate
point or points along its length substantially as described.
2. A filament so supported thickened at the point or points of support.
3. A looped filament with 2, 3, or more loops supported substantially as shewn
in Figures 1 & 2.
4. Supporting the filament of an incandescent lamp by attaching an intermediate
point or points to the stem.