Improvements in the Manufacture of Incandescence Electric Lamps.
Year: 1889

page_text: Improvements in the Manufacture of Incandescence Electric
Lamps.
I, JOHN WIGITAM EDMUNDSON, of Park Road, Gateshead-on-Tyne, in the County
of Durham, Engineer, do hereby declare the nature of this invention to be as
follows:-
As is well known the surface of a carbon conductor forming the illuminating part
of an incandescence electric lamp, unless suitably prepared, will, if heated to incan-
descence in the lamp, in time become disintegrated and the carbon thus detached
will settle upon and blacken the glass of the lamp.
Now in order to remedy this defect and with the view of being able to make as
many conductors as may be desired, all of the same resistance, I prepare carbon
conductors by coating the same with a metallic deposit as 1 will proceed to
describe.
A suitable metal for my purpose is chromium as its fusing point is very high;
it combines with the carbon of the conductor, forms a highly conducting hard
covering to the carbon, fills up the pores, produces a beautifully smooth grey surface,
and is not liable to disintegrate.
After
This deposit of chromium can be produced in various ways; one of these is as
follows. I paint the surface of the carbon with a solution of the soluble chromium
chloride. I generally dissolve the chromium chloride in spirits of wine.
painting as above I warm the carbon either by placing it in an oven or by passing a
current of electricity through it, till the coating is quite dry (taking care not to make
the carbon red hot). I then place the coated carbon in a closed vessel and remove
the air by connecting it to an air pump capable of producing a very high vacuum.
Whilst in this vacuum I pass a strong current of electricity through the carbon
rendering it highly incandescent; the coating is thus decomposed, the chlorine passes
off and the chromium is absorbed by the carbon. This operation can be repeated till
the required coating is obtained, and as each operation reduces the resistance of the
conductor, the resistance of each conductor in a batch of carbons can be made the
same as that in each of the others.
TL 11
J
T1
1000
W. LLOYD WISE,
46, Lincoln's Inn Fields. London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Incandescence Electric
Lamps.
I, JOHN WIGHAM EDMUNDSON, of Park Road, Gateshead-on-Tyne, in the County
of Durham, Engineer, 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:-
As is well known the surface of a carbon conductor forming the illuminating part
of an incandescence electric lamp unless suitably prepared, will, if heated to incan-
descence in the lamp in time become disintegrated and the carbon thus detached will
and blacken the glass of the lamp.
settle upon
Now in order to remedy this defect and with the view of being able to make as
many conductors as may be desired, all of the same resistance, I prepare carbon
conductors by coating the same with a metallic deposit as I will proceed to describe.

page_text: A suitable metal for my purpose is chromium as its fusing point is very high; it
combines with the carbon of the conductor, forms a highly conducting hard covering
to the carbon, fills up the pores, produces a beautifully smooth grey surface, and is
not liable to disintegrate.
After
This deposit of chromium can be produced in various ways: one of these is as
follows. I paint the surface of the carbon conductor with a solution of the soluble
chromium chloride. Spirits of wine is a suitable medium in which to dissolve the
chromium chloride. A suitable strength of solution is obtained by dissolving about
one ounce of chromium chloride in about four ounces of spirits of wine.
painting as above, I warm the carbon either by placing it in an oven, or by passing
a current of electricity through it, until the coating is quite dry (taking care not to
make the carbon red hot). I then place the coated carbon in a closed vessel and
remove the air by connecting it to an air pump capable of producing a very high
Vacuum. Whilst in this vacuum I pass a strong current of electricity through the
carbon rendering it as highly incandescent as possible without producing a short
circuit across the poles in the vacuum; the coating is thus decomposed, the chlorine
passes off, and the chromium is absorbed by the carbon. This operation can be
repeated until the required coating is obtained, and as each operation reduces the
resistance of the conductor, (within certain limits) the resistance of each conductor in
a batch of carbons can be standardised or made the same as that in each of the
others.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. For an incandescence electric lamp, a carbon conductor coated with a metallic
deposit.
2. Coating carbon conductors for incandescence electric lamps with chromium in
the manner described above.
Dated this 20th day of November 1889.