IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1880

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS IN ELECTRIC
LAMPS." A communication from abroad by Patrick Drew, of Brooklyn, in the
County of Kings and State of New York, United States of America.
COMPLETE SPECIFICATION filed by the said William Clark at the Office
of the Commissioners of Patents on the 19th May 1880.
WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex, Patent
Agent. "IMPROVEMENTS IN ELECTRIC LAMPS." A communication from abroad
by Patrick Drew, of Brooklyn, in the County of Kings and State of New York,
United States of America.
These improvements relate to electric lamps having their electrodes contained
within a vacuum chamber of glass, the wires being sealed where they pass through
the glass by mercury or an amalgam enclosed around the wires. The present
Invention is designed to perfect such lamp and permit its construction with greater
facility. The first feature of the Invention consists in the construction of the
glass vacuum chamber and sealing tubes in such manner, that the tube is closed
around the wire at the portion least subject to expansion and contraction, and the
wire in that portion most subject to expansion is free to expand and contract
without affecting the glass. I also form the tube for drawing the air and the
tubes for containing the wires both at one side of the globe, so that the globe may
be made nearly spherical and of uniform thickness. use in the sealing tubes
mercury, or in place thereof dry plaster of Paris, chalk, or other dust or powder
which forms an air tight seal around the wire. Also, to prevent bad effects from
traces of air remaining in the vacuum chamber, I provide a secondary chamber
into which the residual air passes when the lamp is in use.
The improvements are shown in the accompanying Drawing, wherein Figure 1 is
a sectional elevation of an electric lamp embodying the improvements; Figure 2
represents the lamp formed with the secondary chamber; Figure 3 represents one
of the sealing tubes in larger size; Figure 4 represents the paper or other material
in the form it is cut before carbonisation; Figure 5 shows the sealing tubes in a
modified form. Similar letters of reference indicate corresponding parts in the
several Figures.

page_text: A, Figure 1, is the glass globe formed at one side with the tubular extension a,
and inner concentric cylinder a that is closed at the top, and formed with the
sealing tubes b, b. In this Figure the tubes b are formed with bulbs o for
containing mercury to seal the wires, but in Figure 5 the bulbs o are dispensed
with, the tubes being extended down below the extension a, and closed at their
lower ends around the wire. In both cases the conducting wires c pass freely
through the tubes, so that the portion of the wires below the carbon d is free to
expand and contract without danger of cracking the glass. The bulbs o, shown in
Figure 1 containing mercury, give additional security against ingress of air.
In Figure 2 the tubes b are shown as extended upward from the closed lower
end of the tubular extension a, and closed at their upper ends around the wires c.
The tubes b in this form are filled with plaster of Paris, powdered chalk, or other
fine dust placed in the tubes in a dry state, and retained if necessary by a plug of
plastic or other material placed in the lower ends of the tubes. This powdered
material forms an air seal around the wires.
The lamp shown in Figure 2 is formed at the lower end with a small tube e for
use in drawing the air from chamber A, in which is formed a bulb f of suitable size
and in communication with the chamber A. By thus forming the exhausting tubo
and sealing tubes at one side of the globe, I am enabled to produce a chamber of
nearly a spherical form and of uniform thickness throughout. The carbon ribbon d
instead of being connected to the wires e by clamps as heretofore, is shrunk upon
the wire during the process of carbonisation, and is also made of greater thickness
at the point of connection. This I accomplish by cutting the paper or other
material in the form shown in Figure 4, that is, with wings d' at the ends. These
wings are folded or wrapped over the ends of the wires to enclose the same, and
secured by adhesive material if required, and the material then carbonised in the
usual manner.
The wire is thus embedded in the material, and the carbon is
attached securely to the wires, and being of greatest thickness around the wire, the
principal resistance and greatest incandescence is in the carbon beyond the ends of
the wire, and there is no liability of the carbon being cut by the metal. In electric
lamps of this character the slight residuum of air remaining in the chamber causes
more or less waste of the carbon. There is probably a continual circulation of this
air and contact with the carbon, and it is for the purpose of relieving the chamber
A of this air that I use the secondary chamber f. This may be below the chamber
A or above it, as is found most efficient. The residual air will be forced by being
heated when the lamp is in use into the secondary chamber, and remain until the
current is cut off.
Having described the nature of the Invention, and the manner of performing the
same, I declare that what I claim as new and desire to secure by Letters Patent
is
1st. In electric lamps, enclosing tubes for the conducting wires closed at their
outer ends, and formed at their inner ends and portions next the carbon of a size
for wires to pass loosely for the purpose of allowing expansion, substantially as
described.
2nd. In electric lamps, the bulbs for containing mercury or other sealing
material combined with enclosing tubes for the wires, having their ends and
portions next the carbon of a size for the wires to pass loosely, substantially as and
for the purposes set forth.
3rd. In electric lamps, the tubes of the conducting wires packed with plaster of
Paris, chalk, or other fine powdered material, as and for the purposes specified.
4th. The glass chamber or globe for electric lamps formed with the tubular
extension a, sealing tubes b, and drawing tube e at one side, substantially as and
for the purposes set forth.
5th. In electric lamps, the combination with the exhausted chamber A, of the
secondary bulb or chamber in communication therewith, substantially as and for
the purposes set forth.

page_text: 6th. The method of connecting the carbon ribbon and conducting wires which
consists in embedding the wire in the material previous to carbonisation, substan-
tially as described.
7th. The carbon ribbon attached to the conducting wires by being folded or
wrapped thereon, whereby the metallic conductors are embedded in the material,
substantially as and for the purposes set forth.
In witness whereof, I, the said William Clark, have hereunto set my hand
and seal, this Nineteenth day of May, in the year of our Lord One
thousand eight hundred and eighty..
W. CLARK,
(L.S.)