MENTS IN INCANDESCENT ELECTRIC LAMPS. IMP
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said Frederick Leopold Willard
at the Office of the Commissioners of Patents on the 28th June 1882.
FREDERICK LEOpold Willard Electrician 85, Hoxton St N. London
MENTS IN INCANDESCENT ELECTRIC LAMPS.
IMPROVE-
My Invention consists in improvements in the construction of Incandescent
Electric Lamps; or that class of lamp in which a substance offering a considerable
resistance to the passage of an electric current, is heated thereby to a very high
temperature and so emits a brilliant light, but is not consumed; because all air
is exhausted from the vessel containing the heated filiament. As is well known
to electricians the slender filiaments of carbon, in general use are frequently
ruptured, and the lamp rendered useless on account of the expansion, and con-
traction which they undergo when subjected to varying degrees of heat, through
irregularity in the flow of the current, or when the current is switched on or off.
My Invention has for its object, the prevention of rupture from this cause, by
permitting the heated filiament to adjust itself, to sudden variations of heat by
free contraction and expansion, I accomplish this in the following manner-
The leading in wires which may be of Platinum, or other metal, capable of
bearing a high temperature, are fused in the usual manner, into the two ends of
a thin glass bulb: intended to hold the carbon filiament, such bulb having at its
base; a small bulb containing mercury, or some similar substance of a conducting
nature. The filiament, which I make of a special form of carbon, bereafter
described, is cemented with a mixture of coal tar, and coke dust to two platinum
wires, one of which is fused into the glass bulb, forming the body of the lamp, and
constituting one of the leading in, or connecting wires, before referred to, and the
other is allowed to pass into the smaller bulb, before mentioned containing the
merenry, the neck of this small bulb, being narrowed down upon the platinum
wire, connected to the filiament so that the mercury cannot run out, but at the

page_text: same time allowing the wire to move freely up, and down in such neck. Into the
outer end of the small bulb, a platinum connection is fused, and good contact made,
by insertion in the mercury contained in the bulb. The bulb is now exhausted in
any convenient manner; Upon a current of sufficient strength being sent through
the filiament to render it incandescent, no strain is set up in it as it is quite free to
adjust itself by expansion or contraction into the bulb. containing the mercury.
I prepare my carbon filiament from vegitable or animal substances, and have found
a species of wood veneer, commercially known as "white lines" specially suited
to my purposes. I also use Ivory, in thin strips, and have obtained a very stable
conductor from it. A thin strip of the wood veneer, white lines, carbonized by
being baked out of contact with air, until all the volatile substances are driven off:
forms a conductor of high resistance, and of great tenacity. In order to adjust a
filiament, cut from this wood, or from Ivory, to a suitable resistance. I further
carbonize the same, by holding it in the naked flame of an ordinary gas, mineral.
or animal oil lamp, I sometimes treat my wood, or ivory filiaments, with acids or
other chemicals, to rid them of any organic impurity, that might interfere with
their homogenity, when reduced to carbon: also sometimes reduce my wood or
ivory, for filiaments, to a condition of pulp. by treatment with such chemicals, as may
be needful, to obtain such an end. The pulp being of the same character, as that
from which wood paper is made: I then roll such pulp, into sheets, stamp out my
filiaments, and carbonize in the manner above stated. I sometimes deposit platinum
or iridium, electrolytically upon the carbon filiaments. in order to fill up any pores
that may exist or to render the said filiament quite homogeneous; accomplish
this, by immersing the filiament in a solution of platinum. or iridium, and decom-
posing the same, by passing a current through the filiament.

page_text: SPECIFICATION in pursuance of the conditions of the Letters, Patent filed
by the said Frederick Leopold Willard in the Great Seal Patent Office on
the 28th December 1882.
FREDERICK LEOPOld "Willard Electrician Hoxton Street London N. IMPROVE-
MENTS IN INCANDESCENT ELECTRIC LAMPS.
My Invention consists in improvements in the construction of Incandescent
Electric Lamps, or that class of lamp in which a substance offering a considerable
resistance to the passage of an electric current is heated thereby, to a very high
temperature, and so emits a brilliant light, but is not consumed because all air and
as far as possible every trace of oxygen is removed from the vessel containing the
heated filiament. As is well known to electricians, the slender threads or filiaments
of carbon generally used to produce the light are frequently ruptured, because both
ends of the strip or loop are rigidly connected to the leading in wires of the lamp,
and so are not free to contract and expand under the varying degrees of heat to
which they are exposed, by slight alterations in the quantity of current passing
through them. My invention has for its object the prevention of rupture from
this cause by permitting the filiament to expand or contract freely. I accomplish
this in the following manner. The leading in wires which may be of platinum or
other substance which can be readily fused into glass, are inserted in the two ends
of a cylindrical glass bulb in which I place the carbon filiament this bulb has at
its base a small bulb or cylinder containing mercury, or some substance which
when heated does not give off oxygen or any other vapour or gas which can injure
the carbon strip or filiament. This filiament I make from a species of veneer called
"white lines"in the way and manner more particularly described hereafter, and
when thoroughly carbonized, and adjusted to a resistance suited to my purpose,
cement it with a mixture of coal tar, and coke dust to the leading in wire of the
lamp, one of which is fused into the end of the glass bulb as before described, the
other end of my filiament is cemented in a similar manner to another piece of
platinum, or suitable wire which dips into the mercury or other conducting
substance, in the smaller bulb; the other leading in wire being fused into the
smaller bulb, good electrical contact is made with the filiament through the mercury,
or other conducting substance, filling the bulb: the smaller bulb is narrowed down
at the end next the cylinder containing the filiament, so that the glass may form a
very narrow channel, or passage round the platinum wire connecting the filiament
with the mercury, but the wire can move freely up and down, while on the other
hand the passage is not large enough to allow the mercury to escape into the
larger bulb in which the filiament is placed. The cylinder being exhausted in
any suitable manner and connection made with some source of electricity of
sufficient quantity to render the filiament incandescent it is quite free to expand or
contract, and adjust itself to the variation of current employed, can also
accomplish my object with a solid conductor. To do this I narrow down both
ends of the smaller bulb and pass the platinum or other connection from the
carbon through the bulb, and into the narrow neck at the opposite end to the
cylinder containing the carbon. The smaller bulb is now filled with granules of
pure tin. copper. or iron which surround the wire leading from the filiament.
I then fuse my leading in wire into any convenient part of the smaller bulb.
taking care to make good metallic contact, with the granular metal in the bulb
the filiament is quite free to expand, as in the mercury, and this method is less
costly. I use for my filiament, a veneer commercially known as "white lines". but
I have found ivory in thin strips make a very good conductor when carbonized.
I prefer the vencer however. A thin strip of the "white lines" is carbonized by
baking out of contact with air, until all the volatile portion is driven off. It then
forms a conductor of high resistance, and great tenacity. In order to adjust the
filament thus treated, to a suitable resistance, I deposit carbon upon it by holding
it in the naked flame of an ordinary gas, mineral, or animal oil lamp. I sometimes

page_text: treat the filiaments with acids, alkalies, or other substances to destroy all traces of
organic matter likely to interfere with their homogenity, and also reduce the
woody substance to pulp by suitable chemicals. I then roll it into sheets, stamp out.
and carbonize. I also render the filiaments homogeneous, by immersing them in a
solution containing platinum or iridium and decomposing the solution by sending
a current through it: or I can effect the same object by electrolysis. The
filiaments are fastened to the platinum wires by a cement made of cannel coke dust.
and coal tar, the ends being thickened up to increase their surface so as to avoid
heating, when raised to a red heat, this makes a firm joint
Having now generally described my invention, I will do so particularly, by the
help of the drawing Fig Shews the form of Bulb or Cylinder I prefer to use
A. B are the leading in or terminal wires, ( is the joint, and D the filiament.
E is the connecting wire dipping into the smaller bulb F. filled with mercury.
Fig 2 shews another form which is identical with Fig 1 but the bulb F is filled
with granules of metal, in place of mercury, and has two necks the wire being
steadied by these. Fig 3 shews a pear shaped bulb, which can be mounted with
mercury, or granular metal as desired Fig 4 shews a double bulb which can be
mounted with carbons of equal, or unequal resistance as may be desired mercury
or granular metal can be used in either or both bulbs F
Having now described my invention would have it understood that I do not
confine myself to the exact details shewn and described since they can be modified
to some extent without departing from my invention. I lay no claim to the ivory
strips referred to as forming good conductors nor to the woody fibre reduced to
pulp, but what I claim as original and desire to secure by these letters patent is
1st A carbon filiament made from the veneer commercially known as white
. lines so suspended in the exhausted receiver, or vessel as to be free to expand or
contract in the way and manner herein described.
2nd A Cylinder, Sphere or bulb having at one end a smaller cylinder or bulb
to which it is united by a narrow neck, or tube. Such smaller cylinder being filled
with mercury or metallic granules, the connecting wire from the carbon filiament
dipping into such mercury, or passing through such granules into a narrow neck
beyond as and for the purposes herein described
3rd The method of joining the carbon filiaments to the leading in and
connecting wire by a cement made of cannel coke dust, and coal tar heated to
redness.
4th The combination in an exhausted vessel, of a carbon filiament made from
"White Lines" veneer cemented to the leading in and connecting wires, in the way
and manner described, so that the connecting wire contracts or expands into a
bulb containing mercury, or is forced into and drawn out of an elongated tube,
acting as a guide to it the small bulb through which it passes being filled with
metallic granules, and good contact made between such granules, and the leading
wires as shewn and described herein
In Witness whereof I the said Frederick Leopold Willard have hereunto set
my hand and seal this twenty seventh day of December in the year of Our
Tun
FREDERICK LEOPOLD WILLARD 1. s.)
Witness
FRANCIS M. ROGER.
Electrician
21 Finsbury Pavt E.C.