Improvements in Incandescent Electric Lamps.
Year: 1886

page_text: Date of Application, 25th June, 1886.
Complete Left, 25th Mar., 1887.
Complete Accepted, 26th Apr., 1887
PROVISIONAL SPECIFICATION.
Improvements in Incandescent Electric Lamps.
I, JAMES GRIEVE LORRAIN, of Norfolk House, Victoria Embankment, London, W.C.,
Consulting Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to improvements in Incandescent Electric Lamps and has
reference more particularly to lamps having incandescing carbon conductors of
comparatively low resistance.
The chief obstacle in the construction of a practical low resistance incandescent
electric lamp is the difficulty of sealing into the glass the conducting wires, which
lead from the outside of the lamp to the carbon incandescing conductor inside. The
coefficient of expansion under the influence of heat of the material of which these
wires are made is necessarily different from that of the glass into which the wires are
sealed and consequently the sealing becomes imperfect under variations of temperature.
The wires are usually made of platinum which metal has a coefficient of expansion
very near that of glass and with wires of this material the difficulty is easily overcome
in the case of the high resistance incandescent electric lamps at present made because
in that case the current required to render the filament incandescent is so small that
a wire of small sectional area suffices to carry it, and as the expansion and contraction
in a thin wire is small, this thin wire can be easily sealed into the glass. With lamps
of low resistance however the current is large in proportion and therefore the wires
When this is the case the wires
have to be of comparitively large sectional area.
cannot be simply sealed into the glass as in the present high resistance lamps, because
the said wires whether of platinum or other material have to be of comparitively large
sectional area and as the amount of expansion and contraction in a thick wire is com-
paritively great so is the risk in destroying the sealing. One method by which it has
been sought to overcome this difficulty consists in the use of an intermediate enamel
placed between the conducting wire and the glass and having a coefficient of expansion
intermediate between that of platinum (of which the conducting wire is generally
composed) and that of glass. This enamel however introduces a source of weakness
by reason of its uncertain expansion and contraction as compared with that of the

page_text: conducting wires which it surrounds and the glass by which it is surrounded under the
large variations of temperature to which it is subjected so that it frequently renders
lamps otherwise good quite useless and valueless. My invention is designed for the
purpose of obtaining a successful sealing in the case of low resistance incandescent.
electric lamps as exists in the case of the high resistance incandescent electric lamps
at present in use.
In carrying my invention into effect instead of employing a single conducting wire
of comparitively large sectional area passing through the glass to each end or to each
mount of the incandescing carbon conductor (that is two wires in all, one wire passing
to one end or one mount of the incandescing carbon conductor and the other wire to
the other end or other mount of the incandescing carbon conductor) I employ a bunch
of conducting wires of small sectional area passing to each end or mount of the said
incandescing carbon conductor. Each of such bunches may consist of two or more
conducting wires separated at the part where they pass through the glass, in such
manner that each wire passes through the glass individually, that is each one separately
sealed direct and imbedded in and surrounded by the glass and that directly without
the intervention of enamel or other intermediary substance. The conducting wires
constituting these bunches may meet or be brought in contact or joined together
outside the glass, and they may meet or be brought in contact or joined together
inside the glass. Or the conducting wires constituting these bunches may be separate
from one another throughout their whole length and be carried separately to the
incandescing carbon conductor or its mount inside the glass and separately to the
lamp terminal, or a separate conductor in connection therewith, on the outside of
the glass. By this means sealing is obtained as efficient and practical as that of the
high resistance lamps at present in use.
Though by adopting this method I do not require to use enamel at all, yet I may,
when I so desire it, use it as an additional precaution.
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page_text: I JAMES GRIEVE LORRAIN of Norfolk House Victoria Embankment London W.C.
Consulting 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:-
My invention relates to improvements in Incandescent Electric Lamps and has
reference more particularly to lamps having incandescing carbon conductors of
comparatively low resistance.
The
The chief obstacle in the construction of a practical low resistance incandescent
electric lamp is the difficulty of sealing into the glass the conducting wires which lead
from the outside of the lamp to the carbon incandescing conductor inside.
coefficient of expansion under the influence of heat of the material of which these wires
are made is necessarily different from that of the glass into which the wires are sealed
and consequently the sealing becomes imperfect under variations of temperature. The
wires are usually made of platinum which metal has a coefficient of expansion very
near that of glass and with wires of this material the difficulty is easily overcome in
the case of the high resistance incandescent electric lamps at present made because in
that case the current required to render the filament incandescent is so small that a
wire of small sectional area sufficies to carry it and as the total expansion and contrac-
tion in a thin wire is small this thin wire can be easily sealed into the glass. With
lamps of low resistance however the current is large in proportion and therefore the
wires have to be of comparatively large sectional area. When this is the case the
wires cannot be simply sealed into the glass as in the present high resistance lamps
because the said wires whether of platinum or other material have to be of com-
paratively large sectional area and as the amount of expansion and contraction in a
thick wire is comparatively great so is the risk in destroying the sealing. One method
by which it has been sought to overcome this difficulty consists in the use of an
intermediate enamel placed between the conducting wire and the glass and having
coefficient of expansion intermediate between that of platinum (of which the conducting
wire is generally composed) and that of glass. This enamel however introduces a
source of weakness by reason of its uncertain expansion and contraction as compared
with that of the conducting wires which it surrounds and the glass by which it is
surrounded under the large variations of temperature to which it is subjected so that
it frequently renders lamps otherwise good quite useless and valueless. My invention
is designed for the purpose of obtaining a successful sealing in the case of low resistance
incandescent electric lamps as already exists in the case of the high resistance
incandescent electric lamps at present in use.
a
In carrying my invention into effect instead of employing a single conducting wire of
comparatively large sectional arca passing through the glass to each end or to each mount
of the incandescing carbon conductor (that is two wires in all one wire passing to one
end or one mount of the incandescing carbon conductor and the other wire to the

page_text: other end or other mount of the incandescing carbon conductor) I employ a bunch of
separate conducting wires of small sectional area passing to each end or mount of the
said incandescing carbon conductor. Each of such bunches consists of two or more
conducting wires separated to a sufficient distance apart (say about a sixteenth of an
inch in ordinary cases) at the part where they pass through the glass in such manner
that cach wire passes through the glass individually that is each one separately sealed
direct and imbedded in and surrounded by the glass and that directly without the
intervention of enamel or other intermediary substance. The conducting wires
constituting these bunches I sometimes cause to meet or be brought in contact or
joined together outside the glass and similarly to meet or be brought in contact or
joined together inside the glass. At other times I cause the conducting wires
constituting these bunches to be separate from one another throughout their whole
length and be carried separately to the incandescing carbon conductor or its mount
inside the glass and separately to the lamp terminal or a separate conductor in
connection therewith on the outside of the glass. By this means sealing is obtained
as efficient and practical as that in the case of the high resistance lamps at present
in use.
Though by adopting this method I do not require to use enamel at all yet I may
when I so desire it use it as an additional precaution.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same is to be performed I declare that what I claim is :
The improvement in Incandescent Electric Lamps consisting in the use of bunches
of separate conducting wires passing to the ends or mounts of an incandescing carbon
conductor substantially as described.
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