Improvements connected with Electric Lamps having Illuminating Bodies Composed of Second-class Conductors.
Year: 1899

page_text: Date of Application, 16th Oct., 1899-Accepted, 25th Nov., 1899
[Communicated from abroad by ALLGEMEINE ELEKTRICITATS GESELLSCHAFT, of
22, Schiffbauerdamm, Berlin, N.W., Germany.]
Improvements connected with Electric Lamps having Illuminating
Bodies Composed of Second-class Conductors.
I, VICTOR ISIDORE FEENY, of 60, Queen Victoria Street London, E.C., Chartered
Patent Agent, 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;-
-
This invention relates to a resistance for regulating the supply of current in
electric lamps fitted with illuminating bodies composed of second-class conductors.
In lamps furnished with such illuminating bodies, it has been found con-
venient to employ a metal with a high temperature co-efficient, as the material
for the necessary reductor or resistance. Iron is most suited to the purpose, since
within certain limits of temperature, about the condition of dark red heat, it has
the property that with a slight increase of current, the potential difference at the
ends becomes extraordinarily strong. In consequence of this, such a resistance,
composed of iron, acts within certain limits of temperature, nearly the same as
an apparatus which is intended for keeping automatically constant, the strength
of current necessary for the illuminating body.
Without some further provision, however, these favourable properties of the
iron cannot be utilised. When an iron resistance is used in the open air, the
conducting ratio of the wire continually alters under the slowly proceeding
oxidisation of the iron, and in consequence of this the resistance after being used
for some time does not regulate according to the intensity of the current for which
it was originally intended.
Morcover it becomes necessary, for each current intensity, as required by the
illuminating bodies composed of second-class conductors, and being of different
dimensions, or unequal as regards power of conducting, to vary the cross-section
of the wire or the "radiating" surface, or both. Thus, as many resistances of
varied dimensions are required as there are illuminating bodies with different
powers of conduction.
Again, the iron resistances do not admit of regulation and cannot be used at all
in the open air, when it is a question of low current intensity, iron wires of a
smaller diameter than 0.02 millimetre cannot be practically produced. This
minimum cross-section of wire, however, as experiments have shewn, suffices only
for use in the controlling of illuminating bodies which use at least 0.3 ampère.
For illuminating bodies with but a small consumption of current, therefore, the
employment of iron-wire in the open air, as a resistance, is not desirable even if
not impracticable.
All these disadvantages which have attended the use of iron as a resistance material
for illuminating bodies composed of second class conductors, are obviated, by

page_text: enclosing the resistance, wound spirally or otherwise, in a vessel or container
filled with indifferent"
gases.
In addition to the advantages claimed at the outset for iron as a resistance
medium for illuminating bodies composed of second-class conductors, iron resist-
ances enclosed in this particular way, possess the following;
The oxidisation of the iron is avoided and the conductivity of the wire remains
constant, whereby also the current intensity for the illuminating body is kept
constant. Moreover, with wires of the same length and the same cross-section,
the resistance is capable of being regulated within wider limits for the intensity
of current necessary for the illuminating bodies.
This capacity for regulation, of the resistance, is possible in two directions.
In the one direction, with the wire wound spirally, it is possible to vary the pitch
and circumference of the several windings, it being immaterial what form (round,
oval, rectangular, square) be given to the coil, or spiral. The resistance can also
be regulated by varying the gas pressure.
The result of this is that wires of equal length and equal diameter within the
same limits of temperature can be employed for a large number of illuminating
bodies whose conductivity varies.
The effect of the different kinds of winding is that the wire windings lying
more or less closely together mutually influence one another in their generation
of heat. Very closely wound spirals of small diameter quickly reach the dark
red heat stage. The heat radiating from the inner surface of the spiral cannot
be quickly carried off and hence it results that a resistance with narrow windings
is more efficient than such a resistance with wider winding. The process, for
practical purposes, is made obvious from this.
"
The
When the rough regulation has been effected in the manner mentioned, the
subsequent and more delicate regulation follows by the variation of the gas-
pressure, indifferent gas such for example, as hydrogen, nitrogen or car-
buretted hydrogen, being conveyed through the glass vessel containing the
resistance. The effect produced by the varying gas-pressure consists in the fact
that the heat generated by the iron-wire is carried off more or less vigorously as
the gas is more or less compressed. The greatest regulation capacity is afforded
with hydrogen since this gas possesses the greatest heat conducting power.
greater the vacuum, the more favorable is the use of iron wire found to be,
for slight degrees of current intensity. This extends so far that iron wires of
the smallest diameter can be still used in the vacuum, when their employment in
the open air is no longer possible. The thinnest wire commercially obtainable
is 0.02 millimetre in thickness. As mentioned in the introduction, this cross-
section corresponds with a current intensity of 0.3 ampère for the illuminating
body. If, however, this wire be enclosed in a vessel filled with indifferent
gases, and the vessel be exhausted, the resistance is useful also for illuminating
bodies composed of second-class conductors, which require a current intensity of
only 0.15 ampère.
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:
"
(1). A resistance for regulating the current supply in electric lamps fitted
with illuminating bodies composed of second class conductors, the distinguishing
feature of which is that the metal of which the resistance is formed, has a high
temperature co-efficient, as, for example, iron, and is enclosed in a vessel filled
with indifferent" gases, for the purpose of keeping constant the regulation-
capacity of the resistance for the illuminating body, substantially as described.
(2). In the resistance claimed in Claim 1, the winding of wire of equal length
and equal cross section in spiral windings of varying pitch and varying circum-
ferential winding, for the purpose of enabling the conducting power of the wire
to be regulated, substantially as described.

page_text: (3). In the resistance claimed in Claim 1, a further modification of the regula-
tion of the conducting power of the same, characterised by the varying of the
gas-pressure in the vessel enclosing the resistance, substantially as described.
Dated this Sixteenth day of October 1899.
For the Applicant,
GEDGE & FEENY,
Chartered Patent Agents, 60, Queen Victoria Street, London, E.C.