Improvements in Incandescent Electric Lighting Systems.
Year: 1899

page_text: Date of Application, 27th Apr., 1899-Accepted, 20th Jan.,
1900
COMPLETE
SPECIFICATION,
Improvements in Incandescent Electric Lighting Systems.
We, THE BRITISH THOMSON - HOUSTON COMPANY, LIMITED, of 83, Cannon
Street, in the City of London, Electrical Engineers, do hereby declare the nature
of this invention (which has been communicated to us from abroad by Albert
G. Davis, residing at Schenectady, in the County of Schenectady, State of New
York, United States of America, Electrical Engineer), and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement:-
It is now well known that certain substances act as conductors of electricity
at high temperatures, but are insulating at low temperatures, or, speaking
more broadly, tend to have their resistance reduced as their temperature rises.
It has been proposed to utilize such substances as light-giving bodies in electric
lamps. It is necessary in such devices to in some way heat the light giving
material to a high temperature before it will take current, and various arrange-
ments have been proposed for doing this, among which it may be mentioned is
that invented by Edwin W. Rice Jr., described in British Patent application
No. 5,941 of 1899.
A difficulty which has arisen in such devices is that, though the efficiency is
high, the lamp is unstable. Its resistance varies inversely with its temperature,
while its temperature varies more or less directly with the amount of current
flowing through it. Therefore, the greater the temperature, the greater the
conductivity, and the greater the conductivity the greater the temperature,
so that if the lamp once gets beyond a certain temperature it will take
current indefinitely until it is destroyed. It has been proposed to remedy
this difficulty by placing regulating resistances in series with each lamp,
placing with lamps, as usual, in multiple on constant potential mains. This
arrangement, however, involves a considerable waste of energy, and is not
entirely satisfactory.
In the present improved system lamps of the general nature above described
are utilized; that is to say, lamps whose light-giving bodies are of a class the
resistance of which is enormously high at starting and decreases rapidly as
the temperature rises, but such lamps are connected preferably in series, on a
constant-current circuit, either direct or alternating, as may be preferred.
This entirely obviates the objection above noted and gives a more satisfactory
regulation. But as the resistance of the lamps when cold is so high, it is impos-
sible to insert them directly in the system in the manner in which are lamps
are ordinarily inserted. This difficulty is avoided by placing in multiple with
each lamp a resistance which is capable of being gradually short circuited.
This resistance may obviously be highly inductive if desired. It is also pro-
posed to place on each lamp, in multiple with the light-giving body, a starting
coil or resistance, such as is shown in our Patent No. 5,941 of 1899 above
referred to.
The accompanying drawings represent one form which the invention may
take.
Fig. 1 is an elevation of the lamp, partly in section with the cover removed.

page_text: nected, as shown, to the plug E2, which bears against the plug E¹ of the lamp
base. From the metal shell E which forms the other terminal of the lamp, a
wire leads to the terminal №2. It will be seen that a branch circuit is formed
from the metal shell M² through more or less of the resistance R to the ter-
minal N, except when the arm F is in the position shown, which corresponds
to the position shown in connection with the lamp L' in Fig. 3.
This mechanism makes it necessary to turn on the lamp very slowly, to allow
time for the light giving body A to attain a proper temperature before the
resistance is open circuited, but it makes it possible to turn off the lamp very
rapidly, as a right-handed rotation of the ratchet wheel is not opposed by
the pawl M. The pawl M³ is held in place by a spring M" as usual.
It will be obvious that the present invention in its broader aspect, is indepen-
dent of the specific mechanism here shown.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is :-
1 The combination with a source of substantially constant current, of a
light-giving body of high resistance when cold, but conducting when hot, in
series therewith, and means for initially heating said body.
2-The combination with a constant current circuit of a plurality of lamps
in series therewith, each lamp be composed of a body insulating at ordinary
temperatures, means for giving initial heat to each lamp, and means for turning
the lamps on and off without interrupting the circuit.
The combination in a series circuit of a plurality of lamps in series in
said circuit, and an adjustable resistance in multiple with each lamp.
4 The combination in a series circuit of a plurality of lamps, in series in
said circuit, and an adjustable resistance in multiple with each lamp, each lamp
being composed of a body insulating at ordinary temperatures, but conducting
at high temperature, and means for giving initial heat to each lamp.
5 A lamp for electric circuits composed of a body, such as porcelain, mag-
nesia, or similar material, with a resistance in multiple therewith, and a handle
or key for varying such resistance.
G-A lamp for electric circuits composed of a body, such as porcelain, mag-
nesia, or similar material, with a resistance in multiple therewith, and a handle
or key for varying said resistance from zero to infinity substantially.
A lamp for electric circuits composed of a body, such as porcelain, mag-
nesia, or similar material, with a resistance in multiple therewith, and a handle
or key for varying said resistance, from zero to infinity substantially, and
means for preventing a rapid motion of said handle in one direction.
8A lamp for electric circuits composed of a body, such as porcelain, mag-
nesia, or similar material, with a resistance in multiple therewith, and a handle
or key for varying said resistance, and means for preventing a rapid motion of
said handle in one direction.
Toted to do of
1900