Appliance for Preventing the Fraudulent or Erroneous Changing of Glow-lamps in Electric Light Installations.
Year: 1899

page_text: Date of Application, 5th June. 1899 -Accepted, 22nd July,
1899
COMPLETE SPECIFICATION.
Appliance for Preventing the Fraudulent or Erroneous Changing of
Glow-lamps in Electric Light Installations.
We, SIEMENS BROTHERS & Co., LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., Electrical Engineers, do hereby declare the nature of this in-
vention (as communicated to us from abroad by Siemens & Halske Aktien
Gesellschaft, Markgrafen Strasse No. 94, Berlin, S.W., Electrical Engineers,)
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
With electric lighting installations supplied from a central station the want
has been felt of providing consumers with a certain supply of current for a
definite number of glow-lamps at a fixed price. With such an arrangement
the necessity arises for the provision of means for preventing that by the chang-
ing of glow-lamps a greater consumption of current is effected, than that con-
tracted for, as with the ordinary fittings the consumer can without trouble
substitute a 32 candle glow-lamp instead of a 16 candle one.
The present invention relates to means for preventing the fraudulent or
erroneous changing of lamps which is possible with such a method of supply.
The device consists of a small plate composed of three different layers and which
is held in the screw-socket of the lamp fitting as shewn on the accompanying
drawing. The upper and lower layers of the plate, a and consist of insulating
material, while the middle one' bis of metal. This metal plate has a
turned-up edge which is in conducting communication with the socket y of the
lamp fitting, and consequently, also with one pole of the circuit. The three
layers have each a central hole, that in the bottom one being smallest, while
the others gradually increase in size. To the insulating layer c is applied a
metal piece which constitutes the other pole. The lowest part of the glow-
lamp base has a central cylindrical metal stud the diameter of which is made
the smaller, the lower is the strength of current for which the lamp is intended.
This stud fits accurately through the smallest opening of the insulating layer c
without in any way touching the metal layer b, and presses upon the contact d
so as to form the connection with the one pole while the connection of the glow-
lamp with the other pole is effected by the screw thread of the glow-lamp base
and the screw-socket of the fitting.
The middle plate has for its object to prevent the possibility of effecting
an electrical connection with a glow-lamp of higher power, (the plug of which
would be of such size that it cannot pass through the opening in c) by the intro-
duction of pieces of metal or other conducting material.
By the employment of this means a direct short circuiting would be readily
effected between the spring & and the metal plate b, and consequently between
the two poles of the lamp, so that the lamp would not then operate, in which
case the safety fuse of the lamp would burn through and thus interrupt the
circuit.
It will be evident that the above described safety appliance is applicable to
glow-lamp fittings of various constructions.

page_text: Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I claim
is:-
An appliance for preventing the fraudulent or erroneous changing of glow-
lamps in electric light installations, consisting of an insertion piece placed in the
glow-lamp fitting, and composed of two outer layers or discs of insulating
material and an inner layer or disc of conducting metal, which layers or discs
have central holes of increasing size in the direction of the lamp base, the latter
being provided with a metal stud of a size to pass through the smallest hole
for making contact with the second terminal of the lamp while if a lamp with
a larger stud were inserted it would make contact with the said inner metal
disc so as to short circuit the lamp, substantially as described.
Dated this 5th day of June 1899.
ABEL & IMRAY,
Agents for the Applicants.