Year: 1889

page_text: Date of Application, 8th Jan., 1889
Specification Accepted, 16th Mar., 1389
I, ALEXANDER BERNSTEIN of 2 Marlborough Mansions, Victoria Street, Pimlico,
in the county of Middlesex and Mühlenkamp, Hamburg, in the Empire of Germany,
Electrical 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 stateinent:-
My invention relates to the production of a glow-lamp for series lighting, provided
with an improved automatic arrangement for short circuiting the current in case the
incandescent carbon should break.
I have in the specifications of former patents described various arrangements for this
purpose in which the short circuiting or cut-out was accomplished either by means of
an electro-magnet placed in a shunt round the lamp or by means of the chemical
reduction of an oxide of metal. I have also made lamps in which the arrangement
was such that the arc itself formed on the breakage of the carbon, was utilized for the
purpose of melting the two leading-in wires together, which latter were purposely
placed very close to each other. But this action of the are could not be relied upon and
the long are which was formed, caused the lamp to crack and pieces of glass to fall.
The object of my present invention is to obviate these objections and to obtain a safe
and reliable short-circuit inside the lamp and to enable my invention to be clearly under-
stood, I will describe the same by reference to the accompanying drawing which
illustrates an arrangement which I have found advantageous for lamps of low voltage
and strong current.
In this lamp a straight carbon rod or other suitable conductor is employed, the
leading-in wires being sealed into one end of the bulb.
In the drawing a is the glass bulb, b the carbon rod, and c c are the leading-in wires.
These wires are bent to such a shape that they approach each other very closely at a
point d, being normally kept apart by the carbon. Lower down both wires are covered
atff by insulating-sleeves which can be made of glass, e is a spiral spring connected
to the sleeves in such a manner as to tend to bring the leading-in wires together.
Now although the spring always tends to draw the wires together they cannot yield
to the action of the said spring as long as the carbon is intact, but if by the action of

page_text: the current or from other cause a breakage of the carbon should occur, which would
give rise to the formation of an arc then the spring acting upon the leading-in wires
draws the portions of the carbon together so as to prevent an arc. This however does
not prevent the destruction of the carbon from proceeding until the leading-in wires
come in contact at d, whereupon practically no more current will pass through the
carbon. In this case a durable and effective short circuit is formed inside the lamp.
If it be desirable that the total resistance of the lamp should not be altered by the
fracture of the carbon, a semi-conducting substance can be attached to one of the
leading-in wires at d, so that if contact is made there, the current has to pass through
this semi-conductor, the resistance of which may be made the same as the resistance of
the carbon.
For the purpose of improving the contact at d a metallic compound such as I
have described in the specification of my former Patent No. 12315 of 1886, may be
used so that in case the current passes at d the compound is reduced to conducting
metal.
It will be obvious that the arrangement which I have described is especially suitable
for lamps with straight carbon rods and not with loop carbons such as are generally
used in high resistance lamps. But the construction is not confined to lamps with
carbon rods; other forms of carbon may be used, for example, those in which the light-
giving carbon forms a complete circle or other closed curve, the current dividing itself
between the two branches of this curve.
Where it is desirable to use the loop carbon the leading-in wires can be held apart
at their upper end by means of an insulator, such as a glass rod. But in this case the
formation of a long are is not prevented and the leading-in wires cannot make contact
at d until this insulator has been destroyed by the arc.
Instead of using a spiral spring to draw the leading-in wires together these wires
may be themselves made to act as springs. The springs can be replaced by means of
weights but I do not advise this arrangement as the lamp can then only be used in a
certain position.
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.) An improved glow-lamp for series-lighting in which the leading-in wires are
sealed into one end of the bulb and are brought together by the action of a spring
inside the bulb on the light-giving conductor being destroyed.
. (2.) The manufacture and use of the improved glow lamp for series-lighting
hereinbefore described and illustrated in the accompanying drawing.
Dated the 8th day of January 1889.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London,
Agents for the Applicant.