IMPROVEMENTS IN ELECTRIC ARC LAMPS
Year: 1885

page_text: I FRANCIS LAUDER MUIRHEAD of N° 3 Elm Court, Temple E.C. in the City
of London do hereby declare the nature of my Invention for IMPROVEMENTS IN
ELECTRIC ARC LAMPS to be as follows:-
My invention relates to improvements in electric aro lamps and consists of a
method of constructing them whereby one can dispense with the more or less
complicated mechanism usual in such lamps actuated by clockwork or otherwise
which is employed in order to keep the two carbon rods or electrodes at the
distance from each other required to maintain the arc uniform. In a lamp made
according to this invention one, or in some cases both of the electrodes, is constructed
of carbon of hollow cylindrical or other shape so that a core of some refractory
material such as kaolin, steatite &c or marble can be introduced and be allowed to
project into the arc between the two electrodes to the desired extent thus keeping
separate one electrode from the other.
In one form of lamp I have devised only one of the carbon roda is provided with
a core-piece and this core-piece is attached to the armature of an electro-magnet or
is connected with some equivalent apparatus in such manner that while no current
is passing through the lamp it is withdrawn by means of a retractile spring or
On the
like device sufficiently to allow the carbon rods to come into contact.
passage of a current through the lamp and coils of the electro-magnet the
armature is attracted and the corc-piece pushed through the hollow carbon rod
separating it from the other carbon rod when the arc immediately forms between
the two.

page_text: I FRANCIS LAUDer Muirhead of Nº 3 Elm Court Temple E.C. in the City of
London do hereby declare the nature of my Invention for IMPROVEMENTS IN
ELECTRIC ARC LAMPS and in what manner the same is to be performed, to bo
particularly described and ascertained in and by the following statement :—
This invention relates to improvements in electric arc lamps and consists of a
method of constructing them whereby one can dispense with the more or less
complicated mechanism usual in such lamps actuated by clockwork or otherwise
which is employed in order to keep the two carbon rods or electrodes at the
distance from each other required to maintain the arc uniform. In a lamp made
according to this invention one or in some cases both of the electrodes is constructed
of carbon of hollow cylindrical or other shape so that a coro of some refractory
material such as kaolin marble &c. can be introduced and be allowed to project
into the arc between the two electrodes to the desired extent thus keeping separate
one electrode from the other.
The accompanying drawing illustrates the essential parts of one form of lamp
devised according to this invention in which only one of the carbon rods Y is
provided with a core-piece O and this core piece is attached to the armature A of
an electro-magnet or solenoid S. The lamp so constructed operates in such manner
that while no current is passing through the lamp the core or armature A is with-
drawn by means of a retractile spring P sufficiently to allow the carbon rods to
come into contact and on the passage of a current through the lamp and coils of
the electro-magnet the armature A is attracted within the solenoid S and the core
piece C attached to it by the bar B is pushed through the hollow carbon rod raising
the upper carbon rod X when the arc immediately forms between the two.
The armature is made preferably half of iron and half of a non-magnetic
material such as brass in the manner shewn in the drawing in order to obtain
a more uniform action between the solenoid and its armature. The material
composing the core C is rendered incandescent by the beat of the arc adding
brilliant whiteness to its effects. The dimensions of the core picce C for a lamp
of given power depends upon the material used; the best results have been
obtained from marble.
In order to obtain a more uniform regulation of the core piece it is advisable to
wind a quantity of finer wire than that shewn in the drawing on the outside of
the thicker wire and to join it up as a shunt to the arc in opposition to the thicker
wire which is placed in the main circuit..
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 method of regulating the "are" in electric lamps by means of adjustable
core pieces of refractory material substantially as herein before described.
Dated this 10th day of March 1886.