AN IMPROVED ELECTRIC ARC LAMP
Year: 1882

page_text: LETTERS PATENT to Alexander Melville Clark of the firm of A. M and
W Clark of 53 Chancery Lane in the County of Middlesex Fellow of the
Institute of Patent Agents for an invention of AN IMPROVED ELECTRIC ARC
LAMP communicated to him from abroad by La Société Solignac et Cio of
Paris France
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 27th December 1882.
ALEXANDER MELVILLE CLARK of the firm of A. M. and W. Clark of 53 Chancery
Lane in the County of Middlesex, Fellow of the Institute of Patent Agents,
"AN IMPROVED ELECTRIC ARC LAMP [communicated to him from abroad by
La Société Solignac et Cie of Paris, France.]
"
This Invention relates to an improved electric arc lamp in which the upper or
negative carbon is made to act also as a reflector for the light, and it consists in
substituting for the ordinary pencil form electrode a block or stick of carbon of
relatively large section enclosed by and resting in an annular cup or block of
refractory material which by protecting the sides of the carbon from the oxygen
of the air, prevents its lateral combustion and permits only its lower end to be
consumed. This it does evenly over its whole surface which remains flat and
forms a powerful reflector in close proximity to the arc. Moreover, as its rate of
consumption is inappreciable, the lamp may be considerably simplified, as the
upper carbon descends by its own weight in the annular cup of refractory material
in which it rests, a solenoid only being required to raise it from the lower carbon
in order to establish the arc. It therefore remains only to provide means for
feeding the lower carbon which may be done by a counterweight pressing it up
against a fixed collar or abutment.
The Invention is illustrated by way of example in the accompanying drawings,
in which a is the upper carbon surrounded by the annular block b and resting on
an internal lip thereof. This block is held in a casing chung by a stirrup & to the

page_text: core e of a solenoid f, the core being attached to a spring g by which the whole of
this free or movable portion of the lamp is suspended and balanced. h is the lower
carbon pressed upwards by a counter-weight against an annular abutment m
surrounding the point of the carbon. The current enters at the terminal o,
traverses the solenoid, passes through the frame of the lamp to the lower carbon,
returning by the upper carbon and a flexible connection to the insulated
terminal p.
The arc is established by the solenoid raising the block b and upper carbon a
immediately the current passes, the length of the arc being varied by the solenoid
inversely as the intensity of the current, so that an absolutely fixed light is
obtained

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
26th June 1883.
ALEXANDER MELVILLE CLARK of the Firm of A, M, and W, Clark of 53 Chancery
Lane in the County of Middlesex Fellow of the Institute of Patent Agents
"AN IMPROVED ELECTRIC ARC LAMP." A cominunication to me from abroad by
La Société Solignac et Cie of Paris, France.
This Invention relates to an improved electric arc lamp in which the upper or
negative carbon is made to act also as a reflector for the light, and it consists in
substituting for the ordinary pencil form electrode a block or stick of carbon of
relatively large section enclosed by and resting in an annular cup or block of
refractory material which by protecting the sides of the carbon from the oxygen
of the air, prevents its lateral combustion and permits only its lower end to be
consumed. This it does evenly over its whole surface which remains flat and forms
a powerful reflector in close proximity to the arc. Moreover as its rate of con-
sumption is inappreciable, the lamp may be considerably simplified as the upper
carbon descends by its own weight in the annular cup of refractory material in
which it rests, a solenoid only being required to raise it from the lower carbon in
order to establish the arc. It therefore remains only to provide means for feeding
the lower carbon which may be done by a counter-weight pressing it up against a
fixed collar or abutment.
The Invention is illustrated by way of example in the accompanying drawings,
in which a is the upper carbon surrounded by the annular block b and resting on
an internal lip thereof. This block is held in a casing c hung by a stirrup & to the
core e of a solenoid f, the core being attached to a spring g by which the whole of
this free or movable portion of the lamp is suspended and balanced. h is the lower
carbon pressed upwards by a counterweight against an annular abutment m
surrounding the point of the carbon. The current enters at the terminal o,
traverses the solenoid, passes through the frame of the lamp to the lower carbon,
returning by the upper carbon and a flexible connection to the insulated
terminal p.
The arc is established by the solenoid raising the block b and upper carbon a
immediately the current passes, the length of the are being varied by the solenoid
inversely as the intensity of the current, so that an absolutely fixed light is
obtained.
Having described the nature of the said Invention and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
hereinbefore in part recited Letters Patent is.
The improved electric arc lamp in which a block of carbon serving both as
electrode and as reflector is employed in combination with an annular cup of
refractory material and arranged to operate, substantially as herein specified
In Witness whereof I the said Alexander Melville Clark have hereunto set
my hand and seal this twenty sixth day of June, A.D. 1883.