IMPROVEMENTS IN ELECTRIC ARC LAMPS
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, Patent Agents, for
an Invention of IMPROVEMENTS IN ELECTRIC ARC LAMPS communicated to
him from abroad by William Stephen Parker of Little Falls in the County of
Herkimer and State of New York, United States of America
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 13th October 1882.
ALEXANDER MELVILLE CLARK of the firm of A. M. and. W. Clark of 53
Chancery Lane in the County of Middlesex, Patent Agents, "IMPROVEMENTS IN
ELECTRIC ARC LAMPS." [Communicated to him from abroad by William Stephen
Parker of Little Falls in the County of Herkimer and State of New York, United
States of America]
This Invention relates to the class of electric arc lamps in which the upper or
positive carbon is controlled by a clutch actuated by one or more electro magnets.
In all ordinary electric lamps in which the separation of the carbons to form or
regulate an electric arc is effected by the movement of an armature attracted by an
electro magnet, the initial movement of the armature is necessarily slow and the
further movement rapidly accelerated owing to the well known law governing the
action of magnets, that is, that the attractive power of a magnet is inversely as the
square of the distance. The separation of the carbons by the attraction of a magnet
in this class of lamps is, for the reason stated, secured by a variable force which is
strongest when the arc attains its extreme length owing to the forward movement
of the armature in a magnetic field of rapidly increasing strength. In consequence
of this peculiar action of these magnets when the carbons separate to form the arc,
or when they are moved in the operation of feeding, the variations in the arc are
extreme and as a result there is a great fluctuation in the light as well as a variation
in its color. To obviate this I employ one or more magnets in which I use the
repellent force instead of the attractive force. By this means I secure effects the
reverse of those above described, that is I secure a quick separation of the carbons

page_text: and a slower and less marked elongation of the arc by placing a polarized armature
or core in a magnetic field of the same polarity so that like poles are in opposition
to each other. In this way the core or armature of the regulating magnet is in the
strongest magnetic field when it makes its initial movement and is quickly and
forcibly repelled when the current is strengthened by the approach or contact of
the carbons, thereby raising the upper carbon very quickly so as to instantly form
the arc.
This separation of the carbons diminishes the current so that the repellent
action of the regulating magnet is rapidly weakened and the upward movement of
the carbon ceases before the arc is sufficiently extended to yield a violet color or to
diminish the light. The repellant magnet acting thus rapidly to form or lengthen
the arc renders the slight changes necessary to the feeding of the carbon unnoticeable
and inappreciable, the movement of the upper carbon being practically instantaneous.
In this improved electric lamp I may employ a single electro-magnet to control
the upper carbon or I may use two electro-magnets acting differentially, one of them
being wound with coarse wire and the other with fine wire, the former being
included in the arc circuit and the latter in a derived or branch circuit. The cores
of the magnets are adapted to slide vertically and are jointed to opposite ends of a
vibrating lever.
When the current becomes too strong by reason of the approach of the carbons,
the magnetism of the soft iron bobbin of the magnet in the main circuit is increased
so that said bobbin and its core become polarized in the same direction and the core
being free to move is consequently repelled out of the bobbin and in such movement
it acts on a clutch device and raises the upper carbon rod, thus separating the
carbons and lengthening the arc
The lamp frame or case may be of any suitable form. Both magnets are of the
axial type and are wound on tubular bobbins of soft iron containing hollow cores of
soft iron which are suspended by jointed links from opposite ends of the vibrating
lever which is suspended on a support above the magnets. The clutch is hung from
the lever above the lifting magnet at one end only by a link and it is made in two
pieces each forked at one end, the forked ends being connected by knuckle joints
forming a jointed clutch through which the carbon holding rod passes. In the
outer end of the clutch bar a set screw is fitted to bear on the shunt magnet so as
to support the bar at that end.
The end of the vibrating lever supporting the core of the shunt magnet is
connected to a spring which tends to draw that end of the lever down and assist
the rise of the lifting core.
The cores being suspended from opposite ends of the lever are both simultaneously
moved by by increase or decrease of magnetism in either magnet and the combina-
tion forms a differential balance. I provide for regulating the normal position of
the core of the lifting magnet by fitting in the lower end of that magnet a pole
block made as a screw plug that can be set in and out of the magnet
The action of the cores, lever, and clutch mechanism is due to the repulsive
action of the cores and surrounding bobbins in this wise. When the current becomes
too strong by reason of contact of the carbons of shortness of the arc, the magnetism
of the coil of this lifting magnet is increased and the iron bobbin and core become
polarized in the same direction which-upon a well understood principle-results
in the repulsion or upward movement of the core. This action of the latter tilts the
lever thus causing the clutch lever to grip the carbon holding rod and raise it so
that the carbons will be separated and the arc elongated as required, and when such
separation of the carbons has increased the resistance to the passage of the current
to a sufficient degree, the branch circuit polarizes the iron bobbin of the shunt
magnet throughout its whole length so that both ends repel the adjacent
ends of the iron core thereby moving the vibrating lever back to the original position
which causes a release of the clutch and allows the carbon rod to drop far enough
to reduce the resistance of the arc to its normal condition.
I some cases I disconnect the shunt magnet from the circuit or dispense with it
altogether. With this arrangement the main circuit magnet alone is employed, its

page_text: repellant force lifting the carbon holder as the current increases the diminution of
the repellant force permitting the carbon holder to descend of its own gravity. In
some cases I may attach a core or weight to the lever to act as a counter-balance to
the weight of the carbon rod.
The repelling magnet is peculiarly adapted to the control of the electric arc,
readily releasing the carbon holder in case of the weakening or the interruption of
the current so as to allow the upper carbon to approach or touch the lower one. It
gives a very quick initial separating movement to the upper carbon so as to form
the arc in an inappreciable space of time, and at the same time prevents an undue
separation of the carbons by a rapid diminution of the movement of the carbon
and a final stop at the maximum length of the arc.

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 13th April 1888.
ALEXANDER MELVILLE CLARK of the Firm of A, M, and W, Clark of 53 Chancery
Lane in the County of Middlesex Patent Agents "IMPROVEMENTS IN ELECTRIC
A communication to me from abroad by William Stephen Parker of
Little Falls in the County of Herkimer and State of New York, United States of
of America.
ARC LAMPS
This Invention relates to the class of electric are lamps in which the upper or
positive carbon is controlled by a clutch actuated by one or more electro magnets.
In all ordinary electric lamps in which the separation of the carbons to form or
regulate an electric arc, is effected by the movement of an armature attracted by
an electro-magnet, the initial movement of the armature is necessarily slow and
the further movement rapidly accelerated owing to the well known law governing
the action of magnets, that is, that the attractive power of a magnet is inversely as
the square of the distance. The separation of the carbons by the attraction of a
magnet in this class of lamps is for the reason stated, secured by a variable force
which is strongest when the arc attains its extreme length owing to the forward
movement of the armature in a magnetic field of rapidly increasing strength. In
consequence of this peculiar action of these magnets, when the carbons separate to
form the arc, or when they are moved in the operation of feeding, the variations in
the arc are extreme, and as a result there is a great fluctuation in the light as well
as a variation in its color. To obviate this I employ one or more magnets in which I
use the repellent force instead of the attractive force. By this means I secure effects
the reverse of those above described, that is, I secure a quick separation of the
carbons and a slower and less marked elongation of the are by placing a polarised
armature or core in a magnetic field of the same polarity, so that like poles are in
opposition to each other. In this way the core or armature of the regulating
magnet is in the strongest magnetic field when it makes its initial movement and
is quickly and forcibly repelled when the current is strengthened by the approach
or contact of the carbons, thereby raising the upper carbon very quickly so as to
instantly form the arc. This separation of the carbons diminishes the current so
that the repellent action of the regulating magnet is rapidly weakened and the
upward movement of the carbon ceases before the arc is sufficiently extended to
yield a violet color or to diminish the light. The repellent magnet acting thus
rapidly to form or lengthen the arc, renders the slight changes necessary to the
feeding of the carbon unnoticeable and inappreciable, the movement of the upper
carbon being practically instantaneous.
In this improved electric lamp a single electro-magnet may be employed to
control the upper carbon, or two electro-magnets may be used acting differentially,
one of them being wound with coarse wire and the other with fine wire, the former
being included in the arc circuit, and the latter in a derived or branch circuit.
The cores of the magnets are adapted to slide vertically and are jointed to opposite
ends of a vibrating lever. When the current becomes too strong by reason of the
approach of the carbons, the magnetism of the soft iron bobbin of the magnet in
the main circuit is increased so that said bobbin and its core become polarised in
the same direction, and the core being free to move, is consequently repelled out
of the bobbin, and in such movement it acts on a clutch device and raises the upper
carbon rod, thus separating the carbons and lengthening the arc,

page_text: The Invention is illustrated in the accompanying drawings, in which similar
letters of reference indicate corresponding parts in all the figures. Figure 1 is a
horizontal section of a lamp embodying the Invention. Figure 2 is a vertical
section of a lamp with two regulating magnets, and Figure 3 is a vertical section of
a lamp with a single regulating magnet.
The lamp frame or case may be of any suitable form. On the plate A are fixed
the differential magnets B C, the latter being the shunt magnet. Both magnets
are of the axial type and are wound on tubular bobbins of soft iron containing
hollow cores bc of soft iron respectively. These cores are suspended by jointed
links from opposite ends of a lever d suspended on a support e above the
magnets. D is the carbon holder, and E is the clutch hung at one end by a link f
from the lever d above the lifting magnet B. The clutch is made in two pieces
each forked at one end, the forked ends being connected by knuckle joints g
forming a jointed clutch through which the carbon holding rod D passes. In the
outer end of the clutch bar a set screw h is fitted to bear on the magnet C so as to
support the bar at that end. The end of the lever & supporting the core c of the
shunt magnet C is connected to a spring / which tends to draw that end of the
lever down and assist the rise of the lifting core B. The cores being suspended
from opposite ends of the lever, are both simultaneously moved by increase or
decrease of magnetism in either magnet and the combination forms a differential
balance. I provide for regulating the normal position of the core of the lifting
magnet B by fitting in the lower end of that magnet a pole block k made as a
screw plug that can be set in and out of the magnet.
The action of the cores, lever and clutch mechanism is due to the repulsive
action of the cores and surrounding bobbins in this wise:-When the current
becomes too strong by reason of contact of the carbons or shortness of the arc, the
magnetism of the coil B is increased and the iron bobbin and core become polarised
in the same direction which, upon a well understood principle, results in the
repulsion or upward movement of the core b. This action of the latter tilts the
lever d, thus causing the clutch lever E to grip the carbon holding rod D and raise
it so that the carbons will be separated and the arc elongated as required, and when
such separation of the carbons has increased the resistance to the passage of the
current to a sufficient degree, the branch circuit polarises the iron bobbin of the
shunt magnet C throughout its whole length so that both ends repel the adjacent
ends of the iron core c, thereby moving the lever & back to the original position
which causes a release of the clutch E and allows the carbon rod D to drop far
enough to reduce the resistance of the are to its normal condition.
In some cases I disconnect the shunt magnet from the circuit or dispense with it
altogether, as in Figure 8. With this arrangement the main circuit magnet B
alone is employed, its repellent force lifting the carbon holder as the current
increases, the diminution of the repellent force permitting the carbon holder to
descend of its own gravity. In some cases I may employ the core c or weight o³ as
a counterbalance to oppose the weight of the carbon rod D.
It .
The repelling magnet is peculiarly adapted to the control of the electric arc,
readily releasing the carbon bolder in case of the weakening or the interruption of
the current so as to allow the upper carbon to approach or touch the lower one.
gives a very quick initial separating movement to the upper carbon so as to form
the arc in an inappreciable space of time, and at the same time prevents an undue
separation of the carbons by a rapid diminution of the movement of the carbon,
and a final stop at the maximum length of the arc.
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
herein before in part recited Letters Patent is.
1 In an electric lamp the combination with the carbon holder, of one or more
repelling electro-magnets and suitable connecting mechanism, substantially as
herein shown and described, whereby the carbon will be moved and governed by
the repellent action of the magnet or magnets, as set forth.

page_text: 2 The combination of the magnets B C formed of soft iron bobbins wound
respectively with coarse and fine wire, and included in the main and branch circuit
as specified, the soft iron cores 6 c, vibrating lever d, a clutch device E, and the
carbon holding rod D, all as shown and described, whereby increase of magnetism
of coil B causes the core b and its surrounding bobbin to become polarised in the
same direction, so that said core is repelled.
3rd The combination with electro magnet B and its core b adapted to move
freely, of the adjustable stop piece or block k inserted in the lower end of said
magnet, as shown and described.
In Witness whereof I the said Alexander Melville Clark have hereunto set
my hand and seal this thirteenth day of April, A.D. 1883.
•
CLADI