IMPROVEMENTS IN ELECTRIC ARC LAMPS AND IN THE MODE OF REGULATING THE SAME
Year: 1885

page_text: I, MARK HENRY HURRELL of 16 Middleton Road, Hornsey in the County of
Middlesex, Electrical Engineer do hereby declare the nature of my invention for
IMPROVEMENTS IN ELECTRIC ARC LAMPS AND IN THE MODE OF REGULATING THE
SAME to be as follows:―
The present invention relates to certain improvements in electric are lamps by
which they are rendered suitable for use with electric generators giving a current
of approximately constant potential, and more particularly to a new method of
regulating such lamps.
The invention also relates to certain details of construction for ensuring delicacy
of action of the regulating mechanism, for compensating the differences in the
weight of the moving parts produced by the consumption of the carbons, and for
adjusting the position of the carbon of the lower carbon holder.
When an electric generator is supplying a number of separate circuits the
current and the electro-motive force delivered to a lamp in one of such circuits,
are affected by the variations in current or work done in the other circuits, and
by the consequent variations in the electro-motive force of the generator.
With generators of low electro-motive force, as at present constructed and
wound, which supply current to a number of arc and incandescent lamps arranged
in parallel circuits, the electro-motive force, though approximately constant, does
nevertheless under altered conditions of load, vary within certain limits. That is
to say, the electro-motive force rises with an increase of current up to a certain
point; beyond this point and for a considerable space, a continued increase of
current does not affect the electro-motive force; while beyond this limit, with a
still further load, the electro motive force decreases.
Now if an ordinary arc lamp were to be adjusted to feed at an electro-motive
force less than the maximum electro-motive force of the machine, and when the
machine was delivering only a few amperès, the arc would gradually die away,
because the increased electro-motive force necessary to make the lamp feed, would
only be obtainable with a greater current than is available, and as the burning of
the carbons by increasing the resistance diminishes the current, this is rendered
impossible.
On the other hand if an additional load is thrown on the machine, bringing up
the electro-motive force to its maximum, the feed mechanism will be set in motion
and the feed will be continued until the maximum current possible to the machine
with such an electro-motive force, is passing, which would practically destroy the
lamp.
It is the object of my invention to regulate arc lamps in such a manner that
they will adjust themselves to variations in current as well as to variations in

page_text: electro-motive force, and will maintain the arc at is proper and approximate length
- under all conditions both of current and electro-motive force.
I effect this by the use of a shunt coil in parallel with the art, the said coil
being such as will be properly energized to operate or release the feed mechanism
with an electro-motive force about equal to the nominal or mean actual electro
motive force of the machine, and I employ a small auxiliary coil arranged in series
with the arc, and in parallel with a main magnet used for striking the are, for the
purpose of controlling the action of the shunt coil according to the requirements of
the lamp.
This auxiliary coil will, according to the variations in the current under one set
of conditions above indicated, throw additional work on the shunt coil and prevent
or delay its action, while under another set of conditions it will co-operate with
the said shunt coil and render its action easier.
I preferably arrange the shunt coil to act on a lever arm, the movement of
which applies or releases a brake block, and locks or releases a friction disc or drum
in gear with a train of wheels; and the small auxiliary coil I preferably arrange
to act on a pallét or block carried by an adjustable spring arm and connected
by a spring (whose tension can be nicely adjusted) with the said brake block.
In constructing a lamp embodying my invention I preferably support the carbons
by a metal tape or cord passing around pulleys and so connected to the upper and
lower frames or carbon holders of the lamp, that they have a mutual tendency to
approach and bring the carbons into contact.
This metal cord or tape passes around a grooved pulley in gear with the
train of wheels whose rotation is controlled by a friction disc or drum. as above
mentioned.
The feed mechanism and shunt coil above named are carried at one end of a
rocking frame pivotted to the central standard or guide stem of the lamp, the
other end of the rocking frame constituting or carrying an armature controlled
by the electro magnet in the main line, which main magnet is fixed to the upper
frame of the lamp and serves to rock the frame when the current passes. The
fulcrum on which the frame rocks is so arranged with reference to the pulley
round which the cord passes, that the sudden rocking of the frame will give the
whole of the slack to the lower carbon holder, thus causing the lowering of the
negative carbon holder or frame and effecting the striking of the arc.
The feed mechanism and its electro magnet together form a counter-balance
to the negative holder or frame and thus the main line magnet has a minimum of
work thrown on it.
The end of the spring lever controlled by the small auxiliary coil may overlie
the armature by which the brake of the feed mechanism is controlled or operated,
and absolutely block it when in its extreme position; but in action the regu-
lation of the arc is mainly effected by the small auxiliary coil which is on a shunt
of the main electro-magnet and which adjusts the work to be done by the shunt
coil according to the requirements of the case.
"
"
To compensate for the decreasing weight of the lower carbon holder or frame as
the negative carbon burns away, I mount a copper plunger on its upper portion,
which plunger dips into a tube of mercury carried by the lamp frame and thus as
the lower carbon consumes and loses weight its holder rises and gradually draws
the plunger out of the mercury and makes good such loss of weight.
The lower carbon holder bas loops or guides which slide on rods forming part of
the lamp frame, and its lower portion. is divided and centred on a single point and
provided with a pair of adjusting screws whereby it may be set to any angle, in
planes cutting at right angles, and the carbons be properly adjusted in line.

page_text: Improvements in Electric Arc Lamps and in the mode of
Regulating the same.
I MARK HENRY HURRELL of 16 Middleton Road, Hornsey, in the County of
Middlesex, 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 statement :--
The present invention relates to certain improvements in electric arc lamps, by
which they are rendered suitable for use without re-adjustment of regulating gear,
1st with electric generators whose electro-motive force increases constantly with an
increasing load; 2nd with generators whose electro-motive force increases up to
a certain limit with increasing load, is then constant up to a certain further limit,
beyond which limit it may fall; and 3rd with generators whose electro motive force
is constant for all loads.
In the accompanying drawing,
Fig. 1 is a side elevation of a lamp constructed according to my invention.
A is a vertical tube forming part of the main frame of the lamp; upon this
tube the lower carbon holder B is capable of sliding up and down.
C is a horizontal table firmly secured to the tubular rod A, and provided with
a socket D in which slides the upper carbon holder E.
F is an electro magnet in the main circuit of the lamp, the purpose of which is
to drop the lower carbon holder, and thereby strike the arc, as will be presently
explained.-G is a double lever pivotted at g to the upper part of the tubular
socket D.-One end of this double lever carries a train of clock work H, and
the armature of the electro magnet F.-The opposite end of the lever carries
an electro magnet I, the coils of which are in a circuit derived from the main
circuit, and also a solenoid J, which is included in the same derived circuit.
The primary object of my invention is to so regulate arc lamps, that they will
adjust themselves to variations in current, as well as to variations in electro-motive
force, and will maintain the arc at its proper length under varying conditions.―
I have found that if a lamp is adjusted to a definite current with its most
suitable electro motive force, and then, if from any cause the electro motive force
is required to be either increased or decreased, the proportion in which the electro
motive force should be increased or decreased, in order to maintain a steady arc, is
from one eighth to double, or to half the current respectively. This adjustment
of the lamp I effect by means of the shunt coiled magnet I, which is coiled in
parallel with the arc, such magnet being so energized as to draw down the
armature of the magnet, and thereby release the feed mechanism, together with
a small auxiliary solenoid J, arranged in series with the arc, and as shunt to the
main electro magnet F, which is used for striking the arc.-The solenoid coil J
will, as the main current increases in quantity under one set of conditions, throw
additional work onto the shunt magnet I, and as the current decreases in quantity,
under other conditions, will decrease the work of the magnet I.-In ordinary series

page_text: wound machines, where the electro motive force rises with a decreased current,
this solenoid coil is unnecessary.
The magnet I is arranged to act on an armature i carried by a spring lever i¹,
the movement of which applies or releases a brake block 2, and thereby locks or
releases a friction disc h in gear with the clock train H.-The spring lever ¿¹
having no pivot, there is no friction, and therefore no additional work is thrown on
the magnet I, which has only to overcome the tension of the spring.-This it does
by attracting the armature i. The solenoid J I preferably arrange so as to operate
by a friction bowlj on a curved part of the adjustable spring arm -The friction
bowl is carried by an elastic arm 7, which arm is rigidly attached to the core of
the solenoid. The proper adjustment of the solenoid J may he effected by means
of the screw j³.
In constructing a lamp according to my invention, I preferably support the
carbon holders by means of a metal tape or cord K, which passes around'a pulley L
in gear with the clock work train, and the rotation of the clockwork is controlled
by the friction disc h, as above described.
The tape or cord is connected to the upper and lower carbon holders, and the
weight of the upper carbon holder is in excess of the weight of the lower carbon
holder, so that they have a mutual tendency to approach, and thereby to bring the
carbons into contact.-The clock work H, the shunt magnet I, the solenoid J, the
armature f, and the spring lever i¹, are all rigidly connected to the double lever G,
this rigid connection ensuring exact and unvarying adjustment...
The fulcra g of the lever G are so arranged with reference to the pulley L, round
which the cord K passes, that the sudden rocking of the frame G, when the
armature j is acted on by the electro magnet F, will give the whole of the slack of
the cord to the lower carbon holder B, thus lowering the negative carbon, and
effecting the striking of the arc.-The positive carbon holder E is made heavy
enough to drive the train with certainty, but its weight in no way affects the
balance of the lever G, nor is the carbon holder E affected by the movements of
the lever G, because the point at which the part of the cord K, which supports the
upper carbon holder, becomes tangential to the pulley L, is in a line with the fulcra
of the lever G, one of which fulcra is shown at g.
The weight of the feed mechanism and the shunt magnets is so balanced, that
the main line magnet F has but little work to effect in striking the arc.-I keep
this balance constant, and at the same time maintain absolute electrical connection
for the negative carbon holder B, by mounting a copper plunger 6 on the upper
part of the negative holder.-This plunger passes through a slot in the upper part
of the frame A, and dips into mercury contained in the lower part of the frame A.
As the negative carbon is consumed, its weight is decreased, but as the holder B
rises, it will, at the same time, partially withdraw the buoyant. plunger 6 from the
mercury, and thus make good the loss of weight.
Fig. 2 shows a transverse section on the line 1-2 of the lower end of the
negative carbon holder B, the part 6 of which is provided with a centre point b²,
and also with a pair of adjusting screws 63 (one only, 63, of which, is shewn).-
This part 6¹ has cut in it two slots concentric to the pivot 6, through which slots
the adjusting screws pass. The pivot 63, in conjunction with the adjusting screws
and slots, allows of the upper end of the negative carbon being readily and easily
adjusted with respect to the positive carbon.
Having now described the nature of my said invention, and in what manner the
same is to be performed, I declare that what I claim is :-
1st In electric are lamps, controlling the clockwork train by a break block
carried by the spring lever substantially as and for the purpose set forth.
2nd The means for regulating the tension of the spring lever i, substantially as
described and shown.
3rd Supporting the whole of the regulating gear on the double lever G, substan-
tially as and for the purpose set forth.

page_text: 4th Supporting the carbon holders by a cord which passes over a pulley, the
rocking of which about a point at or near its circumference, strikes the arc, as
described, without disturbing the position of the upper carbon, and at the same
time the weight of the upper holder may be increased to any desirable extent,
without affecting the lever G, as set forth.
5th The means for compensating for the loss of weight in the negative carbon,
substantially as described and shown.
6th The adjustment of the axial position of the negative carbon in relation to
the positive carbon, by the pivot 6s and screws 6³, as described and shown in
Figs. 1 and 2 of the accompanying Drawings.