Improvements in Electric Arc Lamps.
Year: 1894

page_text: COME LEIE SPECIFICATION.
Improvements in Electric Arc Lamps.
I, JAMES DEVONSHIRE Secretary of The British Thomson-Houston, Limited, of
38 Parliament Street, Westminster, in the County of Middlesex, (a communication
from Elihu Thomson, of Lynn, County of Essex, State of Massachusetts, U.S.A.) 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:-
This invention relates to electric arc lamps, and has for its object the production
of a simple feeding mechanism working positively and yet with delicacy. In this
invention a derived circuit coil or magnet is employed acting against a retractor, such
as a weight or spring and a feeding circuit comparatively independent in its feeding
action but dependent for the times of action on the first magnet. This invention
will be made clear by reference to the drawings which accompany this Specification,
wherein Figure 1 is a diagrammatic illustration of a lamp adapted for use on alternating
current circuits, and Figure 2 a similar view of a lamp operated by continuous
currents.
The carbons E, E' are mounted as usual, E being sustained on a rack-rod R,
which engages with a pinion communicating motion to a gear-wheel G, which in
turn engages with a pinion on a second shaft communicating motion to a detent
wheel D. These wheels are mounted in a frame which is pivoted at P, and has a
retractile spring S to separate the electrodes E, E¹ by raising the core I; the
spring might be applied in any other suitable position. This separation of the
electrodes follows from the movement upwards of the shaft of the wheel G, which
carries a pinion engaging with the rack rod, when the spring acts to raise the
core I. K represents a shunt magnet coil, in a derived circuit of comparatively
high resistance around the arc. Its terminals are connected, as shown, to the leads
or terminals of the lamp T, T', the frame work of the lamp not being shown. The
main current leaves T, passes to a contact brush s, then to the rack-rod R, down
through the arc E, E, and back to T', the other terminal, while a portion goes
through the coil K, and pulls down the core I, when the spring S and the power of
the magnet K are properly adjusted. The pulling down of the core I and the
frame to which it is attached makes a contact at a between a piece carried on the
frame to which I is attached and a stationary piece. This closes a secondary
circuit including the contact a, the coil Z around the coil I in inductive relation
to K, the coil F on the small feeding magnet core, a contact between the detent or
catch d and the detent wheel D carried on the frame. The magnet F however has
an armature N, suitably mounted so that it can move towards the magnet core,
which, when it so moves, opens the contact between the detent d and the detent
wheel D. The means for carrying the armature N are omitted, as they can be
varied indefinitely, a spring may be applied to give a suitable rectractile force
when necessary.
On the opening of the contact between d and D, the local circuit
through Z, a, F, d, D is broken, one or more teeth of the wheel D escapes the
detent d and a feeding action is thereby produced, as the detent d is all that
prevents the turnings of the wheels and descent of the rack-rod R. The current
which actuates the feeding magnet F is set up by induction from the coil K around
the coil Z, which is a secondary to the coil K upon the same core, and since this is
a circuit local to the lamp it can be selected of such small current as to give little
or no spark at the contacts. When the lamp has fed its carbons and forms an arc
in the usual manner, that is by the magnet K pulling down the core and allowing

page_text: the carbons to feed together, and the spring S reasserts itself to separate the
carbons after they touch-by reason of the diminished current in the coil K, the
current being diverted from it into the path formed by the carbons, the arc will
continue burning until, by its resistance, due to its increased length, the magnet K
is again sufficiently energized to pull down the frame, close the contact a, thereby
closing the local feed circuit through Z and F, lift the armature N. pull up the
detent d and allow the wheel D to rotate tooth by tooth, and so feed the carbons
until the force of the magnet K again weakens and allows the contact a to be
opened by the rectractile action of the spring S. These actions continue at
intervals during the working of the lamps. The rim of the wheel D is preferably
made of a thin strip of corrugated silver and the detent or catch d is also made of
silver.
Figure 2 represents the lamp mechanism as it is arranged to work with continuous
currents, either in a separate circuit or in series with other lamps. It differs but
little from the mechanism of Figure 1, the feeding circuit in this case being not a
local circuit inductively operated, but a second shunt of high resistance around the
arc, the magnet K being also of high resistance. From the terminal T', or the
negative terminal of the lamp, connection is taken at 1, which branches through
coil K at 2, then passes to the upper or movable contact at a, which in this case is
insulated from the frame which carries the wheelwork. The lower or stationary
contact is connected to one end of a coil Z, wound around I in a direction to
oppose the magnetic force of K, and the other terminal of the coil Z¹ goes to the
feeding magnet coil F, the armature of which, as before, is connected to the
detent d of the wheel D. The frame of the lamp, however, has communication
with the entering terminal T, and the derived circuit, which has just been traced is
connected through said frame, as indicated, by the wheel D. The coil Z' may be
dispensed with in some cases, though it is conducive to a delicate action of the
feeding mechanism. If omitted, the lower contact at a is connected directly to a
terminal of the feeding magnet F. The action is as follows. Under the influence
of the spring S, the carbons E, E' are separated at the start. Connecting the
lamp with a potential difference between the carbons E, E' sufficient to more than
maintain a normal arc, energizes the shunt magnet K, pulling down the core I or
armature of the magnet against the action of the spring S, and closing the contact
at a, thus establishing the secondary shunt through this contact coil Z', feeding
magnet E, detent d and wheel D. In this case F is arranged to attract its
armature N and raise the detent d from the wheel D to allow a tooth to pass, but
as the contact between d and D is in circuit with the magnet F, the opening of
such contacts interrupts the circuit, drops the detent d on the wheel D. The
magnet F is again energized, breaks the connection and raises the detent, and so,
tooth by tooth, the wheel D escapes the detent, and slowly the carbons E, E',
move together; when they touch the magnet K is weakened or shunted, thereby
releasing its armature I, which is pulled up by the spring S and opens the contact
at a, thus stopping the feeding action, at the same time it goes far enough to
separate the carbons and form an arc. This continues until gradually the magnet K
regains its strength as the arc lengthens, and at last closes the contact at a, throwing
on the feeding magnet F, which, as before, controls not only the feed of the wheel D
but its own circuit, thus a very gradual feeding action is obtained, and this
continues until the carbon has been fed sufficiently. The purpose of the coil Z' is to
make the action of the feeding mere precise and delicate. As it is wound to oppose
the magnetization given by the coil K on the core I, it tends to release this core the
instant the contact a is closed, and thereby open said contact. Under such
circumstances the feeding action becomes more delicate, and tooth by tooth the
wheel D escapes the detent or catch d and the carbon rod is correspondingly and
gradually given its feeding movement, while the feeding action is at the same time
continued until the are has been brought to its normal condition. The feeding
action is therefore perfectly positive and gradual, and the mechanism of Figures 1
and 2 agree in this particular,-that each of them uses for the main regulation a

page_text: derived circuit, each of them uses a supplemental opposing circuit Z, Z, and a
feeding magnet F interrupting its own circuit as well as allowing the teeth of the
wheel D to escape. It is sometimes desirable to make the feeding magnet F in the
case of continuous working a little sluggish in its action on the armature, and this
is accomplished by surrounding the magnet core of F with a closed copper circuit
or band.
$9.
The lamp here shown is dependent upon derived circuit coils for the regulation
of the arc.
It starts with the carbons separated and has the so-called "floating'
electrode which gives it the power of recovery in case over-feeding occurs. It is
not dependent upon the strength of the main current passing through the carbons
but only on the voltage in the arc, while it secures the same kind or character of
feeding as other lamps. The derived circuit magnet K may be pointed out as
having control of a contact which is in the feeding magnet circuit, as is also the.
contact d, and wheel D, and that there are also opposing coils Z, Z', respectively,
Z for alternating currents having a secondary which generates by induction.
opposing currents and weaken the magnetism of the core, while Z is connected in,
a second shunt and wound to oppose the coil K. Many variations of the arrange-
ment here shown may be made, for instance, in Figure 1, the secondary Z might
be wound upon a separate transformer core, the primary of which was fed by
alternating currents either in circuit with K or in any other relation to the line..
So in Figure 2, the opposing coil Z1 might be omitted and the feeding magnet F
fed by a battery current, if at hand, or, as is shown, in a second shunt of high
resistance around the arc.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and the spring,
a circuit controlled by the contact, a magnet in such circuit, and a detent actuated
by the magnet, such detent controlling the feed of the electrode.
2. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact operated by the coil and the spring,
a circuit controlled by the contact, a coil in such circuit opposing the action of the
derived circuit feeding coil, a magnet also included in the same circuit, and a
detent controlled by the magnet and controlling the feed of the lamp.
3. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact operated by the coil and a spring,
a local circuit controlled by the contact and including a second coil energized by
induction from the derived circuit coil when its local circuit is closed, and a magnet
operated by the current induced in the second coil and actuating a detent controlling
the feed of the lamp.
4. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and a spring, a
circuit controlled by the contact, a coil in such circuit wound to oppose the derived
circuit coil and energized by induction therefrom, a magnet also in such circuit
energized by the current induced in the second coil, and a detent operated by such
magnet controlling the feed of the lamp.
5. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and the spring,
a circuit controlled by the contact, a second coil in such circuit energized by
induction from the derived circuit coil, a magnet also included in such circuit
energized by the current induced in the second coil, and a detent controlling the
feed of the lamp and operated by the magnet, such detent forming a part of the
induced circuit and acting to break the circuit when attracted by the magnet.
6. In an electric are lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and the spring,

page_text: a circuit controlled by the contact, a magnet in such circuit and a detent operated
by the magnet and controlling the feed of the lamp, such detent forming a part of
the circuit and acting to open the circuit when attracted by the magnet.
7. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil, and the spring,
a circuit controlled by the contact, a second coil in such circuit energized by
induction from the derived circuit coil and wound in a direction to oppose such
derived circuit coil, a magnet also included in such circuit and energized by the
currents induced in the second coil, and a detent controlling the feed of the lamp,
forming part of the circuit, and operated by the magnet, substantially as set out
herein.
8. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and the spring,
a second derived circuit controlled by the contact, a magnet in such circuit, and a
detent actuated by such magnet controlling the feed of the lamp and forming part
of the circuit.
9. In an electric arc lamp, a derived circuit coil tending to draw the electrodes
together, a spring opposing the coil, a contact actuated by the coil and the spring,
a second derived circuit controlled by the contact, a coil wound to oppose the
first coil included in such second derived circuit, a magnet also included in the
second derived circuit, and a detent operated by the magnet, forming part of
the derived circuit, and controlling the feed of the lamp, substantially as set out
and described herein.
Dated this 18th day of September 1894.