Improvements in Electric Arc Lamps.
Year: 1896

page_text: Date of Application, 3rd Jan., 1896-Accepted, 22nd Feb., 1896
Improvements in Electric Arc Lamps.
A communication by THE ELECTRIC ARC LIGHT COMPANY, a corporation
organized and existing under the laws of the State of New York, of 73 Watts
Street, New York, in the County and State of New York, United States of
America.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street,
Manchester, hoth in the County of Lancaster, 118 New Street, Birmingham
in the County of Warwick and 31 High Holborn in the County of Middlesex,
Civil 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 invention relates to electric are lamps, the object being to prolong the life
of the electrodes, to permit an economical operation on constant potential circuits,
with a lamp of simple construction by creating an abnormal drop of potential in
the arc, to promote steadiness in the arc, and secure a uniform distribution of light,
and to adapt the lamp for service on commercial circuits where the potential
difference of the supply mains may vary in different systems and in different parts
of the same system. In carrying out the invention, the arc is provided with a
transparent or translucent envelope or enclosure provided with a gas-check which
will afford egress for the gases developed by the are and permit a limited supply
of air to enter the enclosure, and suspend the positive electrode so that it may be
fed through contracted opening in the arc, enclosing envelope. The arc
regulating coils are in series with the arc, and act upon an armature provided with
In scries with the
a friction-clutch to control the feed of the positive carbon.
lamp coils and are is placed a small auxiliary resistance to produce a fractional
drop of potential, the amount of resistance being such that the are will have a
maximum steadiness and freedom from flaring, although operated on circuits of
considerable difference of voltage, but not sufficient to produce any considerable
waste of current in heat.
The several features of novelty of the invention will be hereinafter particularly
described and definitely pointed out in the claims.
In the accompanying drawings which illustrate the invention,
Figure 1 is an elevation partly in section of the operative parts of a lamp
embodying the invention;
Figures 2 and 3 are a plan and section, respectively, of the gas-check employed
to limit the ingress of air and egress of the gaseous products of combustion;
Figure 4 is a top plan view of the auxiliary resistance and lamp-switch;
Figure 5 is a central vertical section of the upper part of the lamp on a plane
at right angles to that of Figure 1 ;
Figure 6 is an enlarged view of the feed-regulating devices;
Figure 7 is a section on the plane indicated by the trace line of Figure 6,
looking in the direction of the arrows; and
Figure 8 is a diagram of the circuit through the lamp and its operating
devices.
Referring to the drawings, 1 is a small envelope of clear or translucent glass about
three inches in diameter on a ceutral plane; it is flanged at the bottom and provided

page_text: with a sheet-metal ring 2 spun on the lower neck of the envelope so as to remain
permanently a part of the same; the ring 2 is provided with a coarse screw-thread
adapted to screw over the outside of the socket 3 which supports the negative
carbon. A washer of asbestos 4 between the base of the envelope and the socket
makes practically an air-tight joint. On the upper part of the envelope rests a
metallic gas-check 5, the details of which are seen in Figures 2 and 3. It is
provided with a central opening sufficiently large to permit easy transit of the
positive carbon 6. It may be formed as shown of two pieces screwing together
at 7, one forming a closed chamber around the perforated stem of the other; a
number of narrow slots 8 in the wall of the stem establishes communication between
the dead-air chamber and the space between the positive carbon and the wall of
the gas-check. A device so constructed obstructs the ingress of air to the
enclosing envelope around the arc, probably by establishing eddy-currents in the
space around the positive electrode where it passes through the gas-check; by so
obstructing the access of air to the are the life of the electrodes is greatly
prolonged and greater steadiness of light results. A wide flange 9 is formed on
the upper piece of the gas-check, and the lower piece is less in diameter than the
top of the envelope, thus permitting the gas-check to move laterally and preventing
binding of the positive carbon in transit into the envelope. The socket which
supports the negative carbon is mounted on a yoke 10 connecting by hollow rods
with the body of the lamp. The carbon-holder or carrier for the positive
electrode slides freely in guides 11, 12, and is lifted and controlled by a friction-
clutch acting in a manner similar to a pair of lazy-tongs, the ends of which are
pivoted at 13, 13ª to an iron armature 14 secured to two upright iron cores
extending into the regulating solenoids. In the free ends of the Lungs are studs
or pins 15, 15, see Figures 1, 6 and 7, adapted to engage stops 16, 16 mounted on
the lamp-frame. Clutch-blocks 17, 17ª are pivoted at an intermediate point of the
arms. The two arms are each composed of parallel bars united so as to constitute
a rigid frame swinging freely on pivots 13, 13. Thus it will be seen that when the
magnets are energised and the armature raised, the weight of the blocks and arins
firmly clutch the carbon-carrier and spring an are; when, however, the carbon
wastes sufficiently to bring the pins 15, 15 to rest upon the stops 16, 16, the
clutch-blocks are forced apart and the carbon-carrier is free to slide through them.
The solenoids 18, 18 are provided with an iron yoke 19; the cores are rigidly
secured to the armature 14. A good conductive connection between the frame
of the lamp and the carbon-carrier is made by means of two copper brushes 20)
bearing upon the carbon-carrier at opposite sides and in good conductive relation
to a metallic standard 21 mounted on the lamp frame. The movements of the
armature are steadied by dash-pots 22, 22 cumprising pistons connected by links
with the sides of the armature and working in cylinders closed at the upper end;
the pistons require no lubrication and simply form air-cushions. On the upper
part of the lamp is mounted a series of perpendicularly grooved porcelain
blocks 23, see Figures 1 and 5, over which is wound a resistance spiral of German
silver, Krupp, or other resistance wire, 24, one end of which connects with an
insulated binding-post, see Figures 1 and 4, and the other end with the insulated
pivot of a switch 25, see Figures 4 and 8. When the lamp is in action, the
switch 25 rests on contact-stud 26 which connects with the arc-regulating solenoids;
thence a connection is made to the lamp-frame and through brushes 20 (Figure 5)
to the carbon-carrier and across the are to the negative electrode, and thence by
insulated conductor 27 (see Figure 1) housed in one of the hollow rods to the
negative binding-post.
The operation of the lamp will now be understood. On closing the switch, the
magnets are energized and the arc sprung by a lifting up of the armature 14. As
the carbons burn away, the drop of potential in the are increases; the potential in
the mains being constant, the drop through the solenoids decreases and less current
passes through them; this permits the carbons to approach until the drop across
the are is normal. This process continues until pins 15, 15 strike the stops 16, 16*

page_text: and the clutch is opened, permitting the carbon-carrier to slip; instantly the magnet
iucreases in strength and prevents the rod from descending too far. If through
some accident, such as oil or grease on the rod, it should slip too far, the magnet
will instantly pull it back, until the normal length of are is attained. After a lamp
has been freshly trimmed it will burn for from three to five hours without calling
the clutch into action so far as feeding is concerned; during this period the
solenoids solely perform the regulating function; when the carbons have wasted
enough to bring the pins 15, 15 into engagement with the stops 16, 16", the clutch
is called into action. The lamp will burn until the carbon-carrier rests on the top
of the gas-check, when the leed will of course he arrested and the lamp automatically
cut out of circuit.
By the organization hereindescribed, my correspondent is enabled to adapt the
same lanp to operate on circuits having a considerable difference of voltage, say
from 100 to 120, without hissing or flaming and without great losses from large idle
resistances, and with a current of small amperage. For example, with a resistance
of four ohms, the lamp hereindescribed will produce on an 110 volt circuit a drop of
potential in the arc of 85 volts and will consume from four to five ampères of
current. The magnet resistance is about two-thirds of an ohin and comprises
about 400 turns of No. 14 copper wire in each coil; the coils are wound to saturate
the cores at their lowest position with a normal working current, thus ensuring
steady regulating action in all stages of the long range of movement of the cores.
The are drop may be uniformly maintained at a higher value in an enclose are
than in the open air or in a chamber to which the air has free access; the gas-check
by preventing draughts and maintaining the gas-currents uniforms in the enclosure,
steadies the light and prevents hissing or flaming. It is preferable to use square
or blunt-tipped carbons as contra-distinguished from pointed carbons.
In my
correspondents' lamp a carbon 12 inches long and seven sixteenths inch in diameter
will burn for from 100 to 150 hours, depending on the voltage of the circuit.
One of the advantages resulting from the employment of a small auxiliary
resistance, say about one sixth that of the arc, is that the same lamp may be used
on circuits differing in voltage. Circuits in which the voltage is nominally 110 may
at parts really measure as high as 115 to 118 or as low as 105 to 102, or any degree
between these limits, depending on the nature of the wiring and the speed at which
the generator is driven. A lamp with a large idle resistance will not operate
efficiently at any voltage, on account of the large losses in beat, and they will be still
less efficient if the voltage for which they are designed be changed, as in all cases
the resistance absorbs the greater part of the drop. In my correspondents'
construction, the resistance absorbs the smaller part of the drop, leaving the arc to
take care of from 75 to 85 volts or more, and an arc enclosed as described and
provided with a gas-check will effectively accommodate this range of voltage.
Thus it will be seen that a different adjustment is not needed for changes of voltage
over a considerable range, a feature of great practical advantage in avoiding
annoying adjustments and flickering of light.
The lamp hereindescribed is well adapted for alternating currents; for such use,
however, the solenoid core should be laminated, as by forming it of a bundle of
soft iron wire. Instead, moreover, of employing a mere resistance a choke coil
would be preferable in such uses to absorb the fractional drop outside of the are.
The are enclosing envelope acts as a damper on the sound given out by the arc in
alternating lamps.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is :-
1. An are lamp having a transparent or translucent envelope around the are
provided with a contracted opening through which the positive electrode may feed,
and a small auxiliary resistance in series with the arc, the arc and idle resistance
bearing such a relation that the ratio of their voltage drops will exceed unity.

page_text: 2. An arc lamp having a transparent or translucent envelope around the arc
provided with a contracted opening through which the positive electrode may feed,
a gas-check to obstruct ingress of air while permitting egress of the gaseous products
of the arc, an arc regulating device, and a small auxiliary resistance in series with
the arc, for the purpose described.
3. An arc lamp having its arc surrounded by a closed envelope having a
contracted opening through which the positive electrode feeds, a dead-air chamber
surrounding the carbon where it passes through said opening, and openings formed
in the wall of said chamber next the carbon.
4. An arc lamp having a transparent or translucent envelope around the arc
flanged at the bottom and provided with a clamp embracing the flange and
detachably secured to the envelope support.
5. An arc lamp having a transparent or translucent envelope around the arc
flanged at the bottom, a washer of heat-resisting packing material in the support,
and a clamp for firmly securing the envelope to the support to make a gas-tight
joint.
6. An arc lamp having two are regulating solenoids, a yoke uniting the cores,
and a dash-pot connected at each side of the yoke.
7. An arc lamp having an arc regulating magnet and a friction-clutch comprising
two parallel arms pinching the carbon-carrier, and means for spreading the arms
and releasing the carrier when the latter descends a determinate distance.
Dated this 2nd day of January 1896.
WM. P. THOMPSON & Co.,
Agents.