Improvements in Electric Arc Lamps.
Year: 1897

page_text: Date of Application, 25th Nov., 1897—Accepted, 1st Jan., 1898
Improvements in Electric Arc Lamps.
I, THOMAS SPENCER, of 1229 Callowhill Street, Philadelphia, Pennsylvania,
United States of America, 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:-
1
This invention relates to arc lamps of that type in which the arc is enclosed
within a small transparent or translucent chamber to which air from the atmos-
phere has difficult access and in to which the carbon pencil or electrode is fed by
regulating mechanism as the carbons waste away under the action of the arc. The
invention is particularly designed to permit such a lamp to be operated on an
alternating current circuit. In the attempts that have been made heretofore with
such lamps on an alternating current circuit, it has been found necessary to use
cored carbons in order to permit the arc to be maintained with a sufficiently small
current to admit of operation at a reasonable efficiency. A further difficulty has
been found in the fact that solid carbons prevent the lamp from starting, by reason
of the coating of graphite which is formed at their confronting ends. In enclosed
arcs, however, cored carbons cause a deposit on the small chamber which surrounds
the arc which interferes with the effectiveness of the light. This coating is prin-
cipally due to the large amount of silicious material used in the cores of such
carbons. It is a further object of my invention to permit solid carbons which are
made commercially of a high degree of purity to be used in such lamps, my lamp
being so constructed that the are may be effectively maintained with a current of
small amperage. It is a further object of my invention to provide a clutch which
will be sensitive in action, admitting of feed at very short intervals without
possibility of over-feed.
In carrying out the invention, I provide a mechanism for controlling the feed
of the carbous which is very sensitive to slight changes of current strength and
will act promptly in preventing a rupture of the arc. I provide also means for
causing an increased current to flow when the lamp is started, in order to break
down the graphite deposit above referred to and permit the lamp to start with
certainty. My lamp comprises a clutch of increased sensitiveness and an arc-
regulating coil containing inductance and provided with means for adjusting the
lamp to different rates of alternation of the supply circuit: it comprises also a
transformer forming part of the lamp structure by which the voltage of the
current may be increased from 50 or 100 volts, which is ordinarily maintained on
commercial alternating current circuits, to a point which will permit an effective
lamp action, means being provided for adjusting the voltage within sufficiently
wide limits to accommodate such variations of voltage as are found to exist in
different commercial circuits, and leave the lamp in its best working condition.
It comprises also means for increasing the amperage of the current when the lamp
starts for this purpose I prefer to employ a small choke-coil forming part of the
lamp structure. although other devices may be substituted for this, as will be
hereinafter more fully explained.
In the accompanying drawings which illustrate the invention,

page_text: Figure 1 is a sectional view, part in elevation, of a lamp embodying my
improvements;
Figure 2 is a side elevation of the upper part of a lamp, the direction of view
being at right angles to that of Figure 1;
Figure 3 is a top plan view of the regulating coil and inductance which springs
and controls the arc;
Figures 4 and 5 are side elevations and plan respectively of the small choke-
coil employed to furnish additional starting current when the lamp is started;
Figures 6 and 7 are elevations, on planes at right angles to each other, of the
device which controls the increase of starting current;
Figures 8 and 9 are elevations, on planes at right angles to each other, of the
clutch I prefer to employ and
Figure 10 is a diagrammatic illustration of a lamp embodying my invention.
Referring first to Figure 10, 1 and 2 represent an alternating current supply
circuit, which in commercial practice may carry nominally 50 or 100 volts but
practically varies somewhat from these limits. These voltages are insufficient to
maintain a constant arc, and I provide a transformer 3 by which the voltage may
be raised to a minimum value of 150 volts, thereby permitting the lamp to be
used on ordinary, commercial circuits. The transformier shown is of a character
known as the auto-transformer and comprises a single coil enclosing a laminated
iron core. I wind this transformer so that it will be capable of raising the voltage
of the line current from 50 or 100 to 150 volts, and provide a range of contacts 4, 5,
cte, by which the number of active turns may be raised by connecting a flexible
conductor 6 with the desired contact. 7 is the arc-regulating coil of the lamp;
it comprises an almost complete magnetic circuit for a coil 8, said circuit being
formed of four piles of laminated iron plates, such as is shown in Figure 3. The
magnetic circuit is open on the inside, as shown in Figure 10, to promote a good
operation on a tapering core 9 connected to a tube 10, which carries the clutch
mechanism and in which is suspended by a clutch the rod which carries the
movable carbon.
The upper end of the tube 10 is connected to a dash-pot by which the feed-action
is steadied, said dash-pot being suitably supported from the top-plate of the lamp.
In parallel are with the regulating coil is a small choke-coil 12 which leads to an
insulated contact 13 provided with a carbon-button confronting a similar button
mounted on a cut-out device 14 electrically connected with the lamp frame, said
device being adapted to cut into and out of the arc-circuit the branch including
the choke-coil for the purpose of increasing the current through the arc at the
moment of starting. A suitable switch is provided on the lamp for making and
breaking the circuit, which it has been deemed unnecessary to illustrate. As thus
constituted the mode of operation is, briefly, as follows:-
The transformer 3 raises the voltage of the operating current to 150 volts or
thereabout. The carbons being held together by the weight of the carbon-holding
rod and its connected parts, a disk or projection 15 engages a pin on the cut-out 14
and tilts the latter so as to bring the carbon-buttons into contact; thus the choke-
coil branch of the circuit is closed and a stronger current passes through the are
than is permitted after the lamp is lighted. This increased strength of current
serves to break down the graphite deposit at the junction of the carbons and
permits an are to be drawn when the regulating coil 7 lifts the core 9 and
separates the carbons. The cut-out device shown in the diagram is, for simplicity of
illustration, shown somewhat different, as will be hereinafter more fully described;
the action of the clutch will be apparent after the other figures of the drawings
have been described.
Referring now to Figures 1 and 2 it will be seen that the choke-coil 12 is hung
upon posts at the top of the lamp-casing, and that the transformer 3 and the
regulating coil 7 are supported in a line on four vertical posts, 16, 16, 16b, 16° to
which they are clamped. The construction of the transformer and the operating
coil is similar, except that the magnetic circuit on the former is completely closed

page_text: as
as shown in Figure 1, whereas the latter is open on the inside to permit a suction
on the core 9. Each of these coils is provided with a magnetic frame or skeleton
formed of four bundles of sheet-iron 17, 17ª, 17b, 17° held together by brackets
at the top and bottom, as indicated in Figures 2 and 3; the bolts which clamp the
bundles of plates to the brackets serve also to lock together the several plates of
each bundle. The choke-coil may be conveniently made shown in
Figures 4 and 5 of four piles of iron laminae bolted together into a rectangular
frame and provided with two small wire-coils of sufficient carrying capacity and
inductance to raise the starting current to double the normal amperes. The auto-
transformer 3, as indicated in Figures 1 and 10, is provided with two connected
windings of wire of different size, the one being made coarser than the other to
increase its carrying capacity for the operating current of the lamp; the mode
of connection and the relationship of the coils is indicated in the diagram
Figure 10. The core 9 is rigidly connected with a tube 10, the top of which
carries a plunger 18 of a dash-pot supported on a post on the under face of the
top-plate of the lamp. The rods, 16, 16, 16° etc., are of sufficient length to permit
vertical adjustment of the regulating coil 7, which may be set at different positions
by loosening the clamps which surround the rods and adjusting to the position
desired; this adjustment varies the inductance of the regulating coil by shifting
the magnetic field with relation to the core 9. The latter it will be observed is
made tapering, which gives an increased range of adjustment. By this con-
struction the lamp may be easily accommodated to different periodicities of
alternating current. By rendering the regulating coil adjustable with relation
to the working position of its core, its inductance may be varied so that the same
working current may flow with any periodicity between 7200 and 16,000 reversals
per minute.
The carbon-holding rod 19 which may be made of brass square in
cross-section is provided on one edge with teeth, as indicated in Figures 6 and 8,
the rack being housed within the tube 10 which connects with the core of the
regulating coil. The lower end of the tube 10, which passes through the core,
carries a disk 15 which controls the movements of the cut-out 14. The practical
construction of this cut-out is shown in Figures 6 and 7. The cut-out is pivoted
or trunnioned in suitable bearings below its centre of gravity and is provided with
two studs, 20 and 21 projecting into the path of the disk 15; these studs are so
spaced with relation to the limits of movement of the regulating core that the
disk 15 will engage the lower stud 21 just before the carbons come into contact,
thereby tilting the cutout 14 and bringing the two carbon-buttons 22, 22" into
engagement when the are goes out. The branch circuit to the choke-coil being
thereby completed, an increased current flows through the arc breaking down the
graphite deposit and causing the core 19 to rise and bring the disk 15 into engage-
ment with the stud 20, thereby tilting the cut-out and opening the contact
between the carbon-buttons 22, 22º. One of these buttons is mounted on the
tilting weight 14 and the other on an insulated bracket secured to the frame of the
lamp, as indicated in Figures 1 and 6, the branch-circuit through the choke-coil
being led to the bracket. The clutch I prefer to employ comprises a dog 24, seen
best in Figures 8 and 9, pivoted on an extension or bracket fastened to the lower
end of the tube 10. A slot cut in the bracket permits the nose of the dog to
engage the rack on one corner of the carbon-holding rod 19, as clearly shown in
Figure S a spring 25 tends to hold the dog in engagement with the rack. The
dog is provided with a horizontal extension 26 which bears upon the bed-plate of
the lamp-frame, as shown in Figure 1. When the carbons are in contact the
weight of the carbon and its holder forces the dog away from the rack and releases
the carbon-rod. Pivoted to the same bracket which carries the dog 24 are two
links 27, 27 upon which is pivotally supported a clutch-shoe 28 provided with a
V-shaped groove embracing one corner of the carbon-rod 19. Two light coil
springs mounted on the arbor 29 on which the dog 24 is pivoted give a normal
downward tendency to the links. The parts are so arranged that the arm 26 of
the dog will engage when moving upwardly with a screw or lug on one of the

page_text: links. In lieu of the choke-coil for increasing the strength of current, the cut-
out 14 may be arranged to short-circuit part of the operating coil when the con-
tacts are brought together, as indicated by dotted lines in Figure 10, which serves
to cut down the inductance and permit an increased current to flow when the lamp
is starting this organization, however, is not so effective as the choke-coil which
latter is much to be preferred in practice.
As thus constituted the operation of the lamp is as follows:-
When there is no current passing, the magnet 7 is de-energized and the core and
its connected parts drop, bringing the arm 26 upon the bed-plate of the lamp,
as seen in Figures 1 and 2: this throws the dog away from the rack and by engage-
ment with the stud on the link to which the brake-shoe is pivoted, raises the latter
and frees the carbon-holding rod, permitting it to drop until it is arrested by the
engagement of the two carbons. When the lamp is thrown into circuit, the
regulating magnet 7 is energized, lifting up the core 9 and freeing the arm 26
thus permitting the brake shoe 28 to fall and bind on the square edge of the
carbon-rod immediately afterwards the dog 24 engages with the rack and posi-
tively prevents slipping of the clutch. Thus the arc is sprung and will continue
to burn until the core 9 has been lowered sufficiently to bring the arm 26 into
engagement with the bed-plate, when the dog and friction-clutch are released from
the carbon-rod, permitting the latter to feed, after which an increase of current-
strength again lifts the core 9 and preserves the lamp in operation. It will be
noted that the carbon-holder is gripped on two opposite edges causing a
symmetrical movement and preventing binding when feeding is necessary; also
that if the friction-clutch should by accident permit the carbon rod to slip, as is
sometimes the case and is the occasion of considerable difficulty in clutch-fed lamps.
the dog comes instantly in to action and acts as a lock against overfeed. Thus the
clutch serves to regulate the feed for very small increments and the dog prevents
derangement from jars, vibration, or other causes.
Having now particularly described & ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is:
1. An alternating current are lamp provided with two paths for current to the
electrodes, one of said paths including a cut-out automatically actuated when the
are is sprung, whereby a starting current of abnormal strength is admitted to
the electrodes.
2. An alternating current are lamp provided with a regulating coil and a cut-
out automatically actuated when the arc is sprung to cut down the current
strength, whereby a starting current of abnormal strength is admitted to the
electrodes.
8. An alternating current are lamp provided with a regulating-coil, an
independent branch circuit leading to the are, an inductance in said branch cir-
cuit, and a cut-out controlled by the lamp mechanism to open the branch when the
are is started.
4. An alternating current are lamp provided with a transformer wound to
deliver a voltage sufficient to maintain the are with a current of small amperage,
and means for automatically raising the current-strength when the arc is being
started, for the purpose described.
5. An alternating current are lamp provided with an arc-regulating coil
adjustable relatively to the core, whereby the inductance of the coil when the lamp
is starting may be adjusted.
6. An alternating current are lamp provided with a transformer and arc-
regulating coil housed within the lamp and supported on a plurality of vertical
rods, and means for adjusting the regulating coil on said rods so as to shift it with
relation to its core.
7. An alternating current are lamp containing two branch circuits one
including the regulating coil and the other a tilting cut-out to close or open the

page_text: other branch when the carbons are in or out of engagement, for the purpose
described.
S. A feed-regulator for an arc lamp comprising a carbon-holder provided with
teeth, a dog co-operating with the teeth, and a friction-clutch controlled by the
regulating coil to feed the carbon-holder, said clutch co-operating with the dog to
set the latter after a definite range of movement of the clutch.
9. A feed-regulator for an arc lamp comprising a dog 24 engaging one side of
the carbon-holder, said dog having an extension adapted to engage a fixed part of
the lamp to release the holder, and a clutch-shoe 28 impelled into engagement
with the other side of the carbon-holder, said clutch-shoe being released after and
through the agency of said dog.
10. A feed-regulator for an arc lamp comprising a dog 24 engaging a rack on
one corner of the carbon-holder, said dog having an extension 26 adapted to engage
a fixed part of the lamp, and a clutch shoe adapted to engage the opposing corner
of the carbon-holder, said clutch shoe being controlled by the dog.
11. A feed-regulator for an alternating current arc lamp comprising regulating
coil 7, core 9, a clutch movable therewith comprising dog 24 engaging one corner
of rack 19, link 27, clutch-shoe 27 engaging an opposite corner of the rack, and
projection 26 co-operating with a fixed part of the lamp to release the dog and
clutch-shoe when the core descends a determinate distance.
Dated this 25th day of November 1897.
BOULT & WADE,
Agents for the Applicant.