Improvements in Electric Arc Lamps and Magnets therefor.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 20th Oct., 1900
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps and Magnets therefor.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by George E. Stevens,
residing at Lynn, in the County of Essex, State of Massachusetts, United States
of America, Electrical Engineer) and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement: —
The present invention relates to electric arc lamps, and has for its object the
improvement of their construction, and to that end consists in the parts and
combination of parts as hereinafter described and claimed.
In the accompanying drawings, which show an embodiment of this invention,
Fig. 1 is a side elevation of an arc lamp with the casing and outer globe removed;
Fig. 2 is a section through the magnet coil on the line 2-2 of Fig. 3; Fig. 3
is an inverted plan view of the magnet coil; Fig. 4 is a detail view in section
of the globe and lower carbon-securing device; Fig. 5 is a section taken on the
line 55 of Fig. 4, looking upward; Fig. 6 is a sectional view taken on the
line 66 of Fig. 4; Fig. 7 is a sectional view taken on the line 7-7 of Fig. 3,
and Figs. 8 and 9 are front and side elevations respectively of an auxiliary sup-
port for the clutch.
The lamp frame consists of an upper head A and a lower head B the head B
comprising two flat discs separated from each other by an air space B', and con-
nected by a hub B².
Situated on each side of the frame, and extending downwardly, are side tubes D,
and the lower head B is secured to the tubes by screws or other suitable means.
Extending downwardly from the upper frame head A are sockets D¹ adapted
to receive the upper ends of the side tubes D). Secured to the upper head and
extending upward is a resistance dome E, to which is secured the resistance-
carrying frame E. The resistance frame consists of a number of vertically ex-
tending pieces containing notches for the reception of the insulating bushings E²,
and mounted in the bushings is a coiled resistance E3 which is included in circuit
with the lamp to cut down the potential. Situated above the resistance dome
and secured thereto is a cap F for protecting the interior of the lamp.
In arc lamps as ordinarily constructed, there is more or less heating due to
the passage of current through the coils, and also to the upward passage of heat
from the arc. As the coils become heated, their resistance, and particularly
that of the shunt coil-increases, and consequently the current flowing therein
decreases. When this occurs the balance previously existing between the shunt
and the series coil is destroyed, and the arc becomes abnormally long before suffi-
cient current is forced through the shunt winding to cause it to move the arma-
ture and trip the clutch. To overcome this objection the two windings are sepa-
rated by an air space which communicates with openings in the spool flanges,
so that air admitted near the base of the lamp is permitted to pass upward between
the coils or parts of a single coil and through the openings in the top flange and

page_text: out. In certain instances it is desirable to divide the winding forming a single
coil into two or more parts and to separate the parts by an air space, and we aim
to embrace such a construction in the claims."
Referring to Fig. 2, the construction and arrangement of the coil will be
more clearly seen." The spool is provided with two flanges of iron or other
magnetic material, H and H¹, and these flanges are secured together by a tube I,
the ends of which are spun down over shoulders h formed thereon. This tube
is made of non magnetic material, so that the armature which is connected to
the carbon tube 0 of the lamp, will not stick as it moves up and down. Sur-
rounding this tube and acting as a spacer to separate the flanges of the magnetic
spool, is a copper tube J; in addition to separating the heads of the magnet, this
copper tube acts to damp the sudden movement of the armature of the magnet
due to the changes in the strength of the current passing through the shunt
winding G and the series winding G².
Surrounding the copper tube and the inner faces of the spool flanges is a body
of insulation K, which serves to protect the winding from the metal parts of the
spool.
In constructing the magnet the spool is assembled and the insulation K placed
thereon; the spool is then placed in a lathe, and the required number of turns
of wire wound thereon. As soon as this is done, a second spool L, made of sheet
brass or other non-magnetic material and having end flanges L', is slipped end-
wise over the first spool and winding and is retained in place by an iron ring M
located at the lower end of the spool and forming a part of the magnetic circuit.
This ring is provided with four radially extending projections M¹, as shown in
Figs. 3 and, which overlap four corresponding radially-extending projections H³
on the lower flange H¹ and are secured thereto by the screws m. The openings
formed between the lugs communicate with the space between the windings,
and permit a current of air to circulate from the bottom to the top of the magnet.
Formed on the upper flange are lugs H³ which serve to centre the spool and hold
it in place. It is preferable to wind and insulate the fine wire coil G¹ on the
spool L prior to mounting it on the first mentioned spool, since the wire is so
fine that it is likely to be broken in the lathe. By providing a suitable wind-
ing machine for the shunt coil all danger of breaking the wire is entirely obviated.
If desired, however, the spool L may be wound after it is placed in position on
the series spool.
Situated on the top of the magnet flange H and retained in place by screws,
is a guide plate N for centering and guiding the movements of the carbon tube 0.
Situated below the lower flange and supported on lugs formed integral there-
with is a second guide plate N1, which assists the upper guide plate N to guide
the movements of the carbon tube; these plates are each provided with shoulders
to centre them and a rounded surface n for engaging with the tube. The arrange-
ments of parts is such that these plates can readily be replaced when worn. After
the spool containing the shunt winding has been mounted in place, the pieces
of iron or other magnetic material Pare mounted in place and secured to the
upper flange H and to the ring M by screws p. These curved pieces serve to
complete the magnetic circuit of the spool, the armature shown in dotted lines
forming the balance of the magnetic circuit.
Situated on each side of the carbon tube 0, and connected thereto in any suit-
able manner, is a dash-pot Q, which dash-pots are arranged to damp the move-
ments of the carbon tube. Extending downward from the lower head B are the
side rods D. These rods support the yoke R, which carries the lower carbon
holder and the holding device for the inner globe cylinder V. Mounted within
the tubes D are rods Y, which carry the outer globe holder Y¹. These rods I
are arranged to move vertically within the tube D. and are held in their raised
position by means of the bail Y2, which is controlled by the milled head or
handle Y³ To lower the outer globe, the bail Y2 is raised by means of the
handle, which permits the rods to slip downwards through the side tubes D.

page_text: In arc lamps of the enclosed type it is desirable under certain conditions to
be able to remove the lower carbon without removing the enclosing globe from
the lamp, and also to provide a single means for holding or clamping both the
lower carbon and the cylinder.
Referring to Fig. 4, R represents the yoke connecting the side tubes D, and
formed in the centre of the yoke and extending upward is a cylindrical exten-
sion R¹ which is screw-threaded on its upper end to receive the nut R2. Mounted
within the extension is a clutch consisting of three tapered members R3, each
member having a groove on the bottom end to receive the flat spring r, which
tends at all times to press them outward and release the lower carbon S. Situated
above the clutch members is a ring or collar T having a conical bore, adapted
to receive the tapered pieces forming the clutch R³. Mounted on the top of
this ring is a sheet of asbestos or other heat resisting material U, which renders
the lower end of the globe practically air tight when it is clamped in place.
Between the inner globe or cylinder V and the nut R2 is a coiled spiral spring W,
although any other device may be employed which will adjust itself to slight
irregularities of the globe or cylinder V. The yoke R is bored out on its under
side to permit the insertion of the carbon S, and under this opening is a spring
pressed plate X arranged to close the opening and make it practically air-tight,
and also to prevent the dropping of carbon dust.
When it is desired to re-carbon the lamp, the plate X is swung to one side,
and the nut R2 released, which causes the ring T to relieve the pressure on the
members of the clutch R³, so as to allow the lower carbon to drop downward
through the yoke. The upper carbon may be removed from the upper holder
and permitted to follow the lower carbon, after which a new carbon may be
inserted in the upper holder and forced upward through the carbon tube and
followed by the lower carbon. As soon as the lower carbon has been raised to.
its proper height, the nut R2 is set, which causes the clutch R³ to grip the lower
carbon, and the spring W to grip the cylinder V. This arrangement permits
the retrimming of a lamp in a building where the dust and dirt from the car-
bon would be destructive; and it also enables us to provide a lamp in which the
danger of breaking the globe is eliminated to a large degree, since they do not
have to be removed from the lamp.
More or less difficulty is experienced in recarboning lamps having a gravity
feed, owing to the fact that when no current is flowing through the magnet coil
or coils, the feed mechanism will permit the upper carbon to fall; this is objec-
tionable at times, and particularly when the trimmer is engaged in fixing the
lower carbon and cleaning or adjusting the arc-enclosing cylinder. To overcome
this objection we propose to employ a mechanical support which is the equivalent
in its action of the feed magnet or magnets employed in regulating the lamp.
In other words, an auxiliary support is provided, normally inactive, but which
is manually thrown into operative position to support the feed mechanism when
it is desired to recarbon the lamp.
Referring to Figs. 8 and 9, 0 represents the carbon tube, on the lower end
of which is mounted a clutch O' of any desired type, the one shown consisting
of a pair of pivoted jaws which are arranged to grip the upper carbon between
them. Situated at one side of the carbon and secured to the head B, is a post 02,
and mounted in the post is a bell-crank lever 03 having a weighted outer end 04
normally extending to withdraw it from engagement with the clutch O¹. A pin o
limits the anti-clockwise movement of the lever, and the ball on the opposite
end of the lever limits the clockwise movement.
We have termed this an "auxiliary support" for the carbon, since it is entirely
inoperative during the normal operation of the lamp.
When it is desired to recarbon, the new upper carbon is mounted in the holder
in the ordinary manner, the carbon tube 0 and clutch are then moved upward
by hand, and the lever 03 moved into engagement with the clutch; this causes
the clutch to grip and hold the carbon in just the same way as if the magnets

page_text: were energized, and a new lower carbon may be inserted without trouble...It
is of course evident that the upper carbon need not occupy its normal position,
but be raised to a point above it to facilitate trimming.
With an arrangement of this kind there is always the possibility of the trimmer
leaving the clutch in its suspended position, which will prevent the lamp from
burning. To prevent this, the release of the clutch, is rendered automatic, as
well as manual, so that, no matter what position the upper carbon and clutch
occupy after retrimming, they will automatically return to their operative posi-
tion as soon as current is turned on the lamp. This is accomplished in the pre-
sent instance by the weight 0 on one end of the bell crank lever which auto-
matically returns to the position shown in dotted lines, where it is out of the
way of the normal movement of the clutch, as soon as the magnet draws up its
armature the tube and the attached clutch. If the upper carbon is not pro-
perly adjusted when the clutch first drops, the latter will strike the cap 05, which
acts as a tripping floor, and the carbon will be permitted to feed.
It is evident that the construction of the auxiliary support may be widely varied
without departing from the spirit of our invention.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is;-
1 In a magnet for an electric are lamp, the combination of a spool upon
which a portion of the wire is wound, a flange for the spool having a ventilating
opening, a second spool arranged to be slipped over the first and receive a por-
tion of the winding, and a detachable ring which surrounds one of the flanges
of the first named spool and serves to retain the second spool in place.
2 In an electro-magnet for an electric are lamp, the combination of a spool
upon which a portion of the wire is wound, a second spool to receive a portion
of the winding and to be slipped over the first mentioned spool, and separated by
an air space therefrom, and means for securing the spools in such a manner that
they may be separated without disturbing the winding on either spool.
3-In an electro-magnet for an electric are lamp, the combination of a pair
of magnetic spool flanges, a tube connecting the flanges, a coil wound on and
insulated from the tube, a second coil wound on a spool which is slipped over the
first, but separated from the first coil by an air space, and magnetic material
connecting the flanges of the spool and forming a part of the magnetic circuit.
4-In an electro-magnet for an electric arc lamp, the combination of a pair
of magnetic spool flanges, a non-magnetic tube arranged to hold the flanges
together by being spun over shoulders formed on the flanges, a closed band of
good conducting material for damping the effect of changes in strength of the
magnet, a winding mounted on a spool and arranged to be slipped endwise over
the tube and one of the flanges, a ring for retaining the spool in place, which
forms a part of the magnetic circuit, and pieces of magnetic material which join
one of the spool flanges with the ring.
5 In a magnet structure for electric arc lamps, the combination of a pair of
spool flanges connected by a tube, a spool arranged to be slipped over the first
and to be separated therefrom by an air space, and means for separating and
centering the two spools with respect to each other.
6 In a magnet structure for electric arc lamps, the combination of a pair of
spool flanges made of magnetic material and connected by a tube of non-magnetic
material, a second spool arranged to be slipped over the first and to be separated
therefrom by an air space, shoulders formed on the upper flange for centering
the second spool, a ring for securing the second spool in place and forming a
part of the magnetic circuit, lugs on the ring which engage corresponding lugs
on the lower flange of the first named spool, and strips of iron which connect
one of the spool flanges with the ring.
7 In a magnet for an electric are lamp, the combination of a spool flange

page_text: made of magnetic material and forming a part of the magnetic circuit and pro-
vided with ventilating openings, a guide plate secured to the flange for guiding
the carbon tube, a second spool flange also made of magnetic material and pro-
vided with projections, a winding or section of winding mounted on a spool, a
second spool containing a winding arranged to be slipped endwise over the first
and separated therefrom by an air space, and a ring of magnetic material for
holding the spool in place, and provided with lugs which engage with the lugs
on the lower spool flange.
8 In a magnet for an electric arc lamp, the combination of a spool flange
made of magnetic material and forming a part of the magnetic circuit and pro-
vided with ventilating openings, a guide plate secured to the flange for guiding
the carbon tube, a second spool flange also made of magnetic material and pro-
vided with projections, a winding or section of winding mounted on the spool, a
second spool containing a winding arranged to be slipped endwise over the first,
and separated therefrom by an air space, a ring of magnetic material for hold-
ing the spool in place, and provided with lugs which engage with the lugs on
the lower spool flange, and strips of magnetic material for completing the
magnetic circuit.
9 In an electric arc lamp, the combination of a support having an opening
to receive the carbon, a friction clutch mounted on the support, a globe holder,
and means for holding the globe and forcing it downward against the clutch to
cause it to grip the carbon.
10 In an electric arc lamp, the combination of a support, a friction clutch
mounted on the support, a tapered collar or ring operating the clutch, a globe
holder, and means for forcing the globe downward against the collar or ring to
actuate the clutch.
11 In an electric arc lamp, the combination of side rods, a yoke connecting
the side rods, a cylindrical extension formed on the yoke, a friction clutch for
gripping the carbon, composed of separate individually adjustable members, a
ring having a conical bore arranged to fit down over the clutch members, a globe
or cylinder arranged to be seated on the ring, and devices acting both to clamp
the globe in place and to force it downward against the ring to actuate the clutch.
12 In an electric arc lamp, the combination of a pair of side rods, a yoke con-
necting the rods, a cylindrical extension having a straight bore carried thereby,
a friction clutch composed of a number of individually-adjustable members, the
members having a straight bore and a tapered periphery, a globe, a flexible
medium between the globe and the clamping-nut, a clamping nut for compress-
ing the medium, actuating the clutch and securing the globe in place.
13-In an arc lamp, the combination of a cylindrical extension having an open-
ing in the bottom, a carbon clutch mounted in the sleeve and composed of sepa-.
rately-adjustable pieces, means for causing the pieces to grip the carbon, means
for causing the pieces to release the carbon, and a plate for covering up the
opening in the bottom of the cylindrical extension.
14 In an electric arc lamp, the combination of a clutch for controlling the
feed of a carbon, with an auxiliary support for suspending the clutch during
trimming, which forms no part of the feeding mechanism.
15 In an electric arc lamp, the combination of a carbon, means for supporting
and feeding the carbon, and an auxiliary support which performs no function in
the normal operation of the lamp, but is arranged to hold the carbon during
trimming.
16-In an electric arc lamp, the combination of a carbon, an auxiliary support
for sustaining said carbon which is normally idle except when the lamp is re-
trimmed, and means for automatically moving the auxiliary support out of
engagement with the carbon when current is admitted to the lamp.
17 In an electric arc lamp, the combination with a carbon, a clutch for feed-
ing the carbon, and an auxiliary support, which is normally idle, for engaging

page_text: with and supporting the clutch in operative position when no current is flowing
in the lamp.
18 Ih an electric are lamp, the combination of a carbon, a clutch for feeding
the carbon, an auxiliary support, which is normally idle, for engaging with and
supporting the clutch in operative position when no current is flowing in the
lamp, and means for automatically removing the support from engagement with
the clutch when current is admitted to the lamp.
'
19 In an arc lamp, the combination of a carbon, a clutch therefor, a tripping
device for the clutch, an auxiliary support for holding the clutch in operative
position during the time when current is cut off from the lamp, and means for
automatically releasing the clutch when current is admitted to the lamp, and
permitting it to strike the tripping floor for the purpose of regulating the length
of the arc.
Dated this 20th day of October 1899.
THE BRITISH THOMSON-HOUSTON CO. LTD.
J. J. MANHEIM,
Directors.
A. R. MONKS,
ALFRED CLEMENTS,
Assistant Secretary.