Improvements in Electric Arc Lamps.
Year: 1898

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
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 Charles E.
Hartham, 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 performed 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 to
improve their construction, and to this end consists in parts and the combination
of parts hereinafter described and claimed.
In the accompanying drawings which show an embodiment of the invention,
Fig. 1 is a front elevation of a lamp with the outer globe in section; Fig. 2 is
a side elevation of the mechanism employed to support the cylinder cap; Fig. 3
is a front elevation of the same; Fig. 4 is a plan view of the cap support, with
portions broken away; Fig. 5 is a front elevation of a lamp with the globe and
casing in section; Fig. 6 is a detail of the globe locking device; Fig. 7 is a
sectional detail of the resistance supporting frame, and also of the canopy;
Fig. 8 is a detail of the resistance support, and Fig. 9 is a detail illustrating the
means employed in insulating the side rods.
In manufacturing electric arc lamps, it is desirable from a selling point of
view, to make them attractive, and it is necessary to construct them as cheaply
as possible. The mechanism of the lamp is usually surrounded by a casing, and
in order to make this casing as cheaply as possible, it is constructed of sheet
metal and made into the form of a cylinder A having suitable bands or ornamen-
tations A¹ formed by rolling the sheet metal of which it is composed between
rolls during the process of construction. Mounted on the ends of the cylinder A
are cornices A2 and A3; these cornices are similar in construction and are formed
by the same formers. As it is necessary to ventilate the lamp casing, the side a
of the lower cornice is made a trifle shorter than the side a¹, so that air can enter
at a point above the outer globe B, and pass upward through the lamp parts,
thereby keeping the temperature of the lamps down to a predetermined amount.
In Fig. 11 is shown the construction of the cornices. For convenience and
cheapness of construction the cornices are made of two pieces a and a¹, which
lap over each other at point a². The two pieces are formed separately and are
afterwards secured together by spinning, which makes a water-tight joint
between them. In so far as the construction of the cornices is concerned, it
does not matter whether they are provided with side portions a and a¹ of the
shape and length shown or not, the essential feature being to make the cornices
in two parts and to secure them in the manner shown.
The side a of the cornice is secured to the casing A in any suitable manner,
as for example, by riveting or soldering. The upper cornice A³ is reversed with
respect to the lower one and extends above the casing A, and is secured in place
by riveting or soldering the long side a¹ to the casing. The upper cornice

page_text: commonly surrounds a resistance in a direct-current lamp, and a reactance in an
alternating-current lamp, and for ventilating the resistance or reactance the long
side a¹ of the cornice A³ is perforated by a series of small holes A4, as shown in
Figs. 5 and 7. When the lamp is intended for out-of-door service, a metal
cover C is provided, resembling an inserted saucer,, which extends down over
the short side a of the upper cornice and prevents water from entering the casing.
By making the cornices similar and reversing the upper one, sufficient room is
provided at the top for the resistance or reactance, and the size of this resistance
or reactance may be varied without altering the size of the casing; this makes
all of the lamps present a uniform appearance, whether they are intended for
alternating or continuous current.
When a lamp is intended for indoor use, where ornamental appearance is an
Secured to
important feature, the arrangement shown in Fig. 7 is employed.
the ceiling or other suitable support, is a ceiling-board D made of insulating
material, as porcelain, for example. On the under side of the board is a hook I)i
arranged to support the lamp by the ring D², which ring is insulated from the
lamp be the bushing D³. The bushing is mounted in a U-shaped casting D
which is screw-threaded to the resistance-supporting dome E. Electrical con-
nection between the hanger board and the lamp is made by the cables F and F¹.
Surrounding the ceiling board, cables and hook, is a split canopy so arranged
that one-half of it may be swung outward on hinges G¹ to permit inspection, and
also to permit the removal of the lamp. The canopy is provided with enlarged
heads G2, and a contracted neck G³, the upper head surrounding the ceiling
board D, and the lower head the cornice A3. The lower head is slotted to receive
the actuating handle of the switch H. Secured to the neck of the canopy is an
internal flange or collar G4 which closely surrounds the U-shaped casting D³,
suitable openings being provided for the reception of the cables F and F1; this
prevents the heat from passing upward to the ceiling. The heat passes outward
from the casing through the space between the upper cornice A3 and the canopy,
and also through the holes G5 in the canopy.
It will be seen that the canopy projects downward over the cornice so that the
lamp presents an unbroken ornamentation from the globe to the ceiling, a
feature which adds greatly to the appearance of the lamp.
In direct-current lamps designed for constant potential circuits, it is customary
to mount a resistance in the top of the lamp, and for this purpose a cast metal
dome E is provided, having radial slots E¹ for the reception of the blocks of in-
The dome is made
sulating material E2 which carry the resistance coil 3.
hollow in order to radiate the heat generated by the resistance coil, and also to
receive certain of the operating parts of the lamp. In the present instance the
upper end of the tube I and the dash-pot I are within the dome. On the lower
end of the dome is a cylindrical flange E5 adapted to be secured to the lamp
frame J by screws.
Situated at the bottom of the insulating blocks E, and formed integral with
the flange E, are beveled lugs or projections e, arranged to secure the blocks
at their lower end.
The blocks E are preferably made of porcelain, or other non-combustible
material, and are provided with openings E for the reception of the resistance
coils 3. Between the blocks and the slots E in the dome are strips of asbestos
or similar material e', which compensate for any slight irregularities in the
parts, and at the same time assist in retaining the blocks in place. The insulat-
ing blocks are secured in place at the top by a plate K having downwardly pro-
jecting feet K which rest upon the upper beveled ends thereof. The plate also
acts as a support for the binding posts L and L', and is secured to the dome by
screws.
Referring more particularly to Fig. 5, the method of winding the resistance
will be described. The resistance wire is first coiled like a spiral spring and the
spring round around the dome, the outer end of the resistance is connected to

page_text: the binding post L¹, and is wound in an anti-clockwise direction until it arrives
at the insulating bushing M, where it is given half a turn, and the balance of the
coil wound in a clockwise direction, and finally secured to insulating bushing M¹.
The inner end of the resistance is so arranged that it may be connected to any
cne of the loops M² formed on the magnet winding M3; this is to adapt the lamp
for use on different circuits, or for different currents.
In order to adjust a lamp for use on different circuits, it is often necessary to
change the amount of resistance in circuit therewith, and for this purpose a two-
part clamp or slider (Fig. 10) is provided, and so arranged that it may be slid
along two turns of the coil and cut out more or less resistance. By arranging
the resistance coil in such manner that part is wound in one direction and part
in the reverse direction, a wide range of regulation by the resistance is obtained.
When the clamp N is in the position shown, current in passing through the
coil M³ to the binding post L, or vice versa, is practically shunted past two turns
of the resistance wire; whereas, if the clamp N is placed across the two lower
turns only a single turn of resistance is cut out; sliding the clamp along the wire
will of course vary the amount of resistance in circuit.
The arrangement of the resistance wire and its supports is a particularly
desirable one, for it permits the adjusting of the wire after it has been mounted
in place, and where the turns of wire of which the resistance is composed are
close together, this is an important feature.
In order to prevent carelessness on the part of the trimmer, the globe B is
carried by a holder B which is secured to the lower ends of rods B2, and the rods
in turn are locked in their raised position by the pivoted bail B. The bail is
controlled from the outside of the casing by a thumb-nut 14; this necessitates
the use of both hands when the globe is lowered, for the globe has to be raised
slightly before the hoop-shaped end of the latch can be withdrawn from the
openings B in the side rods.
To prevent the entrance of water into the outer globe B a cylindrical flange A³
is mounted on the lower end of the casing A, which flares outward over the open-
ing in the globe. In order to make a tight joint between the flange and the
globe, and also to compensate for different sized globes, the globe is supported
by an adjustable holder which in the present instance comprises a cast metal
holder having a loose-fitting cup-shaped ring 03 at its upper end for receiving
the globe. By making the ring a loose fit, the holder may be rotated with-
out turning the globe. The holder is supported from cross piece B¹ by a screw-
threaded stud (2 having a cut-away portion (%, and extending across this
cut-away portion is a pin 04, which prevents the removal of the support, but
permits it to be freely adjusted in a vertical direction.
In retrimming the lamp, the holder () is first turned in a direction to lower
the globe, the globe and holder are them. moved bodily upward, which permits
the withdrawal of the hooked latch 133, and after this has been done the globe
may be lowered in the usual way. To return the parts of the lamp to their nor-
mal position after retrimming, the reverse of the operation is performed.
In retrimming lamps it frequently happens that the trimmer will drop the
cap or the inner cylinder and thus break the outer globe. When the cap is cold
this is not so liable to occur, but when the cap is too hot to be taken in the hand
and it is necessary to use pliers or some similar device, there is a great liability of
accident. To guard against this the cap is permanently secured to the lamp,
but it is so arranged that it may be removed from its normal position when it
is desired to insert a new carbon in the upper holder. Since it is desirable to
have the floor of the clutch which controls the feed of the upper carbon located
at a fixed point with respect to the working parts of the lamp, there is provided
a fixed support which constitutes a floor for the clutch, and at the same time
serves to prevent the cylinder cap from dropping.
Referring more particularly to Figs. 2, 3 and 4, the support consists of a flat
metal plate P having two upwardly-extending lugs P¹ and two downwardly.

page_text: extending lugs P2 and P3; lug P2 being arranged to support the free end of the
cylinder cap Q after the cylinder Q has been removed; and lug 13 to form a
hinge support for one side of the cap. The support P is retained in place by
two vertically-extending rods P which are screw-threaded to the under side of
the frame J. The holes in the outer ends of the holes P are large enough to
make an easy fit, so as to permit the support to adjust itself, and by taking out
the pins the support may be removed from the lamp. The arrangement of
the support l' and the rods 14 is such that the support is practically capable of
universal motion; that is to say, there is enough play between the parts so that
the support can tilt both on a horizontal and a vertical axis.
The clutch is secured to the lower end of the tube I, and consists of a pair of
collars S and $1 which are connected by side bars S2. Pivotally secured to the
lower collar S¹ is a pair of clutch members §³ arranged to grip the upper carbon
and feed it downward as the carbons are consumed. The clutch members are
provided with extensions S5 arranged in such manner that they will when the
tube I is lowered a certain amount, strike the top of the support P and trip the
clutch. By referring to Fig. 4 it will be seen that the support P is provided
with a rectangular central opening Q: this opening is arranged to receive the
downwardly-extending lugs S of the clutch members, thereby shortening the
space required by the clutch.
The opening between the collars S and S¹ of the clutch is so arranged that the
carbon can be held by the fingers or pliers, or the contact device secured to the
end of the carbon, can be held while the carbon is inserted in place.
The cylinder cap Q is substantially circular in outline, and is provided with
a U-shaped lug Q2 on one side, which extends around the lug 13 on the support
and the ends of the lug are connected by a pin Q3. The cap is provided with
two circular flanges, the upper one being arranged to rest on the top of the
cylinder Q, while the lower one is somewhat smaller than the cylinder, and
forms, together with the cylinder, a gas chamber for preventing the free entrance
of air at this point. The cap is normally supported by the cylinder Q', as shown
by the full line position, but when it is desired to retrim the lamp, the cylinder-
holding device is released; and the cylinder lowered until the cap rests on
the lugs 12 and 13 in the manner shown in the broken-and-dotted lines (Fig. 3).
The upper carbon is then raised, either by hand or with a pair of pliers, which
permits the cap to be moved slightly to the right, and the flattened edge of the
cap Q will slip past the end of the lug 12 and permit the cap to drop to the
position shown in dotted lines (Fig. 3), the pin Q3 preventing it from dropping.
With this arrangement the cap is out of the way, and does not interfere with the
retrimming of the lamp, and at the same time is prevented from dropping and
breaking the globe. After the new carbons have been placed in the lamp, the
cap is placed in the broken-and-dotted line position, and the cylinder mounted
in place, which moves the cap upward to the full-line position.
It is necessary in certain types of lamps to insulate the lower carbon holder
from the side frames, and it has been a matter of considerable difficulty to pro-
vide a satisfactory construction. In Fig. 9 the construction is shown in detail,
in which T represents the frame connecting the sides tubes T¹, (the latter are
shown in Fig. 5), and is provided with a hole or opening at its outer end for the
reception of the tube. Mounted within the hole is a metal bushing comprising
a main body T2 and a washer T. Between the metal bushing and the frame is
an insulating bushing T preferably composed of mica, but other forms of in-
sulating material may be used if desired. The metal and insulating bushings are
secured in place by riveting the main body 12 of the metal bushing over the
washer T. The frame T is secured to the side tubes by means of the hollow
screws T5. The arrangement above described is particularly useful where it is
desired to remove the frame T, for the insulation is so arranged that it is not
disturbed, and the metal bushing makes a good working fit with the tube. With
other construction previously employed, it was necessary to use a new insulating

page_text: bushing each time the lamp was taken down, whereas with the present con-
struction a single bushing lasts as long as the lamp.
our said
Having now particularly described and ascertained the nature of
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-A casing for an electric arc lamp, comprising a main body with cornices
secured thereto, which are reversed with respect to each other.
2-A casing for an electric arc lamp, comprising a main cylindrical body
having cornices secured thereto at or near both ends.
3-In a casing for an electric arc lamp, the combination of a cylindrical body
portion, with a cornice secured thereto, the cornice being secured of two pieces
which are mechanically united.
4 In a casing for an electric arc lamp, the combination of a cylindrical body
portion having ventilating openings therein, and cornices secured to the cylindri-
cal body, one of the cornices being so arranged that it covers the ventilating
openings in the casing.
In a casing for an electric are lamp, the combination of a cylindrical body
portion, cornices therefor, each cornice comprising a long and a short side, and
so arranged that the long side is secured to the cylindrical portion.
G-The combination of an electric arc lamp, a fixed support, means for sup-
porting the lamp, a split canopy which surrounds the means employed for sup
porting the lamp.
7 The combination of an electric arc lamp, a casing surrounding the lamp
mechanism, means for supporting the lamp from the ceiling or other support,
and a canopy which surrounds the supporting means and extends down over the
casing so as to form a smooth ornamentation from the support to the bottom of
the casing.
8-In an electric arc lamp, the combination of a canopy for covering the lamp
support, consisting of a cylindrical body of metal having two enlarged heads
with a contracted neck.
9 In an electric are lamp, the combination of a ceiling board, means for sup-
porting the lamp, a canopy surrounding the support, and an integral collar or
flange which prevents the heat from passing upward from the lamp to the ceiling
board.
10 In an electric arc lamp, the combination of a ceiling board, means for
supporting the lamp, a canopy surrounding the support, an integral collar or
flange which prevents the heat from passing upward from the lanp, and venti-
lating openings permitting the free egress of heated air from the lamp.
11 In an electric arc lamp, the combination of a cast metal resistance dome,
notched radial extending blocks mounted thereon, and a coiled resistance wire
mounted on the blocks, the arrangement of the coils being such that one part
of the wire is wound in a clockwise direction and the balance in an anti-clock-
wise direction.
12 In an electric arc lamp, the combination of a cast-metal resistance dome,
notched radial blocks mounted thereon, a coiled resistance wire mounted on the
blocks, the arrangement of the coils being such that one part of the wire is
wound in a clockwise direction and the balance in an anti-clockwise
direction, and an adjustable slider mounted on the resistance wire for varying
its active length.
13 In an electric arc lamp, the combination of a cast-metal resistance dome
having beveled lugs secured to the base, a support at the top of the dome having
downwardly-extending feet, and insulating blocks mounted in the dome and
secured in place by the feet and beveled lugs.
14 In an electric arc lamp, the combination of a cast-metal resistance dome
having a flange at its lower end formed integral therewith, beveled lugs on the
flange, a sheet metal support located at the top of the dome and having down-

page_text: wardly-extending feet, insulating blocks mounted on the dome between the feet
and the beveled lugs, and a layer of non-combustible material between the
blocks and the dome, which serves to compensate for slight irregularities..
15 In an electric are lamp, the combination of a resistance dome, insulating
blocks mounted thereon, coiled resistance wire mounted thereon in spirals, the
arrangement being such that one part of the wire is wound anti-clockwise and
the balance clock-wise, means for holding the resistance at the point of turning
and means for securing the outer ends of the wire...
41***
"
16 In an electric arc lamp, the combination of a supporting frame, a cast-
metal resistance dome secured thereto, and provided with a screw-threaded
extension, and a support for the lamp mounted in each extension..
17 In an electric arc lamp, the combination of a globe-holder, a looking
device therefor, means for limiting the upward movement of the globe, and
means for adjusting the globe so arranged that it is necessary to lower the globe
slightly before the lock can be released.
"
18 In an electric are lamp, the combination of a globe-holder, a locking
device therefor, and means so arranged that it is necessary to lower the globe
slightly before the lock can be released.
19-In an electric are lamp, the combination of a globe, a vertically-adjust-
able support for the globe, a lock for securing the globe in position, and means
for raising the globe slightly against a stationary part of the lamp so as to pre-
vent the entrance of water and dirt into the globe, the arrangement of the
globe-holder and the lock being such that it is necessary to lower the globe
holder slightly before the lock can be released.
י,
20-In an electric arc lamp, the combination of a globe, a globe-holder mounted
on a screw. threaded stud, carried, by a suitable frame, an outwardly flaring
flange against which the globe is normally pressed, and a lock for the holder,
comprising a moving bail having hooked ends and a pair of vertically-movable
side-rods; the relation between the lock and the holder being such that it is
necessary to slightly lower the globe before the lock can be released.
21 In a globe holder for an electric arc lamp, the combination of a screw-
threaded stud, a holder mounted thereon and arranged to be vertically adjust-
able, means for preventing the holder from being removed from the stud during
the normal operation of the lamp, and a loosely mounted, cut-shaped ring for
supporting the outer globe, which is so arranged that the holder may be rotated
without moving the globe.
22 In an electric arc lamp, the combination of a cylinder surrounding the
carbons, a cap for restricting the passage of air into the cylinder, and means for
holding the globe at one side of its normal position, while the lamp is being
trimmed.
23-In an electric arc lamp, the combination of a cylinder surrounding the
carbons, a cap which normally rests on the top of the cylinder for restricting the
passage of air into the cylinder, means for holding the cap after the cylinder
has been removed, and means permitting the cap to hang downward and at one
side of the carbons while the lamp is being retrimmed.
t
24 As an article of manufacture, a combined support for a cylinder cap and
the floor of a clutch, comprising a substantially circular plate having an en
Jarged.central opening to receive parts of the clutch, with a pair of upwardly-
extending supporting lugs, and a pair of downwardly-extending cap retaining
lugs..
25-In an electric are lamp, the combination of a tube surrounding the car-
bon, a clutch mounted on the tube, the said clutch comprising two connected
collars having a space between them, and so arranged that the upper. carbon, can
be gripped by hand between them, and clutch members for gripping the carbon.
26 In an electric are lamp, the combination of side rods, a frame.connecting
the side-rods, and an insulating bushing between the frame and side-rods, com-

page_text: prising a body of insulating material which is secured in place by a metal
sleeve.
27-In an electric arc lamp, the combination of a frame, with an insulating
bushing mounted in said frame, the bushing comprising a body of mica which
is retained in place by a metal sleeve, and a washer, the said sleeve being united
over the washer.
Datca
THE BRITISH THOMSON-HOUSTON Co. LTD.
A. R. MONKS,
W. MARTINDALE,
Directors.
ALFRED CLEMENTS,
Assistant Secretary.