Improvements in or relating to Arc Lamps.
Year: 1891

page_text: Date of Application, 25th Mar., 1891
Complete Specification Left, 24th Dec., 1891-Accepted, 30th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in or relating to Arc Lamps.
We, FREDERICK RICHARD BOARDMAN, of 3 Forest Drive, Manor Park, in the
County of London, Electrical Engineer, and JOSEPH SINCLAIR FAIRFAX, of
433 Strand, in the County of London, Consulting Engineer, do hereby declare the
nature of this invention to be as follows:-
Our invention consists of improvements in or relating to are lamps, and it
comprises certain combinations of refractory material with one or both of the
carbon electrodes, and the new or improved application of a mouldable material
(also of a refractory nature), in the framework of an arc lamp, which has insulating
and reflecting qualities. These improvements are applicable, wholly or partially, to
existing types of arc lamps.
We surround, or partially enclose, the end of one or both of the carbon electrodes
with a sleeve or cap of refractory material, for the purpose of avoiding much of
the waste of the heated part of the carbon electrodes, of improving the colour of the
light produced, (making it more of the character of sunlight), adding to the
efficiency of the lamp by preventing flickering and in part shielding the highly
heated carbon points from the chilling effects of cold air currents, thereby adding
to the life of the carbons, and to the number of hours during which a lamp may be
used without re-trimming. We may also keep the light-giving portion of the lamp
at a fixed point for search light, photographic and other purposes, but this is not
essential in all cases.
2
A cap of refractory material, such as fire clay, is suitably moulded, burnt, and
fitted upon the end of an electrode, so as to enclose the same and to be heated thereby
to incandescence. The cap has a small central hole, sufficiently large to permit the
egress of the heated carbon vapour from the electrode, thus absorbing nearly all
heat radiation from the latter and reducing the rapid combustion resulting from
unrestricted currents of air combining with the carbon. The cap is rounded on
the outside surface and is held in its position upon the carbon by a nipple of iron,
steel or other suitable material, which forms a part of a metallic case or holder for
the carbon. This carbon holder contains a spiral spring which acts upon the
carbon to keep it tightly pressed against the refractory cap, which in turn is
pressed against the enclosing nipple, the latter being so formed as to allow the cap
to slightly protrude through the central orifice thereof. Suitable means
provided whereby the nipple may be readily attached to or detached from the
carbon holder, and to allow of renewals of the cap or of the carbon. The nipple,
or the holder, may be secured in any convenient manner, and at any desired focal
point within the globe of the lamp; the other electrode being relatively adjusted
In some
thereto, for regulating or for striking the arc, by any known means.
cases, we may make one of the carbon electrodes hollow and introduce an adjustable
pencil carbon through the bore of the hollow carbon for the purpose of striking the
arc in lighting the lamp.
.
are
The means we have already described may be used together in an arc lamp, but
in order to dispense with the hollow and pencil carbons, required for lighting, we
may enlarge the opening of the refractory cap of the adjustable electrode, to allow
the latter to pass through, thus converting the cap into a sleeve. In this case,
the adjustable carbon may be moved and regulated in any convenient manner, either
alone, or the surrounding sleeve with its metal nipple may be adjustable indepen-
dently, or in concert with the adjustable carbon.

page_text: In some cases, we provide means for securing the refractory pieces at a suitable
distance apart to allow of the play of the arc between; this distance however, may
be absolutely fixed, or adjustable with relation to each other by moving one or
both of the pieces with the nipple or holder pertaining thereto to the required
distance apart; but the adjustable carbon itself is automatically moved in any
known manner either for lighting the lamp or regulating the resistance.
In any
case it will be seen that there is a clear space between the opposing surfaces of the
two pieces of refractory material; and that, therefore, the voltaic arc, or luminous
stream of carbon vapour, is free to play around in all directions as with ordinary
carbon electrodes; but the extreme points of the arc can no longer start from, or
terminate upon, the sides of the carbons, as those points are limited to the area of
the central holes in the refractory material. Thus, in addition, to the luminous
effect of the voltaic arc as it plays between the electrodes, there is the incandescence
of the two separate refractory pieces, (with the warmer tint of light peculiar to the
material), and as each piece exposes a large area of light giving surface, and the
surfaces are at an appreciable distance apart, the light is much more diffused than
usual, is of a pleasant character, and is not accompanied by the intense dark
shadows sharply defined-which characterizes other kinds of arc lamps.
We may also combine refractory material with carbon electrodes, by making, for
example, a thin batter of fire clay and water, or a liquid siliceous mixture, and
immerse the carbons therein so as to coat them with the said substance. This is
subsequently dried, heated or baked, and the carbons, thus treated, are burnt in a
lamp in any known manner, or combined with the cap or sleeve already described,
or the two methods combined.
This
The carbon electrodes are usually enclosed within a glass globe, covered by a
plate or slab of metal, slate, porcelain or other suitable material, which also serves
to carry the circuit connections and regulating apparatus. We prefer, however, to
employ an artificial marble for the cover, a material which has not been used
heretofore for the said purpose. The kind of artificial marble used is mainly or
wholly composed of silica, moulded and pressed to the form and dimensions
required, burnt in a kiln until it becomes a hard compacted mass of great strength,
white in colour, not affected by any heat to which it is likely to be exposed, a good
non-conductor of electricity, and capable of being used as a. reflector.
material is moulded with suitable orifices or other means for receiving the various
connections and devices for working the lamp in the proper relative positions, so
as to greatly reduce the cost of fitting up lamps, and made interchangeable with
others of the same size and type. Moreover, the under side of the cover, (or side
exposed to the light) is formed and adapted to act as a reflector and to diffuse the
light over an extended area. The marble cover therefore serves as an inter-
changeable framework to carry the lamp fittings and globe, and being a good
insulator, reduces the risk of short circuiting or of giving a shock to any one
handling it while the current is on, while being white; and properly formed, it
reflects light instead of absorbing it.
The lower part of the globe may be closed by a small plate or disc of the said
marble material, adapted also, if required, to carry the lower carbon holder, and to
permit the latter to be readily detached for trimming or other purposes. This
fower disc of marble may be also formed to reflect light, falling thereon, to the
under side of the cover, at such an angle as to ensure distribution outside of the
lamp. The artificial marble is composed of burnt sand, burnt flint, or a com-
bination thereof, mixed with silica of soda, or other like siliceous liquid, which is
moulded and burnt in a kiln.
It will be understood that our said improvements may be modified to suit lamps
placed horizontally, or upon standards, or other type of lamp than the hanging
lamp to which we have referred. And also that we may establish electrical
connection with the lower carbon holder, either by the means of holding the nipple
in its relative position, by one or more supporting arms which may be used for
connecting the upper and lower parts of the lamp together, or by any other suitable

page_text: means. The glass globe may be attached directly to the marble top by a flange
and clips, or by any other suitable means for the purpose.
Dated this 25th day of March 1891.
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in or relating to Arc Lamps.
We, FREDERICK RICHARD BOARDMAN, of 3 Wesley Road Southend, in the
County of Essex, (formerly of Manor Park, in the County of London), Electrical
Engineer, and JOSEPH SINCLAIR FAIRFAX, of 433, Strand, in the County of
London, Consulting Engineer, do hereby declare the nature of our invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
Our invention consists of improvements in or relating to arc lamps, and it
comprises certain combinations of refractory material with one or both of the carbon
electrodes, and the new or improved application of a mouldable material, (also of a
refractory nature), which has insulating and reflecting qualities, in the framework
of an arc lamp. These improvements are applicable-wholly or partially-to
existing types of arc lamps.
We surround, or partially enclose, the end of one or both of the carbon electrodes
with a sleeve or cap of refractory material, in the manner shown by the accom-
panying drawings. This is done for the purpose of avoiding much of the waste of
the heated part of the electrodes, improving the colour of the light produced, adding
to the efficiency of the lamp by preventing flickering, and shielding (in part) the
highly heated carbon points from cold air currents; thereby prolonging the life of
the carbons and the time during which a lamp will burn without re-trimming. We
may also keep the light-giving portion of the lamp at a fixed point for search
light, photographic, and other purposes; but this is not essential in all cases.
In the further description of the invention reference is made to the accom-
panying drawings. Fig. 1 is a section through a lamp adapted for an alternating
current, in which the electrodes a and b, each having a refractory cap c,
are contained in metal holders d, e, so that their points are at a fixed distance
apart, thus determining the length of the arc. The holders d and e are respectively
screwed into sockets and g whereby the length of are may be adjusted to any
required distance, while a nipple is screwed on to the end of each holder to retain
the refractory cap e in position. A central hole in each cap c is provided,
sufficiently large to permit the egress of the heated carbon vapour from the
electrodes. The upper carbon b has an axial orifice through which a pencil carbon i
is advanced or withdrawn for lighting purposes by the magnetic action of a coil j
upon an iron core k adapted to hold the pencil carbon i; in the manner described
in the Specifications of F. R. Boardman, (one of the parties hereto), No. 10833
of 1887, and No. 3133 of 1890; or other convenient manner. A spiral spring lis
placed behind each carbon, within each holder, to force the carbon forwards as it
is consumed.
The sockets and g, which carry the holders d and e, are respectively
supported upon a lower and an upper plate of moulded refractory material-or
artificial white marble-which is also a good insulating material. The lower
plate m is cup-shaped beneath to reduce its diameter, (as shown in Fig. 1), and thus
to avoid obscuring the light too much just below the lamp. But the upper plate n
is larger and flatter, and is arranged to carry the striking and regulating portion
of the lamp and the terminals. The faces of the marble material (m and n) placed
next to the light are formed to reflect the light outwards in any required direction

page_text: or angle; and each plate is formed with a flange adapted to receive curved arms or
screwed rods o for sustaining the lower part of the lamp from the upper, and for
carrying the glass globe between them. A close cover g of sheet metal is fitted
over the top to exclude moisture.
In the lamp shown in Fig. 2, the bottom and top plates (m and n) of artificial
marble, are alike and reversible, and carry between them a cylindrical glass shade p.
The sustaining bolts or arms o are jointed near the top, and by means of suitable
slots at the bottom, the bolts may be easily loosened and swung out of the way for
lamp trimming purposes. The upper carbon holder e (of iron), with its contained
carbon and refractory cap c, is adjustable and regulated by the magnetic effect of
the conducting coil j, of which it forms the core.
The artificial marble is mainly or wholly composed of silica, moulded and pressed
to the form and dimensions required, and then burnt in a kiln until it becomes
a hard, compacted mass of great strength, white in colour, not affected by the heat
to which it is subjected, and moulded to the exact form required to receive the
several parts of the lamp so as to form an interchangeable framework of insulating
material. The exact method of making the said insulating and refractory material
is described in Specification to Letters Patent No. 5808 of 1888 and in others
therein named, to which we refer; but we prefer to indurate the said material with
a suitable wax such as paraffine to avoid short circuiting from moisture absorbed
from the atmosphere.
Fig. 3 is a section through the two holders of a lamp, both fixed in relative
position to each other, but with the upper carbon made to slide freely in
the holder e and moved therein in any known manner for striking the arc, or
regulating the resistance of the lamp. A nipple is attached to the holder e to
secure the refractory cap e in position, but unlike the former examples it allows for
the movement through it of the carbon while shielding the latter to some
extent from cold air.
Fig. 4 has a lower carbon a in a fixed holder d with cap c and enclosing nipple
as before, but the electrode b is coated on the outside with a coating of fire clay
and water or of a siliceous mixture such as silicate of soda. This is subsequently
dried, heated or baked, and the carbon b-thus protected from the air-is used as
an electrode in any ordinary manner in an arc lamp, or in combination with the
carbon electrode and cap c as shown in the figure. Two carbon electrodes,
coated in the manner indicated for b, as above, may be used in any lamp in the
known manner.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :
1. In an arc lamp, the combination of a carbon electrode with a cap of refractory
material, the said cap fitting over and seated upon the end of the said carbon
electrode and having an orifice allowing the passage of heated carbon vapour,
substantially as and for the purpose herein described.
2. In an arc lamp, the combination of a carbon electrode with a refractory cap
covering the end of the said carbon except at its central point, a metal holder, and
nipple, substantially as and for the purpose herein described.
3. In an arc lamp, the combination of a carbon electrode with a refractory cap
situated at the burning end of the said carbon, a metal holder, retaining nipple, and
spring adapted to keep the carbon seated against the cap, substantially as and for
the purpose herein described.
4. In an arc lamp, the combination of a metal holder and socket relatively
adjustable with an outer detachable nipple fitting over the outer end of the said
holder and adapted to hold a ring or cap of refractory material, substantially as
and for the purpose herein described.
5. In an arc lamp, a refractory insulating framework or carrying plate of

page_text: artificial white marble, moulded to receive desired parts of the lamps in their
relative positions and to form a reflecting surface on the side towards the light,
substantially as and for the purpose herein described.
6. An arc lamp having circuit connections and comprising two carrying plates
of insulating material, each carrying a carbon holder in a fixed position but
relatively adjustable to determine the length of arc, with suitable means to keep
the carbons to the required point and to strike the arc, substantially in the manner
described and shown with reference to Fig. 1.
7. An arc lamp having circuit connections and comprising two carrying plates of
insulating material, one carrying a carbon holder in a fixed position, and the other
an electro magnetic device adapted to actuate a moveable core and carbon holder
for lighting and regulating the lamp, substantially in the manner described and
shown with reference to Fig. 2.
8. A carbon electrode for an arc lamp having a thin siliceous or refractory
coating on its outer surface, adapted to exclude air, substantially as and for the
purpose herein described.
Dated this 24th day of December 1891
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicants.