IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1881

page_text: LETTERS PATENT to Alexander Muirhead, of 27, Regency Street, and John
Hopkinson, of 4, Westminster Chambers, Civil Engineer, both in the City of
Westminster, for an Invention of IMPROVEMENTS IN ELECTRIC LAMPS."
55
PROVISIONAL SPECIFICATION left by the said Alexander Muirhead and
John Hopkinson at the Office of the Commissioners of Patents on the 12th
January 1881.
ALEXANDER MUIRHEAD, of 27, Regency Street, and JOHN HOPKINSON, of
4, Westminster Chambers, Civil Engineer, both in the City of Westminster..
"IMPROVEMENTS IN ELECTRIC LAMPS.".
This Invention bas for its object improvements in electric lamps, and relates both
to the mechanism of the lamps and the carbon used therewith.
According to this Invention one carbon may be carried on a rod upon which
two screws are cut, crossing each other; the thread of each screw works into a nut.
Of these nuts one is fixed whilst the other may revolve. The revolution of the
latter, caused by the descent of the rod through it, is controlled through a brake
by an electro-magnet; it permits the nut to revolve, and the screwed rod to
descend when the electric arc is too long, and stops its revolution when it is not
too long. For the sake of simplicity and economy we generally make one of the
screws of infinite pitch; in other words one screw is replaced by a groove in the
rod parallel to its axis, and the female screw of the nut is replaced by a key within
a cylindrical socket. A convenient form of brake is a wire, cord, or band embracing
the nut, or a pulley geared to the nut. One end of this string is fixed, whilst the
other is held and slackened or tightened by the electro-magnets.
Where very great continuity of feed is preferred we employ a fluid brake, in
which the resistance is varied by the proximity of a fixed and moving surface
immersed in fluid controlled by an electro-magnet.
The carbons are parted for starting the light by a second electro-magnet, which
may operate either the upper or lower carbon.
In some cases, particularly when it is desired to use long carbons, we find it
convenient to push the carbons through a fixed holder which has sliding electrical
contact with the carbon by means of suitable brushes. These sliding contacts may

page_text: be placed comparatively near to the arc, so that the electric resistance of the lamp
is materially reduced. The carbon may be advanced by the screw arrangement
just described, or by means of a weight, the descent of which is controlled through
a clock train by an electro magnet. The arc may be started by a separate electro-
magnet in order to avoid complication in the mechanism which causes the carbons.
to advance.
We make use of metallic carbon or glance coal and foliated graphite, and we
prepare carbon from silk, cotton, hornbeam, gumootie fibre, manilla paper (prepared
by soaking in solution of starch), bone-cartilage or osseim freed from earthy matter
or gelatine by carbonizing them in a closed porcelain tube freed from air by passing
vapour of either carbon sulphide or wood-spirit through it previously to being
heated to redness. .
We fill the glass globes of incandescent lamps in which the carbon filament is
contained with vapour of carbon sulphide before hermetically sealing the same,
and we sometimes platinize the carbon filaments.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Muirhead and John Hopkinson in the Great Seal
Patent Office on the 12th July 1881.
ALEXANDER MUIRHEAD, of 27, Regency Street, and JOHN HOPKINSON, of
4, Westminster Chambers, Civil Engineer, both in the City of Westminster.
"IMPROVEMENTS IN ELECTRIC LAMPS."
Our Invention has for its object improvements in electric lamps, and relates both
to the mechanism of the lamps and the carbon used therewith.
According to our Invention one of the carbon electrodes is carried on a rod upon
which two screws are cut, crossing each other.
The thread of each screw works into a nut. Of these nuts one is fixed, whilst
the other may revolve, and the revolution of the latter, caused by the descent of
the rod through it, is controlled through a brake by an electro magnet, which
permits the nut to revolve and the rod carrying the carbon to descend when the
electric arc is too long, and stop its revolution when it is not too long. For the
sake of simplicity and economy one of the screws is made of infinite pitch; in other
words, one screw is replaced by a groove in the rod parallel to its axis, and the
female screw of the nut is replaced by a key within a cylindrical socket. A conve-
nient form of brake is a wire, cord, or band embracing a pulley geared to the
revolving nut through a pinion. One end of this band is fixed, whilst the other,
attached to the armature of an electro-magnet, is held and slackened or tightened
by the electro-magnets, but it is found to be sufficient to allow the armature to
bear directly on the circumference of the pulley, and so to control the brake
wheel.

page_text: Where very great continuity of feed is preferred a fluid brake is attached to the
above brake wheel, in which the resistance is varied by the proximity of a fixed
and moving surface immersed in fluid controlled by an electro-magnet.
The carbons are parted for starting the light by a second electro-magnet, which
may operate either the upper or the lower carbon.
In the Drawings Figure 1 is a view of an electric lamp constructed according to
this Invention; Figure 2 is a detached view of the brake wheel, with the controlling
electro magnet; Figure 3 illustrates the application of a fluid résistance to the
brake wheel; Figure 4 illustrates the application of the fluid resistance to the
revolving nut of the lamp; Figure 5 illustrates the wire form of brake sometimes
employed.
Referring to Figure 1 of the Drawings, A is the rod carrying the upper carbon C
and having cut on it a screw B, B, and groove D, D, the screw B, B, working in
the fixed nut E, E, (better shewn in plan in Figure 2) and the socket of the
revolving wheel F. The socket contains a key o, Figure 2, working in the
groove D, D. The wheel F is geared into a lantern pinion G on the same axis as
the break wheel H, and the revolution of the latter, caused by the descent of the
rod A through the fixed nut E and the socket of the wheel F, is controlled by the
armature K of the electro magnet I, I. The coils of this electro magnet are
connected to the terminals and to the insulated rod leading to the lower carbon,
and thus a shunt to the arc is formed. The armature K. of the electro-magnet I, I,
is kept bearing against the brake wheel H by means of an adjustable spring L,
the tension of which is overcome by the current in the coils of the electro
magnet I, I, and the wheel permitted to revolve whenever the arc is too long.
The lower carbon M of the lamp is carried by a holder N attached to the
armature R, R, of another electro-magnet O, O, and is kept pressing against the
upper carbon C by the spring P.
The action of the lamp is simply as follows:-Supposing the carbons to be in
contact, on passing a current through the lamp circuit from X¹ to X2 the electro
magnet 0, 0, will be excited and draw down the armature R, R, together with the
lower carbon M, the upper carbon C being prevented from following by the brake,
and thus the arc will be formed between C and M. As the carbons burn away the
resistance of the arc to the passage of the current becomes greater, and consequently
the current in the coils I, I, of the electro magnetic shunt becomes greater until
the magnet so excited is strong enough to overcome the tension of the spring. L,
when the brake wheel H will be liberated and the rod A carrying the upper carbon
allowed to approach the lower one to the required distance.
The mode of application of fluid resistance to the brake wheel H is shown in
Figure 3, in which the same letters hold for the corresponding parts in Figures 1
and 2. In this arrangement the brake wheel H, now made of iron, becomes the
armature of the shunt electro-magnet I, I, and is carried on the same axis with the
pinion-wheel G, and a circular plate S, from which depend a number of fans T, T,
dipping into a double cylindrical vessel V, V, of glycerine or other fluid. In its
normal position the wheel H is kept bearing on the upper surface of the revolving
nut F by a flat steel spring p applied to the axis of the pinion wheel. The pinion
wheel G, fitting loosely into the teeth of the wheel F, permits the easy motion up
and down of the armature H.; the resistance of the glycerine to the revolution of
the fans connected to the brake wheel produces a steadier fall of the screw A and
consequently a more continuous feed of the upper carbon electrode.
Sometimes we apply this arrangement directly to the wheel F, as shewn in.
Figure 4, and in this case we take advantage of being able to float the wheel F in
the glycerine (T, T, then being a hollow chamber or chambers of suitable capacity),
thereby we diminish the resistance to the descent of the screw A by lessening
friction of F on the rollers r, r.
Figure 5 shews the application of the wire or band form of brake to our lamp.
The band b, b, is fixed at one end d passed round the pulley H and fastened to the

page_text: armature K, which is held by the spring L and slackened or tightened by the
electro magnet I, I.
In some cases, particularly when it is desired to use long carbons, we find it
convenient to push the carbons through a fixed holder, which makes contact with
the carbon by means of sliding contacts in the shape of rollers or brushes. These
sliding contacts may be placed comparatively near the arc, so that the electric
resistance of the lamp is materially reduced.
Our Invention also relates to lamps in which carbon filaments are employed.
We prepare carbon filaments from silk, horn-beam, gumootie fibre, manilla paper
(previously prepared for the purpose by soaking in starch solution or syrup to fill
up the pores with carbonaceous matter), bone cartilage or ossein freed from earthy
matter or gelatine in the following manner :- -We take a number of threads or
strips of these materials and embed them in powdered charcoal or lampblack in a
porcelain tube. We then pass the vapour of either carbon bisulphide or woodspirit
through the porcelain tube until all the air has been driven out, when we close the
tube and gradually heat it to redness for about an hour. The strips are then found
to be thoroughly carbonized and converted into strong steel like filaments. Instead
of sealing up the porcelain tube previously to being heated to redness we sometimes
pass the vapour of bi-sulphide of carbon or, of wood-spirit continually through the
tube during the carbonizing process; the vapour can then either be burnt in a
small jet at a distance from the furnace or allowed to condense in a receiver. In
constructing incandescent lamps of these carbon filaments we secure the ends of
the filaments; formed first of all into loops, to thin metallic conductors by means of
clips; we next cement these conductors into long closely fitting glass tubes; and,
lastly, we pass these tubes through holes in the globes accurately ground to receive,
them and fix with a silicated cement.
We fill the glass globes in which these carbon filaments are contained with
vapour of carbon sulphide before hermetically sealing the same, and we sometimes
platinize the carbon filaments by dipping them into a solution of ammonio chloride
of platinum and afterwards heating them carefully to redness.
What we claim as our improvements in electric lamps is,-
First. The method for feeding forward one of the carbons of an arc lamp by
means of the screwed rod d rotating a nut or its equivalent f, in connection with
which is a brake relieved by an electro magnet i.
Second. In combination with the screwed rod d and the nut or its equivalent f,
the fluid brake t, u, either with or without a mechanical brake, and electro
magnet i.
Third. The preparation of the carbon for carbon filament lamps from silk,
hornbeam, gumootie fibre, manilla paper (previously saturated with soluble
carbonaceous matter), bone cartilage or ossein (freed from earthy matter), or
gelatine, by igniting these substances in a vessel from which air is excluded by the
vapour of carbon sulphide or wood spirit.
Fourth. In carbon filament lamps, charging the glass globe in which the carbon
filament is enclosed with carbon sulphide.
In witness whereof, I, the said Alexander Muirhead, have hereunto set my
hand and seal, this Eleventh day of July, in the year of our Lord One
thousand eight hundred and eighty one. ·