IMPROVEMENTS IN ELECTRIC ARC LAMPS
Year: 1883

page_text: LETTERS PATENT. to Joseph Edward Lord Clark of Brixton in the County.
of Surrey, William John Kemp Clark, also of Brixton aforesaid, and Robert
Davey Bowman of Leytonstone in the County of Essex for an Invention of
" IMPROVEMENTS IN ELECTRIC ARC LAMPS"
PROVISIONAL SPECIFICATION left by the said Joseph Edward Lord Clark,
William John Kemp Clark, and Robert Davey Bowman at the Office of the
Commissioners of Patents on the 5th March 1883.
JOSEPH EDWARD LORD CLARK of Brixton in the County of Surrey, WILLIAM
JOHN KEMP CLARK also of Brixton aforesaid, and ROBERT DAVEY BOWMAN of
Leytonstone in the County of Essex, IMPROVEMENTS IN ELECTRIC ARC)
LAMPS"
This invention relates to improvements in electric arc lamps and consists first,
of improved means for regulating the feed of the carbons, and secondly, of means
for varying the length of the arc to suit currents of different intensity.
We will describe the first part of our invention as applied to a lamp in which
the carbon electrodes are mounted in suitable holders, of which the lower one.
remains practically in one position, and the upper one descends gradually to
maintain the arc as the carbons, are consumed..
J
According to our invention, the descent of the upper carbon holder is regulated
in a gradual and steady manner by means of the following arrangement of
mechanism. Pivotted to the metal frame, which is in connection with the
positive current, is a lever, the short end of which is connected with or attached to
a suitable brake adapted to fit against, and retain in position the upper carbon
holder, when pressed against it. The long end of this brake lever is arranged to
be moved by an electro magnet excited by a small branch current from the main'
circuit, but in order to prevent the long end of the lever being moved or vibrated
too quickly, which would prevent the descent of the carbon holder in an efficient
and easy manner, we attach to the said long arm a flexible armature, it may be a
stiff piece of watch spring having a bar of steel attached at its free end, and, this
flexible armature is so constructed that it will' be drawn towards the electro
magnet sometime before it exerts sufficient pull on the lever to remove the brake
and allow the carbon holder to fall. Moreover it will retard the release of the
lever arm and consequently allow a perceptible feed to take to take place, before
the brake is able to press again upon the holder and check its descent.
"
112
:

page_text: Fitted to the other side of the long arm of the lever is a small platinum spring
adapted, when the arc is of its normal length, to make contact with an adjustable
screw. This arrangement ensures a slight rubbing action between the contact surfaces
which tends to preserves the brightness and good contact of the .parts. A light
spiral spring of adjustable tension is also connected with the long arm of the
brake lever and may be so adjusted as to put on the brake when the flexible
armature has been completely released from the electro magnet, and to offer a
proper degree of resistance to such electro magnet.
The action is as follows. Under normal conditions the current flows through the
upper frame of the lamp, pivot pin, long arm of the brake lever, and platinum
spring to the contact screw, and thence to the positive electrode, a branch circuit
being led from the contact screw or other suitable point around the electro
magnet by which the brake lever is actuated and thence to the return wire.
When the arc lengthens more current passes by the branch circuit the electro
magnet is excited, its flexible armature is attracted and the brake released but not
until a steady pull has been put on the lever arm by the said flexible armature
and its magnet. So soon however as the are has been shortened by the approach
of the carbons the pull of the electro magnet will cease, and the descent of the
upper carbon holder will be checked by the application of the brake. We would
here observe that we do not limit ourselves to the precise form of the brake itself
nor to the substance of which it is made.
With the view of still further securing precision in the feeding of the carbons in
addition to the above arrangement we combine with the solenoid by which the
lower carbon holder is drawn down to strike the arc, a separate branch circuit
passing round the solenoid in the reverse direction to the main circuit so that
should the first described feed regulator. not act promptly, the current in the
second branch circuit will be increased thereby partially neutralizing the attractive
power of the solenoid upon the lower holder; and allowing a light spiral spring to
lift the said bolder and consequently decrease the space between the points of the
two carbons. The first described feed regulator is intended under normal
conditions to act before the differential solenoid arrangement just described, but
should it fail to act or be late. in acting the differential solenoid will come into
action and maintain the constancy of the arc.
<
Our invention also relates to means for preventing any sudden increase of
intensity in the current from causing the carbons to flare and splutter and consists
in the use of a differential solenoid and lever by which a variable restraining
force will be applied to the brake lever tending to apply the brake to the upper
holder in opposition to the pull of the electro magnet by which the said brake is
released.
:
To this end the slight spiral spring attached to the end of the long arm of the
brake lever, is adjustably secured to one end of a bell crank lever pivotted to a
part of the lamp frame and the other end of this bell crank lever is linked to the
core of a differential solenoid. Should the intensity of the main current suddenly
increase a pull will be put on the bell crank lever and the brake lever will be held
in action. Its armature will not be attracted by the electro magnet so readily as
it otherwise would and the feed will therefore be deferred until the length of the
arc is increased to suit the increased intensity of current.
When the proper length of arc'is obtained the current in the branch circuit
around the differential solenoid will be able to counteract the diminishing force of
the current in the main solenoid coil, and allow the core to descend and the bell
crank lever to rock, thereby slackening the tension on the restraining spring of
the brake lever, and allowing the electro magnet to act and pull off the brake
gradually as the arc becomes too long.
34

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Edward Lord Clark, William Joho Kemp Clark, and
Robert Davey Bowman in the Great Seal Patent Office on the 5th September
1883.
"
JOSEPH EDWARD LORD CLARK of Brixton in the County of Surrey, WILLIAM
JOHN KEMP CLARK also of Brixton aforesaid, and ROBERT DAVEY BOWMAN of
Leytonstone in the County of Essex IMPROVEMENTS IN ELECTRIC LAMPS
"
:
»
This Invention relates to improvements in electric arc lamps and consists firstly:
of improved means and apparatus for regulating the feed of the: carbons, and
secondly of means for varying the length of the are to suit currents of different
intensity.
We will describe the first part of our Invention as applied to a lamp in which
the carbon electrodes are mounted in suitable holders of which the lower one
remains practically in one position and the upper one, descends gradually to
maintain the arc as the carbons are consumed in a manner hereafter described.
The descent of the upper carbon-holder is regulated in a gradual and steady
manner by means of the following arrangement of mechanism as shown in side
elevation Figure 1 and in front view at Figure 2.
Pivotted to the metal frame a which is in connection with the positive current,
is a lever b, the short end b¹ of which is connected with or attached to or forms in
itself a suitable brake, adapted to fit against, and retain in position, the upper
carbon holder c. The long end of this brake lever b is arranged to be moved by
an electro magnet or solenoid d excited by a small branch current from the main
circuit. But in order to prevent the long end of the lever b being moved or
vibrated too quickly (which would prevent the descent of the carbon holder in an
efficient and easy manner) we attach to the said long arm a flexible or spring.
armature e,
it may be a bit of watch spring, having a bar of steel attached at its:
free end. This spring armature is so constructed that it will be drawn towards the.
electro magnet, sometime before it exerts sufficient pull on the lever, to remove the
brake b' and allow the carbon holder c to fall, moreover it will retard the release
of the lever arm b and consequently allow a perceptible feed to take place before
the brake is able to press again upon the holder c and check its descent.
Fitted to the other end of the long arm of the lever b is a small platinum
spring a Figs 1 and 1b adapted, when the arc is at its normal length, to make
contact with an adjustable spring stop or screw f' as also shown in another modi-
fication at Figures 3 and 4. This arrangement ensures a slight rubbing action
between the contact surface, which tends to preserve the brightness and good
contact of the parts. A slight spiral spring of adjustable tension may be connected
with the long arm of a brake lever and may be so adjusted as to put on the brake
when the flexible armature has been completely released from the electro-magnet
and to offer a proper degree of resistance to such electro niagnet but what we prefer.
to employ is the adaptation of the spring e connected to the lever brake b¹ as before
described.
The action is as follows:-Under normal conditions the current flows through
the upper frame a of the lamp, pivot pin g the long arm b of the lever brake
and platinum contact x and f' and thence to the electrode, a branch. current is
directed from the contacts x, for other suitable points, around the electro-magnet
or solenoid & by which the brake.lever b is actuated, and thence to the return wire,
when the are lengthens, more current travels through the branch circuit, and the
1

page_text: .
electro magnet d is excited, its armature b is attracted and the lever released, but
not until a steady pull has been exerted on the lever arm of the said armature b.
So soon however as the arc has been shortened by the approach of the carbons, the
pull of the electro-magnet d will cease, and the descent of the upper carbon holder c
will be checked by the application of the brake b¹, we would here observe that we
dó not limit ourselves to the precise form of the brake itself as it may be of the
jambing ring or saddle type, or it may be a screw or stop.
Our Invention also consists in means for preventing any sudden increase of
intensity current, from causing the carbons to flare and splutter, and consists in
the use of a differential solenoid or electro magnet j and lever armature or core i
by which a variable restraining force will be applied to the brake lever b tending
to apply the same to the upper carbon holder c in opposition to the pull of the
electro magnet d by which the said brake is released.
In place of the spiral spring we may employ a pair of platinum contacts so as to
put in or cut out the magnet d'as shown in all the figures to which similar letters
refer to like parts.
Figure 3 is a sectional elevation of a lamp of a modified form, and Figure 4 is a
view on the opposite side, Figure 5 is a front view Figure 6 is a back view and
Figure 7 a plan with the cover removed. This modification consists in the employ-
ment of a commutating electro magnet or solenoid j effecting the above object.
The only difference in these Figures to Figures 1 and 2 is that we employ an electro
magnet attracting a pendulum armature k which when attracted to a vertical
position makes contact at 7 and directs the current to the magnet d through
the opposite contacts f¹ and x which latter releases the brake b and effects the feed
of the carbon. This will be clearly understood with reference to the diagrams
Figure 1 in the retaining position and Figure 1b when feeding.
In some cases a slight spiral spring may be attached to the long end or arm of
the brake lever and adjustably secured to one end of a bell crank lever, pivotted to
a part of the lamp frame, and the other end of this bell crank lever may be linked
to the core of a differential solenoid or to the armature of an electro. magnet so that
should the intensity of the main circuit suddenly increase, a pull will be exerted
on the bell crank lever, and the brake will be maintained in action, Its armature
or core will not be attracted to the electro magnet or solenoid so readily as it
otherwise would be and the feed will therefore be deferred until the length of the
arc has increased, to suit the increased intensity of the current. When the proper
length of arc is attained the current in the branch circuit around the differential
solenoid will be able to counteract the diminishing force of the current in the main
solenoid coil and allow the core to descend and the bell crank lever to rock,
thereby slackening the tension on the restraining spring of the brake lever and
allowing the electro magnet to act and pull off the brake gradually as the arc
becomes too long.
With the view of still further ensuring the precision in the feeding of the carbons
in addition to the above arrangement, we combine with the solenoid or electro
magnet m Figure 3 by which the lower carbon holder n is drawn down to determine
the arc. A separate branch circuit passes around the solenoid or electro magnet m
in the reverse direction to the main circuit, so that should the. feed regulator not
act promptly the current in the second branch circuit, will be increased thereby
partly neutralizing the attractive power on the solenoid or electro magnet upon the
lower holder n and allowing a light spiral spring, to lift the said holder n and
consequently to decrease the space between the points of the two carbons, and
which means effect the establishing of the arc to suit the intensity of current, the
first attached feed regulator, is intended to act before: the differential solenoid
arrangement before described, but should it be late in acting the differential solenoid
will come into action and maintain the constancy of the arc.
In some cases it may be arranged on the upper part of lamp so as to give the
upper carbon the power to recede or approach as desired.
Having thus described and ascertained the nature of our invention and in what

page_text: manner the same can advantageously be employed we would have it understood
that what we claim is:-
First. The employment of an electro magnet or solenoid for the attraction of an
armature or core forming part of a lever which latter effects the retention or feed
of the carbon holder and operating in conjunction with the spring contact e
substantially in the manner set forth and as shown in the accompanying
drawings.
-
Second. The employment of a differential solenoid, or electro-magnet, in
combination, and operating in conjunction with another solenoid or electro magnet
as herein set forth, and illustrated in the accompanying drawings.
Third. In the employment of a differential solenoid or electro magnet, the
means hereinbefore described for effecting the commutating and directing of the
current, over the feeding device, as the arc increases, substantially as set forth with
reference to the diagrams Figs 1" and 1b and the other views on the accompanying
drawings.
Fourth. The employment of a differential solenoid or magnet m for separating
the carbons and establishing the arc independently of the feeding arrangement as
herein described and illustrated with reference to Figure 3 of the accompanying
drawings.
In witness whereof we the said Joseph Edward Lord Clark, William John
Kemp Clark and Robert Davey Bowman have hereunto set our hands and seals
this Fourth day of September in the year of our Lord One thousand eight
hundred and eighty three.
Witness
'
JAS FREDK PHILLIPS
of the firm of Phillips & Leigh
Patent Agents
22 Southampton Buildings
W.C.
JOSEPH. E. L. CLARK.
WILLIAM J K CLARK
R. D. BOWMAN
(L.S.)
(L.S.)
(L.S.)