IMPROVEMENTS IN ELECTRIC ARC LAMPS
Year: 1884

page_text: We FREDERICK THORNTON of 228 Burdett Road Telegraph Engineer and
OTTO ROMANZE of 6 Florence Terrace Millwall Telegraph Instrument Maker
both in the County of Middlesex do hereby declare the nature of our invention
for "IMPROVEMENTS IN ELECTRIC ARC LAMPS" to be as follows:-
This invention has for its object improvements in electric arc lamps.
For controlling the descent of the upper carbon we form a screw rack upon the
stem of its holder, and cause a worm to gear with this rack. The worm we carry
by a slide which can slide end wise of the stem and which we suspend from the core
or armature of a solenoid.
The worm we employ is of a quick threaded pitch so that the weight of the
carbon holder and stem when resting upon the threads of the worm may be sufficient
to cause it to revolve. To prevent too rapid rotation of the worn we prolong its
axis upwards and mount a wheel on its upper end, which wheel is obstructed from
revolving rapidly-it, might be by arms upon it working in a thick liquid or it
might have escapement teeth around its periphery into which the pallets of an
escape lever are made to engage so that the rotation of the wheel is controlled by
the rate at which this lever can vibrate-or any other suitable means for preventing
too rapid a rotation of the wheel might be adopted.
When a current is switched on to the lamp the arc is struck by the lifting of the
solenoid core as in the lamp described in the specification of a former Patent granted
to us No 3901 in the present year-and the wheel at the upper end of the axis of
the worm is thereby either brought against a fixed point or a point carried by the
escape lever and so the rotation of the wheel and consequent descent of the upper
carbon is prevented,—but as the upper carbon burns away and less current passes
through the coils of the solenoid the solenoid core is drawn downwards by the
weight of the carbon holder and the wheel is free to revolve and the carbon to
descend until the current passing through the coils of the solenoid is again sufficient
to lift the carbon holder and so stop the wheel from turning. By making the
wheel of comparatively large diameter and by placing the point or stop in a position
for a serrated surface formed around the upper surface of the wheel near its
circumference-the feed given at any one movement to the upper carbon may be
extremely small and yet the carbon can descend very quickly should the current
be switched off from the lamp or should the arc be extinguished from any other
Cause

page_text: The weight of the solenoid core and of the slide which is suspended from it wo
counterbalance by springs the tension on which can be regulated so that they can
lift the core and the slide which carries the worm if the weight of the upper carbon
holder is not also sustained by them so that to strike the arc the solenoid has only
to lift a portion of the weight of the upper carbon holder and carbon and therefore
a current of lower electro motive forco can be employed than in most other arc
lamps.
In order to prevent the solenoid core from being drawn upwards by the springs
whenever the current is switched off from the lamp and whenever the upper carbon
consequently descends and rests upon the lower carbon we provide a spring catch
to then catch over a pin projecting from the solenoid core or the slide which is
suspended from it.
The catch keeps the carbons in contact and prevents them from separating until
a current of sufficient strength is passing through the solenoid to lift the upper
carbon, the spring catch then yields and allows the carbon to rise and the are to be
struck.
When the carbon holder is pressed upwards the worm and its axis can revolve
without revolving the wheel so that the carbon holder can be raised rapidly by
hand whenever a fresh carbon is to be placed into the holder.

page_text: Improvements in Electric Arc Lamps.
We, FREDERICK THORNTON of 228 Burdett Road Telegraph Engineer and
OTTO ROMANZE of 6 Florence Terrace Millwall Telegraph Instrument Maker
both in the County of Middlesex do hereby declare the nature of our invention
for "IMPROVEMENTS IN ELECTRIC ARC LAMPS" and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:-
This Invention has for its object improvements in electric arc lamps.
For controlling the descent of the upper carbon we form a screw rack upon the
stem of its holder, and cause a worm to gear with this rack. The worm we carry
by a slide which can slide end wise of the stem and which we suspend from the core
or armature of a solenoid.
The worm we employ is of a quick threaded pitch so that the weight of the
carbon holder and stem when resting upon the threads of the worm may be sufficient
to cause it to revolve. To prevent too rapid rotation of the worm we prolong its
axis upwards and mount a wheel on its upper end, which wheel is obstructed from
rovolving rapidly-it might be by arms upon it working in a thick liquid or it
might have escapement teeth around its periphery into which the pallets of an
escape lever are made to engage so that the rotation of the wheel is controlled by
the rate at which this lever can vibrate--or any other suitable means for preventing
too rapid n rotation of the wheel might be adopted.
When a current is switched onto the lamp the arc is struck by the lifting of the
solenoid core as in the lamp described in the specification of a former Patent granted
to us No 3901 in the present year-and the wheel at the upper end of the axis of
the worm is thereby either brought against a fixed point or a point carried by the
escape lever and so the rotation of the wheel and consequent descent of the upper
carbon is prevented-but as the upper carbon burns away and less current passes
through the coils of the solenoid the solenoid core is drawn downwards by the
weight of the carbon holder and the wheel is free to revolve and the carbon to
descend until the current passing through the coils of the solenoid is again sufficient
to lift the carbon holder and so stop the wheel from turning. By making tho
wheel of comparatively large diameter and by placing the point or stop in a position
for a serrated surface formed around the upper surface of the wheel near its
circumference, the feed given at any one movement to the upper carbon may be
extremely small and yet the carbon can descend very quickly should the current
be switched off from the lamp or should the arc be extinguished from any other
cause.
The weight of the solenoid core and of the slide which is suspended from it we
counterbalance by springs the tension on which can be regulated so that they can
lift the core and the slide which carries the worm if the weight of the upper carbon
holder is not also sustained by them so that to strike the are the solenoid has only
to lift a portion of the weight of the upper carbon holder and carbon and therefore

page_text: a current of lower electro motive force can be employed than in most other are
lamps.
In order to prevent the solenoid core from being drawn upwards by the springs,
whenever the current is switched off from the lamp and whenever the upper carbon
consequently descends and rests upon the lower carbon we provide a spring catch
to then catch over a pin projecting from the solenoid core or the slide which is
suspended from it.
The catch keeps the carbons in contact and prevents them from separating until
a current of sufficient strength is passing through the solenoid to lift the upper
carbon, the spring catch then yields and allows the carbon to rise and the arc to be
struck.
When the carbon holder is pressed upwards the worm and its axis can revolve
without revolving the wheel so that the carbon holder can be raised rapidly by
hand whenever a fresh carbon is to be placed into the holder.
In the drawings hereunto annexed we have shewn an electric arc lamp
constructed as above described.
Figures 1 and 2 are elevations of the lamp, Figure 3 is a plan in section taken
on the line 1, 1, Figure 1 and Figure 4 is a plan in section taken on the line 2, 2.
A is the upper carbon holder having a screw rack on one face of its stem B-C is
the worm of quick threaded pitch which gears with the teeth of the rack-it
is fixed on an axis D the lower end of which is carried in bearings in the slide E
.which slide can move a short distance up or down through guide holes in the cross
plates F which form part of the frame of the lamp.
The slide E also sorves as a guide for the stem B of the upper carbon holder.
G is the solenoid coil and H its armature from the lower end of which the slide E
is suspended. The solenoid is as described in the specification herein before
mentioned wound with wire through which the main current passes and also with
a fine wire outer coil through which a shunt current passes whenever the resistance
of the are gets too high and which tends to draw the solenoid core downwards in
opposition to the upward pull of the larger coil. The coils are carried between two
cross plates forming part of the framing of the lamp as shewn at Figures 1 and 2.
In the lamp shewn in the drawing the armature is hollow and both the stem B
of the upper carbon holder and the axis D of the scrow worm C pass up through it
but if preferred the lamp might be constructed so that they both pass up at the
side of the core and of the solenoid.
The too rapid rotation of the axis is in the arrangement shown in the drawing
prevented by an escape lever engaging with the teeth of an escapement wheel on
the axis. The upper end of the axis has fixed upon it a ratchet wheel I above
which is an escapement wheel J which is loose upon the end of the axis but which
carries on its under side a pawl which by a spring is made to engage with the teeth
of the ratchet wheel so that the escapement wheel is driven whenever the axis D
is caused to revolve by tho descent of the carbon holder but remains at rest if the
axis be revolved in the opposito direction by the raising of the carbon holder.
K (see Figure 3) is the escape lever the pallets of which engago with the teeth of
the escapement wheel-it has an arm K¹ projecting from it which carries at its end
a point L just above the upper face of the escapement wheel.
When the current passes through the carbons of the lamp and the solenoid core
is lifted to strike the arc the axis D is lifted with it-the upper face of the escape-
ment wheel is thereby brought against this point and as fine radial serrations are
formed in that part of the face of the wheel which is so brought against the point
the oscillations of the escape lever are stopped.
M M are the springs by which the core of the solenoid coil is suspended—tho
springs M are carried by screw rods which are supported by nuts N screwed on to
them as shown at Figure 2 so that by turning these nuts the upward pull of the
springs on the solenoid core can be regulated that the solenoid has only to lift a
portion of the weight of the upper carbon aud its holder to strike the arc.

page_text: O is a pin or projection standing out from the slide E and P is a spring catch to
catch over this projection whenever the slido drops to its lowest position so that
whenever the upper carbon holder drops to such an extent that the carbons touch
the carbons will not be separated unless a current of sufficient strength for striking
the arc is passing-the upward pull of the solenoid would then overpower the
spring catch but until the spring catch was so overpowered no separation of the
carbons could take place.
In this way all difficulty in striking the are when the current is first turned on
to light the lamp is avoided.
The electrical connection in the lamp are as follows:-
The current passes by the wire R to the frame which carries the lower carbon
and passes through the carbons to the stem B of the upper carbon holder from
which by the wire S it enters the main solenoid coil and passes off from this coil by
the wire S to the small electro magnet coil Z of a cut out such as is described in
the Specification herein before mentioned and passes off by the wire T. The
current passing through the small electro magnet coil of the cut out causes the cut
out armature to be drawn downwards against the action of a spring as described in
the before mentioned specification and so breaks all metallic connection between
two metallic bars V. V.
When no current passes through the lamp and consequently no current through
the coil of the cut out the cut out armature is pressed upwards by its spring and
the copper disc W carried by its upper end is thereby pressed upwards against V
and Vso completing the circuit through the resistance coils U the current then
passing from the wire R through these coils to V and through the disc W to V' and
from thence to the wire T.
R¹ S are fine brush wires from the wires R. S. to the fine wire coil by which the
main solenoid coil is surrounded.
The action of the lamp is as follows. To start the lamp the top carbon is allowed
to descend till it touches the bottom carbon, the resistance through the carbons is
then less than through the resistance coils Q and R and the current will pass
through the carbons-the current at the same time passing through the solenoid
coil will draw the core H upwards and separate the top and bottom carbons and so
establish the arc. As the arc elongates the current through the main coil diminishes
and increases through the shunt coil the solenoid core therefore drops and allows
the escapement lever to oscillate. The escapement wheel J will so be allowed to
turn one or two teeth and the carbons will be brought closer together the current
will immediately increase and the core will again be drawn upwards and the move-
ment of the vibrating lever will be arrested.
When the carbons are used up or when from any other cause the lamp fails to
work, the core of the cut out being no longer held down by the passage of current
through its coil is pressed upwards by its spring and makes contact between V
and V the current then passes from the wire R to the wire S through the
resistance coils.
In the lamp shown in the drawing the bottom carbon holder is carried by the
frame of the lamp but as will be readily understood provision might be made for
raising the bottom carbon in any ordinary manner so as to allow the focus of the
arc always to remain in the same position relatively to the lamp.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is
(1.) The employment of a screw rack on the stem of the upper carbon holder and
of a worm gearing with this rack and carried by a slide suspended from a solenoid
core together with means for arresting the rotation of the worm or allowing it to
rotate according as the solenoid core is drawn upwards or downwards, substantially
as described.

page_text: (2.) The employment of a spring catch to hold down the upper carbon holder
until the current passing through the carbons is of sufficient strength to form an
are of the required length so as to allow of the whole weight of the solenoid core
and it may be also part of the weight of the carbon holder being balanced sub-
stantially as described.
(3.) The construction of electric arc lamps substantially as herein before described
and illustrated in the drawing annexed.