IMPROVEMENTS IN ELECTRIC ARC LAMPS
Year: 1884

page_text: I, MARK HENRY HURRELL of the British Electric Light Company Limited
Turnmill Street in the City of London Electrical Engineer do hereby declare the
nature of my Invention for "IMPROVEMENTS IN ELECTRIC ARC LAMPS" to be as
follows:-
According to this Invention the upper carbon holder is as usual made capable of
sliding upwards or downwards in suitable guides-it has a toothed rack formed on
one side of it into which gears à pinion having an escapement wheel on its axis by
which the downward movement of the holder is controlled as is usual.
In order to move the upper carbon a sufficient distance away from the lower
carbon to allow of an arc being formed I employ a solenoid or magnet to act directly
by a clutch or pawl or other mechanism either upon the carbon holder itself or
upon the spindle of the pinion or upon a wheel on this spindle so as to lift the
carbon holder and by the same movement I bring escapement mechanism into gear
with the teeth of the escapement wheel to subsequently control the downward
movement of the carbon holder.
The escapement mechanism I actuate by a shunt solenoid coil-this coil together
with a two armed lever escapement which is to be rocked by it I carry by one arm
of a lever the other arm of which is acted on by the movements of the core of a
fixed solenoid or of the armature of a magnet through the coils of which the
current passes.
When no current passes through the lamp the core of the solenoid
or magnet armature falls and lifts the escapement clear of the teeth of the escape-
ment wheel, this liberates the carbon holder and allows it to drop freely, the
current then again passes causing the solenoid core or magnet armature to be lifted
thereby lifting the upper carbon a regulated distance and lowering the escapement
lever to bring it into gear with the teeth of the escapement wheel. The downward
movement of the carbon holder is then controlled by the escapement. As the
resistance in the lamp increases more current passes through the shunt coil until it
attains sufficient strength to lift the core. The core is jointed to one arm of the
escapement lever and when the core is lifted it rocks the escapement lever in one
direction so disengaging the tooth at one end of the lever from the teeth of the
escapement wheel and simultaneously causing the tooth at the opposite end of the
lever to become engaged with the wheel By this movement the current through
the shunt coil is also broken so that the core again at once drops thereby rocking the

page_text: lever in the opposite direction and so again allowing the escapement wheel to turn
a distance equal to half the distance between its teeth and also again establishing
the circuit through the shunt coil. The amount of forward feed at each movement
of the core of the shunt coil is therefore always uniform. The upward movement
may be given to the carbon holder either by passing the carbon holder through a
hole in the end of a lever arm which is jointed to the solenoid core or magnet
armature so that when a current is passing through the lamp the lever arm will be
drawn into a horizontal position and then the carbon holder can drop freely
through it and so that when a current is not passing and the core drops the lever
arm will be brought into an inclined position and therefore caused to grasp and
hold the carbon holder so that when the core again rises the carbon holder will be
lifted a distance by the arm. Or the spindle of the pinion might be turned a
distance at each upward movement of the solenoid core by what is known as a
friction or silent pawl carried by a lever which can turn around the spindle and
which at its end is coupled to the solenoid core. When the solenoid core is lifted
I cause a prolongation of the pawl to come against a stop so as then to turn the
pawl into a position to be clear of the spindle so that the spindle may then turn
with the greatest freedom. When the solenoid core drops, the pawl again comes
into action ready to turn the spindle a distance when the core again rises and as
the core rises it continues to turn the spindle until.the prolongation of the pawl
comes against the stop and throws the pawl out of action. An adjusting screw is
provided by which the amount of movement then given to the spindle can be
adjusted.
The core of the solenoid coil might also act directly upon a lever arm carrying
at its end a spring tooth or pawl to act directly upon the teeth of the escapement
wheel. In this case the spring tooth would be held clear of the teeth of the
escapement wheel when a current was passing and the solenoid core was therefore
held up and when the solenoid core dropped the tooth would yield and pass the
teeth of the escapement wheel whilst when the core was raised the tooth would
engage with the teeth of the escapement wheel and turn it a distance before again
becoming disengaged from the teeth of this wheel.
Dated this 19th day of January. 1884.

page_text: "
I MARK HENRY HURRELL of the British Electric Light Company Limited of
Turnmill Street in the City of London Electrical Engineer, do hereby declare the
nature of my 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-
According to this invention the upper carbon holder is as usual made capable of
sliding upwards or downwards in suitable guides-it has a toothed rack formed on
one side of it into which gears a pinion having an escapement wheel on its axis by
which the downward movement of the holder is controlled as is usual.
The escapement mechanism I actuate by a shunt solenoid coil which rocks a two
armed lever escapement carried by one arm of a lever the other arm of which is
acted on by the movements of the core of a fixed solenoid or of the armature of a
magnet through the coils of which the main current passes. When no current
passes through the lamp the core of this solenoid or magnet armature being no
longer attracted the escapement is carried away from and clear of the teeth of the
escapement wheel, this liberates the carbon holder and allows it to drop freely the
current then again passes causing the solenoid core or magnet armature to move
the escapement lever to bring the escapement into gear with the teeth of the
escapement wheel. The downward movement of the carbon holder is then
controlled by the escapement.
As the resistance in the lamp increases more current passes through the shunt
coil until it attains sufficient strength to draw in or attract its core or armature.
The core or armature then acts upon one arm of the escapement lever and rocks
this lever in a direction to disengage from the teeth of the escapement wheel, the
escapement tooth which previously locked and retained it and simultaneously causes
the tooth at the opposite end of the escapement lever to become engaged with the
wheel. By this movement the current through the shunt coil is also broken or its
action reversed so that the core or armature is no longer attracted and allows the
escapement lever to rock in the opposite direction and so again allows the escapement
wheel to turn a distance and again establishes the circuit through the shunt coil.
The movements of the escapement lever I prevent from being too rapid as herein
after described.
Figure 1 is a front view and Figure 2 an end view of an electric arc lamp
constructed in the above manner.
A is the upper carbon holder capable of sliding up and down in suitable guides.
A' is a toothed rack formed on one side of its stem. B is a pinion which gears.
therewith and which has an escapement wheel C on its axis-D is a two armed
lever escapement the two teeth D₁ D' of which engage alternately with the teeth
of the escapement wheel. The axis of the lever escapement D is carried at the end
of one arm of a lever E which turns on a centre at E¹. The opposite arm of the
lever carries the armature F1 of an electro magnet F through the coils of which
the main current passes. E is a counterbalance weight by which when no current
is passing the armature F¹ is drawn away from the magnet F and the lever escape-
ment drawn away from the escapement wheel-G is an electro magnet the coils of
which have a high resistance and through which a shunt current passes from the
main circuit. G¹ is the armature of the magnet G. A projection from it rests

page_text: upon a pin which projects from one of the arms of the escapement lever D as shewn
at Figure 1.
As the resistance of the lamp increases and causes the shunt current passing
through the coils of the magnet G to be of sufficient strength to attract the
armature G¹ the tooth D¹ of the escapement lever is drawn away and disengaged
from the escapement wheel and the tooth D² made to engage therewith.
To establish a circuit through the shunt coils G whenever the tooth D¹ is
engaged with the escapement wheel and to break the circuit when it is disengaged
from the wheel the tooth D is insulated from the lever D which carries it-and is
connected by a loose wire with one end of the coil whilst the opposite end of the
coil is in connection with the negative carbon whilst the escapement" wheel is in
electrical connection with the positive carbon. In order to prevent sparking at the
times when the tooth D¹ moves towards or away from the escapement wheel the
core of the electro magnet G has around it a second smaller coil of low resistance
wound in the opposite direction to the first mentioned coil one end of this coil is
connected to the wire going to the tooth D¹ and the other with any positive part
of the lamp Consequently when the pallet is in connection with the escapement
wheel the current flows from the escapement to the negative holder but when the
insulated pallet is free from the wheel the current has to flow first through the
second or additional copper wire low resistance coil and then through the first
resistance coil to the negative terminal the circuit through the high resistance coil
is therefore never broken and sparking is avoided.
To prevent any rapid movement of the escapement lever D either in one direction
or the other the lever has an arm descending from it which carries a closed vessel H
containing mercury-this vessel is curved and is concentric with the axis of the
lever D. The weight of the vessel and the mercury is counterbalanced by the
counterbalance I.
Across the centre of the vessel H is a division with a small passage through it
through which the mercury can slowly pass.
Neither the pull of the electro magnet G which tends to rock the lever D in one
direction or the weight J carried by the weighted arm K which tends to rock it in
the opposite direction is sufficient to completely lift the mercury in the vessel but
is sufficient only to cause a small difference in level between the mercury in the
two ends of the vessel and thereby cause mercury to flow from one end of the
vessel to the other-the lever D therefore can only be rocked slowly in one direction
or the other.
In place of the mercury vessel H being carried by the axis of the escapement
lever D it might as shewn in the diagram view Figure 3 be carried together with
the counterbalance weight I on an independent axis and be connected to the
armature lever D so that when one is rocked the other has to rock also.
The two positions of the escapement lever D are shewn in diagrams Figures 3
and 4. These diagrams also shew the shunt coil and the second coil which acts in
opposition thereto at the time when the tooth D' of the escapement lever. moves
away from the escapement wheel.
In Figures 1 and 2 the lower carbon holder is shown to be supported by the
.rocking lever E and it is balanced by a weight a little heavier than the negative
holder and carbon. When the current passes through the coils of the magnet F
and the lever is thereby rocked the negative carbon is lowered a distance sufficient
to strike the arc.
In lamps in which the negative carbon is drawn up as it is consumed the
pulley L which as in other lamps is made to wind up a cord L¹ connected to the
lower carbon holder and so to draw up the lower carbon I cause to be moved
endwise in the manner shewn at Figure 5 along a spiral key or thread on its axis
whenever a current passes through the coils of the magnet F and so unwind a short
length of cord from the pulley and allow the lower carbon to drop the distance
requisite to strike the arc.

page_text: Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
First. In combination with a toothed rack on the stem of the upper carbon
holder and pinion gearing therewith having an escapement wheel on its axis--the
two armed escapement lever having its axis carried by a rocking lever acted upon
by a solenoid or electro magnet through the coils of which the current passes
substantially as described.
:-
Second. The means substantially as herein before described for preventing rapid
movement of the 'escapement lever.
Third. The construction of electric arc lamps substantially as herein before
described and shewn at Figures 1 and 2 (and at Figure 5).
Doted this 20th dose of Ontahan 1001
MARK H. HURRELL.
-
Carpmael & Co.,
Agents for the Applicant.