Improvements in Arc Lamps.
Year: 1891

page_text: -COMPLETE SPECIFICATION.
Improvements in Arc Lamps.
I JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex,
Gentleman, do hereby declare the nature of this invention, which has been com-
municated to me from abroad by Charles Bellens of 111 Boulevard Magenta,
Paris in the Republic of France, Engineer, and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
This invention relates to improvements in arc lamps and consists in an automatic
regulating mechanism hereinafter described so constructed that the upper carbon
being movable is caused to gradually and slowly approach the fixed carbon in
proportion as it burns away. The said upper carbon is securely fixed or retained
in the required position until an increase of resistance in the are caused by the
burning away of the carbons brings the feed mechanism into action. By this
means the flickering or jumping of the light which is produced in apparatus in
which the carbon holders are too readily influenced by the slightest variations
of the current is obviated.
And in order that the said invention may be well understood I will now proceed
to describe the same with reference to the accompanying drawings..
Figure 1 of the accompanying drawings represents the regulating mechanism in
front elevation.
Figure 2 represents the mechanism in side elevation.
The lower part of the lamp presents no special feature and is not represented
in these drawings.
The lamp is constructed with two metal discs or plates 1 and 2 connected by
three pillars 3, '3', and 3".
To the underside of the plate 2 are screwed hollów rods 4, 4'. These rods
which are electrically insulated from the plate 2 are connected at their lower ends
by a horizontal bar (not shewn in the drawings) supporting the lower carbon.
These rods also act as guides for a movable upper carbon holder 5.
The regulating mechanism hereinafter described is arranged between the plates 1
and 2. Upon the plate 2 is fixed an electro-magnet provided with fine wire
coiled on two bobbins 6, 6 arranged in derivation upon the main circuit-that is
to say, one of the extremities of this fine wire is connected to the terminal at
which the current enters the lamp, the other being connected to the terminal at
which the current leaves the lamp. By means of this arrangement the intensity
of the current passing in the fine wire of the electro-magnet increases in propor-
tion to the resistance of the main circuit and consequently in proportion to the
increase in the distance between the carbons. The upper part of the soft iron core
of this double electro-magnet is arranged in such a manner as to be capable of
actuating an armature in the form of an oscillating lever or plate 7 composed of
soft iron oscillating upon two trunnions 8 supported by the pillars 3 and 3". The
long arm of this lever plate is prevented from rising beyond a certain distance
by adjustable stop screws 9, 9¹. It is pressed against these screws in the position
represented in the drawing by the action of a spring 10 when no current is passing
in the electro magnet 6, 6¹ the said spring acting upon the short arm of the lever
and being capable of adjustinent by means of a screw 11.
On the lower side of the armature 7 there are screwed two bearings 12, 121
supporting a horizontal spindle 13. Upon this spindle there are provided (firstly),
a clock spring barrel 14 containing an internal coiled spring 15 and connected
with a ratchet wheel 16, and (secondly) a large spur wheel 17 loose upon the
spindle 13 and carrying a pawl 18 maintained in gear with the ratchet wheel 16

page_text: •
upon
by a spring 19. The coiled spring contained in the barrel 14 constantly tends to
wind
this barrel a conducting strip or ribbon 20 of thin copper which supports
the upper carbon holder 5 but the winding does not take place unless this carbon
holder is elevated by hand, the coiled spring not having sufficient strength in itself
to raise the carbon holder.
On the upper side of the armature 7 there are fixed four supports 21, 211, 22, 22¹
which form bearings for three horizontal spindles 23, 24, 25. Upon the spindle 23
are fixed a pinion 26 gearing with the toothed wheel 17 and a toothed wheel 27
gearing with a pinion 28.
Upon the spindle 24 are fixed the aforesaid pinion 28 and a toothed wheel 29
gearing with a pinion 30. Upon the spindle 25 are fixed the aforesaid pinion 30
and a notched wheel 31. The latter when the apparatus is at rest (Figure 1) is
locked and rendered immovable by a catch or tooth 32 on the end of a lever 33
rocking upon a centre 34. The long arm of this lever when released is depressed
or placed in the locking position represented in Figure 1 by a spring 35 its descent
being limited by an adjusting screw 36 provided with a lock nut and which comes
in contact with the underside of the upper plate 1 (Figure 1).
The current entering the lamp through the lead or thick wire connected with a
terminal 37 passes through the, metal work of the regulating mechanism, which is
insulated as hereinbefore stated from the two rods 4 and 4' into the copper ribbon 20
and passes thence to the socket 38 of the carbon holder 5 which is insulated from
the guides by ebonite washers 5'. The current after traversing the two carbons
passes along the rod 4¹ and reaches the terminal 39 which is insulated from the
rest of the apparatus, being connected to the said rod by a brass strip 40.
varying proportion of current passes through the fine wire electro-magnet 6, 6¹
connected in derivation to the two terminals as hereinbefore explained.
A
The apparatus thus constructed acts as follows. When at rest the carbons are
always separated from one another by a short distance. When the current passes
through the lamp the electro-magnet being in derivation on the terminals of the lamp
attracts the rocking armature plate 7. The train of gearing and the barrel carried
by the plate 7 are lowered bodily therewith and the carbons are brought into
contact. At this moment the carbons present extremely small resistance; the
difference of potential at the terminals of the lamp is also extremely small and the
attractive force of the electro-magnet 6 6¹ diminishes considerably. The lever 7
now rises and elevates the whole train of gearing and the barrel and likewise the
upper carbon which is thus separated from the lower carbon and strikes the arc..
In proportion as the carbons burn away, the distance between the points increasing
the resistance of the are increases, likewise, the difference of potential at the terminals
also increases and consequently the attracting power of the electro-magnet in-
creases. The lever 7 being more powerfully attracted, descends as well as the
spindle of the gear wheel 25 which moves with the said lever. This wheel being
moved away from the catch or tooth 32 by which it was locked is set free and the
upper carbon descending under the influence of its weight approaches the lower
carbon and actuates the train of gearing carried by the spindles 13, 23, 24 and 25.
The inertia of these parts retards the descent of the upper carbon. If the
carbon descends to the extent of th of a millimetre for example the wheel 25
describes a relatively large fraction of a revolution. At the same time as the
positive carbon descends in order to approach the negative carbon the resistance
of the arc diminishes as well as the difference of potential at the terminals of the
lamp. The power of the electro-magnet thus diminishes and the armature lever 7
elevates the wheel 25 the teeth of which re-engage with the tooth 32 and arrest the
rotary movement of the said wheel. All these gearings and the carbon now remain
at rest until an increased distance between the carbons resulting from their burning
away produces a fresh increase of resistance and a fresh movement of the armature
and of the wheels.
These movements are renewed frequently and periodically. Every time the
notched wheel moves to the extent of one tooth the upper positive carbon descends

page_text: to the extent of a very small fraction of a millimetre. The sensitiveness of the
apparatus depends on the number of teeth on the periphery of the wheel 25 on the
depth of these teeth, on the number of wheels carried by the armature 7; on
the relation between the diameters of the said wheels and the diameters of their
respective pinions, and on the distance of the last wheel 25 of the train from the
tooth 32. Whenever the apparatus comes into action the wheel 25 advances to the
extent of one tooth which corresponds to a very slight downward movement of
the upper carbon. The variations in the resistance of the are between the con-
secutive movements of the apparatus are practically nil and consequently the
intensity of the arc remains constant. In order to regulate the lamp for a desired
degree of intensity it is sufficient to adjust the antagonistic force of the armature 7
which is done by regulating the action of the spring 10 by means of the screw 11.
A delicate adjustment is obtained by regulating the distance between the tooth 32
and the wheel 25 by means of the screw 36. The distance between the carbons
and consequently the length and intensity of the luminous are may be adjusted and
regulated within certain limits by means of the stop screws 9, 9¹ and by the
screw 11 which enables the tension of the spring 10 to be regulated and causes it
to present more or less resistarce to the attraction of the electro magnet 6, 6'.
When the carbons are worn away and it is desired to replace them by fresh rods
it is simply necessary to push up the upper carbon holder 5 by hand to the upper
limit of its stroke. During this movement the coiled spring 15 contained within
the barrel rotates the latter in such a manner as to coil thereon the copper
ribbon 20 the pawl 18 slipping during this movement over the teeth of the ratchet
wheel 16. The burnt out stumps may then be readily removed and replaced by
fresh carbons. After this operation it is advisable to restore the carbons to the
normal distance by hand in order to enable the lamp to light immediately and
automatically.
The lamp hereinbefore described and illustrated in the accompanying drawings is
given merely as an example and the form proportions and materials and details of
the mechanism may evidently be modified if required. In the example hereinbefore
described the lower carbon is fixed so that the position of the luminous point
becomes lower in proportion as the carbon wears away, but this regulating
apparatus may be combined with any suitable arrangement for maintaining the arc
in one position.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
First In a regulating mechanism for an arc lamp the combination of a rocking
armature or lever plate acted on by a spring and carrying a train of gearing
actuated by one of the carbon holders and locked by a catch or tooth the
movements of the said plate and of the gearing being controlled by an electro
magnet arranged in derivation upon the main circuit so that the carbons are
brought together and returned to their original distance in lighting the lamp and
are subsequently maintained at the required distance apart as they burn away
substantially as hereinbefore described and illustrated in the accompanying
drawings.
Second-The arrangements and combinations of parts constituting the improve- -
ments in are lamps substantially as hereinbefore described.
Dated this 6th day of August 1891.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, Agents.