Year: 1887

page_text: Date of Application, 12th May, 1887
Complete Left, 16th Jan., 1888
Complete Accepted, 23rd Mar.. 1888
I, ALEXANDER SIEMENS, of 12 Queen Anne's Gate, Westminster in the County of
Middlesex, Civil. Engineer, do hereby declare the nature of this invention to be as
follows:
My invention relates to an improved electric are lamp of the following construction.
The two carbon holders are mounted on two vertical rods one of which has a screw
thread on its lower part and screws through the lower carbon holder while the other
has a screw thread on its upper part and screws through the upper carbon holder; the
holders also have eyes through which pass the non-threaded parts of the rods, so that
the rod that actuates the one carbon holder acts as a guide to the other. The screw
threads of the rods are both to the samo hand, and the rods being rotated in contrary
directions as will be presently explained, the carbon holders are thereby caused to
approach each other, the thread or threads of the rod for the upper carbon holder
being made of double the pitch of the thread of the rod for the lower carbon holder,
when carbons of the same diameter are used in both holders, or the pitch of the thread
may be the same in both rods, when carbons of suitable diameter are used, and in
both cases the focus will remain unaltered.
The rods carry toothed wheels gearing with each other so that on rotary motion
being imparted to the one rod, such motion is also imparted in the contrary direction
to the other.
The automatic rotation of the rods for effecting the automatic advance of the
carbons is effected as follows:
The wheel of the rod for the upper carbon holder has a rim within which is a spring
brake strap, the two ends of which are connected to one end of a lever in such a
manner that when the lever is moved in one direction it first causes the brake strap to
bite on the wheel rim and then carries the wheel with it by means of the brake thus
rotating the rods, while when the lever is moved in the contrary direction it releases
the brake strap so that the lever can move back to its original position, leaving the
rods stationary. For effecting this motion of the lever it is pivotted to a bar, one end
of which is connected to an adjustable spring while the other end is connected to the
armature of an electro-magnet whose coils are in a shunt of the lamp circuit, the
го
.
77

page_text: connection between the coils and the shunt circuit being made by a contact spring on
the armature when this is removed from the magnet so that the connection is broken
when the armature is attracted by the magnet. The spring connected to the bar that
carries the brake lever is so adjusted in strength that when the carbons of the lamp
are at the normal distance apart the current passing through the shunt is too weak to
cause the electro magnet to attract the armature in opposition to the spring, and
consequently the bar and brake lever are held in the backward position in which no
feed of the carbon is effected. When by the burning of the carbons the resistance of
the are has increased sufficiently to cause a current of sufficient strength to pass
through the electro magnet to attract the armature in opposition to the spring the
armature in advancing will move forward the bar and brake lever so as to cause this
to rotate the rods through a small part of a revolution, as before described, and thus
effect the advance of the carbons..
When, however, the armature is thus attracted, it breaks the connection
between the shunt circuit and the electro magnet, so that this ceases to attract the
armature, whereupon this and the brake lever are drawn back by the spring into the
original position, to be again moved forward as soon as the resistance of the arc has
again slightly increased. Thus a continuous step-by-step automatic feed of the
carbons is effected.
It is evident that the mechanical arrangements may be varied so that the rotative
motion is produced by the spring instead of by the armature.
For automatically moving the carbons apart for producing the are in the first
instance, the screw rod of the lower carbon holder is capable of a slight vertical
motion and carries the armature of an electro magnet the coils of which are in the
lamp circuit, so that on the current passing through the lamp, the electro magnet
draws down the armature with the rod and carbon holder so as to separate the
carbons.
The armature is connected to springs acting in opposition to the electro magnet so
that, when the current ceases, the springs draw the armature and rod up so as to
bring the carbons in contact again. The rol of the upper carbon holder has a
hand wheel on its lower end by means of which the rods can be rotated and con-
sequently the carbons moved together or apart by hand. The rod of the upper carbon
holder carries a sleeve held between collars so that the rod cannot move longitudinally
therein and this sleeve has an external screw thread screwing through a bush
rotatable by hand in the casing of the lamp, so that by rotating the bush upon the
screwed sleeve (which is prevented from rotating by a stud entering a slot therein)
the rod may be moved upward or downward to a certain extent and thus, by shifting
the position of the upper carbon, the focus of the lamp can be adjusted. To admit of
this longitudinal motion the rod is made capable of sliding in the boss of its before
described toothed wheel.
The above described improved construction of electric are lamp is more particularly
applicable to holophote apparatus such as was described in the Provisional Specifi-
cation to my application for a Patent No. 683 of 1887, but it may also be applied
with advantage for electric lighting generally.
Doted th 10 1
1007

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
1, ALEXANDER SIEMENS of 12 Queen Anne's Gate, Westminster in the County of
Middlesex, Civil Engineer do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement:-
My invention relates to an improved electric arc lamp of the following construction.
The two carbon holders are mounted on two vertical rods one of which has a screw
thread on its lower part and screws through the lower carbon holder while the
other has a screw thread on its upper part and screws through the upper carbon
holder;
the holders also have eyes through which pass the non threaded parts of
the rods; so that the rod that actuates the one carbon holder acts as a guide to
the other. The screw threads of the rods are both to the same hand and the rods
being rotated in contrary directions as will be presently explained, the carbon holders
are thereby caused to approach each other, the thread or threads of the rod for the
upper carbon holder being made of double the pitch of the thread of the rod for the
lower carbon holder, when carbons of the same diameter are used in both holders, or
the pitch of the thread may be the same in both rods when carbons of suitable
diameter are used and in both cases the focus will remain unaltered.
The rods carry toothed wheels gearing with each other so that on rotary motion
being imparted to the one rod such motion is also imparted in the contrary direction
to the other.
The automatic rotation of the rods for effecting the automatic advance of the
carbons is effected as follows:
The wheel of the rod for the upper carbon holder has a rim within which is a spring
brake strap, the two ends of which are connected to one end of a lever in such a
manner that when the lever is moved in one direction it first causes the brake strap to
bite on the wheel rim and then carries the wheel with it by means of the brake, thus
rotating the rods, while when the lever is moved in the contrary direction it releases
the brake strap so that the lever can move back to its original position, leaving the
rods stationary.
For effecting this motion of the lever it is pivotted to a bar one end of which is
connected to an adjustable spring while the other end is connected to the armature of
an electro-magnet whose coils are in a shunt of the lamp circuit, the connection
between the coils and the shunt circuit being made by a contact spring on the
armature when this is removed from the magnet so that the connection is broken
when the armature is attracted by the magnet.
The spring connected to the bar that carries the brake lever is so adjusted in
strength that when the carbons of the lamp are at the normal distance apart the
current passing through the shunt is too weak to cause the electro-magnet to attract
the armature in opposition to the spring, and consequently the bar and brake lever
are held in the backward position in which no feed of the carbon is effected. When

page_text: by the burning of the carbons the resistance of the arc has increased sufficiently to
cause a current of sufficient strength to pass through the electro magnet to attract
the armature in opposition to the spring, the armature in advancing will move
forward the bar and brake lever so as to cause this to rotate the rods through a small
part of a revolution as before described and thus effect the advance of the carbons.
When, however the armature is thus attracted it breaks the connection between the
shunt circuit and the electro magnets, so that this ceases to attract the armature,
whereupon, this and the brake lever are drawn back by the spring into the original
position to be again moved forward as soon as the resistance of the arc has again
slightly increased.
Thus a continuous step by step automatic feed of the carbons is effected.
I will now proceed to describe more fully the construction of an arc lamp having
my said improvements applied thereto, for which purpose I will refer to the accom-
panying drawings in which Fig. 1 shews a sectional elevation, Fig. 2 shews a
section on line Y Y Fig. 1, Fig. 3 a section on line Z Z and Fig. 4 a sectional plan.
The lamp consists of a metal case supporting two rods 41 and 42 upon the screwed
parts of which are carried two carbon holders 43 and 44 part of each rod forming a
guide for the carbon holder carried by the other rod. Upon the end of the rod 41
which is prolonged through the bottom of the case is fixed a hand wheel 45 which
when turned causes through the action of the two pinions 46 and 47 these screwed
rods to rotate in opposite directions about their axes, and thus to make the carbon
ends forming the arc to approach or recede from one another.
A second hand wheel 48 to which is attached the nut 49. turning in a guide
furnished by the bottom of the lamp case and working upon the screw 50 forming a
part of or attached to the rod 41 is designed to move the latter in the direction of its
length when it is required to alter the position of the focus of the arc, provision being
made by slot 51 to allow it to slide through the pinion 46.
To the rod 42 is fixed the armature 52 of the electro magnet 53 which when excited
by the passage of the current on the starting or re-starting of the lamp attracts the
armature and holds it down against the action of the springs 54 and thus drawing
down the rod and with it the carbon holder, forms the arc.
The teeth of the pinion 47 are made of sufficient length, so that the operation of
drawing down the rod 42 does not slide them out of gear with the pinion 46.
Upon the underneath side of the pinion 46 is a circular recess 55 into which fits a
tapering brake ring 56 divided at its thickest part by an oblique cut as shewn and to
the two ends of the ring thus formed is pivotted a lever 57 by two pins placed in the
acute angles made by this cut and the inner and outer circumference of the ring.
Near the other end of the lever is pivotted by the pin 58 a link 59 at one end of
which is a hole, in which is intruded the finger 60 carried by the armature 61 of the
electro magnet 62 to one pole of which the armature is secured by the bracket 63 and
the spring 64 which allows it to take up a vibratory motion.
On the back of the armature is a contact spring 65 which makes and breaks contact
with the end of the screw 66 so that when the spring touches the screw, the circuit
through the clectro magnet 62 is complete and when it is away from the screw this
circuit is broken. At the other end of the link 59 and connected with it by the smaller
link 67 is the finger 68 carried by the spring 69 which turns upon the pin 70 and acts
in opposition to the-attraction-of the electromagnet 62, its force being adjusted by
the screw 71. The spring 72 secured to the link 59 and resting against the lever 57
is intended to take up any back lash there may be in the joint between the lever
and the link.
When the lamp is at work and the arc of normal length, the tension of the
spring 69 is adjusted so that the spring contact 65 rests against the screw contact 66
and so completes the circuit through the electro magnet 62 which is a shunt to that
passing through the arc.
As the resistance of the arc increases by consumption of the carbons and the
current in the shunt rises, the electro magnet becomes powerful enough to attract the
armature away from the contact 66 and in so doing breaks the circuit through itself,

page_text: when the armature immediately falls back again upon this contact. In this way a
vibratory movement of the armature is set up which communicating itself to the
link 59 and the lever 57 alternately tightens and slackens the brake ring 56 and
during that portion of the vibration where the ring is tight the rod 41 is turned
with the brake by the vibrating lever.
As long as this vibrating action continues the rod is turned in one direction by
quickly recurring impulses which are communicated to the other rod 12 by the
pinions 46 and 47 with the result that both rods are turned in such a nanner as to
bring the ends of the carbons nearer together and thus shorten the arc.
When the arc becomes sufficiently short this action coases owing to the weakening
of the shunt current and the armature again rests back upon the contact 66.
In this position the lever 57 rests against the stop screw 73 which then forms a
fulcrum upon which this lever is tilted by the action of the spring 69 in such a
manner as to slacken the brake ring 56 and leave the rods 41 and 42 free from the
resistance of the brake, and at liberty to be worked by hand.
The automatic feeding mechanism may be so arranged that the feeding movement
is produced by the spring 69 and the return movement by the armature instead of
vicê versû as described. A switch 74 may be provided to cut out the automatic
feeding mechanism when the hand gearing is to be employed.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what
I claim is :-
1. An electric arc lamp wherein the carbon holders are mounted upon two screwed
rods geared together so that by rotating in contrary directions they cause the carbon
holders to approach each other the one rod having a step by step rotary motion imparted
to it by means of a brake strap and lever controlled by a spring and by the armature
of an electro magnet through the coils of which a shunt current from the lamp
circuit is made to pass, the several parts being arranged and operating as herein
described.
2. In an electric arc lamp arranged and operating as set forth in the preceding
claim so arranging the armature of the electro magnet in the shunt circuit that
when it is drawn away by the spring owing to the shunt current being too weak
to cause the electro-magnet to attract it, it makes a contact so as to close the shunt
circuit but when it is attracted by the electro magnet owing to an increase in the
shunt circuit, it breaks the shunt circuit and thus renders the electro magnet
inoperative again, substantially as herein described.
3. In electric are lamps the combination of the screwed rods 41 and 42, toothod
wheels 46, 47 brake strap 56, lever 57, adjustable spring 69, armature 61 with
contact 65 and electro magnet 62 in a shunt circuit of the lamp, arranged and
operating, substantially as herein described with reference to the accompanying
drawings.
Dated this 16th day of Ton 1920