Improvements in Electric Arc Lamps.
Year: 1895

page_text: Date of Application, 3rd Aug.. 1895-Accepted, 14th Sept., 18.95
Improvements in Electric Arc Lamps.
We, THE ROGERS ARC LAMP COMPANY LIMITED, of 34 Victoria Street,
Westminster, Electrical Contractors, and JAMES WILLIAM ROGERS, of
7 Hargrave Park, Upper Holloway, in the County of Middlesex, 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 :-
In our lamps the two carbon holders are connected together by a chain which is
passed over a chain wheel and so the hoiders hang suspended on opposite sides of
the wheel.
The weight of the upper carbon holder somewhat exceeds that of the lower
holder so that when the chain wheel is free to turn the carbons run together.
On the same axis with the chain wheel there is a brake drum and a chain
tightened around the drum serves to hold it. So long as the electric current is
passing through the lamp, one end of the brake chain is held by an electro inagnet
of peculiar construction whilst a weight suspended from the other end of the chain
tightens it sufficiently around the drum to prevent movement.
The weight is of iron and it forms the core of a solenoid which shunts the arc.
Such is the general outline of the arrangement and the operation is as follows:-
When no current is passing through the lamp the brake chain is slack around the
drum and the carbons are in contact. On the passage of the current the electro
magnet draws down the end of the chain with which it is connected and in doing
so it turns the drum and lifts the weight from an adjustable stop upon which it
previously was supported. In this way the carbons are separated, the arc is struck
and the light is exhibited.
As the carbons burn away the resistance of the arc increases until sufficient
current passes in the solenoid to support the weight forming its core; the brake
chain is thus thrown sufficiently slack to permit the brake drum to turn.
A very
slight movement of the carbons takes place checked immediately by the brake as
the current passing through the solenoid decreases.
One of the features of the invention is the above mentioned electro magnet; it
consists of a broad ribbon of copper wound with a somewhat wider ribbon of
asbestos paper into a cylindrical coil.
A core piece of soft iron is soldered to the copper ribbon and in the winding this
core becomes enclosed in the coil. To complete the roll the outer end of the
copper ribbon is soldered down ou to the body of the coil.
The core piece is only about half the length of the coil so that a void space is
left within, and this receives a cylindrical iron rod which is freely moveable and
serves as the armature, to it one end of the brake chain is attached. The coil
made as above described offers little resistance to the current and it is not liable
to injury by heat.
The way in which the carbon holders are guided constitutes another feature of
the invention.
The stems of these carbon holders require to be accurately guided in order that
the points of the carbons may come together in a vertical line. To provide for
this three guides are arranged for each holder. The stem of the upper carbon
holder is passed through a guide passage in the lower plate of the lamp frame and
also there is attached to its upper end an arm extending Interally to a sleeve. The

page_text: arın is fixed to the sleeve and this surrounds an upright guide pillar forming part
of the frame of the lamp. The sleeve does not closely fit the guide pillar but at
each end of the sleeve three pins are screwed into it at equal distances apart
around the circumference. The points of these pins just come into contact
with the guide pillar. By these means the movement of the sleeve up and down
is very truly guided.
The stem of the lower carbon holder is guided in an analogous way; a sleeve
or tube is fixed by its upper end into the lower plate of the lamp frame and projects
downwards through it. The stem passes freely through the sleeve but is con-
trolled by pin points at the upper and the lower end of the sleeve. There are
three pins in each set as already described and they are screwed in until all
are just in contact with the stem. Rotary movement of this stem is prevented
by a forked arm fixed to it at its upper end; the forked arm extends laterally
to and embraces a vertical guide pillar forming part of the frame. The carbon
sockets at the lower end of the stems are fitted with V pieces and set screws
and these parts are made to nip the carbons between them.
The chain which serves as a brake strap is of peculiar construction, it consists
of hollow globular bead like links connected together by minute double headed
pins. In operation this brake strap permits the drum to turn, if not continuously,
by steps of inappreciable length, so maintaining the distance between the carbons
practically constant. It is probably to the great freedom in the joints of the chain
and to the fact that the surfaces in contact with the drum are more or less free to
roll that the perfection of the action is mainly due.
In order that our invention may be fully understood and readily carried into
effect we will proceed to describe the drawings annexed.
DESCRIPTION OF THE DRAWINGS.
Figures 1 and 2 are elevations of a lamp in accordance with our invention; it is
drawn to a reduced scale.
Figure 3 is a vertical section taken at the upper part of the lamp.
Figure 4 is a horizontal section taken on the line 4-4 in Figures 1 and 2.
The remaining figures show detached portions of the lamp and are referred to in
the course of the following description.
The main frame of the lamp consists of a top plate a and a bottom plate b con-
nected by columns cd and e but nevertheless electrically insulated the one from
the other by insulating ferrules in the positions the drawings indicate.
In Figure 2 the column c is broken in order that the parts behind it may not be
obscured. is a post fixed by its upper end to the plate a, by its lower end it
supports the platform g. On this platform the electro magnetic appliance / and the
solenoid coil i stand and are fixed. k is an axis, the chain wheel and the metal
drum m are fixed upon it. One end of the axis k has its bearing upon the post f
and the other end is carried by a bracket piece n fixed to the plate a.
01
o is the upper carbon holder and p is the lower carbon holder, parts are broken
away from each, the dimensions of the drawing not permitting them to be shown of
their full length. The upper carbon holder o passes through an insulating guiding
ferrule b' in the plate b and at its upper part it has a head consisting of an arm of
and a tube or sleeve o²; a plan of these parts is seen in Figure 5. The parts o,
and o² are firmly fixed together and the sleeve o encircles the column d. A section
close to the upper end of the sleeve is represented full size by Figure 6; there are,
as will be seen, three guiding pins screwed into the sleeve and between the ends of
these pins there is just 100m for the column d to pass freely. At the lower end of
the sleeve there is a precisely similar arrangement of guiding pins. The sleeve
can travel from end to end of the column d. The lower carbon holder p
passes through a tube which is firmly fixed to the plate 6 and near each end of
this tube there are guiding pins as is shown by the full size section Figure 7.
the upper end of the carbon holder p there is a forked arm p' represented by
At

page_text: Figure 8, it embraces the column c.
Thus the arrangement is such that the
carbon holders can pass up and down very truly and with very little friction.
At the top of each carbon holder is a hook and the chain r connects them, it
passes from one hook to the other over the chain wheel 1. The terminal link of
the chain at 1 is of silk to electrically isolate the one holder from the other.
Around the drum m two and a half turns of another metal chains pass. Figure 9
shows a portion of this chain to the same scale as the main figures. Figure 10 is
a section of the chain drawn to an exaggerated scale; this sort of chain is well
known to jewellers and others.
Figure 11 illustrates the construction of the electro-magnetic appliance . A
core piece h¹ is taken; the cylindrical part of this core piece is of soft iron and to
it is soldered one end of the copper ribbon h which is long enough to go say
twenty times round the core piece. It is necessary that the magnet should be of
sufficient power to lift the preponderating weight of the upper carbon holder.
³is a ribbon of asbestos paper somewhat wider than the copper ribbon 2, it is laid
upon it and the two are rolled up together. The roll is finished by soldering
down the far end of the copper ribbon on to the exterior of the roll. is a rod
like core attached to one end of the chains it enters within the coil h, the part
inside the coil is of soft iron but the part above which is encircled by a coiled
spring t is of brass. The spring t is interposed between the top of the coil h and
the head on the rod, it sustains the rod * and keeps it at a distance from the
core about equal to the separation which has to be made between the carbons in
striking the arc.
To the other end of the chains the soft iron rod u is attached, it passes freely
down through the solenoid i, it serves as a core to this solenoid and the solenoid
tends to lift it. The solenoid coil is wound in the ordinary way with many turns
of fine wire so that it offers a high resistance and only a small current passes
through it but sufficient when the arc is long to lift the core.
A brass stem u¹ is fixed onto the head of the core rod u and an adjustable
nut u² screwed on this stem comes to rest on the top of the coil and regulates the
distance the rod u can fall.
The electrical connections are as follows: Starting from the insulated
binding post v, to which one of the main leads is attached, a copper ribbon h*
passes to the ribbon ³, these copper ribbons may be in one piece. From h¹ the
current passes to the platform g and post f and so to the plate a and column e
which latter is connected by the flexible copper ribbon e' with the upper
carbon holder o. The lower carbon holder p is electrically connected in the
following way with the insulated binding post w which receives the other main
lead from w the current passes by the column c to the lower plate 6 and thence
by the post 62 and the flexible conducting ribbon a, it reaches the holder p.
The solenoid coil is connected at one end by the covered wire with the
column c and at the other end with the platform g on which the coil stands.
The way in which the carbons are fixed in the carbon holders is shown by
Figure 1 and also by the Figures 12 and 12. Figure 11 is an underside view of
the foot of the upper carbon holder and Figure 12 is a plan of the foot of the
lower carbon holder. y and z are the two carbons, in each case it will be seen that
the extremity of the carbon is placed in a V groove which accurately determines
its position and it is held there by a pinching screw; good electrical connection is
thus established between the carbons and their holders.
When the current is first turned on the rod like armature is drawn towards
the core until the two are in contact, the spring t being compressed. The
chains is thus pulled upon, it turns the axis k through a small angle and the
carbons are separated. At the same time the core u of the solenoid is lifted and
it then hangs by the chains and keeps this chain sufficiently tight to prevent the
drum m from turning. As the carbons burn away the arc offers increased resistance
and the solenoid soon receives sufficient current to slacken the chain & by
sustaining the weight of the core u. A state of equilibrium is attained and after

page_text: that an imperceptible movement of the carbons exactly compensates the loss by
burning away.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
1. The general arrangement of the lamp, that is to say the carbon holders
suspended by a chain passing over a wheel, the brake drum on the axis of this
wheel, the brake chain wound upon the drum, an electro-magnetic appliance in the
main circuit acting upon one end of the brake chain, and a weight controlled by
an electro-magnetic appliance in a shunt circuit acting upon the other end of the
brake chain, the whole operating substantially as described.
2. The magnet in the main circuit which serves to strike the are and which is
constructed substantially as described of a broad ribbon of copper wound with
asbestos paper or the like into a roll upon an iron core piece soldered to the
copper ribbon and extending part only of the length of the roll which roll also
receives within it a freely moving armature connected with the brake as herein set
forth.
3. The carbon holders and their guiding parts arranged substantially as
described by which arrangement it is ensured that the carbon holders shall move
freely and truly.
4. The regulating brake controlling the approach of the carbons and consisting
of a drum with a chain composed of globular beads and pins wound around it and
with the tension of the chain controlled by an electro magnetic appliance
substantially as described.
5. The lamp substantially as described.