Improvements in Electric Arc Lamps.
Year: 1897

page_text: Date of Application, 25th Sept., 1897—Accepted, 6th Nọv., 1897
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, do hereby declare the nature of
this invention (as communicated from abroad by Sigmund Bergmann, of 572 First
Avenue, New York City, United States of America, Electrical Engineer) and in
what manner the same is to be performed to be particularly described and ascer-
'tained in and by the following statement :-
This invention relates to electric-magnetic governing devices, and is more
specifically designed to be applied to the governing or regulation of electric arc
lamps.
While the invention is applicable in a general way to all kinds of electric are
lamps, it is most successfully employed in connection with lamps having the
arc enclosed in a small glass globe, known in the trade as the enclosed arc lamp,
in which a less extended amount of feed of the carbon carrier is necessary than
in lamps where the arc is exposed.
Numerous different mechanisms have heretofore been designed and employed.
for feeding down automatically the carbon carrier as the voltaic arc consumes the
carbon, but in all the practically successful forms of apparatus, various forms of
mechanical clutches or escapements have been employed, resulting in a more
or less complicated mechanism. The dispensing with these intermediate mechanisms
has been suggested, and the attachment of the carbon carrier direct to the core of
the helix or solenoid traversed by the electric current employed in the lamp, has
been offered as a substitute, but none of these attempts have been successful so
far as I know, by reason of the fact that the solenoid exerted an unequal pull on
the core for the varying positions of the core within the solenoid, and consequently
the feeding of the lamp was uneven, the arc being shortened as the carbon was
fed down, and finally extinguished completely before the lamp had burned more
than a very short time.
The invention overcomes this difficulty by a novel design of solenoid and core,
whereby the masses of the two are relatively so proportioned that the solenoid
exerts the same pull upon the core, whatever its position within the solenoid at
least between certain extreme limits.
By reason of this great simplification of the governing mechanism, I am also
able to dispose the other parts of the lamp, such as the resistance coil, about the
solenoid in compact form, resulting in other features of novelty and improved
construction.
The preferred form of this invention is illustrated in the accompanying two
sheets of drawing, in which :-
Figure 1 is a side elevation and partial section of the improved form of lamp.
Figure 2 is an enlarged detail of the preferred form of solenoid, and co-operating
soft iron core.
Figure 3 is a section on line 3-3 of Figure 2.
A
5 illundenta modifications of this invention

page_text: 1
Figure 6 and Figure 7 are diagrams illustrating the principle of the invention.
Figure 8 is an enlarged detail view. shewing the arrangement of resistance coils
rendered possible by the simple form, of lamp.
Throughout the drawings like. reference numerals refer to like parts.
1 represents the casing for the governing mechanism of the lamp.
2-2 are the side rods supporting the lower carbon holder 3.
4 is the small glass globe enclosing the arc formed between the lower carbon 5
and the upper carbon 6.
7 is the upper carbon holder, which is a soft iron hollow cylinder forming a core
closely fitting into the spool 8 of the solenoid 10
9 is a cover or button closely fitting into and closing the upper end of the spool 8,
air tight. The winding of the solenoid, 10, is increased at either extremity, there
being the extra coils 11, 12 and 13, on the upper end of the solenoid, and the
extra coils 14, 15, 16, 17, 18, 19, 20, 21, and 22, on the lower end of the solenoid.
23 represents the resistance coils which reduce the tension of the currents
supplied to the arc, and which are wound around the inner casing 23 a of the lamp,
being supported on porcelain, or other non-conducting cleats, 23 b. These resist-
ance coils are preferably reversed in their direction at one or more points, passing
around an insulating button 30 for this purpose, so as to form two adjacent portions
of the coil, 28, 29, through which the current runs in opposite directions.
adjustable metallic clamp 31, being movable along the loop thus formed, cuts out
more or less of the loop from the circuit and thereby adjusts the amount of
forces.
An
The electrical circuit of the lamp is through the resistance coils 23, through.
the solenoid 10, to the spool 8, from the spool to the carbon carrying core 7, and
out by way of any suitable connections with the lower carbon holder 3.
The method of operation of this invention is as follows:-
The winding of the solenoid in the manner represented in Figure 2, co-operates
with the soft iron core 7, in such manner that the vertical component of the
various magnetic attractions exerted by the solenoid upon that portion of the core
within the solenoid, shall always be the same as long as the core has at least a
given short portion of its upper end in the solenoid and is not elevated beyond a
point which leaves its extremity a short distance below the dover 9, which closes
the upper end of the spool.
This results from the state of facts indicated in the diagram, Figures 6 and 7.
Assuming the core to be in the position indicated in Figure 6, then the centre of
effect of the magnetic actions on it may be assumed to be at the point 24, which
is approximately the central point of that portion of the core within the solenoid.
This magnetic pull or attraction will be exerted principally by the coils com-
posing the adjacent portion of the solenoid, and those shortly above, so that the
point at which these radial magnetic attractions center, on any one side, might be
represented at 26, and the force of each set of these radial components, represented
by the length and direction of an arrow at 24-27. Of course there would be a
number of pairs of these forces, as 24-27 and 24-27 a, and their common
resultant would be represented by the diagonal 24-25 of the parallelogram of
resistance in the lamp.
When the core is raised to the higher position, as shewn in Figure 7, then
the centre of magnetic attraction 24 b, would still be the centre of the larger
portion of the core now within the solenoid, which would be raised considerably
above the point. 24, as shewn in Figure 6. The centres of magnetic attraction
might be represented in this case at 266 and 26 c, which would also be higher
than the points 26 and 26 a, but the increase of height of these points
would not be as great as the increase in height of the point 24 to 24b.
In other words, the angle which the radial components of magnetic attraction
would make with the horizontal plane (assuming the solenoid to be vertical) would
decrease as more and more of the core is inserted in the helix, and by properly
winding the helix, as represented, this decrease in the angle can be made to be

page_text: approximately proportionate to the increase in the strength of these radial com-
ponents of magnetic attraction (represented by the increased length of the
arrows, 24 b-276 and 24 6-27 c) which would of course result from bringing
more and more of the solenoid into action.
If this proportion is preserved it is evident that the vertical resultant 24 b-256
(being the diagonal of the parallelogram 24 b, 27 b, 25 b, 27c,) will be the same as
the resultant 24-25 (being the diagonal of the parallelogram of forces represented
in Figure 6, 24, 27, 25, 27 a). Consequently the desired result, to wit, obtaining
of a uniform vertical lift on the core at its various positions within the helix,
will have been secured. I arrive at the proper winding to secure this by trial,
being guided by the variation in the amperage of current necessary to maintain
the core in such position as to produce the proper length of arc when a straight
solenoid is employed, and different positions of the core are experimented with.
By then increasing the winding at the various corresponding portions of the solenoid
so as to give the ampere terms which I have empirically determined to be necessary
to sustain the core in that position, I obtain an almost perfect result.
It is evident that certain variations could be made in the design of the helix
and core so long as the relative relation between the masses above indicated, is
preserved; thus, the helix might be wound upon a wooden spool so that its external
walls would be straight, as shewn in Figure 4, while the variations in winding
would be produced by variations in the thickness of its interior walls.
Again, a straight helix might be used and a core of varying cross section would
then be employed with it, as illustrated in Figure 5; the constant magnetic pull
then resulting from the variable amount of iron in the core submitted to the
action of the helix, instead of from the reverse arrangement, as shewn in Figure 2.
In every case it is desirable to have the core or at least the upper portion
thereof, 32, which is preferably made of brass, fit tightly to the bore of the spool 8, .
so that the air will be trapped between it and the cover 9, (closing the upper end
of said spool) and thereby produce a dash-pot action, steadying the core in its
feeding action as the carbon is consumed, and the core lowered by a weakening
of the magnetic action of the solenoid produced by a weakening of the current
through the elongation of the arc.
The adjustable resistance illustrated in Figure 8, is of special importance,
inasmuch as the voltage of commercial circuits varies within certain limits, and it
is impossible for the manufacturer of lamps to make a lamp which will exactly
fit all commercial circuits, for the above reason.
With the construction illustrated in Figure 8, however, one can manufacture
a lamp containing a resistance equal to the maximum voltage in use in commercial
circuits employing that type of lamp, and then the person putting the lamp in
position can cut the resistance down to suit the conditions by moving the adjustable
clamp 31, along the loop formed by the portions 28 and 29 of the resistance.
It has been stated in general terms that the angle which the radial components
of magnetic attraction make to the horizontal plane should decrease approximately
in an inverse ratio as the strength of that magnetic attraction increases. As these
angles are always small, this statement is sufficiently accurate for practical
purposes. The mathematician will understand, however, that to be accurate it
should be said that the sine of the angle decreases in inverse proportion to the
increase in strength of the magnetic attraction.
With small sizes of angle the variation of the angle in degrees is nearly equal
to the variation in the sine of the angle, so that the simpler statement before given
is probably sufficient for practical purposes and will be more readily understood
by those not familiar with trigonometrical terms.
ffi
Having now particularly described and ascertained the nature of this in-
vention and in what manner the same is to be performed I declare that what I
claim is:-
1. For regulating the are of an electric arc lamp, a coil of insulated wire, wound

page_text: on a spool of uniform cross section, but having more convolutions wound about
its extremities than about its middle portion, in combination with a movable soft
iron core of uniform cross section closely fitting the bore of the spool, which is
covered at the top, substantially as, and for the purposes, set forth.
2. A regulating solenoid for an electric arc lamp consisting of a coil of insulated
wire and a movable soft iron core carrying the upper carbon, the masses of the
two at various parts of their lengths being so related one to the other, that
the angle which the direction of radial magnetic attraction of the coil on the core
makes with the horizontal plane, decreases approximately as the strength of said
attraction increases owing to the increased length of core within the helix, so that
the vertical resultant of the radial attraction remains approximately constant for
all positions of the core within the helix, substantially as described
3. In an electric are lamp in combination with the regulating solenoid, resist-
ance coils wound around the exterior of the solenoid, portions of these resistance
coils being reversed in loop form, and an adjustable metallic clamp connecting the
looped portions so that a greater or less portion of the coils may be cut out of
circuit to adjust the resistance, substantially as described.
Dated this 25th day of September 1897.
ABEL & IMRAY,
Agents for the Applicant.