Improvements in Electric Arc-lighting.
Year: 1894

page_text: Date of Application, 22nd May, 1894-Accepted, 23rd June, 1894
[Communicated from abroad by THE HIGHAM ELECTRIC COMPANY, of Portland,
Maine, United States of America.].
Improvements in Electric Arc-lighting.
I, CHARLES AUBREY DAY, of 321, High Holborn, in the County of London,
Chartered Patent Agent, 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 :-
This invention relates to electric arc-lighting, but more particularly to multiple
or constant potential arc-lighting, and its object is to provide means whereby little
or no resistance will be required in the arc branch to obtain "stability" of current,
as will be best understood by the following explanation and by reference to the
accompanying drawings in which :-
Fig. 1, is a diagram of a form of clutch lamp, shown for purpose of illustration.
Fig. 2, is a similar diagram showing the invention as correctly applied:
Fig. 3, is a view of a modification,-and-
Fig. 4, is a diagram illustrative of the performance or operation of the
improvement.
In the diagrams, Figs. 1 and 2, A, represents the upper carbon carried by a
movable holder A', while B, represents the lower or fixed carbon. Acting upon
the movable carbon holder is a clutch D, one end of which touches upon a stop d,
on the frame, while the other end is connected through a link d¹, to a lever L,
pivoted at 1. S, is a fine wire coil in a shunt circuit around the are and acting
magnetically upon solenoid core 1. C, is a coarse wire coil in the main circuit;
and also acting magnetically upon solenoid core l, but tending to move it in an
opposite direction to that imparted by coil S. Q, is an adjustable spring to act
upon lever L, against the magnetization of coil C.
In Fig. 2, coil K, is a coil of high self-induction connected in the main circuit,
in series with coil or coils of the lamp or lamps, while Q', is a short spring, acting
both for tension and compression, connecting lever L, through a dash pot P, to the
frame of the lamp. The circuits between the terminals X, Y, of the lamp, shown
in both diagrams, are indicated by arrow heads.
It has been discovered that a very marked condition of "stability" is obtained
when spring Q, is made very short, as shown in Fig. 1, and that best results for
"stability" are obtained when the same is made sufficiently short, (so as to increase
sufficiently in tension when stretched) to prevent increase of current from
lengthening the are by means of the series coil C, more than would just be
necessary to prevent a fall of electric potential at the arc when the current
intensity rises.
Under this adjustment, in connection with multiple arc-lighting, a lamp would
run with less "pumping" or "hammering" in the sense meant by "instability,"
but there would be a very serious objection produced in another direction,
amounting to prohibition of the short spring. For instance, on the first drawing
of the are, in lighting the lamp, an almost infinitely great amount of current would
be required to pass through coil c to draw the necessary length of arc to check
the heavy rise of current occasioned by the rapidly increasing tension of the short
spring as the arc is being lengthened. In fact, if the spring Q, be made sufficiently
short to obtain the maximum condition of "stability" the drawing of the are would
almost amount to a theoretical impossibility ;-at best, the lamp would burn at very
great varying degrees of candle power, first being abnormally bright and then

page_text: :
getting less bright as the carbons burn away, until it would get, perhaps, below the
normal candle power, when carbon A, would feed down slightly and up would go
the candle power again. The same thing would be repeated, only not to such a
great extent, at every feeding of the carbon.
With the long spring Q, now made use of as shown in dotted lines in Fig. 1, it
will be understood that only a slight increase of current is required in coil r, above
the normal to draw the arc to the full length, inasmuch as the long spring Q, gains
but little in tension when stretched; whereby the lamp would burn at a practically
uniform brilliancy, although more resistance would be required in the arc branch
to obtain "stability" than would be the case with the short spring.
It is the object of this invention, however, to provide means whereby a short and
long spring can be used in one lamp. Fig. 2, of the drawings will serve to show
how this can be carried out. Q, is the long spring, shown in dotted lines in Fig. 1,
while Q is a spring acting both for tension and compression, and arranged to serve
the purpose of the short spring in limiting the movement of lamp magnet mechanism
in the lengthening or shortening of the arc, considering the dash-pot P, as-a fixed
connection. As the dash-pot connection, however, will be a slow yielding one,
the long spring (Q) adjustment will be allowed to slowly take effect, that is,
the dash-pot P, will allow the proper length of are to be slowly drawn and the
brilliancy to be practically kept constant while spring Q, will prevent the lamp
magnet mechanism from moving quickly more than would just be necessary to
prevent a fall of electric potential at the arc when the current intensity rises, or
a rise of potential when the current falls.
The high self-induction coil K, shown in Fig. 2, together with the short
spring Q, and dash-pot P, constitute the present invention. The operation or
performance of this improvement is graphically illustrated in diagram Fig. 4, and
is as follows:-The full curved line in the diagram presents a wave variation of
current flowing through coil K, and lamp, the line of dashes, the resultant
movement of the carbon A, and holder A', in lengthening and shortening the arc
under the limiting action of the short spring Q, considering the dash-pot P, as a
fixed connection, and the dotted line indicates the drop and fall of potential at the
are due to coil K, while the straight line indicates the normal condition of all; the
duration of time is laid off along the abscissas and the intensity of current, the drop
and fall of potential due to coil K, and movement of the upper carbon, along the
ordinates. From this diagram it will be seen that the movement of the upper
carbon is slightly behind in phase of the current flowing through the lamp (which
is occasioned by the inertia and friction of the movement of lamp-magnet
mechanism) and, consequently, leaving a slight deficiency between the current aud
the lengthening and shortening of the arc, as indicated by the cross-hatches, shown
in the diagram. Now, the self-induction offered to the current by coil K, will be
precisely one quarter of a wave difference in phase from the wave variations of
current flowing through the lamp, as shown by the dotted line in the diagram;
from which it will also be seen that the said deficiency between the current and
movement of the upper carbon can be readily compensated for by the drop and fall
of electric potential at the arc, occasioned by the self-induction of coil K, as also
indicated by cross-hatches, whereby, if coil K, is sufficiently large, stability” of
current will be obtained' within a small wave variation of about 2% or 3% as will
be understood without further description.
66
Other forms of slow yielding connection may be employed in place of the
dash-pot. Thus, in Fig. 3, there is shown a rotating fan f, in bearings in the frame
geared up to a rack pl, which is connected to the spring Q'.
Although there is shown but one form of lamp embodying these improvements, it
should be understood that various other forms and arrangements or modifications of
parts could be easily devised by any-one skilled in the art without departing from
the scope of this invention.
For greater clearness, it may be explained that in the specific example illustrated
in Fig. 2. the spring O'. is the "elastic-connection:" feature: of the claim which

page_text: follows, while the dash-pot P, or its equivalent is the "slow yielding connection,"
and the coil K, is the "inductive coil."
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 ;-
•
The combination of an arc-lamp or lamps having suitable carbon feeding or
regulating mechanism, with an inductive coil in the main circuit in series with the
arc and series windings of said lamp or lamps and an elastic and slow yielding
connection arranged serially together between the said mechanism and frame of
said lamp or lamps, substantially as described and for the purpose set forth.
Dated this 22nd day of May 1894.
DAY, DAVIES & HUNT,
321, High Holborn, London, W.C., Agents for the Applicant.