Improvements in Electric Arc Lamps.
Year: 1895

page_text: Date of Application, 23rd July, 1895-Accepted, 24th Aug., 1895
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
I, DANIEL HIGHAM, of 168 High Street, Boston, State of Massachusetts,
United States of America, Electrical 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:-
This invention relates to electric arc-lighting, but more particularly to constant
potential arc-lighting, and its object is to provide means whereby two or more sets
of carbons can be burned in series in one lamp, with less mechanism than has been
employed heretofore, as more fully explained hereinafter.
The type of arc lamp now in use in which two sets of carbons are burned in
series is known as a "twin " lamp, and has two sets of feeding mechanism in. which
shunt windings are employed to control the proper length of each respective arc,
and also suitable cut-outs are employed to save the burning out of a shunt winding
(when the carbons are consumed) by opening the circuit of the shunt winding,
which controls the length of the arc of the set of carbons which burn out first, as
is well known to the art.
It is the object of this invention, to do away with the use of shunt windings and
consequently with the need and use of cut-outs and to produce means by which two
sets of carbons can be burned in series in one lamp, without the use of two sets of
feeding mechanism in the sense meant by a "twin" lamp. The view in the
accompanying drawing is a diagram illustrative of the present invention, as applied
to a lamp having two sets of carbons connected in series.
A and A¹ represent the upper carbons carried by movable holders a and a¹,
while 6 and 6 represent the lower or fixed carbons. Acting upon the movable
holders a and a¹ are clutches E and E' provided with insulated bushings and r²,
to prevent electrical connection of the carbon holders with each other. At the
outer ends of the clutches are adjustable screws e and e¹ which are adapted to
touch upon rods D and D' adjacent to the carbons. The other ends of the clutches
are carried by a hanger G forming part of a U-shaped solenoid core K through
which the carbon holders are shown as passing for clearness of illustration, and
this solenoid core is magnetically acted upon by the series windings or coils C.
The rods D and D' are fixed to the frame of the lamp at d and d' and are made of
copper or other material which will expand readily by the heat given out from the
The other end of the rods D and D' are supported by the frame at fand ƒ¹.
The adjustment of screws e and e¹ should be such that when touched upon the
rods D and D¹, both clutches will release, as near as possible, both carbon holders
at the same time, and the series windings or coils C should be such that the desired
or normal current will just sustain the weight of the solenoid
core, clutches and
carbon holders, to maintain the arcs.
arcs.
The circuit between the lamp terminals X and Y is indicated by the arrows and
is as follows:
From the incoming binding post ✗, the current flows through the carbons A 6
and arc P, thence through conductor 3 to the carbons A' 6' and arc P¹, thence
through conductor 4 to the series coils C C and outgoing binding post Y.
The operation is as follows:
When current is first switched on (from a suitable constant potential circuit
having a suitable resistance in the lamp branch) the series coils C will draw up the
solenoid core K and engage the clutches E and E' with the carbon holders a and a¹

page_text: to draw the proper length of arcs. As the carbons burn away at the points, the
coils C will lower down the solenoid core K, clutches E and E' and carbon holders a
and a¹ until the screws e and e¹ on the clutches touch on the rods D and I)' and release
the clutches from the carbon holders, but if it should happen that arc P for
instance, would not burn its carbons as much as arc P₁, as illustrated in the
drawing, then rod D₁ will be heated up from the heat of the adjacent arc P' more
than rod D will be heated from its adjacent arc P, whereby rod D¹ will be
expanded in length, more-than-rod-D, and-will-cause-clutch-EL-to-release-its-carbon-
holder al without disengaging clutch E, and so on, the carbon holder having the
longest arc at its carbon points will always be fed down and the normal length of
each are will be approximately maintained, as will be readily understood without
further description.
Although I have illustrated but one form of arc lamp embodying my invention it
should be understood that various other forms or arrangements and modifications
could be easily devised by any one skilled in the art without departing from the
scope of my invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
An electric arc lamp, having electric arcs connected in series, suitable feeding
mechanism, provided with series magnet windings controlling the same to regulate
the current at the desired or normal amount and means whereby the normal length
of said arcs are maintained by the heat given out by said arcs, substantially as
described.
Dated this 23rd day of Jul 1905
ABEL & IMRAY,
Agents for the Applicant.