Improvements in Electro-magnets and in their Application to Arc Lamps.
Year: 1889

page_text: Date of Application, 24th Aug.. 1839
Complete Specification Left, 23rd May, 1890-Accepted, 24th Nov., 1890
Improvements in Electro-magnets and in their Application to
Arc Lamps.
J, HENRY HARPER, of 3, Cornwall Gardens, Queen's Gate, in the County of
Middlesex, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
This invention relates to electro-magnets adapted for use with electric are lamps
and for other purposes, and consists of an improved method of constructing and
arranging the core, and an improved mode of winding the solenoid, whereby the
device is specially adapted for use with are lainps or other electrical appliances worked
on the series' system.
.
Assuming a solenoid and core constructed according to this invention to be
applied, by way of example, to regulating the working of one of a series of are lamps,
the solenoid proper or bobbin consists of two bodies of wires arranged concentrically,
but so wound or electrically connected as to conduct the current in opposite
directions. The outer or 'series' coil, composed of coarse wire, consists, by
preference, of several coils arranged in series and wound upon a lining tube, which
may be of brass.
The inner or parallel' coil is composed of fine wire, and is also
wound upon a brass lining tube. The lower end of each tube is formed or furnished
with a collar for carrying the weight of the wire. The upper extremity of the inner
tube is fastened direct to a metal carrying plate; the upper extremity of the outer
tube being secured, by means of a flange and through the intervention of a vulcanite
disc, to the same carrying plate. The wires conducting the current to and from the
inner or parallel' coil are led through the vulcanite disc. The lower extremity of
the outer tube is similarly insulated. The core consists of a tube of soft iron turned
and bored cylindrical and of substantially the same length as the tube carrying the
outer or 'series' coils of the solenoid. The tube is closed at the lower end by
means of a plug or cap and is provided at its upper end with a funnel-shaped and
axially-perforated plug, through which a rod works as in a guide. The rod is freely
suspended at its upper extremity on a transverse pin mounted in a cap above the
carrying plate before referred to; whilst attached to the lower extremity of the rod
is a plunger, preferably of barrel-shape and fitting loosely within the tubular core.
Through the funnel-shaped plug, with which the upper extremity of the tubular core
is provided, the interior of the latter is charged with glycerine or other suitable
liquid. As the influence of the solenoid upon the core varies with each change of
resistance in the circuit, such variations frequently taking place with great rapidity,
the liquid-charged core (to which the upper or positive carbon of the lamp is
attached) in conjunction with the stationary plunger immersed in the liquid operate
as a dashpot to regulate and control the flickering effect which would otherwise result
from the sensitiveness of the apparatus. The funnel-shaped core-plug may be
provided with rollers for the purpose of guiding the plunger-rod and reducing friction
to a minimum.
300.
1000
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Electro-magnets and in their Application to
Arc Lamps.
I, HENRY HARPER, of 3, Cornwall Gardens, Queen's Gate, in the County of
Middlesex, 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 electro-magnets or solenoids adapted for use with electric
arc lamps, and consists of an improved method of constructing and arranging the
core, and an improved mode of winding the solenoid coil, whereby the device is
specially adapted for use with arc lamps.
In the accompanying drawings,
Fig. 1 is a vertical section of an electro-magnet constructed according to the
present invention; Fig. 2 being a diagram shewing the way in which the electric
current flows through the solenoid coils.
+ 86
"
Assuming the improved solenoid and core to be applied by way of example to
regulating the working of one of a series of are lamps, the solenoid proper or
bobbin A consists of two bodies a and a¹ of wire arranged concentrically, but so
wound or electrically connected as to conduct the current in opposite directions.
The outer or "series coil a, composed of coarse wire in the circuit of the lamp,
consists by preference of several coils arranged in series and wound upon a lining
tube B which may be of brass. The inner shunt or "paralle!" coil a¹ is composed
of fine wire and is also mounted upon a brass lining tube B¹. This coil may,
however, be dispensed with in the case of a lamp which is one of a set connected
parallel." The lower end of the tube B is formed or furnished with a collar C for
carrying the weight of the wire a; the lower end of the tube B1 being also provided
with a collar C¹ for carrying the weight of the wire a¹. The upper extremity of
the tube B is fastened directly to a metal carrying plate D. The upper extremity
of the tube B is secured by means of a flange E and through the intervention of an
insulating vulcanite disc F to the carrying plate D. The lower extremity C of the
outer tube is similarly insulated by a vulcanite disc F¹. The wires x and x¹, con-
ducting the current to and from the inner or "parallel " coil, are led through the
vulcanite discs F and F¹. The core G consists of a tube g of soft iron turned and
bored cylindrical and of substantially the same length as the tube B. The tube g is
closed at the lower end by means of a plug or cap g¹, and is provided at its upper
end with a funnel-shaped and axially-perforated plug g2 through which works a
rod g³. The rod is freely suspended at its upper extremity on a transverse pin 94
mounted in a cap 95 above the carrying plate D; whilst, attached to the lower
extremity of the rod, is a plunger 96, preferably of barrel shape and fitting loosely
within the tube g. Through the funnel-shaped plug g², the tube is charged with
glycerine or other suitable liquid. As the influence of the solenoid A upon the
core G varies with each change of resistance in the circuit, such variations frequently
taking place with great rapidity, the liquid-charged core (to which the upper or
positive carbon H of the lamp is attached, and in which the suspended plunger g is
immersed) operates as a dashpot to prevent the flickering effect which would other-
wise result from the sensitiveness of the apparatus.
The action of the improved electro-magnet is as follows:-The current is conducted
from the positive pole of the generator through the wire to one of the terminals 4
of the lamp. Thence it flows in a certain direction through the coil a to the upper
or positive carbon H, where it is subdivided; the greater part flowing across the
voltaic arc into the lower or negative carbon H¹ and the remainder-a comparatively
small portion-passing by x to the coil a¹. The direction of the current whilst
passing through the convolutions of the coil a¹ is opposed to that of the current 5
passing through the coil a. The subdivided portions of the current flowing respec-
tively from the lower or negative carbon H¹ and from the coil by ¹ reunite at the

page_text: other terminal of the lamp and are thence conducted through the wire y' to the
negative pole of the generator. When the carbons H and H₁ are in contact, there is
practically no resistance in the circuit and a current of full volume flows through the
coil a, the core G being in consequence lifted and the carbons moved asunder until
the resistance through the voltaic arc is such that equilibrium is established and the
carbons are no longer moved apart. The movement of the carbons is governed and
its suddenness controlled by the dashpot and suspended plunger. The greater the
resistance through the arc, the greater is the difference of potential at the ends of the
fine wire coil at. Consequently, when the carbons are near together, a comparatively
small current flows through the coil a¹; but when the carbons are a considerable
distance apart, a correspondingly larger current flows through that coil. The
attractive force of the current flowing through the outer coil a is diminished by and
in proportion to the current flowing in the opposite direction through the inner
coil a. The attractive force of the solenoid upon the core varies, therefore,
inversely with the resistance of the arc; that is, the nearer the carbons are together.
the greater is the force available for drawing them apart, and the further the
distance between the carbons, the less is the force available for keeping them
separated.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. In an electric arc lamp, being one of a set connected parallel,' the combination,
with a movable iron core to which the upper carbon is directly attached, of a single
wound solenoid coil in the lamp circuit, acting by its attraction in opposition to
gravity on the core, so as to regulate the span of the are, substantially as herein
described.
2. In an electric arc lamp, being one of a set connected 'in series,' the com-
bination, with a movable iron core to which the upper carbon is directly attached,
of a compound solenoid, consisting of a coil in the lamp circuit having an enclosed
coil in a shunt thereto, both coils acting on the same part of the core, but being
connected so as to act differentially, in conjunction with gravity, for regulating the
span of the arc, substantially as herein described.
3. In an electric are lamp having the upper carbon directly attached to the iron
core of a single-wound regulating solenoid, making that core tubular with a stationary
piston and a charge of suitable liquid enclosed within it, so as to act as a dashpot to
damp oscillations of the carbon, substantially as herein described.
4. In an electric arc lamp having the upper carbon directly attached to the iron core
of a diffential regulating solenoid, making that core tubular with a stationary piston
ind a charge of suitable liquid enclosed within it, so as to act as a dashpot to damp
oscillations of the carbon, substantially as herein described.
5. Constructing a differential solenoid by winding the one coil of insulated wire
apon an insulated tube, enclosing this tube within a second insulated tube, and
vinding on this outer tube the other coil of insulated wire, so that each bobbin is
ndependently removable, substantially as herein described.
A way of May 1950.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicant.