IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1882

page_text: LETTERS PATENT to Benjamin Joseph Barnard Mills of the Firm of Harris
and Mills of 23 Southampton Buildings in the County of Middlesex Patent
Agent for an Invention of “IMPROVEMENTS IN ELECTRIC LAMPS." A com-
munication from abroad by William Maulsby Thomas of Cincinnati in the
County of Hamilton and State of Ohio in the United States of America
Electrician.
PROVISIONAL SPECIFICATION left by the said Benjamin Joseph Barnard
Mills at the Office of the Commissioners of Patents on the 7th February
1882.
46
BENJAMIN JOSEPH BARNARD MILLS of the Firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent. IMPROVE-
MENTS IN ELECTRIC LAMPS." [A communication from abroad by William Maulsby
Thomas of Cincinnati in the County of Hamilton and State of Ohio in the
United States of America Electrician.]
This Invention is more particularly designed for thoso " arc electric lamps
whose electrodes are maintained at proper polar separation by direct attachment of
one of them to a soft iron armature or suction-core suspended within a coil or liclix
whose magnetism is dependant on the electric current.
Electric lamps of this kind of which those of Archereau and Gaiffe may be
considered types, have seldom passed beyond the domain of the lecture room
principally, it is believed, either because of the limited duration of their efficiency
or else of the too abrupt character of the automatic adjustment ("righting ") of the
electrode interval.
This defect is inherent in their construction, being an incident of the necessarily
variable magnetic potential of the coil in its constantly changing relations to the
core as the carbon shortens by consumption.
The present Invention overcomes the above difficulty by a contrivance hereinafter
described that maintains a uniform distance between the suction core and the place
of current-delivery of the coil.
In association with a carbon thus operated, it is preferred to employ a fixed
negative electrode, composed of or tipped with a highly refractory metal such, for
example, as iridium or one of the native alloys of that inetal
Such negative electrode being while in operation immovable and being moreover
practically indestructible, it follows that the positive electrode alone requires to be
invested with capacity for self adjustment and consequently the point of light

page_text: remaining in one place is available for focussing and like purposes, which
purposes are further subserved by the exceptional promptness and delicacy of self
adjustment of the arc-interval and consequent comparative steadiness and uniformity
of illumination.
The coil (helix) consists of a single layer of covered wire compactly wound.
The positive electrode is preferably composed of compressed lamp black or other
form of carbon such as customarily employed in arc electric lamps, and is attached
to a metallic stem preferably tubular to whose other extremity is secured a soft
iron core, whose occupancy of an electro magnetic coil that constitutes the
positive terminus of a dynamo or other suitable generator, causes the suspension
of the said electrode within the coil, whenever the electric fluid is in motion.
The proper height of suspension is secured by the following means.
The insulating wrapping or envelope is removed from one or more (preferably
two diametrically opposite) tracks upon the periphery of the coil and two
sliding shunts or conductors are held clastically in contact with these exposed
portions.
These conductors being attached to the stem of the positive clectrode and rising
and sinking with it, carry off the electric charge or current from their point of
contact and cut off or throw out of the magnetic field so much of the coil as
extends, for the time being beneath them.
To secure the highest possible sensitiveness of action, the contact of said sliding
conductors is preferably obtained by anti-friction whiccls.
The points of contact of conductors with the coil tracks, travelling slowly down
the latter, keeping pace with the diminishing carbon length, brings additional
convolutions within the magnetic field and secures a uniform and steady are by the
constancy of the magnetic action.
An increase of electrode interval such for example as occurs from the sloughing
off of burnt portions from the positivo electrode is of course accompanied by a
slackening of the electric current, with--consequent-reduction of magnetic force,
which yielding momentarily to the gravity of the electrode, the arc-interval
becomes lessened, the electrical resistance diminished and the current increased
until the positive electrode being thereby restored to its normal distance from the
negative electrode, a practically uniform light is obtained.
In addition to the above described automatic accommodation of the parts a
means of discretional adjustment of the relative heights of the suction core and the
sliding conductor enables the apparatus to be set at will to any desired arc average
for greater or less illumination.
A further means of discretional adjustment may consist of a controlable counter-
poise by which the effectual or virtual weight of the suction core and adjuncts may
be reduced to just sufficient for effectiveness.
This comparative levity of the electrode prevents the liability of injury to the
tips on sudden cessation of the current.
With the above principal features of the Invention may be associated one or
more other useful features hereinafter explained.
86
The positive wire from a dynamo" or other suitable generator connects by
binding post with a coil of insulated wire which is wrapped around a non magnetic
bobbin preferably a longitudinally split brass tube.
The ends of this tube are secured in collars of gutta percha, vulcanite or other
non conducting substance of proper strength.
The negative electrode employed is preferably inetallic and stationary and may
be of any suitable construction for example.
Depending from the lower collar is a pendant from whose pan there rises ver-
tically and in alignment with the coil a copper or other metallic post or column,
which post is tipped with iridium or with some other refractory alloy of that
metal.
The suction core or armature may be a cylinder of soft iron preferably tubular.
Screwed or otherwise securely fastened in the lower end of the core is a brass or

page_text: copper stem also preferably tubular which terminates below in a clamp that holds
the carbon constituting the positive electrode.
A bail on the core enables engagement of a cord which being carried over a
sheave terminates at its other extremity in a counterpoise which being loaded at
discretion has the effect of reducing the virtual gravity of the positive electrode to
the amount sufficient to balance the coil suction and thus secure the desired arc
interval in the normal condition of the apparatus.
Held by a set screw to the tubular stem is a brass cross bar from whose extremities
arise two rods of spring brass in whose suminits are journalled a pair of brass anti-
friction wheels which by virtue of the elasticity of the rods press moderately against
the periphery of the coil on diametrically remote sides thereof.
Along the narrow tracks traversed by the wheels the silk, cotton or other
insulating envelope of the wire is removed so as to leave naked the metallic surface
of the wire at that part and to bring the wheels in direct electrical communication
with the wire of the (for the time being) point of contact.
One side of the pendant communicates with a binding post on a collar which
connects by wire with another binding post on another collar from which post a
wire conducts to the negative electrophore.
The operation of the device is simple and obvious. The shunt wheels having
with their supporting frame been by means of the set scrow fixed at their proper
height relatively to the core and the counterpoise having been suitably loaded so
ns to diminish the virtual weight of the core and its appendages to that which
just serves to cause their descent at any relaxation of coil magnetism a connection
of the wires with the generator causes the positive current to flow and the positive
electrode to detach itself from the negative so as to create an arc interval.
Any wear or dislodgment of the carbon tip has the well known effect of
increasing the tension and decreasing the electric flow with corresponding reduction
of coil magnetism.
This permits the weight of the positive element to provail over the coil suction
until the two opposing forces-gravity and magnetism-being restored to equili-
brium the normal arc-distance is resumed.
So prompt and at the same time so delicate are these movements and counter
movements that the light is practically uniform.
Experimental tests show that the lower effective end of the coil, preserving a
constant relation to the core and the coil's magnetic activity being largely concen-
trated at what is for the time being its delivery end, a substantially uniformn
magnetic action is socured notwithstanding the change in virtual length or
magnetised coil
The above described preferred form of the Invention may be varied in non
essential particulars, for example.
While preferring for the reasons stated to employ a metallic negative electrode,
the right is reserved to substitute ope of carbon which may be shifted simul-
taneously with the positive by any of the automatic expedients now in use and
instead of the gravitating counter balance herein described, any proper equivalent
may be employed such as a compensating spring.
Furthermore, the transverse section of the belix wire instead of being circular
may be oblong, with its greatest dimensions perpendicular to the helical axis.
As the functions of the Invention may be discharged in connection with a single
contact wheel, but one such wheel and a single bared track may employed, the
duties of the other wheel then being simply that of a guide, but inasmuch as an
additional wheel and bared track secures the contact of one wheel before the other
has ceased contact a practically unbroken contact is obtained while the sensi-
tiveness of the automatic adjustinent is doubled.
The preferred number of contact wheels is two, but for still greater sensitiveness
three or more equidistant contact wheels may be employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Benjamin Joseph Barnard Mills in the Great Seal Patent Office
on the 4th August 1882.
BENJAMIN JOSEPH BARNARD MILLS of the Firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex Patent Agent. "IMPROVE-
MENTS IN ELECTRIC LAMPS." A communication from abroad by William Maulsby
Thomas of Cincinnati in the County of Hamilton and State of Obio in the United
States of America, Electrician.
This improvement is more particularly designed for those "are" electric lamps
whose electrodes are maintained at proper polar separation by direct attachment of
one of them to a soft iron armature or suction core suspended within a coil or helix
whose magnetism is dependent on the electric current.
Electric lamps of this kind of which those of Archereau and Gaiffe may be
considered types have seldom passed beyond the domain of the lecture room,
principally it is believed either because of the limited duration of their efficiency
or else of the too abrupt character of the automatic adjustment ("righting") of
the electrode interval.
This defect is inherent in their construction, being an incident of the necessarily
variable magnetic potential of the coil in its constantly changing relations to the
core as the carbon shortens by consumption.
The present Invention overcomes the above difficulty by a contrivance herein-
after described that maintains a uniform distance-between the suction core and the
place of current delivery of the coil.
In association with a carbon thus operated it is preferred to employ a fixed
negative electrode composed of or tipped with a highly refractory metal such for
example as iridium or one of the native alloys of that metal.
Such negative electrode being while in operation immoveable and being more-
over practically indestructible, it follows that the positive electrode alone requires
to be invested with capacity for self adjustment and consequently the point of
light remaining in one place is available for focussing and like purposes, which
purposes are further subserved by the exceptional promptness and delicacy of self
adjustment of the are interval and consequent comparative steadiness and
uniformity of illumination.
The coil (helix) consists of a single layer of covered wire compactly wound.
The positive electrode is preferably composed of compressed lamp black or other
form of carbon such as customarily employed in are electric lamps and is attached
to a metallic stem preferably tubular to whose other extremity is secured a soft
iron, core whose occupancy of an electro magnetic coil that constitutes the positive
terminus of a dynamo or other suitable generator, causes the suspension of the said
electrode within the coil whenever the electric fluid is in motion.
The proper height of suspension is secured by the following means:-
The insulating wrapping or envelope is removed from one or more (preferably
two diametrically opposite) tracks upon the periphery of the coil, and two sliding
shunts or conductors are held elastically in contact with these exposed portions.
These conductors being attached to the stem of the positive electrode and rising
and sinking with it carry off the electric charge or current froin their point of
contact and cut off or throw out of the magnetic field so much of the coil as
extends for the time being beneath them.
To secure the highest possible sensitiveness of action, the contact of said sliding
conductors is preferably obtained by antifriction wheels.

page_text: at c Figure 1 the silk cotton or other insulating envelope of the wire is removed
so as to leave naked the metallic surface of the wire at that part and to bring the
wheels in direct electrical communication with the wire of the (for the time being)
point of contact.
One side of pendant G communicates with binding post V on collar F which
connects by wire W with binding post X on collar E from which post a wire Y
conducts to the negative electrophore.
The operation of the device is simple and obvious. The shunt wheels U having
with their supporting frame S. T. been by means of set screw R fixed at their
proper height relatively to the core K and the counterpoise Q having been suitably
loaded so as to diminish the virtual weight of the core and its appendages to that
which just serves to cause their descent at any relaxation of coil magnetism, a
connection of the wires A and Y with the generator causes the positive current to
flow as indicated by the arrows and the positive electrode to detach itself from the
negative, so as to create an arc-interval.
Any wear or dislodgment of the carbon tip has the well known effect of
increasing the tension and decreasing the electric flow with corresponding reduction
of coil magnetism. This permits the weight of the positive element to prevail
over the coil suction until the two opposing forces gravity and magnetism being
restored to equilibrium, the normal arc distance is resumed.
So prompt and at the same time so delicate are these movements and counter
movements that the light is practically uniform.
Experimental tests shew that the lower effective end of the coil preserving a
constant relation to the core and the coils magnetic activity being largely concen-
trated at what is-for the time being its delivery end, a substantially uniform
magnetic action is secured notwithstanding the change in virtual length or
magnetized coil.
The above described preferred form of the Invention may be varied in non-
essential particulars, for example:--
While preferring for the reasons stated to employ a metallic negativo electrode,
the right is reserved to substitute one of carbon which may be shifted simul-
taneously with the positive by any of the automatic expedients now in use and
instead of the gravitating counter balance herein described any proper equivalent
may be employed such as a compensating spring. Furthermore the transverse
section of the helix wire instead of being circular as shewn may be oblong,
with its greatest dimensions perpendicular to the helical axis.
As the functions of the Invention may be discharged in connection with a single
contact wheel, but one such wheel and a single bared track may be employed, the
duties of the other wheel then being simply that of a guide but inasmuch as an
additional wheel and bared track secures the contact of one wheel before the other
has ceased contact, a practically unbroken contact is obtained while the sensitiveness
of the automatic adjustment is doubled. The preferred number of contact wheels
is two, as shewn, but for still greater sensitiveness, three or more equi-distant
contact wheels may be employed.
Claim is not made broadly to the employment of suction coils with shifting
magnetic fields nor the use of a counterpoise suction core having direct mechanical
attachment to the carbon holder nor is claim made to the association of a carbon
positive electrode with a metal negative electrode such expedients being old.
Electric lamps with insulated helices and conductors travelling along said helices
so as to shunt the current from the negative electrode into and out of the helix in
order to cause the magnetic field to shift in conformity to the movement of the
electrode regulated thereby, are also known to be old and are not claimed.
Having thus described the nature of the said Invention and the mode in which
the same is carried into effect I would have it understood that what I claim is
First. In combination with an electro magnetic helix connected at one end
with the positive wire from the generator and constituting the terminus thereof
one or more conductors which travel on naked tracks on the external peripheries

page_text: of the convolutions of the helix and have electrical connection with the positive
electrode and mechanical attachment to the suction core substantially as set
forth.
Second. In combination with an electro magnetic helix that constitutes the
terminus of the positive wire from the generator one or more conductors which
travel upon naked tracks on the peripheries of the convolutions and have electrical
connection with the positive electrode and direct mechanical attachment by means
of adjustable fastening R to the suction core substantially as set forth.
Third. In the described combination, the stationary negativo electrode J of
refractory metal, the stationary electro magnetic coil or helix C constituting the
terminus of the positive electrophore the positive electrode N one or more con-
ductors U that traverse naked tracks c. upon the peripheries of the coil convolutions
and which have electrical connection with the positive electrode and direct
mechanical attachment to the suction core substantially as set forth.
Fourth. In combination with the electro magnetic helix C, c the shifting
conductors U the positive electrode N and the suction core K the adjustable
counterpoise O. P. Q. substantially as set forth.
In witness whereof I the said Benjamin Joseph Barnard Mills have here-
unto set my hand and seal this Third day of August in the year of our
Lord One thousand eight hundred and eighty two.