Improvements in Electric Arc Lamp Mechanism.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electric Arc Lamp Mechanism.
GERALD PERCIVAL, 30, Old Georges Street, Cork, Electrical Engineer, I do
hereby declare the nature of this invention to be as follows:-
-
The supporting of one or both the carbons, between which the electric arc is to
be formed by a float or floats so arranged that a part of the float or floats is always
submerged in the liquid in which it floats, a further portion projects to the outside
of the liquid such float in its simplest form resembling a hydrometer for taking
specific gravity of liquids. The float being so weighted and its stem so proportioned
that in conjunction with a solenoid & core or equivalent magnetic device & acting
upon them the length of are when the lamp is at work is maintained within the
required limits. The floating portion of the arrangement when extra range of
action is desired being itself supported on a second float giving a telescopic arrange-
ment. In some cases the second carbon may be attached to a cord & pulley
arrangement connected to the first carbon holder or equivalent mechanism for
giving an increased range of motion or keeping the arc at a uniform height. The
arrangement being such as to have little tendency to jamb or stick when in action.
Dated this 7th day of April 1897.
GERALD PERCIVAL,
30, Old Georges Street, Cork, Electrical Engineer.
GERALD PERCIVAL, 30, Old Georges Street, Cork, 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:
My invention consists in the supporting of one or both the carbons between
which the electric arc is to be formed by a float or floats so arranged that part
of the float or floats is always submerged in a suitable liquid this portion being
of such size and buoyancy as to give the necessary support to its self and the parts
[Prise 8d.1

page_text: attached to it, and a further portion which projects to the out side of the liquid.
This portion being of such form and section at each point in its length as to
yield when immersed the necessary support to the carbon it supports and to the
parts attached to it, the combination of the two portions in the simplest form
resembling a hydrometer such as is commonly used for taking specific gravity of
liquids, consisting of a bulb or float and ballast weight both immersed in liquid
and a stem partly immersed, being in all cases so far as possible constructed so
as to float with the stem vertical, to avoid unnecessary friction in any guide
required to keep it in line with second carbon of lamp. In a lamp of the simplest
form the float is made of such volume as when immersed in the liquid in which it
is to work, to just support the weight of ballast, stem & carbon-holder, and the
stem of such cross-section, that when a carbon is placed in the carbon holder on
top of stem the whole arrangement sinks a certain ammount in the liquid, if the
carbons are of such size that they burn away equal lengths in the same time the
section of stem should be such that one inch of the carbon it supports will sink
the arrangement. two inches, if one carbon burns twice as fast as the other the
sinking must be three inches for one of carbon if it supports the slow burning
carbon but only one and a half inches if it supports the quick-burning carbon,
and in similar proportion for other rates of burning, such float stem & carbon is
supported in a vessel containing suitable liquid, and having a support for the
second carbon vertically over the floating carbon-holder, and insulated from it
current being supplied to the carbons and an are struck between the carbons it
will be maintained between them and the carbons automatically approach as they
burn, provided a considerable margin of pressure or "PD." be allowed on the
supply circuit over and above that actually required by a short arc, the initial
striking of the are being done by hand, or by any ordinary arc striking device.
For lamps required to give as constant a light as possible I use one or other or a
combination of the following devices. For a lamp using short carbons, I use an
iron core usually tapered attached to the underside of the float depending from
it and forming the ballast weight and surrounded for a part of its length by a
solenoid carrying either the current which passes through the arc or a current
shunted from the arc, and wound with suitable wire, or the solenoid may be wound
with a compound winding and carry both currents the core being only slightly
entered by its small end into the solenoid when the lamp starts being so positioned
as to be drawn upwards if the solenoid is shunt wound and downwards if series
wound, the variations in pull on the iron core being compensated for by either
varying the section and consequently the floating tendancy of the stem of the
hydrometerlike arrangement, so that the floating tendancy and the pull of the
solenoid on the core shall be in equilibrium at all points of the stroke of the core.
When the proper current is flowing in the solenoid, I usually obtain the right
form of the stem of the arrangement by constructing a stem uniform and some-
what too small, in the first instance and then adding collars to increase its section
as may be required at different parts, and from the diameter and position of these
plotting out the required form for the exterior of the permanent stem. When
the arrangement described would be inconvenient, I compensate the variation in
pull of the solenoid by arranging a series of small weights hung on cords or
chains at different hights which the float in riseing lifts these weights being such
as to compensate for the increase at each point.
When it is necessary that the position of the arc should be constant I support the
second carbon in a holder on a chain or cord over a pulley connected through an
insulator with the lower carbon holder, two or more chains or cords & pulleys may
be used to avoid side strains, in which, case, I usually provide a ring of metal or
porcelain for the carbon to pass through at a short distance from the arc to ensure
centrality.
In the form of lamp described the carbons are above the float and the containing
vessel, but in lamps with the carbons below the body of lamp a crosshead may be

page_text: attached to the top of stem of floating part and a pair of rods dependant from it
reach down out side the containing vessel and support the carbon holder.
In the telescopic or long range lamp, the simple form of float stem and carbon
holder bolasted to float upright is contained in a vessel having a float at its upper
part, and this vessel is also contained in an outer vessel both vessels being filled
with liquid to the right hight, the inner vessel having a core of iron depending
from it, into a tubular continuation of the outer vessel in which it is free to move
up and down, this tube being surrounded at a suitable height by a regulating
solenoid, usually compound wound. The float at upper part of this vessel has a
portion usually of reduced diameter projecting above the liquid in outer vessel,
this projecting portion being more or less immersed according to position of core
in solenoid, is made of such section that at all points of the working range of its
motion, it is in equilibrium when the proper current is flowing in the solenoid.
The vessel rising when too little or no current is passing bringing the carbons
together, and when the are current flows the solenoid pulls the core until an
equilibrium is obtained. The lower carbon as it is consumed rising with its float,
irregularites being compensated by rising and falling of inner containing vessel
actuated by its core & solenoid.
Care must be taken that the float or floats are of permanent and reliable form
& material such as not materially to change their form or specific gravity in relation
to the liquid, either with changes of temperature or pressure.
Various liquids may be used such as water, glycerine, or a mixture of the two,
or oil, &c. The latter is particularly suitable if the lamp is to be used with an
enclosed arc.
The moving carbon holders should be connected to the supply terminals by very
flexible conductors, or by a wire dipping in mercury, such part of the weight of
these as may be supported by the float, being allowed for in adjusting its floating
power.
In the drawings Fig. 1 represents a section of the simple form with a tapered
iron core I with its small end upward and surrounded by a shunt coil W, at its
upper end, this upper end being attached to the lower side of float F by its lower
stem S the float having a parallel upper stem S projecting above the liquid and
carrying the carbon holder H and carbon C the compensation for variation in pull
of solenoid on core being obtained by the chains & weights L at different heights
as shown, is the containing vessel, and Y the flexible connection between
terminal T on vessel & stem S.
Fig. 2 represents the telescopic form, the parts FSH & B, being the float, stem,
carbon holder, & ballast, to float upright V. A the vessel containing them and
having the float V at its upper part and a projecting part P and a core of iron I
from it, all contained in the outer vessel having a tubular continuation X to
contain the iron core I and surrounded by the solenoid W in this case shown as
series wound.
Drawings are in proportion which may be used, but not to scale, as actual size
depends on length of carbons to be consumed, and number of amperes lamp is to
burn with.
The supports for upper carbon holders are not shewn, as these may be any con-
venient form, and in Fig. 1 the connections of shunt coil are shown diagramatically
by lines K.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The supporting of the carbons in an arc lamp by a float or floats constructed
substantially as described.
2. The controlling of such floats by means of solenoids & cores.
3. Compensating for variations by varving the section of float stem.

page_text: 5. The combination of any or all these devices substantially as described and
for the purposes set forth.
Dated this 7th day of February 1898.
GERALD PERCIVAL,
30, Old Georges Street, Cork, Electrical Engineer.