Improvements in Arc Electric Lamps.
Year: 1890

page_text: Date of Application, 17th Oct., 1890-Accepted, 22nd Nov., 1890
COMPLETE SPECIFICATION.
Improvements in Arc Electric Lamps.
I JAMES EGLINTON ANDERSON GWYNNE of Victoria Embankment Essex Street in
the County of Middlesex Civil 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 :-
The object of this invention is to produce an electric arc lamp which may be
cheaply made, and also efficient in action, and said invention constitutes an improve-
ment upon the lamps described in and by the Specifications of Letters Patent granted
to Charles Denton Abel, No. 1397 of A.D. 1880, and to William Robert Lake
No. 2712 of A.D. 1882. A method of construction is defined therein, according to
which the upper carbon is carried by the moveable core of a solenoid. According to
my invention, I adopt the same principle broadly but have modified the construction
in order to attain the objects as hereinbefore set forth.
In order that my invention may be the better understood I have appended the
accompanying sheet of drawings in which
Figure 1 is a partly sectional elevation of the preferred form of the lamp according
to my invention and
Figure 2 is a plan view of the same with the top plate or cover removed.
Figure 3 is an elevation of a core designed to act as an automatic brake and
Figures 4. 5 and 6 are cross sections of cores intended to be employed for the same
purpose.
Figure 7 is a section of a guide bush which also may be used as a regulator or
brake.
In carrying my invention into effect I employ a long solenoid A which may consist
of two separate windings, one of low resistance in series with the main circuit, and
one of higher resistance placed as a shunt, the magnetic induction of which tends to
neutralise the effect of the series winding. It is perfectly immaterial so far as the
action of the separate windings relatively to each other is concerned which of them is
placed nearest to the core, although in practice it is better to wind the shunt
wire over the layers of series wires. The solenoid A is wound upon a parallel
tube B the ends of which may project beyond the flanges for purposes of attach-
ment. A parallel or approximately parallel iron core E which may be solid or
tubular is arranged to slide freely within the tube B and said core carries the upper
carbon F by means of a suitable clip or holder attached to the lower end thereof. The
core is arranged in such a manner that when the entire length of carbon is
adjusted a clearance corresponding to the maximum length of the arc is left, so
that the attraction of the solenoid when in operation may strike the arc by lifting
the core.
In a focussing lamp such as the one chosen for illustration it is necessary
to provide means for raising the lower carbon so that the position of the arc remains
constant until the carbons are entirely consumed. I accomplish this by passing one
or more cords or flexible metallic connectors c c¹ over a pulley or pulleys 66¹ one
end of each cord or connector being attached to screw clips upon the lower
extremity of the core E and the other end to a rod G carrying the lower carbon H.
It is preferable however to employ two rods G. G supporting the lower carbon H by
means of a suitable holder I attached to a cross bar J. The carbon holder I be
provided with screws or other suitable device for the proper alignment of the are
when necessary. A similar arrangement may also be fitted upon the upper carbon
holder if desired. The pulleys bb' may be pivotted between the extensions of a pair
of clips d' which are adapted to fit the solenoid and yet allow the wheels bb₁ to
revolve freely. A similar pair of clips d carry the terminals e, e¹, both of which are
may

page_text: electrically insulated. A screwed cap f is screwed upon the extension of tube B
which passes through the cover preferably insulated therefrom, and the suspension
ring g or equivalent device may be attached thereto so that the actual weight of
the lamp is not dependent upon the cover or case. In order to ensure a perfectly
uniform line of feed, independently of any motion of the lamp, which may occur
in high winds, on shipboard and under similar circumstances I prefer to employ
guide tubes which are attached to the base plate but insulated therefrom, and are
fitted to the guide rods G. G. in such a manner that these may slide freely without
appreciable friction.
Now in the Specification of Letters Patent No. 2712 of A.D. 1882 hereinbefore
referred to, an iron core is described which is directly attached to the upper carbon
without the intervention of gearing levers or clockwork escapements and in order to
'effect the regulation of the lamp the magnetic mass of said core varies in proportion
to the ratio of the feed and current strength, in other words said core is made tapering
from end to end and passed through the magnetic centre of a comparatively short
solenoid. In a lamp constructed according to my improvements as herein set forth I
produce the same effect by employing a long solenoid A which is suitably wound and
the electrical resistances of the two windings are carefully balanced so as to meet the
requirements of any particular case of application. The highest position of the
parallel core within the solenoid when carrying an upper carbon which touches
the lower carbon both of full length relatively to the calibre of the lamp, leaves
sufficient clearance for the magnetic action of the solenoid to strike the are and the
subsequent descent of said core is dependent upon the variations of the magnetic force
or in other words is always proportional to the ampere turns thereof. Therefore in
my improvements I am enabled to dispense with a tapering core or a step wound
solenoid but I find that it is necessary to provide a magnetic brake or mechanical
check for destroying the momentum of the impulses imparted to the core whilst
feeding and preventing that intermittent action which in electric are lamps is usually
terined "pumping." I effect this object by destroying the uniformity of the magnetic
mass of the core and causing the magnetic lines of force to be distorted, so that a
frictional check is naturally imposed upon the feed said check being always pro-
portional to the current passing around the helices forming the solenoid. The core
may be slit at its upper extremity as shewn by the elevational view Figure 3, that the
two segments' so formed may expand by magnetic repulsion and grip the interior
surface of the solenoid tube or a longitudinal groove may be cut in the core as shewn
by S in the cross section Figure 4. As alternative means for effecting the same
object I may refer to the cross sectional views Figures 5 and 6 which represent
a non magnetic insertion j and an iron wire or other longitudinal projection k
respectively.
Or I may employ a bush for the base plate through which the core E passes, said
bush having a magnetic segment m as shewn by Figure 7. A further modification of
the brake as described may consist in the insertion of a magnetic segment in the
solenoid tube B Figure 1 or one or more pieces of iron wire placed so as to con-
centrate the lines of force upon one side of the solenoid and its core to produce a
frictional check thereon.
more
I also as an auxiliary check may provide a core with a screw thread formed
upon its external surface throughout the length thereof and attach one or
balanced pawls n by means of free pivots in brackets o fixed upon the base plate L.
An extension p enables the pawl to be released if necessary and a vertical or diagonal
play or freedoin of motion is provided upon the pivot, so that the screw thread upon
the core engaging with the pawl allows said core to rise sufficiently to strike the are,
an adjustable balance weight a allowing of certain regulation. If two pawls are
employed the arrangement is preferably such that the limit of the upward vertical
movement is equal to half the pitch of the screw thread upon the core.
When employ a tubular core as herein before referred to, I may utilise the hollow
space thereof for carrying an additional length of upper carbon which may be fed
downwards when the portion which extends below the holder is consumed.

page_text: 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;
First. In an improved are electric lamp the employment and construction of a
parallel or approximately parallel solid or tubular moveable core, rigidly fixed to the
carbon holder in combination with a differentially wound solenoid, and with a magnetic
brake, or mechanical check substantially as described and shewn by the drawings.
Second. In an improved are electric lamp the construction of solenoid cores to act
as magnetic and frictional brakes, as herein described and shewn by Figures 3. 4. 5
and 6 of the accompanying drawings.
Third. In an improved are electric lamp as referred to in the preceding claims, the
employment of an externally screwed core in combination with balanced pawls sub-
stantially as herein described and shewn by the drawings.
Fourth. In an improved are electric lamp the construction and use of clips d d'
Figures 1 and 2 for carrying the pulleys and terminals, substantially as and for the
purposes described with reference to the drawings.
Dated this Fifteenth day of Outoher One thousand eight hundred and ninety
FREDK. WALKER,
11, Furnival Street, Holborn, London, E.C., Agent for the Applicant.