Improvements in Arc Lamps.
Year: 1895

page_text: Date of Application, 5th June, 1895
Complete Specification Left, 5th Mar., 1896-Accepted, 16th May, 1896
Improvements in Arc Lamps.
JOSEPH DEVONPORT FINNEY ANDREWS 45 Fulham Park Gardens
Fulham S. W. do hereby declare the nature of this invention to be as follows:-
My invention relates to the regulation and maintenance of the electric arc at
the most suitable length for lighting purposes with constant electric pressure but
under considerable changes in the strength of the current. A control of the
length of the arc is effected by an electro magnet having an armature which is
formed by means of an extension to act as a brake by magnetism and friction on
an iron wheel. Attached to this wheel on the same axis is another wheel over
which passes a band carrying the carbons one at each end of it fixed by suitable
holders which I guide in line with one another by tubes one for each carbon
through which they pass the lower tube preferably having a slot throughout its
length to permit of the band being attached to the holder. These tube guides are
suitably attached by brackets and screws to the frame of the lamp and the band
pulley being arranged above the tube the band of the upper carbon passes through
the centre of the tube. When the current passes through the electro magnet the
armature becomes magnetised by induction and is attracted to the iron wheel and
when it moves towards the magnet it rotates the wheel a sufficient distance to
strike the arc when the current is shut off the armature returns to its former
position by the exertion of a spring or weight. I may modify the above arrange-
ment by converting the wheel itself into an electro magnet in which case the
armature would effect the rotation of the wheel by being attracted to a fixed piece
of iron. When I require the lamp to work in series I arrange an electro magnet
having its coil in shunt to the electric arc so as to act in opposition to the magnet
previously described the coil of which was in series with the arc. To effect the
automatic adjustment of the arc lamp for different strengths of current I employ
another armature which would be attracted to the magnet in opposition to a spring
or weight which would be adjusted to prevent the armature approaching with the
smallest current at which the lamp is desired to work but when the current is
increased this armature will be attracted to the poles so as to partially close the
magnetic field and maintain it at the same strength as when the weaker current
was used.
When the current is again reduced this extra armature would release.
If a lamp is desired to work with more than two distinct strengths of current
two or more bridging armatures may be used to maintain the magnetic influence on
the adjusting armature of the arc constant. A finer adjustment to different
strengths of current may be obtained by attaching to the bridging armature an
arm which alters the adjustment of the spring of the adjusting armature when the
bridging armature moves to or from the pole the spring being provided with
suitable adjusting nuts or screws. O instead of attaching the spring to an
armature bridging the controlling magnet of the lamp I may employ a separate
magnet with an armature to act on the adjusting spring or weight if such be used
to regulate the lamp in which case I may not employ the bridging armature.
FAL T
1005

page_text: CUMI LETE SPECIFICATION.
Improvements in Arc Lamps.
JOSEPH DEVONPORT FINNEY ANDREWS, Electrical Engineer, 45 Fulham
Park Gardens, London, S. W. 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 rel.. es to the regulation and maintenance of the electric arc at the
most suitable length for lighting purposes with constant electric pressure but
under considerable changes in the strength of the current. A control of the
length of the arc is effected by an electro-magnet N. S. having an armature B.
which is formed by means of an extension C. to act as a brake by magnetism and
friction on an iron wheel D. attached to this wheel on the same axis is another
wheel H over which passes a band K carrying the carbons L. M. one at each end
of it fixed by suitable holders P. R. which I guide in line with one another by
tubes E. Fone for each carbon through which they pass, the lower tube preferably
having a slot throughout its length to permit of the band being attached to the
holder by means of an arm I. These tube guides are suitably attached by brackets
and screws to the frame of the lamp and the band pulley being arranged above the
tube the band of the upper carbon passes through the centre of the tube. To
facilitate the insertion of the bottom carbon into the holder, I arrange the arm J
carrying the bottom carbon holder tube to swivel in its bearing ( so that it can be
turned aside free from the top holder. When in position it is kept in line with the
top holder by a pin Q in a slot. When the current passes through the electro
magnet N. S. the armature B becomes magnetised by induction and is attracted to
the iron wheel D and when it moves towards the magnet it rotates the wheel
sufficiently to strike the arc; when the current is shut off the armature returns to
its former position by its own weight. For the purpose of adjustment the armature
is suspended by the spring X through the medium of the rocking frame Y. the
spring being attached by its upper end to an adjusting screw G and nut G¹.
To effect the automatic adjustment of the lamp to different strengths of current I
employ another armature U which would be attracted to the magnet in opposition
to a spring V, which would be adjusted to prevent the armature approaching with
the smallest current at which the lamp is desired to work but when the current is
increased this armature will be attracted to the poles so as to partially close the
magnetic field and maintain it at the same strength as when the weaker current
was used.
When the current is again reduced this extra armature would be
released.
If a lamp is desired to work with more than 2 distinct strengths of current
another bridging armature U₁ may be used to maintain the magnetic influence on
the adjusting armature of the arc constant. A finer adjustment to different
strengths of current may be obtained by attaching to the bridging armature an
arm W. which bears on a nut Z on the screw & so as to tension or relax the
spring X according to the variations of the current. Instead of attaching the
spring to an armature bridging the controlling magnet of the lamp I may employ a
separate magnet with an armature to act on the adjusting spring or weight, if such
be used to regulate the lamp in which case I may not employ the bridging
armature. When require the lamp to work in series I arrange an electro
magnet T having its coil in shunt to the electric arc so as to act in opposition
to the magnet previously described the coil of which was in series with the arc.
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 :-
1st. The regulation of the correct length of the electric arc by means of a

page_text: magnetic brake substantially as described and illustrated in the accompanying
drawing.
2nd. The contrivance for maintaining the adjustment of the arc constant under-
varying strengths of current by the application of an armature bridging the
magnetic field of the controlling magnet and by the addition of an adjustable-
spring actuated by the same armature on a separate armature or a separate
armature and magnet substantially as described and illustrated.
3rd. The arrangement of carbon holder guides by tubes substantially as described.
and illustrated.