IMPROVEMENTS IN ELECTRIC LAMPS AND IN ELECTRO-MAGNETS, APPLICABLE ΤΟ THESE AND TO OTHER ELECTRICAL PURPOSES"
Year: 1881

page_text: LETTERS PATENT to Joseph Devonport Finney Andrews, of No. 23, Regency
Street, Westminster, in the County of Middlesex, for an Invention of
"IMPROVEMENTS IN ELECTRIC LAMPS AND IN ELECTRO-MAGNETS, APPLICABLE
ΤΟ THESE AND TO OTHER ELECTRICAL PURPOSES"
PROVISIONAL SPECIFICATION left by the said Joseph Devonport Finney
Andrews at the Office of the Commissioners of Patents on the 7th April
1881.
JOSEPH DEVONPORT FINNEY ANDREWS, of No. 23, Regency Street, Westminster,
in the County of Middlesex. " IMPROVEMENTS IN ELECTRIC LAMPS AND IN ELECTRO
MAGNETS APPLICABLE TO THESE AND TO OTHER ELECTRICAL PURPOSES."
In the Specification of a Patent granted to me on the 11th June 1879, No. 2321,
I described electric lamps in which discs or plates of carbon were fixed at a little
distance apart parallel to each other, and the voltaic arc was presented at their
edges. In those lamps the electrical currents were conducted to and from the
centres of the carbons when they were of disc shape, and to and from corresponding
ends of the carbons when they were in the form of slabs or plates. According to
my present Invention in one form of disc lamp I employ two discs fixed parallel to
each other at a little distance apart, one of these carbons having a countersunk
central hole, and being connected to the conductors at its outer edge, while the
other carbon which has no hole is connected to the conductors at its centre. The
are then presents itself at the edge of the countersunk hole, and moves round it as
the carbon consumes, or may be made to revole round it by inductive action from
a neighbouring coil or magnet. Both carbons may have central countersunk holes,
and be connected to the conductors at their outer edges. When parallel plates of
carbon are used I connect these plates to the conductors at their opposite ends,
and I make one shorter than the other, so that the arc extends from the edge of
the shorter to the face of the longer carbon. One of the plates may be of different
density from the other, or either may be a compound plate consisting of two or
more layers of different densities or constitution. When carbon rods are used the

page_text: difference of density or constitution may present itself in successive concentric
layers. When two carbon plates are arranged, as described in my Specification
above referred to, the one plate fixed and the other or part of it on a frame pivotted
below, so that the upper edge of the moveable carbon plate can approach to or
recede from that of the fixed plate, I effect the kindling of the arc and the regula-
tion of the distance of the upper edges of the plates in the following manner:-In
the base of the lamp I fix an electro magnet, the core of which is divided
lengthwise into two parts, each somewhat less than a semicylinder. One of these
half cores is fixed, and the other is connected to the pivotted frame of the carbon
plate. The coil surrounding the two half cores is in the circuit of the lamp.
When there is no current a weight or spring keeps the two half cores nearly close
together, the upper edge of the two carbon plates being then in contact. When a
current passes through the coil and carbons the two half cores become magnetic,
and having corresponding poles next each other the moveable half core is repelled
from the other, and the edges of the carbon plates being thus separated the arc is
established. Should the carbons be too far apart the electro magnet becomes
weakened, allowing the half cores and the carbons to approach each other; or
should the carbons be too near the electro magnet acquires more power to cause
repulsion of the half cores, and they and the carbons become consequently separated.
An electro magnet having a divided core, as described above, is obviously applicable
generally in lieu of an electro magnet and armature, the moveable half core
operating as the armature repelled from the other half core when both are
magnetised by the passage of an electric current through the coil surrounding
-both. Instead of dividing the core into two parts lengthwise it may be divided into
a greater number of parts, which will repel each other when magnetised by the
passage of a current through the coil surrounding them. Two half cores may be
jointed together at or about their middle, like the two blades of scissors, in which
case the magnetic repulsion will cause them to open apart. When instead of discs,
plates, or slabs, rods of carbon are employed, I construct an electric lamp in the
following manner :-The upper carbon is held in a guide, in which it is free to
slide, but it is usually prevented from sliding downwards by the arm of a lever
pressed against it by a weight or spring. On the framing of the lamp is fixed an
electro magnet with spring armature, having an arm carrying a cam clutch, which
in the middle position of the armature leaves the carbon free, but which when the
armature moves from its middle position away from the electro magnet, in
obedience to the spring, or towards the electro magnet, in opposition to the spring,
clutches the carbon causing it to move down or up, as the case may be. The lever,
which is made by the weight or spring to hold the carbon in its guide, has an arm
against which the armature comes to bear when it moves to its extreme position,
thus releasing the carbon from the pressure of the weight or spring. The action of
the apparatus is as follows:-While the lamp receives no electricity the armature
is drawn back by a spring, releasing the pressure on the carbon, and lowering it
till it meets the lower carbon. When the lamp is put in circuit the electrical
current passing freely from the one carbon to the other, and also through the coil
of the electro magnet, kindles the lamp and also causes the armature to be attracted
towards the electro magnet. The armature, by its movement towards its middle
position having the carbon engaged in its clutch, raises the carbon, establishing the
arc between the carbons, and allowing the weight or spring again to press on the
carbon. If, owing to increased distance between the carbons the electrical resistance
is too great, the electro magnet becomes weakened, and the armature recedes from
it, lowering the carbon until the resistance is again diminished, and thus according
as the resistance due to distance between the carbons varies that distance is
automatically varied by the action of the electro magnet and its armature, so as to
maintain practical constancy in the voltaic arc. The cam clutch worked by the
armature may be of various forms. It may consist of a piece attached to the
armature lever, which piece is hollowed in one face to fit against the side of
the carbon, and has hinged to it a yoke embracing the other side of the carbon,

page_text: and kept in a horizontal position by springs. When by the movement of the
armature lever and hollowed piece the yoke is canted out of its horizontal position
either way, one or other of its edges bites the carbon and causes it to move with it.
According to another form the armature arm may have its end rounded to a
curvature of larger radius than the length of the arm from its fulcrum, so that
when the arm moves upwards or downwards from its middle position it bears
against the carbon, causing it to move with it; or the arm may carry two curved
cams, one or other of which clutches the carbon, and causes it to move upwards or
downwards with the armature lever, as the case may be.
When it is desired to retain the arc in one position the lower carbon may also
have a cam clutch connected to the armature of the electro magnet, so that both
carbons are moved simultaneously towards or away from one another, according as
the resistance of the arc is increased or diminished. When a number of electric
lamps are worked in parallel circuit from a general conductor I introduce into each
lamp circuit a resistance which comes into action at the moment of kindling the
lamp, and becomes automatically shunted out as soon as the lamp is kindled. For
this purpose I provide an electromagnet, the coil of which is connected from the
general conductor to earth, or to the return wire through a resistance. As long as
the lamp remains unkindled the armature of the electro magnet is attracted, but
when by the kindling of the lamp the electro magnet becomes weakened its
armature dropping makes contact which completes circuit direct from the carbon
to earth, or to the return wire, shunting out thereby the coil of the electro magnet
and the resistance.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Devonport Finney Andrews in the Great Seal Patent
Office on the 6th October 1881.
55
JOSEPH DEVONPORT FINNEY ANDREWS, of No. 23, Regency Street, Westminster,
in the County of Middlesex. IMPROVEMENTS IN ELECTRIC LAMPS AND IN ELECTRO
MAGNETS APPLICABLE TO THESE AND TO OTHER ELECTRICAL PURPOSES."
In the Specification of a Patent granted to me on the 11th June 1879, No. 2321,
I described electric lamps in which discs or plates of carbon were fixed at a little
distance apart parallel to each other, and the voltaic arc was presented at their
edges. In those lamps the electrical currents were conducted to and from the
centres of the carbons when they were of disc shape, and to and from corresponding
ends of the carbons when they were in the form of slabs or plates. According to
my present Invention in one form of disc lamp, as shewn in Fig. 1, I employ two
discs a and b, fixed parallel to each other at a little distance apart, one of these
carbons a having a countersunk central hole c, and being connected to the
conductors at its outer edge, while the other carbon b, which has no hole, is con-
nected to the conductor at its centre, or it may be at its edge, as shewn in Fig. 1.
The arc then presents itself at the edge of the countersunk hole, and moves round
it as the carbon consumes, or may be made to revolve round it by inductive action
from a neighbouring coil or magnet. Both carbons may have central countersunk
holes, as shewn in Fig. 2, and be connected to the conductors at their outer edges.
When parallel plates of carbon are used I connect these plates to the conductors at
their opposite ends, as shewn in Fig. 3, the one extending beyond the other, so
that the arc presents itself between the edge of the one and face of the other
carbon. One of the plates may be of different density from the other, or either
may be a compound plate consisting of two or more layers of carbon of different
densities or constitution. When carbon rods are used the difference of density or
constitution may present itself in successive concentric layers. When two carbon
plates are arranged, as described in my Specification above referred to, the one
plate fixed and the other or part of it on a frame pivotted below, so that the upper
edge of the moveable carbon plate can approach to or recede from that of the fixed
plate, I effect the kindling of the arc and the regulation of the distance of the
upper edges of the plates as shewn in Fig. 4. In the base of the lamp I fix
an electro magnet, the core of which is divided lengthwise into two parts a
and b, each somewhat less than a semicylinder. One of these half cores a is fixed
and the other b is connected to the frame c of the carbon plate, which frame is
pivotted at d. The coil surrounding the two half cores a and b is in the circuit of
the lamp. When there is no current the weight of the frame and upper half core
keeps the two half cores nearly close together, the upper edges of the two carbon
plates being then in contact. When a current passes through the coil and carbons
the two half cores become magnetic, and having corresponding poles next each
other, the moveable half core is repelled from the other, and the edges of the carbon
plates being thus separated the arc is established. Should the carbons be too far
apart the electro-magnet becomes weakened, allowing the half cores a and b and
consequently the carbons to approach each other; or should the carbons be too
near the electro-magnet acquires more power to cause repulsion of the half cores,
and they and the carbons become consequently separated. An electro-magnet
having a divided core, as described above, is obviously applicable generally in lieu
of an electro-magnet and armature, the moveable half core operating as the
armature repelled from the other half core when both are magnetised by the
passage of an electric current through the coil surrounding both. Instead of

page_text: dividing the core into two parts lengthwise, it may be divided into a greater
number of parts, which will repel each other when magnetised by the passage of a
current through the coil surrounding them. Two half cores may be jointed together
at or about their middle like the two blades of scissors, in which case the magnetic
repulsion will cause them to open apart. Fig. 5 is a longitudinal section, and
Fig. 6 a plan of such an arrangement applied as a galvanoscope. Within the coil a
is fixed a pair of half cores b, b, and on an index arm c pivotted between them is
fixed another pair of half cores d, d, which are repelled when a current is passed
through the coil, moving the index in the direction of the arrow.
When instead of discs, plates, or slabs, rods of carbon are employed, I construct
an electric lamp as shewn in section at Fig. 7, and in plan at Fig. 8. The upper
carbon a is held in a guide tube b; an electro-magnet c, having its coil in the
circuit of the lamp, has facing it an armature d, which is kept away from it by an
adjustable spring e. The armature has two arms f, between which is pivotted a
semicircular bush g, and a U shaped yoke h. A spring on the armatare lever
bears against the tail of the yoke h, tending to cant the yoke into an inclined
position, its canting movement being limited by a stop k. When the lamp is put
in circuit the armature d is attracted, the yoke h is canted, and so made to pinch
the carbon tube b, which it raises along with it, thereby starting the arc. When
owing to consumption of the carbon the resistance of the arc becomes too great, the
magnet closes attractive power, its armature d is withdrawn by its spring e, and
the yoke coming then to bear on the stop k becomes sufficiently released from its
grip of the tube b to permit the tube and carbon to slide a little downwards, and
thereupon the slight movements imparted to the armature and yoke by variations
in the resistance of the are vary the distance of the carbons as required for regula-
tion. Instead of employing a single clutch of the form shewn in Figs. 7 and 8, a
double one may be employed, as shewn in Fig. 9, the lower clutch yoke h¹ serving
to draw the carbon tube b through the upper clutch, the pivot of which has a little
freedom of movement in the slot of the arm f. This arrangement effects a more
regular and gradual feed of the carbon. Another form of clutch is shewn in
elevation at Fig. 10, and in plan at Fig. 11. In this case the armature lever f
carries a bush g, which loosely embraces the tube b, and has mounted in it two
cams l, l, which have arms m, m, drawn together by a spring n, but having their
movement limited by the stop k. The carbon tube is held with a certain degree of
tightness by a weighted cam lever o bearing against it. In case of the lamp being
extinguished the tail of this lever is moved aside by the armature d, and the tube b
is thus released from o, allowing the carbon to descend to contact with the lower
carbon. The action of the lamp provided with clutches of the kind described with
reference to Figs. 7, 8, 9, 10, and 11 is as follows:-While the lamp receives no
electricity the armature is drawn back by the spring, releasing the pressure on the
carbon guide, and lowering it till it meets the lower carbon. When the lamp is
put in circuit the electrical current passing freely from the one carbon to the other,
and also through the coil of the electro-magnet, kindles the lamp, and also causes
the armature to be attracted towards the electro-magnet. The armature by its
movement, having the carbon engaged in its clutch, raises the carbon, establishing
the arc between the carbons. If, owing to increased distance between the carbons
the electrical resistance becomes too great, the electro magnet becomes weakened,
and the armature recedes from it, lowering the carbon until the resistance is again
diminished, and thus according as the resistance due to distance between the
carbons varies, that distance is automatically varied by the action of the electro-
magnet and its armature, so as to maintain practical constancy in the voltaic arc.
When it is desired to retain the arc in one position the lower carbon may also
have a cam clutch connected to the armature of the electro-magnet, so that both
carbons are moved simultaneously towards or away from one another, according as
the resistance of the arc is increased. or diminished. When a number of electric
lamps are worked in parallel circuit from a general conductor I introduce into each
lamp circuit a resistance which comes into action at the moment of kindling the

page_text: lamp, and becomes automatically shunted out as soon as the lamp is kindled. For
this purpose I provide for each lamp an arrangement such as is shewn at Fig. 12,
1, 1, being the wires of the general circuit arc while the lamp is extinguished con-
nected through a resistance r and the coil of an electro magnet c, which in that case
keeps its armature d away from contact with e; but when the arc is started
between the carbons a, b, the diminished attraction of c fails to hold up d, which
making contact at e short circuits the current, which then mostly passes outside the
resistance r.
с
Having thus described the nature of my said Invention, and in what manner the
same is to be performed, I claim,-
First. The use for electric lamps of a disc having a central countersunk hole,
substantially as and for the purposes set forth with reference to Figs. 1 and 2.
Second. The arrangement of plate carbons herein described with reference to
Fig. 3.
Third. The use of a divided core for an electro magnet, so arranged that when
the magnet is excited the parts of the cone repel each other, substantially as herein
described with reference to Figs. 4, 5, and 6.
Fourth. The construction of electric lamp with carbon clutch arranged and
operating substantially as herein described with reference to Figs. 7 and 8, or with
the modified forms of clutch described with reference to Fig. 9 and to Figs. 10
and 11.
Fifth. The use in combination with an electric lamp of a resistance and electro-
magnet and its armature, arranged and operating as and for the purpose herein set
forth with reference to Fig. 12.
In witness whereof, I, the said Joseph Devonport Finney Andrews, have
hereunto set my hand and seal, this Sixth day of October, in the year of
our Lord One thousand eight hundred and eighty-one.