IMPROVE- MENTS IN APPARATUS FOR ELECTRIC LIGHTING
Year: 1878

page_text: LETTERS PATENT to Charles William Siemens, of No. 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, for the Invention of "IMPROVE-
MENTS IN APPARATUS FOR ELECTRIC LIGHTING."
Sealed the 25th October 1878, and dated the 22nd August 1878.
PROVISIONAL SPECIFICATION left by the said Charles William Siemens at
the Office of the Commissioners of Patents on the 22nd August 1878.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in the
County of Middlesex. * IMPROVEMENTS IN APPARATUS FOR ELECTRIC LIGHTING."
My Invention relates to apparatus for producing electrical light by providing
graduated feed and automatic adjustment of the carbons employed for that purpose,
with means of supplying fresh carbons and of furnishing reversing currents.
At the tops of two insulated metal standards I fix metal tubes or troughs, which
may incline downwards and forwards so that carbon rods inserted in those tubes
would nearly meet in point in the middle of the front part of the apparatus. I
make these tubes or troughs rather massive so as freely to conduct electricity to
the carbons and to conduct away beat, and I extend them to very nearly the points
of the carbons, giving them nibs of platinum or other material which will not fuse.
At the end of each tube or trough next the light a spring, which may be of
platinum, is provided at the one side to press the end of the carbon against the
opposite side so as to give a certain amount of retarding friction. At the other end
of each tube or trough are mounted two or more sets of rollers, between which the
carbon rod is passed, being pressed between the rollers by the moderate pressure of
a spring or weight. These rollers are caused to revolve slowly by worin or other
suitable gear, driven by clockwork arranged at the base of the apparatus, the movo-
ment of the rollers giving a slow and constant foed forwards of the carbons as their
points become consumed.

page_text: When the electric current passes through the carbons always in one direction the
one set of rollers is driven faster than the other so as to give the one carbon a
quicker feed as it is more rapidly consumed. When alternating currents are
employed the feeding rollers are equally speeded, the consumptions of both carbons
being in that case approximately the same.
The clockwork which drives the feed rollers is provided with a flyer or pair of
flyers to regulate its speed, and on the rapidly revolving spindle of the flyors is
fixed an arm or friction wheel, immediately above which is a weight attached to
the middle of a thin strip of metal, such as iron, platinum, or copper, which is fixed
horizontally across from standard to standard of the apparatus, and is so adjusted
that the weight in its middle is just clear of the arm or wheel on the flyer spindle
when the carbon points are in proper relative position for producing the luminous
arc. If by their feeding movement they approach too near to each other, thereby
diminishing electrical resistance, the metal strip becomes heated by the passage of
more electricity through it, and expands in length so that the weight in its middle
descends and forms a stop to the revolving arm of the flyer spindle, or puts such
friction on the wheel that the clockwork movement becomes arrested or retarded,
and consequently the feed of the carbons is stopped or rendered slow until the
distance of their points becomes such as is suitable for producing the luminous arc.
The electrical resistance being thus again increased the metal strip becomes cooled
and contracted in length, the weight is lifted off the arm or friction wheel, and the
clockwork and feed thereupon go on as before.
When a friction wheel is employed a spring rubber is attached to the metal strip,
and this rubber becomes more or less pressed on the wheel, according to the greater
or less amount of current passing through the strip. In this case the flyers may be
dispensed with.
For providing a continuous supply of carbons I adopt the following arrange-
ment: The back end of each carbon is made with a countersunk hollow, and tho
front end with a conical point. As the carbon in the lamp advances so that its
back end approaches the foremost of the rollers the attendant serves the point of a
fresh carbon with a cement made of pasty caoutchouc solution, or of carbon powder
and adhesive gum, and inserts this carbon into the tube, pressing its gummed point
into the countersunk end of the previous carbon. Both carbons now advance
together, the point of the fresh carbon following up the termination of the con-
Bumed one.
In approaching the point of ignition the cement becomes hardened and
carbonised, uniting the two carbons into one continuous conductor.
Instead of making the carbon points meet each other directly I arrange their
guide tubes so that the one carbon would if extended beyond its tube just pass at
the side of the other carbon if it were extended likewise. The consumption of the
carbon has then the effect of producing a concave hollow near the point, which by
reflection increases the amount of light omitted in the forward direction.
As in order to get equal consumption of both carbons it is of advantage to
employ alternating currents, I provide for obtaining these from dynamo-electric
machines such as usually are employed to produce constant currents of one direc-
tion. I effect this by placing on the rotating axis of the machine a commutator,
consisting of successive plates connected respectively and alternately to the
electrodes of the machines, and having a pair of tangent wire brushes bearing
against them, these brushes being connected respectively to electrodes for the
external circuit. As the axis revolves bringing its alternate positive and negative
plates in contact with the brushes, the current in the external circuit is reversed,
the rapidity of reversal depending on the number of plates and speed of the
commutator.