IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1882

page_text: LETTERS PATENT to William Edward Ayrton, Professor of Technical Physics,
Fellow of the Royal Society, and John Perry, Professor of Mechanical
Engineering and Applied Mathematics in the City & Guilds of London
Technical College, Finsbury in the county of Middlesex for an invention
of IMPROVEMENTS IN ELECTRIC LAMPS.
PROVISIONAL SPECIFICATION left by the said William Edward Ayrton
and John Perry at the Office of the Commissioners of Patents on the
3rd June 1882.
WILLIAM EDWARD AYRTON Professor of Technical Physics Fellow of the Royal
Society, and JOHN PERRY Professor of Mechanical Engineering and Applied
Mathematics in the City and Guilds of London, Technical College Finsbury in the
County of Middlesex IMPROVEMENTS IN ELECTRIC LAMPS
The adjustment and feeding of our Lamps is performed through the agency of
an Electro-magnet rigidly attached to the upper part of a frame. The upper
Carbon-holder passes through the centre of the Electro-magnet which may be a
magnet of one or more coils, but we prefer to use one hollow cylindric coil with or
without a hollow wrought iron core. We use a frame work of any shape which
enables the carbons to meet and to be in the same straight line. There is a tube
partly of brass and partly of soft iron which is capable of sliding freely inside the
electro-magnet or solenoid. It carries a plate at one end, on which are placed two
little standards which act as hinges for two levers. The levers are L shaped at
their other ends and pass round the carbon-holder on the side remote from its
binge; the levers are slightly out of the horizontal and we find that although they
are small, their weight is sufficient to prevent the carbon-holder from falling
between them. It is easy to see that the Carbon-holder can move quite freely in
one direction, but is unable to move in the other direction, unless the tube, plate,
hinges & levers move with it. The tube, plate, hinges and levers carrying the
holder are hung by spiral springs from the framing and in the normal condition of
the lamp when the electric arc has been formed the downward suction of the tube

page_text: together with the weights of the movable parts just balances the upward pull of
the springs. A small increase in the magnetism of the solenoid causes a downward
motion of the tube and Carbon-holder. A small loss of magnetism causes an
upward motion of the tube and Carbon-holder. Now the electro-magnet is wound
with a coil of considerable resistance which acts as shunt to the Electric arc.
When the arc gets too long so that its resistance increases, more current passes
through the magnet or solenoid and the carbon falls, shortening the arc. It cannot
fall more than a very short distance, however, before the two little levers come in
contact with a stop which diminishes their grip and lets the holder slide inde-
pendently of the tube and plate. This is the feeding arrangement. Should the
light from any cause go out, the magnetism of the solenoid gets very great, the
carbon-holder falls rapidly until the Carbons touch. A strong current passes
through the carbons, very little Electricity passes through the shunt circuits; the
magnetism of the solenoid is weakened, and the springs lift the tube, and plate, and
carbon-holder through a distance which is easily adjustable at starting, and which
is the length of are required. We have described the arrangement as if the plate
and levers were on the upper side of the solenoid because this is a form which we
have found to work most satisfactorily but we have constructed & used a Lamp
in which the plate and lever arrangement is below the solenoid. Instead of acting
on the carbon-holder we in some cases act on the bare carbon itself without using
the carbon-holder.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Edward Ayrton and John Perry in the Great Seal
Patent Office on the 2nd December 1882.
WILLIAM EDWARD AYRTON, Professor of Technical Physics, Fellow of the
Royal Society, and JOHN PERRY, Professor of Mechanical Engineering and Applied
Mathematics, in the City and Guilds of London Technical College, Finsbury in the
County of Middlesex IMPROVEMENTS IN ELECTRIC LAMPS
The adjustment and feeding of our lamp is performed through the agency of an
electro-magnet rigidly attached to the upper part of a frame A B.
The upper
carbon-holder passes through the centre of the Electro-magnet which may be a
magnet of one or more coils but we prefer to use one hollow cylindric coil as on
sheet 2 with or without a hollow wrought iron core. In sheet 2 there is no core
shown. We use a framework of any shape which enables the carbons to meet and
to be in the same straight line. There is a tube partly of brass and partly of soft
iron which is capable of sliding freely inside the electro-magnet or solenoid. It
carries a frame CC at one end on which are hinges D and F for two levers DE
and F G. The levers are L shaped at the places H. and I and pass round the
carbon-holder or the carbon itself, each pressing against the carbon-holder on the
side remote from its hinge; the levers are slightly out of the horizontal and we
find that although they are small, their weight is sufficient to prevent the carbon-
holder from falling between them It is easy to see that the carbon-holder can
slide quite freely upwards but is unable to move downwards unless the tube frame
and levers move with it. The tube, frame, and levers carrying the carbon-holder
or carbon are hung by spiral springs JK from the framing, and in the normal
condition of the Lamp when the Electric arc has been formed, the downward
suction of the tube together with the weights of the movable parts just balance
the upward pulls of the springs. A small increase in the magnetism of the solenoid
causes a downward motion of the tube and carbon-holder. A small loss of
magnetism causes an upward motion of the tube and carbon-holder. Now the
electro-magnet is wound with a coil of considerable resistance which acts as a
shunt to the Electric arc. When the arc gets too long so that its resistance
increases, more current passes through the magnet or solenoid and the carbon falls,
shortening the arc. It cannot fall more than a very short distance, however, before
the two little levers come in contact with stops at E and G and this diminishes
their grip and lets the carbon slide independently of the tube and frame C―This
is the feeding arrangement. Should the light from any cause go out, the magnetism
of the solenoid gets very great, the carbon-holder falls rapidly until the carbons
touch, a strong current passes through the carbons; very little electricity passes
through the shunt circuit, the magnetism of the solenoid is weakened, and the
springs lift the tube, and frame C with the levers and carbon, through a distance
which is easily adjustable and which is the length of are required. The frame C
and levers may be on the upper side of the solenoid instead of the lower side as
shown in the figures. Having now described and particularly ascertained the
nature of our said invention and the manner in which the same may be practically
carried into effect, we beg to say that what we consider to be novel and original
and therefore claim as the invention secured to us by the hereinbefore in part
recited letters patent is
First. The use of a tube L M as moveable core of a solenoid or electromagnet,
partly of iron L N and partly of brass N M or other non-magnetic substance on
the end of which is the frame C on which are hinged two gripping levers
substantially as described.

page_text: Second. The form of Electro magnet substantially as shown in figure 2 sheet 1,
in which by the use of the iron pieces PR Q and US T we cause an intense
magnetic field to be formed in the space R S.
In Witness whereof we the said William Edward Ayrton and John Perry
have hereunto set their hands and seals, this second day of November in
the year of our Lord 1882.
W. E. AYRTON (L.S.)
JOHN PERRY (L.S.)