IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by John Scudamore Sellon and Henry
Edmunds at the Office of the Commissioners of Patents on the 6th May
1879.
JOHN SCUDAMORE SELLON, of Hatton Garden, in the County of Middlesex,
Metallurgist, and HENRY EDMUNDS, of the same Place, Engineer. "IMPROVEMENTS
IN ELECTRIC LAMPS."
This Invention relates, firstly, to that class of electric lamps in which the light is
obtained by the incandescence of a rod or wire of iridium in a closed circuit.
Owing to the great difficulty, if not impossibility, of making the iridium rods or
wires of an uniform gauge it is necessary to provide some means of adjusting and
regulating the energy of the electric current to each lamp in a circuit. Thus,
supposing threo lamps to be included in one circuit, No. 1 requiring for its perfect
incandesence a current equivalent to 20, No. 2, a current equal to 15, and No. 3,
one equal to 10, it will be obvious that a current that will secure the required
incandesence of the wire of No. 2 would fall short of the energy required for No. 1,
but on the contrary would supply sufficient energy to fuse the wire of No. 3.
To obviate this defect we propose to supply to all the lamps in a circuit the
maximum current required to secure the proper incaudesence of any one of the
lamps, and in such of the lamps as may not require the full current we connect
the two sides of the space bridged over by the incandescent wire by passing as
many fine wires from side to side as we may find necessary to carry over the
surplus current. By this means we are enabled to ensure in each lamp the exact
amount of energy required for its proper incandescence.
The second part of the Invention relates to lamps in which iridium, platinum, or
iridio-platinum wires may be used for producing the light, and consists of an
arrangement for closing the circuit and cutting out any lamp of a series before the
fusing point of the incandescent wire is reached.
In order to effect this object we mount the illuminating wire at the extremities
of two short posts or arms connected cach with one pole of the circuit. Bridging
over the space at the base of these posts is a spring blade which is capable of
closing the circuit and cutting out the posts with their illuminating wire. The free
end of this spring blade is held out of contact with the base of the adjacent post by
means of a fine tension wire pendent from the top of the post, and forming with
the spring a second circuit for the passage of the current from one post to the other.
When the energy of the current is in excess of the requirements of the lamps, and

page_text: the risk of fusing the illuminating wire is imminent, the tension of the pendent
wire will relax, and the spring blade will consequently fall, and making contact
with the base of the adjacent post will cut the lamp out of circuit.
Should however the illuminating wire become fused or accidentally displaced the
current will notwithstanding be maintained, as the tension wire will be instantly
fused, and the circuit closed by the descent of the spring blade.
It should be remarked that by fitting an adjusting screw immediately under the
spring blade such a delicate adjustment may be effected that on the illuminating
wire becoming overheated the lamp may be momentarily cut out of the circuit, thus
allowing the wire to cool down without a perceptible break in the light being
produced.
The Invention relates, lastly, to an arrangement of lamp in which two illuminating
rods or wires are used, the second one being brought into circuit on the fusion of
the first. In this lamp three posts or arms are employed for carrying the
illuminating wires, two of these being fixed posts, and the intermediate one
jointed.
This jointed post is fitted with a spring which gives it a tendency to move back
from the post with which it is connected by its illuminating wire. The wire in
this case will be provided with studs at its extremity to receive the strain which
will be put upon the wire by the jointed post. In rear of this jointed post will be
the second post, which is connected by a second illuminating wire with the first
fixed post. This post is insulated, and is fitted with an adjusting screw in line
with the first mentioned illuminating wire, and when by any accident the first wire
is fused the second wire will be brought into circuit, and thus the light will be
maintained.