Year: 1886

page_text: 1, WALTER ROBERT JOHNSTON of Qu Appelle North West Territories Canada,
Electrical Engineer do hereby declare the nature of this invention to be as follows:-
My invention relates to an arc electric lamp of the following kind. The one carbon,
the negative, which consumes less rapidly than the other, is a straight rod projecting
down from a clamp or holder. The other or positive carbon is made about double
the length of the negative, to allow for its more rapid consumption, and, in order to
accommodate this increased length within the same height as the negative carbon, it
is made in the form of a helical rod extending down with it to the same length
making several convolutions around the central rod but at a little radial distance from
it, that distance being such as is suitable for the arc. The two carbon clamps being
connected in a circuit, and momentary conduction being made from the lower
extremity of the one rod to that of the other, the arc is started between these
extremities, and afterwards it goes on gradually consuming both carbons at the same
rate in respect of height. In order to ensure the maintenance of the are at the
extremities of the carbons so that it shall not pass from the one to the other at some
other place, I prefer to coat the outer surface of the helical rod with metal such as
copper, so as to give good conductivity down the whole length of the helix along that
part of it which is farthest from the central rod, and so to convey the current quite to
its extremity. Any known switch or cut off may be applied to short circuit the
current when the carbons become consumed nearly to their clamps or holders.
1007
ABEL & IMRAY,
28, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: An Improvement in Arc Electric Lamps.
I, WALTER ROBERT JOHNSTON of Qu Appelle North West Territories Canada,
Electrical Engineer 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 relates to an are electric lamp of the following kind. The one carbon,
the negative, which consumes less rapidly than the other, is a straight rod projecting
down from a clamp or holder. The other or positive carbon is made about double the
length of the negative, to allow for its more rapid consumption, and, in order to
accomodate this increased length within the same height as the negative carbon, it
is made in the form of a helical rod extending down with it to the same length making
several convolutions around the central rod but at a little radial distance from it, that
distance being such as is suitable for the arc. The two carbon clamps being connected
in a circuit, and momentary conduction being made from the lower extremity of the
one rod to that of the other, the arc is started between these extremities, and after-
wards it goes on gradually consuming both carbons at the same rate in respect of
height. In order to ensure the maintenance of the arc at the extremities of the
carbons so that it shall not pass from the one to the other at some other place, I prefer
to coat the outer surface of the helical rod with metal such as copper, so as to give
good conductivity down the whole length of the helix along that part of it which is
farthest from the central rod, and so to convey the current quite to its extremity.
Any known switch or cut off may be applied to short circuit the circuit the current
when the carbons become consumed nearly to their clamps or holdors.
The helical carbon rod may be produced either by helically coiling a carbon rod
while in a plastic condition and then rendering it rigid by heating, or by moulding
the plastic material in a helical mould in which it is subjected to the requisite heat for
rendering it rigid as described in the Specification to my application for Letters
Patent No. 8156 dated 19th June 1886.
I am aware that it has been proposed to twine a flexible carbon rod helically
around a cylindrical core of carbon with insulating material interposed between the
core and the helix, and to carbonise the whole. I therefore make no general claim to
such a form of electric lamp but having now particularly described and ascertained
the nature of this invention and in what manner the same is to be performed I declare
that what I claim is :-
The use in electric are lamps of a rigid helically coiled positive carbon rod
surrounding a straight negative carbon rod, the two rods being made of equal
diameters and the helical rod being coiled to such pitch that in consuming, its
extremity will always remain in the same plane with the extremity of the straight rod
so that the electric arc will pass from the extremity of the one to that of the other
substantially as herein described.
ABEL & IMRAY,
Agents for the Applicant.