Improvements in Covered or Insulated Electric Cables or Conductors and a Compound therefor.
Year: 1890

page_text: Date of Application, 1st July, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
Improvements in Covered or Insulated Electric Cables or Conductors
and a Compound therefor.
I JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this Invention which has been
communicated to. me from abroad by John Haven Cheever of New York City in
the County and State of New York United States of America Manufacturer and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
This Invention has reference more particularly to the tube or sheath constituting
the outside covering and protection to the enclosed wire or group of wires forming
an electric cable or multiple electric conductor.
Hitherto such sheath or covering has been usually formed either of lead or of a
rubber compound. The general demand is for a lead encased cable which is regarded
as of superior merit. The manufacture of such cables moreover is easily carried on
owing to the facility with which the lead casing can be applied by the well known
operation of a pipe press.
A rubber covering cannot be applied with certainty in the same way since it lacks
those properties which enable lead to be easily worked. Ordinarily the rubber
coverings are applied by winding a strip of unvulcanized compound spread on a
backing of cloth around the cable and then vulcanizing.
The object of the present invention is the production of a cable covered with a
vulcanizable compound, having the appearance and desirable properties of a lead
tubing and having also other advantageous characteristics that do not appertain to
that metal.
The compound which I employ is composed of rubber plumbago asbestos and
sulphur preferably in the proportions of eleven parts by weight of rubber nine parts
by weight of plumbago nine parts by weight of asbestos and two parts by weight of
sulphur.
The materials are mixed together which may be effected in any suitable mill so as
to produce uniformity in the mass and after application to the exterior of the
conductor as hereinafter pointed out the compound is vulcanized in a manner well
understood.
The compound described resembles lead in the important respect that it may with
facility be applied to a cable by the operation of the core and die of a pipe-press,
thus producing a continuous, seamless sheath of any desired length composed of a
rubber compound a product which heretofore it has been difficult to realize in practice.
Moreover after being squeezed through the die of a pipe press the surface of the
compound acquires a metallic lustre which resembles that of a lead pipe.
This compound has the property of high electrical resistance and is not subject to
corrosion. It is also capable of resisting a high degree of heat, which, in a coating
for conductors used to convey high tension currents, is very desirable. In these
respects the compound is superior to lead for the purposes of the Invention.
The proportions of the several ingredients are given above by way of example as
producing a compound which is very effective as a cable covering but it will be
understood that the said proportions may be somewhat varied without departing from.
the nature of the invention.
Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. As a covering for electric conductors or cables the within described compound

page_text: of rubber plumbago asbestos and sulphur combined in the proportions or in sub-
stantially the proportions herein before set forth.
2. An electric cable having a continuous seamless covering composed of rubber,
plumbago asbestos and sulphur substantially as hereinbefore described.
Dated this 1st day of July 1890
J. H. JOHNSON & Co.