IMPROVEMENTS IN THE INSULATION OF WIRES AND OTHER ELECTRIC CONDUCTORS USED FOR THE PRODUCTION AND TRANSMISSION OF ELECTRIC CURRENTS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office of
the Commissioners of Patents on the 19th August 1882. Communicated to
him from abroad by I. M. Hirsch of the City of Chicago in the County
of Cook and the State of Illinois United States of America
JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman IMPROVEMENTS IN THE INSULATION OF WIRES AND OTHER ELECTRIC
CONDUCTORS USED FOR THE PRODUCTION AND TRANSMISSION OF ELECTRIC
CURRENTS a communication to me from Abroad by I. M. Hirsh of the City
of Chicago in the County of Cook and the State of Illinois United States of
America
"
The said Improvements are two fold and relate firstly to wires to be used in the
construction of dynamo electric or such electric machines as are subjected to an
elevation of temperature by reason of resistance to the current in the wires of such
apparatus or from other causes. This heat gradually or suddenly as the case may
be destroys all ordinary insulation while the improved insulation is not destroyed,
nor is its insulating power even permanently diminished by the application of heat
of such intensity as would completely destroy the ordinary insulation. The second
improvement relates to wires used external to electric machines and to conductors
of currents of electricity above and below earth or water-Conductors of Electric
currents insulated according to this improved method may safely be placed into
the ground or water they may be used for Ocean Cables or air lines without danger
of losing the current into the ground or water by leakage and without danger from
excessive induction. For this last reason a great number of wires can be placed in
one Cable which may be used for telephoning or telegraphing without danger of
interference of one wire with any other as is the case at present or for other
electric currents of greater volume
According to the first improvement there is taken in the first place mineral
gelatine of the formula Si O. H. O which is prepared from any silicious solution by
neutralisation with acids in liquid form at the ordinary temperature or by fusion
at a white heat with Si O or with alumina. In the first case any excess of acid
used for neutralising is carefully avoided in the second instance the fused mass is

page_text: agitated with boiling water which dissolves the mineral gelatine and leaves the
excess of Si O and Alumina undissolved. This gelatinous solution so obtained is
placed in a tank containing a drum or pulley over which the wire to be insulated
is passed either by hand or preferably by machinery at such a speed that it
will coat itself with and carry along a coating of the gelatine of the desired
thickness.
It is preferred to pass the wire from the drum in a vertical direction for a
considerable distance (say about thirty to One hundred and fifty feet) in order to
allow all surplus gelatine to flow back downward into the tank without rendering
the surface of the coating irregular by drying drops of gelatine The space through
which the coated wire passes is heated and for this purpose it is preferred to pass
the wire upward through a pipe into which hot air is carried which dries the
coating before it reaches a second pulley or drum of large dimensions over which
the wire passes into a second tank, containing like the first tank a large drum or
pulley over which the coated wire is drawn-This second tank is filled with a
solution of Sulphur cresol rosin and crude paraffin in methylic alcohol containing
suspended sulphur ground glass or fine sand all in a state of fine division or by
preference pulverised mineral wool treated with acids for the complete removal of
all traces of metal or oxide in the same.
The relative proportion of these substances may be varied the object of this bath
being the production of a waterproof coating to protect the first insulating layer
Both these Baths may be applied to wire naked or covered with cotton or other
fibre in the ordinary way-The second bath not only produces an elastic coating
but possesses in itself high insulating power The sulphur present in this second
solution dissolved as also suspended besides insulating has another office, namely,
to combine with any excess of alkali which perchance has escaped neutralisation
and would impair its insulating quality-In employing silicates as Insulators the
power or degree of insulation is increased with the diminution of alkali in the
compound The sulphur also aids the cresol in preventing the danger to the cable
from insect life which (the Hylophaga) has been destructive to other cables-The
wire after passing the second bath described contained in a closed tank to prevent
volatilisation of the solvent passes again through a tube or worm space in a vertical
direction, so as to dry before being wound upon a large drum or directly upon the
coils of dynamo or other machines.
The second part of the Improvement in insulating electric conductors consists
in addition to this first treatment as described in the application of one or more
layers of insulated solenoid tape which is prepared in the following manner.
Tape strips of cloth or twine of any fibrous tissue (by preference mineral fibre
is used) are first passed over drums or pulleys through the two baths hereinbefore
described. The saturated strips of cloth, tape or twine, are then (before drying
them) passed over rollers which coat one side of such tape strips of cloth or twine
of any fibrous tissue with finely powdered graphite or some metal in a state of
fine division like bronze powder Any metal will answer finely powdered graphite
is preferred although tape upon which an exceedingly thin film of metal was
galvanically deposited has been found to give very good results-Tape thus
prepared is upon one side a conductor while its body and other side is well
insulated and at the same time waterproof It has been found that by winding
such tape around a wire or other Conductor of Electricity almost at right angles
to the wire any current which the primary current would be capable of inducing
would be induced in this "solenoid tape" and that if the number of layers of this
solenoid be multiplied alternating the direction of the winding of this tape namely
making the first one a right handed helix the next a left handed the third again
a right handed helix that regardless of the volume of the primary current no
induced current could pass and that the primary current or such portion of it as
might leap from the primary conductor could leap only to the solenoid tape and
being conducted back to the original conductor by the solenoid tape the latter
prevented any and all escape of primary current or leakage so that the positive

page_text: and negative cable may be brought into close proximity to each other without
danger of short circuiting this result has never before been obtained currents for
electric lights have been passed through such solenoid cables in close proximity to
each other in the ground and in water The resinous substances applied to this
solenoid tape may be replaced by any other of the resins or gums in part or totally
like shellac india rubber or gutta percha or their equivalent but the current
confining property of my solenoid tape renders the employment of these expensive
resins and gums superfluous.
Each end of the solenoid tape is tied closely to the main conductor after soldering
to it at the point of contact a piece of zinc or other metal more electropositive
than the conductor-By these means the oxidation of the conductor is completely
prevented which together with the zinc or other electro positive metal forms a dry
battery completely and for ever protecting the electro negative element (which is
here the conductor) from oxidation should oxygen in any shape or form gain access
to the same. This however is prevented by the waterproof compound of the tape
if well applied and closely wound upon the wire or cable This zinc or electro
positive metal may also be soldered to the conductor or deposited upon it at other
places than the place of contact with the solenoid tape
A cable completed in this manner may be protected from external injury by an
armour of iron wire.