IMPROVEMENTS IN THE MANU- FACTURE AND PRESERVATION OF INSULATED ELECTRIC CONDUCTORS AND IN
Year: 1882

page_text: LETTERS PATENT to Edwin Thomas Truman of Old Burlington Street in the
County of Middlesex for an Invention of IMPROVEMENTS IN THE MANU-
FACTURE AND PRESERVATION OF INSULATED ELECTRIC CONDUCTORS AND IN
PROVISIONAL SPECIFICATION left by the said Edwin Thomas Truman at
the Office of the Commissioners of Patents on the 2nd December 1882.
EDWIN THOMAS TRUMAN of Old Burlington Street in the County of Middlesex
"IMPROVEMENTS IN THE MANUFACTURE AND PRESERVATION OF INSULATED
ELECTRIC CONDUCTORS AND IN COMPOUNDS THAT MAY BE USED FOR THE SAME
AND FOR OTHER PURPOSES
"
My Invention consists in employing as the insulating material of insulated
electric conductors an improved compound consisting of black lead of commerce
ordinarily termed plumbago or graphite combined with a good insulator such as
gutta percha, or india rubber or ozokerit.
My improved compound enables me to provide an insulator of greater durability
and hardness and one less affected by heat and other injurious influences than
ordinary insulators formed of compounds hitherto used. I am also able to produce
a much cheaper insulated conductor than when ordinary insulating material such
as gutta percha for example is employed. The proportions of plumbago which I use
will vary according to the particular purpose for which the conductor is intended;
from about 20 to 50 per cent will for many purposes be a suitable proportion.
Instead of mixing the black lead, plumbago or graphite with other insulators
I sometimes apply to the conducting wires a layer or layers of black lead plumbago
or graphite and a layer or layers of other insulators alternately, or I apply a layer
or layers of a mixture composed of black lead, plumbago or graphite and other
insulators and a layer or layers of other insulators alternately.

page_text: When a coating of black lead, plumbago or graphite is used in the manner
proposed by me for the outer layer of an insulated conductor it not only protects
the gutta percha or other insulating material from oxidation (as it does when it is
mixed with the gutta percha or other material) but it is also useful when applied
as a surface coating, as a lubricant to facilitate the motion of the covered conductors,
as for instance when they are being drawn under ground through pipes. And in
order to still further preserve the insulated conductors I cover up the parts which
are exposed in the joint boxes of the pipes with black lead plumbago or graphite.
I also cover up other insulated conductors in a similar manner.
The black lead, plumbago or graphite when not mixed with gutta percha or
other good insulator may be incorporated with any suitable material which will
agglomerate or bind together its particles so as to make them adhere to one
another.
I, in some cases, also impregnate or cover with black lead or plumbago, tapes,
threads or strands used in the manufacture of insulated electric conductors or
cables in place of or in combination with the materials hitherto ordinarily
employed..
In some cases it will be found advantageous to treat the improved compounds
herein before referred to by the process ordinarily termed vulcanising.
My improved compounds either in a vulcanised condition or not can be used
not only in the manufacture of electric conductors but for other purposes.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edwin Thomas Truman in the Great Seal Patent Office on the
2nd June 1883.
EDWIN THOMAS TRUMAN of Old Burlington Street in the County of Middlesex
"IMPROVEMENTS IN THE MANUFACTURE AND PRESERVATION OF INSULATED
ELECTRIC CONDUCTORS AND IN COMPOUNDS THAT MAY BE USED FOR THE SAME
AND FOR OTHER PURPOSES
"
My invention relates to the employment as an insulating material for insulating
electric conductors of an improved compound consisting of black lead of commerce
ordinarily terined plumbago or graphite combined in sufficient proportion with a
good insulator such as gutta percha or india rubber or ozokerit.
My improved compound enables me to provide an insulator of greater durability
and hardness and one less affected by heat and other injurious influences than
ordinary insulators formed of compounds hitherto used. I am also able to produce
a much cheaper insulated conductor than when ordinary insulating material such
as gutta percha for example is employed.
In some cases graphite or plumbago has been proposed to be used in small
proportions, as ingredients employed in insulating compounds, but as far as I am.
aware there has been no use of or proposition to use plumbago or graphite
combined in the large proportions with gutta percha as used by me in the manner
and for the purposes herein set forth. When the gutta percha is of low quality I
find that I can form a very useful and comparatively cheap compound by
combining with 50 parts of the gutta percha about 20 to 30 of graphite, and with
improved qualities of gutta percha I can combine with advantage from 30 to
50 parts of graphite with a like quantity of gutta percha. It must always be
borne in mind that the graphite when combined with gutta percha in large
quantities so as to make a compound having good insulating properties as proposed
by me must be well dried graphite and when so used it effectively adds to the
bulk of the insulating compound which is thereby manufactured economically
without sacrifice of efficiency as regards insulation, while the durability of the
insulator is much increased. This is owing to the fact that the graphite acts as a
preservative of those qualities of the gutta percha which it important that it
should retain so as to act for the greatest possible period as a good insulator.
In carrying out my invention I find it desirable to select black lead of commerce
which when quite dry possesses the best insulating quality. Having dried it I sift
it carefully by passing it through a bolting cloth or other fine sieve. Then I take
gutta percha which has been thoroughly cleaned and dried and I mix and
incorporate the dry black lead therewith. The proportions of black lead to the
gutta percha are in all cases large so that the black lead adds substantially to the
bulk of the insulating compound as above indicated. The mixture may be effected
either in an ordinary masticator or in a condenser such as is described in the
specification of former Letters Patent granted to me and dated 25th March 1870
N° 878, or by means of any other suitable apparatus which will cause the gutta
percha and black lead to become thoroughly incorporated. I thus obtain a good
and durable insulating compound which can be applied to conducting wires by any
of the ordinary covering machines. By mixing ozokerit with the black lead and
gutta percha in the proportions of about 0-3 of ozokerit to about 10 parts of black
lead and 15 of gutta percha I also obtain a good and durable insulating compound.
In this case also the black lead must be carefully sifted and dried and the
ingredients should be thoroughly incorporated.

page_text: I use black lead as a surface coating for the outer layer of an insulated con-
ductor by causing it to be well rubbed into the surface of the insulated conductor.
I use it sometimes alone or sometimes mixed with ozokerit or other like material
which will not injure the substances with which the wire is insulated and the
black lead not only protects the gutta percha or other insulating material from
oxidation (as it does with reference to the gutta percha when mixed therewith as
herein before stated) but it effects a very useful purpose when applied as a surface
coating by acting as a lubricant to facilitate the motion of the covered conductors,
as for instance when they are being drawn under ground through pipes or other
confined apertures. And in order to still further preserve the insulated conductors
I cover up the parts which are exposed in the joint boxes of the pipes with
powdered black lead, either alone or mixed with ozokerit or other like substance
which will not make with the black lead a compound that will become brittle when
dry or set, or injure the substances with which the wire is insulated. I also use
the improved insulating compounds hereinbefore mentioned to cover up other
insulated conductors in a similar manner such for example as the coils of wire in a
dynamo electric machine.
I, in some cases also, impregnate or cover with black lead alone or mixed with
other suitable material such as ozokerit, tapes, threads or strands used in the
manufacture of insulated electric conductors or cables in place of the insulating
materials hitherto ordinarily employed.
In some cases it will be found advantageous to treat the improved compounds
herein before referred to by the process ordinarily termed vulcanizing but the
vulcanization must be such as will not interfere with the flexibility of the
compounds.
My improved compounds either in a vulcanized condition or not can be used not
only in the manufacture of electric conductors but for other purposes.
I am aware that in the specifications of several prior patents reference is made
to a proposed use of graphite or plumbago or black lead as an ingredient mixed
with other substances usually combined with india rubber or gutta percha so ns to
form insulating compounds and in some cases the ingredients proposed to be used
with the graphite or plumbago or black lead would act injuriously upon the
insulating compound proposed to be made, as for instance where oils or oleaginous
substances are proposed to be introduced into the compound. But in no case prior
to the date of my application on the 2nd December 1882 has there been, so far as 1
know, any use of or any proposition to use graphite or plumbago or black lead as
hereinbefore described, that is in the large proportions indicated as compared with
the india rubber or gutta percha with which it is to be combined so that the
graphite is made to constitute a substantial part of the compound and act with
material effect as an insulating material the result being that a very efficient
compound can be produced more economically than has hitherto been the case.
Nor has there been so far as know any use of or proposition to use graphite or
plumbago or black lead alone or combined with ozokerit and with or without
mixture with gutta percha for the purpose of impregnating tapes used in the
manufacture of insulated electric conductors for which purpose the graphite
answers very well.
Nor has there been, so far as I know, any use of or any proposition to use
graphite or plumbago or black lead as an outer surface coating for wires covered
with insulating compounds such coating being used so as to preserve the coated
insulator from injury and to facilitate the laying of the insulated wires when
they have to be drawn through confined apertures or places where it is important
to overcome friction for which purposes both as regards preserving the surfaces of
the insulator and as regards assisting friction to be overcome by a lubricating
action I have found the graphite to answer very well.
I therefore claim as iny Invention :—
First The manufacture of electric conductors by covering wires or conductors
with a compound formed of black lead of commerce combined in or in about the

page_text: proportions herein before stated with gutta percha or india rubber with or without
ozokerit as hereinbefore described.
Second-The combination of black lead and its use as a coating as hereinbefore
described for the purpose of preserving or protecting and of lubricating insulated
electric conductors substantially as hereinbefore set forth.
Third: The employment of black lead to impregnate or cover tapes, threads or
strands used in the manufacture of insulated electric conductors or cables as
herein before described.
Fourth-The manufacture in the manner and for the purposes as herein set
forth of the improved compounds hereinbefore described formed of black lend
combined with gutta percha or india rubber with or without ozokerit in or in
about the proportions stated.
In witness whereof I the said Edwin Thomas Truman have hereunto set
my hand and seal this second day of June One thousand eight hundred
and eighty three.
EDWIN THO8. TRUMAN (L.S.)