Improvements in or relating to Treating or Manufacturing Certain Forms of Insulated Electric Conductors.
Year: 1891

page_text: Date of Application, 12th May, 1891-Accepted, 20th June, 1891
COMPLETE SPECIFICATION.
Improvements in or relating to Treating or Manufacturing Certain
Forms of Insulated Electric Conductors.
A communication from abroad by JAMES B. WILLIAMS, M.D., of Berkeley, in
the County of Alameda and State of California, United States of America.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool and 6, Bank Street, Manchester, both
in the County of Lancaster, and 323, High Holborn in the County of Middlesex,
Civil 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 :-
The object of this invention is a method whereby certain forms of insulated
electric conductors may be advantageously manufactured or treated after manu-
facture, and its novelty consists in the steps of the process and their relation to
each other, as will be hereinafter more fully set forth.
The forms of the insulated electric conductors referred to consist briefly of
the combination, with a central conductor substantially circular in cross section,
of a surrounding dielectric and an intermediate covering or separating device
placed between the conductor and the dielectric whereby they are separated and
air spaces or passages formed between them. The specific forms of such con-
ductors and their adjuncts will in all probability be made the subject of other
patents and are immaterial to the understanding of this process which is applicable
to all conductors having the features mentioned.
In the drawings,
Figure 1 is a central longitudinal section of a conductor and its adjuncts.
Figure 2 is a transverse section of the same.
Figure 3 is a perspective view showing the dielectric in partial section, and
Figure 4 is a section of the same with a plan view of the apparatus employed in
its treatment.
In these,
W is the central metallic conductor, I is the dielectric surrounding the same,
C is the intermediate covering or separating device which is in all cases secured to
the exterior surface of the conductor and which touches the interior surface of the
dielectric only at the extremities of certain raised portions thereof which are sub-
stantially equidistant from the axis of the conductor. In the form illustrated, the
raised portions consist of bosses or projections c which support the dielectric and
leave the air spaces A. between it and the conductor W.
Over the dielectric after it is put in position is placed, under conditions requiring
its use, a water-proof protecting covering L generally made of lead, and, if deemed
desirable, an additional outer covering F consisting of fibrous material treated with
a water-proof paint. N and N¹ are suitable nozzles inserted at the ends of the
conductor between the intermediate covering and the dielectric and are each
provided with a cock G and G¹ having passages and g'. The nozzle N is
connected, by means of the pipe p, to a reservoir R which is adapted to contain
warm dry air and provided with a pressure gauge H communicating with its
interior. A similar pressure gauge His placed intermediate the cock G¹ and the
insulated conductor W. The nozzle N¹ opens into the outer air.
If, upon an examination of the insulated conductor, after the waterproof pro-
tecting covering L has been applied, it is found that the dielectric has been forced
into the air spaces between it and the conductor during the process of its manu-
facture so that the air spaces, where it is intended that they should be continuous,

page_text: have been partially destroyed; or, if the dielectric is not sufficiently compact and
substantially circular in cross section when the air spaces either partial or complete
do exist, then, by the process which is about to be described, the dielectric is made
compact, it is made to rest lightly on all or the greater portion of the raised
surfaces of the intermediate covering or separating device and the air passages are
restored to their proper condition.
After the dielectric has received its outer waterproof protecting covering L, it
is kept comparatively straight and placed in a suitable chamber of convenient
length, say 200 feet, where it may be so arranged that it shall project a few inches.
outside thereof at each end. This chamber must be so arranged that it can be
closed and uniformly heated to say 200 degrees Fahrenheit. The air spaces at
each end of the conductor are then made to communicate with each other if they
do not already do so. The nozzles N and N are then introduced between the
intermediate covering and the dielectric at each end of the latter and secured in
place and thus placed in communication with each other through the air spaces or
passages formed between the dielectric and the conductor. One of the nozzles N
is made to communicate by means of the pipe p with the reservoir R containing air
under a pressure which can be varied and to which is attached a pressure gauge
communicating with its interior. The other nozzle N is made to communicate
with the atmosphere. This nozzle is also provided with a pressure gauge H¹ placed
intermediate the cock G¹ and the conductor W. The indications of these two
gauges should be exactly alike at all the pressures which are to be used in the
treatment. The chamber containing the insulated conductor is then gradually and
continuously heated to a temperature sufficient to render the whole mass of the
material of which the dielectric is composed slightly adhesive. This temperature
and the length of time required for this purpose can be ascertained by previous
experiment. The stop cock G is then opened and the air from the reservoir under
a low pressure is gradually admitted to the air spaces through the pipe p and the
nozzle N communicating therewith, until it is known that the air has passed the
entire length of the dielectric, when the stop cock G' farthest from the reservoir is
gradually closed and the pressure of the air is gradually increased and maintained
until the dielectric under its influence is made sufficiently compact, substantially
circular in cross section and to rest lightly on all, or the greater portion, of the
raised portions of the intermediate covering or separating device. The degree of
pressure to be exerted and the length of time required to effect this purpose must
be ascertained by previous experiment, and, for the sake of convenience, tables-may
be made to facilitate reference thereto. After being so treated, the finished con-
ductor is allowed to cool, the pressure being maintained until cold, when it is then
removed from the chamber and is ready for use.
Dr. Williams has found this method of subjecting the insulated conductor to the
action of warm dry air under pressure an efficient process whereby the vulcanisation
of the materials of which the dielectric is composed may be effected. As is well
known, vulcanisation is usually accomplished by means of steam on account of 'the
ease with which its temperature and pressure may be controlled, but steam cannot
in practice be made perfectly dry and the efficiency of the usual product of such
vulcanisation is much impaired by the presence of moisture during the process of
treatment, hence it is by no means a good medium for this purpose in many
instances. When this invention is to be used for purposes of vulcanisation, the
chamber in which it is effected must be capable of being heated to say 300 degrees
Fahrenheit and the apparatus must be also capable of keeping the air under
pressure up to say 75 lbs. per square inch, and the dielectric should be surrounded
by a flexible metallic sheath made of lead.
F
Different materials may of course be employed to form the dielectric and they
will naturally require different degrees of temperature, different conditions of
pressure and different lengths of time in order that the best results may be
obtained and this data can best be secured by previous experiment in each
tase.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is:
1. The method of treating an insulated electric conductor, consisting of a con-
ductor surrounded by a dielectric with intermediate air spaces between them, which
consists in, First, raising the said dielectric to a suitable temperature, Second,
passing warm dry air through the said air spaces, and Third, in maintaining the air
under pressure in said intermediate air spaces, as set forth.
2. The method of treating an insulated electric conductor formed as described
which consists in, First, heating the conductor in a closed chamber until the
materials of which its dielectric is composed become slightly adhesive, Second,
in passing warm dry air through the air spaces between the conductor and the
dielectric, and Third, in maintaining the air under pressure within said air spaces,
as set forth.
3. The method of vulcanising the materials of the dielectric of an insulated
electric conductor of the form described, said dielectric having been formed in
position without vulcanisation, which consists in subjecting it to the action of warm
dry air under pressure contained in the intermediate spaces between the conductor
and the dielectric, the temperature, degree of pressure and length of time required
being suited to the particular materials employed in each instance.
Dated this 11th dow of N 1901
WM. P. THOMPSON & Co.,
Agents for the Applicant.