Improvements in Electric Cables.
Year: 1898

page_text: Date of Application, 22nd Nov., 1898-Accepted, 14th Jan.,
1899
COMPLETE SPECIFICATION.
Improvements in Electric Cables.
I, EDWIN TRUMAN GREENFIELD, of No. 527 West 34th Street, New York, in
the Borough of Manhattan, and State of New York, United States of America,
Electrician, 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:-
This invention relates particularly to improvements in electric cables designed
for ocean service, and has for its objects:-
First, to devise an armoured cable of such a nature that the insulation of the
cable will be thoroughly protected from the attacks of borers or other insects or
animals which usually attack cables of this nature when sunk in the body of
the ocean;
Second, to devise an armoured cable of such a nature that its exterior armour
will fully protect it, the cable, from unnatural wear when it is suspended over
ledges of rock in the body of the ocean; and,
Third, to provide a cable of the nature indicated in which the armour is of
steel, phosphor-bronze, or any preferred metal having the desired strength and
qualities for adapting it for use in the ocean, and in making such armour of a
flexible nature so that the completed cable may be wound upon a drum in the
usual way when it is desired to lay it in the bed of the ocean;
Fourth, to provide a lead or equivalent covered cable with a flexible protecting
armour which will protect the lead covering from the action of metal slivers when
drawn into a conduit.
The invention will be fully understood by referring to the drawings, in which,
Figure 1 illustrates in side elevational view a short length of this improved
flexible armoured cable, illustrating also the manner of constructing the
same; and
Figure 2 is a part longitudinal sectional view of Figure 1.
Figure 3 being an enlarged end elevational view of the structure as seen
looking at Figure 1 from the left of the drawings toward the right, and
Figure 4 is an end elevational view of an armoured lead covered cable con-
structed in accordance with this invention and embracing a number of independent
insulated conductors.
Prior to this invention ocean cables and armoured conductors generally had
been made in which a strip of metal constituting the armour had been wound
spirally around the cable in such manner as to form a protecting casing or
coating, but no one as far as I am aware had constructed an armoured cable of
the nature indicated, in which the armour was made of one or more spirally
wound strips of metal so interlocked in its windings as to make the armour
flexible and also to prevent the rupturing of the armour at any point by bending
the cable to ordinary degrees of curvature, and in this feature lies the essential
novelty of the invention.

page_text: Referring to the drawings in detail:-
C represents the conducting core or cable proper which is of the usual form,
consisting of a number of copper conductors twisted as shown, and T the insu-
lation around such cable, the same being of such material and arrangement as is
customary in the construction of ocean cables and needs therefore no special
description here, it only being important that this insulation be of such a nature
as to effectually protect the interior core or conductor C, which arrangement may
be as shown, or a single conductor or a number of individual conductors separated
from each other by definite spaces, as is often the case in connection with cables
where it is desired to assemble a series of independent conductors within one cable.
N and M represent spirally wound strips of metal, preferably of Bessemer steel,
although they may be of any metal having the desired strength and flexibility
and not readily attacked by salt water, such for instance as any of the well known
metallic bronzes like phosphor-bronze or such as will readily suggest themselves
to the maker. The inner strip M is so constructed that when wound upon the
outer surface of the insulation T it presents an outward concave or curvilinear
surface throughout its length and is also provided with a central line or row of
projections or lugs II, while the outer strip N, which is wound upon it in such
manner as to break joints, is curved in a reverse direction or inwardly, and has
constructed upon its inner surface a series of lateral indentations D). These two
strips are wound about the insulation T of the cable in the manner shown, so that
they break joints and that the outwardly extending row of projections I is located
between the windings of the strip N, and it will be noticed that by virtue of their
opposite curvature and the intervening rows of projections or lugs I, there is
formed a continuous locking joint between all of the parts of the armour, such
locking joint preventing the unwinding of the end portions thereof and also any
possibility of separating the several convolutions by any reasonable longitudinal
strain upon the completed cable.
It will also be apparent that by virtue of the reverse curvature of these two
strips N and M, when in position, there is given great flexibility to the entire
structure, so that it may be bent to almost any degree of curvature, therefore
adapting it to be wound upon a drum or drums as cables are ordinarily wound and
placed on shipboard prior to laying them. It will be understood that the pro-
jections or lugs I might be replaced by a continuous longitudinal ridge or rib,
but it is found that better results are obtained by the use of such lugs. It is
also apparent that there might be a series of such inwardly projecting lugs in the
strip M for giving further interlocking capability to the entire structure.
It is also obvious that there might be more than two layers of spirally wound
armour strips if desired, but it is found that two such strips when constructed, as
herein before described, give ample protection to the insulation and sufficient
strength to the structure for all practical purposes.
In Figure 4 is shown in end elevational view a well known form of lead covered
cable, such as is used in telephonic service and provided with this novel form of
flexible armour, CC representing a definite number of independent insulated
telephonic conductors and L the lead or equivalent yielding metallic covering of
the entire cable, the armoured strips N and M surrounding said covering.
There is no limit in the construction of metallic armoured electric cables of the
type indicated to an armour of two metallic strips of the curvilinear structure
shown, and it is to be understood that the claims hereinafter made are designed
to be of such scope as to include two or more metallic strips oppositely curved or
bent in such manner that their adjoining edges will act to interlock and firmly
hold the entire armour in position around the outer insulation of the cable itself.
Neither is there a limit to the use of the herein before described armoured electric
cable to ocean service, as the same may be used in any place where it is found
necessary to furnish an armoured protection to such cables, as for instance, in
connection with electric light and power systems where it is desired to convey

page_text: high potential currents through districts of service which might render the use
of ordinary conductors dangerous, this armoured cable giving a sufficient pro-
tection from the attacks of all extraneous sources to render it reasonably safe.
This novel form of flexible armour makes it also possible to thoroughly protect
the well known form of lead covered cables, now used in telephony in conduits,
from the damaging effects of metal slivers during the time that such cables are
being drawn into position within the conduits; and also affords an effective pro-
tection against damage during shipment, thereby rendering it absolutely certain
that the cables will be in perfect condition after they are drawn into their
permanent resting places.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is;-
1. A flexible armoured electric cable consisting of an insulated conductor
having two or more metallic armour strips spirally wound thereon and curved in
opposite directions, substantially as described.
2. A flexible armoured electric cable consisting of an insulated conductor or
core and two or more metallic armour strips spirally wound thereon, said armour
strips being curved in opposite directions and breaking joint with each other,
substantially as described.
3. A flexible armoured electric cable consisting of a flexible insulated conductor
and two or more metallic armour strips spirally wound thereon, the armour strips
being curved in opposite directions and one of them provided with a centrally
located row of locking lugs or projections I, substantially as described.
4. A flexible armoured electric cable consisting of one or more insulated con-
ductors surrounded by a lead or equivalent yielding metallic covering, in
combination with a flexible metallic armour consisting of two or more strips of
metal spirally wound thereon and curved in opposite directions, substantially as
described.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.