U.S. patent number 3,728,474 [Application Number 05/199,064] was granted by the patent office on 1973-04-17 for shielded power cable.
This patent grant is currently assigned to Anaconda Wire and Cable Company. Invention is credited to Edwin H. Arnaudin, Jr..
United States Patent |
3,728,474 |
Arnaudin, Jr. |
April 17, 1973 |
SHIELDED POWER CABLE
Abstract
Electric power cables with semiconducting jackets have stranded
or bunched drain conductors embedded in the jackets, in line with
the cable axis.
Inventors: |
Arnaudin, Jr.; Edwin H. (Eden,
NC) |
Assignee: |
Anaconda Wire and Cable Company
(N/A)
|
Family
ID: |
22736059 |
Appl.
No.: |
05/199,064 |
Filed: |
November 15, 1971 |
Current U.S.
Class: |
174/115;
174/120SC; 174/105SC |
Current CPC
Class: |
H01B
9/026 (20130101) |
Current International
Class: |
H01B
9/02 (20060101); H01B 9/00 (20060101); H01b
009/02 () |
Field of
Search: |
;174/115,113R,113C,108,107,12R,12SC,15SC,15R,16SC,126R,128,12SC |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Grimley; A. T.
Claims
I claim:
1. An electric power cable comprising:
A. a conductor,
B. a wall of insulation surrounding said conductor,
C. a thick jacket of semiconducting polymeric material directly
surrounding said wall of insulation, and
D. a plurality of bunch stranded drain conductors embedded in said
jacket substantially in line with the axis of said cable,
E. said drain conductors each comprising a plurality of wires, each
of the wires within one of said plurality of wires being helically
wound around at least one other wire within said plurality of
wires.
2. The cable of claim 1 wherein said wires are selected from the
group consisting of copper and copper alloys.
3. The cable of claim 1 wherein said wires are selected from the
group consisting of aluminum and aluminum alloys.
4. The cable of claim 1 wherein said bunch-stranded drain
conductors are flattened to an oval shape
5. The cable of claim 2 wherein said bunch-stranded drain
conductors are flattened to an oval shape.
6. The cable of claim 3 wherein said bunch-stranded drain
conductors are flattened to an oval shape.
Description
BACKGROUND OF THE INVENTION
In Plate et al. U.S. Pat. No. 3,474,189 issued Oct. 21, 1969 an
electric power cable is described having a thick semiconducting
polymeric jacket applied directly over the cable insulation and
undulatory drain wires embedded in the jacket. These wires are not
wrapped helically around the cable but lie on axes parallel to,
i.e. in line with, the cable axis. The undulations increase the
cable flexibility, since they prevent the wires in the outside arc
of a bend in the cable from stretching or breaking. They do require
special equipment, however, such, for example, as that described in
Menasoff patent 3531962.
SUMMARY
I have now found that a sufficiently flexible cable can be made
with embedded drain wires that have been manufactured on
conventional equipment such as stranders or, preferably, bunchers.
Thus a cable of my invention comprises a conductor, a wall of
insulation surrounding the conductor, a thick jacket of
semiconducting polymeric material directly surrounding the wall of
insulation and a plurality of drain conductors embedded in the
jacket substantially in line with the cable axis. The conductors
each comprises a plurality of wires and each of these wires is
helically wound around at least one other wire within the same
plurality forming that drain conductor. The drain conductors are
preferably copper or aluminum or alloys of copper or aluminum and
preferably comprise bunched strands in which case the diameters of
the wires are preferably 0.005-0.010 inch for copper and
0.007-0.012 inch for aluminum. Advantageously the bunched strands
have been flattened to an oval section to cover a greater area of
the cable surface, and reduce the thickness of jacket necessary to
contain them.
BRIEF DESCRIPTION OF THE DRAWING:
FIG. 1 shows a pictorial view, partially cut away, of one
embodiment of a cable of my invention.
FIG. 2 shows a pictorial view, partially cut away, of another
embodiment of the cable of my invention.
FIG. 3 shows a pictorial view, partially cut away, of still another
embodiment of the cable of my invention.
FIG. 4 shows a pictorial view of still another embodiment of the
cable of my invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring to the Figures, my cable, indicated generally in FIG. 1
by the numeral 10, comprises a conductor 11, a layer of insulation
12 and a semiconducting jacket 13 none of which is, of itself,
novel and which are adequately described in the aforementioned U.S.
Pat. No. 3,474,189, the disclosures of which, where relevant, are
included in the present description. A novel feature of the present
invention resides, however, in a drain wire 14 comprising bunched
copper strand. "Bunched strand" is a term well established in the
cable arts and corresponds to the term "bunched-stranded conductor"
defined in ASTM Designation B 354-70a. Bunched strands are
manufactured by machines known as "bunchers" or "bunch-stranders"
for making an electrical conductor from a relatively large number
of fine wires by twisting the wires together without a symmetric
geometrical pattern. The American Standard for Testing Materials
(ASTM) has a designation B 174-75 for Bunch-Stranded Copper
Conductors for Electrical Conductors which tabulates the following
construction for bunch-stranded conductors
TABLE 1
Size of Minimum number of wires in conductor Size of wires, Awg
Conductor Awg No. No. 28 No. 30 No. 32 No. 34 No. 36 No. 38 No. 40
12 41 65 104 14 26 41 65 104 16 16 26 41 65 104 165 18 10 16 26 41
65 104 165 20 7 10 16 26 41 65 104
A feature of bunched strands that adds to their utility for my
invention resides in the absence of any straight central wire like
those that are found in concentric stranded conductors. Such a
central strand would be stretched, possibly to the breaking point,
upon bending the cable 10. The fact that bunchers are available in
most cable plants or can be purchased from commercial sources
without recourse to special designing and fabricating provides an
advantage to the use of bunched strand in my present invention. To
manufacture my cable 10 the bunched strands 14 are paid through the
extrusion die during the extrusion of the jacket 13 and the
extrusion head can be adjusted or designed to embed the conductor
14 tangent to the outer surface of the jacket as in FIG. 1 or well
below the surface as illustrated by a cable 16 in FIG. 4. The
bunched strands may also be embedded so as to project from the
surface and expose a portion of the metal as exemplified for an
elastic cored strand 17, to be further described below, in FIG. 3.
Because of its higher conductivity and resistance to
moisture-induced corrosion I prefer copper or copper alloys for the
conductors 14 and 17, but where corrosion presents no problem
aluminum or aluminum alloys of high electrical conductivity may
also be used.
FIG. 2 illustrates an embodiment of my invention wherein a bunched
drain conductor 18 has been flattened, by passage through rolls, to
an oval shape, before being embedded in the cable jacket. This
flattening has the advantage of affording a greater area of
metallic shielding to the cable surface and a greater area of
contact between the metal of the conductors and the semiconducting
jacket composition. It also allows a reduction in the thickness of
jacket necessary to embed the drain conductors. Reduction in the
radial dimension of bunched conductors to as little as 30 percent
of their original diameter is feasible for copper conductors and as
little as 50 percent for aluminum conductors although, in the case
of aluminum alloys, that do not become embrittled during the
operation of rolling, somewhat greater reductions are possible.
If a group of parallel wires are wrapped as a unit around a core
that is later withdrawn from the wrapped strand, each of the wires
will have been wrapped around all of the others, unless, during the
wrapping operation the group of wires was back-twisted around its
own axis as is done during planetary stranding. This wrapping of
the "parallel" wires around themselves is readily demonstrated by
the impossibility of lifting one of the wires from the strand after
the core has been withdrawn. In a bunched strand each of the wires
wraps around at least some of the remaining wires in the bunch and
so acquires an additional length that adds flexibility. In the
embodiment of FIG. 3 the wires are not bunch stranded but are
evenly wound around a flexible core 19 which may preferably
comprise an extruded filament of the same semiconducting stock as
the jacket 13 but may comprise other filaments such as
polycarbonate and polyimide that will not melt or disintegrate at
the extrusion temperatures of a particular jacket stock.
The foregoing description has been exemplary rather than definitive
of my invention for which I desire an award of Letters Patent as
defined in the appended claims.
* * * * *