Electricity: conductors and insulators – Conduits – cables or conductors – Conductive armor or sheath
Reexamination Certificate
1998-10-08
2002-01-08
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Conductive armor or sheath
C174S10500R, C174S1060SC, C174S036000
Reexamination Certificate
active
06337441
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a shielded multi-core cable in which a plurality of insulator rods each having embedded therein one of a plurality of conductive cores, are tightly received in a cylindrical shielding conductive pipe so that the conductive cores are ;held therein around the center axis thereof, and the invention also pertains to a method of making such a shielded multi-core cable.
DESCRIPTION OF THE RELATED ART
A conventional shielded multi-core cable and its manufacturing method will be described with reference to
FIGS. 21 through 24
; the manufacturing method involves a sequence of steps described below.
The manufacture begins with the preparation of an insulator-covered wire G which has plural, for example, two conductive cores A
1
and A
2
circular in cross-section, for instance, and embedded side by side in a cylindrical insulator rod F at equal angles around the center axis thereof (FIGS.
21
A and B), and a cylindrical conductive pipe E which has an inner diameter &phgr;
E1
nearly equal to or larger than the outer diameter &phgr;
F2
of the insulator rod F (FIGS.
21
C and D).
Then, the insulator-covered wire G is inserted into the conductive pipe E (FIGS.
22
A and B).
For the sake of brevity, the conductive pipe E is shown to have an inner diameter &phgr;
E1
substantially equal to the outer diameter &phgr;
F2
of the insulator rod F of the insulator-covered wire G.
Next, the conductive pipe E having inserted therein the insulator-covered wire G is subjected to drawing by means of a drawing die K (
FIGS. 23A and B
) having a circularly-sectioned through hole H whose inner diameter &phgr;
H
gradually varies lengthwise thereof from one end having an inner diameter &phgr;
H1
nearly equal to or larger than the outer diameter &phgr;
E2
of the conductive pipe E to the other end having an inner diameter &phgr;
H2
smaller than the outer diameter &phgr;
E2
of the conductive pipe E. That is, the conductive pipe E is drawn through the through hole H of the drawing die K from the one end of the larger inner diameter &phgr;
H1
to the other end of the smaller inner diameter &phgr;
H2
(FIG.
23
A). By this, a conventional shielded multi-core cable M is obtained which has a construction in which two conductive cores A
1
′ and A
2
′, embedded side by side in a cylindrical insulator rod F′ tightly fitted in and held integrally with a cylindrical shielding conductive pipe E′, lie in juxtaposition to each other in the shielding conductive pipe E′ which has an outer diameter &phgr;
H2
′ equal to the smaller inner diameter &phgr;
H2
of the through hole H of the drawing die K (FIGS.
24
A and B).
In this instance, since the inner diameter &phgr;
E1
′ of the shielding conductive pipe E′ of the shielded multi-core cable M is smaller than the inner diameter &phgr;
E1
of the conductive pipe E, the insulating material forming the insulator rod F of the insulator-covered wire G is forced out of the shielding conductive pipe E′ of the shielded multi-core cable M. The excess insulating material is removed after the drawing step.
The conventional shielded multi-core cable M (FIGS.
24
A and B), fabricated by the method depicted in
FIGS. 21 through 24
, is commonly used after being subjected to an end treatment as depicted in FIG.
25
. One end portion of the shielding conductive pipe E′ is peeled off to expose one end portion of the insulator rod F′, and the exposed end portion of the latter is partly removed to expose the two conductive cores A
1
′ and A
2
′ at one end thereof. Occasionally the situation arises where it is desirable that the free end portion of the two conductive cores A
1
′ and A
2
′ be widely spaced apart.
Since the two conductive cores A
1
′ and A
2
′ are embedded side by side in the common insulator rod F′, however, there is no choice but to gradually open up the space between the two cores A
1
′ and A
2
′ from the free end position of the insulator rod F′ toward their free ends by making a cut in the insulator rod F′ between the two conductive cores A
1
′ and A
2
′ ftom the free end of the rod F′ to that of the shielding conductive pipe E′.
Accordingly, when it is required that the free ends of the two conductive cores A
1
′ and A
2
′ be widely spaced apart in practical use, it is impossible to meet the requirement without elongating the exposed free end portions of the two conductive cores A
1
′ and A
2
′ in the abovementioned end treatment or making a cut in the insulator rod F′ from the free end thereof toward that of the shielding conductive pipe E′ between the conductive cores A
1
′ and A
2
′ after the end treatment.
Thus, the conventional shielded multi-core cable M depicted in
FIG. 24
has a shortcoming that the space between the free ends of the two conductive cores A
1
′ and A
2
′ cannot be opened up in the practical use after the end treatment without making a cut in the insulator rod F′ from the free end thereof toward that of the shielding conductive pipe E′ or increasing the lengths of the exposed free end portions of the conductive cores A
1
′ and A
2
′.
Furthermore, according to the conventional shielded multi-core cable fabricating method shown in
FIGS. 21 through 24
, if it is possible to obtain, in the step of its preparation (FIGS.
21
A and B), the insulator-covered wire G of a construction in which the two conductive cores A
1
and A
2
embedded side by side in the insulator rod F are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod F (that is, the conductive cores A
1
and A
2
are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod F, the line joining the centers of the conductive cores A
1
and A
2
passes through the center of the insulator rod F and the conductive cores A
1
and A
2
are both exactly symmetrical with respect to the center of the insulator rod F), the shielded multi-core cable M can be obtained which has the construction wherein the two conductive cores A
1
′ and A
2
′ embedded side by side in the insulator rod F′ are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod F′ (that is, the conductive cores A
1
′ and A
2
′ are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod F′, the line joining the centers of the conductive cores A
1
′ and A
2
′ passes through the center of the insulator rod F′ and the conductive cores A
1
′ and A
2
′ are both exactly symmetrical with respect to the center of the insulator rod F′).
In practice, however, since the two conductive cores A
1
and A
2
are both disposed at positions off the center axis of the insulator rod F, it is difficult to prepare the insulator-covered wire G of the abovementioned construction in which the two conductive cores A
1
and A
2
embedded side by side in the insulator rod F are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod F (that is. the conductive cores A
1
and A
2
are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod F, the line joining the centers of the conductive cores A
1
and A
2
passes through the center of the insulator rod F and the conductive cores A
1
and A
2
are both exactly symmetrical with respect to the center of the insulator rod F).
On this account, difficultly is encountered in producing, by the step of drawing the conductive pipe E with the insulator-covered wire G inserted therein, the shielded multi-core cable M in which the two conductive cores A
1
′ and A
2
′ embedded side by side in the insul
Costellia Jeffrey L.
Koakkus Kabushiki Kaisha
Mayo, III William H
Nixon & Peabody LLP
Reichard Dean A.
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