SHIELD WIRE

Abstract

A shield wire (P) that facilitates terminal processing is provided. This shield wire (P) includes a plurality of core wires and an inclusion (2) twisted together to form a core (3) having a cross-sectional circular shape, a drain wire (4) laterally wound around an outer periphery of the core, a shield tape (5) wound around, and a sheath (6) further disposed outside the shield tape (5). The shield tape (5) includes metal thin films (5b and 5c) on surfaces of a resin film (5a). An adhesive layer (7) is interposed between the shield tape and the sheath. The shield tape is adhesively integrated with the sheath by the adhesive layer.

Claims

1. A shield wire (P) comprising: a plurality of core wires (1 and 1′) and an inclusion (2) twisted together to form a core (3) having a cross-sectional circular shape; a drain wire (4) laterally wound around an outer periphery of the core (3) over a whole length of the core (3); a shield layer formed on the outer periphery of the core (3); and a sheath (6) further disposed outside the shield layer, wherein the shield layer is formed by winding a shield tape (5) around the outer periphery of the core (3) to have the drain wire (4) interposed, the shield tape (5) including metal thin films (5b and 5c) formed on surfaces of a resin film (5a), an adhesive layer (7) is interposed between the shield tape (5) and the sheath (6), the shield tape (5) is adhesively integrated with the sheath (6) by the adhesive layer (7), the shield layer is stripped together with the sheath (6) when the sheath (6) is stripped, and a filling rate of the inclusion (2) inserted in a space (s) surrounded by outer peripheral circles (c.sub.1) of the respective core wires (1 and 1′) and a circumscribed circle (c.sub.2) of the twisted wires is 1.0 or more.

2. (canceled)

3. The shield wire according to claim 1, wherein a plurality of nicks (8) is formed on the shield tape (5) in a direction intersecting with a longitudinal direction of the wire (P) over the longitudinal direction.

4. The shield wire according to claim 1, wherein the adhesive layer (7) is formed on a whole surface of an outer periphery of the shield layer by extrusion molding of a thermoplastic adhesive resin.

5. A method for manufacturing the shield wire (P) according to claim 4, comprising: forming the core (3) by twisting the core wires (1 and 1′) and the inclusion (2); laterally winding the drain wire (4) around the outer periphery of the core (3) while causing the core (3) to travel in a longitudinal direction of the core (3); subsequently winding the shield tape (5) as a winding tape; forming the adhesive layer (7) by extruding the thermoplastic adhesive resin on an outer peripheral surface of the shield tape (5); and further disposing the sheath (6) outside the adhesive layer (7) by the extrusion molding.

6. The shield wire according to claim 3, wherein the adhesive layer (7) is formed on a whole surface of an outer periphery of the shield layer by extrusion molding of a thermoplastic adhesive resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a cross-sectional view of one embodiment of a shield wire according to the present invention.

[0031] FIG. 2 is a front view of a main part partially cut of the embodiment.

[0032] FIGS. 3(a) and 3(b) are cross-sectional views of respective examples of shield tapes of the embodiment.

[0033] FIG. 4 is a perspective view for describing terminal processing of the embodiment.

[0034] FIGS. 5(a) to 5(e) are explanatory views of cross-sectional areas of spaces in a shield wire according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0035] FIGS. 1 and 2 illustrate one embodiment of a shield wire P according to the present invention. This shield wire P is for a robot cable. This shield wire P includes four paired twisted wires 1′ (this paired twisted wire 1′ is also a core wire referred in each claims in CLAIMS), an inclusion 2 between these respective paired twisted wires 1′, a core 3, a drain wire 4, a shield tape 5 forming a shield layer, an adhesive layer 7, and a sheath (a protecting layer) 6. The paired twisted wires and the inclusion 2 are twisted together and included in the core 3. The drain wire 4 is laterally wound around an outer peripheral surface of this core 3 over a whole length of the core 3. The shield tape 5 is laterally wound around a whole circumference of this core 3 to have the drain wire 4 interposed. The sheath (the protecting layer) 6 is disposed on this shield tape (the shield layer) 5. The adhesive layer 7 is disposed between this shield tape 5 and the sheath 6.

[0036] The paired twisted wire 1′ is constituted of two core wires 1 and 1 twisted with one another. The twisted pitch can be set appropriately according to a usage configuration. The core wire 1 constituting the paired twisted wire 1′ includes a copper alloy twisted wire 1a whose cross-sectional area is 0.2 mm.sup.2 and an insulating coating 1b, which is polyvinyl chloride or the like, disposed on the copper alloy twisted wire 1a. The number, diameter, and the like of these core wires 1 and the paired twisted wires 1′ can be set appropriately according to a usage aspect. In this embodiment, the core wire 1 includes the insulating coating 1b made of polyvinyl chloride. These insulating coatings 1b have different colors, such as of red, green, black, and white, as necessary. This ensures identification of the insulating coatings 1b.

[0037] As the conductor 1a of the core wire 1, other than copper alloy, a well-known material, such as tin-plated annealed copper, aluminum, and aluminum alloy, can be appropriately employed. As the insulating coating 1b, other than polyvinyl chloride, a well-known material, such as polyethylene, cross-linked polyethylene, polypropylene, and fluororesin, can be appropriately employed.

[0038] The inclusion 2 is constituted of a staple yarn and the like. The inclusion 2 is used for roundly finishing the core 1′ when twisting the respective paired twisted wires 1′ (the core wires 1). Other than the staple yarn, a well-known material, such as a PPC yarn, a paper tape, a paper yarn, a jute yarn, a kynol yarn, a cotton yarn, a polyvinyl chloride (PVC) yarn, and a polyethylene (PE) yarn, can be appropriately employed. In this embodiment, the staple yarn is used.

[0039] The core 3 of this shield wire P is made by the paired twisted wires twisted with one another to have this inclusion 2 interposed. Therefore, as illustrated in FIG. 1, the core 3 has a cross-sectionally circle. The core 3 has a cross-sectional circular shape. Most of the outer peripheral surface of the core 3 having the cross-sectional circular shape is occupied by the inclusion 2 made of the staple yarn. The staple yarnhas a high release property. Therefore, a surface of the core 3 has the high release property from the shield layer.

[0040] A filling rate of the inclusion 2 inserted in a space (the above-described cross-sectional area of spaces of the above-described paired twisted wires 1′ is set to be 1.0 or more.

[0041] The drain wire 4 is constituted of a copper alloy twisted wire whose cross-sectional area is 0.2 mm.sup.2. The drain wire 4 is vertically attached or laterally wound. In this embodiment, one drain wire is laterally wound. The number of the drain wire 4 can be arbitrarily set.

[0042] The shield tape 5 serves as a tape that maintains the cross-sectional circular shape of this core 3 by being wound around to have the drain wire 4 interposed, which is wound around the outer peripheral surface of the core 3. As illustrated in FIG. 3(a), the shield tape 5 may include a metal thin film 5b formed on one surface of a resin film 5a. As illustrated in FIG. 3(b), the shield tape 5 may include the metal thin film 5b and a metal thin film 5c formed on two surfaces of the resin film 5a. The shield tape 5 with the metal thin film 5b formed only on one surface has this metal thin film 5b surface facing a core 3 side.

[0043] Examples of the resin film 5a, which is used, includes a conventionally used resin, such as polyester, polyolefin, polyphenylene sulfide, polyamide, polyester amide, polyether, polystyrene, polyvinyl chloride, and polyethylene terephthalate (PET). In this embodiment, a PET film having a thickness of 12 μm is used. In the case where the metal thin films 5b and 5c are formed on two respective surfaces of the resin film 5a, the metal thin films 5b and 5c may employ mutually different materials. The metal thin films 5b and 5c may have mutually different surface roughnesses. The metal thin films 5b or 5c on a sheath 6 side can obtain an creased adhesive strength to the sheath 6 when the metal thin films 5b or 5c on the sheath 6 side have rougher surfaces.

[0044] As a forming means of the metal thin films 5b and 5c, conventionally used deposition, sputtering, foiling, and the like of a metal, such as aluminum, copper, argentum, gold, and nickel, can be employed. In this embodiment, as illustrated in FIG. 3(b), the aluminum deposition layers 5b and 5c having a thickness of 0.1 μm are employed.

[0045] The sheath 6 is made of a well-known resin, such as polyvinyl chloride, polyethylene, polyurethane, or polyester. In this embodiment, the polyvinyl chloride is employed.

[0046] As the adhesive layer 7, a material having h adhesive property to the resin film 5a or the metal thin film 5c, and the sheath 6 is appropriately employed. In this embodiment, polyester-based thermoplastic adhesive resin is used.

[0047] The adhesive layer 7 may be formed of thermoplastic adhesive resin of polystyrene-based, vinyl acetate-based, polyethylene-based, polypropylene-based, polyamide-based, rubber-based, acrylic-based, or the like. Add-in material such as metal powders, carbon black, filler, or stiffener may be added to the adhesive layer 7. However, if these add-in materials are added more than a specific amount, the add-in materials may easily expose from a surface of the adhesive layer so that the satisfactory adhesive property to the sheath 6 may not be guaranteed. Therefore, when adding these add-in materials, amounts of these add-in materials are appropriately chosen considering the adhesive property.

[0048] This adhesive layer 7 may be formed on a surface of the resin film 5a or the metal thin film 5c (may be the shield tape 5 attached with the adhesive layer 7) before the shield tape 5 is wound around the core 3. However, as described later, an adhesive layer can be formed after the shield tape 5 is wound around.

[0049] The shield wire P in this embodiment has the above-mentioned configuration. For manufacturing the shield wire P, first, a supply drum for the paired twisted wire 1′ constituted of the core wires 1 and a supply bobbin for the inclusion 2 are installed to a twisting machine. Then, each are brought out and pass through a predetermined position in a wide hole of a panel strip of the twisting machine. After completion of preparation, the twisting machine is driven and the core 3 having the cross-sectional circular shape is formed by twisting the paired twisted wires 1′ and the inclusion 2 together. Next, the drain wire 4 is laterally wound around the outer periphery of this core 3. Furthermore, the shield tape 5 is laterally wound around this outer peripheral surface. Thus, the shield layer is formed.

[0050] Next, the adhesive resin is extruded by an extruder to a whole surface of the outer periphery of the core 3 around which this shield tape 5 is wound. Thus, the adhesive layer 7 is formed on the outer peripheral surface of the core 3 to have a winding layer (the shield layer) of the shield tape 5 interposed.

[0051] The sheath 6 is disposed by further extruding and molding the resin by the extruder onto an outside of the adhesive layer 7 formed on the shield tape 5 wound (the shield layer formed) around the core 3. Thus, the shield wire P according to the present invention is manufactured. An extruding temperature of the above-described adhesive resin is 170° C. and a speed of the above-described adhesive resin is 20 m/s. An extruding temperature of the resin for the sheath is 170° C. and a speed of the resin for the sheath is 20 m/s.

[0052] Such fabricated shield wire P can be used as robot cable for communication, for electric power, or the like. Then, as illustrated in FIG. 1, most surface of the core 3 is occupied by the inclusion 2 made of the staple yarn. The core 3 is configured so as to easily move with respect to the shield tape 5 (the sheath 6). Therewith, a whole circumference surface of the shield tape 5 is integrated with the sheath 6 by being certainly adhered to the sheath 6. In view of this, with this shield wire P, the shield tape 5 (the sheath 6) easily moves with respect to the core 3 when repeatedly receiving the bending action in accordance with the movement of a robot. Therewith, a crack is less likely to occur in the shield layer constituted of the shield tape 5. Therefore, compared with a conventional similar type shield wire, flexibility and bending resistance of the shield wire P are excellent.

[0053] In terminal processing of this shield wire P, first, as illustrated in FIG. 4, a nick t is made over a whole circumference of the sheath 6 at a terminal portion having a necessary length by scissors or a stripper.

[0054] This nick t is also made at the shield layer (the shield tape 5) to the extent that the drain wire 4 is not cut (the nick t is not made at the drain wire 4). In this case, the core 3 is formed so as to have the cross-sectional circular shape. Therefore, the shield layer (the shield tape 5) of this terminal is certainly adhered to (integrated with) a whole surface of an inner periphery of the sheath 6 with the adhesive layer 7 formed on a whole surface of an outer periphery of this shield layer by the extrusion molding of the adhesive resin, in view of this, the nick t can be easily made at the shield layer (the shield tape 5), as well as the sheath 6.

[0055] Next, wider the state where the nick t is made, using the stripper or the like, the sheath 6′ of the terminal is moved as an arrow in the Figure. Then, the terminal sheath 6′ is stripped via this nick t.

[0056] In this stripping, since a shield tape 5′ of this terminal is adhered to (integrated with) the sheath 6′ with the adhesive layer 7, the shield tape 5′ is certainly stripped with this sheath 6′. Then, the core 3 is exposed (from a chain-line state to a solid-line state in FIG. 4).

[0057] Subsequently, tests were performed on strippabilities of the sheath 6 corresponding to amounts of the inclusion inserted between the paired twisted wires 1′ when the paired twisted wire 1′ has two core wires, four core wires, and five core wires.

[0058] First, shield wires having a strip length of approximately 300 m were fabricated by the above-described manufacturing method to be respective sizes of the wires for examples 1 to 3 and comparative examples 1 to 2 illustrated in Table 1. Next, one each of samples of approximately 20 cm was extracted at points of 50 m, 100 m, and 150 m from a start starting end). Thereafter, stripping tests of the sheath 6 were performed for three times in total.

[0059] As evaluation criteria, it was evaluated as “qualified” when the sheath 6 was stripped together with the shield layer (the shield tape 5) for all the three times when the sheath 6 is stripped with the nick t made on the sheath 6 by the above-described method. On the other hand, when the the sheath 6 was stripped without being together with the shield layer even once in the three times, it was evaluated as “disqualified.”

TABLE-US-00001 TABLE 1 Outer diameter of core wire Number (outer diameter Outer of paired Outer Outer of circumscribed Twisted diameter Outer twisted wires diameter of diameter of circle of paired outer of shield diameter Number conductor insulator twisted wire) diameter layer of sheath of wires mm mm mm mm mm mm Example 1 2 0.5 1.08 1.84 4.0 4.6 6.6 Example 2 4 0.5 1.08 1.84 4.7 5.3 7.3 Example 3 5 0.5 1.08 1.84 5.3 5.9 7.9 Comparative 2 0.5 1.08 1.84 4.0 4.6 6.6 example 1 Comparative 4 0.5 1.08 1.84 4.7 5.3 7.3 example 2 Space area (s) Inclusion (staple surrounded by yarn) inserted in outer periphery space of core wires (c.sub.1) of core wire Cross-sectional Total cross- and circumscribed area (mm.sup.2) of sectional area circle (c.sub.2) of staple yarn × (filling amount) twisted wire number of of inclusion Filling rate Evaluation mm.sup.2 insertions mm.sup.2 of inclusion result Example 1 5.34 0.07 × 87 6.09 1.14 Qualified Example 2 4.16 0.07 × 81 5.67 1.36 Qualified Example 3 4.28 0.07 × 94 6.58 1.54 Qualified Comparative 5.34 0.07 × 44 3.08 0.58 Disqualified example 1 Comparative 4.16 0.07 × 40 2.80 0.67 Disqualified example 2

[0060] As shown in Table 1, the strippabilities of this sheath 6 were evaluated as qualified in the stripping tests when the filling rates of the inclusion 2 were 1.14, 1.36, and 1.54. When the filling rates were 0.58 and 0.67, the strippabilities were evaluated as disqualified. From this, it was shown that the shield layer (the shield tape 5) as well as the sheath 6 is stripped when the inclusion filling rate is 1.14 or more. Accordingly, it is estimated that the inclusion filling rate is preferred to be 1.0 or more.

[0061] As illustrated in FIG. 2, in the case where a plurality of nicks 8 extending in a direction intersecting with a longitudinal direction of the wire is formed on the shield tape 5 over a whole length of the shield tape 5 in the longitudinal direction, when the terminal sheath 6′ is stripped, the shield tape 5′ (the shield layer) of the terminal is torn off via the nicks 8 and stripped with the sheath 6′ irrespective of whether the nick t reaches the shield tape 5 or not. This is because the shield tape 5 is adhered to the sheath 6 to cause stripping force to be applied to the shield tape 5. Disposing this nick 8 improves the flexibility of the shield tape 5, which is wounded around.

[0062] The nick 8 may be in a perforation pattern. The nick 8 may be preliminarily formed on the resin film 5a. Alternatively, after the metal thin films 5b and 5c are formed, the nick 8 may be formed to reach these metal thin films 5b and 5c only or both the resin film 5a and the metal thin films 5b and 5c. At this time, the nick 8 may pass through the shield tape 5 or may be a half cut.

[0063] After stripping (removing) of the sheath 6′ and the shield tape 5′ of the terminal is finished, the drain wire 4 is removed from the core 3 as is conventionally done. Then, after operations, such as stripping the insulating coating 1b of the core wire 1, the core wire 1 and the drain wire 4 are coupled to terminals of various kinds of connector or electrical device.

[0064] For the conductor 1a of the core wire 1 and the drain wire 4 described above, an aggregated twisted wire or a single wire of the above-described copper alloy wire or the like can be employed.

[0065] It is obvious that the shield wire P according to the present invention can be used for not only the robot cable, but also various cables or the like that request the bending resistance.

[0066] The above-disclosed embodiment is all considered as illustrative and not restrictive. The scope of the invention is indicated by the appended claims. All variations and equivalents which fall within the range of the appended claims are intended to be embraced therein.

LIST OF REFERENCE NUMERALS

[0067] P: Shield wire [0068] t: Nick onto sheath and shield tape [0069] 1: Core wire [0070] 1′: Paired twisted wire [0071] 1a: Conductor of core wire [0072] 1b: Insulating coating of core wire [0073] 2: Inclusion [0074] 3: Core ade by twisting core wire (paired twisted wire) and inclusion [0075] 4: Drain wire [0076] 5: Shield tape (shield layer) [0077] 5′; Stripped terminal shield tape (shield layer [0078] 6: Sheath (protecting layer) [0079] 6′: Stripped terminal sheath [0080] 7: Adhesive layer [0081] 8: Nick of shield tape