WO2007112230A2

WO2007112230A2 - Wire mold spacer, wire connection kit, wire fabrication method and wire

Info

Publication number: WO2007112230A2
Application number: PCT/US2007/064369
Authority: WO
Inventors: Hiroyuki Chiba
Original assignee: 3M Innovative Properties Company
Priority date: 2006-03-24
Filing date: 2007-03-20
Publication date: 2007-10-04
Also published as: JP2007259623A; TW200803100A; WO2007112230A3

Abstract

This invention provides a mold spacer for a wire, a wire connection kit, a wire fabrication method and a wire capable of improving the connection reliability of a joined portion. When forming an insulative wire covering by molding resin on a joint (6) of wire (1), a resin filling space to be filled in with a liquid resin (15) is formed between the joint (6) and mold case (10). Liquid resin (15) is poured in the resin filling space and solidified to form a wire mold spacer constituting an insulative covering (7) of predetermined thickness. The spacer comprises a cylindrical spacer body mounted on or adjacent to joint (6), and a multiplicity of pins projected radially outward from the outer surface of the spacer body with at least a plurality of projection ends adapted to contact the inner wall surface of the mold case (10).

Description

WIRE MOLD SPACER, WIRE CONNECTION KIT, WIRE FABRICATION

METHOD AND WIRE

Field of the Invention

This invention relates to a wire or cable mold spacer mounted on or near a joined portion of two wires or cables. The spacers may be employed in the resin molding of an insulative wire or cable core covering uniformly around the joined portion or the wires or cables. Wire (or cable) connection kits, wire (or cable) fabrication methods and wires (or cables) including the spacers also are provided.

Background

A wire (or synonymously a "cable") mold spacer may be mounted on or near the joined portion of two wires to secure a resin filling space between the joined portion and a mold case when a wire core covering is resin molded around the joint. Some spacers include a sheet of unwoven fabric rounded into a cylinder or a meshed tube. The spacers often are formed of a resin material such as polyester or olefin.

A wire (or synonymously a "cable") joint includes an exposed portion where the inner and outer cover portions of the wire cores are removed and two or more wires are interconnected. By resin molding a covering portion over the joint, the insulation characteristic and waterproofness of the joined portion can be secured, and the connection quality of the joint can be maintained for a significant time, even indefinitely.

Fig. 1 shows a conventional mold spacer 102 with a sheet of unwoven fabric (including braided resin) rounded into a cylinder. Mold spacer 102 may be used when injecting a liquid resin 104 of relatively low viscosity (i.e., under about 3000 mPa-s) such as an epoxy resin into mold case 103. Generally, as shown in Fig. 1, mold spacer 102 is mounted adjacent to, and locally at, opposite sides of joined portion 101 of electric wire 100 to secure a resin filling space between the joint and mold case and to control flow of the resin poured into the central region of the mold case. The low viscosity liquid resin 104 is used to improve the permeability (i.e., facilitate flow) of liquid resin 104. The partial use of an unwoven fabric can also improve the flowability of liquid resin 104.

The viscosity of the liquid resin, however, increases with the decrease in temperature. A liquid resin low in viscosity at processing temperatures will therefore increase in viscosity (to about 5000 mPa-s or more) and decrease in fluidity at normal ambient temperatures so that the insulation characteristic and waterproofness at the joint are adversely affected with the decrease in temperature. Also, the unwoven fabric often varies in fiber thickness and mesh, and an unwoven fabric having a thin fiber and a large mesh is easily crushed under a load. Where joined portion 101 (which has a tendency to bend) comes into contact with the inner wall surface of mold case 103, for example, mold spacer 102 may be crushed and result in a narrowed resin filling space between the joint 101 and mold case 103. A thick fiber and a small mesh, on the other hand, hardens the mold spacer 102, and the unwoven fabric sheet may be difficult to bend into a cylinder, requiring greater labor to mount the unwoven fabric onto joint 101.

Another example is a mold spacer 112 formed of the meshed tube shown in Figs. 2 and 3. Mold spacer 112 is useful with the injection of a liquid resin 114 that is low in viscosity, such as a polyurethane resin. As such, the spacer must not adversely affect the permeability or the flowability of liquid resin 114. Fig. 9 shows the state in which mold spacer 112 is mounted on joined portion 111 of electric wire 110. A comparatively large resin filling space is formed between the mold spacer 112 and the mold case 113. The use of a mold spacer 112 of this type can secure the resin filling space at least as large as the thickness of the mold spacer 112.

A tube is also sometimes used as a mold spacer. In such a case, the wire joint is arranged in a mold case, and a resin filling space is formed between the case and the joint. With solidification of the liquid resin poured into the case, a wire core cover is formed around the joint. A mold spacer of this type, however, must be resin molded into a cylinder, and the spacer must therefore be mounted on one of the wires before molding the wire core covering onto the joint. This mold spacer hampers connection of the wires and leads to a lower level of operability. Also, a multiplicity of mold spacer types corresponding to individual wire diameters are required. This increases the cost of resin molding dies and requires an inefficient increase in inventory burden. It is also difficult to set the joint properly and accurately in position at the center of the accommodation space within the mold case. Particularly where the wires exhibit a tendency to bend, the joint can be unbalanced, and the fluidity of the liquid resin can be adversely affected, reducing the stability of the connection quality of the joint. Brief Summary

In one aspect, the present invention provides a mold spacer for a wire (or cable) that can positively secure the resin filling space between a joint (or splice) and a mold case and can uniformly form a wire covering of predetermined thickness around the joint for improved connection reliability. In other aspects, the invention provides wire connection kits, wire fabrication methods and wires employing such mold spacers.

In on specific embodiment, the invention provides a mold spacer for a wire (or cable) interposed between a wire (or cable) joint or splice and a mold case to thereby form a resin filling space that may be filled with a liquid resin between the joint or splice and the mold case. The liquid resin poured into the resin filling space may be solidified to form an insulative wire covering of a predetermined thickness. In one embodiment, the spacer may generally be characterized as comprising a cylindrical body that is capable of being mounted on or near a wire joint or splice and a multiplicity of pins projecting radially outward from the outer surface of the body with a plurality of such projections adapted to contact the inner wall surface of a mold case.

According to other embodiments of the invention, the body of the mold spacer may be substantially planar in an original shape and may be formed into a cylinder by causing projected pins formed at one end of the spacer body to engage its the other end. The projection pins may be relatively short at or near the central portion of the joint or splice (that is larger in diameter), relatively long at the ends of the joint or splice (that are smaller in diameter than the central portion).

In some embodiments the mold may be partially or fully formed as a mesh. Where such a mesh is used, it may be of any shape or geometry, including polygonal. The mesh may be relatively narrower in the direction the spacer body is bent into a cylinder and relatively larger in a perpendicular direction. As a specific, non-limiting example, the mesh may be rhombic or hexagonal. The long axis of the mesh may be arranged in a direction perpendicular to the direction in which the spacer body is bent into a cylinder, and the short axis of the mesh may be arranged in the direction in which the spacer body is bent into a cylinder. Other aspects of the invention provide a wire connection kit that may comprise: a mold case for accommodating a wire (or cable) joint or splice; a liquid resin that forms an insulative wire covering on or adjacent to the joint or splice after being poured into the mold case and solidified for a predetermined length of time; and a mold spacer as described above that may be mounted on the joint or splice to form a resin filled space in the mold case.

The invention also provides a method of fabricating a wire (or cable) wherein a mold spacer as described above is mounted on or near a joint or splice to form a resin filling space to be filled with a liquid resin poured between the joint or splice and a mold case. Liquid resin is poured into the filling space and solidified to form a covering of predetermined thickness on or adjacent to the joint or splice. In one embodiment of the method, projecting pins on are brought into contact with the inner wall surface of the mold case to set the joint or splice at or near the center of the mold case.

Brief Description of the Drawings

Figure 1 shows a sectional view of a conventional wire joint. Figure 2 shows a sectional view of a second conventional wire joint. Figure 3 shows a perspective view of the mold spacer depicted in Fig. 2.

Figure 4 shows a sectional view of one embodiment of a wire joint employing a mold spacer according to the invention.

Figure 5 shows a sectional view taken in line A-A of the electric wire shown in Fig. 4. Figure 6 shows a perspective of a spacer body according to one aspect of the invention in a substantially planar form.

Figure 7 shows a perspective view of a mold spacer formed by bending the spacer body depicted in Fig. 6 into a cylinder.

Figure 8 shows a plan view of the state in which core wires are interconnected through a pressure sleeve with the inner and outer coverings removed before a mold spacer is mounted on the joined portion of the wires.

Figure 9 shows a plan view of the state in which a mold spacer is mounted on the joint depicted in Fig. 8.

Figure 10 shows a sectional view of the state in which the joined portion of Fig. 9 is accommodated in a mold case having a half structure.

Detailed Description of Preferred Embodiments In preferred embodiments, the mold spacers of the invention generally include a substantially cylindrical body having a plurality of pins projecting radially outward from the outer surface of the spacer body. The mold spacer may be mounted on a splice or joint so that a resin filling space corresponding to at least the length of the projection pins can be formed between the joined portion and the inner wall surface of a mold case. It is therefore possible to form a covering of predetermined thickness around the joint or splice that improves the insulation characteristic, waterproofness, connection reliability of the joint or splice. As used in this description, the terms "wire" and "cable" and the terms "joint" and "splice" are used interchangeably, and the invention is to be construed to apply equally to both respectively. The projection pins can be formed in any geometric shape including a truncated cone shape, circular cylindrical shape, truncated pyramid shape or prismatic shape. Each of the projection pins can also be formed as a protrusion or bump having a truncated top.

The original flatness of the spacer body makes it possible to mount the spacer on a joint after being formed by interconnection of the core wire portions of the wires. As a result, the operability of connecting the joints of the wires is not adversely affected. The size of the spacer body can be changed in accordance with the diameter of the wires. A multiplicity of spacers of different sizes, therefore, are not required for different wire sizes or different numbers of core wires, thereby reducing the spacer cost. Also, the projecting pins from one end of the spacer body may be made to engage the other end of the spacer body to connect the two ends of the spacer body to each other. The spacer body bent into a cylinder is prevented from being elastically restored into the original shape by the elastic restitutive power of itself. As a result, the labor of attaching the spacer repeatedly to a joint from which it is detached is saved, improving the connection workability of the wire. The projection length of the projection pins may be relatively short at the central portion of a joint and relatively long at the two ends of the central portion. By doing so, a joint having a thick central portion and thinner ends can be brought into contact with the inner wall surface of the mold case through the spacer in a balanced fashion. The length of the projection pins can also be changed in keeping with the thickness of the joint. The spacer body may be formed as a mesh, and therefore the permeability and the flowability of a liquid resin high in viscosity can be improved. In this way bubbles are prevented from being left in the mold case for a higher hermeticity of the wire covering by resin molding. In one specific configuration a polygonal mesh may be formed with a small width in the direction in which the spacer body is bent into a cylinder, allowing for an ease of bending. The rhombic or hexagonal mesh can also enhance the bendability of the spacer body. A hexagonal mesh can increase the internal angle of the mesh and prevent bubbling in the mesh.

A wire connection kit may be provided that includes a wire mold spacer together with a mold case, a liquid resin, a sealing member and various tapes, so that a wire covering of a predetermined thickness can be uniformly formed around a joint of splice by solidification of the liquid resin. As a result, the insulation characteristic and the waterproofness of the joined portion can be improved while at the same time enhancing the connection reliability of the joint or splice.

The projection pins of a mold spacer may be brought into contact with the inner wall surface of a mold case and a joint or splice may be set in position at the center of the mold case. In this way, the liquid resin can be uniformly filled in the resin filling space formed between the joint and the mold case. As a result, a wire covering of predetermined thickness can be formed around the joint, thereby improving the insulation characteristic and the waterproofness of the joint while at the same time enhancing the reliability of its connection.

A set of preferred embodiments of the invention are explained in detail below with reference to the drawings. Fig. 4 shows an electric wire according to an embodiment of the invention. An electric wire 1 according to this embodiment includes wire members (each making up a bundle of a multiplicity of signal lines) of a predetermined length interconnected to lengthen the wire, and is used, for example, as a signal transmission cable arranged along a tram railroad or a road side. Electric wire 1 includes a pair of signal cables 2, 2 each having a core wire portion

4b exposed by removing a covering portion (outer cover) at its forward end. A mold case 10 accommodates joint 6 for electrically connecting core wire portions 4b of the signal cable pair 2, 2 to each other. Liquid resin 15 may be poured into mold case 10 and form an insulative covering portion 7 around joint 6 after curving. Mold spacer 23 is mounted on joint 6 in such a manner to form a resin filling space in mold case 10. Mold case 10, liquid resin 15 and mold spacer 23 make up an electric wire connection kit. Each signal cable 2, as shown in Figs. 4 and 8, is covered with an insulative outer cover 3 around a multiplicity of signal lines 4. The outer cover 3 is formed of a polyvinyl chloride or polyethylene resin or similar material which is flexible and has a high ability to protect the lines 4. Each signal line 4 includes a core wire portion (e.g., copper wire) 4b and an outer covering portion (inner cover) 4a as shown in Fig. 5. Inner cover 4a, like outer cover 3, may be formed of a material such as a polyvinyl chloride or polyethylene resin. At the forward end of the signal cable 2, the outer cover 3 is removed and the signal line 4 is exposed over a predetermined length. Similarly, the inner cover 4a of the signal line 4 is removed and the core wire portion 4b is exposed over a predetermined length. The end portion of the outer cover 3 may be wound and sealed with a sealing tape 14 to prevent the poured liquid resin 15 from flowing in along signal line 4.

The core wire portions 4b of the signal cable pair 2, 2 exposed with outer cover 3 removed at a forward end are arranged in opposed relation to each other and interconnected electrically through a connector. The connector may include a pressure- bonding sleeve 5 or any other common suitable connector such as a pressure-filling connector. Pressure -bonding sleeve 5 is a copper cylinder having open ends into which core wire portions 4b of signal cable pair 2, 2 are inserted. With core wire portions 4b inserted from the ends, the cylinder wall of the pressure -bonding sleeve 5 may be fastened using a hand tool or the like. In this way, core wire portions 4b are connected to each other electrically to form joint 6. Signal cable 2 is not limited to the particular signal cable depicted. A shield tape or the like may also be attached on the inside of the outer cover 3. The mold case 10 depicted in Figs. 4 and 10 or 7 are configured as a pair of cases having a half structure molded with resin. The half cases each engage via an engaging means and can be integrally assembled. The internal space of mold case 10 constitutes an accommodation space 11 for accommodating joint 6 of electric wire 1. The ends of mold case 10 are open, and signal cable 2 is led out from open end 12. There may be a slight gap between the opening of open end 12 and signal cable 2, which may be sealed with sealing putty 25 and adhesive vinyl tape 26. As a result, the interior of the mold case 10 constitutes a hermetic accommodation space 11, and liquid resin 15 is prevented from leaking out of mold case 10 while insulative covering 7 is molded around joint 6.

A liquid of a high producibility which has a high insulation characteristic and a high waterproofness as well as a high strength and a high elasticity preferably is used for liquid resin 15. Polyurethane resin and epoxy resin are considered suitable. Polyurethane resin is low in viscosity at normal temperature and especially high in resin permeability and flowability. Epoxy resin, in spite of having a high viscosity at normal temperature, is high in strength, insulation characteristic and waterproofness like polyurethane resin. Epoxy resin, though inferior to polyurethane resin in permeability and flowability for its high viscosity, is improved in both permeability and flowability by use of a mold spacer 23 according to the invention having a large mesh (grating), thereby preventing bubbles from being left in mold case 10.

Mold spacer 23, as shown in Figs. 4, 6, 7 may be molded from a polyvinyl chloride or polyester resin or a like material. Other resin materials having acceptable adhesion with the poured liquid resin can be used as a molding material.

The mold spacer 23 depicted in Fig. 6 includes an originally substantially flat or planar spacer body 21 and a multiplicity of projection pins 22 projecting in a direction perpendicular to one surface of spacer body 21. Mold spacer 23 may optionally be formed with a rough surface to improve its adhesion with the liquid resin. Spacer body 21 is meshed with a regular arrangement of substantially hexagonal meshes (grating). The size of each mesh is determined taking account of the fluidity of viscous liquid resin 15. In the case of a liquid resin with a viscosity of between about 3,000-5,000 mPa-s, the shortest distance in the minor axis direction of each mesh may be set preferably to the order of over 5 mm, and in the case of 1,000-2,000 mPa-s, the shortest distance may be set to the order of over 1 mm. The mesh may also be formed to a size smaller than the pressure sleeves 5 shown in Fig. 8. The thickness of the spacer body 21 is set preferably to between about 0.5 and about 2.0 mm taking the case of bending into consideration.

As shown in Fig. 6, substantially hexagonal meshes are arranged with a long axis P, i.e., the length in a direction perpendicular to the direction in which spacer body 21 is bent, and a short axis Q in a direction in which spacer body 21 is bent. With this arrangement of short axis Q in the direction in which spacer body 21 is bent, the bending ease of spacer body 21 is increased and the tendency of the body to elastically restore to its original shape is reduced. Thus, cylindrical mold spacer 23 corresponding to the size of joint 6 can be easily assembled. Also depicted in this embodiment, hexagonal meshes having a shape crushed along short axis Q can increase the inner angle of the polygon arranged along long axis P, thereby making it possible to suppress or prevent the generation of bubbles when injecting a liquid resin.

Long axis P of the mesh represents the direction along a larger width of the mesh, and short axis Q the direction along a smaller width of the mesh. The directions of long axis P and short axis Q are assumed to cross each other at right angles. The mesh is not limited to the hexagon shown in this embodiment. The mesh may include, for example, circles, ellipsoids, rhombi or other polygons. In the case where the mesh is polygonal, the larger the inner angle on the long axis P of the polygonal mesh, the more preferable to prevent the generation of bubbles at the time of injecting the liquid resin. Specifically, the inner angle is desirably larger than at least about 25°.

Projection pins 22 are each formed from a portion (lattice point) where adjacent meshes are in contact with each other. As shown in Fig. 6, substantially all projection pins 22 are projected vertically upward. Each projection pin 22 is formed in the shape of a truncated cone with a flat forward end. The flat forward end of projection pin 22 prevents it from being buckled when it comes in contact with the inner wall surface of the mold case 10 (see, e.g., Fig. 5). Each projection pin 22 is thus in stable contact with and supportingly kept pressed against the inner wall surface of mold case 10.

Projection pins 22 may include a first group of shorter pins arranged at or near a central portion of joint 6 having a relatively larger diameter, and a second group of longer pins arranged at opposite ends of joint 6 having a diameter smaller than that near the central portion. In this embodiment, the longer projection pins 22 are arranged outside of the central portion of the joined portion 6. The other projection pins 22 are formed at substantially the same projection length. In mounting the mold spacer 23 on joint 6 in such a manner to contain the joint, the shorter projection pins 22b are arranged on joint 6 having a larger diameter while the longer projection pins 22a are arranged on the small- diameter portions on the sides of the joint. By doing so, the thickness difference between the large-diameter joint 6 and the small-diameter portions on the sides of the joint can be adjusted by the length of the projection pins 22, with the result that projection pins 22 can be kept in substantially equal contact with the inner wall surface of mold case 10. Also, by arranging the projection pins of different projection lengths along the joint, it is possible to keep up with the thickness variations of the joint flexibly with the number of signal lines in a bundle. The projection length of the projection pins can be arbitrarily set based on the relation between the thickness and material of the projection pins. From the viewpoint of the flowability of the liquid resin, pin strength and producibility, however, the projection length is normally set to 2 to 20 mm, or preferably 5 to 10 mm. Figs. 4, 7, and 9 show mold spacer 23 formed by bending the flat spacer portion

23 into a cylinder to contain joint 6 (not shown). By bending spacer body 21 into a cylinder, projection pins 22 are radially projected outward from the outer surface of spacer body 21 (see Fig. 5). Spacer body 21, due to its elasticity, tends to restore to its original shape by elastic restitutive power when bent into a cylinder. Since the projection pin formed at one end of spacer body 21 is engaged by the other end of spacer body 21 , however, spacer body 21 is prevented from being restored to its original flat form. In this sense, projection pin 22 also functions as an engaging pin. Incidentally, according to this embodiment, an auxiliary fixing band 27 may be used on both sides of joint 6 to mount mold spacer 23 closely on or near the joint. Once mold spacer 23 is mounted on joint 6 and accommodated in mold case 10

(see Fig. 10), mold spacer 23 may be arranged between joint 6 and mold case 10, and projection pins 22 of mold spacer 23 may be brought into contact with the inner wall surface of mold case 10. This forms a resin filling space (to be filled with liquid resin 15) between joint 6 and mold case 10. In the embodiment depicted in Fig. 10, mold case 10 is comparatively large, and the resin filling space in the upper part of the case is larger than the resin filling space in the lower part. Where the mold case 10 is of such a size to adapt clearly to joint 6 (as shown in Fig. 5), however, projection pins 22 help set joint 6 in position at or near the center of mold case 10 so that liquid resin 15 may be uniformly filled in around joint 6. Also, in the case where electric wire 1 has a tendency to bend, the projection pins 22 contacting the inner wall surface of mold case 10 help correct the bending tendency and secure the resin filling space. In this way, liquid resin 15 poured into mold case 10 is filled and solidified in the resin filling space. Thus, insulative covering 7 may be molded by resin on and in the vicinity of joint 6.

This invention is not limited to the specific embodiments illustrated and described above, and can be embodied in other forms. Although the mold spacer 23 is formed by bending the spacer body 23 into a cylinder in the aforementioned embodiment, for example, the projection pins may be formed radially outward from the outer surface of a cylindrical member molded in advance.

Also, mold spacer 23, though formed to cover both joint 6 and a substantial portion of the adjacent wire, it could also be mounted in such a manner as to contain only joint 6, for example in the case where the portion of electric wire 1 accommodated in mold case

10 has little or no tendency to bend.

Also, the size, shape, position and number of the projection pins 22, which are determined by the material of the mold spacer 23, the thickness (diameter) of joint 6, the thickness of insulative covering 7 and the type of liquid resin 15, are not limited to the specific embodiments disclosed herein.

Claims

What is claimed is:

1. A mold spacer for a wire or cable, comprising: a substantially cylindrical body; and a plurality of pins projecting substantially radially outward from an outer surface of the body with at least a plurality of projection ends thereof adapted to contact the inner wall surface of a mold case.

2. The mold spacer of claim 1 where the spacer is capable of being interposed between a wire or cable joint and a mold case to form a resin filling space.

3. The mold spacer of claim 1 wherein the body is substantially planar in an original shape and may be formed into a cylinder by causing the projected pins formed at one end of the body to engage the other end.

4. The mold spacer of claim 2 wherein the projection pins are short along the portion of the body adjacent to that portion of a wire or cable joint large in diameter, and long along the portion of the body adjacent to that potion of the joint that is smaller in diameter.

5. The mold spacer according to any of the preceding claims wherein at least a portion of the body is formed as a mesh.

6. The mold of claim 5 wherein each mesh of the spacer body is substantially polygonal and narrower in the direction the body is capable of bending into a cylinder than in the direction perpendicular to the bending direction.

7. The mold spacer of claim 6 wherein the mesh is rhombic or hexagonal and the long axis of the mesh is arranged in the direction perpendicular to the direction in which the spacer body is bent into a cylinder, the short axis of the mesh being arranged in the direction in which the spacer body is bent into a cylinder.

8. A wire connection kit comprising: a mold case for accommodating a wire or cable joint or splice; a liquid resin that forms an insulative wire or cable core covering on the joint or splice after being poured into the mold case and solidified for a predetermined length of time; and a mold spacer as described in any one of claims 1 to 7 mounted on the joint or splice to form a resin filled space in the mold case.

9. A method of fabricating a wire or cable to form a covering portion of a predetermined thickness on a wire or cable joint or splice, the method comprising: mounting a mold spacer as described in any one of claims 1 to 7 on the joint or splice to form a resin filling space to be filled with a liquid resin poured between the joint or splice and a mold case; and injecting liquid resin into the resin filling space; wherein projected pins of the mold spacer for the wire are brought into contact with an inner wall surface of the mold case so that the joint or splice is set in a position at or near the center of the mold case.