KR20040062997A - Flexible interconnect cable with ribbonized ends and method of manufacturing - Google Patents

Abstract

The flexible interconnect cable is made by a method comprising providing a core and wrapping a conductive shield element around the core. An insulating sheath layer is extruded around the core to surround the shielding element, and a multi-wire cable having a ribbon end and a separate intermediate portion is connected to one end of the core. The core is removed from the sheath to insert the cable component into the sheath. The final assembly has a shield and an intermediate portion of the cable component that is loosely contained within the sheath.

Description

FLEXIBLE INTERCONNECT CABLE WITH RIBBONIZED ENDS AND METHOD OF MANUFACTURING

Certain applications require miniaturized multi-wire cable assemblies. If a significant number of conductors are required, very fine conductors are used to prevent bulky and undesirable cables. To limit electrical noise and interference, coaxial wires with shields are used for the conductors. A dielectric sheath surrounds the central conductor and electrically separates it from the conductive shield. Such bundles of wires are surrounded by a conductive knit shield and an outer protective sheath.

In some applications that require a plurality of different conductors, it is desirable for the cable to be very flexible, flexible, or loose. In applications such as cables for connecting to medical ultrasound transducers, rigid cables having adequate resistance to bending can make imaging of ultrasound images difficult. However, in sheaths protecting conventional cables, wire bundles may be undesirably rigid.

In addition, cable assemblies with many conductors can be time-consuming and expensive to assemble to other components. When each wire is used in a bundle, it may not be easy to identify the wire end corresponding to the wire selected at the other end of the bundle when a tedious continuity test is required. Generally, the wire end at one end of the cable is connected to a component such as a connector or a printed circuit board, and the connector or board is connected to a test rig that conducts each wire one at a time, so that the assembler has identified the wire end. Can be appropriately connected on the second connector or the substrate.

Ribbon cables where the wire is protected from one end of the cable to the other end can address this problem. However, all the wires of the welded ribbon resist bending and create undesirable rigid cables. In addition, ribbons folded along transverse multiple fold lines may not produce dense cross sections, which may undesirably increase volume and may not provide a circular cross section suitable for many applications.

This application is a continuation of US patent application Ser. No. 09 / 822,550, filed Mar. 30, 2001.

FIELD OF THE INVENTION The present invention relates to multi-wire cables, and more particularly to coaxial wiring of small instruments.

1 is a perspective view of a cable assembly according to a preferred embodiment of the present invention.

2 is a perspective view of a wiring component according to the embodiment of FIG.

3 is an enlarged cross-sectional view of an end portion of the wiring component according to the embodiment of FIG.

4 is an enlarged cross-sectional view of the cable assembly according to the embodiment of FIG.

5 is an enlarged cross-sectional view of the cable assembly in a curved state according to the embodiment of FIG.

6 is a schematic side view of a first process in a preferred method of making a cable assembly.

7A and 7B are cross-sectional views of cable jacket components of a preferred embodiment of the present invention.

8 is a side view of the cable assembly at selected stages of manufacture in accordance with the method of claim 6.

9 is a side view of the cable assembly at selected stages of manufacture in accordance with the method of claim 6.

10 is a side view of the cable assembly at selected stages of manufacture in accordance with the method of claim 6.

11 is a side view of the cable assembly at selected stages after manufacture according to the method of claim 6.

The present invention overcomes the limitations of the prior art by providing a cable assembly and a manufacturing method. The method includes providing a core and wrapping a conductive shield element around the core. An insulating sheath layer is extruded around the core to surround the shielding element, and a multi-wire cable having a ribbon end and a separate intermediate portion is connected to one end of the core. The core is removed from the sheath to insert the cable component into the sheath. The final assembly has a shield and an intermediate portion of the cable component that is loosely contained within the sheath.

1 shows cable assembly 10 having connector end 12, transducer end 14, and flexible connecting cable 16. The connector end and the transducer end are shown as examples of components that can be connected to the cable 16. In this example, the connector end includes a circuit board 20 having a connector 22 for connecting to an electronic device such as an ultrasonic imaging device. The connector end includes a connector relief 24 and a strain relief 26 surrounding the cable end. On its opposite end, ultrasonic transducer 30 is connected to the cable.

The cable 16 comprises a plurality of fine wires 32 coaxially shielded. As also shown in Fig. 2, the wires are arranged in groups 33, each group having a ribbon-like ribbon portion 34 at its individual end and an elongated loose portion extending over most of the length of the cable between the ribbon portions. 36 is provided. Each ribbon portion includes a single layer of wire arranged side by side and attached to each other and trimmed to expose the shielding layer and the center conductor for each wire. In the loose part, the wires are not connected to each other except at their ends.

The shield and conductor of each wire are connected to a circuit board or to any electrical component or connector by any conventional means as required by the use in which the cable is used. The loose portion 36 of the wire extends the entire length of the cable between the strain reliefs, ie across the strain reliefs, into the housing in which the ribbon portion is arranged and connected.

The ribbon portion 34 makes specific indications so that the assembler correlates the opposing ribbon portions of a given group and correlates the ends of specific wires within each group. The group identifier 40 is printed on the ribbon portion such that the first wire identifier 42 on each ribbon portion allows the first wire to be identified on the individual ends in the order of each ribbon. It is important that each group have a one-to-one correspondence in order of the wires in each ribbon portion. Thus, the assembler can identify the nth wire from the identified first end of the given group "A" as the corresponding nth wire in the opposing ribbon, without the need for trial and error continuity tests to find the appropriate wire. have. This correspondence is ensured even if the loose middle portion 36 of each group can be moved relative to each other or with the middle portion of another group in the cable.

Figure 3 shows a cross-sectional view of the individual end portions with the wires connected together in the outer sheath layer 44 of the weld joint 46, with the conductive shield 50 of each wire being electrically insulated from the other portions. Inner dielectric 52 and center conductor 54 remain insulated. In another embodiment, the ribbon portion may be secured using an adhesive between the connecting sheath layer 44 by bonding each sheath layer to a common strip or sheet or by a mechanical clip.

Figure 4 shows a cable cross section through most of the length of the cable spaced from the ribbon portion and reflecting the middle portion. The wire is loosely received in the cylindrical flexible cable sheath 60. As shown in FIG. 1, conductive knit shield 62 is present on the inner surface of the shield to surround all wires and form a bore 64. Referring to Figure 4, the bore diameter is chosen slightly larger than the diameter needed to house all the wires densely. When the wire is kept straight, as shown in FIG. 4, when the bore intersection is free to slide into a flat structure that is reduced from the circular intersection, the cable bends to the least resistance in the hermetic band as shown in FIG. To provide performance.

In a preferred embodiment, there are eight groups with 16 wires each, but these numbers can vary substantially, and some embodiments can use all wires within a single group. The wire preferably has an outer diameter of 0.04 cm (0.016 inch), but these dimensions can range in any size depending on the application. The cable has a total outer diameter of 0.84 cm (0.330 inch) for the jacket portion 60 and the outer shell has a diameter of the bore of 0.69 cm (0.270 inch). Since loose wires are bundled with a cross section slightly larger than the sum of the wire regions, there is considerable clearance in the bore at steady state. This allows the wire to glide to be flexible around it, minimizing wire-to-wire friction that can occur when the wires are hermetically wrapped together, such as conventional methods where the wire shield is wrapped around the wire bundle. In a preferred embodiment, a bending radius of 1.91 cm (0.75 inch) or about twice the cable diameter provides minimal bending force when the cable is folded between two fingers and bent to a natural radius. Inherently, the bending radius and low resistance to bend are limited slightly less than the total bending resistance of each component. Since each wire is quite thin and has a minimum resistance to bend at a radius on the scale of the cable diameter, the sum of the wire resistances is slightly added to the bending resistance of the sheath and shield, creating a total bending resistance.

Manufacturing method

FIG. 6 shows a skin manufacturing apparatus 70 that includes a shielding knitting or loom 72 and an extruder 74. The nylon core tube 76 having a diameter of 0.64 cm (0.250 inch) and having a smooth outer surface has a bore diameter of 0.51 cm (0.200 inch). The core tube can be any other wide range of materials and can have a central core. The tube is fed to a knitting machine, which wraps the fine conductive metal strand 80 around the tube to form a shield 62. The enclosed and shielded core is thus fed to an extruder 74, which extrudes the shell 60 around the shielded core tube to form the final shell component 82, shown in cross section in FIGS. 7A and 7B. . In a preferred embodiment, the outer material is flexible PVC and other materials include thermoplastic elastomers or polyurethanes. The shield is extruded at limited low temperatures such that the sheath material remains viscous, does not excessively puncture the voids or gaps between the shield wires, and does not make significant contact with the core except as minimally shown in FIG. 7B. This avoids adhesion that can make core tube extraction difficult. The sheath material partially encapsulates a portion of the shielding wire by at least partially surrounding it, and in selected embodiments is perforated through the gaps between the wires to contact or access the surface of the core.

However, the sheath material at least partially encapsulates the shielding wire, creating an adhesion that helps keep the shield and the sheath interior in contact with each other over the entire length without being separated during manufacture, assembly, or use of the cable. Thus, the shielding wire is not detached from the shield but is attached along its entire length. This provides an elastic resistance to the tensile force and facilitates returning to its original length once the tensile force is removed. When fully compressed around the wire to resist increasing tensile forces, the shielding wire provides a stretching limit, and the elasticity of the sheath then causes the shield to return to its original length and diameter around the wire, providing the desired flexibility as described above. to provide. In some applications, these functions and advantages can be achieved if the shield is separated from the sheath as long as the sheath is loose with respect to the cable wire and attached to the sheath at each end.

8 shows the sheath segment 82 (including the core, shield and sheath) cut to provide an end 86. Opposite ends (not shown) are similarly cut. The sheath layer is cut in line 90 to remove the end portion 92 comprising about 15 cm (6 inch) segments on each end without damaging the shielding wire and core. As shown in Fig. 9, the end portion is removed, and the shielding wire 62 is folded cylindrically with respect to the outside of the shell 60, and fixed to the end by a band of adhesive tape 94. In this step, the ends of the shield can be selectively secured to the shield by the attachment of the strain relief element 96. The strain relief element may be an over-molded elastomer covering the folded back portion of the shielding wire or may be a rigid clamping type device that tightens the shielding and sheath end in an annular gap or nip. Without the strain relief element, the folded rear shield end resists movement from the shell by axial tension from the opposite end.

As shown in Figure 10, the cable ribbon 33 is connected at one end to one end of the core 76 by a fabric sheath 100 that is folded around the contents as tension is applied. Other embodiments, such as clips, tapes or other hooks, may be employed so long as they easily pass through the bore of the sheath without damaging the sheath of the sheath and are thin enough to protect the ribboned end of the wire as it passes through the sheath. Until each cable of approximately the same length is exposed at each end of the sheath, the core 76 is pulled from the end opposite the connected ribbon 33 and the core is shown in FIG. 11 showing the final cable part. As separate from the ribbon. The cable part has a ribbon-like end exposed at each end, an indication identifying each group at each end, and a first wire of each group for subsequent work. The wire may be laser stripped to expose the center conductor and shield in each wire and connected to the connector of the circuit element as described above.

In another embodiment, the strain relief element can be added after ribbon insertion and the folded rear shield wire can be trimmed. In some embodiments, the shielding wire is efficiently attached to the inside of the shell during sheath extrusion, eliminating the need for back folding and end taping to prevent the shield from slipping or necking during ribbon insertion. In other embodiments, the shield can be loosened or easily detached from the interior of the shell, such that the illustrated rear folding of the shield end is required.

Although the preferred and other embodiments have been described above, the present invention is not limited thereto.

Claims (20)

Each wire having a first end and an opposing second end, the first ends of the wires being fixed to each other in a first sequential arrangement, the second ends of the wires being fixed to each other in a second sequential arrangement based on the first arrangement A plurality of wires having an intermediate portion separated from each other between the first and second ends, A cable assembly comprising an outer shell with an inner shield that loosely surrounds all wires. The cable assembly of claim 1, wherein the shield comprises a plurality of knitted wires. The cable assembly of claim 1, wherein the sheath comprises an outer portion forming a bore having an inner surface, wherein the shield is a tube in contact with the surface. 4. The cable assembly of claim 3, wherein the insulation tube comprises a portion at least partially encapsulating a selected portion of the shield. The cable assembly of claim 1, wherein the first and second ends are ribboned. 2. The cable assembly of claim 1, wherein the first ends of the wires are arranged adjacent to one another in parallel in a selected order, and the second ends of the wires are arranged adjacent to one another in parallel in a selected order. 7. The cable assembly of claim 6, comprising an indication on the first end and the second end that sequentially identifies the individual ends of the first wire. The cable assembly of claim 1 comprising a plurality of sets of wires, said wires being secured in each set, said sets being separated from each other. The cable assembly of claim 8, comprising an indication on each end of each set of wires that distinguishes the set of wires from another set of wires. A method of manufacturing a cable assembly, Providing a core, Wrapping a conductive shield element around the core; Forming an envelope by applying an insulating envelope layer to surround the shielding element; Removing the core from the skin; Inserting a multi-wire cable component into the sheath. The method of claim 10, wherein the core is a smooth plastic cylinder. The method of claim 10, wherein wrapping the conductive shield comprises wrapping a plurality of wires around the core. The method of claim 10, wherein forming the skin comprises extruding the skin layer around the shield. The method of claim 10 including attaching a cable component to the core prior to removing the core from the sheath. The method of claim 10 comprising removing the end portion of the skin layer and folding the exposed end portion of the shield on the remaining skin layer before removing the core. The method of claim 10 comprising attaching a strain relief element to an end portion of the sheath prior to removing the core. The method of claim 10, wherein the cable component comprises a plurality of wires having end portions that are ribbon-shaped and have an intermediate portion between the first and second ends that are separated from each other. A method of manufacturing a cable assembly, Providing a core, Wrapping a conductive shield element around the core; Extruding an insulating envelope layer to surround the shielding element; Attaching a multi-wire cable component having a ribbon end and a separate intermediate portion to an end of the core, Removing the core from the sheath to insert a cable component into the sheath. 19. The method of claim 18 comprising removing the end portion of the skin layer and folding the exposed end portion of the shield onto the remaining skin layer prior to removing the core. 19. The method of claim 18 comprising attaching a plurality of multi-wire cable components having a ribbon-shaped end and a separate intermediate portion to an end of the core.