WIRE ROPE

Abstract

A wire rope for use in a medical procedure includes a multi-strand coil formed by twisting multiple metal wires together. In the wire rope, gaps are located between the multiple metal wires along an axis of the multi-strand coil. The gaps between the multiple metal wires include a first gap and a second gap that differ in width.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2011-279058 filed in the Japan Patent Office on Dec. 20, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

The disclosed embodiments relate to a medical device. More specifically, the disclosed embodiments relate to wire ropes. Wire ropes are multi-strand coils formed by twisting multiple wires together (see FIG. 7). Japanese Unexamined Patent Application Publication No. 9-49517 discloses a structure of a flexible shaft including a core shaft. In this structure, wires are each helically wound around the core shaft while having minute gaps between turns of the wires, Japanese Unexamined Patent Application Publication No. 2001-280333 discloses a flexible shaft in which at least one of an outer-layer wire and an inner-layer wire is wound while having regular gaps between turns of the wire. Japanese Unexamined Patent Application Publication No. 7-14448 discloses a method of manufacturing a multilayer cable in which multiple core wires, serving as an inner layer, are twisted together in a direction that is opposite to the direction in which multiple core wires, serving as an outer layer, are twisted together.

SUMMARY

However, the existing wire ropes, particularly the multi-strand coils, have the following drawbacks. When a force is applied to a wire rope in such a direction as to twist or untwist the wire rope around the axis while the wire rope is bent, the wires are heated by frictional heat due to the wires rubbing against each other or by heat due to plastic deformation. Thus, the wires may become deformed or cut.

The flexible shaft disclosed in Japanese Unexamined Patent Application Publication No. 9-49517 has excellent flexibility since gaps are provided between turns of each wire. However, each of the layers of the flexible shaft is constituted by a single wire. Thus, when the flexible shaft is bent and is twisted around, heat is generated in the shaft and the wires may be cut as a result of the heat generated. Moreover, cutting the wires severely degrades the durability of the flexible shaft and the flexible shaft may be broken.

In the flexible shaft disclosed in Japanese Unexamined Patent Application Publication No. 2001-280333, the wires are wound while having gaps between some adjacent turns of the wires in the longitudinal direction. However, the remaining part, other than the one wound with the gaps, is tightly wound. Since the tightly wound part of the wires of the flexible shaft suffers from heat generated therein, the durability of the whole flexible shaft is greatly reduced.

In the cable disclosed in Japanese Unexamined Patent Application Publication No. 7-14448, the wires are each wound with no gaps between turns. Thus, the cable is more likely to experience increased heat, and therefore also exhibits reduced durability, as in the flexible shafts described in Japanese Unexamined Patent Application Publication Nos. 9-49517 and 2001-280333.

Embodiments of the present invention are made in view of the above-discussed circumstances. Therefore, an object of the exemplary embodiments is to provide a wire rope that has excellent durability and excellent flexibility by reducing, or preventing wires from rubbing against each other to thereby suppress heat generation.

In an aspect, a wire rope includes a multi-strand coil formed by twisting a plurality of metal wires together, and gaps are located between the plurality of metal wires along an axis of the multi-strand coil.

By providing gaps between the metal wires in this manner, adjacent metal wires are less likely to interfere with one another and thus the wire rope bends easily. Moreover, if, for example, torque is applied along the axis of the wire rope by bending the wire rope, the metal wires are less likely to come into contact with one another and thus heat generation due to friction can be prevented. Consequently, the wire rope according to the disclosed embodiments of the present invention exhibits higher durability than the existing wire ropes.

The wire rope according to the embodiments of the present invention has higher durability and excellent flexibility by gaps being provided between turns of each of metal wires to prevent heat generation due to friction between the metal wires when the wires are bent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a wire rope according to a first embodiment when viewed in vertical section.

FIG. 2A is a graph showing performance test results of both the wire rope according to the embodiments of the present invention and a related art wire rope.

FIG. 2B is a schematic diagram of a configuration for the test depicted in FIG. 2A.

FIG. 3 schematically illustrates a wire rope according to a second embodiment when viewed in vertical section.

FIG. 4 schematically illustrates a wire rope according to a first modification of the second embodiment when viewed in vertical section.

FIG. 5 schematically illustrates a wire rope according to a second modification of the second embodiment when viewed in vertical section.

FIG. 6 schematically illustrates a wire rope according to a third modification of the second embodiment when viewed in vertical section.

FIG. 7 schematically illustrates a related art wire rope when viewed in vertical section.

DETAILED DESCRIPTION OF EMBODIMENTS

Wire ropes according to embodiments of the present invention will be described referring to the drawings.

As illustrated in FIG. 1, a wire rope 1A according to a first embodiment of the present invention includes a multi-strand coil 10 formed by twisting multiple metal wires 11 together. The materials of the metal wires 11 are not limited to any particular type of material, so long as the materials exhibit high hardness. Accordingly, the materials of the metal wires may include, but are not limited to stainless steel wires, carbon steel wires, steel wires for springs, or any other metal exhibiting a hardness that is at least as high as the hardness of steel.

Gaps are located between the metal wires 11 of the multi-strand coil 10 along the axis of the multi-strand coil 10. Accordingly, the metal wires 11 are arranged so that the metal wires do not contact one another (i.e., without touching each other).

For instance, in one embodiment, such as the one depicted in FIG. 1, the gaps between the metal wires 11 include gaps d1 and d2 that differ in width. Specifically, the gaps between the metal wires 11 include narrow gaps d1 and wide gaps d2, which are wider than the narrow gaps d1.

As described above, locating gaps between the metal wires 11 improves the flexibility of the wire rope 1A. This is because, when the wire rope 1A is bent, the metal wires 11 easily approach one another without interfering with one another at the inner side of the bent portion. If, for example, torque is applied along the axis of the wire rope 1A by bending the wire rope 1A, the metal wires 11 are less likely to come into contact with one another. This prevents heat generation due to friction between the metal wires 11 and prevents the metal wires 11 from being cut or suffering from other defects. Thus, the durability of the wire rope 1A improves.

The gaps between the metal wires 11 may include gaps of varying width. For instance, as shown in FIG. 1, the metal wires 11 may include narrow gaps d1 and wide gaps d2 that differ in width. Thus, if the wire rope 1A is bent into various shapes, the metal wires 11 can be flexibly deformed in accordance with these shapes. Thus, the wire rope 1A has a favorable flexibility and heat generation due to friction can be reliably prevented.

Referring now to FIGS. 2A and 2B, a durability test for wire ropes and the results of the test will be described. Wire ropes 1A according to the first embodiment and wire ropes 100 according to a related art (see FIG. 7) were used for the test. In the test, the durability of the wire ropes was measured under the following conditions. As illustrated in FIG. 2B, the wire ropes were bent, with one end of each wire rope being connected to a motor, and the other end of the wire rope being connected to a brake. The motor was driven in order to consecutively apply torque along the axis of the wire rope. Tests were conducted under the following conditions: the diameters of bent portions R were set at 40 mm, 45 mm, and 50 mm; the rotational speed of the motor was 1800 (rpm); and the braking force was 20 (N·mm). The test was conducted until audible failure from the tested wire rope was heard, and the time at which audible failure was heard was recorded as the durability (sec).

FIG. 2A shows the test results. The durability of both the wire rope 1A according to the first embodiment and the wire rope 100 according to the related art both increased, as the diameter of the bent portion R of the tested wire rope became larger. However, the durability of the wire ropes 1A according to the first embodiment was approximately 200%, at maximum, of the durability of the corresponding wire ropes 100 according to the related art. That is, the observed durability of the wire ropes 1A according to the first embodiment was nearly double that of the wire ropes 100 according to the related art. The durability of the wire ropes 1A according to the first embodiment exhibited superior durability results to those of the related art for at least the following reasons. The metal wires 11 of the wire ropes 1A are less likely to rub against each other, therefore heat generation due to friction between the metal wires 11 is prevented, and thus the metal wires 11 are prevented from being cut.

The gaps between the metal wires 11 need not be limited to any particular configuration. For instance, in alternate embodiments the wire rope 1A may include gaps of uniform width between the metal wires 11. However, in order for the metal wires 11 to be flexibly deformable in accordance with various shapes into which the wire rope 1A is bent, it is preferable that the gaps between the metal wires 11 include the narrow gaps d1 and the wide gaps d2 that differ in width.

The arrangement of successive narrow gaps d1 and wide gaps d2 may vary. For instance, as illustrated in FIG. 1, the wire rope 1A may have a portion in which multiple narrow gaps d1 are successively formed and a portion in which multiple wide gaps d2 are successively formed. However, in other embodiments, the narrow gaps d1 and the wide gaps d2 may be alternately formed or may be formed at random.

From the view point of flexibility of the metal wires 11 with which the metal wires 11 are deformable in accordance with various shapes into which the wire rope 1A is bent, it is preferable that the narrow gap d1 and the wide gap d2 are formed alternately or at random. In the first embodiment, other gaps whose width differs from those of the narrow gaps d1 and the wide gaps d2 may be further provided between the metal wires 11.

Referring to FIG. 3, a second embodiment will be described now. Portions that are the same as those in the first embodiment will not be described and the same portions are denoted by the same reference numerals.

As illustrated in FIG. 3, a wire rope 1B according to a second embodiment of the present invention includes a multi-strand coil 10 and a multi-strand coil 20 that is disposed inside the multi-strand coil 10. Hereinbelow, the multi-strand coil 10 disposed on the outer side is referred to as an outer multi-strand coil 10, and the multi-strand coil 20 disposed on the inner side is referred to as an inner multi-strand coil 20.

The outer multi-strand coil 10 is wound around the outer circumference of the inner multi-strand coil 20. The multi-strand coils 10 and 20 are arranged such that the outer multi-strand coil 10 is wound in the same direction as the inner multi-strand coil 20. A winding angle α, at which the outer multi-strand coil 10 is wound when viewed in vertical section, is made different from a winding angle β, at which the inner multi-strand coil 20 is wound when viewed in vertical section. Specifically, the winding angle α is formed between the center line CL of the wire rope 1B when viewed in vertical section and the center line of each metal wire 11 of the outer multi-strand coil 10, and the winding angle β is formed between the center line CL of the wire rope 1B when viewed in vertical section and the center line of each metal wire 21 of the inner multi-strand coil 20.

As described above, winding the outer multi-strand coil 10 and the inner multi-strand coil 20 in the same direction negligibly distorts the multi-strand coils 10 and 20 when torque is applied to the wire rope 1B. Thus, the entirety of the wire rope 1B has a higher torque resistance. In addition, the multi-strand coils 10 and 20 are in point contact with one another since the winding angle α of the outer multi-strand coil 10 and the winding angle β of the inner multi-strand coil 20 are different from each other. Consequently, the metal wires 21 of the inner multi-strand coil 20 are prevented from entering the gaps between the metal wires 11 of the outer multi-strand coil 10. In this embodiment, the winding angle α of the outer multi-strand coil 10 is larger than the winding angle β of the inner multi-strand coil 20. Thus, tension in the longitudinal direction of the metal wires 11 of the outer multi-strand coil 10 can be reduced. This can reduce fatigue of the metal wires 11 of the outer multi-strand coil 10 and the wire rope 1B can therefore exhibit a higher durability.

A first modification of the second embodiment will be described now.

As illustrated in FIG. 4, a wire rope 1C according to the first modification includes an outer multi-strand coil 10 and an inner multi-strand coil 20, which are wound in the same direction. The winding angle α of the outer multi-strand coil 10 when viewed in vertical section is smaller than the winding angle β of the inner multi-strand coil 20 when viewed in vertical section.

If torque is applied to the wire rope 1C having the above-described configuration, the multi-strand coils 10 and 20 are less likely to be distorted and the entirety of the wire rope 1C has a higher torque resistance. In addition, since the multi-strand coils 10 and 20 are in point contact with one another, the metal wires 21 of the inner multi-strand coil 20 are prevented from entering the gaps between the metal wires 11 of the outer multi-strand coil 10.

A second modification of the second embodiment will be described now.

As illustrated in FIG. 5, in a wire rope 1D according to the second modification, a space s is provided between the inner circumference of an outer multi-strand coil 10 and the outer circumference of an inner multi-strand coil 20.

The wire rope 1D having this configuration can be easily bent because metal wires 11 of the outer multi-strand coil 10 and metal wires 21 of the inner multi-strand coil 20 are less likely to interfere with one another. If torque is applied along the axis of the wire rope 1D by bending the wire rope 1D, heat generation due to friction is more reliably prevented. Thus, the wire rope 1E can have a higher durability.

A third modification of the second embodiment will be described now.

As illustrated in FIG. 6, in a wire rope 1E according to the third modification, gaps d11 and d12 between metal wires 11 of an outer multi-strand coil 10 are wider than gaps d13 between metal wires 21 of an inner multi-strand coil 20.

The wire rope 1E having this configuration is more easily bent. If torque is applied along the axis of the wire rope 1E by bending the wire rope 1E, heat generation due to friction can be more reliably prevented. Thus, the wire rope 1E can have a higher durability.

The embodiments of the present invention are not limited to the above-described embodiments and the embodiments may be modified or combined as appropriate within a scope not departing from the gist of the invention.

The gaps d1, d2, d11, and d12 between the metal wires 11 may be provided at least at main portions of the wire ropes 1A to 1E, the main portions being deformable into curves in the longitudinal direction.

The ranges for the diameter of the individual wires 11 may range from 0.25 mm to 0.30 mm. The diameter of the wire rope may range from 1.2 mm to about 1.5 mm. The gap d1 may range from 0.5 mm to 0.15 mm. The gap d2 may range from 0.15 to 0.25 mm. As such, gaps d1 and d2 may have different dimensions, and may in fact have any range of dimensions, as long as d1 and d2 are randomly located in an axial direction of rope. The diameter of the inner wire rope may range from 0.6 mm to 1.0 mm, while the diameter of the individual inner wires 21 may range from 0.10 mm to 0.25 mm. The winding angles may vary. For instance, winding angle α may vary from 45° to 75°, while winding angle β may range from 45° to 75°. The diameter for the inner wire rope may range from 0.50 mm to 0.85 mm. The gaps d11, d12 and d13 may range from 0.12 mm to 0.15 mm; 0.15 mm to 0.25 mm; and 0.04 mm to 0.11 mm, respectively

The wire ropes 1A to 1E are each preferably usable as a component of tools, such as an endoscopic surgical tool in which a driving core shaft is inserted into the outer multi-strand coil 10 and the inner multi-strand coil 20, or as a component of an industrial component.

Claims

1. A wire rope for use in a medical procedure, the wire rope comprising:

a first multi-strand coil including a plurality of metal wires, wherein the first multi-strand coil has gaps between the plurality of metal wires along an axis of the first multi-strand coil.

2. The wire rope according to claim 1, wherein the gaps between the plurality of metal wires include a first gap and a second gap that differ in width.

3. The wire rope according to claim 1, further comprising:

a second multi-strand coil,

wherein the second multi-strand coil is disposed inside the first multi-strand coil such that the first multi-strand coil on an outer side is wound around an outer circumference of the second multi-strand coil on an inner side, and

wherein the first multi-strand coil on the outer side is wound in the same direction as the second multi-strand coil on the inner side, and an angle at which the first multi-strand coil on the outer side is wound when viewed in vertical section differs from an angle at which the second multi-strand coil on the inner side is wound when viewed in vertical section.

4. The wire rope according to claim 2, further comprising:

a second multi-strand coil,

wherein the second multi-strand coil is disposed inside the first multi-strand coil such that the first multi-strand coil on an outer side is wound around an outer circumference of the second multi-strand coil on an inner side, and

wherein the first multi-strand coil on the outer side is wound in the same direction as the second multi-strand coil on the inner side, and an angle at which the first multi-strand coil on the outer side is wound when viewed in vertical section differs from an angle at which the second multi-strand coil on the inner side is wound when viewed in vertical section.

5. The wire rope according to claim 3, wherein the angle at which the first multi-strand coil on the outer side is wound when viewed in vertical section is larger than the angle at which the second multi-strand coil on the inner side is wound when viewed in vertical section.

6. The wire rope according to claim 4, wherein the angle at which the first multi-strand coil on the outer side is wound when viewed in vertical section is larger than the angle at which the second multi-strand coil on the inner side is wound when viewed in vertical section.