wire rope

Abstract

To provide a wire rope with good operability. [Solution] The wire rope comprises a core strand having a plurality of first strands twisted together, and a plurality of side strands having a plurality of second strands twisted together and twisted around the core strand, where Dr is the rope diameter of the wire rope, Pr is the length of the twist of the wire rope, Dc is the outer diameter of the core strand, and Pc is the length of the twist of the core strand, then the first ratio Rr represented by the following formula (1) and the second ratio Rc represented by the following formula (2) satisfy the following formula (3). Rr = Pr / Dr ... (1) Rc = Pc / Dc ... (2) 1.0

Description

[[Technical Field]]

[0001] The technology disclosed in the present specification relates to a wire rope. [[Background Art]]

[0002] A known operating rope includes a plurality of strands twisted together. The strands include a plurality of element wires twisted together (see, for example, Patent Document 1). [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 5-230782 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In a known rope, if the elongation of the rope itself when pulled is too large, the tensile load is absorbed by the elongation. This phenomenon may reduce the operability of the rope.

[0005] The present specification discloses a technology capable of solving the above-described problem. [[Means for Solving the Problem]]

[0006] The wire rope disclosed by the present specification comprises: a core strand including a plurality of first element wires twisted together; and a plurality of side strands including a plurality of second element wires twisted together, the side strands being twisted around the core strand, wherein when the rope diameter of the wire rope is defined as Dr, the lay length of the wire rope is defined as Pr, the outer diameter of the core strand is defined as Dc, and the lay length of the core strand is defined as Pc, a first ratio Rr represented by the following formula (1) and a second ratio Rc represented by the following formula (2) satisfy the following formula (3).

[0007] Rr = Pr / Dr ... (1) Rc = Pc / Dc ... (2) 1.0 <Rr / Rc ··· (3) [Brief explanation of the drawing]

[0008] [Figure 1] Partially enlarged side view of the wire rope of the embodiment [Figure 2] Cross-sectional view of the wire rope of the embodiment, taken along line II-II in Figure 1. [Figure 3] Partially enlarged side view of the core strand of the embodiment [Figure 4] A graph illustrating the relationship between the spring rate and initial elongation of a wire rope. [Figure 5] A graph showing the relationship between the Rr / Rc value and the spring rate in a wire rope tensile test. [Figure 6] A graph showing the relationship between the Rr / Rc value and the initial elongation in a wire rope tensile test. [Modes for carrying out the invention]

[0009] (Embodiment) The embodiment will be described with reference to Figures 1 to 3. The wire rope 100 of this embodiment is used, for example, as an operating wire for an endoscope.

[0010] As shown in Figures 1 and 2, the wire rope 100 comprises a core strand 110 and a plurality of side strands 120. The wire rope 100 is formed by twisting the plurality of side strands 120 around the core strand 110. The wire rope 100 has a two-layer structure in which the core strand 110 is located in the center and the plurality of side strands 120 are arranged around the core strand 110. Each side strand 120 extends spirally around the core strand 110.

[0011] As shown in Figures 2 and 3, the core strand 110 is formed by twisting together one first core wire 111 and a plurality of first side wires 112. The core strand 110 has a two-layer structure in which the first core wire 111 is located in the center and the plurality of first side wires 112 are arranged around the first core wire 111. Each first side wire 112 extends spirally around the first core wire 111. The first core wire 111 and the first side wires 112 may have the same outer diameter or they may have different outer diameters. In this specification, "equal outer diameter" includes not only cases where the outer diameters are perfectly equal, but also cases where the outer diameters are slightly different due to unavoidable manufacturing tolerances, etc. The material of the first core wire 111 and the first side wires 112 may be, for example, metal, and more specifically, stainless steel such as SUS302, SUS304, or SUS316. The materials of the first core wire 111 and the first side wire 112 may be the same or different. The first core wire 111 and the first side wire 112 are examples of the first strands in the claims.

[0012] Each of the multiple side strands 120 is formed by twisting together one second core wire 121 and multiple second side wires 122, similar to the core strand 110. Each side strand 120 has a two-layer structure in which the second core wire 121 is located in the center and the multiple second side wires 122 are arranged around the second core wire 121. Each second side wire 122 extends spirally around the second core wire 121. The second core wire 121 and the second side wires 122 may have the same outer diameter or different outer diameters. The material of the second core wire 121 and the second side wires 122 may be metal, for example, and more specifically, stainless steel such as SUS302, SUS304, or SUS316. The material of the second core wire 121 and the second side wires 122 may be the same or different. The second core wire 121 and the second side wire 122 are examples of the second strand wire in the claims.

[0013] There are no particular restrictions on the twisting direction of the wire rope 100; it may be a standard Z twist, a standard S twist, a Lang Z twist, or a Lang S twist.

[0014] When the rope diameter of the wire rope 100 is Dr, the lay length of the wire rope 100 is Pr, the outer diameter of the core strand 110 is Dc, and the lay length of the core strand 110 is Pc, a first ratio Rr represented by the following formula (1) and a second ratio Rc represented by the following formula (2) satisfy the following formula (3).

[0015] Rr=Pr / Dr ··· (1) Rc=Pc / Dc ··· (2) 1.0<Rr / Rc ··· (3)

[0016] The rope diameter Dr is represented by the diameter of a circumscribed circle Cr in a cross section perpendicular to the central axis Axr of the wire rope 100 (see FIG. 2). The length Pr is represented by the spacing distance (pitch) between the vertex position of one side strand 120 and the next vertex position formed by the side strand 120 after one turn around the core strand 110 when the side strand 120 is viewed along the central axis Axr (see FIG. 1). The outer diameter Dc is represented by the diameter of a circumscribed circle Cc in a cross section perpendicular to the central axis Axc of the core strand 110 (see FIG. 2). The length Pc is represented by the spacing distance (pitch) between the vertex position of one first side wire 112 and the next vertex position formed by the first side wire 112 after one turn around a first core wire 111 when the core strand 110 is viewed along the central axis Axc (see FIG. 3).

[0017] When the wire rope 100 is used as an operation wire, the wire rope 100 is pushed and pulled, and a component connected to the wire rope 100 is operated by this pushing and pulling. When the wire rope 100 is pulled, a tensile load is applied to the wire rope 100. If the elongation of the wire rope 100 itself is too large at this time, the tensile load is absorbed by the elongation, so that an expected pulling amount may not be obtained.

[0018] When the value of Rr / Rc of the wire rope 100 exceeds 1.0, better operability is maintained compared to when the value of Rr / Rc is 1.0 or less. The reason therefor is described below.

[0019] FIG. 4 is a graph showing the relationship between load and elongation for a general wire rope, with tensile load plotted on the vertical axis and elongation of the wire rope plotted on the horizontal axis. In the figure, the range from the origin to point A is the range where initial elongation occurs, the range from point A to point B is the range where elastic elongation occurs, and point C indicates the point at which the wire rope breaks. Generally, in the initial stage when a tensile load is applied to a new wire rope, elongation that does not recover even when the load is removed occurs. This elongation is generally called "initial elongation" and may also be referred to as "permanent set". Initial elongation occurs when a tensile load is applied to a new wire rope in which the element wires and strands are not sufficiently in close contact with each other, during the process in which the element wires and strands come into close contact. Next, when a load acts on the wire rope from which initial elongation has been removed, elongation proportional to the load occurs. This elongation is called "elastic elongation" and is elongation that recovers to the original state when the load is removed. In the present specification, in the range where elastic elongation is established, that is, the range from point A to point B in FIG. 4 which is the linear portion of the load-elongation curve, the magnitude of the slope of the straight line AB is defined as the spring rate value, and the elongation value at intersection D between the extension line of the straight line AB and the horizontal axis is defined as the initial elongation value.

[0020] The fact that the wire rope 100 satisfies 1.0 < Rr / Rc, that is, the first ratio Rr is larger than the second ratio Rc, means that the twist angle θr of the wire rope 100 is smaller than the twist angle θc of the core strand 110. The twist angle θr of the wire rope 100 is represented by the angle formed between the central axis Axr of the wire rope 100 and the side strands 120 (see FIG. 1). The twist angle θc of the core strand 110 is represented by the angle formed between the central axis Axc of the core strand 110 and the first side wire 112 (see FIG. 3).

[0021] When the first ratio Rr is larger than the second ratio Rc, that is, when the twist angle θr of the wire rope 100 is smaller than the twist angle θc of the core strand 110, when a tensile load is applied to the wire rope 100, the amount of diameter reduction of the rope diameter Dr is larger than the amount of diameter reduction of the outer diameter Dc of the core strand 110. In other words, the wire rope 100 is tightened such that the side strands 120 press against the core strand 110, and the core strand 110 and the side strands 120 interfere with each other strongly. For this reason, the core strand 110 and the side strands 120 integrally receive the tensile load. This increases the spring rate compared to when the first ratio Rr is smaller than the second ratio Rc. A higher spring rate means that within the range where elastic elongation occurs, even if the load applied to the wire rope 100 changes, the change in elongation of the wire rope 100 is small. This is considered to make it less likely for the tensile load to be absorbed by the elongation of the wire rope 100.

[0022] Furthermore, even in the initial stage when a tensile load is applied to a new wire rope, the initial elongation tends to be reduced. It is considered that the reason for this is that the core strand 110 and the side strands 120 strongly interfere with each other before the strands 110, 120 and the core wires 111, 121 and side wires 112, 122 provided therein come into close contact. This is also considered to contribute to a certain extent to improving the operability of the wire rope 100.

[0023] From the above, the wire rope 100 satisfying 1.0 < Rr / Rc is less likely to absorb tensile load due to elongation of the wire rope 100 itself, and is likely to maintain good operability. Such a wire rope 100 is suitable for operation ropes.

[0024] The number of the first side wires 112 may be, for example, 6 or more and 8 or less. The number of the second side wires 122 included in one side strand 120 may be, for example, 6 or more and 8 or less. The plurality of side strands 120 may have the same outer diameter Do as each other. The outer diameter Dc of the core strand 110 may be 1.0 times or more and 1.2 times or less the outer diameter Do of the side strand 120. The outer diameter Do of the side strand 120 is the diameter of the circumscribed circle Co of the side strand 120. The value of Rr / Rc may satisfy 1.0 < Rr / Rc ≤ 2.3, may satisfy 1.3 ≤ Rr / Rc ≤ 2.3, may satisfy 1.0 < Rr / Rc ≤ 1.6, or may satisfy 1.3 ≤ Rr / Rc ≤ 1.6. When the wire rope 100 includes at least one of these requirements, the operability of the wire rope 100 can be maintained even better. [Example]

[0025] Samples S1 to S7 of wire ropes having the same configuration as the above embodiment were prepared. Sample S2 is a generally commercially available wire rope. Sample S1 is a generally commercially available wire rope that has been subjected to pre-tensioning with a load of 147 N (15 kgf). Samples S3 to S7 are wire ropes in which the outer diameter of the strands and the twist pitch are designed so that Rr / Rc reaches a target value. The configuration common to samples S1 to S7 is as follows.

[0026] <Common Configuration of Samples> · Length of wire rope: 180 mm · Number of first side wires: 6 · Material of first core wire and first side wires: SUS304 · Number of second side wires: 6 · Material of second core wire and second side wires: SUS304 · Number of side strands: 6 · Twist direction: ordinary S-twist

[0027] Three samples were prepared for sample S1, and tensile tests were performed. Each sample was set in a rope tensile testing machine and pulled at 10 mm / min until breakage, obtaining a load-elongation curve. From the obtained load-elongation curve, the magnitude of the slope of the straight line in the load-elongation curve range from 50 N to 100 N was determined and used as the spring rate value of that sample. The elongation value at the intersection of the extension of the straight line and the horizontal axis was used as the initial elongation value of that sample. The average value of the spring rates and the average value of the initial elongations of the three samples were used as the spring rate value and initial elongation value of sample S1.

[0028] Samples S2-S7 were tested in the same way as sample S1.

[0029] Table 1 shows the Rr / Rc, spring rate, and initial elongation values ​​for each sample, Figure 5 shows a graph illustrating the relationship between the Rr / Rc value and the spring rate, and Figure 6 shows a graph illustrating the relationship between the Rr / Rc value and the initial elongation.

[0030] [Table 1]

[0031] Table 1 and Figure 5 show that, compared to samples S1-S3 with an Rr / Rc value of 1.0 or less, samples S4-S7 with an Rr / Rc value greater than 1.0 showed an increase in spring rate. In the range of Rr / Rc from 1.003 to 1.546, the spring rate increased gradually as the Rr / Rc value increased. From a comparison between sample S6 and sample S7, it is considered that the spring rate does not change much even when the Rr / Rc value is increased to 1.6 or higher.

[0032] Table 1 and Figure 6 show that in samples S1-S4, where the Rr / Rc value was 1.003 or less, there was variation in the initial elongation values, but in samples S5-S7, where the Rr / Rc value was 1.3 or more, the values ​​were consistently low.

[0033] The technologies disclosed herein are not limited to the embodiments described above and can be modified in various forms without departing from their essence, for example, the following modifications are possible. (1) The wire rope can be used as a control wire applied to medical devices other than endoscopes, such as medical robots. (2) Wire rope may also be used as industrial wire in products such as automobiles, office automation equipment, home appliances, and amusement equipment.

Claims

1. A wire rope (100), A core strand (110) having multiple first strands (111, 112) twisted together, It comprises a plurality of second strands (121, 122) twisted together, and a plurality of side strands (120) twisted around the core strand (110), Equipped with, When the rope diameter of the wire rope (100) is Dr, the length of the twist of the wire rope (100) is Pr, the outer diameter of the core strand (110) is Dc, and the length of the twist of the core strand (110) is Pc, the wire rope (100) is such that the first ratio Rr represented by the following formula (1) and the second ratio Rc represented by the following formula (2) satisfy the following formula (3). Rr=Pr / Dr... (1) Rc=Pc / Dc... (2) 1.0<Rr / Rc... (3)

2. A wire rope (100) according to claim 1, The first ratio Rr and the second ratio Rc satisfy the following formula (4): Wire rope (100). 1.3≦Rr / Rc... (4)

Images