Method for improving bending durability of flexible tube

Abstract

To solve the problems that a flexible tube having an upper winding made of iron and a lower winding made of iron is inferior to a flexible tube having an upper winding made of brass and a lower winding made of iron in bending durability evaluation of the flexible tube, the flexible tube having the upper winding made of brass is expensive in material cost, the flexible tube encounters a recycling treatment issue due to a combination of different kinds of metals, and the bending characteristics of the flexible tube changes due to a difference in expansion coefficient of the metal materials caused by a temperature change.SOLUTION: An iron upper winding of the flexible tube is subjected to heat treatment such as annealing to make the hardness of the material nearly equal to that of brass. Thus, the generation of squeak noise at the time of bending in the bending durability evaluation of the flexible tube is made almost equal to that of a flexible tube whose upper winding is made of brass.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention is a method for reducing the creaking noise that occurs when bending a flexible tube in an evaluation of its bending durability by lowering the hardness of the upper winding portion of the flexible metal tube. [Background technology]

[0002] Conventionally, bent metal flexible tubing has a double structure consisting of an upper winding and a lower winding, as shown in [Figure 1], and this material is mainly composed of the following three combinations. a. Upper winding material: iron + lower winding material: iron b. Upper winding material: brass + lower winding material: iron c. Upper winding material: brass + lower winding material: stainless steel Each material has its advantages and disadvantages, with type a being able to be manufactured at low cost and being able to handle a wide variety of surface treatments such as plating and painting. Furthermore, since it is a combination of the same iron material, it has the advantage of being easy to recycle for reuse, but in terms of bending durability, the creaking noise that occurs when bending is caused by friction between the hard irons, so it is louder than the other two types b and c. The structure that generates the creaking sound during the bending durability evaluation is shown in Figure 2. As shown in [Figure 2], when a flexible tube is bent, the upper winding on the outside of the bent flexible tube rubs against the lower winding and bites into the interior of the flexible tube, while the upper winding on the inside of the flexible tube in the bending direction is pushed outward, also rubbing against the lower winding. When this friction is applied and the bearing is repeatedly bent, a creaking noise is generated due to the influence of wear particles and other factors. As shown in Figure 3, one principle for reducing squeaking noise when bending is to combine a flexible tube lower winding made of a hard material with a flexible tube upper winding made of a soft material. The conventional method is to change the upper winding to a low-hardness brass to reduce the squeaking noise when bending (b). However, the material is more expensive than steel and recycling requires disassembly. Furthermore, because the metals are different materials, their expansion rates with temperature change are different, and sudden temperature changes can cause changes in bending characteristics. c) is made of a material that improves bending durability and corrosion resistance, but on the other hand, the material is expensive and there are limited surface treatments that can be used, which creates problems with disassembly during recycling and changes in bending characteristics due to temperature changes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 08-146410 discloses an example of a microphone unit using a flexible tube, which uses electrical circuit control to reduce echoes and noise such as creaking sounds when the flexible tube is bent.

[0004] It is recognized that the squeaking noise that occurs when bending flexible tubing as the number of flexing cycles increases during flex durability evaluations is caused by friction between the upper and lower windings of the flexible tubing. To reduce the noise caused by this friction, it is necessary to lower the hardness of one or both of the metal materials that come into contact and rub against each other. However, because the lower winding of the flexible tubing is made of spring material, there are limitations to adjusting the hardness of this material. To address this issue, the hardness of the triangular deformed wire that forms the upper winding has been reduced, but the conventional method of changing the material to brass makes the material more expensive than iron, and there are also issues with recycling and changes in bending characteristics due to differences in the expansion rates of different metals caused by temperature changes. In the present invention, the material of the upper winding remains iron, but its hardness is made equivalent to that of brass, thereby reducing material costs, solving the problems of recycling and the change in bending characteristics due to temperature changes, and enabling the production of flexible tubing with a wide range of surface treatment options.

[0005] This manufacturing method achieves the same bending durability as a flexible tube using a brass upper winding by subjecting the upper winding of the flexible tube to heat treatment such as annealing to make it as hard as brass.

[0007] The upper winding of the flexible tube is made of iron, which allows for the manufacturing of flexible tubes that have excellent bending durability at low material costs, are easy to recycle, and have a wide range of surface treatment options. [Brief explanation of the drawings]

[0008] [Figure 1] Cross section of flexible tube [Figure 2] Movement of the upper winding when bending the flexible tube [Figure 3] Principle of reducing squeaking noise when bending flexible tubes DETAILED DESCRIPTION OF THE INVENTION

[0009] A flexible tube with an iron upper winding and an iron lower winding that has the same squeaking noise generation characteristics in a bending durability test as a flexible tube with a brass upper winding and an iron lower winding, achieved by subjecting the upper winding of a conventional iron flexible tube to heat treatment such as annealing to make the hardness of the material equivalent to that of brass. [Explanation of symbols]

[0010] 1 Flexible tube upper winding 2 Flexible tube underwinding 3) Flexible tube upper winding pinched 4. Extrusion of the upper winding of the flexible tube 5. Upper winding of flexible tube made of soft material 6. Flexible tube underwound wire made of hard material

Claims

[Claim 1] An article characterized by improving the bending durability of a flexible metal tube by subjecting the iron upper winding of the flexible metal tube to heat treatment or the like to reduce the hardness of the material.

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