JPH0130656Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a control cable in which an inner cable is slidably inserted into an outer tube so as to transmit operating force in both directions (push and pull) or in one direction.

Problems to be Solved by Conventional Technologies and Ideas In recent years, inner cables have been used as operating force transmission members for various devices because they have the advantage of being able to be freely routed, so inner cables can be freely slid into flexible outer tubes. Inserted control cables are increasingly being used, but the most important thing for this type of control cable is to reduce the sliding resistance between the outer tube and the inner cable to improve load transmission efficiency. Therefore, conventionally, a liner made of thermoplastic synthetic resin such as Teflon, polyethylene, polyacetal, or nylon was fitted around the inner circumference of the outer tube to reduce the sliding resistance with the inner cable. Ta. Among these liner materials, Teflon is the most suitable because it has an extremely small coefficient of friction and excellent wear resistance, but it is difficult to mold by extrusion due to its extremely large molecular weight and degree of polymerization and high melt viscosity. It has the disadvantage of high manufacturing cost. On the other hand, thermoplastic synthetic resins such as polyethylene, polyacetal, or nylon can be manufactured inexpensively by extrusion molding, but they have a higher coefficient of friction than Teflon and are inferior in abrasion resistance, so the control cable has a large curvature. It had some drawbacks that made it unsuitable for use under the harsh conditions of rigging.

Purpose The present invention was developed against the background of the above, and its purpose is to provide a control cable with an inexpensive liner, a low coefficient of friction, and excellent wear resistance.

Means to Solve the Problem The inventor of this invention believes that the reason why extruded thermoplastic synthetic resin liners such as polyethylene, polyacetal, or nylon have a higher coefficient of friction and lower abrasion resistance than Teflon is due to their molecular structure. Focusing on the fact that the cause is the presence of amorphous parts where molecular chains have been cut and crystal defect parts where the parallelism of molecular chains is disordered, after extrusion molding, these amorphous parts and crystal defects can be removed. They attempted to increase the degree of crystallinity and degree of molecular parallelism by removing the molecular chains. Since the crystalline parts are also heated uniformly, the strength is reduced and the dimensional accuracy is low, making it unsuitable for liners for control cables that require high precision in the inner and outer diameters. Therefore, the inventor
As a result of further research, they came up with the idea of selectively heating and stretching only the amorphous and crystalline parts, and adopted the microwave selective heating method. This microwave selective heating method utilizes the property that the crystalline part, amorphous part, and crystal defect part of a crystalline molecule are heated by selectively absorbing microwaves of different frequencies. In the process of stretching under microwave heating in conjunction with external heating, the amorphous and crystal defective areas are heated more selectively than the crystalline areas, that is, the crystalline areas are heated by heat conduction and the whole is heated. By stretching under conditions that do not result in uniform heating, the decrease in tensile modulus of the crystalline part during stretching is suppressed, and stretching stress is effectively applied to amorphous parts and crystal defect parts where molecular chains tend to move easily. For example, in polyacetal, crystalline parts are selectively treated with microwaves at a frequency of around 10 Hz, amorphous parts are selectively treated with microwaves at a frequency of around 1 kHz to 1 MHz, and crystal defect parts are selectively oriented with microwaves at a frequency of around 1 GHz. Because it is heated, the temperature is around 1KHz to 1MHz.
By irradiating microwaves with a frequency around 1 GHz, only the amorphous parts and crystal defect parts are heated without heating the crystal parts to a very high temperature, and the crystallinity and molecular parallelism are improved by stretching. be.

Embodiment Hereinafter, an embodiment of the present invention will be described based on FIG.

In this example, a tube 1 is tightly wound with a flat steel wire.
The outer periphery of the outer tube 4 is covered with a jacket 2 made of synthetic resin, and the inner periphery is fitted with a liner 3 made of extruded polyacetal and stretched approximately 10 times by the microwave selective heating stretching method. The conventional extruded polyacetal liner through which the inner cable 5 is freely inserted has a crystallinity of 60 to 70%.
Therefore, the molecular parallelism is close to 0, but the liner 3 of this example has both crystallinity and molecular parallelism.
It became close to 100%, and the friction coefficient decreased to about 1/2.
For this reason, the outer tube 4 has a radius of curvature of 150 mm.
When we measured the load transfer efficiency of the inner cable by bending it 180 degrees, we found that when using a conventional outer tube fitted with an extruded liner,
The improvement was from 78 to 80% to 83 to 86%, which is comparable to the value obtained when using an outer tube fitted with a Teflon liner.

In addition to the polyacetal used in the above embodiment, the present invention can also be applied to a control cable using an outer tube fitted with a liner made of extruded thermoplastic synthetic resin such as polyethylene or nylon. Even for polyolefins, such as polypropylene, which inherently do not have polar groups and which cannot be heated by microwaves, the microwave selective heating stretching method can be applied by selectively dispersing polar molecules in the amorphous portion in advance. be able to. Further, the stretching ratio is preferably 10 times or more for any synthetic resin.

As is clear from the above explanation, the control cable of the present invention is a control cable in which the inner cable is slidably inserted into the outer tube to transmit push/pull operation force in both directions or in either direction. , a liner formed by extruding a thermoplastic synthetic resin such as polyethylene, polyacetal or nylon and stretching it using a microwave selective heating stretching method is fitted around the inner periphery of the outer tube, the liner Because of the extremely high degree of crystallinity and molecular parallelism, the coefficient of friction decreases and
It can be manufactured at a lower cost than using a Teflon liner, and since the liner is heated by microwaves and the temperature rises from inside, thick materials can be stretched without distortion. Since a normal crystal part is not heated more than necessary, the accuracy of the inner and outer diameters is high, and the inner cable is tightly fitted into the outer tube, allowing the inner cable to slide smoothly.As a result, the load transmission efficiency of the inner cable and It has the effect of improving durability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. 1: Tube, 3: Liner, 4: Outer tube, 5: Inner cable.

Claims (1)

[Scope of utility model registration request] In a control cable in which an inner cable is slidably inserted into an outer tube to transmit operating force in both directions of pushing and pulling or in either direction, the inner periphery of the outer tube is made of thermoplastic synthetic material such as polyethylene, polyacetal, or nylon. A control cable characterized by a tube made of extruded resin fitted with a liner that is stretched using a microwave selective heating stretching method.