JPS6010894B2 - Tension control method in plastic extrusion process - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves feeding a conductor or cable core into an extruder by means of a track-type feeding capstan having two sets of shoes, extrusion-coating the conductor or cable core with plastic in the extruder, and continuing cooling. The present invention relates to a tension control method when the above-mentioned extrusion-coated filament is tension-manufactured using a track-type tension capstan having two sets of shoes.

In the normal plastic extrusion process, as shown in Figure 1, a conductor or cable core 2 is supplied from a supply 1, and an extruder 3
It consists of a series of steps in which plastic is extruded and coated in a water tank 4, cooled in a water tank 4, and tensioned by a tension capstan 5 to drive the filament and wound around a winding reel 6.

In this case, the driving force of the filament coated with extruded plastic is provided only by the tension capstan, so as long as there is no slippage of the filament with respect to the tension capstan, the peripheral speed and linear velocity of the tension capstan are the same, and the above In order to prevent slippage as much as possible, in the case of a track type capstan, two sets of upper and lower shoes are pressed against the linear body to drive the capstan. However, when a highly foamed plastic insulator is applied to the conductor, the wire is quite soft and if the two pairs of shoes are used to prevent slippage, the cross section of the wire will be deformed, resulting in insufficient electrical power. It is not possible to form a layer of highly foamed insulation with mechanical functionality.

Therefore, in such a case, a conductor feeding capstan 7 is installed just before the extruder 3, and the conductor is fed at a constant speed while a high foam plastic insulator is applied, cooled with water, and then pulled while being loosely connected with a tensioning capstan. things are done.

In order to achieve a loose pressure contact, it would be impossible to use a conventional tension capstan with a shoe made of hard rubber, as it would cause slippage, but it is impossible to make a loose pressure contact. If used, it can be pressed with gentle force without causing too much slippage. In the above case,
Since the force that drives the linear body is generated in two places: the conductor feeding capstan and the tensioning capstan, a dancer roller is installed somewhere between the two capstans to eliminate the difference in drive line speed caused by the difference in the slippage of each capstan. This is absorbed as sag in the striatum, and a signal is sent to one of the capstans to increase or decrease the rotation depending on the movement of the dancer roller, so that the sag in the striatum is always constant. need to be controlled.

However, in the case of a coaxial core in which highly foamed plastic is applied onto the conductor, such tension control methods have an adverse effect on the electrical properties of the finished core. This is because if a dancer roller is installed between the two capstans to take up the slack in the filament, it will either be before or after the extruder, but if it is in front, the conductor will be bent by the dancer roller, so it will bend. This causes a problem in that the electrical properties of the coaxial core, such as VSWR, are deteriorated, and if it is provided after the extruder, the highly foamed insulator layer is bent and deformed. The present invention has been made in order to solve the above-mentioned problems of the conventional technology.The conductor or cable core is fed into an extruder by a track-type feeding capstan having two shoes, and the plastic 3 is then extruded and coated. In the case of pulling with a track type tension capstan having two shoes, the circumferential speed of the tension capstan is set to 1.
The present invention relates to a tension control method characterized in that the peripheral speed of the tension capstan is always kept at least 31.2 times faster than the linear speed of the filament.

To carry out the method of the present invention, a track type capstan or the like having a hard rubber shoe is used as the feeding capstan, and the conductor or cable core 4 is firmly pressed without bending, and the traction thereof is as much as possible. To prevent slippage between the striatum and the capstan.

In addition, in the case of a tension capstan, the striated body to be towed is made of plastic, and in some cases it is made of a fairly soft material, such as the highly foamed plastic insulator of the coaxial core, so foamed polyurethane rubber is used on the hard rubber shoe. Using a belt layer provided with a belt layer or a reinforcing layer such as cloth on top of the belt layer, the filament is pulled while being pressed against it and causing a slight slippage. The peripheral speed V of the feeding capstan is the same as the linear speed V of the filament, and the peripheral speed V2 of the tension capstan is maintained in the relationship V2>V=V. If it is set to 0 in this way, there will be no need for a sag absorption device for the filament body, which installs a dancer roll or the like between the two capstans and absorbs tension fluctuations due to the difference in slip between the two capstans.
In addition, since the tension capstan portion is constantly in a state of dynamic friction, the tension force due to friction is extremely stable compared to conventional ones, and the tension can be suppressed to fluctuations within ±3%. In actual practice, we used a tension capstan in which layers of a rubber-containing flat belt, foamed polyurethane rubber, and polyester cloth were sequentially provided on a hard rubber shoe. 80% foamed polyethylene on outer diameter 12'
Manufactured to match.

In this case, the peripheral speed of the feeding capstan and the linear speed of the filament were 10 per minute. When we examined the tension in the filament by changing the circumferential speed of the capstan, we found that the tension was extremely stable at 12/min or 13 skin/min, as shown in Figure 2. Incidentally, the conventional tension variation range was 6±lk9. 0 In this way, in the method of the present invention, the circumferential speed V of the tensile capstan
Send 2 and cuff.

By keeping the circumferential speed V2 of the tension capstan at 1.2 times or more of the linear velocity V of the stan, the relationship between the tension capstan and the striatum is made frictionless. The tension applied to the filament is extremely stable because the filament is in the taut state, and this is the most effective method for manufacturing coaxial cores in which the conductor is made of highly foamed plastic. As can be seen from Fig. 2, the tension becomes even more stable if it is increased by 1.3 times or more. It goes without saying that the method of the present invention can also be applied to general plastic extrusion, ie, applying a solid plastic on a conductor or applying a plastic sheath on a cable core.

The method of the present invention not only does not require the installation of dancer rollers, but also has the advantage that it is not necessary to synchronize both capstans.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional general extrusion process, and FIG. 2 is a diagram showing the relationship between the circumferential speed V2 of a tension capstan and the tension of a filament in an example of plastic extrusion according to the method of the present invention. In the figure, 7 is a feeding capstan, and 5 is a tension capstan. Oh figure juice 2 figure

Claims (1)

[Claims] 1. The conductor or cable core is fed into an extruder by a track type infeed capstan having two sets of shoes, extruded and coated with plastic in the extruder, and then cooled and then transferred to a track type tension capstan having two sets of shoes. In the step of tensile manufacturing the extrusion coated filament, the peripheral speed of the feeding capstan is 1
．． Operate the tension capstan at more than twice the circumferential speed,
Always keep the peripheral speed of the tension capstan 1 higher than the linear speed of the filament.
．． A method for controlling tension in a plastic extrusion process, which is characterized by maintaining tension at least twice as quickly.