JPH0419922A - Manufacturing method of high foam plastic insulated wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a highly foamed plastic insulated wire.

[Prior Art] Conventionally, when trying to manufacture a highly foamed plastic insulated wire by extrusion, the inner diameter of the foam 1 becomes smaller as shown in FIG. is inevitably larger than the diameter d of the core wA2. In the figure, D' is the outer diameter of the foam 1.

[Problems to be Solved by the Invention] There is a problem that the contact force between the core wire 2 and the foam 1 is very small, and the foam 1 is easily crushed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a highly foamed plastic insulated wire that can improve the adhesion between the core wire and the foam.

[Means for solving the problem] The above purpose is to remove a predetermined unnecessary portion of the foam extruded around the core wire by slitting it in the longitudinal direction, and to remove the removed foam from the outside around the core wire. This is achieved by manufacturing highly foamed plastic insulated wires that are tightened to

[Function] Since the above means is provided, the core wire and the foam can be easily brought into close contact with each other.

[Example] The present invention will be described below based on the illustrated example. FIG. 1 shows an embodiment of the invention. Note that parts that are the same as those in the conventional system are given the same reference numerals, and therefore their explanations will be omitted. In this example, a predetermined unnecessary portion M of the foam 1 extruded around the core wire 2a was removed by slitting in the longitudinal direction, and the removed foam 1 was tightened around the core wire 2a from the outside.

By doing this, the core wire 2a and the foam 1 can be easily brought into close contact with each other, eliminating the need to use a dummy core wire as in the past, and making it easy to manufacture highly foamed plastic insulated wires. It is possible to obtain a method of manufacturing a highly foamed plastic insulated wire that enables the following.

That is, in the extrusion step, extrusion is carried out while paying attention to the wall thickness and foaming effect, and the outer diameter and inner diameter of the foam 1 are left as they are and ignored (see FIG. 3(A)).

In the next slitting process, the angle θ of the unnecessary part is calculated based on the inner diameter of the foam 1 and the diameter d of the core wire 2a, and the slit blade is adjusted to cut the unnecessary part in the longitudinal direction (see figure (b)). ), remove it (see figure (c)). Immediately after that, core wire 2
To prevent part a from popping out, press and tape it for 1 second as shown in the same figure (d). The above-mentioned θ can be calculated from the inner diameter D of the foam 1 and the diameter d of the core 12a using the following formula.

As described above, according to this embodiment, it is possible to manufacture a highly foamed plastic insulated wire with a good comradery ratio and in which the insulator is in close contact with the core wire more easily than in the past.

In addition, since the outer diameter of the foam after extrusion does not need to be finished to a specified diameter from the beginning, it is possible to increase the magnification and achieve high foaming, and there is no need to reduce the die diameter to the pail limit. Problems such as foreign matter clogging are less likely to occur, and productivity and work efficiency are improved.

In this example, the slits in the foam were made parallel to the longitudinal direction, but they do not have to be parallel and may be in a spiral shape or the like. Further, the outermost layer need not be particularly taped, and an ultra-thin skin layer-like coating may be applied while appropriately fusing the foam.

Further, if the foam in the unnecessary portion after slitting is re-pulverized and mixed with the extrusion compound for use, the loss will be reduced compared to the case described above.

The materials of foamed plastic are fluororesin, polyethylene,
Although there are no particular restrictions on polypropylene, the shape of the cross section to be extruded must be a circular shape with uniform wall thickness since unnecessary portions must be slit and tightened after extrusion.

Effects of the Invention As described above, the present invention removes a predetermined unnecessary portion of the extruded foam by slitting it in the longitudinal direction around the core wire.
Since the removed foam was tightened around the core wire from the outside to produce a highly foamed plastic insulated wire, the core wire and the foam were easily brought into close contact.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the manufacturing process of an embodiment of the method for manufacturing a highly foamed plastic insulated wire of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a highly foamed plastic insulated wire produced by a conventional method for manufacturing a highly foamed plastic insulated wire. It is a diagram. 1: Foam, 2a: Core wire

Claims (1)

[Claims] 1. In a method for producing a highly foamed plastic insulated wire by extruding a foam around a core wire, a predetermined unnecessary portion of the foam extruded around the core wire is removed in the longitudinal direction. A method for manufacturing a highly foamed plastic insulated wire, characterized in that the highly foamed plastic insulated wire is manufactured by removing the foam by slitting and tightening the removed foam around a core wire from the outside.