JPH0244986Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a nipple for extrusion molding of insulation and sheathing for electric wires and cables, and more specifically, a nipple for extrusion molding of insulation and sheathing for electric wires and cables. The present invention relates to a nipple which prevents the accumulation of dregs of an extrusion composition.

[Conventional technology]

Extrusion molding of insulation and sheathing for electric wires and cables
Plastic mixtures such as vinyl chloride and polyethylene are melted using a cylinder screw equipped with a heating means, and foreign substances are removed using a breaker plate and wire mesh placed at the tip of the cylinder, and then the mixture is extruded using a crosshead. The direction is changed and the core is coated through the die and nipple.

Here, the shape of the surface of the die nipple in contact with the mixture is adjusted so that the mixture flows smoothly without stagnation; The flow becomes slow, and the flow is disturbed in areas where the surface shape changes suddenly or at the end of the die nipple.
The molten mixture is solidified and deposited, and when the deposit becomes large, it flows together with the mixture and forms a lump on the surface of the extruded body.

In order to prevent this from happening, it has been proposed to heat the end face of the die with a burner.
This has the effect of preventing debris from accumulating on the die end face. However, no effective measures have been taken to deal with the debris that accumulates at the tips of nipples, especially in pipe extrusion.

Therefore, as shown in Fig. 2, the inventors of the present invention manufactured a nipple 22 whose outer diameter gradually decreases toward the tip, and whose tip becomes the same as the passage hole 21 of the core a. Test extrusion molding was then carried out, but dregs 23 were deposited on the tips of nipples 22 and lumps formed in the extruded product b, making it impossible to obtain the expected effect.

[Purpose of invention]

The present invention was developed in view of the above points, and aims to provide a nipple in which admixture residue does not accumulate at the tip of the nipple in pipe-type extrusion molding of insulators and sheaths of electric wire cables. It is something.

[Means to achieve the purpose]

In order to achieve the above purpose, in this invention,
In a pipe-type extrusion nipple in which the tip of the nipple protrudes downstream from the end face of the extrusion die, the core passage hole is tapered to gradually become larger toward the tip, and the inner diameter of the taper and the outer diameter of the nipple are separated at the tip. The diameters are made to be approximately the same.

[Effect]

In the nipple configured in this manner, the extruded product is separated from the tip of the nipple, and since the tip is shaped like a cutting edge, it is easy to cut (separate) from the extruded product. Therefore, molding debris is normally generated due to friction between the nipple and the molding, but this does not occur because the nipple is sharp.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Reference numeral 11 denotes a nipple body, and an approach portion 12 is provided on the upstream side of the nipple body 11, through which the core a can easily pass. Reference numeral 13 denotes a holding portion of the core a, the inner diameter of which gradually increases in a tapered shape 15 from the holding portion of the core a toward the tip 14 of the nipple body 11;
The tip 14 has approximately the same outer diameter as the nipple.

The nipple main body 11 has its rear part screwed and supported by a nipple holder (not shown), and its tip 14
The die 16 is held by a die holder (not shown).
protrudes from the end face of

As described above, the coating mixture b is set in the crosshead of the extrusion molding machine and extruded into a pipe shape.
As shown in the figure, the inner diameter of the extruded mixture b is larger than the outer diameter of the core a when it leaves the nipple, but since the extrusion speed of the core a is faster than the extrusion speed of the mixture b, it is squeezed and becomes the core a. Close to.

As mentioned above, the more acute the angle θ of the taper part of the nipple to be extruded, the more effective it is. Good extrusion molding is possible when θ is 30 degrees, and when it approaches 60 degrees, there are some lumps. However, there was no practical problem and good results were obtained even at 45 degrees.

Also, if θ is made small, good results can be obtained, but if it is made too small, the strength of the nipple tip cannot be maintained, so the limit is about 20 degrees.

Although it is not possible to actually observe the accumulation of scum in this invention because it is inside the extruded coating, when the outer casing after molding is cut open and looked at, scum is found on the inner surface of the outer casing. First, it is thought that the dregs flowed out together with the admixture before it grew, that is, while it was still small.

[Effect of idea]

As explained above, if the nipple of the present invention is used in pipe extrusion molding, a high-quality extrusion molded product can be obtained without any lumps occurring on the outer cover even after continuous operation for a long time.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
FIG. 2 is a longitudinal sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 11... Nipple body, 12... Approach part, 13... Core holding part, 14... Tip of nipple, 15... Taper, 16... Die, a...
Core, b...Extruded product (mixture).

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a nipple for pipe type extrusion molding in which the tip of the nipple protrudes downstream from the end face of an extrusion molding die, the passage hole of the core gradually becomes larger toward the tip, and A nipple for pipe extrusion molding that is characterized by approximately matching the outside diameter. (2) The pipe-type extrusion molding nipple according to claim (1) of the utility model registration, characterized in that the inclination angle of the tip of the passage hole is 60 degrees or less.