JPS6228018Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a crosshead for an extruder for producing a two-layer insulated wire, which is mainly used in communication cables and has an inner layer made of foamed plastic material and an outer layer made of solid plastic material. .

In the production of this type of double-layer insulated wire, the insulation materials of both the inner and outer layers are generally extruded by two extruders, an inner layer insulation extruder and an outer layer insulation extruder, and then processed into one crosshead nipple and die. A device is employed that simultaneously extrudes two layers of insulation material around the core wire into a conical extrusion gap formed between them. In this method, it is important to make the thickness of both the inner and outer insulation layers uniform with respect to the core wire. There was a problem that a pressure difference occurred in some parts, and the thickness of the insulating layer became uneven. In order to solve this problem, various methods have been proposed for uniformly distributing the pressure of both the inner and outer insulating materials over the entire outer circumference of the core wire, but satisfactory results have not yet been obtained.

The present invention solves this problem, and embodiments thereof will be described below with reference to the accompanying drawings. A die 6 having a conical recess 4 and an extrusion hole 5 is provided in a circular hole 3 bored in a sleeve 2 detachably attached to the crosshead main body 1, and a shaft integrated with a nipple holder 7 supported in the circular hole 3. A conical nipple 9 formed at the tip of the head 8 is inserted into the conical recess 4 of the die 6.
Install it facing the A conical extrusion gap a communicating with the extrusion hole 5 between the nipple 9 and the conical recess 4, and the extrusion gap a between the shaft head 8 and the circular hole 3.
An extrusion hole 5 is formed in the nipple holder 7, the shaft head 8, and the nipple 9.
It is conventional practice to provide a core wire insertion hole 10 that communicates with the sleeve 2, and to drill an inner layer insulating material passage 11 that communicates with the circular hole 3 of the sleeve 2 from an extrusion port 21 of an inner layer insulating material extruder (not shown) in the sleeve 2. It is similar to

In the present invention, the outer layer insulation material is passed from an extrusion port 22 of an outer layer insulation material extruder (not shown) through the outer layer insulation material passage 12, and from a ring-shaped outer layer insulation material passage 14 formed between a ring 13 fitted on the sleeve 2 and the sleeve 2. 8 or more communicating with the circular hole 3 in 2, preferably
Through about 16 radial passages 15, the annular groove 16 formed in the inner wall of the circular hole 3 is communicated with, and between the inner circumference of the annular groove and the outer circumference of the die 6, an annular squeeze-out gap d is formed which communicates with the extrusion passage b. is formed and polymerized and merged with the outer periphery of the inner layer insulation material extruded into the extrusion passage b.

In the figure, 17 is an inclined rectifying surface formed on the nipple holder 7, 18 is a holding plate for preventing the die 6 from coming out,
19 is a nut for fixing the plate of the nipple holder 7.

The present invention has the above configuration, and the inner layer insulation material such as foamed polyethylene extruded from the extrusion port 21 of the extruder is passed from the inner layer insulation material passage 11 to the circular hole 3.
The outer periphery of the core wire 20 that enters the core, is guided to the rectifying surface 17, is extruded through the extrusion gap b, the conical extrusion gap a, and the extrusion hole 5, and advances at a constant speed through the cord insertion hole 10 and inside the extrusion hole 5. Cover. On the other hand, the outer layer insulating material such as solid polyethylene resin passes from the outer layer insulating material passage 12 through the ring-shaped passage 14 and has a large number of radial passages 15.
The material passes through the annular groove 16 on the inner circumference of the sleeve 2, passes through the squeeze gap d, is extruded to the outer circumference of the inner layer insulation material, merges with the inner layer insulation material, and the inner and outer insulation materials form two layers, forming a conical extrusion gap a. and is extruded through the extrusion hole 5. At this time, the outer layer insulating material in the ring-shaped passage 14 is divided by a large number of radial passages 15 and assembled in the annular groove 16, so that the local pressure difference of the material is alleviated, and furthermore, a relatively small squeeze out It is pushed out into the gap d. In this way, the crosshead of the present invention changes the flow path resistance discontinuously using the radial passages, annular grooves, and squeezing gaps, so the pressure of the insulating material becomes uniform over the entire circumference due to the resistance, and the inner layer insulation The outer insulating material can be merged with the outer periphery of the material to coat the outer periphery of the inner insulating material layer with a uniform thickness.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1. 1...Crosshead body, 2...Sleeve, 3
... Circular hole, 12 ... Outer layer insulating material passage, 13 ... Ring, 15 ... Radial passage, 16 ... Annular groove, 2
1... Inner layer insulation material extrusion port, 22... Outer layer insulation material extrusion port, b... Inner layer insulation material extrusion gap, d...
...The squeezing gap of the outer insulation layer.

Claims (1)

[Scope of utility model registration request] In a crosshead for extruding two-layer insulated wire used to extrude plastic into two layers on a core material, a ring-shaped passage of an outer layer insulating material is provided on the outer periphery of a sleeve that is detachable to the crosshead, and a ring-shaped passage is provided on the inner periphery of a circular hole of the sleeve. A number of radial passages bored in the sleeve communicate with the annular groove formed in the sleeve, and the annular groove communicates with the outside of the inner layer insulation material extrusion passage through an annular squeezing gap formed inside the sleeve, and the outer layer insulation A crosshead for extruding two-layer insulated wire, characterized in that the flow resistance of the material passage is discontinuously changed by the radial passage, the annular groove, and the squeezing gap, and further, both the inner and outer insulating materials are merged and polymerized.