JPS6110962Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement in an extrusion die used for pelletizing resin raw materials such as polyethylene.

This type of resin raw material is pelletized (cut into small pieces) to facilitate transportation and handling. A common method for pelletizing is to extrude a molten resin raw material through a number of nozzle holes provided in a die, and then cut the resin under water using a rotating cutter while contacting the surface of the die. Therefore, in the extrusion die used for this purpose, the end of the nozzle hole that comes into contact with the cutter is made of a hard material.

In this respect, the part of the die body that communicates with the nozzle hole is often made into a chip, and the nozzle chip is made of a hard sintered material such as cermet, ceramic, or cemented carbide, that is, at least harder than the metal of the die body. This method is made of sintered material.

As nozzle tips made of such hard sintered material, there are generally known two types of nozzle tips: round type 1 (see Figure 1) and tile type 2 (see Figure 2). It is fixed to one surface of a die body 3 made of metal such as steel by brazing, usually in one-to-one correspondence with the nozzle holes 4 of the die body 3. In this case, each nozzle tip 1, 2 is provided in a ring-shaped region 3a on one surface of the metal die body 3, due to the arrangement of the cutter shaft and extrusion shaft, or to equalize the extrusion pressure.

By the way, there is a large difference in the coefficient of thermal expansion between the metal that constitutes the die body 3 and the hard sintered material that constitutes the nozzle tips 1 and 2 (for example, the coefficient of thermal expansion of SUS410 is 10 × 10 ^-6 /℃). (On the other hand, that of cemented carbide is ^6.2 It has been found that there is a risk that the chips may occur or the chips may fall off. In such a case, the operation of the plant will be disrupted. In particular, if the nozzle chips 1 and 2 fall off, the extremely hard chips will be mixed into the pellet raw material, which will have a serious impact on the related plants. In addition,
This situation also occurs when the chip falls off due to a defect in the brazing process itself.

Therefore, it is desired to improve the fixation of the chips, but in order to increase the efficiency of extrusion molding using this type of die, there are usually a large number of nozzle holes 4, 300 to 1500, and the inside of the die also has a large number of nozzle holes 4. Since there are steam pockets to increase the temperature, special measures are required to secure the nozzle tip.

This invention has been devised in consideration of the above points, and provides an extrusion die in which the nozzle tip is firmly fixed by other mechanical means without using problematic brazing.

Hereinafter, with reference to the attached Figures 3 to 5,
The content of this idea will be clarified.

In this invention, the nozzle chips 1 and 2 described above are equivalent to the nozzle chips 1 and 2, and have a shape similar to the ring-shaped region 3a on the side of the die body 3, are made of a hard sintered material, and have through holes corresponding to the nozzle holes 4. A hard plate member 6 having a plurality of holes 5 is used. This hard plate member 6 may be an integral piece as shown in FIG. 3, or in some cases, the whole may be divided into a plurality of fan-shaped pieces 61 as shown in FIG. can. The latter split type has more free ends than the former one-piece type, so it is possible to further reduce the factors that cause cracks due to temperature changes in the die. By increasing the width of the plate member 6 itself, the number of through holes 5 can be increased.

In addition, in this invention, such a hard plate member 6
is pressed against one surface of the die body 3 by the inner ring 7 and outer ring 8, and these inner ring 7 and outer ring 8 are located at the inner and outer periphery of the hard plate member 6 to be fixed, respectively. The hard plate member 6 is pressed against the die body 3 by a screw fastener 9, with at least a portion of the side surface resting on each of the inner and outer side surfaces of the hard plate member 6.

In the case of the illustrated embodiment, the inner circumferential side surface 6a of the plate member 6 on which one side surface 7a of the inner ring 7 rests, and the outer circumferential side surface 6 of the plate member 6 on which one side surface 8a of the outer ring 8 rests.
b have tapered surfaces that match each other, but each side surface 6a, 6b on the plate member 6 side may be a curved surface, or each side surface 6a, 6b; 7a, 8a
It is also possible to provide a step and fit the stepped portions together. In short, the inner ring 7 and the outer ring 8 may be configured to press each side surface of the hard plate member 6 against the die body 3.
However, when each side surface 6a, 6b; 7a, 8a is a tapered surface, and each side surface 7 of inner and outer rings 7, 8
a, 8a are tapered surfaces, while each side surface 6a, 6b of the plate member 6 is a curved surface, the inner and outer rings 7, 8 not only apply force to press down the plate member 6, but also apply force to the plate member 6. Since a force is also generated to pinch the plate member 6, the plate member 6 can be held more firmly. In those cases, as shown in FIG. 4, it is preferable to provide protrusions 7b and 8b for maintaining the posture at the lower portions of the opposite sides of the inner and outer rings 7 and 8. Then, when the screw fastener 9 is tightened, the inner and outer rings 7 and 8 will press down on the hard plate member 6 using the protrusions 7b and 8b as fulcrums, so that the firmness of the holding can be further ensured. It can be made into something. The inner ring 7 can be integrated with the die body 3, but from the viewpoint of making the hard plate member 6 stronger, it is better to separate it as in the above-mentioned embodiment.

As described above, in this invention, a hard plate member 6 having the same shape as the ring-shaped region 3a on the die body 3 side is used as the nozzle tip. Since the inner ring 7 and the outer ring 8 are used to press and fix the die body 3 against one surface of the die body 3, the hard plate member 6 can be firmly fixed without using brazing. In addition, since the extrusion die of this invention is basically the same as a conventional die, conventional die bodies etc. can be used, and furthermore, if the plate member 6 is damaged, it can be replaced. It is extremely advantageous in terms of repair as it can be easily replaced.

[Brief explanation of the drawing]

Fig. 1 shows a conventional example, in which a is a front view and b is a sectional view taken along line X-X. Fig. 2 shows another conventional example, in which a is a front view and b is a sectional view taken along line 3 is a front view showing an embodiment of this invention,
Figure 4 is a sectional view taken along the Z-Z line in Figure 3;
The figure is a front view showing another embodiment of this invention. 3...Dice body, 3a...Ring-shaped area,
4... Nozzle hole, 5... Through hole, 6... Hard plate member, 7... Inner ring, 8... Outer ring, 9...
Screw fasteners.

Claims (1)

[Scope of utility model registration request] A metal die body having a plurality of nozzle holes over a ring-shaped area, and a die body made of a hard sintered material having the same shape as the ring-shaped area and having a plurality of through holes corresponding to the nozzle holes. It has a hard plate member, and an inner ring and an outer ring that press and fix the hard plate member against one surface of the die body, and these inner ring and outer ring are connected to the inner and outer peripheral parts of the hard plate member. The hard plate member is pressed against the die body by a screw fastener, with at least a part of the side surface resting on each of the inner and outer sides of the hard plate member. extrusion die.