KR20100090104A - Screw of extruding apparatus - Google Patents

Abstract

PURPOSE: A screw for an extruding device is provided to minimize oxidation, carbonization, and early cross-linkage of resin by increasing head force of the screw. CONSTITUTION: A screw for an extruding device comprises a screw body unit(22) and a screw head unit(23). The screw body unit has a flight on the surface. The screw head unit is formed in the front end of the screw body unit and is composed of an increase section(S1), a retaining section(S2), and a decrease section (S3). The diameter of the screw head unit is increased from the screw body unit in the increase section. The increased diameter is uniformly maintained in the retaining section. The diameter of the screw head unit is decreased in the decrease section.

Description

Screw in Extrusion Unit {SCREW OF EXTRUDING APPARATUS}

The present invention relates to a screw of an extrusion apparatus, and more particularly to a screw head provided in the front end of the screw.

In general, the extrusion device is a device for injecting the molten resin into a mold manufactured to match the shape of the product to be molded.

This extrusion device melts the solid resin granules by mechanical energy caused by the rotation of a screw installed in the barrel and thermal energy by a heater mounted outside the barrel, and then injects and solidifies the molten resin into the mold to obtain a product having a desired shape. Serve

The screw installed in the barrel is composed of a body portion having a flight on the surface for conveying and melting the resin grains and a head portion for preventing backflow of the resin when injecting the molten resin into the mold.

In general operation of the extrusion apparatus, the pellet resin supplied through the hopper is introduced into a barrel equipped with a heater, and when the screw connected to the hydraulic motor or the electric motor rotates, the screw is generated. The solid resin is melted by shear heat and heat generated from the heater. The molten resin passes through the screw head portion and accumulates at the front end of the head portion.

When the melt is continuously accumulated at the front end of the screw head part and the weighing is completed, the screw stops rotating, advances axially with the pressure and speed suitable for the molding conditions, and pushes the molten resin into the mold through the barrel outlet.

When the stagnation of the resin occurs in the screw head portion of the extrusion device as described above, the residence time of the resin is long, the oxidation or carbonization of the resin due to the decomposition of the polymer may occur. In particular, in the case of crosslinkable polymers, premature crosslinking occurs due to the stagnation of the resin, and the quality is extremely poor. In addition, when the pressure at the tip of the screw head portion is low, bubbles of volatile materials are liable to occur, and solid bed break-up may occur, thereby preventing melting.

Therefore, in the extrusion apparatus, it is important to restrain the stagnation in the screw head portion during extrusion of the molten resin to ensure smooth flow of the resin and at the same time to secure an appropriate screw head pressure to prevent the backflow of the resin.

Conventionally, in order to ensure smooth resin flow in the screw head portion and to form an appropriate screw head pressure, the diameter of the screw head portion is increased from the point where the rod-shaped structure is coupled to the end of the screw head portion or the flight ends. The structure of the screw head portion was developed in which the diameter decreased linearly to the rear end.

However, the screw head portion combining the rod-shaped structure has a problem that is difficult to apply to the extrusion device having the breaker plate and the screen mesh. In addition, the screw head portion, which decreases after the diameter is increased, can obtain a high screw head pressure, but in order to form a larger screw head pressure, the diameter of the screw head must be increased to maintain a very narrow gap, so that the molten resin has a high speed. This may cause oxidation of the resin due to heat generation. In addition, when the resin suddenly passes through the narrow passage through the narrow passage, stagnation may occur on the wall of the screw head portion and the reducer, which may cause oxidation of the resin.

Accordingly, the present invention is to solve the above problems, by changing the structure of the screw head portion to improve the flowability of the resin in the screw head portion and at the same time maintain the screw head pressure properly to suppress the backflow phenomenon of the resin It is to provide a screw of the extrusion device.

Screw of the extrusion device according to an embodiment of the present invention for achieving the above object is a screw of the extrusion device that is installed to be rotated in the barrel in which the resin is injected, the screw body portion having a flight on the surface ; And a screw head portion formed at the front end of the screw body portion. Here, the screw head portion is composed of a rising section in which the diameter increases from the screw body portion, a holding section in which the increased diameter is kept constant, and a decreasing section in which the diameter decreases.

In addition, the reduction interval may be reduced by two or more slopes.

The reduction section may include a first reduction section that is reduced in parallel with the inner surface of the reducer installed in the screw head and a second reduction section that is reduced by a larger slope than the first reduction section.

In addition, the end diameter of the screw head portion may be 1/3 to 1/5 of the diameter of the screw body portion.

In addition, the extrusion device according to an embodiment of the present invention for achieving the above object, a barrel having a hopper to which the resin is injected; A screw rotatably installed in the barrel, the screw including a body having a flight on its surface and a head formed at a front end of the body; Reducers disposed on the outer surface of the head portion spaced at a predetermined interval; And a screen mesh installed at the front end of the head in the reducer to increase the head pressure. Here, the head portion of the screw is composed of a rising section of increasing diameter from the body portion of the screw, a holding section of maintaining the increased diameter is constant and a decreasing section of decreasing diameter.

The screw of the extrusion apparatus according to the embodiment of the present invention reduces the backflow phenomenon of the resin which may be caused by the high pressure formed by the breaker plate and the screen mesh.

In addition, the screw of the extrusion apparatus according to the embodiment of the present invention reduces the residence time of the molten resin, while increasing the screw head force while maintaining a low shear force to minimize the oxidation and carbonization phenomenon and early crosslinking phenomenon of the resin.

The screw of the extrusion device according to an embodiment of the present invention can increase the heat transfer in the barrel and screw surface to melt the unmelted resin.

Hereinafter, a screw of an extrusion apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 is a schematic cross-sectional view of an extrusion apparatus according to an embodiment of the present invention.

Referring to Figure 1, the extrusion apparatus 100 according to an embodiment of the present invention is disposed so as to rotate inside the barrel 10 and the barrel 10 having a hopper 11 into which the resin is injected on one side. It includes a screw 20 for transferring the injected resin. The screw 20 is composed of a screw body portion 22 having a spiral flight 21 around the longitudinal direction and a screw head portion 23 connected to the front end of the screw body portion 22.

A reducer 30 connected to the barrel 10 is installed outside the screw head 23, and a screen mesh 40 is installed inside the reducer 30 to increase the screw head pressure and to increase the mixing efficiency. do. The screen mesh 40 increases the screw head pressure to increase the mixing efficiency, while the molten resin flows back in the direction in which the hopper 11 is installed by the high pressure in front of the resin, thereby increasing the residence time of the resin. Therefore, there is a need for a screw having a structure that prevents a backflow phenomenon of the resin due to the high pressure applied under the low shear force while maintaining the mixing effect at the end of the screw head portion 23.

Here, the screw 20 of the extrusion apparatus according to the embodiment of the present invention forms a suitable screw head pressure to facilitate the melting of the resin, reduce the resin stagnation in the barrel 10 and reducer 30, It is provided with a screw head portion 23 having a structure capable of obtaining a high screw head pressure in the shear force.

FIG. 2 is a partially enlarged view of the extrusion apparatus shown in FIG. 1, and FIG. 3 is a partial perspective view of a screw of the extrusion apparatus according to the embodiment of the present invention.

Referring to FIGS. 2 and 3, the screw head unit 23 includes a rising section S1, a holding section S2, and a reducing section S3.

The rising section S1 is a section in which the diameter increases from the screw body portion 22. For example, the increase rate of the diameter may be constant (tilt constant), but may be changed in various ways depending on the situation.

The holding section S2 is a section in which the diameter increased in the rising section S1 is kept constant. The length of the holding section S2 is adjusted to maintain an appropriate screw head pressure in accordance with the resin used and the operating situation of the extrusion apparatus.

That is, in a situation where a relatively high screw head pressure is required, the length of the holding section S2 is increased to prevent the resin backflow from the end of the screw head 23 due to the high pressure of the holding section S2. Thus, the amount of resin remaining in the screw head 23 for a long time can be reduced. In addition, by maintaining the appropriate interval between the barrel 10 and the screw head 23 by the holding section (S2), induces a pressure rise under a low shear force to minimize the viscous heat generated by the shear force.

The reduction section S3 is a section in which the diameter of the holding section S2 decreases. The reduction section S3 prevents the flow path from expanding suddenly after the holding section S2, thereby minimizing the oxidation of the resin due to stagnation between the surface of the screw head 23 and the wall surface of the reducer 30.

In the present embodiment, the reduction section S3 is a first reduction section S3-1 that decreases in parallel with the inner surface of the reducer 30 and a second that is reduced by a larger slope than the first reduction section S3-1. It consists of a reduction section S3-2. That is, the interval of the flow path is kept constant in the first reduction period S3-1, and the interval of the flow path is gradually increased in the second reduction period S3-2.

However, the reduction section S3 is not limited to this embodiment. That is, the reduction section may be formed to have two or more gradually increasing slopes, and may be formed of a curve rather than a straight line.

In addition, it is preferable that the end diameter D1 of the screw head portion 23 is 1/3 to 1/5 of the diameter D2 of the screw body portion 22. This is to prevent the screen mesh 40 installed at the front end of the screw head 23 from being pushed back and to reduce the gap between the wall surface of the reducer 30 and the surface of the screw head 23.

Extrusion apparatus 100 according to an embodiment of the present invention can be applied to melt and transport resins that are sensitive to oxidation or carbonization, that is, polyvinyl chloride (PVC), crosslinked polyethylene (XLPE), rubber (rubber) and the like.

The screw 20 of the extrusion apparatus according to the embodiment of the present invention as described above suppresses the backflow in the screw head portion 23, minimizes the oxidation by increasing the residence time of the resin in the barrel 10, low shear force This can reduce the occurrence of oxidation of the resin due to the shear force, and can increase the thermal conductivity in the screw 20 and the barrel 10 to melt the unmelted resin under low shear force.

In addition, the interval between the wall surface of the reducer 30 and the surface of the screw head portion 23 is reduced by the reduction section S3 of the screw head portion 23, thereby eliminating the phenomenon in which the flow path suddenly widens. That is, the space between the reducer 30 and the screw 20 is reduced to stick to the surface of the screw 20 so that the rotating resin can be pushed in the die direction without flowing in the die direction, and similarly the wall surface of the reducer 30. It is possible to reduce the oxidation time of the resin by reducing the residence time in the screw head portion 23 by pushing the resin attached to the die direction.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

1 is a schematic cross-sectional view of an extrusion apparatus according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the extrusion apparatus shown in FIG. 1. FIG.

3 is a partial perspective view of a screw of the extrusion apparatus according to the embodiment of the present invention.

Claims (7)

A screw of an extrusion device which is installed to rotate inside the barrel in which the resin is injected, Screw body portion having a flight on the surface; And It includes a screw head portion formed in the front end of the screw body portion, The screw head portion, The screw of the extrusion device, characterized in that consisting of a rising section in which the diameter increases from the screw body portion, a holding section in which the increased diameter is kept constant and a reducing section in which the diameter decreases. The method of claim 1, The reduction section is a screw of the extrusion apparatus, characterized in that for reducing at least two slopes. The method of claim 2, The reduction section is a screw of the extrusion apparatus characterized in that the first reduction section is reduced parallel to the inner surface of the reducer installed in the screw head portion and the second reduction section is reduced by a slope larger than the first reduction section. The method of claim 2, Screw diameter of the screw head portion is an extrusion device, characterized in that 1/3 to 1/5 of the diameter of the screw body portion. A barrel having a hopper into which resin is introduced; A screw rotatably installed in the barrel, the screw including a body having a flight on its surface and a head formed at a front end of the body; Reducers disposed on the outer surface of the head portion spaced at a predetermined interval; And A screen mesh installed in the front end of the head in the reducer to increase the head pressure, Head portion of the screw, Extrusion apparatus, characterized in that consisting of a rising section in which the diameter increases from the body portion of the screw, a holding section in which the increased diameter is kept constant and a reducing section in which the diameter decreases. The method of claim 5, The reduction section is characterized in that the extrusion device is reduced by at least two slopes. The method of claim 5, Extrusion device, characterized in that the end diameter of the head portion is 1/3 to 1/5 of the diameter of the body portion.

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