JP3678518B2 - Screw shaft for elastomer extruder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screw shaft for an elastomer extruder that can effectively suppress the occurrence of air accumulation in an extruded product and can improve product quality when extrusion molding is performed using an elastomer material.
[0002]
[Background Art and Problems to be Solved by the Invention]
For example, when extruding an elastomer product having a constant cross-sectional shape such as a tire tread rubber or a side wall rubber, an extruder having a screw shaft disposed in the center hole of a cylinder provided with a molding nozzle at the front end is used. Used, the elastomer material in the cylinder is kneaded and extruded from the molding nozzle by the rotation of the screw shaft.
[0003]
As this screw shaft, as shown in FIGS. 6A and 6B, for example, an elastomer material that has been conventionally sent from the screw shaft flows smoothly forward without resistance at the shaft front end. The protrusion part a which protrudes on a cone shape or a truncated cone is formed.
[0004]
However, when this screw shaft is used, as shown in an enlarged view in FIG. 7, the extrusion pressure at the shaft front end portion b is reduced as compared with the extrusion pressure at the outer portion c (blade side). The air in the elastomer material easily collects in the shaft front end portion b. For example, as shown in FIGS. 8A and 8B, the air reservoir e is hollow in the central portion or thick portion of the elastomer product d. In other words, the quality of the product is deteriorated and defective products are generated.
[0005]
Therefore, the present invention is based on the formation of a recess at the front end of the screw shaft, and generates a vortex-like turbulent flow at the front end portion of the shaft, and disperses air that tends to concentrate on the front end portion of the shaft over the entire material. Accordingly, an object of the present invention is to provide a screw shaft for an elastomer extruder that can suppress the formation of a concentrated air reservoir and solve the above problems.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the screw shaft for the elastomer extruder of the present invention is rotatably arranged in the center hole of the cylinder of the elastomer extruder, and is mixed with the elastomer material to be fed from the inlet on the rear end side. A screw shaft that pushes toward the nozzle port on the front end side while kneading,
A base shaft extending concentrically in the center hole and a screw blade extending spirally toward the front end on the outer periphery of the base shaft, and at the front end of the base shaft are concentric with the center line of the base shaft and rearward It is characterized by the formation of a dent that is recessed toward.
[0007]
The concave portion preferably has a cone shape or a spherical shape with the center line portion of the base shaft as the deepest portion, and the diameter D1 of the concave portion at the front end of the base shaft is not less than 0.6 times the diameter D of the base shaft, and The depth H of the dent is preferably 0.05 to 0.23 times the diameter D of the base shaft.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the elastomer extruder 2 on which the screw shaft 1 is arranged has a cylinder 5 extending substantially horizontally from one side of the extruder body 3, and is attached to the front end of the cylinder 5 for molding. A head 7 having a nozzle port 6.
[0009]
In this example, as shown in FIG. 2, the cylinder 5 includes cylinders 5A, 5B, and 5C that are divided into, for example, three in the axial direction, and the cylinders 5A, 5B, and 5C are flanges at end portions facing each other. The Fs are joined together by connecting bolts. Also, the peripheral wall on the rear end side of the cylinder 5 is provided with a charging port 9 for charging the elastomer material, and around the heating medium flow through which steam, hot water, etc. for heating and kneading the elastomer material increase efficiency. A path 10 is formed over substantially the entire length thereof.
[0010]
The head 7 has, for example, a tapered flow path 12 that continues to the center hole 11 of the cylinder 5, and the nozzle port 6 that matches the product cross-sectional shape is opened through the flow path 12.
[0011]
A screw shaft 1 that pushes toward the nozzle port 6 while kneading the elastomer material supplied from the charging port 9 is disposed in the center hole 11 of the cylinder 5.
[0012]
The screw shaft 1 has a base shaft 13 concentrically extending in the center hole 11 and having a rear end connected to the drive motor M via a speed reducer, and a spiral on the outer periphery of the base shaft 13 toward the front end side. And extending screw blades 14.
[0013]
In the present example, as shown in FIG. 3, the base shaft 13 has a cap body 16 detachably provided at the front end of the main portion 15, and a recessed portion 17 is formed at the front end of the cap body 16. The screw blades 14 are formed in a spiral shape such as one or two lines over substantially the entire length of the main portion 15.
[0014]
The cap body 16 is formed with a screw portion 20 that is screwed into a screw hole 15A provided at the front end of the main portion 15 through a step at the rear end of the head portion 19 having substantially the same diameter as the main portion 15. In addition, the cap body 16 and the main part 15 are airtightly connected using a sealing material 21 disposed on the stepped portion. Further, the head portion 19 of the cap body 16 is formed with a recessed portion 17 that is recessed rearward. The recessed portion 17, by forming the center line X and concentric front Symbol cornerstone 13, is formed on the center line X on a cone having a deepest portion 17A (conical).
[0015]
As shown in FIG. 4, the elastomer material extruded into the flow path 12 by the screw shaft 1 is influenced by the pushing force by the screw blades 14 in the flow F <b> 1 of the wall surface side portion C of the flow path 12. The extrusion pressure is increased. On the other hand, in the shaft front end side portion B, the volume is increased and the pressure is further reduced due to the formation of the recessed portion 17, and as a result, the elastomer material in the shaft front end side portion B is dragged by the flow F1 and spiraled. Turbulent flow F2 is generated. As a result, the air in the elastomer material is finely dispersed throughout, and a high-quality elastomer product substantially free of air accumulation can be produced with a simple structure and high yield.
[0016]
In order to smoothly generate the vortex-like turbulent flow F2, the diameter D1 of the recess 17 at the front end of the base shaft 13 is set to 0.6 times the diameter D of the base shaft 13 and the depth H is set to 0 of the diameter D. 0.05 to 0.23 times is preferable. In this example, the depth H is set to about 0.14 times the diameter D, and the top portion that becomes the deepest portion 17A is smoothly formed by an arc surface to smooth the flow of the turbulent flow F2. In this example, the diameter D1 of the recess 17 is about 0.85 times the diameter D, and the region Y between the front edge 17e of the recess 17 and the outer periphery of the base shaft 13 is smoothly connected by an arc surface. doing. Thus, the flow F1 and the turbulent flow F2 in the wall surface portion C are smoothly joined.
[0017]
When the diameter D1 is less than 0.6D and when the depth H is less than 0.05D, the volume and pressure decrease in the shaft front end side portion B are insufficient, and the material by the flow F1 is obtained. If the drag becomes small and the depth H exceeds 0.23D, it becomes a resistance of the spiral flow, and both of them inhibit the generation of the turbulent flow F2.
[0018]
In order to obtain a smooth spiral flow, the recess 17 can be formed in a spherical shape as shown in FIG. 5 in addition to the cone shape.
[0019]
【Example】
Using the screw shaft having the cone-shaped recess shown in FIG. 3, the tire tread rubber shown in FIG. 8 (A) is extruded and the presence or absence of air accumulation at that time is disassembled. confirmed. The outer diameter of the screw blade in the screw shaft used was 199.2 mm, the diameter D of the base shaft was 130 mm, the depth H of the recess was 14.0 mm, and the diameter D1 was 112 mm.
[0020]
As a result of the experiment, it was confirmed that no air reservoir having a visible size was observed, and that the air in the product was surely fragmented and dispersed throughout.
[0021]
【The invention's effect】
Since the present invention is configured as described above, a vortex-like turbulent flow can be generated at the front end portion of the shaft, and air that tends to concentrate on the front end portion of the shaft can be dispersed and subdivided over the entire material. As a result, a high-quality elastomer product substantially free of air accumulation can be produced with a simple structure and high yield.
[Brief description of the drawings]
FIG. 1 is a side view of an extruder equipped with an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the cylinder together with a screw shaft.
FIG. 3 is an enlarged cross-sectional view showing a recess at the front end of the screw shaft.
FIG. 4 is a cross-sectional view for explaining the effect of the embodiment product.
FIG. 5 is a cross-sectional view showing another example of a recess.
FIGS. 6A and 6B are side views showing a front end shape of a conventional screw shaft. FIGS.
FIG. 7 is a cross-sectional view showing a material flow in a conventional screw shaft.
FIGS. 8A and 8B are cross-sectional views of an elastomer product for explaining problems caused by conventional extrusion molding. FIGS.
[Explanation of symbols]
2 Elastomer Extruder 5 Cylinder 6 Nozzle Port 9 Input Port 11 Center Hole 13 Base Shaft 14 Screw Blade 17 Recessed Part 17A Deepest Part X Baseline Center Line

Claims (3)

A screw shaft that is rotatably arranged in the center hole of the cylinder of the elastomer extruder, and extrudes toward the nozzle port on the front end side while kneading the elastomer material that is input from the input port on the rear end side,
A base shaft extending concentrically in the center hole and a screw blade extending spirally toward the front end on the outer periphery of the base shaft, and at the front end of the base shaft are concentric with the center line of the base shaft and rearward A screw shaft for an elastomer extruder having a recess recessed toward the surface.   2. The screw shaft for an elastomer extruder according to claim 1, wherein the concave portion has a cone shape or a spherical shape with a center line portion of the base shaft as a deepest portion.   The said recessed part made diameter D1 in the front end of the said base axis more than 0.6 times the diameter D of a base axis, and made the depth H of the recessed part 0.05 to 0.23 times the diameter D of the base axis. The screw shaft for an elastomer extruder according to claim 2.

Images