JPH06270230A - Screw of twin-screw extruder - Google Patents

Abstract

PURPOSE:To enhance the feed capacity of a material to be extruded without increasing equipment cost and material cost by providing an auxiliary flight between the pitches of the flight on the outer peripheral surface of a shaft part in the same direction as the flight over the range from the position entering a compression zone to the midway part of a feed zone. CONSTITUTION:An upwardly opened feed zone 4 and the compression zone extending from the feed zone 4 in a material feed direction are provided in a casing 1. A screw 2 wherein a flight 9 is spirally provided on the outer peripheral surface of a shaft part is inserted in the casing 1 in a freely rotatable manner from the feed zone 4 to the compression zone 5. An auxiliary flight 15 spirally formed in the same direction as the flight 9 is provided between the pitches of the flight 9 on the outer peripheral surface of the shaft part 8 over the range from the position slightly entering the compression zone to the midway part of the feed zone.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a screw for a twin-screw extruder.

[0002]

2. Description of the Related Art Conventionally, a twin-screw extruder of this type has a casing having therein a feed zone that opens upward and a compression zone that extends in the material conveying direction from the feed zone, and a spiral shape on the outer peripheral surface of the shaft portion. And a screw having a flight of 1., and a pair of left and right screws are rotatably inserted inward from the feed zone to the compression zone.

In such a twin-screw extruder, the extruded material such as rubber supplied to the feed zone is extruded into the compression zone by the flight of the screw, and the extruded material is supplied to the roller die provided at the outlet of the casing. And formed into a sheet (for example, Japanese Patent Laid-Open No. 4-10
3328, JP-A-4-103329, and JP-B-116593).

[0004]

By the way, in the conventional twin-screw extruder, for example, as shown in FIG. 5, a material that is easily crushed by the rotation of a screw (a material that easily becomes broken such as masticated rubber) is used. When pushing out,
The material near the inlet of the compression zone 24 is pushed into the compression zone 24 by the flight 26 of the screw 25 in the direction of arrow C in FIG. 5, while the internal pressure of the compression zone 24 causes the material to move in the spiral direction of the flight 26. A backflow phenomenon occurs in which the backflow phenomenon is pushed back in the direction of arrow D in FIG.
Due to this backflow phenomenon, there has been a problem that the feed capability is considerably reduced.

On the other hand, as a means for avoiding such an inconvenience, the compression zone is lengthened to reduce the pressure rise gradient in the compression zone, or a large number of dimples are provided on the inner peripheral surface of the compression zone of the casing (actual exploitation 62). -1
No. 42507). However, the former method has a drawback in that the length of the screw is lengthened, so that the entire equipment is lengthened, the strength of the screw support portion is increased, and the capacity of the screw drive source is significantly increased.

Further, the latter means has a drawback that the inner surface of the casing requires dimple processing, resulting in high cost and that the material adhered in the dimple remains as an impurity when the material is changed. In view of such circumstances, it is an object of the present invention to improve the feed ability of the material to be extruded without causing a rise in equipment cost or material cost.

[0007]

[Means for Solving the Problems] In order to achieve the above object,
The technical means taken by the present invention is to provide a feed zone that opens upward and a compression zone that extends in the material conveying direction from the feed zone in a casing, and use a screw having a spiral flight on the outer peripheral surface of the shaft portion. In a twin-screw extruder rotatably inserted from the feed zone to the compression zone, between the pitches of the flights on the outer peripheral surface of the shaft portion, an auxiliary flight having a spiral shape in the same direction as the flight is provided to the compression zone side. It is a point provided within the range from the slightly entered position to the middle of the feed zone.

[0008]

[Function] Since the auxiliary flight has a spiral shape in the same direction as the flight between pitches of the flights, it pushes the material to be extruded that has entered the compression zone in the material conveying direction, and the material to be extruded presses the internal pressure of the compression zone. Suppress the flow into the feed zone. On the other hand, since the auxiliary flight is provided in the range from a position slightly entering the compression zone side to the middle part of the feed zone, it is not necessary to increase the driving force of the screw so much, and the auxiliary flight is added to the screw. Therefore, it is possible to manufacture at a significantly lower cost than in the case where dimples are formed on the inner peripheral surface of the casing.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. In the figure, a twin-screw extruder according to the present embodiment is provided with a casing 1 that receives a material to be extruded such as rubber or plastic supplied from a kneader (not shown) and a relative rotation inwardly facing each other inside the casing 1. The casing 1 is provided with a pair of right and left screws 2 that are freely inserted, and an upper opening 3 is formed in the upper portion of the casing 1.

That is, in the casing, there are formed a feed zone 4 communicating with the opening and a compression zone 5 having a cross-sectional eyeglass hole shape extending from the feed zone 4 in the material conveying direction. Are rotatably arranged around horizontal axes parallel to each other from the feed zone 4 to the compression zone 5. A conveying chute 6 for supplying a material to be extruded is connected to the opening 3, and a discharge port 7 that opens in the axial direction of the screw is provided on the front end side of the screw of the casing 1.

The screw 2 is formed by integrally providing a spiral flight 9 on the outer peripheral surface of a shaft portion 8 having a substantially cylindrical shape,
A portion of the casing 1 corresponding to the feed zone 4 is a feed portion 10 of the extruded material, and a tip portion thereof is a compression portion 11 of the extruded material. The outer periphery of the compression portion 11 is the inner peripheral surface of the compression zone 5. Is blocked by.

The pitches of the flights 9 in the feed section 10 and the compression section 11 of the screw 2 are set to be unequal pitches which are long in the feed section 10 and short in the compression section 11, and thus the flight 9 in each screw 2 is large.
The twisting directions of are set opposite to each other. Further, the outer diameter of the flight 9 is formed along an outer diameter reference line 12 shown by a virtual line in FIG. 1, and the outer diameter reference line 12 is
The tapered shape is such that the diameter gradually decreases from the feed portion 7 to the compression portion 8.

A base end portion of the screw 2 projects from the casing 1, a gear 13 is formed on the projecting portion, and the gears 13 of the respective screws 2 mesh with each other. The base end of each screw 2 is supported at two points by a gear case (not shown) via bearings 14, and thus each screw 2 is supported in a cantilever manner inside the casing 1.

An electric motor (not shown) is connected to the base end side of one screw 2. Therefore, the screws 2 rotate in the opposite directions at the same speed through the meshing of the gears 12, and this rotation direction is a direction in which the material to be extruded supplied from the opening 3 is meshed between the pair of screws 2. ing. The twisting direction of the flight 9 is the direction in which the material caught by the above rotation is conveyed to the discharge port 7 side.

On the other hand, in this embodiment, as shown in FIG. 2, an auxiliary flight 15 for suppressing the backflow phenomenon of the material to be extruded is provided integrally with the shaft portion 8 of the screw 2.
The auxiliary flight 15 is formed in a spiral shape in the same direction as the flight, and is arranged between the pitches of the flights 9 on the outer peripheral surface of the shaft portion 8. Also,
The range where the auxiliary flight 15 is provided is set to a range from a position slightly entering the compression zone 5 side of the casing 1 to a midway portion of the feed zone 4 of the casing 1.

That is, in this embodiment, the auxiliary flight 1
The front end 16 of 5 is from the inlet 17 of the compression zone 5 to the outlet 7
The auxiliary flight 15 is disposed at a position slightly displaced to the side, the rear end portion 18 of the auxiliary flight 15 is disposed substantially in the center of the feed zone 4 in the material conveying direction, and the peripheral end of the intermediate portion 19 of the auxiliary flight 15 is the outer diameter of the flight 9. It is formed along the reference line 12.

The front end portion 16 and the rear end portion 18 of the auxiliary flight 15 are both rubbed on the outer peripheral surface of the shaft portion 8. A roller die 20 is arranged in front of the discharge port 7 with a slight gap between the discharge port 7 and the roller die 20. The roller die 20 is a pair of upper and lower parts that rotate around a horizontal axis perpendicular to the axial direction of the extrusion screw 5. The calendar rollers 21 and 21 are provided. This calendar roller 2
1, 21 are forcibly driven by a rotation driving device (not shown), and the extruded material extruded from the outlet 7 of the casing 1 is formed into a sheet.

According to the twin-screw extruder having the above-described structure, the material to be extruded batch-fed by the conveying chute 6 from the kneading machine or the like is received in the feed zone 4 and the space between the screws 2 is rotated by the rotation of the pair of screws 2. It is pushed into the compression zone 5 while being bitten. At this time, the material between the flights 9 tends to flow out in the direction of the arrow A in FIG. 2 due to the pressure received from the inner peripheral surface of the casing 1 at the moment when it enters the compression zone 5, but the intermediate portion 19 of the auxiliary flight 15 does this. By pushing back in the direction of arrow B in the figure, the backflow phenomenon, which has been a problem in the past, is reliably suppressed.

Further, in this embodiment, the auxiliary flight 15 exhibiting such an action is provided only in the range from the position slightly entering the compression zone 5 side to the midway portion of the feed zone 4 of the casing 1, so that the screw 2 A reliable material feed is guaranteed without significantly increasing the driving force. Further, since the front end portion 16 of the auxiliary flight 15 is rubbed with the shaft portion 8 of the screw 2, the pitch interval of the original flight 9 is not narrowed more than necessary, and the screw 2 is installed as the auxiliary flight 15 is installed. There is almost no decrease in the feed ability of the.

3 and 4 show a second embodiment of the present invention. The present embodiment is different from the first embodiment in that the auxiliary flight 15 is provided in the minimum range capable of preventing the backflow, and in the present embodiment, the compression zone 5 is used.
The auxiliary flight 15 is provided only on the opposite side of the portion of the flight 9 closest to the entrance 17 of the.

That is, when the original peripheral edge of the flight 9 comes closest to the inlet 17 of the compression zone 5 (state of FIG. 3)
Assuming that the peripheral end point of the flight 9 is T and that the position where this peripheral end point T is inverted by 180 ° around the axis of the screw 2 is point M, the auxiliary flight 15 according to the present embodiment moves from point M to the screw 2 The angular displacement around the axis is defined as x, and this x is provided over a range where it is approximately −90 ° or more and 90 ° or less.

FIG. 4 is a development view of the shape of the auxiliary flight 15, that is, the relationship between the angular displacement x around the axis of the screw 2 and the height y of the auxiliary flight 15 from the peripheral surface of the shaft portion 8 at x. It is a graph shown. As can be seen from this figure, in the range of -45 ° <x <45 °, the height y of the auxiliary flight 15 is set to the maximum value y1, and -90 ° <x <
In the range of −45 ° and 45 ° <x <90 °, the auxiliary flight 15 is rubbed on the shaft portion 8 so that the height y gradually becomes zero. The maximum value y1 means the height y when the peripheral edge of the auxiliary flight 15 is on the outer diameter reference line 12.

The reason why the auxiliary flight 15 is provided in the above-mentioned range in this embodiment is that the material to be extruded is most remarkably returned in that range. Therefore, in this embodiment,
The auxiliary flight 15 is provided in the minimum required range to reliably prevent the backflow phenomenon, and the auxiliary flight 15 is not provided in other ranges to reduce the material cost.

The present invention is not limited to the above-mentioned embodiment, and for example, the present invention is a parallel shaft and flight 9.
The outer diameter reference line 12 can also be used in a twin-screw extruder having a cylindrical screw 2. In addition, the present invention relates to the screw 2
Can also be used in a so-called cone type twin-screw extruder in which the taper is tapered and the axis of the screw 2 is not parallel.

[0025]

As described above, according to the present invention,
The auxiliary flight suppresses the backflow phenomenon in the vicinity of the inlet of the compression zone, and since it is not necessary to increase the driving force of the screw so much and can be manufactured at low cost, it does not cause a rise in equipment cost or material cost, etc., The feed ability of the material to be extruded can be improved.

[Brief description of drawings]

FIG. 1 is a side sectional view of a twin-screw extruder according to a first embodiment.

FIG. 2 is an enlarged side view of a screw.

FIG. 3 is an enlarged side view of a screw according to a second embodiment.

FIG. 4 is a shape development view of an auxiliary screw.

FIG. 5 is a side sectional view of a conventional twin-screw extruder.

[Explanation of symbols]

 1 Casing 2 Screw 4 Feed zone 5 Compression zone 8 Shaft 9 Flight 15 Auxiliary flight

Claims (1)

[Claims] 1. A feed zone (4) opening upward and a compression zone (5) extending from the feed zone (4) in the material conveying direction are provided in a casing (1), and an outer peripheral surface of a shaft portion (8). A twin-screw extruder in which a screw (2) having a spiral flight (9) is rotatably inserted from the feed zone (4) to the compression zone (5) on the outer peripheral surface of the shaft portion (8). Flight in (9)
Between the pitches, the auxiliary flight (15) having a spiral shape in the same direction as the flight (9) is within a range from a position slightly entering the compression zone (5) side to a midway portion of the feed zone (4). A screw of a twin-screw extruder characterized by being provided.