JPH03231825A - Screw for extruder - Google Patents

Abstract

PURPOSE:To deepen a channel depth in a feed portion without reducing the torsional strength of the feed portion and stabilize the introduction of an extrusion material by making the width of a flight in the feed portion wider. CONSTITUTION:The width W of a flight 3 in the compression portion C of a screw is arranged wider than that in the metering portion M thereof, and the width of the flight in the feed portion F wider than that in the compression portion C. In this case, the flight 3 is shaped into a spiral form and, therefore, when the width W of the flight 3 is widened provided that the depth G of a screw channel 2 is specified, the cross-sectional area of the screw is increased by that much to make the torsional strength of the screw greater. Accordingly, if the width of the flight 3 in the feed portion F is made wider, it becomes possible that the channel depth in the feed portion F is made deeper without reducing the torsional strength of the feed portion F, thus improving the introduction of an extrusion material and stabilizing an extruder output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screw used in a plastic extruder.

[Prior art]

Generally, a screw for an extruder has spiral grooves 2 and flights 3 formed at a constant pitch on the outer periphery of a shaft portion l, as shown in FIGS. 3 and 4. It consists of a feed section F for extruded materials, a compression section C, and a metering section M. Depth G of groove 2
is deepest at the feed section F, gradually becomes shallower at the compression section C, and shallowest at the metering section M. In the conventional screw, the width W of the flight 3 is constant.

〔assignment〕

The depth of the groove in the feed section is determined by the pellet size of the extruded material (
However, in cases where the outer diameter of the screw is small, the compression ratio is small, or the extruder output is small, the depth of the groove in the feed section may be If the diameter is increased, the outer diameter of the shaft portion 1 becomes smaller and the strength decreases, so there is a problem that the feed portion is twisted when extrusion is performed.

If the depth of the groove in the feed section is made shallow in order to prevent this twisting, the extruded material will bite into it unstablely and the discharge amount will fluctuate.

[Means for solving problems and their effects]

The present invention provides a screw for an extruder that solves the above-mentioned problems, and its configuration is as shown in FIGS. 1 and 2.
As shown in the figure, the width W of the flight 3 is wider at the compression section C than at the metering section M, and wider at the feed section F than at the compression engine section C.

Flight 3 is formed in a spiral shape, so if groove 2
When the depth G of is constant, when the width W of the flight 3 is increased, the cross-sectional area of the screw increases accordingly, and the torsional strength of the screw increases. Therefore, by increasing the width of the flights in the feed section as described above, it is possible to increase the depth of the groove in the feed section without reducing the torsional strength of the feed section. A screw with a stable discharge amount can be constructed.

〔Example〕

The present invention will be explained in detail below.

Cylinder inner diameter (screw outer diameter) D = 30mm.

Screw length L” 105011m, L/D-35
In order to coat a conductor with PFA (tetrafluoroethylene rubber fluoroalkyl vinyl ether copolymer) by extrusion, which requires high shearing force, using an extruder, the following screw was prototyped.

The width W of the flight 3 was set to 41 mm at the metering section M and 10 to 15 mm at the feed section F, and gradually widened in the compression section C from the metering section M side to the feed section F side. On the other hand, the depth G of the groove 2 is 0.6 to 1.2 mm in the metering part M and 4.6 m+w in the feed part F, and in the compression part C, as it goes from the metering part M side to the feed part F side, Gradually deepen (
I made it so.

Using this screw, an extrusion experiment was conducted under the following conditions.

■ Extruder temperature Cylinder base: 335°C Middle part 1: 350°C Middle part 2: 350°C Open end = 350°C Flange part: 3
40℃ Head section = 320℃ Die section = 320℃ ■ Screw rotation speed: 2. Orpm■ Extrusion speed (
Line speed) 75m 7 sets n ■Conductor outer diameter: 0.24sn (0.08mmφ silver plated, clear silver plating twisted)■ Insulation outer diameter: 1. Om end As a result, the manufactured insulation tklA has an outer diameter of 1.0 ± 0
．． 051, which was extremely stable. This indicates that the discharge amount is stable.

The screw was also inspected for twisting and elongation after use, and no twisting or elongation had occurred even after 5,000 hours of use.

Next, for comparison, we made the following prototype screw.

The width of the flight was constant 411Ill over the entire length, and the depth of the groove was the same as in the previous example (metering part 0.
6-1.2 vs, feed section 4.6+u+).

As a result of an extrusion experiment using this screw under the same conditions as in the above example, it was found that after 50 hours of use, approximately 2
A twist of 85 turns occurs, and the overall length of the screw is 5
It was a+m longer.

In addition, for comparison, the following screw was prototyped.

The width of the flight was constant 4 m5 over the entire length, and the depth of the groove was the same as in the previous example except that it was 2.0 - 1 at the feed section (0.6 to 1.2 am at the metering section).
).

As a result of an extrusion experiment using this screw under the same conditions as in the previous example, the outer diameter of the manufactured insulated wire was 1.0±
0.21, and the outer diameter variation was large.

This is because the grooves in the feed section are shallow, so that the extruded material does not bite stably, which causes the discharge amount to fluctuate.

〔Effect of the invention〕

As explained above, according to the present invention, by increasing the width of the flights in the feed section, the depth of the groove in the feed section can be increased without reducing the torsional strength of the feed section, thereby preventing the extruded material from digging into the feed section. It is possible to perform extrusion molding with stable extrusion molding and therefore with a stable discharge amount.

[Brief explanation of drawings]

Figure 1 is a side view showing the basic configuration of the extruder screw according to the present invention, Figure 2 is a sectional view taken along the line ■-■ in Figure 1, and Figure 3 is the basic configuration of the conventional extruder screw. The side view shown in FIG. 4 is a sectional view taken along the line IV-TV in FIG. 3. 1: Shaft part '2: * 3: Flighted: Feed part C: Compressor part M: Metering part W: Width of flight G: Depth of groove

Claims (1)

[Claims] 1. A screw for an extruder, characterized in that the flight width is wider at the compression section than at the metering section, and wider at the feed section than at the compression section.