JPH0826452A - Raw material supply screw - Google Patents

Abstract

PURPOSE:To provide a raw material supply screw capable of reducing respectively the cyclic variation of raw material supply per screw rotation for the raw material having a large angle of repose or in the low speed rotation region of the screw. CONSTITUTION:A raw material supply screw is composed of a main flight 30 having screw parts planted in a fixed pitch 1 over the region of 2-3 pitches from a single thread screw of the fixed pitch 1 to the terminal end at the raw material ejecting side of a raw material supply screw 14 and a sub-flight 32 having the same screw parts planted with a half pitch phase difference between the main flights 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a plastic raw material such as pellets or powder (hereinafter sometimes referred to as powder or granular material or raw material) as an extruder or an injection molding machine (hereinafter simply referred to as a molding machine). (Referred to collectively) as a raw material supply screw of a raw material supply device for supplying a fixed amount (continuously or intermittently) (hereinafter, may be simply referred to as a screw), and particularly improves precision in quantitative supply of plastic raw material. The present invention relates to a screw for supplying a raw material.

[0002]

2. Description of the Related Art Generally, a molding machine, as shown in FIG.
A raw material supply device 12 for supplying a constant amount of the plastic raw material M is attached to the molding device (particularly the molding screw) 10. This raw material supply device 12 is usually equipped with a raw material supply screw 14 consisting of a single-threaded screw having a constant pitch.
6 is arranged as a so-called screw feeder. Incidentally, this screw feeder has a simple structure due to the screw characteristics, and exhibits an excellent quantitative supply property. Therefore, this screw feeder will be described in the following description. Further, in FIG. 5, reference numeral 18 is a hopper for storing the raw material M,
Reference numerals 20 denote variable speed motors that rotate the screw 14 at an appropriate speed.

The raw material supply device (screw feeder) 12 may be provided with a weight type control device 26 including a weight sensor 22 and a control means 24. In this case, the raw material discharge amount is calculated from the total weight change of the raw material supply device 12, and the rotation speed of the motor 20 is appropriately controlled based on the calculated value, so that the raw material supply device 12 can accurately supply the fixed amount of raw material. Moreover, it can be achieved with high accuracy.

[0004]

However, the above-mentioned conventional screw for supplying raw material has the following basic drawbacks.

First, the physical properties (angle of repose) of the granular material, which is the basis of the basic problem, will be described. That is, in FIG. 6 and FIG. 7, the maximum granular angle (repose angle) α at which the deposition surface stabilizes differs depending on the type of the granular material. If the same deposition length is 1, the amount of deposition is smaller at a smaller angle of repose α2 than at a larger angle of repose α1 (FIG. 6), and at the same angle of repose α1, a smaller deposition length. It is clear that the height l / 2 is less than the larger deposition length l (FIG. 7). This physical property (angle of repose) affects, as will be described below, a decrease in the accuracy of the screw quantitative supply, and in particular, an increase in the amount of periodic fluctuation per rotation of the screw.

That is, in FIG. 8, which is an enlarged view of the raw material discharge side end portion of the raw material supply screw 14 in FIG. 5, the raw material M to be supplied has a poor fluidity portion M1 corresponding to the angle of repose α, It falls from the falling region (pitch width) 1 at the extreme end shown in the figure in a state of being composed of the good fluidity portion M2. As a result, as shown in FIG. 4 (this figure is compared with the characteristic according to the present invention described later), the supply amount q '
It is obvious that, per revolution of the screw 14, a large amount of periodic fluctuation Δq ′ with respect to the target value q0 is introduced. In addition, in the illustrated example, the angle of repose α is set to a size that just extends over the pitch width l, but if the angle of repose α becomes larger, the poor fluidity portion M1 is generated.
Is further increased, and thus the periodic fluctuation amount Δq ′ is further increased. It is also clear that the magnitude of this periodic fluctuation is relatively increased in the low rotation region of the screw.

As described above, in the conventional screw for supplying the raw material, in the screw having the weight type control device 26 (see FIG. 5), even if the average target value q0 is accurately achieved, the screw amount per screw rotation is increased. It was not possible to sufficiently enhance the accuracy of the quantitative supply due to the occurrence of periodic fluctuations.
Therefore, when a plurality of different raw materials are mixed by using a plurality of raw material supply devices, that is, when a so-called composite product is formed, the quality of the product is deteriorated due to the variation of the raw material mixing ratio. Incidentally, as a countermeasure against such a difficulty (the periodic fluctuation), it is proposed to gradually narrow the screw pitch toward the raw material discharge end portion (for example, see Japanese Patent Publication No. 4-60807). In this case, although the raw material is gradually and densely (uniformly) compressed toward the end portion, the average quantitative supply accuracy is improved, but the periodic fluctuation caused by the physical properties (angle of repose) is reduced. It does not have the effect.

Therefore, an object of the present invention is to reduce the periodic fluctuation of the raw material supply per screw rotation for a raw material having a large angle of repose or in a low speed rotation range of the screw, respectively. To provide.

[0009]

In order to achieve the above object, the raw material supply screw according to the present invention has a raw material discharge side end portion of a powdery granular material raw material supply screw consisting of a single-thread screw having a constant pitch. , A plurality of thread portions over a range of 2 to 3 pitches.

In this case, the multi-threaded screw portion can be composed of a double-threaded screw portion.

The double threaded portion is composed of a main flight in which the screw parts are installed at a constant pitch, and a subflight in which the same screw parts are installed at a half pitch phase difference between the main flights. Or, or, a main flight in which the wire rod is advanced toward the terminal portion at a constant pitch, and a sub-flight in which the wire material is folded back from the terminal portion with a half-pitch phase difference between the main flights. Can consist of:

[0012]

In the present invention, the raw material discharge side end portion of the screw is composed of a plurality of threaded portions for dividing the space between the single threaded screws (main flights) having a constant pitch. That is, the width of the falling area in which the raw material falls (supply) is reduced to a multiple of the main flight width (pitch width). Therefore, according to the present invention, the periodic fluctuation of the raw material supply amount per screw rotation is not significantly affected by the repose angle of the raw material or the rotation speed of the screw, in other words, for the raw material with a large repose angle. , Or in the low speed rotation range of the screw, it can be greatly reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a screw for supplying a raw material according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional configuration shown in FIGS. 5 to 8 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the raw material supply screw according to the present invention has the same basic structure as the above-mentioned conventional screw. That is, as is clear from FIG. 5, the raw material supply screw 14 is composed of a single-thread screw having a constant pitch, forms the raw material supply device 12 together with the cylinder 16, and transfers the plastic raw material M to the molding device (molding screw) 10. It is configured to supply a fixed amount.

However, the raw material supplying screw 1 of the present invention
As shown in FIG. 1, in addition to the above-mentioned configuration, 4 has a raw material discharge side end portion configured as a plurality of threaded portions over a range of 2 to 3 pitches. That is, in the present embodiment, the double threaded portion is formed, and the double threaded portion is the main flight 30 in which threaded parts are installed at a constant pitch l.
And a sub-flight 32 in which the same screw parts are installed with a phase difference of half pitch between the main flights 30.

Therefore, according to the present invention, in FIG. 3 (this figure corresponds to FIG. 8 showing the above-mentioned conventional screw), the raw material M to be supplied (dropped) is in the drop region. Since the width is reduced from the conventional width 1 to half of the conventional width l, even if the repose angle α of the raw material is the same as the conventional one, the ratio of the portion M2 having good fluidity is It is clear that it is greatly increased as compared with that of the poor fluidity portion M1. Therefore, as shown in FIG.
In the above, it is apparent that the periodic fluctuation amount Δq per rotation of the screw 14 of the raw material supply amount q is significantly reduced as compared with the conventional cyclic fluctuation amount Δq ′.

As described above, according to the present invention, the periodic fluctuation of the raw material supply amount per screw rotation is not largely affected by the repose angle of the raw material or the rotation speed of the screw, in other words, the repose angle of the screw. It is possible to significantly reduce both large raw materials and low-speed rotation regions of the screw.
Therefore, the quantitative supply accuracy of the raw material supply screw can be basically improved.

FIG. 2 shows another embodiment of the screw for supplying raw material according to the present invention. In this embodiment,
In the double threaded portion in the previous embodiment, the wire rod has a constant pitch l.
And a sub-flight 36 in which the wire rod is wound back from the end portion with a phase difference of a half pitch between the main flights 34. . It should be noted that, in this embodiment as well, it is clear that the same effects and advantages as in the previous embodiment are exhibited, and therefore detailed description thereof will be omitted.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit of the present invention. For example, it is self-evident that the multiple threaded portion can be configured as a triple or four threaded portion as desired.

[0020]

As described above, in the raw material supplying screw according to the present invention, the raw material discharge side end portion of the powdery granular material raw material supplying screw consisting of the single-thread screw having a constant pitch has a range of 2 to 3 pitches. Since the multi-threaded portion is formed over the entire length, the width of the falling region of the raw material in the screw for feeding raw material of this type can be reduced to one-third that of the conventional one. The periodic fluctuation of the raw material supply amount per screw rotation in the raw material supply amount is not affected by the repose angle of the raw material or the rotation speed of the screw. Therefore, it becomes possible to greatly reduce the periodic fluctuations with respect to the raw material having a large repose angle or in the low speed rotation range of the screw.

As described above, according to the present invention, it is possible to basically improve the precision of the quantitative supply of the raw material supply screw.

[Brief description of drawings]

1A and 1B show an embodiment of a raw material supply screw according to the present invention, in which FIG. 1A is a front view and FIG. 1B is a side view of essential parts.

2A and 2B show another embodiment of the raw material supply screw according to the present invention, in which FIG. 2A is a front view and FIG.

FIG. 3 is a side view of an essential part showing the state of dropping and feeding the raw material in the raw material supply screw according to the present invention.

FIG. 4 is a waveform diagram showing a comparison of periodic fluctuations in the amount of raw material supply per screw rotation in the raw material supply screw according to the present invention and the conventional raw material supply screw.

FIG. 5 is a schematic explanatory view showing a configuration arrangement of a raw material supply device in a molding machine.

FIG. 6 is an explanatory diagram showing the angle of repose of a powder or granular material.

FIG. 7 is an explanatory diagram showing the angle of repose of a powder or granular material different from that in FIG.

FIG. 8 is a side view of essential parts showing a state where a raw material is dropped and supplied in a conventional raw material supply screw.

[Explanation of symbols]

 10 molding device (molding screw) 12 raw material supply device 14 raw material supply screw 16 cylinder 18 hopper 20 motor 30, 34 main flight 32, 36 subflight

Claims (4)

[Claims] 1. A raw material discharge side end of a screw for supplying a powdery granular material, which is composed of a single-thread screw having a constant pitch, is constituted as a multiple-thread screw portion over a range of 2 to 3 pitches. Screw for raw material supply. 2. The raw material supply screw according to claim 1, wherein the multi-threaded portion comprises a two-threaded portion. 3. The double thread part is composed of a main flight in which screw parts are laid at a fixed pitch, and a subflight in which the same screw parts are laid at a half pitch phase difference between the main flights. The raw material supplying screw according to claim 2. 4. The double thread part has a phase difference of a half pitch between the main flight in which the wire rod is wound forward toward the terminal end at a constant pitch and the wire rod is folded back from the terminal end in the main flight. 3. The sub-flight which is rewound.
The raw material supply screw described.