JPH05309720A - Screw for resin molding machine - Google Patents

Abstract

(57) [Summary] [Object] To provide a screw for an injection molding machine capable of homogenizing the temperature and kneading state of a molten plasticized resin. [Structure] In a screw for a resin molding machine, in which a sub-flight that separates a screw groove on the resin material supply side and a screw groove on the molten plasticized resin discharge side is provided between the main flights in a partial range of the screw housed in the cylinder barrel, A gap between the outer peripheral surface of the main flight and the inner wall surface of the cylinder barrel is not changed in the resin injection direction, and the outer diameter of the sub flight is gradually reduced in the resin injection direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasticizing screw used in a resin molding machine such as an extruder or an injection molding machine.

[0002]

2. Description of the Related Art FIG. 5 is a partially cut vertical sectional view of a conventional screw for a resin molding machine, and FIG. 6 is a vertical sectional view showing a gap change between a cylinder barrel and a sub flight. In the figure, as the screw 1 has a groove depth of a screw groove from the supply side A to the molten plasticized resin discharge side B, the supply section FZ and the compression section CZ are shown.
And a measuring section MZ, and a main flight 2 that is continuous over the entire length is provided.

The main flight 2 at the boundary between the supply section FZ and the compression section CZ branches off from the main flight 2 at the boundary between the compression section CZ and the metering section MZ, and the sub-flight 6 merges again with the facing main flight 2. ing. The auxiliary flight 6 divides the resin material supply side screw groove 7 into the molten plasticized resin discharge side screw groove 8.

Further, a clearance α between the inner wall surface of the cylinder barrel 4 and the outer peripheral surface of the main flight 2 in the compression section CZ and the measuring section MZ, and a clearance between the inner wall surface of the cylinder barrel 4 and the outer peripheral surface of the auxiliary flight 6. β is configured to be constant from the supply side FZ to the measurement side MZ.

Reference numeral 3 is a feed hopper for feeding the resin into the cylinder barrel 4, and reference numeral 5 is a heater for heating the resin transferred by the screw 1 through the cylinder barrel 4.

Now, in FIG. 5, the resin supplied from the feed hopper 3 to the supply portion FZ receives the thermal energy from the heater 5 and the shear energy due to the rotation of the screw 1,
It is transferred to the front while melting gradually.

In the compression section CZ, the solid resin is dammed by the sub-flight 6, and as the screw 1 rotates, a strong shearing action forms a molten film between the cylinder barrel 4 and the solid resin. The melting force of the solid resin rapidly accelerates the melting of the surface of the solid resin. Thus,
The molten resin gets over the auxiliary flight 6 and is transferred from the resin material supply side screw groove 7 side to the molten plasticized resin discharge side screw groove 8.

[0008]

However, in the screw for a resin molding machine as described above, when the rotation speed of the screw 1 is increased, the speed at which the resin is extruded increases,
The time that the resin stays in the cylinder barrel 4 is shortened, so that the heating from the heater 5 cannot be sufficiently received. Therefore, there is a drawback that the unmelted portion of the resin is not sufficiently converted into the molten portion, and the molten plasticized resin is discharged in a state where the unmelted material is mixed.

Therefore, in order to obtain a sufficient melting and kneading effect, the ratio of the effective length L of the screw to the diameter D (hereinafter referred to as L /
It is necessary to increase the size of the screw 1. Therefore, the device using the screw 1 becomes large in size, which not only causes the drawbacks of increased weight and cost, but also increases the L of the screw.
The larger / D, the easier the mechanical galling phenomenon occurs. Therefore, if the gap between the cylinder barrel 4 and the sub-flight 6 is reduced in order to obtain a sufficient melting effect, a stable discharge pressure and a kneading effect without increasing the L / D of the screw, there is a drawback that the processing capacity decreases. It was

[0010]

In order to solve such a problem, a screw for an injection molding machine according to the present invention is provided with a screw groove on the resin material supply side within a partial range of the screw housed in the cylinder barrel. In a screw for a resin molding machine in which a sub-flight that separates into the thread groove on the discharge side of the molten plasticized resin is provided between the main flights, the gap between the outer peripheral surface of the main flight and the inner wall surface of the cylinder barrel does not change in the resin injection direction. In addition, the outer diameter of the sub-flight is gradually reduced in the resin injection direction.

[0011]

[Function] In the compression section, a sub flight that forms a weir is arranged between the resin material supply side screw groove and the molten plasticized resin discharge side screw groove, and the outer diameter of this sub flight is gradually reduced in the resin injection direction. Try to do it. Therefore, a certain amount of resin sent from the supply side receives a large shear energy on the feed hopper side when overcoming the sub-flight and a small amount on the screw tip side to reduce the temperature and kneading of the molten plasticized resin. The condition can be homogenized.

[0012]

1 to 4 show an embodiment of a screw for an injection molding machine according to the present invention, FIG. 1 is a partially cut vertical sectional view of a screw for an injection molding machine, FIG. 3 is a vertical cross-sectional view showing a change in the clearance between the cylinder barrel and the flight or the sub-flight in the injection direction of the resin, and FIG. 4 is a partial cross-sectional view showing the flow state of the resin at each cross section of points A to D in FIG. ..

In the figure, the screw 1 is divided into a supply section FZ, a compression section CZ and a measuring section MZ. In addition, the sub-flight 6 is arranged in the compression section CZ, and the sub-flight 6
Are divided into a resin material supply side screw groove 7 and a melt plasticizing discharge side screw groove 8, respectively.

As shown in FIG. 3, the clearance α between the cylinder barrel 4 and the main flight 2 in the compression section CZ is constantly constant in the resin injection direction. Regarding the clearance β between the cylinder barrel 4 and the auxiliary flight 6, the supply unit FZ
A gap beta ₁ between the outer peripheral surface and the inner wall surface of the cylinder barrel 4 sub flight 6 at the boundary portion of the compression section _CZ, further, the compression unit C
And a gap β ₃ between the outer peripheral surface of the sub-flight 6 and the inner wall surface of the cylinder barrel 4 at the boundary between Z and the measuring section MZ,
It is configured such that the gap spacing gradually increases as β ₁ <β ₃ .

Regarding the depth of the screw groove in the compression portion CZ, first, in the resin material supply side screw groove 7, H ₁ > H ₂ > H ₃ > H ₄ from the deep groove portion to the shallow groove portion in the resin injection direction. As shown in the above-described resin material supply side screw groove 7, the molten plasticized resin discharge side screw groove 8 is further reduced in depth from the deep groove portion to the shallow groove portion in the resin injection direction.
_The configuration is such that the taper is continuously reduced so that ₁ > L ₂ > L ₃ > L ₄ . Reference numeral 1a indicates a screw body.

The operation of the screw for an injection molding machine constructed as above will be described. In FIG. 1, the feed hopper 3
The resin supplied from the supply unit FZ to the supply unit FZ receives the thermal energy from the heater 5 and the shearing energy generated by the rotation of the screw 1, and is gradually melted before being transferred.

In the compression section CZ, the solid resin having moved from the supply section FZ is blocked by the sub-flight 6, and as the screw 1 rotates, its solid shearing action causes a molten film between the cylinder barrel 4 and the solid resin. Are formed, and the shearing force of the molten film rapidly promotes melting of the surface of the solid resin. Furthermore, since the molten resin that has moved over the sub-flight 6 has a shallower melt-plasticized resin discharge side screw groove 8 between the compression portions CZ, it receives shearing energy due to the rotation of the screw 1 further from the compression portion CZ. Weighing unit MZ
The resin is completely melted in the region moving to and the kneading property is improved.

In particular, in the present invention, the gap β between the inner wall surface of the cylinder barrel 4 and the outer peripheral surface of the sub-flight 6 in the compression section CZ is gradually increased in the resin injection direction. The molten plasticized resin moves smoothly from the screw groove 7 side to the sub flight 6 to the molten plasticized resin discharge side screw groove 8 side. Therefore, the shearing energy when overcoming the sub-flight 6 is large on the side of the feed hopper 3 and small on the side of the tip of the screw 1, and the temperature and kneading state of the molten plasticized resin can be homogenized.

In the present invention, the sub-flight 6 is arranged in the compression section CZ, but the present invention is not limited to this.
It may be configured such that it is widely arranged in the Z area up to the position where it is located.

[0020]

As is apparent from the above description, according to the present invention, the screw groove accommodated in the cylinder barrel is divided into the screw groove on the resin material supply side and the screw groove on the molten plasticized resin discharge side. In the screw for a resin molding machine in which the sub-flight is provided between the main flights, the gap between the outer peripheral surface of the main flight and the inner wall surface of the cylinder barrel is not changed in the resin injection direction, and the outer diameter of the sub-flight is Since the resin is gradually reduced in the injection direction of the resin, the resin sent from the supply side receives a large shear energy on the feed hopper side when passing over the sub-flight arranged in the compression section, and the tip of the screw It becomes smaller on the side, and the temperature and kneading effect of the molten plasticizing resin can be further increased and homogenized. By increasing the kneading effect, color unevenness, warpage, sink marks, etc. can be eliminated.

[Brief description of drawings]

FIG. 1 is a partially cut vertical sectional view of a screw for an injection molding machine according to the present invention.

FIG. 2 is a development view of a screw according to the present invention.

FIG. 3 is a vertical cross-sectional view showing a change in a clearance between a cylinder barrel and a flight or a sub-flight in a resin injection direction according to the present invention.

FIG. 4 is a partial cross-sectional view showing a resin flow state in each cross section of points A to D in FIG. 2 according to the present invention.

FIG. 5 is a partially cut vertical sectional view of a conventional screw for an injection molding machine.

FIG. 6 is a vertical cross-sectional view showing a gap change between a conventional cylinder barrel and a sub flight.

[Explanation of symbols]

1 Screw 2 Main Flight 3 Feed Hopper 4 Cylinder Barrel 5 Heater 6 Sub-Flight 7 Resin Material Supply Side Thread Groove 8 Molten Plasticized Resin Discharge Side Thread Groove α Gap between inner wall of cylinder barrel and outer circumference of main flight β Cylinder Gap between the inner wall surface of the barrel and the outer peripheral surface of the secondary flight

Claims (1)

[Claims] 1. A screw for a resin molding machine, wherein a sub-flight that separates a screw groove on the resin material supply side and a screw groove on the molten plasticized resin discharge side is provided between main flights in a partial area of the screw housed in the cylinder barrel. In the above, the gap between the outer peripheral surface of the main flight and the inner wall surface of the cylinder barrel is not changed in the resin injection direction, and the outer diameter of the sub-flight is gradually reduced in the resin injection direction. Screw for resin molding machine.