JPS6335403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a screw for an extruder, injection molding machine, blow molding machine, or the like (hereinafter referred to as a molding machine) for molding a thermoplastic resin.

Kneading and mixing of the resin using a screw in a molding machine is extremely important, and if this is insufficient, the molded product will be non-uniform and have poor properties, resulting in a defective product. Note that kneading refers to melting the resin material pellets by compressive force and shearing force, and mixing refers to mixing molten and unmolten materials.

[Prior art]

In order to improve kneading and mixing, as shown in FIGS. 1 and 2, conventionally, two eccentric rings 12 and 13, which are eccentric rings arranged in opposite phases, are provided between one pitch of the screw 11. is proposed. In this method, when the pellet moves from the gap 15 on the deep side to the gap 16 on the shallow side of the cylinder 14 in the trough 12, compressive force acts, but there is no peak between the two troughs 12 and 13. , even if the valley 12 on one side becomes shallower and kneading is attempted due to the wedge effect between the cylinder 14 and the valley 12,
The pellets flowed to the valley part 13 on the other side where the gap was deep and there was less resistance, and the pellets were hardly mixed.

[Purpose of the invention]

The present invention eliminates such drawbacks, and its purpose is to arrange second and third flights smaller than the outer diameter of the first flight and the second and third flights between the first flight and the first flight, and in the valley formed by these flights. By making the center valley and the left and right valleys eccentric circles with opposite phases, when the pellets move from deep to shallow valleys in each valley, the strong compressive force of the wedge effect ensures reliable kneading. The molten resin is mixed by forcibly moving from a shallow valley to a deep valley on the other side over the second and third flights. Our purpose is to provide kneading screws.

[Key points of the invention]

The thermoplastic resin high kneading screw of the present invention has a first flight, a second flight and a third flight formed between one pitch of the first flight and having an outer diameter smaller than the outer diameter of the first flight, and three flights. Formed by the flight, the central trough and left and right troughs are eccentric circles with opposite phases to the screw axis, and the sum of the flow passage cross-sectional areas of the left and right valleys is approximately equal to the flow passage cross-sectional area of the central trough. It is characterized by consisting of three equal valleys.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 3 to 8 showing one embodiment. The screw 31 is a three-thread screw having a second flight 33 and a third flight 34 having an outer diameter smaller than the outer diameter of the first flight between each pitch of the first flight 32, and these three flights 32 to 34 A central valley 35 and left and right valleys 36 and 37 are formed by this. Note that the outer diameter of the first flight 32 is slightly smaller than the inner diameter of the cylinder 14. As shown in FIGS. 4 and 5, the valleys 35 to 37 have circular cross sections and are eccentric to the axis of the screw 31, and the valleys 36 and 37 are arranged in opposite phases to the valley 35. . Also each valley 35 to 3
The circles 7 have the same diameter, the shallowest dimension of the distance from the inner surface of the cylinder 14 to the bottom of the valley is α, the deepest dimension is β, and the distance between the inner surface of the cylinder 14 and the top of the second flight 33 and the third flight 34 is Let the distance be γ. The relationship between α and γ is γα, but the figure shows the case where γ>α.

Next, the operation of the embodiment described above will be explained. When the depth of the valleys 36 and 37 in the pellet within one pitch of the first flight 32 changes from β to α, and similarly when the depth of the valley 35 changes from β to α, the wedge between the valley bottom and the cylinder 14 Due to the effect, it receives strong compressive force and receives reliable kneading. The kneaded and melted resin is forced to cross the top gap γ of the second flight 33 and the third flight 34, and flows from the shallow α part to the deep β part, and the resins in each 35 and the valleys 36 and 37 are mixed. .

〔Effect of the invention〕

As explained above, the thermoplastic resin high kneading screw of the present invention has a first
It is a three-way screw having a second flight and a third flight with an outer diameter smaller than the flight, and these three flights form a central valley and left and right valleys, and these valleys have a circular cross section and are aligned with the screw axis. It is eccentric to the center, and the eccentricity of the center valley and the left and right valleys are arranged in opposite phases. Furthermore, among the distances from the inner surface of the cylinder to the bottom of the valley, the shallowest dimension was α, the deepest dimension was β, and the distance between the tops of the second and third flights from the inner surface of the cylinder 14 was γ.

With this configuration, when the depth of the valley between the pitches of the first flight changes from β to α, the pellets are reliably kneaded by the strong compressive force of the wedge effect, and the kneaded and molten resin is It is forced to go over the tops of the second and third flights and moves from the shallower gap to the deeper one into the adjacent valley where it is mixed. At this time, the depth of the valley on one side becomes shallower, the cross-sectional area of the flow path decreases, and the pressure increases.
P1 is high, the depth of the trough on the other side becomes deeper, the cross-sectional area of the flow path increases, and the pressure P2 is low, and the sum of the cross-sectional areas on both sides is always almost the same, so the kneaded and melted resin will flow smoothly. Mixed over the second and third flights.

Further, the resin in the channel is divided into three parts by one compression due to the three-thread screw, and is effectively kneaded. Furthermore, when the valley depth becomes shallow in the case of a two-thread screw, the molten resin passes over the top of the second flight and is guided to the deeper valley side, but since the weir by the flight is only on one side, the molten resin on the opposite side to the weir is guided to the deeper side. They were left behind without guidance, and their efficiency was declining. In the present invention, as shown in FIG. 7, when the valley depth becomes shallow, the molten resin is guided to the deeper sides on both sides, so the efficiency doubles. Furthermore, as shown in FIG. 8, since the molten resin in the left and right valleys flows from both sides to the central valley, there are many advantages such as improved mixing of the resins. As a result, the physical properties of the molded product were good, the resin temperature was uniform, and a homogeneous molded product was obtained.

Note that when the number of threads is greater than three threads, the resin will be split more, but the cross-sectional area of the flow path between each pitch of the first flight will decrease, which is undesirable. Increasing the distance between them will reduce the feed efficiency and reduce the overall efficiency.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional example, FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, and FIGS. 3 to 8 show an embodiment of the present invention. , Fig. 4 is a sectional view taken along line 4-4 in Fig. 3, and Fig. 5 is a sectional view taken along line 5-5 in Fig. 3.
Line sectional view, Figure 6 is an expanded view of the 5-5 line cross section,
Figure 7 is a sectional view taken along line 7-7 of Figure 6, and Figure 8 is a cross-sectional view of Figure 6.
A sectional view taken along line 8-8 in the figure is shown. 31... Skrill, 32... 1st flight, 3
3...Second flight, 34...Third flight, 3
5... Central valley, 36... Valley on the left, 37... Valley on the right.

Claims (1)

[Claims] 1. A first flight, a second flight and a third flight that are formed between one pitch of the first flight and have an outer diameter smaller than the outer diameter of the first flight, and a flight that is formed by the three flights and the center thereof. The trough and the left and right troughs are eccentric circles with opposite phases with respect to the screw axis, and the sum of the flow passage cross-sectional areas of the left and right valleys is approximately equal to the flow passage cross-sectional area of the central trough. If the shallowest dimension of each valley depth from the inner surface of the cylinder is α and the deepest dimension is β, then when the valley depth changes from α to β, the left and right A highly kneaded thermoplastic resin screw, characterized in that the valleys in the center change in the same phase and the valley in the center changes in an opposite phase.