An improved split screw

Abstract

The utility model discloses an improved separation type screw rod, including screw rod and the main screw edge and vice screw edge of setting on the screw rod, vice screw edge includes first vice screw edge section and second vice screw edge section, wherein first vice screw edge section sets up in separation section starting position, second vice screw edge section sets up in separation section end, first vice screw edge section is connected with second vice screw edge section, the lead of first vice screw edge section is greater than the lead of second vice screw edge section, the lead of main screw edge maintains unchangeable on separation section simultaneously, the lead of main screw edge is less than the lead of second vice screw edge section, the application has combined Maillefer separation section and Bar separation section's superiority, through reducing the lead of second vice screw, avoided the problem that the plasticizing capacity descended caused by solid phase groove in Maillefer separation section narrow more and more, improved the plasticizing efficiency of screw rod, while maintaining the solid phase groove of being wider, make liquid phase groove not too narrow, influence the performance of melt delivery.

Description

Technical Field

[0001] This utility model relates to the design of a single-screw extruder, and more particularly to an improved split-type screw. Background Technology

[0002] Single-screw extruders are widely used due to their simple structure, ease of manufacture, high processing efficiency, and low price. They are the most technologically mature and widely used type of extruder. To improve the performance of single-screw extruders, researchers have long been working on improving the core component—the screw—resulting in a variety of new screw designs. Among these new screws, the barrier screw (also known as the split screw), invented in the early 1970s by Mailefer of Switzerland, has had the greatest impact. This type of screw can improve plasticizing efficiency and extrusion output by allowing solid-liquid separation during melting. Furthermore, the material undergoes stronger shearing action when crossing the barrier screw edges (also known as the secondary screw edges), thus improving plasticizing quality. Due to these characteristics, the barrier screw remains widely used to this day, and many improved versions based on its structure have emerged.

[0003] The existing Mailfer separation section has a shape that is relatively consistent with hydrodynamics. However, due to the decreasing size of its solid phase tank, the increase in its plasticizing capacity is relatively limited. This is because the melting rate of the material mainly depends on the contact area between the solid phase tank and the barrel. The melt tank (liquid phase tank) in the subsequent improved Bar separation section is very deep, and its melt conveying efficiency is much lower than that of the Mailfer separation section. It is also prone to material deposition and decomposition. In addition, at the end of the separation section, the liquid phase tank changes from narrow and deep to wide and shallow. This rapid change in the spiral channel geometry does not help stabilize extrusion.

[0004] Therefore, this application proposes a solution to address the shortcomings of the separation section in these two types of split screws. Summary of the Invention

[0005] Purpose of the utility model: The purpose of this utility model is to provide an improved split screw that enables the screw to have higher plasticizing efficiency and at the same time has good melt conveying capacity.

[0006] Technical Solution: The present invention discloses an improved split-type screw, comprising a screw and a main screw ridge and a secondary screw ridge disposed on the screw, characterized in that: the secondary screw ridge comprises a first secondary screw ridge segment and a second secondary screw ridge segment, the first secondary screw ridge segment being disposed at the beginning of the split section, the second secondary screw ridge segment being disposed at the end of the split section, the first secondary screw ridge segment being connected to the second secondary screw ridge segment, the lead of the first secondary screw ridge segment being greater than the lead of the second secondary screw ridge segment, and the lead of the main screw ridge remaining constant in the split section, the lead of the main screw ridge being less than the lead of the second secondary screw ridge segment.

[0007] Preferably, the lead of the second helical segment is 85%-90% of the lead of the first helical segment.

[0008] Preferably, the length of the second threaded section is not greater than that of the first threaded section.

[0009] Preferably, the main screw edge and the auxiliary screw edge are spaced apart to form a continuous and independent solid phase tank and a liquid phase tank.

[0010] Preferably, the depth of the solid phase tank gradually decreases from the inlet to the end.

[0011] Preferably, the depth of the liquid phase tank increases from the inlet to the end.

[0012] Beneficial effects: Compared with the prior art, this utility model has the following advantages:

[0013] This invention combines the advantages of the Mailfer separation section and the Bar separation section. By reducing the lead of the second screw thread, it avoids the problem of decreased plasticizing capacity caused by the increasingly narrow solid phase tank in the Mailfer separation section, thereby improving the plasticizing efficiency of the screw. At the same time, while maintaining a relatively wide solid phase tank, it prevents the liquid phase tank from becoming too narrow, which would affect the performance of melt delivery. Attached Figure Description

[0014] Figure 1 The separation section structure is for the existing Maillefer type separation screw.

[0015] Figure 2 The separation section structure is for the existing Bar-type separation screw.

[0016] Figure 3 This is the separation section structure in the separation screw of this application. Detailed Implementation

[0017] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0018] See appendix Figure 1 In the existing Mailefer type separator screw, the separation section structure consists of two main screw ribs 1 and 2 with different leads. When the screw rotates, the material is conveyed forward and gradually melts. The molten material passes through the 2nd screw rib, which is slightly lower than the main screw rib 1, from the solid phase tank 3 into the liquid phase tank 4. As the material continues to melt, the solid phase tank 3 becomes narrower and the liquid phase tank 4 becomes wider until the material is completely plasticized. Since the melting rate of the material mainly depends on the contact area between the solid phase tank 3 and the barrel, the plasticizing capacity gradually decreases as the solid phase tank 3 becomes narrower.

[0019] See appendix Figure 2The existing Bar-type separator screw has the same starting section structure as the Mailfer type. When the liquid phase channel 4 is sufficiently wide, the secondary screw ridge 2 begins to parallel to the main screw ridge 1. Consequently, the cross-sectional area of ​​the solid phase channel 3 decreases due to the reduced screw channel depth, while the depth of the liquid phase channel 4 increases. The advantage of this geometry is that the width of the solid phase channel 3 does not decrease continuously like in the Mailfer geometry, but remains constant at a relatively large value. This increases the contact area between the solid phase channel 3 and the barrel, improving melting performance. However, because the liquid phase channel 4 is very deep within the separator section, its melt conveying efficiency is much lower than that of the Mailfer separator section, and it is prone to material deposition and decomposition. Furthermore, at the end of the separator section, the liquid phase channel 4 changes from narrow and deep to wide and shallow; this rapid change in screw channel geometry does not contribute to stable extrusion.

[0020] See appendix Figure 3 The improved split screw in this application includes a screw and a main screw 1 and a secondary screw 2 disposed on the screw. The secondary screw 2 includes a first secondary screw 21 and a second secondary screw 22. The first secondary screw 21 is disposed at the beginning of the split section, and the second secondary screw 22 is disposed at the end of the split section. The first secondary screw 21 and the second secondary screw 22 are connected, and the lead of the first secondary screw 21 is greater than the lead of the second secondary screw 22. At the same time, the lead of the main screw 1 remains unchanged in the split section, and the lead of the main screw 1 is less than the lead of the second secondary screw 22.

[0021] By reducing the lead of the second screw section 22, the problem of decreased plasticizing capacity caused by the increasingly narrow solid phase tank 3 in the Mailfer separation section is avoided, thus improving the plasticizing efficiency of the screw.

[0022] In this embodiment, the lead of the second screw section 22 is 85%-90% of the lead of the first screw section 21.

[0023] In this embodiment, the length of the second threaded segment 22 is not greater than that of the first threaded segment 21.

[0024] In this embodiment, a continuous and independent solid phase tank 3 and liquid phase tank 4 are spaced between the main screw 1 and the auxiliary screw 2.

[0025] In this embodiment, the depth of the solid phase tank 3 gradually decreases from the inlet to the end.

[0026] In this embodiment, the depth of the liquid phase tank 4 increases from the inlet to the end.

[0027] By combining the characteristics of the separation section structure of the Bar-type separating screw, while maintaining a relatively wide solid phase tank 3, the liquid phase tank 4 is not too narrow, which would affect the performance of melt conveying.

Claims

1. An improved split-type screw, comprising a screw and a main screw rib (1) and a secondary screw rib (2) disposed on the screw, characterized in that: The secondary screw thread (2) includes a first secondary screw thread segment (21) and a second secondary screw thread segment (22). The first secondary screw thread segment (21) is located at the beginning of the separation section, and the second secondary screw thread segment (22) is located at the end of the separation section. The first secondary screw thread segment (21) and the second secondary screw thread segment (22) are connected. The lead of the first secondary screw thread segment (21) is greater than the lead of the second secondary screw thread segment (22). The lead of the main screw thread (1) remains unchanged on the separation section, and the lead of the main screw thread (1) is less than the lead of the second secondary screw thread segment (22).

2. An improved split screw according to claim 1, characterized in that: The lead of the second sub-screw section (22) is 85%-90% of the lead of the first sub-screw section (21).

3. An improved split screw according to claim 1, characterized in that: The length of the second sub-screw segment (22) is not greater than that of the first sub-screw segment (21).

4. An improved split screw according to claim 1, characterized in that: The main screw edge (1) and the secondary screw edge (2) are separated by a continuous and independent solid phase tank (3) and liquid phase tank (4).

5. An improved split screw according to claim 4, characterized in that: The depth of the solid phase tank (3) gradually decreases from the inlet to the end.

6. An improved split screw according to claim 4, characterized in that: The depth of the liquid phase tank (4) increases from the inlet to the end.

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