An extrusion screw and a method of making the same

Abstract

An extrusion screw and a manufacturing method thereof, the extrusion screw comprises a screw body and screw flights, the screw flights comprise a feeding section, a melting section, a transition section and a discharging section, the melting section is a double screw flight, the melting section comprises a melting first section, a melting second section and a melting third section, the pitch of the main screw flight of the melting first section is smaller than the pitch of the auxiliary screw flight of the melting first section, the pitch of the main screw flight of the melting second section is equal to the pitch of the auxiliary screw flight of the melting second section, the pitch of the main screw flight of the melting third section is smaller than the pitch of the auxiliary screw flight of the melting third section, wherein the pitch of the main screw flight of the melting section remains unchanged, the pitch of the auxiliary screw flight of the melting third section is greater than the pitch of the auxiliary screw flight of the melting first section, and the pitch of the auxiliary screw flight of the melting first section is greater than the pitch of the auxiliary screw flight of the melting second section, the manufacturing method comprises manufacturing a rod-shaped structure, manufacturing the transition section, manufacturing the screw flights of the feeding section, the main screw flight and the auxiliary screw flight, and manufacturing the screw flights of the discharging section, and the advantages of the present application are that the material is sufficiently melted and mixed, and the extruded material is dense and smooth.

Description

Technical Field

[0001] This invention relates to the field of screw manufacturing technology, and more particularly to an extrusion screw and its manufacturing method. Background Technology

[0002] A Chinese invention patent application with application number CN201410591589.7 entitled "A Polyolefin Extrusion Screw" discloses a polyolefin extrusion screw. Its main body is sequentially provided with a feeding section, a compression section, a metering section, a barrier section, and a mixing section. The feeding and metering sections have a single-thread structure. The compression section has a main thread and an auxiliary thread with different pitches, forming a solid phase tank connected to the feeding tank and a liquid phase tank connected to the metering tank, respectively. The outer diameter of the auxiliary thread is smaller than the outer diameter of the main thread. The barrier section has several pairs of feed spiral blind grooves and discharge spiral blind grooves formed by non-common threads and common threads, respectively. Each pair of feed spiral blind grooves and discharge spiral blind grooves is separated by a common thread. The inlet of the feed spiral blind groove is connected to the metering tank, and the outlet of the discharge spiral blind groove is connected to the mixing section. The outer diameter of the common thread is smaller than the outer diameter of the non-common thread. The mixing section has parallel convex teeth, and the length of the screw is 42 times the outer diameter of the screw. The invention features a high screw speed, high output, and good plasticizing quality. However, the bottom diameter of the double-helix structure groove on the right side of the barrier section of the extrusion screw varies only slightly, leaving room for improvement in the extrusion and mixing effect on the material. Therefore, the structure of the extrusion screw needs further improvement. Summary of the Invention

[0003] The first technical problem to be solved by the present invention is to provide an extrusion screw that provides sufficient material melting, good mixing effect, dense extruded material, and smooth extrusion, in light of the above-mentioned existing technology.

[0004] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: This extrusion screw includes a rod body and screw ribs disposed on the rod body. The screw ribs include a feeding section, a melting section, a transition section, and a discharge section. The melting section is characterized by being a double screw rib, comprising a first melting section, a second melting section, and a third melting section. The pitch of the main screw rib of the first melting section is less than the pitch of the secondary screw rib of the first melting section. The pitch of the main screw rib of the second melting section is equal to the pitch of the secondary screw rib of the second melting section. The pitch of the main screw rib of the third melting section is less than the pitch of the secondary screw rib of the third melting section. The pitch of the main screw rib of the melting section remains unchanged, the pitch of the secondary screw rib of the third melting section is greater than the pitch of the secondary screw rib of the first melting section, and the pitch of the secondary screw rib of the first melting section is greater than the pitch of the secondary screw rib of the second melting section.

[0005] As an improvement, the depth of the secondary spiral groove formed by the front side of the main spiral ridge and the rear side of the secondary spiral ridge in the melting section can preferably be gradually increased first, and then gradually decreased starting from the middle position of the three melting sections.

[0006] Further improvements include gradually decreasing the depth of the main spiral groove formed by the front side of the secondary spiral ridge and the rear side of the main spiral ridge in the molten section, and ensuring that the rate of decrease in the depth of the main spiral groove is greater than the rate of decrease in the depth of the secondary spiral groove at the point where the depth of the secondary spiral groove begins to decrease.

[0007] In a further improvement, the width of the main spiral ridge of the molten section can preferably be greater than the width of the secondary spiral ridge of the molten section, and the top surface height of the main spiral ridge of the molten section can preferably be greater than the top surface height of the secondary spiral ridge of the molten section.

[0008] As an improvement, the feeding section can preferably be a single spiral ridge, with the spiral ridge of the feeding section smoothly connected to the main spiral ridge of the melting section at both ends.

[0009] Further improvements can be made by preferably having a larger pitch for the main screw thread in the melting section than for the screw thread in the feeding section.

[0010] Further improvements include the discharge section being preferably a single screw thread, with the screw pitch of the discharge section equal to that of the feed section, and the rod diameter corresponding to the discharge section being greater than that corresponding to the feed section and the melting section.

[0011] As an improvement, the transition section can preferably be three spaced-apart barrier discs, with spiral grooves circumferentially distributed on the outer wall of the barrier discs. This reduces material backflow and allows for thorough mixing of the material, resulting in a more uniform material composition.

[0012] As an improvement, a guide head can preferably be detachably screwed to one end of the rod, and a trapping groove and a drive spline are provided at the other end of the rod. The guide head guides the material and improves the extrusion effect.

[0013] The second technical problem to be solved by the present invention is to provide a method for manufacturing an extrusion screw that produces materials with sufficient melting and good mixing, and produces dense and smooth extruded material, in light of the above-mentioned existing technology.

[0014] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: A method for manufacturing this extrusion screw, characterized by comprising the following steps:

[0015] 1. Fabricate the blank into a rod-shaped structure according to its dimensions;

[0016] 2. Create a transition section near one end of the rod-shaped structure;

[0017] 3. Make the feed section screw rib and the main screw rib of the melting section on the rod body located behind the transition section. The pitch of the feed section screw rib and the pitch of the main screw rib of the melting section remain unchanged, so that the main screw rib of the melting section and the feed section screw rib are smoothly connected at the connection position between the melting section and the feed section.

[0018] 4. Make secondary screw ribs for the molten section at the corresponding positions of the molten section, such that the pitch of the main screw rib of the molten section is less than the pitch of the secondary screw rib of the molten section, the pitch of the main screw rib of the molten section is equal to the pitch of the secondary screw rib of the molten section, and the pitch of the main screw rib of the molten section is less than the pitch of the secondary screw rib of the molten section. Among these, the pitch of the secondary screw rib of the molten section is greater than the pitch of the secondary screw rib of the molten section, and the pitch of the secondary screw rib of the molten section is greater than the pitch of the secondary screw rib of the molten section.

[0019] 5. Make the discharge section screw ribs on the rod body located on the front side of the transition section, thus completing the manufacturing of the extrusion screw.

[0020] Compared with the prior art, the advantages of the present invention are: a variable molten section structure is provided, wherein the molten section is a double-spiral section, comprising a first molten section, a second molten section, and a third molten section. The pitch of the main spiral ridge of the first molten section is smaller than the pitch of the secondary spiral ridge of the first molten section; the pitch of the main spiral ridge of the second molten section is equal to the pitch of the secondary spiral ridge of the second molten section; and the pitch of the main spiral ridge of the third molten section is smaller than the pitch of the secondary spiral ridge of the third molten section. The pitch of the main spiral ridge of the molten section remains constant, while the pitch of the secondary spiral ridge of the third molten section is greater than the pitch of the secondary spiral ridge of the first molten section. The pitch of the secondary screw ridge is greater than that of the secondary screw ridge in the melting section. As the material is pushed forward by the screw ridge in the melting section, the pitch of the secondary screw ridge constantly changes, causing the volume of the main and secondary screw grooves formed by the secondary screw ridge and the main screw ridge to change accordingly. This results in the material being subjected to constantly changing extrusion and shearing forces, achieving full melting and good mixing, fully extruding gas, making the material compact and dense, less prone to breakage during extrusion, and making extrusion smoother. The depth of the main and secondary screw grooves also constantly changes, further increasing the stress variation on the material and further improving the material processing effect. Attached Figure Description

[0021] Figure 1 This is a front projection view of an embodiment of the present invention;

[0022] Figure 2 for Figure 1 Exploded structural diagram;

[0023] Figure 3 yes Figure 1 The diagram shows the changes in the depth of the main thread groove and the secondary thread groove;

[0024] Figure 4 yes Figure 1 Cross-sectional view along line AA;

[0025] Figure 5 yes Figure 1 Cross-sectional view along the BB line;

[0026] Figure 6 yes Figure 1 Cross-sectional view along the CC line. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] like Figures 1 to 6 As shown, the extrusion screw of this embodiment includes a rod body 1 and a screw rib disposed on the rod body 1. The screw rib includes a feeding section A, a melting section B, a transition section C, and a discharge section D.

[0029] The molten section B is a double-threaded section, comprising a first molten section B1, a second molten section B2, and a third molten section B3. The pitch of the main thread of the first molten section is less than the pitch S2 of the secondary thread of the first molten section. The pitch of the main thread of the second molten section is equal to the pitch S3 of the secondary thread of the second molten section. The pitch of the main thread of the third molten section is less than the pitch S4 of the secondary thread of the third molten section. The pitch S1 of the main thread of the molten section remains unchanged. The pitch S4 of the secondary thread of the third molten section is greater than the pitch S2 of the secondary thread of the first molten section. The pitch S2 of the secondary thread of the first molten section is greater than the pitch S3 of the secondary thread of the second molten section.

[0030] Figure 3 Curve K2 represents the depth variation curve of the secondary spiral groove 12. In molten section B, the depth of the secondary spiral groove 12, formed by the front side of the main spiral ridge and the rear side of the secondary spiral ridge, initially increases gradually. Then, starting from the middle of molten section B3, the depth of the secondary spiral groove 12 gradually decreases. Curve K1 represents the depth variation curve of the main spiral groove 11. In molten section B, the depth of the main spiral groove 11, formed by the front side of the secondary spiral ridge and the rear side of the main spiral ridge, gradually decreases. At the point where the depth of the secondary spiral groove 12 begins to decrease, the rate of decrease in the depth of the main spiral groove 11 is greater than the rate of decrease in the depth of the secondary spiral groove. The width of the main spiral ridge 13 in the molten section is greater than the width of the secondary spiral ridge 14 in the molten section, and the top surface height of the main spiral ridge 13 in the molten section is greater than the top surface height of the secondary spiral ridge 14 in the molten section.

[0031] The feed section A has a single screw thread, and the screw thread of the feed section is smoothly connected to the main screw thread 13 of the melting section. The pitch S1 of the main screw thread of the melting section is greater than the pitch of the screw thread of the feed section.

[0032] The discharge section D is a single screw thread, and the pitch of the screw thread in the discharge section is equal to the pitch of the screw thread in the feed section. The rod diameter corresponding to the discharge section is greater than the rod diameter corresponding to the feed section and the melting section.

[0033] The transition section C consists of three spaced-apart barrier discs, with spiral grooves 15 circumferentially distributed on the outer wall of the barrier discs.

[0034] A guide head 2 is detachably screwed to one end of the rod body 1, and a cut-off groove and a transmission spline 16 are provided at the other end of the rod body 1.

[0035] The above-mentioned method for manufacturing an extrusion screw includes the following steps:

[0036] 1. Fabricate the blank into a rod-shaped structure according to its dimensions;

[0037] 2. Create a transition section C near one end of the rod-shaped structure;

[0038] 3. Make the feed section screw rib and the main screw rib 13 of the melting section on the rod 1 located behind the transition section. The pitch of the feed section screw rib and the pitch S1 of the main screw rib of the melting section remain unchanged, so that the main screw rib 13 of the melting section and the feed section screw rib are smoothly connected at the connection position of the melting section B and the feed section A.

[0039] 4. The pitch of the main screw thread in the first melting section is less than the pitch S2 of the secondary screw thread in the first melting section; the pitch of the main screw thread in the second melting section is equal to the pitch S3 of the secondary screw thread in the second melting section; the pitch of the main screw thread in the third melting section is less than the pitch S4 of the secondary screw thread in the third melting section; wherein, the pitch S4 of the secondary screw thread in the third melting section is greater than the pitch S2 of the secondary screw thread in the first melting section; and the pitch S2 of the secondary screw thread in the first melting section is greater than the pitch S3 of the secondary screw thread in the second melting section.

[0040] 5. Make the discharge section screw rib on the rod body 1 located in front of the transition section, thus completing the manufacturing of the extrusion screw.

Claims

1. An extrusion screw, comprising a rod body (1) and a screw rib disposed on the rod body (1), the screw rib comprising a feed section (A), a melting section (B), a transition section (C), and a discharge section (D), characterized in that: The molten section (B) is a double-screw section, comprising a first molten section (B1), a second molten section (B2), and a third molten section (B3). The pitch of the main screw of the first molten section is less than the pitch of the secondary screw of the first molten section (S2). The pitch of the main screw of the second molten section is equal to the pitch of the secondary screw of the second molten section (S3). The pitch of the main screw of the third molten section is less than the pitch of the secondary screw of the third molten section (S4). The pitch of the main screw of the molten section (S1) remains unchanged. The pitch of the secondary screw of the third molten section (S4) is greater than the pitch of the secondary screw of the first molten section (S2). The pitch of the secondary screw of the first molten section (S2) is greater than the pitch of the secondary screw of the second molten section (S3).

2. The extrusion screw according to claim 1, characterized in that: The depth of the secondary spiral groove (12) formed by the front side of the main spiral ridge and the rear side of the secondary spiral ridge on the melting section (B) gradually increases first, and then the depth of the secondary spiral groove (12) gradually decreases starting from the middle position of the melting section (B3).

3. The extrusion screw according to claim 2, characterized in that: In the molten section (B), the depth of the main spiral groove (11) formed by the front side of the secondary spiral ridge and the rear side of the main spiral ridge gradually decreases, and at the position where the depth of the secondary spiral groove (12) begins to decrease, the depth of the main spiral groove (11) decreases at a rate greater than that of the secondary spiral groove.

4. The extrusion screw according to claim 3, characterized in that: The width of the main screw ridge (13) of the molten section is greater than the width of the secondary screw ridge (14) of the molten section, and the top surface height of the main screw ridge (13) of the molten section is greater than the top surface height of the secondary screw ridge (14) of the molten section.

5. The extrusion screw according to any one of claims 1 to 4, characterized in that: The feeding section (A) is a single spiral ridge, and the spiral ridge of the feeding section is smoothly connected to the main spiral ridge (13) of the melting section.

6. The extrusion screw according to claim 5, characterized in that: The pitch (S1) of the main screw edge in the melting section is greater than the pitch of the screw edge in the feeding section.

7. The extrusion screw according to claim 5, characterized in that: The discharge section (D) is a single screw thread. The pitch of the screw thread in the discharge section is equal to the pitch of the screw thread in the feed section. The diameter of the rod corresponding to the discharge section is greater than the diameter of the rod corresponding to the feed section and the melting section.

8. The extrusion screw according to any one of claims 1 to 4, characterized in that: The transition section (C) consists of three spaced-apart barrier discs, with spiral grooves (15) circumferentially distributed on the outer wall of the barrier discs.

9. The extrusion screw according to any one of claims 1 to 4, characterized in that: A guide head (2) is detachably screwed to one end of the rod (1), and a cut-off groove and a transmission spline (16) are provided at the other end of the rod (1).

10. A method for manufacturing an extrusion screw according to any one of claims 1 to 9, characterized in that: Includes the following steps, 1. Fabricate the blank into a rod-shaped structure according to its dimensions; 2. Create a transition section (C) near one end of the rod-shaped structure; 3. Make the feed section screw rib and the main screw rib of the melting section (1) on the rod (1) located behind the transition section. The pitch of the feed section screw rib and the pitch (S1) of the main screw rib of the melting section remain unchanged, so that the main screw rib of the melting section (13) and the feed section screw rib are smoothly connected at the connection position of the melting section (B) and the feed section (A).

4. The pitch of the main screw thread of the first molten section is less than the pitch of the secondary screw thread of the first molten section (S2), the pitch of the main screw thread of the second molten section is equal to the pitch of the secondary screw thread of the second molten section (S3), and the pitch of the main screw thread of the third molten section is less than the pitch of the secondary screw thread of the third molten section (S4). Among these, the pitch of the secondary screw thread of the third molten section (S4) is greater than the pitch of the secondary screw thread of the first molten section (S2), and the pitch of the secondary screw thread of the first molten section (S2) is greater than the pitch of the secondary screw thread of the second molten section (S3).

5. Make the discharge section screw rib on the rod (1) located in front of the transition section, thus completing the production of the extrusion screw.

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