Screw rotor and method for manufacturing a screw rotor

Abstract

To provide a screw rotor which is lighter, more resistant to corrosion, and easier to manufacture in complex forms, than conventional metal screw rotors.SOLUTION: A screw rotor 1 is made of polymer. The screw rotor 1 includes a shaft 2 and a rotor body 3 thereon. The polymer of the shaft 2 is reinforced with fibers. The shaft 2 is characterized by elements 5a that engage the rotor body 3 or corresponding elements on the rotor body 3, such that the elements 5a prevent an axial and / or rotational movement of the shaft 2 with respect to the rotor body 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a screw rotor.

[0002] More specifically, the screw rotor according to the invention is intended for fluid-injection compressors, expanders, and vacuum pumps.

Background Art

[0003] It is known that such screw rotors are conventionally manufactured from cast iron or steel, cast into a raw spiral shape or forged into a raw cylindrical shape, which is then finished by rough and fine grinding, filing, milling, and other cutting operations on the shaft and main body of the screw rotor (with spiral profile) to obtain its final finished spiral shape.

Summary of Invention

Problem to be Solved by the Invention

[0004] This finishing is necessary because the casting process cannot achieve the very high-precision tolerance ranges required to allow the final machine to function properly.

[0005] Even if such conventional screw rotors function properly, finishing by grinding, filing, milling, and other such processes is very labor-intensive and time-consuming.

[0006] Furthermore, all of this increases costs.

[0007] Another drawback is that a large amount of material is removed by machining during the finishing process, resulting in the loss or waste of raw materials.

[0008] Another drawback is that such conventional screw rotors are heavy because they use cast iron or steel.

[0009] The object of the present invention is to provide a solution to at least one of the aforementioned and other drawbacks. [Means for solving the problem]

[0010] The subject of the present invention is a screw rotor made of polymer, the screw rotor comprising a shaft and a rotor body thereon, the polymer of the shaft being reinforced with fibers, the shaft featuring an element that engages with the rotor body or a corresponding element on the rotor body, the element being configured to prevent the shaft from moving axially and / or rotationally relative to the rotor body.

[0011] By using polymers, screw rotors become not only lighter than conventional metal screw rotors, but also more corrosion-resistant and easier to manufacture in complex shapes.

[0012] Such screw rotors can be manufactured, for example, by an injection molding process, which makes it possible to produce a raw helical shape that is already close to the final finished helical shape, thus limiting or eliminating the need for machining the raw helical shape to meet the required tolerances.

[0013] Furthermore, machining composite screw rotors is far simpler and easier than processing cast iron or steel screw rotors.

[0014] This means that the finishing process requires far less work and time, resulting in significant cost savings.

[0015] Furthermore, because the starting point is already an unprocessed spiral form close to the final form, less material is lost.

[0016] While this invention only requires the use of fiber-reinforced polymer for the shaft, it does not preclude the manufacture of the rotor body from fiber-reinforced polymer.

[0017] The element of an axis is the deviation of the axis into or out of the surface of the axis, which means a deviation toward the axis's centerline or a deviation away from the axis's centerline.

[0018] The elements of the shaft, and corresponding or matching elements on or within the rotor body, create mechanical obstructions between the shaft and the rotor body, thereby allowing axial forces and torques to be transmitted from the shaft to the rotor body and vice versa. While the elements may be positioned on the shaft itself, the elements of the shaft can also be formed by intermediates or keys positioned in designated recesses on the shaft.

[0019] Preferably, the fibers within the shaft extend primarily in the axial direction. This provides the shaft with the necessary rigidity and strength.

[0020] In the screw rotor of a screw compressor, for example, it is known that very strong axial and gas forces act on the screw rotor, and for this reason, it is very important that the shaft has the necessary rigidity.

[0021] The rotor body may consist of two or more concentric layers, the inner layers featuring elements that engage with subsequent layers, the elements preventing one layer from moving axially and / or rotationally relative to the subsequent layers.

[0022] Such rotor bodies are used, in particular, to manufacture large screw rotors by injection molding, with a maximum thickness of 8 millimeters per layer.

[0023] By injection molding the rotor body in multiple steps or stages, the amount of material added at each step or stage can be limited, thereby facilitating monitoring of the injection molding process and the subsequent cooling process. This helps optimize the final mechanical properties of the screw rotor. The element has the same function as the aforementioned element of the shaft.

[0024] Furthermore, the subject matter of the present invention is a method for manufacturing a screw rotor composed of a shaft and a rotor body, characterized in that the screw rotor is made of a polymer, and the method comprises: A) a step of preparing the shaft, B) a step of injection-molding the rotor body using a designated mold, wherein the shaft is used as an insert into the mold, including the above steps.

[0025] By carrying out the process in at least two steps, the injection molding process of step B becomes much easier compared to an injection molding process in which the screw rotor is injection-molded in a single step, and in particular, it is easy to monitor in the multi-stage process according to the present invention with regard to materials, dimensional shrinkage, and reduction of mechanical properties.

[0026] Another advantage is that by using the shaft as an insert in the mold for the rotor body, the rotor body is cast onto or around the shaft, and as a result, the casting of the rotor body causes a thermal bond between the shaft and the rotor body.

[0027] This ensures that the shaft cannot move relative to the rotor body, the reason being that with the injection molding of the rotor body, the surface of the shaft is reheated due to contact with the high-temperature molten fiber-reinforced polymer injected onto the shaft, thus making it possible to cause a thermal bond with the material of the rotor body cast around the shaft.

[0028] On the condition that the features of the present invention are described in detail, in the following, without these descriptions having any limiting features, several examples of preferred variants will be used to describe the method for manufacturing the screw rotor according to the present invention with reference to the accompanying drawings. [Brief Description of the Drawings]

[0029] [Figure 1]This is a schematic perspective view of a possible embodiment of the screw rotor according to the present invention. [Figure 2] This is an explanatory diagram showing the axis of the screw rotor in Figure 1. [Figure 3] This is a schematic cross-sectional view along line III-III in Figure 2. [Figure 4] This is a schematic cross-sectional view along line IV-IV in Figure 1. [Figure 5] This is a schematic diagram showing a modified example of the embodiment in Figure 2. [Figure 6] This is a schematic diagram showing a modified example of the embodiment in Figure 2. [Figure 7] This is a schematic diagram showing a modified example of the embodiment in Figure 2. [Modes for carrying out the invention]

[0030] The screw rotor 1 according to the present invention, schematically shown in Figure 1, consists of a shaft 2 and a rotor body 3 on the shaft 2.

[0031] The screw rotor 1 can be used in a fluid injection compressor, expander, or vacuum pump.

[0032] In the illustrated embodiment, the rotor body 3 is cylindrical. However, the possibility of the rotor body 3 being conical is not ruled out. The advantage of using a conical rotor is that forces are better distributed and compression can be increased.

[0033] In Figure 2, axis 2 is shown separately.

[0034] According to the present invention, the screw rotor 1 is made of polymer.

[0035] In this case, with respect to the present invention, at least the shaft 2 is made of a polymer reinforced with fibers 4, and the rotor body 3 can be made of polymer without fibers 4, but in the embodiments shown herein and described below, the rotor body 3 is also made of a polymer reinforced with fibers 4.

[0036] The polymer can be, for example, a polyamide or polyimide. However, the present invention is not limited to these. For example, the polymer can also be a polyether ether ketone (PEEK).

[0037] In some cases, the polymer may be a thermosetting polymer, such as epoxy, vinyl ester, or unsaturated polyester.

[0038] Fiber 4 is not essential, but preferably includes carbon fiber or glass fiber. The fiber may also include organic polymers such as aramid fiber. Carbon nanotubes are also possible.

[0039] In a possible embodiment, the polymer reinforced with fibers 4 is a so-called self-reinforcing polymer, where the fibers are made of the same polymer as the matrix material.

[0040] Preferably, the self-reinforcing polymer is a polymer polyamide, polyimide, or PEEK reinforced with 10 to 60 weight percent of fibers. Preferably, the weight percentage of fibers is between 25 and 45 percent.

[0041] It is not ruled out that the shaft 2 may be made of a different polymer than the rotor body 3, and the rotor body 3 may be made of a polymer reinforced with or not reinforced with fibers 4.

[0042] Therefore, for example, the fiber-reinforced polymer of the shaft 2 can have the same or a higher softening temperature as the fiber-reinforced polymer of the rotor body 3.

[0043] The difference in softening temperatures between the different layers preferably varies between 0 and 20 degrees Celsius.

[0044] This leads to advantages, particularly in the fabrication or manufacture of the screw rotor 1, as will be clearly stated below.

[0045] In this case, although not essential to the present invention, the fibers 4 within the axis 2 mainly extend in the axial direction X-X'.

[0046] This is schematically shown in the cross-sectional view in Figure 3.

[0047] This orientation of the fibers 4 results in the shaft 2 having the necessary rigidity. It is well known that during machine operation, the shaft 2 is subjected to strong axial and gas forces at the location where the screw rotor 1 is attached.

[0048] As can be seen from Figure 3, shaft 2 is a solid shaft 2. The possibility of shaft 2 being hollow is not ruled out; hollow means that a cavity in the longitudinal direction runs through shaft 2. This prevents the so-called flow problem during the manufacturing of shaft 2.

[0049] In this case, although not required, the fibers 4 of the rotor body 3 are oriented arbitrarily or randomly.

[0050] According to the present invention, as is clear from Figures 2, 3, and 4, axis 2 is characterized by elements 5a and 5b.

[0051] Some of these elements 5a can engage with the rotor body 3, and some of these elements 5b can engage with corresponding elements 5c within the rotor body 3, all of which are designed so that elements 5a, 5b, and 5c prevent the shaft 2 from moving axially and / or rotationally relative to the rotor body 3.

[0052] This will be explained using diagrams.

[0053] As can be seen from Figures 2 and 3, axis 2 is characterized by two elements 5a of ring-shaped projections, and the projections on axis 2 are periodically symmetric with respect to the axial direction X-X' and are coaxial with the center line XX of axis 2.

[0054] Periodically symmetrical means that a section or segment rotates and repeats around a central line.

[0055] These elements 5a, in this case, relate to ring-shaped projections, but these elements 5a may also include projections, grooves, or rings of different shapes.

[0056] These elements 5a can be engaged with the rotor body 3 itself, as shown in Figure 1.

[0057] Such element 5a can transmit axial force from the shaft 2 to the rotor body 3 and vice versa.

[0058] In practice, these elements 5a constitute stoppers for the rotor body 3 on the shaft 2 and inversely, so that when an axial force is applied to the rotor body 3, this force can be transmitted to the shaft 2 through these stoppers.

[0059] It is not ruled out that these elements 5a may be placed in a different location further away from the end 6 of the shaft 2. In this case, these elements 5a do not engage with the rotor body 3 itself, but engage with the corresponding elements 5c of the rotor body 3.

[0060] Furthermore, the shaft 2 is characterized by a plurality of elements 5b that can engage with the corresponding elements 5c of the rotor body 3.

[0061] In this case, these elements 5b relate to the projection along the axial direction X-X' of axis 2, which results in a hexagonal cross-section of axis 2.

[0062] As can be seen from the comparison between Figure 1 and Figure 2, these elements 5b are located on the axis 2 on which the rotor body 3 is positioned.

[0063] As can be seen in Figure 4, the rotor body 3 is characterized by a corresponding element 5c that engages with the element 5b of the shaft 2.

[0064] These elements 5b and 5c enable torque to be transmitted from the shaft 2 to the rotor body 3. This is particularly suitable for driving the screw rotor 1 via the shaft 2 by a motor.

[0065] Instead of projections extending in the axial direction X-X', grooves, rings, etc., can be similarly used as elements 5b and 5c.

[0066] As can be seen from Figures 1 and 2, in this case, the shaft 2 is characterized by a coupling component 8 on its surface 7, which is characterized by a thread 9 into which a bolt can be placed.

[0067] Using this bolt, shaft 2 can be connected to, for example, the drive shaft of a motor, or something similar.

[0068] In the illustrated embodiment, the screw rotor 1 is composed of a shaft 2 together with the rotor body 3, but it is not excluded that the rotor body 3 itself is composed of two or more concentric layers, in which case the inner layers are characterized by elements 5b, 5c that engage with subsequent layers, and the elements 5b, 5c prevent one layer from moving axially and / or rotationally relative to the subsequent layers.

[0069] In other words, this principle is fundamentally very similar to the principle of the shaft 2 and rotor body 3 described above.

[0070] In the case of the large screw rotor 1, this is particularly advantageous during the manufacturing process, as will be explained below.

[0071] The screw rotors shown in Figures 1 to 4 can be manufactured according to the method of the present invention.

[0072] The method for manufacturing a screw rotor 1 made of polymer reinforced with fiber 4 by injection molding is basically as follows: A) Steps to prepare the axis, B) A step of injection molding the rotor body 3 using a specified mold, wherein the aforementioned shaft 2 is used as an insert into the mold, This includes two steps.

[0073] Step A described above is not mandatory, but preferably includes the step of injection molding the shaft 2 of the screw rotor 1 using the specified mold.

[0074] However, this is not essential to the present invention. Shaft 2 can also be formed, for example, by extrusion molding.

[0075] In step A, the mold can be used together with elements 5a and 5b to injection mold the shaft 2, so that the aforementioned elements 5a and 5b are formed on the shaft 2.

[0076] To ensure that the fiber 4 extends axially in the direction X-X' within the axis 2, the polymer reinforced with the fiber 4 can be injected into the mold in the direction X-X'.

[0077] Next, by using the shaft 2 as an insert into the mold of the rotor body 3, the corresponding element 5c is efficiently and automatically formed within the rotor body 3.

[0078] By using a fiber-reinforced polymer for the shaft 2 that is different from the fiber-reinforced polymer used for the rotor body 3, the fiber-reinforced polymer used for the shaft 2 has the same or a higher softening temperature as the polymer used for the rotor body 3, and the shaft 2 will not melt or soften as a whole when the rotor body 3 is cast around it. Thus, the mechanical properties of the shaft 2 remain intact, and even if the polymer of the shaft 2 softens somewhat, the fibers 4 of the shaft 2 will not lose their orientation.

[0079] With respect to step B, it is not excluded that the injection molding of the rotor body 3 be carried out in two or more steps, in which a series of base materials are used in each step to add more material to the rotor body 3, and the rotor body parts manufactured in the previous step are used as inserts in the subsequent mold.

[0080] Therefore, the rotor body 3 itself can be made of two or more concentric layers, and using the base material together with element 5c is such that element 5c is provided on the inner layer. Element 5c engages with subsequent layers cast around the inner layer.

[0081] This method is particularly advantageous for large screw rotors 1 because it allows for greater restriction of the material added at each step, and cooling can be monitored to ensure that no mechanical tension is generated or is significantly reduced.

[0082] If the rotor body 3 is conical, it has the advantage of being able to be demolded, that is, it can be removed from the mold very easily.

[0083] In order to insert the aforementioned connecting part 8 into the surface 7 of the shaft 2, the connecting part 8 is positioned within the mold of the shaft 2 at the respective surface 7 locations of the shaft 2.

[0084] Therefore, the connecting part 8 can be integrated with the shaft 2 during the casting process.

[0085] Alternatively, after step B, the aforementioned connecting component 8 can be positioned by self-tapping into a designated cavity on the surface 7 of the shaft 2.

[0086] It will be clear that the embodiments illustrated and described in Figures 1 to 5 only show some of the possible embodiments of elements 5a and 5b.

[0087] In another possible embodiment shown in Figure 5, elements 5a, 5b include at least one projection 5b that is spiral or helical in shape around the axis 2.

[0088] Instead of protrusions, elements 5a and 5b can also be spiral or helical grooves.

[0089] The projection, or element 5b, is positioned at the location of the axis 2 on which the rotor body 3 is placed, so that the corresponding element is formed on the rotor body 3 during the injection molding process.

[0090] The helical element 5b can transmit a combination of rotational force and axial force in order to prevent the axis 2 from moving in the axial direction and rotational direction relative to the rotor body 3.

[0091] Figure 6 shows an additional embodiment in which the shaft 2 is characterized by an element 5b that can engage with a corresponding element 5c located in the rotor body 3.

[0092] In this case, element 5b is a ring-shaped projection around axis 2.

[0093] This element 5b is positioned at the location of the axis 2 on which the rotor body 3 is placed. This element 5b can transmit axial force from the axis 2 to the rotor body 3 and vice versa.

[0094] Figure 7 shows yet another modification, in which axis 2 is characterized by multiple elements 5b in the form of elongated projections that extend axially along axis 2 and are dispersed around it.

[0095] Based on the aforementioned modifications, it is clear that elements 5a and 5b can be embodied in various ways, and that the illustrated embodiments are by no means restrictive.

[0096] The present invention is not limited to the exemplary embodiments shown in the drawings. Rather, the method and screw rotor according to the present invention can be realized in various modifications without exceeding the scope of the invention. [Explanation of symbols]

[0097] 1. Screw rotor 2 axes 3. Rotor body 4 Fibers 5a, 5b, 5c elements

Claims

1. A screw rotor, wherein the screw rotor (1) is made of a polymer, the screw rotor (1) comprises a shaft (2), the shaft (2) includes a rotor body (3) on the shaft (2), the polymer of the shaft (2) is reinforced with fibers (4), the shaft (2) comprises first elements (5a, 5b) that engage with the rotor body (3) or a corresponding second element (5c) of the rotor body (3), the first and second elements (5a, 5b, 5c) prevent the shaft (2) from moving axially and / or rotationally relative to the rotor body (3), the polymer of the shaft (2) is different from the polymer of the rotor body (3), and the polymer of the shaft (2) has the same or a higher softening temperature as the polymer of the rotor body (3).

2. The screw rotor according to claim 1, wherein the first elements (5a, 5b) include at least one groove, ring, projection, or the like, and the projection in the axial direction (X-X') on the surface perpendicular to the axis (2) is periodically symmetric and coaxial with the axial direction (X-X') of the axis (2).

3. The screw rotor according to claim 1 or 2, wherein the first elements (5a, 5b) include at least one groove, ring, projection, or the like extending in the axial direction (X-X'), thereby positioning the first elements (5a, 5b) on the axis (2) on which the rotor body (3) is located.

4. The screw rotor according to any one of claims 1 to 3, wherein the overall shape of the rotor body (3) is cylindrical or conical.

5. The screw rotor according to any one of claims 1 to 4, wherein the shaft (2) is hollow.

6. The screw rotor according to any one of claims 1 to 5, wherein the first elements (5a, 5b) include at least one helical groove, projection, or the like around the shaft (2).

7. The screw rotor according to any one of claims 1 to 6, wherein the fibers (4) within the shaft (2) extend mainly in the axial direction (X-X').

8. The screw rotor according to any one of claims 1 to 7, wherein the rotor body (3) is made at least partially of a polymer manufactured and reinforced with fibers (4).

9. The screw rotor according to claim 8, wherein the fibers (4) of the rotor body (3) are oriented arbitrarily or randomly.

10. The screw rotor according to any one of claims 1 to 9, wherein the polymer forming the screw rotor is polyamide, polyimide, or PEEK.

11. The screw rotor according to any one of claims 1 to 9, wherein the polymer forming the screw rotor is a thermosetting polymer.

12. The screw rotor according to any one of claims 1 to 11, wherein the fiber (4) includes carbon fiber or glass fiber.

13. The screw rotor according to any one of claims 1 to 12, wherein the fiber (4) comprises an organic polymer.

14. The screw rotor according to claim 13, wherein the fiber (4) made of an organic polymer is an aramid fiber.

15. The screw rotor according to any one of claims 1 to 9, wherein the polymer forming the screw rotor is an aramid polymer reinforced with aramid fibers.

16. The screw rotor according to any one of claims 1 to 15, wherein at the end face of the shaft (2), the shaft (2) is provided with a connecting component (8), and the connecting component (8) has a screw thread (9) inside which a bolt can be placed.

17. The screw rotor according to any one of claims 1 to 16, wherein the rotor body (2) is composed of two or more concentric layers, the inner layer having a second element (5c) that engages with a subsequent layer, and the second element (5c) prevents the one layer from moving in the axial and / or rotational direction relative to the subsequent layer.

18. A method for manufacturing a screw rotor (1) comprising a shaft (2) and a rotor body (3), wherein the screw rotor (1) is made of a polymer, and the polymer of the shaft (2) is different from the polymer of the rotor body (3), and the polymer of the shaft (2) has the same or a higher softening temperature as the polymer of the rotor body (3). The aforementioned method, A) The step of preparing the shaft (2), B) A step of injection molding the rotor body (3) using a designated mold, wherein the shaft (1) is used as an insert into the mold, Methods that include...

19. The method according to claim 18, wherein step B, in which the rotor body (3) is injection molded, is performed in two or more steps, and in each of the steps, more material is added to the rotor body (3) by using a series of base materials, and the portion of the rotor body (3) manufactured in the preceding step is used as an insert into a subsequent mold.

20. The method according to claim 18 or 19, wherein step A for preparing the shaft (2) includes the step of injection molding the shaft (2) of the screw rotor (1) using a designated mold.

21. The method according to claim 20, wherein the polymer reinforced with fibers (4) is injected into the mold in an axial direction (X-X') in order to injection mold the shaft (2).

22. The method according to claim 20 or 21, wherein in step A, the mold is used together with elements (5a, 5b), the elements (5a, 5b) are configured to prevent the shaft (2) and the rotor body (3) thus manufactured from moving radially and / or axially relative to each other.

23. The method according to any one of claims 20 to 22, wherein in the mold for the shaft (2), a coupling component (8) is positioned at the end face of the shaft as an insert into the mold, and the coupling component (8) has threads (9) in which a bolt can be placed inside, or after step B, the coupling component (8) is positioned by tapping in a designated cavity at the end face of the shaft (2).

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