Screw rotor and method for manufacturing 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] Such screw rotors have conventionally been manufactured from cast iron or steel, cast in an unprocessed helical shape or forged into an unprocessed cylindrical shape, which is then finished by rough and fine grinding, filing, milling, and other cutting operations on the axis of the screw rotor (with helical profile) and the body, and it is known that the final finished helical shape can be obtained.

Summary of the Invention

Problems to be Solved by the Invention

[0004] This finishing is necessary because in the casting process, it is not possible to obtain the form of a very high-precision tolerance range required for the final machine to function properly.

[0005] Even if such a conventional screw rotor functions properly, finishing by grinding, filing, milling, and other such processes is very laborious and time-consuming.

[0006] Furthermore, all of this increases the cost.

[0007] Another drawback is that a large amount of material is removed by machining during the finishing process, and the raw material is lost or wasted.

[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 a polymer, the screw rotor being composed of a shaft and a rotor body thereon, the polymer of the shaft being reinforced with fibers, and the shaft being characterized by engaging elements with the rotor body or corresponding elements in the rotor body, the elements being adapted to prevent the shaft from moving axially and / or rotationally with respect to the rotor body.

[0011] By using a polymer, the screw rotor not only becomes lighter than a conventional metal screw rotor, but also has higher corrosion resistance and is easier to manufacture in a complex shape.

[0012] Such a screw rotor can be made, for example, by an injection molding process, which makes it possible to manufacture a raw helical shape that is already close to the final finished helical shape, and the finishing by cutting the raw helical shape required to bring it within the required tolerances will be limited in scope or eliminated altogether.

[0013] Furthermore, the processing of a composite screw rotor is much simpler and easier than processing a screw rotor made of cast iron or steel.

[0014] This means that the work and time required for the finishing process are much less, thereby resulting in a significant cost savings.

[0015] Furthermore, since the starting point is a raw helical form that is already close to the final form, less material is lost.

[0016] In the present invention, it is only necessary to use a fiber-reinforced polymer for the shaft, but manufacturing the rotor body from a fiber-reinforced polymer is not excluded either.

[0017] An element of the shaft is a deviation of the shaft into or from the surface of the shaft, which means a deviation towards or away from the center line of the shaft.

[0018] The elements of the shaft and the corresponding or matching elements on or in the rotor body create mechanical obstructions between the shaft and the rotor body, so that axial forces and torques can be transmitted from the shaft to the rotor body and vice versa. The elements can be arranged on the shaft itself, but the elements of the shaft can also be formed by an intermediate body or key arranged in a specified recess on the shaft.

[0019] Preferably, the fibers in the shaft mainly extend axially. This provides the required rigidity and strength to the shaft.

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

[0021] The rotor body can be composed of two or more concentric layers, and the inner layer is characterized by elements that engage with subsequent layers, and the elements prevent one layer from moving axially and / or rotationally relative to the subsequent layer.

[0022] Such a rotor body is used especially for manufacturing large screw rotors by injection molding, and the maximum thickness of each layer is 8 millimeters.

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

[0024] Furthermore, the subject 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) preparing a shaft; B) injection molding the rotor body using a specified mold, wherein this shaft is used as an insert into the mold; and includes.

[0025] By performing 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. In particular, with respect to materials, shrinkage of dimensions, and reduction of mechanical properties, it is easy to monitor in the multi-step process according to the present invention.

[0026] Another advantage is that by using the shaft as an insert within the mold of the rotor body, the rotor body is cast over 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 because when using injection molding of the rotor body, the surface of the shaft is reheated due to contact with the hot melt fiber-reinforced polymer injected into 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 of explaining the features of the present invention in detail, hereinafter, several examples of preferred modifications are described with reference to the accompanying drawings, without any limiting features, for a method for manufacturing a screw rotor according to the present invention.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0030] The screw rotor 1 according to the present invention schematically shown in FIG. 1 is composed 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 type compressor, expander, or vacuum pump.

[0032] In the illustrated embodiment, the rotor body 3 is cylindrical. However, the possibility that the rotor body 3 is conical is not excluded. The advantage of using a conical rotor is that the force is more evenly distributed and compression can be enhanced.

[0033] In FIG. 2, the shaft 2 is shown alone.

[0034] According to the present invention, the screw rotor 1 is made of a 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 a 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 a polyimide. However, the present invention is not limited thereto. For example, the polymer can also be a polyetheretherketone (PEEK).

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

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

[0039] In a possible embodiment, the polymer reinforced with the fiber 4 is a so-called self-reinforced polymer, where the fiber is made of the same polymer as the mold.

[0040] Preferably, the self-reinforced polymer is a polymer polyamide, polyimide, or PEEK reinforced with 10 to 60 weight percent of the fiber 4. Preferably, the weight percent of the fiber is between 25 and 45 percent.

[0041] It is not excluded that the shaft 2 is made of a polymer different from the rotor body 3, and the rotor body 3 can be made of a polymer reinforced or not reinforced with the fiber 4.

[0042] Thus, for example, the polymer reinforced with the fiber 4 of the shaft 2 can have the same or a higher softening temperature than the polymer reinforced with the fiber 4 of the rotor body 3.

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

[0044] This leads to advantages, particularly regarding the production or manufacture of the screw rotor 1, as will be specified below.

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

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

[0047] Due to this orientation of the fibers 4, the shaft 2 will have the required rigidity. During the operation of the machine, it is well known that the shaft 2 is subjected to strong axial forces and gas forces at the location where the screw rotor 1 is attached.

[0048] As can be seen from FIG. 3, the shaft 2 is a solid shaft 2. The possibility that the shaft 2 is hollow is not excluded, and being hollow means that a longitudinal cavity penetrates the shaft 2. This prevents the so-called flow problems during the production of the shaft 2.

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

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

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

[0052] This will be explained with reference to the drawings.

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

[0054] Periodically symmetric means that a section or segment is rotationally repeated around a center line.

[0055] These elements 5a are, in this case, associated with ring-shaped protrusions, but these elements 5a can also include protrusions, grooves, or rings of different shapes.

[0056] As shown in FIG. 1, these elements 5a can engage with the rotor body 3 itself.

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

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

[0059] It is not excluded to arrange these elements 5a at another 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 are associated with protrusions along the axial direction X-X' of the shaft 2, whereby the cross-section of the shaft 2 becomes hexagonal.

[0062] As can be seen from the comparison of FIGS. 1 and 2, these elements 5b are located on the shaft 2 on which the rotor body 3 is arranged.

[0063] As can be seen from FIG. 4, the rotor body 3 is characterized by corresponding elements 5c that engage with the elements 5b of the shaft 2.

[0064] With such elements 5b and 5c, torque can 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 the protrusion 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 FIGS. 1 and 2, in this case, the shaft 2 is characterized by the coupling part 8 on its surface 7, which is characterized by the thread 9 in which a bolt can be arranged inside.

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

[0068] In the illustrated embodiment, the screw rotor 1 is composed of the 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 this case, the inner layer is characterized by elements 5b and 5c that engage with the subsequent layer, and the elements 5b and 5c prevent one layer from moving in the axial direction and / or the rotational direction with respect to the subsequent layer.

[0069] In other words, this principle is very similar in essence to the principle of the aforementioned shaft 2 and rotor body 3.

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

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

[0072] The method of manufacturing the screw rotor 1 made of a polymer reinforced with fibers 4 by injection molding is basically A) a step of preparing a shaft, and B) A step of injection molding the rotor body 3 using the specified mold, wherein the aforementioned shaft 2 is used as an insert into the mold; It includes two steps.

[0073] Although not essential, preferably, the aforementioned step A includes a step of injection molding the shaft 2 of the screw rotor 1 using the specified mold.

[0074] However, this is not essential for the present invention. The shaft 2 can also be extrusion molded, for example.

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

[0076] For the purpose of ensuring that the fiber 4 extends axially X-X' within the shaft 2, the polymer reinforced with the fiber 4 can be injected into the mold in the axial 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 will be efficiently and automatically formed within the rotor body 3.

[0078] By using a polymer reinforced with the fiber 4 for the shaft 2 that is different from the polymer reinforced with the fiber 4 used for the rotor body 3, the polymer reinforced with the fiber 4 used for the shaft 2 has the same or 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. In this way, the mechanical properties of the shaft 2 remain intact, and when the polymer of the shaft 2 softens to some extent, the fiber 4 of the shaft 2 will not lose its orientation.

[0079] Regarding step B, the injection molding of the rotor body 3 is not excluded from being carried out in two or more steps. In each of these steps, by using a series of base materials, more material is added to the rotor body 3, and the rotor body parts manufactured in the previous steps are used as inserts in subsequent molds.

[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 should be such that element 5c is provided on the inner layer. Element 5c engages with a subsequent layer cast around the inner layer.

[0081] This method can more restrict the material added in each step, so it is particularly advantageous for the large screw rotor 1, and the cooling can be monitored so that no mechanical tension is generated or it significantly decreases.

[0082] When the rotor body 3 is conical, there is an advantage that the rotor body 3 can be demolded, that is, it can be removed very easily from the mold.

[0083] To insert the aforementioned coupling part 8 into the surface 7 of the shaft 2, the coupling part 8 is arranged at the position of each surface 7 of the shaft 2 within the mold of the shaft 2.

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

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

[0086] In the embodiments illustrated and described in FIGS. 1 to 5, it will be clear that only some possible embodiments of the possible embodiments of elements 5a, 5b are shown.

[0087] In another possible embodiment shown in FIG. 5, elements 5a, 5b include at least one protrusion 5b in a spiral or helical shape around axis 2.

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

[0089] The protrusion, or element 5b, is located at the position of axis 2 on which rotor body 3 is disposed, such that corresponding elements are formed on rotor body 3 during the injection molding process.

[0090] The helical element 5b can transmit a combination of rotational force and axial force to prevent axial and rotational movement of axis 2 relative to rotor body 3.

[0091] FIG. 6 shows an additional embodiment, where axis 2 is characterized by an element 5b that can engage with a corresponding element 5c on rotor body 3.

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

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

[0094] FIG. 7 shows yet another variant, where axis 2 is characterized by a plurality of elements 5b in the form of elongated protrusions that extend axially along axis 2 and are distributed around it.

[0095] Based on the foregoing variants, it is clear that elements 5a, 5b can be embodied in various ways and the illustrated examples are in no way limiting.

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

Explanation of Signs

[0097] 1 Screw rotor 2 Shaft 3 Rotor body 4 Fiber 5a, 5b, 5c Elements

Claims

1. A screw rotor, characterized in that the screw rotor (1) is made of a polymer, the screw rotor (1) is composed of a shaft (2), the shaft (2) has a rotor body (3) on the shaft (2), the polymer of the shaft (2) is reinforced with fibers (4), the shaft (2) is characterized by a first element (5a, 5b) that engages with the rotor body (3) or a corresponding second element (5c) of the rotor body (3), and the first and second elements (5a, 5b, 5c) are configured to 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 a softening temperature equal to or higher than that of the polymer of the rotor body (3).

2. The first element (5a, 5b) includes at least one groove, ring, protrusion, or the like, and the protrusion in the axial direction (X-X') on the surface perpendicular to the shaft (2) is periodically symmetric and coaxial with the center line (X-X') of the shaft (2). The screw rotor according to Claim 1.

3. The first element (5a, 5b) includes at least one groove, ring, protrusion, or the like that extends in the axial direction (X-X'), whereby the first element (5a, 5b) is positioned at a position on the shaft (2) where the rotor body (3) is disposed. The screw rotor according to Claim 1 or 2.

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

5. The shaft (2) is hollow. The screw rotor according to any one of Claims 1 to 4.

6. The first element (5a, 5b) includes at least one helical groove, protrusion, or the like around the shaft (2). The screw rotor according to any one of Claims 1 to 5.

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

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

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 fibers (4) include carbon fibers or glass fibers.

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

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

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 position of the end face of the shaft (2), the shaft (2) is provided with a coupling component (8), and the coupling component (8) has a thread (9) capable of arranging bolts inside.

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, and the inner layer is provided with a second element (5c) engaging with the subsequent layer, and the second element (5c) is configured to prevent the one layer from moving in the axial direction and / or the rotational direction with respect to the subsequent layer.

18. A method for manufacturing a screw rotor (1) composed of a shaft (2) and a rotor body (3), wherein the screw rotor (1) is made of a polymer, the polymer of the shaft (2) is different from the polymer of the rotor body (3), and the polymer of the shaft (2) has a softening temperature equal to or higher than that of the polymer of the rotor body (3). The method comprises: A) preparing the shaft (2); B) injection molding the rotor body (3) using a specified mold, wherein the shaft (1) is used as an insert into the mold. The method includes the above steps.

19. Step B of injection molding the rotor body (3) is carried out in 2 or 3 or more steps, and in each of said steps, by using a series of base materials, more material is added to the rotor body (3), and the part of the rotor body (3) manufactured in the previous step is used as an insert into the subsequent mold, the method according to claim 18.

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

21. For injection molding the shaft (2), the polymer reinforced with fibers (4) is injected axially (X-X') into the mold, the method according to claim 20.

22. In step A, the mold is used together with elements (5a, 5b), and the elements (5a, 5b) are configured to prevent the shaft (2) and the rotor body (3) manufactured in this way from moving relative to each other in the radial and / or axial directions, the method according to claim 20 or 21.

23. In the mold for the shaft (2), a coupling part (8) is arranged as an insert into the mold at the position of the end face of the shaft, and the coupling part (8) is provided with a thread (9) in which a bolt can be arranged inside, or after step B, the coupling part (8) is arranged by tapping in a specified cavity of the end face of the shaft (2), the method according to any one of claims 20 to 22.

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