METHOD FOR PRODUCING A SLIDE BEARING BUSH, ... AND USE OF A CARBON-FILLED POLYMER MATERIAL
The use of a carbon-filled thermoplastic polymer for plain bearing bushings through injection molding addresses production complexity and environmental concerns, achieving cost-effective and durable bushings with enhanced performance.
Patent Information
- Application Number
- JP2025514196
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-07
- Filing Date
- 2023-08-29
- Publication Date
- 2025-09-11
AI Technical Summary
Existing plain bearing bushings for pumps, particularly in heating circuits and dishwashers, face issues with wear, noise emissions, and high production costs due to complex manufacturing processes using polytetrafluoroethylene (PTFE) that also raise environmental and health concerns due to PFAS compounds.
Manufacture plain bearing bushings using a carbon-filled thermoplastic polymer material with a high carbon content and a melting point of ≤230°C, produced through injection molding, eliminating the need for wet mixing, drying, and sintering steps, and avoiding PFAS compounds.
The method results in cost-effective, environmentally friendly, and health-safe production of plain bearing bushings with improved sliding properties and wear resistance, allowing for recyclability and reduced energy consumption.
Smart Images
Figure 2025530178000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a plain bearing bushing, a plain bearing bushing for a pump, and a method of manufacturing a pump for a dishwasher or the like, wherein the plain bearing bushing is made of a carbon-filled polymer material, the material comprising a thermoplastic polymer. [Background technology]
[0002] Plain bearing bushings are well known in the prior art and are commonly used to mount pump shafts, such as circulation pumps in heating circuits or dishwashers. In particular, the pump gear in such pumps is rotatably mounted within the pump casing. The pump and / or the plain bearing in the pump casing are surrounded by or in contact with the pumped medium and / or the liquid in question. To ensure a long service life of the pump, special requirements are placed on the sliding pairing of the pump shaft and the plain bearing. The shaft can be made of, for example, corrosion-resistant steel, ceramic material, or composite material. In pumps for heating circuits or dishwashers, the pumped water contains dirt or corrosive substances. Dishwasher water is particularly heavily contaminated with dirt, which is primarily composed of food residues. This water also contains a high salt content, alkaline detergents, and abrasive additives. Therefore, the material of the plain bearing is subject to considerable wear, which can affect the service life and noise emissions of the pump.
[0003] It is known to manufacture such plain bearing bushings for pumps from graphite-filled polytetrafluoroethylene (PTFE). Such composite materials are produced by mixing polytetrafluoroethylene with graphite in a wet blending process and then drying. The molding step is carried out, for example, by dry pressing the material and sintering it at approximately 300°C. Post-processing steps are also required to achieve the desired durability. This manufacturing method allows the polytetrafluoroethylene to be filled with up to 25% graphite by volume. Polytetrafluoroethylene's good sliding properties, its chemical resistance, its resilience against hard dirt particles, and its high-temperature resistance make it possible to manufacture durable, quiet plain bearing bushings. However, manufacturing such plain bearing bushings is relatively complicated and therefore expensive.
[0004] Furthermore, polytetrafluoroethylene is a perfluoroalkyl and polyfluorinated alkyl ester (PFAS) that is widely used, especially in textiles, electronic devices, food contact materials, and pharmaceuticals. These are generally persistent substances that are not readily biodegradable in the environment, and increasing concentrations can be detected in organisms and in the environment. They are also considered to be at least partially harmful to health and the environment. For this reason, the European Union (EU) has already restricted the use of some of these substances. There is reason to suspect that the use of these substances may be subject to further restrictions in the future. Therefore, it is desirable to find suitable materials that do not exhibit the aforementioned problems. Summary of the Invention [Problem to be solved by the invention]
[0005] The present object of the present invention is therefore to propose a method for producing a plain bearing bush, a plain bearing bush, a pump and a use, all of which allow for inexpensive production and use that do not raise concerns regarding the environment and health. [Means for solving the problem]
[0006] This object is achieved by a method having the features of claim 1, a plain bearing bushing having the features of claim 12, a pump having the features of claim 13 and the use of a material having the features of claim 18. [Brief explanation of the drawings]
[0007] [Figure 1] FIG. 2 is a side view of the plain bearing bush 10. DETAILED DESCRIPTION OF THE INVENTION
[0008] In a method according to the invention for manufacturing a plain bearing bush for a pump, in particular a circulation pump or the like, the plain bearing bush is made of a carbon-filled polymer material, the material comprising a thermoplastic polymer, the thermoplastic polymer being fusible and having a melting point of ≦230°C, the material having a thermoplastic polymer content of >20% to 65% by volume and a carbon content of >35% to 80% by volume, the material being free of per- or polyfluorinated alkyl compounds (PFAS), and the plain bearing bush is formed by an injection molding process.
[0009] Therefore, the material and / or molding compound is first formed by a mixture of the specified carbon content and thermoplastic polymer. The plain bearing bushing is then manufactured by injecting the material into a mold using an injection molding method. This is made possible, in particular, by using a thermoplastic polymer that is fusible at a specific melting temperature. Therefore, in contrast to polytetrafluoroethylene, which is not fusible, the injection molding method is possible, eliminating numerous work steps. In particular, wet mixing, drying, sintering, and post-processing steps can be omitted. It is also possible to significantly increase the carbon content of the material and reduce the thermoplastic polymer content, which also saves costs. Other possible advantages include less shrinkage during injection molding, thus better dimensional accuracy, as well as a lower thermal expansion coefficient and higher thermal conductivity of the plain bearing bushing. Additionally, any incorrectly manufactured plain bearing bushings can be reused as recyclates using the injection molding method. Furthermore, the relatively low melting temperature requires relatively less energy, which can save costs. Furthermore, by filling the polymer material with the aforementioned carbon content, the sliding properties and wear resistance of the plain bearing bushing can be improved, and the high achievable filler content leads to further cost savings. Finally, the use of materials that do not contain perfluoroalkyl compounds and polyfluorinated alkyl compounds makes it possible to manufacture plain bearing bushings without any environmental or health concerns. Overall, the method according to the present invention makes plain bearing bushings significantly simpler and therefore more cost-effective, and does not raise any environmental or health concerns for production.
[0010] The material may advantageously have a thermoplastic polymer content of 20% to <50% by volume and a carbon content of >50% to 80% by volume, and it has been found that the method can be carried out particularly efficiently with these thermoplastic polymer contents and carbon contents.
[0011] The material may consist primarily of carbon and a fusible thermoplastic polymer, but in principle it is also possible to add other polymers or other additives to the material, which may be processed using injection molding techniques.
[0012] In particular, the material may not comprise fluoropolymers, in particular polytetrafluoroethylene (PTFE) or ethylene tetrafluoroethylene copolymers (ETFE), which belong to the perfluoroalkyl and polyfluorinated alkyl compounds.
[0013] Advantageously, the material may be free of polyethylene (PE), which makes it possible to design a plain bearing bush that is resistant to relatively high temperatures.
[0014] Advantageously, a portion of MoS2 (molybdenum (IV) sulfide or molybdenum disulfide) can be added to the material, which can further improve the sliding properties of the plain bearing bushing.
[0015] Advantageously, the thermoplastic polymer may have a melting point ≧170° C. In alternative embodiments of the method, the melting point may be ≧180° C., ≧190° C., or ≧200° C.
[0016] Advantageously, the thermoplastic polymer may have a water absorption of ≧0.05% and ≦3%, preferably ≧0.1% and ≦2%. The plain bearing bushing may also advantageously be used when it comes into contact with liquids, in particular water. The thermoplastic polymer may also have a water absorption of ≧0.5% and ≦3%, or ≧1% and ≦2%.
[0017] Advantageously, the thermoplastic polymer has a density ≥ 1.0 g / cm 3 and ≦1.5g / cm 3 may have
[0018] Additionally, the thermoplastic polymer may have a dimensional stability temperature of ≧110° C. and ≦160° C. at 0.45 MPa.
[0019] Advantageously, the thermoplastic polymer may have an elastic modulus and / or tensile modulus ≧1000 MPa and ≦3500 MPa. The thermoplastic polymer may also have an elastic modulus and / or tensile modulus ≧1500 MPa and ≦3500 MPa.
[0020] Advantageously, the thermoplastic polymer may be resistant to chemicals, in particular, the thermoplastic polymer may have good chemical resistance to fats, oils, solvents, fuels, alkalis, and salt solutions.
[0021] The carbon used may be graphite, a primarily carbonaceous solid material, petroleum coke, or a mixture of these materials. The material in question may initially be in powder form, which makes it significantly easier to mix with the thermoplastic polymer. In particular, a relatively high carbon content in the material makes it possible to form a particularly chemically resistant and temperature-stable plain bearing bushing. Furthermore, the high carbon content means that a particularly favorable friction coefficient of the plain bearing bushing can be achieved.
[0022] As part of the method, a molding compound of the material may be formed by melting a thermoplastic polymer and mixing it with carbon, after which the molding compound may be placed in an injection mold using an injection molding machine. Homogeneous mixing with carbon can easily occur, for example, in an extruder and / or compounder. The use of an injection molding machine also makes it possible to form relatively long plain bearing bushings and / or plain bearing bushings with relatively high aspect ratios of almost any geometry. In contrast, when formed by dry pressing, the production of long plain bearing bushings and / or plain bearing bushings with high aspect ratios is not easily possible because wall friction effects prevent uniform compression and therefore result in inhomogeneous material properties across the length of the plain bearing bushing.
[0023] The material may be compounded and / or processed in a single screw extruder, preferably a twin screw extruder, which also allows the raw product to be fed back into the material stream.
[0024] Furthermore, it can be provided that the plain bearing bush is machined at least on the bearing surface. Although particularly dimensionally accurate plain bearing bushes can already be obtained using injection molding methods, an even more accurate fit to the shaft or axle of the pump gear can be achieved by machining. In particular, it is also possible to machine the plain bearing bush after injection molding, for example by vibration finishing. One surface of the plain bearing bush can then advantageously be designed as a sliding surface.
[0025] The plain bearing bushings can be plasticized, granulated, and / or fragmented, and the material thus produced can be used to manufacture new plain bearing bushings using the method according to the invention. For example, plain bearing bushings manufactured using the method according to the invention can be classified as crude products due to dimensional or other manufacturing errors. These plain bearing bushings can then be plasticized, granulated, and / or fragmented, and then plasticized, and this material can then be processed as recycle in an injection molding process. This can save a considerable amount of material.
[0026] A plain bearing bushing according to the present invention for a pump, particularly a circulation pump, is made of a carbon-filled polymer material, the material comprising a thermoplastic polymer, the thermoplastic polymer being fusible and having a melting point of ≦230°C, the material having a thermoplastic polymer content of >20% to 65% by volume and a carbon content of >35% to 80% by volume, the material being free of perfluorinated or polyfluorinated alkyl compounds (PFAS), and the plain bearing bushing is formed by an injection molding process. Regarding the advantages of the plain bearing bushing according to the present invention, please refer to the description of the advantages of the method according to the present invention. In particular, the production of the plain bearing bushing using an injection molding process does not result in any density differences, such as may occur during dry pressing and sintering of the material. Further advantageous embodiments of the plain bearing bushing are derived from the characterizing remarks of the dependent claims, with reference to claim 1.
[0027] A pump according to the present invention, for a dishwasher or the like, comprises an electric motor for driving a pump gear of the pump, the electric motor being made of a stator, a rotor and a shaft, the rotor and the pump gear being attached to the shaft, the shaft being rotatably mounted in at least one plain bearing of the pump between the rotor and the pump gear, the plain bearing comprising a plain bearing bush according to the present invention.
[0028] The plain bearing bushing may be arranged on the shaft so that it is in contact with the liquid that can be transported by the pump. For example, the plain bearing bushing may be mounted in a pump casing so that the liquid necessarily comes into contact with and / or flows around the plain bearing bushing. In this case, it may be provided that the pump gear of the pump is arranged directly adjacent to the plain bearing bushing on the shaft.
[0029] It is further provided that only the pump is provided with a plain bearing bush. In principle, two or more plain bearing bushes can be mounted on the shaft. However, in order to maintain the mounting location, only one plain bearing bush can be provided, which is relatively long and / or has a relatively high aspect ratio. This means that the length of the plain bearing bush can be determined so that tilting of the shaft is avoided and a sufficiently safe mounting of the shaft is possible.
[0030] Advantageously, the electric motor can be designed as a canned motor, which makes it possible to completely seal the rotor against the liquid to be conveyed, thereby forcing the liquid to flow around the rotor.
[0031] The rotor may be made of permanent magnets or squirrel-cage windings, and the spacer disks of the pump, attached to the shaft, abut against the axial side surfaces of the plain bearing bushings. The spacer disks then allow the rotor to be axially mounted and, if necessary, can absorb the axial forces of the pump gear. The spacer disks may be attached to the shaft, or the shaft may form the spacer disks. Preferably, the spacer disks may be made from the material of the shaft or from a different material.
[0032] Further advantageous embodiments of the pump are derived from the characterizing statements of the dependent claims with reference to claim 1.
[0033] According to the invention, a carbon-filled polymer material is used to form a plain bearing bushing for a pump by injection molding, the carbon-filled polymer material having a melting point of ≦230°C, a thermoplastic polymer content of >20% to 65% by volume, and a carbon content of >35% to 80% by volume, the material being free of perfluorinated or polyfluorinated alkyl compounds (PFAS). Further advantageous embodiments of the use of this material are derived from the characterizing statements of the dependent claims with reference to claims 1 and 12.
[0034] In the following, one embodiment of the present invention will be described in even greater detail with reference to the drawings.
[0035] The drawing shows a side view of a plain bearing bush 10. The plain bearing bush 10 is rotationally symmetrical and has a through hole 11 for receiving the shaft of a pump. Furthermore, a collar 13 is formed at one end 12 of the plain bearing bush 10. An inner surface 14 of the through hole 11 forms a radial sliding surface 15, and a side surface 16 of the collar 13 forms an axial sliding surface 17 for the shaft (not shown here) and / or a spacer disc placed on the shaft. The plain bearing bush 10 can be pressed via its outer surface 18 against a bearing seat in a pump casing (not shown here) of a pump. In particular, a ratio of the length L to the diameter D of the plain bearing bush 10 of ≥ 2:1 is selected. This is made possible by the fact that the plain bearing bush 10 is formed using an injection molding method.
[0036] When manufacturing the plain bearing bushing 10, a carbon-filled polymer material is used, which comprises a fusible thermoplastic polymer and is free of perfluoroalkyl and polyfluorinated alkyl compounds. First, a homogeneous molding compound having a thermoplastic polymer content of >20% to 65% by volume and a carbon content of >35% to 80% by volume is formed, for example, using an extruder. Using an injection molding machine, the molding compound having a melting point of ≦230°C is placed in an injection mold, thus forming the plain bearing bushing 10 shown. [Explanation of symbols]
[0037] 10. Plain bearing bush 11 Through hole 12 End 13 Colors 14 Internal surfaces 15 Radial sliding surface 16 Side Surface 17 Axial sliding surface, axial side surface 18 External Surface
Claims
1. A method for manufacturing a plain bearing bush (10) for a pump, in particular a circulation pump or the like, the plain bearing bush being made of a carbon-filled polymer material, the carbon-filled polymer material comprising a thermoplastic polymer, the method comprising: the thermoplastic polymer is fusible and has a melting point of 230°C or less; the carbon-filled polymeric material having a thermoplastic polymer content of from greater than 20% to 65% by volume and a carbon content of from greater than 35% to 80% by volume; the carbon-filled polymeric material is free of perfluorinated or polyfluorinated alkyl substances (PFAS); 3. The method of claim 2, wherein the plain bearing bushing is formed by an injection molding process.
2. 2. The method according to claim 1, characterized in that the carbon-filled polymer material does not contain a fluoropolymer, in particular polytetrafluoroethylene (PTFE) or ethylene tetrafluoroethylene copolymer (ETFE).
3. 3. The method according to claim 1 or 2, characterized in that the carbon-filled polymer material does not contain polyethylene (PE).
4. MoS 2 4. The method according to claim 1, wherein a portion of molybdenum (IV) sulfide is added to the carbon-filled polymer material.
5. 5. The method according to claim 1, wherein the thermoplastic polymer has a melting point of 170°C or higher.
6. 6. The method according to any one of claims 1 to 5, characterized in that the thermoplastic polymer has a water absorption of ≧0.05% and ≦3%, preferably ≧0.1% and ≦2%.
7. The thermoplastic polymer has a viscosity of 1.0 g / cm 3 or more and 1.5g / cm 3 7. The method according to claim 1, characterized in that it has a density of:
8. 8. The method according to claim 1, wherein the thermoplastic polymer is resistant to chemical agents.
9. 9. The method according to claim 1, wherein the carbon used is graphite, a predominantly carbonaceous solid material, petroleum coke, or a mixture of these materials.
10. 10. The method according to claim 1, wherein the carbon-filled polymer material is formed by melting the thermoplastic polymer and mixing it with carbon, and then the carbon-filled polymer material is placed in an injection mold by an injection molding machine.
11. 11. The method of claim 10, characterized in that the carbon-filled polymeric material is compounded in a single-screw extruder, preferably a twin-screw extruder.
12. A plain bearing bush (10) for a pump, in particular a circulation pump or the like, said plain bearing bush being made of a carbon-filled polymer material, said carbon-filled polymer material comprising a thermoplastic polymer, the thermoplastic polymer is fusible and has a melting point of 230°C or less; the carbon-filled polymeric material having a thermoplastic polymer content of from greater than 20% to 65% by volume and a carbon content of from greater than 35% to 80% by volume; the carbon-filled polymeric material is free of perfluorinated or polyfluorinated alkyl substances (PFAS); The plain bearing bush (10) is characterized in that the plain bearing bush is formed by an injection molding method.
13. 1. A pump for a dishwasher or the like, comprising an electric motor for driving a pump gear of the pump, The electric motor is made up of a stator, a rotor, and a shaft; the rotor and the pump gear are attached to the shaft; the shaft is rotatably mounted in at least one plain bearing of the pump so as to be between the rotor and the pump gear; A pump, wherein the plain bearing comprises a plain bearing bush (10) according to claim 12.
14. 14. Pump according to claim 13, characterized in that the plain bearing bush (10) is arranged on the shaft so that it is in contact with the liquid that can be transported by the pump.
15. 15. Pump according to claim 13 or 14, characterized in that only the pump is provided with a plain bearing bush (10).
16. 16. Pump according to any one of claims 13 to 15, characterized in that the electric motor is designed as a canned motor.
17. The rotor is made of a permanent magnet or a cage winding, 17. Pump according to any one of claims 13 to 16, characterized in that the spacer discs of the pump, mounted on the shaft, abut against the axial side surfaces (17) of the plain bearing bush (10).
18. 1. Use of a carbon-filled polymer material having a melting point of ≦230° C., a thermoplastic polymer content of more than 20% to 65% by volume, and a carbon content of more than 35% to 80% by volume, the carbon-filled polymeric material is free of perfluorinated or polyfluorinated alkyl substances (PFAS); The use of a carbon-filled polymer material to form a plain bearing bush for a pump by an injection molding process.