Shoe for hydrodynamic bearing and related manufacturing method

Abstract

The invention relates in particular to a shoe (10) for hydrodynamic bearings, characterized in that the shoe (10) comprises a polymeric material part (1) and a support base (2) of metallic material, the support base (2) being provided with connecting means (3; 6; 7), the polymeric part (1) being cast onto the base (2) so as to fill the connecting means (3; 6; 7) provided on the base (2) as well, obtaining a firm connection and a shape complementary to the base (2). The invention also relates to a method for manufacturing the shoe (10).

Description

[Technical Field]

[0001] The present invention relates to a shoe for a hydrodynamic bearing.

[0002] The present invention also relates to a method for manufacturing the bearing shoe.

[0003] More particularly, the present invention relates to polymeric coated shoes for use in generators, turbines, pumps and transmission components. [Background technology]

[0004] Currently known polymer coated bearings of this type are essentially based on a mechanical bond between the metal substrate and the coating polymer itself.

[0005] The solution proposed by the present invention is in the field of hydrodynamic generator bearings, as described for example in DE 10 200 04 13 56 A1.

[0006] Patent document 1 describes a bearing for the rotor of a rotary machine rotating around a vertical axis of rotation, in particular a hydrodynamic generator. The bearing is designed as a plain bearing and comprises an axial bearing and a radial bearing. These bearings are usually coated with white metal (tin alloy - white metal or "Babbitt metal").

[0007] However, in many cases, polymer coated bearings are used.

[0008] Known types of shoes primarily use sintered bronze or welded metal mesh or a series of small grooves machined into the bearing support.

[0009] Typically, in all known types of shoe solutions, once the intermediate layer is created, a polymer layer is pressed into it under conditions of high temperature and pressure.

[0010] This creates a mechanical connection between the metal and the polymeric material.

[0011] This technology is characterized by a high degree of complexity, which also means that the cost of the final product is high.

[0012] Indeed, the known methods for obtaining shoes involve various steps to produce the final product and require the use of specialized equipment, which (in addition to the increased costs mentioned above) also limits the potential suppliers.

[0013] A further problem with known and currently employed techniques is that they are necessarily limited in the size that can be processed.

[0014] Furthermore, once parts are connected, they cannot be later disconnected without destroying the connection.

[0015] Therefore, if the sliding surface is damaged by wear or bearing seizure, the polymer layer cannot be replaced.

[0016] A recent solution that attempts to address the above-mentioned problems is that described in US Pat. No. 5,629,499, which attempts to overcome the above-mentioned problems by proposing a solution in which the polymer and metal parts are separated, creating a shoe that can also be removed later if necessary (e.g. due to excessive wear).

[0017] However, the solution according to Patent Document 2 has several drawbacks, such as the need for very precise machining tolerances to ensure the connection between the parts, and the reduced possibility to control the overall tolerance of the parts (tolerances for bearing shoes are on the order of a hundredth of a millimeter).

[0018] Among the known patent documents, particular mention is made of those relating to the specific solution proposed by the present invention.

[0019] Patent Document 3 describes a hydrodynamic bearing that has a substantially uniform layer structure on its circumference, comprising a base, a lead-free sliding layer that is thinner in the edge regions than in the central region, and a polymer coating that is thicker in the edge regions than in the central region, so that the surface level of the coating is substantially flat when viewed in axial cross section. This creates a kind of paint reservoir in the edge regions, which is particularly useful during the initial start-up phase of a rotating machine where wear occurs. Here, the bearing and the shaft adapt to each other, increasing resistance to edge seizure and improving alignment between the bearing and the shaft.

[0020] On the other hand, Patent Document 4 describes a composite bearing in which a support metal is fixed to a resin layer. In this composite bearing, polytetrafluoroethylene (PTFE) is added to a base resin essentially composed of polyetheretherketone, so that the proportion of polytetrafluoroethylene in the resin layer is 0.1 to 50 wt %. The polytetrafluoroethylene is then dispersed in the base resin in the form of particles.

[0021] Patent Document 5 describes a material for low-friction bearings that includes a matrix formed by mesh screen wire fused with a metal support sheet. Polytetrafluoroethylene or other polymeric resin fills the gaps inside the screen, thereby tightly blocking them together and giving the bearing material high strength.

[0022] Patent document 6 describes a composite material for use in plain bearings, which provides a metallic support and at least one reinforcing material with an open structure, the support and the reinforcing material being connected via a metallic connection.

[0023] Patent Document 2 describes a bearing shoe for a hydrodynamic generator that includes a polymeric portion and a metal base, which are combined to form the bearing shoe. Because the polymeric portion and the metal portion are separated, maintenance in the event of a bearing failure is simplified and speeded up.

[0024] In particular, Patent Document 2 proposes a stationary bearing shoe for a hydrodynamic generator, which is designed using a simplified method compared to conventional polymer-coated bearing shoes, and which can reduce production costs while enhancing the main advantages of high thermomechanical resistance and low wear of mixed lubrication. This is a bearing shoe for a hydrodynamic generator in which a polymer portion and a metal base are combined to form the bearing shoe. This shoe is characterized in that the polymer portion is a separate polymer plate, the metal base is a support plate, and the polymer plate is fixed to the support plate but is removable.

[0025] According to Patent Document 2, the polymer plate is fixed to the stationary plate by a stationary plate seat that fits perfectly to the polymer plate seat. The stationary plate provides both the seat and an offset that protrudes from the surrounding plate, forming a sealing strip with reduced thickness. The polymer plate and the support plate may have the same edge contour. Again, according to Patent Document 2, the support plate and the polymer plate may be connected by at least one bolt. Furthermore, in the solution proposed in Patent Document 2, a locking means may be provided on the edge of the polymer plate, which interacts with the side wall of the pocket in the stationary plate. In particular, the locking means may comprise a key and slot joint extending along the edge of the polymer plate. A removable fixing plate may be provided on one side of the support bearing, allowing the polymer plate to be inserted from one side by sliding it inward and locking the polymer plate in its sliding position in the pocket when closed. The fixing plate may be fixed to the stationary plate by a fixing screw.

[0026] In one example reported in Patent Document 2, the polymeric portion is at least partially composed of polyetheretherketone (PEEK).

[0027] PEEK is a material known to have advantageous properties in terms of strength, superior to other polymers, and can be at least partially composed of polytetrafluoroethylene (PT-FE).

[0028] Finally, according to WO 02 / 04999, the polymeric portion may be constituted by a composition of different polymers and by a filler constituted by carbon fibres and / or graphite.

[0029] US Pat. No. 5,629,999 constitutes the primary prior art document relevant to the invention described herein. [Prior art documents] [Patent documents]

[0030] [Patent Document 1] International Patent No. 2004 / 001241 [Patent Document 2] European Patent Application Publication No. 3276191 [Patent Document 3] International Patent No. 2013 / 178266 [Patent Document 4] U.S. Patent No. 6,332,716 [Patent Document 5] U.S. Patent No. 5,229,198 [Patent Document 6] US Patent Application Publication No. 2005 / 0260431 Summary of the Invention

[0031] The solution proposed by the present invention fits into this context, proposing a bearing shoe consisting of a polymer part and a metal base joined in an innovative way, which allows for a significant reduction in costs by simplifying the production method.

[0032] In addition, the solutions proposed by the present invention make it possible to significantly improve the behavior of the part, such as increasing the yield of the part at the most loaded point of the shoe or introducing sensors under the polymer layer to monitor its behavior.

[0033] These and other results are obtained with a hydrodynamic bearing shoe having the features set forth in independent claim 1.

[0034] Further configurations of the shoe according to the invention are set forth in the dependent claims. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a perspective view of a bearing shoe according to the present invention; [Figure 2] FIG. 2 is an enlarged cross-sectional view of the shoe of FIG. [Figure 3] FIG. 2 is a detailed view of the shoe of FIG. 1. [Figure 4] FIG. 2 is a perspective view of a second embodiment of a metal base of a bearing shoe according to the present invention. [Figure 5] FIG. 2 is a perspective view of a second embodiment of a polymeric portion of a bearing shoe according to the present invention. [Figure 6] FIG. 6 is a perspective view of the two elements shown in FIGS. 4 and 5. [Figure 7] FIG. 7 is a detailed view of the shoe of FIG. 6. [Figure 8] 8 shows the trends in pressure loads on the bearings of the embodiments of FIGS. 5, 6 and 7. FIG. [Figure 9] FIG. 10 is an exploded perspective view of a third embodiment of a shoe according to the present invention. [Figure 10] FIG. 10 is a perspective view of a metal base of a fourth embodiment of a shoe according to the present invention. [Figure 11] FIG. 11 is a cross-sectional view of the base of FIG. 10. [Figure 12] FIG. 10 is a perspective view of a metal base of a fifth embodiment of a shoe according to the present invention. [Figure 13] FIG. 13 is a cross-sectional view of the base of FIG. 12. DETAILED DESCRIPTION OF THE INVENTION

[0036] The invention will now be described, by way of non-limiting illustrative example, in accordance with preferred embodiments thereof, with particular reference to the following fixed drawing figures:

[0037] Referring now to the figures in the drawings, and particularly initially to FIGS. 1-3, there is shown a stationary bearing shoe, generally designated 10, and in particular a hydrodynamic generator bearing comprising a polymeric portion 1 and a metal base 2.

[0038] In an embodiment of the shoe 10 according to the invention, it is provided that the polymeric part 1 is constituted by a polymeric plate cast / molded on a metal base 2 which constitutes a support plate.

[0039] The solution according to the invention proposes to cast (in the preferred embodiment described, by 3D printing, although this technique should in no way be interpreted as limiting the scope of the invention) one or more layers of polyetheretherketone (hereinafter also referred to by the acronym PEEK) reinforced with carbon fiber or graphite onto a metal base 2. The use of PEEK should not be understood as limiting the scope of protection of the invention. For example, the polymeric material may be constituted by other polymers, such as polyethylene terephthalate (PTFE), or mixtures thereof. In fact, the polymeric element can also be made, for example, from PTFE or a mixture of PEEK and PTFE, supplemented with carbon fiber or graphite.

[0040] Along at least one of the sides defining the periphery of the metal base 2, the metal base 2 is treated to create an undercut 3 (the geometry of the undercut 3 is shown in detail in FIG. 3).

[0041] Due to the construction of the undercut 3, the polymer plate cannot slide freely within the undercut 3, and therefore it is impossible to apply the technique described in Patent Document 2, for example.

[0042] In addition, it is not possible to use the hot pressing techniques inherent in some solutions of the known art.

[0043] In this embodiment of the shoe 1 according to the invention, the undercut 3 provided for the connection between the polymer part 1 and the base 2 has a depth of the order of millimeters, so that it is not possible to precisely fix the polymer plate pressed onto it by heat.

[0044] The undercuts 3 and their distribution are only one example of a coupling means that can be provided on the shoe 10 according to the invention, as will be seen below.

[0045] The solution proposed by the invention allows the polymeric part 1, which is fixed to the metal base 2, to be fixed directly to the base itself.

[0046] This process can be carried out by using a machine to deposit molten polymer onto the metal surface, thereby filling the undercuts, and then fixing the polymer part 1 onto the metal base 2.

[0047] The solution proposed by the invention offers significant advantages over currently known solutions, in particular the following advantages:

[0048] - the manufacturing costs of polymer-coated guides and thrust bearings can be reduced due to less material waste and a significantly lower need for precision machining for the bond between polymer and metal, since tight tolerances are not required to perform undercuts 3, which are fully or partially (in any case sufficiently) filled to ensure a secure bond between the polymer and the metal support;

[0049] By making cuts along a specially made sheet in the metal support, it is possible to separate the polymeric part 1 from the metal base 2. In this way, if the metal base 2, the metal support, is damaged or needs to be replaced, it can be reused to create a new shoe 10.

[0050] Further machining in the metal base 2 can further facilitate both the adhesion of the polymeric portion 1 to the base 2 and the operation of the entire bearing 10. Indeed, by increasing the thickness of the polymeric material in areas that are subject to higher pressures during operation, it is possible to take advantage of the yielding properties of the material itself, and in particular of PEEK, to better distribute the pressure on each single shoe 10. This advantage is illustrated in figures 4 to 8 of the drawings, where a cavity 4 is provided on the metal base 2, with a tapered step towards the centre of the cavity 4. Figure 8 shows the pressure relief effect obtained with this embodiment.

[0051] It is possible to introduce a sensor 5 into the shoe 10 between the PEEK part 1 and the metal base 2 to monitor both its operational state and its health. An embodiment of this type is shown in FIG.

[0052] 10 and 11, a further embodiment of a shoe 10 according to the invention is shown, in which a groove 6 is formed on the base element 2, which groove 6 provides a bond between element 1 and element 2 when the polymeric material of element 1 is cast.

[0053] In Figures 12 and 13, a groove 7 is made on the base element 2, in which groove 7 the bond between element 1 and element 2 is formed when the polymeric material of element 1 is cast.

[0054] Although the present invention has been described above according to its preferred embodiments, it is understood that it can be modified by those skilled in the art without departing from its scope of protection, as defined in the appended claims.

Claims

1. A shoe (10) for a hydrodynamic bearing, The shoe (10) is characterized in that it provides a polymeric material part (1) and a support base (2) of metallic material, said support base (2) providing coupling means (3; 6; 7); a polymeric part (1) is cast onto said base (2) so as to fill also said connecting means (3; 6; 7) provided on said base (2) and to obtain a firm connection and a shape complementary to said base (2); In the surface of the metal base (2) into which the polymeric material is poured, at least one cavity (4) is realized corresponding to the area of ​​the bearing subjected to higher pressure; The cavity (4) has a stepped shape that gradually decreases toward the center of the cavity (4).

2. 2. Shoe (10) according to claim 1, characterized in that the coupling means (3; 6; 7) are provided around and / or inside the base (2).

3. Shoe (10) according to claim 1 or 2, characterized in that the coupling means are constituted by one or more undercuts (3) and / or by grooves or hollows (6; 7).

4. The shoe (10) according to any one of claims 1 to 3, characterized in that the polymeric part (1) is made of polyetheretherketone (PEEK), PTFE or a mixture thereof, with the addition of carbon fibres or graphite.

5. A shoe (10) according to any one of claims 1 to 4, characterized in that the metal base (2) is made of sheet steel, aluminum, copper or other metal or metal alloy.

6. The shoe (10) according to any one of claims 1 to 5, characterized in that one or more sensors (5) are provided between the metal base (2) and the polymeric part (1) for measuring one or more parameters of the shoe (10).

7. A method for manufacturing a shoe (10) according to any one of claims 1 to 6, characterized in that the polymer material of the part (1) is cast onto a metal base (2).

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