CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/046,875, filed July 1, 2020. The entire content of this application is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

Fluid-film bearings can support axial and radial loads imposed on a shaft or rotor in a turbomachinery or power generation equipment such as turbines, pumps, compressors, and the like. Thrust bearings can carry loads exerted along the axial direction of the shaft, while journal bearings can carry loads exerted along the radial direction, including the weight of the shaft itself. Bearing pads or shoes can be components of a bearing assembly that are positioned opposing the rotating surface of a shaft where axial or radial loads are supported. This surface can be referred to as a collar surface or a runner surface in the case of thrust bearings, or as a journal surface in the case of journal bearings. A very thin fluid film can be included between the bearing pads and the rotating collar or journal surfaces. The thin film can flow through a gap of reducing cross-sectional area (e.g., a reducing wedge) in the direction of rotation, which can create hydrodynamic pressures in the film that apply supporting force to the shaft. Depending on the application, the bearing pads can have a fixed surface profile or they can include a tiltable surface profile.

The fluid film between the bearing pads and the shaft surface can be thinner than a single human hair in normal operation. Thus, physical contact between the shaft and the bearing pads can occur at various stages of the operation of the machine. In order to protect the surfaces of the bearing pads and the shaft, a thin protective layer can be placed on the surface of a bearing pad that faces the collar or the journal surface. This protective layer can be composed of a metal alloy such as Babbitt alloy or White metal, which can act as a sacrificial metal alloy. The metal alloy can be strong enough to withstand the pressure and temperatures created by the fluid film during normal operation of the rotating shaft, while soft enough to wear and yield when metal-to- metal contact occurs. This layer is crucial in determining the performance and life of the fluid- film bearings. As machines are increasingly designed to produce higher power and become more efficient, the operating conditions of the bearings become more difficult due to the increase in operating temperature and pressures that the protective layer of the bearing pads experience.

One attempt to address this issue is to replace the metal alloy layer of the bearing pads with a high temperature thermoplastic polymer (e.g., Polyether ether ketone (PEEK), and the like) that has superior tribological properties compared to Babbitt alloy or White metal, such as higher strength, higher melting temperature, lower coefficient of friction, higher resistance to wear, and the like. However, a challenge in using polymer as the sacrificial layer is that polymers such as PEEK fail to form a chemical bond with the metal base of a bearing pad. Further, existing coupling techniques such as adhesives, welding, and mechanical fastening either fail to produce a strong bond between the two dissimilar materials or they create other issues such as cracking under mechanical and thermal stress experienced during operation, which can limit the operational lifespan of a bearing.

SUMMARY

Bearing pad assemblies, and methods and systems for manufacturing the same, are described herein. In one aspect, a bearing pad assembly can include a body having a first surface a set of tangs extending distally away from the first surface of the body, and a sacrificial layer disposed over the first surface and coupled to the body via the set of tangs.

This aspect can include a variety of embodiments. In one embodiment, the sacrificial layer can include a thermoplastic material. In some cases, the thermoplastic material can further include polyether ether ketone (PEEK).

In another embodiment, the body can further include steel alloy, copper alloy, iron alloy, or a combination thereof. In another embodiment, the set of tangs can further include steel alloy, copper alloy, brass alloy, or a combination thereof.

In another embodiment, the set of tangs can further include a set of hooks. In another embodiment, the set of tangs can be embedded within the sacrificial layer, such that at least a portion of the sacrificial layer is positioned between a set of distal ends of the set of tangs and the first surface.

In another embodiment, the bearing pad assembly can further include either a thrust bearing pad assembly or a journal bearing pad assembly. In another aspect, a system for manufacturing a bearing pad assembly can include a mold, including a top end, a bottom end, an exterior surface, and an interior surface, where the bottom end and the interior surface defines a bottom recess, where the top end and the interior surface define a top recess, and where the top end, the bottom end, and the interior surface define a cavity within the mold, a top cap having a first a first top end, where the first top end is configured to couple to the top end of the mold via the top recess, and a bottom cap having a first bottom end, where the first bottom end is configured to couple to the bottom end of the mold via the bottom recess, where the bottom end is further configured to position a bearing pad blank and a sacrificial layer into the cavity when coupled to the mold, where the mold is further configured to heat a temperature of the sacrificial layer beyond a glass transition temperature of the sacrificial layer.

This aspect can include a variety of embodiments. In one embodiment, the system can further include at least one handle coupled to the exterior surface of the mold. In another embodiment, the mold, the bottom cap, and the top cap can further include steel alloy, nickel alloy, aluminum alloy, or a combination thereof. In another embodiment, the system can further include a center pin disposed transversally within the cavity, where the bottom cap is further configured to couple to an end of the center pin when coupled to the mold.

In another aspect, a system for manufacturing a bearing pad assembly can include a first plate having a first surface, a second plate having a second surface facing towards the first surface, and a heating element configured to heat a sacrificial layer sheet to at least a glass transition temperature for the sacrificial layer sheet, where the first plate and the second plate are configured to apply, via the first surface and the second surface, mechanical pressure to a bearing base blank and the sacrificial layer sheet while the bearing base blank and the sacrificial layer are heated by the heating element.

In another aspect, a method of manufacturing a bearing pad assembly can include positioning the bearing pad body, a set of tangs, and a sacrificial layer into a mold, compacting the body, the set of tangs, and the sacrificial layer in the mold, heating the mold to at least a glass transition temperature for the sacrificial layer, and cooling the sacrificial layer to below the glass transition temperature.

In another aspect, a method of manufacturing a bearing pad assembly can include positioning a bearing pad body, a set of tangs, and a sacrificial layer sheet between a first surface of a top plate and a second surface of a bottom plate, heating the sacrificial layer sheet to at least a glass transition temperature for the sacrificial layer, compressing the body, the set of tangs, and a sacrificial layer sheet via the top plate and the bottom plate, and cooling the sacrificial layer sheet to below the glass transition temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference characters denote corresponding parts throughout the several views.

FIG. 1 illustrates a thrust bearing according to an embodiment of the claimed invention..

FIG. 2 illustrates a journal bearing according to an embodiment of the claimed invention.

FIG. 3 depicts a cross-sectional view of a section of a thrust bearing pad according to an embodiment of the claimed invention.

FIG. 4 depicts a cross-sectional view of a journal bearing pad assembly according to an embodiment of the claimed invention.

FIG. 5 depicts a top perspective view of an intermediary layer with a hook array according to an embodiment of the claimed invention.

FIGS. 6 and 7 depicts systems for compression molding a thrust bearing pad assembly according to embodiments of the claimed invention.

FIG. 8 depicts a system for compression molding a journal bearing pad assembly according to an embodiment of the claimed invention.

FIG. 9 depicts a system for hot-press molding a thrust bearing pad assembly according to an embodiment of the claimed invention.

FIG. 10 illustrates a method for compression molding a bearing pad assembly according to an embodiment of the claimed invention.

FIG. 11 illustrates a method for hot-press molding a bearing pad assembly according to an embodiment of the claimed invention.

FIGS. 12 - 14 are photographs of journal bearing pad assemblies generated via compression molding according to embodiments of the claimed invention FIGS. 15 and 16 are photographs of bearing pad assemblies generated via a hot-press method according to embodiments of the claimed invention.

FIG. 17 illustrates a template for cutting a bearing pad assembly from a bearing pad blank according to an embodiment of the claimed invention.

FIG. 18 is a photograph of a cut bearing pad assembly compared to a bearing pad blank according to an embodiment of the claimed invention.

FIGS. 19(a) and 19(b) are photographs of metal foam for an intermediate layer according to embodiments of the claimed invention.

FIGS. 20(a) and 20(b) are photographs of PEEK-bonded 5-inch outer diameter steel disc with a copper foam interface layer according to an embodiment of the claimed invention.

FIG. 21 is a photograph of a microscope image of the interface of a PEEK-bonded steel disc using copper metal foam as the intermediate layer according to an embodiment of the claimed invention.

DEFINITIONS

The instant invention is most clearly understood with reference to the following definitions.

As used herein, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about.

As used in the specification and claims, the terms “comprises,” “comprising,” “containing,” “having,” and the like can have the meaning ascribed to them in U.S. patent law and can mean “includes,” “including,” and the like.

Unless specifically stated or obvious from context, the term “or,” as used herein, is understood to be inclusive.

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 (as well as fractions thereof unless the context clearly dictates otherwise).

DETAILED DESCRIPTION OF THE INVENTION Bearing Pad Assembly

Embodiments described herein relate to bearing pad assemblies. A bearing pad assembly can include a set of layers. These bearing pad assemblies can be coupled to a variety of bearings for use in industrial machinery. For example, FIG. 1 illustrates a top perspective view of an embodiment of a thrust bearing 10 in accordance with an embodiment of the claimed invention. The thrust bearing 10 can include a base ring 11 and one or more bearing pad assemblies 12.

The bearing pad assembly 12 can itself include a base metal portion 13 and a coating portion 14. The base ring 11 and the base metal portion 13 of the bearing pad assembly 12 can be composed of steel or any other suitable material known in the art (e.g., an aluminum alloy, a nickel alloy, a copper alloy, an iron alloy, and the like). Further, the coating portion 14 can be composed of a thermoplastic material, such as PEEK, PTFE, or from any other suitable material known in the art (e.g., other organic thermoplastic polymers, and the like).

Similarly, FIG. 2 illustrates a top perspective view of a journal bearing 20 according to an embodiment of the claimed invention. The journal bearing 20 can include a aligning ring 21, and one or more bearing pad assemblies 22. The bearing pad assemblies 22 can include a base metal portion 23 and a coating portion 24. The aligning ring 21 and the base metal portion 23 of the bearing pad assembly 22 can be composed of materials similar to those recited compositions for the base ring 11 and base metal portion 13 of FIG. 1. The coating portion 24 can be composed of materials similar to those recited compositions for the coating portion 14 of FIG. 1.

FIGS. 3 and 4 illustrate side cross-sectional views of bearing pad assemblies 30 and 40 respectively. Bearing pad assemblies 30 and 40 can be examples of bearing pad assemblies 12 and 22 illustrated in FIGS. 1 and 2, respectively. The bearing pad assembly 30 can include a tang array 31, as shown in FIG. 3. The tang array 31 can be composed of multiple hooks, such as hooks 32 and 33. Likewise, the bearing pad assembly 40 can include a tang array 41, as shown in FIG. 4. The tang array 41 can be composed of multiple hooks, such as hooks 42 and 43. The hooks of the tang arrays 31 and/or 41 can be arranged in multiple rows and/or columns.

In some embodiments, adjacent rows of hooks can be staggered or off-set such that the hooks in a first row are positioned in between gaps of the hooks forming an adjacent row. In some embodiments, the hook array can further include an intermediate layer 34, as shown in Figure 16. In some such embodiments, the intermediate layer 34 can be composed of a thin steel or aluminum alloy sheet. However, other materials can be used as the intermediate layer, for example a nickel alloy, a bronze alloy, and the like.

The intermediate layer 34 can include a thickness of different ranges. For example, the intermediate layer 34 can include a thickness of between approximately 0.02 to 0.05 inches (.508 - 1.27 mm). In other embodiments, the intermediate layer can include a thickness of approximately 0.1 and 0.2 inches (between .254 and .508 mm) (e.g., .125 inches). In yet other embodiments, the intermediate layer can be thicker, such as between approximately 0.5 and 0.75 inches (12.7 mm and 19 mm). In other embodiments, a thicker intermediate layer can be used.

In some cases, the intermediate layer can be a substitute for base portion 35 and brazing compound 36, particularly for embodiments including thick intermediate layers.

The intermediate layer can be metallically bonded to the base portion, such as the base portion 35 and 45 of FIGS. 3 and 4, respectively, through any suitable manner known in the art including but not limited to brazing, welding, tack welding, or some combination thereof. In other embodiments, the tangs may be formed on the base portion directly and in lieu of the intermediate layer.

In some embodiments, as shown in FIGS. 3 and 4, the hooks 32, 33, 42, and 43 can be curved such that the curved tips of the hooks extend vertically over at least some of the coating portion 36 and 46, respectively. In some embodiments, adjacent rows can include curved tips that extend in opposite directions. In other embodiments, the curved tips can extend in the same direction. In other embodiments, the tangs can be straight, such that the straight tips of the tangs form a substantially vertical line to the base of the respective tang. Persons of skill in the art will recognize that the tang array 31 can include any suitable type of tang, and each tang can include a curved tip, a straight tip, a corkscrew tip, or any other suitable shape, or any combination suitable shapes, in any suitable orientation, linear, rectilinear, radial, spiral, etc. Additionally, persons of skill in the art will recognize that tangs can be of any suitable size, and that the size can be dependent on the thickness of the intermediate layer for embodiments implementing an intermediate layer. For example, an intermediate layer having a thickness of 0.125 inches (3.175 mm) can have tangs between 0.04 and 0.05 inches (1 mm and 1.27 mm) in height.

In some cases, recesses can be adjacent to a tang, and can be a result from the manner in which the tangs are manufactured. In some embodiments, recesses can be shaped as angled troughs, such that at least some of the material of the coating portion is disposed vertically beneath the main body of tang. In other embodiments, the recesses can be shaped as straight troughs, which can descend substantially vertically from the base of the respective tang. In some embodiments, adjacent tang rows can include recesses which extend in opposite directions from the hooks 31 to which they are paired. In other embodiments, a hook row can include recesses which extend in the same direction from the respective hook to which a recess is paired. Persons of skill in the art will recognize that the recesses paired with the hooks in the tang array can be of any suitable type, having angled troughs, straight troughs, corkscrew or spiraled troughs, or any other suitable shape, or any combination suitable shapes, in any suitable orientation, linear, rectilinear, radial, spiral, etc. in accordance with the claimed invention.

In some embodiments, commercially available intermediate layers with tang arrays used in other industries, such as GRIPMETAL™ sheets, can be used. Such sheets are described and claimed in Canadian Patent Publication CA2127339, and U.S. Patents Nos. 9,291,225 and 10,010,923, which are incorporated herein by reference in their entirety. Similarly, the tang arrays can be formed on the base materials through the manufacturing processes described and claimed in Canadian Patent Publication CA2127339 and U.S. Patent Publication No. 2016/0375480, which is incorporated herein by reference in its entirety. In other embodiments, GRIPMETAL™ sheets having the required thickness of the base portion can be used, thereby obviating the need for an intermediate layer.

In some embodiments, metal foams can be utilized as the intermediate layer (e.g., intermediate layer 34). Metal foam can be a sponge-like material that includes high porosity due to air bubbles created in the metal while in liquid form. The foam metal can have an irregular surface with a high surface area, with which a coating such as PEEK can bond at high temperatures. Examples of metal foams as the intermediate layer are discussed in more detail below with reference to FIGS. 19 - 21. Embodiment for Thrust Bearing Pad Assembly

A steel base portion and a tang array for a thrust bearing pad assembly can be prepared with a .05 inch (1.27 mm) thick GRIPMETAL™ sheet. The tang array can include hooks with .015 inches (.381 mm) in height. The GRIPMETAL™ intermediate layer can be brazed to a 3 inch (76.2 mm) steel disc base portion using a 2 mil (.005 mm) nickel strip as bonding material. The nickel strip can be melted at 1850° F (1010° C) in a vacuum furnace after being placed between the steel base and the GRIPMETAL™ sheet. Subsequently, a coating portion composed of PEEK or another suitable thermoplastic material can be formed on top of the combined GRIPMETAL™ sheet and steel base portion.

Embodiment for Journal Bearing Pad Assembly

A brazing procedure can also be used in the production of a journal bearing pad base portion. As shown in FIG. 5, a GRIPMETAL™ sheet can be bent into a tube by sizing, spacing or otherwise protecting the tangs from being distorted during the rolling process. The tube can then be placed inside a base portion ring with a 2 mil (.05 mm) nickel -based brazing alloy located between the base portion and the tube (e.g., brazing layer 36 of FIG. 3). The sandwich of the base portion, brazing alloy, and tube can further be tack welded at discrete points along the ring perimeter to further couple the tube and the base portion. The base portion and tube can then placed in a vacuum furnace for brazing at 1850° F (1010° C), thereby securing the tube to the base portion with a strong metallic bond. Subsequently, a coating portion composed of PEEK or another suitable thermoplastic material can be formed on the combined GRIPMETAL™ sheet and base portion.

Embodiments with Metal Foam as the Intermediate Laver

Metal foam is a sponge-like material that has high porosity that is obtained by various processes that create air bubbles in the metal while it is in liquid form. The metal is then cooled, creating a porous network of cavities when the metal is solidified. Examples of materials that can be used to create metal foam include, but are not limited to, copper, nickel, and aluminum. FIG. 19(a) depicts metal foam sheets that can act as the intermediate layer, and FIG. 19(b) depicts steel discs with copper foam brazed on the top surface, according to embodiments of the claimed invention. The table below illustrates metal foam characteristics that can be implemented as the intermediate layer described above.

The metal foam sheets can be brazed on thicker steel parts that act as the main body of the thrust and journal bearing pads. In FIG.19(b), the sheet of copper foam is shown as bonded to a thicker steel part via brazing. The brazing method used a nickel strip for bonding all the materials listed above. The brazing procedure can also be used in the production of journal bearing pads with PEEK linings by bending the foam sheet into a tube form first and then placing it inside a thicker ring with a 2-mil nickel-based brazing alloy between the base metal and the metal foam. The ring is then placed in a vacuum furnace for brazing and the metal foam is secured to the base metal with a strong metallic bond.

Once the top surface of a steel disc or the inner surface of a circular steel ring is textured using the metal foam layer, the next phase is to mold the thermoplastic into the textured surface. Molding the Thermoplastic

The coating portion (e.g., coating portion 14 of FIG. 1) can then be molded onto the metal foam sheet. The cover portion material, such as PEEK or another thermoplastic, can be placed in a mold with the metal foam and based portion. The mold can be heated sufficiently enough to initiate a transition phase of the cover portion, such that the cover portion interfaces with the metal foam by flowing into the pores of the metal foam even at high pressures. As the mold cools, the cover portion solidifies, bonding the cover portion to the metal foam. Different molding techniques are described in greater detail below.

Thickness measurements were taken before and after the molding process was performed and it was observed that the compression molding procedure resulted in a compression of the copper foam layer in the amount of 67% in terms of average foam thickness. The PEEK-bonded steel disc using copper foam as the interface layer is shown in FIGS. 20(a) and (b). The diameter of this disc is 5" while the steel thickness is 0.5". The total thickness of the PEEK layer and the copper foam layer is about 0.25". FIG. 21 depicts a steel and PEEK interface at 20 ^c magnification. As FIG. 21 illustrates, the PEEK was able to flow inside the copper foam layer and fill the pores during the compression molding process. This ensures a strong mechanical bond between the PEEK layer and the steel base.

Compression Molding the Coating Portion onto the Tang Array and Base Portion

In some cases, bearing pad assemblies can be manufactured through a molding process referred to herein as compression molding. This process can include melting the coating portion at high temperature in an oven and then applying high pressures on the molten coating portion, via a hydraulic press, to press the coating portion onto the tang array and base portion.

FIG. 6 illustrates an embodiment of a molding system for compression molding one or more thrust bearing pad assemblies, such as bearing pad assembly 12 described in FIG. 1. The molding system can include a mold 61, a bottom cap 62, and a top cap 63. The mold 61 can be hollow, and can be sized and shaped to receive a disc base blank. The disc base blank can include a base portion, a tang array, and optionally, an intermediary layer. The mold 61 can further be provided with handles 65 so that it can be easily transported between an oven and a hydraulic press. The mold 61, bottom cap 62, and top cap 63 can be made from steel or other suitable material that is thick enough to maintain its shape without deforming while the mold system is in the press.

FIG. 7 illustrates another embodiment of a molding system for compression molding a thrust bearing pad. The molding system can include a mold 71, a bottom cap 72, a center pin 73, and a hollow top cap 77. The mold 71 can be hollow, and can be sized and shaped to receive an annular thrust bearing base blank. The mold 71 can further include handles 75 so that it can be easily transported between an oven and a hydraulic press. The bottom cap 72 can include a recess 76 sized to receive the center pin 73. The hollow top cap 77 can include a hole or recess that can be sized to receive the center pin 73. The center pin 73 can be sized to fit in the recess 76, within the inner radius of annular base blank, and within the hole or recess in the hollow top cap 77. The mold 71, the bottom cap 72, and the hollow top cap 77 can be composed of steel or other suitable material that is thick enough to maintain its shape without deforming while the mold system is in the press.

FIG. 8 illustrates an embodiment of a molding system for compression molding a journal bearing pad assembly, such as journal bearing pad assembly 22 as described in FIG. 2. The molding system can include a mold 81, a bottom cap 82, a center pin 85, and a hollow top cap 86. The mold 81 can be hollow, and can be sized and shaped to receive an annular journal bearing base blank. The journal bearing base blank can include a base portion, a tang array, and optionally an intermediate layer. The mold 81 can also include handles 84 so that the system can be easily transported between an oven and a hydraulic press. The bottom cap 82 can include a recess 87 sized to receive the center pin 85. The hollow top cap 86 can include a hole or recess that can also be sized to receive the center pin 85. The center pin 85 can further be sized to fit in the recess 87, within an inner radius of the journal bearing base blank, and within the hole or recess in hollow top cap 86. The radius of the center pin 85 can in some cases be substantially smaller than the inner radius of the journal bearing base blank to leave space for the coating portion. The mold 81, bottom cap 82, and hollow top cap 86 can be composed of steel or any other suitable material that is thick enough to maintain its shape without deforming while the mold system is in the oven.

Hot-Press Molding the Coating Portion onto the Tang Array and Base Portion

In some cases, bearing pad assemblies can be manufactured through a molding process referred to herein as hot-press molding. This process can include melting the coating portion at high temperature in an oven and then applying high pressures on the molten coating portion, via a hydraulic press, to press the coating portion onto the tang array and base portion. In some cases, the coating portion can be coupled to the tang array and base portion of the bearing pad assembly without melting completely. Thus, the hot-press can in some cases be a simple and resource-efficient method for manufacturing the bearing pad assemblies described herein.

FIG. 9 illustrates a hot-press system for implementing a hot-press method. The hot-press system can include a top plate 91 and a bottom plate 92.

The bottom plate 92 can be sized and shaped to receive a bearing base blank. Further, the bottom plate 92 can be configured with a heating element for heating the bottom plate 92 to a predefined temperature. For example, FIG. 9 illustrates the bottom plate 92 with a set of electrical conductors along with resistors, which can heat the bottom plate 92.

A bearing base blank can be placed on a surface of the bottom plate 92. The bearing base blank can include a base portion, a tang array, and optionally an intermediate layer. Further, a coating portion sheet can be placed on top of the bearing base blank. The coating portion sheet can be in a solid phase, and thus can rest on top of the bearing base blank. The top plate 91 can be sized and shaped to contact an exposed surface (e.g., a surface not contacting the base blank) of the coating portion sheet. Further, the top plate 91 can be configured to apply pressure to the coating portion and base blank. For example, the top plate 91 or bottom plate can be coupled to an actuator for moving the plates proximally towards each other.

The heating element of the bottom plate 92 can be activated to increase the temperature of the bottom plate 92. As the temperature of the bottom plate 92 increases, thermal conductivity and/or radiation can increase the temperature of the coating portion sheet. The increase in temperature can soften (e.g., initiating a phase change of) the coating portion sheet, thereby allowing (e.g., due to the applied pressure of the top plate 91) the tangs of the base blank to penetrate or interlock with the coating portion sheet. Subsequently, the temperature of the bottom plate 92 can be decreased (e.g., back to room temperature), and the pressure can be decreased from the top plate 91. This can allow for the coating portion sheet to harden (e.g., reverse the phase change), thereby providing a structural bond between the coating portion sheet and the base blank.

Compression Molding Method

FIG. 10 depicts a flow diagram for compression molding a bearing pad assembly according to embodiments of the claimed invention. Compression molding can include: preparing the base blank 1001, positioning the base blank in the mold 1002, inserting the center pin 1003, filling the mold with coating portion material 1004, closing the mold 1005, compacting the cover material 1006, heating the mold system 1007, compressing the heated cover material 1008, cooling the molding system 1009, disassembling the molding system 1010, annealing the blank 1011, and cutting the blank 1012.

Preparing the base blank 1001 can include preparing a base blank as described above with reference to the thrust bearing pad assemblies and journal bearing pad assemblies.

Preparing the base blank 1001 may include bonding an intermediary layer having a tang array to a base portion. Preparing the base blank 1001 can alternatively include forming a tang array on the base portion by repeatedly using a texturing tool with a knife to strike the base portions. Preparing the base blank 1001 can further include spraying portions of the surface of the base blank that are not intended to be covered with the coating portion with a release agent for easier removal of those parts from the mold. The mold can also be sprayed with release agent to prevent the cover material from bonding to the mold and to further facilitate the release of the base blank from the mold.

Positioning the base blank 1002 can include positioning the base blank within the mold, and securing the base blank in place by securing a bottom cap to the mold. Inserting the center pin 1003 can be an optional step used for mold systems that include an annular blank, and may include inserting the center pin through the annular blank and into a recess in the bottom cap.

Filling the mold with coating portion material 1004 can include filling the mold with sufficient coating portion material to form a bearing pad assembly. As discussed above, the coating portion material is preferably a thermoplastic material, such as PEEK. In some embodiments, the coating portion material can be composed of approximately 70% pure PEEK, and approximately 30 % fillers. For example the mold can be filled with a mixture that is 70% PEEK, 10 % PTFE, 10% graphite, and 10% carbon fibers. Other fillers can be used with the disclosed concepts, and any suitable ratio of PEEK and fillers, or any other suitable thermoplastic materials can be used.

Closing the mold 1005 can include positioning a top cap onto the mold, and ensuring that a retaining pin, if present, is aligned with the hole or recess in the top cap. Compacting the cover material 1006 can include placing the mold in a hydraulic press, and using the hydraulic press to apply a force to the top cap. The hydraulic press can exert a force sufficient to apply a pressure (e.g., of approximately 5000 psi (34.5 MPa)) to the interior of the mold. Any suitable compacting pressure can be used in compacting the cover material 1006. Heating the mold system 1007 can include placing the mold in an oven and heating the mold to a desired temperature. The mold can be heated to a temperature of approximately 800° F (427° C), which is slightly higher than the melting point of PEEK, or to any other suitable temperature.

Compressing the heated cover material 1008 can include moving the molding system to the hydraulic press, and using the hydraulic press to apply a force to the top cap. The hydraulic press can apply a force sufficient to create an internal pressure (e.g., of approximately 2000- 5000 psi (13.8-34.5 MPa)) within the mold. This force can assist in pressing the molten cover material into the tang array on the base blanks, thereby strengthening the bond between the cover material and the tang array, and improving the structural strength of the bearing pad assembly.

Cooling the molding system 1009 can include placing the mold system in a temperature- controlled environment. The temperature controlled environment can be kept at room temperature or at any other suitable temperature. Disassembling the molding system 1010 can include removing the top cap and bottom cap from the mold, and subsequently removing the base blank and its coupled coating portion from the mold. Annealing the blank 1011 can include placing the base blank in an oven and annealing the base blank at 400° F (204° C), which in some cases can release internal stresses in the base blank.

Cutting the blank 1012 can include cutting a disc blank into a desired bearing pad assembly shape, such as the trapezoidal shape with curved edges on the inner and outer diameter, as illustrated in FIG. 17. In some cases, annular blanks can be cut radially to form multiple blanks, as illustrated in FIGS. 12 - 14. Accordingly, thrust bearing pad assemblies and journal bearing pad assemblies can be cut into the desired shape.

FIG. 11 illustrates a flow diagram for a hot-press method for manufacturing bearing pad assemblies according to an embodiment of the claimed invention. The hot-press method can include: preparing a preformed sheet of cover material 1101, heating the preformed sheet over a base blank 1102, compressing the preformed sheet and base blank 1103, cooling the blank 1104, and cutting the blank 1105.

Preparing the preformed sheet of cover material 1101 can include manufacturing or obtaining a commercially available preformed sheet of cover material. For example, preformed sheets of thermoplastic material, such as a PEEK sheet of desired size can be obtained. The PEEK sheet can be commercially available by various plastics manufacturers in the varying sizes and thicknesses, and with various configurations of PEEK-to-filler ratios. Preparing the preformed sheet of cover material can further include cutting the sheet of cover material to a similar, (e.g., slightly larger) shape than the base blank.

Heating the preformed sheet over a base blank 1102 can include placing the prepared sheet of cover material over the base blank and placing both in an oven, such as the hot-press system discussed in FIG. 9. The base blank and sheet of cover material can be heated up to a suitable temperature (e.g., less than the melting temperature of the coating portion sheet). For example, for a PEEK cover material, the combination of the base blank and the prepared PEEK sheet can be heated to approximately 500° F (260° C), which is over the glass transition temperature of PEEK material but below its melting point, such that PEEK does not melt but becomes rubbery. Excess cover material from the cover material sheet can be machined off. Compressing the preformed sheet and base blank 1103 can include placing the combined cover material sheet and base blank onto a base plate of a hot-press system such that the cover material sheet is adjacent to the base plate. In some cases, a hydraulic press, or other suitable machinery can be used to apply a force onto the bottom of the base blank to push its tang array into the softened cover material. A top plate can be used to provide uniform pressure to the base blank. The force can be applied at the interfaces where there is contact between the base blank and the cover material sheet. For example, a 3 inch (76.2 mm) bearing pad assembly bonded through the hot-press method with a PEEK cover material sheet can be bonded with a pressure of around 100 psi (.69 MPa). The top plate can further include heaters to keep the base blank heated while compressing the preformed sheet and base blank. For example, for PEEK cover material, the top plate can keep the base blank at approximately 650° F (343° C) during this process.

Cooling the blank 1104 can include placing the resulting compressed cover material sheet and base blank in a temperature-controlled environment. The temperature-controlled environment may be kept at room temperature or at any other suitable temperature.

Cutting the blank 1105 can include cutting a bearing pad assembly blank into the desired bearing pad shape, such as the trapezoidal shape with curved edges on the inner and outer diameter as discussed below with respect to FIG. 17. Alternatively, the bearing pad assembly blank can be radially to form multiple blanks, as illustrated in FIGS. 15, 16, and 18.

EQUIVALENTS

Although preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

INCORPORATION BY REFERENCE

The entire contents of all patents, published patent applications, and other references cited herein are hereby expressly incorporated herein in their entireties by reference.