WO2018112368A1

WO2018112368A1 - Non-walking bushing, and method of forming same

Info

Publication number: WO2018112368A1
Application number: PCT/US2017/066718
Authority: WO
Inventors: Yoshihiro Murakami
Original assignee: Polygon (Hong Kong) Ltd.
Priority date: 2016-12-15
Filing date: 2017-12-15
Publication date: 2018-06-21

Abstract

A bushing to reside between an outer housing and an inner rotatable member, and a method of forming the bushing, the bushing including an inner layer configured to contact the inner rotatable member, and an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing, wherein the outer layer comprises epoxy and metal particulates configured such that the outer layer has a coefficient of friction (COF) with a higher value than a COF of the inner layer.

Description

NON- WALKING BUSHING, AND METHOD OF FORMING SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Patent

Application Serial Number 62/498,099, filed on December 15, 2016, which is incorporated herein in its entirety by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0002] Not Applicable.

FIELD OF INVENTION

[0003] The present invention pertains generally to a mechanical bushing, and, more particularly, to a non-walking bushing that resists rotation and drift in an axial direction.

BACKGROUND

[0004] As known in the art a bushing is a bearing that is inserted into a housing or similar aperture to provide a bearing surface for a rotary application, such as a mechanical member that extends through the axis of the bushing and rotates in a continuous or reciprocal manner. Composite and/or plastic bushings, developed in the 20^th century, have been known in the art and used for some time. Most of the usage of these bushings are for mechanical operation under relatively light loading conditions.

[0005] Recently, the development of new materials has added to the strength of such bushings, and therefore operational conditions have become heavier than previously known or undertaken. The structure of plastic or composite bushings has been improved by some measure in strength by using glass fiber windings in the bushing materials. However, composite and/or plastic bushings suffer many drawbacks that hinder the mechanical application of these bushings due to the bushings rotating in the housing bores in which the bushings are situated, and/or "walking" out from the housing bores when used in relatively higher loading conditions. Another drawback is the heavy edge loading due to the cantilevered circumstances resulting from the walking of the bushing, which can destroy the structure of the bushing.

[0006] The composite or plastic bushing's innermost layer's coefficient of friction

(COF) against a shaft (pin) material has been conventionally improved by adding a coating or using liners which lower the friction, and such an improvement helps the composite or plastic bushings stay in place in the housing bore somewhat, but is still very limited in success when dealing with higher load conditions. Also, the glass fiber wound into the backing layer has increased the repeated fatigue resistance of the bushing to prevent the structures from being destroyed by the higher loading impacts. However, there still exists a need for improved fatigue resistance, as well as a need for preventing the walking action of the bushings during mechanical operation.

BRIEF SUMMARY

[0007] According to various example embodiments of the present general inventive concept, a bushing, and a method of forming the bushing, is provided in which an outer layer of the bushing has a higher coefficient of friction than that of a layer formed inward from the outer layer, such that "walking" of the bushing is inhibited during mechanical operation.

[0008] Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the present general inventive concept.

[0009] The foregoing and/or other aspects and advantages of the present general inventive concept may be achieved by a bushing configured to reside between an outer housing and an inner rotatable member, the bushing including an inner layer configured to contact the inner rotatable member, and an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing, wherein the outer layer comprises epoxy and metal particulates configured such that the outer layer has a coefficient of friction (COF) with a higher value than a COF of the inner layer. [0010] The foregoing and/or other aspects and advantages of the present general inventive concept may also be achieved by a method of forming a bushing to reside between an outer housing and an inner rotatable member, the method including forming an inner layer configured to contact the inner rotatable member, and forming an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing, wherein the forming of the outer layer includes adding metal particulates to an epoxy such that the outer layer has a coefficient of friction (COF) with a higher value than a COF of the inner layer.

[0011] Other features and aspects may be apparent from the following detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE FIGURES

[0012] The following example embodiments are representative of example techniques and structures designed to carry out the objects of the present general inventive concept, but the present general inventive concept is not limited to these example embodiments. In the accompanying drawings and illustrations, the sizes and relative sizes, shapes, and qualities of lines, entities, and regions may be exaggerated for clarity. Photographs of example embodiments of materials formed according to example embodiments of the present general inventive concept are provided, but do not limit the scope of the inventive concept to those embodiments pictured. A wide variety of additional embodiments will be more readily understood and appreciated through the following detailed description of the example embodiments, with reference to the accompanying drawings in which:

FIG. 1 illustrates a perspective view of a bushing according to an example embodiment of the present general inventive concept;

FIGS. 2A-2B illustrate a cross section of the bushing of FIG. 1;

FIG. 3 is a photograph of a testing piece material including an epoxy mixed with glass fibers; FIG. 4 is a photograph of a testing piece material including an epoxy mixed with aluminum fibers according to an example embodiment of the present general inventive concept;

FIGS. 5A-5B illustrate a friction test and comparison performed with the materials photographed in in FIGS. 3-4; and

FIG. 7 is a flow chart illustrating a method of forming a bushing according to an example embodiment of the present general inventive concept.

DETAILED DESCRIPTION

[0013] Reference will now be made to the example embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings and illustrations. The example embodiments are described herein in order to explain the present general inventive concept by referring to the figures.

[0014] The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the structures and fabrication techniques described herein. Accordingly, various changes, modification, and equivalents of the structures and fabrication techniques described herein will be suggested to those of ordinary skill in the art. The progression of fabrication operations described are merely examples, however, and the sequence type of operations is not limited to that set forth herein and may be changed as is known in the art, with the exception of operations necessarily occurring in a certain order. Also, description of well-known functions and constructions may be simplified and/or omitted for increased clarity and conciseness. The descriptions herein do not limit the present general inventive concept to any of the specific embodiments illustrated by the drawings or descriptions themselves.

[0015] Note that spatially relative terms, such as "up," "down," "right," "left,"

"beneath," "below," "lower," "above," "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over or rotated, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted

accordingly.

[0016] According to various example embodiments of the present general inventive concept, a novel non-walking bushing, and a method of providing the non-walking bushing, is provided so as to have at least two layers in a radial direction, at least the outer layer being provided with one or more materials having a high coefficient of friction (COF) that is not provided in at least the inner-most layer of the bushing. Such a high COF on the outermost layer of the bushing inhibits movement of the bushing relative to the housing or otherwise structure in which the bushing is provided, while maintaining the lower COF on one or more layers inward from the outermost layer so as not to inhibit the movement of the mechanical body designed to move within the bushing. As previously discussed, the undesirable movement of the bushing relative to the bushing's housing may be referred to as "walking," and could result in the bushing becoming completely displaced from the housing. Thus, increasing the COF to inhibit movement of the bushing relative to the housing contributes to a more desirable "non-walking" bushing. It will be understood that other example embodiments of the present general inventive concept may provide the higher COF on the innermost layer of the bushing for other application such as, for example, an application in which the body housing the bushing is configured to rotate or otherwise move, and wherein it may be beneficial to have the movement of the bushing fixed relative to the body located inside the bushing.

[0017] Example embodiments of the present general inventive concept may provide valuable improvements in the inhibition of the walking bushing phenomenon in the use of composite and/or plastic bushings in pivot points of mechanical equipment. For proper mechanical operation, the bushing needs to stay in the same position in the housing bore. One method to prevent a walking bushing is to increase the interference of the outer diameter of the bushing and the inner diameter of the housing bore, or to decrease friction at the contact points of the inner surface of the bushing and the outer surface of the shaft (pin) so that the coefficient of friction (COE) of the shaft and bushing shall be smaller than that of the bushing and housing bore. Various example embodiments of the present general inventive concept increase the friction forces of the face contact area at the outer diameter of the bushing and the inner diameter of the housing bore. Various example embodiments provide a bushing structure with multiple layers, wherein the inner layer and a reinforcement layer (backing layer) can be made by conventional methods such as using a smooth liner or special coating at the inner surface of the bushing. In other various example embodiments, a special low friction material may be used as the inner layer of the bushing while a reinforcement layer can use existing methods such as fiberglass reinforced thermoset plastics. Various example embodiments of the present general inventive concept may add another outer layer, or modify a reinforcement layer, by winding or otherwise adding, imbedding, etc., metal particulates to the outer layer to increase the friction of the surface of the outer diameter of the bushing and the surface of the inner diameter of the housing bore. The metal particulates may be added to the outer layer by a number of methods, using a number of materials, such as, for example, winding the layer with plastic impregnated metal fiber, adding plastic impregnated with short length metal fiber, adding metal powder to an epoxy, and so on.

[0018] FIG. 1 illustrates a perspective view of a bushing according to an example embodiment of the present general inventive concept. The bushing 10 is of a conventional length and diameter, and is offered simply to show a perspective of a typical bushing. While the layers configured according to the present general inventive concept are not indicated in FIG. 1, it is understood that the different layers as described herein are provided. Example embodiments of the present general inventive concept are not limited by any of the dimensions illustrated in FIG. 1 or any of the remaining drawings/photographs.

[0019] FIGS. 2A-2B illustrate a cross section of the bushing of FIG. 1. The example embodiment of the bushing 10 illustrated in FIGS. 2A-2B includes an inner layer 40 provided at the inner surface of the bushing 10 to contact a rotatable member residing therein, an outer layer 20 provided at the outer surface of the bushing 10 to contact an outer housing in which the bushing resides, and a middle or backing layer 30 provided between the inner layer 40 and outer layer 20 to reinforce the bushing 10 between those layers. Other various example embodiments of the present general inventive concept may provide more or fewer layers, and in different configurations, without departing from the scope of the present general inventive concept. In the example embodiment illustrated in FIGS. 2A-2B, the outer layer 20 is an epoxy layer containing short metal fiber, the middle layer 30 is an epoxy layer containing glass fiber, and the inner layer 40 includes polytetrafluoroethylene (PTFE). The PTFE may be provided to the inner layer 40 in a number of ways, such as by mixing with an epoxy or coated on an epoxy. In various example embodiments, a PTFE coating itself may be considered the inner layer 40 of the bushing. Also, in various example embodiments the middle and inner layer may be combined to form one layer, the middle and outer layer may be combined to form one layer, and so on. The present general inventive concept provides the addition of metal particulates to the outermost layer that contacts the housing, and some example embodiments may simply have the metal particulates provided throughout the bushing to form the outermost layer, with a coating of PTFE on the inner diameter of the bushing to provide the innermost layer.

[0020] In the example embodiment illustrated in FIGS. 2A-2B, the outer layer 20 is made of a cured epoxy containing aluminum fiber. However, various example embodiments of the present general inventive concept may employ other metals, or combinations of metals, such as, for example, tungsten, copper, iron, brass, and so on. These and other metals and/or combinations of metals may be used in addition to, or in place of, the aluminum fiber. The metal particulates may be in long or short fiber form, powder, etc. The metal particulates may be added at various times during the process of forming the material of the layer, and may be somewhat uniform throughout the outer layer, or concentrated near the outer perimeter of the outer layer. In various example embodiments in which aluminum fiber is contained in the epoxy, the aluminum fiber may be added to the liquid epoxy during the manufacturing process before the epoxy is cured. This outer layer is the key to holding the bushing in the housing bore and staying at the same position due to the increased COF of the metal infused outer layer abutting the steel or other housing material. In the example embodiment illustrated in FIGS. 2A-2B, the middle layer 30 serves as the backing layer to reinforce the structure, and is made of epoxy with wound glass fiber. The inner layer 40 is the thrusting layer made of PTFE lining or coating, or an epoxy with an imbedded PTFE, or the like. As previously described, in various example embodiments the outer layer 20 and middle layer 30 may also be combined into one outer layer by the manufacturing process, such as by adding aluminum fiber to the glass fiber winding surface of the bushing while the liquid epoxy is impregnated with the glass fiber. [0021] FIG. 3 is a photograph of a testing piece material including an epoxy mixed with glass fibers. The testing piece photographed in FIG. 3 is an epoxy to which glass fiber has been added, which represents a conventional bushing. FIG. 4 is a photograph of a testing piece material including an epoxy mixed with aluminum fibers according to an example embodiment of the present general inventive concept. The testing piece photographed in FIG. 4 is an epoxy to which aluminum fiber has been added, which represents the outer layer of a bushing according to an example embodiment of the present general inventive concept. These testing pieces, i.e., an epoxy block 50 containing glass fiber and an epoxy block 80 containing aluminum fiber and glass fiber, were formed to perform a comparison bench test which is described in relation to FIGS. 5A-5B.

[0022] FIGS. 5A-5B illustrate a friction test and comparison performed with the materials photographed in in FIGS. 3-4. In the testing illustrated in FIGS. 5A-5B, one end of a testing bench 60 was rotated away from a flat surface 70 upon which it rested until a testing block resting on the testing bench overcame the friction that held it in place and began to slide downward. As illustrated in FIG. 5A, the epoxy block 50 containing only the glass fiber began to slide downward when the bench 60 was rotated to a position of 19.2 degrees from the flat surface 70. By comparison, as illustrated in FIG. 5B, the epoxy block 80 containing aluminum fiber and glass fiber did not begin to slide downward until the bench 60 was rotated to a position of 26.4 degrees from the flat surface 70. Therefore, it is shown that the COF of the epoxy block 80 is increased after adding aluminum fiber to the epoxy. FIG. 5A illustrates the epoxy block 50 with glass fiber moving down the test bench 60 at 19.2 degrees and an arctangent of approximately 0.34, and FIG. 5B illustrates the epoxy block 80 with glass fiber and aluminum fiber moving down the test bench 60 at 26.4 degrees and an arctangent of approximately 0.46. Static friction forces may be calculated by the formula Ρ=μΝ, where F is the static friction force, μ is the COF, and N is the normal vertical force to the sliding slope. The arctangent represents the static COF, and the result of the test shows that the epoxy block 80 with the added aluminum fiber has an approximately 35% increase of static friction compared to the epoxy block 50 without the aluminum fiber. Thus, an example embodiment of the present general inventive concept with such an outer layer structure may increase the thrusting resistance by approximately 35%. This resistance directly affects the holding force of the bushing and inhibits the bushing from rotating in the housing bore and walking out from the housing bore. The percentage of increase may be changed by the amount of metal particulates added to the epoxy, and/or by the type of metal particulates. In various example embodiments, an epoxy with metal particulates will have a minimum of 25% increased static COF compared to an epoxy with only glass fiber.

[0023] FIG. 6 is a flow chart illustrating a method of forming a bushing according to an example embodiment of the present general inventive concept. It is understood that the numerical identifiers of the operations shown in FIG. 6 are provided merely to aid in the visual representation of the operations, but the operations are not limited to any order. Also, various example embodiments of the present general inventive concept may have more or fewer operations, in different combinations and/or sequences, and so on. In operation 610 of the example embodiment illustrated in FIG. 6 a first layer material is produced by adding glass fiber to an epoxy. In operation 620 a second layer material is produced by adding metal particulates to an epoxy. In operation 630 the first layer material is formed into an inner annular layer of the bushing. In operation 640 the inner-most surface of the inner annular layer is coated with PTFE. In operation 650 the second layer material is formed onto the outer-most surface of the inner annular layer to form an outer annular layer of the bushing. Thus, a bushing is produced in which metal particulates are provided in an outer layer that contacts a housing such that the friction between the bushing and the housing is increased.

[0024] It is understood that the operations shown in FIG. 6 are merely one example embodiment of a method of forming a bushing according to the present general inventive concept. As previously described, in various example embodiments one or more layers may exist between the inner-most and outer-most layer. In various example embodiments glass fiber may only be added to layers other than the inner-most layer, and/or may be added to the outer layer along with the metal particulates. In various example embodiments a metal powder may be added to the outer layer rather than, or in combination with, metal particulates. In various example embodiments, the inner-most layer is simply a coating of PTFE. Similarly, in various example embodiments of the present general inventive concept the operations may not be as delineated as shown in the example embodiment illustrated in FIG. 6. In various example embodiments, rather than producing different materials, the epoxy or other base material may be formed continuously in a direction away from the innermost surface, and at some point a glass fiber winding may be introduced to the epoxy, and at a later point a metallic winding or powder may be introduced to the epoxy either along with or in place of the glass fiber. Various other operations and structures may be employed in the process according to sound engineering judgment.

[0025] Various example embodiments of the present general inventive concept provide a non-walking bushing made of composite and/or plastics and having at lest two layers, the outer layer being wound with plastic impregnated metal fiber or impregnated with short length metal fiber or other fiber or its powder so as to have a high COF against the housing material, so that the bushing structure stops the bushing from rotating and/or walking out of the housing bore. Various example embodiments of the present general inventive concept provide a production method to increase the COF by mixing a material having a higher COF into the liquid plastic material of a bushing, or by adding such material on the outer surface of the bushing before curing the liquid plastic during the structure building process.

[0026] Various example embodiments of the present general inventive concept may provide a bushing to reside between an outer housing and an inner rotatable member, the bushing including an inner layer configured to contact the inner rotatable member, and an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing, wherein the outer layer comprises epoxy and metal particulates configured such that the outer layer has a COF with a higher value than a COF of the inner layer. The metal particulates may include at least one of aluminum, tungsten, copper, iron, brass, or any combination thereof. The metal particulates may be in fiber or powder form. The bushing may further include at least one middle layer formed between the inner and outer layers, the middle layer being configured to reinforce the bushing. The middle layer may include epoxy and glass fiber. The COF of the outer layer may be at least 25% higher than a COF of the middle layer. The COF of the outer layer may be at least 35% higher than the COF of the middle layer. The inner layer may include or be coated with PTFE. The inner layer may include epoxy and glass fiber, and may be coated with PTFE. The outer layer may include epoxy, aluminum fiber, and glass fiber.

[0027] Various example embodiments of the present general inventive concept may provide a method of forming a bushing to reside between an outer housing and an inner rotatable member, the method including forming an inner layer configured to contact the inner rotatable member, and forming an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing, wherein the forming of the outer layer includes adding metal particulates to an epoxy such that the outer layer has a COF with a higher value than a COF of the inner layer. The metal particulates may include at least one of aluminum, tungsten, copper, iron, brass, or any combination thereof. The metal particulates may be in fiber or powder form. The method may further include forming at least one middle layer formed between the inner and outer layers to reinforce the bushing. The inner layer may be a coating of PTFE formed on the middle layer. The middle layer may include epoxy and glass fiber. The forming of the outer layer may include adding an amount of the metal particulates such that the COF of the outer layer is at least 25% higher than a COF of the middle layer. The outer layer may include glass fiber along with the epoxy and metal particulates. The inner layer may include epoxy and glass fiber, and is coated with PTFE.

[0028] Numerous variations, modifications, and additional embodiments are possible, and accordingly, all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the present general inventive concept. For example, regardless of the content of any portion of this application, unless clearly specified to the contrary, there is no requirement for the inclusion in any claim herein or of any application claiming priority hereto of any particular described or illustrated activity or element, any particular sequence of such activities, or any particular interrelationship of such elements. Moreover, any activity can be repeated, any activity can be performed by multiple entities, and/or any element can be duplicated.

[0029] It is noted that the simplified diagrams and drawings included in the present application do not illustrate all the various connections and assemblies of the various components, however, those skilled in the art will understand how to implement such connections and assemblies, based on the illustrated components, figures, and descriptions provided herein, using sound engineering judgment. Numerous variations, modification, and additional embodiments are possible, and, accordingly, all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the present general inventive concept. [0030] While the present general inventive concept has been illustrated by description of several example embodiments, and while the illustrative embodiments have been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the general inventive concept to such descriptions and illustrations. Instead, the descriptions, drawings, and claims herein are to be regarded as illustrative in nature, and not as restrictive, and additional embodiments will readily appear to those skilled in the art upon reading the above description and drawings. Additional modifications will readily appear to those skilled in the art. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.

Claims

1. A bushing to reside between an outer housing and an inner rotatable member, the bushing comprising:

an inner layer configured to contact the inner rotatable member; and

an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing;

wherein the outer layer comprises epoxy and metal particulates configured such that the outer layer has a coefficient of friction (COF) with a higher value than a COF of the inner layer.

2. The bushing of claim 1, wherein the metal particulates include at least one of aluminum, tungsten, copper, iron, brass, or any combination thereof.

3. The bushing of claim 2, wherein the metal particulates are in fiber or powder form.

4. The bushing of claim 1, further comprising at least one middle layer formed between the inner and outer layers, the middle layer being configured to reinforce the bushing.

5. The bushing of claim 4, wherein the middle layer comprises epoxy and glass fiber.

6. The bushing of claim 5, wherein the COF of the outer layer is at least 25% higher than a COF of the middle layer.

7. The bushing of claim 6, wherein the COF of the outer layer is at least 35% higher than the COF of the middle layer.

8. The bushing of claim 1, wherein the inner layer comprises polytetrafluoroethylene (PTFE).

9. The bushing of claim 1, wherein the inner layer is coated with

polytetrafluoroethylene (PTFE).

10. The bushing of claim 9, wherein the inner layer comprises epoxy and glass fiber, and is coated with PTFE.

1 1. The bushing of claim 1 , wherein the outer layer comprises epoxy, aluminum fiber, and glass fiber.

12. A method of forming a bushing to reside between an outer housing and an inner rotatable member, the method comprising:

forming an inner layer configured to contact the inner rotatable member; and forming an outer layer configured to reside in a receiving portion of the outer housing and to contact the outer housing;

wherein the forming of the outer layer includes adding metal particulates to an epoxy such that the outer layer has a coefficient of friction (COF) with a higher value than a COF of the inner layer.

13. The method of claim 12, wherein the metal particulates include at least one of aluminum, tungsten, copper, iron, brass, or any combination thereof.

14. The method of claim 13, wherein the metal particulates are in fiber or powder form.

15. The method of claim 12, further including forming at least one middle layer formed between the inner and outer layers to reinforce the bushing.

16. The method of claim 15, wherein the inner layer is a coating of

polytetrafluoroethylene (PTFE) formed on the middle layer.

17. The method of claim 15, wherein the middle layer comprises epoxy and glass fiber.

18. The method of claim 17, wherein the forming of the outer layer includes adding an amount of the metal particlulates such that the COF of the outer layer is at least 25% higher than a COF of the middle layer.

19. The method of claim 12, wherein the outer layer comprises glass fiber along with the epoxy and metal particulates.

20. The method of claim 12, wherein the inner layer comprises epoxy and glass fiber, and is coated with polytetrafluoroethylene (PTFE).