Self-lubricating bushings, bearings and bearing assemblies

Self-lubricating bushings and bearings that include lubricant inserts that have central axes that are aligned substantially parallel to the central axes of their respective bushings or bearings. The lubricant inserts present a side edge that is substantially flush with the corresponding bearing surface of the bushing or bearing. The exposed edges of the inserts can extend to the longitudinal edges of the bearing surface of the bushing or bearing. The bearings and bushing can be incorporated into bearing assemblies.

TECHNICAL FIELD

The present invention relates to self-lubricating bushings, bearings and bearing assemblies. More particularly, the present invention relates to self-lubricating bushings and bearings that incorporate solid lubricant materials therein in such a way that allows for reduced dimensions of the bushings and bearings and improved performance characteristics as compared to conventional bushing and bearing configurations.

BACKGROUND ART

Bearings are used to reduce frictional forces between two or more parts that are configured and designed to have relative motion and provide support therebetween. In general, bearings can be classified as sliding bearings in which the bearing elements are separated by a film of lubricant and rolling element bearings in which ball bearings, roller bearings, needle bearings, and the like are provided between the moving parts.

Slide-type bearings include all varieties of bearings in which the primary motion involves sliding one surface over or against another. Accordingly, all types of journal or sleeve bearings which are used to position a shaft or movable part in a radial direction are slide-type bearings. Moreover, all types of thrust bearings, which are used in general to prevent movement of a rotating shaft in an axial direction and as guides for linear motion of various types are also slide-type bearings.

Conventional bearings require a lubricant such as a grease or oil that is often periodically applied between the bearing surfaces, i.e., the surfaces of the bearing elements and any surface that are opposed and moved relative to the bearing elements.

A significant improvement over conventional bearings was the development of self-lubricating bearings which incorporate lubricant materials or compositions into the bearing design so that a layer of lubricant is provided and maintained between the bearing surfaces.

Self-lubricating bearings are particularly useful in extreme environments where temperature extremes can degrade conventional lubricants or adversely affect their performance. Self-lubricating bearings also can be used in applications in which conventional lubricants may present an undesirable contamination such as for example in food, textile, drug, pollution control, printing applications, etc. In other applications in which conventional lubricants can adversely react chemically, such as in chemical processing and plating equipment, self-lubricating bearings idea.

A common self-lubricating bearing design includes a bearing structure that is provided with pockets or cavities in the bearing surface into which a lubricating component such as graphite is held. In use, a thin layer of the lubricating component is distributed from the pockets or cavities between the bearing surfaces.

Conventional materials from which self-lubricating bearings are made include copper alloys such as bronze, aluminum bronze, manganese bronze and hardened steel and steel-backed copper alloy structures.

Conventional solid lubricants that are used in self-lubricating bearings include amorphous graphite, polyimide graphite fiber reinforced composites, and molybdenum disulfide.

The present invention is directed to self-lubricating bushings, bearings and bearing assemblies that include unique configurations of solid lubricant inserts.

DISCLOSURE OF THE INVENTION

According to various features, characteristics and embodiments of the present invention which will become apparent as the description thereof proceeds, the present invention provides a self-lubricating bushing that includes:

a main body that has a generally cylindrical shape defined by an annular wall having an inner surface and an outer surface and a central axis; and

a plurality of elongated lubricant inserts that have a central axis

said lubricant inserts being provided in bores formed in the main body and aligned so that side edge portions of the lubricant inserts are substantially flush with at least one of the inner surface and the outer surface of the annular wall of the main body.

The present invention also provides a bearing assembly which includes:

an outer bushing having a main body portion that has a generally cylindrical shape defined by an annular wall having an inner surface and an outer surface and a central axis;

an inner bushing having a main body portion that has a generally cylindrical shape defined by an annular wall having an inner surface and an outer surface and a central axis, said inner bushing being configured to be received within the outer bushing so that the outer surface of the inner bushing is opposed to the inner surface of the outer bushing; and

a plurality of elongated lubricant inserts that have central axes, and are provided in bores formed in at least one of: i) the main body of the outer bushing and aligned so that side edge portions of the lubricant inserts are substantially flush with the inner surface of the main body of the outer bushing; and ii) the main body of the inner bushing and aligned so that side edge portions of the lubricant inserts are substantially flush with the outer surface of the main body of the inner bushing.

Whether the bushings are provided alone or in a bearing assembly, the central axes of the lubricant inserts are substantially parallel to the central axis of the main body of the bushings and the side edge portions of the lubricant inserts that are substantially flush with the inner wall of the main body of the bushings comprise edge portions that extend along the entire length of the lubricant inserts.

The main body of the bushings and the plurality of lubricant inserts can have lengths that are substantially equal. Otherwise, the main body of the bushings can have a length that is greater than the length of the plurality of lubricant inserts. In one embodiment the length of the plurality of lubricant inserts is about half of the length of the main body of the bushings and the plurality of lubricant inserts alternatively extend inward from opposite ends of the main body of the bushings.

The lubricant inserts extend to at least one end of the main body of the bushings, and can extend to both ends of the main body of the bushings. The main body of the bushings can have a recess at one or both of the opposite ends.

The main body of the bushings has an inside diameter, IDb, the central axes of the plurality of lubricant inserts are aligned about common diameter CDiof the main body of the bushings that is greater that the inside diameter and each of the plurality of lubricant inserts has a radius Ri, wherein IDb<CDi<(IDb+2Ri)

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is directed to self-lubricating bushings and bearings that incorporate solid lubricant materials therein in such a way that allows for reduced dimensions of the bushings and bearings as compared to conventional bushing and bearing configurations. The bushings, bearings and bearing assemblies of the present invention include unique configurations of solid lubricant inserts which have central axes that can be aligned with the central axes of the bushings or bearings so as to be substantially parallel therewith. Alternatively, the central axes of the solid lubricant inserts can be skewed with respect to the central axes of the bushings or bearings and otherwise generally extend in the axial direction of the bushings or bearings (as opposed to the radial direction of the bushings or bearings).

The bushings and/or bearings are generally cylindrically shaped and can include stepped, grooved, flanged, recessed, or other shaped portions that may be useful to incorporate the bushings or bearings into bearing assemblies. The bushings or bearings can be made from any type of conventional bearing material including, but not limited to, copper alloys such as bronze, aluminum bronze, manganese bronze, brass, copper and hardened steel and steel-backed copper alloy structures.

The solid lubricants that are inserted into the bushing and bearings of the present invention can include any conventional solid lubricants that are used in self-lubricating bearings including, but not limited to, amorphous graphite, polyimide graphite fiber reinforced composite, molybdenum disulfide, etc.

The pockets into which the solid lubricants are inserted can be produced by drilling or machining the blank bushings and bearings.

The ability to reduce the dimensions of the bushings or bearings is achieved in part by the unique manner in which the solid lubricant can be position to extend completely to the edges of the bushings or bearings according to the present invention.

The bushings or bearings of the present invention, including bearing assemblies such as snap bearing designs provide for self-lubrication and resistance to high load/thrust, extreme temperatures and volatile environments at low rpm's.

FIGS. 1A-1Fare cross-sectional depictions of patterns in which sleeve-type bearings are conventionally drilled or formed with grooved patterns into which a solid lubricant is provided. In each ofFIGS. 1A-1Fthe solid lubricant that is embedded into the walls of the bearings is identified by reference number1.FIG. 1Adepicts a design in which the solid lubricant1is inserted into arrays of through-holes2that are provided, e.g. drilled, in the sides of the bearing at substantially right angles to the axis of the bearing.FIGS. 1B-1Fprovides various channel configurations into which the solid lubricant1is provided. InFIG. 1Ba single spiral shaped channel3is provided in the inner wall4of the bearing. InFIGS. 1C-1Evarious cross-helical shaped channels5are provided in the inner walls6of the bearings. InFIG. 1Fa plurality of parallel channels7are provided which are generally angled with respect to the central axis of the bearing.

FIGS. 1A-1Fare presented to show the present state of the art of oiless or self-lubricating bearings.

FIG. 2is a perspective view of a conventional self-lubricating bushing design. In typical fashion, the bushing depicted inFIG. 2includes holes10that are drilled though the sides11of the bushing12into which the solid lubricant material13is placed. As those skilled in the art of self-lubricating bearings are well familiar, the number, diameter and pattern of holes10are important to ensure that a thin layer of the lubricating material is spread between the bearing surfaces. As the length of the bushing12decreases it becomes increasingly difficult to provide sufficient hole configurations which will apply a thin layer of the lubricating material so that it spreads out between the bearing surfaces. This difficulty is compounded by trying to avoid structurally weakening the bushing by increasing the ratio of apertured to non-apertured surface area of the sides of the bushing12.

In order to provide self-lubricating bushings and bearings that can have short lengths, the inventors or the present invention conceived of a novel way to align and provide solid lubricant inserts into the bushings and bearings.

FIG. 3is a perspective view of a self-lubricating bushing design according to one embodiment of the present invention.FIG. 4is an end view of the bushing ofFIG. 3.FIG. 5is a sectional view of the bushing ofFIG. 4taken along section line5-5. The bushing14shown inFIGS. 3-5, has a generally cylindrical shaped body having an inner and outer diameter and a radial thickness. A plurality of holes15are drilled or machined in opposite ends of the bushing14so as to partially intersect the inner surface16of the bushing14as shown. The holes15have radial centers which are aligned along a common diameter of the bushing which is referred to herein as the center diameter of the inserts (CDi, SeeFIG. 13). The holes15are evenly spaced apart along the center diameter of the inserts with holes15in opposite ends of the bushing14being evenly off-set as depicted so that every other hole15around the circumference extends from an opposite end of the bushing14.

The holes15are filled with a solid lubricant using conventional techniques which will ensure that the resulting lubricant inserts17are held securely within the holes15. The holes15are aligned and configured so that an exposed edge of each lubricant insert17is substantially flush with the inner surface16of the bushing14so as to apply a thin film of lubricant between bearing surfaces when the bushing14is in use. In order to prevent the lubricant inserts17from being removed from the holes15in the radial direction, the following relationship can be followed: IDb<CDi<(IDb+2Ri), where IDbthe Inside Diameter of the bearing, Ri=the Radius of the inserts17(or holes15) and CDi=Center Diameter of the inserts. This relationship will help ensure that the lubricant inserts17will be physically or structurally secured within holes15. It is otherwise (or additionally) possible to rely upon chemical bonding to secure the lubricant inserts17in the holes15. It is also possible to provide non-circular holes15and complementary shaped non-cylindrical shaped lubricant inserts17which are configured to prevent the lubricant inserts17from being removed from the holes15in the radial direction. For example, the holes15and lubricant inserts17could include dove-tailed shapes, trapezoidal shapes, and other cooperative engaging shapes. It is also possible to use holes15and lubricant inserts17that do not have cooperative engaging shapes and rely upon chemical bonding to secure the lubricant inserts17from being removed from the holes15in the radial direction. For example, the holes15and lubricant inserts17could have complementary rectangular cross-sectional shapes.

In the embodiment of the self-lubricating bushing depicted inFIGS. 3-5, the lubricant inserts17extend at least about half of the length of the bearing14as best depicted inFIG. 5, so that, with the lubricant inserts17extending alternatively from opposites ends of the bearing14, their combined lengths provide a lubricant film that is applied across the entire inner surface of the bearing14.

FIG. 6is an end view of the bushing according to another embodiment of the present invention.FIG. 7is a sectional view of the bushing ofFIG. 6taken along section line7-7. The bearing20shown inFIGS. 6 and 7includes a plurality of lubricant inserts21that extend across the full length of the bearing20. Otherwise, this embodiment is similar to the embodiment depicted inFIGS. 3-5. The bearing design shown inFIGS. 6 and 7is not as mechanically strong as that ofFIGS. 3-5since the bearing14inFIGS. 3-5does not disrupt the inner surface16of the bearing14across the entire length of the inner wall, but instead staggers or alternates the holes15in which the solid lubricant inserts17are provided.

FIGS. 8-13which are discussed below are directed to a snap-ring bearing assembly that incorporates the bearing designs of the present invention. The bearing assembly is designed to perform well in extreme high/low temperature ranges where exposure to chemicals and/or debris is possible. The bearing assembly is also resistant to high loads and thrust. The design of the bearing assembly effects routing debris away from the wearing surface and embedding the debris into the lubricant, e.g. graphite, inserts, thereby making the bearing assembly resistant to dust and other foreign material.

FIG. 8is an exploded view of a bearing assembly according to one embodiment of the present invention. The bearing assembly includes an outer bushing30and an inner bushing31configured to be received in the outer bushing30, and a retainer32which secures the inner bushing31within the outer bushing30.

The inner bushing31has a generally cylindrical shape with a flange33extending radially outward on one end and an annular groove34provided in the outer wall35near the other end. The annular groove34is sized to receive the retainer32as discussed below.

The outer bushing30has a generally cylindrical shape with a first recess36on one end that is configured to receive retainer32therein and a second recess37(SeeFIG. 11) on the other end that is configured to receive the flange33of the inner bushing31as discussed below.

The outer bushing30includes a plurality of solid lubricant inserts39in the inner wall40thereof. In the embodiment shown inFIGS. 8-10the outer bushing30has a plurality of lubricant inserts39that are arranged in a manner similar to that shown and discussed in reference toFIGS. 2-5above. That is, the lubricant inserts39are arranged so as to extend alternatively from opposite ends of the outer bushing30and be exposed along the inner wall40thereof.

The retainer32can be a convention al snap-ring as shown, which is sized and configured to be received in annular groove34provided in inner bushing31. Any other suitable mechanical retaining element could also be used.

FIG. 9is a perspective view of the bearing assembly ofFIG. 8.FIG. 10is a cross-sectional view of the bearing assembly ofFIG. 9. As best shown inFIG. 10, the assembly is produced by inserting the inner bushing31into the outer bushing30until the flange33on the end of the inner bushing31abuts against the stepped portion41of the recess37provided in the end of the outer bushing30. When the inner bushing31is positioned in this fashion, the annular groove34provided in the outer wall35of the inner bushing31near the opposite end of the flange33is substantially level with the bottom surface42of the recess36provided in the opposite end of the outer bushing30. The retainer32can then be expanded, inserted into recess36and released to engage the inner bushing31about annular groove34. In this manner, the inner bushing31is held in place by abutment between flange33and recess37in the end of the outer bushing30and abutment between the retainer32and the recess36in the other end of the outer bushing30, while being free to rotate within the outer bushing30.

FIG. 11is a cross-sectional view of the outer bushing of the bearing assembly ofFIG. 10. As depicted, the diameter of the upper recess36is larger than the diameter of the lower recess37. As a practical matter, the diameter of the upper recess36has to be large enough to allow for insertion and removal of the retainer32from the annular groove34provided in the outer wall35of the inner bushing31. The lubricant inserts45are shown inFIG. 11(andFIG. 10), as extending through to the end of the of the outer bushing30and intersecting the edges of flange37while the opposite lubricant inserts45that extend from the other end of the outer bushing30terminate at the level of flange36due to the relative diameters of the recesses36and37. The effect is that the lubricant inserts45extend to both ends of the outer bushing30at the inner wall40.

FIG. 12is a top view of the outer bushing of the bearing assembly ofFIG. 10.FIG. 13is a bottom view of the outer bushing of the bearing assembly ofFIG. 10.FIGS. 12 and 13depict an exemplary embodiment in which the relative diameters of the recesses36and37in comparison to the inner wall40of the outer bushing30and the size and configuration of the lubricant inserts45. It is to be understood of course that the relative dimensions shown in the figures are provided as non-limiting examples and that the inner and outer bushings30and31can have different relative dimensions than those shown.

FIG. 14is a side view of the inner bushing of the bearing assembly ofFIG. 10.FIG. 14shows relative dimensions of the annular groove34and the flange33that are provided on the opposite ends of the inner bushing, it being understood that the relative dimensions and configurations are compatible with the bearing assemble ofFIGS. 8-13and that in other embodiments the dimensions and configurations can be different from that shown.

It is noted that the bearings and bushings of the present invention can be configured so that the exposed side edge portions of the lubricant inserts are either substantially flush with the inner or outer surfaces of the bearings and bushings, or substantially flush with both the inner or outer surfaces of the bearings and bushings.

Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications can be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described above.