Bushing kits, bearings, and methods of installation

A bushing kit and a method of installing the same with a mandrel having a tapered region. The bushing kit includes an inner member and an outer bushing. The inner member may include an inner surface having an engagement portion, such as a coating, plating, and/or lining, such as a self-lubricating coating. The method of installing the bushing kit includes passing the tapered portion of the mandrel through the outer bushing to radially expand the outer bushing into the structural workpiece and possibly induce some amount of residual compressive stress in the structural workpiece. Contemporaneously, the inner member is passed into the radially-expanded outer bushing before the outer bushing is permitted to radially inwardly rebound or spring back. The outer bushing is then permitted to radially contract onto the inner member to form an interference fit therewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure generally relates to installable members and methods of installing the members in an opening of a workpiece.

2. Description of the Related Art

Conventional solid lubrication lined or coated bushings, bearings, or the like are utilized for a variety of applications and in a variety of industries. These bushings and/or bearings are generally referred to as “self-lubricating” bushings and/or bearings and are employed where lubricant cannot be supplied continuously or repeatedly. One type of self-lubricating bearing is a KARON® bearing manufactured by Kamatics Corporation, which is a subsidiary of Kaman Corporation. The KARON® bearing includes a machinable self-lubricating liner system that resists swelling.

Self-lubricating bushings and/or bearings are typically installed into an opening of a structural workpiece by either press fit techniques or conventional freeze (i.e., shrink) fit techniques. Both of these techniques permit the self-lubricating bushing and/or bearing to be installed without causing damage to the inner diameter surface, which may be a soft lubricated liner or may be silver-coated, for example.

The process of shrink fitting includes sufficiently cooling the bushing and/or bearing in cryogenic fluid to reduce the outer diameter and rapidly placing it into the structural workpiece. Alternatively, the process of press fitting is where the bushing and/or bearing has a slightly larger outer diameter than the diameter of the receiving opening, and the bushing and/or bearing is forced into the opening. One drawback of both of these processes is that they cause damage to structural material surrounding the opening. Another drawback is that the amount of interference fit is limited because of a number of factors. In shrink fitting, for example, the temperature may not be low enough to sufficiently shrink the outer diameter of the bushing or bearing or the installation may not be fast enough to place the bushing or bearing before the outer diameter returns to the normal size at ambient temperature (e.g., the operating temperature). In press fitting, the tolerances between the bushing and/or bearing and the opening in the structural workpiece will vary, which may result in at least some assemblies not achieving a desired amount of interference. In addition, press fitting is typically limited to being used on smaller assemblies; otherwise the pressing forces exceed the capabilities of even large mechanical presses. These drawbacks, in turn, may lead to manufacturing difficulties, increased manufacturing costs, in-service problems, and/or degraded operational performance of the components that were fit together.

One option for installing bushings and/or bearings, especially in components that will undergo repetitive load cycles and/or may be susceptible to accumulating fatigue damage, is the FORCEMATE® installation method developed by Fatigue Technology, Inc. The FORCEMATE® installation method utilizes a tapered mandrel installed in a puller tool, for example, to pass the mandrel through an initially clearance fit bushing that has been positioned in the opening of the structural workpiece. The tapered mandrel radially expands the bushing into the opening to obtain a controlled and consistently higher interference fit than would be achievable by either the shrink or press fit processes. In addition, the FORCEMATE® installation method induces beneficial residual compressive stresses into the structural material surrounding the opening, which may advantageously extend the fatigue life of the component, assembly, or installation. The FORCEMATE® installation method, as well as other cold-working methods; tooling, and the like, such as the BUSHLOC®, FORCETEC®, and FLEXMATE® methods are described in U.S. Pat. Nos. 3,566,662; 3,892,121; 4,187,708; 4,423,619; 4,425,780; 4,471,643; 4,524,600; 4,557,033; 4,809,420; 4,885,829; 4,934,170; 5,083,363; 5,096,349; 5,405,228; 5,245,743; 5,103,548; 5,127,254; 5,305,627; 5,341,559; 5,380,136; 5,433,100; and in U.S. patent application Ser. Nos. 09/603,857; 10/726,809; 10/619,226; and 10/633,294.

The FORCEMATE® and other installation methods identified in the preceding paragraph have been found to be less than optimal for installing self-lubricated bushings and/or bearings because the operation of passing (e.g., pushing or pulling) the mandrel through the bushing and/or bearing may damage the lubricated liner and/or coating. To limit such damage, the amount of radial expansion must be reduced, however this results in less than optimum fatigue life enhancement of the surrounding structure and less than optimum fixity between the bushing or bearing and the structure.

Based on the foregoing, it is desirable to have an installable component (e.g., a bushing, fitting, fastener, bearing, and the like), an assembly, or a kit, as well as method of installing the same. Benefits of cold expansion of the structural workpiece can be achieved while minimizing, reducing, limiting, or substantially preventing damage the self-lubricated component, bearing, or like device.

SUMMARY OF THE INVENTION

At least one embodiment generally relates to a bushing kit and method of installing the same with a mandrel having a tapered region. The bushing kit comprises an inner and an outer bushing. The inner bushing may include an inner surface having a specialized coating, plating, and/or lining, such as a self-lubricating coating. The method of installing the bushing kit includes passing the tapered portion of the mandrel through the outer bushing to radially expand the outer bushing into the structural workpiece and possibly induce some amount of residual compressive stress in the structural workpiece. Contemporaneously, the inner bushing is pulled into the radially expanded outer bushing such that as the outer bushing radially rebounds or springs back, a tight interference fit is achieved between the inner and outer bushings. Further, the positioning of the inner bushing on the mandrel and the insertion of the inner bushing into the outer bushing may be accomplished without altering the integrity of the specialized coating, plating, and/or lining on the inner surface of the inner bushing. In one embodiment, the bushing kit and installation method may be used to achieve a rapid, consistent and controlled interference fit of lubricant-lined metal bushings/bearings into either metallic or composite structural workpieces.

In some embodiments, an assembly kit installable into an opening in a workpiece comprises an outer bushing having an inner surface and an outer surface, the inner surface having an inner perimeter, the outer surface having an outer perimeter sized to closely fit within the opening of the workpiece, the outer bushing radially expandable into the opening of the workpiece; and an inner member having an outer surface with an outer perimeter sized to form a clearance fit with the inner perimeter of the radially expanded outer bushing and further sized to form an interference fit with the inner perimeter of the outer bushing after the outer bushing has at least partially radially contracted onto the inner member when the outer bushing and the inner member are at substantially the same temperature.

In some embodiments, a bushing installation comprises a workpiece having an opening; an outer member in a first expanded configuration being positioned in the opening, the outer member having an inner surface and an outer surface, the inner surface having an inner perimeter and defining a passageway, the outer surface having an outer perimeter forming an interference fit with the workpiece because of a sufficient outward displacement of the outer member from an initial configuration to a second expanded configuration; and an inner member positioned in the passageway of the outer member, the inner member having an outer surface forming an interference fit with the inner surface of the outer member because of a sufficient inward displacement of the outer member from the second expanded configuration to the first expanded configuration.

In some embodiments, a mandrel coupleable to an installation tool to install an outer bushing and an inner member of a bushing kit into an opening in a structural workpiece, the mandrel comprises an engagement portion sized and shaped to cooperatively engage a portion of the installation tool; a tapered region coupled to the engagement portion for movement therewith, the tapered region having a minimum perimeter portion and a maximum perimeter portion, the tapered region configured to engage and radially expand the outer bushing as the tapered region passes therethrough and thereby provide an interference fit of the outer bushing with at least a portion of the structural workpiece; and a receiving portion coupled to the tapered region and proximate the maximum perimeter portion thereof, the receiving portion having an outer perimeter sized to receive the inner member that forms an interference fit with the outer bushing expanded with the tapered region and sized to be smaller than the maximum perimeter portion of the tapered region.

In some embodiments, an installation system for installing an outer bushing and an inner member of a bushing kit into an opening in a structural workpiece, the installation system comprises a mandrel comprising an engagement portion configured to be received by an installation tool for moving the mandrel; a tapered region coupled to the engagement portion, the tapered region having a minimum perimeter portion and a maximum perimeter portion, the tapered region operable to radially expandingly urge the outer bushing into the structural workpiece as the maximum perimeter portion of the mandrel passes through the outer bushing; and a receiving portion positioned proximate the maximum perimeter portion of the tapered region, the receiving portion coupled to the tapered region to move the inner member into the outer bushing after the outer bushing has been radially expanded by the maximum perimeter portion such that the outer bushing contracts to form an interference fit with the inner bushing.

In some yet other embodiments, a method of installing an outer bushing and an inner member into an opening in a structural workpiece, the method comprises moving a first portion of a mandrel through the outer bushing, the mandrel comprising the first portion, a tapered region, and a receiving surface, the inner member positioned on the receiving surface; moving the tapered region of the mandrel through the outer bushing to successively radially expand the outer bushing into the structural workpiece, the tapered region extending from a minimum perimeter portion to a maximum perimeter portion; moving the inner member into the radially-expanded outer bushing, the inner member having an outer perimeter that is not greater than the maximum perimeter portion of the mandrel when the inner member is positioned on the receiving surface of the mandrel; and allowing at least a portion of the radially-expanded outer bushing to radially contract onto the inner member to form an interference with the inner member.

In yet other embodiments, a method of installing an articulatable bearing into an opening in a structural workpiece, the method comprises positioning a mandrel carrying the bearing through the opening, the mandrel comprising a tool section configured to engage an installation tool, a tapered section, and a receiving section holding the bearing; moving the tapered section of the mandrel through the opening to radially expand the opening of the structural workpiece so as to induce compressive residual stresses in the workpiece; moving the bearing into the radially-expanded opening with the mandrel; and allowing at least a portion of the radially-expanded opening to contract inwardly to couple the bearing to the workpiece.

In one aspect, an assembly kit installable into an opening in a workpiece includes an outer bushing having an inner surface and an outer surface, the inner surface having an inner perimeter, the outer surface having an outer perimeter sized to closely fit within the opening of the workpiece, the outer bushing radially expandable into the opening of the workpiece; and an inner member having an outer surface with an outer perimeter sized to form a clearance fit with the inner perimeter of the radially expanded outer bushing and further sized to form an interference fit with the inner perimeter of the outer bushing after the outer bushing has at least partially radially contracted onto the inner member, wherein the outer bushing and the inner member are at substantially the same temperature when assembled.

In another aspect, a mandrel coupleable to an installation tool to install an outer bushing and an inner member of a bushing kit into an opening in a structural workpiece includes a tapered region comprising a minimum perimeter portion extending to a maximum perimeter portion, the tapered region positioned proximate the engagement portion, the tapered region operable to radially expandingly urge the outer bushing into the structural workpiece as the maximum perimeter portion of the mandrel passes through the outer bushing; a receiving surface positioned proximate from the tapered region, the receiving surface having an outer perimeter sized to receive the inner member, the outer perimeter of the receiving surface sized to be smaller than the maximum perimeter portion of the tapered region; and a collar positioned downstream from the receiving surface, the collar engageable with the mandrel to contact the inner member.

In yet another aspect, a method of installing an outer bushing and an inner member into an opening in a structural workpiece includes moving a first portion of a mandrel through the outer bushing, the mandrel comprising the first portion, a tapered region, and a receiving surface, the inner member positioned on the receiving surface; moving the tapered region of the mandrel through the outer bushing, the tapered region having a minimum perimeter portion extending to a maximum perimeter portion, the tapered region successively radially expanding the outer bushing into the structural workpiece; moving the inner member into the radially-expanded outer bushing, the inner member having an outer perimeter that is not greater than the maximum perimeter portion of the mandrel when the inner busing is positioned on the receiving surface of the mandrel; and allowing at least a portion of the radially-expanded outer bushing to radially contract onto the inner member to form an interference with the inner member.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, one skilled in the art will understand that the embodiments may be practiced without these details. In other instances, well-known structures and methods associated with cold working and/or installing a component (e.g., a bushing or a bearing) into an opening in a structural workpiece may not be shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. It is appreciated and understood that the process of installing the component into the opening of the structural workpiece may or may not result in the creation of an annular zone of residual compressive stress in the structural workpiece or workpieces.

In the following description and for purposes of brevity, reference shall be made to cold working and/or radial expanding of the structural workpiece. This reference is not intended to limit or otherwise narrow the scope of the disclosed embodiments. The process of cold expansion is to be broadly interpreted as any process that radially expands at least some of the material surrounding the opening in the structural workpiece, even if the expansion is for the purpose of impeding the growth of a fatigue crack. It is further understood that cold expanding the opening of the structural workpiece may or may not induce beneficial compressive residual stresses and may or may not produce fatigue-enhancing benefits in the structural workpiece.

The headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.

As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a bushing that includes “a flange” includes a bushing with a single flange or a bushing with two or more flange, or both. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the context clearly dictates otherwise.

The following description relates to a bushing kit and a method of installing the bushing kit into the structural workpiece. The bushing kit may include one or more installable components. The bushing kit in some embodiments includes an inner member and an outer bushing. The inner member may include an engagement portion that defines at least a portion of a surface for contacting another component. The engagement portion can be a coating, plating, lining, or other suitable feature that remains substantially unaltered during the installation process. In some embodiments, the engagement portion comprises a lubricant or other material with a material hardness that is less than the material hardness of another portion of the inner member, using the same material hardness test. The engagement portion can be configured to minimize, reduce, limit, or substantially prevent corrosion, fretting, and other forms of wear. For example, the engagement portion can comprise a high wear material (e.g., a lubricant) that reduces frictional forces to improve service performance. In some embodiments, the inner member is a movable or articulatable bearing, such as a spherical bearing. The inner member may be installed in a multi-step process to ensure proper functioning of the installed bearing.

Installing the bushing kit according to at least one embodiment may advantageously achieve a desired amount of cold expansion of the structural workpiece while contemporaneously achieving an interference fit to secure the inner member with the outer bushing. Further, the integrity of the outer bushing and inner member can be maintained during the installation process. In addition, the amount of interference in the installed assembly (e.g., interference between the inner member and the outer bushing or the interference between the outer bushing, or both) can be accurately controlled. The assembly can be configured to achieve a wide range of interferences suitable for various operating conditions.

These advantages, as well as other or additional advantages over conventional bushing kits and installation methods, will become apparent and be appreciated by those skilled in the art after reviewing the following detailed description, claims, and figures.

FIG. 1shows an installation100comprising a bushing kit102installed into a structural workpiece104, according to one illustrated embodiment. The structural workpiece104includes an opening106extending at least partially through the thickness of the structural workpiece104. The illustrated opening106is a through-hole extending between opposing outer surfaces of the workpiece104

The term “bushing kit” as used herein generally refers, without limitation, to an outer member and an inner member that are installed into the opening in the structural workpiece. The bushing kit102ofFIG. 1, for example, includes an outer member108in the form of a bushing and an inner member110. It is understood and appreciated that one or more of the components of the bushing kit may be elements other than bushings, such as, for example, fittings, fasteners, sleeves (including split sleeves), and the like. The components (e.g., the outer member108) can comprise metal (e.g., steel, aluminum, bronze, and the like), non-metals, polymers, plastics (e.g., nylon, polyurethane, and the like), elastomers, rubbers, and other expandable materials. The inner member, for example, may be a bearing, a sleeve, a liner, a bushing, a fastener, or some other component or element that can be placed on a mandrel and pulled into a radially expanded outer member.

The outer bushing108can be expanded from a first configuration to a second configuration in order to form an interference fit with the workpiece104. A cold expansion process can radially expand the outer bushing108, without appreciably raising the temperature of the bushing108or workpiece104, to cold work the workpiece104to induce residual stresses in the workpiece104, thereby enhancing fatigue performance of the installation100. The residual stresses are preferably compressive stresses that can minimize, limit, inhibit, or prevent crack initiation, crack propagation, and other failures or problems.

As used herein, the term “workpiece” is broadly construed to include, without limitation, a parent structure having at least one hole or opening (e.g., a circular opening, elliptical opening, polygonal opening, and the like) suitable for receiving at least one expandable member. In some embodiments, the bushing kit102can be installed in the structural workpiece104in the form of a bulkhead, lug, fuselage, engine or other structural member of an aircraft. The structural workpiece104can also be a rail, component of transportation vehicle (e.g., a train, automobile, helicopter, and the like), and other structural members that may experience static or cyclic loading. The structural workpiece104can comprise one or more metals (e.g., steel, aluminum, titanium, and the like), polymers, plastics, composites, and other materials suitable for engaging installable members.

FIG. 2shows the outer bushing108and the inner member110of the bushing kit102, according to one illustrated embodiment. The outer bushing108includes an inner surface114defining a passageway and an outer surface116. Optionally, the outer bushing108may also include a radial flange118. The inner surface114includes an inner perimeter120. The outer surface116includes an outer perimeter122that is sized to closely fit (e.g., clearance fit with a minimal amount of clearance) within the opening106of the structural workpiece104. The outer bushing108may be made from a wide variety of materials that permit the outer bushing108to be radially expanded in the opening106of the structural workpiece104. The expanded outer bushing108can then radially contract (e.g., elastically contact) onto the inner member110. The bushing108can experience plastic deformation to form a permanent interference fit with the workpiece104and elastic deformation to contract onto and form an interference fit with the inner member110.

The outer bushing108can have a monolayer or multilayer main body123, illustrated as a generally tubular body. For example, a layer of material can be applied to the inner surface or outer surface of the main body123. The applied material can be a lubricant (e.g., solid lubricants, liquid lubricants, and the like), metal, sealant, or other suitable material for engaging the workpiece104or the inner member110, as well as other components, if needed or desired. Similarly, the inner member110can have a monolayer or multilayer construction.

The inner member110includes an outer surface124and an inner surface126. In one embodiment, the inner surface126comprises an engagement portion112configured to engage another component. The engagement portion112can be a layer (e.g., a coating or plating) of a wear resistant material, lubricant (e.g., an anti-fretting lubricant), or anti-fretting material that is applied to the inner member110. The engagement portion112can reduce friction, for example friction between the inner member110and another component (not shown) that may move relative to the inner member110.

One type of engagement portion112may be a silver coating applied for wear purposes that may include an amount of silver iodide to enhance the lubricity of the silver coating. Alternatively or additionally, the inner surface126can be formed of a polymer, such as synthetic resin lubricants like polytetrafluoroethylene (PTFE), TEFLON®, nylon, NEDOX® CR+, blends, mixtures, and combinations thereof. These materials can be generally referred to as “soft” because they are generally softer than the main bushing material (e.g., steel). Thus, these relatively soft engagement portions are generally more prone to being damaged during the installation process.

The outer surface124of the inner member110includes an outer perimeter128that is sized to be equal to (e.g., maximum tolerance conditions) or at least slightly smaller than the inner perimeter120of the “radially expanded” outer bushing108. This relative sizing allows the inner member110to be passed (e.g., pulled, pushed, or both) into the outer bushing108such that the inner member110props open the outer bushing108. In some embodiments, the inner member110can be inserted into the outer bushing108without damaging the inner surface114of the outer bushing108. The relative sizing of the bushing108and inner member110can also permit the inner member110to be passed into the radially expanded outer bushing108so that the outer bushing108can contract (e.g., collapse, constrict, and the like) about the inner member110. The bushing108can elastically contract to form an interference fit with the inner member110, which both supports and limits the radial contraction of the outer bushing108.

FIG. 3shows another installation200comprising a bushing kit202installed into a structural workpiece204, according to one illustrated embodiment. The structural workpiece204includes an opening206extending at least partially through the thickness of the structural workpiece204. The bushing kit202includes an outer bushing208and a bearing209. The bearing209can be an assembled spherical bearing comprising a race210and a ball212. The race210can have an inner surface211configured to closely surround at least a portion of the ball212movable with respect to the race210. The ball212can have a curved outer surface213complementary to the inner surface211of the race210. The illustrated outer surface213is partially spherical in shape and is configured to conform closely to the inner surface211of the race210.

Different installation processes can be used depending on whether the race210is a one-piece or multi-piece race. For example, a one-piece annular race210and the ball212can be pre-assembled and inserted together into the outer bushing208. Interference in the installation200can reduce tolerances of the assembled bushing kit202. A two-piece race may be installed into the outer bushing208before the ball212is placed into the race212.

In two-piece split race embodiments, the two halves of the race mate to form a multi-piece annular race that engages the ball212. Each of the outer faces215,217may include a groove that forms a displaceable edge. Once the ball212is placed in the race210, a tool (e.g., a stake) can be placed in the groove to stake the displaceable edge outwardly over the bushing208, thereby locking the bushing kit202to the workpiece204. The staked edge can rotationally and translationally fix the race210to the workpiece204.

When the bushing kit202is installed, the interference can press the race210towards the ball212. Clearance can be provided between the race210and the ball212to accommodate for these compressive forces. The clearance between the race210and ball212, before assembly, can be large or small to accommodate high interference or low interference, for example.

An optional liner214may be positioned between the race210and the ball212to allow the spherical bearing to be self-lubricating. The liner214can comprise a lubricant to promote proper relative movement between the ball212and the race210.

Tooling for Installing a Bushing Kit

FIG. 4Ashows a mandrel assembly300including a mandrel301having an engagement portion302, a tapered region304, a receiving surface306, and a collar308. The engagement portion302permits the mandrel301to be connected to an installation or puller tool. The tapered region304includes a minimum perimeter portion310, a maximum perimeter portion312, and a transition perimeter portion313extending therebetween. As shown inFIG. 6A, the tapered region304includes a taper angle324. The tapered region304is positioned downstream, as indicated by the arrow314, from the engagement portion302and operates to radially expand the outer bushing108ofFIG. 1into the opening106of the structural workpiece104. Accordingly, the maximum perimeter portion312of the mandrel301is at least slightly larger than the inner perimeter120of the outer bushing108.

A uniform perimeter region316with a perimeter generally equal to the maximum perimeter portion312may be positioned adjacent to the maximum perimeter portion312of the tapered region304of the mandrel301. The uniform perimeter region316can be useful during the manufacturing of the mandrel assembly301. In some embodiments, the mandrel301may not have a uniform perimeter region in order to reduce the axial length of the mandrel301. The maximum perimeter portion312, for example, can extend from the receiving section306.

The receiving surface306is positioned near the tapered region304and includes an outer perimeter317sized to receive the inner member110. The outer perimeter317can be sized to receive (e.g., loosely receive with a clearance fit) the inner member110so as to minimize, limit, or substantially prevent damage to the inner surface126of the inner member110. When the inner member110is positioned along the receiving surface306(seeFIG. 5A), the inner member110can be axially fixed with respect to the mandrel301. The outer perimeter317can be sized to be smaller than the maximum perimeter portion312of the tapered region304.

Referring again toFIG. 4A, a shoulder318can form the transition between the maximum perimeter portion312or the uniform perimeter region316and the receiving surface306. The illustrated shoulder318is in the form of an annular step. Other shoulder configurations are also possible.

FIGS. 6B to 6Eshow shoulders used to generate somewhat uniform distributions of residual stresses in the outer bushing108. The shoulder318ofFIG. 6Bdefines an arcuate outer surface319extending from the uniform perimeter region316to the receiving surface306. The outer bushing108can cam easily over the shoulder318and onto the inner bushing110.FIG. 6Cshows a down-tapered shoulder318. The rate of taper of the shoulder318can be increased or decreased to decrease or increase the distance between the inner member110and the uniform perimeter region316. The shape, size, and position of the shoulder318can be selected based on the desired interaction between the mandrel301and the outer bushing108.FIG. 6Dshows the shoulder318comprising a plurality of steps from the uniform perimeter region316to the receiving surface306.FIG. 6Eshows the shoulder318connecting the maximum perimeter portion312to the receiving surface306.

The height of the shoulder318can be selected based on the configuration of the inner member110and the installation process.FIG. 6Ashows the shoulder318with a height H that is generally equal to the wall thickness T of the inner member110. In some embodiments, the wall thickness T of the inner member110, including the engagement portion112, is less than the height H of the shoulder318of the mandrel301. In some embodiments, at least a portion of the wall thickness T of the inner member110is greater than or equal to the height H of the shoulder318of the mandrel301. As will be further detailed below, these relative sizes permit the inner member110to be slid into the radially-expanded outer bushing108during installation without appreciably altering the inner surface114of the outer bushing108.

Referring toFIGS. 4A and 4B, the collar308is positioned downstream from the receiving surface306and engages the mandrel301to position the inner member110during the installation process. The receiving surface306is interposed between the shoulder318and the collar308. As shown in the embodiment ofFIG. 5A, the collar308can serve as a stop to position the inner member110at least proximate to the shoulder318of the mandrel301.

The illustrated collar308includes internal threads that engage a threaded region320of the mandrel301. The collar308can be rotated about the threaded region320to adjust the distance between the shoulder318and the face309(FIG. 4A) of the collar308for contacting the inner member110. The collar308, once placed on the mandrel301, may be torqued down to provide at least a slight compression force on the inner member110depending on the compressive strength capacity of the inner member110. In this manner, the collar308and shoulder318cooperate to limit or substantially prevent axial movement of the inner member110along the mandrel301.

The collar308ofFIG. 4Acan have an outer perimeter321that is less than the outer perimeter122of the outer bushing108such that the collar308can be inserted into and through the opening106in the workpiece104for one-side (e.g., blind-side) processing. After the bushing kit102is installed, the collar308can be separated from the threaded region320to remove a mandrel main body323of the mandrel301from the kit102.

Method(s) for Installing at Least One Type of a Bushing Kit

FIG. 5Ashows the outer bushing108placed in the opening106of the structural workpiece104. The outer bushing108is in an initial configuration with the inner perimeter120less than outer perimeter128of the inner member110that is supported on the receiving surface306and just about to be pulled into the outer bushing108. The inner perimeter of the inner member110can be sized to be loosely received on the receiving surface306to limit or substantially prevent damage to any coating, plating, and/or liner that forms or comprises the inner surface126of the inner member110.

FIG. 5Bshows the outer bushing108being radially expanded by the mandrel301and the inner member110about to be inserted into the radially expanded outer bushing108. The mandrel301is pulled through the workpiece (as indicated by the arrow331) to expand the outer bushing108from the initial configuration (seeFIG. 5A) with the tapered section304. The outer perimeter128of the inner member110can be equal to or less than the maximum perimeter portion312of the tapered region304of the mandrel301. This allows the inner member110to be inserted into the outer bushing108with at least a slight clearance fit.

FIG. 6Ashows a detailed view of a region of the mandrel301, which is approximately defined by the intersection of the tapered region304, the receiving surface306, and the shoulder318, with the inner member110positioned on the receiving surface306. The wall thickness T of the inner member110is selected to be approximately equivalent to or smaller than the height H of the shoulder318of the mandrel301, which advantageously permits the inner member110to be passed into the radially-expanded outer bushing108with at least a minimal amount of clearance between the inner surface114of the outer bushing108and the outer surface124of the inner member110. In one embodiment, the transition from the maximum perimeter portion312and/or the uniform perimeter region316of the mandrel301to the outer surface124of the inner member110is a very small step and barely discernable.

The bushing kit102, which may include the outer bushing108and the inner member110according to one embodiment, is installed through two distinct yet interdependent actions. These actions are carried out in succession and through a pulling or pushing action of the mandrel301. Reference herein has been made to “pulling” the mandrel301, however it is appreciated that the mandrel301may also be pushed through the structural workpiece104. The two distinct yet interdependent actions, are as follows: (1) radially cold expanding the outer bushing108into the opening106of the structural workpiece104; and (2) pulling the inner member110into the radially-expanded outer bushing108, where the inner member110is pre-positioned on the mandrel301to closely follow a maximum cold expansion portion of the mandrel301, which has been otherwise referred to as the maximum perimeter portion312and/or the uniform perimeter region316of the mandrel301.

By locating the inner member110on the mandrel301, as previously described, the inner member110can be pulled or pushed into the outer bushing108before the outer bushing108has had an opportunity to elastically, radially spring back or contract from its radially expanded state. Hence, as the radially-expanded outer bushing108does begin to elastically, radially spring back or contract, the radial spring back brings the outer bushing108into contact with the inner member110to form a secure interference fit therewith.

These distinct yet successive actions may achieve at least two advantages, which were briefly summarized above. The first advantage is that an amount of residual compressive stress is induced into the structural workpiece104by the radial expansion of the outer bushing108. The residual compressive stress may enhance the fatigue life of the structural workpiece104. The second advantage is that a tight interference fit between the inner member110and the outer bushing108can be achieved without damaging or altering the integrity of the inner surfaces of either of the respective inner or outer bushings110,108. Further, additional or alternative advantages may be achieved as will be apparent to those skilled in the art after reviewing other aspects of the description, claims, and/or figures.

FIG. 7illustrates a method400of installing at least one type of bushing kit into a structural workpiece, according to one embodiment. For discussion and exemplary purposes, the bushing kit comprises an inner member and an outer bushing. It is appreciated that the bushing kit may take other forms, such as the outer bushing and spherical bearing combination described above and illustratedFIG. 3.

At401, an amount of radial expansion of the outer bushing is selected to achieve a corresponding amount of residual compressive stress in the structural workpiece surrounding the outer bushing. Determining the desired amount of residual compressive stress in the structural workpiece and the amount of interference fit between the inner and outer bushings may be an iterative process to achieve specific design goals, for example installing the bushing kit into a reinforced composite structural workpiece. This iterative process may involve varying or altering one or more of the components (i.e., the structural workpiece, the inner, and/or the outer bushing) and/or various installation parameters in one or more of the following ways, for example, the material properties, the mandrel pulling force, the component dimensions (e.g., wall thickness), the type of coating, plating, or liner, etc. The effect of the wall thickness of one or both of the inner and/or outer bushings, accordingly, is discussed below with respect to the graphs presented inFIGS. 8 and 9.

At402, a final inner perimeter of the post-expanded outer bushing is pre-determined from testing, closed form solutions, analysis (e.g., numerical analysis), mathematical or computer models, FEA simulations, and the like. The testing and/or analysis is conducted to determine how much elastic spring back versus plastic deformation occurs during the process of radially expanding the outer bushing. The testing and/or analysis may, among other things, be conducted to obtain empirical data and/or to account for various dynamic and/or nonlinear aspects of the assembly or installation, for example aspects such as the constituent material properties, installation temperatures, mandrel pulling forces, dimensional effects (i.e., a thick versus a thin structural workpiece), etc.

By knowing the final inner perimeter dimension or dimensions of the post-expanded outer bushing, a desired amount of radial interference between the non-expanded outer bushing and the inner member may be selected at404. The term “radial interference” is used herein for clarity and brevity, but it is understood that the bushings and/or the opening in the structural workpiece may be non-circular such that the amount of interference may need to be expressed with alternate language. It is generally understood that when components are assembled with an “interference fit,” a contact pressure is present between the components after assembly.

If not already present, the non-expanded outer bushing can be placed in the opening of the structural workpiece at408. At410and412, the inner member is placed onto the receiving surface of the mandrel and secured onto the mandrel with the nut or collar. At414, a force is applied to the mandrel, for example a pulling or pushing force, to longitudinally and/or axially advance the mandrel through the inner bushing, causing the tapered region of the mandrel to radially expand the outer bushing to achieve the desired amount of residual compressive stress in the structural workpiece surrounding the outer bushing.

At416, the maximum cold working portion of the mandrel is moved through the outer bushing as the collar urges the inner member into the radially expanded outer bushing. At418, the outer bushing elastically, radially contracts to form an interference fit with the inner member. When the mandrel is removed from the inner member, the bushing kit is securely installed in the structural workpiece and the inner surface of the inner member is unaltered from the installation process.

Exemplary Embodiments of Tailored Installations

FIGS. 8 and 9show examples of various “tailored” residual stress or strain states in the final installation. Varying the wall thickness between the inner and/or outer bushings as well as the respective material properties, level of expansion, and other processing criteria of the installable members allows for “tailoring” of the residual stress or strain state in the structural workpiece.

FIG. 8is a graph that shows that radially expanding a thinner-walled outer bushing, in contrast to a thicker-walled outer bushing, may result in a higher amount of radial strain in the structural workpiece during the expansion process combined with a higher amount of elastic spring-back of the outer bushing after expansion. Note that the graph ofFIG. 8illustrates the effect of radially expanding the outer bushing without any influence from an inner bushing. Curve502ofFIG. 8shows the amount of radial strain in the structural workpiece during cold expansion of the outer bushing. Curve504shows that the amount of radial strain in the structural workpiece is reduced after the thinner-walled outer bushing has had an opportunity to rebound or spring back.

FIG. 9is a graph that shows the radial strain in the structural workpiece with the installation of both an outer and an inner bushing as compared to the installation of the outer bushing only. Curve506ofFIG. 9is the same as curve504ofFIG. 8and shows the resultant radial strain in the structural workpiece if the outer bushing is permitted to spring back without an inner bushing present. Curve508ofFIG. 9shows that the presence of a thick-walled inner bushing within the outer bushing reduces the amount of spring back of the outer bushing, thus maintaining a higher amount of radial strain in the structural workpiece. In sum, the graph ofFIG. 9shows that the thicker walled inner bushing is better able to react to the contact pressure of the outer bushing, and in turn essentially prop the outer bushing in the opening of the structural workpiece to maintain a higher amount of radial strain in the structural workpiece. Additionally, a high interference can be achieved-without over-expanding the outer bushing108. The high interference can increase the pullout forces required to remove the assembled outer bushing108and inner bushing110.

In the preceding examples, the fatigue life enhancement is accomplished by the radial strain induced in the structural workpiece. In addition, the amount of spring-back of the outer bushing in addition to the relative sizing of the inner and outer bushings, provides the interference fit between the inner and outer bushings. In one embodiment, the desired amount of interference is sufficient to keep the inner bushing from migrating under operation, vibration, and/or other types of loads.

Advantages of the Bushing Kit and the Method of Installing the Bushing Kit

One advantage of the bushing kits and methods of installation thereof is that the contemporaneous radial expansion of the outer member followed by the insertion of the inner member into the outer member and then followed by at least some amount of radial contraction of the outer member onto the inner member results in secure joint that provides increased resistance to push-out and migration of the members when compared to conventional shrink-fit or press-fit methods. Further, the installation can be accomplished with both the inner and outer members at substantially the same temperature. In some embodiments, the average temperature of the inner member can be less than about 10 degrees Celsius of the average temperature of outer member. In some embodiments, for example, the average temperature of the inner member can be less than 5 degrees Celsius of the average temperature of outer member. This eliminates the need to freeze or heat one of the respective members, which reduces manufacturing time and costs. Thermal processes can often lead to the formation of a condensate, which in turn leads to corrosion. Thus, the installation of the bushing kits can results in reduced condensation and corrosion as compared to installation processes requiring thermal processing.

In addition, the bushing kits may be advantageously installed with special coatings, platings, and/or liners, where these coatings, platings, and/or liners are not subjected to damage during the installation process. Special liners have previously been incompatible with cold-expansion installations due to the inability of the special liners to handle the extreme stresses inherent during a “mandrelized” radial-expansion process. The described methods of installing such bushing kits are quicker, less expensive, and provide a more robust and secure installation than conventional methods.

The cold expansion of the outer member may impart beneficial residual compressive stress in the surrounding base material (i.e., the structural workpiece) to extend the fatigue life and damage tolerance of the structural workpiece, specifically when the structural workpiece experiences tension loading.

Another possible advantage is that the configuration of the final installation may be tailored to achieve a desired amount of residual stress in the structural workpiece while also achieving a desired amount of interference between the inner and outer members. Thus, the bushing kits and/or installation methods may accommodate use in metallic or composite structural workpieces.

Further, the installation of the separate outer bushing and inner member may be advantageous during a rework situation where the inner member containing the liner needs to be replaced, especially in the field. The inner member can be removed while the outer bushing is kept secure in the structural workpiece to preclude damage to the structural workpiece. By way of example, an inner-liner bushing may be installed and removed and then re-installed in a composite structural workpiece while keeping the outer bushing in place so that the laminates of a composite structural workpiece are not disturbed or damaged (e.g., delamination).

Installing bushings into composite materials is a well-known problem because it is difficult to shrink fit into place due to the concern of causing delamination of the composite structural workpiece. The bushing kits and methods generally described herein may preclude such damage by initially installing a lightly radially-expanded outer bushing, which is concurrently followed by an inner member. In such an installation, the ratio of bushing wall thickness could be varied to optimize the overall installation.

Additional and Alternate Embodiments

The bushing kits and installation process may be optimized by varying the relative thickness ratio of the inner and outer bushings. For example, it may be desirable to obtain a higher level of expansion of a thinner outer bushing for the benefit of inducing a higher level of residual stress into the structural workpiece. Relatively large strains can be generated in the material of the workpiece surrounding the outer bushing. In turn this would also allow the outer bushing to “spring-back” by a greater amount and increase the relative interference between the inner and outer bushings. The size and properties (e.g., compressibility) of the inner bushing can be selected for a desired amount of spring back, interference, and final tolerances of the installation.

The bushing kits can produce a wide range of fits, including high interference fits to low interference fits. A high interference bushing kit, for example, can be configured for a high level of retention to, for example, reduce, limit, or substantially prevent migration of one or more of the installed bushings. A relatively thick inner member can be placed into an outer bushing to prop open the outer bushing and control spring back of the outer bushing. The amount of spring back of the outer bushing can be reduced to increase the interference between the outer bushing and the workpiece. In some embodiments, the inner bushing is a stout, thick-walled member that rigidly supports the outer bushing. The outer bushing tends to spring-back from its maximum expanded configuration during the expansion process to an unrestrained configuration (that is, the configuration of the outer bushing if the inner member is not present). The maximum expanded configuration and unrestrained configuration of the outer bushing define a maximum spring-back distance of the outer bushing. The inner bushing can limit spring back of the outer member to less than about 5%, 10%, 20%, 30%, or 40% of the maximum spring back distance. Thus, extremely high interferences can be obtained. Other amounts of spring back are also possible.

The stout inner bushing can have a wall thickness that is substantially greater than the wall thickness of the outer bushing. Additionally or alternatively, the inner bushing can be made of a rigid material, for example, materials with a high modulus of elasticity. The inner bushing can maintain its shape throughout and after the installation process to ensure that proper tolerances are achieved.

A low interference bushing kit, when installed, can have a sufficient amount of interference to limit or substantially prevent unwanted migration with respect to the workpiece, while keeping strains in the workpiece at or below an acceptable level. A workpiece in which the bushing kit is installed may be damaged when subjected to high strains.

The workpiece104ofFIG. 1, for example, may comprise a composite material that is susceptible to damage due to high strains. The composite material can include, without limitation, reinforcing elements (e.g., fibers, particles, and the like), fillers, binders, matrix, and the like. Wood, fiberglass, polymers, plastics, metals, ceramics, glass, and the like can be combined to produce a workpiece104with properties that are different from the properties of its constituents individually. In some embodiments, the workpiece104can comprise a fiber-reinforced composite, particle-reinforced composite, laminate (e.g., a stack of laminas), or combinations thereof. The matrix of the reinforced composites can be made of metal, polymers, ceramics, and other suitable materials for encapsulating other reinforcement features. The laminates can be unidirectional laminates, cross-ply laminates, angle-ply laminates, symmetric laminates, and the like.

The bushing kit can be installed in the opening of the composite workpiece, or other type of low strain workpiece, while maintaining the integrity of the workpiece. The outer bushing108, for example, can be easily inserted into the opening106. The mandrel301can expand the outer bushing108to form an interference fit with the workpiece104. To minimize, limit, or substantially prevent damage to the material surrounding the opening106, the amount of radial expansion can be below a threshold amount of expansion that would cause unwanted damage to the workpiece104.

Composites may have relatively low strain capabilities as compared to metals. Expansion of the outer bushing108can cause compressive loading in the composite material surrounding the opening106. If the compressive loading is too high, fibers in a fiber-reinforced composite material can buckle, which in turn affects the material's properties. Micro-buckling of fibers may significantly reduce the water resistance of the composite material because buckled fibers may cause micro-cracking of the matrix surrounding the fibers. Splitting due to Poisson's ratio effect, matrix yielding, fiber splitting, debonding (e.g., fiber debonding, interlamina debonding, and the like), and other failure modes are often caused by compressive loading or high strains.

Advantageously, the bushing kit102can be installed using sufficiently low levels of strain to control the amount of damage, if any, to the workpiece104. The outer bushing108, for example, can be installed with a slight interference fit, as well as other types of fits that keep the outer bushing108in the opening106until the inner member110is installed. The outer bushing108thus applies outwardly directed compressive forces to the workpiece104without compromising the structural integrity of the workpiece104.

The inner bushing110in the form of a low compressibility bushing can be placed into the expanded outer bushing108. As noted above, the inner bushing110can limit spring-back of the outer member108to less than about 5%, 10%, 20%, or 30% of the maximum spring back distance. In some embodiments, the inner bushing110can support the outer member108to produce a slight increase or decrease in the compressive forces applied to the workpiece104. For example, the compressive forces applied to the workpiece104, when the inner bushing is installed, can be at least 95%, 90%, 80%, or 70% of the maximum compressive forces applied by the outer bushing108to the workpiece104when the outer bushing108is at its maximum expanded state. In some, the compressive forces applied to the workpiece104can be at least 60%, 50%, 40%, or 30% of the maximum compressive forces applied by the outer bushing108to the workpiece104when the outer bushing108is at its maximum expanded state. Other compressive forces are also possible.

In another embodiment and as shown inFIG. 10, the installation method may be used for installing spherical bearings comprising a race210and a ball212into an outer bushing208and an opening in a structural workpiece204.FIG. 10shows a mandrel600having a contact portion604that cooperates with a portion608of a collar or nut606to secure the race210on the mandrel600. The mandrel600includes a first recess611to loosely receive the ball212of the spherical bearing while the collar606includes a corresponding recess613to receive the opposite side of the ball212. This type of mandrel600may allow installation shops and/or repair facilities to easily remove and replace spherical bearings and re-install same-size replacement spherical bearings or oversized spherical bearings, if necessary.

FIGS. 11 to 13show bushing kits that may be generally similar to the bushing kit102, except as further detailed below. The bushing kit700ofFIG. 11includes a pair of outer bushings701,702sandwiched between a workpiece704and an inner member710. The inner member710can extend between opposing ends714,716of the respective outer bushings701,702.

The outer bushing701includes a tubular section722and a radial flange section724at one end of the tubular section722. The tubular section722extends axially and has an outer diameter that substantially conforms to an opening730in the workpiece704. The radial flange section724extends radially outward and can abut or be adjacent to an outer surface740of the workpiece704.

Similarly, the outer bushings702includes a tubular section750and a radial flange section752at one end of the tubular section750. The tubular section750has an outer diameter that substantially conforms to the opening730in the workpiece704. The radial flange section752can abut or be adjacent to the outer surface760of the workpiece704.

The outer bushings701on one side of the workpiece704can be inserted into and expanded in the opening730. The outer bushing702and inner member710on the other side of the workpiece704can be installed in a similar manner as the outer bushing108and inner member110described above. The inner member710can be pulled into and through the outer bushings701,702until in the desired position. When assembled, the inner ends770,772of the outer bushings701,702can be position near each other. In some embodiments, the inner end770contacts the inner end772. In other embodiments, the inner end770is spaced from, but proximate to, the inner end772.

FIG. 12shows a pair of nested bushings800,802. The outer bushings802includes a radial flange section810near or against a first face812of a workpiece814. A tubular section820of the outer bushing802is interposed between a tubular section822of the inner bushing800and the workpiece814.

In some embodiments, the bushing kit may include a third bushing or liner installed with the aforementioned inner and outer bushings.FIG. 13shows an outer member840between a tubular section842of an inner bushing850and a workpiece860. The outer member840is in the form of a sleeve that extends the length of an opening864in the workpiece860. Another member can be installed into the inner bushing850with the mandrels described herein.

In some embodiments, an opening in a work piece may be expanded via a mandrel, and a bushing, bearing or other member inserted before the opening contracts inwardly, creating an interference fit. In some embodiments, an outer race holding a bearing, for example a spherical bearing, may be inserted into a work piece using such an approach.

The various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents, patent applications and publications referred to in this specification as well as U.S. Pat. Nos. 3,566,662; 3,892,121; 4,187,708; 4,423,619; 4,425,780; 4,471,643; 4,524,600; 4,557,033; 4,809,420; 4,885,829; 4,934,170; 5,083,363; 5,096,349; 5,405,228; 5,245,743; 5,103,548; 5,127,254; 5,305,627; 5,341,559; 5,380,136; 5,433,100; and in U.S. patent application Ser. Nos. 09/603,857; 10/726,809; 10/619,226; and 10/633,294 are incorporated herein by reference. Aspects can be modified, if necessary or desired, to employ devices, features, elements (e.g., fasteners, bushings, and other types of expandable members), and concepts of the various patents, applications, and publications to provide yet further embodiments. For example, the mandrel301ofFIG. 4Acan be used to installed two or more expandable members disclosed in the incorporated patents, applications, and publications.

These and other changes can be made in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all types of bushing kits and/or other assemblies that are installable in an opening of a structural workpiece and that operate in accordance with the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to be determined entirely by the following claims.