Dry-lubricating lead-in edge for press-fit assemblies and associated methods

A dry-lubricating apparatus, for press fitting onto a mating part, includes (a) a frame, (b) a rubber gasket fixed to the frame to create an interference with a mating surface of the mating part so as to enable the press fitting, and (c) a lead-in edge fixed to at least one of the frame and the rubber gasket. The lead-in edge includes a dry lubricant such that, when the dry-lubricating apparatus is slid onto the mating part, along the mating surface and with the rubber gasket trailing the lead-in edge, a portion of the dry lubricant is abraded off the lead-in edge to reduce friction between the rubber gasket and the mating surface.

BACKGROUND

Wheel bearings generally require a bearing seal that seals between the bearing and the external environment, to prevent contaminants from entering the bearing and to prevent or reduce loss of oil from the bearing. A part of the bearing seal is affixed to the rotating part of the wheel assembly (the hub), and another part of the bearing seal is affixed to the stationary part of the wheel assembly (the axle). A dynamic seal is formed between the rotating and stationary seal parts. The dynamic seal is, for example, a labyrinthine path between the rotating and stationary seal parts with an elastomer lip bridging the gap therebetween. The rotating seal part, the axle, the stationary seal part, and the hub are all concentric. Typically, assembling the wheel assembly with the seal requires (a) press fitting the rotating seal part onto the axle to rigidly couple the rotating seal part to the axle, and (b) press fitting the stationary seal part into the hub to rigidly couple the stationary seal part to the hub. The rotating seal part may be equipped with a rubber gasket that forms a stationary seal between the rotating seal part and the axle. Similarly, the stationary seal part may be equipped with a rubber gasket that forms a stationary seal between the stationary seal part and the hub.

SUMMARY

In an embodiment, a dry-lubricating apparatus, for press fitting onto a mating part, includes (a) a frame, (b) a rubber gasket fixed to the frame to create an interference with a mating surface of the mating part so as to enable the press fitting, and (c) a lead-in edge fixed to at least one of the frame and the rubber gasket. The lead-in edge includes a dry lubricant such that, when the dry-lubricating apparatus is slid onto the mating part, along the mating surface and with the rubber gasket trailing the lead-in edge, a portion of the dry lubricant is abraded off the lead-in edge to reduce friction between the rubber gasket and the mating surface.

In an embodiment, a method for dry-lubricated press-fit assembly of a first part onto a second part includes pressing the first part onto the second part by sliding the first part along a mating surface of the second part such that, during the sliding, the mating surface abrades a dry lubricant off a lead-in edge of the first part so as to reduce friction between the mating surface and a rubber gasket, of the first part, trailing the lead-in edge.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Disclosed herein are apparatuses with a dry-lubricating lead-in edge for press-fit assemblies, as well as methods for their manufacture and use. In situations where a first part needs to be press fit onto a second part, the first part may be equipped with a dry-lubricating lead-in edge, as disclosed herein, to reduce friction between the two parts during the process of press fitting. The dry-lubricating edge may thereby reduce the forces required for press fitting and/or eliminate the need for using a wet lubricant.

FIGS. 1 and 2illustrate one scenario of use of the presently disclosed dry-lubricating lead-in edge.FIG. 1is an isometric full-section view of a drive-wheel end100of a vehicle, such as a tractor. The section used inFIG. 1contains the rotation axis190of drive-wheel end100. Drive-wheel end100includes a bearing seal150.FIG. 2is a cross-sectional view showing bearing seal150in further detail, with the cross section taken in a plane that includes rotation axis190(outside the view ofFIG. 2).FIG. 2depicts the portion of bearing seal150also depicted inFIG. 1in the region indicated by arrow198. Bearing seal150includes two dry-lubricating lead-in edges that aid installation of bearing seal150in drive-wheel end100.FIGS. 1 and 2are best viewed together in the following description.

Drive-wheel end100includes an axle shaft110, an axle120, a hub assembly130, a bearing system140, and bearing seal150. Hub assembly130is rigidly attached to axle shaft110and is configured to accommodate a wheel (not shown inFIGS. 1 and 2) of the vehicle. Axle120supports at least part of the load of the vehicle. To engage drive-wheel end100, an engine rotates axle shaft110via a drive line, which causes hub assembly130to rotate about axle120.

Bearing system140reduces friction between hub assembly130and axle120. For this purpose, bearing system140includes an inboard bearing142and an outboard bearing144. In one implementation, bearing system140further includes (a) a spacer146limiting endplay of inboard bearing142and outboard bearing144, (b) a lock ring148, a lock washer147, and a spindle nut149secured to axle120, and (c) a snap ring141secured to hub assembly130. Spacer146, lock ring148, lock washer147, spindle nut149, and snap ring141cooperate to keep inboard bearing142and outboard bearing144properly positioned. Bearing system140requires lubrication, such as oil or grease, at inboard bearing142, outboard bearing144, and bearing seal150to achieve low-friction rotation of hub assembly130about axle120.

Bearing seal150seals an “oil side”186, associated with bearing system140and its lubrication, from an “air side”188that is external to drive-wheel end100. Bearing seal150serves to prevent or at least reduce (a) loss of lubrication from oil side186to air side188, and (b) penetration of contaminants (e.g., external fluids, particles, and/or dirt) from air side188to oil side186and into bearing system140. Penetration of such contaminants into bearing system140may be detrimental to the bearing system lubricant, increase friction in bearing system140, and cause damage in bearing system140.

As shown inFIG. 2, bearing seal150includes a dry-lubricating seal case202and a dry-lubricating sleeve204. Each of seal case202and sleeve204encircles the rotation axis of bearing seal150(i.e., rotation axis190,FIG. 1). The x-axis of coordinate system292, depicted inFIG. 2, is parallel to rotation axis190. The y-axis of coordinate system292is perpendicular to rotation axis190. Sleeve204is rotatable, relative to seal case202, about rotation axis190. Seal case202is affixed to hub assembly130, and sleeve204is affixed to axle120. Seal case202and sleeve204are a distance apart from each other to form a labyrinthine path294from oil side186to air side188. Bearing seal150may include one or more elastomers bridging across labyrinthine path294between seal case202and sleeve204, for example the elastomer240depicted inFIG. 2. Elastomer240encircles rotation axis190, is affixed to a radially innermost edge217of seal case202, and forms a lip242that contacts an innermost axial leg256of sleeve204. Labyrinthine path294, optionally together with elastomer240, forms a dynamic seal. To avoid leaks around bearing seal150, seal case202is affixed to hub assembly130in such a way as to form a static seal therebetween, and sleeve204is affixed to axle120in such a way as to form a static seal therebetween.

Herein, “radial” refers to the dimensions orthogonal to rotation axis190, “axial” refers to the dimension parallel to rotation axis190, “radial leg” refers to a leg with a predominantly radial orientation, and “axial leg” refers to a leg with a predominantly axial orientation.

As part of the process to assemble drive-wheel end100with bearing seal150installed therein, sleeve204is press fit along direction194onto axle120, and seal case202is press fit along direction192into hub assembly130. Subsequently, hub assembly130is mounted on axle120such that seal case202and sleeve204come together to form bearing seal150.

Seal case202includes a frame210, a rubber gasket220, and a dry-lubricating lead-in edge230. Rubber gasket220enables press fitting of seal case202into hub assembly130, and lead-in edge230provides dry lubrication for this press fitting process. Rubber gasket220is affixed to an outer-diameter leg212of frame210. Rubber gasket220forms a surface222which may, but need not, be ribbed. Rubber gasket220creates an interference with a mating surface281of hub assembly130, thereby enabling press fitting of seal case202into hub assembly130. Outer-diameter leg212and mating surface281may be concentric. Typically, the degree of interference between rubber gasket220and mating surface281, required to securely fasten seal case202to hub assembly130, produces a need for lubrication at the interface between surface222and mating surface281so as to keep the forces, required for the press fit assembly of seal case202into hub assembly130, manageable (e.g., at a level that does not impose risk of damaging seal case202or hub assembly130). Lead-in edge230is coupled to one or both of frame210and rubber gasket220. The material of lead-in edge230is composed of or includes a dry lubricant. When seal case202is slid along mating surface281, in the process of press fitting seal case202into hub assembly130, mating surface281abrades material off lead-in edge230. This material is, or includes, dry lubricant. Since surface222of rubber gasket220trails lead-in edge230, dry lubricant abraded off lead-in edge230lubricates the interface between surface222and mating surface281.

In the absence of dry-lubricating lead-in edge230, addition of a separate lubricant, typically a wet lubricant, would be required to keep the press fitting forces manageable. However, addition of such a separate lubricant is an extra process step as compared to a process that utilizes dry-lubricating lead-in edge230. In addition, a separate lubricant could potentially come into contact with and thus contaminate other surfaces during the assembly process. This is particularly concerning if the separate lubricant is a wet lubricant, since wet lubricants tend to attract dirt. Dry-lubricating lead-in edge230eliminates the need for addition of a separate lubricant, and dry-lubricating lead-in edge230inherently deposits lubricant only where it is needed. Furthermore, since the lubricant provided by lead-in edge230is dry, the risk of this lubricant attracting dirt is greatly diminished, as compared to a wet lubricant.

Sleeve204includes a frame250, a rubber gasket260, and a dry-lubricating lead-in edge270. In a manner similar to that discussed for seal case202, rubber gasket260enables press fitting of sleeve204onto axle120, and lead-in edge270provides dry lubrication for this press fitting process. Rubber gasket260is affixed to inner-most axial leg256of frame250. Rubber gasket260forms a surface262which may, but need not, be ribbed. Rubber gasket260creates an interference with a mating surface283of axle120, thereby enabling press fitting of sleeve204onto axle120. Inner-most axial leg256and mating surface283may be concentric. Typically, the degree of interference between rubber gasket260and mating surface283, required to securely fasten sleeve204to axle120, produces a need for lubrication at the interface between surface262and mating surface283so as to keep the forces, required for the press fit assembly of sleeve204onto axle120, manageable. Lead-in edge270is coupled to one or both of frame250and rubber gasket260. The material of lead-in edge270is composed of or includes a dry lubricant. When sleeve204is slid along mating surface283, in the process of press fitting sleeve204onto axle120, mating surface283abrades material off lead-in edge270. This material is, or includes, dry lubricant. Since surface262of rubber gasket260trails lead-in edge270, dry lubricant abraded off lead-in edge270lubricates the interface between surface262and mating surface283. Dry-lubricating lead-in edge270thus provides benefits similar to those provided by dry-lubricating lead-in edge230.

Lead-in edges230and270may be chamfered, as shown inFIG. 2, rounded, or square. Lead-in edge230may be attached only to rubber gasket220, or only to frame210, without departing from the scope hereof. Similarly, lead-in edge270may be attached only to rubber gasket260, or only to frame250, without departing from the scope hereof.

In the embodiment depicted inFIG. 2, frame210of seal case202includes outer-diameter leg212, a radial leg214, an axial leg216, and a radial leg218, serially connected to each other in the order listed. Radial leg218forms innermost edge217. Without departing from the scope hereof, frame210may be configured with more, fewer, or different legs than those depicted inFIG. 2, as long as frame210includes outer-diameter leg212and is capable of cooperating with sleeve204to form a labyrinthine path. Edges where two legs of frame210connect to each other may be rounded, although depicted inFIG. 2as being square.

In the embodiment depicted inFIG. 2, frame250of sleeve204includes inner-most axial leg256, a radial leg254, and an axial leg252, serially connected to each other in the order listed. Without departing from the scope hereof, frame250may be configured with more, fewer, or different legs than those depicted inFIG. 2, as long as frame250includes inner-most axial leg256and is capable of cooperating with seal case202to form a labyrinthine path. Edges where two legs of frame250connect to each other may be rounded, although depicted inFIG. 2as being square.

Bearing seal150may further include a retaining ring280that encircles rotation axis190.

Without departing from the scope hereof, bearing seal150may be used in other types of wheel assemblies, and/or to seal other types of bearings, than depicted inFIG. 1. Generally, though, seal case202is press fit to a radially inward-facing mating surface of one part, and sleeve204is press fit to a radially outward-facing mating surface of another part.

FIG. 3illustrates, in cross-sectional view, one dry-lubricating apparatus300, including a chamfered dry-lubricating lead-in edge330, for press fitting onto a mating part380. Apparatus300includes a frame310, a rubber gasket320, and chamfered dry-lubricating lead-in edge330. Frame310includes a leg312, and optionally also at least one additional leg314. Rubber gasket320is affixed to leg312. In one example, rubber gasket320is molded onto leg312. Rubber gasket320has a surface322. Surface322may be ribbed. Lead-in edge330is affixed to one or both of frame310and rubber gasket320. Apparatus300is configured to be press fit onto a mating surface381of mating part380by sliding apparatus300along mating surface381in direction392.

It is understood that leg312may have any thickness, for example a thickness that greatly exceeds the thickness of rubber gasket320and/or exceeds the length of leg312along direction392.

Lead-in edge330is composed of, or includes, a dry lubricant. When apparatus300is slid along mating surface381along direction392, mating surface381abrades material off lead-in edge330. This material is or includes dry lubricant. Surface322of rubber gasket320trails lead-in edge330and is therefore slid across dry lubricant deposited onto mating surface381after having been abraded off lead-in edge330. Thus, lead-in edge330provides dry lubricant that reduces friction between rubber gasket320and mating surface381. By virtue of dry-lubricating lead-in edge330, dry-lubricating apparatus300may be press fit onto mating part380without using a separate lubricant, e.g., a wet lubricant. Dry-lubricating apparatus300thereby facilitates a simple and clean press fit assembly process, as compared to press fit assembly processes without dry-lubricating lead-in edge330, without imposing challenging force requirements on the press fit assembly process.

In certain embodiments, apparatus300has a cylindrical shape. In one such embodiment, surface322faces radially inward and apparatus300is configured to be press fit into a bore of mating part380, with mating surface381defining an inner-diameter of this bore. Seal case202is an example of this embodiment of apparatus300. In another such embodiment, surface322faces radially outward and apparatus300is configured to be press fit onto a cylinder of mating part380, with mating surface381defining an outer-diameter of this cylinder. Sleeve204is an example of this embodiment of apparatus300.

In another embodiment, apparatus300, or at least leg312, is non-cylindrical but yet of an enclosed shape (e.g., square) configured to be press fit around mating part380having a cylindrical or non-cylindrical mating surface381. In a related embodiment, apparatus300, or at least leg312, is non-cylindrical but surface322is outward-facing and of an enclosed shape (e.g., square) configured to be press fit into a bore of mating part380. This bore may be cylindrical or non-cylindrical. In certain implementations of these two embodiments, the shape of mating surface381mimics the general shape of leg312. In other implementations of these two embodiments, the shape of mating surface381differs from the general shape of leg312.

In yet another embodiment, leg312is planar and apparatus300is configured to be press fit onto a planar mating surface381.

More generally, the configuration apparatus300is applicable to situations where a first part needs to be press fit onto a second part, regardless of the exact shape of these parts. In such situations, the first part may have the configuration of apparatus300to reduce friction between the two parts during the process of press fitting.

Dry-lubricating lead-in edge330has a chamfer332. Chamfer332may ease the step of initially slipping apparatus300onto mating surface381and/or reduce gripping during sliding of apparatus300on mating surface381. Chamfer332is oriented at an angle362to mating surface381. Angle362is, for example, in the range between 15 and 30 degrees, or in the range between 10 and 45 degrees. In the dimension parallel to direction392, chamfer332has extent360. Extent360may be in the range between one and five millimeters, such as in the range between 1.8 and 3.0 millimeters.

In an embodiment, lead-in edge330has a non-chamfered portion334that trails chamfer332. This embodiment of lead-in edge330may cause a greater amount of dry lubricant being abraded off lead-in edge330by mating surface, and thus made available to rubber gasket320, than embodiments of lead-in edge330without non-chamfered portion334.

Rubber gasket320has thickness364away from leg312. Lead-in edge330may extend away from leg312to the level of thickness364(when not compressed by press fitting), as depicted inFIG. 3. Alternatively, lead-in edge330may extent away from leg312to a level that as less than thickness364or more than thickness364. The amount of dry lubricant abraded off lead-in edge330by mating surface381may be tuned by adjusting the several parameters of apparatus300, such as the material of lead-in edge330, the extent of lead-in edge330away from leg312relative to thickness364, the length of extent360, and angle362. The optimal shape and composition of lead-in edge330may depend on the compressibility of rubber gasket320and/or the friction properties of surface322and mating surface381.

Lead-in edge330may be hydrophobic and/or corrosion resistant, for example to help protect the interface between rubber gasket320and mating surface381. Such protection is particularly advantageous when the interface between rubber gasket320and mating surface381must form a static seal, such as the static seal between seal case202and hub assembly130and the static seal between sleeve204and axle120.

In one embodiment, lead-in edge330is composed of, or includes, a thermoplastic, such as polyoxymethylene (e.g., Delrin). In another embodiment, lead-in edge330is composed of, or includes, polytetrafluoroethylene. In yet another embodiment, lead-in edge330includes molybdenum disulfide and/or graphite. For example, lead-in edge330may be a mixture of a (a) polymer and (b) molybdenum disulfide and/or graphite. Polymer-based embodiments of lead-in edge330may be formed as a mechanically stable structure, e.g., a rigid or flexible solid ring, that is then mounted on rubber gasket320and/or frame310. Alternatively, lead-in edge330is a wax, or wax-like material, that is molded on rubber gasket320and/or frame310. Lead-in edge330may be composed of a wax, such as beeswax, paraffin, or carnauba wax. Alternatively, lead-in edge330includes a wax and one or more additional dry lubricants, e.g., molybdenum disulfide, graphite, and/or polytetrafluoroethylene.

FIG. 4illustrates, in cross-sectional view, one dry-lubricating apparatus400, including a rounded dry-lubricating lead-in edge430, for press fitting onto mating part380(FIG.3). Apparatus400is similar to apparatus300except for lead-in edge430replacing lead-in edge330. Lead-in edge430is similar to lead-in edge330apart from chamfer332being replaced by a rounded edge432. Rounded edge432may have radius of curvature in the range between one and five millimeters, for example between 1.8 and 3.0 millimeters.

In a modification of apparatus400, lead-in edge430is square, corresponding to a radius of curvature of zero.

FIG. 5illustrates, in perspective view, one cylindrical dry-lubricating apparatus500being press fit onto a radially outward-facing cylindrical mating surface581of a cylinder580. To show the different components of apparatus500, a section of apparatus500is cut away inFIG. 5, and cylinder580is depicted as being see-through. It is understood that apparatus500encircles cylinder580. Apparatus500is an embodiment of apparatus300.

Apparatus500includes a frame510, a rubber gasket520having a radially inward-facing surface522, and a chamfered lead-in edge530. Frame510, rubber gasket520, and lead-in edge530are cylindrical embodiments of frame310, rubber gasket320, and lead-in edge330, respectively. Apparatus500is press fit onto cylinder580along a direction592. In one implementation, the diameter588of mating surface581is in the range between 3 and 15 inches.

In an alternative embodiment, not illustrated inFIG. 5, apparatus500is instead configured with a rounded lead-in edge and is thus an embodiment of apparatus400, or apparatus500is configured with a square modification of lead-in edge430of apparatus400. Cylinder580may be hollow or solid, without departing from the scope hereof.

FIG. 6illustrates, in perspective view, one cylindrical dry-lubricating apparatus600being press fit into a bore of a cylinder680against a radially inward-facing cylindrical mating surface681of cylinder680. To show the different components of apparatus600, a section of apparatus600is cut away inFIG. 6, and cylinder680in depicted as being see-through. Apparatus600and cylinder680share a common cylinder axis690encircled by each of cylinder680and apparatus600. Apparatus600is an embodiment of apparatus300.

Apparatus600includes a frame610, a rubber gasket620having a radially outward-facing surface622, and a chamfered lead-in edge630. Frame610, rubber gasket620, and lead-in edge630are cylindrical embodiments of frame310, rubber gasket320, and lead-in edge330. Apparatus600is press fit into the bore of cylinder680against mating surface681along a direction692. In one implementation, the diameter688of mating surface681is in the range between 4 and 16 inches.

In an alternative embodiment, not illustrated inFIG. 6, apparatus600is instead configured with a rounded lead-in edge and is thus an embodiment of apparatus400, or apparatus600is configured with a square modification of lead-in edge430of apparatus400. Without departing from the scope hereof, cylinder680may be replaced with a non-cylindrical object forming a bore defined, at least in part, by a radially inward-facing cylindrical mating surface.

FIG. 7illustrates one dry-lubricating apparatus700with a dry-lubricating lead-in edge730snap fit onto a rubber gasket of apparatus700and also directly coupled to a frame of apparatus700. As depicted inFIG. 7, lead-in edge730is chamfered and apparatus700is an embodiment of apparatus300. However, without departing from the scope hereof, lead-in edge730may instead be rounded, in which case apparatus700is an embodiment of apparatus400, or lead-in edge730may be square such that apparatus700is an embodiment of a modification of apparatus400having a square lead-in edge430. Apparatus700may be cylindrical and form an embodiment of apparatus500or600.

In addition to lead-in edge730, apparatus700includes frame310and a rubber gasket720. Rubber gasket720is an embodiment of rubber gasket320, shaped to allow direct coupling between a lip732of lead-in edge730and frame310. In addition, rubber gasket720forms an undercut724. Lead-in edge730includes a protruding ridge734shaped to fit in undercut724. Lead-in edge730is a solid piece formed separately from the frame310and rubber gasket720. When mounting lead-in edge730in apparatus700, protruding ridge734is snapped into undercut724. This snap fit, together with portion732leading a portion722of rubber gasket720, may improve retention of lead-in edge730in apparatus700, especially when apparatus700is slid along mating surface381in direction392.

In cylindrical embodiments of apparatus700(e.g., as shown inFIGS. 5 and 6), lead-in edge730is a ring and may be press fit onto one or both of rubber gasket720and frame310to further improve retention of lead-in edge730in apparatus700.

FIG. 8illustrates one dry-lubricating apparatus800with a dry-lubricating lead-in edge830snap fit onto a rubber gasket of apparatus800without being directly coupled to the frame of apparatus800. Apparatus800is a modification of apparatus700, wherein lead-in edge830is not directly coupled to frame310of apparatus800. Apparatus800implements a rubber gasket820that occupies the space that, in apparatus700, is occupied by lip732.

FIG. 9illustrates one dry-lubricating apparatus900with a dry-lubricating lead-in edge930mounted exclusively to the frame of apparatus900. As depicted inFIG. 9, lead-in edge930is chamfered and apparatus900is an embodiment of apparatus300. However, without departing from the scope hereof, lead-in edge930may instead be rounded, in which case apparatus900is an embodiment of apparatus400, or lead-in edge930may be square such that apparatus900is an embodiment of a modification of apparatus400having a square lead-in edge430. Apparatus900may be cylindrical and form an embodiment of apparatus500or600.

In addition to lead-in edge930, apparatus900includes frame310and a rubber gasket920. Rubber gasket920is an embodiment of rubber gasket320, shaped to (a) allow direct coupling between lead-in edge930and frame310and (b) exclusively trail lead-in edge930.

In one embodiment, lead-in edge930is a solid piece formed separately from the frame310and rubber gasket920. This embodiment of lead-in edge930may be press fit onto frame310. In another embodiment, lead-in edge930is a wax or wax-like material that is deposited on frame310, next to rubber gasket920, in softened form and then, subsequently, allowed to harden.

FIG. 10illustrates one method1000for dry-lubricated press-fit assembly of a first part onto a second part. The first part is, for example, apparatus300. Method1000includes a step1010that press fits the first part onto the second part by sliding the first part along a mating surface of the second part such that the sliding causes the mating surface to abrade a dry lubricant off a lead-in edge of the first part so as to reduce friction between the mating surface and a rubber gasket, of the first part, trailing the lead-in edge. In one example of step1010, apparatus300is press fit onto mating part380by sliding apparatus300along mating surface381in direction392. As discussed above in reference toFIG. 3, mating surface381abrades a dry lubricant off lead-in edge330, and this dry lubricant reduces friction between rubber gasket320and mating surface381.

In one embodiment, step1010includes a step1012of sliding a ring-shaped part onto the outer diameter of a cylinder. In one example of step1012, apparatus500is slid onto cylinder580as shown inFIG. 5. In another example of step1012, sleeve204is slid onto axle120as discussed above in reference toFIGS. 1 and 2. In another embodiment, step1010includes a step1014of sliding a ring-shaped part into a bore. In one example of step1014, apparatus600is slid into bore682as shown inFIG. 6. In another example of step1014, seal case202is slid into hub assembly130as discussed above in reference toFIGS. 1 and 2.

FIG. 11illustrates one method1100for manufacturing a dry-lubricating apparatus for press fitting onto a mating part. Method1100is for example used to manufacture apparatus300. Method1100includes a step1110of disposing a lead-in edge on at least one of a frame and a rubber gasket fixed to the frame to create an interference with a mating surface of the mating part so as to enable said press fitting. The lead-in edge includes a dry lubricant. In one example of step1110, lead-in edge330is disposed on one or both of frame310and rubber gasket320.

In one embodiment, step1110includes a step1112of press fitting a solid ring onto at least one of the frame and the rubber gasket. In one example of step1112, lead-in edge530is press fit onto one or both of frame510and rubber gasket520. In another example of step1112, lead-in edge630is press fit onto one or both of frame610and rubber gasket620. Step1112may include a step1114of snapping a protruding ridge of the lead-in edge into an undercut in the rubber gasket. In one example of step1114, protruding ridge734is snapped into undercut724, as depicted inFIGS. 7 and 8.

In another embodiment, step1110includes steps1116and1118. Steps1116and1118are an alternative to step1112. Step1116applies softened wax onto at least one of the frame and the rubber gasket. Step1118allows the wax to harden to form the lead-in edge from the wax. In one example of steps1116and1118, a softened wax is applied to one or both of frame310and rubber gasket320, whereafter the wax is allowed to harden to form lead-in edge330, as illustrated inFIG. 3.

Step1110may include a step1120or a step1122. Step1120disposes the lead-in edge on an inner-diameter leg of the frame such that the lead-in edge faces radially inward. In one example of step1120, lead-in edge270is disposed on inner-most axial leg256of frame250and/or rubber gasket260, to form dry-lubricating sleeve204. Step1122disposes the lead-in edge on an outer-diameter leg of the frame such that the lead-in edge faces radially outward. In one example of step1122, lead-in edge230is disposed on outer-diameter leg212of frame210and/or rubber gasket220, to form dry-lubricating seal case202.

Dry-lubricating lead-in edge1230may have a chamfer1232(as depicted inFIG. 12). Chamfer1232is similar to chamfer332. However, without departing from the scope hereof, dry-lubricating edge1230may be configured with a rounded edge (similar to rounded edge432) instead of chamfer1232, or be configured with a square edge that is neither chamfered nor rounded.