Decorative capped wheel nut and method of assembly

A decorative cap and wheel nut or bolt insert, and a method of assembling them. The insert is coated and/or plated and includes a hex-shaped section and a section having a circular cylindrical outer surface. A cap includes a hex cross-section segment and a circular cylindrical cross-section segment. The hex cross-section segment of the cap slips easily over the hex section of the insert while the circular cylindrical cross-section segment has a smaller ID than the OD of the circular cylindrical insert section whereby an interference fit is formed between them when the insert is press fit into the cap.

FIELD OF THE INVENTION

This invention relates generally to wheel nuts or bolts for securing a vehicle wheel, i.e., a tire and rim, on a motor vehicle. It relates particularly to a decorative capped wheel nut or bolt and a method of assembly.

BACKGROUND OF THE INVENTION

Decorative capped wheel nuts and bolts are well-known in the automotive art. A decorative capped wheel nut, for example, conventionally comprises a nut insert and a decorative cap which is fastened to the insert by welding, crimping or with an adhesive. Examples of these constructions are illustrated in various prior art patents, including the Toth U.S. Pat. No. 4,955,773, the Bydalek U.S. Pat. No. 5,772,377, the Chaivre U.S. Pat. Nos. 4,018,133, and 4,056,862, the Baltzell U.S. Pat. No. 4,764,070 and the Somers et al. U.S. Pat. No. 6,036,420, for example. It is also known to form threads in a cap and in a lug nut and thread the cap onto the nut. See the Nolan et al. U.S. Pat. No. 5,180,266 in this regard.

All methods described in the prior art require relatively complex structures, assembly procedures and/or additional components. Assemblies produced by welding require expensive and sophisticated equipment for practical implementation of production. Practical options for plating the inserts are limited where welding is employed, placing welded designs at a disadvantage for achieving high corrosion resistance. Crimped designs require the addition of components, i.e., a sealant or o-ring, which complicates automated assembly. The use of adhesives causes similar problems. Because of the nature of the welding processes, or the introduction of extra components, production rates for these assembly processes are low.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved decorative capped wheel nut or wheel bolt.

Another object is to provide a decorative capped wheel nut or wheel bolt wherein the decorative cap is secured to the nut or bolt insert without welding, applying an adhesive, or using a sealant or O-ring.

Yet another object is to provide a decorative cap and insert assembly which is simpler and less expensive, but just as reliable, as prior art assemblies.

Still another object is to provide a new and improved method of assembling a decorative cap and nut or bolt insert.

The foregoing and other objects are realized in an insert and cap assembly wherein the components are securely fastened together by creating an interference fit between the cap and the insert. Specifically, the insert includes at least one section with a plated, coated or plated and coated circular cylindrical outer surface. The cap has a corresponding segment with a circular cylindrical inner surface which has an inside diameter 0.010 to 0.030 inches smaller than the outside diameter of the coated circular cylindrical outer surface. The insert is press fit into the cap, driving the cap's cylindrical inner surface over the insert's coated circular cylindrical outer surface. A 0.002 to 0.006 inches interference fit is formed around the interfering circular cylindrical surfaces.

The improved method of retaining a cap on the insert body requires only two components, the cap and the insert, thus reducing the extra expense of an additional component and the complexities of introducing this extra component into the assembly process. It also allows the use of all types of coating, plating and coating or plating alone on the insert, which is not possible using current welding assembly methods. Further cost savings may be achieved with higher assembly rates using simple hydraulic, pneumatic, or mechanical press equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and particularly toFIGS. 1–6, a decorative capped wheel nut assembly comprising a first embodiment of the present invention is seen generally at10. The wheel nut assembly10includes a nut insert12and a decorative cap14fastened securely together by a method embodying features of the invention.

As seen inFIGS. 3,4and6, the nut insert12comprises a body21having a cylindrical bore23extending axially through it from a hex-shaped section24on one end to a frusto-conical base25on the other. The nut insert12is commonly referred to as a hex-nut insert and is fabricated in a conventional manner of carbon steel. The frusto-conical base25is adapted to seat in a conventional manner in a wheel rim aperture (not shown) to fasten the wheel rim to a vehicle wheel stud (not shown). The bore23is internally threaded at its inner end27to receive the stud.

The nut insert12is coated in a conventional manner to prevent oxidation of exposed areas. In the embodiment illustrated a coating of GEOMET brand coating material available from Metal Coatings International, Inc. of Chardon, Ohio, is applied. GEOMET is a coating comprised mainly of overlapping zinc and aluminum flake in an inorganic binder, and is chromium free. It is applied over the entire insert12to a thickness of 0.001 inches.

Between the hex-shaped section24and the frusto-conical base25, the insert body21has two cylindrical body sections31and33. The section31of the illustrated insert body21has a cylindrical outer (coated) surface35with an outside diameter (OD) of 0.930 inches. The surface35has an axial length of 0.130 inches. The section33has a cylindrical outer (coated) surface39with an OD of 0.955 inches. The surface33has an axial length of 0.0625 inches. A radially extending shoulder41is formed between the two cylindrical surfaces31and33.

As seen inFIGS. 2,5and6, the cap14comprises three axially aligned wall segments; a dome-shaped end wall segment51, a hex cross-section side wall segment53and a circular cylindrical side wall segment55. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment53are such that it slips easily over the coated, hex-shaped section24of the insert body. According to the invention, however, as will hereinafter be further discussed, the internal cross-sectional dimension of the circular cylindrical side wall segment55is such that a predetermined interference fit is formed between the inner surface57of the wall segment55and the coated cylindrical outer surface35of the insert body21when the cap14is press fit onto the insert12.

The cap14is fabricated of stainless steel sheet with a nominal thickness of 0.018 to 0.020 inches. The inside diameter (ID) of the cylindrical wall segment55is preferably 0.910 inches. When the cap14is pressed onto the insert12, the cylindrical wall segment55undergoes both plastic and elastic deformation. The portion of deformation that is plastic serves to allow a reasonable manufacturing tolerance for both components. The elastic deformation results in tensile hoop stresses in the cap14and constitutes the mechanism by which the cap14is retained on the insert12. The resulting interference fit is approximately 0.0025, varying with changes in cap wall thickness or mechanical properties of the cap material.

FIG. 7illustrates the assembly of a nut insert12into a cap14in a simple mechanical press P. The press P comprises a fixed die D1in which the cap14is seated. A movable die D2receives the insert12and drives it downwardly onto the cap14under the influence of pressure exerted in a conventional manner by the mechanical press P. The fixed die D1receives the cap14is a well W. The well W is dimensioned to permit the radial expansion of the cylindrical side wall segment55which takes place in the cap14as the insert12is press fit into the cap14.

Referring now toFIGS. 8 and 9, a decorative capped wheel nut assembly comprising a second embodiment of the invention is seen generally at110. The assembly110includes a nut insert112and a decorative cap114fastened together according to the present invention.

The nut insert112comprises a body121having a cylindrical bore123extending axially through it from a cylindrical section131on one end to a frusto-conical base125on the other. The base125is adapted to seat in a wheel rim aperture (not shown). The bore123is internally threaded at127. The insert112is coated in a manner previously discussed.

Between the conical base125and the cylindrical section131, there is a hex-shaped section124. The hex-shaped section124corresponds to the hex section24in the insert body21of the assembly10.

The axially outer, or end cylindrical section131, has a coated cylindrical outer surface135with an OD of 0.660 inches. The surface135has an axial length of 0.190 inches.

As seen inFIG. 8the cap114, which is again formed from stainless steel sheet, comprises four axially aligned segments; a dome shaped end wall segment151, a cylindrical side wall segment155, a hex-shaped side wall segment153and a frusto-conical lip152. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment153are such that it slips easily over the coated hex-shaped section124in the insert body121.

The ID of the cylindrical wall segment155is 0.640 inches. When the cap114is pressed onto the insert112, the cylindrical wall segment155undergoes both plastic and elastic deformation in the manner hereinbefore discussed with relation to the cap14. The elastic deformation constitutes the mechanism by which the cap114is retained on the insert112. The resulting interference fit is approximately 0.0025, again varying with changes in cap wall thickness or mechanical properties of the cap material.

Referring now toFIGS. 10 and 11, a decorative capped wheel nut assembly comprising a third embodiment of the invention is seen generally at210. The assembly210includes a nut insert212and a decorative cap214fastened together according to the invention.

The nut insert212comprises a body221having a cylindrical bore223extending axially through it from a cylindrical section231on one end to a frusto-conical base225on the other. The base225is adapted to seat in a wheel rim aperture (not shown). The bore223is internally threaded at227. Like the inserts12and112, the insert212is coated.

Between the conical base225and the cylindrical section231there is a hex-shaped section224. The hex-shaped section224corresponds to the section24in the insert body21of the insert24.

Between the hex-shaped section224and the frusto-conical base225, the insert body221has two cylindrical body sections233and234. The axially outer cylindrical section233of the illustrated insert body221has a coated cylindrical outer surface235with an outside diameter (OD) of 0.930 inches. The surface235has an axial length of 0.130 inches. A radially extending shoulder241is formed between the two cylindrical surfaces233and234.

The end cylindrical section231has a coated cylindrical outer surface236with an OD of 0.660 inches. The surface236has an axial length of 0.190 inches.

As seen inFIG. 11, the cap214, again formed of stainless steel sheet, comprises four axially aligned segments; a dome shaped end wall segment251, an end circular cylindrical side wall segment255, a hex-shaped side wall segment253and a circular cylindrical side wall segment252. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment253are such that it will slip freely over the coated hex-shaped section224in the insert body221.

The ID of the cylindrical wall segment255is 0.640 inches. When the cap214is pressed onto the insert212, the cylindrical wall segment255undergoes the aforedescribed plastic and elastic deformation as it is forced over the coated cylindrical surface236. The resulting interference fit is again approximately 0.0025.

The ID of the cylindrical wall segment252is 0.910 inches. As such, an interference fit of 0.0025 inches is effected at the same time between the wall segment252and the coated outer surface235of the end cylindrical section231.

InFIGS. 12–15the invention is seen in the context of a wheel bolt rather than a wheel nut. Referring specifically toFIGS. 12 and 13, a decorative capped wheel bolt assembly comprising a fourth embodiment of the invention is seen generally at310. The assembly310includes a bolt insert312and a decorative cap314.

The bolt insert312comprises a bolt body321fabricated of carbon steel in a conventional manner. The body321includes a hex-shaped section324at one end and an externally threaded base327at the opposite end. The insert312is coated in a manner previously discussion.

Between the hex-section324and the threaded base327, a circular cylindrical section331and a frusto-conical section333are formed. The circular cylindrical section331has a coated cylindrical outer surface335. The OD of surface335is 0.895 inches. The surface335has an axial length of 0.165 inches.

The frusto-conical section333is adapted to seat in a wheel rim aperture (not shown) to fasten the wheel rim to a vehicle wheel. The threaded base327of the insert312threads into the wheel hub in a well known manner.

The cap314, again formed from stainless steel sheet, comprises three axially aligned segments, a dome shaped end wall segment351, a hex-shaped side wall segment353and a cylindrical side wall segment355. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment353are such that it slips easily over the coated hex-shaped section324in the insert body321.

The ID of the cylindrical wall segment355is 0.875 inches. When the cap314is pressed onto the insert312, the cylindrical wall segment355undergoes the aforedescribed plastic and elastic deformation as it is forced over the coated surface335on the bolt body321. The resulting interference fit is again approximately 0.0025 inches.

Referring now toFIGS. 14 and 15, of a decorative capped wheel bolt assembly comprising a fifth embodiment of the invention is seen generally at410. The assembly410also includes a bolt insert413and a decorative cap414.

The bolt insert412comprises a bolt body421fabricated of carbon steel in a conventional manner. The body421includes a hex-shaped section424near one end and an externally threaded base427at the opposite end. The insert412is coated in a manner previously discussed.

Axially outside the hex-section424, the insert412includes a circular cylindrical section431. The circular cylindrical section431has a coated cylindrical outer surface435. The OD of surface435is 0.615 inches. The surface435has an axial length of 0.150 inches.

The insert412also has a spherical section433adapted to seat in a conventional manner in a wheel rim aperture (not shown) to fasten the wheel rim to a vehicle wheel. The threaded base427of the insert412threads into the wheel in a well known manner.

The cap414, again formed from stainless steel sheet, comprises three axially aligned segments; a dome shaped end wall segment451, a cylindrical side wall segment455, a hex-shaped side wall segment453and a flared lip456. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment453are such that it slips easily over the coated hex-shaped section424in the insert body421.

The ID of the cylindrical wall segment455is 0.595 inches. When the insert412is pressed into the cap414, the cylindrical wall segment455undergoes the aforedescribed elastic deformation. As it is forced over the coated cylindrical surface435on the bolt body421, an interference fit of approximately 0.0025 inches is effected around the coated surface435.

FIGS. 16 and 17illustrate yet a sixth embodiment of a capped wheel assembly embodying features of the invention at510. The assembly510includes a nut insert512and a decorative cap514.

The nut insert512comprises a body521having a cylindrical bore523extending axially through it from a hex-shaped section524on one end to a frusto-conical base525on the other. The base525is adapted to seat in a wheel rim aperture (not shown). The bore523is internally threaded at527. Like the inserts12and112, the insert512is coated.

Between the hex-shaped head524and the frusto-conical base525, the insert body521has a body section533. The body section533of the illustrated insert body521has a coated cylindrical outer surface535with an OD on 1.160 inches and an axial length of 0.130 inches. Below the cylindrical body section surface535, and above the frusto-conical base525, there is an undercut534.

The cap514comprises three axially aligned wall segments; a dome-shaped end wall segment551, a hex cross—section side wall segment553, a circular cylindrical side wall segment555and a crimp section556. The configuration and internal cross-sectional dimensions of the hex-shaped side wall segment553are such that it slips easily over the coated, hex-shaped section524of the insert body (before the inward crimp section556is formed). The internal cross-sectional dimension of the circular cylindrical side wall segment555is such that a predetermined interference fit is formed between the inner surface557of the wall segment555and the coated cylindrical outer surface535of the insert body521when the cap514is press fit onto the insert512.

The cap514is fabricated of stainless steel sheet with a nominal thickness of 0.018 to 0.020 inches. The inside diameter (ID) of the cylindrical wall segment555is preferably 1.140 inches. The cap514is pressed onto the insert512and the cylindrical wall segment555undergoes plastic and elastic deformation. The resulting interference fit is approximately 0.0025.

In this embodiment of the invention, the crimp section556is formed inwardly after the insert512is press fit into the cap514in the aforedescribed manner. Crimping may be accomplished as a continuation of the press-fit operation. The crimp section556is crimped into engagement with the undercut534on the insert body521. The crimp feature is offered as an option where the assembly510may be subject to extreme wrenching abuse, and assures that it will remain intact under such conditions. It also provides a pleasing decorative appearance to the assembly. The interference fit and the crimp then both serve to hold the cap514securely on the insert512with the interference fit serving the further function of blocking the entry of moisture at the juncture of surfaces535and537.

It should be pointed out at this point that the various inserts described might be plated first, and then coated. They might also be plated in a conventional manner and not coated. The invention contemplates employing any of these approaches to protecting a carbon steel insert from the elements. It should also be understood that although only the third embodiment assembly210(FIGS. 10 and 11) illustrates using separate interference fits at two axially spaced, mating cylindrical surfaces, the invention contemplates the use of either one or two sets of mating cylindrical surfaces in any embodiment as a matter of choice.

While preferred embodiments of the invention have been described, it should also be understood that the invention is not so limited and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.