Concentric knurl ball joint

Abstract

A replacement ball joint assembly (10) adapted to be pressed into a previously used and possibly distorted receiving hole (26) in a suspension component such as a control arm (28). A socket housing (12) of the assembly (10) includes a plurality of generally annular, concentric knurls (36) each having a respective crest portion (38) and separated one from another by intervening relief grooves (40). The crest portions (38) of the knurls (36) may be tapered so as to provide a lead-in feature to minimize misalignment during a press-in installation operation. The knurls (36) are preferably softer than the control arm material so that they yield during press-in rather than further disfiguring or enlarging the receiving hole (26). Displaced material from the crest portions (38) of the knurls (36) flows into the relief grooves (40).

Claims

1. A method for replacing a ball joint assembly in a vehicle suspension component, said method comprising the steps of: providing a vehicle suspension component having a worn-out ball joint assembly lodged in a cylindrically shaped receiving hole; removing the worn-out ball joint assembly from the suspension component to expose the cylindrical receiving hole; providing a replacement ball joint assembly having an exterior side wall with a lead-in end and an axially spaced exterior stop flange; forming a plurality of generally annular knurls about the exterior side wall, each knurl having a crest portion establishing an outer diameter, a plurality of the knurls adjacent the lead-in end having a smaller outer diameter than a last knurl adjacent the stop flange, and with each knurl being separated from the next adjacent knurl with an intervening relief groove; and and forcibly pressing the replacement ball joint assembly into the exposed cylindrical receiving hole in the suspension component while simultaneously displacing crest material from at least one of the knurls into an immediately adjacent one of said in relief grooves.

2. The method of claim 1 wherein said forming step includes creating a frusto-conically tapered crest portion on at least a first knurl adjacent the lead-in end.

3. The method of claim 1 wherein said forming step includes developing each knurl with an axial width and developing each relief groove with an axial span; the axial width of each knurl being greater than the axial span of each relief groove directly adjacent thereto.

4. The method of claim 1 wherein said forming step includes machining each knurl in a substantially annular configuration.

5. The method of claim 1 wherein the knurls are of a material with a softer material hardness than the suspension component.

6. The method of claim 1 wherein said step of forcibly pressing the replacement ball joint includes bringing the exterior stop flange into direct contact with the suspension component.

7. The method of claim 1 wherein the outer diameter of at least one of the plurality of knurls adjacent the lead-in end is smaller than a diameter of the receiving hole in the suspension component while the outer diameter of the last knurl is larger than the diameter of the receiving hole whereby pressing of the ball joint assembly into the receiving hole of the suspension component creates an interference fit between at least the crest of the last knurl and the receiving hole but not between the crest of at least one of the plurality of knurls adjacent the lead-in end and the receiving hole.

8. The method of claim 1 wherein the cylindrical receiving hole is distorted after removal of the worn-out ball joint assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein:

(2) FIG. 1 is an exemplary, fragmentary view of a vehicular wheel and its associated suspension components including an upper control arm, lower control arm and steering knuckle, with press-fit style ball joint assemblies disposed there between;

(3) FIG. 2 is an exemplary view of a press-fit ball joint assembly being installed into a lower control arm using a C-frame press tool, installation sleeve and adapter;

(4) FIG. 3 is an enlarged view of a prior art socket housing enlarged from the area circumscribed at 3 in FIG. 2 and showing the traditional axial, spline-like knurls;

(5) FIG. 4 is a cross-sectional view of a replacement ball joint assembly according to the subject invention;

(6) FIG. 5 is a fragmentary elevation showing a replacement ball joint assembly according to the subject invention poised for insertion into a receiving hole in a suspension component;

(7) FIG. 6 is a fragmentary view like that in FIG. 5 but further advanced to depict the first knurl adjacent the lead-in end of the socket housing serving as a pilot feature to reduce the tendency for misalignment;

(8) FIG. 7 is a view as in FIG. 6 showing a still further advancement with the ball joint assembly in a fully seated condition;

(9) FIG. 8 is an enlarged, fragmentary view of a portion of the exterior side wall of the socket housing illustrating a tapered, lead-in angle formed by the crests of the respective knurls in one embodiment of the invention; and

(10) FIG. 9 is another enlarged view showing the forcible pressing of a replacement ball joint assembly into an exposed receiving hole in a suspension component whereby crest material from the relatively soft knurls is displaced into the relief grooves in response to attrition with the receiving hole, whereby damage to the inside diameter of the receiving hole is minimized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(11) Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a replacement ball joint assembly according to the subject invention is generally shown at 10 in FIG. 4. The assembly 10 includes a cup-like socket housing 12, preferably formed from a metal such as steel, in which is captured the articulating ball head portion 14 of a ball stud 16, also preferably formed from steel or other suitable material. The ball stud 16 includes a mounting shaft 18 that extends integrally away from the ball head portion 14, outwardly from the socket housing 12. The mounting shaft 18 may have a tapered connection surface and a threaded end 20, although the specific shapes and attachment techniques for the mounting shaft 18 may vary from one application to the next.

(12) The socket housing 12 defines a central axis A, and includes an exterior side wall having a lead-in end 22 and an axially spaced exterior stop flange 24. In practice, the lead-in end 22 is inserted first into a receiving hole 26 in a suspension component 28, as viewed in FIGS. 5 and 6. During a press-fit operation, the socket housing 12 is forced, such as through application of the screw of a C-frame tool, until the stop flange 24 abuts the suspension component 28 in surface-to-surface contact as shown in FIG. 7. The socket housing 12 may include a ring groove 30 for receiving a snap ring or other type of supplemental retention device once the assembly 10 has been seated in the suspension component 28.

(13) A dust boot 32 may be employed, as needed, to provide an enclosure to seal the socket housing 12 from external contaminants as well as to retain the lubricant or grease at the articulating interface with the ball head portion. The assembly 10 is adapted to receive grease or other lubricant through a grease fitting 34.

(14) Turning now to FIGS. 5-9, the socket housing 12 is shown in enlarged detail to better illustrate the exterior side wall of the socket housing 12. The portion of the exterior side wall between its lead-in end 22 and stop flange 24 is configured with a plurality of generally annular knurls 36. Each knurl 36 has a crest portion 38 which establishes its respective outer diameter. The knurls 36 are axially separated from one another by intervening relief grooves 40. As perhaps best shown in FIGS. 8 and 9, flanks 42 of each knurl 36 extend almost radially to interconnect each side of its crest 38 to an adjacent relief groove 40. A back-up relief groove 44 is disposed between the last knurl 36B and the stop flange 24.

(15) The knurls 36 are preferably formed in a machining operation so as to minimize the effects of work-hardening, thereby maintaining the material hardness of the knurls 36 in the softest possible condition. Furthermore, the knurls 36 are formed so that the first knurl 36A adjacent the lead-in end 22 has a smaller outer diameter than the last knurl 36B adjacent the stop flange 24. The smaller first knurl 36A is designed, relative to the receiving hole 26 in the suspension component 28 to provide a piloting or lead-in feature to help center the ball joint assembly 10 during installation and thereby prevent inadvertent misalignment or damage to the suspension component 28. Preferably, this relative sizing results in a repair scenario in which pressing of the ball joint assembly 10 into the suspension component 28 experiences an interference fit between at least the last knurl 36B and the receiving hole 26 but not between the crest of the first knurl 36A and the receiving hole 26. In one preferred embodiment, the crests 38 of all the knurls 36 are aligned with a frusto-conical taper like that illustrated in FIG. 8, wherein the broken line represents a cylinder equivalent in diameter to the last knowl 36B. The broken line in FIG. 9 represents the theoretical cylindrical edge of a receiving hole 26, and highlights the manner in which the degree of interference between the crests 38 and the receiving hole 26 increases in the direction of the last knurl 36B. In an alternative configuration, all of the crests 38 may have a true cylindrical exterior configuration but merely stepped diameters providing similar functionality. In yet another variation, only the first two or three knurls 36A, 36 are formed with a tapered lead-in configuration on their crests 38, whereas the remaining knurls 36 leading up to the last knurl 36B are each formed with a proper cylindrical configuration. Of course, many other variations are possible without departing from the spirit of this invention.

(16) Referring again to FIGS. 8 and 9, it can be observed that each knurl 26 has an axial width while each relief groove 40 has an axial span. The dimensional relationships between the knurls 36 and grooves 40 is such, in one exemplary embodiment, that the axial width of each knurl 36 is greater than the axial span of each relief groove directly adjacent thereto by approximately 50%. A configuration like that depicted here provides an advantageous blend of installation convenience, holding power and alignment functionality without the shortcomings found in prior art designs like that of FIG. 3. More specifically, the relief grooves 40, 44 backing each respective knurl 36 allow for displaced crest material (evident from the curls illustrated in FIGS. 7 and 9) to flow during the installation process. Traditional axial knurl designs like that of FIG. 3 do not allow for this flow of material and, as a result, cause a buildup of displaced material which can accumulate under the stop flange of the housing, thereby creating a buildup of pressure during installation. This shortcoming is avoided by the subject invention where such displaced crest material flows directly into an adjacent relief groove 40, 44 without the undesirable buildup of stress and pressure. As a result, the inside diameter of the receiving hole 26 is better preserved, thereby enabling the possibility of future repair or replacement operations.

(17) As shown in FIG. 5, the knurls 36 are preferably substantially annular and discrete. However, those of skill in the art will appreciate that in an alternative configuration the knurls 36 could be cut in a thread-like pattern resulting in something of an Acme-style thread pattern while still maintaining other relationships and attributes as described above. Such an alternative configuration would result in generally annular knurls instead of the substantially annular knurls depicted in the drawings.

(18) As alluded to previously, the knurls 36 and associated relief grooves 40 are preferably machined into the metallic socket housing 12 using conventional machine techniques. In other words, material may be removed from the socket housing 12 with a cutting tool. This compares to traditional processes which require high pressure forging to unseat the material and form the spline-like knurls as shown in FIG. 3. Machining, on the other hand, provides for much better process control and less wear on the machine tools. The design furthermore improves the installation of the ball joint assembly 10 by a mechanic. Such installation improvements are attributed to the formation of the lead-in taper on the first knurl 36 and possibly on additional knurls 36 as well so that the socket housing 12 can be received at least initially into the receiving hole 26 in the correct orientation. In addition, the latter concentric knurls 36, 36B are designed to wipe away during installation, thereby preserving the inside diameter of the mating receiving hole 26 instead of damaging the receiving hole like in traditional axial knurl designs.

(19) The generous relief grooves 40 provide space for displaced crest material to flow into during the press-in process. This avoids the problems associated with traditional knurl designs (FIG. 3) which incubate a build-up of displaced material under the stop flange of the housing, thereby causing undesirable stress concentrating as well as further damage/distortion to the receiving hole 26.

(20) The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention is defined by the following claims.