Concealed Head Self-Clinching Ball Stud

A self-clinching, concealed head ball stud. The ball stud includes a rounded protrusion on one end for mating with a spring clip, and a flange and a beveled structure on the other end for installation into a counterbored hole in a sheet metal panel.

BACKGROUND

Ball studs are well-known mechanical fastening devices used in conjunction with purposefully designed spring-catch fasteners, or clips, as a convenient method for hardware components that require repeated engagement and disengagement, such as cabinet doors, inspection panels, and the like.

A typical installation sequence for a ball stud application is shown inFIGS.1-2. A first metal panel10has a hole12formed through the panel, and a spring catch fastener20is securely affixed to the metal panel10above the hole12, for example, by rivets22or other known fasteners. In addition, a second metal panel30has a ball stud40installed through a hole32in the panel, and the ball stud, in this case having a male-threaded stud41, is secured to the panel using a washer42and threaded nut44. An alternative using a female-threaded ball stud would be installed in the panel with a washer and male-threaded screw. The first panel10and second panel30are then snapped together by pushing the ball stud40through the hole12in the first panel and through the spring clips21of the catch fastener20.

In all cases, however, some portion of the ball stud or attachment hardware extends from and is visible from the exterior outer surfaces. Further, while a metal displacement process is known and used for captivation of many different types of fastener parts—for example, standoffs, threaded studs, guide pins and ball studs—for the most part, these products are installed from the back side of the sheet so there is a visible circular or hexagonal line around the head of the part and clear differences in material appearances. For appearance purposes alone this is normally not desirable. In areas where the designer does not want these visual incongruities, the fabricator will sometimes grind the surface smooth and then apply paint. It should be obvious that such a process is time-consuming, adds cost, and provides an opportunity for differing levels of quality. Also, there is sometimes a need to maintain a complete seal between both sides of the sheet to prevent an ingress of fluids or gases. Since the holes are punched through the sheet, the displacement of material to captivate the parts may not be sufficient.

DETAILED DESCRIPTION

A new ball stud is designed for use with a self-clinching method that mounts in a blind counterbored hole formed in a panel. As shown inFIG.3, the ball stud140looks conventional, with a body having a rounded protrusion on its top portion for engaging with a spring clip fastener. In this case, however, the bottom portion of the ball stud body includes a foot or beveled ring142at the bottom end and a flange or flat ring144between the body of the ball stud and the foot, as further described herein.

The ball stud140can be made in a machining process typically using one or more of the following materials: carbon steel, heat treated carbon steel, stainless steel and/or heat-treated stainless steel. Further, the ball stud140could be installed into either aluminum, carbon steel or stainless steel sheets. The ball stud140should typically be finished with zinc-plating (for carbon steels) or passivated (for stainless steels).

Although the ball stud could be manufactured in many different sizes, one example of a commonly sized ball stud, shown with reference toFIGS.4A and4B, includes a cylindrical base portion141with a diameter D1measuring 0.277 inches. The ball portion143extends symmetrically up and in from the base portion141to a narrow waist portion145which measures W1=0.156 inches in diameter; then slightly outward to a nominal diameter at point147measuring W2=0.187 inches before the ball portion rounds off the at the top149. The height H1of the ball portion from the base portion141to the bulge point147is 0.231 inches, and the height H2of the ball portion from the narrow waist portion145to the bulge point147is 0.102 inches. The annular flat ring has a diameter D2=0.337 inches; that is, larger than the diameter of the base portion141.

The length of the ball stud may be varied to accommodate different material thicknesses. For example, the length S from the top of the flat ring144to the bulge point147of the ball portion143, and the length L from the top of the flat ring to the top149of the ball portion, can be adjusted to provide a shorter or longer ball stud. As an example of a shorter ball stud, the length S is 0.328 inches (+/−0.005) and the length L is 0.421 inches (+/−0.010). In an example of a longer ball stud, the length S is 0.532 inches (+/−0.005) and the length L is 0.625 inches (+/−0.010).

The foot142is preferably a beveled circular structure, e.g., a frustum, having a maximum diameter D3=0.311 inches that is slightly smaller than that of the counterbored hole112in the metal sheet, while the combined height H3of the foot and the flange144is slightly less than the thickness of the metal sheet. As one example, for a metal sheet having a minimum thickness of 0.062 inches, the counterbored hole should be 0.043 inches deep minimum, and the combined height H3of the foot and flange roughly matches that depth. The bevel angle α is an acute angle but relatively large, for example, in a range between 20 degrees and 40 degrees.

In use, the metal sheet or panel110has a hole112counterbored on the interior side, as shown onFIG.3. The diameter of the counterbored hole112is slightly larger than the diameter of the beveled foot142but smaller than the flange144. Referring toFIG.5, the ball stud140is pressed into the counterbored hole using a conventional press such that the flange144displaces the sheet metal around the hole and the sheet metal cold flows in the recess between the angled portion of the beveled foot142and the flange. The beveled foot142thus acts to help secure the cold flow connection between the flange144and the sheet metal110. As a result, the method of attachment is thus not visible from the exterior of the component.

Advantageously, since the hole in the panel is counterbored and not punched through, the back side of the panel remains unblemished and sealing requirements are maintained. However, the step of creating a counterbored hole in the panel is more expensive as it requires a machining step, whereas a thru-hole can be simply punched.

While the disclosure has been described in connection with specific embodiments, the disclosure is not limited to these embodiments, and that alterations, modifications, and variations of these embodiments may be carried out by the skilled person without departing from the scope of the disclosure.