Patent Application
20050186046
The present invention relates to a self-piercing nut that comprises a nut body for punching a hole in a metal panel as any of relatively thick panels in such a manner that a generally circular edge of the hole is caulked to bite and fix the nut in position, even if thickness of the thick panels varies within a considerably wide range.
The prior art self-piercing nuts have been used mainly in manufacture of automobile cars so as to fasten relatively thin metal panels thick about 1.0 mm.
However, certain high-stress type self-piercing nuts have recently been demanded for use with relatively thick metal panels (thick about 1.6 mm to 3.2 mm) to be incorporated in buildings or the like architectures.
An example of the high-stress type self-piercing nuts is known in the art (see for example the Japanese Patent Publication No. 61-49528) that had been proposed by the present inventor.
The present invention was made to improve this nut to meet the recent requirement noted above.
An object of the present invention is therefore to provide a novel self-piecing nut designed for use with relatively thick metal panels even if they are of varied thickness.
In order to achieve this object, a self-piercing nut proposed herein may comprise a generally square nut body with four side walls, a pilot portion formed on and integral with the nut body and around a central threaded bore thereof, and this portion having a projected end face to punch a hole in a metal panel and having an outer periphery tapered to inwardly reduce diameter across a nut axis. The present nut may further comprise a panel engaging groove formed around and outside the pilot portion and opened sideways at regions except for four corners of the nut boy, and four independent corner posts that are formed integral with the respective corners so as to provide four seat faces, such that the metal panel will be brought into a forced contact with the corner posts. The pilot portion has an end face projected beyond the seat faces in a direction of the nut axis. The nut body is a pressed article of boron steel and has entirely been hardened by the quenching method for strengthening the pilot portion as to its punching force. Also characteristically, a height ‘H’ defined between a bottom of the panel engaging groove and the pilot portion end face is substantially equal to an allowable maximum thickness of the metal panel, and another height ‘h’ defined between the seat face of each corner post and the pilot portion end face is substantially equal to an allowable minimum thickness of the metal panel.
In use, the pilot portion will punch a round hole in the metal panel so that a circular edge of this hole is forcibly caulked into the panel engaging groove. The seat faces of corner posts will bite the panel at its areas near the circular edge if the thickness of the panel is greater than a threshold, and in this occasion the corner posts will buckle vertically and swell sideways more or less to a noticeable degree. As a result of such a deformation, the self-piercing nut will obtain a sufficient resistance to puling-off and idle rotations.
It will now be apparent that the present self-piercing nut is particularly adapted for use with relatively thick metal panels, nevertheless allowing this nut to be used in common for fixation thereof to any metal panels of considerably different thickness. In any case, this nut thus strongly attached to the panels will withstand well any external forces tending to pull off or idly rotate this nut.
Now some embodiments of the present invention will be described referring to the accompanying drawings.
FIGS. 1 to 4 show a self-piercing nut 1 provided herein and comprising a nut body 2 that is generally square. This nut body having four side walls 4 is chamfered at its four corners 5, and a central threaded bore 3 penetrates the nut body. A pilot portion 6 surrounding the central bore has an outer periphery tapered to inwardly reduce diameter across the nut axis and an end face 7 for punching a hole in a metal panel. A panel engaging groove 8 surrounding such a pilot portion 6 is opened sideways at the side walls 4, but closed sideways at the corners. Four discrete corner posts 4 integrally protrude from the respective corners of the nut body 2 so as to provide seat faces 10 for a forced contact with the metal panel. The end face 7 of pilot portion 6 is projected ahead the seat faces 10 of corner posts 9.
The nut body 2 is made from a strong boron steel rod so as to reinforce the pilot portion 6 to such a degree that a hole can be punched in any thicker metal panels. In manufacture, a piece of such a boron steel rod will be pressed into the shape at first, before quenched and hardened. Preferably in this invention, the boron steel may contain about 0.17% or less by weight of carbon so that it will obtain a Rockwell hardness HRC-30 or higher by the hardening process.
In order to make versatile the self-piercing nut 1 of the invention to be useful with many metal panels of different thickness, a configuration as will be seen from
For example, the maximum and minimum thickness ‘H’ and ‘h’ may be about 3.2 mm and about 1.6 mm, respectively.
If the outer periphery of pilot portion 6 has an uneven contour in cross section due to corrugation, indentations or the like, then the circular edge 22 will be bitten by such an uneven periphery to further strengthen this nut in its resistance to idle rotations.
As described above, the present self-piercing nut is adapted to fixation to relatively thick metal panels such as those which are usually incorporated into buildings or the like architectures.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2004-047564 | Feb 2004 | JP | national |
