Self-pierce rivet

Details Self-pierce rivet Self-pierce rivet

1998-11-23

2001-07-24

Hughes, S. Thomas (Department: 3726)

Metal working

Means to assemble or disassemble

Means to drive self-piercing work part

C029S525060, C029S524100, C411S502000

Reexamination Certificate

active

06263560

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns a self-pierce rivet.
Self-pierce rivets in current use have a round head and a round shank and are used in conjunction with a round setting die which has a semi-toroidal cavity and a central anvil. In a typical application the diameter of the shank would be 5 mm, the diameter of the head would be 8 mm and the diameter of the die cavity would be 9 mm.
The term “self-pierce” is normally applied to a semi-tubular rivet used to fasten incompressible materials such as metals. Because the materials are incompressible, the rivet, when applied to a workpiece, displaces a volume of workpiece material equal to the volume of the part of the rivet that enters the material. A principal function of the die is to form the displaced material into a round “button”.
There is in common usage another form of self-pierce rivet, generally known as a “bifurcated” rivet. Such a rivet has a slotted shank and is not as strong as a rivet of semi-tubular construction. Consequently, it is normally used to fasten compressible materials such as wood and leather. In this case, the legs of the rivet pierce through the workpiece with far less material displacement and are caused to splay outwardly by the die, thereby securing the components of the workpiece. The die is circular in form and the rivet can be presented to it in any axially angular position.
These designs of self-pierce rivets have limitations in application in that often they cannot allow be applied in the optimum position for effective fastening. For example, when applied to flanges the ideal position for the fastener is one where the shank of the rivet is immediately adjacent to the wall of the flange. With current designs, this is not possible because the rivet head, the rolled portion of the shank, and the displaced material far beyond the shank and consequently the rivet has to be applied in a position offset from the wall. This offset reduces the structural rigidity of the riveted assembly and increases the width of the flange required for riveting.
SUMMARY OF THE INVENTION
U.S. Pat. No. 1,639,530 describes a staple constructed for ready removal. The head is provided on opposite sides with outwardly extending extensions which extend the entire width of the head and from one leg to the other. The extensions form means whereby the claws of a hammer or other tool can be inserted under the flanges for removal purposes. Moreover, the opposite sides of the legs at the lower edges thereof are bevelled to provide sharp points, the opposing bevels ensuring the legs will not bend on insertion and thereby facilitating removal.
It is an object of the present invention to overcome the above-stated disadvantages of known self-pierce rivets. According to one aspect of the present invention there is provided a self-pierce rivet comprising a shank and an enlarged head at one end of the shank, the other end of the shank being provided with an axially extending slot, wherein the head is non-circular and is formed with substantially mutually perpendicular major and minor dimensions, the minor dimension of the head extending substantially parallel to the slot, the minor dimension of the head being such that the head does not extend in the direction of the minor dimension substantially beyond the cross-section of the shank of the rivet on at least one side of the shank.
Thus, a self-pierce rivet can be provided in which, at least on one side thereof, neither the head of the rivet, nor the workpiece material displaced when the rivet is applied, projects substantially beyond the shank. Thus, when the rivet is presented to the workpiece with the one side foremost a flange can be fastened at a point much closer to a wall than has hitherto been possible. This permits the use of much reduced flange widths. For example, in many cases it is possible to reduce the flange width of an automotive body pressing by fifty percent while still meeting in full the industry requirements for rigidity and security.
Thus, the shank of the self-pierce rivet according to the present invention effectively has two legs which will roll outwardly in a direction substantially parallel to the major dimension of the head when the rivet is applied. Consequently, the shape of the button of displaced material formed when the rivet is applied is modified in that material is not displaced to any significant extent in the direction of the slot.
The slot may have parallel walls, or may be tapered such that the slot narrows with increasing distance from the free end of the shank, or the slot may be profiled.
The shank may be provided with a central hole extending from the free end of the shank towards the head. The central hole may extend substantially the length of the shank. The central hole may be generally cylindrical or may be tapered, for example frustoconical, with the wider part of the hole in the region of the free end of the shank, or may be profiled. The central hole may be provided with an outwardly tapered mouth. Where a central hole is provided, the axial extent of the central hole may be at least as great as the axial extent of the slot.
The shank may be circular in cross-section or may be formed with one or more straight sides in a plane substantially parallel to the major dimension of the head.
The head may be rectangular. The term “rectangular” includes herein geometrical rectangles and also generally rectangular shapes which may, for example, have rounded corners and/or curved shorter sides.
The head may have a major dimension which extends beyond the cross-section of the shank of the rivet on at least one side of the shank.
The major dimension of the head may be at least
1
.
3
times the corresponding dimension of the shank.
According to another aspect of the present invention there is provided a combination of a self-pierce rivet as hereinbefore defined and a setting die, wherein the setting die is formed-with a cavity having a major dimension and a minor dimension in alignment respectively with the major dimension and the minor dimension of the head of the rivet.
The major dimension of the cavity may be at least about 1.3 times the minor dimension thereof.
The setting die may incorporate a divider to facilitate outward roll of the rivet.
The cavity of the setting die may be formed with at least one open side in the major dimension thereof.
According to a further aspect of the present invention there is provided a method of fastening shouldered workpieces by means of a combination of a self-pierce rivet and a setting die as hereinbefore defined, wherein the rivet is applied to the shouldered workpiece in a manner so as to cause the shank to splay in opposite directions corresponding to the major dimension of the head of the rivet.
The material of the workpiece displaced during application of the rivet is preferably restricted in the minor direction of the head to not more than 1.1 times the corresponding dimension of the shank of the rivet.


REFERENCES:
patent: 231979 (1880-09-01), Ball
patent: 951997 (1910-03-01), Stimpson
patent: 1121641 (1914-12-01), Lounsbury
patent: 1639530 (1927-08-01), Payson
patent: 3585666 (1971-06-01), Wahl
patent: 3606415 (1971-09-01), Friedling et al.
patent: 5359765 (1994-11-01), Auriol et al.
patent: 5722144 (1998-03-01), Bora
patent: 5752305 (1998-05-01), Cotterill et al.
patent: WO9535174 (1995-06-01), None

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