CLINCH NUT

Abstract

A metal clinch fastener has portions thereof selectively hardened to enable use of the fastener with metal members of differing hardness values. The selective hardening of the fastener enables mounting with application of required forces for piercing and/or plastic deformation of the metal member without undesirable deformation or distortion of the fastener. The screw thread region or zone of the fastener has a relatively lesser hardness suitable and may be pre-threaded or later threaded by engagement with a thread forming screw.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a clinch fastener selectively hardened in accordance with the invention;

FIGS. 2, 3, 4 and 5 are graphs correlating hardness and ultimate tensile strength for steel based upon data reported in SAE J417b;

FIG. 6 is a sectional view similar to FIG. 1 showing a clinch fastener selectively hardened in accordance with a second embodiment of the invention;

FIG. 7 is a sectional view similar to FIG. 1 showing a pre-threaded clinch fastener selectively hardened in accordance with a third embodiment of the invention;

FIGS. 8 through 10 respectively comprise a perspective view, a bottom plan view and a sectional view of a clinch nut including a specific piercing and/or engagement geometric configuration that may be induction hardened in accordance with the invention;

FIGS. 11 through 13 are similar to FIGS. 8 through 10 and show another clinch nut including a specific piercing and/or engagement geometric configuration that may be induction hardened in accordance with the invention;

FIGS. 14 through 16 are similar to FIGS. 8 through 10 and show another clinch nut including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIGS. 17 through 19 are similar to FIGS. 8 through 10 and show another clinch nut including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIGS. 20 and 21 respectively comprise a perspective view and a sectional view, taken along the line 21-21 in FIG. 20, of a fastener including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIGS. 22 and 23 respectively comprise a perspective view and a sectional view, taken along the line 23-23 in FIG. 22, of a fastener including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIGS. 24 and 25 respectively comprise a perspective view and a sectional view, taken along the line 25-25 in FIG. 24, of a fastener including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIGS. 26 and 27 respectively comprise a perspective view and a sectional view, taken along the line 27-27 in FIG. 26, of a fastener including a specific piercing and/or engagement geometric configuration that is induction hardened in accordance with the invention;

FIG. 28 is a sectional view similar to FIG. 1 showing a fastener selectively hardened in accordance with the invention and illustrating the generally continuous heat hardened outer zone substantially enclosing an inner zone having a lesser hardness;

FIG. 29 is a sectional view similar to FIG. 28 showing a fastener hardened in accordance with a modification of the invention; and

FIG. 30 is a sectional view similar to FIG. 29 showing a fastener hardened in accordance with a further modification of the invention.

Claims

1. A self-clinching metal fastener for attachment to a plastically deformable metal member, said fastener including a body portion having a central axis and an axially extending pilot portion surrounding a central bore which may be a smooth bore thread blank or pre-threaded, said pilot portion having a transverse extent including an inner zone adjacent said bore and an outer zone adjacent an outer periphery of said pilot portion, and said outer zone having a hardness greater than that of said inner zone.

2. The fastener of claim 1, wherein said fastener has an axial length and said bore extends along the entire axial length of the fastener through said body portion and pilot portion, said inner zone extends along substantially the entire axial length of said fastener, and said outer zone has a cylindrical shape and extends along substantially the entire axial length of said pilot portion.

3. The fastener of claim 1, wherein said outer and inner zones are joined by an intermediate zone having an hardness that decreases in a transversely inward direction toward said axis.

4. The fastener of claim 3, wherein said pilot portion has a compression strength, and said outer and intermediate zones cooperate to increase said pilot portion compression strength by about 60% or more as compared with an identical pilot portion having an as-formed hardness.

5. The fastener of claim 1, wherein said outer zone has a hardness in the range of from about 40 Rc to about 60 Rc and said inner zone has a hardness in the range of from about 32 Rc to about 90 Rb.

6. The fastener of claim 1, wherein said fastener is pre-threaded and said inner zone has a hardness in accordance with the intended property class strength level for the fastener.

7. The fastener of claim 1, wherein said outer zone has an ultimate tensile strength of about 218,550 psi or 1,500 MPa and said inner zone has an ultimate tensile strength of about 113,850 psi or 785 Mpa.

8. The fastener of claim 1, wherein said body portion includes a bottom end face adjacent said pilot portion and including a bottom zone having a hardness greater than that of said inner zone.

9. The fastener of claim 8, wherein said bottom zone includes shaped elements for deforming and receiving plastically deformable metal, said shaped elements being selected from the group consisting of lugs, protuberances, notches, recesses, inclined walls, grooves and re-entrant shaped grooves.

10. The fastener of claim 9, wherein said bottom zone has a hardness substantially equal to the hardness of said outer zone.

11. The fastener of claim 10, wherein said bottom end face has an annular shape surrounding said pilot portion and includes a groove having an inclined inner wall forming an undercut for receiving metal plastically deformed from said metal member.

12. The fastener of claim 8, wherein said body portion includes an annular top end face surrounding said bore and being axially remote of said annular bottom end face, said annular top end face including a top zone having a hardness greater than that of said inner zone.

13. The fastener of claim 12, wherein said top zone has a hardness substantially equal to the hardness of said outer zone.

14. The fastener of claim 12, wherein said body portion includes a peripheral body face joining said annular top end face and annular bottom end face, said body portion including a peripheral zone extending along at least a portion of said peripheral body face and having a hardness greater than that of said inner zone.

15. The fastener of claim 13, wherein said top zone, peripheral zone and bottom zone cooperate to provide said fastener with joined and substantially continuous zones of increased hardness at substantially all locations in the fastener radially outward of said inner zone.

16. The fastener of claim 15, wherein said bottom zone includes shaped elements for deforming and receiving plastically deformable metal, said shaped elements being selected from the group consisting of lugs, protuberances, notches, recesses, inclined walls, grooves and re-entrant shaped grooves.

17. The fastener of claim 14, wherein said peripheral zone has a hardness substantially equal to the hardness of said outer zone.

18. The fastener of claim 14, wherein said bottom zone, top zone and peripheral zone each have a hardness in the range of from about 40 Rc to about 60 Rc and said inner zone has a hardness in the range of from about 32 Rc to about 90 Rb.

19. The fastener of claim 18, wherein said bottom zone, top zone and peripheral zone each have an ultimate tensile strength of about 218,550 psi or 1,500 MPa and said inner zone has an ultimate tensile strength of about 113,850 psi or 785 Mpa.

20. The fastener of claim 1, wherein said fastener is a nut, said bore is a smooth bore thread blank, said inner zone extends transversely outward from said bore a distance at least equal to about an outer diameter of a thread to be formed in the bore, said inner zone has a hardness suitable for threading by engagement with a thread forming screw, said inner and outer zones forming the full transverse extent of said fastener, and said outer zone providing a substantially continuous zone of increased hardness at substantially all locations in the fastener radially outward of said inner zone.

21. A self-clinching metal fastener for attachment to a plastically deformable metal member, said fastener including a body portion having a central axis and an axially extending pilot portion surrounding a central bore which may be a smooth bore thread blank or pre-threaded, said fastener having a transverse extent including an inner zone adjacent said bore and an outer zone adjacent an outer periphery of said pilot portion, said inner and outer zones forming the full transverse extent of said fastener, said outer zone having a hardness greater than that of said inner zone, and said outer zone providing a substantially continuous zone of increased hardness at substantially all locations in the fastener radially outward of said inner zone.

22. The fastener of claim 21, wherein said inner zone extends along said central axis, said inner zone has a generally cylindrical shape in said pilot portion and radially extends to provide said inner zone with a bulbous shape in said body portion.

23. The fastener of claim 21, wherein said inner zone extends along said central axis and has a generally cylindrical shape.

24. The fastener of claim 21, wherein said inner zone has a hardness value of about 90 Rb at said bore and transitions to about 60 Rc at the outer zone.

25. A self-clinching metal fastener for attachment to a plastically deformable metal member, said fastener including a body portion having a central axis and an axially extending pilot portion surrounding a central smooth bore thread blank, said pilot portion having a transverse extent including an inner zone adjacent said bore and an outer zone adjacent an outer periphery of said pilot portion, said inner zone having a hardness suitable for threading by engagement with a thread forming screw and said outer zone having a hardness greater than that of said inner zone.

26. The fastener of claim 25, wherein said inner zone has a hardness substantially equal to that of the nut as formed or as through-hardened.

27. The fastener of claim 26, wherein said body portion includes a bottom end face adjacent said pilot portion and including a bottom zone having a hardness greater than that of said inner zone, said body portion includes a peripheral body face joining said annular top end face and annular bottom end face, said body portion including a peripheral zone extending along at least a portion of said peripheral body face and having a hardness greater than that of said inner zone, said top zone, peripheral zone and bottom zone cooperating to provide said fastener with joined and substantially continuous zones of increased hardness at substantially all locations in the fastener radially outward of said inner zone.

28. The fastener of claim 27, wherein said bottom zone includes shaped elements for deforming and receiving plastically deformable metal, said shaped elements being selected from the group consisting of lugs, protuberances, notches, recesses, inclined walls, grooves and re-entrant shaped grooves.

29. A process for making a clinch fastener of the type including a body portion having a top face and a bottom face connected by a peripheral body face extending about the body portion and an axially extending pilot portion surrounding a central bore which may be a smooth bore thread blank or pre-threaded, comprising the steps, a) providing said fastener having a substantially uniform as formed or as through-hardened hardness,b) selectively hardening a transverse extent of said pilot portion to form an inner zone adjacent said bore and an outer zone adjacent an outer periphery of said pilot portion having differing hardness values,c) said inner zone having a hardness substantially equal to that of the nut as formed or as through-hardened, andd) said outer zone having a hardness greater than that of said inner zone whereby said fastener may be used to pierce and/or plastically deform metal members having hardness values greater than the hardness values of metal members with which a similar fastener having said as formed or as through-hardened hardness may be used.

30. The process of claim 29, wherein said inner zone has a hardness of about 32 Rc or less and may be threaded with a thread forming screw.

31. The process of claim 29, wherein said fastener is pre-threaded and said inner zone has a hardness in accordance with the intended property class strength level for the fastener.

32. The process of claim 29, including the further step of selectively hardening said body portion to form a bottom zone extending along said bottom face.

33. The process of claim 31, including the further steps of selectively hardening said body portion to form a top zone extending along said top face, said top zone having a hardness greater than that of said inner zone, and selectively hardening said body portion to form a peripheral zone extending along said peripheral body face, and thereby causing said top zone, peripheral zone and bottom zone to cooperate to provide said fastener with joined and substantially continuous zones of increased hardness at substantially all locations in the fastener radially outward of said inner zone.

34. The process of claim 31, wherein said bottom zone includes shaped elements for deforming and receiving plastically deformable metal, said shaped elements being selected from the group consisting of lugs, protuberances, notches, recesses, inclined walls, grooves and re-entrant shaped grooves, and the step of forming said bottom zone includes hardening said shaped elements.