Self-piercing riveting
A self-piercing rivet includes a substantially cylindrical shank having an outside diameter and a head. The shank has a central blind bore that defines an inside diameter and an annular piercing end spaced from said head. The ratio of the difference between the outside and inside diameters of the shank in the region around the bore to the outside diameter of the shank is in the range 0.47 to 0.52.
1. A self-piercing rivet comprising a substantially cylindrical shank having an outside diameter and a head, the shank having a central blind bore defining an inside diameter and an annular piercing end spaced from said head, characterized in that the ratio of the difference between the outside and inside diameters of the shank in the region around the bore to the outside diameter of the shank is in the range 0.47 to 0.52.
2. A self-piercing rivet according to claim 1 , wherein the ratio of the cross sectional area of the shank in the region around the bore to the outside diameter of the shank is in the range 3.0:1 to 3.6:1.
3. A self-piercing rivet according to claim 2 , wherein the ratio of the cross-sectional area of the shank in the region around the bore to the outside diameter of the shank is 3.1:1.
4. A self-piercing rivet according to claim 1 , wherein the ratio of the diameter of the head to the outside diameter of the shank is 1.4.
5. A self-piercing rivet according to claim 1 , wherein the ratio of the diameter of the head to the outside diameter of the shank is in the range 1.35 to 1.47:1.
6. A self-piercing rivet according to claim 1 , wherein the ratio of the effective length of the rivet to the depth of the bore is in the range 1.56 to 2.4.
7. A self-piercing rivet according to claim 1 , wherein the annular piercing end comprises a first portion that is radially outboard of a second portion, the second portion being a conical taper intermediate the first portion and the bore.
8. A self-piercing rivet according to claim 7 , wherein the first portion defines a surface that is generally disposed such that it extends substantially perpendicular to a central axis of the rivet.
9. A self-piercing rivet according to claim 7 , wherein the first portion defines a surface that is generally disposed such that it is inclined at an angle of between 0° and 10° to the perpendicular to the central axis.
10. A self-piercing rivet according to claim 7 , wherein the surface defined by the first portion is substantially flat.
11. A self-piercing rivet according to claim 7 , wherein the surface defined by the first portion is arcuate.
12. A self-piercing rivet according to claim 7 , wherein the first portion is inclined to a central axis of the rivet at a shallower angle than the second portion.
13. A self-piercing rivet according to claim 7 , wherein the annular conical taper defines an included angle of substantially 90 degrees.
14. A self-piercing rivet according to claim 7 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.33 to 0.66:1.
15. A self-piercing rivet according to claim 7 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.4 to 0.7:1.
16. A self-piercing rivet according to claim 7 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.5 to 0.7:1.
17. A self-piercing rivet according to claim 7 , wherein the ratio of the length of the first portion to the thickness of the shank is substantially 0.5:1.
18. A self-piercing rivet according to claim 7 , wherein the ratio of the length of the first portion to the thickness of the shank is substantially 0.6:1.
19. A self-piercing rivet according to claim 1 , wherein the head has an upper portion and a transition region defined between the upper portion and the shank, the transition region having a radius of curvature in the range 0.8 mm-1.2 mm.
20. A self-piercing rivet according to claim 1 , where the head has an upper portion and a transition region defined between the upper portion and the shank, the transition region having a radius of curvature of substantially 1 mm.
21. A self-piercing rivet according to claim 1 , wherein the bore is defined by a substantially cylindrical surface, that is concentric with the outside surface of the shank, and a base surface, there being a transition region between the cylindrical surface and the periphery of the base surface, the transition region having a radius of curvature of 0.4 mm.
22. A self-piercing rivet according to claim 1 , wherein the bore is defined by a substantially cylindrical surface, that is concentric with the outside surface of the shank, and a base surface, there being a transition region between the cylindrical surface and the periphery of the base surface, the transition region having a radius of curvature of greater than 0.3 mm.
23. A self-piercing rivet according to claim 1 and made from medium carbon steel containing manganese and boron.
24. A self-piercing rivet according to claim 1 , wherein the rivet is heat-treated to a hardness of at least 350Hv.
25. A self-piercing rivet according to claim 1 , wherein the shank of the rivet has an outside diameter of 5.5 mm and the cross sectional area of the shank in the region around the bore is greater than 16.5 mm 2 .
26. A self-piercing rivet insertion system comprising a punch for applying an insertion force to a rivet, a die into which the material being riveted is deformed and a rivet as claimed in claim 1 .
27. A self-piercing rivet comprising a substantially cylindrical shank having an outside diameter and a head, the shank having a central blind bore defining an inside diameter and an annular piercing end spaced from said head, characterized in that the ratio of the difference between the outside and inside diameters of the shank in the region around the bore to the outside diameter of the shank is in the range 0.47 to 0.52, wherein the annular piercing end comprises a first portion that is radially outboard of a second portion, the second portion being a conical taper intermediate the first portion and the bore.
28. A self-piercing rivet according to claim 27 , wherein the first portion defines a surface that is generally disposed such that it extends substantially perpendicular to a central axis of the rivet.
29. A self-piercing rivet according to claim 27 , wherein the first portion defines a surface that is generally disposed such that it is inclined at an angle of between 0° and 10° to the perpendicular to the central axis.
30. A self-piercing rivet according to claim 27 , wherein the surface defined by the first portion is substantially flat.
31. A self-piercing rivet according to claim 27 , wherein the surface defined by the first portion is arcuate.
32. A self-piercing rivet according to claim 27 , wherein the first portion is inclined to a central axis of the rivet at a shallower angle than the second portion.
33. A self-piercing rivet according to claim 27 , wherein the annular conical taper defines an included angle of substantially 90 degrees.
34. A self-piercing rivet according to claim 27 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.33 to 0.66:1.
35. A self-piercing rivet according to claim 27 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.4 to 0.7:1.
36. A self-piercing rivet according to claim 27 , wherein the ratio of the length of the first portion to the thickness of the shank is in the range 0.5 to 0.7:1.
37. A self-piercing rivet according to claim 27 , wherein the ratio of the length of the first portion to the thickness of the shank is substantially 0.6:1.