Die for self piercing rivet

Abstract

A die for use in a self-piercing rivet fastening device comprising a die and a punch for driving a self-piercing rivet into fastened members arranged on top of the die, wherein the upper surface of the die defines a cavity formed for receiving portions of the fastened members thrust out by the self-piercing rivet driven by the punch, and the cavity is formed as a concave spherical surface having a single radius R centered on the central axis of the cavity.

What is claimed is: 
     
         1 . A die for use with a self-piercing rivet fastening device including a punch operable for driving a self-piercing rivet, with a large-diameter head and hollow cylindrical legs extending down from the head, into a first and a second fastened members arranged on top of the die, and the die comprises:
 a cavity formed in an upper surface of the die, the cavity ( 36 ) including a round bottom surface in a central portion of the cavity, and an inclined surface on an outer periphery between the bottom surface and the upper surface of the die, and wherein an inclination angle (θ) defined between the inclined surface and the upper surface of the die is from 7 to 15°.   
     
     
         2 . A die for use with a self-piercing rivet fastening device including a punch operable for driving a self-piercing rivet, with a large-diameter head and hollow cylindrical legs extending down from the head, into a first and a second fastened members arranged on top of the die, and the die comprises:
 a cavity formed in an upper surface of the die, the cavity including a concave spherical surface defining a single radius (R) centered on a central axis of the cavity.   
     
     
         3 . A die according to  claim 1 , wherein, when the self-piercing rivet is driven into the fastened members, the legs pierce the first fastened member on the punch side, the tips of the legs push downward through the second fastened member on the receiving side adjacent to the die, the die receives the fastened member on the receiving side deforming the tips of the legs so as to expand outward radially and remain inside the die without piercing the second fastened member on the receiving side adjacent to the die, and the first and second fastened members are fastened to each other by the head and the expanded legs of the self-piercing rivet. 
     
     
         4 . A die according to  claim 1 , wherein the upper surface of the die and an upper portion of the cavity are continuous at an obtuse angle. 
     
     
         5 . A die according to  claim 1 , wherein a depth (D) from the upper surface of the die to the central portion of the cavity is in a range including from 0.5 mm to 1.5 mm, particularly from 0.5 mm to 1.4 mm, and preferably from 0.5 mm to 0.9 mm. 
     
     
         6 . A die according to  claim 1 , wherein the diameter (φ) of the cavity at the upper surface of the die is in a range from 10 mm to 18 mm, particularly from  11  mm to 15 mm or from  13  mm to 18 mm. 
     
     
         7 . A die according to  claim 1 , wherein the round bottom surface is flat. 
     
     
         8 . A die according to  claim 1 , wherein the round bottom surface is a concave spherical surface. 
     
     
         9 . A die according to  claim 1 , wherein the radius of the concave spherical surface is in a range including 9 mm to 70 mm, particularly from 14 mm to 70 mm, and preferably from  20  mm to 60 mm. 
     
     
         10 . A die for use in a self-piercing rivet fastening device wherein a punch drives a self-piercing rivet, with a large-diameter head and a hollow cylindrical legs extending down from the head, into a first and a second fastened members arranged on top of the die, and the die comprises:
 a die body defining an axis and partially defining a cavity open in an axial upward direction toward the punch, the die body including an upper surface, a central bottom surface axially below the upper surface and facing the axially upward, and an inclined surface radially between the bottom surface and the upper surface of the die, and wherein an inclination angle (θ) of the inclined surface from the upper surface of the die is in the range including 7° to 15°.   
     
     
         11 . A die for use in a self-piercing rivet fastening device wherein a punch drives a self-piercing rivet, with a large-diameter head and a hollow cylindrical legs extending down from the head, into a first and a second fastened members arranged on top of the die, and the die comprises:
 a die body partially defining a cavity open upwards toward the punch around a central axis, the die body including an upper surface, and a concave spherical surface having a single radius centered on the central axis of the cavity.   
     
     
         12 . A die according to  claim 11 , wherein the upper surface of the die and an upper portion of the concave spherical surface are continuous at an obtuse angle. 
     
     
         13 . A die according  claim 11 , wherein an axial depth defined between the upper surface of the die and the central portion of the cavity includes the range from 0.5 mm to 1.5 mm. 
     
     
         14 . A die according  claim 11 , wherein an axial depth defined between the upper surface of the die and the central portion of the cavity includes the range 0.5 mm to 0.9 mm. 
     
     
         15 . A die according to  claim 11 , wherein a diameter (φ) of the cavity at the upper surface of the die includes the range from  10 mm to 18 mm. 
     
     
         16 . A die according to  claim 11 , wherein a diameter (φ) of the cavity at the upper surface of the die includes one of the range from 11 to 15 mm and from 13 mm to 18 mm. 
     
     
         17 . A die according to  claim 10 , wherein the central bottom surface is flat. 
     
     
         18 . A die according to  claim 10 , wherein the central bottom surface is a concave spherical surface. 
     
     
         19 . A die according to  claim 11 , wherein the radius of the concave spherical surface is in the range including 9 mm to 70 mm. 
     
     
         20 . A die according to  claim 11 , wherein the radius of the concave spherical surface is in the range including 20 mm to 60 mm.