Method and apparatus for manufacturing slip stopper

1. A method for manufacturing a slip stopper, comprising:

forming a plurality of protruding portions on a metal plate so as to protrude in the plate thickness direction; and

forming concave portions in the protruding portions defined by shear planes that extend substantially perpendicular to the plate surface of the metal plate to form a slip stopper and have been half-blanked from a protruding surface side of the protruding portions so as not to open through holes in the metal plate.

2. The method according to claim 1 , further comprising:

placing the metal plate between a punching assembly and a die assembly of a first punching die unit prior to forming the plurality of protruding portions; and

relatively moving the metal plate relative to the first punching die unit and a second punching die unit after forming the plurality of protruding portions, to place the metal plate between a punch assembly and a die assembly of the second punching die unit.

3. The method according to claim 1 , wherein the concave portions comprise a central concave portion and radial drain channels.

4. The method according to claim 3 , wherein the central concave portion is depressed from an upper surface of the protruding portion and each drain channel has an upper surface at one end extending from an upper surface of the central concave portion and at the other end joining the plate surface of the metal plate.

5. An apparatus for manufacturing a slip stopper, comprising:

a first punching die unit that forms a plurality of protruding portions on the surface of a metal plate so as to protrude in the plate thickness direction; and

a second punching die unit that forms concave portions respectively in the protruding portions formed by the first punching die unit by creating shear planes that extend substantially perpendicular to the plate surface of the metal plate to form a slip stopper and have been half-blanked from a protruding surface side of the protruding portions so as not to open through holes in the metal plate.

6. The apparatus according to claim 5 , wherein the first punching die unit comprises:

a punch assembly having a punch with a concave face, a punch head, a punch body slideably holding the punch, and a retractor that biases the punch into a retracted position within the punch body;

a die assembly including a die having a convex face to oppose the concave face of the punch, a die body mounting the die, an ejector plate slideably mounted in the die body relative to the die; and a pushing member that pushes the ejector plate toward the punch body; and

a striker.

7. The apparatus according to claim 6 , wherein the second punching die unit comprises:

a punch assembly having a punch with a concave face having a central projection and radial projections, the radial projections having a decreasing height of projection from the central projection to no projection at the edge of the concave face, a punch body receiving the punch for reciprocal movement, a stripper plate slideably received on the punch adjacent the concave face, a first retractor that biases the punch into a retracted position within the punch body, and a second retractor that retracts the stripper plate within the punch body;

a die assembly comprising a die body, a die mounted in the die body and having a convex face substantially complementary to the concave face of the punch, an ejector plate slideably mounted in the die body relative to the die, and a pushing member that pushes the ejector plate toward the punch body; and

a striker.

8. The apparatus according to claim 7 , wherein the pushing member in each of the first punching die unit and the second punching die unit is a urethane spring.

9. The apparatus according to claim 7 , wherein the retractor in each of the first punching die unit and the second punching die unit is a spring.

10. The apparatus according to claim 7 , wherein the punch assembly of the first punching die unit further comprises a flange between the punch head and the punch, the punch head, flange and punch being assembled into a unitary structure.

11. The apparatus according to claim 5 , wherein the second punching die unit comprises:

a punch assembly having a punch with a concave face having a central projection and radial projections, the radial projections having a decreasing height of projection from the central projection to no projection at the edge of the concave face, a punch body receiving the punch for reciprocal movement, a stripper plate slideably received on the punch adjacent the concave face, a first retractor that biases the punch into a retracted position within the punch body, and a second retractor that retracts the stripper plate within the punch body;

a die assembly comprising a die body, a die mounted in the die body and having a convex face substantially complementary to the concave face of the punch, an ejector plate slideably mounted in the die body relative to the die, and a pushing member that pushes the ejector plate toward the punch body; and

a striker.

12. The apparatus according to claim 11 , wherein the first punching die unit comprises:

a punch assembly having a punch with a concave face, a punch head, a punch body slideably holding the punch, and a retractor that biases the punch into a retracted position within the punch body;

a die assembly including a die having a convex face to oppose the concave face of the punch, a die body mounting the die, an ejector plate slideably mounted in the die body relative to the die; and a pushing member that pushes the ejector plate toward the punch body; and

a striker.

13. The apparatus according to claim 12 , wherein the pushing member in each of the first punching die unit and the second punching die unit is a urethane spring.

14. The apparatus according to claim 12 , wherein the retractor in each of the first punching die unit and the second punching die unit is a spring.

15. The apparatus according to claim 12 , wherein the punch assembly of the first punching die unit further comprises a flange between the punch head and the punch, the punch head, flange and punch being assembled into a unitary structure.