Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2002-04-23
2004-11-09
Compton, Eric (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C029S852000, C029S861000
Reexamination Certificate
active
06813829
ABSTRACT:
This application claims the benefit of Japanese Application 2001-131225, filed Apr. 27, 2001, the entirety of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a method for removing punched fragments, and a method for producing an article by punching including the method for removing punched fragments. More particularly, the present invention relates to a method for removing punched fragments which can be easily performed on the upper side of a die and is suitable for use in punch work with an extra-fine punch or punch work performed with small punching pitch, and a method for producing an article by punching including the method for removing punched fragments.
In recent years, in the application of punch work using a punch and a die, there has been an increasing demand for forming perforations with smaller diameters and in higher density.
For example, in the case of a circuit board on which electronic components are mounted, it is required to provide numerous small perforations with high precision so that a circuit can be formed with higher density while maintaining high reliability, taking into consideration the cooling effect.
When providing a large number of small perforations on a workpiece for punching, it is essential that the punching operation be performed in such a way that high precision perforations are arranged with uniform spacing, but at the same time it is also important to thoroughly remove punched fragments, which are generated while forming perforations on the workpiece, from the punching machine using a punch and a die, in particular, from the surrounding area of the workpiece to prevent the punched fragments from plugging the product. If the punched fragments are not thoroughly removed and, for example, have entered the perforations of a workpiece for punching, it they will render the product defective, resulting in a reduced product yield. Frequent recurrence of such defects will cause an increase in manufacturing cost, eventually leading to a loss of competitiveness.
FIG.
2
(
a
) and FIG.
2
(
b
) illustrate an example of a conventional process of punch work using a punch and a die.
As shown in FIG.
2
(
a
), a thin workpiece
3
for punching is first mounted on a die
12
as a preparatory step, and the workpiece
3
is perforated with a punch
10
as shown in FIG.
2
(
b
). The punched fragments are removed in the next step, conventionally maintaining the condition as shown in FIG.
2
(
b
), namely, in a condition whereby the punch
10
is protruding into a counterbore
21
of a die
12
after performing punching on the workpiece
3
on the die
12
.
Since most of the punched fragments fall into the counterbore
21
side of the die when perforations are formed by the punch
10
, the punched fragments have been removed from the counterbore
21
side of the die by means of vacuum suction, or conversely by blowing with compressed air, or alternatively by having the punched fragments adhere to an adhesive medium, so that punched fragments will not remain in the perforations on the workpiece
3
. However, it has been observed that a part of the punched fragments sometimes remains attached to the punch
10
, causing a plugging by punched fragments that enters the perforation when the punch
10
is pulled up.
Further, the method for removing punched fragments as described above is applicable for a punching machine such as the one illustrated in FIG.
2
(
a
) and FIG.
2
(
b
), which employs a larger diameter for the punch
10
and a greater punching pitch that can allow a wide distance between juxtaposing punches and therefore has ample space in the counterbore
21
of the die. However, when forming perforations on the workpiece
3
with a smaller diameter and in higher density as in the requirement in recent years, it becomes unavoidable to use an extra-fine punch and a narrower punching pitch. For such a punching machine, which employs a smaller diameter for the punch
10
and a narrow punching pitch allowing only a shorter distance between juxtaposing punches, the removal of the punched fragments as described above has been difficult to apply.
For example, along with the trend toward making perforations with an increasing degree of miniaturization and in higher density, it is becoming popular to use punching machines employing an extra-fine punch tip and a minuscule punching pitch, such as the one for which the punching process is as shown in FIG.
3
(
a
) and FIG.
3
(
b
). The difference in structure between this punching machine and a punching machine, for which the punching process is as illustrated in FIG.
2
(
a
) and FIG.
2
(
b
), exists in the counterbore
21
of the die. In the configuration as illustrated in FIG.
2
(
a
) and FIG.
2
(
b
), ample cubic size is secured at the counterbore
21
of the die to permit smooth removal of punched fragments, whereas in the configuration as illustrated in FIG.
3
(
a
) and FIG.
3
(
b
), the counterbore
21
is made much smaller as a means of preventing the die
12
from losing rigidity. As a result, it does not provide sufficient cubic size for a smooth removal operation of punched fragments.
For a punching machine such as described above, in particular, the frontal portion X of the punch
10
with a reduced diameter cannot be made too long from a durability standpoint. At the same time, since it is desirable to have the punching tip protrude into the counterbore
21
of the die for easy removal of punched fragments, the corresponding distance Y of the opening at the die
12
also cannot be made long. This decreases the thickness of the upper side of the counterbore
21
of the die, thereby reducing rigidity of the die
12
.
Therefore, it is necessary to make the size of the counterbore
21
of the die smaller to increase rigidity of the die
12
. However, since such a design has made it difficult to secure the cubic size required for a removal operation of punched fragments, the removal of punched fragments could not be performed adequately.
When a narrower punching pitch is employed, greater shearing force from the punch
10
works against the workpiece
3
, thereby increasing the load on the die
12
. Because of this, for the purpose of increasing the strength of the die
12
, reinforcement such as a rib member at the counterbore
21
of the die has often been provided. However, such reinforcement has made the configuration of the die
12
more complex, further reducing the space available at the counterbore
21
of the die and thereby making it very difficult to remove the punched fragments according to the above method. This results in insufficient removal of punched fragments, causing punched fragments to remain inside the perforations of the workpiece
3
and eventually leading to a reduced product yield, for example.
As described above, the removal of punched fragments is an important step that has substantial impact on the product yield in punch work, whereas, in particular, for the type of punch work that is required to form perforations with an increasing degree of microminiaturization and in higher density, it is becoming more and more difficult to apply a means for removing punched fragments from the counterbore part underneath a die. While the above suggests that there is a need for any alternative means of completely removing punched fragments from a punching machine so that no punched fragment remains inside the perforations made on a workpiece for punching, a suitable method has not been proposed so far.
The present invention has been made in the light of the above-described problems, and an object thereof is to solve the problems associated with the prior art. More specifically, an object of the present invention is to provide a method for removing punched fragments usable for punch work, which can be easily performed even under the condition where a die is reinforced to allow very narrow space for a counterbore of a die, and, in particular, which can ensure that no punched fragment remains inside the perforations bei
Kitamura Kazumasa
Takeuchi Yukihisa
Tsuji Hiroyuki
Yamaguchi Yoshinori
Burr & Brown
Compton Eric
NGK Insulators Ltd.
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