Metal deforming – By use of non-deforming work-gripping clamp and relatively... – With interrelated clamp closer and tool mover
Reexamination Certificate
2000-06-20
2001-07-24
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
With interrelated clamp closer and tool mover
C072S315000, C072S383000, C072S400000, C072S452700
Reexamination Certificate
active
06263717
ABSTRACT:
This application is based on Japanese Patent Application No. 11-190277 filed Jul. 5, 1999, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a press-forming die set adapted to perform a pressing operation on a workpiece in the form of a thin sheet, so as to form a negative-angle portion on the workpiece. The press-forming die set includes a first die (e.g., an upper die and a second die (e.g., a lower die), which are moved toward and away from each other in a press-forming direction, usually, in the vertical direction. The workpiece is placed on the second die such that the inner surface of the workpiece is held in contact with the second die. This inner surface of the workpiece is referred to as “inner mounting surface”. In the present application, the term “negative-angle portion” is interpreted to mean a portion of the press-formed workpiece which portion is bent with respect to the above-indicated press-forming direction such that the bent portion in question of the workpiece is inclined with respect to the press-forming direction, so as to generally extend under the inner mounting surface of the press-formed workpiece.
2. Discussion of Related Art
To form such a negative-angle portion on a thin sheet such as a thin metal or plastic sheet, there has been conventionally used a press-forming die set which includes a linear slide cam or a rotary cam. Where the linear slide cam is used to form the negative-angle portion, the linear slide cam is incorporated in a side guide cam provided on the lower die, and the upper die is vertically moved down toward the lower die on which the workpiece is placed, so that a downward movement of a cam fixed on the upper die causes a movement of the linear slide cam in the horizontal direction so as to bend a portion of the workpiece, for forming the negative-angle portion. After the formation of the negative-angle portion, the linear slide cam is moved away from the workpiece in a direction parallel to the surface of the formed negative-angle portion, which generally extends under the inner mounting surface of the workpiece. Thus, the negative-angle portion can be easily formed using the linear slide cam.
Where the negative-angle portion is formed on the workpiece by a press-forming die set including the linear slide cam, as described above, the linear slide cam is required to be moved in the direction parallel to the surface of the formed negative-angle portion, in order to remove the formed workpiece (product) from the die set. However, the negative-angle portion cannot be formed by the die set including the linear slide cam, where the width of the product obtained by press-forming the workpiece is relatively small, since the linear slide cam cannot be moved in the direction parallel to the formed negative-angle portion.
In a known press-forming die set including a rotary cam to form the negative-angle portion, on the other hand, the rotary cam having a negative-angle forming portion is incorporated in the lower die or in the side guide cam provided on the lower die, such that the rotary cam is rotatable about an axis parallel to the bottom surface of the lower die which is perpendicular to the press-forming direction. An example of such a press-forming die set is disclosed in JP-A-60-166122. Another example of such a known press-forming die including a rotary cam is shown in
FIG. 6
, which does not show an upper die and a lower die. In this die set, a workpiece
100
is placed on a guide cam
102
provided on the lower die, so that an inner mounting surface
104
of the workpiece
100
is held in contact with the upper surface of the guide cam
102
, such that the inner mounting surface
104
is parallel to the bottom surface of the lower die. The upper die is adapted to be lowered toward the lower die in a direction perpendicular to the inner mounting surface
104
. To bend the workpiece
100
so as to form a negative-angle portion
112
, the rotary cam
106
is rotated in the clockwise direction “a” indicated in
FIG. 6
, so that a negative-angle forming portion
108
of the rotary cam
106
is moved toward a negative-angle forming portion
110
provided on the upper die, whereby the negative-angle forming portions
108
and
110
cooperate to form the negative angle portion
112
on the workpiece
100
. After the formation of the negative-angle portion
112
, the rotary cam
106
is rotated in the counterclockwise direction so that the negative-angle forming portion
108
is moved away from the negative-angle portion
112
. In this case, therefore, the negative-angle portion
112
can be formed even where the width of the formed product having the negative-angle portion
112
is comparatively small, provided that the diameter of the rotary cam
106
can be made relatively small.
Where the negative-angle portion
112
is formed by the die set including the conventional rotary cam
106
, this rotary cam
106
is required to be rotated so as to prevent an interference of its negative-angle forming portion
112
with the negative-angle portion
112
of the press-formed workpiece
100
(i.e., product), when the product is removed from the die set. For removing the product from the die set so as to prevent the interference, the angle of the movement path of the negative-angle forming portion
108
of the rotary cam
106
with respect to the inner mounting surface
104
of the workpiece
100
should decrease as the negative angle of the negative-angle portion
112
with respect to the pressforming direction increases. That is, when the negative-angle portion
112
generally extends almost parallel to the inner mounting surface
104
, the negative-angle forming portion
108
is required to be moved away from the negative-angle portion
112
(negative-angle forming portion
110
) in a direction almost parallel to the inner mounting surface
104
of the press-formed workpiece
100
.
The angle of the movement path of the negative-angle forming portion
108
of the rotary cam
106
with respect to the inner mounting surface
104
decreases with an increase in the diameter of the rotary cam
106
. Therefore, the diameter of the rotary cam
106
should increase with an increase in the negative angle of the negative-angle portion
112
with respect to the pressforming direction. However, it is difficult to incorporate the rotary cam
106
in the guide cam
102
where the diameter of the rotary cam
106
is relatively large. Further, a dimension “b” of the product (press-formed workpiece
100
) decreases with an increase in the diameter of the rotary cam
106
, so that the strength of the guide cam
102
decreases with an increase in the diameter of the rotary cam
106
. Accordingly, the strength of the guide cam
102
is not sufficient when the width dimension of the product is comparatively small. Where the negative angle of the negative-angle portion
112
is excessively large, for instance, where the negative-angle portion
112
is almost parallel to the inner mounting surface
104
, that is, almost perpendicular to the press-forming direction, the negative-angle forming portion
108
of the rotary cam
106
interferes with the inner mounting surface
104
, namely, the path of movement of the negative-angle forming portion
108
intersects the inner mounting surface
104
. In this instance, therefore, the rotary cam
106
cannot be rotated, unless the configuration of the product to be manufactured is suitably changed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a press-forming die set which permits a press-forming operation on a workpiece so as to form a negative-angle portion, even where the product to be manufactured by press-forming the workpiece has a relatively small width dimension and where the negative-angle portion has a comparatively large negative angle with respect to the press-forming direction.
Extensive researches and studies by the present inventor revealed that the problems experienced in
Burns Doane , Swecker, Mathis LLP
Crane Daniel C.
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
Press-forming die set including rotary cam having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Press-forming die set including rotary cam having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Press-forming die set including rotary cam having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543041