Title: Self-piercing rivet setting apparatus and system
Abstract: A self-piercing rivet setting apparatus (9) comprises a punch (14) and a die (18) for driving a self-piercing rivet into a plurality of workpieces including a receiving-side workpiece adjacent to the die. The self-piercing rivet has a large-diameter head and a hollowed leg. The leg is driven to pierce the workpieces while allowing the front end of the leg to be expanded and deformed in its radial outward direction and to be stayed in the receiving-side workpiece without passing therethrough, to connect the plurality of workpieces with each other by the expanded leg and the head. The die includes a first die member (26) having a first cavity (25), and a second die member (30) having a second cavity (27) and a protruding pin (29) provided at the center of the second cavity. The first cavity is adapted to allow the leg of the self-piercing to be driven into the workpieces in a straight direction when the self-piercing rivet is pressed by the punch (14). The second cavity and the protruding pin are adapted to allow the leg of the self-piercing rivet being piercing the workpieces to be expanded and deformed in its radial outward direction.
Patent Number: 6,910,263 Issued on 06/28/2005 to Naito
| Inventors:
|
Naito; Nobuharu (Toyohashi, JP)
|
| Assignee:
|
Newfrey LLC (Newark, DE)
|
| Appl. No.:
|
854320 |
| Filed:
|
May 26, 2004 |
Foreign Application Priority Data
| Dec 25, 2001[JP] | 2001-391576 |
| Current U.S. Class: |
29/798; 29/243.53; 29/432.2 |
| Intern'l Class: |
B23P 019/00 |
| Field of Search: |
29/798,245.53,432.1,432.2,524.1,715,788,796
|
References Cited [Referenced By]
U.S. Patent Documents
| 1279362 | Sep., 1918 | Krueger.
| |
| 2465534 | Mar., 1949 | Havener.
| |
| 5722144 | Mar., 1998 | Bora.
| |
| 5752305 | May., 1998 | Cotterill et al.
| |
| 6161279 | Dec., 2000 | Suboski.
| |
| 6263560 | Jul., 2001 | Edwards.
| |
| 6276050 | Aug., 2001 | Mauer et al.
| |
| 6385843 | May., 2002 | Singh et al.
| |
| 6742235 | Jun., 2004 | Blacket et al.
| |
| 6842962 | Jan., 2005 | Blacket.
| |
| 2004/0261259 | Dec., 2004 | Naito.
| |
Primary Examiner: Bryant; David P.
Attorney, Agent or Firm: Harness, Dickey & Pierce, P.L.C.
Parent Case Text
CROSS REFERENCE TO OTHER APPLICATIONS
The present application is a continuation of pending international patent application
PCT/US02/39910, filed Dec. 13, 2002 which designates the United States, and which
claims priority of Japanese patent application 2001-391576, filed Dec. 25, 2001.
Claims
1. A self-piercing rivet setting apparatus comprising a punch and a die for driving
a self-piercing rivet into a plurality of workpieces including a receiving-side
workpiece adjacent to the die, the self-piercing rivet having a large-diameter
head and a hollowed leg extending from the head, wherein when the self-piercing
rivet is driven into the workpieces, the leg is driven to pierce the workpieces
while allowing the front end of the leg to be expanded and deformed in its radial
outward direction and to be stayed in the receiving-side workpiece adjacent to
the die without passing therethrough to connect the plurality of workpieces with
each other by the expanded leg and the head; and
wherein the die includes a first die member having a first cavity, and a second
die member having a second cavity and a protruding pin provided at the center of
the second cavity, the first cavity being adapted to allow the leg of the self-piercing
rivet to be driven into the workpieces in a straight direction when the self-piercing
rivet is pressed against the first die member by the punch, and the second cavity
and protruding pin of the second die member being adapted to allow the leg of the
self-piercing rivet being piercing the workpieces to be expanded and deformed in
its radial outward direction.
2. The apparatus as defined in claim 1, wherein the first die member is disposed
at a position facing with the punch until the leg of the self-piercing rivet is
driven into the workpieces in a straight direction and starts piercing the receiving-side
workpiece adjacent to the first die member, and the second die member is disposed
at the position facing with the punch in place of the first die member to allow
the leg of the self-piercing rivet being piercing the receiving-side workpiece
to be expanded and deformed in its radial outward direction when the leg of the
self-piercing rivet starts piercing the receiving-side workpiece.
3. The apparatus as defined in claim 2 further including a C-shaped frame, wherein
the punch is attached to one of the ends of the C-shaped frame to be movable toward
the other end of the C-shaped frame, and the first and second die members are attached
to the other end of the C-shaped frame, and wherein the other end of the C-shaped
frame is provided with a rotary table for supporting the first and second die members,
the rotary table being operable to allow either one of the first and second die
members to be selectively positioned at the position facing with the punch so as
to receive the self-piercing rivet to be driven by the punch.
4. The apparatus as defined in claim 1, which includes a plurality of die members
to be replaceably used as at least one of the first and second die members, depending
on a piercing depth of the leg of the self-piercing rivet with respect to the workpieces.
5. A self-piercing rivet setting system having self-piercing rivet setting apparatuses
each including a punch and a die for driving a self-piercing rivet into a plurality
of workpieces having a receiving-side workpiece adjacent to the die, the self-piercing
rivet having a large-diameter head and a hollowed leg extending from the head,
wherein when the self-piercing rivet is driven into the workpieces, the leg is
driven to pierce the workpieces while allowing the front end of the leg to be expanded
and deformed in its radial outward direction and to be stayed in the receiving-side
workpiece adjacent to the die without passing therethrough to connect the plurality
of workpieces with each other by the expanded leg and the head; and
wherein the self-piercing rivet setting system comprises a first self-piercing
rivet setting apparatus including a first die which has a first cavity, the first
cavity of the first die member being adapted to allow the leg of the self-piercing
rivet to be driven into the workpieces in a straight direction when the self-piercing
rivet is pressed against the first die by the punch; a second self-piercing rivet
setting apparatus including a second die which has a second cavity and a protruding
pin provided at the center of the second cavity, the second cavity and protruding
pin of the second die member being adapted to allow the leg of the self-piercing
rivet being piercing the workpieces to be expanded and deformed in its radial outward
direction; and exchanging means for placing the first self-piercing rivet setting
apparatus with respect to the workpieces until the leg of the self-piercing rivet
is driven into the workpieces in a straight direction and starts piercing the receiving-side
workpiece, and for placing the second self-piercing rivet setting apparatus with
respect to the workpiece in place of the first self-piercing rivet setting apparatus
to allow the leg of the self-piercing rivet being piercing the receiving-side workpiece
to be expanded and deformed in its radial outward direction when the leg of the
self-piercing rivet starts piercing the receiving-side workpiece.
Description
FIELD OF THE INVENTION
The present invention relates to a self-piercing rivet setting apparatus for
setting, into a plurality of workpieces, a self-piercing rivet having a large-diameter
head and a hollowed leg extending from the head. More specifically, the present
invention relates to the self-piercing rivet setting apparatus for connecting a
plurality of workpieces, such as two or more panels (or a panel and a component),
by using a self-piercing rivet in a sheet-metal assembly operation such as automobile
assembling (particularly, an aluminum body assembly operation).
One example of a self-piercing rivet setting apparatus is described in Japanese
Patent Laid-Open No.
08-505087. FIG. 1 in this publication shows one example
of a self-piercing rivet. The self-piercing rivet comprises a large-diameter head
and a hollowed leg extending from the head. When the self-piercing rivet is driven
into workpieces, such as two body panels, by a punch and a die of the setting apparatus,
the front end of the leg is expanded and deformed as the leg pierces the panels,
and the panels are finally connected with each other by the expanded leg and the
head. The self-piercing rivet is suitable for connecting aluminum body panels to
which welding is not applicable. The demand for the self-piercing rivet is increasing
because aluminum bodies are increasingly employed to facilitate weight reduction
in automobile bodies. In particular, since the self-piercing rivet is driven to
pierce a punch-side workpiece but stay in a receiving-side workpiece adjacent to
the die without passing therethrough, the rivet does not form any opening in the
surface of the receiving-side workpiece. This advantageously maintains a sealing
performance and good appearance of the receiving-side workpiece.
In a conventional self-piercing-rivet driving operation, if the punch-side workpiece
has a greater thickness in a rivet-driving direction than that of the receiving-side
workpiece adjacent to the die, a radial piercing length, that is, an undercut amount
of the leg of the rivet obliquely piercing the receiving-side workpiece can be
reduced, resulting in insufficient connecting strength. Such a condition will be
described in conjunction with FIG. 1. FIG. 1 shows the condition when a
self-piercing rivet 1 is driven into two workpieces 2 and 3
to connect the punch-side workpiece 2 (a plurality of punch-side workpieces
may be provided in lieu of the illustrated example) with the receiving-side workpiece
3 adjacent to the die. The self-piercing rivet 1 has a large-diameter
head 5 and a hollowed leg 6 extending from the head. When the punch-side
workpiece 2 has a greater thickness than that of the receiving-side workpiece
3 as shown in FIG. 1, the radial piercing length or the undercut amount
7 of the leg of the rivet obliquely piercing the receiving-side workpiece
is reduced, and thereby the workpiece 3 cannot be connected to the workpiece
2 with a sufficient strength. At the preset stage, it is typically required
to limit a ratio of the thickness of the punch-side workpiece to the thickness
the receiving-side workpiece adjacent to the die no more than the ratio of 2 to
1 (2:1) to assure a sufficient connecting force.
The above limitation (or the need for preventing the receiving-side workpiece
from having a thickness of one-half or less of the thickness of the other workpiece
in a self-piercing rivet driving region of the workpieces) imposes the restriction
on the rivet-driving direction. For example, in FIG. 1, if the ratio of the thickness
of the workpiece 2 to the other workpiece 3 exceeds 2:1 such as 3:1
or 4:1, and the self-piercing rivet is driven into the workpiece 3 as the
receiving-side workpiece, an insufficient undercut amount 7 is resulted
to thereby obtain undesired connecting strength. Thus, the workpiece 2 must
be placed as the receiving-side workpiece by turning over the rivet setting apparatus
or turning over both the workpiece 2 and the workpiece 3 to connect
the workpiece 2 to the workpiece 3 with a sufficient strength. However,
the rivet-setting operation cannot be carried out at a desirably increased speed
due to a time required for turning over the setting apparatus or the workpieces.
Besides, the turning-over operation per se can get into difficulties due to the
restrictions on the workpiece shapes, the rivet-driving region and other factors.
It is therefore an object of the present invention to provide a self-piercing
rivet setting apparatus capable of reducing or eliminating the restriction on a
rivet-driving direction with respect to a workpiece.
SUMMARY OF THE INVENTION
In order to achieve the above object, the present invention provides a self-piercing
rivet setting apparatus comprising a punch and a die for driving a self-piercing
rivet into a plurality of workpieces including a receiving-side workpiece adjacent
to the die. The self-piercing rivet has a large-diameter head and a hollowed leg
extending from the head. In this self-piercing rivet setting apparatus, when the
self-piercing rivet is driven into the workpieces, the leg is driven to pierce
the workpieces while allowing the front end of the leg to be expanded and deformed
in its radial outward direction and to be stayed in the receiving-side workpiece
adjacent to the die without passing therethrough, to connect the plurality of workpieces
with each other by the expanded leg and the head. Further, in the self-piercing
rivet setting apparatus, the die includes a first die member having a first cavity,
and a second die member having a second cavity and a protruding pin provided at
the center of the second cavity. The first cavity is adapted to allow the leg of
the self-piercing rivet to be driven into the workpieces in a straight direction
when the self-piercing rivet is pressed against the first die member by the punch.
The second cavity and the protruding pin of the second die member are adapted to
allow the leg of the self-piercing rivet being piercing the workpieces to be expanded
and deformed in its radial outward direction.
According to the above self-piercing rivet setting apparatus, until the
front end of the leg of the self-piercing rivet starts piercing the receiving-side
workpiece adjacent to the die, the first die member allows the leg to be driven
into the workpiece in a straight direction. Then, when the leg starts piercing
the receiving-side workpiece, the front end of the leg is widely expanded in its
radial outward direction by the second die member to provide a sufficient undercut
amount. The sufficient undercut amount can achieve an adequate connecting force
even if the receiving-side workpiece has a thin thickness of one-half or less of
that of the other workpiece (or the punch-side workpiece). This makes it possible
to reduce or eliminate the restriction on the rivet-driving direction with respect
to the workpieces. Thus, the complicated operation of turning over either the setting
apparatus or the workpieces as in the conventional setting apparatus can be skipped
or omitted to thereby achieve a speedy setting operation. Further, the setting
operation can be carried out even in the conventionally impossible rivet-driving
direction. The eliminated restriction on the rivet-driving region provides widened
applicable area or region suitable for the self-piercing rivet setting operation.
In the above self-piercing rivet setting apparatus, the first die member may
be
disposed at a position facing with the punch until the leg of the self-piercing
rivet is driven into the workpieces in a straight direction and starts piercing
the receiving-side workpiece adjacent to the first die member. Then, the second
die member may be disposed at the position facing with the punch in place of the
first die member to allow the leg of the self-piercing rivet being piercing the
receiving-side workpiece to be expanded and deformed in its radial outward direction
when the leg of the self-piercing rivet starts piercing the receiving-side workpiece.
The setting apparatus may further include a C-shaped frame. In that case, the punch
is attached to one of the ends of the C-shaped frame to be movable toward the other
end of the C-shaped frame, and the first and second die members are attached to
the other end of the C-shaped frame. Further, the other end of the C-shaped frame
is provided with a rotary table for supporting the first and second die members.
The rotary table is operable to allow either one of the first and second die members
to be selectively positioned at the position facing with the punch to receive the
self-piercing rivet to be driven by the punch. In the self-piercing rivet setting
apparatus according to the present invention, the number of the die members is
not limited to two but it may be three or more. Further, these die members may
be selectively replaced depending on a piercing depth of the self-piercing rivet.
The present invention also provides a self-piercing rivet setting system having
self-piercing rivet setting apparatuses each including a punch and a die for driving
a self-piercing rivet into a plurality of workpieces having a receiving-side workpiece
adjacent to the die, the self-piercing rivet having a large-diameter head and a
hollowed leg extending from the head, wherein when the self-piercing rivet is driven
into the workpieces, the leg is driven to pierce the workpieces while allowing
the front end of the leg to be expanded and deformed in its radial outward direction
and to be stayed in the receiving-side workpiece adjacent to the die without passing
therethrough to connect the plurality of workpieces with each other by the expanded
leg and the head. The self-piercing rivet setting system of the present invention
comprises a first self-piercing rivet setting apparatus including a first die which
has a first cavity, the first cavity of the first die member being adapted to allow
the leg of the self-piercing rivet to be driven into the workpieces in a straight
direction when the self-piercing rivet is pressed against the first die by the
punch; a second self-piercing rivet setting apparatus including a second die which
has a second cavity and a protruding pin provided at the center of the second cavity,
the second cavity and protruding pin of the second die member being adapted to
allow the leg of the self-piercing rivet being piercing the workpieces to be expanded
and deformed in its radial outward direction; and exchanging means for placing
the first self-piercing rivet setting apparatus with respect to the workpieces
until the leg of the self-piercing rivet is driven into the workpieces in a straight
direction and starts piercing the receiving-side workpiece, and for placing the
second self-piercing rivet setting apparatus with respect to the workpiece in place
of the first self-piercing rivet setting apparatus to allow the leg of the self-piercing
rivet being piercing the receiving-side workpiece to be expanded and deformed in
its radial outward direction when the leg of the self-piercing rivet starts piercing
the receiving-side workpiece.
According to this system, the first self-piercing rivet setting apparatus
allows the leg to be driven into the workpiece in a straight direction until the
front end of the leg of the self-piercing rivet starts piercing the receiving-side
workpiece adjacent to the die. Then, when the leg starts piercing the receiving-side
workpiece, the front end of the leg is widely expanded in its radial outward direction
by the second self-piercing rivet setting apparatus, to provide a sufficient undercut
amount. The sufficient undercut amount can achieve a desired connecting force even
if the receiving-side workpiece has a thin thickness of one-half or less of that
of the punch-side workpiece. This makes it possible to reduce or eliminate the
restriction on the rivet-driving direction with respect to the workpieces. Thus,
the complicated operation of turning over either the setting apparatus or the workpieces
as seen in the conventional setting apparatus can be skipped or omitted to achieve
a speedy setting operation. Further, the setting operation can be carried out even
in the conventionally impossible rivet-driving direction. The eliminated restriction
on the rivet-driving region provides widened applicable area or region suitable
for the self-piercing rivet setting operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing connected workpieces with a self-piercing
rivet driven by a conventional setting apparatus.
FIG. 2 is a front view of a self-piercing rivet setting apparatus according
to one embodiment of the present invention.
FIG. 3 is a top plan view of a die when seeing from the arrow III of the self-piercing
rivet setting apparatus in FIG. 2.
FIG. 4 is a sectional view of a first die member and a punch in the condition
when a self-piercing rivet is being driven into workpieces by using the first die
member of the self-piercing rivet setting apparatus shown in FIGS. 2 and 3.
FIG. 5 is a sectional view of a second die member and the punch in the condition
when a self-piercing rivet is driven into workpieces to connect the workpieces
with each other by using the second die member of the self-piercing rivet setting
apparatus shown in FIGS. 2 and 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the drawings, an embodiment of the present invention will
now be described. FIG. 2 schematically shows the entire structure of a self-piercing
rivet setting apparatus
9 according one embodiment of the present invention.
In FIG. 2, the self-piercing rivet setting apparatus
9 includes a C-shaped
frame
11 having a coupling portion
10 to be coupled with an articulated
robot arm (not shown). The C-shaped frame
3 is an integral rigid body including
an upper horizontal arm, a vertical arm having the coupling portion
10 attached
thereto, and a lower horizontal arm. A rivet setting assembly
13 of the
self-piercing rivet setting apparatus is attached to or one of the ends or the
end of the upper horizontal arm of the C-shaped frame
11. The setting assembly
13 is provided with a punch
14 movably attached to the front-end
(the lower end in FIG. 2) thereof. A receiver unit
15 extends from the punch
14 to the front-end side. A self-piercing rivet (see the self-piercing rivet
1 in FIG. 1) is fed to and held in the receiver unit
15 and driven
by the punch
14. A spindle type driving unit
17 is provided on the
upper side of the punch
14. The spindle type driving unit
17 is operable
to press the punch
14 so as to drive the self-piercing rivet held in the
receiver unit on the lower side of the punch. A die
18 is attached to the
other end or the end of the lower horizontal arm of the C-shaped frame
11.
For example, the spindle type driving unit
17 comprises an electric driving
motor, a reduction gear assembly
21 and a gear assembly
22 for transmitting
a rotation force of the motor, and a spindle
23 adapted to move vertically
while rotating according to the rotation force of the motor through a belt. When
the spindle moves downward according the rotation force of the motor, this movement
is transmitted to the punch
14, and then the punch
14 strongly presses
the self-piercing rivet held in the receiver unit
15, toward the die
18.
A plurality of workpieces (for example, see the workpieces
2 and
3
in FIG. 1) are placed on the die
18. According to the downward movement
of the punch
14, the self-piercing rivet is driven into the plurality of
workpieces to connect these workpieces with each other. The C-shaped frame
11
elastically supports the setting assembly
13 and the die
18 to absorb
an impact force during the rivet-driving operation.
In the present invention, the die
18 comprises a plurality of die members.
In FIGS. 2 and 3, the die
18 includes a first die member
26 having
a cavity
25 adapted to allow the leg of the self-piercing rivet to be driven
into the workpieces in a straight direction when the self-piercing rivet is pressed
by the punch, and a second die member
30 having a cavity
27 and a
protruding pin
29 provided at the center of the cavity
27 which are
adapted to allow the leg of the self-piercing rivet being piercing the workpieces
to be expanded and deformed in its radial outward direction. While the illustrated
embodiment has the die
18 comprised of two die members, the die
18
may be comprised of three or more die members each having a different shape. In
the illustrated embodiment, the cavity
25 of the first die member
26
is formed as a simple cylindrical hole having a diameter capable of receiving a
pressure deformation of the workpieces caused by a pressing force of the leg of
the self-piercing rivet. The cavity
27 of the second die member
30
is formed as a cylindrical hole which surrounds the central protruding pin
29,
and has a diameter greater than the outer diameter of the leg and a depth less
than the cavity
25 to expandingly deform the leg of the self-piercing rivet
in its radial outward direction.
The first die member
26 and the second die member
30 are attached
onto a rotary table
31. According to rotation of the rotary table, either
one of the first and second die members
26 and
30 is selectively
positioned at a position facing with the punch to receive the self-piercing rivet
to be driven by the punch
14. To this end, a rotational drive device
33
such as a motor attached to the C-shaped frame is provided to rotate the rotary
table
31 about a shaft
35 in FIG. 3 as shown by the arrow in FIG.
2 to position either one of the first and second die members
26 and
30
below the punch
14. Further, a control unit (not shown) of the self-piercing
rivet setting apparatus
9 controls the rotational drive device
33
to position either one of the first and second die members
26 and
30
below the punch
14 at a predetermined timing.
With reference to FIGS. 4 and 5, an operation of driving the self-piercing rivet
using the self-piercing rivet setting apparatus
9 will be described below.
In FIG. 4, the self-piercing rivet
1 is automatically fed from a feeding
unit (not shown) to the receiver unit
15, and held in the receiver unit
15 to locate it below the punch
14. The workpieces
2 and
3
to be connected with one another are placed between the die
18 and the punch
14. It is to be understood that the number of the workpieces may be tow
or more. In the present invention, at a first step of the rivet-driving operation,
the first die member
26 is positioned below the punch
14 by the rotation
of the rotary table
31. The punch
14 is moved downward by the spindle
type driving unit
17 (FIG. 2) to drive the self-piercing rivet
1
into the punch-side workpiece
2. During this rivet-driving operation, the
hollowed leg
6 of the self-piercing rivet
1 progressively pierces
the workpiece
2, and the configuration of the cavity
25 of the first
die member
26 allows the leg
6 of the self-piercing rivet
1
to be driven into the workpiece
2 in a straight direction. The punch
14
continues to press the self-piercing rivet until the piercing depth of the leg
6 reaches the receiving-side workpiece
3 adjacent to the first die
member
26. When the leg
6 starts piercing the receiving-side workpiece
3, the resulting reaction force is transmitted to the punch
14. At
detecting of the reaction force, the spindle type driving unit
17 temporarily
stops providing the pressing force to the punch
14.
After the pressing force to the punch
14 is stopped, the rotary table
31 is rotated to position the second die member
30 at a position
below the punch
14 and under the receiving-side workpiece
3 of the
workpieces
2 and
3. After the second die member
30 is positioned
in its place, the spindle type driving unit
17 applies the pressing force
to the punch
14 again to restart driving into the receiving-side workpiece
3 the self-piercing rivet which has just started piercing the receiving-side
workpiece
3. The configuration of the cavity
27 and the central protruding
pin
29 of the second die member allows the leg
6 of the self-piercing
rivet being piercing the receiving-side workpiece
3 to be expanded and deformed
in its radial outward direction. Referring to FIG. 5, when the front end of the
leg
6 of the self-piercing rivet
1 pierces the receiving-side workpiece
3 adjacent to the second die member
30, the top of the protruding
pin
29 contacts the die-facing side of the receiving-side workpiece
3.
The protruding pin
29 acts to stick the contact area of the receiving-side
workpiece
3 due to the pressure of the receiving-side workpiece by the pressing
force of the punch
14. Since the protruding pin
29 is located at
the center of the opening of the leg
6 of the self-piercing rivet, the front
end of the leg
6 of the self-piercing rivet
1 is widely expanded
in its radial outward direction. Thus, the leg
6 is expanded and deformed
widely in its radial outward direction to pierce the receiving-side workpiece.
Then, the rivet-driving operation is completed before the front end of the led
6 is pushed through the receiving-side workpiece. As a result, the leg
6
is largely deformed in its radial direction to provide a sufficient piercing length
or undercut amount
37 in the radial direction of the leg
6. The two
workpieces
2 and
3 are connected with each other by the expanded
and deformed leg
6 and the large-diameter head
5. In the present
invention, the sufficient undercut amount
37 of the expanded leg
6
allows the workpieces
2 and
3 to be connected with an adequate connecting
force even if the receiving-side workpiece
3 has a thin thickness of one-half
or less of the other workpiece (or the punch-side workpiece). This makes it possible
to reduce or eliminate the restriction on the rivet-driving direction with respect
to the workpieces. Thus, the complicated operation of turning over the setting
apparatus or the workpieces as in the conventional self-piercing rivet setting
apparatus can be skipped or omitted to achieve a speedy setting operation. Further,
the setting operation can be carried out even in the conventionally impossible
rivet-driving direction. The eliminated restriction on the rivet-driving region
provides widened applicable area or region suitable for the self-piercing rivet
setting operation.
When the number of the die members is three or more, a cavity of a die member
corresponding to the first die member is formed in a configuration allowing the
leg of the self-piercing rivet to be driven into the workpieces in a straight direction
until the front end of the leg reaches a receiving-side workpiece. With respect
to the remaining die members corresponding to the second die member, a cavity and
a protruding pin of each die member are formed in respective configurations varied
to the other die members to thereby allow the leg of the self-piercing rivet to
be widely expanded in its radial outward direction after the front end of the leg
reaches the receiving-side workpiece. When the self-piercing rivet is driven into
a plurality of workpieces, the die members are sequentially replaced while controlling
the punch to repeat the pressing operation to the self-piercing rivet and the stop
of the pressing operation.
In another embodiment, a self-piercing rivet setting system is provided. This
self-piercing rivet setting system comprises a first self-piercing rivet setting
apparatus and a second self-piercing rivet setting apparatus. The first self-piercing
rivet setting apparatus includes a first die which has a first cavity. The second
self-piercing rivet setting apparatus includes a second die which has a second
cavity and a protruding pin provided at the center of the second cavity. In this
embodiment, the first cavity of the first self-piercing rivet setting apparatus
is adapted to allow the leg of the self-piercing rivet to be driven into the workpieces
in a straight direction when the self-piercing rivet is pressed by the punch. The
second cavity and the protruding pin of the second self-piercing rivet setting
apparatus are adapted to allow the leg of the self-piercing rivet being piercing
the workpieces to be expanded and deformed in its radial outward direction. The
self-piercing rivet setting system further include exchanging means for placing
the first self-piercing rivet setting apparatus to the workpieces until the leg
of the self-piercing rivet is driven into the workpieces in a straight direction
and starts piercing the receiving-side workpiece, and for placing the second self-piercing
rivet setting apparatus to the workpiece in place of the first self-piercing rivet
setting apparatus to allow the leg of the self-piercing rivet being piercing the
receiving-side workpiece to be expanded and deformed in its radial outward direction
when the leg of the self-piercing rivet starts piercing the receiving-side workpiece.
The exchanging means for replacing and positioning the first and second self-piercing
rivet setting apparatuses may be achieved by use of a tool changer.
According to the present invention, until the front end of the leg of the
self-piercing rivet starts piercing the receiving-side workpiece adjacent to the
die, the protruding pin does not act on the receiving-side workpiece. Then, when
the front end of the leg of the self-piercing rivet starts piercing the receiving-side
workpiece, the protruding pin reliably acts on the receiving-side workpiece. Thus,
the leg is driven into the workpieces in a straight direction until the leg enters
in the receiving-side workpiece. However, when the leg starts piercing the receiving-side
workpiece, the protruding pin acts to widely expand the front end of the leg in
its radial outward direction to provide a sufficient undercut amount. The sufficient
undercut amount can achieve an adequate connecting force even if the receiving-side
workpiece has a thin thickness of one-half or less of that of the other workpiece
(or the punch-side workpiece). This makes it possible to reduce or eliminate the
restriction on the rivet-driving direction with respect to the workpieces. Thus,
the complicated operation of turning over the setting apparatus or the workpieces
as in the conventional setting apparatus can be skipped or omitted to achieve a
speedy setting operation. Further, the setting operation can be carried out even
in the conventionally impossible rivet-driving direction. The eliminated restriction
on the rivet-driving region provides widened applicable area or region suitable
for the self-piercing rivet setting operation.
*
