Note: Descriptions are shown in the official language in which they were submitted.
CA 02162638 1999-06-02
IMPROVED METHOD OF ATTACHING A FASTENER
TO A PANEL AND INSTALLATION APPARATUS
FIELD OF THE INVENTION
The present invention relates to an improved installation apparatus and method
s of attaching a female fastener element, such as a self riveting nut
fastener, to a metal
panel, wherein a small hole is first formed in the panel by a piercing quill
through the
fastener bore and the annular riveting portion is then driven against the
panel to enlarge
the panel hole, then through the panel opening and locked to the panel in a
female die
member. The improved apparatus includes a tapered or conical punch which
pierces an
i o opening in the panel, then enlarges the panel opening to receive the
riveting portion of
the fastener.
CA 02162638 1999-06-02
RELATED PATENTS
This application discloses improved methods and installation tooling which may
be utilized in connection with the fasteners disclosed in U.S. Patents
5,564,873 of 15
October 1996 and U.S. Patent 5,237,733 issued 24 August 1993..
BACKGROUND OF THE INVENTION
The present invention relates to improvements in the method of attaching self
attaching or self riveting female fasteners and installation tooling which
results in an
improved installation of the fastener in a metal panel and reduces the
likelihood of
installation tooling breakdown or breakage of the piercing tool and female die
member.
to Self piercing and self clinching or riveting female fasteners are used by
the
automotive industry and other mass production industries, such as the
appliance industry,
to attach various parts to a metal panel, such as a bracket, frame member, or
the like.
Examples of pierce nuts are shown in U.S. Patent Nos. 3,299,500 and 3,315,138,
assigned to the assignee of this application. The prior art also includes a
number of self
1 s riveting nuts, including nuts having an annular skirt or barrel
-2-
2i~2638
docket/160152-618
portion, wherein the free end of the barrel portion is deformed radially
outwardly
in a die member to form a mechanical interlock between the nut fastener and
the
panel as disclosed, for example, in U.S. Patent Nos. 4,398,239 and 4,018,257.
The
self riveting nuts disclosed in such patents are, however, secured to a panel
in a
pre-pierced panel opening, requiring two separate operations. The method of
installing the nut fastener disclosed in these patents also require very
precise
centering of the nut relative to the pre-pierced panel opening, wherein a
spring-biased pin is received through the panel opening and the nut is
centered on
the pin, prior to installation. Further, the nut and panel installation does
not have
sufficient pull-out strength for many applications. U.S. Patent No. 3,926,236,
also
assigned to the assignee of this application, discloses a method of attaching
a nut
wherein the panel is pierced by a punch which extends through the nut bore to
pierce and secure the nut in a continuous operation. However, the fastener is
not
a riveting-type fastener having a barrel portion extending through the pierced
panel
opening. Self-riveting fasteners have also been used by the container
industry, for
example, for attaching a flange or tag ring for reception of a threaded plug
as
disclosed, for example, in U.S. Patent No. 3,800,401.
This application and the above-identified related patents and patent
applications disclose methods and apparatus for permanently attaching male and
female fasteners to a panel, such as nuts and bolts, in a'continuous
operation. The
preferred methods of installation and installation apparatus do not require
pre-piercing of the panel, although self-attaching fastener elements of this
type may
be installed in a pre-pierced panel opening. Certain difficulties have,
however, been
-3-
2 i 5~~3~
docketN60152-618
experienced in installing female fastener elements in a panel, particularly
where the
barrel portion of the female element is used to pierce the panel opening. As
will
be understood, if the female fastening element is a nut-type fastener, the
bore of the
nut must remain clear of obstructions following installation for receipt of a
stud or
bolt. The method of installation and installation apparatus is also preferably
suitable
for mass production applications, such as used by the automotive and appliance
industries.
Self riveting fasteners of the type disclosed herein are particularly strong
in
resisting pull-out and cam-out of the fastener from the panel. Pull resistance
is
tested by threading a bolt in the threaded bore of the female fastener and
pulling in
a direction opposite to the direction of installation. The pull-out strength
in many
applications is greater than the tensile strength of the bolt. Cam-out is the
strength
of the installation to a cantilevered load. However, certain applications,
such as
automotive seat track and belt applications, also require improvements in
push-through strength and resistance to torque. Resistance to torque is
generally
provided by barbs or ribs on the body of the fastening element which may
result in
stress cracks in the panel.
Further, in most applications, it is desirable for the fastener to be
installed
flush or slightly below the metal panel. These objects were achieved with the
nut
fastener and method of installation disclosed in the parent application of
this
application, Serial No. 092,593; however, the piercing of the panel through
the nut
bore as disclosed resulted in further problems with the installation tooling,
particularly in mass production applications. The female die which receives
the
-4-
2 i 6?6~8
docket/160152-618
punch and cooperates with the punch to pierce the panel and form the nut
barrel into
a mechanical interlock with the panel was subject to failure from stress
cracks in the
die post surrounding the bore. This problem could be alleviated by using a
punch
or quill having a smaller diameter; however, the punch was then subject to
breaking. Further, a slight misalignment between the die button and the punch
may
result in a poor installation. Finally, stresses were generated in the panel
surrounding the hole which receives the nut, sometimes resulting in stress
cracking.
There was, therefore, a need to improve the method of installation and
installation apparatus to eliminate these problems, including punch or quill
and die
button breakage, panel stress cracking, and misalignment between the punch and
die
button resulting from normal tolerance build-up in mass production
applications.
The method of assembly and installation apparatus of this invention
accomplishes
these additional objectives and results in an improved female fastener and
panel
assembly. Other advantages and meritorious features of this invention will be
more
fully understood from the following description of the preferred embodiments,
appended claims and drawings, a brief description of which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side perspective view of a self attaching nut fastener of the
general type useful in the method of this invention;
Figure 2 is an end view of the self attaching nut fastener of Figure l;
Figure 3 is a cross-sectional view of the self-attaching nut fastener shown in
Figures l and 2;
-5-
2162638
docketN60152-618
Figure 4 is a side cross-sectional view of the nut fastener shown in Figures 1
to 3 following installation of the fastener in a metal panel;
Figure 5 is a partial side view of a preferred embodiment of the punch used
in the method and apparatus of this invention;
Figure 6 is a side partially cross-sectioned view, of one embodiment of the
installation apparatus of this invention installing the fastener illustrated
in Figures 1
to 3; and
Figures 7 to 10 are side partial cross-sectional views similar to Figure 6
illustrating the installation method and apparatus of this invention
illustrating
sequentially the installation of a female fastener element in a panel
utilizing the
method and apparatus of this invention.
DESCRIPTION OF THE PREFERRED INSTALLATION
APPARATUS AND METHOD OF THIS INVENTION
The embodiment of the self riveting female fastener element 20 shown in
Figure 1 to 3 includes a body portion 22, a tubular barrel portion 24 and a
radial
flange portion 26 integral with the body portion 22. As described more fully
in the
above-referenced related patents, the free end 28 of the barrel portion 24
preferably
includes a chamfer which extends radially outwardly from the internal surface
31
of the barrel portion 24 to the arcuate bearing surface 34. The body portion
22 in
the disclosed embodiment includes an internally threaded bore 32 which is
coaxially
aligned with the internal cylindrical surface 31 of the tubular barrel portion
24. The
bore 32 may, however, be unthreaded, for example, to receive a thread forming
screw or bolt. The body portion further includes a conical exterior lead-in
-6-
2162638
docketJ160152-618
surface 36, a plurality of flats 38, forming a polygonal surface which resists
torque
or turning of the fastener in fastener and panel assembly shown in Figure 4,
and a
plurality of grooves 40 which extend through the junction of the flat surfaces
38 into
the conical surface 36 and into the flange portion 26 as best shown in Figure
1. As
described more fully in the above-referenced parent application, the
combination of
flat surfaces 38 and grooves 40 provide improved torque resistance of the
fastener 20 in the panel.
Figure 4 illustrates the female fastener element 20 of Figures 1 to 3
installed
in a panel 44. The panel portion 46 surrounding the panel opening is received
in
a U-shaped portion 50 deformed in the tubular barrel portion 24 formed at the
free
end 28 of the barrel portion. The U-shaped portion 50 forms a secure
mechanical
interlock between the fastener element and the panel and the body portion 22
and
barrel portion 24 are received in a tubular panel portion 48 formed in the
panel
during the installation of the fastener element in the panel to provide a
flush
installation or slightly below the panel, as described below. As shown, the
tubular
panel portion 48 is received into the grooves or channels 40 to prevent
rotation of
the fastener element 20 in the panel following installation. Figures 5 to 10
illustrate
a preferred embodiment of the installation apparatus and method of this
invention,
including the steps of installing a female fastener element of this type in a
panel 44.
Figure 5 illustrates a preferred embodiment of the punch or piercing quill 52.
The punch 52 includes a cylindrical portion 54, which may have a shape other
than
cylindrical, a tapered or conical portion 56 and a cylindrical end portion 58.
The
cylindrical end portion 58 preferably has a diameter which is substantially
less than
2162638
docket A~60152-618
the diameter of the internal surface 31 of the female fastening element 20.
The
conical portion 56 has a minor diameter 60 which is generally equal to the
diameter
of the cylindrical portion 58 and a major diameter at 62 which is greater than
the
internal diameter of the threaded bore 32 of the fastener element, which in
the
disclosed embodiment is the crest diameter of the threads. The effective
diameter
of the conical portion 56 will be a function of the panel thickness and the
nut size;
however, the conical punch utilized in the installation apparatus of this
invention is
specifically designed to accommodate various nut sizes, and panel thicknesses.
In
a typical application, the conical portion 56 is tapered outwardly from the
cylindrical
portion 58 at an angle of about 2.5° and the tapered portion should be
finish ground
and formed of tool steel. The cylindrical end portion 58 is provided to assure
accurate grinding of the conical portion 56. The cylindrical portion may be
any
convenient length.
Figure 6 illustrates an installation apparatus for installing a self riveting
female fastener element 20 generally as shown in Figures 1 to 3. The disclosed
embodiment of the installation apparatus includes an installation head 66 and
a
female die member or die button 68. The installation head includes a nose
member 70 which engages the panel 44 during installation of the fastener
element,
a plunger passage 72, which receives the fastener element during installation
and a
reciprocable plunger 74 which engages the flat driven face 42 of the fastener
element. In the disclosed embodiment, the die button assembly includes a body
portion 76, a moveable die member 78 having an annular concave die cavity 80
and
a projecting central die post 82 and an axial bore 84 which receives the
piercing
_g_
2162038
docket 1!60152-618
quill or punch 52, as described below. The disclosed embodiment of the die
button
assembly 68 further includes a base member 86 having an axial bore 87
coaxially
aligned with the bore 84 of the die member 78 and the die member 78 includes a
tubular extension 88 which is telescopically received in the bore 87 of the
base
member 86. The die member 78 is resiliently biased upwardly in Figure 6 by a
coil
spring 90 and the relative upward movement of the die member is limited by
stop
surface 92.
In a typical application, the installation head 66 is attached to the upper
die
shoe of a die platen (not shown) and the die button assembly 68 is received in
a
configured opening in the lower die shoe (not shown). As described more fully
in
the above-referenced related patents and patent applications, a self riveting
fastener
element 20 is installed with each stroke of the die press. As will be
understood,
however, the method of this invention may be utilized with any conventional
die
press and the entire assembly may be reversed, such that the self riveting
fastener
element 20 is installed upwardly in the die press. The method of this
invention will
now be described with reference to Figures 6 to 10. In a normal operation, the
panel 44 is first received on the annular panel supporting surface 94 of the
body
portion 76. In many applications, the panel will be clamped in place on the
die
shoe to prevent any relative movement of the panel during the installation of
the
fastener element 20. The fastener element is then received in the plunger
passage 72 and the plunger 74 moves the fastener until the free end 28 of the
fastener element engages the panel 44, as shown in Figure 6. The fastener
element
is now ready for installation. As shown, the tubular barrel portion 24 of the
-9-
2162638
docket/160152-618
fastener element 20 is coaxially aligned with the concave annular die cavity
80 and
the die post 82 is coaxially aligned with the internal surface of the barrel
portion to
receive the barrel portion, as described below.
The piercing quill or punch 52 is then driven downwardly against the
panel 44, as shown by arrow 96 in Figure 7, causing the end 58 of the punch to
pierce the panel. The panel is pierced between the outer surface of the end 58
of
the punch and the internal surface of the die bore 84 and the die member 78 is
moved downwardly against the force of the return spring 90, as shown by arrow
98.
This is done to entrap the slug so that it is not dropped prematurely. The
free
end 28 of the tubular barrel portion 24 remains in contact with the panel 44;
however, the fastener element 20 is not driven into the panel by the plunger
74
during this step of the method of this invention.
The end 58 of the punch is then driven through the panel, piercing a slug 98
from the panel, as shown in Figure 8. The conical portion 56 is then driven
into
the opening 100 formed in the panel 44, enlarging the panel opening before
receipt
of the barrel portion 24 of the fastener element 20, as shown in Figure 8. The
plunger 74 is then driven downwardly against the driven face 42 of the
fastener
element 20 as shown by arrow 102, driving the free end 28 of the barrel
portion
against the panel, which deforms the panel portion adjacent the panel opening
100
downwardly into a tubular shape 48, as shown in Figure 9. The die member 78 is
then bottomed against the face member 86. The tubular barrel portion 24 of the
fastener element 20 is substantially simultaneously received in the annular
concave
die cavity 80, which deforms the free end 28 of the barrel portion radially
outwardly
-10-
21b2b38
docketN60152-618
onto a U-shaped 50, as shown in Figure 10, entrapping the edge 46 of the
panel,
and forming a secure mechanical interlock, as described above in regard to
Figure 4. Details of the installation apparatus not shown are disclosed in the
above-referenced related applications and patents.
The diameter of the cylindrical portion 54 of the punch 52 is nearly equal to
the internal diameter of the bore through the reciprocable plunger 74. As set
forth
above, the major diameter 62 of the punch is preferably larger than the
internal
diameter of the female fastener element bore 32 to accommodate different
fastener
sizes and panel thicknesses. The installation head 66 is set to drive the
punch 52
through the fastener element bore 32 until the conical portion 56 is nearly
equal to
the internal diameter of the fastener bore 32 at the opening to the fastener
bore,
which is the effective diameter "D" of the conical portion 56 in any
installation.
The method of this invention then includes supporting a metal panel 44 on
a die member 78 having an axial bore 84 and a concave annular die cavity 80
surrounding the die bore; then, locating the free end 28 of the fastener
element
adjacent the panel 44, opposite the die member 78, with the free end 28 of the
fastener element facing the panel; then driving the free end 58 of the punch
through
the fastener element bore 32 against the panel to pierce a slug 98 from the
panel,
forming an opening in the panel having a diameter substantially less than the
diameter of the tubular barrel portion 24; continuing to drive the conical
portion 56
of the punch through the panel hole, to enlarge the hole, as shown in Figure
8; then
driving the free end 28 of the barrel portion 24 against the panel, to further
enlarge
the panel opening; and, substantially simultaneously deforming the free end 28
of
-11-
2162638
docket 1f60152-618
the fastener element radially outwardly in the concave annular die to form a
mechanical interlock between the barrel portion 50 and the panel portion 46,
forming a secure mechanical interlock between the panel and the riveting
portion of
the fastening element.
This method substantially improves the life of the installation tooling
because, as set forth above, the conical portion 56 of the punch reduces punch
breakage while permitting the use of a larger opening 84 through the die
member,
thereby reducing die button breakage. Further, the enlargement of the panel
opening before the barrel portion 24 is driven through the panel opening,
reduces
stresses in the panel and thereby reducing stress cracking of the panel. The
conical
surface 56 of the punch also compensates for some misalignment between the
punch 52 and the die button 78. Such misalignment may result from tolerance
build-up in the die press, as set forth above. The conical surface 52
accurately
guides the punch 52 into the nut bore if there is a slight misalignment,
permitting
the use of a larger diameter punch, which is very important to the method of
this
invention.
As will be understood, various modifications may be made to the installation
apparatus and method of this invention within the purview of the appended
claims.
For example, the method and apparatus of this invention may be utilized with
different nut configurations as disclosed, for example, in the above-
identified
patents. Further, the die button assembly 68 may be modified to include a
fixed
die 78 and, as set forth above, the self attaching fastener element 20 may be
installed upwardly in a die press. The fastener element installation apparatus
and
-12-
' 262638
docketN60152-618
method of this invention therefore achieves the several objects of the
invention set
forth above, including improved installation apparatus life and an improved
fastener
and panel assembly. The method and apparatus of this invention may be utilized
to install fastener elements of the type disclosed herein in steel panels
normally used
by the automotive and appliance industries, including brackets and including
relatively thin metal panels such as now used by the automotive industry for
body
panels. Having thus described the improved method of attaching a female
fastener
element to a metal panel and improved installation apparatus, the invention is
now
claimed as set forth below.
-13-
