U.S. patent number 3,688,385 [Application Number 04/873,829] was granted by the patent office on 1972-09-05 for method of making a riveted jointure.
This patent grant is currently assigned to Ermal C. Fraze, Dayton, OH. Invention is credited to Omar L. Brown.
United States Patent |
3,688,385 |
|
September 5, 1972 |
METHOD OF MAKING A RIVETED JOINTURE
Abstract
An easy opening container wall including a container wall of
sheet material having a line of weakness therein defining a tear
portion at least partially removable from the container wall. A
hollow rivet is formed integrally with the sheet material of the
tear portion and projects through an aperture of a tab. The hollow
rivet is headed by a punch which forces the material making up the
bead of the rivet tightly against the region of the tab immediately
surrounding the aperture therein so that the area of engagement
between the bead and the tab is generally annular and has
substantial radial width.
Inventors: |
Omar L. Brown (Dayton, OH) |
Assignee: |
Ermal C. Fraze, Dayton, OH
(N/A)
|
Family
ID: |
25362415 |
Appl.
No.: |
04/873,829 |
Filed: |
November 4, 1969 |
Current U.S.
Class: |
29/509;
29/524.1 |
Current CPC
Class: |
B21D
51/383 (20130101); Y10T 29/49943 (20150115); Y10T
29/49915 (20150115) |
Current International
Class: |
B21D
51/38 (20060101); B21d 039/00 (); B23p
011/00 () |
Field of
Search: |
;29/509,522 ;220/54
;113/121C,116FF |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Charlie T. Moon
Attorney, Agent or Firm: Smyth, Roston & Pavitt
Claims
I claim:
1. A method of joining an apertured tab of sheet material to a
container wall wherein the container wall has a line of weakness
forming a tear portion and a hollow rivet with a peripheral wall
and a transverse end wall is attached to the container wall and
projects through the aperture of the tab, said method comprising:
providing a punch having a working surface with the working surface
having a first region and a bead forming region with the bead
forming region at least substantially circumscribing the first
region and tapering axially of the first region toward the
container wall as it extends radially outwardly; supporting the
rivet against inward collapse by inserting a support member into
the hollow rivet with the support member being spaced from the
transverse end wall; relatively advancing said punch and the rivet
toward each other to impact the first region of the working surface
against the transverse end wall to axially collapse said hollow
rivet with consequent radial outward flow of material to form a
bead integrally joining the peripheral wall and the transverse end
wall with the relative advance of the punch and rivet causing said
bead forming region to force the bead against the region of the tab
immediately surrounding the aperture; said step of relatively
advancing being carried out without substantially deforming said
support member; relatively moving the support member and the rivet
to withdraw the support member from the rivet without destroying
the rivet, the withdrawal of the support member occurring after the
formation of the bead.
2. A method as defined in claim 1 wherein said step of relatively
advancing is carried out to cause the area of engagement between
the bead and said region of the tab to be generally annular and to
have substantial radial width.
3. A method as defined in claim 1 wherein said bead forming region
tapers smoothly toward the container wall as it extends radially
outwardly and correspondingly shapes the surface of the bead which
it engages.
4. A method as defined in claim 1 wherein the container wall has a
sealant coating on the inner surface thereof and said step of
relatively advancing is carried out without squeezing of the
material of the transverse end wall of the rivet between the
support member and the punch to thereby avoid extrusion of the
material of the transverse end wall to thereby maintain the sealant
coating intact during the rivet heading operation.
5. A method as defined in claim 1 wherein the inner periphery of
the bead forming region is generally aligned with the inner surface
of the peripheral wall prior to the axial collapse of the
rivet.
6. A method as defined in claim 1 wherein said first region is
generally flat and blends smoothly with said second region, said
working surface defining a cavity opening toward the rivet.
7. A method of joining an apertured tab of sheet material to a
container wall wherein the container wall has a line of weakness
forming a tear portion and a hollow rivet with a peripheral wall
and a transverse end wall is attached to the container wall and
projects through the aperture of the tab, said method comprising:
providing a punch having a working surface defining a cavity having
an inner end and sloping sides which slope radially outwardly as
they extend away from the inner end, said working surface having a
first region defining at least a portion of the inner end of the
cavity and a bead forming region defining at least a portion of the
sides of said cavity, said bead forming region at least
substantially circumscribing the first region; relatively
positioning the punch and the container wall so that the cavity
opens toward the transverse end wall; supporting the rivet against
radial inward collapse by inserting a support member into the
hollow rivet with the support member being spaced from the
transverse end wall; relatively advancing said punch and the rivet
toward each other to impact the first region of the working surface
against the transverse end wall to initiate axial collapse of said
hollow rivet with consequent radial outward movement of material to
at least initiate formation of a bead with the relative advance of
the punch and rivet causing said bead forming region to engage some
of the material of the bead and shaping the surface of the material
so engaged so that said surface tapers axially away from the first
region as it extends radially outwardly whereby said surface has a
configuration which mates with the sides of said cavity; and
relatively moving the support member and the rivet to withdraw the
support member from the rivet without destroying the rivet, the
withdrawal of the support member occurring after the formation of
the bead.
8. A method of joining an apertured tab of sheet material to a
container wall wherein the container wall has a sealant coating on
the inner surface thereof and a line of weakness forming a tear
portion and wherein a hollow rivet with a peripheral wall and a
transverse end wall is attached to the container wall and projects
through the aperture of the tab, said method comprising: providing
a punch having a working surface with the working surface having a
first region and a bead forming region with the bead forming region
at least substantially circumscribing the first region and tapering
radially outwardly whereby said regions define a cavity which opens
toward the rivet; supporting the container wall; supporting the
rivet against radial inward collapse by inserting a support member
into the hollow rivet with the support member being spaced from the
transverse end wall; relatively advancing said punch and the rivet
to impact the first region of the working surface against the
transverse end wall to initiate axial collapse of said hollow rivet
with consequent radial outward flow of material to initiate
formation of a bead with the relative advance of the punch and
rivet causing said bead forming region to engage the bead and force
the portion so engaged axially of the outer surface of the
transverse end wall whereby the bead is forced against the region
of the tab immediately surrounding the aperture; said step of
relatively advancing being carried out without extruding the
material of the transverse end wall; and relatively moving the
support member and the rivet to withdraw the support member from
the rivet without destroying the rivet, the withdrawal of the
support member occurring after the formation of the bead.
Description
The invention relates to a joint between first and second members
of sheet material positioned face to face wherein a portion of the
first member is formed into a hollow rivet that extends through an
aperture in the second member. This type of joint is commonly used
in an easy opening container wall wherein the hollow rivet is
formed in a tear portion and extends through an aperture in a tab
that serves as manual means for severing the tear portion. A joint
of this general type is disclosed, for example, in Fraze, U.S. Pat.
No. 3,191,564.
In order to form a rivet bead of requisite strength, it is
necessary to extrude material of the transverse end wall of the
rivet between cooperating die surfaces during the rivet heading
operation. This assists the radial outward flow of metal to form a
bead of substantial strength. Recently rivets of this type have
been made in smaller diameters to facilitate opening of the
container. In addition the aluminum alloys from which the container
wall is constructed have become harder. These factors combine to
make the need for extrusion even more important in making a strong
joint.
One problem with extrusion of the transverse end wall is that the
sealant coating applied to the interior surface of the container
wall is fractured or destroyed during the extruding operation. The
sealant coating is applied to the inner surfaces of metal
containers to keep the product from making contact with the bare
metal. Such a sealant coating is not only tenaciously adherent to
the metal but is also sufficiently ductile to survive the usual
punch press operations that are required to form a can top and to
join the can top to the can body. The sealant coating will also
survive the rivet forming operations as where the rivet is formed
in a coining operation.
The sealant coating will not, however, survive the subsequent
operation of heading of the hollow rivet by squeezing the
transverse end wall of the rivet between cooperating die members to
extrude the metal radially outwardly. One reason for the sealant
coating rupturing inside the hollow rivet in the course of the
heading operation is the high unit stress involved in drastically
squeezing the sheet metal. Another reason for failure of the
sealant coating is that the prior rivet forming operations weaken
the sealant coating. In any event, it has been discovered that the
sealant coating inside of the hollow rivet is usually ruptured to
expose bare metal to the acid action of a carbonated beverage
within the container with consequent deterioration of the beverage.
Accordingly, the rivet heading operation which produces the
strongest rivet ruptures the sealant coating and without the
extrusion of the transverse end wall the riveted jointure is not
sufficiently strong.
The present invention teaches that one reason that prior art
riveted jointures do not possess maximum strength is that the tab
and the bead of the rivet are in substantially line contact.
Specifically, the underside of the bead is generally frustoconical
and the aperture through the tab is generally cylindrical.
Accordingly, the conical bead surface engages the circular rim or
corner of the aperture along a circular line which surrounds the
rivet. The line contact between the tab and the rivet results in
high stresses acting on the rivet and on the region of the tab
immediately surrounding the aperture therein. Furthermore, the
relatively sharp rim of the aperture may have a cutting effect on
the rivet.
According to the present invention, the bearing area between the
rivet and the tab is materially increased as a result of the
forcing of the metal of the bead downwardly against the region of
the tab immediately surrounding the aperture. Thus, with the
present invention, the bead engages the tab in an annular region
having substantial radial width. This results in reduced stress on
the bead of the rivet and on the region of the tab immediately
surrounding the aperture and reduces the tendency of the rim of the
aperture to cut the bead during manipulation of the tab.
Because of the increased strength of the joint as a result of the
large bearing area between the bead and the tab, it is no longer
necessary to extrude the material of the transverse end wall of the
rivet during the rivet heading operation. Thus, the sealant
coacting on the inner surface of the transverse end wall is
maintained intact throughout the riveting operation.
In practicing the method of this invention, the transverse end wall
of the rivet is struck to axially collapse the rivet to cause
radial outward movement of the material of the rivet to form a bead
or larger dimensions in plan than the aperture through the tab. The
material making up the bead is forced further toward the tab than
the transverse end wall to thereby cause the bead to tightly engage
the tab along an annular region which has substantial radial
width.
The rivet heading operation can be advantageously carried out with
a punch having a working surface with a bead forming region of the
working surface surrounding and projecting axially of a first
region of the working surface. Preferably, the bead forming surface
slopes toward the tab as it extends radially outwardly.
Accordingly, the first region of the punch engages the transverse
end wall of the rivet to cause the axial collapse thereof. The bead
forming region, being advanced axially of the first region, engages
the material making up the bead and forces the latter tightly
against the tab. Because the bead forming region is advanced
axially of the first region, the bead is forced closer to the tab
than is the transverse end wall with the result that the underside
of the bead is forced flat against the tab.
The invention, together with further features and advantages
thereof, may best be understood by reference to the following
description taken in connection with the accompanying illustrative
drawings.
FIG. 1 is a top plan view of an easy opening container constructed
in accordance with the teachings of this invention.
FIG. 2 is an enlarged fragmentary plan view of a portion of the
easy opening container wall.
FIG. 3 is an enlarged fragmentary sectional view taken along line
3--3 of FIG. 2.
FIG. 4 is a sectional view similar to FIG. 3 showing a prior art
riveted joint construction.
FIG. 5 is an enlarged sectional view of a portion of the container
wall and of the hollow rivet with the hollow rivet projecting
through an aperture of the tab prior to the rivet heading
operation. The tooling for use in the rivet heading operation is
also illustrated in section.
FIG. 6 is a sectional view similar to FIG. 5 with the rivet heading
tooling having been advanced to form a bead on the rivet.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings and in particular to FIG. 1 thereof,
reference numeral 11 designates an easy opening container wall
constructed in accordance with the teachings of this invention. The
easy opening container wall 11 includes a container wall 13
constructed of aluminum or aluminum alloy and having a peripheral
attaching flange 15 for attaching the easy opening container wall
11 to a can body (not shown).
The container wall 13 has a line of weakness in the form of a
scoreline 17 therein which defines a tear portion 19 which is
removable from the container wall 13 to form a pouring opening. A
hollow rivet 21 is formed integrally with the sheet material of the
tear portion 19 adjacent a leading end 23 of the scoreline 17. The
hollow rivet 21 anchors a tab 25 to the leading end of the tear
portion 19. The container wall 13 may be formed with ribs 27 and 29
along opposite edges of the scoreline 19 and a large rib 31 may
also be formed in the container wall.
The tab 25 is preferably constructed of sheet material such as an
aluminum alloy and may take the form shown in FIG. 2. In the
embodiment illustrated, the tab 25 has an outer reinforcing bead 33
which substantially circumscribes the tab 25 except for an end
portion of the tab adjacent the rivet 21. The tab also has a
generally circular inner reinforcing bead 35 which defines a
generally circular finger receiving opening 37.
As shown in FIG. 3, the tab 25 has an elevated region 39 and a
bottom wall or depressed region 41 with a sloping connecting wall
43 integrally joining the wall 41 to the elevated region 39. The
elevated region 39 and the connecting wall 43 completely surround
the bottom wall 41. An aperture 45 of circular configuration in
plan is formed in the bottom wall 41. A planar, annular, flat
surface or seat 47 on the bottom wall 41 surrounds the aperture
45.
The rivet 21 anchors the tab 25 to the leading end of the tear
portion 19. By lifting the ring portion of the tab 25, a rupturing
force is transmitted through the rivet 21 to the leading end 23 of
the scoreline 17 to rupture the latter. By exerting an outward
pulling force on the tab 25 the tear portion 19 can be completely
removed from the container wall 13.
Before considering the characteristics and features of the rivet 21
and a preferred manner of making same, consideration should be
given to a typical prior art rivet configuration shown in FIG. 4.
In FIG. 4, where corresponding reference character followed by the
letter a are used to designate corresponding parts, a rivet 21a is
formed integrally with a container wall 13a and projects through an
aperture 45a of a tab 25a to mount the tab on the container wall.
The container wall 13a may be identical to the container wall 13
and have a scoreline 17a therein defining a tear portion 19a in
which the rivet 21a is formed. The tab 25a has sharp rim or corner
49.
The rivet 21a has a transverse end wall 51, some of the material of
which has been extruded radially outwardly during the rivet heading
operation to form a bead 53 which extends all around the rivet 21a.
As shown in FIG. 4, the sharp corner 49 engages the frustoconical
underside of the bead 53 to define the sole region of engagement
between the upper face of the tab 25a and the rivet 21a. That is,
the bead 53 engages the corner 49 and then projects upwardly away
from the tab 25a so that the region of engagement between the upper
face of the tab 25a and the rivet 21a is in the form of a circular
line. Accordingly, when the tab 25a is raised to sever the leading
end of the tear portion 19a, the stress on the corner 49 and the
portion of the bead 53 engaging the corner 49 is very high. This
makes it necessary to utilize a bead having substantial dimensions
and substantial strength in order to withstand the high stress. In
addition, there is a danger of failure of the tab due to distortion
of the sheet metal of the tab surrounding the aperture 45a.
The present invention solves the problems inherent in the
construction shown in FIG. 4 by providing a bead 55 (FIG. 3) which
is clamped tightly against the seat 47 over a relatively large
area. Specifically, the bead 55 circumscribes the aperture 45, and
the area of engagement between the bead and the seat 47 is annular
and has a substantial radial dimension. The bead 55 has a flat,
annular, inner surface 57 which firmly engages the seat 47. The
large area of engagement between the surfaces 47 and 57 reduces the
stress on the bead 55 and on the bottom wall 41 so that the joint
will withstand a relatively high force applied to the tab 25 during
manipulation thereof to remove the tear portion 19. By comparing
FIGS. 3 and 4, it can be seen that the entire bead 55 has been
displaced downwardly from the position which the bead 53 occupies.
The bead 55 has an upper or outer surface 59 which is generally
annular in plan and which curves toward the bottom wall 41 as it
extends radially outwardly.
FIGS. 5 and 6 illustrate a preferred manner of making the rivet 21.
In FIG. 5, a hollow rivet 61 which has been formed integrally with
the leading end of the tear portion 19 projects through the
aperture 45 of the tab 25. The hollow rivet 61 may be formed
according to known processes and includes a dome-shaped transverse
end wall 63 and a cylindrical peripheral wall 65 integral with the
end wall 63. The peripheral wall 65 fits within the aperture 45
with a minimum amount of clearance. The inner surface of the
container wall 13 has a sealant coating 66 adhered thereto.
A head portion 67 of a tool or support member 69 is inserted into
the hollow rivet 61 to prevent radial inward collapse of the
peripheral wall 65 during the rivet heading operation. The head
portion 67 has an end face 71 which is spaced from the transverse
end wall 63.
A punch 73 having a working face 75 is suitably mounted above the
rivet 61. The working surface 75 has a central region 77 positioned
above the transverse end wall 63 and a peripheral bead forming
region 79 which surrounds the central region 77. The bead forming
region 79 slopes toward the container wall 13 as it extends
radially outwardly. Thus, the region 79 is advanced axially of the
region 77 in that it lies closer to the tab 25 and the container
wall 13 than the central region 77. Although the contour of the
working surface 75 may be varied, preferably, the bead forming
region 79 is arcuate in cross section and blends smoothly with the
central region 77 which may be substantially planar. Viewed
differently, the working surface 75 is concave with the concavity
opening toward the rivet 61.
Although the portion of the working surface 75 which is formed by
the planar central region 77 can be varied, in the embodiment
illustrated the diameter of the central region 77 is preferably
equal to the internal diameter of the peripheral wall 65.
Furthermore, the central region 77 is preferably co-axial with the
rivet 61 so that the central region 77 terminates at lines x and y
(FIG. 5) which lines extend axially of the rivet 61 and lie along
the inner surface of the peripheral wall 65. The bead forming
region 79 begins at the central region 77 and projects radially
outwardly therefrom to substantially the periphery of the punch
73.
By relatively advancing the punch 73 and the tool 69, the central
region 77 will contact the transverse end wall 63 and begin to
axially collapse the rivet 61. The axial collapse of the rivet 61
is accompanied by an outward movement of the metal of the rivet to
begin formation of the bead 55. Ultimately, the bead will be
contacted by the bead forming region 79 and displaced downwardly
thereby from the position which it would normally occupy toward the
bottom wall 41. The displacement of the bead 55 causes the surface
57 to engage the seat 47 along an area which circumscribes the
aperture 45 and which has substantial width as described
hereinabove with reference to FIG. 3.
The outer surface 59 is forced axially downwardly and shaped by the
region 79. As shown in FIG. 6 the surface 59 lies axially inwardly
of the outer surface 81 of the transverse end wall 63.
The entire rivet heading operation is carried out with little or no
extrusion of the transverse wall of the rivet. As shown in FIG. 6,
the end face 71 of the tool 69 is spaced from the transverse end
wall 63 of the rivet and also spaced from the sealant coating 66.
Accordingly, the sealant coating 66 remains intact throughout the
entire rivet heading operation. As shown in FIG. 3, the head
portion 67 of the tool 69 is withdrawn from the rivet subsequent to
completion of the work operation shown in FIG. 6. By comparing
FIGS. 5 and 6 it is readily apparent that the rivet heading
operation does not deform the head portion 67.
Although an exemplary embodiment of the invention has been shown
and described, many changes, modifications, and substitutions may
be made by one having ordinary skill in the art without necessarily
departing from the spirit and scope of this invention.
* * * * *