U.S. patent number 3,871,314 [Application Number 05/299,447] was granted by the patent office on 1975-03-18 for method of making folded can ends and folded can end product.
This patent grant is currently assigned to Van Dorn Company. Invention is credited to Donald E. Stargell.
United States Patent |
3,871,314 |
Stargell |
March 18, 1975 |
Method of making folded can ends and folded can end product
Abstract
A method of cold drawing, forming and otherwise cold working a
sheet metal blank to form a can end member for seaming to one end
of a can body in which the can end has a continuous score line
along which the can end is severed for complete removal of an end
panel, and in which a protective metal fold is formed in the can
end with portions of the fold metal extending to a location
circumferentially outward beneath and beyond the score line
location to present a dull hazard-free edge on the end panel when
torn from the can end member. The metal working procedure includes
steps of blanking, drawing, panel forming, curling, redrawing,
resizing, coining, scoring, out-folding and embossing, by cold
working operations performed on a thin sheet metal blank to produce
a can end, accompanied by forming an integral rivet to join a pull
tab to the end panel portion of the can end. A can end with a
continuous annular three layer fold having a continuous annular
score line in the top layer. The two lower layers extend radially
beneath and beyond the location of the score line. There is a
100.degree. sector of the three layer fold part extending on either
side of a center line of a pull tab connected to the can end used
to sever the score line which is thicker than the remaining extent
of the continuous fold; and the top layer in the sector has a
clearance space above the two lower layers.
Inventors: |
Stargell; Donald E. (North
Canton, OH) |
Assignee: |
Van Dorn Company (Cleveland,
OH)
|
Family
ID: |
23154826 |
Appl.
No.: |
05/299,447 |
Filed: |
October 20, 1972 |
Current U.S.
Class: |
413/13; 413/3;
413/6; 413/14 |
Current CPC
Class: |
B21D
51/383 (20130101) |
Current International
Class: |
B21D
51/38 (20060101); B21d 051/40 () |
Field of
Search: |
;113/15R,15A,121C
;220/90.6,54,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; C. W.
Assistant Examiner: Keenan; M. J.
Attorney, Agent or Firm: Frease & Bishop
Claims
I claim:
1. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, scoring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; successively decreasing the depth of the cup bottom
wall below the shoulder; and successively decreasing the radius of
curvature of the lower corner in preparation for folding the metal
between the shoulder and lower corner to form an annular triple
fold-S-shaped in cross section between the shoulder and lower
corner.
2. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, scoring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; successively forming a curved corner radius at the
underside of the shoulder with a radius of curvature decreasing in
size to provide a pivot point from which the metal between the
shoulder and lower corner is folded to form an annular triple fold
S-shaped in cross section, and then folding the metal by pressure
applied to the shoulder to move the shoulder toward the cup bottom
wall.
3. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, scoring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; and coining an annular zone of metal located between
the upper corner and shoulder during one of the bulging
operations.
4. The method defined in claim 3 in which the metal in the coined
annular area between the upper corner and shoulder is scored with
an annular score line during the second of the successive bulging
operations.
5. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, scoring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending the side wall of a cup drawn from a metal
blank and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; successively forming a curved corner radius at the
underside of the shoulder with a radius of curvature decreasing in
size to provide a pivot point from which the metal between the
shoulder and lower corner is folded to form an annular triple fold
S-shaped in cross section; coining an annular zone of metal located
between the upper corner and shoulder during one of the bulging
operations; scoring the metal in the coined annular zone between
the upper corner and shoulder with an annular score line during the
second of the successive bulging operations; successively
decreasing the depth of the cup bottom wall below the shoulder;
successively decreasing the radius of curvature of the lower corner
in preparation for folding metal between the shoulder and lower
corner to form an annular triple fold S-shaped in cross section
between the shoulder and lower corner; and then folding the metal
by pressure applied to the shoulder to move the shoulder toward the
cup bottom wall.
6. The method defined in claim 1 in which the operation of forming
the annular fold panel includes the steps of forming a conical
annular band extending directly between an upper concavely curved
corner formed in an axially extending side wall of a cup drawn from
a metal blank and a lower curved corner connected with the cup
bottom wall; and then redrawing the blank to reform the metal in
the conical annular band to provide a rounded shoulder having upper
convex and lower concave surfaces in cross section intermediate the
upper and lower corners connected with the upper corner by an
annular horizontal portion extending inward from said upper corner
and connected with the lower corner by a downwardly inwardly
tapered band portion.
7. The method defined in claim 6 which includes the step of coining
the metal in the annular zone of said horizontally extending
portion located inward of the upper corner at the same time that
the first of the successive bulging operations is performed.
8. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, socring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; coining an annular zone of metal located between the
upper corner and shoulder during one of the bulging operations; and
forming the inner annular edge of the coined annular zone to define
a break point located radially inward of the outer surface of the
outward bulge formed by the one bulging operation.
9. The method defined in claim 8 in which the coined metal in the
annular zone is scored to form an annular scored tear line located
radially outward of said break point.
10. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold by a series of successive drawing,
redrawing, resizing, scoring and folding operations in which said
successive operations include forming an annular fold panel
extending directly between an upper concavely curved corner formed
in an axially extending side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly convex shoulder in the fold panel
between the upper and lower corners; successively bulging the cup
wall portion circumferentially outward between the shoulder and
lower corner; successively forming a curved corner radius in the
underside of the shoulder with the radius of curvature decreasing
in size to provide a pivot point from which the metal between the
shoulder and lower corner is folded to form annular triple fold
S-shaped in cross section; coining an annular zone of metal located
between the upper corner and shoulder during one of the bulging
operations; forming the inner annular edge of the coined annular
zone to define a break point located radially inward of the outer
surface of the outward bulge during one of the bulging operations;
scoring the coined metal in the annular zone to form an annular
scored tear line on the coined surface located radially outward of
said break and pivot points during the second of the successive
bulging operations; locating the break and pivot points radially
inward of the bulge formed by the second of the successive bulging
operations; and then folding the metal by pressure applied to the
shoulder to move the shoulder toward the cup bottom wall.
11. The method defined in claim 1 including the steps during the
successive shoulder forming and bulging operations of forming and
reforming a rivet bubble adjacent the lower curved corner.
12. The method defined in claim 11 in which the rivet bubble is
initially formed during the step of forming the annular upwardly
convex shoulder in the fold panel, and in which the rivet bubble is
reformed during one of the bulging operations.
13. The method defined in claim 12 in which an area adjacent the
reformed rivet bubble and between the rivet bubble and bulged blank
portion is coined during the reforming of the rivet bubble.
14. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold which includes the steps of drawing a
sheet metal blank to form a primary cup shape having cup bottom,
side and open end flange walls, and forming a conical annular band
connected with the cup side and bottom walls directly by concave
curved upper and concave curved lower corners; curling the open end
cup flange wall; redrawing the blank to form a rounded shoulder in
said conical band having upper convex and lower concave surfaces in
cross section intermediate the upper and lower corners; resizing
the redrawn blank and coining metal in an annular zone located
between the upper corner and shoulder and outwardly bulging the
metal between the shoulder and lower corner while decreasing the
curvature of the lower concave surface of said shoulder to form a
pivot point; scoring a continuous score line in the coined annular
zone and further bulging the blank metal between the shoulder and
lower corner; and then folding the bulged metal between the
shoulder and lower corner to form a continuous annular triple layer
fold generally S-shaped in cross section continuously around the
blank with the scored coined annular zone located in the upper fold
layer and above the two lower fold layers.
15. The method defined in claim 14 including the further steps of
forming a rivet bubble in the cup shape blank adjacent the lower
corner, assembling a pull tab to said rivet bubble after the
folding operation has been completed, and assembling and staking a
pull ring to the rivet bubble.
16. The method defined in claim 15 in which the pull ring is formed
with a nose and is located with the pull ring longitudinal axis
extending radially of the can end through the center of the staked
rivet and nose.
17. The method defined in claim 16 including the steps of locating
the pull ring nose above the triple fold; and forming the triple
fold with a greater thickness in a predetermined arc extending from
either side of the nose around the can end, than the thickness of
the remainder of the arucate extent of the continuous triple
fold.
18. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold, which includes the steps of drawing a
cup shape having cup bottom and side walls, and forming a conical
annular fold panel band connected with the cup side and bottom
walls directly by concave curved upper and concave curved lower
corners; forming a shoulder having upper convex and lower concave
surfaces in cross section in the fold panel intermediate the upper
and lower corners; and successively bulging areas of the fold panel
between the shoulder and lower corner, and coining and scoring to
the areas between the shoulder and upper corner in preparation for
folding the metal between the shoulder and lower corner to form a
triple fold.
19. In a method of cold working a sheet metal blank to form a can
end member having a recessed end panel extending from a recessed
corner and connected with the corner by an annularly scored
protective metal triple fold, which includes the steps of drawing a
cup shape having cup bottom and side walls, and forming a conical
annular fold panel band connected with the cup side and bottom
walls directly by concave curved upper and concave curved lower
corners; forming a shoulder having upper convex and lower concave
surfaces in cross section in the fold panel; forming bulged walls
in the fold panel below the shoulder; coining metal in an annular
zone outward of the shoulder to form break and pivot points in the
regions respectively of the upper convex and lower concave surfaces
of the shoulder; forming a continuous annular score line in the
coined metal; locating the pivot point radially inward of the
bulged outer surface; and folding the bulged surface about the
pivot point by pressure applied to the shoulder to move the
shoulder toward the cup bottom wall.
20. The method defined in claim 19 in which the folding of the
bulged surface about the pivot point forms a continuous annular
triple fold generally S-shaped in cross section between the
shoulder and lower corner; and in which the triple fold is formed
with a greater thickness in a predetermined arc thereof than the
thickness of the remaining arcuate extent of the continuous annular
triple fold.
21. The method defined in claim 2 in which the folding of the metal
by pressure applied to the shoulder forms a continuous annular
triple fold generally S-shaped in cross section between the
shoulder and lower corner; and in which the triple fold is formed
with a greater thickness in a predetermined arc thereof than the
thickness of the remaining arcuate extent of the continuous annular
triple fold.
22. The method defined in claim 1 in which the operations of
forming the annular fold panel and convex shoulder include the
steps of forming a conical annular band extending directly between
the upper and lower corners, and then redrawing the blank to reform
the metal in the conical annular band to provide the upwardly
convex shoulder in the fold panel between the upper and lower
corners; in which after the successive decrease of lower corner
curvature, the metal is folded between the shoulder and lower
corner by pressure applied to the shoulder to move the shoulder
toward the cup bottom wall to form a continuous annular triple fold
generally S-shaped in cross section between the shoulder and upper
corner; and in which the triple fold is formed with a greater
thickness in a predetermined arc thereof than the thickness of the
remaining arcuate extent of the continuous annular triple fold.
Description
CROSS REFERENCE TO RELATED APPLICATION
The can end structure with protective fold is an improvement on the
structure shown in copending application of McKernan and Stargell,
Ser. No. 229,678, filed Feb. 28, 1972.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a practical and successful procedure for
manufacturing sheet metal preferably aluminum, can end structures
for food product cans which may be opened easily by tearing a
portion of the can end along a score line formed in the end member
wherein the cans and can ends may be of the general types shown in
Henning et al U.S. Pat. No. 3,490,643 and in Bernard J. McKernan
application Ser. No. 70,843 filed Sept. 9, 1970, now U.S. Pat. No.
3,784,048 and wherein the can end structures have a
hazard-eliminating protective triple metal thickness dull edge fold
formation on the end panel removed from the can end structure when
torn therefrom.
2. Description of the Prior Art
A number of can designs have been supplied to and used by food
packers for packaging small quantities of snack foods such as
puddings for children's lunch boxes. These cans have been made of
aluminum and have had full opening container ends, the end panels
of which are torn out using pull-rings attached to the can end
panels.
Problems have been encountered in the use of such cans. Zipping off
the lid or removable end panel in the can end wall is not always
easy for children; all to frequently they cut their fingers on the
sharp lid edge or on the rim left inside the can, and the lid
almost never comes off without a thick coating of pudding sticking
to its underside. The child tempted to lick the lid stands a good
chance of cutting his tongue on the sharp edge. The removed lid has
been found to be sharp enough to slice a chicken leg.
A report by a school teacher about cut tongues suggested that the
can design should be changed to eliminate the hazard, and suggested
that this would be easier than attempting to change the natural
tendencies of a child to lick pudding sticking to the underside of
a removed lid. One trade journal has described the cans as
dangerous and has questioned whether the convenience of the cans is
worth their hazard.
As a result, food packers that have used such cans have called for
a solution to the problem which will eliminate the dangers and
hazards.
The can end structure shown in said application Ser. No. 229,678
satisfies this need. However, there have been substantial
difficulties encountered in providing for the manufacture of such
can end structures. These difficulties involve a number of factors.
First, the thinness of and variations in the thickness of the
aluminum sheet material, used to permit tearing out of an end panel
along a score line, renders cold working operations to form a fold
of triple thickness extending annularly around a recessed panel
portion in the can end member and with the three layers of the fold
extending generally parallel with the plane of the sheet aluminum
panel portion extremely difficult to perform without tearing the
blank metal, or thinning it to such an extent as to weaken the can
end beyond required limits.
Next, the location of the triple fold in a recessed panel,
initially drawn in a metal blank, offset from a terminal annular
bead flange provided on the can end structure for subsequent
seaming at a cannery to a can body, in an annular zone very close
to a recessed corner defining the panel recess, and with a
continuous generally circular score line located intermediate the
fold and corner at a required location with respect to the fold,
may promote thinning of the metal in the blank at various stages in
the metal working procedures to an unacceptable degree or in an
uncontrollable manner.
Further, the formation of a rivet integrally in the blank, the
riveting thereof to mount a pull ring on the panel portion to be
torn from the can end, and the location of the rivet in the can end
close to the zone of the can end where the score line is initially
ruptured by the pull ring, all add to the complications encountered
in attempts to provide practical, satisfactory, successful and
readily controlled procedures or series of cold working operations
which are repeatable under high speed production conditions to
fabricate can end products which meet the required specifications
for the stated folded can end structure. In addition, the stiffness
of the prior application three layer fold renders the initial
severing of the score line difficult in opening the can to remove
the panel portion.
These considerations, and the difficulties encountered in
attempting to eliminate the complications and to solve the problems
that have arisen, thus have presented a need for effective,
satisfactory and efficient procedures for the manufacture of folded
sheet metal can ends, and for a folded can end in which the folded
zone is easy to bend when initially rupturing the score line.
SUMMARY OF THE INVENTION
Objectives of the invention include providing a new procedure or
series of cooperatively interrelated metal cold working, forming,
drawing, etc. steps or operations for the efficient and successful
production of metal can ends with protective metal folds of the
character described; providing a new procedure for the manufacture
of such metal can ends with protective metal folds which eliminates
undesirable thinning of the metal in the blanks at various stages
during forming, reforming, working, etc., of the metal and which
coins and hardens the metal in predetermined selected areas while
avoiding hardening incident to the cold working steps in other
areas during successive metal working operations; providing a
series of metal working steps for forming the described metal can
ends with protective metal folds, which adapt to the thinness of
the sheet metal material blanks used to permit tearing out of an
end panel along a score line from the end product, without tearing
the blank metal during manufacture, and which adapt to the various
locations of the triple fold formed, of the score line with respect
to the fold, and of the relative location of the score line and
fold with respect to the corner which defines the recessed panel in
which the fold and score line are located, without promoting an
unacceptable degree of metal thinning during the metal working
operations carried out; providing a new procedure of interrelated
steps for forming a metal can end with protective metal fold,
during which procedure a rivet is formed integrally in the blank
and riveted to attach a pull ring to the described can end
structure, which pull ring subsequently is used for tearing an end
panel from the can end structure with a triple fold which defines
the torn edge of the panel removed and protects such torn edge from
being the source of possible injury; and providing a new procedure
for the manufacture of metal can end structures with protective
metal folds and providing such can end structures which eliminate
difficulties heretofore encountered in the manufacture and use of
such products, achieves the indicated objectives simply,
effectively and efficiently, and solves problems that have existed
in attempting to satisfy the need for a practical and satisfactory
procedure for the manufacture of the described folded can ends and
for an easily opened can end.
These objectives and advantages are obtained by the discoveries,
procedures and methods of making folded can ends, the general
nature of which may be stated as including the steps of forming a
sheet metal blank to primary cup shape having cup bottom, side and
open end flange walls; forming a conical annular band connected
with the cup side and bottom walls by curved upper and lower
corners; forming the cup open end wall with an outwardly downwardly
extending continuous flange; curling the outwardly downwardly
extending flange to rounded bead-like formation; then drawing the
blank to reform metal in the conical annular band to provide a
rounded shoulder having upper convex and lower concave surfaces in
cross section intermediate the upper and lower corners connected
with the upper corner by an annular horizontal portion extending
inward from said upper corner and connected with the lower corner
by a downwardly inwardly tapered band portion; then resizing the
redrawn blank and coining the metal in an annular zone of said
horizontally extending portion located inward of said upper corner
and at the same time outwardly bulging the tapered band between
said shoulder and lower corner, simultaneously during said resizing
step decreasing the curvature of the lower concave surface of said
shoulder to form a fold pivot point, forming the inner annular edge
of the coined horizontal upper surface portion to define a break
point located radially inward of the outer surface of the outward
bulge; then scoring the coined metal in said annular horizontal
zone to form an annular scored tear line on the coined upper
surface located radially outward of said break and pivot points,
and simultaneously during said scoring step further outwardly
bulging the resized blank between the shoulder and lower corner;
then folding the metal between the shoulder and lower corner to
form a continuous annular triple layer fold generally S-shaped in
cross section continuously around the blank with the annular score
line in the coined metal located in the upper fold layer and above
the two lower fold layers; during said redrawing, resizing, coining
and scoring steps forming a rivet bubble in the cup bottom wall
adjacent the location of the triple fold, coining metal in the cup
bottom wall around the rivet bubble, and scoring a bend line in the
coined area around the rivet bubble and between the bubble and fold
location; then assembling a pull ring to the rivet bubble, locating
the pull ring in predetermined position, and staking the rivet
bubble metal against the pull ring; then stamping indicia on the
bottom wall and probing the assembled blank to detect the presence
or improper location of the pull ring; carrying out the successive
described steps as cold working operations; sharpening the radius
of curvature of the pivot point during its formation; reducing the
distance from the shoulder to the cup bottom wall during successive
cold working operations; and reducing the radius of curvature of
the lower corner during successive cold working operations.
Summarizing, the new concept provides a method of cold working a
sheet metal blank to form a can end member having a recessed end
panel extending from a recessed corner and connected with the
corner by an annularly scored protective metal triple fold by a
series of successive drawing, redrawing, resizing, scoring and
folding operations in which said successive operations include
forming an annular fold panel extending between an upper curved
corner formed in the side wall of a cup drawn from a metal blank
and a lower curved corner connected with the cup bottom wall;
forming an annular upwardly inwardly convex shoulder in the fold
panel between the upper and lower corners; successively bulging the
cup wall portion circumferentially outward between the shoulder and
lower corner; successively decreasing the depth of the cup bottom
wall below the shoulder; and successively decreasing the radius of
curvature of the lower corner in preparation for folding the metal
between the shoulder and lower corner to form an annular triple
fold S-shaped in cross section.
The objectives also are obtained by the new can end which has a
three layer fold with a substantial sector thereof, preferably
about 100.degree., with portions extending on either side of the
center line of a pull tab secured to the can end and used to sever
a panel portion on a continuous score line formed at a location in
the upper fold layer overlying the two fold layers below; and with
the thickness of the sector being greater than that of the
remainder of the continuous fold. The upper layer of the fold in
the sector is spaced above or has a clearance above the other two
fold layers below; so that the upper layer is easily bent inside
the score line prior to bending the remaining fold layers in
initiating rupture of the can end along the score line by pull tab
movement.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred methods, steps, operations, procedures and products
constituting preferred embodiments of the invention--illustrative
of the best mode in which applicant has contemplated applying the
principles--are set forth in the following description and shown in
the drawings and are particularly and distinctly pointed out and
set forth in the appended claims.
FIG. 1 is a top plan view of a stage blank produced by a first
blanking or drawing operation performed on a sheet metal starting
blank;
FIG. 2 is a diagrammatic cross-sectional view looking in the
direction of arrows 2--2, FIG. 1;
FIG. 3 is a greatly enlarged fragmentary sectional view of a corner
of the drawn stage blank shown in FIG. 2, illustrating the dies
used in the drawing and flange forming stages of the blanking
operation;
FIG. 4 is a diagrammatic view illustrating the next curling
operation performed on the flange of the drawn stage blank shown in
FIG. 2;
FIG. 5 is a view similar to FIG. 2 showing the curled stage blank
with a curled or beaded flange produced by the curling operation of
FIG. 4;
FIG. 6 is a view similar to FIG. 1 illustrating the redrawn stage
blank produced by redrawing the blank of FIG. 5;
FIG. 7 is a section looking in the direction of the arrows 7--7,
FIG. 6;
FIG. 8 is a fragmentary view similar to and on the same scale as
FIG. 3 of a greatly enlarged portion of the redrawn stage blank of
FIG. 7 and the dies used for the redraw operation, and also
illustrating the initial formation of the rivet bubble, the section
also being on the line 7--7, FIG. 6;
FIG. 9 is a fragmentary view similar and on the same scale as FIG.
8, illustrating the initial stage of drawing tab positioning
dimples, looking in the direction of the arrows 9--9, FIG. 6;
FIG. 10 is a view similar to FIG. 8 illustrating the further step
of redrawing the rivet bubble;
FIG. 11 is a view similar to FIG. 9, illustrating the redrawing of
the tab positioning dimple, looking in the direction of the arrows
11--11, FIG. 12;
FIG. 12 is a view similar to FIGS. 1 and 6 illustrating the redrawn
stage blank produced by the operations illustrated in FIGS. 10 and
11;
FIG. 13 is a view of the stage blank illustrated in FIG. 12,
looking in the direction of the arrows 13--13, FIG. 12;
FIG. 14 is a further substantially enlarged fragmentary view of a
portion of FIG. 10;
FIG. 15 is a view similar to FIG. 12 showing the stage blank after
scoring;
FIG. 16 is an enlarged fragmentary section view similar to FIG. 10
illustrating the scoring operation and the scoring dies, looking in
the direction of the arrows 16--16, FIG. 15, with the stage blank
of FIG. 15 in the dies;
FIG. 17 is an enlarged view, similar to FIG. 14, of a portion of
FIG. 16 illustrating the scoring step to produce the tear line
score;
FIG. 18 is a view on an enlarged scale similar to FIG. 17 of
another portion of FIG. 16, showing the bend line score adjacent
the rivet bubble;
FIG. 19 is a view similar to FIG. 16 illustrating the folding
operation, looking in the direction of the arrows 19--19, FIG. 20,
and showing the new product characteristics;
FIG. 20 is a view similar to FIG. 15 of the folded stage blank;
FIG. 21 is an enlarged view of a portion of FIG. 19, showing the
fold formation adjacent the rivet bubble;
FIG. 22 is an enlarged view similar to FIG. 21 but showing the fold
formation at 180.degree. from the location of FIG. 21 looking in
the direction of arrows 22--22, FIG. 20;
FIG. 23 is a fragmentary section illustrating the dies used to form
the thumb clearnace panel shown in FIG. 20, taken on the line
23--23, FIG. 20;
FIG. 24 is a view similar to FIG. 19 illustrating the assembly of a
pull tab on the folded can end, and the staking of the rivet to
secure the pull tab, looking in the direction of the arrows 24--24,
FIG. 25, and showing the new product;
FIG. 25 is a view similar to FIG. 20 illustrating the pull tab
assembled to the can end;
FIG. 26 is a view similar to FIG. 24 illustrating a final operation
of code stamping and detecting a missing or misaligned pull tab,
taken on the line 26--26, FIG. 27; and
FIG. 27 is a fragmentary view similar to a portion of FIG. 25
illustrating the final folded can end produced by the operations
illustrated.
Similar numerals refer to similar parts throughout the
drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The new method is illustrated in the drawings for the manufacture
of a can end member or structure for a typical small-sized can,
such as shown in said copending application Ser. No. 229,678.
However, the new method is not limited to the manufacture of the
particular size of can end illustrated, because the can end may be
of any desired size for use or assembly with can bodies of various
sizes, shapes, or capacities, or of any one of a number of types
made by various manufacturers, and which can ends have a continuous
score line in the can end wall adjacent the double seam which
extends directly between the concavely the can body and end wall.
For example, cans and can ends of such various sizes are shown in
U.S. Pats. Nos. 3,490,643 and 3,682,350.
The can ends may be made of very thin gauge aluminum sheet
material. Such material, for example, may have a thickness of
0.010". As received from the aluminum sheet material in sheets or
coiled strip, the material may have gauge variations of plus or
minus 0.0005". Material this thin and with the indicated gauge
variations presents problems of avoiding tearing or undue thinning
when subjected to a number of successive cold forming or working
operations which are necessary to produce a can end structure such
as shown in said copending application Ser. No. 229,678 with a
protective fold.
I have discovered a series of interrelated operations and related
controls which may be used to avoid difficulties that have been
encountered in attempting to solve the complex problem that has
existed. This series of operations or steps and critical features
thereof and controls exercised are set forth in detail under
appropriate headings below.
BLANKING OPERATION
A starting blank of aluminum sheet material of the gauge described
is drawn in dies illustrated in FIG. 3, including a punch 1 and die
cavity forming members 2 and 3, in a blanking press. Initially the
blank as it is being drawn has an outwardly directed terminal
flange portion indicated in dot-dash lines at 4, but the portion 4
is drawn downward at 5 by the secondary punch 6 at the end of the
blanking operation, thus producing the drawn stage blank 7 (FIGS. 1
and 2).
Blank 7 has a rim 8 inverted channel-shaped in cross section, which
later provides for seaming the can end to one end of a can body.
Blank 7 also has a recessed wall 9. The wall 9 is connected with
the rim 8 by a conically-shaped annular band 10. The annular and
angular shape in cross section of band 10, and the width or extent
thereof which extends directly between the concavely curved corners
11 and 12 are important aspects of the blanking operation
interrelated with subsequent operations. The band 10 between
corners 11 and 12 provides what may be called the "fold-panel" in
the drawn stage blank 7. The angular or conical shape of the band
or fold panel 10 is provided to control metal thinning during
subsequent operations which finally culminate in folding metal
originating in the fold panel 10. The upper concavely curved corner
11 as shown in FIGS. 2, 3, 4 and 5 is formed in the axially
extending side wall portion of the cup blank 7 with the axial cup
wall portion located and extending directly above the corner 11.
The "fold panel" band 10 extends downward inward in cross section
and is connected with the cup bottom wall by the lower curved
corner 12.
CURLING OPERATION
The next operation is shown in FIG. 4. The drawn stage blank 7 is
rolled between usual curling rolls 13 in a known manner to provide
a rounded bead-like formation 14 in the downturned flange 5 of
blank 7. This curling operation produces a typical bead 14 in the
curled stage blank 15 indicated in FIGS. 4 and 5.
REDRAW OPERATION
In the next operation, the curled stage blank 15 is redrawn in dies
illustrated in FIGS. 8 and 9. This redraw operation reforms the
fold panel or band 10 of FIGS. 3 and 4 to the shape illustrated in
FIG. 8. The redraw dies illustrated in FIG. 8 include relatively
movable upper punch members 16 and 17 and die cavity forming
members 18 and 19. Initially, during the redraw operation, punch 16
and die member 18 reform a portion of the upper end of bank 10
horizontally, as indicated at 20. The remainder of the annular band
10 is reformed at 21, slightly downwardly inwardly tapered, as
shown, from a rounded shoulder 22 to the curved corner 23, reformed
from curved corner 12 of curled stage blank 15.
The horizontal annular wall portion 20 extends annularly between
recessed shoulder 24, and the rounded convex shoulder 22. The
recessed shoulder 24 is curved and originates from the curved
corner 11 illustrated in FIG. 3.
Generally, the metal in the blank portions 20, 21, 22 and 23 is not
thinned during the redraw operation because its movement during
reforming is inward toward the center of the blank 15 which is the
starting blank for the redraw operation.
During the redraw operation, a rivet bubble 25 is drawn upwardly in
the recessed wall 9 of the curled stage blank 15, as shown in FIGS.
6, 7 and 8. This bubble 25 is formed by the cooperative action of
the die cavity formation 26 in upper punch member 17 and the
rounded nose at the upper end of rivet punch 27. The wall of bubble
25 is pinched slightly at 28 between rivet punch 27 and die cavity
26. This slightly thins the metal in the pinched zone 28 during
bubble formation to provide the necessary flow of metal into the
top 29 of the bubble 25 to prevent undue thinning of the metal in
the zone 29 where a rivet head ultimately will be formed.
Also during the redraw operation, tab positioning dimple bubbles 30
are drawn in the recessed wall 9 on opposite sides of a diameter of
the redrawn stage blank 31 (FIG. 6) which passes through the center
of the rivet bubble 25, as indicated for example, by the section
line 7--7 in FIG. 6. The upper punch member 17 is formed with
openings 32 to permit the dimple bubbles 30 to be drawn upward
therein by locator punches 33 movable in the lower die cavity
member 19.
One of the important aspects of the invention is the formation of
the relatively sharp rounded shoulder 22 connecting the horizontal
portion 20 of the reformed band 10 with the reformed tapered band
portion 21. The radius of the underside of the rounded shoulder 22
in cross section, should approximate 0.005" or approximately
one-half the gauge of the metal in the starting blank aluminum
sheet material. It is important, as will be explained below, to
form this curved shoulder as sharply as possible during the redraw
operation without tearing, breaking, thinning or work hardening the
metal in the shoulder zone as a result of the redraw operation.
It is indicated below that in a subsequent operation, the radius of
the underside of shoulder 22 in cross section should be reduced to
a radius smaller than 0.005" when further reformed. It is important
in the redraw operation (FIG. 8) to form the radius 22 before
reforming as closely as possible to the ultimate reduced reformed
radius required to be formed in the subsequent operation.
Another important aspect of the redraw operation is the clearance
provided, as illustrated in FIG. 8, between the inner and outer
surfaces of the reformed tapered band portion 21 so as to reduce
work hardening of the metal in this zone to a minimum. The depth of
the recessed wall 9 below curled flange 14 in the redrawn stage
blank 31 is not materially changed from such depth in curled stage
blank 15.
One of the other matters of importance in the redraw and rivet
bubble forming operation shown in FIG. 8 is the relative locations
of the rivet bubble 25, the rounded shoulder 22 and the recessed
shoulder 24. It is desirable for many reasons to locate the center
of the rivet bubble 25 as close as possible to the rounded shoulder
22 and to locate the rounded shoulder 22 as close as possible to
the recessed shoulder 24. However, this relationship must be
achieved without either unduly thinning or unduly work hardening
the metal in the regions of these related elements during the
redraw operation.
RESIZE AND RIVET REDRAW OPERATION
In the next operation, certain portions of the redrawn stage blank
31 are resized, and the rivet and dimple bubbles 25 and 30 are
redrawn to final form. This metal working is shown in FIGS. 10, 11
and 14, and the resized stage blank 34 resulting therefrom is shown
in FIGS. 12 and 13.
The dies for the resizing operation illustrated in FIGS. 10, 11 and
14 include relatively movable upper punch members 35 and 36 and an
upper rivet reforming die 37 movable in upper punch 36, and lower
die cavity forming members 38 and 39 and rivet reforming punch 40.
The upper punch 36 (FIG. 11) also is formed with openings 41
cooperatively arranged with the lower dimple punches 42 movable in
lower die cavity member 39 for reforming the dimple bubbles 30.
Special punch and die formations are provided in the tools for the
resize and rivet redraw operation, best illustrated in FIG. 14. The
annular nose of upper punch member 35 is relieved at its outer
annular corner 43. The nose has a flat projecting annular coining
surface 44 which thins and coins the metal in the zone 45 of the
blank against the upper surface 46 of the lower die member 38. The
annular corner 47 of lower die cavity member 38 has a fillet radius
of 0.002". This radius is reduced from the fillet radius of the die
member 18 in FIG. 8 which formed the 0.005" inside corner fillet
radius for the rounded shoulder 22 of redrawn stage blank 31. This
sharp corner radius 47 in die member 38 imparts a corresponding
shape at 47a to the undersurface of the rounded shoulder 48 in the
resized state blank 34.
The coining of the metal in the coined zone 45 thins the metal and
the metal flows slightly inward toward the center of the resized
blank 34 so that the point, indicated by the circle 49, herein
called a "break point", where the annular coining surface 44 of the
nose of upper punch 35 intersects with the outer rounded surface 50
of the rounded shoulder 48 of resized blank 34, is located radially
inward of the sharp radius zone 47a of the blank, herein called
"blank pivot point".
During this resizing or coining operation of the coined zone 45,
the recessed depth of the recessed wall 9 of the resized blank 34
(FIG. 10) below the coined zone 45 (0.082") is reduced by
preferably approximately 0.010" from the similar recessed depth of
the recessed wall 9 of redrawn blank 31 (0.093") below the
horizontal portion 20 of the blank (FIG. 8). At the same time that
the recessed depth of wall 9 is reduced, the curvature of corner 23
is reduced from a radius of 0.038" in FIG. 8 to a radius of 0.028"
in FIG. 10.
This reduction in recess depth, along with the coining of the
coined zone 45 in recessed blank 34, as well as the clearance
illustrated between upper punch member 36 and lower die member 38,
results in forming a slight prebulge indicated at 51 in the annular
wall portion 52 of the resized blank 34. The prebulge extends
between the rounded shoulder 48 and the curved corner 23 of the
blank.
At the same time that the coining and prebulging is occurring, the
rivet reforming punch 40 and upper rivet die 37 reform the rivet
bubble 25 of redrawn stage blank 31 to the final rivet shape shown
in FIG. 10 wherein the rivet bubble 53 has a substantially
cylindrical wall 54 connecting the bubble 53 with the recessed wall
9 of the blank 34.
During reforming of the rivet, the metal surrounding the rivet
annularly around the cylindrical wall 54 is coined at 55 by the
nose formation 56 on rivet die 37.
Also during the blank resizing and rivet reforming or redraw
operation, the dimple bubbles 30 of the redrawn stage blank 31 are
reformed as shown in FIG. 11 to the reformed dimple shape indicated
at 57 between the upper punch member dimple opening 41 and the
dimple punch 42.
An important feature of the resize and rivet redraw operation is
the formation of the slight prebulge 51 in the annular wall 52 of
the resized stage blank 34. The prebulge is provided in this
operation to facilitate the folding and formation of a fold in a
subsequent operation. As previously indicated, the prebulging
results from the reduction in the height of the blank from the
coined zone 45 to the recessed wall 9, as well as from the coining
of the coined zone 45 to reduce the size of the inside radius
formation of the rounded shoulder 48.
The clearance illustrated between the recessed blank shoulder 24
and the outer annular corner 43 of the upper punch member 35
prevents any metal working during the operation of the metal in the
recessed shoulder 24 which subsequently becomes the chuck radius
for receiving the chuck of a seaming tool by which the curled
flange 14 of the blank is seamed to a can body. The upper surface
of the coined zone 45 of the blank, as shown, is located inside the
chuck radius 24 and may be termed a "chuck face" of the blank.
Furthermore, the coining of coined zone 45 assists in sharpening
the pivot point 47a formed by the sharp annular corner 47 and
locates the break point 49 inside the diameter of the opening 58 in
die 38 which forms the inner extremity of the rounded shape 47a
formed in the blank by the 0.002" radius corner 47 so that the
break point 49 is inside of the pivot point 47a on which the metal
ultimately is folded.
SCORING OPERATION
In the next operation illustrated in FIGS. 16, 17 and 18, certain
portions of the resized stage blank 34 are scored to provide the
scored stage blank 59 (FIG. 15).
The dies for the scoring operation illustrated in FIGS. 16 to 18,
include relatively movable upper punch members 60, 61 and 62, die
cavity forming members 63 and 64, and rivet pilot and locator pin
65.
In carrying out the scoring operation, the main upper punch member
61 which is spring loaded, bottoms on the resized stage blank 34
inserted between the punch, and the die cavity members 63 and 64
and properly located therein by the rivet pilot pin 65. Thereafter,
the scoring punches 60 and 62 move home. The score blade 66 on the
nose of upper punch member 60 for forming the continuous score line
67 where the panel of the can end is torn from the container
subsequently when opening the container, is shown in FIG. 17. The
score blade 68 on upper punch member 62 forming a fold line score
69 adjacent the rivet bubble 53 on which the initially ruptured
portion of the end panel to be removed, bends when tearing the
panel from the can end, is shown in FIG. 18.
The score blades 66 and 68 score the coined portions 45 and 55,
respectively, of the resized stage blank 34 in carrying out the
scoring operation, as shown in FIGS. 16 to 18. Tear out score line
67 preferably is deeper, as shown in FIG. 17, than the fold line
score line 69 as shown in FIG. 18. Furthermore, the score line 67
in cross section is angularly shaped, rather than the symmetrical
shape of the score line 69. This angular shape of the score line 67
controls the location of the tear along the score to protect the
edge of the torn panel as described in application Ser. No.
229,678.
The depth of the scoring operation die cavity (FIG. 16) formed by
lower die cavity members 63 and 64 is less than the depth of the
die cavity (FIG. 13) for the resize and rivet redraw operation
(FIG. 10). Thus, the height of the recess of resized stage blank 34
when placed in the die cavity shown in FIG. 16, is greater than the
die cavity; so that a greater prebulge 70 is formed in the annular
wall 71 of scored stage blank 59 as the scoring dies move home.
This greater prebulge reduces the radius of the curved corner 23 of
the recessed wall 9 in the resized stage blank 34 to subsequently
one-half in the resulting radius of the curved corner 72 in the
scored stage blank 59.
Preferably, the radius at the corner 23 in FIG. 10 is 0.028" while
the radius of curved corner 72 is scored stage blank 59 is
preferably 0.015".
The annular space in the scoring operation dies (FIG. 16) between
the outer cylindrical surface of the telescoped upper punch member
61 and the inner cylindrical surface (2.227" diameter) of the lower
die cavity member 63 is radially wider than the corresponding
annular space (2.220" diameter of cavity in member 38) in the dies
for the resizing and rivet redraw operation (FIG. 10). This
enlarged scoring die annular space permits the increased prebulge
70 of the annular bulged wall 71 of scored stage blank 59 to occur,
as shown.
At the same time, the break point 49 and the pivot point 50 in the
scored stage blank 59 (FIGS. 16-17) each are located substantially
radially inside of the location of the outer surface of the
prebulge 70 in annular bulged wall 71.
FOLDING OPERATION
The next operation illustrated in FIGS. 19 to 21 folds metal in the
scored stage blank 59 to form the folded stage blank 73 (FIG.
20).
The dies for the folding operation illustrated in FIGS. 19, 21 and
22, include relatively movable upper punch members 74, 75 and 76,
die cavity forming members 77, 78 and 79, and rivet pilot and
locator pin 80.
In carrying out the folding operation, a scored stage blank 59 is
entered in the die cavity formed by members 77, 78 and 79, located
in proper position by locator pin 80. Upper punch member 75, which
is spring pressed, first moves downward to clamp recessed wall 9
against the upper surface of die cavity member 78. Meanwhile, upper
punch member 76 telescopes over the rivet bubble 53 locating stage
blank 59 in proper position with respect to the punch and die
members cooperatively with the rivet locating pin 80. At the same
time, outer upper punch member 74 moves downward and its nose
formation 81 engages the coined zone 45 which has been scored at
67, and pushes the coined zone 45 downward into the die cavity
until the undersurface 82 of the coined zone 45 bottoms on the
upper annular surface 83 of the die cavity member 77 (FIG. 21).
During the described motion of upper punch member 74, the prebulged
portion 70 of annular bulge wall 71 of stage blank 59 continues to
bulge outwardly and folds generally in S-shape to form the triple
fold indicated generally at 84 in FIG. 21. The die cavity 85 in
which the triple fold 84 is formed (FIG. 21) has a greater depth
throughout an arc of 50.degree. at either side of a diameter
passing through the center of the rivet 53 and the center 86 of
folded stage blank 73 (FIG. 20) than the metal thickness of the
three folds. This produces a fold clearance 87 between the top and
middle fold layers throughout the 100.degree. arc. The die
clearances between members 75 and 78 and the recessed wall 9
permitting this thickened fold throughout the 100.degree. arc are
indicated at 88a and 88b in FIG. 21. The fold 89 formed throughout
the remaining 260.degree. of the fold formation differs, as shown
in FIG. 22 (which is the section taken on the line 22-22, FIG. 20
at 180.degree. from the section line 19 where the sectional views
of FIGS. 19 and 21 are taken) from the formation of the fold 84
with its fold clearance 87.
In FIG. 22, the triple fold 89 is not as thick as the triple fold
84 of FIG. 21, being only slightly greater than the thickness of
the three layers of the fold, because the die clearances 88a and
88b of FIG. 21 are not present in the 260.degree. arcuate portion
of the dies extending from either end of the 100.degree. arcuate
portion of the dies wherein the triple fold shape 84 is formed.
As indicated, this 100.degree. arc thickened triple fold zone 84 is
located outward of the rivet bubble 53 and extends along the fold
from either side of the rivet bubble 53 to allow the top layer of
the triple fold, in which the score line 67 is contained, to flex
slightly at the time when a pull ring secured to the rivet later is
moved to initiate fracturing the can end along the score line
67.
The dies used for the folding operation also preferably include an
upper punch member 90 (FIG. 23) movable in the central region of
the upper punch member 76, and a cavity formation 91 below punch 90
in die cavity member 79. The punch 90 and die cavity 91 form a
thumb indentation 92 in the center of the recessed wall 9 of folded
stage blank 73.
Where a message is to be embossed in a can end, as indicated at 93,
embossing formations may be incorporated in the punch and die
members 76 and 79.
TAB ASSEMBLY AND RIVET STAKING OPERATION
The next operation illustrated in FIG. 24 involves the assembly of
a pull ring tab 94 to the folded stage blank 73, to produce the
assembled can end 95 shown in FIG. 25.
The dies for assembling a pull ring tab 94 with the folded stage
blank 73, and for staking the rivet 53 to secure the tab 94 to the
can end shown in FIG. 24, include punch members 96, 97 and 98, tab
locator members 99 and die cavity members 100 and 101 and lower
staking punch 102.
In carrying out the tab assembly and rivet staking operation, a
folded stage blank 73 is placed in the die cavity formed by members
100, 101 and 102 with punch nose 103 of lower staking punch 102
telescoped in the rivet bubble 53 of blank 73.
A rivet opening 104 in a pull tab 94 is slipped over the rivet
bubble 53. The pull tab 94 when thus assembled on folded stage
blank 73 (FIG. 25) has its side edges engaged with the reformed
dimples 57. These dimples 57 thus serve as tab positioning dimples
to locate the axis of the tab 94, passing through the center of the
pull ring finger opening 105 and the center of the tab rivet
opening 104, radially of the assembled can end 95.
Upper punch member 96 then moves downward to the position shown in
FIG. 24 and spring loaded punch 97 moves home so that its annular
ring-like nose 106 clamps the tab 94 against the coined area 55 of
the blank 73 surrounding the rivet bubble 53. The under-surface of
coined area 55 is seated on the annular face 107 of lower staking
punch 102.
Meanwhile, tab locators 99 press downward and bottom on on the
triple fold 84 at either side of the nose 108 of tab 94 to control
the location of the pull tab 94. Tab locators 99 each have tapered
noses 109 which will engage the sides of the pull tab nose 108 and
straighten the pull tab to correct position in the event that it
has rotated out of position on the rivet bubble 53.
While the folded stage blank 73 and pull tab 94 are thus positioned
and held in the tab assembly and staking operation dies, the upper
riveting punch 98 moves downward within tubular punch 97 and
bottoms against the punch nose 103 of lower staking punch 102, as
shown in FIG. 24. This riveting and staking operation reforms the
rivet bubble 53 to the shape shown in FIG. 24 wherein the center
portion of the rivet head is thinned and coined at 110, and an
outturned rivet head fold flange 111 is formed annularly around and
overlapping the pull tab 94 at its rivet opening 104.
STAMP AND TAB CHECK OPERATION
The final operation in the manufacture of the described folded can
end is illustrated in FIG. 26 and involves the stamping of desired
indicia on the can end and checking the assembled can end 95 to
determine whether the tab 94 is missing or has rotated to an
improper position. This final stamp and tab check operation
produces the final folded can end 112, illustrated in FIG. 27.
The dies used in the stamp and tab check operation (FIG. 26)
include a lower die 113, and stamping die 114 movable in an upper
clamping die 115, and a probe rod 116 also movable in die 115.
The assembled can end 95 of FIG. 25 is placed on die 113 and held
in position by upper die 115. Stamping die 114 descends and stamps
indicia such as a part number 117, a manufacturer number 118, and
other information 119, preferably in the wall of the thumb
indentation 92. At the same time, probe rod 116 descends and
strikes the ring portion 120 of the pull ring tab 94 if the pull
ring tab 94 is present and located in proper position. If the pull
ring tab 94 is missing or improperly located, probe rod 116 will
descend further and signal a missing or rotated tab.
IN GENERAL
The progressive operations described are designed to be carried out
in the high speed production of the improved folded can ends. The
successive operations, as indicated, control or prevent thinning of
the blank in various areas or zones in one or more of the
operations. Further, the preparation of the fold zone is started in
the first blanking operation by the formation of the conically
shaped annular band or fold panel. Successive metal working
operations performed on the metal in this fold panel, including the
prebulging steps, increase the diameter of the bulged portion
successively, and reduce the height of the recess for the recessed
wall 9, prepare the metal originating in the fold panel for
folding, subject the metal to progressive prebulging and ultimately
fold the metal to form the triple fold.
Along with the increase in the prebulged diameter, and the decrease
in the recess depth, are the sharpening of the pivot point 47
around which the metal pivots during the folding operation; and the
reduction in the radius of curvature of the curved corner 23-72 in
successive operations to more sharply define the curved corner at
the bottom of the recess in preparation for folding.
Another aspect of the interrelated character of the successive
operations is the coining of various zones of the metal being cold
worked, particularly where the scorelines subsequently are formed,
whereby the scoring operations can be adequately controlled despite
the thinness of the metal worked.
Another important aspect of the procedure is the formation of and
location of the break point 49 at the inner periphery of the
annular coined zone 45 and radially inward of the location of the
pivot point 47 as well as radially inward of the outer surface of
the prebulged portion 70 of the scored stage blank 59.
The described relationship and changes in dimensional
characteristics of the prebulge, recess depth, pivot point and
break point, as well as the related locations of coined areas and
score lines, insure the ability to provide the triple fold 84
during the folding operation very close to the location of the
rivet which secures a pull ring tab 94 to the can end, which tab 94
in turn ultimately is used to fracture a panel along the continuous
score line 67 when it is desired to open a can in which improved
folded can end has been seamed.
Another characteristic of the metal working operations described is
the resultant fold clearance 87 in the segment of the fold adjacent
that portion of the triple fold 84 overlapped by the nose 108 of
the pull tab 94. This facilitates the initial bending of the upper
layer of the triple fold 84 when rupture of the can end is
initiated by pull tab 94 along the score line which is torn. At the
same time, the end panel torn away initially bends on fold line
score 59.
Another aspect of the new concept relates to the particular
structure and arrangement of the three layer fold and its
components. As stated in describing the procedure for manufacturing
the can end, the resultant fold clearance 87 in the segment of the
fold adjacent that portion of the fold overlapped by the nose 108
of the pull tab 94 facilitates initial bending of the upper layer
of the triple fold when rupture of the can end is initiated by the
pull tab 94. This clearance 87 spaces the upper layer of the fold
in the fold segment, which may be a sector of about 100.degree.,
above the two lower fold layers, as shown in FIGS. 19, 21 and 24.
The spacing or clearance 87 increases the thickness of the three
layer fold in the 100.degree. sector, as compared with the
thickness of the fold in the remaining 260.degree. sector thereof,
as illustrated in FIG. 22.
The score line 67 (FIGS. 19, 21, 24) in the top surface of the
upper layer of the three layer fold is located radially
intermediate the location of the outwardly convex lower reverse
bend 121 between the two lower layers of the three layer fold, and
the inwardly convex upper reverse bend 122 having the fold
clearance 87 between the top and middle layers of the three layer
fold. Thus, when the panel portion is removed from the can end by
severing along the score line 67, the torn outer edge of the upper
fold layer is located inwardly of and does not project radially
beyond the lower reverse bend 121 of the fold between the two
bottom layers of the three layer fold.
FIG. 24 illustrates other important aspects of the new folded can
end structure. The upper reverse bend 122 forms a downward offset
in the can end recessed portion 9 which is bounded by the three
layer fold. The lowermost fold layer extends inward toward the
center of the can end flatwise, coplanar with the coined zone 55 in
which the rivet 110-111 is formed, which connects the pull tab 105
to the can end. The fold line score 69 is formed in this flatwise
extending portion intermediate the rivet and three layer fold.
Thus, the can end is free of any stiffening offsets, corrugations
or shoulders between the fold line score 69 and the three layer
fold which if present would stiffen the can end metal and impede
folding of the metal on the fold line 69 during initial rupture of
the continuous score line 67 by the pull tab 105.
The pull tab 105 also has an offset 123 formed therein between the
rivet and nose 108 corresponding to and spaced from the offset
connected with the flatwise extending portion of the can end. The
undersurfaces of the nose 108 of the pull tab 105 contacts the top
surface of the top fold layer (FIG. 24) and extends to a location
overlapping the continuous score line 67. This provides a position
control for the extreme outer end of the nose 108 so that concave
movement of the can end resulting from heat processing the contents
of a container closed by the can end which may move the end of the
pull tab nose 108 slightly to the right (FIG. 24) retains the
location of the extreme end of the nose 108 intermediate the spread
of the top opening in cross section of the score line 67 so that a
shear force may be imparted to the score line 67 to initiate
severing the can end on the score line by pull tab movement.
Accordingly, the present invention provides new procedures for the
manufacture of folded can ends by a series of cold working,
forming, drawing, etc., operations which are mutually related and
interrelated to control metal thinning and to direct and control
metal flow and reforming of very light gauge, preferably aluminum,
sheet metal; provides a procedure which achieves the described
objectives by successive and progressive metal working operations
that can be carried out and controlled in high production
facilities; provides an efficient procedure for the manufacture of
the indicated desirable folded sheet metal can end structure;
provides a procedure which accomplishes the many new functions
described; provides a procedure including the described coordinated
critical factors which have enabled the successful production of a
folded can end structure having the described characteristics;
provides a procedure which overcomes difficulties encountered in
attempting to devise an efficient method of making the desired
folded can end structure; provides a procedure which achieves the
objectives and satisfies needs existing in the art; and provides
the described new folded can end product.
In the foregoing description, certain terms have been used for
brevity, clearness and understanding; but no unnecessary
limitations are to be implied therefrom beyond the requirements of
the prior art, because such terms are used for descriptive purposes
and are intended to be broadly construed.
Moreover, the description of the improvements is by way of example
and the scope of the present invention is not limited to the exact
details shown or described, or to the specific articles
illustrated, since the invention may be applied to the manufacture
of the various sizes and shapes of folded can ends.
Having now described the features, discoveries and principles of
the invention, the operations and procedures of preferred method
steps thereof, the construction and operation of new die
arrangements and their coordinated design, the characteristics of
the stage blanks produced, the new products produced, and the
advantageous, new and useful results obtained thereby; the new and
useful methods, steps, operations, procedures, products,
combinations, structures, arrangements, discoveries and principles
are set forth in the appended claims.
* * * * *