Note: Descriptions are shown in the official language in which they were submitted.
7BS~
This is a divlsional of Canadian application Serial
No.471,597 filed ~anuary 7, 1985.
SHELL FOR CAN
Background of the Invention
This invention relates to metal shells used to
form ends of can type containers. Most can type
containers, for example beer cans and soft drink cans, are
required to withstand internal pressure, rough handling,
and substantial temperature differences, yet maintain a
complete hermetic seal to protect the contents of the
can. Cans of this type are used in vary large volumes,
billions of cans per year, and at present the metal most
used for this purpose is aluminum due to its light weight,
comparative inexpensiveness and workability.
The typical modern can consists of a unitary deep
drawn body, usually with a necked inward throat at the top
which terminates in an outwardly extending body curl, and
an end for the can which comprises the shell (to which the
present invention pertains) provided with self-opening
structure such as tear tabs and related score lines in the
shell. The shells are manufactured from sheet metal by
severing a suitable blank from a strip thereof, forming
the blank to define a central panel surrounded by a
reinforcing countersink and chuck wall configuration, and
a shell curl which is designed to interact with the body
curl in seaming apparatus to attach the end to the can
with the requisite hermetic seal. In most instances the
underside of the shell or end curl is provided with a
- sealing compound to assist in the formation of the seal.
The shell is the basic part of the end and is
formed from the blanks, then the shells are operated upon
in converting apparatus which adds the desired score
lines, tear tab, and the integ~al rivet attachment between
the shell and the tab, all in known manner. ~he sealing
` lX678~
DRT 003 P2 -2-
compound may be applied to the underside of the shell,
specifically to the downward facing or bottom portion of
the shell curl, either before the converting operation, or
after, the former being more typical.
One of the major endeavors of designers of can
ends is to provide a shell of as thin material as is
possible, since this can result in substantial savings of
material, and therefore expense. However the integrity of
the shell, and its ability to withstand buckling from
internal pressures in particular, imposes restrictions
upon the use of very thin material in the sheil
formation. The ability of the thin metal to withstand the
drawing and working imposed upon the blank during the
formation of the shell generally calls for use of somewhat
thicker metal, in order to accommodate thinning in the
region where the reinforcing structure is formed in the
shell.
In typical prior art operations for the forming
of shells, a blank is severed from sheet material, usually
steel or aluminum, and it is then formed to a shape
comprisin~ a generally flat central panel and a chuck wall
extending, in this initial stage, upwardly and outwardly
from the central panel, blending into a curved flanged
portion. In one prior art metho~ the blank is formed to
include a groove around the central panel inward from the
chuck wall. This initial blank is then subjected to a
curling operation to form a curled edge on the flange, the
curled edge being turned somewhat under the flanged
portion.
From the curling operation, the partially formed
shells are fed through further tooling where they are
gripped in the flange portion, while ~he curled edge is
protected in the tooling against deformation. If the
~7854
DRT 003 P2 -3-
groove is already in the blank, then the groove may be
reformed. If not, the thus clamped blank is moved against
a stationary support applied against the major underside
of the central panel~
There is an unsupported region in the shell
comprising the edge of the central panel which overlaps
and extends beyond the stationary support, out to the
region where part of the chuck wall is clamped. This
collapsing action places the blank in compression, and
results in a reshaping of the unsupported band of material
between the chuck wall and the central panel, into a shape
which defines a reinforcing channel or countersink at the
bottom of the chuck wall and into the periphery of the
central panel. Thus, the formation of the end shells
lS according to the prior art requires a three stage
operation, and the above described formation of a
reinorcing channel shape into the shell results from a
working of a band of the metal blank between the chuck
wall and the central panel which is essentially
uncontrolled and thus susceptible to breaks, distortion,
or potential thinning of the shell at this critical point
in its structure.
In addition, prior art shells are subject to a
condition in the region of the peripheral flange and
curled edge which is known in the art as "earring". When
the blank of metal is severed from the supply strip,
usually a strip withdrawn from a roll thereof9 prior
practice is to cut or sever a round blank, and little
attention is given to the grain direction of the metal,
which runs lengthwise of the strip. It has been known for
some time, but apparently uncorrected, that forming of the
metal (particularly thin aluminum) in operations which are
L2~:i785~
DRT 003 P2 -4-
intended to produce a round shell, results in some
distortion of the shape from the initial round blank,
because the metal tends to stretch slightly more with the
grain than across the grain, and to stretch even further
at 45 to the grain. The result of such uneven "growth'l
of the metal appears as a slight deformation in the edge
of the blank which is subjected to the curling o?eration.
The curled under edge thus is somewhat closer to the chuck
wall in certain areas than in others around the shell;
i.e. the end curl becomes irregular with respect to the
chuck wall.
This situation can result in one of two
difficulties. If the shell is manufactured such that the
enlarged rearrings" on the periphery form the primary seal
in the seam of the end to the can, then the end curl of
the blank betwen the "earrings" is short, and must rely
more upon the sealing compound ~o maintain the hermetic
seal since the metal of the end curl may not tuck
completely under the curl on the can body in those
regions. In terms of describing the completed seam, it
can be said that the end or cover hook does not extend
completely behind the body hook throughout the seam.
Alternatively, to achieve a hermetiG seal between
the end and the body, the design may accommodate for the
enlargement of the "earrings", such that the edge between
such earrings is completely tucked under the body curl
during seaming. This, however, leaves an excess of metal
in the cover or end hook extending into the seam in the
region where the earrings exist, and this can lead to
puncturing of the thin can body in the region of the neck,
or to wrinkling of the excessive material within the
curled seam, thereby destroying the uniformity of the
s~
DRT 003 P2 -5-
seam. Whatever the result, the tendency is to have an
unacceptably great percentage of cans which leak after
they have been filled and sealed. This of course is
unacceptable from the standpoint that the packaged product
is lost, and additional damage from spillage, etc. may
also result.
Summary of the Invention
The above parent application claims a
method and apparatus whereby the aforementioned earring
problem is essentially overcome, and furthermore in which
a shell is provided having more unifrom thickness
throughout its extent, including the requisite chuck wall
and the re-enforcing panel wall connecting between the
chuck wall and the central panel of the shell. In
addition, the invention provides a shell having an
improved partial curl at its periphery in which the inward
edge of the curl is pre-formed such that during the
seaming operations, when the end formed from the shell is
attached to a can, the curl will roll smoothly into the
curled seam, minimizing the possibility of wrinkled seams
and/or punctures or cuts of the can neck in the region of
the seamn
The earring is minimized, and the inner curl
diameter spacing from the chuck wall of the shell is made
more uniform and concentric, by forming the shell from a
blank which is multi-sided in configuration rather than
circular. The shape of the blank is such that the
diameter of the blank parallel to the grain of the strip
from which it is formed is less than the diameter of the
blank transverse to the grain direction. The dlameters
with and transverse to the grain ai~d at 454 to the grain
direction are different and the ~ransition of the side
~Z6~85~L
DRT 003 P2 6-
edges of the blank are rounded. This initial forrnation of
the blank, together with controlled forming and drawing
operations on the blank to form the shell, results in a
final shell product having the desired concentricity and
uniform spacing of curl diameter with respect to the chuck
wall, having more constant thickness, thus resulting in a
better and more uniform seam in the ultimate finished can
and thereby minimizing the number of failures encountered.
The invention of the present divisional
provid~s a finished shell, in which the
shell is formed in two steps solely by reclprocable
tooling in one or more presses, for example a standard
single action press. No additional curling or ~he Iike is
necessary to finish.the desired pre-formed curl at the
periphery of the shell.
The object of the invention, therefore, is to
provide a unique shell for making can ends which is
characterized by minimized earring, more uniform
concentricity of the inner and outer curl with the chuck
wall, more uniform thickness especially through the
connection between the chuck wall and the central panel,
and an improved pre-formed curl arolund the periphery of
the shell~
j785~
DRT 003 P2 -7-
Other objects and advantages of the invention
will be apparent from the following description, the
accompanying drawings and the appended claims.
Brief Description of the Drawings
Fig~ 1 is a view of the top of a typical beverage
can, with a portion broken away and shown in cross-section
to illustrate the seam between the can body and the end;
Fig. 2 is a broken and shortened cross-sectional
view of a shell for a can end, as provided by this
invention;
Fig. 3 illustrates a fragment of a strip of sheet
metal material, illustrating the configuration of blanks
to be severed rom such material for the formation of
shells, in accordance with the invention;
Figs. 4, 5, 6 and 7 are enlarged ~about two and
one-half times) partial cross-sectional views of tooling
used in accordance with the invention at a first operating
station to form a partially completed shell, the
peripheral configuration of which is shown in Fig. 7;
Figs. 8, 9, 10 and 11 are similar enlarged
partial cross-sectional view of the tooling and its
sequential operation at a second station to complete the
formation of shells in accordance with the invention; and
Fig. 12 is a similar view illustrating a
modification o~ the second station tooling.
Descript _n of the Preferred Embodiment
The making of a shell according to the invention
is generally divided into two operations, each of which
can be carried out within a conventional single-action ram
press having a specially adapted ~ooling. A typical press
~X~8S~a
DRT 003 P2 -8-
*
utilized is a Minster P2-45, although many other models
are also suitable for use.
Initially, the relatively thin metal stock S
(Fig. 3) from which the shell is ultimately formed is fed
to one or more stations within the press. The press ram
operates at each of these first stations to separate a
blank B from the stock, and to partially form the shell
from the blank.
The partially completed shell formed at each of
the first stations is then transferred ~o a corresponding
second station within the same press, where the forming of
the shells is completed, the press is opened, and the
completed shells are discharged from the press.
In a preferred form of the invention, for each
stroke of a single press, a partially formed shell is
finished by each second tooling station while a blank is
produced and partially formed by each first station
tooling. Moreover, the transfer of shells between
stations is accomplished so that a shell partially formed
in a first station by one press stroke is completed at the
second station by the next succeeding stroke. It should
be understood, however, that the first and second stations
and corresponding tooling can readily be loca~ed in
different presses, and the partially formed shells can be
transferred immmediately from one press to the other
(second), or the partially formed shells can be collected
from the first press and later processed in second station
tooling by the second press.
Blank Confiauration
Referring to Figs. 1 and 3, a portion of the
strip of material from which the bl~nks are cut is shown
at S in Fig, 3, and the shape of the blank is indicated
*Trademark
78r;~
DRT 003 P2 -9-
within the area designated B which, as will be described,
is a multi-sided form with rounded transitions from one
side to the next, rather than an accurate circle of the
same diameter througho~t. Referring to Fig. 1, the seam
between a typical end and the body of a can is seen to
include the body hook BH and the end or cover hook CH, and
the region of overlap between these two is indicated by
the dimension OL. A q~antity of sealing compound is
located in the area between the top of the body hook and
the undersurface of the end, however this compound is not
illustrated in Fig. 1.
The effect of earring is either to cause a very
small amount of overlap, or to cause excessive overlap in
- which case the end of the end or cover hook interfers wi~h
the bending of the seam parts at the top of the seam, or
punctures the wall of the can body in this region.
It has been discovered that the earring effect or
distortion can be greatly minimized if the shape of the
blank B is properly selected with respect to the grain of
the material, which is indicated by an arrow and
appropriate legend in Fig. 3. Thin sheet metal material,
for example aluminum and steel, tends to "grow" or stretch
more in the direction of the grain and in a direction at
45 to the grainl rather than across the grain. The
dimensions stated are exemplary onlyt but serve to
illustrate the principles applied in designing the shape
of the Dlank in accordance with the invention. The
diameter of the blank B along its horizontal axis I--I
diameter, as shown in Fig. 3 f is the largest, since it is
in this direction that the blank least tends to grow as it
is worked in forming the shell. A typical dimension along
this diameter, for a typical size blank to form one
i78~
DRT 003 P2 -10-
standard size of an end is 2.987 inches. The vertical
diameter V--V of the blank, on the other hand, is
typically 2.980 inches. The diameter III--III of the
blank at 45 in each direction from the vertical diameter
is 2.974 inches; the diameter IV--IV of the blank at 22.5
in each direction from the diameter V--~V is 2.982 inches;
and the diameter II--II at 22.5 in each direction from
horizontal is 2.984 inches. A blank of this
configuration, when produced in accordance with the
invention from 0.0114 aluminum, results in a shell which
has an inner curl diameter ICD ~Fig. 2) that is round
within 0.003 to 0.005 inch, and that is concentric to the
chuck wall of the shell (as later described) within 0.003
to 0.005 total indicator reading, and is essentially
absent any earring. It should be understood that the
foregoing dimensions are specifically applicable to a
certain size shell made from a certain metal, and are
intended to be exemplary of the invention, its principals,
and its application. This information is not restrictive
as to the scope of the invention.
Referring to Fig. 2, there is shown in
cross-section, substantially enlarged beyond the normal
size of an actual shell, the configuration of a finished
shell as provided by the invention. The shell is, of
course, an integral metal part, made from a suitable metal
blank, shaped as previously described, and in its final
configuration including a flat central panel 10, a
countersunk reinforcing area 11 extending into a
relatively straight upward and outward shaped chuck wall
12, and a lip or curl edge portion 13 which terminates at
the inner curl diameter.
7~
DRT 003 P2 -11-
First Station Toolin~ and Operation
The press tooling for each of the first stations
is shown in Figs. 4 - 7. The upper tooling is connected
for operation by the press ram, while the lower tooling is
fixed to the press frame.
The lower tooling includes die cut edge 14, over
which the metal stock S as it enters the tooling at a
level generally indica~ed by line 16. Die cut edge 14,
along with die form ring 18 are solidly supported on a
suitable base member. Additionally, the lower tooling
includes draw ring 24, positioned between die form ring 18
and die cut edge 14. A center pressure pad 25 is located
concentrically within form ring 18. Draw ring 24 is
supported by springs (not shown), mounted in the base
member, wnich, compress due to pressure exerted upon draw
ring 24 when the tooling is closed. The center pressure
pad 25 is also supported by a spring (not shown) which
will compress in response to force exerted by the upper
tooling.
When the tooling i5 open, draw ring 24 and center
pressure pad 25 are retained in the lower tooling with
draw ring 24 bottoming against die cut edge 14 and center
pressure pad 25 against form ring 18. The uppermost
surface of draw ring 24 is then at a position some
distance below the lowest point of shear on the die cut
edge 14, while the uppermost surface of the center
pressure pad 25 is some distance above draw ring 24 and
below the lowest point of shear on die cut edge 14.
The upper tooling is provided with blank punch 30
positioned to cooperate with draw ring 24 for as the
tooling is closed. A knockout and positioner 32 is
located above die form ring 18, and punch center 34 is
3L2~j785~
DRT 003 P2 -12-
provided with an appropriate configuration to produce the
partially completed shell, as well as to clamp a blank in
cooperation with center pressure pad 25. Blank punch 30,
knockout and positioner 32, and punch center 34 are all
closed simultaneously upon the lower tooling as the press
ram is lowered.
The sequential operation of the first station
tooling to produce the blank from the stock and partially
form a shell is shown in Figs. 4 - 7. In Fig. ~, the
tooling is shown already partially closed. The stock S
enters the tooling along a line indicated at 16, and as
the press ram is lowered, a flat blank B is produced by
shearing the stock material between die cut edge 14 and
blank punch 30.
Since the blank punch 30 and punch center 34 move
simultaneously, the lowermost surface of blank punch 30
must lead the lowermost surface of punch center 34 by some
dis- tance so punch center 34 does not interfere with the
stock S during blanking.
Further, the distance by which blank punch 30
leads punch center 34 is less than the distance at which
the uppermost surface of center pressure pad 25 is above
the uppermost surface of draw ring 24 in lower tooling
12. This causes the entire central panel of blank B to be
clamped between punch center 34 and center pressure pad 25
first, followed by pinching o~ the outermost part of blank
B between blank punch 30 and draw ring 24 before any
forming begins. Use of the central clamping secures the
blank B in a centered position within the tooling during
subsequent forming of a shell from the blank. Holding the
blank in a centered position contributes to controlled
working of the blank and minimizing variation in the
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~678~
DRT 003 P2 -13-
curled lip portion provided at the outer edge of the
completed shell, providing a more even amo~nt of material
for later seaming.
As the press ram continues downward, the blank
punch 30, support ring 32, and punch center 34 all
continue to move simultaneously. At the point illustrated
in Fig. 5, the blank is still pinched between blank punch
30 and draw ring 24 and between punch center 34 and pad
25, beginning the formation of the shell over die orm
ring 18. It will be noted that as the blank B is formed
over form ring 18, it is pulled from between blank punch
30 and draw ring 24.
Referring to Fig. 6, the press ram continues to
move downward as the punch center 34 begins to form the
chuck wall 12 on blank B. The blank material is no longer
held between the blank punch 30 and the draw ring 24, but
is still held between punch center 34 and pad 25, and the
` draw ring 24 no longer controls the formation of the
shell. The clearance between the inside diameter of the
blank punch 30 and the outside diameter of the die form
ring 18 is selected to provide an appropriate amount of
drag or resistance on the b}ank B to insure poper
formation. The inside diameter of blank punch 30 slightly
narrows above the curves shown at 49 lshown exaggerated
for clarity). Thus, near the end of the press stroke, as
can be seen~by comparing Figs. 4 and 5, the drag on the
outermost portion of blank B is increased. This is to
insure that this portion of the resulting shell 48 is
drawn more tightly over die form ring 18 so that the curl
found in shell 48 extends to the very edge of shell 48,
without any straight or~less than fully carled portions.
~Zki785~
DRT 003 P2 -14-
In Fig. 7, the tooling is shown in its closed
position with the press ram bottomed against appropriate
stop blocks. The first portion of the shell formation
operation is completed, with the flat central panel 10
terminating at a relatively large radius area 52 to
produce a soft stretch so as not to overwork the material
in this area. The large radius area 52 forms the junction
region of chuck wall 12 with the cen~ral panel 10, and
will later form the shell countersink and panel form
radius. A sufficiently large radius is provided that a
much tighter radius can later be provided for the shell
countersink while maintaining sufficient material
thickness. It can be seen from Fig. 7 that the reverse
bends applied to the inner wall of die center form ring 18
and the outer wall of punch center 34 serve to produce a
straight chuck wall 12 without either inward or outward
bowing, enabling the shell to fit accurately within the
second station tooling.
The shell is further provided with a lip S3
extending generally outwardly and upwardly fro~ the chuck
wall 51, but having general downward curvature. ~ip 53 is
provided with two distinct curvatures, giving lip 53 a
~gull-wing" cross-sectional configuration. Its portion
adjacent chuckwall 12 has only slight relative c~rvature
and thus provides the upward extension of lip 53, while
the outermost portion is provided with a relatively sharp
downward curvature by dieform ring 18. However the outer
edge of lip 53 is located to at least even with, if not
above, the point where lip 53 connects with the shell
chuck wall 12.
Upon ciosure of the tooling, knockout and
positioner 32 does not contact the partly completed
DRT 003 P2 -15-
shell. Once the forming operation has been completed, the
press ram is raised to open the tooling, and the shell
pre-form is held within blank punch 30 by the tight fit of
its lip 53 therein, and is carried upward by the upper
tooling. Once the lowermost portion of the shell pre-form
has cleared the stock level indicated in Fig. 3 at 16,
knockout and positioner 32 halts its upward movement while
blank punch 30 and punch center 34 continue to rise with
the press ram. When upward movement of knockout and
positioner 32 is stopped the shell pre-form will contact
it, and this pushes the shell pre-form from within the
still-moving blank punch 30.
The partly formed shell 48 is then held in
position on knockout and positioner 32 through application
of a vacuum, via appropriate passageways (not shown)
through the upper tooling to the surface of punch center
34. This vacuum then causes the shell pre-form to adhere
to the surface of knockout and positioner 32 until it is
removed.
Upon completion of the f irst operation upon the
shell, it is moved by a transfer system, such as described
in copending Canadian application Serial No. 471,601
filed concurrently herewith and assigned to the same
assignee, to a corresponding one of a plurality of second
stations for completion of the formation process.
Second Station Tooling and Operation
.~ _
The tooling for the second station is shown in
Figs. 8 - 11, including upper tooling 61 supported on the
press ram and lower tooling 62 supported on the press
bed. The lower tooling 62 includes a curl die 64 and
panel form punch 66, both fixeâ ~n turn ~o suitable base
members. An insert 71 is mounted within panel form punch
66. A spring pressure pad 72 is concentrically mounted
7~4
DRT 003 P2 -16-
between curl die 64 and panel form punch 66, supported by
a plurality of springs 74 (not shown) mounted within the
base which supports the lower tooling. A fitting 75, for
connection of a source of vacumn, leads into vacumn
passageways 76, 78 provided to supply vacuum to the upper
surface of panel form punch 66.
The upper 61 tooling includes a curl form punch
and positioner 84 having a projection 85 for defining the
forming characteristics of the lower surface of form punch
and positioner 84. Additionally, panel form die 86 is
mounted generally for movement along with the form punch
and positioner 84. Panel form die 86 is supported from
the press ram through a plurality of springs 90 (not
shown~, which are selected to provide a "dwell" in the
downward movement of panel form die 86 as the press ram is
lowered.
Vacuum passageways 92, 93 are provided through
panel form die 86, form punch and positioner B4, and their
mounting respectively, thus vacuum may be supplied to the
lower face of panel form die 86.
The sequential operation of the tooling of each
of the second stations for completion of a shell is shown
in detail in Figs. 9 - 11. The shell pre-form enters the
open tooling of the second station and is properly
positioned on the lower tooling. The large radius area 52
and chuck wall 12 are supported by the spring pressure pad
72, with the entire central panel 10 supported some
distance above insert 71. The shell pre-form is located
and held in place by the vacuum supplied to the upper
surface of panel form punch 66.
In Fig. 9, lowering of the press ram causes panel
form die 86 to contact chuck wall 12, clamping it between
854
DRT 003 P2 -17-
panel form die 86 and spring pressure pad 72. The spring
pressure on form die 86 is selected to be more easily
compressible than the springs supporting the pressure pad,
so that once contact with chuck wall 12 is made, panel
form die 86 is held in position by spring pressure pad 72
and begins to dwell despite further lowering of the press
ram. Subsequently, form punch and positioner 84 contacts
lip 53.
As seen in Fig. 9 and 10, continued downward
movement of the press ram causes the form punch and
positioner 84 to begin to push shell lip 53 toward its
intended final configuration. The shell preform continues
to be clamped between panel form die 86 and spring
pressure pad 72, with panel form die 86 continuing to
dwell until downward movement of the press ram causes
spacer 96 to bottom against a base plate, shown in Fig. 8.
Once spacer 96 has bottomed against a base plate/
then further downward movement of the tooling by the press
ram causes the panel form die 86 to move downward, as
shown in Fig. 10, forcing the spring pressure pad 72 to
move downward as well. Insert 71 includes a raised center
91 which now is positioned ayainst the shell pre-form
panel 50. Downward movement of spring press~re pad 72
effectively causes upward movement of the panel 50 with
respect to the remainder of shell pre-form, reducing the
distance between the uppermost portion of the shell
pre-form and the panel 50. The shell material from the
large panel radius area 52 begins to pull away from the
spring pressure pad 72 and wrap around the edges of the
panel form punch 66 and the panel form die 86 (Figs. ~ and
10). The wrapping action takes place under precise
DRT 003 P2 -18-
control with little drawing of the shell material, to
produce a pressure resistant panel for the completed shell
by reforming the large radius area 52 into the countersink
98. Raised center portion 91 of insert 71 causes panel 50
to be bowed slightly upward. This is to counteract a
tendency of panel 50 to bow downwardly during shell
forming, and thus resulting in a flat finished panel.
Simultaneously, the shell lip 53 enters the curl die 64
for final shaping.
The tooling is shown in its closed position in
Fig. 11. The completed shell 48, now includes a pressure
resistant panel 50 surrounded by countersink 98 and a die
curled lip 53 having a hook portion, i.e. an outer curl
edge section of relatively lesser radius of curvature,
suitable for seaming onto a can. The reasons for
formation of the "gull-wing" lip 53 at the first station
10 can now be readily appreciated. By pre-curling the
outer portion of lip 53 to a relatively sharp radiusl
extending to the edge of the shell, the natural tendency
f the outermost edge to resist die curling and remain
relatively straight can be overcome. Moreover, by forming
the less sharply curved portion of lip 53 at the first
station, so as to extend upwardly as well as outwardly
from chuck wall 12, some travel distance is provided for
lip 53 during die curling of the outermost portion. If
lip 53 were to be formed at the first station to extend
from chuck wall 12 at the final desired angle,
satisfactory die curling of the outer edge cannot be
accomplished.
The result of these operations is to produce a
shell which is characteri~ed by its more uniform thickness
throughout its cross section, and by uniformity of the
s~-~
DRT ~03 P2 -19-
spacing between chuck wall 12 and the inner curl diamer,
i.e. the edge of the curled lip 53.
An alternative embodiment for the upper tooling
61 is shown in Fig. 12, wherein the completed shell is
coined about the outer edge of panel 50 adjacent wall ~8
for additional strength. While coining of shells is
typically performed in a separate coining press, the
embodiment of Fig. 12 enables coining to be performed as
part of the forming process, eliminating the need for
separate equipment and a separate process. The central
portion of panel form die 86 is provided with an annular
recess into which a coining ring 97 and a spacer 99 are
placed. Coining ring 37 is in turn secured by retainer
101 which is attached to panel form die 86. Spacer 99 is
selected so that when the tooling is fully closed as shown
in ~ig. 12, the working surface 100 of coining ring 97
contacts the shell 10A and provides sufficient compression
to properly coin the outer edge of panel 50 of shell 10A.
As the tooling bQegins to open, vacuum applied to
the shell 10A through passageway 92 in panel form die 86
raises the shell 10A along with upper tooling 61. Since
vacuum is also applied to shell 10A through panel form
punch 66, to lift the shell 10A from the lower tooling 62,
it is necessary to apply a greater vacuum to the upper
side of shell 10A than that applied to the lower side. In
addition, upward movement of pressure pad 72 by springs 74
aids in initial stripping of shell 10A from lower tooling
62. Once shell panel 50 is away from the working surfaces
of panel form punch 66 and insert 71, venting of the lower
vacuum occuring through additional openings (not shown) in
such working surfaces. This reduces the amount of vacuum
DRT 003 P2 -20-
required on upper tooling 61 to lift the completed shell
48 from lower tooling 62.
After the upper tooling 61 has lifted the shell
10A sufficiently to clear lower tooling 62, upward
movement of form punch and positioner 84 is halted while
upward movement of retainer 80 and panel form die 86
continues. Once these portions clear shell 48 it is
removed from the second station tooling and ejected from
the shell forming apparatus.
While the method and product herein described,
and the form of apparatus for carrying this method into
effect, constitute preferred embodiments of this
invention, it is to be understood that the invention is
not limited to this precise method, product and form of
apparatus, and that changes may be made in either without
departing from the scope of the invention, which is
defined in the appended claims.
