Note: Descriptions are shown in the official language in which they were submitted.
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B~CR~ROUND OF THE INVENTION
This invention relateæ to sanitary cans and more
particularly to sanitary cans whera the bottom wall is
integral with the side wall is distinct from a can body where
the bottom wall is a separate disc which is seamed or ~oined
to the cylindrical side wall. Such cans7 which flnd
application as packages for a variety of food products are
manufactured by a draw/redraw process wherein steel strip is
blanked, drawn and redrawn to fonm a basic container body.
The basic container body ~s then flanged, contoured or
profiled, trimmed and may even have the side wall strengthened
by beading. The instant application is directed to the
contouring or profiling of the integral bottom wall of the
container body to strengthen it and provide a stable
configuration.
A major market for the drawn can is the pet food market
where the can is packed at low vacuum and its conten~s are
sub~ected to severe process1ng conditlons. The can must be
capable of withstanding the internal pressures developed
dur~ng processing and pasteurization to avoid permanent
distortionr That is, any d~stor~ion or bulging which occur3
during the processing must be overcome by the springback or
pullback properties of the can body when the can has cooled.
Permanent distortion is termed buckling. Such a
condition is objectionable because it lnterferes with
container stacklng and even more so because it suggests that
the container contents may be spoiled~ and therefore is
unmarketable.
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Bucklin~ can occur during sPrvice as well as during
processing. For example, cans packaged with pet food at a
West l'oast cannery at sea level, and shipped over the Rocky
Mountains to Denver, Colorado were ound ~o be permanently
distended by the low atmospheric pressure encountered at the
elevated altitudes during shipment.
This cannery has established a specification which called
for the can to resi3t buckling at internal pressures as high
as 25 psi and to have springback retention wherein the can
body returned to its original eonfiguration when the internal
pressures did not exceed 20 psi.
While heavy plate such as 701b. plate will necessarily
afford increased strength and resistance to permanent
distention, such a solution imposes an economic penalty which
must ultimately be borne by the consumer.
Accordingly, it is an ob;ect of this invention to provide
a sanitary can body with an integral bottom wall which affords
a high level of resistance to permanent dlstortion by buckling
and where the springback retention of ~he integral bottom wall
ensure a stable configuration.
It is further an ob~ect of this invention to provide a
sanitary can body wherein the buckle resistance exceeds ~5 psi
and the sprlngback retention exceeds 20 psl.
It is further an ob~ec~ of this invention to provide a
sanitary can body with an integral bottom wall which affords a
high level of buckle and springback retention when
msnufectured of high strength light weight plate.
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12;~4430
It is finally an object of this lnvention to provide a
method for manufacturing sanitary can bodies of light weight
high strength plate which is compatible with conventional
equipment and which ensures a high level of buckle resistance
and springback retention.
SUMMARY QF TH~ I~VENTION
It may be seen that the aforementloned objects of the
inventlon may be attained in a sanitary can body of the type
having a peripheral outer flange at the top end of the can
body, a cylindrical side wall symmetrical about an axis of
rotation and joined to said flange, and a bottom wa~l Integral
with the side wall and wherein the improvement is a profiled
¦ bottom wall comprising a peripheral rim, an annular upwardly
directed coun~ersink groove, an annular outer panel, an
snnular midpanel and an inner panel.
The peripheral bottom rim is ormed with an inwardly
inclined outer rim wall, and an inner rlm wall, with said
inner snd outer rim walls converging to form the root of the
rimO The rim root is substantially tangent to a base plane~
¦which in turn is perpendicular to the axis of rotation. The
linner wall of the rim is substantially perpendlcular to the
base plane.
The annular countersink groove is upwardly directed being
adjacent to and inwardly disposed of the rim, the countersink
groove is formed with a radius of curvature of .050"
culminating at the crest of the groove. The outer groove wall
merges with the inner rim wall.
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The annular outer panel, is disposed inwardly of ~he
countersink groove and concentric theretoO The panel lies iD
a plane parallel ~o the base plane. The plane o the outer
panel lies between the base plane which is tangent to the root
of the rim and a plane tangent to the groove crest. The outer
panel i8 ~oined to the inner wall o~ ~he countersink groov~ by
a fllet or concavity which has a radius of curvature of .035".
The annular midpanel is disposed inwardly of the outer
panel, concentric and parallel thereto and lying on a plane
between the plane of the outer panel and the plane tangent to
the groove crest. The midpanel is joined to the outer panel
by an ogee. The ogee consists of an outer f;let and an inner
convergence each of which have a radius o curvature of .035".
The inner panel is disposed inwardly of the midpanel and
parallel thereto and lies on a plane between the midpanel
plane and the plane tangent to the crest of the groove. The
inner panel is joined to the midpanel by an ogee with an outer
filet and an inner convergence each w~th a radius of curvature
of .035".
The profiled bottom wall ls preferably drawn taut and
placed in tension so that the panels resist permanent
distention.
The sanitary can body is preferably made of TFS-CT
chromium treated tln free steel) which has been double
educed with a DR9 temper and having a plate welght of 60 lbs.
er base box and a plate thickness of .0066~. A sanitary can
anufactured by joining a closure to this sanitary can body
as been found to resist buckling when sub~ected to
4430
internal pressures as high as 30-32 psi. Further9 lt has been
shown that when ~he internal pressure does not exceed 30 psi
the can body will exhibit springback by returning to the
original configuration when the internal pressure is released.
The integral bottom wall of the sanitary can body is
profiled by receiving the unprofiled can body in a cushioned
barrel which has a bore substanti~lly equal in diam~ter to the
external diameter of the finished can body, and whPrein the
flange of the can body is supported by the barrel. The flange
i~ clamped to the barrel. A punch sleeve with an external
diameter subs~antially equal to the internal diameter of the
can is introduced lnto the can body so that the nose of the
punch sleeve engages the peripheral of the bottom wall o the
can body thereby formlng the outer wall of ~he peripheral
bottom rim. The invention will be described as if the
portions of the tooling move independently. This is not
essential to ~he satisfactory performance of ~he invention
since some of the tool can move as a uni~. The cushloned
barrel and the punch ~leeve are advanced carrying forward the
clamped can body and causing the can body to engage a
peripheral bead of a first or lower profile pad thereby
completing formation of the bottom rim and pulling the planar
bo~tom panel tightly across the crest of the peripheral bead.
A second or upper profile pad, coaxially received within the
punch sleeve, is then advanced to engage the ~ight planar
bottom wall between the flrst and second proflle pads thereby
pulling the bottom wall over the peripheral bead to form the
countersink groove and to initiate the forming of the outer
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panel, ~he mldpanel and the inner panel. Further advanclng
the second prufile pad to over6trike the bottom wall and
thereby to fully set and define the countersink groo~e, the
outer panel, the midpanel and the inner panel to tension the
bottom wall and make the panel tau~ and flat. In another
arrangement the upper profile pad and sleeve may move together
as a unit when forming the end profile.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
Figure 1 is an elevatlonal view of a sanitary can body
with an integral bottom wall.
Figure 2 is a plan view of the sanitary can body of
Figure 1.
Figure 3 is an enlarged sectional view of the can body
taken in elevstion along the line 3-3 of Figure 2.
Figure 4 is an enlarged fragmentary cross sectlonal view
through the dies for profiling the bottom wall of the can
body. ThP can body is shown mounted on the puneh ln position
for paneling.
Figure 5 is an enlarged fragmentary cross sect~on view
through the dies for profiling the bottom wall of the can
body. The ~an body is shown advanced by the punch sleeve so
that the bottom wall is pulled tight.
Figure 6 i5 an enlarged fragmentary cross sectional view
through the dies for profillng the bottom wall of the can
body. The bottom wall is shown fully engaged by the upper and
lower profiling pads whereby the panels are pulled taut and
placed in tension.
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DETAILED DESCRIPTION OF T~E ILL~STRATED EMBODIMENT
Turning now in detail to Figures 1 and 2 of the appended
drawings therein lllustrated is a sanitary can body embodying
the present invention and comprising a cylindrical can body
with a side wall an integral bottom, profiled to provide a
stable configuration~ res1stant to buckling and with good
springback retentlon. The can body has an open top wi~h a
peripheral flange to which a can closure may be seamed in a
conventional manner. The can body i9 drawn from chromium
treated tin free steel wh~ch has been double reduced with a
DR9 temper and a 60 lb plate weight. The can body ls employed
for packagin~ low vacuum food products, specifically pet
foods. The can body is a 307 x 112 with a flange diameter 34
equal to 3.500", an internal diameter 36 equal to 3.300" and a
¦ can height 38 of 1.750". Merely by changing the diameter of
the bottom inner panel 58 is is possible to employ the
configuration described to a wide range of can diameters.
The can body 20 has a side wall 26 which is inwardly
inclined toward the base to form a peripheral rim 40 with a
roo~ 41 upon which ~he can body rests~ The can body, which is
symmetrical about axis of rotation 11-11 has a peripheral
flange 22. The bottom wall 24 of the can body is profiled
w~th a countersink groove 46, an outer planar panel 52, a
midplanar panel 55 and an inner or central planar panel 58.
For convenience, a one-quarter section of the can body is
shown in elevation in Figure 3. It should be noted however,
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~hat dimensions 34, 36, 59, 60, 62, 64, 66, 68, 70 and 72 of
Figure 3 are diametrical distances rather than radial
distances from the ll-ll axis.
The peripheral flange 22 of the can bod~ 20 joins the
side wall 26 with a conver~ence having a radlus of curvation
30 of .050". A break in the side wall occurs at 28, .2" above
the plane of the base of the container body to form the
periplleral supportlng rim 40. The outer wall 42 of the rim is
lnwardly inclined to the slde wall 26. The outer wall 42
meets the inner wall 45 at the root of the rim 41, the
location at which the plane of the ba~e of the container body
effectively is tangent to the rim. The outer wall of the rim
is formed with a convergence having a radius of curvature 43
equal to .044", with an origi~ located a distance 78 equal to
.051" above the base plane and on a circle with a diameter 59
equal to 3.128". The inner wall of the rim is formed with a
convergenee having a radius of curvature 44 equal to .OS0"
wlth an origin located a distance 80 equal ~o .057" above the
base plane and lying on a circle with a diameter 60 equal to
3.102". The inner wall of the rim above the convergence is
straight and essentially perpendicular to the base plane.
The countersink groove 46 is formed with a radius of
cur~vature 48 equal to .050" the outer wall 49 of which merges
with the inner rlm wall 50. The inner wall of the groove
meets the outer wall of the groove at the crest of ~he groove
47 which lies a distance 76 equal to .150" above the base
plane, and on a circle with a diameter 62 equal to 2.884l'.
The origin of radius 48 necessarily also lies on a circle with
a diameter 62.
4 ~ 3 ~
A filet with a radius o curvature 58 equal to .035"
merges a planar panel 52 with the inner wall 50 of the
countersink groove. l'he ilet has an origin, a distance 82
equal ~o .115" above the base plane and lying on a ~ircle with
a diameter S4 equal ~o 2.696". The planar panel 52 has a
surface which is parallel to the base plane.
~n ogee comprising a filet with a radius of curvature 53
equal to ~035" and a convergence with ~ radius of curva~ure 54
~ equal to .035" outermerges planar panel 52 with midplanar
panel 55. The origin of radius 53 is a dlstance 82 equal to
.115" above base plane and lies on a circle with a diameter 66
equal to 2.210". The convergence radius 54 has its origin
distance 84 equal to .069" and lies on a circle w~th a
diameter 68 equal to 2.056". Planar panel 55 is parallel to
the base plane.
An ogee comprising a filet with a radius of curvature 56
equal to .035" and a con~ergence with a radius of curvature 57
equal to .035" merges midplanar panel 55 with inner planar
panel 58. The origin of radius 56 is a distance 86 equal to
.143" abo~e the base plane and lies on a circle with a
diameter 70 equal to 1.566". The origin of radius 57 is a
distance 88 equal to .097" above the base plane and lies on a
circle wi~h a diameter 72 equal to 1.413". Inner panel 58 is
parallel to the base plane.
Figures 4 through 6 relate to tool~ng configurations and
their use in manufacturing the aforementioned can body.
The can body is manufactured from precoated tin ree
steel (TFS-CT) plate which has been double reduced. The steel
strip has a DR9 temper with a plate weight of about 60 lbs.
1224~t~3~ 1
per base box. DR9 is a mill product specifica~ion which
relates to the process by whlch the metal is cold reduced ln
two stages with an annealling step between the cold working
operations. The DR9 temper deno~es a plate which is hard and
S which has a high tensile s~rength. The base box terminology
for plate weight ls standard in the can maklng industry; it
originally referred to the amount of steel in a base box of
tin pla~e consisting of 112 sheets of steel each sheet sheared
to 14" X 20". Today the base box refers to the amount of
ste~l in 31360 square incheq whether in the form of coll or
cut sheet.
The preferred method of manufacture employs ~wo presses.
In the first press steel strip is blanked in~o a disc and
subsequently drawn into a shallow cup of large di~meter. In
the second press the shallow cup with a planar bottom is
deposited on the end of a cylindrical barrel whi h has a bore
diameter substantially equal ~o the external diameter of ~he
fin~shed can body. A punch wi~h an external di~meter
substantially equal to the internal diameter of the finished
can body enters the supported cup and pulls the cup down
between the outer wall of the punch and the inner wall or bore
of the barrel thereby redrawing the shallow cup lnto ~ can
body of reduced ~iameter and increased height. At thls point
the bottom wall of the can body is still planar. Where the
lnished height of ~he can body is substantially ~reater than
he cup height, it may be necessary to employ two redraw
perations. This may be done by employing a single
-10-
1~4~3~) ~
multi station press as described in U.S Patent 4,262,510 or
alternatlvely a series of presses may be employed with the
proiling and flanging l~mited to the last press.
In accordance wlth the present inventlon the can body 20
is shown in Figure 4 after redrawing and in preparation for
bo~tom profiling~ As shown in Figure 4, the bottom wall at
this point is still of planar configuration, the flange 22 is
formed and is captured between the top wall of the barrel 93
and ~ clamplng ring gO. It should be noted that the barrel is
cushioned by suitable means, typically with a pneumatic
cushion. The side wall 26 of the container body is shown
captured between the cylindrical barrel 93 and the sleeve 92
o~ the punch. The nose 98 of the punch at this point has
engaged the bottom wall of the can body there by forming the
outer wall 42 o the peripheral rim of the container bottom.
The container is carried down by the advancing punch and
barrel which operate ln cooperation. The upper profile pad 94
is shown in a retracted positlon.
The lower profile pad 96 is proximate to the advancing
can body and tooling but has not at this point bePn engaged
thereby~ 99 is a lif~ ou~ and clamp~ng device which ~s shown
in a retracted positlon.
In Figure 5 the advancing punch and barrel have carried
the can body forwArd to engage the peripheral bead 108 of the
lower profile pad 96 thereby completing formation of the
bot~om rim of the can body and pulling the planar bottom
43~il
tightly across the crest 109 of the bead. The root 41 of the
rim is shown lying between the outer rim wall 42 and ~he inner
rim wall 45, and in contact with the upper surface of the lift
out 99.
In Figure ~ the upper profile psd 94 which is coaxlally
received within the pu~ch sleeve 92 is advanced to engage the
tight planar bottom wall 23 thereby pulling the bottom wall
over the crest of the perlpheral bead 108 to ~orm the
countersink groove and ~o initiate the forming of an outer
panel 52, a mid~anel 55 and an Inner panel 58. The advance of
the punch is further increased to effect an overstriking of
the bottom wall by introducing a shim 102 between the die
block lO0 and the lower profile pad 96. This shim effects a
.020" overstrike to accentuate the profile panels, place the
panels ln tenæion and ma~e them tau~.
In Figure 6, the upper profile pads are tightly radlused
to further assist in tensioning the panels of the bottom wall,
thus, the peripheral bead of the lower profile pad 96 is
formed with a radius of curvature .050" to form the outer bead
wall 110, and the inner bead wall lll, with the outer and
inner walls meeting at the crest of the bead lO9. The upper
panel plate 115 is formed with corner radii 112 and 113 equal
to .035"~ The plate walls 116 and 117 are substantially
parallel to the axis of rotstion 11-ll and there~ore
2~ substantially perpendicular to the planar face of 115. The
lower panel bead ring is formed with a radius of curvation 114
equal to .035" and perpendlcular side walls 121 and 122. The
~ 3 O
upper paneling bead ring i8 similarly formed with a radius of
curvature 118 equal to .035" and with perpendicular side walls
119 and 120. The lower paneling plate which forms profile
panel 58 i8 formed with 8 corner radiu~ 124 equal to .035" and
with a perpendicular slde wall.
The clearance be~ween perpendicular tooling surfaces 117
and 121 and between surfaces 120 and 123 is equal to the stock
thickness plus abou~ .0005" whereas the clearance between the
inner wall o the perlpheral bead defined by radlus 108 and
perpendicular wall 116 is about .0025".
The radial displacement between the origins of radius 113
and radius 118 i8 .322". The radical dlsplacement between the
origins of radius 114 an~ 124 is .322".
Sanitary can bodies produced according to this method
from TFS-CT steel double reduced to a DR9 temper, with a plate
weight of only 60 lbs. per base box, have consistently
resisted internal pressures of 30-32 psi wlthou~ exhibiting
buckling or permanent distortion. Further; these can bodies
have shown good springback retention where the internal
pressure has not exceeded 30 psi~ These capabillties enable
the sontainer to meet the customersl requirements of 25 psl
buckle resistance and 20 psi springback retention with light
weight plate despite the normal variations which may be
encountered under production conditions.
Thus, it may be seen that the instant novel method has
produced a high strength can body from light weight plate.
The can body has a high level of buckle resistance, good
springback retentlon and may be manufactured with tooling
~L2~44~0
whlch is compatible with conventional apparatus.
While this invention has been described in relation to a
307 X 112 sanitary can for pet food it has been successfully
employed for a variety of sanitary type cans including 300 X
405, 300 X408 3/4~ 301 X 106 and 307 X 200.25.
While ~he detailed disclosure and the drawings show and
explain the upper profile pad 94 and the sleeve 92 as moving
independently with respect to one another, that technique is
used primarlly for clarity in connection with the explanation
of the invention herein. Those skilled in the art will no
doubt appreciate that the movement of the upper profile pad 94
and the sleeve 92 can be simultaneous in order to facilitate
the simplicity of the tooling design and construction.
Likewise, other changes and modifications to the dimensions,
shapes and structures can be included without departing from
the overall concept set forth in the claims of this disclosure.
