U.S. patent application number 11/975926 was filed with the patent office on 2009-04-23 for method and apparatus for producing untrimmed container bodies.
Invention is credited to Dubravko Nardini.
Application Number | 20090100892 11/975926 |
Document ID | / |
Family ID | 40562097 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090100892 |
Kind Code |
A1 |
Nardini; Dubravko |
April 23, 2009 |
Method and apparatus for producing untrimmed container bodies
Abstract
Exemplary embodiments of the invention relate to an apparatus
and method for producing untrimmed container bodies from pre-cut
metal blanks. The method involves cupping a pre-cut metal blank by
positioning the blank against an immovable draw punch comprising an
annular body having an inner surface adapted to form a redraw die
and an outer surface, and drawing a periphery of the blank over the
outer surface of the draw punch with an encircling draw die to form
a cup having an open end, a closed end and an interior. The cup is
then inverted and redrawn by forcing a redraw punch into the closed
end of the cup to draw the closed end through the redraw die until
the cup is inverted to form an inverted cup with a closed end
supported on the punch. The inverted cup while supported on the
redraw punch is passed through one or more ironing rings to
lengthen the inverted cup to form an untrimmed container body
having a closed end. The closed end of the untrimmed container body
is shaped by engaging the closed end of the untrimmed container
body with one or more end shaping tools while supported on the
redraw punch. The apparatus comprises tools, actuators and a solid
support structure adapted to carry out the method.
Inventors: |
Nardini; Dubravko; (Oxford,
GB) |
Correspondence
Address: |
Christopher C. Dunham;c/o Cooper & Dunham LLP,
1185 Ave. of the Americas,
New York
NY
10036
US
|
Family ID: |
40562097 |
Appl. No.: |
11/975926 |
Filed: |
October 22, 2007 |
Current U.S.
Class: |
72/347 |
Current CPC
Class: |
B21D 22/24 20130101;
B21D 22/28 20130101 |
Class at
Publication: |
72/347 |
International
Class: |
B21D 22/00 20060101
B21D022/00 |
Claims
1. Apparatus for making an untrimmed container body from a pre-cut
metal blank, comprising: shaping tools and actuators for operating
said tools with sufficient force for shaping said blank into an
untrimmed container body; and a support structure for supporting
said shaping tools and actuators while allowing necessary movements
of some of said tools; wherein said shaping tools include: a
combined draw punch and redraw die comprising an annular body
having an inner surface, an outer surface and an end surface
defining an opening at an operational end of the annular body that
initially contacts said blank, said end surface and said outer
surface together functioning in use as said draw punch, and said
inner surface functioning in use as said redraw die, said annular
body being fixed on said structure against movement relative
thereto during use; a draw die having a die surface dimensioned to
encircle said outer surface of said annular body at a spacing
effective for cupping of said blank, said draw die being movable in
use along said outer surface from said operational end to form a
cup from said blank; a redraw punch comprising a cylinder having an
outer surface dimensioned to penetrate said opening at said
operational end of said annular body with a spacing from said inner
surface effective for redrawing said cup, said redraw punch being
movable at a leading end thereof into said opening and through said
annular body to invert said cup to thereby form an inverted redrawn
cup having an open end and a closed end; one or more ironing rings
aligned with said annular body and positioned to iron an outer
surface of said inverted redrawn cup supported on said leading end
of said redraw punch after said leading end passes through and
emerges from said annular body, to thereby lengthen said inverted
redrawn cup to form an untrimmed container body having a closed
end; and a container body end shaper positioned in spaced alignment
with said one or more ironing rings to contact said closed end of
said untrimmed container body supported on said operational end of
said redraw punch, said shaper being profiled to shape said closed
end when said closed end is forced thereagainst by said redraw
punch.
2. The apparatus of claim 1, wherein said tools further include an
annular draw holder confronting said annular draw die and adapted
to grip a periphery of said blank between said annular draw holder
and said annular draw die with a force that allows said periphery
to be withdrawn and guided during drawing of said blank.
3. The apparatus of claim 1, wherein said tools further include an
annular redraw holder confronting said operational end of said
combined draw punch and redraw die and adapted to grip an outer
part of said cup between said holder and said combined draw punch
and redraw die with a force that allows said outer part to be
withdrawn and guided during redrawing of said cup.
4. The apparatus of claim 3, wherein said annular redraw holder has
an inner surface that contacts and provides lateral support for
said outer surface of said redraw punch.
5. The apparatus of claim 1, wherein said end shaper is spaced from
said one or more ironing rings by a distance that provides only
minimal clearance between said untrimmed container body and said
one or more ironing rings when said redraw punch is extended fully
thereagainst.
6. The apparatus of claim 1, having two or more of said ironing
rings, said two or more ironing rings being positioned next to each
other with minimal spacing therebetween.
7. The apparatus of claim 1, wherein said redraw punch passes
through an aperture in said support structure and is supported at
and driven from an end opposite to said operational end.
8. The apparatus of claim 7, wherein said redraw punch has a length
no greater than a distance between said aperture and said container
body end shaper.
9. Apparatus for making untrimmed container bodies from pre-cut
metal blanks, comprising: shaping equipment for said blanks
comprising tools, including a draw die, a combined draw punch and
redraw die, a draw holder, a redraw punch, a redraw holder, one or
more ironing rings, a container body bottom domer and an outer
retainer ring, as well as actuators for moving tools with
sufficient force for shaping said blanks into container bodies; a
structure for supporting said shaping equipment while allowing
movement of some of said tools necessary for making said container
bodies; wherein: said combined draw punch and redraw die comprise a
single annular body having an inner surface, an outer surface and
an end surface at an open operational end of the annular body that
initially contacts said blanks, said end surface and said outer
surface together functioning in use as said draw punch, and said
inner surface functioning in use as said redraw die, said annular
body being fixed on said structure against movement relative
thereto during use; said draw die has a die surface dimensioned to
encircle said outer surface of the annular body at a spacing
effective for cupping of said blanks, said draw die being movable
in use along said outer surface to form cups from said blanks; said
redraw punch comprises a cylinder having an outer surface
dimensioned to penetrate said open operational end of said annular
body at a spacing from said inner surface effective for redrawing
said cups, said redraw punch being movable at a leading end thereof
into said open operational end and through said annular body to
invert said cups as they are redrawn to thereby form inverted
redrawn cups having open ends and closed ends; said container body
end domer and outer retainer ring are positioned in spaced
alignment with said annular body to contact said closed ends of
said inverted redrawn cups supported on said leading end of said
redraw punch, and to shape said closed ends when forced
thereagainst by said redraw punch; and said one or more ironing
rings are positioned between said annular body and said bottom
domer and are aligned effectively to iron outer surfaces of said
inverted redrawn cups supported on said operational end of said
redraw punch as said punch moves toward said bottom domer, to
thereby lengthen said inverted redrawn cups and form untrimmed
container bodies.
10. A method of making an untrimmed container body from a pre-cut
metal blank, comprising: cupping a pre-cut metal blank by
positioning the blank against an immovable draw punch comprising an
annular body having an inner surface adapted to form a redraw die
and an outer surface, and drawing a periphery of the blank over
said outer surface of the draw punch with an encircling draw die to
form a cup having an open end, a closed end and an interior;
inverting and redrawing said cup by forcing a redraw punch into
said closed end to draw said closed end through said redraw die
until said cup is inverted to form an inverted cup supported on
said punch, said inverted cup having a closed end; passing the
inverted cup while supported on said redraw punch through one or
more ironing rings to lengthen said inverted cup to form an
untrimmed container body having a closed end; shaping said closed
end of said untrimmed container body by engaging said closed end of
said untrimmed container body with one or more end shaping tools
while supported on said redraw punch; and withdrawing said punch
from said untrimmed container body.
11. The method of claim 10, wherein said closed end of said
untrimmed container body is shaped by engaging said closed end with
a domer shaped to form an inwardly-extending dome at said closed
end, and a support ring to conform a periphery of said closed end
to a profile of said redraw punch at a leading end thereof.
12. The method of claim 10, wherein said annular body, said ironing
rings and said end shaping tools are positioned relative to each
other to minimize distance required to be traveled by said redraw
punch when forming said untrimmed container body from said cup.
Description
BACKGROUND OF THE INVENTION
[0001] I. Field of the Invention
[0002] This invention relates to the production of container bodies
made of metal. More particularly, the invention relates to
apparatus and methods for forming untrimmed beverage container
(can) bodies, particularly such bodies made of aluminum and
aluminum alloys. Untrimmed bodies of this kind as subsequently
trimmed and provided with a container end closure to create a
competed container.
[0003] II. Background Art
[0004] Beverage container bodies are generally produced in two
forming steps carried out in different machines. The first step
involves cutting a flat circular blank from a sheet of metal and
creating a shallow cup from the blank in a drawing operation. The
second step involves reducing the cup diameter and thinning and
elongating the sides of the cup to produce a full-length container
body by redrawing and ironing operations. Ironing involves passing
the redrawn cup (supported on a punch, mandrel or the like) through
a number of dies or rings of progressively smaller diameter to thin
and stretch the sidewalls of the container body. The container body
is then normally trimmed and shaped at the open end and provided
with a closure in the form of a generally flat can lid. The metal
for the container bodies is normally supplied to the fabricator in
the form of a metal coil or roll and the fabricator stamps circular
flat metal pieces or blanks from the metal roll as part of the
overall container body forming operation. This produces a
significant amount of metal waste in the form of a flat web with
punched-out circular holes. The metal waste is normally returned to
the metal supplier for recycling, but this is an inefficient
procedure because it involves transporting a certain percentage of
metal first to the fabricator and then from the fabricator back to
the metal supplier. In circumstances where the metal fabricator and
can body producer are located in different countries, some
governments apply taxes or duties on both metal sheet imports and
scrap metal exports, thus further reducing the economic benefit of
supplying the metal in the form of continuous sheet.
[0005] In addition, the indicated two-step procedure is not fully
efficient because an intermediate product (a shaped cup) is created
in one kind of apparatus and is then transferred to a second kind
of apparatus (a redraw and ironing machine) for the second stage of
the process. This can result in significant wastage of both time,
factory floor space and invested capital. Moreover, the redraw and
ironing operations often cannot produce container bodies of
consistent thickness and unwrinkled appearance because there is
often an unwanted degree of play between the punch, die and ironing
elements that creates non-uniformity in production. This play is
often produced because the redraw die operates under considerable
force and the operational end is necessarily positioned at quite a
distance from the driven end where the punch is held and receives
its driving force (e.g. from a hydraulic piston). Consequently, a
degree of flexing of the punch may take place that results in play
at the operational end.
[0006] Attempts have been made in the past to overcome some or all
of these disadvantages, but problems still persist.
[0007] For example, U.S. Pat. No. 3,167,044 granted on Jan. 26,
1965 to Henrickson discloses a process in which flat round metal
blanks or work pieces are pre-formed and then fed into can
body-forming apparatus. The can body is then produced by a single
drawing step, followed by ironing stages and a bottom-forming step.
Accordingly, the procedure still requires a multi-stage operation,
even though the use of round metal blanks may reduce metal waste
generated during the forming process.
[0008] U.S. Pat. No. 3,733,881 granted on May 22, 1973 to Donald C.
Grigorenko discloses apparatus that drawing, reverse redrawing, and
ironing steps carried out essentially in a single operation. In
this case, however, round metal blanks are punched out of a
continuous strip of metal as a first step. Additionally, the
apparatus is arranged such that the various moving components may
encounter a high degree of play, therefore resulting in a lack of
uniformity in the can bodies thus produced, or even a degree of
metal wrinkling or seaming during the drawing and ironing
procedures.
[0009] U.S. Pat. No. 4,732,031 granted on Mar. 22, 1988 to Bulso,
Jr. et al. discloses apparatus which creates a can body by a
drawing, reverse redrawing and ironing operations. However, the
ironing operation is carried out in a different machine than the
drawing and reverse redrawing operations.
[0010] There is therefore a need for an improved beverage container
forming method and apparatus that overcomes at least some of the
disadvantages mentioned above.
SUMMARY OF THE INVENTION
[0011] An exemplary embodiment provides apparatus for making an
untrimmed container body from a pre-cut metal blank. The apparatus
includes shaping tools and actuators for operating the tools with
sufficient force for shaping the blank into an untrimmed container
body, and a support structure for supporting the shaping tools and
actuators while allowing necessary movements of some of the tools.
The support structure, which may be made of steel, cast-iron,
aluminum or other metal or strong material, is preferably
sufficiently strong to resist flexing when subjected to the forces
required for container production, and preferably provides a rigid
support so that various tools can be held without movement, flexing
or play as the container is formed.
[0012] The shaping tools include a combined draw punch and redraw
die having an annular body including an inner surface, an outer
surface and an end surface at an operational end of the annular
body that initially contacts the blank. The end surface and the
outer surface together function in use as a draw punch, and the
inner surface (at least immediately adjacent to the end surface)
functions in use as a redraw die. The annular body is fixed
(preferably rigidly) on the support structure against movement
relative thereto during use. Despite its lack of movement relative
to the support structure, the annular body may function as a draw
punch because it cooperates with a movable draw die that shapes the
blank on the draw punch. The draw die preferably contacts the
surface of the blank opposite to the surface contacting the draw
punch and has a die surface dimensioned to encircle the outer
surface of the annular body of the draw punch with a spacing
effective for cupping of the blank therebetween. The draw die is
movable in use along the outer surface of the annular body from the
operational end towards an open opposite end, thus forming a cup
from the blank.
[0013] The tools further include a redraw punch comprising a
cylinder having an outer surface dimensioned to penetrate the
operational end of the annular body at a spacing from the inner
surface thereof effective for redrawing the cup. The redraw punch
is thus movable at its leading end into the open end of the annular
body to invert the cup to thereby form an inverted redrawn cup
having an open end and a closed end supported on the redraw punch.
One or more ironing rings are positioned adjacent to the open
opposite end of the annular body and are aligned with the annular
body, thus being positioned to iron an outer surface of the
inverted redrawn cup supported on the leading end of the redraw
punch after the leading end emerges from the open end of the
annular body, to thereby lengthen the sides of the inverted redrawn
cup to form an untrimmed container body having a closed end.
[0014] The tools also preferably include a container body end
shaper positioned in spaced alignment with the one or more ironing
rings to contact the closed end of the untrimmed container body
supported on the leading end of the redraw punch, the shaper being
profiled to shape the closed end when the closed end is forced
thereagainst by the redraw punch.
[0015] The apparatus preferably includes a holding or gripping
device for gripping the untrimmed container body as the redraw
punch is withdrawn from it, and a device for removing the
thus-liberated untrimmed container body from the apparatus for
further processing.
[0016] By commencing the forming operation from a pre-cut flat
metal blank, the distance between the leading end of the redraw
punch and the operational end of the annular body of the combined
draw punch and redraw die can be kept small (just wide enough to
receive a flat metal blank fed in from one side). This means that
the supporting structure and the redraw punch can be made shorter
that would be the case if a pre-formed drawn cup were used as a
starting point. A shorter supporting structure and, particularly, a
shorter redraw punch means that the apparatus is less likely to
encounter flexing and play under the forces required for the
forming operations, thus producing more regular container bodies.
The need for a separate cupping apparatus is also avoided because
initial cupping is integrated as part of the operation.
Furthermore, by commencing from a pre-cut metal blank rather than a
flat metal sheet, the operator of the apparatus may be supplied
with blanks pre-cut at or near the fabricator of metal sheet, thus
avoiding the need to transport waste metal over large distances and
across country borders.
[0017] The tools of the above apparatus may further include an
annular draw holder confronting the annular draw die and adapted to
grip a periphery of the blank between the annular draw holder and
the annular draw die with a force that allows the periphery to be
withdrawn and guided during drawing of said blank. As the blank is
drawn into a shallow cup, the annular draw holder keeps the
periphery of the blank in contact with the annular draw die, but
nevertheless allows the perhiphery to be pulled out of such contact
as the walls of the cup being formed. The force applied to the draw
holder may be applied by means of a spring or other means, such as
a hydraulic or pneumatic piston and cylinder arrangement.
[0018] The tools of the apparatus also preferably include an
annular redraw holder confronting the operational end of the
combined draw punch and redraw die. This is adapted to grip an
outer part of the initially-formed cup between the holder and the
operational end of the combined draw punch and redraw die with a
force that keeps the outer part to be held against the operational
end but allows the outer part to be withdrawn and guided during
redrawing of the cup. The annular redraw holder may also have an
inner annular surface dimensioned to surround and support the outer
surface redraw punch, thus assisting with the minimization of
flexing of the leading end of the redraw punch by providing lateral
support as the redraw punch performs the redraw operation. For
similar reasons, the redraw punch may pass through a narrow
aperture in the supporting structure, the sides of which provides
guidance and support for the redraw punch as it carries out the
redraw and ironing operations. The redraw punch passes through the
aperture and is supported at and driven from an end opposite to the
operational end of the redraw punch. The redraw punch preferably
has a length no greater than the distance between the aperture and
the end shaper of the container body.
[0019] In order to allow further minimization of the length of the
redraw punch, the end shaper may be spaced from an end one of the
one or more ironing rings by a distance that provides only minimal
clearance between the open end of the untrimmed container body thus
formed and the end one of the ironing rings when the redraw punch
is extended fully. Similarly, the ironing rings, when there is more
than one, are preferably positioned as close as possible together
and to the open end of the annular body. There is therefore minimal
spacing between these elements. The apparatus of claim 1, wherein
said redraw punch passes through an aperture in said support
structure and is supported at and driven from an end opposite to
said operational end.
[0020] Another exemplary embodiment of the invention provides a
method of making an untrimmed container body from a pre-cut metal
blank. The method involves cupping a pre-cut metal blank by
positioning the blank against an immovable draw punch comprising an
annular body having an outer surface and an inner surface adapted
to form a redraw die, and drawing a periphery of the blank over the
outer surface of the draw punch with an encircling draw die to form
a cup having an open end, a closed end and an interior. The cup is
then inverted and redrawn by forcing a redraw punch into the closed
end of the cup to draw the closed end through the redraw die until
the cup is inverted to form an inverted cup with a closed end
supported on the punch. The inverted cup while supported on the
redraw punch is then passed through one or more ironing rings to
lengthen the inverted cup to form an untrimmed container body
having a closed end. The closed end of the untrimmed container body
is then shaped by engaging the closed end of the untrimmed
container body with one or more end shaping tools while supported
on the redraw punch. Finally, the redraw punch is removed from the
untrimmed container body.
[0021] The initial cup is drawn in a direction away from the redraw
punch that contacts the closed end of the cup, i.e. such that the
open end faces away from the redraw punch. Consequently, the redraw
punch cause the initial cup to be inverted as it is redrawn. That
is to say, after the redraw operation, the redraw punch passes
through the open end of the inverted redrawn cup and supports the
inverted redrawn from the interior. The draw punch and redraw die
is preferably held immobile by fixing it rigidly to a supporting
structure. At the start of the method, the leading end of the
redraw punch is preferably positioned close to the operational end
of the combined draw punch and redraw die with just enough
clearance to allow a pre-cut metal blank to be positioned
therebetween when introduced laterally between these elements.
[0022] The apparatus and method are preferably arranged in such a
way that the drawing and ironing operations can be carried out with
a minimum amount of play in the apparatus such that uniformity of
the container bodies, such as uniform wall thickness, can be
ensured. All of the initial cupping, the redraw, ironing and end
shaping are carried out in a single apparatus and the redraw punch
requires only a single punch stroke to achieve the necessary
redraw, ironing and end shaping steps.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGS. 1 to 7 are simplified schematic representations of an
exemplary apparatus showing various stages in the formation of an
untrimmed container body from a flat metal blank;
[0024] FIGS. 8A and 8B are representations showing apparatus
according to an exemplary embodiment of the invention (FIG. 8A),
and a modification of such an embodiment intended to commence a
forming operation from a pre-drawn cup (FIG. 8B), to illustrate a
preferred advantage of the exemplary embodiments; and
[0025] FIGS. 9A and 9B are photographs of container bodies at
various stages of production from metal blanks, FIG. 9A showing
stages in a conventional method and FIG. 9B showing stages in a
method according to exemplary embodiments herein.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0026] The present invention makes it possible, at least in
preferred forms, to fabricate an untrimmed beverage container body
in a single apparatus using a minimum number of steps and with good
precision, preferably commencing from a round flat metal blank
(sized to form an individual can body without significant waste)
rather than from a flat or rolled sheet of metal.
[0027] FIGS. 1 to 7 of the accompanying drawings illustrate various
steps in a method according to one exemplary embodiment of the
invention. In these views, the apparatus is shown in a simplified
form for ease of illustration and description. It will, however, be
appreciated to a person skilled in the art that a significant
amount of ancillary apparatus and accompanying drive equipment will
be required in order to produce a functional apparatus. Preferably,
the moving parts of the apparatus are driven by pneumatic or
hydraulic equipment, or possibly by mechanical means (e.g.
screw-threaded collars mounted on rotated threaded rods, or the
like). This kind of supporting and additional equipment is
illustrated in U.S. Pat. No. 3,733,881 mentioned above (the
disclosure of which is incorporated herein by reference).
[0028] As shown in FIG. 1, a round flat metal blank 10 (which is
preferably pre-cut from a metal sheet at another location) is
positioned in the apparatus with its periphery aligned between an
annular draw holder 11 and a confronting annular draw die 12. The
metal blank may be introduced into the apparatus horizontally from
one side (e.g. the front or rear in the orientation shown in the
drawing). Inwardly of the tools 11 and 12, the metal blank 10 is
also positioned between a combined draw punch & redraw die 13
and a confronting annular redraw holder 14. Still further inwardly,
the blank 10 is aligned with a cylindrical redraw punch 15 having a
profiled tip 16 at a leading end 17 thereof. The combined draw
punch & redraw die 13 is rigidly mounted on a supporting
structure 18 so that it is supported by and immovable relative to
the structure. This ensures that the combined punch & redraw
die 13 is subjected to no, or only minimal, movement, flexing and
play during the various forming steps. The other elements just
mentioned are movable, as will be explained later.
[0029] The apparatus shown in FIG. 1 also includes a set of
immovable ironing rings 20 of progressively smaller inner diameter
in the downward direction of the drawing, an annular outer
retaining ring 21, and a container bottom domer 22. Together, the
ring 21 and domer 22 form a shaping tool, or end shaper, for the
closed end of the untrimmed container body formed in the earlier
steps. These various parts form the principal shaping tools of the
apparatus and are mounted on the supporting structure for operation
in the manner shown in the subsequent figures. The redraw punch 15
is held at its upper end (not shown) opposite to the leading end 17
and is moved in an upward or downward direction by a hydraulic
piston/cylinder device, or an equivalent actuator (not shown). The
domer 22 is fixed in place on the supporting structure 18 and is
immovable during the various operations but the retaining ring 21
is movable. Various load-producing elements 23A, 23B, 23C
represented as coil springs in the drawings provide controlled
forces and pressures on the workpiece during the forming operation.
These elements (or at least some of them) may actually be springs,
but more typically are pneumatic or hydraulic piston/cylinder
combinations used to apply loading during the various operations of
the embodiments.
[0030] During the initial drawing operation, annular draw die 12 is
driven with considerable force by a drive element (not shown), e.g.
a hydraulic pistion/cylinder combination. The redraw holder 14 is
also driven by an actuator (not shown) so that it may be raised
against the force of element 23A to allow the flat metal blank 10
to be inserted into the apparatus. Thereafter, the holder 14 may be
allowed to descend onto the surface of the blank.
[0031] It will be noted that the combined draw punch & redraw
die 13 is in the form of a single annular body 25 having an inner
surface 26, an outer surface 27 and an end surface 28 at an
operational (upper) end 29 of the tool. As will be more apparent
from the subsequent description, the end surface 28 and the outer
surface 27 co-operate to form a draw punch, and the inner surface
26, at least at its upper end that has a smaller diameter than the
remainder, forms a redraw die.
[0032] FIG. 2 shows the blank 10 clamped firmly between the draw
holder 11, draw die 12, the combined draw punch & redraw die 13
and the redraw holder 14 at the start of the shaping operation. The
clamping is effected by downward movement of the elements 12 and 14
from the positions shown in FIG. 1. It will be noticed from FIGS. 1
and 2 that the redraw holder 11 has a slight recess at its inner
end that exactly matches the outer diameter of the blank 10. This
facilitates the proper alignment of the blank in the apparatus.
[0033] FIG. 3 represents an intermediate stage of a first or
initial step of the shaping operation in which the draw die 12 is
moved downwardly with considerable force from an actuator (not
shown). The draw holder 11, presses the periphery of the blank
against the surface of the draw die 12 under the action of the
element 27. The draw die 12 has an inner surface 30 shaped and
dimensioned to encircle the outer surface 27 with a spacing
effective for cupping the blank 10. The draw die 12 moves along the
outer surface 27 of the combined draw punch and redraw die 13 and
commences to draw the periphery of the blank 10 into the shape of
cup, forming a sidewall 31 from the blank 10. As the initial
cupping operation proceeds, the periphery of the blank is
progressively drawn out of the cooperative gripping engagement
between the draw die 12 and the draw holder 11. The completion of
this operation is shown in FIG. 4 in which the metal blank 10 has
been drawn into a shallow-sided initial cup 10A having an open end
facing down (away from the redraw punch 15).
[0034] The next step of the method is shown in FIG. 5 in which the
redraw punch 15 is forced (as shown by the arrow) into the bottom
32 of the initial cup 10A of FIG. 4 to penetrate the open
operational end 29 of the annular body 25, thus initiating a redraw
operation to produce a redrawn cup 10B of smaller diameter than the
initially drawn cup 10A. As this operation proceeds, the periphery
of the initially drawn cup 10A is gradually pulled between the
cooperating surfaces of the redraw holder 14 and the combined draw
punch & redraw die 13. The redraw punch 15 has an outer surface
35 that is of smaller diameter than that of the inner surface 26 of
the combined punch and redraw die 13 by a dimension similar to the
metal thickness effective for the illustrated redrawing and
inversion step. As already noted, the inner surface 26 adjacent to
the operational end surface 28 may be of slightly smaller diameter
than at positions further along the annular body 25 (as shown) to
avoid undue friction between the inverting cup and the annular body
25 as the operation proceeds.
[0035] Referring to FIG. 6, as the redraw punch 15 is moved
downwardly even further and passes through the open opposite
(lower) end of the annular body 25. The inverted redrawn cup 10B is
supported on the leading end 17 of the punch 15 and it is caused to
pass through the series of progressively narrower ironing rings 20,
thereby elongating and thinning the sidewalls 31B of redrawn cup
10B to form an elongated container body 10C. The operational
surfaces of the ironing rings may be fed with a suitable lubricant
during the ironing stage of the operation, e.g. from suitable
conduits or glands (not shown).
[0036] As shown in FIG. 7, at the end of the downward stroke of the
redraw punch 15, the bottom 32B of the container body 10C is shaped
between the profiled cooperating elements of the tips 16 of the
redraw punch 15 at its leading end 17, the bottom domer 22 and the
outer retaining ring 21 (which is yieldably supported by the
element 23C, preferably a spring, and is free to move under the
force of the redraw punch 15 towards the domer 22 to a final
position as shown in FIG. 7). The deformation of the metal thereby
produced provides the container body 10C with a shaped bottom end.
The profile thereby imparted is effective to provide the container
with greater rigidity and to make it better able to resist outward
forces produced by liquids under pressure (e.g. carbonated
beverages) eventually held within the container.
[0037] The shaped but untrimmed container body thus formed may then
be removed from the apparatus by conventional removal equipment
(not shown) after the redraw punch 15 has been raised and withdrawn
from the container body. For example, the apparatus may be provided
with a gripping or holding device that holds the container body as
the redraw punch 15 is withdrawn upwardly, and the same device or
another may remove the untrimmed container body, thus liberated,
from the apparatus.
[0038] The container body may then be subjected to a conventional
trimming operation at the open end to provide the container body
with a desired length, and then a necking operation (shaping of the
open end of the container), coating and/or decorating steps,
pre-filling (if appropriate) and closure (incorporation of a
generally flat lid element at the open end of the container body to
produce a complete container). These steps are carried out in other
apparatus and are conventional, and thus not illustrated.
[0039] As noted earlier, the combined draw punch and redraw die 13
is held fixed and immovable throughout all of the illustrated steps
of the method by virtue of being rigidly mounted on the supporting
structure 18 of the apparatus. In addition, the redraw punch 15 may
be kept relatively short because the redraw starts from an inverted
cup configuration. As the redraw punch is normally supported at its
upper end, e.g. by a rod extending from a piston and cylinder
device (not shown), the shorter the punch, the less it will be
subject to sideways movement and play at the tip 16. Thus, not only
is a complete untrimmed container body created in a single
apparatus, but the apparatus may be made desirably rigid at those
parts subject to the greatest forces during the various operations,
thereby ensuring uniformity of the resulting container bodies (wall
thickness and lack of wrinkling and seeming). It is estimated that
the stroke length of the redraw punch may be 5-30%, more normally
5-20%, less than that required for conventional apparatus that
commences with a pre-formed cup. For example, a standard 22 inch
punch stroke required for a conventional apparatus can be reduced
to 18 or 19 inches in equivalent apparatus according to the
exemplary embodiments. This effect is illustrated by FIGS. 8A and
8B. FIG. 8A shows an apparatus equivalent to that of FIG. 1. FIG.
8B illustrates a modification of the apparatus of FIG. 8A intended
to commence a forming operation using a pre-drawn cup 100 rather
than a pre-cut flat blank 10. To accommodate insertion of the cup
100 into the apparatus, not only does the supporting structure 18
have to be made longer, but also the punch 15 has to be made longer
by an amount X (the height of the initial cup). This would increase
the likelihood of uncontrolled play and flexing during the forming
operation.
[0040] Other measures may be taken to keep the length of the redraw
punch 15 as short as possible. For example, the ironing rings 20
may be placed closely together, and the domer 22 may be positioned
as close as possible to the ironing rings, leaving only sufficient
clearance to allow the untrimmed container body 10C to be removed
from the apparatus.
[0041] It will also be noted that the redraw punch 15 is supported
somewhat against lateral flexing by the inner surface of the redraw
holder 14, which closely surrounds the outer surface of the punch,
and further support for the punch may be provided by the narrow
aperture 40 in the supporting structure 18 through which the punch
extends.
[0042] FIG. 9A is a photograph showing a container body at various
stages of formation according to a previous shaping method, and
FIG. 9B shows a container body at equivalent stages of preparation
according to the shaping method described above in connection with
FIGS. 1 to 7. It is to be noted that, in FIG. 9A, the cup shown on
the extreme left hand side is in an upturned position compared to
the other stages shown in the photograph, i.e. in the forming
operation, the cup would start with the open end facing up in order
to form the other intermediate stages shown to its right. This
initial cup is formed in other equipment. In FIG. 9B, the initial
cup on the left is shown in the correct orientation, and is formed
during a first stage of the method in the apparatus shown. The
inversion of the cup caused by the redraw operation is clearly
apparent.
[0043] It is found in at least some exemplary embodiments that the
draw and redraw steps may be carried out as quickly as just the
draw operation of a conventional container body fabrication
apparatus. This is because of the shorter travel of the redraw
punch 15 (by an amount equivalent to the height of the cup).
[0044] The apparatus of the exemplary embodiments may preferably
operate at a throughput speed of 200-700, more preferably, 400-500
containers per minute. Normally, the diameter of the pre-formed
metal blank is preferably within the range of 3-24 inches (7.6-61
cm), more preferably 3-12 inches (7.6 to 30.5 cm), more even more
preferably 4.5-8 inches (11.4 to 20.3 cm). The initial metal gauge
of the blanks is preferably 0.007-0.08 inches (0.178-2.03 mm), more
preferably 0.009-0.025 inches (0.229-0.635 mm). The cup/redraw cup
height is preferably 0.5-12 inches (1.3-30.5 cm), more preferably
1-6 inches (2.5-15.2 cm), and the cup/redraw cup diameter is
preferably 0.75-6 inches (1.3-15.2 cm), more preferably 1-4 inches
(2.5-10.2 cm). The force required to carry out the draw or redraw
operations is normally 1,000 to 10,000 lb.f., more preferably
1,500-7,000 lb.f.
* * * * *