METHOD AND APPARATUS FOR PRODUCING UNTRIMMED CONTAINER BODIES

TECHNICAL FIELD

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.

BACKGROUND ART

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 Hd. 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.

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 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. Attempts have been made in the past to overcome some or all of these disadvantages, but problems still persist.

For example, U.S. Patent 3,167,044 granted on January 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.

U.S. Patent 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.

U.S. Patent 4,732,031 granted on March 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.

There is therefore a need for an improved beverage container forming method and apparatus that overcomes at least some of the disadvantages mentioned above.

DISCLOSURE OF THE INVENTION

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 for example 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.

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.

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.

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.

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.

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. 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.

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. 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.

Ideally, the redraw punch passes through a supporting aperture in the support structure and is supported at and driven from an end opposite to the operational end. 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 preferably 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.

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. 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

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;

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 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

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.

Figures 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. Patent No. 3,733,881 mentioned above.

As shown in Figure 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.

The apparatus shown in Figure 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.

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 23 A 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.

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.

Figure 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.l and 2 that the redraw holder 11 has a slight recess in its upper surface around its inner end that exactly matches the outer diameter of the blank 10. This facilitates 5 the proper alignment of the blank in the apparatus.

Figure 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 surface 27. The draw

10 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

15 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 Figure 4 in which the metal blank 10 has been drawn into a shallow-sided initial cup 1OA having an open end facing down (away from the redraw punch 15).

The next step of the method is shown in Figure 5 in which the redraw punch

20 15 is forced (as shown by the arrow) into the bottom 32 of the initial cup 1OA 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 1OB of smaller diameter than the initially drawn cup 1OA. As this operation proceeds, the periphery of the initially drawn cup 1OA is gradually pulled between the cooperating surfaces of the redraw holder 14 and

25 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 down the annular body 25 (as shown) to avoid undue friction between the inverting cup and the annular body 25 as the operation proceeds.

Referring to Fig. 6, 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 1OB 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 3 IB of redrawn cup 1OB to form an elongated container body 1OC. 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).

As shown in Figure 7, at the end of the downward stroke of the redraw punch 15, the bottom 32B of the container body 1 OC 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 23 C, 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 1OC 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. It should be realized that the domer 22 and retaining ring 21 could be omitted, if desired. For example, if a container having a generally flat lower end was desired, there would be no need for the shaping produced by these elements. End- shaping in the illustrated manner is, however, normally preferred. 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, laterally from the apparatus.

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-fϊlling (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. 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. 8 A 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.

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 1 OC to be removed from the apparatus.

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.

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 shaping 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.

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).

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 (7.6-61cm), more preferably 3-12 inches (7.6 to 30.5 cm), more even more preferably 4.5-8 inches (1 1.4 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.