Method and apparatus for producing untrimmed container bodies
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.
I. Field of the Invention
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.
II. 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 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.
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.
Attempts have been made in the past to overcome some or all of these disadvantages, but problems still persist.
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.
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.
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.
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 INVENTIONAn 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.
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. 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.
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.
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.
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.
As shown in
The apparatus shown in
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.
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.
The next step of the method is shown in
Referring to
As shown in
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.
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.
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
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.
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.
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 (7.6-61 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.
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.
Type: Application
Filed: Oct 22, 2007
Publication Date: Apr 23, 2009
Inventor: Dubravko Nardini (Oxford)
Application Number: 11/975,926
International Classification: B21D 22/00 (20060101);