WO2014170476A1

WO2014170476A1 - Shred-less blanking

Info

Publication number: WO2014170476A1
Application number: PCT/EP2014/057990
Authority: WO
Inventors: Paul Robert Dunwoody
Original assignee: Crown Packaging Technology, Inc.; Crown Packaging Uk Plc
Priority date: 2013-04-18
Filing date: 2014-04-17
Publication date: 2014-10-23
Also published as: GB201307045D0

Abstract

A method of creating blanks for metal containers and associated pieces of scrap from sheet metal by firstly indenting the surface of a metal sheet to a precise, pre-determined depth along a path corresponding to the periphery of each blank, but leaving the blank tethered along the path. Secondly, tearing the tether apart. The path of the indentation coincides with the path of the indentation of adjacent blanks.

Description

SHRED-LESS BLANKING

Technical Field

This invention relates to methods and apparatus for manufacturing sheet metal blanks, and in particular to blanking and drawing sheet metal cups as an initial part of a multi-stage process in the manufacture of cans and ends for food and beverage packaging, and to the cans, ends and scrap produced by those methods.

Background Art

It is common to manufacture cans and ends by firstly blanking and drawing cups (that are also often known as “shells”) from coils or sheets of metal. Such coils or sheets may have organic coatings, as is commonly the case for ends, or not, as is commonly the case for cans that are to be manufactured using a wall-ironing process. The term cup is commonly used to refer to a cylinder that is formed open at the top and closed at the bottom, and the term shell is commonly used to refer to a cylinder that is formed open at the bottom and closed at the top.

Conventionally, blanks are cut by a shearing process with tools comprising a punch and die. Often the punches and dies, and consequently the blanks that are cut using them are circular. However, non-circular blanks may be cut with non-circular tools to make non-circular cans, and also non-circular blanks may be cut with non-circular tools to make circular cans wherein the blank shape is adapted to compensate for the anisotropic properties of the metal sheet. For simplicity, the explanation and description of the invention that follows will be for circular tools and blanks; however the invention also incorporates non-circular blanks produced from non-circular tools.

Conventionally, a metal sheet or coil is intermittently moved within an arrangement of a number of sets of tools, where each set of tools is spaced and the material is moved to cut blanks in a honeycomb-like pattern, designed to optimise the number of blanks that can be made from the metal. The accuracy of the intermittent movement must be carefully controlled to avoid the edges of the blanks from overlapping. To achieve this, it is necessary to leave a web or “shred” of sheet metal between the blanks as they are cut, and a honeycomb-shaped “skeleton” of sheet metal is left behind after blanks are cut. Typically there is 0.5 to 1.0mm of shred left between each blank, although there may be more or less than this. A significant amount of the metal that is left behind as scrap comprises this shred between blanks, and so the necessity to leave this shred adds to the cost of manufacturing and wastes material resources. In addition, the skeleton is flimsy and may tangle, and expensive handling systems are often needed to cut and convey it in such a way as to avoid jams.

Blanks that are cut using a shearing process, often have a burr at the cut edge depending perpendicularly from the blank. Such burrs can cause scratches on organic coatings, can impede handling, can detach and cause contamination, and can detract from the quality and performance of the can or end that is produced. In particular, such burrs can interfere with blank-holding tools in drawing operations, and can increase the risk of wrinkling during drawing.

The goals of this invention have been to provide methods and apparatus for cutting blanks that eliminate the need to leave shred between blanks, that produce small pieces of scrap in place of a skeleton and that produce blanks having cut-edges without a perpendicular burr.

To achieve these goals, a method of indenting the surface of sheet metal along a path has been invented. A similar method is commonly used to create a line of weakness in for example an easy-open can end, and is commonly referred to as “scoring”. However, scoring of surfaces carried out in metal packaging manufacture of the prior art is limited to discrete paths that do not coincide with adjacent paths.

The manufacture of blanks by creating an indentation along a path in hot pressing of sheet metal, is used for example as described in

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. However, hot pressing is not suitable for high-speed cold-forming of cans and ends. Other processes are known, which involve the creation of indentations and blanking. However these are adaptations of conventional shearing processes rather than adaptations of a scoring processes and do not eliminate the shred between blanks.

Disclosure of Invention

This invention provides a method of forming blanks for metal containers and associated pieces of scrap from sheet metal by indenting the surface of a metal sheet to a precise, pre-determined depth along a path corresponding to the periphery of each blank. In particular, the path of the indentation coincides with the path of the indentation of adjacent blanks.

The invention also provides improved blanks and pieces of scrap that avoid perpendicular burrs being formed at their edges and produces small pieces of scrap that are easy to convey away. Most importantly, the invention provides metal packaging that requires less metal.

Provided that any inaccuracy of the positioning of the metal sheet is controlled to be less than the width of the indentation, the path of the indentation can be controlled to coincide with the path of the indentation of adjacent blanks. Thus separate small pieces of scrap will be created, and there will be no shred between adjacent blanks. These small pieces of scrap may be conveyed away without need for cutting.

Unless it is possible to control the width of the coil of sheet metal, or the dimensions of the metal sheet, and its initial positioning very accurately, it will be necessary to use a coil width or sheet size that is slightly larger than that which would otherwise be required. As a result, some “edge-shred” would remain between the edges of the coil or sheet and the blanks closest to these edges. Additional tools may be required to cut break the scrap at these edges into small pieces, or the scrap at these edges may need to be removed as a string of pieces connected by the edge shred.

The profile of the edges of the blanks and of the shred produced by this invention will be determined primarily by the profile of the tool used to indent the surface of the sheet metal, and the anvil opposing it. When the indentation is made by this tool, the metal in the sheet will be pushed radially inwards towards the centre of the blank on the radially inner side of the tool, and radially outwards away from the centre of the blank on the radially outer side of the tool. The metal sheet would therefore tend to thicken and/or bulge near the path of the penetration. It is therefore preferable for the metal sheet to be simultaneously deformed during penetration, such that the metal is displaced away from the path of the penetration to prevent any undesirable thickening or bulging. Whatever tool profiles might be used to deform the sheet will thus secondarily determine the profile of the edges of the blanks and of the shred produced by this invention. Any burr or sharp edge, and the direction in which it depends, will be determined by the profiles of the tools. However, the direction of the burr will generally be radial with respect to the blank. This direction differs significantly from the perpendicular burr associated with the shearing process of the prior art. This difference may be particularly useful in the manufacture of articles from organic or polymer coated material in which conventional shearing processes otherwise weaken the bond between the coating and the metal adjacent to the cut-edge, so that hairs of the coating can be torn away during further forming.

In a first embodiment of the invention, the method is carried out in two distinct stages. In the first stage of this embodiment, the sheet metal is moved into position between an anvil and an indenting tool. The indenting tool is moved towards the anvil, or vice versa, to a position where it will indent the sheet metal to a precisely controlled depth. Either or both of the indenting tool and the anvil may preferably have adjacent distorting tool portions to simultaneously distort the sheet metal to generate radial tension across the path of the indentation. The indenting tool is then retracted. In the second stage of this embodiment, the indented sheet metal is moved into position central to a die. An arrangement of tools is then moved towards the die, or vice versa, wherein tools radially outside the die tear off the scrap portion along the path of the indentation. The arrangement of tools may preferably incorporate a clamping tool which applies a blank-holding force to the metal, and a drawing tool which is moved through the die, or vice versa, to draw the blank to create a cup or shell.

In a preferred version of the first embodiment of the invention, the profile of one or more of the indenting tool, the distorting tools or the anvil surface is modulated around the path of the indentation. Modulations such as increasing the depth of penetration, increasing the tension across the path of the penetration or altering the profile of the penetrating tool can be used to pry the metal sheet apart to a greater extent. Such modulations can be used to fracture the metal at selected regions of the path, and ease the subsequent tearing of the scrap from the blanks.

In a second e mbodiment of the invention, the method is combined into one stage, and may comprise any of the aspects of the first embodiment described above. The sheet metal is moved into position between an anvil and an indenting tool. The indenting tool is moved towards the anvil, or vice versa, to a position where it will indent the sheet metal to a precisely controlled depth. Either or both of the indenting tool and the anvil may preferably have adjacent distorting tool portions to simultaneously distort the sheet metal to generate radial tension across the path of the indentation. The indenting tool penetrates the metal thickness sufficiently to cause fracture along the path of the indentation, thus separating the blank from the remainder of the sheet.

The tooling apparatus of the second embodiment may preferably be adapted to draw a cup or shell from the blank and may thus also comprise a die, a clamping tool and a drawing tool. The drawing tool is moved to draw the blank through the die or vice versa to create a cup or shell, whilst the clamping tool applies a blank-holding force to supress wrinkling. The indenting tool and anvil may be combined with the die and clamp ring in any combination. An arrangement of tools radially outside the die may be used to assist tearing and move the pieces of scrap.

The second embodiment is advantageous in comparison with the first, because the tooling requires less space and it is not necessary to move the sheet metal accurately between the two stages.

Particularly if a cup is drawn fully through the die using the method of the second embodiment, then it is preferable to either limit the movement of the penetrating tool towards the anvil and/or move the penetrating tool away from the anvil to prevent the penetrating tool from directly contacting the anvil, which might damage the penetrating tool or anvil.

In a third embodiment of the invention, the penetrating tool and anvil of the first or second embodiment may be replaced with an alternative apparatus for indenting the metal surface. Such an alternative apparatus may for example comprise a laser or a high pressure fluid jet.

In any of the above embodiments, the accuracy of positioning may be enhanced by perforating regions of the sheet metal that are to become scrap at the same time as forming the indentation, and inserting guide pins into these perforations after the sheet metal has been moved approximately to the next position. Alternatively, other features may be formed and then used for location after the sheet has been moved.

In any of the above embodiments, the scrap may be removed by a flow of air or by mechanical conveying. Also, additional components can be added to the tooling in order to form further features, such as those typical of a can or an end.

In any of the above embodiments, additional components can be added to further adapt the scrap for ease of conveying, handling and recycling, and the invention includes any scrap formed by the method if the invention.

Brief Description of Drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which;

Fig 1 shows a cross section of the blank and draw tooling of the prior art

Fig 2 shows a coil skeleton produced using multiple blanking tool-sets of the prior art

Fig 3 shows the coil remaining after blanking using multiple tool-sets of the first embodiment of the invention

Fig 4 shows the coil remaining after blanking using multiple tool-sets of the first embodiment with positioning holes illustrated

Fig 5 shows the coil remaining after blanking using multiple tool-sets of the second embodiment of the invention

Fig 6 shows the coil remaining after blanking using multiple tool-sets of the second embodiment with positioning holes illustrated

Fig 7 gives an example of a blank according to the invention

Fig 8 gives an example of a piece of scrap according to the invention

Fig 9 shows a cross section of example of tooling used to produce a cup, shown with the tools open.

Fig 10 shows a cross section of example of tooling used to produce a cup, shown with the tools moved to start forming the blank.

Fig 11 shows a cross section of example of tooling used to produce a cup, shown with the tools moved to cut the blank.

Fig 12 shows a cross section of example of tooling used to produce a cup, shown with the tools drawing a cup.

Fig 13 shows a cross section of example of tooling used to produce a cup, shown with the tools having moved to draw the cup through and then retracted to a position where the sheet metal is able to be moved.

Fig 14 shows a cross section of example of tooling used to produce a shell, shown with the tools open.

Fig 15 shows a cross section of example of tooling used to produce a shell, shown with the tools moved to start forming the blank.

Fig 16 shows a cross section of example of tooling used to produce a shell, shown with the tools moved to cut the blank.

Fig 17 shows a cross section of example of tooling used to produce a shell, shown with the tools drawing a shell.

Fig 18 shows a cross section of example of tooling used to produce a shell, shown with the tools having drawn a shell.

Fig 19 shows a cross section of example of tooling used to produce a shell, shown with the tools having retracted to release the cup.

Fig 20 shows a cross section of tooling used to produce a cup, shown with the tooling in a position just prior to separation of the blank from the sheet.

Figs 21-40 show cross sections of examples of combinations of indentations and deformations just prior to separation of the blank from the metal sheet.

Mode(s) for Carrying Out the Invention

Figure 1a shows a cross-section of set of blank and draw tools of the prior art in an open position together with a metal sheet (1). The tools comprise a plate (11), a combined blanking punch and draw die (12), a clamping tool (13), a cutting die (14) and a drawing punch (15), The face (16) of the combined blanking punch and draw die has a cutting edge (17) at its outer diameter and a drawing profile (18) at its inner diameter. The cutting die has a cutting edge (19) that opposes the cutting edge (17).

Figure 1b shows the tools moved to a position where the clamping tool applies a force to the metal sheet.

Figure 1c shows the tools moved to a position where the opposed cutting edges have moved past one another to cut the metal sheet into a blank (2) and a skeleton (3).

Figure 1d shows the tools moved to a position where the drawing punch (15) has drawn the blank (2) into a cup (4).

Figure 2a shows a plan view of a skeleton of the prior art (3) formed by four sets of tools used to create four blanks from a coil or strip of sheet metal in each stroke of a press. After each stroke of the press, the coil is moved by a distance slightly larger than the diameter of the blanks. The four sets of tools are positioned to cut the blanks to form the four holes (5). The remaining holes in the skeleton have been formed in previous strokes of the press. To enable the scrap material of the skeleton to be removed, it is normal to cut the skeleton along a line 6 during each stroke of the press, into pieces represented by the area between the line 6 and 6’.

Figure 2b shows a partial cross-sectional view through the skeleton along the arrowed line (b). This shows a region of shred (7) remaining between the holes after cutting the blanks.

Figure 2c is a perspective view of the skeleton (3) and figure d is a detailed view within the circle (d) of figure 2c. Figure 2d shows another region of shred (7’) remaining between the holes after cutting the blanks.

Figure 3a shows a plan view of the sheet (30) of the first embodiment of the invention, as blanks and pieces of scrap are created. In this example, four sets of tools are used to create four circular indentations (31) during each stroke of the press. After each stroke of the press, the sheet (30) is moved by a distance equivalent to the diameter of the blanks. In this way, and by positioning the four sets of tools as shown, the circular indentations (31) are formed tangential to those formed in the previous stroke of the press, and to all their neighbours. Preferably the indentations are sufficient to only fracture the metal sheet at and around the tangents, leaving un-fractured metal along the indentations away from the tangents.

A further four sets of tools are used to tear the un-fractured indentations to create blanks at the four positions (33), and consequently separate pieces of scrap at positions (34), and edge-scrap (35) at the edges of the sheet (30).

Figure 3b shows a partial cross-sectional view through the sheet (30) along the arrowed line (b).

Figure 3c is a perspective view of the sheet (30) and figure 3d is a detailed view within the circle (d) of figure 3c. Figure 3d shows the indentations meeting tangentially at positions 36.

Figure 4 illustrates examples of positions where perforations (37) may be formed in conjunction with forming the indentations of figure 3. The remaining perforations shown are those formed in previous strokes of the press, and these perforations may be used to accurately position the sheet (30). It is not necessary to form perforations at all the positions shown, and only two perforations need be formed in each stroke to fully control the position of the sheet. If desired, the positions of the perforations nearest to the edge of the sheet may be moved closer to the edge of the sheet than shown in the figure.

Figure 5a shows a plan view of the sheet (40) of the second embodiment of the invention, as blanks and pieces of scrap are created. In this example, four sets of tools are used to create four blanks leaving four holes at positions (41) during each stroke of the press. After each stroke of the press, the sheet (40) is moved by a distance equivalent to the diameter of the blanks. In this way, and by positioning the four sets of tools as shown, the holes (41) are formed tangential to those formed in the previous stroke of the press, and to all their neighbours. Consequently, separate pieces of scrap are created at positions (42), and edge-scrap (43) is created at the edges of the sheet (40).

Figure 5b shows a partial cross-sectional view through the sheet (40) along the arrowed line (b).

Figure 5c is a perspective view of the sheet (40) and figure 5d is a detailed view within the circle (d) of figure 5c. Figure 5d shows the holes meeting tangentially at positions (44).

Figure 6 illustrates examples of positions where perforations (45) may be formed in conjunction with forming the blanks. The remaining perforations shown are those formed in previous strokes of the press, and these perforations may be used to accurately position the sheet (40). It is not necessary to form perforations at all the positions shown, and only two perforations need be formed in each stroke to fully control the position of the sheet. If desired, the positions of the perforations nearest to the edge of the sheet may be moved closer to the edge of the sheet than shown in the figure.

Figure 7a is a perspective view of a blank (50), and figure 7b is a plan view of a blank (50).

Figure 7c is a cross-sectional view through the blank 50 along arrowed line (c).

Figure 7d is a detailed view within the circle (d) of figure 7c. The edge (51) of the blank (50) has a region (52), where a tool has penetrated, and a region 53, where the blank has torn from the sheet. The blank 50 has a deformed region (54) near to the edge 51.

Figure 8a is a plan view of a piece of scrap (60). The piece of scrap has three curved edges (61), which meet tangentially at three points (62).

Figure 8b is a cross-sectional view through the piece of scrap (60) along arrowed line (b).

Figure 8c is a detailed view within the circle (c) of figure 8b.

Figure 8d is a detailed view within the circle (d) of figure 8b. The edge (61) of the piece of scrap (60) has a region (63), where a tool has penetrated, and a region 64, where the piece of scrap has torn from the sheet. Although not shown in the figure, the piece of scrap (60) may have a deformed region near to the edge 61. The piece of scrap may also have perforations as illustrated in figures 4 and 6. In practice, the piece of scrap will have additional distortions due to the lack of strength of its shape.

Fig 9a is a cross-sectional view of an example of a set of tooling used to produce a cup, shown with the tools open, and with a metal sheet (71) in position. Figure 9b is a detailed view within the circle (b) of figure 9a. The set of tooling comprises a drawing die (72), an anvil (73), a clamping tool (74), a penetrating tool (75) having a penetrating portion (76) and a drawing punch (89). The metal sheet (71) is resting on the face (77) of anvil (73), which is positioned above the face (78) of the drawing die (72) to leave a gap (80) between the metal sheet (71) and the drawing die (72). A blank has previously been formed from the metal sheet (71), leaving a curved edge (61), which coincides tangentially below the penetrating portion (76) of the penetrating tool (75).

Fig 10a is a cross-sectional view of the tooling of figure 9, shown with the tools moved in preparation to form the blank. Figure 10b is a detailed view within the circle (b) of figure 10a. As the tools are moved to this position, the face (79) of the clamp tool (74), and the penetrating portion (76) of the penetrating tool (75) contact the metal sheet (71) approximately simultaneously.

Fig 11a is a cross-sectional view of the tooling of figure 9, shown with the tools moved by an axially applied force to form a blank (80) from the metal sheet (71). Figure 11b is a detailed view within the circle (b) of figure 11a, and figure 11c is a detailed view within the circle (c) of figure 11a. The penetrating portion (76) has pushed into the metal sheet (71) at the same time as movement of the face (79) of the clamping tool (74) relative to the face (77) of the anvil (73) has deformed the metal sheet (71) and pulled it radially inwards within the periphery of the penetrating portion (76) to create a deformed region (81). These combined movements cause the metal sheet (70) to deform and create and tear the blank (80), from the remaining metal sheet (71’). The radially inward pulling of the metal sheet avoids any increase in thickness of the blank adjacent to its edge as the penetrating portion is pushed into the metal sheet. Any ragged metal arising from the tearing of the metal sheet will depend (for clarity, that is to be attached and extend in a direction) radially outwards from the edge of the blank or radially inwards from the edge of the remaining sheet. The indentation made by the penetrating tool coincides tangentially with the penetration made when the previous blank was formed from metal sheet. A plurality of sets of tools to produce a plurality of blanks as previously described will create separate pieces of scrap material (60) as illustrated in figure 8 from the remaining sheet. The axially applied force is now transmitted through the blank (80) to hold it firmly between the face (79) of the clamping tool (74) and the face (78) of the drawing die (72).

Fig 12a is a cross-sectional view of the tooling of figure 9, shown with the tools drawing a cup (82) from the blank. Figure 12b is a detailed view within the circle (b) of figure 12a. Axial movement of the drawing punch 89 draws metal radially inwards across the face of the drawing die (72). While the cup is being drawn from the blank, it has a flange portion (83), which is prevented from wrinkling by the axially applied clamping force as the cup increases in height and the flange reduces in diameter. The deformed region (81) has been pulled radially inwards and is now flattened between the face (79) of the clamping tool (74) and the face (78) of the drawing die (72), and has become part of the flange portion (83).

It is preferable to avoid direct contact between the penetrating portion (76) of the penetrating tool (75) and the anvil (73), to avoid risk of damage to either. This can be achieved by additional tool components or portions to prevent such contact, or by moving one of the penetrating tool (75) or the anvil (73) away from one another once the blank has been formed and the cup is being drawn as is shown in figure 12b.

Whilst it is possible to create a cup with a flange by limiting the axial movement of the drawing punch, further axial movement of the drawing punch (89) will further draw the cup and will eliminate the flange (83), to form the fully-drawn cup of figure 13a

Fig 13a is a cross-sectional view of the tooling of figure 9, shown after the cup (84) has been fully drawn and has been removed from the drawing punch (89). The drawing punch (89), clamping tool (74) and the penetrating tool (75) have all been retracted to a position where any remaining scrap pieces (60) and the remaining sheet metal (71’) are able to be moved in readiness to produce another cup.

Figure 13b is a detailed view within the circle (b) of figure 13a.

Fig 14a is a cross-sectional view of an example of a set of tooling used to produce a shell, shown with the tools open, and with a metal sheet (101) in position. Figure 14b is a detailed view within the circle (b) of figure 14a. Figure 14c is a detailed view within the circle (c) of figure 14a. Figure 14d is a detailed view within the circle (d) of figure 14a. The set of tooling comprises a drawing die (102), an anvil (103), a clamping tool (104), a penetrating tool (105) having a penetrating portion (106), a drawing punch (107) and a stopping tool (108). The metal sheet (101) is resting on the face (110) of anvil (103), which is approximately level with the face (111) of the clamping tool (104) and is positioned above the face (112) of the drawing punch (107) to leave a gap (113) between the metal sheet (101) and the drawing punch (107). A blank has previously been formed from the metal sheet (101), leaving a curved edge (61), which coincides tangentially below the penetrating portion (106) of the penetrating tool (105). The stopping tool (108) has a stopping face (114), which is set at a precise distance from the extremity of the penetrating portion (106) of the penetrating tool (105) that is less than the thickness of the metal sheet (101).

Fig 15a is a cross-sectional view of the tooling of figure 14, shown with the tools moved in preparation to form the blank. Figure 15b is a detailed view within the circle (b) of figure 15a. Figure 15c is a detailed view within the circle (c) of figure 15a. As the tools are moved to this position, the face (115) of the drawing die (102), and the penetrating portion (106) of the penetrating tool (105) contact the metal sheet (101) approximately simultaneously.

Fig 16a is a cross-sectional view of the tooling of figure 14, shown with the tools moved to form a blank (120) from the metal sheet (101). Figure 16b is a detailed view within the circle (b) of figure 16a. Figure 16c is a detailed view within the circle (c) of figure 16a. Figure 16d is a detailed view within the circle (d) of figure 16a. An axial force is applied via the clamping tool 104 to hold the metal sheet firmly between face (111) of the clamping tool (104) and the face (115) of the drawing die (102). The axial movement of the drawing die (102) pushes the clamping tool via the metal sheet (101) where it is to form the blank (120). The penetrating portion (106) has pushed into the metal sheet (101) at the same time as movement of the face (115) of the drawing die (102) relative to the face (110) of the anvil (103) has deformed the metal sheet (101) and pulled it radially inwards within the periphery of the penetrating portion (106) to create a deformed region (121). These combined movements cause the metal sheet (101) to deform and create and tear the blank (120), from the remaining metal sheet (101’). The radially inward pulling of the metal sheet avoids any increase in thickness of the blank adjacent to its edge as the penetrating portion is pushed into the metal sheet. Any ragged metal arising from the tearing of the metal sheet will depend (for clarity, that is to be attached and extend in a direction) radially outwards from the edge of the blank or radially inwards from the edge of the remaining sheet. Figure 16d shows that the indentation made by the penetrating tool coincides tangentially with the penetration made when the previous blank was formed from metal sheet. A plurality of sets of tools to produce a plurality of blanks as previously described will create separate pieces of scrap material (60) as illustrated in figure 8 from the remaining sheet. The depth to which the penetrating portion can indent the metal sheet (101) is restricted by the stopping face (114) of the stopping tool (108) coming into contact with the metal sheet, and this prevents any contact of the penetrating portion (106) with the face (110) of the anvil (103).

Fig 17a is a cross-sectional view of the tooling of figure 14, shown with the tools drawing a shell (130) from the blank (120). Figure 17b is a detailed view within the circle (b) of figure 17a. Figure 17c is a detailed view within the circle (c) of figure 17a. Figure 17d is a detailed view within the circle (d) of figure 17a. Axial movement of the drawing die (102) draws metal radially inwards across its face (115). While the shell (130) is being drawn from the blank (120), it has a flange portion (131), which is prevented from wrinkling by the axially applied clamping force as the shell height increases and the flange reduces in diameter. The deformed region (121) has been pulled radially inwards and is now flattened between the face (111) of the clamping tool (104) and the face (115) of the drawing die (102), and has become part of the flange portion (131).

Whilst it is possible to create a shell with a flange by limiting the axial movement of the drawing die, further axial movement of the drawing die (102) will further draw the shell and will eliminate the flange (131), to form the fully-drawn shell (132) of figure 18a. Figure 18b is a detailed view within the circle (b) of figure 18a. Figure 18c is a detailed view within the circle (c) of figure 18a. Figure 18d is a detailed view within the circle (d) of figure 18a.

Fig 19a is a cross-sectional view of the tooling of figure 9, shown after the shell (132) has been fully drawn and has been removed from the drawing punch (107) and drawing die (102). The tools have all been retracted to a position where the shell (132) any remaining scrap pieces (60) and the remaining sheet metal (101’) are able to be moved in readiness to produce another cup. Figure 19b is a detailed view within the circle (b) of figure 19a. Figure 19c is a detailed view within the circle (c) of figure 19a. Figure 19d is a detailed view within the circle (d) of figure 19a.

Fig 20a is a cross-sectional view of a tool used to produce a shallow cup-shaped article from a sheet of metal 140. Figure 20b is an enlarged view of the region circled in fig 20a and fig 20c is a further enlarged view of the region circled in fig 20b. The tooling is shown in a position where the tools have been moved to a position wherein the blank is just about to separate from the sheet and just before the blank is to be drawn into a cup.

This tooling comprises a lower tool 150, which has a curved portion 151 around which the walls of the cup are drawn, an anvil portion 152, distorting

portions

153 and 154, and a face 155 which will oppose the inner clamping tool 180. The tooling also has an indenting tool 160 directly opposing the anvil portion 152 of the lower tool 150, an outer clamping tool 170, an inner clamping tool 180 and a draw punch 190. In the position shown, the indenting tool has simultaneously distorted and indented the sheet to create a path of weakness.

The invention is not limited to the examples shown in the figures above. It will be apparent to the person skilled in the art how to arrange the apparatus of the invention in a large number of ways to achieve the method wherein a metal sheet is indented and torn, and to achieve the preferred method wherein the metal sheet is indented and deformed and torn. For simplicity, the following figures do not show the tools, but illustrate the tool surfaces by way of the shape they impart to the metal sheet.

Figures 21 to 40 illustrate examples of combinations of indentations and deformations just prior to separation of the blank from the metal sheet.

Figure 21 illustrates a simple indentation formed by an indenting tool opposing a flat anvil without an adjacent deforming tool.

Figure 22 illustrates an indentation formed by an indenting tool opposing a flat anvil without an adjacent deforming tool, wherein the indenting tool is provided with a wide surface to limit its penetration and avoid thickening of the metal adjacent to the indentation.

Figure 23 illustrates an indentation formed by an indenting tool opposing a curved anvil surface without an adjacent deforming tool, to allow displaced metal to move freely to assist separation of the blank from the metal sheet and to accommodate any waviness created during penetration.

Figure 24 illustrates an indentation formed by an indenting tool opposing a curved anvil surface without an adjacent deforming tool, wherein the indenting tool is provided with a wide surface.

Figure 25 illustrates an indentation formed radially outward from a deformation. (This illustration relates to the tooling examples shown in figures 11 and 16.)

Figure 26 illustrates an indentation formed radially outward from a deformation, wherein the slope of the radially inner indentation wall is steeper than the slope of the radially outer indentation wall.

Figure 27 illustrates an indentation formed radially outward from a deformation, wherein the slope of the radially outer indentation wall is steeper than the slope of the radially inner indentation wall.

Figure 28 illustrates an indentation formed radially outward from a deformation, wherein the indenting tool is provided with a wide surface to limit its penetration and avoid thickening of the metal adjacent to the indentation.

Figure 29 illustrates an indentation formed radially outward from a deformation, wherein the tip of the indenting tool is rounded.

Figure 30 illustrates an indentation formed radially outward from a deformation, wherein the tip of the indenting tool is truncated.

Figure 31 illustrates an indentation formed radially outward from a deformation, wherein the truncated tip of the indenting tool is angled to promote separation at its radially inner edge.

Figure 32 illustrates an indentation formed radially outward from a deformation, wherein the truncated tip of the indenting tool is angled to promote separation at its radially outer edge.

Figure 33 illustrates an indentation between a radially inner deformation and a radially outer deformation.

Figure 34 illustrates an indentation, formed by an indenting tool opposing a curved anvil surface, between a radially inner deformation and a radially outer deformation.

Figure 35 illustrates an opposite-sided indentation between a radially inner deformation and a radially outer deformation.

Figure 36 illustrates an opposite sided indentation, formed by an indenting tool opposing a curved anvil surface, between a radially inner deformation and a radially outer deformation.

Figure 37 illustrates an opposite-sided indentation to that of figure 24.

Figure 38 illustrates an indentation coincident with a deformation.

Figure 39 illustrates an indentation radially within a deformation.

Figure 40 illustrates an opposite-sided indentation coincident with a deformation.

In addition to the examples described above, the invention includes any number and any combination of any of the features described.

Claims

A method of forming blanks for metal containers and associated pieces of scrap from sheet metal by

- indenting the surface of a metal sheet to a precise, pre-determined depth along a path corresponding to the periphery of each blank

characterised in that the path of the indentation coincides with the path of the indentation of adjacent blanks.
A method according to claim 1, wherein the metal sheet is moved before tearing each blank and associated scrap portions from the metal sheet.
A method according to claim 1, wherein the surface of the metal sheet is indented and the blank and associated scrap portions are torn or prised apart from the remainder of the metal sheet, along the path of the indentation, in a single movement.
A method according to any one of the preceding claims, wherein the method includes feeding the metal sheet between an indenting tool and an opposing anvil and moving the indenting tool towards the anvil and/or moving the anvil towards the indenting tool to indent the surface of the metal sheet to a precise, pre-determined depth.
A method according to claim 4, further comprising distorting the sheet metal with portions of the indenting tool and/or anvil, the distorting portions generating radial tension across the path of the indentation, by simultaneously distorting and indenting the metal sheet.
A method according to claim 4, further comprising clamping the sheet metal with portions of the indenting tool and/or anvil, the clamping portions applying compression to the surface of the metal sheet adjacent to the path of the indentation.
A method according to any one of the preceding claims, wherein the blanks are arranged on the metal sheet in a honeycomb pattern.
A method according to any one of the preceding claims, further comprising perforating regions of the metal sheet, which are to become pieces of scrap.
A method according to any one of the preceding claims, further including removing the pieces of scrap by a flow of air or mechanical conveying.
A method according to any one of the preceding claims, wherein a cup or shell is formed by the addition of drawing tools radially within the path of the indentation.
A method according to any one of the preceding claims, wherein any of the indenting tool, the anvil, distorting tools, drawing tools or clamping tools are combined or moved simultaneously.
An apparatus for carrying out the method defined in any one of the preceding claims.