Method of expanding a cylindrical metal precursor in the manufacture of a three-piece can, method of manufacturing a three-piece can, three-piece cans and shaping mandles

Description

1 / 23 “METHOD FOR EXPANDING A CYLINDRICAL METAL PRECURSOR IN THE MANUFACTURE OF A THREE-PIECE CAN, METHOD FOR MANUFACTURING A THREE-PIECE CAN, THREE-PIECE CANS AND FORMING MANDRELS” Field of invention

[001] The present invention relates to methods for shaping cylindrical metal precursors used to manufacture cans and to cans thus produced, in particular for packaging powdered products, such as infant nutrition and milk formula. The present invention further relates to an apparatus suitable for carrying out such methods. Background of the technique

[002] Metal cans have been used for packaging powdered materials for many years, as they can be sealed for long-term storage and are relatively easy and inexpensive to produce. The aesthetics of such metal cans play a huge role in the customer experience. The shape of a can can be visually appealing as well as provide a real function, such as a handle. Several can constructions are known, including those commonly called two-piece cans and three-piece cans. In the case of two-piece cans, the base and side wall are produced in one step from a single piece of metal, usually being a combination of deep stamping and necking. Three-piece cans generally comprise a cylindrical side wall with a longitudinal seam and two ends that are connected to the side wall by a single or double fold seam.

[003] Although two-piece and three-piece cans exhibit many similarities, fundamental differences in their production lead to significant differences. Two-piece cans generally lack a longitudinal seam and can withstand significantly greater distortion forces and pressures during manufacturing. In a three-piece can, the longitudinal seam will always be a point of asymmetry, which will distort differently from other areas of the circumference. The expansion of the can may be limited by the strength of this seam. Due to the greater deformations common in the production of two-piece cans, this Petition 870250094031, dated 10 / 14 / 2025, page 54 / 135 2 / 23 is generally only applicable to aluminum or softer alloys. Three-piece cans are more commonly made of steel. Another important difference is the need to trim the top edge of two-piece cans before applying the closure. Due to the longitudinal extension during the deep drawing process, the top edge of the can body may no longer be level. To achieve the required tolerance for proper seaming, the top edges of such can bodies are usually trimmed, requiring an additional step. Such cutting processes introduce metal particulates into the production environment and may be less preferable for certain sensitive products. Three-piece cans do not need to be stamped in the longitudinal direction and thus can remain well within acceptable tolerances for end seaming.

[004] To create a specific body shape for a three-piece can, an expansion forming process can be used, in which a cylindrical mandrel is expanded by stretching portions of a cylindrical precursor from an initial diameter to a larger diameter. Such mandrels typically comprise a plurality of longitudinally extending segments arranged radially around a longitudinal geometric axis of the mandrel. The segments have arched surfaces that engage an inner surface of the precursor as the mandrel expands by the action of wedges or cam surfaces. It will be understood that the depth of any profile, relief, or contour on the final can will be dependent on the amount by which the can is stretched.

[005] In existing procedures that attempt to achieve a high degree of stretch, it has been found that the final body shape shows vertical parting lines in the gaps between the mandrel segments. These parting lines may be present in different locations around the entire circumference of the body. The parting lines may be visible to the naked eye and are detrimental to the aesthetics of the final can, especially on otherwise smooth or single-colored surfaces. The parting lines form due to local stretching of the metal sidewall over the edges of the segments. This is exacerbated as the segments move further apart and the unsupported sidewall between segments forms flat strips that no longer follow the same curvature as the arched surfaces. Often, a milder and more ductile grade of steel needs to be used to avoid this. Petition 870250094031, dated 10 / 14 / 2025, page 55 / 135 3 / 23 cracking problems occur at the location of these dividing lines. This has the effect of making the final packaging less strong and more vulnerable to dents.

[006] Patent Publication DE102011100506A1 describes a method for expanding a cylindrical tube, in particular to produce cans that are circular in cross-section. In a first expansion step, shaped lamellae are expanded outwards by an actuating arm provided with wedge surfaces, whereby the tube is expanded to the desired shape. The shaped lamellae are then moved back again so that they are no longer in contact with the inner wall of the tube. The shaped lamellae are then rotated around their longitudinal geometric axis relative to the tube. In a second expansion step, the shaped lamellae are again moved radially outwards to the same extent as in the first expansion step. In this second expansion step, the shaped lamellae shape the areas of the cylinder that did not have direct contact with the shaped lamellae at the end of the first expansion.

[007] Such existing two-stage expansion methods are time-consuming, as they require a rotation step, involving additional time and tooling. Even so, such methods may be unable to achieve high degrees of expansion without the aforementioned cracking problems occurring at the end of the second stage. Furthermore, mandrel rotation is unsuitable for producing certain profiled surfaces, as mandrel rotation can disturb the intended position of the profile. In general, only rotationally symmetrical shapes can be made with this process.

[008] It would be desirable to provide alternative methods for expanding cylindrical metal precursors, in particular suitable for the manufacture of three-piece cans for both symmetrical and asymmetrical designs. Summary of the invention

[009] According to a first aspect of the invention, a method is provided for expanding a cylindrical metallic precursor in the manufacture of a three-piece can, the method comprising the steps of: arranging the precursor, which has an initial diameter, around a forming mandrel, the forming mandrel having a plurality of segments that Petition 870250094031, dated 10 / 14 / 2025, page 56 / 135 4 / 23 extend longitudinally and are radially arranged around a longitudinal geometric axis of the forming mandrel, the segments having arched surfaces to engage an inner surface of the precursor wall; in a first step, a first subgroup of the plurality of segments acts to expand outwards to engage with the inner surface of the precursor wall and expands at least a portion thereof to a first diameter that is larger than the initial diameter of the precursor; and in a second step, a second subgroup of the plurality of segments acts to expand outwards and also engage with the inner surface of the precursor wall, whereby the second subgroup expands at least a portion of the precursor to a second diameter that is larger than the first diameter.This method allows for a greater degree of expansion of the wall of a cylindrical metal container, so that greater variations in diameter can be achieved between recessed portions and the rest of the wall.

[0010] Hereafter, the reference to recessed portions will refer to areas of the container wall that have been deliberately expanded less than other areas of the wall for the purpose of producing a profiled outer surface. These recessed portions may still be in a position that corresponds to the initial diameter or may have been expanded, but by a smaller amount than the rest of the wall. The method is particularly suitable for welded steel containers made of high-quality steel. In the past, high degrees of expansion could only be achieved by choosing more ductile steels in order to avoid cracking problems. The possibility of using these stronger steels allows for better performance in top load, side load and dent resistance of the final packaging. This allows for a lower wall thickness for the can.As the individual segments expand outwards in different stages, a better distribution of tensile forces in the metal is created. As a result, the final can can be up to 25% thinner than existing cans: where common cans are made with a wall thickness of 0.24 to 0.25 mm, a thickness of 0.18 to 0.20 mm can be used. Furthermore, the precursor can be expanded by up to 30% of its initial diameter without cracking. Petition 870250094031, dated 10 / 14 / 2025, page 57 / 135 5 / 23

[0011] The segments can be distributed into any suitable subgroups that allow the desired expansion procedure in one tool stroke. There may be more than two subgroups, and not all subgroups need be equal in number. However, in a preferred embodiment, the first subgroup consists of alternating segments around the longitudinal geometric axis of the forming mandrel, and the second subgroup consists of all the remaining segments. In this case, the number of segments in each subgroup will be identical. Expanding the body first with only half of the segments at once and then subsequently with all the segments allows for a better distribution of the stretching forces during the critical final stages of expansion.

[0012] Segment groups can be actuated to expand at different speeds, depending on their initial positions and the overall expansion stage achieved. The expert will be familiar with the actuators and wedges required for such expansion. The absolute rate of expansion of the precursor wall may be greater during the initial expansion stages than in the final expansion stages. The relative speeds of the different subgroups will also vary. In one embodiment, during the first stage, the segments of the second subgroup may be actuated to expand outward at a speed that is at least slightly greater than the speed at which the segments of the first subgroup expand outward. This is because they will generally be initially more retracted than the segments of the first subgroup and thus need to catch up with them before participating in the wall expansion in the second stage.In this context, the reference to the first stage refers to the portion of the expansion where only the segments of the first subgroup engage the inner surface. The reference to the second stage refers to the portion of the expansion in which both subgroups are in contact with the inner surface. Thus, in the first stage, contact with the wall is limited to one subgroup of segments while the second subgroup remains free from contact with the wall. However, it should be understood that, despite the reference to two stages, these are only temporary stages in the operation and the process may otherwise be continuous without requiring removal or readjustment. Petition 870250094031, dated 10 / 14 / 2025, page 58 / 135 6 / 23 chuck between stages.

[0013] In the second stage, the first subgroup also expands from the first diameter to the second diameter. In this way, all longitudinal portions of the precursor that are in contact with the segments are enlarged into a cylinder with its entire circumference at the second larger diameter. The method therefore allows expanding all or most of a precursor into a cylinder of a larger diameter, this being the second diameter.

[0014] Once the segments of the second subgroup have caught up with the segments of the first subgroup, all segments can be actuated to expand outwards at the same speed during the second stage. The two subgroups of segments can alternatively be expanded at different speeds. However, the expert will understand that the precise speed of expansion will depend on the design of the cam or wedge surfaces used and the interrelation between the groups of segments.

[0015] In view of the present description, the second stage is considered to begin when the second subgroup comes into contact with the precursor wall. However, it will be understood that the action and movement of the subgroups may be continuous. In one embodiment, the second stage may comprise an initial stage in which the arched surfaces of the second subgroup are engaged with the inner surface of the precursor, but still radially inward to the arched surfaces of the first subgroup. At this stage, only a portion of the arched surfaces of the second subgroup comes into contact with the precursor wall.

[0016] In one embodiment, the second stage may comprise an intermediate stage in which the arched surfaces of the second subgroup are radially aligned with the arched surfaces of the first subgroup. This intermediate stage may begin from a position where the edges of the arched surfaces of adjacent segments are initially engaged, i.e., the arched surfaces form an almost complete circumference without gaps. It will be understood that, although the circumference may be complete, it may not be a perfect circle, since the individual segments may have curvatures of a slightly larger diameter than the precursor at that point. Petition 870250094031, dated 10 / 14 / 2025, page 59 / 135 7 / 23 Expansion. After an initial stage of the second phase in which a central part of the second subgroup of segments engages the precursor, a point will be reached where the entire surface of all segments engages the precursor wall. After that, all segments can be expanded to a final, almost uniform curvature that corresponds to the arched surfaces of the second subgroup. During this intermediate stage (which may also be the final stage), the segments will move apart slightly, leaving gaps between adjacent segments.

[0017] In one embodiment, the second stage may comprise a final stage, following the intermediate stage, in which the arched surfaces of the second subgroup move radially outward beyond the arched surfaces of the first subgroup. This final stage may provide a slight overstretch of the precursor to remove any remaining marks caused by the edges of the segments of the first subgroup during the first stage.

[0018] Although other diameters may be considered, the precursor may be expanded in the first stage to a first diameter that is preferably between 10% and 20% larger than the initial diameter of the precursor. A first stage with an expansion to a first diameter in this range can generally be achieved without unacceptable levels of stress on the precursor walls at the edges of the segments, particularly when working with high-quality steel.

[0019] After the second stage, a circumferential gap may be present between the edges of the arched surfaces of adjacent segments. The manner in which the expansion is achieved and the number of segments allow the width of this gap to be limited. In embodiments, the gap cannot exceed 5 mm, preferably does not exceed 2 mm, and most preferably does not exceed 1.5 mm. As a result, the visibility of vertical dividing lines in the final form can be prevented or avoided.

[0020] In one embodiment, the second diameter is preferably between 20% and 30% larger than the initial diameter of the precursor. The method and its associated apparatus provide a greater expansion of a precursor than would normally be possible for high-quality steels. This confers a Petition 870250094031, dated 10 / 14 / 2025, page 60 / 135 8 / 23 A larger margin allows for improved aesthetics of a can made from a durable material. Expanding only part of the container's surface in the first step, while carefully providing an ideal distribution of material force in the second step, ensures optimal expansion without harmful parting lines or other distortion. In this way, an optimally expanded container body with a smooth, flawless outer surface can be obtained.

[0021] In one embodiment, the first and second stages can be performed without rotating the precursor relative to the mandrel. The method of the invention avoids the need to rotate the precursor at any point during the process. This is more time-efficient and reduces potential errors in realigning the precursor for further expansion. Furthermore, the expansion can be achieved with a relatively simple and unique device. However, it is not excluded that a slight rotation may be provided in order to further avoid the presence of parting lines or to intensify a particular intended contour or profile.

[0022] The method can make use of arched segment surfaces that all have the same curvature at a given longitudinal position along the longitudinal geometric axis and / or that have a constant curvature at all positions along their longitudinal extent. However, designs with surfaces of different shapes can also be considered. The arched surfaces of one or more of the plurality of segments can be profiled in the longitudinal direction so that, after the second step, the expanded precursor body has a profiled outer surface. The method can thus provide an expanded cylinder with a gripping portion and / or any pattern that is satisfactory to the customer. In order to avoid variations in the upper and lower edges of the precursor body, each segment can have the same longitudinal profile length despite variations in the actual profile. In this way, trimming of the ends of the expanded precursor can be avoided.In this context, the longitudinal profile length is the path length when following the surface of a segment (or the precursor body) from a first reference position to a second reference position corresponding to the top and bottom of the can. In general, it may be desirable for the top and bottom ends to be the same length. Petition 870250094031, dated 10 / 14 / 2025, page 61 / 135 9 / 23 of the expanded precursor do not deviate by more than 0.5 mm from a smooth plane perpendicular to a longitudinal geometric axis of the body, preferably less than 0.25 mm or less than 0.1 mm.

[0023] In one embodiment, at least one first segment may have a longitudinal profile different from a second segment, or all segments may have different longitudinal profiles, while all segments have the same longitudinal profile length. The expert will recognize that several attractive tin designs can be created while respecting the geometric requirement that each longitudinal section of the wall must have equal length. In particular, designs can be created that are non-rotational symmetrical around the longitudinal geometric axis of the tin.

[0024] The longitudinal profile may comprise, at an end portion of all segments, a curve towards the longitudinal geometric axis of the forming mandrel. This profile of the segments allows a lower or upper portion of the can to remain at or near the initial diameter, or at least to maintain a diameter that is significantly smaller than the second diameter. This can be useful for ensuring a smaller base for stacking purposes or for reducing the presence of a sharp corner at the base. This curvature at the base is advantageous for access with a ladle, for example, which has a corresponding curved shape. At the upper end of the can, a smaller diameter may facilitate connection with a lid assembly, allowing the outer circumference of the lid assembly to remain within the outer circumference of the can.

[0025] The overall design of the expanded precursor at the end of the second stage will generally depend on the combined external surfaces of all segments and the degree to which they have been expanded. The expanded precursor body may have a profiled external surface in which portions of the external surface have the second diameter and other portions of the external surface are recessed relative to the second diameter by at least 10%, 12%, or 15%, and preferably at least 20%. The recessed portions may form a raised design or pattern relative to an otherwise uniform external surface. In this context, the term uniform is intended to denote a surface Petition 870250094031, dated 10 / 14 / 2025, page 62 / 135 10 / 23 cylindrical of constant diameter, i.e., 2D curved. However, it is not excluded that an external tool may also be provided to engage an external surface of the precursor, in particular to exert a force to lower portions of the external surface inwards, for example, on contours of the curved surfaces of some or all segments.

[0026] A can can be manufactured by expanding a cylindrical metal precursor using the method described above followed by: attaching a base to one of two open-end portions of the expanded precursor body. In the present context, the reference to the manufacture of a three-piece can is not intended to require that three pieces necessarily be combined together, but merely to the technique for forming a side wall without ends. In embodiments, only the base may be attached in one manufacturing step and an upper open end may be folded over or otherwise provided with a rim and closed with a separate closure. However, in preferred embodiments, the method may further comprise attaching a separate rim to the other of the two open-end portions to form a three-piece can.In this way, a sealed container with sufficient volume and an attractive shape can be created for the preservation of products, particularly infant nutritional products.

[0027] The base and / or rim is preferably fixed without first trimming the end portions of the expanded precursor body. As discussed above, the expanded precursor preferably has a constant and exact length around its circumference within the tolerances for stitching, where trimming is not necessary. It will be understood that it is desirable to avoid trimming, since any such procedure could create metal debris. In the past, length variation and the need for trimming were also avoided by retaining or clamping the ends of the can during expansion. This, however, can lead to other disadvantages such as wrinkling and / or cracking, and imposes additional limitations on both the equipment and the design. The present solution also avoids the need for clamping the ends of the can during expansion.

[0028] The invention also includes the three-piece can as follows Petition 870250094031, dated 10 / 14 / 2025, page 63 / 135 11 / 23 described above and hereafter. The can body may have an outer diameter and a profiled outer surface, wherein a first portion of the outer surface is recessed by at least 10% or 12% or 15% and preferably by at least 20% relative to a second portion of the outer surface which has the outer diameter. The method allows a wide choice of designs, with a high expansion threshold, preferably up to 30% of the initial diameter, even when using thin, high-strength steel, as discussed above. In preferred embodiments, highly anisotropic steel with little directionality may be used, such as tin-plated steel (TPS) TS275 according to the EU Packaging Steel standard EN10202, preferably having a yield strength / 0.2% strain (Rp) between 225 and 325 N / mm2.

[0029] In a particular embodiment, parts of the first portion and the second portion may be located in the same longitudinal position on the outer surface, i.e., at the same height on the can wall. The outer design of the can may be rotationally asymmetrical about the longitudinal geometric axis. Alternatively, reflection symmetry may be achieved with respect to a chosen face of the can, which is highly desirable for branding purposes. This is, in particular, achievable if each longitudinal section of the can body has the same longitudinal profile length.

[0030] In a desirable embodiment, the profile comprises a recessed circumferential groove encircling the can, wherein the longitudinal position of the groove varies around the circumference. The groove may have a constant shape, i.e., cross-sectional shape, around the circumference, or it may vary in shape, for example, depth and width around the circumference. However, this variation must remain within the general requirement that each longitudinal section of the can body has the same longitudinal profile length.

[0031] In certain embodiments, the first recessed portion may be a smaller part of the outer surface of the can and the second portion, which has the outer diameter, may be a larger part of the outer surface. The larger part may be more than 50% or more than 60% or more than 70% or more of Petition 870250094031, dated 10 / 14 / 2025, page 64 / 135 12 / 23 which is 80% of the outer surface of the can. This larger part can generally be flat, that is, with a constant curvature that corresponds to the maximum outer diameter.

[0032] According to another aspect of the invention, a forming mandrel is provided for expanding a cylindrical metal precursor in the manufacture of a three-piece can. The mandrel may comprise an actuating arm and a plurality of longitudinally extending segments arranged around the actuating arm, each of the segments having an inner cam surface and an arched outer surface for engaging an inner surface of a precursor positioned on the mandrel. The segments each have a longitudinal profile and, in one embodiment, at least one first segment may have a longitudinal profile different from a second segment, while all segments have the same longitudinal profile length.

[0033] In certain embodiments, all segments may have different longitudinal profiles, but the same overall longitudinal profile length. For example, each segment may have a generally flat profile with a recessed channel, and the longitudinal position, cross-sectional shape, and / or orientation of the recessed channel may vary from segment to segment around the circumference. In this way, a groove or contour can be created throughout the body of a mandrel-formed can without causing variations in the overall length of the can around its circumference.

[0034] Additionally or alternatively, the segments comprising a first subgroup of segments and a second subgroup of segments, wherein the actuating arm is longitudinally movable relative to the segments and has a plurality of wedge surfaces, arranged to contact the cam surfaces of the respective segments and move the first subgroup and the second subgroup radially outward at respective different speeds in a series of steps to expand the mandrel from a first state to a final state. The forming mandrel of the invention allows the expansion of a high-quality steel cylinder in a single process, which provides better control of the stretching forces on the material.

[0035] The first subgroup may consist of an even number of Petition 870250094031, dated 10 / 14 / 2025, page 65 / 135 13 / 23 segments equal to or greater than 6, preferably equal to or greater than 8, or up to 12 or more. The second subgroup may consist of an identical number of segments. By increasing the number of segments, a better distribution of forces can be achieved and, for a given expansion, the overall gap between adjacent segments at the conclusion of the operation can be reduced. A total of up to 24 segments may therefore be present.

[0036] The plurality of wedge surfaces may comprise a first set of wedge surfaces radially aligned with segments of the first subgroup and a second set of wedge surfaces radially aligned with segments of the second subgroup. Because each segment has an associated wedge surface, control of the expansion of each segment can be achieved. As a result, each step of the expansion method of the invention can be performed accurately. The wedge surfaces may be separate surfaces on a single wedge body or may be formed by multiple wedge bodies assembled together. It will also be understood that the wedge surfaces may be arranged in tandem in the longitudinal direction in order to provide a balanced expansion force at two points along the longitudinal geometric axis for each segment.

[0037] Each of the plurality of wedge surfaces can be defined by a wedge angle relative to the longitudinal geometric axis of the forming mandrel. A wedge angle of the first set of wedges can be constant throughout the longitudinal movement of the actuating arm, and the wedge angle of the second set of wedges can also be constant, but greater than the wedge angle of the first set of wedges. In one embodiment, this wedge angle can initially be greater than the wedge angle of the first set of wedges and subsequently equal to it. By controlling the wedge angle of the second set of wedges so that it is different from and greater than the angle of the first set, the second subgroup of segments can reach the first subgroup of segments.

[0038] In one embodiment, the first subgroup of segments may have a lower cut, whereby the second subgroup of segments may be recessed behind the arched outer surfaces of the first subgroup in Petition 870250094031, dated 10 / 14 / 2025, page 66 / 135 14 / 23 first stage. Thus, the overall initial diameter of the mandrel can be reduced for insertion into the precursor. Furthermore, after the expansion process is complete, the mandrel can be collapsed again for removal, even if some regions of the precursor are still at or near the initial diameter.

[0039] The arched surfaces of the segments of the first and second subgroups may have different sizes. In particular, the segments of the first subgroup may be larger than those of the second subgroup. In a preferred embodiment, the arched surfaces of the first and second subgroups may be of equal size. This ensures that in the final critical expansion step, the inner surface of the precursor is subject to balanced expansion and any gaps between the segments are equally spaced.

[0040] It will be understood that the ability to provide significant expansion offers considerable scope for forming cans with different aesthetic, functional, and ergonomic shapes, while it remains possible to remove the mandrel after the expansion stage is complete. In certain designs, it may be desirable to only fully expand the smaller regions of the can's outer surface to a maximum limit, leaving the larger regions with a smaller expansion. In general, in the final state, a larger portion of the arched surfaces of all segments may have a diameter corresponding to a maximum outer diameter of the can, and a smaller portion may be recessed by at least 10%, preferably 15%, and more preferably 20%, relative to the outer diameter. For the sake of definition, where reference is made to the can's diameter, this will thus refer to the maximum outer diameter.The larger portion can be more than 50%, 60%, 70%, or 80% of the can's outer surface. This larger portion can generally be flat, that is, with a constant curvature that corresponds to the maximum outer diameter.

[0041] An additional advantage of such high expansion is that, for the same can volume, less material is needed. The material reduction can be at least 2.5%, or 5%, or even 7.5% of the total can weight. Brief description of the drawings

[0042] The embodiments of the present invention will be described in the heading Petition 870250094031, dated 10 / 14 / 2025, p. 67 / 135 15 / 23 example, with reference to the attached drawings, in which:

[0043] Figure 1A shows a flowchart representing a sequence of steps for manufacturing a three-piece can from a metal blank (raw metal) and including an expansion step,

[0044] Figure 1B shows an illustration of a top and a side wall of an expanded cylindrical metallic precursor according to methods known in the art,

[0045] Figure 2A shows a cross-sectional view of an expansion apparatus, for expanding a cylindrical metallic precursor, in which the apparatus is shown in a contracted state before expansion, with the precursor positioned around the apparatus,

[0046] Figure 2B shows a cross-sectional view of the expansion apparatus of Figure 2A, after the expansion is complete,

[0047] Figure 3 shows a cross-section through the mandrel of Figure 2A in position III-III,

[0048] Figures 4A to 4C show a longitudinal section obtained at position IV-IV in Figure 3 obtained at different stages during the expansion of the mandrel;

[0049] Figure 5A shows a cross-sectional view of two adjacent segments in the mandrel of Figure 3 before a first expansion stage,

[0050] Figure 5B shows a cross-sectional view of two adjacent segments in the mandrel of Figure 3 at the beginning of a second expansion stage,

[0051] Figure 5C shows a cross-sectional view of two adjacent segments in the mandrel of Figure 3 at a further stage of expansion,

[0052] Figure 5D shows a cross-sectional view of two adjacent segments in the mandrel of Figure 3 at a final stage of expansion,

[0053] Figure 5E shows a cross-sectional view of two adjacent segments in the mandrel of Figure 3 in an alternative final stage of expansion, and Petition 870250094031, dated 10 / 14 / 2025, page 68 / 135 16 / 23

[0054] Figures 6 to 8 show three exemplary expanded container bodies according to the method of the invention. Description of modalities

[0055] Figure 1A shows a sequence 100 of steps 110-160 for the manufacture of a three-piece can from a metal blank 1. This sequence comprises, in particular, an expansion step 140. Other steps will be known to those skilled in the art and described only briefly. In step 110, a metal sheet is cut into a flat blank 1. In step 120, the blank may be coated and cured. After this optional step, the flat blank 1 is welded onto a generally cylindrical precursor 2 in step 130. The precursor 2 has a metal body with two open ends and a vertical seam (not shown) present where the side wall has been joined to itself to form a cylinder. The metal body of the cylindrical precursor 2 is generally a steel body, prepared from a steel blank. In step 140, a portion of the wall of the cylindrical metal precursor 2 is expanded outwards.The resulting expanded container 3 has a shape that is contoured and diverges from the original cylindrical shape. This step can be performed according to the method of the invention, described further below. In step 150, the expanded container 3 can be subjected to any of flanging (F, as shown) and / or other processes known in the art comprising, for example, any of printing or edge turning (not shown). In step 160, the expanded container 3 can be provided with closures 4, 5 fixed to each of the two open ends with or without sealing and / or pre-filling. This completes the manufacturing cycle of the three-piece can. It should be noted that this sequence serves merely as an example and the expansion step of the invention can also be part of other sequences known in the art for manufacturing a three-piece can.However, it will be noted that in the illustrated embodiment, there is no need to trim the ends of the container before the closing step 160.

[0056] Figure 1B shows an illustration of a top and side view of a cylindrical precursor 2 of diameter d before and after expansion into an expanded body 3 according to expansion methods known in the art. The illustration of the expanded body exaggerates the shape of the precursor in order to illustrate the Petition 870250094031, dated 10 / 14 / 2025, page 69 / 135 17 / 23 problem of expansion methods known in the art. Instead of a round body of diameter D, the surface of the resulting body 3 has a number of vertical parting lines (S). These lines correspond to locations of high stretch in the metal wall during expansion. The vertical parting lines formed between adjacent segments of an expansion mandrel (not shown) and do not follow the curvature of the mandrel. In this illustration, this would correspond to the locally flat section between every two of six segments.

[0057] Figure 2A shows a cross-sectional view of a conventional expanding apparatus 10, which is shown to explain the underlying principle for expanding a cylindrical metallic precursor 2. The apparatus is shown in a retracted state, i.e., before expansion. The expanding apparatus 10 comprises a housing 11 and a forming mandrel 13 extending from the housing 11. The forming mandrel 13 comprises a plurality of similar segments 14 spaced around an expanding arm 12. Each segment 14 has an arched contact surface A for contacting or engaging an inner surface I of a cylindrical precursor 2 placed around the segments 14. Each segment 14 additionally has a cam surface 18 on its inner side, facing the expanding arm 12. In the retracted state, the contact surfaces A of the segments 14 are radially spaced inward to the inner surface I of the container body 2.A proximal end 12A of the expander arm 12 and the ends 20 of the segments 14 are received within the housing 11. A distal end 13B of the mandrel 13 has a reduced diameter.

[0058] The expanding arm 12 is axially movable within the housing (along the geometric Z-axis) to cause the expansion of the segments 14. The segments 14 extend longitudinally along the expanding arm 12. A pair of wedges 16 is positioned around the expanding arm 12 in tandem. The expanding arm 12 and the wedges 16 form the actuator of the forming mandrel 13. Each wedge 16 has a plurality of wedge surfaces 17, each of which contacts a coupling cam surface 18 of the segments 14. The axial movement of the expanding arm 12 together with the wedges 16 causes the wedge surfaces 17 to traverse the surfaces of Petition 870250094031, dated 10 / 14 / 2025, page 70 / 135 18 / 23 came 18 to expand segments 14 outward to make contact with the inner surface I of precursor 2.

[0059] Figure 2B shows a cross-sectional view of the same expansion apparatus 10 from Figure 2A, shown in a finally expanded state. This view shows how the expanding arm 12 has been moved proximally in the direction of the housing 11 (Z direction). This axial movement caused the wedge surfaces 17 to cooperate with the corresponding cam surfaces 18 of the segments 14 to force the segments 14 radially outward for engagement with the inner surface I of the precursor 2. The inner surface I of the precursor 2 is deformed accordingly to adopt the shape of the expanded mandrel 13. The distal end 13B of the mandrel defines the smallest inner diameter of the expanded precursor 2.

[0060] When the expansion is complete, the expanding arm 12 is moved axially away from the housing 11 and the segments 14 can be brought back to a collapsed or retracted position. The precursor 2 can then be removed from the forming mandrel 13. It will be understood that the mandrel 13 must collapse sufficiently so that the larger outer diameter can pass through the smaller diameter portion of the precursor 2. In conventional expanding devices, such as apparatus 10 of Figure 2, about 6 or 8 segments 14 can be provided, all of them being substantially identical.

[0061] Figure 3 shows a cross-sectional view in the (XY) plane of a forming mandrel 12 of an expanding apparatus 10 according to the invention. Similar numbers will be used for similar components, as in the case of the conventional apparatus of Figure 2. The mandrel 13 is shown in its initial state, before any expansion, with an outer diameter of d1.

[0062] The forming mandrel 13 comprises twelve segments 14, which surround the expanding arm 12. In this case, the segments 14 are divided into two subgroups, namely the first subgroup segments 14A and the second subgroup segments 14B. The first subgroup segments 14A are spaced outward from the second subgroup segments 14B at the initial outer diameter d1. It will also be observed that the segments 14A Petition 870250094031, dated 10 / 14 / 2025, page 71 / 135 19 / 23 have lower cutting flanks 19. This allows the second subgroup segments 14B to be recessed behind the arched contact surfaces A of the first subgroup segments 14A in this initial state of the chuck 13.

[0063] The first subgroup segments 14A have the first cam surfaces 18A on their inner side, while the second subgroup segments have the second cam surfaces 14B on their inner side. Due to the presence of the lower cutting flanks 19, the second cam surfaces 18B are slightly narrower than the first cam surfaces 18A, although the respective arched contact surfaces A of all segments 14 are of identical size.

[0064] The expanding arm 12 contains a wedge 16, with wedge surfaces 17, which are also divided into first wedge surfaces 17A and second wedge surfaces 17B. These surfaces engage respectively with the first and second cam surfaces 18A, 18B of the segments 14.

[0065] Figure 4A schematically shows the wedges 16, illustrating the profiles of the wedge surfaces 17 and cam surfaces 18 of the forming mandrel 13 of Figure 3 in a longitudinal section in position III-III. The first wedge surfaces 17A, which act on the first subgroup segments 14A, are shown in the upper half of the figure, while the second wedge surfaces 17B, which act on the second subgroup segments 14B, are shown in the lower half of the figure. Also shown in this view is a channel 40 formed in the arched surfaces A of the mandrel 13. The channel 40 has a depth that is almost equal to the overall expansion of the mandrel 13. It also corresponds to a diameter of a distal portion 13B of the mandrel 13. The channel 40 extends around the entire circumference of the mandrel 13, but varies in its longitudinal position from segment to segment.However, the width and depth of channel 40 are, for each segment 14, arranged so that the profile length of each segment 14 following the arched surface A longitudinally is identical.

[0066] Dealing first with the first wedge surfaces 17A and the first coupling cam surfaces 18A, these have an angle Petition 870250094031, dated 10 / 14 / 2025, page 72 / 135 20 / 23 constant α1 which generally corresponds to that of the conventional apparatus 10 in Figure 2. In the case of the second wedge surfaces 17B, these have a two-step surface. A first part of the surface, denoted 17Bi, has an angle α2, which is greater than the angle α1 of the first wedge surfaces 17A. A second part 17Bii of the surface has an angle α1 which, again, corresponds to that of the first wedge surface 17A. In the illustrated embodiment, the first and second parts 17Bi and 17Bii have approximately equal length. Similarly, the second cam surfaces 18B are also in two parts, where a first part 18Bi has an angle α2 and a second part has an angle α1.

[0067] Figure 4B shows the forming mandrel 13 of Figure 4A, with the expanding arm 12 and wedges 16 partially retracted in the proximal direction relative to the segments 14. The first wedge surface 17A has progressed along the respective first cam surface 18A, causing the first subgroup segments 14A to move radially outward. The second wedge surface 17B has also progressed along the respective second cam surface 18B. As depicted, during this part of the movement, the first part 17Bi of the second wedge surface and the first part 18Bi of the second cam surface are in sliding engagement and impose the expansion of segment 14B at angle α2. Since angle α2 is greater than angle α1, the second subgroup segment 14B has moved radially outward by a distance that is greater than that of the first subgroup segment 14A.

[0068] Figure 4C shows the forming mandrel 13 of Figure 4A, with the expanding arm 12 and wedges 16 almost fully retracted in the proximal direction relative to the segments 14. The first wedge surface 17A continued along the respective first cam surface 18A, causing the segments of the first subgroup 14A to continue to move radially outward at the same speed, as imposed by the angle α1. The second wedge surface 17B progressed further along the respective second cam surface 18B, so that now the second first part 17Bii of the second wedge surface 17B and the second part 18Bii of the second cam surface Petition 870250094031, dated 10 / 14 / 2025, page 73 / 135 21 / 23 18B enter into sliding engagement for the first time. From this point in the trajectory, the additional proximal movement of the expanding arm 12 causes the expansion of the second subgroup segment 14B to be imposed by the inclination of these parts. This will occur at angle α1 at the same speed as that of the first subgroup segment 14A.

[0069] Figure 5A shows an enlarged view of two adjacent segments 14A, 14B of Figure 3 at the beginning of a first expansion stage. The arched surface A of the first subgroup segment 14A contacts the inner surface I of the precursor 2 and causes the curvature of the inner surface I to conform to its curvature. The arched surface A of the second subgroup segment 14B is radially spaced inward from the inner surface I by a distance Rx. Also visible are the lower shear flanks 19 of the first subgroup segment 14A and a pair of transition ears 30 behind which the second subgroup segment 14B is recessed. During this expansion stage, all the stretching of the precursor is caused by the first subgroup segments 14A, in contact with only about half of the inner surface I.

[0070] Figure 5B shows an enlarged view of segments 14A and 14B at the point where the second subgroup segment 14B first contacts the inner surface I of precursor 2. At this point, the second subgroup segment 14B is still radially inward to the first subgroup segment 14A. Although from this point some stretching of precursor 2 will occur by engagement of the second subgroup segment 14B, nevertheless, the lateral edges of the first subgroup segments 14A at the position of the transition ears 30 are a critical location P, where striations can be created in precursor 2. With reference to Figure 4B, this figure still corresponds to the expansion period represented, where the first part 17Bi of the second wedge surface and the first part 18Bi of the second cam surface are in sliding engagement and impose the expansion of segment 14B at angle α2.

[0071] Figure 5C shows an enlarged view of segments 14A and 14B during a second stage of the expansion step at the point where the arched surfaces A of all segments 14 align for the first time. In the illustrated embodiment, this also corresponds to the point where the edges Petition 870250094031, dated 10 / 14 / 2025, page 74 / 135 22 / 23 sides of adjacent segments 14 touch precisely and therefore there is no gap between adjacent segments 14. It will be understood that this is a chosen position and it is not necessary for the mandrel 13 to pass through this gapless configuration. This corresponds to the position shown in Figure 4C, where the first part 17Bi of the second wedge surface and the first part 18Bi of the second cam surface first enter into sliding engagement. From this point onward, all segments will expand at the same speed and the arched surfaces A of all segments 14 will remain radially aligned.

[0072] Figure 5D shows an enlarged view of segments 14A and 14B during a final stage of the expansion step. The arched surfaces A of all segments 14 remain aligned, but have now expanded to a second diameter d2 which is larger than the initial diameter d1. During the expansion from the position shown in Figure 5C, segments 14A, 14B moved apart, creating a circumferential gap 32 between the adjacent segments 14A, 14B. It will be understood that the circumferential gap 32 also extends in a longitudinal direction from mandrel 13.

[0073] Figure 5E shows an enlarged view of segments 14A and 14B in an alternative final expansion stage. In this situation, the second subgroup segment 14B has expanded to a diameter that is slightly larger than the second diameter d2. This can be used to stretch the precursor 2 slightly away from the edges of the first subgroup segment 14A at the transition ear position 30. This can be used to provide a slight overstretch at the critical location P, to remove previously created striations. This alternative final stage can be achieved by an additional portion of the second cam surface 18B, following the second portion 18Bii.

[0074] Figure 6 shows the completed can 3 after finishing the expansion step and after providing top and bottom closures 4, 5. A profile 42 is provided around the outer surface, which corresponds to channel 40 in mandrel 13. Figures 7 and 8 represent alternative cans 3, all of which have contoured outer surfaces. As a result of the improved expansion achievable with the revealed mandrel, it is possible to achieve diameter variations of Petition 870250094031, dated 10 / 14 / 2025, page 75 / 135 23 / 23 up to 30%, while ensuring an otherwise smooth and flawless surface of can 3.

[0075] The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those skilled in the art. In particular, different numbers of segments and different wedge angles and profiles can be used to create cans of different designs. Consequently, although specific embodiments have been described, they are only examples and do not limit the scope of the invention. Petition 870250094031, dated 10 / 14 / 2025, page 76 / 135

Claims

1 / 6 Claims 1. METHOD FOR EXPANDING A CYLINDRICAL METALLIC PRECURSOR IN THE MANUFACTURE OF A THREE-PIECE CAN, the method being characterized in that it comprises the steps of: - arranging the precursor, which has an initial diameter, around a forming mandrel, the forming mandrel having a plurality of longitudinally extending segments arranged radially around a longitudinal geometric axis of the forming mandrel, the segments having arched surfaces to engage an inner surface of the precursor, - acting, in a first step, a first subgroup of the plurality of segments to expand outwards to engage with the inner surface of the precursor and expand at least a portion thereof to a first diameter that is greater than the initial diameter of the precursor, - acting, in a second step,A second subgroup of the plurality of segments expands outward and also engages with the inner surface of the precursor, whereby the second subgroup expands at least a portion of the precursor to a second diameter that is larger than the first diameter, - in which the arched surfaces of the plurality of segments are profiled in the longitudinal direction, so that, after the second step, the expanded precursor body has a profiled outer surface with a first portion of the outer surface being recessed by at least 10% relative to a second portion of the outer surface having the outer diameter, and the first portion and the second portion are in the same longitudinal position of the outer surface, but in different circumferential positions and a longitudinal profile length in all circumferential positions around the can is equal.

2. METHOD, according to claim 1, characterized in that the first subgroup consists of alternating segments around the longitudinal geometric axis of the forming mandrel and the second subgroup consists of all the remaining segments.

3. METHOD, according to any of the claims 1 Petition 870250094031, of 10 / 14 / 2025, pp. 130 / 135 2 / 6 to 2, characterized in that during the first step, the segments of the second subgroup are actuated to expand outward at a speed that is greater than the speed at which the segments of the first subgroup expand outward.

4. METHOD, according to any one of claims 1 to 3, characterized in that during the second step, the first subgroup expands from the first diameter to the second diameter.

5. METHOD, according to any one of claims 1 to 4, characterized in that during the second stage, all segments are actuated to expand outwards at the same speed.

6. METHOD, according to any one of claims 1 to 5, characterized in that the second step comprises an initial stage in which the arched surfaces of the second subgroup are engaged with the inner surface of the precursor and radially inward to the arched surfaces of the first subgroup.

7. METHOD, according to any one of claims 1 to 6, characterized in that the second step comprises an intermediate stage in which the arched surfaces of the second subgroup are radially aligned with the arched surfaces of the first subgroup and the edges of the arched surfaces of adjacent segments are initially engaged.

8. METHOD, according to any one of claims 1 to 7, characterized in that the second step comprises a final stage in which the arched surfaces of the second subgroup are radially outward from the arched surfaces of the first subgroup.

9. METHOD, according to any one of claims 1 to 8, characterized in that the first diameter is between 10% and 20% larger than the initial diameter of the precursor.

10. METHOD, according to any one of claims 1 to 9, characterized in that, after the second step, a circumferential gap is formed between the edges of the arched surfaces of adjacent segments and the width of the gap does not exceed 5 mm, Petition 870250094031, dated 10 / 14 / 2025, page 131 / 135 3 / 6, preferably does not exceed 2 mm, more preferably does not exceed 1.5 mm.

11. METHOD, according to any one of claims 1 to 10, characterized in that the second diameter is between 20% and 30% larger than the initial diameter of the precursor.

12. METHOD, according to any one of claims 1 to 11, characterized in that the first and second steps are performed without rotation of the precursor relative to the mandrel.

13. METHOD, according to any one of claims 1 to 12, characterized in that the profile comprises, in an end portion of all segments, a curve towards the longitudinal geometric axis of the forming mandrel.

14. METHOD FOR MANUFACTURING A THREE-PIECE CAN, characterized in that it comprises the steps of: expanding a cylindrical metal precursor by a method as defined in any one of claims 1 to 13; attaching a base to one of two open-end portions of the expanded precursor body; attaching a hoop to the other of the two open-end portions, preferably without trimming the open-end portions.

15. FORMING MANDREL for expanding a cylindrical metal precursor in the manufacture of a three-piece can, the mandrel being characterized in that it comprises: an actuating arm; and a plurality of longitudinally extending segments arranged around the actuating arm, each of the segments having an inner cam surface and an arched outer surface for engaging an inner surface of a precursor positioned on the mandrel, the segments comprising a first subgroup of segments and a second subgroup of segments, the outer surfaces each having a longitudinal profile wherein at least one first segment has a longitudinal profile different from a second segment, while all segments have the same profile length. Petition 870250094031, dated 10 / 14 / 2025, p.132 / 135 4 / 6 longitudinal in which the actuating arm is longitudinally movable relative to the segments and has a plurality of wedge surfaces, arranged to contact the cam surfaces of the respective segments and move the first subgroup and the second subgroup radially outwards at respective different speeds in a series of steps to expand the mandrel from a first state to a final state in which a larger part of the arched surfaces of all segments has a diameter that corresponds to a maximum external diameter of the can and a smaller part is recessed by at least 10%.

16. MANDREL, according to claim 15, characterized in that the first subgroup consists of an even number of segments equal to or greater than 6, preferably equal to or greater than 12, and the second subgroup consists of an identical number of segments.

17. MANDREL, according to any one of claims 15 to 16, characterized in that the plurality of wedge surfaces comprises a first set of wedge surfaces radially aligned with segments of the first subgroup and a second set of wedge surfaces radially aligned with segments of the second subgroup.

18. MANDREL, according to claim 17, characterized in that the wedge angle of the first set of wedge surfaces is constant throughout the longitudinal movement of the actuating arm and the wedge angle of the second set of wedge surfaces is initially greater than the wedge angle of the first set of wedge surfaces and subsequently equal to it.

19. MANDREL, according to any one of claims 15 to 18, characterized in that the first subgroup of segments has a lower cut, whereby the second subgroup of segments can be recessed behind the arched outer surfaces of the first subgroup in the first state of the mandrel.

20. MANDREL, according to any one of claims 15 to 19, characterized in that the arched surfaces of the first subgroup Petition 870250094031, of 10 / 14 / 2025, pp. 133 / 135 5 / 6 and of the second subgroup are of equal size.

21. MANDREL, according to any one of claims 15 to 20, characterized in that, in the final state, a larger portion of the arched surfaces of all segments has a diameter that corresponds to a maximum external diameter of the can and a smaller portion is recessed by at least 15% and more preferably 20%, relative to the external diameter.

22. MANDREL, according to any one of claims 15 to 21, characterized in that all segments have different longitudinal profiles, but the same overall longitudinal profile length.

23. MANDREL, according to any one of claims 15 to 22, characterized in that each segment has a generally flat profile with a recessed channel and the longitudinal position, cross-sectional shape and / or orientation of the recessed channel vary from segment to segment around the circumference.

24. THREE-PIECE CAN, characterized in that it has an outer diameter and a profiled outer surface, wherein a first portion of the outer surface is recessed by at least 10% relative to a second portion of the outer surface which has the same outer diameter, and the first portion and the second portion are in the same longitudinal position on the outer surface, but in different circumferential positions, and the longitudinal profile length in all circumferential positions around the can is equal.

25. A can, according to claim 24, characterized in that the profiled outer surface comprises a recessed groove encircling the can.

26. A can, according to claim 25, characterized in that the longitudinal position, shape and / or orientation of the groove varies around the circumference.

27. A can, according to any one of claims 24 to 26, characterized in that the outer surface has a profile that is rotationally asymmetric about the circumference, but has reflection symmetry about a plane through a longitudinal geometric axis of the can.

28. CAN, according to any of the claims in Petition 870250094031, dated 10 / 14 / 2025, pp. 134 / 135 6 / 6 27, characterized in that it comprises a single continuous groove. Petition 870250094031, dated 10 / 14 / 2025, pp. 135 / 135

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