A method for manufacturing a non-axisymmetric tubular metal body, intended to form a side wall of a container

Abstract

The present invention relates to a method for manufacturing a non-axisymmetric tubular metal body (10), intended to form a side wall of a container, preferably a metal can. The method comprises the following steps: - a supplying stage, to supply a cylindrical body (20), with a longitudinal axis (20'), - at least one first radial expansion step, to obtain a tubular preform from said cylindrical body (20), - an angular indexing step, to index said tubular preform about said longitudinal axis, and - at least one second radial expansion step, to obtain said non-axisymmetric tubular metal body (10) from the said tubular preform (30).

Description

[0001] Title of the invention: A method for manufacturing a non-axisymmetric tubular metal body, intended to form a side wall of a container Technical field of the invention

[0002] The present invention relates to the technical field of methods for manufacturing non-axisymmetric tubular metal bodies, intended to form a side wall of a container.

[0003] Background of the Invention

[0004] In the field of manufacturing tubular metal bodies, many methods are known for shaping components intended for applications such as containers.

[0005] Traditionally such tubular bodies are made from flat rectangular blanks rolled and welded.

[0006] The shaping of these tubular bodies relies on mechanical expansion or stamping processes.

[0007] These methods generally produce tubular parts with regular shapes, often circular or axisymmetric, well-suited to specific industrial needs.

[0008] However, there is an increasing number of cases where non-axisymmetric shapes are required to meet specific design requirements.

[0009] Traditional expansion and stamping processes are not optimized for producing non-axisymmetric tubular metal bodies, or they require complex and costly secondary operations to adjust the final shape.

[0010] In response to this issue, some more recent processes incorporate specific expansion and molding steps to attempt to achieve more complex shapes. However, these techniques require specific tooling for each type of shape, making them unsuitable for mass production or customized shapes.

[0011] Consequently, there remains a persistent need to develop a more efficient and flexible process for manufacturing non-axisymmetric tubular metal bodies, enabling a reduction in production steps while ensuring a high degree of precision in the final shape. Such a method would optimize the manufacturing process, reducing both production costs and the time required to achieve a specific geometry.

[0012] Summary of the Invention

[0013] To overcome the aforementioned drawback of the prior art, the present invention proposes a method for manufacturing non-axisymmetric tubular metal bodies that optimizes the production process, reduces the number of required production steps, and maintains a high degree of precision in the final shape.This method specifically involves a sequence of radial expansion steps and angular indexing that allow for the creation of non-cylindrical geometries without the need for costly and complex secondary operations.

[0014] More specifically, the invention relates to a method for manufacturing a non-axisymmetric tubular metal body, intended to form a side wall of a container, preferably a metal can.

[0015] The process comprises the following steps:

[0016] - a supplying stage, to supply a cylindrical body, preferably a welded cylindrical body, with a longitudinal axis,

[0017] - at least one first radial expansion step, to obtain a tubular preform from said welded cylindrical body,

[0018] - an angular indexing step, to index said tubular preform about said longitudinal axis, and

[0019] - at least one second radial expansion step, to obtain said non-axisymmetric tubular metal body from the said tubular preform.

[0020] The present invention addresses notably two primary aspects: improving product quality. By employing a two-step radial expansion method, the invention achieves significant advancements in both areas.

[0021] Dividing the radial expansion into two distinct steps allows for a more controlled deformation of the tubular body, thereby minimizing marks or irregularities caused by the expansion process.

[0022] This ensures a smoother surface finish and enhanced geometric precision, particularly important for applications requiring high aesthetic or functional standards.

[0023] Additionally, the ability to refine the shape progressively reduces the occurrence of defects, which could compromise the integrity or appearance of the final product.

[0024] Moreover, by limiting the degree of deformation at each step, the method reduces the mechanical stress imposed on the metallic structure during the expansion process.

[0025] This staged approach significantly lowers the risk of structural failure, such as cracking or buckling, which can occur when deformation is concentrated in a single, high-intensity step.

[0026] Furthermore, the progressive deformation allows for better material flow and stress distribution, enhancing the overall reliability and consistency of the manufacturing process.Other non-limiting and advantageous features of the process according to the invention, taken individually or in all technically possible combinations, are as follows.

[0027] In a preferred embodiment, said at least one first radial expansion step is configured to obtain a tubular preform having:

[0028] - a non-round shape or round shape,

[0029] and

[0030] - having one of the following combinations:

[0031] -- 100% of expansion and lower than 100% of surface change,

[0032] -- lower than 100% of expansion and 100% of surface change,

[0033] -- lower than 100% of expansion and of surface change,

[0034] and said at least one second radial expansion step is configured to obtain said non-axisymmetric tubular metal body having:

[0035] - a final, non-round shape, or

[0036] - a near-final, non-round shape, whereof at least a part is at a final shape and at least a part is at a non-final shape.

[0037] According to this preferred embodiment, the at least one first radial expansion step and the at least one second radial expansion step are advantageously selected from:

[0038] - the at least one first radial expansion step is implemented to obtain a tubular preform non-round, 100% expansion and lower than 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape;

[0039] - the at least one first radial expansion step is implemented to obtain a tubular preform non-round, lower than 100% expansion and 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape;

[0040] - the at least one first radial expansion step is implemented to obtain a tubular preform non-round, lower than 100% of expansion and of surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape;

[0041] - the at least one first radial expansion step is implemented to obtain a tubular preform round, 100% expansion and lower than 100% surface change, and the at leastone second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape;

[0042] - the at least one first radial expansion step is implemented to obtain a tubular preform round, lower than 100% expansion and 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape;

[0043] - the at least one first radial expansion step is implemented to obtain a tubular preform round, lower than 100% of expansion and of surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body, at the final shape.

[0044] The radial expansion step is preferably carried out by radial expansion tools having moving segments or stretching dies.

[0045] The method further comprising preferably a stretching step, for stretching the extremities of said cylindrical body, before the at least one first radial expansion step.

[0046] The method further comprises preferably, before the at least first radial expansion step, a prior angular indexing step, about a longitudinal axis of said cylindrical body.

[0047] The cylindrical body comprises preferably a weld line and in that said prior angular indexing step is adjusted so that said weld line is angularly offset with respect to the defined space between two segments.

[0048] Different radial expansion tools are preferably used for each radial expansion step.

[0049] The present invention further relates to:

[0050] - a non-axisymmetric tubular metal body obtained by the method according to the invention,

[0051] - a container comprising a non-axisymmetric tubular metal body according to the invention.

[0052] Of course, the various features, variations, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive.

[0053] Detailed description of the inventionMoreover, various other features of the invention emerge from the appended description made with reference to the drawings that illustrate non-limiting embodiments of the invention, where:

[0054] [Fig. 1] is a general and schematic view of a cylindrical body which is manufactured into a non-axisymmetric tubular metal body;

[0055] [Fig. 2] is a view of a stretching step, for stretching the extremities of said cylindrical body, before the at least one first radial expansion step, to obtain a stretched cylindrical body;

[0056] [Fig. 3] is a view of a first radial expansion step, to obtain a tubular preform, here of round shape, from said cylindrical body;

[0057] [Fig. 4] is a view of a second radial expansion step, to obtain the non-axisymmetric tubular metal body from the said tubular preform of round shape;

[0058] [Fig. 5] is a view of a first radial expansion step, to obtain a tubular preform, here of non-round shape, from said cylindrical body;

[0059] [Fig. 6] is a view of a second radial expansion step (i.e. segments forming), to obtain the non-axisymmetric tubular metal body from the said tubular preform of nonround shape;

[0060] [Fig. 7] is a view of another embodiment for a second radial expansion step (i.e. die forming), to obtain the non-axisymmetric tubular metal body from the said tubular preform of non-round shape.

[0061] It should be noted that in these figures, the structural and / or functional elements common to the different variations may have the same references.

[0062] As shown schematically according to Figure 1, the present invention relates to a method for manufacturing a non-axisymmetric tubular metal body 10, intended to form a side wall of a container, preferably a metal can.

[0063] By “container, preferably a metal can”, it is meant a structure designed to hold and store materials, for food and non-food stuffs, such as powders or other particulate products.

[0064] This container is particularly suitable for industrial, commercial, or consumer applications where durability, structural integrity, and the ability to preserve the contents are critical.

[0065] The container comprises advantageously:

[0066] - a side wall formed by the non-axisymmetric tubular metal body 10,- a bottom wall, and

[0067] - a cover.

[0068] The assembly of the bottom wall and the cover to the side wall, is, for example, achieved by metal seaming, ensuring a robust and airtight construction that preserves the integrity of the contents while providing mechanical strength and durability.

[0069] For the purposes of the present invention, the tubular metal body is preferably made from steel alloy or an aluminum alloy.

[0070] By “tubular metal body”, it is meant a structure having a hollow, elongated shape with a continuous wall, typically formed from a metallic material.

[0071] In general, a tubular body may have a cross-sectional shape that is axisymmetric (e.g., circular, also named round) or non-axisymmetric (e.g., irregular, also named non-round).

[0072] By “non-axisymmetric tubular metal body 10”, it is meant a cross-sectional shape which deviates from perfect symmetry about its longitudinal axis 10’.

[0073] Unlike axisymmetric tubular bodies, which typically have circular cross-sections, a non-axisymmetric tubular metal body 10 features radial deformations 11 forming outward (convex) or inward (concave) contours (also named patterns or reliefs) distributed along portions of its circumference.

[0074] These contours, advantageously formed along specific portions of the tubular body’s height, create irregular or complex geometries tailored to meet specific design or functional requirements.

[0075] The term “non-axisymmetric” refers advantageously to the absence of uniformity or rotational symmetry about the central longitudinal axis 10’. This unique characteristic allows the tubular metal body to achieve notably enhanced design flexibility, while maintaining precise radial deformations 11 over selected portions of its geometry.

[0076] In the invention, as shown Figure 1 , the process comprises steps to manufacture the non-axisymmetric tubular metal body 10 from a cylindrical body 20.

[0077] According to the invention, the method of manufacturing comprises the following steps:

[0078] - a supplying stage, to supply a cylindrical body 20, with a longitudinal axis 20’ (Figure 1),- possibly a stretching step (Figure 2), for stretching the extremities 22 of said cylindrical body 20, before the at least one first radial expansion step,

[0079] - possibly a prior angular indexing step, to index said cylindrical body 20 about said longitudinal axis 20’, before the at least first radial expansion step,

[0080] - at least one first radial expansion step (Figure 3 or Figure 5), to obtain a tubular preform 30 having a longitudinal axis 30’, from said cylindrical body 20,

[0081] - an angular indexing step (Figure 4 and Figure 6), to index said tubular preform 30 about said longitudinal axis 30’, and

[0082] - at least one second radial expansion step (Figure 4 and Figure 6), to obtain said non-axisymmetric tubular metal body 10 from the said tubular preform 30.

[0083] The present invention thus relates also to:

[0084] - the non-axisymmetric tubular metal body 10 obtained by the method according to the invention, and

[0085] - the container comprising a non-axisymmetric tubular metal body 10 according to the invention.

[0086] Radial expansion steps - General overview

[0087] In general, the method comprises “radial expansion step” which refers to a controlled manufacturing operation in which a tubular structure, such as a cylindrical body or a tubular preform, is subjected to forces that deform it radially outward from its longitudinal axis.

[0088] This process is used to modify the cross-sectional geometry of the structure while preserving its structural integrity and maintaining its longitudinal alignment.

[0089] The radial expansion is preferably achieved using specialized tools, such as segmented dies, expandable mandrels, moving segments, stretching dies, or other mechanical devices, which apply outward forces uniformly or selectively along the inner or outer circumference of the tubular body.

[0090] For example, in first embodiment, these tools 50 operate by employing moving segments 51 , which are components that move radially outward or inward in a synchronized manner to deform the tubular body with high precision.

[0091] The moving segments 51 are configured to apply distributed forces along the circumference of the tubular body, ensuring a smooth and precise radial deformation.

[0092] This mechanism allows the tubular body to expand evenly, minimizing risks of defects such as thinning, cracking, or buckling of the material.The segments 51 can be adjusted to create specific geometries, including round, non-round, or complex cross-sectional shapes.

[0093] For example, in a second embodiment, the tools 50 operate by employing stretching dies 55.

[0094] The stretching dies 55 are carried out by two opposing die elements that move towards each other, applying controlled forces.

[0095] The system is adaptable to various stages of the radial expansion process, whether it is the first radial expansion step (producing intermediate preforms) or the second radial expansion step (refining the shape to achieve the final geometry).

[0096] The expansion can result in either a round, or non-round, cross-sectional shape oriented perpendicularly to the longitudinal axis 10’ of the metal body 10, depending on the desired design or functional requirements.

[0097] The radial expansion steps play a pivotal role in forming the non-axisymmetric tubular metal body, and in particular the radial deformations 11. They allow for precise control over the shaping of patterns or reliefs by applying targeted forces during the expansion process.

[0098] This ensures that the desired non-axisymmetric geometries are achieved with high accuracy and consistency, while maintaining the structural integrity of the tubular body.

[0099] The radial expansion steps may be defined by at least one of the following parameters:

[0100] a) round or non-round:

[0101] The expansion process may involve transitioning the workpiece from a round (circular or axisymmetric) shape to a non-round (irregular or asymmetric) shape. b) percentage of expansion:

[0102] This parameter represents the relative increase in size of the tubular structure during an expansion step, compared to its final form. It describes how much the structure is expanded radially before reaching its target geometry. This parameter is particularly useful for defining controlled deformation steps, ensuring the desired final dimensions are achieved.

[0103] In particular, by “percentage of expansion”, it is advantageously meant the ratio between the current radial deformation and the maximum radial deformation of the final geometry. This parameter is measured relative to the final radius. A 100%expansion indicates that the tubular preform has achieved its final target dimensions in terms of size for a specific operation, typically the round portion.

[0104] By “percentage of expansion”, it is also advantageously meant the dimensional ratio between the radial envelope of the preform at a given moment and the maximum radial envelope of the final body. Concretely, this parameter measures the attainment of the diameter or overall dimensions of the part. An expansion of 100% means that the preform has reached its final radial footprint, i.e., its outer diameter corresponds to that of the finished product, regardless of the presence or absence of local deformations on the surface.

[0105] By "100% of expansion", it is advantageously meant that the tubular preform has achieved its final target dimensions in terms of size for a specific operation, such as the completion of a round portion. This value specifically refers to the achievement of the final target radius at the maximum radial points of the cross-section. Such a state corresponds to a preform that has reached its final outer radial envelope, for instance, a smooth cylindrical shape at the final diameter, even if the material has not yet been fully deformed to create the final non-axisymmetric contours. In this context, the radial expansion results in a radius that corresponds exactly to the desired final dimensions, representing 100% of the final radius.

[0106] By "lower than 100% of expansion", it is advantageously meant that the radial expansion of the tubular structure has not yet reached the final target dimensions of the non-axisymmetric tubular metal body.

[0107] c) percentage of surface change:

[0108] This parameter refers to the relative increase in the surface area of the structure during an intermediate stage of expansion, as compared to its final surface area. It provides a measure of the overall material deformation required to achieve the desired final shape, taking into account non-axisymmetric geometries.

[0109] Unlike expansion, which concerns the global envelope, surface change concerns the topography of the wall.

[0110] In another words, by "percentage of surface change", it is advantageously meant the ratio between the surface area of the structure at a given intermediate stage and the total surface area of the final non-axisymmetric tubular metal body. This parameter provides a measure of the overall material flow and deformation required to form complex geometries. A surface change lower than 100% indicates that while thestructure may have reached its maximum radial expansion, the material has not yet been fully deformed to create the radial deformations forming the outward (convex) or inward (concave) contours of the final design.

[0111] By "100% of surface change", it is advantageously meant that the ratio between the surface area of the structure at a given intermediate stage and the total surface area of the final non-axisymmetric tubular metal body is equal to one.

[0112] This parameter specifically refers to the achievement of the total developed surface area of the final product, including all intricate reliefs and non-axisymmetric contours. In this state, preferably, the surface area is fully adjusted to match the final geometry, providing a complete measure of the overall material flow and deformation required to form complex geometries. Reaching 100% of surface change may occur even when the expansion is partial, meaning the structure has not yet been expanded to the full radial distance required to reach the final radius. This configuration is particularly ideal for managing mechanical material stress and preparing the structure for a final finishing step.

[0113] By "lower than 100% of surface change," it is advantageously meant that the total developed surface area of the intermediate structure is less than the total developed surface area of the final non-axisymmetric tubular metal body.

[0114] By "total developed surface area", it is advantageously meant the cumulative surface area of the wall of the non-axisymmetric tubular metal body once it has reached its complete final geometry.

[0115] For the avoidance of doubt, all percentages of expansion and surface change described herein are preferably calculated relative to the final geometry of the finished non-axisymmetric tubular metal body. Preferably, the “100% expansion” value specifically refers to the achievement of the final target radius at the maximum radial points of the cross-section, while “100% surface change” refers to the total developed surface area of the final product, including all intricate reliefs and non-axisymmetric contours.

[0116] Moreover, the parameters of expansion and surface change are technically decoupled. A state of 100% expansion with lower than 100% surface change corresponds to a preform that has reached its final outer radial envelope (e.g., a smooth cylindrical shape at the final diameter) but lacks the internal or external radial deformations 11, such as embossments or concavities. Conversely, a state of lowerthan 100% expansion with 100% surface change describes a preform where the metal has been pre-stretched to its final surface area (material flow) but is still contained within a smaller radial footprint to manage mechanical stress before the final shaping.

[0117] In particular, the first radial expansion step enables precise control over the expansion process to achieve either round or non-round shapes, defined preferably by the following parameter combinations:

[0118] a) 100% of expansion and lower than 100% of surface change

[0119] In this scenario, the tubular structure undergoes full radial expansion, reaching its maximum intermediate size relative to the final shape. The surface area increase is controlled at lower than 100%, determined by the traces or positions of the expanding segments for example. This is particularly suited when a detail needs to be created in a subsequent step.

[0120] In another words, preferably, the tubular structure reaches its maximum intermediate size (e.g., a full round shape), but the surface area remains lower than the final state because the specific patterns, reliefs, or non-axisymmetric details (which require additional material stretching) have not yet been created.

[0121] Also in another words, the preform has been expanded to its final diameter (100% expansion), but its wall remains predominantly smooth or simplified. It has not yet undergone the local stretching necessary to form the complex patterns (reliefs) that would increase its total developed surface area. The transition to 100% surface will occur during a subsequent step by local forming without changing the global diameter.

[0122] b) lower than 100% of expansion and 100% of surface change

[0123] Here, the expansion is partial, defined by lower than 100% of the total radial increase required to reach the final shape. However, the surface area is fully adjusted to match the final geometry. This approach is ideal for scenarios requiring preparation for a finishing step.

[0124] Preferably, the surface area is fully adjusted to match the final geometry (often to prepare for a finishing step and manage material stress), but the structure has not yet been expanded to the full radial distance required to reach the final radius.

[0125] Preferably also, the material has been pre-stretched to reach its final developed surface area (all patterns are formed), but the part is maintained within a restricted radial envelope (reduced diameter). The next step will consist of “unfolding” orexpanding this shape to reach the final diameter without further stretching the material locally.

[0126] c) lower than 100% of expansion and of surface change

[0127] This scenario allows for customized combinations of partial expansion and partial surface adjustments, enabling flexibility in tailoring the intermediate shape.

[0128] These scenarios provide a versatile framework for shaping tubular bodies into round or non-round geometries, balancing radial deformation and surface control to meet specific design and functional requirements.

[0129] Moreover, these parameters allow precise calibration of the expansion process, optimizing the control over the geometry of the intermediate and final shapes. They also help minimize mechanical stresses and surface defects while ensuring consistent quality of the final product.

[0130] Each radial expansion step results in a tubular preform, or a non-axisymmetric tubular metal body, with a specific shape that can be classified as:

[0131] - final / full

[0132] or

[0133] - near-final I near-full,

[0134] based on its degree of conformity to the desired end geometry.

[0135] A shape is considered “final” when it matches 100% of the intended final geometry, as defined by the application's design and functional requirements. The final shape is the completed product, fully meeting all geometric and functional requirements.

[0136] This corresponds to a full radial expansion process, where the deformation reaches the complete target dimensions in all sections of the tubular preform.

[0137] A shape is deemed “non-final” or “near-final” when it is less than 100% of the final geometry.

[0138] In some embodiments, this occurs when at least a part of the metal piece conforms to the final shape, while other parts remain in an intermediate state requiring further processing.

[0139] The percentage of finality can vary, with non-final shapes typically representing a deformation that is less than 100% of the target geometry.

[0140] In other words, the degree of finality is thus defined as a percentage of the final shape:- 100% indicates the preform has achieved its final geometry in terms of both size and shape,

[0141] - less than 100% indicates a partially final shape, where the deformation has not yet reached the full dimensions of the final geometry (i.e. the deformation has not yet reached the full size and shape), preferably for a part or all the shapes.

[0142] Moreover, radial expansion is also measured relative to the final radius:

[0143] - for final shapes, the radial expansion results in a radius that corresponds exactly to the desired final dimensions (100% of the final radius),

[0144] - for non-final shapes, the radial expansion produces a radius that is smaller than the final target radius, corresponding to the percentage of finality achieved during the process.

[0145] In other words, “100% of a final shape” means achieving the final shape for a specific operation. This includes completing 100% of the round portion in the first radial expansion step, followed by adding a non-axisymmetric detail in the second radial expansion step.

[0146] For instance, this is typically illustrated in Scenario F4 below, where the first expansion produces a fully round shape (100% of the round geometry), and the second expansion refines it by introducing non-axisymmetric features.

[0147] Moreover, different radial expansion tools 50 are preferably used for each radial expansion step.

[0148] This refers to the use of distinct sets of radial expansion tools 50 for each radial expansion step in the manufacturing process. Each set of tools is specifically designed or configured to perform a targeted operation, adapting to the evolving geometry and requirements of the tubular body as it progresses through different stages of deformation.

[0149] The tools vary in design, size, and functionality to accommodate changes in the shape, dimensions, and material characteristics of the tubular body between the first and second radial expansion steps.

[0150] For example, the first radial expansion tools 50 may be designed for uniform expansion to create a final or near-full percentage of expansion; the second radial expansion tools 50 may include customized segments for producing non-axisymmetric geometries.

[0151] An angular indexing step - General overviewAn “angular indexing step” involves rotating and aligning the tubular piece about its longitudinal axis to achieve a precise angular orientation.

[0152] This step ensures that specific features, such as decorations or patterns on the tubular preform, are aligned with the geometric shape or functional elements of the final product.

[0153] Preferably, the indexing is performed using sensors and alignment systems that detect:

[0154] - internal features, such as the weld line, identified using an internal sensor capable of detecting the seam's position along the preform’s interior surface;

[0155] - external features, such as printed or embossed markings, detected using optical sensors or cameras positioned externally to identify the specific decorative element.

[0156] Angular indexing systems are well-known in the manufacturing field, particularly in processes involving decorated or pre-printed tubular bodies.

[0157] For instance, a tubular preform with a printed white square must be aligned with the weld line before the radial expansion step. This ensures that the decoration corresponds with specific contours or patterns formed during expansion, creating a visually and functionally integrated final product.

[0158] Supplying Stage

[0159] This step involves supplying a tubular structure known as a cylindrical body 20, which serves as the foundational element for subsequent processing.

[0160] By “welded cylindrical body”, it is preferably meant a tubular structure with a substantially cylindrical shape, formed by joining the edges of a metallic sheet or blank along a longitudinal weld line 21 using a welding process.

[0161] This cylindrical body serves as a precursor or intermediate product in the manufacturing process of tubular components, such as containers or structural elements, and is characterized by its uniform wall thickness and the presence of a weld line 21 running along its length.

[0162] Possible stretching step

[0163] This optional stretching step involves elongating the extremities 22, located at both axial ends of the cylindrical body 20, preferably through a die process.

[0164] The die operation is carried out by two opposing die elements T that move towards each other, applying controlled forces to the ends of the cylindrical body 20.This die operation is an advantageous preparatory step that enhances the ability of the cylindrical body 20 to withstand the stresses of radial expansion. By conditioning the material at the extremities, it ensures uniform expansion behavior and prevents localized weaknesses that could otherwise compromise the final geometry or structural performance.

[0165] Possible angular indexing step before the first radial expansion

[0166] The angular indexing system is designed to rotate the cylindrical body until a detected feature - such as the internal weld line or an external marking -matches the desired angular position.

[0167] This step may be interesting for ensuring that the geometric, functional, or decorative elements of the tubular body are correctly aligned with the tools and reguirements for the subseguent first radial expansion.

[0168] In particular, once the feature is detected, the system rotates the cylindrical body about its longitudinal axis until the detected feature matches the predefined angular position. This precise alignment ensures that the cylindrical body is correctly oriented before the first radial expansion step, preventing potential misalignments that could lead to defects or distortions in the intermediate geometry created during this step.

[0169] Preferably the indexing ensures that the weld line is positioned appropriately relative to the radial expansion tools 50, avoiding excessive stresses or deformation during the expansion process.

[0170] In particular, said prior angular indexing step is advantageously adjusted so that said weld line 21 is angularly offset with respect to the defined space between two segments.

[0171] The preliminary angular indexing step is mandatory for non-round expansions and serves as a preparatory step in the manufacturing process. Indeed, for non-round shapes, precise alignment of the tubular body ensures that the non-axisymmetric features are correctly positioned relative to the radial expansion tools 50. This alignment allows the accuracy of the final geometry and prevents misalignments that could compromise the structural or aesthetic guality of the product.

[0172] In the case of round expansions, while not strictly advantageous, the preliminary angular indexing step provides a significant advantage. It allows the positioning of traces or features resulting from the operation (such as weld lines or tooling marks) inpredetermined locations on the tubular body. This ensures a more controlled and predictable outcome, optimizing both functionality and appearance.

[0173] The “spaces between two segments” refer to the gaps where the radial expansion tools 50 apply the least direct force or experience the highest deformation stresses during operation.

[0174] The offset prevents the weld line 21 from aligning with the areas of maximum deformation or stress concentration, minimizing the risk of material failure, such as cracking or thinning, during radial expansion.

[0175] By offsetting the weld line, the method ensures a more uniform distribution of forces during expansion, preserving the structural integrity of the tubular body.

[0176] It also aligns external decorative features, such as printed patterns or markers, with the geometry resulting from the first radial expansion.

[0177] Depending on the shape and the specific requirements of the tubular body, this position can be modified to ensure optimal placement of the weld line 21 for either visual aesthetics and / or to minimize stresses within the tubular body during the radial expansion process.

[0178] This step lays the groundwork for the later stages of manufacturing, including the second radial expansion and any additional shaping or stretching processes.

[0179] At least one first radial expansion step

[0180] The “at least one first radial expansion step” involves expanding the cylindrical body 20 radially outward to create a tubular preform 30 with defined geometric and structural characteristics.

[0181] Preferably, the process modifies the cross-sectional shape of the cylindrical body while preserving its longitudinal axis 30', which remains a reference for subsequent manufacturing stages.

[0182] The radial expansion is performed using specialized tools, which apply controlled outward forces along the inner or outer circumference of the cylindrical body.

[0183] This step thus creates an intermediate structure, named “tubular preform” or ‘preform”, transitioning from the cylindrical welded body 20 to a shape ready for further shaping or refinement.

[0184] The resulting tubular preform 30 may have either a round (Figure 3) or non-round (Figure 5) cross-sectional shape, depending on the following steps of the method.In particular, said at least one first radial expansion step is configured to obtain a tubular preform 30 having:

[0185] - a non-round shape having one of the combinations below:

[0186] -- 100% of expansion and lower than 100% of surface change,

[0187] -- lower than 100% of expansion and 100% of surface change,

[0188] -- lower than 100% of expansion and of surface change,

[0189] or,

[0190] - a round shape having one of the combinations below:

[0191] -- 100% of expansion and lower than 100% of surface change,

[0192] -- lower than 100% of expansion and 100% of surface change,

[0193] -- lower than 100% of expansion and of surface change.

[0194] In particular, even when the first radial expansion step achieves 100% of the expansion (the final radius), the second radial expansion step transforms the intermediate geometry into the non-axisymmetric final shape. Preferably, in this specific sequence, the first step establishes the overall size, while the second step performs the localized material redistribution required to create non-round contours without exceeding the material's structural limits.

[0195] An angular indexing step

[0196] The alignment system rotates the tubular preform until the detected feature (weld line or external marking) matches the desired angular position.

[0197] This step is advantageously critical for ensuring that the geometry and functional or decorative elements of the tubular preform are aligned with the tools or subsequent processing requirements.

[0198] In particular, once the feature is detected, the system rotates the tubular preform about its longitudinal axis until the detected feature matches the predefined angular position. This precise orientation ensures that the preform is correctly aligned for the next processing step, avoiding misalignments that could lead to defects or mismatches in geometry and design.

[0199] The angular indexing step plays a pivotal role in preparing the tubular preform for the second radial expansion. It ensures that the features introduced during the first radial expansion are correctly positioned relative to the tools and geometry of the second expansion. This is critical for achieving a coherent and functional final shape.Indeed, the first radial expansion may introduce preliminary geometric features, such as non-round contours or partial patterns. The indexing ensures that these initial features are positioned precisely relative to the expansion tools 50 for the second radial expansion, avoiding misalignments that could distort the final shape.

[0200] The second radial expansion often refines the tubular preform into a more complex non-axisymmetric shape. By correctly orienting the preform beforehand, the indexing step ensures that the final geometry reflects the intended design without defects.

[0201] At least one second radial expansion step

[0202] This second radial expansion step builds upon the tubular preform 30 created in the first radial expansion step.

[0203] The tubular preform 30, whether round or non-round, serves as the intermediate structure for achieving the desired non-axisymmetric geometry of the tubular metal body 10.

[0204] The second radial expansion step utilizes also specialized tools, that apply precise outward forces to transform the tubular preform 30 into the desired non-axisymmetric tubular metal body 10.

[0205] This step ensures that the longitudinal axis of the tubular body is preserved while allowing for the targeted deformation of specific regions, creating complex non-round geometries.

[0206] The at least one second radial expansion step is advantageously configured to obtain said non-axisymmetric tubular metal body 10 having:

[0207] - a final, non-round shape, or

[0208] - a near-final, non-round shape, whereof at least a part is at a final shape and at least a part is at a non-final shape.

[0209] In other words, the second radial expansion step further modifies this preform to achieve the final or near-final non-round geometry.

[0210] In one configuration, the second radial expansion step fully expands the tubular preform 30 into a non-round shape, achieving 100% finality across all regions.

[0211] In another configuration, specific areas of the non-axisymmetric tubular metal body 10 are expanded to their final shape (100%), while others remain at a non-final shape (<100%), facilitating additional processing or adjustments.In particular, the term “near-final, non-round shape” refers to the geometry obtained after the second radial expansion step. This shape, while advanced, remains incomplete and is intended for further refinement in at least one additional radial expansion step to achieve the final geometry.

[0212] Preferably, the non-axisymmetric tubular metal body 10 obtained by this two-step expansion method is characterized by a unique grain structure and stress distribution profile. Preferably, unlike bodies formed in a single high-intensity expansion, the present body exhibits a more uniform wall thickness in the transition zones between axisymmetric and non-axisymmetric regions and is substantially free from the mechanical scoring marks typically associated with high-friction single-step shaping.

[0213] Embodiments

[0214] The at least one first radial expansion step and the at least one second radial expansion step are advantageously configured to achieve varying levels of finality in the geometry of the tubular preform 30 and the non-axisymmetric tubular metal body 10, depending on the desired final shape and the manufacturing strategy.

[0215] The levels of finality are defined for example in terms of the percentage of the final geometry achieved during each step.

[0216] According to the invention, different embodiments are possible, e.g.:

[0217] Table 1

[0218]

[0219]

[0220] The following embodiments align with the steps outlined in the Table 1, offering a detailed framework for understanding how different combinations of expansion processes contribute to the production of non-axisymmetric tubular metal bodies.

[0221] These embodiments directly complement the Table 1 provided above, illustrating the specific configurations of the first and second radial expansion steps, including their respective roles in achieving either final or near-final shapes.

[0222] Embodiment F1 :

[0223] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 non-round, 100% expansion and lower than 100% surface change, and - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape;Embodiment F2:

[0224] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 non-round, lower than 100% expansion and 100% surface change, and - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape;

[0225] Embodiment F3:

[0226] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 non-round, lower than 100% of expansion and of surface change, and - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape;

[0227] Embodiment F4:

[0228] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 round, 100% expansion and lower than 100% surface change, and

[0229] - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape;

[0230] Embodiment F5:

[0231] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 round, lower than 100% expansion and 100% surface change, and

[0232] - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape;

[0233] Embodiment F6

[0234] - the at least one first radial expansion step is implemented to obtain a tubular preform 30 round, lower than 100% of expansion and of surface change, and

[0235] - the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body 10, at the final shape.

[0236] Of course, various other modifications can be made to the invention within the scope of the appended claims.

Claims

22CLAIMS

1. A method for manufacturing a non-axisymmetric tubular metal body (10), intended to form a side wall of a container, preferably a metal can, which method comprises the following steps:- a supplying stage, to supply a cylindrical body (20), with a longitudinal axis (20’), - at least one first radial expansion step, to obtain a tubular preform (30) from said cylindrical body (20),- an angular indexing step, to index said tubular preform (30) about said longitudinal axis (30’), and- at least one second radial expansion step, to obtain said non-axisymmetric tubular metal body (10) from the said tubular preform (30).

2. The method of claim 1 , wherein said at least one first radial expansion step is configured to obtain a tubular preform (30) having:- a non-round shape or round shape,and- having one of the following combinations:-- 100% of expansion and lower than 100% of surface change,-- lower than 100% of expansion and 100% of surface change,-- lower than 100% of expansion and of surface change,and said at least one second radial expansion step is configured to obtain said non-axisymmetric tubular metal body (10) having:- a final, non-round shape, or- a near-final, non-round shape, whereof at least a part is at a final shape and at least a part is at a non-final shape.

3. The method of claim 2, wherein the at least one first radial expansion step and the at least one second radial expansion step are selected from one of the following embodiments:- the at least one first radial expansion step is implemented to obtain a tubular preform (30) non-round, 100% expansion and lower than 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape;- the at least one first radial expansion step is implemented to obtain a tubular preform (30) non-round, lower than 100% expansion and 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape;- the at least one first radial expansion step is implemented to obtain a tubular preform (30) non-round, lower than 100% of expansion and of surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape;- the at least one first radial expansion step is implemented to obtain a tubular preform (30) round, 100% expansion and lower than 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape;- the at least one first radial expansion step is implemented to obtain a tubular preform (30) round, lower than 100% expansion and 100% surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape;- the at least one first radial expansion step is implemented to obtain a tubular preform (30) round, lower than 100% of expansion and of surface change, and the at least one second radial expansion step is implemented to obtain a non-axisymmetric tubular metal body (10), at the final shape.

4. A method according to any one of Claims 1 to 3, wherein radial expansion step is carried out by radial expansion tools (50) having moving segments (51) or stretching dies (55).

5. A method according to any one of claims 1 to 4, further comprising a stretching step, for stretching the extremities (22) of said cylindrical body (20), before the at least one first radial expansion step.

6. A method according to any one of claims 1 to 5, further comprising, before the at least first radial expansion step, a prior angular indexing step, about a longitudinal axis (20’) of said cylindrical body (20).

7. A method according to claims 4 and 6, in combination, wherein said cylindrical body (20) comprises a weld line (21) and in that said prior angular indexing step is adjusted so that said weld line (21) is angularly offset with respect to the defined space between two segments (51).

8. A method according to any one of claims 1 to 7, wherein different radial expansion tools (50) are used for each radial expansion step.

9. A non-axisymmetric tubular metal body (10) obtained by the method according to any one of claims 1 to 8.

10. A container comprising a non-axisymmetric tubular metal body (10) according to claim 9.

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