CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63/411,066 filed on September 28, 2022, which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] The present disclosure relates generally to manufacturing articles, such as beverage containers, and, more particularly, to systems, devices, and methods for electromagnetic forming articles.

BACKGROUND

[0003] Pre-form articles are used in forming various articles, such as various containers, including metal beverage cans. FIGS. 1 and 2 show a pre-form article 100 used in forming metal beverage cans. The pre-form article 100 includes a domed bottom 102 with a sidewall 104 extending therefrom. The pre-form article 100 is generally produced from a drawn-wall ironing process or an impact-extrusion process. The pre-form article 100 includes a generally uniform initial diameter DI throughout the length of the pre-form article 100. The thickness of the sidewall 104 may vary along the length of the pre-form article 100 to optimize material usage relative to the structural performance effects of the final geometry.

[0004] Referring now to FIGS. 3 and 4, an example article 300 formed from, for example, the pre-form article 100 of FIGS. 1 and 2, is shown. The formed article 300 includes the domed bottom 102 and a sidewall 304. The formed article 300 includes a plurality of diameters including an opening diameter D2, an upper diameter D3, a midsection diameter D4, and a lower diameter D5. In the illustrated example, the formed article 300 includes an hourglass shape where the upper diameter D3 and lower diameter D5 are generally larger than the midsection diameter D4. In some aspects, the opening diameter D2 is generally the same as the initial diameter DI . More complex shapes may also be produced. An article may have any number of alternating small and large diameters. Non-circular cross sections and asymmetric shapes are also possible.

[0005] Referring now to FIGS. 5 and 6, an exemplary formed article 500 having an embossed pattern is shown. The formed article 500 includes the domed bottom 502 and a sidewall 504. The formed article 500 includes a plurality of diameters including an opening diameter D6, a sidewall diameter D7, and a bottom diameter D8. In the illustrated example, the uniformly expanded sidewall 504 has a sidewall diameter D7 that is larger than the opening diameter D6 or the bottom diameter D8.

[0006] The formed articles 300 and 500 of FIGS. 3-6, among others, can be produced by electromagnetic forming starting from the pre-form article 100 of FIGS. 1 and 2, among others. For example, an electromagnetic coil can be inserted into the interior of a pre-form article made of metal so that the pre-form article wraps around the electromagnetic coil with a narrow clearance. The electromagnetic coil is connected to a capacitor bank that stores energy. Upon triggering the capacitor bank, a strong pulsed current passes through the electromagnetic coil. An eddy current is induced in the pre-form article close to the coil. The currents in the electromagnetic coil and the pre-form article are opposite in direction, which creates a repelling force that expands the pre-form article outward.

[0007] The electromagnetic coil and pre-form article are placed inside a forming mold that defines the final shape of the pre-form article after expansion. The thin wall of the pre-form article is displaced outward with an internal force from firing the electromagnetic coil and is confined by the mold. This creates the shapes and features intended to be placed on the article formed from the pre-form article. For example, the sidewall 504 in FIGS. 5 and 6 can include embossing or raised ridges 506, which is a positive pattern formed by and corresponding with, for example, contact between a pattern disposed on the inner surface of a mold.

[0008] The eddy current flows in the surface of pre-form article, which is called the skin effect. Magnetic fields with higher frequencies induce eddy currents at shallower depths. As the frequency decreases, the magnetic fields tend to penetrate the metal in which the eddy currents are induced. As a result, lower frequencies produce low efficiencies in forming, especially for thin metal pre-form articles. For can material, the working frequency is much higher than that for forming thicker metal.

[0009] A single pulse of electrical energy can be applied to the electromagnetic coil for forming an article having a desired shape from a pre-form article. However, the resulting article from a single pulse of electrical energy may not include all of the detail from the mold without increasing the amount of energy to levels that may also damage the pre-form article. Further, simply increasing the number of pulses of electrical energy to be more than one still may not cause the pre-form article to acquire all of the detail from the mold. Alternatively, the first pulse of electrical energy may still damage the pre-form article or not efficiently form the preform article within a series of pulses. [0010] In addition, the time period for applying force to a pre-form article during electromagnetic forming is also very short. Thus, the forming also occurs in a very short time; typically less than 100 microseconds. At this short time, a pressure difference between the inside and the outside of the pre-form article is inevitable. Rapid expansion of the pre-form article leaves no time for enough air to fill the volume within the pre-form article. As a result, the air pressure inside of pre-form article drops suddenly. Meanwhile, the air between the preform article and the mold is rapidly compressed, causing the pressure outside of the pre-form article to increase. The air pressure difference will compress the expanding pre-form article.

[0011] To alleviate the compression problem, air is supplied to the inside of the pre-form article and venting is provided to the mold. However, neither of these approaches makes the air pressure difference go away because of the short time in which forming takes place (e.g., less than 100 microseconds). Although the air pressure is lower than the forming pressure, the former increases gradually and the latter drops quickly. Given the thickness of aluminum preform article, the surface often shows undesirable bumpiness due to compression.

[0012] As air in a mold is detrimental to forming, proper venting is critical to high quality forming. It is common in practice to create a vacuum between the pre-form article and the mold to eliminate trapped air. However, creating a vacuum significantly slows down the process, so it is not viable in high-speed production. Further, even with a high vacuum, some air still remains, which limits the ability to produce smooth surfaces.

[0013] Thus, there exist needs for systems, devices, and methods for electromagnetic forming of pre-form articles that do not suffer from the above issues.

SUMMARY

[0014] According to aspects of the present disclosure, a method of electromagnetically forming an article is disclosed. The method includes providing an electromagnetic coil inserted at least partially within a pre-form article, with the pre-form article inserted at least partially within a mold. The method further includes applying a first electrical energy to the electromagnetic coil to produce an electromagnetic force. The electromagnetic force is configured to expand a sidewall of the pre-form article toward an inner surface of the mold such that a gap of about 0.5 mm to about 1.5 mm is formed between the inner surface and the sidewall at a largest diameter of the pre-form article. The method further includes applying at least a second electrical energy to electromagnetic coil to produce at least a second electromagnetic force. The at least the second electromagnetic force is configured to expand the sidewall of the preform article to substantially form against the inner surface. [0015] Aspects of the method include the gap formed between the inner surface and the sidewall at the largest diameter of the pre-form article being about 0.5 mm to about 1.0 mm.

[0016] Aspects of the method further include the gap formed between the inner surface and the sidewall at the largest diameter of the pre-form article being about 0.5 mm to about 0.7 mm.

[0017] Aspects of the method further include the first electrical energy causing the sidewall to expand to about 80% of expansion required to substantially form against the inner surface.

[0018] Aspects of the method further include the at least the second electrical energy including two electrical energies. A first of the two electrical energies causing the sidewall to form against the inner surface. A second of the two electrical energies causes the sidewall to acquire additional detail from the inner surface of the mold.

[0019] Aspects of the method further include the first electrical energy causing the sidewall to impact and bounce off of the inner surface.

[0020] Aspects of the method further include the pre-form article being made of aluminum.

[0021] Aspects of the method further include the first electrical energy and the second electrical energy being generated with a same amount of energy.

[0022] Aspects of the method further include the first electrical energy and the at least the second electrical energy being generated with different amounts of energy.

[0023] Aspects of the method further include providing a plurality of holes within the mold to vent air from between the sidewall of the article and the inner surface to outside of the mold during expansion of the sidewall in response to the first electrical energy and the at least the second electrical energy. The method further includes providing a plurality of hollow indentations on an outer surface of the mold to reduce backpressure as the air vents to the outside of the mold during expansion of the sidewall.

[0024] Aspects of the method further include measuring displacement of the sidewall of the pre-form article during expansion of the sidewall toward the inner surface of the mold with a displacement sensor within the mold. According to some aspects, the method further includes determining a number of the at least a second electrical energy for applying to the pre-form article via the electromagnetic coil based on the measuring the displacement of the sidewall. The displacement sensor can be configured to measure displacement of the sidewall as a function of time.

[0025] According to aspects of the present disclosure, a method of determining electrical energy required to electromagnetically form an article is disclosed. The method includes providing an electromagnetic coil inserted at least partially within a pre-form article, with the pre-form article inserted at least partially within a mold. The mold includes a displacement sensor configured to measure expansion of the pre-form article within the mold. The method also includes applying an electrical energy to the electromagnetic coil to produce an electromagnetic force. The electromagnetic force is configured to expand a sidewall of the pre-form article toward an inner surface of the mold. The method also includes measuring an expansion of the sidewall of the pre-form article with the displacement sensor in response to the electrical energy. The method further includes repeating the providing, the applying, and the measuring for a plurality of times with a new one of the pre-form article and a different electrical energy for a plurality of electrical energies. The method further includes determining a final electrical energy required to apply to the sidewall of the pre-form article based on the measured expansions of the sidewall of the pre-form articles in response to the plurality of electrical energies so that a deflection of the sidewall of the pre-form article off of the inner surface of the mold in response to the expansion falls within a predefined threshold.

[0026] Aspects of the method include the final electrical energy being determined based on a distance between the inner surface and the sidewall at a largest diameter of the pre-form article. [0027] Aspects of the method further include the predefined threshold being based on a gap remaining between the sidewall and the inner surface of the mold, the gap being 0.5 mm to about 1.5 mm wide. Aspects of the method further include the gap being about 0.5 mm to about 1.0 mm. Aspects of the method further include the gap being about 0.5 mm to about 0.7 mm.

[0028] Aspects of the method further include the plurality of electrical energies being increasing amounts of electrical energy that cause the sidewall of the pre-form article initially to not contact the inner surface of the mold and cause the sidewall of the pre-form article finally to contact the inner surface of the mold and bounce off with maximum inward deflection.

[0029] Aspects of the method further include the displacement sensor being provided within the mold corresponding to a location of a largest diameter of the pre-form article.

[0030] According to aspects of the present disclosure, a mold segment is disclosed. The mold segment includes an inner surface having a geometry corresponding to a mirror geometry to be formed on a sidewall of a pre-form article. The mold segment also includes an outer surface, opposite from the inner surface. The mold segment also includes an aperture in the inner surface. The mold segment also includes a displacement sensor within the aperture. The displacement sensor is configured to measure displacement of a sidewall of a pre-form article in response to application of an electromagnetic force that causes the sidewall of the pre-form article to expand towards the inner surface. [0031] Aspects of the mold segment include a plurality of vents configured to allow air to pass from the inner surface to the outer surface. The outer surface can include one or more indentations that limit backpressure from forming in response to the air passing from the inner surface to the outer surface. The one or more indentations can be connected.

[0032] According to aspects of the present disclosure, a mold segment is disclosed. The mold segment includes an inner surface having a geometry corresponding to a mirror geometry to be formed on a sidewall of a pre-form article. The mold segment also includes an outer surface, opposite from the inner surface. The mold segment also includes a plurality of vents configured to allow air to pass from the inner surface to the outer surface. The outer surface includes one or more indentations that limit backpressure from forming in response to the air passing from the inner surface to the outer surface.

[0033] Aspects of the mold segment include an aperture being in the inner surface. The mold segment also includes a displacement sensor within the aperture. The displacement sensor is configured to measure displacement of a sidewall of a pre-form article in response to application of an electromagnetic force that causes the sidewall of the pre-form article to expand towards the inner surface.

[0034] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.

[0036] FIG. 1 shows a perspective view of a pre-form article used in forming articles, such as metal beverage cans.

[0037] FIG. 2 shows a side view of the pre-form article of FIG. 1.

[0038] FIG. 3 shows a perspective view of an example article that can be formed by electromagnetic forming.

[0039] FIG. 4 shows a side view of the example article of FIG. 3.

[0040] FIG. 5 shows a side view of another example of an article that can be formed by electromagnetic forming.

[0041] FIG. 6 shows a perspective view of the example article of FIG. 5. [0042] FIG. 7 illustrates a cross-sectional view of an electromagnetic coil and multi-segment mold with a pre-form article, according to aspects of the present disclosure.

[0043] FIG. 8 shows a detailed view of a portion in FIG. 7 after application of electrical energy, according to aspects of the present disclosure.

[0044] FIG. 9 shows a plot of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure.

[0045] FIG. 10 shows another plot of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure.

[0046] FIG. 11 shows another plot of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure.

[0047] FIG. 12 shows another plot of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure.

[0048] FIG. 13 shows a plot comparing displacements of pre-form articles during electromagnetic forming, according to aspects of the present disclosure.

[0049] FIG. 14 shows a perspective view of a mold segment, according to aspects of the present disclosure.

[0050] FIG. 15 shows a cross-sectional view of the mold segment of FIG. 14, according to aspects of the present disclosure.

[0051] FIG. 16 shows a perspective view of the inner surface of another mold segment, according to aspects of the present disclosure.

[0052] FIG. 17 shows a perspective view of the outer surface of the mold segment of FIG. 16, according to aspects of the present disclosure.

[0053] FIG. 18 shows a perspective view of a pre-form article after application of a first pulse of electrical energy, according to aspects of the present disclosure.

[0054] FIG. 19 shows a perspective view of a pre-form article after application of a second pulse of electrical energy, according to aspects of the present disclosure.

[0055] FIG. 20 shows a perspective view of a pre-form article after application of a third pulse of electrical energy, according to aspects of the present disclosure.

[0056] FIG. 21 shows a flow diagram of a process of electromagnetically forming an article, according to aspects of the present disclosure.

[0057] FIG. 22 shows a flow diagram of a process of determining electrical energy required to electromagnetically form an article, according to aspects of the present disclosure.

[0058] While the invention is susceptible to various modifications and alternative forms, specific forms thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION

[0059] The present disclosure is directed to applying multiple pulses of electrical energy to an electromagnetic coil for producing electromagnetic forces that form articles with better surface quality. Aspects of the present disclosure involve applying a first pulse of electrical energy to expand a pre-form article so that, after expanding, it is approaching or almost touching a mold. The pre-form article approximately takes the shape of the mold but lacks the fine details and optimal surface quality. Instead, the electrical energy is controlled so that the resulting expansion pressure prevents every part of the pre-form article from contacting the mold after the expansion stops. Subsequent pulses of electrical energy provide further expansion pressure on the pre-form article to complete the forming.

[0060] After the first pulse of electrical energy, a gap between a sidewall of the pre-form article and mold still exists. The gap can be about 0.5 mm to about 1.0 mm wide. With less than, more than, or the same amount of electrical energy as the first pulse, each subsequent pulse of electrical energy provides additional forming to the pre-form article by promoting further contact the pre-form article against the mold. With each subsequent pulses, the volume growth of the pre-form article continues to decrease, so the inside pressure drop continues to decrease as well. On the other side, the volume between the pre-form article and the mold only shrinks a little with subsequent pulses. This makes the pressure increase smaller at subsequent pulses. In addition, any compressed air supplied to inside of the can, if present, and venting on of the mold, if present, should be able to mitigate the pressure drop inside the pre-form article and pressure increase outside of the pre-form article. All these allow the multiple pulses to form a smooth (or generally smooth) resulting article.

[0061] The sidewall of the pre-form article moves at higher speeds when the electric energy increases. Speeds of about 70 meters per second (m/s) to about 150 m/s have been observed depending on different electrical energy. As the speed increases, the sidewall stops closer to the mold until after a threshold speed, above which the sidewall bounces back and leaves a larger and larger gap as the electric energy further increases. Thus, a graph of speed versus the resulting gap is similar to a quadratic curve, with the gap in the ordinate and the electrical energy or speed in the abscissa. The curve has a minimum point, which generally is considered optimal. A lower or higher speed than the speed for the minimum point only makes the gap bigger. More wrinkles are produced after the first pulse due to compression and bouncing off. If the pre-form article appears to be uneven or wrinkled, the electrical energy or speed of the sidewall was excessively high.

[0062] After the first pulse of electrical energy, the pre-form article almost fills the cavity of the mold, except for some gaps, with uneven thickness, due to slight bouncing of the sidewall of the pre-form article off of the mold. As a result, one or more subsequent pulses of electrical energy are applied, which can have the same voltage or different voltages as the first pulse of electrical energy. The one or more subsequent pulses of electrical energy further expand the pre-form article toward the mold but only at slight increments of expansion. The small expansion causes minimal external pressure. With a proper second pulse of electrical energy, the sidewall of the pre-form article will conform to mold. A third or subsequent pulse(s) of electrical energy work the same way but may not be needed.

[0063] Referring to FIG. 7, an electromagnetic coil 700 is shown inserted within a pre-form article 702. The pre-form article 702 is inserted within a mold 704 formed of a plurality of mold segments 706. Each of the mold segments 706 includes an inner surface 708. Applying electrical energy to the electromagnetic coil 700 produces an electromagnetic force. The electromagnetic force causes the sidewall 710 of the pre-form article 702 to expand toward the inner surface 708. According to aspects of the present disclosure, the first pulse of electrical energy applied to the electromagnetic coil 700 is controlled so that the sidewall 710 of the preform article 702 is a set distance from the inner surface 708 after the expansion. Specifically, FIG. 8 shows a detailed view of the portion 8 in FIG. 7 after application of the first electrical energy to the electromagnetic coil 700. The sidewall 710 of the pre-form article 702 has been expanded such that a distance D9 between the inner surface 708 and the sidewall 710 of the pre-form article 702 is in the range of about 0.5 mm to about 1.5 mm. The distance D9 being within this range corresponds to an optimum first electrical energy applied to the electromagnetic coil 700 for expanding the pre-form article. The optimal electrical energy produces a sidewall speed of about 100 m/s to about 120 m/s, which is in the preferred range of about 70 to about 150 m/s. According to some preferred aspects, the distance D9 after the first pulse of electrical energy can be about 0.5 mm to about 1.0 mm. According to some even further preferred aspects, the distance D9 after the first pulse of electrical energy can be about 0.5 mm to about 0.7 mm. According to some aspects, the distance D9 constitutes the pre-form article expanding about 80% of the expansion required to substantially form against the inner surface 708. [0064] According to preferred aspects, the distance D9 is within the foregoing ranges after the sidewall 710 of the pre-form article 702 makes contact with, and bounces off of, the inner surface 708 of the mold segment 706. This allows the sidewall 710 of the pre-form article 702 to form part of the shape of the inner surface 708 without suffering from wrinkles or other deformations. The distance D9 also results from an amount of electrical energy that is not too excessive. Specifically, an excessive electrical energy of the first pulse would cause at least portions of the sidewall 710 of the pre-form article 702 to violently hit the inner surface 708. Further, some areas of the sidewall 710 of the pre-form article 702 may impact the inner surface 708, and some areas of the sidewall 710 of the pre-form article 702 may hit a layer of high- pressure air between the pre-form article 702 and the inner surface 708. The violent impact of the sidewall 710 of the pre-form article 702 on the inner surface 708, along with the pressure imbalance, would cause the sidewall 710 of the pre-form article 702 to move back inward, away from the inner surface 708. The momentum the sidewall 710 of the pre-form article 702 carries, if too large, will produce severe wrinkles and creases. The overly intense impact and compression may also cause the sidewall 710 to tear, creating a ruptured pre-form article 702. In areas where the sidewall 710 of the pre-form article 702 hits cushioning air, a softer bounce creates minor bumpiness and leaves a gap. Thus, a first pulse of electrical energy that results in a gap between the pre-form article 702 and the inner surface 708 of the distance D9 described above, alleviates or minimizes the above issues.

[0065] FIG. 9 shows a plot 900 of displacement of a pre-form article (e.g., pre-form article 702) during electromagnetic forming, according to aspects of the present disclosure. Specifically, the y-axis 902 shows the displacement of a sidewall (e.g., sidewall 710) of the pre-form article as a function of time shown on the x-axis 904. The origin 908 represents the pre-form article before being exposed to electrical energy to cause the pre-form article to expand.

[0066] The curve 906 within section 910 generally shows how the sidewall of a pre-form article rapidly expands upon being exposed to an electromagnetic force. Point 912 along the curve 906 generally represents the point in time at which the electromagnetic force stops. The curve 906 within section 914 generally shows how momentum of the sidewall may cause the sidewall to continue expanding for a period of time after application of the electromagnetic force stops. Point 916 along the curve 906 generally represents the final expansion of the sidewall after both the electromagnetic force and the momentum stop.

[0067] The curve 906 in FIG. 9 generally shows displacement of a pre-form article when the electrical energy is not high enough. The electrical energy is not high enough because the sidewall does not reach the inner surface of mold. For example, a layer of air between the sidewall and the inner surface of the mold may cushion the sidewall and prevent maximum expansion. As a result, the electrical energy must be increased so that the sidewall comes into contact with the inner surface of the mold. This allows the sidewall of the pre-form article to expand while still staying close to the inner surface of the mold after momentum is exhausted. [0068] FIG. 10 shows another plot 1000 of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure. Specifically, the y- axis 1002 again shows the displacement of a sidewall of a pre-form article as a function of time shown again on the x-axis 1004. The origin 1008 again represents the pre-form article before being exposed to electrical energy to cause the pre-form article to expand.

[0069] The curve 1006 within section 1010 generally shows how the sidewall of a pre-form article rapidly expands upon being exposed to an electromagnetic force. Point 1012 along the curve 1006 generally represents the point in time at which the electromagnetic force stops. The curve 1006 within section 1014 generally shows how momentum of the sidewall affects expansion after the electromagnetic force stops. Point 1016 along the curve 1006 generally represents the final expansion of the sidewall after both the electromagnetic force and the momentum stop.

[0070] The curve 1006 includes a peak 1018 before the point 1012. The peak 1018 represents the sidewall of the pre-form article hitting the inner surface of the mold and/or pressure imbalance. Hitting the inner of the mold causes the sidewall of the pre-form article to bounce back inward, as represented by the reduction in displacement after the peak 1018. The distance between peak 1018 and the final displacement at point 1016 represents the distance (e.g., distance D9) between the expanded sidewall and the inner surface of the mold after application of first pulse of electrical energy.

[0071] FIG. 11 shows another plot 1100 of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure. Specifically, the y- axis 1102 again shows the displacement of a sidewall of a pre-form article as a function of time shown again on the x-axis 1104. The origin 1108 again represents the pre-form article before being exposed to electrical energy to cause the pre-form article to expand.

[0072] The curve 1106 within section 1110 generally shows how the sidewall of a pre-form article rapidly expands upon being exposed to an electromagnetic force. Point 1112 along the curve 1106 generally represents the point in time at which the electromagnetic force stops. The curve 1106 within section 1114 generally shows how momentum of the sidewall may cause the sidewall to continue expanding for a period of time after the electromagnetic force stops. Point 1116 along the curve 1106 generally represents the final expansion of the sidewall after both the electromagnetic force and the momentum stop.

[0073] The curve 1106 includes a peak 1118 before the point 1112. The peak 1118 represents the sidewall of the pre-form article hitting the inner surface of the mold and/or a cushion or high-pressure air. Hitting the inner of the surface and/or the cushion of air causes the sidewall of the pre-form article to bounce back inward, as represented by the reduction in displacement after the peak 1118. The difference between the displacement at the peak 1118 versus the displacement at the point 1112 where the electromagnetic force stops indicates the severity of the sidewall of the pre-form article hitting and bouncing off of the inner surface of the mold. For example, the severity of the bounce back in FIG. 11 is greater than the severity of the bounce back in FIG. 10.

[0074] FIG. 12 shows another plot 1200 of displacement of a pre-form article during electromagnetic forming, according to aspects of the present disclosure. Specifically, the y- axis 1202 again shows the displacement of a sidewall of a pre-form article as a function of time shown again on the x-axis 1204. The origin 1208 again represents the pre-form article before being exposed to electrical energy to cause the pre-form article to expand.

[0075] The curve 1206 within section 1210 generally shows how the sidewall of a pre-form article rapidly expands upon being exposed to an electromagnetic force. Point 1212 along the curve 1206 generally represents the point in time at which the electromagnetic force stops. The curve 1206 within section 1214 generally shows how momentum of the sidewall may cause the sidewall to continue expanding for a period of time after application of the electromagnetic force stops. Point 1216 along the curve 1206 generally represents the final expansion of the sidewall after both the electromagnetic force and the momentum stop.

[0076] The curve 1206 includes a peak 1218 before the point 1212. The peak 1218 again represents the sidewall of the pre-form article hitting the inner surface of the mold and/or a cushion of high-pressure air. Hitting the inner surface of the mold and/or the cushion of high- pressure air causes the sidewall of the pre-form article to bounce back inward, as represented by the reduction in displacement after the peak 1218. The difference between the displacement at the peak 1218 versus the displacement at the point 1212 where the electromagnetic force stops indicates the severity of the sidewall of the pre-form article hitting and bouncing off of the inner surface of the mold. For example, the severity of the bounce back in FIG. 12 is greater than the severity of the bounce back in FIGS. 10 and FIG. 11.

[0077] FIG. 13 shows a combined plot 1300 of the curves 906, 1006, 1106, 1206 in FIGS. 9- 12, respectively, according to aspects of the present disclosure. As described above, the y-axis 1302 again shows the displacement of sidewalls of pre-form articles as a function of time shown again on the x-axis 1304. The origin 1308 again represents the pre-form articles before being exposed to electrical energy to cause the pre-form articles to expand.

[0078] As shown, the curve 1006 results in the largest final displacement. The curve 1206 includes the largest bounce back and results in the smallest final displacement. The sidewall of the pre-form article corresponding to the curve 1206 also includes wrinkles or other deformations, such as tears, that cannot be removed from sidewall. The curves 906 and 1106 end with substantially the same final displacement. However, the sidewall of the pre-form article corresponding to the curve 1106 may also include wrinkles or other deformations that cannot be removed from the sidewall because of the severity of the bounce back. While the pre-form article corresponding to the curve 906 may not have wrinkles or other deformations, the larger gap between the sidewall and the mold will require higher electrical energy in subsequent pulses because the sidewall is farther away from the electromagnetic coil than the first pulse. The curve 1006 ends up with the shape closest to the mold, and this allows subsequent pulses with the same or even less energy than the first pulse to complete forming.

[0079] According to some aspects, subsequent pulses of electrical energy can be the same energy, higher energy, or lower energy than first pulse in energy level. Because the pre-form article is farther away from the electromagnetic coil after the first pulse of electrical energy, the force delivered to the pre-form article is lower for the same amount of electrical energy. However, because the amount of expansion that is needed for subsequent pulses is lower, the electrical energy for subsequent pulses can still be the same energy or lower. According to some aspects, the charged voltage for a first pulse can be about 7.5 kilovolts (kV). The second pulse of voltage can be, for example, about 7.3 kV to about 7.8 kV, to get different level of details. Subsequent pulses of electrical energy after the second pulse also can have the same energy, higher energy, or lower energy than first pulse. According to some aspects, using three pulses of about 7.4 kV or three consecutive pulses of about 7.5, about 7.4 and about 7.3 kV results in the richest details and fullest comers. The specific voltages used provide the most refined finish to the resulting article formed from the pre-form article.

[0080] FIG. 14 shows a perspective view of mold segment 1400, according to aspects of the present disclosure. FIG. 15 shows a cross-sectional view of the mold segment 1400 in FIG. 14 along the line 14-14. The mold segment 1400 is one segment within a plurality of the mold segment 1400 (or other mold segments) that together form a mold for shaping a pre-form article in a desired final article, such as a beverage container. For example, there can be two, three, four, etc. of the mold segment 1400 that form a mold. The mold segment 1400 is generally for shaping a sidewall of a pre-form article. The mold segment 1400 includes an outer surface 1402 and an inner surface 1404, opposite from the outer surface 1402. The inner surface 1404 contacts a sidewall of a pre-form article during expansion of the pre-form article within a mold formed with the mold segment 1400. Generally, the inner surface 1404 has a geometry corresponding to a mirror geometry to be formed on a sidewall of a pre-form article. Thus, the inner surface 1404 can have various shapes, patterns, etc. for defining a desired appearance of the sidewall of the pre-form article and, as a result, the formed article.

[0081] The mold segment 1400 includes an aperture 1406 through which a displacement sensor 1408 extends. The displacement sensor 1408 measures displacement of a sidewall of a preform article towards the inner surface 1404 of the mold segment 1400 during expansion. According to some aspects, the displacement sensor 1408 emits light towards the sidewall of a pre-form article and detects the reflected light. The intensity of the light reflected back from the sidewall is converted to a voltage output. As the sidewall moves closer to the displacement sensor 1408, the intensity of the reflected light increases. The recorded output voltage can be converted back to distance between the displacement sensor 1408 and the sidewall.

[0082] One or more displacement sensors 1408 can be placed in the mold segment 1400 to monitor expansion of the sidewall of the pre-form article during the expansion process discussed above. The displacement sensors 1408 are preferred to be fiber optic displacement sensors so that they are not affected by the strong electromagnetic fields created by pulsing the electrical energy. Therefore, the mold segment 1400 can include an aperture 1406 for each displacement sensor 1408 so that the displacement sensor 1408 can access the interior of the mold segment 1400 to detect expansion of the pre-form article during the application of the pulses of electrical energy.

[0083] According to some aspects, the displacement sensor 1408 measures an amount of maximum displacement. According to some aspects, the displacement sensor 1408 measures displacement as a function of time. Measuring the displacement as a function of time allows for a greater understanding of whether and how a sidewall of a pre-form article deflected off of the inner surface 1404 of the mold segment 1400 and/or a cushion of high-pressure air during expansion. Thus, the displacement sensor 1408 allows for determining an optimal electrical energy for a first pulse of electrical energy when electromagnetically forming an article. By analyzing the displacement, an electrical energy that gives the least amount of bounce back and the largest diameter of the pre-form article can provide the conditions for obtaining the best final quality for the formed article. [0084] The location of the aperture 1406 and the displacement sensor 1408 can vary. According to some aspects, and as shown in FIG. 15, the location of the aperture 1406 and the displacement sensor 1408 can correspond to the location of the largest diameter of a pre-form article. The location of the largest diameter of a pre-form article generally experiences the largest amount of expansion. Thus, having the aperture 1406 and the displacement sensor 1408 at the corresponding location of the mold segment 1400 accurately measures the greatest amount of expansion of a pre-form article. However, the aperture 1406 and the displacement sensor 1408 can be at different locations, both relative to the mold segment 1400 and relative to the largest diameter of the pre-form article. Further, although only one aperture 1406 and displacement sensor 1408 are shown in FIGS. 14 and 15, according to some aspects there can be multiple apertures 1406 and displacement sensors 1408, particularly for situations where a pre-form article may have several different locations that have the largest diameter.

[0085] According to some aspects, each mold segment of a mold can be or include the elements described herein with respect to the mold segment 1400, such that each mold segment includes the aperture 1406 and the displacement sensor 1408. Alternatively, fewer than all of the mold segments of a mold (e.g., only one or two or three of the mold segments for a mold with four mold segments) can be or include the elements described herein with respect to the mold segment 1400, such as.

[0086] As discussed above, a vacuum can be created within a mold. Without a vacuum, preform articles often rupture due to trapped air. However, adding vents to molds can reduce the likelihood of rupture. Yet, vents also have limitations.

[0087] Referring to FIG. 16, a perspective view of another mold segment 1600 for electromagnetic forming articles is shown, showing the inner surface 1604, according to aspects of the present disclosure. FIG. 17 shows a perspective view of the outer surface 1602 of the mold segment 1600 in FIG. 16, according to aspects of the present disclosure. Similar to the mold segment 1400 described above, the mold segment 1600 is one segment within a plurality of the mold segments (e.g., mold segments 1600 or other mold segments) that together form a mold. For example, there can be two, three, four, etc. of the mold segment 1600 that form a mold. According to some aspects, the mold segment 1400 and the mold segment 1600 can be used in the same mold.

[0088] The mold segment 1600 includes a plurality of apertures or vents 1606 that are configured to allow air to vent from the inner surface 1604 to the outer surface 1602 during the electromagnetic forming of articles. Specifically, the rapid expansion of the sidewall of a preform article can cause air pressure to build at the inner surface 1604. The apertures 1606 act as vents that vent the air to the outer surface 1602. This helps to reduce the air pressure at the inner surface 1604, which helps reduce the force exerted by the pressurized air on the expanding sidewall of the pre-form article. The apertures 1606 can be directly in the inner surface 1604 or, as shown in FIG. 16, the apertures 1606 can be recessed, such as in recessed tracks 1607. The recessed tracks 1607 prevent the pre-form article from contacting with the vents 1606, leaving bumps. The recessed tracks 1607 also provide more room for air, relieving some pressure due to expansion. The apertures 1606 can be maximized in area to facilitate the flow of air. While the apertures 1606 are shown in FIG. 16 as holes, the apertures 1606 can be enlarged to slots or other shapes.

[0089] In some instances, the air may vent through the apertures 1606 so quickly that air pressure may build at the outer surface 1602. Therefore, the outer surface 1602 includes indentations 1608. The indentations 1608 provide areas of space that accommodate the venting air without building pressure. Specifically, the mold segment 1600 is held within a mold holder or carrier (not shown). The indentations 1608 provide sufficient space for the venting air so that backpressure does not build outside of the mold. The indentations 1608 further advantageously reduce the weight of the mold segment 1600.

[0090] The vents 1606, in combination with multiple pulses of electrical energy, allow for evacuating air from within the mold using a pre-form article rather than having to pull a vacuum. Specifically, the first pulse of electrical energy can cause the electromagnetic force that expands the sidewall of the pre-form article. Expansion of the pre-form article forces air out of the mold through the vents 1606 within the mold segment 1600. When one or more subsequent pulses of energy are applied to generate subsequent one or more electromagnetic forces, less air is within the mold, which results in less pressure buildup as the pre-form article expands.

[0091] The multiple pulse-forming methods according to the embodiments of the present disclosure can be used in forming various articles, including any thin-wall metal structure that can be formed into shapes defined by a mold. The multiple pulse forming methods according to the embodiments of the present disclosure enable an article to be formed substantially free of wrinkles and other surface deformations that are typically found in articles formed from a single pulse of electrical energy or from multiple pulses of electrical energy, in which at least the first pulse of electrical energy was not optimized to provide optimum expansion without (or substantially without) wrinkles and other deformations.

[0092] Referring to FIGS. 18-20, perspective views of a pre-form article 1800 after first, second, and third pulses of electrical energy, respectively, are shown according to aspects of the present disclosure. Specifically, the pre-form article 1800 in FIG. 18 is after a first pulse of electrical energy, where it is close to fully expanded but lacks details. FIG. 19 shows the pre-form article 1800' after a second pulse of electrical energy. The pre-form article 1800' has a lot of surface details showing it has been in good contact with inner surface of the mold. FIG. 20 shows the pre-form article 1800" after a third pulse of electrical energy. The surface is smoother than after the second shot.

[0093] FIG. 21 shows a flow diagram of a process 2100 of electromagnetically forming an article, according to aspects of the present disclosure. At step 2102, an electromagnetic coil is inserted at least partially within a pre-form article. The pre-form article is then inserted at least partially within a mold. According to some aspects, the mold can include a plurality of holes to vent air from between the sidewall of the article and the inner surface to outside of the mold during expansion of the sidewall in response to the first electrical energy and the at least the second electrical energy, as discussed further below. Further, there can be a plurality of hollow indentations on an outer surface of the mold to reduce backpressure as the air vents to the outside of the mold during expansion of the sidewall.

[0094] At step 2104, a first electrical energy is applied to the electromagnetic coil to produce an electromagnetic force. As discussed above, the electromagnetic force is configured to expand a sidewall of the pre-form article toward an inner surface of the mold such that a gap of about 0.5 mm to about 1.5 mm is formed between the inner surface and the sidewall at a largest diameter of the pre-form article. According to some aspects, the gap formed between the inner surface and the sidewall at the largest diameter of the pre-form article is preferably about 0.5 mm to about 1.0 mm. According to some further aspects, the gap formed between the inner surface and the sidewall at the largest diameter of the pre-form article is more preferably about of about 0.5 mm to about 0.7 mm. According to aspects, the first electrical energy causes the sidewall to expand about 80% of expansion required to substantially form against the inner surface. The first electrical energy can be large enough to cause the sidewall of the pre-form article to impact the inner surface of the mold, impact a high-pressure cushion of air, or both before deflecting off and retracting back toward the center of the mold, towards the electromagnetic coil.

[0095] At step 2106, at least a second electrical energy is applied to the electromagnetic coil to produce at least a second electromagnetic force. The at least the second electromagnetic force is configured to expand the sidewall of the pre-form article to substantially form against the inner surface. According to some aspects, the at least the second electrical energy can be two electrical energies. The first of the two electrical energies can cause the sidewall to form against the inner surface. The second of the at least two electrical energies can cause the sidewall to acquire additional detail from the inner surface of the mold.

[0096] The first electrical energy and the second electrical energy can be generated with a same amount of energy. Alternatively, the first electrical energy and the at least the second (and subsequent, if any) electrical energy can be generated with different amounts of energy.

[0097] During the expansion of the sidewall of the pre-form article, the displacement of the sidewall of the pre-form article can be measured with a displacement sensor within the mold. As a result, a number of the second electrical energies to apply to the pre-form article via the electromagnetic coil can be determined based on the measured displacement of the sidewall. The displacement sensor can be used to measure displacement of the sidewall as a function of time, only a maximum displacement of the sidewall, or a combination thereof.

[0098] FIG. 22 shows a flow diagram of a process 2200 of determining electrical energy required to electromagnetically form an article, according to aspects of the present disclosure. At step 2202, an electromagnetic coil is inserted at least partially within a pre-form article, with the pre-form article inserted at least partially within a mold. Further, the mold includes a displacement sensor configured to measure expansion of the pre-form article within the mold. According to some aspects, the displacement sensor can be provided within the mold corresponding to a location of a largest diameter of the pre-form article.

[0099] At step 2204, an electrical energy is applied to the electromagnetic coil to produce an electromagnetic force. The electromagnetic force is configured to expand a sidewall of the pre-form article toward an inner surface of the mold.

[0100] At step 2206, an expansion of the sidewall of the pre-form article is measured with the displacement sensor in response to the electrical energy.

[0101] At step 2208, steps 2202-2206 are repeated for a plurality of times with a new pre-form article and a different electrical energy for a plurality of electrical energies. The plurality of electrical energies can be increasing amounts of electrical energy that cause the sidewall of the pre-form article initially to not contact the inner surface of the mold and cause the sidewall of the pre-form article finally to contact the inner surface of the mold and bounce off with maximum inward deflection.

[0102] At step 2210, a final electrical energy required to apply to the sidewall of the pre-form article is determined based on the measured expansions of the sidewalls of the pre-form articles in response to the plurality of electrical energies so that a deflection of the sidewall of the preform article off of the inner surface of the mold in response to the expansion falls within a predefined threshold. The final electrical energy can be determined based on a distance between the inner surface and the sidewall at a largest diameter of the pre-form article. The predefined threshold can be based on a gap remaining between the sidewall and the inner surface of the mold. The gap can be 0.5 mm to about 1.5 mm wide. Alternatively, the gap can be about 0.5 mm to about 1.0 mm wide. Alternatively, the gap can be about 0.5 mm to about 0.7 mm wide.

[0103] Each of the above embodiments and obvious variations thereof are contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and aspects.

[0104] As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0105] It should be noted that the terms “exemplary” and “example” as used herein to describe various embodiments are intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

[0106] Any references herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” etc.) are merely used to describe the orientation of various elements in the Figures. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0107] Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may also be made in the design, operating conditions, and arrangement of the various exemplary embodiments without departing from the scope of the present invention.