Mold assembly and method for manufacturing container body

Abstract

A mold assembly comprising: a housing; a die for stretching and / or thinning the wall of the metal cup mounted on the end of the punch to form a container body; and a support mechanism for the mold or a mold holder in which the mold is mounted. The support mechanism is configured to allow the die or die holder to tilt relative to the housing to reduce misalignment of the longitudinal axis of the die relative to the punch during stretching and / or wall thinning of the metal cup. The mold assembly further includes a chamber disposed in the housing and adapted to seal a fluid therein. The chamber is sealed by one or more surfaces coupled to or disposed on the mold or mold holder such that tilting of the mold during stretching and / or wall thinning of the metal cup resists fluid sealed in the chamber from moving the one or more surfaces.

Description

Technical Field

[0001] The present invention relates to the manufacture of container bodies and particularly, but not exclusively, to the manufacture of can bodies, such as beverage can bodies. Background Art

[0002] In a known can body forming machine for producing thin-walled metal two-piece can bodies by a "draw and wall thinning" (DWI) process, a metal cup is supplied to the body forming machine and carried by a punch on the end of a punch rod through a series of dies to produce a can body of the desired size and thickness. The series of dies may include a re-drawing die for reducing the diameter of the cup and extending its side walls and one or more thinning dies for thinning the cup walls into the can body. The area or bracket within the body forming machine frame where the dies are placed is called a "tool kit." The can body carried on the punch eventually contacts a bottom forming tool or "dome die" to form a shape such as a dome on the can bottom. An exemplary body forming machine is described in WO9934942.

[0003] Traditionally, alignment and realignment of the body forming machine is a complex and time-consuming process that requires the laborious performance of skilled operators (often in short supply) only after a serious problem has occurred. When setting up the can body forming machine, the punch and its drive components are typically fixed in place on the body forming machine frame. This aligns the punch axis with the main axis of the body forming machine. Other components, including, for example, the redraw die, ironing die, and dome die, are then aligned with the punch.

[0004] Can body forming machines typically operate at high speeds for extended periods of time to produce in excess of about 300 to 400 can bodies per minute. However, the quality of the can bodies produced can vary significantly over time due to, for example, variations in the alignment of machine components, variations in coolant temperature and flow rate, variations in the lubrication of the machine, and / or variations in the quality of the cups being fed (e.g., due to variations in the quality of the metal coil from which the cups are made). Even tiny foreign matter (such as dirt) between the dies may be sufficient to cause poor alignment. In some cases, wear on the dies may limit their working life to only a few days or less, particularly if there is imperfect alignment of the dies relative to the punch, which can be problematic because precision machine components (such as dies) are expensive and time-consuming to manufacture.

[0005] In some cases, misalignment of the die relative to the punch can be corrected by inserting shims (usually thin sheets of metal foil) behind one or more of the dies in the tooling. However, this method relies on the operator's experience and judgment to select the correct shim thickness and placement, and there can be considerable variability between operators.

[0006] Poor-quality can bodies can lead to waste and downtime in can production. This can happen, for example, because the body-forming machine itself must be realigned or repaired, or because other machines downstream in the production line are adversely affected by the poor-quality cans produced. Unfortunately, the high-speed, high-volume nature of the can production industry means that lost production time can be very costly for manufacturers.

[0007] EP0005084 describes the use of springs to accommodate radial movement of the die relative to the punch. GB2301055 describes a redraw die having a spherical bearing surface mounted in a die holder, the die holder having an arcuate surface that cooperates with the spherical bearing surface to allow a redraw sleeve in contact with the front face of the redraw die to reorient the redraw die. Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a mold assembly comprising: a housing; a mold for stretching and / or wall thinning a metal cup mounted on the end of a punch to form a container body; and a support mechanism for the mold or a mold holder in which the mold is mounted. The support mechanism is configured to allow the mold or the mold holder to tilt relative to the housing to reduce misalignment of the longitudinal axis of the mold relative to the punch during stretching or wall thinning of the metal cup. The mold assembly also includes a chamber disposed in the housing and adapted to seal a fluid in the chamber. The chamber is sealed by one or more surfaces coupled to or disposed on the mold or the mold holder such that tilting of the mold during stretching and / or wall thinning of the metal cup moves the one or more surfaces against the fluid sealed in the chamber.

[0009] The movement of one or more surfaces can redistribute the fluid in the cavity in response to tilting of the mold or mold holder. The fluid can provide resistance to mold movement while still allowing the mold to be tilted by the punch, thereby reducing misalignment of the longitudinal axis of the mold relative to the punch.

[0010] In use, the chamber is filled with a fluid, such as a hydraulic fluid and / or a pneumatic fluid. For example, the chamber can be filled with a hydraulic fluid, such as mineral oil or water. Alternatively or additionally, the chamber can be filled with a compressed gas, such as air or nitrogen. Typically, high-pressure gas is used, for example greater than 5 bar, or greater than 10 bar, for example about 13.8 bar (200 psi). In some cases, the hydraulic fluid can solidify when the mold assembly is not in use. For example, a solid wax or grease that liquefies when the mold assembly is in use (for example due to the heat generated by the punch driving the metal cup through the mold) can be used. In some embodiments, the mold assembly may include a cooling circuit comprising an inlet for connecting to a coolant supply and an outlet for discharging the received coolant from the mold assembly, the cooling circuit being in heat exchange relationship with the mold assembly. The melting point of the hydraulic fluid can be selected to be lower than the temperature of the coolant, for example in some cases the melting point can be 40 to 50°C.

[0011] Preferably, the cavity is completely filled with hydraulic fluid (i.e., to minimize any residual gas in the cavity) to limit compressibility. Hydraulic fluid may also be preferred (compared to compressed gas) because there may be no internal pressure (to suppress) when the mold assembly is not under any load.

[0012] The longitudinal axis of the die can be defined relative to the front face of the die (e.g., the longitudinal axis can extend in a direction perpendicular to the front face of the die) or relative to a channel (hole) through the die through which the metal cup passes (e.g., the longitudinal axis can extend in a direction parallel to the channel). Tilt of the die can refer to the change in angle between the longitudinal axis of the die and the axis defined by the punch (e.g., the axis along which the punch moves or reciprocates). Generally, the die can be tilted in any direction to reorient its longitudinal axis, such as about a vertical or horizontal direction, or some combination of vertical and horizontal directions. Thus, tilting the die can change the pitch and / or yaw of the die relative to the punch. Tilt of the die can also be referred to as pivoting or rotating the die. In some cases, the die can also be referred to as a "floating" die. In some embodiments, the die assembly can be configured such that the die can tilt greater than 0.01 degrees, greater than 0.03 degrees, greater than 0.05 degrees, or even greater than 0.1 or 0.2 degrees during stretching and / or wall thinning. The ability to tilt the mold by these amounts can mean that the mold (and / or other components used in the stretching and / or wall thinning process) can be manufactured with less precision than would otherwise be necessary.

[0013] Typically, stretching and / or wall thinning a metal cup involves passing the metal cup through a die to increase the height of the sidewall of the metal cup (defined relative to the bottom of the metal cup) while reducing the thickness of the sidewall.

[0014] In some embodiments, a cavity extends between the housing and the mold or mold holder. The support mechanism may include a first sealing element and a second sealing element that form respective seals between the housing and the mold or mold holder. In some examples, one or more surfaces capable of resisting fluid movement may be provided on the mold or mold holder to form walls of the cavity.

[0015] Each sealing element can be, for example, an O-ring mounted between the mold or mold holder and the housing. Each sealing element is preferably elastomeric. In some embodiments, the sealing element can be configured so that the mold is aligned with the punch during multiple strokes of the punch, that is, after the mold is displaced (i.e., deflected) and / or tilted by the punch, the mold may not return to the same position relative to the housing. The sealing element is preferably configured so that the integrity of the seal is maintained when the mold is tilted, that is, the fluid remains trapped in the chamber.

[0016] Typically, as the punch forces the metal cup through the die, slight misalignments between the die and the punch result in unbalanced forces acting on the die, causing the die to move relative to the housing (the magnitude of these movements is typically very small). The fluid provides resistance to inhibit or limit movement of the die within the housing so that the sealing elements, the housing, and / or the die are not damaged by the impact of the punch. Preferably, a substantially incompressible hydraulic fluid is used to minimize movement of the die, such as displacement along the longitudinal axis. When a pneumatic fluid (e.g., compressed gas) is used, the pressure can be selected to ensure that displacement of the die in the direction of the punch is limited to less than a predetermined distance.

[0017] For example, when the die is a redraw die, when the longitudinal axis of the die is misaligned with the punch (i.e., misaligned with the direction the punch moves when entering the die), the front face of the die tilts to a lesser degree, causing a portion of the front face to tilt toward the approaching metal cup. This portion contacts the metal cup slightly earlier than another portion of the front face of the punch that tilts away from the metal cup. Consequently, contact with the metal cup can reorient the front face of the die so that it is parallel to the bottom of the metal cup mounted on the punch (thus better aligning the longitudinal axis of the die with the punch). Consequently, the combined effect of the contact force applied by the metal cup to the front face of the die and the reaction force from the fluid acting on the corresponding rear face of the die can dynamically improve die alignment during the redraw process. Thus, the need for static adjustments by the machine operator can be avoided or minimized. When the die is a thinning die, the forces exerted on the die when the metal cup passes through the die's central hole or channel (orifice) are unbalanced, causing the die to coaxially align with the metal cup (and the punch).

[0018] In some embodiments, the chamber can extend between a face of the mold or mold holder that extends transversely to the longitudinal axis and a corresponding face of the housing that extends transversely to the longitudinal axis. For example, the face of the mold or mold holder and the face of the housing can be substantially flat and parallel to each other. This configuration can allow the mold or mold holder to move in a direction parallel to the punch. In this configuration, the chamber can also have a larger cross-sectional area. For example, the face of the mold or mold holder can be in contact with the fluid over most (e.g., substantially all) of its surface area. Therefore, compared to a chamber with a smaller cross-sectional area, the force applied by the mold or mold holder to the fluid can be distributed over a larger area, which allows the mold to be more easily redirected (i.e., less force is required from the punch).

[0019] Alternatively or additionally, the cavity may extend between a first surface (e.g., an annular surface) of the mold or mold holder extending about the longitudinal axis and a corresponding first surface (e.g., annular surface) of the housing extending about the longitudinal axis. Thus, the cavity can accommodate movement of the mold or mold holder in a direction transverse to the longitudinal axis (i.e., perpendicular to the punch). The first sealing element may include a sealing ring (e.g., an O-ring) disposed between the first surface of the mold or mold holder and the first surface of the housing. The first surface of the mold or mold holder may taper in a direction parallel to the longitudinal axis, which may facilitate mounting the sealing ring to the mold or mold holder. Preferably, the first surface of the mold or mold holder and the first surface of the housing form corresponding side walls of the cavity (i.e., walls of the cavity extending substantially along the longitudinal axis).

[0020] To accommodate tilting, when in use, the mold and / or mold holder can be spaced apart from adjacent mold assemblies (or other tool kit components) and / or parts of the housing or mold holder that may hinder or limit the tilting movement of the mold during normal use. For example, the support mechanism can be configured so that the mold and / or mold holder does not contact the housing. That is, the support mechanism can hold the mold and / or mold holder at a small distance away from the housing. In some embodiments, the mold and / or mold holder can be spaced apart from the housing by a distance of at least 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015"). When the mold assembly is installed in the tool kit, the mold assembly can be configured so that, for example, the front of the mold can be spaced apart from adjacent tool kit components by a distance of, for example, 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015").

[0021] The cavity may also extend between a second surface of the mold or mold holder extending about the longitudinal axis (i.e., a surface different from the first surface of the mold or mold holder, such as an annular surface) and a corresponding second surface of the housing extending about the longitudinal axis (e.g., an annular surface). The second sealing element may include a sealing ring (e.g., an O-ring) disposed between the second surface of the mold and the second surface of the housing. Thus, the mold or mold holder may be radially supported between the first and second sealing rings, with the fluid confined within the cavity by the sealing rings. This configuration may provide the mold or mold holder with sufficient freedom of movement to adjust the alignment of the mold or mold holder and / or the position of the punch relative to the mold or mold holder during stretching and / or wall thinning. Preferably, the second surface of the mold or mold holder and the second surface of the housing form corresponding sidewalls of the cavity. The second surface may be disposed on a portion of the housing that extends (axially, i.e., in a direction parallel to the longitudinal axis of the mold) into a recess (e.g., an annular recess) in the mold or mold holder. The recess may, for example, be provided in the form of an annular channel extending into the die or die holder and may adjoin (eg open into) a channel of the die or die holder through which the metal cup passes during stretching and / or wall thinning.

[0022] Typically, each sealing ring conforms to the surface on which it is disposed, which surface may be of any shape (i.e., cross-section), such as circular or oval (e.g., rounded), square or rectangular, X-shaped or double X-shaped, polygonal with rounded corners, etc. In some embodiments, one or more (e.g., all) of the sealing rings may be elastomeric.

[0023] In some embodiments, the mold can be nested within a mold holder. In this context, "nested" refers to radial nesting such that the outer periphery of the mold is surrounded by the inner periphery of the mold holder. The mold holder and the mold define a channel through which the metal cup passes during stretching and / or wall thinning. The mold holder can be supported by a first sealing element and a second sealing element, and the mold is supported by the mold holder. The mold can be removed from the mold holder to facilitate replacement and / or maintenance of the mold, for example after the inner periphery of the mold is damaged or worn. Another mold (for example, a mold with a different inner diameter and / or inner profile) can then be installed into the mold holder. The mold assembly can be provided (e.g., sold) as part of a kit, in some cases having more than one such mold. Similarly, in other cases, the mold assembly can be provided with an installed mold holder but without a mold.

[0024] In some embodiments, the support mechanism is configured to allow the die or die holder to deflect transversely to the longitudinal axis during stretching or wall thinning. For example, the die or die holder can be mounted in an elastomeric ring (e.g., an O-ring) that allows the die or die holder to deflect transversely to the longitudinal axis during stretching or wall thinning. In addition to misalignments that can be corrected by tilting the die, such movement can compensate for misalignments between the die and the punch (e.g., axial misalignment, such that the longitudinal axis is offset relative to the punch).

[0025] In some embodiments, the housing can include a sealable inlet (e.g., a threaded hole) through which fluid is supplied to the chamber. Of course, more than one sealable inlet (e.g., two, three, or more) can be used. In other embodiments, the fluid can be sealed in the chamber during manufacture of the mold assembly. Thus, the mold assembly can be installed in a tool kit for a tank body molding machine, for example, without requiring an operator of the tank body molding machine to fill the chamber with fluid.

[0026] Preferably, the mold assembly (particularly the mold) is for forming one or more of: a beverage can (eg a two-piece can), a food can, a paint can, an aerosol can, or the like.

[0027] Optionally, the die is a thinning die (i.e., a die suitable for wall thinning) or a redraw die (i.e., a die suitable for stretching / redrawing). For example, the redraw die can be configured so that the metal cup can be clamped between a redraw sleeve and the front face of the die during redrawing.

[0028] According to a second aspect of the present invention, a tank body forming machine is provided, comprising one or more mold assemblies according to the first aspect. For example, the tank body forming machine may include: a mold assembly according to the first aspect, wherein the mold is a redrawing mold (i.e., a mold suitable for stretching / redrawing); and one or more other mold assemblies according to the first aspect, wherein the mold is a thinning mold (i.e., a mold suitable for wall thinning). In embodiments, the thinning mold may have a smaller inner diameter than the redrawing mold.

[0029] According to a third aspect of the invention, there is provided a method of manufacturing a container body from a metal cup using one or more mold assemblies according to the first aspect. The method comprises forcing a metal cup through a mold of each of the one or more mold assemblies using a punch. Tilting of the mold and / or mold holder allows for automatic correction of misalignment of the axis of the mold with the punch, i.e., so that the axis of the mold is parallel to the punch as the punch passes through the mold. Thus, the metal cup can be stretched and / or wall-thinned to have a desired height and sidewall thickness. The method may comprise regulating the pressure of a fluid in a chamber to control the amount by which the mold can tilt during stretching and / or wall-thinning of the metal cup. For example, the pressure may be adjusted depending on the diameter of the container being manufactured.

[0030] In some embodiments, during the stretching (re-stretching) of the metal cup, for example, the load on the die in the direction of the punch can be about 20 kN to about 25 kN. The thinning load can be about 3 kN to about 10 kN (preferably 7 kN to 9 kN). The die assembly can be configured so that the hydraulic fluid and / or pneumatic fluid can provide an equal but opposite reaction force to offset the load from the punch. In particular, the fluid can be selected to provide the reaction force so that the die moves less than a predetermined distance (e.g., less than 10 microns) in the direction of the punch under the load from the punch.

[0031] In some embodiments, the mold assembly includes one or more pistons, each piston providing a seal against a corresponding one of the one or more surfaces of the cavity. The pistons can be arranged such that tilting the mold or mold holder causes at least one of the one or more pistons to move against the fluid sealed in the cavity. In some embodiments, where the mold assembly includes multiple pistons, the one or more pistons can be arranged such that one or more pistons oppose the movement of the fluid sealed in the cavity, causing the fluid to oppose the movement of one or more other pistons in the mold or mold holder. For example, tilting the mold or mold holder can cause one or more pistons to move in a direction parallel to the punch, while redistribution of the fluid in the cavity can cause one or more other pistons to move in the opposite direction to assist in tilting the mold or mold holder. In some examples, each piston can move within a corresponding channel forming part of the cavity. Preferably, each channel and corresponding piston are arranged (substantially) parallel to the punch. The pistons can be arranged such that tilting the mold or mold holder causes at least one of the pistons to move along its corresponding channel in the direction of the punch.

[0032] For example, the pistons may be angularly spaced about the longitudinal axis of the mould.Preferably, there are three or more pistons to allow the mould to be tilted along two orthogonal axes.

[0033] In some embodiments, the mold assembly may include one or more channels disposed in the housing and adapted to seal a fluid therein, each channel being sealed by a respective (adjustment) piston coupled to the mold and having a respective adjustment mechanism for applying pressure to the fluid in the channel to move the piston and tilt the mold or mold holder relative to the housing, whereby the adjustment mechanism or each adjustment mechanism may be used to reduce misalignment of the longitudinal axis of the mold relative to the punch. In some embodiments, each of the channels may be in fluid communication with a respective chamber (e.g., the chambers mentioned above with respect to the first aspect) such that movement of the piston increases or decreases the pressure of the fluid in the chamber to cause tilting of the mold. Each of the chambers is disposed in the housing and adapted such that a fluid may be sealed therein by a respective one or more surfaces coupled to or disposed on the mold or mold holder such that pressure from the fluid may move the one or more surfaces to tilt the mold.

[0034] According to a fourth aspect of the present invention, there is provided a mould assembly comprising: a housing; a mould for stretching and / or thinning the wall of a metal cup mounted on the end of a punch to form a container body; and a support mechanism for the mould, the support mechanism being configured to allow the mould to tilt relative to the housing. One or more channels may be provided in the housing and adapted to seal a fluid in the one or more channels. Each channel may comprise a respective piston coupled to the mould and a respective adjustment mechanism for applying pressure to the fluid in the channel to move the piston and tilt the mould relative to the housing. The adjustment mechanism or each adjustment mechanism may thus be used to reduce misalignment of the longitudinal axis of the mould relative to the punch.

[0035] For example, the pistons may be angularly spaced about the longitudinal axis of the mold (e.g., when there are three pistons, they may be spaced 120 degrees apart, although the spacing need not be uniform). Preferably, there are three or more pistons to allow the mold to be tilted along two orthogonal axes.

[0036] Each adjustment mechanism may, for example, comprise a threaded member (e.g., a bolt) engaged in a threaded opening leading to the channel, wherein screwing the threaded member into (or out of) the threaded opening reduces (increases) the volume of the channel to change the force on the corresponding piston, thereby tilting the mold. Alternatively, for example, the mold may be disposed in a mold holder, with the piston acting on the mold holder.

[0037] Optionally, each adjustment mechanism may be computer controlled (eg, via a wired or wireless connection) so that misalignment of the longitudinal axis of the die relative to the punch can be reduced while the die assembly is in use.

[0038] In some embodiments, the mold assembly may include one or more sensors that are configured or configurable to provide a corresponding signal indicating that the longitudinal axis of the mold is misaligned relative to the punch. In general, a variety of different types of sensors can be used. For example, one or more (e.g., each) of the channels may include a corresponding pressure sensor for measuring the pressure exerted by the corresponding piston on the fluid in the channel during the stretching and / or wall thinning process. Alternatively or in addition, the sensor may include one or more force sensors (e.g., load cells), each force sensor being oriented to measure the force on the mold at a corresponding position about the longitudinal axis of the mold, for example, the force sensor may be disposed between the housing and the corresponding face of the mold.

[0039] The signal can be provided to a computer device that controls each adjustment mechanism, and the computer device adjusts one or more (e.g., each) of the adjustment mechanisms based on the signal to reduce the misalignment. The computer device can implement a feedback control loop so that the adjustment maintains the correct or desired alignment of the mold, for example, despite varying operating conditions such as temperature changes, mold wear, etc. For example, a proportional-integral-derivative (PID) controller can be used to adjust each of the adjustment mechanisms to minimize an error signal determined by the sensor signals. The error signal can, for example, be a measure of the difference (or ratio) between the sensor signals.

[0040] Alternatively or additionally, the signals provided by the sensors may be visually displayed (eg, on a graphical user interface) or otherwise communicated to a user, who may then employ one or more adjustment mechanisms to reduce the misalignment.

[0041] According to a fifth aspect of the present invention, a method of aligning a machine for manufacturing container bodies from metal cups, such as a can body forming machine, is provided. The machine includes one or more mold assemblies according to the fourth aspect. The method includes applying pressure to a fluid in a chamber using one or more adjustment mechanisms to move one or more corresponding pistons and tilt the mold relative to the housing.

[0042] In each of the above aspects, the mold assembly can include one or more additional molds coupled to the mold such that tilting the mold also tilts the additional molds. For example, the mold and additional molds can be fixed to each other so that they move / tilt as a single unit. Preferably, the additional molds are positioned closer to the inlet of the tool kit relative to the mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic vertical cross-sectional view of a punch, a redraw sleeve, and a tool kit of a can body forming machine according to the prior art;

[0044] Figure 2is a schematic vertical cross-sectional view of a punch, a redraw sleeve, and a redraw die assembly according to one embodiment of the present invention;

[0045] Figure 3 yes Figure 2 a schematic vertical cross-sectional view of the redraw die assembly shown;

[0046] Figure 4 is a schematic vertical cross-sectional view of a thinning die assembly according to one embodiment of the present invention;

[0047] Figure 5 is a schematic vertical sectional view of a tool kit for a tank body forming machine according to one embodiment of the present invention; and

[0048] Figure 6 is a schematic vertical cross-sectional view of a mold assembly according to one embodiment of the present invention. DETAILED DESCRIPTION

[0049] Figure 1 Components of a can body forming machine 100 are shown, including a tool kit 102, a ram 106, and a redraw sleeve 108. The tool kit 102 includes a redraw die 110 and a plurality of ironing dies 112A-C arranged one behind the other along an axis Z with spacer rings 114A-C therebetween. The dies and spacer rings each have a corresponding aperture or passageway that is aligned about the axis Z to provide a passageway extending through the tool kit 102 through which the ram 106 can reciprocate.

[0050] In operation, the punch 106 drives a metal cup (not shown) through the dies 110, 112A-C to stretch and thin the wall of the metal cup to form a can body. Before entering the die, the metal cup is mounted on a redraw sleeve 108, which is received by the metal cup so that the sidewall of the metal cup extends around the circumference of the redraw sleeve 108 and the front face 116 of the redraw sleeve 108 and the punch 106 contacts the bottom of the metal cup (the front portion of the punch 106 may be referred to as a punch). The punch 106 and the redraw sleeve 108 drive the bottom of the metal cup relative to the front face 118 of the redraw die 110 (i.e., the face of the redraw die 110 that is oriented toward the punch 106), so that the bottom of the metal cup is clamped between the redraw sleeve 108 and the front face 118 of the redraw die 110. The forward movement of the redraw sleeve 108 is interrupted by the tool kit 102, while the punch 106 continues to pass through the redraw sleeve 108, forcing the bottom of the metal cup through the redraw die 110, thereby "stretching" the metal cup from between the redraw sleeve 108 and the surfaces 116, 118 of the redraw die 110, thereby reducing the diameter of the metal cup and lengthening its sidewalls. The punch 106 continues to force the metal cup through the channel defined by the thinning dies 112A-C and other tool kit components. The subsequent thinning dies 112B, C have continuously decreasing inner diameters, causing the sidewalls of the metal cup to further lengthen and thin as the metal cup passes through the tool kit 102.

[0051] Figure 2 A die assembly 200 is shown, which includes a redraw die 202 and a housing 204. The redraw die 202 is generally annular, with an inner diameter selected to allow a punch 206 to pass through the redraw die 202. Only a small amount of radial clearance is provided between the punch 206 and the redraw die 202 to (partially) accommodate the thickness of the sidewall of the metal cup 208 during the stretching process. The redraw die 202 has a front face 210 against which the bottom of the metal cup 208 is clamped by a redraw sleeve 212 at the beginning of the stretching process. The redraw die 202 has a flange portion 207 that is spaced from the front face 210 and has a larger outer diameter than the front face 210 of the redraw die 202. The flange portion 207 of the redraw die 202 is received by a corresponding channel formed in the front face 214 of the housing 204. The flange portion 207 of the re-draw die 202 is spaced (inwardly) from the housing 204 so as to define a cavity 216 between the housing 204 and the re-draw die 202 .

[0052] In use, chamber 216 is filled with hydraulic fluid, such as mineral oil, but other fluids, such as compressed air (or other pneumatic gases) may be used instead of or in addition to the hydraulic fluid. However, it is preferred that chamber 216 is completely filled with hydraulic fluid to ensure uniformity and reduce compressibility.

[0053] The housing 204 includes a cylindrical inner sidewall 218A located radially inward of the flange portion 207 of the re-draw die 202 and abutting or spaced apart from a lip 220 formed on the inner surface of the re-draw die 202. An O-ring 222A is disposed between the inner sidewall 218 of the housing 204 and the flange portion 207 of the re-draw die 204, the O-ring surrounding the inner sidewall 218 of the housing 204. In this example, the O-ring 222A is disposed in a circumferential groove in the flange portion 207 of the re-draw die 202. However, the O-ring 222A may alternatively or additionally be disposed in a groove formed in the inner sidewall 218 of the housing 204. A second O-ring 222B is disposed between the cylindrical outer sidewall 218B located radially outward of the flange portion 207 of the re-draw die 202. In this example, the O-ring 222B is located in a circumferential groove formed around the flange portion 207 of the re-draw die 202, but like the first O-ring 222A, the second O-ring 222B may additionally or alternatively be located in a groove formed in the outer sidewall 218B of the housing 204. Preferably, both O-rings 222A, B are located in grooves on the re-draw die 202 so that the re-draw die 202 can be easily removed from the housing 204 and replaced, for example, if the re-draw die 202 becomes worn or damaged.

[0054] The two O-rings 222A, B seal the chamber 216 to prevent hydraulic fluid from leaking from the chamber 216 due to the large forces exerted on the die assembly 200 by the metal cup 208, the ram 206 and the re-draw sleeve 212 during the drawing process.

[0055] In this example, the O-rings 222A, B are made of an elastomeric material (e.g., nitrile rubber (NBR)) so that the re-draw die 202 can deflect a small amount within the housing 204 without allowing hydraulic fluid to leak from the chamber 216. Specifically, the O-rings 222A, B can be deformed by the re-draw die 202 to allow the re-draw die 202 to tilt when the metal cup 208 and the re-draw sleeve 212 contact the front face 210 of the re-draw die 202. Thus, the die assembly 200 allows the re-draw die 204 to dynamically reorient after contacting the metal cup so that the front face 210 of the re-draw die 202 is aligned parallel to the front face of the re-draw sleeve 212 during the drawing process. This alignment allows for uniform clamping pressure to be applied to the metal cup 208 during the drawing process, which can reduce or avoid defects (e.g., wrinkles or "indentation lines") that may form in the sidewall of the metal cup 208 as the metal cup 208 is drawn through the re-draw die 202 by the punch 206.

[0056] The housing 204 may include an inlet 224 extending through the outer sidewall 218B through which hydraulic fluid is introduced into the chamber 216. In this example, the inlet 224 is threaded so that the inlet 224 can be sealed, for example, using a bolt 226 threaded into the inlet 224. Thus, in at least some cases, the mold assembly 200 can be used without being attached to any external pressure source.

[0057] Figure 3 An enlarged view of the mold assembly 200 is shown separated from the other components of the tank body forming machine.

[0058] Figure 4 A mold assembly 300 is shown, which is similar to Figure 2 and Figure 3 2. The die assembly 300 is similar to the die assembly 200, except that the die assembly 300 includes a die holder 301 in which the thinning die 302 (rather than the re-stretch die 202) is mounted. The housing 304 of the die assembly 300 also surrounds the die holder 301 and the thinning die 302 along their length (i.e., parallel to the longitudinal axis Z of the thinning die 302), so that the die holder 301 and the thinning die 302 can still be tilted (i.e., reoriented relative to the housing 304 and the punch) after the die assembly 300 is installed in the tooling of the can body forming machine. In some embodiments, the thinning die 307 is removable from the die assembly 300.

[0059] In this example, the thinning die 302 includes a thinning ring 307 through which a punch forces the metal cup to “wall thin” (ie, lengthen and thin) the sidewall of the metal cup 208 after the metal cup 208 is drawn through the re-draw die 202 .

[0060] The mold holder 301 is similar to Figure 2 and Figure 3 The illustrated arrangement of the redraw die 202 and housing 204 is received in a housing 304. Thus, a chamber 310 is provided between the housing 304 and the support ring 308, which is filled with hydraulic fluid (at least when the die assembly 300 is in use). The chamber 310 is sealed by two O-rings 318A, B located between respective annular surfaces of the support ring 308 and the housing 304. The O-rings allow the support ring 308 to be reoriented during the thinning process, as described above with respect to the redraw die 202.

[0061] The die 302 is radially nested within the die holder 301 using an O-ring 312. In some examples, the O-ring 312 can allow the die 302 to deflect slightly within the die holder 301, such as translating radially within the die holder 301, so that the die 302 is concentrically aligned with the punch 206. Thus, the die assembly 300 can allow for concentric and coaxial alignment of the die 302 with the punch 206.

[0062] Figure 5 A tool kit for a tank body forming machine 500 is shown, including a redraw die assembly 502 (which may be a combination of the above Figure 2 and Figure 3 The re-stretch die assembly 200 described above) and the plurality of thinning die assemblies 504A-C (each of which may be a combination of the above Figure 4 300 is described. For each thinning die assembly 504A-C, the die and die holder are spaced apart from the tool kit component 506 located in front of the thinning die assembly 504A-C by a distance (i.e., gap) 508 that provides clearance for the die and die holder to tilt. Similarly, a gap 510 is provided between the interior face (i.e., rear face, oriented away from the direction the punch enters the tool kit) of the die and the interior cylindrical sidewall 318A of the die assembly housing to provide clearance for the die to tilt. In some embodiments, the distance or gap 508, 510 is 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015"), measured along axis Z in this example, but any distance or gap that provides sufficient freedom for the die and die holder to tilt and align with the punch can be used. The distance can be determined by, for example, determining the maximum angle through which the die may need to tilt due to manufacturing tolerances and / or variations in punch alignment in one or more of the die, die holder, die housing, tool kit, etc.

[0063] Figure 6 A mold assembly 600 is shown that includes a mold 602 having a thinning ring 604 and supported by a sealing ring 606 that extends around the periphery of the mold 602 and partially extends into a channel formed on the interior surface of a mounting ring 608. The sealing ring 606 is elastomeric to allow the mold 602 to tilt within the mounting ring 608 during stretching and / or wall thinning. The mold assembly 600 also includes a housing 610 that includes a chamber 612 (e.g., the chamber 612 can be substantially cylindrical) extending about the longitudinal axis Z of the mold. In use, the chamber 612 is filled with hydraulic fluid introduced into the chamber 612 through an inlet 614 extending through the housing 610, which is then sealed with a plug 616 (e.g., a bolt). The chamber 612 includes a plurality of channels 617 extending toward the mold 602, each of which is sealed by a corresponding piston 618 configured to slide within the channel 617 in a direction parallel to the longitudinal axis Z of the mold 602, with sealing rings 620 between the piston 618 and the sidewalls of the channel preventing fluid from leaking from the channel 617. Each of the channels 617 is in fluid communication with the other channels via the chamber 612.

[0064] exist Figure 6In the cross-section of FIG, only one such channel 617 and piston 618 is visible, but chamber 612 includes two other channels and pistons that are angularly spaced from channel and piston 618 about the longitudinal axis Z. When die 602 is tilted during stretching and / or wall thinning of the metal cup, die 602 contacts piston 618, causing it to move along channel 617 to apply pressure to the fluid in chamber 612. This pressure is transferred by the fluid in chamber 612 to the other piston 618, causing it to move outward (i.e., in a direction opposite to the Z direction). Thus, the longitudinal position of piston 618 in its respective channel 617 is adjusted in response to the tilt of die 602.

[0065] In an alternative embodiment of the mold assembly 600, each of the pistons 618 and the channels 617 is not in fluid communication with each other, that is, each channel 617 is isolated from the other channels 617, and each channel 617 has a separate inlet 614 through which fluid is supplied. Each channel 617 has an adjustment mechanism that allows force to be transmitted to each of the pistons 618 by the fluid. For example, each inlet 614 can have a plug 616 (e.g., a threaded member, such as a bolt) that can be displaced (e.g., screwed into) into the inlet 614 to apply force to the fluid in the inlet 614. The longitudinal movement of the piston 618 in response to the force causes the mold 602 to tilt. Therefore, one or more (e.g., each) of the adjustment mechanisms (e.g., plugs 616) can be used to adjust the tilt of the mold 602 to improve its alignment with the punch of the tank body molding machine. For example, the adjustment mechanism can be iteratively adjusted to improve alignment. Compared to the other embodiments described above, once the tilt of the die 602 is correctly aligned, the die 602 can remain substantially in that orientation while the can body forming machine is running, i.e., the alignment is static, not dynamic, and can undergo minimal changes as the punch passes through the die 602.

[0066] In some examples, each plug 616 is coupled to an actuator (e.g., a linear actuator, or a rotary actuator when a threaded plug is used) that controls the displacement of the plug within the inlet 616. Each actuator can be computer-controlled (e.g., via a wired or wireless connection) to adjust the displacement of the corresponding piston in the channel 617. The mold assembly 600 can include one or more sensors (not shown) that can be configured or configured to provide a corresponding signal indicating that the longitudinal axis of the mold is misaligned relative to the punch. In general, a variety of different types of sensors can be used. For example, the actuator can include a force sensor that is configured to measure the force transmitted to the actuator by the piston 618 and the fluid from the mold 602 during stretching and / or wall thinning of the metal cup.

[0067] The signal can be provided to a computer device that controls the actuators, which then adjusts one or more (e.g., each) of the actuators based on the signal to reduce the misalignment. The computer device can implement a feedback control loop so that the adjustments maintain the correct or desired alignment of the mold, for example, despite varying operating conditions such as temperature changes, mold wear, etc. For example, a proportional-integral-derivative (PID) controller can be used to adjust each of the actuators to minimize an error signal determined from the sensor signals. The error signal can, for example, be a measure of the difference (or ratio) between the sensor signals.

[0068] The die assemblies 200, 300, 600 can be used to form a variety of container bodies of different types and sizes, such as beverage cans (e.g., two-piece cans, slim or standard cans, 53 mm or 66 mm diameter cans, etc.), food cans, paint cans, aerosol cans, etc. The metal cup from which the can body is formed can be made from, for example, steel or aluminum sheet, or an alloy containing either, and can be pre-coated (e.g., laminated) with an organic coating, such as polyester. The redraw die assembly 200, thinning die assembly 300, and die assembly 600 described herein can be configured to fit into the tooling of existing can body forming machines, allowing them to be installed as replacements for existing die assemblies without requiring (or requiring only minimal) modification to the tooling.

[0069] Although the sealing element of the above-described embodiment is a sealing ring (O-ring), other forms of sealing elements, such as a diaphragm or a bellows device, may alternatively or additionally be used. Alternatively or additionally, the fluid may be sealed in a flexible housing (e.g., a bag or bladder) contained within the chamber. In this case, different sections of the housing (e.g., opposite ends) may be identified as sealing elements.

[0070] Those skilled in the art will appreciate that various modifications may be made to the above-described embodiments without departing from the scope of the invention. In particular, while specific embodiments of the subject matter have been described, other embodiments are within the scope of the appended claims.

Claims

1. A mold assembly comprising: case; a die for stretching and / or wall-thinning a metal cup mounted on the end of a plunger to form a container body; a support mechanism for the die or die holder in which the die is mounted, the support mechanism being configured to allow the die or die holder to tilt relative to the housing to reduce misalignment of a longitudinal axis of the die relative to the punch during stretching and / or wall thinning of the metal cup; as well as a cavity disposed in the housing and adapted to seal a fluid therein, the cavity being sealed by one or more surfaces coupled to or disposed on the mold or the mold holder such that tilting of the mold during stretching and / or wall thinning of the metal cup moves the one or more surfaces against the fluid sealed in the cavity.

2. The mold assembly according to claim 1, wherein: The cavity extends between the housing and the mold or the mold holder, and the support mechanism includes a first sealing element and a second sealing element that form respective seals between the housing and the mold or the mold holder.

3. The mold assembly according to claim 2, wherein: The cavity extends between a surface of the mold or of the mold holder extending transversely to the longitudinal axis and a corresponding surface of the housing extending transversely to the longitudinal axis.

4. The mold assembly according to claim 2, wherein: The cavity extends between a first surface of the mold or the mold holder extending about the longitudinal axis and a corresponding first surface of the housing extending about the longitudinal axis.

5. The mold assembly according to claim 4, wherein: The cavity extends between a second surface of the mold or the mold holder extending about the longitudinal axis and a corresponding second surface of the housing extending about the longitudinal axis.

6. The mold assembly according to claim 5, wherein: The first surface and the second surface of the mold or the mold holder are located between the respective first surface and the respective second surface of the housing.

7. The mold assembly according to any one of claims 4 to 6, wherein: The first sealing element includes a sealing ring disposed between a first surface of the mold or the mold holder and a first surface of the housing.

8. The mold assembly according to claim 7, wherein: The first surface of the mold or the mold holder tapers in a direction parallel to the longitudinal axis.

9. The mold assembly according to claim 5, wherein: The second sealing element includes a sealing ring disposed between a second surface of the mold or the mold holder and a second surface of the housing.

10. The mold assembly according to claim 9, wherein: The second surface is provided on a portion of the housing that extends into a recess of the mold or the mold holder.

11. A mould assembly according to any one of the preceding claims, wherein: The support mechanism is configured to allow deflection of the die or the die holder transverse to the longitudinal axis during stretching or wall thinning of the metal cup.

12. A mould assembly according to any one of the preceding claims, wherein: The housing includes one or more sealable inlets through which fluid is supplied to the chamber.

13. A mould assembly according to any one of the preceding claims, wherein: The mold assembly includes one or more pistons, each piston providing a respective one of the one or more surfaces sealing the cavity, the one or more pistons being arranged such that tilting the mold causes at least one of the one or more pistons to move against the fluid sealed in the cavity.

14. The mold assembly according to claim 13, wherein: The mold assembly includes a plurality of pistons, the one or more pistons being arranged such that movement of one or more pistons against a fluid sealed in the chamber causes the fluid to move one or more other of the pistons against the mold or the mold holder.

15. The mold assembly according to any of the preceding claims further comprises one or more channels arranged in the housing and adapted to seal a fluid in the one or more channels, each channel being sealed by a respective adjustment piston coupled to the mold and having a respective adjustment mechanism for applying pressure to the fluid in the channel to move the adjustment piston and tilt the mold or the mold holder relative to the housing, whereby the adjustment mechanism or each adjustment mechanism can be used to reduce misalignment of the longitudinal axis of the mold relative to the punch.

16. A tank body forming machine comprising one or more mould assemblies according to any one of the preceding claims.

17. A method of making a container body from a metal cup using one or more die assemblies according to any one of claims 1 to 15, the method comprising forcing the metal cup through the die of each of the one or more die assemblies using a punch.

18. A mold assembly comprising: case; a die for stretching and / or wall-thinning a metal cup mounted on the end of a plunger to form a container body; a support mechanism for the mold or mold holder in which the mold is mounted, the support mechanism being configured to allow the mold or the mold holder to tilt relative to the housing; as well as One or more channels disposed in the housing and adapted to seal a fluid therein, each channel being sealed by a respective piston coupled to the die and having a respective adjustment mechanism for applying pressure to the fluid in the channel to move the piston and tilt the die or the die holder relative to the housing, whereby misalignment of the longitudinal axis of the die relative to the ram can be reduced using the or each adjustment mechanism.

19. The mold assembly according to claim 18, wherein: Each adjustment mechanism is computer controlled so as to reduce misalignment of the longitudinal axis of the die relative to the punch when the die assembly is in use.

20. The die assembly of claim 18 or 19, further comprising one or more sensors configured or configurable to provide a respective signal indicative of misalignment of the longitudinal axis of the die relative to the punch.

21. A method of aligning a machine for making container bodies from metal cups, the machine comprising one or more mold assemblies according to any one of claims 18 to 20, the method using one or more of the adjustment mechanisms to apply pressure to a fluid in a chamber to move one or more corresponding pistons and tilt the mold or the mold holder relative to the housing.

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