Die assembly and method for manufacturing container body

Abstract

The die assembly includes a housing, a die for drawing and / or wall-ironing a metal cup attached to the end of the ram to form a container body, and a support mechanism for the die or a die holder to which the die is attached. The support mechanism is configured to allow the die to be tilted relative to the housing to reduce misalignment of the longitudinal axis of the die relative to the ram during drawing and / or wall-ironing of the metal cup. The die assembly further includes a chamber disposed within the housing and adapted to seal a fluid therein. The chamber is sealed by one or more surfaces coupled to or disposed on the die or die holder, such that tilting of the die during drawing and / or wall-ironing of the metal cup moves the one or more surfaces relative to the fluid sealed within the chamber.

Description

[Technical Field]

[0001] The present invention relates to the manufacture of container bodies, particularly but not exclusively can bodies, for example beverage can bodies. [Background technology]

[0002] In known can bodymakers for producing thin-walled two-piece metal can bodies by the "drawing and wall ironing" (DWI) process, a metal cup is fed into the bodymaker and conveyed by a punch at the end of a ram through a series of dies to produce a can body of the desired size and thickness. The series of dies may include a redraw die to reduce the cup diameter and lengthen the sidewall, and one or more ironing dies to wall iron the cup into the can body. The area or cradle of the bodymaker frame within which the dies are located is known as the "tool pack." The can body conveyed over the punch may eventually contact a bottom-forming tool or "domer" to form a dome-like shape at the bottom of the can. An exemplary bodymaker is described in International Publication No. WO 9934942.

[0003] Traditionally, aligning and realigning bodymakers is a complex, time-consuming process that must be painstakingly performed by skilled operators (who are often in short supply) only after a major problem occurs. When setting up a can bodymaker, the ram and its drive components are typically locked into place on the bodymaker's frame, so that the ram axis is aligned with the bodymaker's main axis. Other components, such as the redraw and ironing die and domer, are then aligned relative to the ram.

[0004] Can body makers typically operate at high speeds for long periods, producing approximately 300 to 400 or more can bodies per minute. However, the quality of the can bodies produced can vary significantly over time due to, for example, changes in the alignment of machine components, the temperature and flow rate of coolant, machine lubrication, and / or the quality of the incoming cup (e.g., due to variations in the quality of the metal coil from which the cup is made). Even small foreign objects, such as debris between the dies, can cause misalignment. In some cases, especially if the die is imperfectly aligned with the ram, die wear can limit the die's life to just a few days or less, which can be problematic because precision machine components such as dies are costly and time-consuming to manufacture.

[0005] Misalignment of the die relative to the ram can sometimes be corrected by inserting shims, typically thin pieces of metal foil, behind one or more dies in the tool pack, however, such an approach relies on the experience and judgment of the operator to select the appropriate thickness and placement of the shim, which can be subject to considerable operator variability.

[0006] Poor quality can bodies can result in waste and downtime in can production. This may occur, for example, because the bodymaker itself needs to be reconditioned or repaired, or because other machinery further down the production line is adversely affected by the poor quality cans being produced. Unfortunately, due to the high speed, high volume nature of the can manufacturing industry, lost production time can be very costly to producers.

[0007] EP 0 005 084 A1 describes the use of springs to accommodate radial movement of the die relative to the ram. GB 2 301 055 A1 describes a redraw die having a spherical bearing surface mounted on a die holder having an arcuate surface cooperating with the spherical bearing surface, and a redraw sleeve contacting the front face of the redraw die to allow the redraw die to be reoriented. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 9934942 [Patent Document 2] European Patent Application Publication No. 0005084 [Patent Document 3] GB Patent Application Publication No. 2301055 Summary of the Invention [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a die assembly comprising a housing, a die for drawing and / or wall-ironing a metal cup attached to the end of a ram to form a container body, and a support mechanism for the die or die holder to which the die is attached. 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 ram during drawing or wall-ironing of the metal cup. The die assembly further comprises a chamber disposed within the housing and adapted to seal a fluid therein. The chamber is sealed by one or more surfaces coupled to or disposed on the die or die holder, such that tilting of the die during drawing and / or wall-ironing of the metal cup moves the one or more surfaces relative to the fluid sealed within the chamber.

[0010] The movement of one or more surfaces can redistribute the fluid within the chamber in response to tilting of the die or die holder. The fluid can provide resistance to die movement while allowing the die to be tilted by the ram, thereby reducing misalignment of the longitudinal axis of the die relative to the ram.

[0011] 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, e.g., greater than 5 bar, greater than 10 bar, e.g., about 13.8 bar (200 psi), is used. In some cases, the hydraulic fluid may solidify when the die assembly is not in use. For example, a solid wax or grease may be used that liquefies as a result of heat generated by a metal cup being forced into the die by a ram when the die assembly is in use. In some implementations, the die assembly can include a cooling circuit in a heat exchange relationship with the die assembly, the cooling circuit including an inlet for connection to a coolant source and an outlet for discharging the received coolant from the die 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 is 40 to 50°C.

[0012] Preferably, the chamber is completely filled with hydraulic fluid (i.e., so that there is minimal residual gas in the chamber) to limit compressibility. Hydraulic fluid may also be preferred (compared to compressed gas) because there is no internal pressure (which needs to be contained) when the die assembly is not under any load.

[0013] The longitudinal axis of the die can be defined relative to the front face of the die (e.g., the longitudinal axis can extend perpendicular to the front face of the die) or relative to the passage (bore) through the die through which the metal cup travels (e.g., the longitudinal axis can extend parallel to the passage). Die tilt can refer to a change in the angle between the longitudinal axis of the die and an axis defined by the ram (e.g., the axis about which the ram moves or reciprocates). Generally, the die can be tilted in any direction to change the orientation of its longitudinal axis, e.g., about the vertical or horizontal direction, or some combination of the vertical and horizontal directions. Thus, die tilt can change the pitch and / or yaw of the die relative to the ram. Die tilt can also be referred to as the pivoting or rotational movement of the die. The die is also sometimes referred to as a "floating" die. In some implementations, the die assembly can be configured to allow the die to tilt by more than 0.01 degrees, more than 0.03 degrees, more than 0.05 degrees, or even more than 0.1 or 0.2 degrees during drawing and / or wall ironing. The ability for the die to tilt by these amounts may mean that the die (and / or other elements used in drawing and / or wall ironing) can be manufactured with a lower level of precision than would otherwise be required.

[0014] Generally, drawing and / or wall ironing of a metal cup involves passing the metal cup through a die to increase the height of the sidewalls of the metal cup (defined relative to the base of the metal cup) while simultaneously reducing the thickness of the sidewalls.

[0015] In some implementations, the chamber extends between the housing and the die or die holder. The support mechanism can include first and second sealing elements that form respective seals between the housing and the die or die holder. One or more surfaces that are movable relative to the fluid can be provided on the die or die holder to form walls of the chamber in some examples.

[0016] Each sealing element may be, for example, an O-ring mounted between the die or die holder and the housing. Each sealing element is preferably elastomeric. In some implementations, the sealing elements may be configured to maintain alignment of the die with the ram over multiple strokes of the ram, i.e., to prevent the die from returning to the same position relative to the housing after displacement (i.e., deflection) and / or tilting of the die by the ram. The sealing elements are preferably configured to maintain seal integrity, i.e., to ensure that fluid remains trapped within the chamber, even when the die is tilted.

[0017] Generally, as the metal cup is forced through the die by the ram, small misalignments between the die and the ram result in unbalanced forces acting on the die, causing it to move relative to the housing (the magnitude of these movements is generally very small). The fluid provides resistance that inhibits or limits the movement of the die within the housing, preventing damage to the sealing elements, the housing, and / or the die from the impact of the ram. Preferably, a substantially incompressible hydraulic fluid is used to minimize die movement, e.g., displacement along the longitudinal axis. If a pneumatic fluid (e.g., compressed gas) is used, the pressure can be selected to ensure that the displacement of the die along the direction of the ram is limited to less than a predetermined distance.

[0018] As an example, if the die is a redraw die, if the longitudinal axis of the die is not properly aligned with the ram (i.e., not properly aligned with the direction of travel of the ram as it enters the die), the front face of the die can tilt only slightly, with a portion of the front face tilted toward the approaching metal cup. This portion contacts the metal cup slightly earlier than another portion of the ram's front face that is tilted away from the metal cup. Contact with the metal cup may thus cause the front face of the die to reorient itself so that it is parallel to the bottom surface of the metal cup attached to the ram (and thus the longitudinal axis of the die may be better aligned with the ram). Therefore, the combined action of the contact force exerted by the metal cup on 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 drawing process. Therefore, the need for static adjustments by the machine operator can be avoided or minimized. If the die is an ironing die, the force exerted by the metal cup on the die as it passes through the central hole or passage (bore) of the die is unbalanced, so that the die is aligned coaxially with the metal cup (and ram).

[0019] In some implementations, the chamber can extend between a surface of the die or die holder extending transversely to the longitudinal axis and a corresponding surface of the housing extending transversely to the longitudinal axis. The surfaces of the die or die holder and the housing can be, for example, substantially planar and parallel to each other. This configuration allows the die or die holder to move in a direction parallel to the ram. This configuration also allows the chamber to have a larger cross-sectional area. For example, the surface of the die or die holder can contact the fluid over a large portion (e.g., substantially all) of its surface area. Thus, the force exerted by the die or die holder on the fluid can be distributed over a larger area compared to a chamber having a smaller cross-sectional area, making it easier to reorient the die (i.e., requiring less force from the ram).

[0020] Alternatively or additionally, the chamber can extend between a first surface (e.g., an annular surface) of the die or die holder extending about the longitudinal axis and a corresponding first surface (e.g., an annular surface) of the housing extending about the longitudinal axis. Thus, the chamber can accommodate movement of the die or die holder transversely to the longitudinal axis, i.e., perpendicular to the ram. The first sealing element can include a seal ring (e.g., an O-ring) disposed between the first surface of the die or die holder and the first surface of the housing. The first surface of the die or die holder can be tapered along a direction parallel to the longitudinal axis, which can facilitate attachment of the seal ring to the die or die holder. Preferably, the first surface of the die or die holder and the first surface of the housing form respective side walls of the chamber (i.e., walls of the chamber extending substantially along the longitudinal axis).

[0021] To accommodate tilting, in use, the die and / or die holder can be spaced from adjacent die assemblies (or other tool pack components) and / or parts of the housing or die holder that may impede or limit tilting movement of the die during normal use. For example, the support features can be configured to prevent the die and / or die holder from contacting the housing. That is, the support features can hold the die and / or die holder a small distance away from the housing. In some implementations, the die and / or die holder can be spaced from the housing by a distance in the range of at least 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015") . When the die assembly is incorporated into a tool pack, the die assembly can be configured, for example, such that the front face of the die is spaced from an adjacent tool pack component by a distance in the range of, for example, 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015" ).

[0022] The chamber can also extend between a second surface of the die or die holder (i.e., a surface different from the first surface of the die or die holder, e.g., an annular surface) extending around the longitudinal axis and a corresponding second surface (e.g., an annular surface) of the housing extending around the longitudinal axis. The second sealing element can include a sealing ring (e.g., an O-ring) disposed between the second surface of the die and the second surface of the housing. The die or die holder is thus radially supported between the first and second sealing rings, and fluid is confined within the chamber by the sealing rings. Such a configuration can provide the die or die holder with sufficient freedom of movement to adjust its alignment and / or position relative to the ram during drawing and / or wall ironing. Preferably, the second surface of the die or die holder and the second surface of the housing form respective side walls of the chamber. The second surface can be provided on a portion of the housing extending (axially, i.e., along a direction parallel to the longitudinal axis of the die) into the recess (e.g., the annular recess) of the die or die holder. The recess may be provided, for example, in the form of an annular groove extending into the die or die holder and may be adjacent to (e.g., open into) a passage in the die or die holder through which the metal cup is passed during drawing and / or ironing.

[0023] Generally, each sealing ring conforms to the surface on which it is placed and can be any shape (i.e., cross-section), such as round or oval (e.g., circular), square or rectangular, X-shaped or double X-shaped, polygonal with rounded corners, etc. In some implementations, one or more (e.g., all) of the sealing rings can be elastomeric.

[0024] In some implementations, the die may be nested within the die holder. In this context, "nested" refers to radial nesting, such that the outer periphery of the die is surrounded by the inner periphery of the die holder. The die holder and die define a passage through which a metal cup is passed during drawing and / or wall ironing. The die holder may be supported by first and second sealing elements, and the die is supported by the die holder. The die may be removable from the die holder to facilitate die replacement and / or maintenance, for example, after damage or wear to the inner periphery of the die. Another die (e.g., one having a different inner diameter and / or internal shape) may then be installed in the die holder. The die assembly may be provided (e.g., sold) as part of a kit, and in one case, there may be multiple such dies. Similarly, in other cases, the die assembly may be provided with the die holder installed but without the die.

[0025] In some implementations, the support mechanism is configured to accommodate lateral deflection of the die or die holder relative to its longitudinal axis during drawing or wall ironing. For example, the die or die holder can be attached to an elastomeric ring (e.g., an O-ring) to accommodate lateral deflection of the die or die holder relative to its longitudinal axis during drawing or wall ironing. In addition to misalignment that can be corrected by tilting the die, such movement can compensate for misalignment between the die and the ram (e.g., axial misalignment such that the longitudinal axis is offset relative to the ram).

[0026] In some implementations, the housing can include a sealable inlet (e.g., a threaded hole) for supplying fluid to the chamber. Of course, one or more (e.g., two, three, or more) sealable inlets can be used. In other implementations, the fluid can be sealed into the chamber during manufacture of the die assembly. Thus, the die assembly can be installed into (for example) a can body maker's tool pack without the need for an operator at the can body maker to fill the chamber with fluid.

[0027] Preferably, the die assembly (particularly the die) is for forming one or more of beverage cans (eg, two-piece cans), food cans, paint cans, aerosol cans, and the like.

[0028] Optionally, the die is an ironing die (i.e., a die suitable for wall ironing) or a redraw die (i.e., a die suitable for drawing / redrawing). The redraw die can be configured, for example, such that during drawing, a metal cup is clamped between a redraw sleeve and a front face of the die.

[0029] According to a second aspect of the present invention, there is provided a can body maker including one or more die assemblies according to the first aspect. For example, the can body maker may include a die assembly according to the first aspect in which the die is a redraw die (i.e., a die suitable for drawing / redrawing), and one or more other die assemblies according to the first aspect in which the die is an ironing die (i.e., a die suitable for wall ironing). In an embodiment, the ironing die may have a smaller inner diameter than the redraw die.

[0030] According to a third aspect of the present invention, there is provided a method for producing a container body from a metal cup using one or more die assemblies according to the first aspect. The method includes using a ram to force the metal cup through each die of one or more die assemblies. Tilting the die and / or die holder automatically corrects misalignment of the die and ram axes, i.e., correcting the die axis to be parallel to the ram as the ram passes through the die. The metal cup can thus be drawn and / or wall-ironed to a desired height and sidewall thickness. The method can include adjusting the pressure of a fluid in the chamber to control the amount by which the die can be tilted during drawing and / or wall-ironing of the metal cup. For example, the pressure can be adjusted depending on the diameter of the container being produced.

[0031] In some implementations, during (re)drawing of the metal cup, the load on the die along the direction of the ram can range, for example, from about 20 kN to about 25 kN. The ironing load can range from about 3 kN to about 10 kN (preferably, from 7 kN to 9 kN). The die assembly can be configured so that hydraulic and / or pneumatic fluids can provide an equal but opposite reaction force to counteract the load from the ram. Specifically, the fluid can be selected to provide a reaction force such that the die moves in the direction of the ram by less than a predetermined distance (e.g., less than 10 microns) under the load from the ram.

[0032] In some embodiments, the die assembly includes one or more pistons, each piston providing a respective one of the one or more surfaces that seal the chamber. The pistons can be positioned such that tilting the die or die holder causes at least one of the one or more pistons to move relative to the fluid sealed in the chamber. In some embodiments where the die assembly includes multiple pistons, the one or more pistons can be positioned such that movement of one or more pistons relative to the fluid sealed in the chamber causes the fluid to move one or more others of the pistons relative to the die or die holder. For example, tilting the die or die holder moves one or more pistons in a direction parallel to the ram, while redistribution of fluid within the chamber moves one or more other pistons in the opposite direction, assisting in tilting the die or die holder. In some examples, each piston can move within a respective channel that forms part of the chamber. Preferably, each channel and corresponding piston is positioned (substantially) parallel to the ram. The pistons may be positioned such that tilting of the die or die holder causes at least one of the pistons to move along a respective flow path toward the ram.

[0033] The pistons may, for example, be angularly spaced about the longitudinal axis of the die, and preferably there are three or more pistons so that the die can be tilted along two orthogonal axes.

[0034] In some embodiments, the die assembly can include one or more fluid channels within the housing, each channel sealed by a respective (adjustment) piston coupled to the die and having a respective adjustment mechanism for applying pressure to the fluid within the channel to move the piston and tilt the die or die holder relative to the housing, thereby reducing misalignment of the longitudinal axis of the die relative to the ram using the or each adjustment mechanism. In some embodiments, each of the fluid channels can be in fluid communication with a respective chamber (e.g., the chambers described above for the first aspect), such that movement of the piston increases or decreases the pressure of the fluid within the chamber to cause tilting of the die. Each of the chambers can be within the housing, and each of the chambers can be adapted to allow fluid to be sealed within the chamber by one or more respective surfaces coupled to or provided on the die or die holder, such that pressure from the fluid can move the one or more surfaces to tilt the die.

[0035] According to a fourth aspect of the present invention, there is provided a die assembly comprising a housing, a die for drawing and / or ironing a metal cup attached to the end of a ram to form a container body, and a support mechanism for the die configured to allow the die to tilt relative to the housing. One or more fluid channels can be provided in the housing and adapted to seal a fluid therein. Each fluid channel can include a respective piston coupled to the die and a respective adjustment mechanism for applying pressure to a fluid in the channel to move the piston and tilt the die relative to the housing. Thus, misalignment of the longitudinal axis of the die relative to the ram can be reduced using the or each adjustment mechanism.

[0036] The pistons can be, for example, angularly spaced about the longitudinal axis of the die (e.g., if there are three pistons, they can be spaced 120 degrees apart, but the spacing need not be uniform). Preferably, there are three or more pistons so that the die can be tilted along two orthogonal axes.

[0037] Each adjustment mechanism can include, for example, a threaded member (e.g., a bolt) engaged with a threaded opening to the flow passage, and threading (unthreading) the threaded member into the threaded opening decreases (increases) the volume of the flow passage, changing the force on the corresponding piston, thereby tilting the die. For example, the die can optionally be mounted in a die holder, and the piston acts on the die holder.

[0038] Optionally, each adjustment mechanism may be computer controlled (e.g., via a wired or wireless connection) to reduce misalignment of the longitudinal axis of the die relative to the ram during use of the die assembly.

[0039] In some implementations, the die assembly can include one or more sensors configurable or configured to provide a respective signal indicative of misalignment of the longitudinal axis of the die relative to the ram. Generally, many different types of sensors can be used. For example, one or more (e.g., each) of the flow channels can include a respective pressure sensor for measuring the pressure that a corresponding piston exerts on fluid in the flow channel during drawing and / or wall ironing. Alternatively or additionally, the sensors can include one or more force sensors (e.g., load cells), each oriented to measure the force on the die at a respective position about the longitudinal axis of the die; for example, the force sensors can be provided between the housing and a respective surface of the die.

[0040] The signal(s) can be provided to a computing device controlling each adjustment mechanism, which adjusts one or more (e.g., each) of the adjustment mechanisms based on the signal(s) to reduce misalignment. The computing device can implement a feedback control loop so that the position adjustments maintain the correct or desired position adjustment of the die despite changing operating conditions, such as temperature changes, die wear, etc. For example, a proportional-integral-derivative (PID) controller can be used to adjust each adjustment mechanism to minimize an error signal determined from the sensor signals. The error signal can be, for example, a measurement of the difference (or ratio) between the sensor signals.

[0041] Alternatively or additionally, the signal(s) provided by the sensor(s) may be visually displayed (e.g., on a graphical user interface) or otherwise communicated to a user, who may then use one or more adjustment mechanisms to reduce misalignment.

[0042] According to a fifth aspect of the present invention, there is provided a method of aligning a machine for producing container bodies from metal cups (e.g., a can body maker), the machine comprising one or more die assemblies according to the fourth aspect, the method comprising using one or more adjustment mechanisms to apply pressure to fluid in chambers to move corresponding piston(s) and tilt the die relative to the housing.

[0043] In each of the above aspects, the die assembly can include one or more additional dies coupled to the die such that tilting of the die similarly causes tilting of the additional die(s). For example, the die and the additional dies may be fixed to one another such that they move / tilt as a single unit. The additional dies are preferably positioned closer to the entrance of the tool pack than the die. [Brief explanation of the drawings]

[0044] [Figure 1]FIG. 1 is a schematic vertical cross-sectional view of a ram, redraw sleeve, and tool pack of a prior art can body maker. [Figure 2] 1 is a schematic vertical cross-sectional view of a ram, redraw sleeve, and redraw die assembly according to one embodiment of the present invention; [Figure 3] 3 is a schematic vertical cross-sectional view of the redraw die assembly shown in FIG. 2. [Figure 4] 1 is a schematic side cross-sectional view of an ironing die assembly according to one embodiment of the present invention; FIG. [Figure 5] 1 is a schematic side cross-sectional view of a can body maker tool pack according to one embodiment of the present invention; FIG. [Figure 6] 1 is a schematic side cross-sectional view of a die assembly according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0045] 1 shows elements of a can bodymaker 100, including a tool pack 102, a ram 106, and a redraw sleeve 108. The tool pack 102 includes a redraw die 110 and a plurality of ironing dies 112A-C arranged in sequence along axis Z with spacer rings 114A-C interposed between the dies. Each of the dies and spacer rings has a respective bore or passageway positioned about axis Z to provide a passageway extending through the tool pack 102 and through which the ram 106 can reciprocate.

[0046] In operation, the ram 106 forces a metal cup (not shown) through the dies 110, 112A-C, drawing and ironing the metal cup to form a can body. Before entering the die, the metal cup is attached to a redraw sleeve 108, which receives the metal cup and extends its sidewalls around the redraw sleeve 108, so that a front face 116 of the redraw sleeve 108 and the ram 106 contact the bottom of the metal cup (the front face of the ram 106 is sometimes referred to as a punch). The ram 106 and the redraw sleeve 108 press the bottom of the metal cup against a front face 118 of the redraw die 110 (i.e., the face of the redraw die 110 facing the ram 106), so that the bottom of the metal cup is sandwiched between the redraw sleeve 108 and the front face 118 of the redraw die 110. While the forward movement of the redraw sleeve 108 is impeded by the tool pack 102, the ram 106 continues to force the bottom of the metal cup through the redraw sleeve 108 and into the redraw die 110, thereby "drawing" the metal cup between the faces 116, 118 of the redraw sleeve 108 and the redraw die 110, reducing the diameter of the metal cup and stretching its sidewalls. The ram 106 continues to force the metal cup through the passage defined by the ironing dies 112A-C and other tool pack components. The subsequent ironing dies 112B, C have successively smaller inner diameters so that the sidewalls of the metal cup are further stretched and thinned as the metal cup passes through the tool pack 102.

[0047] FIG. 2 shows a die assembly 200 including a redraw die 202 and a housing 204. The redraw die 202 is generally annular and has an inner diameter selected to allow a ram 206 to pass through the redraw die 202. Only a small radial clearance is provided between the ram 206 and the redraw die 202 to (partially) accommodate the thickness of the sidewall of a metal cup 208 during drawing. The redraw die 202 has a front surface 210 against which the bottom of the metal cup 208 is clamped by a redraw sleeve 212 at the start of the drawing process. The redraw die 202 has a flange portion 207 that is spaced from the front surface 210 and has a larger outer diameter than the front surface 210 of the redraw die 202. The flange portion 207 of the redraw die 202 is received by a corresponding groove formed in a front surface 214 of the housing 204. A flange portion 207 of the redraw die 202 is spaced apart from (interiorly within) the housing 204 to define a chamber 216 between the housing 204 and the redraw die 202 .

[0048] In use, the chamber 216 is filled with a hydraulic fluid such as mineral oil, although other fluids such as compressed air (or other pneumatic gases) can be used instead of or in addition to the hydraulic fluid. Preferably, however, the chamber 216 is completely filled with hydraulic fluid to ensure uniformity and reduce compressibility.

[0049] The housing 204 is positioned radially inward of the flange portion 207 of the redraw die 202 and has a cylindrical inner sidewall 218A that abuts against or is spaced apart from a lip 220 formed on the inner surface of the redraw die 202. An O-ring 222A is provided between the inner sidewall 218 of the housing 204 and the flange portion 207 of the redraw die 204, the O-ring surrounding the inner sidewall 218 of the housing 204. In this example, the O-ring 222A is seated in a circumferential groove in the flange portion 207 of the redraw die 204. However, alternatively or additionally, the O-ring 222A can be seated in a groove formed in the inner sidewall 218 of the housing 204. A second O-ring 222B is provided between the cylindrical outer sidewall 218B that is positioned radially outward of the flange portion 207 of the redraw die 202. In this example, O-ring 222B is seated in a circumferential groove formed around flange portion 207 of redraw die 202, although additionally or alternatively, like first O-ring 222A, second O-ring 222B can be located in a groove formed in outer sidewall 218B of housing 204. Preferably, both O-rings 222A, B are seated in grooves in redraw die 202 to allow redraw die 202 to be easily removed from and replaced with housing 204, for example, to facilitate replacement of redraw die 202 after it becomes worn or damaged.

[0050] Two O-rings 222A, B seal the chamber 216 to prevent hydraulic fluid from leaking from the chamber 216 as a result of substantial forces on the die assembly 200 generated by the metal cup 208, ram 206 and redraw sleeve 212 during the drawing process.

[0051] In this example, the O-rings 222A, B are made from an elastomeric material, such as nitrile butadiene rubber (NBR), allowing the redraw die 202 to deflect a small amount within the housing 204 without hydraulic fluid leaking from the chamber 216. Specifically, the O-rings 222A, B can be deformed by the redraw die 202 to allow the redraw die 202 to tilt when the metal cup 208 and the redraw sleeve 212 contact the front surface 210 of the redraw die 202. Thus, the die assembly 200 can dynamically reorient the redraw die 204 after contact with the metal cup 208 so that the front surface 210 of the redraw die 202 is aligned parallel to the front surface of the redraw sleeve 212 during the drawing process. Such positioning allows for even clamping pressure to be applied to the metal cup 208 during the drawing process, which can reduce or avoid defects (e.g., wrinkles or "witness lines") that form on the sidewalls of the metal cup 208 as it is drawn through the redraw die 202 by the ram 206.

[0052] The housing 204 may include an inlet 224 extending through the outer sidewall 218B for introducing hydraulic fluid into the chamber 216. In this example, the inlet 224 is threaded so that the inlet 224 can be sealed, for example, with a bolt 226 threaded into the inlet 224. Thus, the die assembly 200 may, at least in some instances, be used without the need to attach it to any external pressure source.

[0053] FIG. 3 shows an enlarged view of the die assembly 200 separated from the other parts of the can body maker.

[0054] 4 shows a die assembly 300 similar to the die assembly 200 of FIGS. 2 and 3, but includes a die holder 301 to which an ironing die 302 (rather than a redraw die 202) is attached. Additionally, a housing 304 of the die assembly 300 surrounds the die holder 301 and ironing die 302 along their length (i.e., parallel to the longitudinal axis Z of the ironing die 302), such that the die holder 301 and ironing die 302 remain tiltable (i.e., can be reoriented relative to the housing 304 and ram) when the die assembly 300 is attached to a can body maker's tool pack. In some implementations, the ironing die 307 may be removable from the die assembly 300.

[0055] In this example, the ironing die 302 includes an ironing ring 307 through which the metal cup is forced by a ram to "irone" (ie, stretch and thin) the sidewall of the metal cup 208.

[0056] The die holder 301 is housed in a housing 304 in a manner similar to the redraw die 202 and housing 204 shown in Figures 2 and 3. Accordingly, 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 disposed between the corresponding annular surfaces of the support ring 308 and the housing 304. The O-rings allow the support ring 308 to change orientation during the ironing process, as described above with respect to the redraw die 202.

[0057] The die 302 is radially nested within the die holder 301 within an O-ring 312. In some examples, the O-ring 312 can allow the die 302 to deflect a small amount within the die holder 301, such as to translate radially within the die holder 301, so that the die 302 is concentrically aligned with the ram 206. Thus, the die assembly 300 can allow for both concentric and coaxial positioning of the die 302 and the ram 206.

[0058] 5 shows a tool pack of a can body maker 500 including a redraw die assembly 502, which may be the redraw die assembly 200 described above in connection with FIGS. 2 and 3, and a plurality of ironing die assemblies 504A-C, each of which may be the ironing die assembly 300 described above in connection with FIG. 4. For each ironing die assembly 504A-C, the die and die holder are spaced a distance (i.e., gap) 508 from a tool pack component 506 located in front of the ironing die assembly 504A-C in the tool pack, providing clearance for tilting of the die and die holder. Similarly, a gap 510 is provided between the inner surface of the die (i.e., the rear surface facing away from the direction in which the ram enters the tool pack) and the inner cylindrical sidewall 318A of the die assembly housing, providing clearance for tilting of the die. In some embodiments, the distance or gap 508, 510 is 0.1 mm to 0.4 mm (e.g., 0.005" to 0.015"), in this case measured along axis Z, although any distance or gap that provides sufficient freedom for the die and die holder to tilt to align with the ram can be used. This distance can be determined, for example, by determining the maximum angle that the die needs to tilt as a result of one or more manufacturing tolerances of the die, die holder, die housing, tool pack, etc., and / or variations in the alignment of the ram.

[0059] 6 shows a die assembly 600 including a die 602 having an ironing ring 604 supported by a seal ring 606 extending around the periphery of the die 602 and partially extending into a groove formed in the inner surface of a mounting ring 608. The seal ring 606 is elastomeric to allow the die 602 to tilt within the mounting ring 608 during drawing and / or wall ironing operations. The die assembly 600 further includes a housing 610 having a chamber 612 extending about a longitudinal axis Z of the die (e.g., the chamber 612 may be substantially cylindrical). 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 stopper 616 (e.g., a bolt). The chamber 612 includes a plurality of channels 617 extending toward the die 602, each sealed with a respective piston 618 configured to slide within the channel 617 in a direction parallel to the longitudinal axis Z of the die 602, with fluid prevented from leaking from the channel 617 by a sealing ring 620 between the piston 618 and the sidewall of the channel. Each of the channels 617 is in fluid communication with the other channels through the chamber 612.

[0060] Although only one such channel 617 and piston 618 is visible in the cross section of Figure 6, chamber 612 includes two additional channels and pistons angularly spaced from channel and piston 618 about longitudinal axis Z. When die 602 is tilted during drawing and / or wall ironing of a metal cup, die 602 contacts piston 618, moving the piston along channel 617 and exerting pressure on the fluid in chamber 612. This pressure is transmitted by the fluid in chamber 612 to the other pistons 618, moving them outward (i.e., in a direction opposite to the Z direction). Thus, the longitudinal position of piston 618 in each channel 617 is adjusted in response to the tilt of die 602.

[0061] In an alternative embodiment of the die assembly 600, the pistons 618 and the channels 617 are not in fluid communication with each other, i.e., each channel 617 is isolated from the other channels 617, and each channel 617 has a separate inlet 614 for supplying fluid thereto. Each channel 617 has an adjustment mechanism that can transmit a force to each of the pistons 618 via the fluid. For example, each inlet 614 can have a stopper 616 (e.g., a threaded member such as a bolt) that can be displaced (e.g., threaded) into the inlet 614 to exert a force on the fluid within the inlet 614. The resulting longitudinal movement of the piston 618 in response to the force causes tilt of the die 602. Thus, one or more (e.g., each) of the adjustment mechanisms (e.g., stoppers 616) can be used to adjust the tilt of the die 602 to improve alignment with the can body maker ram. For example, the adjustment mechanism can be iteratively adjusted to improve alignment. In contrast to the other implementations described above, once the tilt of the die 602 is properly adjusted, the die 602 can remain substantially in that orientation as the can body maker operates, i.e., the positioning is static rather than dynamic and can be subject to minimal variation as the ram passes through the die 602.

[0062] In some examples, each stopper 616 is coupled to an actuator, e.g., a linear actuator or, if a threaded stopper is used, a rotary actuator, that controls the displacement of the stopper within the inlet 616. Each actuator can be computer-controlled (e.g., via a wired or wireless connection) to adjust the displacement of a corresponding piston within the flow passage 617. The die assembly 600 can include one or more sensors (not shown) that can be configured or are configured to provide a respective signal indicative of misalignment of the longitudinal axis of the die relative to the ram. Generally, many different types of sensors can be used. For example, the actuator can include a force sensor configured to measure the force transmitted by the piston 618 and fluid from the die 602 to the actuator during drawing and / or wall ironing of the metal cup.

[0063] The signal(s) can be provided to a computing device that controls the actuators, which then adjusts one or more (e.g., each) of the actuators based on the signal(s) to reduce misalignment. The computing device can implement a feedback control loop so that the alignment maintains the correct or desired alignment of the die despite changing operating conditions, such as temperature changes, die wear, etc. For example, a proportional-integral-derivative (PID) controller can be used to adjust each actuator to minimize an error signal determined from the sensor signals. The error signal can be, for example, a measurement of the difference (or ratio) between the sensor signals.

[0064] The die assemblies 200, 300, 600 can be used to form many different types and sizes of container bodies, such as beverage cans (two-piece, sleek, 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 bodies are produced can be made, for example, from steel, aluminum, or an alloy containing any of these, and can be pre-coated (e.g., laminated) with an organic coating such as polyester. The redraw die assembly 200, ironing die assembly 300, and die assembly 600 described herein can be configured to fit into existing can body makers' tool packs, and can be retrofitted as replacements for existing die assemblies without (or with minimal) modification to the tool pack.

[0065] Although the sealing elements in the above-described embodiments are sealing rings (O-rings), other types of sealing elements may alternatively or additionally be used, such as diaphragms or bellows arrangements. Alternatively or additionally, the fluid may be sealed within a flexible housing (e.g., a bag or sack) contained within the chamber. In such cases, different sections of the housing (e.g., opposite ends) may be considered sealing elements.

[0066] Those skilled in the art will appreciate that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. Although particular embodiments of the subject matter have been described in detail, other embodiments are within the scope of the following claims. [Explanation of symbols]

[0067] 200 Die Assembly 202 Redraw 204 Housing 206 Ram 207 Flange 208 Metal Cup 210 Front 212 Redraw Sleeve 214 Front 216 Chamber 218A Inner sidewall 218B Outer side wall 220 Lip 222A O-ring 222B O-ring 224 Entrance 226 volts

Claims

1. Housing and a die for drawing and / or ironing a metal cup attached to the end of the ram to form a container body; a support mechanism for the die or for a die holder to which the die is attached, 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 ram during drawing and / or ironing of a metal cup; a chamber disposed within the housing and adapted to seal a fluid therein; 1. A die assembly comprising: The chamber is sealed by one or more surfaces coupled to or provided on the die or die holder, such that tilting of the die during drawing and / or wall ironing of a metal cup causes the one or more surfaces to move relative to a fluid sealed within the chamber.

2. 2. The die assembly of claim 1, wherein the chamber extends between the housing and the die or die holder, and the support mechanism comprises first and second seal elements forming respective seals between the housing and the die or die holder.

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

4. 3. The die assembly of claim 2, wherein the chamber extends between a first surface of the die or die holder extending about the longitudinal axis and a corresponding first surface of the housing extending about the longitudinal axis.

5. 5. The die assembly of claim 4, wherein the chamber extends between a second surface of the die or die holder extending about the longitudinal axis and a corresponding second surface of the housing extending about the longitudinal axis.

6. The die assembly of claim 5 , wherein the first and second surfaces of the die or die holder are located between the corresponding first and second surfaces of the housing.

7. 7. The die assembly of claim 4, wherein the first sealing element comprises a sealing ring disposed between the first surface of the die or die holder and the first surface of the housing.

8. The die assembly of claim 7 , wherein the first surface of the die or die holder is tapered along a direction parallel to the longitudinal axis.

9. The die assembly of claim 5 , wherein the second sealing element comprises a sealing ring disposed between the second surface of the die or die holder and the second surface of the housing.

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

11. 11. The die assembly of claim 1, wherein the support mechanism is configured to allow the die or die holder to be biased laterally relative to the longitudinal axis during drawing or wall ironing of a metal cup.

12. 12. A die assembly according to any preceding claim, wherein the housing comprises one or more sealable inlets for supplying fluid to the chamber.

13. 13. The die assembly of claim 1, wherein the die assembly comprises one or more pistons, each of the pistons providing a respective one of the one or more surfaces that seal the chamber, the one or more pistons being arranged such that tilting the die causes at least one of the one or more pistons to move relative to the fluid sealed in the chamber.

14. 14. The die assembly of claim 13, wherein the die assembly comprises a plurality of pistons, one or more of the pistons arranged such that movement of the one or more pistons relative to a fluid enclosed in the chamber causes the fluid to move one or more others of the pistons relative to the die or die holder.

15. 15. The die assembly of claim 1, further comprising one or more flow channels within the housing adapted to seal a fluid therein, each of the flow channels being sealed by a respective adjustment piston coupled to the die and having a respective adjustment mechanism for applying pressure to fluid within the flow channel to move the adjustment piston and tilt the die or 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.

16. A can body maker comprising one or more die assemblies according to any one of claims 1 to 15.

17. 16. A method for producing a container body from a metal cup using one or more die assemblies according to any one of claims 1 to 15, comprising using a ram to force the metal cup through each die of the one or more die assemblies.

18. Housing and a die for drawing and / or ironing a metal cup attached to the end of the ram to form a container body; a support mechanism for the die or for a die holder to which the die is attached, the support mechanism being configured to allow the die to tilt relative to the housing; one or more fluid channels disposed within the housing and adapted to seal a fluid therein; 1. A die assembly comprising: a die assembly, wherein each of the flow paths is sealed by a respective piston coupled to the die and has a respective adjustment mechanism for applying pressure to fluid in the flow paths to move the piston and tilt the die or 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. 20. The die assembly of claim 18, wherein each of the adjustment mechanisms is computer controlled to reduce misalignment of the longitudinal axis of the die relative to the ram during use of the die assembly.

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

21. 21. A method of adjusting the position of a machine for manufacturing a container body from a metal cup, the machine including one or more die assemblies according to any one of claims 18 to 20, the method including using one or more of the adjustment mechanisms to apply pressure to fluid in the chamber to move corresponding piston(s) and tilt the die or die holder relative to the housing.

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