Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/26—Making hollow objects characterised by the use of the objects cans or tins; Closing same in a permanent manner
  • B21D51/2646—Of particular non cylindrical shape, e.g. conical, rectangular, polygonal, bulged
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/26—Making hollow objects characterised by the use of the objects cans or tins; Closing same in a permanent manner

Definitions

• This invention relates generally to the field of consumer packaging, and more specifically to metal cans, such as the steel and aluminum cans that are commonly used for packaging soft drinks, other beverages, food and aerosol products.
• Metal cans for soft drinks, other beverages and other materials are of course in wide use in North America and throughout the world.
• the assignee of this invention, Crown Cork & Seal Company of Philadelphia, is the world's largest designer and manufacturer of such cans.
• U.S. Patent 3,224,239 to Hansson discloses a system and process for using pneumatic pressure to reshape cans. This process utilized a piston to force compressed air into a can that is positioned within a mold. The compressed air caused the can wall to flow plastically until it assumed the shape of the mold.
• a method of manufacturing a metallic can body that is shaped distinctively in order to enhance its visual presentation to consumers includes, according to a first aspect ofthe invention, steps of: (a) providing a can body blank; (b) providing a mold unit that has at least one mold wall that defines a mold cavity conforming to a desired final shape ofthe can body the mold unit being constructed of more than one part, at least one ofthe parts being movable toward another in a direction that is substantially parallel to an axis ofthe can body blank during operation, the mold wall including inwardly extending portions and outwardly extending portions; (c) positioning the can body blank within the mold cavity so as to precompress the can body blank with the inwardly extending portions ofthe mold wall; (d) supplying a pressurized fluid into the mold cavity so that the can body blank is forced by pressure against the mold wall, causing the can body blank to assume the desired final shape ofthe can body, the precompression that is performed in step (c) minimizing
• a method of manufacturing a metallic can body that is shaped distinctively in order to enhance its visual presentation to consumers includes steps of: (a) making a can body blank; (b) at least partially annealing at least a portion ofthe can body blank, thereby giving the annealed portion ofthe can body blank increased ductility; (c) providing a mold unit that has at least one mold wall that defines a mold cavity conforming to a desired final shape ofthe can body, the mold unit being constructed of more than one part, at least one ofthe parts being movable toward another in a direction that is substantially parallel to an axis ofthe can body blank during operation; (d) positioning the can body blank within the mold cavity; (e) supplying a pressurized fluid into the mold cavity so that the can body blank is forced by pressure against the mold wall, causing the can body blank to assume the desired final shape ofthe can body; and (f) substantially simultaneously with step (e), moving at least one ofthe mold parts toward another in the axial direction.
• an apparatus for manufacturing a metallic can body that is shaped distinctively in order to enhance its visual presentation to consumers includes structure for making a can body blank; molding structure comprising a mold unit that has at least one mold wall that defines a mold cavity conforming a desired final shape ofthe can body, said mold wall comprising inwardly extending portionsand outwardly extending portions, the mold unit being constructed of more than one part, at least one ofthe parts being movable toward another in a direction that is substantially parallel to an axis ofthe can body blank during operation; positioning structure for positioning the can body blank within the mold cavity so as to precompress the can body blank by the inwardly extending portions ofthe mold wall; fluid supply structure for supplying a pressurized fluid into the mold cavity so that the can body blank is forced by pressure against the mold wall, causing the can body blank to assume the desired final shape ofthe can body, the precompression minimizing the amount of outward deformation that is required to achieve the final shape ofthe can body; and axial reduction structure for
• an apparatus for manufacturing a metallic can body that is shaped distinctively in order to enhance its visual presentation to consumers includes structure for making a can body blank; structure for at least partially annealing at least a portion ofthe can body blank, thereby giving the annealed portion ofthe can body blank increased ductility; mold structure comprising a mold unit that has at least one mold wall that defines a mold cavity conforming to a desired final shape ofthe can body, the mold unit being constructed of more than one part, at least one ofthe parts being movable toward another in a direction that is substantially parallel to an axis ofthe can body blank during operation; positioning structure for positioning the can body blank within the mold cavity; fluid supply structure for supplying a pressurized fluid into the mold cavity so that the can body blank is forced by pressure against the mold wall, causing the can body blank to assume the desired final shape ofthe can body; and axial reduction structure for moving at least one ofthe mold parts toward another in the axial direction.
• FIGURE 1 is a cross-sectional view taken through a can body blank or pre- form that is constructed according to a preferred embodiment ofthe invention
• FIGURE 2 is a side elevational view of a shaped can body according to a preferred embodiment ofthe invention.
• FIGURE 3 is a diagrammatical view of An apparatus for making a shaped can body according to a preferred embodiment ofthe invention
• FIGURE 4 is a fragmentary cross-sectional view through a mold unit in the apparatus depicted in FIG. 3, shown in a first condition
• FIGURE 5 is a fragmentary cross-sectional view through a mold unit in the apparatus depicted in FIG. 3, shown in a second condition;
• FIGURE 6 is a schematic diagram depicting a pressure supply apparatus for the mold unit depicted in FIG. 3;
• FIGURE 7 is diagrammatical depiction of a precompression step that is performed in the apparatus as depicted in FIG. 3;
• FIGURE 8 is a diagrammatical depiction of a beading step in a method that is performed according to a second embodiment ofthe invention.
• FIGURE 9 is a diagrammatical depiction of a spinning step in a method that is performed according to a second embodiment ofthe invention.
• FIGURE 10 is a diagrammatical depiction of a knurling step that can be performed as a second step in either the second or third embodiments ofthe invention referred to above.
• a can body blank or preform 10 is the body of a two-piece can, which is preferably formed by the well-known drawing and ironing process.
• Can body blank 10 includes a substantially cylindrical sidewall surface 12, a bottom 14, and necked upper portion 16. Altematively, the upper portion of cylindrical sidewall 12 could be straight.
• the can body blank 10 must be washed after the drawing and ironing process, and then must be dried prior to being sent to the decorator.
• the drying process typically is performed at a temperature of about 250 degrees Fahrenheit (which is about 121 degrees Celsius). According to one aspect of this invention, the drying is performed at a higher temperature than is ordinary to partially anneal at least selected portions ofthe can body blank 10.
• a heat source 18 is schematically depicted, which is preferably part ofthe dryer assembly, but could be at any point in the apparatus prior to the molding unit.
• can body blank 10 is preferably formed of aluminum and the partial annealing is preferably accomplished at a temperature that is substantially within the range of about 375 degrees Fahrenheit (about 190.5 degrees Celsius) to about 550 degrees Fahrenheit (about 288 degrees Celsius), with a more preferred range of about 450 degrees Fahrenheit (about 232 degrees Celsius) to about 500 degrees Fahrenheit (about 260 degrees Celsius), and a most preferred temperature of about 475 degrees Fahrenheit (about 246 degrees Celsius). This is in contrast to true annealing, which would be at temperatures over 650 degrees Fahrenheit (about 353 degrees Celsius).
• the purpose ofthe partial annealing is to give the can body blank 10 enough ductility to be formed into a shaped can 20, such as is shown in Figure 2 ofthe drawings, but greater toughness than would be possible if the can body blank were fully annealed.
• the partial annealing could be performed in an oven such as the lacquer or decorator oven, rather than in the dryer.
• can body blank 10 could be fabricated from steel instead of aluminum.
• the preferred temperature range for partial annealing would be substantially within the range of 1 112 degrees Fahrenheit (600 degrees Celsius) to about 1472 degrees Fahrenheit (800 degrees Celsius). More preferably, the partial annealing would be performed at approximately 1382 degrees Fahrenheit (750 degrees Celsius).
• shaped can 20 is decorated and shaped distinctively in order to enhance its visual presentation to consumers.
• can body 20 includes a bottom 26, a shaped sidewall 22 that is shaped to substantially deviate from the standard cylindrical can body shape, such as the shape of can body blank 10.
• the shaped sidewall 22 includes areas, such as ribs 30 and grooves 32, where accentuation of such deviations from the cylindrical shape might be desired.
• decoration is provided on the extemal surface ofthe shaped sidewall 22 in a manner that will accentuate those areas ofthe sidewall where accentuation ofthe deviation from the cylindrical shape is desired.
• a first type of decoration which may be a lighter color
• a second type of decoration 36 which may be a darker color
• shaped sidewall 22 also has a flat area 28, where writing or a label might be applied, and is closed by a can end 24, which is applied in the traditional double seaming process.
• can body blank 10 will be transported to a decorator, where the distinctive decoration will be applied while the can body blank 10 is still in its cylindrical configuration. Markers might also be applied during the decorating process that can be used for registration ofthe decoration to the mold contours during subsequent forming steps, which will be described in greater detail below.
• apparatus 38 includes a mold 40 having a mold wall 46 that defines a mold cavity 42 conforming to the desired final shape ofthe shaped can body 20.
• the mold 40 is ofthe split wall type and the mold wall 46 will include inwardly extending portions 48 that are less in diameter than the diameter D b ofthe cylindrical sidewall 12 of the can body blank 10 depicted by the dotted lines in Figure 7b.
• the mold wall 46 will also include a number of outwardly extending portions that are greater in diameter than the diameter D b ofthe sidewall 12 of the can body blank 10.
• the inwardly extending portions 48 tend to compress the cylindrical sidewall 12 ofthe can body blank
• the perimeter ofthe cylindrical sidewall remains a constant length when compressed in this manner so the perimeter ofthe cylindrical compressed sidewall 12' is the same length as the circumference ofthe sidewall 12 of the can body blank 10.
• the mold unit 40 has three die parts 82, 46 and 84 which comprise neck ring, mold side wall and base support, respectively.
• the die parts are separated from each other by gaps or "split lines" 86 and 88.
• the base support die 84 is made in two parts, with a central part 90 supporting the base dome ofthe can body.
• the neck ring 82 provides simple support to the necked portion of the can body.
• Vent holes 49 are provided (see Figures 4 and 5) to allow trapped air to escape during forming.
• a pair of seal and support rings 92, 94 and a rubber sealing ring 96 are provided to seal the top edge ofthe container body.
• a space saving mandrel 98 passes through the center ofthe seal and support rings 92, 94, 96 to a position just above the base support dome 84.
• the mandrel 98 supplies air to the cavity of a can body within the cavity 42 via a central bore 100 and radial passages 102.
• the apparatus further includes an upper piston and a lower piston 104, 106 which together apply a load to both ends ofthe can in the mould cavity 42.
• Lower piston 106 is moveable upwards by structure of a pressurized air supply which is fed to the piston via passage 108.
• the upper piston is moveable downwards by structure of a pressurized air supply which is fed to the piston via passages 110 and 112.
• the passage 110 is connected to the central bore 100 ofthe mandrel 98 so that the upper piston and can cavity share a common air supply.
• the common air supply is split for the piston 104 and cavity at the junction ofthe air passage 112 and the central mandrel bore 100, within the piston 104 so as to minimize losses and to maintain the same pressure supplied to the cavity and piston.
• means are provided to control the flow rate of air supplied to each piston and the cavity. Cavity pressure and piston pressure can therefore be closely controlled.
• a schematic circuit diagram which shows how air is supplied to the pistons and can cavity is shown in figure 6.
• the upper piston 104 and seal and support rings 92,94 are shown schematically as a single unit 114.
• the base support 84,90 and lower piston 106 are shown as a single unit 116.
• Units 114 and 116 and neck ring 82 are movable, whereas the side wall die 46 ofthe mold is shown fixed.
• the circuit comprises two pressure supplies.
• Pressure supply 1 18 supplies pressurised air to the top piston 104 and cavity ofthe can within the mold cavity 42.
• Pressure supply 120 supplies pressurised air to the lower piston 106 only.
• the two supplies each comprise pressure regulators 122,124, reservoirs 126,128, blow valves 130,132 and exhaust valves 134,136.
• the lower pressure supply 120 includes a flow regulator 138.
• the upper pressure supply 118 may also include a flow regulator, although it is not considered essential to be able to adjust the flow in both supplies. Reservoirs 126, 128 prevent a high drop in supply pressure during the process.
• high pressure air of around 30 bar is introduced to the can cavity and to drive the top ofthe can.
• the air pressure to drive the bottom piston 106 is typically around 50 bar, depending on the piston area.
• the air pressure within the mold cavity 42 provides the force which is required to expand the can body blank outwards but also applies an unwanted force to the neck and base ofthe can which leads to longitudinal tension in the can side wall.
• the two pistons are thus used to drive the top and the bottom ofthe can, providing a force which counteracts this tension in the can side wall.
• the pressure ofthe air supplied to the pistons is critical in avoiding failure ofthe can during forming due to either splitting or wrinkling.
• the balance between the can cavity pressure and the piston pressure is preferably maintained at all times throughout the forming cycle so that the rate of pressure rise in the cavity and behind the pistons should be balanced throughout the cycle, particularly when the can wall yields.
• the rate of pressure rise can be controlled by the flow regulator 138 or by adjusting the supply pressure via the pressure regulators 122,124.
• the apparatus may be operated in one of three different ways.
• the apparatus may be operated so as to simply move the mold parts toward another without exerting any force on the can body. This will reduce the gaps 86, 88 in the mold unit 40 as the can body shrinks longitudinally during the expansion process, and will reduce but not necessarily neutralize axial tensile stress created in the sidewall of the can body during expansion.
• a slight longitudinal or axial force is applied to the can body which is substantially equal to the axial tensile stress in the can body sidewall, thus balancing such stress and protecting the can body from consequential weakening and possible splitting.
• a third mode of operation would be to provide an even greater pressure to drive the outer mold parts toward one another in order to apply an axially compressive force to the can body that would be greater than what would be necessary to cancel the tensile stress in the sidewall during operation.
• a net compressive force is believed to be preferable provided that such a force does not lead to the formation of wrinkles.
• the blow valves 130,132 are first opened. It is possible to have a short delay between the opening times ofthe blow valves if required to obtain a better match between the piston and cavity pressures but there will then need to be a higher rate of pressure rise for one circuit in order to maintain this balance. A delay can also be used to compensate for different pipe lengths, maintaining a pressure balance at the time of forming.
• the upper supply 118 is split for the piston 104 and cavity as close as possible to the piston 104 as described above in reference to Figure 3.
• the apparatus is designed so that, at the latest, when each piston reaches its maximum travel the can is fully reshaped and the gaps 86, 88 are not closed up at the end. Closing ofthe gaps can lead to splitting ofthe can due to excessive tension in the side wall in the same way as does limiting movement ofthe pistons before full expansion has occurred. However, the final gap should not be excessive since any witness mark on the side wall becomes too apparent, although removal of sha ⁇ edges at the split lines alleviates this problem.
• the can body blank 10 is preferably positioned within the mold cavity 42 and its interior space is sealed into communication with a source of pressurized fluid, as described above.
• the cavity 42 is designed so as to impart a slight compression to the can body blank 10 as it is inserted therein.
• the precompression that is effected by the closing ofthe mold halves 52, 54 is performed to deflect the sidewall 12 ofthe can body blank 10 radially inwardly by a distance of R, n that is within the range of about 0.1 to about 1.5 millimeters. More preferably, this distance R, n is within the range of 0.5 to about 0.75 millimeters.
• the distance R ⁇ , by which cylindrical sidewall 12 is radially expanded outwardly to form the outermost portions ofthe shaped sidewall 22 is preferably within the range of about 0.1 to about 5.0 millimeters. A most preferable range for distance R,,,,, is about 0.5 to 3.0 millimeters. Most preferably, R ⁇ , is about 2 millimeters.
• a certain amount of annealing or partial annealing may be usenil, particularly in the case of aluminum can bodies, to obtain the necessary ductility for the expansion step.
• the more complete the annealing the less strong and tough the shaped can 20 will ultimately be.
• the amount of actual radial expansion necessary to achieve the desired pattem is reduced. Accordingly, the amount of annealing that needs to be applied to the can body blank 10 is also reduced.
• the precompression step then, allows the desired pattem to be superimposed on the shaped can 20 with a minimum of annealing and resultant strength loss, thus permitting the cylindrical sidewall 12 ofthe can body blank 10 to be formed as thinly as possible for this type of process.
• the mold wall may be formed of a porous material so as to allow air trapped between the sidewall of the can body blank and the mold wall to escape during operation, although vent holes will probably still be required.
• porous steel which is commercially available from AGA in Leydig, Sweden.
• pressure monitor 69 For pu ⁇ oses of quality monitoring and control, fluid pressure within the mold cavity 46 is monitored during and after the expansion process by structure of a pressure monitor 69, shown schematically in Figure 5.
• Pressure monitor 69 is of conventional construction. If the can body develops a leak during the expansion process, or if irregularities in the upper flange or neck ofthe can creates a bad seal with the gas probe, pressure within the mold cavity will drop much faster in the mold chamber 46 than would otherwise be the case. Pressure monitor 69 will sense this, and will indicate to an operator that the can body might be flawed.
• pressure within the mold chamber could be made high enough to form the can body into, for example, a beading-type pattem wherein a number of circumferential ribs are formed on the container.
• a second method and apparatus for manufacturing a metallic can body that is shaped distinctively in order to enhance its visual presentation to consumers is disclosed in Figures 7 and 9 ofthe drawings.
• a third embodiment is depicted in Figures 8 and 9 of the drawings.
• a distinctively shaped metallic can body is manufactured by providing a can body blank, such as the can body blank 10 shown in Figure 1, that has a sidewall 12 of substantially constant diameter, then radially deforming the can body blank 10 in selective areas by selected amounts to achieve an inte ⁇ nediate can body 74 that is radially modified, but is still symmetrical about its access, and then superimposing a preselected pattem of mechanical deformations onto d e intermediate can body 74.
• a beading apparatus 62 ofthe type that is well known in this area of technology includes an anvil 66 and a beading tool 64.
• a beading apparatus 62 is used to radially deform the can body blank 10 into the radially modified intermediate can body 74 shown in Figure 9.
• the intermediate can body 74 as may be seen in Figure 9, has no deformations thereon that have an axial component, and is substantially cylindrical about the access ofthe can body 74.
• a knurling tool 76 is then used to superimpose the preselected pattem of mechanical deformations, in this case ribs and grooves, onto the intermediate can body, making it possible to produce a shaped can 20 ofthe type that is shown in Figure 2.
• a spinning unit 68 is used to deform the cylindrical sidewall 12 ofthe can body blank 10 radially into the intermediate can body 74.
• Spinning unit 68 includes, as is well known in the technology, a mandrel 70 and a shaping roller 72 that is opposed to the mandrel 70.
• the knurling step shown in Figure 9 is preferably performed on the so formed intermediate can body 74 in a manner that is identical to that described above.
• the can body blank 10 is also preferably partially annealed by the heat source 18 during the drying process, but, preferably, to a lesser extent than that in the first described embodiment.
• the annealing for the second and third methods described above is performed at a temperature that is within the range of about 375 degrees Fahrenheit (about 190 degrees Celsius) to about 425 degrees Fahrenheit (about 218 degrees Celsius).
• the methods described with reference to Figures 7 and 8 thus require less annealing than that described with respect to the previous embodiment, meaning that a stronger shaped can 20 is possible at a given weight or wall thickness, or that the weight ofthe shaped can 20 can be reduced with respect to that produced by the first described method.
• Disadvantages ofthe second and third methods include more machinery and greater mechanical complexity, as well as more wear and tear on the cans, spoilage and possible decoration damage as a result ofthe additional mechanical processing and handling.
• body blank 10 could be formed by altemative processes, such as a draw-redraw process, a draw-thin-redraw process, or by a three-piece welded or cemented manufacturing process.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Containers Having Bodies Formed In One Piece (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Laminated Bodies (AREA)
• Stackable Containers (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)

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• 1996
  • 1996-09-17 BR BR9610795A patent/BR9610795A/pt not_active IP Right Cessation
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