WO2022235743A1 - Procédé de formage de coque d'extrémité de canette à boisson - Google Patents

Procédé de formage de coque d'extrémité de canette à boisson Download PDF

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Publication number
WO2022235743A1
WO2022235743A1 PCT/US2022/027596 US2022027596W WO2022235743A1 WO 2022235743 A1 WO2022235743 A1 WO 2022235743A1 US 2022027596 W US2022027596 W US 2022027596W WO 2022235743 A1 WO2022235743 A1 WO 2022235743A1
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WO
WIPO (PCT)
Prior art keywords
bubble
forming
center panel
panel
shell
Prior art date
Application number
PCT/US2022/027596
Other languages
English (en)
Inventor
Anthony Scott
Original Assignee
Ball Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ball Corporation filed Critical Ball Corporation
Publication of WO2022235743A1 publication Critical patent/WO2022235743A1/fr

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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
    • B21D51/38—Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures
    • 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
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/22—Deep-drawing with devices for holding the edge of the blanks
    • 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
    • B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/002—Processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/005—Processes combined with methods covered by groups B21D1/00 - B21D31/00 characterized by the material of the blank or the workpiece
    • B21D35/006—Blanks having varying thickness, e.g. tailored blanks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D17/00—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions
    • B65D17/28—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions at lines or points of weakness
    • B65D17/401—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions at lines or points of weakness characterised by having the line of weakness provided in an end wall
    • B65D17/4012—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions at lines or points of weakness characterised by having the line of weakness provided in an end wall for opening partially by means of a tearing tab
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2517/00—Containers specially constructed to be opened by cutting, piercing or tearing of wall portions, e.g. preserving cans or tins
    • B65D2517/0001—Details
    • B65D2517/001—Action for opening container
    • B65D2517/0014—Action for opening container pivot tab and push-down tear panel

Definitions

  • the invention relates to can ends for beverage containers; more particularly, the invention relates to a lightweight can end shell and a method for forming same.
  • Common end closures also called lids, can ends, or, simply, ends
  • a central panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “public side,” of the end closure.
  • frangible panel sometimes called a “tear panel,” “opening panel,” or “pour panel”
  • Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end.
  • the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel.
  • This type of container end typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
  • SOT stay-on-tab
  • the can ends are attached to a container, or can, body after filling the container body with a beverage.
  • the container body is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum.
  • the end closures are joined to the can bodies in a process called seaming or double seaming to form the well-known, commercially successful two-piece beverage cans or containers.
  • the end closures for such containers are typically formed during a two-part process.
  • the first process comprises what is commonly referred to as a shell press.
  • the steps of manufacturing begin in the can end shell press where a very thin sheet material, typically aluminum, an aluminum alloy, or a steel, is fed into the shell press.
  • the sheet is blanked forming a cutedge, typically a round or non-round cutedge of the thin metal sheet is formed.
  • non-round cutedge blanks include elliptical cutedges, convoluted cut edges, and harmonic cut edges.
  • a convoluted cutedge may be described as generally having three distinct diameters, each diameter being 45° relative to the others.
  • the cutedge is then formed into an unfinished can end by forming a seaming curl, countersink, panel radius and a center panel.
  • FIG. 3 shows an example of an unfinished or unconverted can end.
  • the unconverted can ends are transferred to a second press assembly called a conversion press.
  • the unconverted can ends are converted or formed into the lids for the well-known two-piece beverage containers used throughout the world.
  • a means for opening the can end or accessing the contents of the container featuring the stay-on tab technology is typically formed in a conversion process for this type of end closure.
  • This process includes the following steps: forming a rivet by first forming a projecting bubble in the center of the center panel and subsequently working the metal of the bubble into a button and into the more narrow projection of metal being a rivet; forming a tear panel by scoring the metal of the center panel wall; forming an inner bead or panel on the tear panel; forming a deboss panel by bending the metal of the panel wall such that a central area of the center panel is slightly lower than the remaining center panel; staking a tab to the rivet; and other subsequent operations such as wipe-down steps to remove sharp edges of the tab, forming lettering on the center panel by scoring, incising, or embossing (or debossing), and restriking a rivet island on the tab surrounding the rivet.
  • the opening of the tear panel is operated by the tab which is attached to the center panel by the rivet, generally through a rivet hole in a rivet island of the tab.
  • the tab is attached to the center panel such that the nose of the tab extends over a proximal portion of the tear panel.
  • a lift end of the tab is located opposite the tab nose and provides access for a user to lift the lift end, such as with the user’s finger, to force the nose against the proximal portion of the tear panel.
  • the score When the tab nose is forced against the tear panel, the score initially ruptures at a vent region of the score of the tear panel. This initial rupture of the score is primarily caused by the lifting force on the tab resulting in lifting of a central region of the center panel, immediately adjacent the rivet, which causes separation of the residual metal of the score.
  • the force required to rupture the score in the vent region typically referred to as the “pop” force, is a lower degree of force relative to the force required to propagate other regions of the score by continued lifting of the lift end of the tab. Therefore, it is preferable that the panel in the area around the rivet only lifts enough to assist with initial score rupture, or pop, and remains substantially stiff and flat to provide the needed leverage for the tab to propagate the separating of the score of the tear panel.
  • the user continues to lift the lift end of the tab which causes the tab nose to be pushed downward on the tear panel to continue the rupture of the score, as an opening force.
  • the tear panel is displaced downward and is rotated about the hinge region to be deflected into the container.
  • the rivet must withstand the forces placed on it and must retain the tab to the can end. If the rivet fails, the tab can become partially or totally detached from the remaining portion of the can end and access to the contents of the container will be adversely affected.
  • the available metal material for forming the rivet integral with the remaining portion of the center panel is reduced.
  • the rivet is formed in the conversion press.
  • the rivet is formed in progressive steps. A first station forms a bubble, a second and a third station reform the bubble into a rivet, and finally after a tab is placed over the rivet, a staking station mechanically secures the tab to the rivet by flattening over the tab a portion of the rivet protruding through an aperture in the rivet island.
  • rivet formation during the conversion process produces various strains in the surface of the metal. Additionally, it is the conventional practice to coin (i.e., compress and thin) the metal of the center panel proximate the base of the rivet during formation thereof. When the rivet is completely formed in the central panel, a button coin band having a generally circular periphery is also formed and is located about the rivet.
  • the rivet and the region immediately surrounding the rivet could become an initiation site for metal failure, such as cracking, tearing, fatigue failure, etc. These types of failures can become pronounced when the starting thickness of the sheet of metal material is reduced to decrease the volume of metal used to produce a converted or finished can end.
  • a portion of the score that fractures first to cause the “pop” must be located very near the rivet and typically within the button coin band surrounding the rivet. This proximity of the score to the rivet places a constraint on the size or diameter of the rivet.
  • Finished can ends also referred to as reformed or converted can ends, are available in many sizes.
  • the different sizes are generally identified as 200, 202, 206, and 209.
  • the sizes are distinguished, in part, by their respective diameters. Of these listed, the 200 can end is the smallest, and the 209 is the largest.
  • One aspect of the present disclosure is directed to a method of forming a beverage can end comprising the steps of: forming a pre-bubble in a center panel of an unfinished can end, the pre bubble defined by a convex protrusion on a public side of the center panel and a concave recess on a product side of the unfinished can end; and transferring the unfinished can end to a conversion press wherein the unfinished can end is converted to a finished can end comprising a tab attached to the center panel by a rivet.
  • the pre-bubble may have an arcuately shaped surface in cross-section.
  • the arcuately shaped surface may be at least substantially a spherical cap.
  • the arcuately shaped surface may be a spherical cap.
  • the unfinished can end may comprise a circumferential curl defining an outer perimeter of the unfinished can end, a radially inwardly extending circumferential wall extending downwardly from the circumferential curl, and a generally U-shaped countersink extending radially inwardly from the circumferential wall, wherein the center panel is positioned about a longitudinal axis and extends from the longitudinal axis radially outwardly towards the generally U-shaped countersink.
  • the center panel of the unfinished can end may be generally planar from an annular, radially outermost portion of the pre-bubble of the center panel towards the generally U-shaped countersink.
  • the method may further comprise the step of forming the pre-bubble into a bubble, wherein the bubble forms a convex protrusion on the public side of the center panel and a concave recess on the product side of the center panel.
  • the bubble may comprise a circumferential discontinuity located radially inwardly from a circumferential outer perimeter of the bubble.
  • a center portion of the bubble may be located radially inwardly from the discontinuity.
  • the center portion of the bubble may comprise a substantially unreformed portion of the pre-bubble.
  • the discontinuity may be located at a distance from the longitudinal axis greater than or equal to a distance of an intersection of the pre-bubble with an adjacent portion of the center panel from the longitudinal axis.
  • the bubble may comprise an annular coin located at a distance from the longitudinal axis greater than the distance of the intersection of the pre-bubble with the adjacent portion of the center panel from the longitudinal axis.
  • the center portion of the bubble may have a thickness substantially equal to a thickness of a cutedge blank from which the unfinished can end is formed.
  • At least a portion of the substantially unreformed portion of the pre-bubble may be at least substantially a spherical cap.
  • the substantially unreformed portion of the pre-bubble may be a spherical cap.
  • the method may further comprise the step of reforming the bubble into a button wherein the button forms a convex protrusion on the public side of the center panel and a concave recess on the product side of the center panel.
  • the method may further comprise the step of reforming the button into a rivet wherein the rivet forms a convex protrusion on the public side of the center panel and a concave recess on the product side of the center panel.
  • the rivet may comprise a circumferential shank extending upwardly from the public side of the unfinished can end to an enclosed central portion, wherein the rivet is located adjacent to a first annular coined region and radially inwardly therefrom, wherein the center panel of the unfinished can end has a second annular coined region surrounding the first annular coined region.
  • the first annular coined region may have a thickness less than a thickness of the second annular coined region.
  • a thickness of the center panel of the unfinished can end directly adjacent and surrounding the second annular coined region may be greater than the thickness of the second annular coined region.
  • the method may further comprise the step of staking a tab to the center panel of the unfinished can end to create a finished can end.
  • a second aspect of the disclosure is directed to a can end shell forming single action press comprising: a cutedge die; an upper tooling comprising: a blanking die configured to cooperate with the cutedge die to cut a disk from a sheet of metallic material during a downstroke of the single action press; a center punch positioned radially inwardly of the blanking die; and a female pre-bubble tool configured to receive a portion of the can end shell therein during the downstroke by the single action press; a lower tooling comprising: a male pre-bubble tool configured to fit within the female pre-bubble tool.
  • the lower tooling may comprise a panel punch opposite the center punch wherein the male pre-bubble tool is located radially inwardly from a radially outer peripheral edge of the panel punch.
  • a curl forming tooling may be located radially outwardly from the center punch and the panel punch.
  • the male pre-bubble tool may have an arcuate forming end.
  • the forming end may be substantially a spherical cap.
  • the forming end may be a spherical cap.
  • the male pre-bubble tool may be configured to contact a product side of a partially formed can end shell during the downstroke of the upper tooling.
  • the center punch may be configured to engage a public side of the partially formed can end shell during the downstroke of the upper tooling.
  • the male pre-bubble tool may be located within a cavity in the panel punch.
  • the cavity may be configured to deliver a fluid pressure to the product side of a fully formed can end shell.
  • the panel punch may be configured to remain engaged with the product side during an upstroke of the lower tooling.
  • a third aspect of the disclosure is directed to a method of forming a beverage can end shell comprising the steps of: forming a pre-bubble in a center panel of a partially formed can end shell, the pre-bubble defined by a convex protrusion on a public side of the center panel and a concave recess on a product side of the partially formed can end; and forming a circumferential generally U-shaped countersink about a periphery of the center panel of the partially formed can end shell subsequent to the forming the pre-bubble step.
  • the method may further comprise the step of blanking a disk from a sheet of material prior to the forming the pre-bubble step.
  • the method may further comprise the step of forming a circumferential curl along a peripheral edge of the disk prior to the forming the pre-bubble step.
  • the method may further comprise the step of drawing the disk into a cup-shape prior to the forming the pre-bubble step.
  • the pre-bubble may have an arcuately shaped surface.
  • the arcuately shaped surface may be at least substantially a spherical cap.
  • the arcuately shaped surface may be a spherical cap.
  • the can end shell may comprise the circumferential curl defining an outer perimeter of the can end shell, a radially inwardly extending circumferential wall extending downwardly from the circumferential curl, the circumferential generally U-shaped countersink extending radially inwardly from the circumferential wall, wherein the center panel is positioned about a longitudinal axis and extends from the longitudinal axis radially outwardly towards the generally U-shaped countersink.
  • the center panel of the can end shell may be generally planar from an annular, radially outermost portion of the pre-bubble of the center panel to the circumferential generally U-shaped countersink.
  • FIG. 1 a is top view of a reformed, converted, or finished can end
  • FIG. 2 is a cross-sectional view of a reformed, converted, or finished can end
  • FIG. 3 is a cross-sectional view of a conventional unfinished or unconverted can end (shell) and forming tools for a forming method of the present disclosure
  • FIG. 4 is a cross-sectional view of a shell being formed according to the present disclosure.
  • FIG. 5 is a partial cross-sectional view of a shell prior to undergoing a first conversion stage of a forming method of the present disclosure
  • FIG. 6 is a partial cross-sectional view of a shell undergoing the first conversion stage of a forming method of the present disclosure
  • FIG. 7 is a partial cross-sectional view of a shell prior to undergoing a second conversion stage of a forming method of the present disclosure
  • FIG. 8 is a partial cross-sectional view of a shell undergoing the second conversion stage of a forming method of the present disclosure
  • FIG. 9 is a partial cross-sectional view of a shell prior to undergoing the third conversion stage of a forming method of the present disclosure.
  • FIG. 10 is a partial cross-sectional view of a shell undergoing the third conversion stage of a forming method of the present disclosure
  • FIG. 11 is a partial cross-sectional view of the shell superimposed with the shell subsequent to the first conversion stage
  • FIG. 12 is a partial cross-sectional view of the shell subsequent to the first conversion stage superimposed with the shell subsequent to the second conversion stage;
  • FIG. 13 is a partial cross-sectional view of the shell subsequent to the second conversion stage superimposed with the shell subsequent to the third conversion stage;
  • FIG. 14 is a top view of a can end of the present disclosure with the tab removed to reveal first and second coined regions surrounding a rivet;
  • FIG. 15 is a partial cross-sectional view of the can end of FIG. 14 taken along IS IS of FIG. 14;
  • FIGS. 16 to 23 are cross-sectional views of an article, process, and apparatus according to the present disclosure wherein a metal blank is formed into a can end pre-form or shell having a rivet pre-bubble in a shell press prior to being formed into a finished can end in a conversion press.
  • beverage can end stock i.e., metal sheet
  • the ability to form a rivet becomes more difficult. This is primarily due to a lack of a necessary volume of metal needed to form the rivet properly.
  • the disclosure allows for additional metal volume to be placed in the area of the rivet through the use of a pre-bubble in the unfinished can end created in the shell press prior to transferring the unfinished can end to the conversion press to produce a converted or finished can end.
  • This disclosure provides a volume of metal on a center panel of an unfinished can end in a location where a rivet for attaching a tab will be formed and located during a conversion process performed on a conversion press.
  • the present disclosure adds a pre-bubble stage to the shell press. It creates an area of increased volume on the center panel within a boundary of a pre bubble. This helps to reduce/eliminate the amount of thinning created in the conversion process during rivet forming, primarily during a step carried out in the conversion press where a tab is staked, or affixed/attached, to the center panel by a rivet.
  • FIG. 3 An unfinished can end, can end shell, or merely shell, 10 is illustrated in FIG. 3.
  • This can end shell 10 comprises a center panel 12 separated from a seaming curl 14 by a circumferential wall 15 extending downwardly from the seaming curl 14 to a strengthening segment 16 which is joined to the center panel 12.
  • the terms “shell” and “can end shell” refer to an article produced on a shell press as shown in FIGS. 4 and 16-24.
  • the terms “finished can end”, finished end”, “converted can end”, and “converted end” refer to a completely formed lid ready for attachment to a beverage container body as illustrated in FIGS. 1 and 2 .
  • the term “unfinished can end” is broader as used herein. “Unfinished can end” refers to any pre converted or pre-fmished can end, regardless of whether the article is within or produced by any particular press in the manufacturing process, e.g., a shell press or a conversion press, unless specified in the claims or the description.
  • Tooling for a shell press and the forming of a can end shell of the present invention are illustrated in FIGS. 16-23. Partial conversion press tooling is illustrated in FIGS. 5-10.
  • the finished can end, or converted end can be later joined to a container body by the seaming curl 14 which is joined to a mating curl of the container body.
  • the seaming curl 14 of the finished can end is integral with the center panel 12 by the circumferential wall 15 and the strengthening segment 16, typically either a generally U-shaped countersink or a fold, which is joined to a peripheral edge of the center panel 12, which defines an outer perimeter of the center panel 12, often through an additional strengthening feature such as a circumferential step or other circumferential wall.
  • the circumferential seaming curl 14 defines an outer perimeter of the finished beverage can end. It is generally centered about a longitudinal or vertical axis 50, preferably located at a center of a pre-bubble for a rivet 38.
  • the circumferential wall 15 extends downwardly from a radially inner portion of the seaming curl 14.
  • the circumferential strengthening segment 16 is joined to a lower segment of the circumferential wall 15 and extends circumferentially about the center panel 12.
  • the can end shell 10 is converted to a finished can end 10' (see FIGS. 1 and 2) at a conversion press.
  • the center panel 12 receives a means for opening the finished end 10'.
  • the means for opening is a tear panel 22 defined by a curvilinear frangible score 21 and a non-frangible hinge segment 25 which extends between terminal ends of the frangible score 21. Accordingly, the hinge segment is defined by a generally straight line between a first end and a second end of the frangible score 21.
  • the tear panel 22 of the center panel 12 may be opened, that is the frangible score 21 may be severed and the tear panel 22 displaced at an angular orientation relative to the remaining portion of the center panel 12, while the tear panel 22 remains hingedly connected to the center panel 12 through the hinge segment.
  • the tear panel 22 is displaced at an angular deflection, as it is opened by being displaced away from the plane of the panel 12. This deflection of the tear panel 22 creates a pour opening 27 through which a fluid in the container can be poured.
  • the frangible score 21 is preferably a generally V-shaped groove formed into a public side 32 of the center panel 12 (see, e.g., FIG. 15). A residual is formed between the V- shaped groove and a product side 34 of the finished can end 10'.
  • the finished can end 10' has a tab 28 secured to the center panel 12 adjacent the tear panel 22 by a rivet 38 which passes through an aperture in a rivet island of the tab 28.
  • the method of manufacturing the rivet 38 forms a basis of the present disclosure.
  • a nose portion 42 of the tab 28 overlays the tear panel 22 in a frangible score 21 breaking position.
  • the user lifts a lift end 40 of the tab 28 to displace the nose portion 42 downward against the tear panel 22.
  • the force of the nose portion 42 against the tear panel 22 causes the score 21 to fracture.
  • the fracture of the score 21 propagates around the tear panel 22, preferably in progression from the first end of the score 21 toward the second end of the score.
  • the tab 28 has a void region, generally a hole in the form of a slot, which partially surrounds the rivet island.
  • the void region has a first leg extending along a first side of the rivet island and a second leg extending along a second side of the rivet island.
  • the frangible score 21 and tab 28 can be recessed within a deboss panel 62 in the center panel 12.
  • the deboss panel 62 is a recessed surface in the center panel 12 which decreases a height of a portion of the center panel 12 in a direction parallel to the longitudinal axis 50 such that a concave surface is formed on the public side 32 of the finished can end 10.
  • the deboss panel 62 is formed in the conversion press.
  • a can end shell, also interchangeably shell, 10 of the present disclosure comprises a circumferential curl 14 defining an outer perimeter of the can end shell 10, a radially inwardly extending circumferential wall 15 extending downwardly from the circumferential curl 14, and a generally U-shaped countersink 16 extending radially inwardly from the circumferential wall 15.
  • a center panel 12 is positioned about a longitudinal axis 50 and extends from the longitudinal axis radially outwardly to the generally U-shaped countersink.
  • pre-bubble tooling of a rivet forming method forms the pre-bubble 66, which extends upwardly in a direction parallel to the longitudinal axis 50 forming a convex protrusion or pre-bubble on the public side 32 center panel 12.
  • a corresponding concave recess is formed on the product side of the center panel 12.
  • the pre-bubble 66 is circumferential about the longitudinal axis 50.
  • the pre-bubble is a formed protrusion equal in thickness as the incoming gauge. This protrusion is smaller in diameter than subsequent conversion bubble forming steps. This allows for increase material volume in the center of the resulting rivet. This helps reduce/eliminate thinning created later in the conversion process during rivet forming, primarily during a step carried out in the conversion press where a tab is staked, or affixed/attached, to the center panel by a rivet.
  • the pre-bubble 66 located about the longitudinal axis 50 is formed by a first set of tooling comprising a public side tooling 78 and a product side tooling 82.
  • the pre-bubble 66 is a metal formation formed in the shell press prior to passing the can end shell 10 to the conversion press. Relative movement between the public side tooling 78 and the product side tooling 82 brings the public side tooling 78 and the product side tooling 82 into contact with the public side 32 and the product side 34 of the center panel 12 of the can end shell 10, respectively.
  • the center panel 12 of the can end shell 10 is generally planar from an annular, radially outermost portion of the pre-bubble 66 of the center panel 12 to the generally U-shaped countersink 16.
  • the pre-bubble 66 is arcuate in cross-section.
  • the pre-bubble 66 has a constant radius of curvature.
  • the pre-bubble is a section of a sphere. More preferably, the pre-bubble is a spherical cap of the sphere. Most preferably, the pre-bubble is a spherical cap of the sphere wherein a height of the spherical cap is less than a radius of the sphere of which the pre-bubble is a spherical cap.
  • a spherical cap, or spherical dome is a portion of a sphere or of a ball cut off by a plane.
  • the pre-bubble 66 may also include a surface having multiple radii of curvature, wherein the pre-bubble does not take the shape of a spherical cap (see, e.g., FIG. 23).
  • One advantage of the pre-bubble is to maintain, not lose, or reduce a thickness of the center panel 12 in subsequent forming operations.
  • the pre-bubble 66 is increased in size into a bubble 86.
  • An internal volume of the pre-bubble is increased as a height increases and a diameter if the pre-bubble is increased.
  • a second set of tooling comprising a public side tooling 90 and product side tooling 94 forms the bubble 86. Relative movement between the public side tooling 90 and the product side tooling 94 brings the public side tooling 90 and the product side tooling 94 into contact with the public side 32 and the product side 34 of the center panel 12 of the unfinished can end, respectively.
  • the bubble 86 is formed in the conversion press after the can end shell 10 has been passed from the shell press to the conversion press.
  • the bubble 86 forms a convex protrusion on the public side 32 of the center panel and a concave recess on the product side 34 of the center panel 12.
  • the reforming of the pre-bubble into a bubble step may include forming an annular, or ring-shaped, coin 88. This compresses the material to further reduce a thickness of the material of the unfinished can end.
  • a central portion 96 of the bubble comprises a portion of unreformed, or at least substantially unreformed, pre-bubble 66.
  • the bubble 86 has a circumferential discontinuity 92 located radially inwardly from a peripheral edge defining an outer perimeter of the bubble 86. This discontinuity 92 surrounds the central portion 96 comprising the at least substantially unreformed remnant portion of the pre-bubble.
  • substantially unreformed encompasses maintaining a spherical cap of the pre-bubble as well as reforming a spherical cap-shaped pre-bubble to a central portion 96 of the bubble located radially inwardly from the circumferential discontinuity 92 having a parabolic surface conic section
  • the bubble 86 comprises a ring-shaped coined region 88 located radially outwardly from the central portion 96 of the bubble 86 and surrounding a central portion 96 of the bubble 86.
  • the thickness of the material of the unfinished can end is greater in a central portion 96 of the bubble 86 than in the annular coin 88
  • the pre-bubble 66 intersects an adjacent portion of the center panel 12, generally a planar portion of the center panel 12 directly adjacent the pre bubble 66. This intersection is positioned at a distance RPB from the longitudinal axis 50.
  • the annular coin 88 is formed radially outwardly of the intersection between the pre-bubble 66 and the adjacent portion of the center panel 12, preferably at a distance greater than or equal to the distance RPB.
  • a radially inner most portion of the annular coin 88 is preferably located a distance from the longitudinal axis 50 greater than or equal to the distance RPB, wherein a thickness in the material of a center portion of the pre-bubble 66 remains substantially constant upon forming the bubble 86.
  • the discontinuity 92 is located at a distance from the longitudinal axis 50 greater than or equal to the distance RPB of the intersection of the pre-bubble with the adjacent portion of the center panel 12 from the longitudinal axis 50.
  • the annular coin 88 is located at a distance from the longitudinal axis greater than the distance RPB from the longitudinal axis 50 of the intersection of the pre-bubble with the adjacent portion of the center panel 12.
  • the center portion of the bubble 86 has a thickness substantially equal to a thickness of a cutedge blank from which the unfinished can end is formed.
  • the term “substantially” is intended to encompass a slight reduction in thickness caused by the forming process of less than 5%.
  • the remaining stages of the rivet-forming method are conventional in nature as understood by one of ordinary skill in the art.
  • the bubble 86 is reshaped or reformed into a button 106.
  • a second set of conversion tooling comprising a public side tooling 110 and a product side tooling 114 forms the button 106. Relative movement between the public side tooling 110 and the product side tooling 114 brings the public side tooling 110 and the product side 114 into contact with the public side 32 and the product side 34 of the center panel 12 of the can end 10, respectively.
  • the step of reforming the bubble 86 into the button 106 includes forcing the ring-shaped coin 88 into a substantially planar relationship with a portion of the center panel 12 directly adjacent to and surrounding the ring-shaped coin 88.
  • the term “substantially” is intended to encompass the change in thickness in the metal of the coined region 88 relative to the uncompressed metal in the adjacent portion of the center panel 12.
  • An inside diameter of the public side tooling 110 coincides with desired final rivet dimensions.
  • a comparison between a shape of the bubble 86 and the button 106 is illustrated in FIG. 13.
  • FIGS. 9 and 10 a third conversion stage of a rivet-forming method is shown.
  • the button 106 is reshaped into the rivet 38.
  • a third set of conversion tooling comprising a public side tooling 122 and a product side tooling 126 forms the button 118. Relative movement between the public side tooling 122 and the product side tooling 126 brings the public side tooling 122 and the product side 126 into contact with the public side 32 and the product side 34 of the center panel 12 of the unfinished can end , respectively.
  • This forming step defines a shank 130 of the rivet 38.
  • the rivet comprises the circumferential shank 130 extending upwardly from the public side 32 of the unfinished can end to an enclosed central portion.
  • a comparison between a shape of the button 106 and the rivet 38 is illustrated in FIG. 13.
  • the resultant finished can end 10' exhibits structural characteristics unique to the forming operation described herein.
  • the product side 34 of the finished can end 10' is illustrated with the tab 28 removed to reveal one of these unique structural forms. More particularly, the can end 10' comprises a plurality of coined portions surrounding the rivet 38. Typically, a single button coin surrounds the rivet 38.
  • the finished can end 10' comprises a first or radially inner annular coined region 134 surrounding the shank 130 and a second or radially outer coined region 138.
  • the center panel 12 has a second annular coined region 138 surrounding a first annular coined region 134, and the rivet 38 is located adjacent to the first annular coined region 134 and radially inwardly therefrom.
  • the first annular coined region 134 has a thickness T134 slightly less than a thickness Ti38 of the second annular coin 138.
  • the tear panel 22, the deboss panel 62, and the frangible score 21 are formed, and the tab 28 is staked to the center panel 12 by striking the enclosed central portion of the rivet 38.
  • the second annular coined region 138 has a radius Ri38 from the longitudinal axis 50 of a radially outermost segment which is greater than a radius R134 from the longitudinal axis 50 of the first annular coined region 134.
  • a radius of a radially innermost segment of the second annular coined region 138 from the longitudinal axis 50 is substantially equal to the radius R134 of the first annular coined region 134 from the longitudinal axis 50.
  • a width of the second annular coined region 138 measured from the radially innermost segment of the second annular coined region 138 to the radially outermost segment of the second annular coined region 138 is less than a width of the first annular coined region 134 measured from the radially innermost segment of the first annular coined region 134 to the radially outermost segment of the first annular coined region 134.
  • An inner pressure sleeve 180 has a nose portion 184 which projects downwardly from a flat bottom surface of a die center punch 188 during an initial downstroke and a final upstroke of the upper tooling.
  • the nose portion 184 has an annular curved surface which extends from a bottom curved end surface to an inclined frusto-conical surface.
  • a bottom end of an outer pressure sleeve 192 has a slightly curved or arcuate surface which opposes and mates with an arcuate crown surface formed on an upper end portion of a die core ring 196.
  • the upper end portion of the die core ring 196 also has an inclined or frusto-conical surface, a curved annular surface and a curved surface which oppose and mate with the corresponding surfaces on the bottom of the inner pressure sleeve 180.
  • a panel punch 200 has a flat top circular surface surrounded by a tapered on frusto-conical surface, a substantial cylindrical surface and an outer tapered or frusto-conical surface which opposes the end surface on the nose portion 184 of the inner pressure sleeve 180.
  • the upper tooling 78 for forming the pre-bubble 66 is a part of, or moves with, the die center punch 184.
  • the lower tooling 82 for forming the pre-bubble 66 resides within a cavity 201 in the panel punch 200.
  • a downstroke (designated by arrows on the individual tooling members) begins, a blank and draw die 202 cooperates with a cutedge die 204 to blank a substantially circular disk 212 from a thin sheet metal, preferably aluminum or an aluminum alloy.
  • a downstroke causes an annular portion of the disk 212 to be clamped between the outer pressure sleeve 192 and the die core ring 196.
  • An outer peripheral edge portion of the disk 170 is drawn downwardly around the upper end portion of the die core ring 196 by the downward movement of the blank and draw die 204 and an opposing lower pressure sleeve 216.
  • the inner pressure sleeve 180 initiates a drawing of the disk 212 within the outer pressure sleeve 192 and die core ring 196.
  • Continuing downstroke of the upper tooling causes the die center punch 188 to cooperate with the inner pressure sleeve 180 to continue drawing of the disk 212 while a radially outer portion of the disk 212 slides between the outer pressure sleeve 216, the die core ring 196, and the blank and draw die 202.
  • the die center punch 188 moves upwardly with the panel punch 200 while the inner pressure sleeve 180 holds the partially formed can end shell 10 between the inner pressure sleeve 180 and the die core ring 196.
  • Contact between inner pressure sleeve 180 and the can end shell 10 is maintained while the panel punch 200 moves against the product side 34 of the partially formed can end shell 10.
  • the completed can end shell 10 moves upwardly from the die core ring 196 and panel punch 200 with the upward movement of the outer pressure sleeve 192 as a result of a fluid pressure directed upwardly against the product side 34 through the channel 201 in the panel punch 200.
  • the pre-bubble 66 is formed prior to forming the countersink 16. This is believed to maintain the thickness of the can end shell material because the cutedge of the metal blank is not constrained and less material stretching will occur.
  • an apparatus of the present disclosure includes a cutedge die 204, an upper tooling and a lower tooling.
  • the upper tooling comprises a blanking die, which may be a blank and draw die 202.
  • the blanking die is configured to cooperate with the cutedge die 204 to cut a disk 212 from a sheet of metallic material during a downstroke of the single action press.
  • the upper tooling further comprises a center punch 188 positioned radially inwardly of the blanking die and a female pre-bubble tool, which is generally the upper pre-bubble tooling 78, configured to receive a portion of a partially formed can end shell therein during the downstroke by the single action press.
  • the center punch is configured to engage a public side of a partially formed can end shell during the downstroke of the upper tooling.
  • the lower tooling comprises a male pre-bubble tool, which is generally the lower pre-bubble tooling 82, configured to fit within the female pre-bubble tool.
  • the male pre bubble tool is configured to contact a product side of a partially formed can end shell during the downstroke of the upper tooling.
  • the male pre-bubble tool has an arcuate forming end.
  • the forming end is substantially a spherical cap. More preferably, the forming end is a spherical cap.
  • the lower tooling comprises a panel punch 200 opposite the center punch 188 wherein the male pre-bubble tool is located radially inwardly from a radially outer peripheral edge of the panel punch 200.
  • the panel punch 200 is configured to remain engaged with the product side 34 of the partially formed can end shell during an upstroke of the lower tooling.
  • the male pre-bubble tool is located within a cavity 201 in the panel punch 200.
  • the cavity is configured to deliver a fluid pressure to the product side 34 of a fully formed can end shell 10.
  • the apparatus comprises a curl forming tooling located radially outwardly from the center punch 188 and the panel punch 200.
  • the curl forming tooling includes the outer pressure sleeve 192 of the upper tooling and the die core ring 196 of the lower tooling.
  • the method includes the step of blanking a disk from a sheet of material prior to the forming the pre-bubble step.
  • the method includes the step of forming a circumferential curl along a peripheral edge of the disk prior to the forming the pre-bubble step.
  • the method includes the step of drawing the disk into a cup-shape prior to the forming the pre-bubble step.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Containers Opened By Tearing Frangible Portions (AREA)

Abstract

Une pré-bulle (66) est formée dans un panneau central (12) d'une extrémité de cannette non finie (10). La pré-bulle (66) forme une saillie convexe sur un côté public (32) du panneau central (12), et un évidement concave sur un côté produit (34) de l'extrémité de cannette non finie (10). L'extrémité de cannette non finie (10) est ensuite transférée à une presse de finition, dans laquelle l'extrémité de cannette non finie (10) est convertie en une extrémité de cannette finie comprenant une languette (28) fixée au panneau central (12) par un rivet (38).
PCT/US2022/027596 2021-05-04 2022-05-04 Procédé de formage de coque d'extrémité de canette à boisson WO2022235743A1 (fr)

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US202163183934P 2021-05-04 2021-05-04
US63/183,934 2021-05-04

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868918A (en) * 1971-12-27 1975-03-04 Aluminum Co Of America Lock-down for a pull tab on a container wall
US3986632A (en) * 1974-08-19 1976-10-19 Owens-Illinois, Inc. Convenience closure with safe edges
US5749257A (en) * 1994-11-09 1998-05-12 Aluminum Company Of America Rivet in a converted can end, method of manufacture, and tooling
US20140110408A1 (en) * 2012-10-18 2014-04-24 Stolle Machinery Company, Llc End closure with coined panel radius and reform step
US20190224739A1 (en) * 2018-01-23 2019-07-25 Stolle Machinery Company, Llc Shell with expandable bubble and tooling therefor
CN110947862A (zh) * 2019-12-30 2020-04-03 广州荣鑫容器有限公司 一种易开盖铆钉铆合结构及其加工方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868918A (en) * 1971-12-27 1975-03-04 Aluminum Co Of America Lock-down for a pull tab on a container wall
US3986632A (en) * 1974-08-19 1976-10-19 Owens-Illinois, Inc. Convenience closure with safe edges
US5749257A (en) * 1994-11-09 1998-05-12 Aluminum Company Of America Rivet in a converted can end, method of manufacture, and tooling
US20140110408A1 (en) * 2012-10-18 2014-04-24 Stolle Machinery Company, Llc End closure with coined panel radius and reform step
US20190224739A1 (en) * 2018-01-23 2019-07-25 Stolle Machinery Company, Llc Shell with expandable bubble and tooling therefor
CN110947862A (zh) * 2019-12-30 2020-04-03 广州荣鑫容器有限公司 一种易开盖铆钉铆合结构及其加工方法

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