Can end with a coined rivet, tooling assembly therefor and a method of forming

A can end including a central panel and a coined rivet disposed on the central panel. A press, a station, and/or a tooling assembly structured to form a coined rivet as well as a method to form the coined rivet is also provided.

FIELD OF THE INVENTION

The disclosed and claimed concept relates to can ends and, more particularly, to can ends made from a sheet material formed into a coined rivet. The disclosed concept also relates to a tooling assembly and associated methods for providing such can ends.

BACKGROUND OF THE INVENTION

Metallic containers (e.g., cans) are structured to hold products such as, but not limited to, food and beverages. Generally, a metallic container includes a can body and a can end. The can body, in an exemplary embodiment, includes a base and a depending sidewall. The can body defines a generally enclosed space that is open at one end. The can body is filled with product and the can end is then coupled to the can body at the open end. The container is, in some instances, heated to cook and/or sterilize the contents thereof. This process increases the internal pressure of the container. Further, the container contains, in some instances, a pressurized product such as, but not limited to a carbonated beverage. Thus, for various reasons, the container must have a minimum strength.

Generally, the strength of the container is related to the thickness of the metal from which the can body and the can end is formed, as well as, the shape of these elements. This application primarily addresses the can ends rather than the can bodies. The can ends are “easy open” ends which include a tear panel and a tab. The tear panel is defined by a score profile, or scoreline, on the exterior surface (identified herein as the “public side”) of the can end. The tab is attached (e.g., without limitation, riveted) adjacent the tear panel. The pull tab is structured to be lifted and/or pulled to sever the scoreline and deflect and/or remove the severable panel, thereby creating an opening for dispensing the contents of the container.

When the can end is made, it originates as a blank, which is cut from a sheet metal product (e.g., without limitation, sheet aluminum, sheet steel). As used herein, a “blank” is a portion of material that is formed into a product; the term “blank” is applicable to the portion of material until all forming operations are complete. In an exemplary embodiment, the blank is formed into a “shell” in a shell press. As used herein, a “shell” or a “preliminary can end” is a construct that started as a generally planar blank and which has been subjected to forming operations other than scoring, paneling, rivet forming, and tab staking, as well as other stations as are known. The shell press includes a number of tool stations where each station performs a forming operation (or which may include a null station that does not perform a forming operation). The blank moves through successive stations and is formed into the “shell.” That is, as a non-limiting example, a first station cuts the blank from the sheet material, a second station forms the blank into a cup-like construct with a depending sidewall, a third station forms the depending sidewall into a countersink and a chuck sidewall, and so forth.

For an “easy open” end, a shell is further conveyed to a conversion press, which also has a number of successive tool stations. As the shell advances from one tool station to the next, conversion operations such as, for example and without limitation, rivet forming, paneling, scoring, embossing, and tab staking (i.e., coupling a tab to the shell via the rivet), are performed until the shell is fully converted into the desired can end and is discharged from the press. Further, the process of creating a rivet and coupling a tab thereto are disclosed in U.S. Pat. No. 4,145,801 and the Description of the Preferred Embodiments in U.S. Pat. No. 4,145,801 is incorporated herein by reference.

In the can making industry, large volumes of metal are required in order to manufacture a considerable number of cans. Thus, an ongoing objective in the industry is to reduce the amount of metal that is consumed. Efforts are constantly being made, therefore, to reduce the thickness or gauge (sometimes referred to as “down-gauging”) of the stock material from which can ends, tabs, and can bodies are made. Presently, can ends are made from sheet metal such as, but not limited to aluminum and steel as well as alloys including those metals. The minimum base thickness for these materials is 0.0082 inch. This is a problem and using a metal material with a thinner base thickness would solve this problem.

Use of a material with a thinner base thickness, however, generates other problems such as, but not limited to, failure of the can end at the rivet. That is, a rivet formed from a material with a base thickness less than 0.0082 inch cannot hold the tab to the can end. This is a problem.

Alternatively, material with a thicker base thickness can be thinned to have a thinner, or partially thinner, final thickness that is less than the base thickness. However, as less material (e.g., thinner gauge) is used, problems arise that require the development of unique solutions. Further, the process of forming the can bodies and can ends cause stress in the material thereby damaging the can bodies or can ends during the forming thereof.

One solution to the problems associated with using thin metal is to provide strengthening constructs in the can end. For example, as disclosed in U.S. Pat. No. 5,755,134, the process of creating a rivet includes forming a bubble in the generally planar blank prior to forming the rivet. As stated in U.S. Pat. No. 5,755,134, forming the bubble includes “moving [ ] sufficient metal into the bubble from the end panel so that a rivet can be formed in subsequent operations . . . .” That is, to increase the strength of the rivet both during and after forming operations, metal is forced into the area that becomes the rivet. Stated alternately, the base thickness of the blank is increased in the area that becomes the rivet. Increasing the base thickness of the area that becomes the rivet means decreasing the thickness in other areas of the can end. This is a problem.

Further, prior to staking, the known rivet buttons have a tapered cross-sectional shape. When a rivet button with such a shape is staked, the rivet button is prone to collapse unevenly. That is, a portion of the rivet may extend over the tab more in one direction than another. This is a problem.

There is, therefore, a need for a can end rivet that does not decrease the material thickness of other areas of the can end. Further, there is a need to decrease the amount of material in the rivet so as to decrease the total amount of material used to create the can end. Further, there is a need to form can ends from a material having a base thickness of less than 0.0082 inch.

SUMMARY OF THE INVENTION

The disclosed and claimed concept provides a can end including a central panel and a coined rivet button disposed on the central panel. The disclosed and claimed concept provides a press, a station, and/or a tooling assembly structured to form a coined rivet as well as a method to form the coined rivet.

DETAILED DESCRIPTION OF THE INVENTION

It will be appreciated that the specific elements illustrated in the figures herein and described in the following specification are simply exemplary embodiments of the disclosed concept, which are provided as non-limiting examples solely for the purpose of illustration. Therefore, specific dimensions, orientations, assembly, number of components used, embodiment configurations and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting on the scope of the disclosed concept.

Directional phrases used herein, such as, for example, clockwise, counterclockwise, left, right, top, bottom, upwards, downwards and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

As used herein, “structured to [verb]” means that the identified element or assembly has a structure that is shaped, sized, disposed, coupled and/or configured to perform the identified verb. For example, a member that is “structured to move” is movably coupled to another element and includes elements that cause the member to move or the member is otherwise configured to move in response to other elements or assemblies. As such, as used herein, “structured to [verb]” recites structure and not function. Further, as used herein, “structured to [verb]” means that the identified element or assembly is intended to, and is designed to, perform the identified verb. Thus, an element that is merely capable of performing the identified verb but which is not intended to, and is not designed to, perform the identified verb is not “structured to [verb].”

As used herein, “associated” means that the elements are part of the same assembly and/or operate together, or, act upon/with each other in some manner. For example, an automobile has four tires and four hub caps. While all the elements are coupled as part of the automobile, it is understood that each hubcap is “associated” with a specific tire.

As used herein, a “coupling assembly” includes two or more couplings or coupling components. The components of a coupling or coupling assembly are generally not part of the same element or other component. As such, the components of a “coupling assembly” may not be described at the same time in the following description.

As used herein, a “coupling” or “coupling component(s)” is one or more component(s) of a coupling assembly. That is, a coupling assembly includes at least two components that are structured to be coupled together. It is understood that the components of a coupling assembly are compatible with each other. For example, in a coupling assembly, if one coupling component is a snap socket, the other coupling component is a snap plug, or, if one coupling component is a bolt, then the other coupling component is a nut.

As used herein, a “fastener” is a separate component structured to couple two or more elements. Thus, for example, a bolt is a “fastener” but a tongue-and-groove coupling is not a “fastener.” That is, the tongue-and-groove elements are part of the elements being coupled and are not a separate component.

As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. Accordingly, when two elements are coupled, all portions of those elements are coupled. A description, however, of a specific portion of a first element being coupled to a second element, e.g., an axle first end being coupled to a first wheel, means that the specific portion of the first element is disposed closer to the second element than the other portions thereof. Further, an object resting on another object held in place only by gravity is not “coupled” to the lower object unless the upper object is otherwise maintained substantially in place. That is, for example, a book on a table is not coupled thereto, but a book glued to a table is coupled thereto.

As used herein, the phrase “removably coupled” or “temporarily coupled” means that one component is coupled with another component in an essentially temporary manner. That is, the two components are coupled in such a way that the joining or separation of the components is easy and would not damage the components. For example, two components secured to each other with a limited number of readily accessible fasteners, i.e., fasteners that are not difficult to access, are “removably coupled” whereas two components that are welded together or joined by difficult to access fasteners are not “removably coupled.” A “difficult to access fastener” is one that requires the removal of one or more other components prior to accessing the fastener wherein the “other component” is not an access device such as, but not limited to, a door.

As used herein, “temporarily disposed” means that a first element(s) or assembly (ies) is resting on a second element(s) or assembly(ies) in a manner that allows the first element/assembly to be moved without having to decouple or otherwise manipulate the first element. For example, a book simply resting on a table, i.e., the book is not glued or fastened to the table, is “temporarily disposed” on the table.

As used herein, “operatively coupled” means that a number of elements or assemblies, each of which is movable between a first position and a second position, or a first configuration and a second configuration, are coupled so that as the first element moves from one position/configuration to the other, the second element moves between positions/configurations as well. It is noted that a first element may be “operatively coupled” to another without the opposite being true.

As used herein, “correspond” indicates that two structural components are sized and shaped to be similar to each other and may be coupled with a minimum amount of friction. Thus, an opening which “corresponds” to a member is sized slightly larger than the member so that the member may pass through the opening with a minimum amount of friction. This definition is modified if the two components are to fit “snugly” together. In that situation, the difference between the size of the components is even smaller whereby the amount of friction increases. If the element defining the opening and/or the component inserted into the opening are made from a deformable or compressible material, the opening may even be slightly smaller than the component being inserted into the opening. With regard to surfaces, shapes, and lines, two, or more, “corresponding” surfaces, shapes, or lines have generally the same size, shape, and contours.

As used herein, a “path of travel” or “path,” when used in association with an element that moves, includes the space an element moves through when in motion. As such, any element that moves inherently has a “path of travel” or “path.” Further, a “path of travel” or “path” relates to a motion of one identifiable construct as a whole relative to another object. For example, assuming a perfectly smooth road, a rotating wheel (an identifiable construct) on an automobile generally does not move relative to the body (another object) of the automobile. That is, the wheel, as a whole, does not change its position relative to, for example, the adjacent fender. Thus, a rotating wheel does not have a “path of travel” or “path” relative to the body of the automobile. Conversely, the air inlet valve on that wheel (an identifiable construct) does have a “path of travel” or “path” relative to the body of the automobile. That is, while the wheel rotates and is in motion, the air inlet valve, as a whole, moves relative to the body of the automobile.

As used herein, the statement that two or more parts or components “engage” one another means that the elements exert a force or bias against one another either directly or through one or more intermediate elements or components. Further, as used herein with regard to moving parts, a moving part may “engage” another element during the motion from one position to another and/or may “engage” another element once in the described position. Thus, it is understood that the statements, “when element A moves to element A first position, element A engages element B,” and “when element A is in element A first position, element A engages element B” are equivalent statements and mean that element A either engages element B while moving to element A first position and/or element A either engages element B while in element A first position.

As used herein, “operatively engage” means “engage and move.” That is, “operatively engage” when used in relation to a first component that is structured to move a movable or rotatable second component means that the first component applies a force sufficient to cause the second component to move. For example, a screwdriver may be placed into contact with a screw. When no force is applied to the screwdriver, the screwdriver is merely “temporarily coupled” to the screw. If an axial force is applied to the screwdriver, the screwdriver is pressed against the screw and “engages” the screw. However, when a rotational force is applied to the screwdriver, the screwdriver “operatively engages” the screw and causes the screw to rotate. Further, with electronic components, “operatively engage” means that one component controls another component by a control signal or current.

As used herein, the word “unitary” means a component that is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body.

As used herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). That is, for example, the phrase “a number of elements” means one element or a plurality of elements.

As used herein, in the phrase “[x] moves between its first position and second position,” or, “[y] is structured to move [x] between its first position and second position,” “[x]” is the name of an element or assembly. Further, when [x] is an element or assembly that moves between a number of positions, the pronoun “its” means “[x],” i.e., the named element or assembly that precedes the pronoun “its.”

As used herein, “about” in a phrase such as “disposed about [an element, point or axis]” or “extend about [an element, point or axis]” or “[X] degrees about an [an element, point or axis],” means encircle, extend around, or measured around. When used in reference to a measurement or in a similar manner, “about” means “approximately,” i.e., in an approximate range relevant to the measurement as would be understood by one of ordinary skill in the art.

As used herein, a “radial side/surface” for a circular or cylindrical body is a side/surface that extends about, or encircles, the center thereof or a height line passing through the center thereof. As used herein, an “axial side/surface” for a circular or cylindrical body is a side that extends in a plane extending generally perpendicular to a height line passing through the center. That is, generally, for a cylindrical soup can, the “radial side/surface” is the generally circular sidewall and the “axial side(s)/surface(s)” are the top and bottom of the soup can.

As used herein, “generally curvilinear” includes elements having multiple curved portions, combinations of curved portions and planar portions, and a plurality of planar portions or segments disposed at angles relative to each other thereby forming a curve.

As used herein, “generally” means “in a general manner” relevant to the term being modified as would be understood by one of ordinary skill in the art.

As used herein, “substantially” means “for the most part” relevant to the term being modified as would be understood by one of ordinary skill in the art.

As used herein, “at” means on and/or near relevant to the term being modified as would be understood by one of ordinary skill in the art.

As used herein, a “coined rivet button” is a portion of a blank20for a can end10that includes a coined top portion18. (All reference numbers discussed below.) That is, a bubble38is formed into an unstaked rivet or button. That is, a “button” is a rivet prior to the staking operation that couples a tab46(discussed below) thereto. The bubble38includes a rivet portion top portion44that is coined when forming the “coined rivet button” That is, the rivet portion top portion44is coined and becomes a generally planar top portion18of both the “coined rivet button”14and the “coined rivet”12. Further, to be a “coined rivet button”14, the area immediately about (encircling) the rivet portion top portion44(the rivet portion sidewall portion42, as discussed below) is not coined when forming the “coined rivet button” or thereafter. Thus, a “coined rivet button,” as used herein, includes a coined top portion18and an un-coined sidewall portion16.

As used herein, a “coined rivet”12is a rivet formed from a “coined rivet button”14and which includes a coined top portion18.

As used herein, to “coin” means to simultaneously engage opposing sides of the blank20and induce plastic flow on the surface of the material. As is known, coining material work hardens the surface(s), while the material therebetween retains its toughness and ductility.

The following description provides for forming a “coined rivet button”14on a can end10and the subsequent “coined rivet”12created by staking a tab46to the “coined rivet button” These elements, and the tooling and associated method used to create these elements, however, can also be incorporated into a shell and the tooling and method of creating that shell. That is, in a shell press (not shown), the portion of the shell that will form the rivet top portion is coined. In an exemplary embodiment, the portion of the shell that will form the rivet is coined while the material is generally planar. In another embodiment, a bubble is formed in the shell blank, the portion of the shell that will form the rivet top portion is coined, and the bubble is reformed into a generally planar portion of the shell. The tooling and the method structured to form such a coined portion of the shell are similar to the coining surfaces578,579(discussed below) and the coining method discussed below. The following description now focuses on creating a coined rivet14in a can end10rather than a shell or preliminary can end.

The following discussion and the Figures use a generally cylindrical can end10,FIG.1, as an example. It is understood that the disclosed and claimed concept is operable with can ends10of any shape and the cylindrical shape discussed and shown is exemplary only. Further, in an exemplary embodiment and for the dimensions described below, the can end is made from aluminum or aluminum alloys and is structured to be coupled to a beverage can; that is, a can structured to contain a beverage such as beer or carbonated beverages. One non-limiting example of a beverage can is a 12 ounce beverage can. It is understood, however, that the concept disclosed below is also applicable to can ends made of other materials such as, but not limited to, steel and steel alloys. It is further understood that steel cans and can ends are typically made from material with a base thickness thinner than aluminum can ends. Thus, a steel can end that includes the down-gauging concept disclosed herein would have a thinner base thickness than the dimensions for an aluminum can, as described below, and a thinner base thickness than the metal used to make the can ends that do not include the down-gauging concept disclosed herein.

As is generally known, a can end10is structured to be, and is, coupled, directly coupled, or fixed in a sealed manner to a can body (not shown) to form a container (not shown). The can end includes a generally planar central panel30, discussed below, and a coined rivet12, as defined below. The coined rivet12is formed from a coined rivet button14(FIG.2). That is, a coined rivet button14protrudes upwardly, as shown, from the central panel30and includes a sidewall16and a generally planar top portion18. The terms sidewall16and top portion18describe the same elements of both the coined rivet12and the coined rivet button14and the same names/reference numbers are used to describe these common elements.

In an exemplary embodiment, the can end10is formed from a sheet material having a base thickness that is less than 0.0082 inch. This solves the problems stated above. As used herein, the base thickness of the sheet material22is also the “average thickness” of the un-coined portions of the central panel30, discussed below. As used herein, the “thickness” is measured along a line substantially normal to the surface of the material or the blank20. The coining process, described below, reduces the thickness of the top portion18to a thickness of less than 0.0082 inch. In an exemplary embodiment, the top portion18has a thickness of between about 0.003 to less than 0.0082 inch. In this example, the sheet material22is formed into a can end10, for a container structured to hold carbonated beverage, i.e., a “soda” or “pop” can. Further details of the coined rivet button14and the coined rivet12are discussed below.

The can end10is, initially, a blank20cut from a sheet22of generally planar material such as, but not limited to aluminum, steel, or alloys of either. That is, in an exemplary embodiment, the sheet22of generally planar material (hereinafter, “sheet material”22) is provided to a press500, shown schematicallyFIG.3, such as a conversion press, that is structured to, and does, form the sheet material22into a can end10(FIG.1). Alternatively, the sheet material22is formed into a shell, hereinafter shell blank20, in a shell press (not shown). The shell blanks20are then provided to the press500, also identified as a “conversion press500.”

The press500includes a number of stations502(some shown schematically) each of which perform a number of forming operations on the shell blank20. The shell blank20moves through the conversion press500on a conveyor504, shown schematically, that is structured to, and does, move with an intermittent, or indexed, motion. In an exemplary embodiment, the conveyor504is a belt506(shown schematically) including a number of recesses, not shown. The belt506moves a set distance then stops before moving the set distance again. As the belt506moves, a blank20is moved sequentially through the conversion press number of stations502where, as noted above, each station502performs a single forming operation, or a number of forming operations, on the blank20.

The conversion press500, or stated alternately each station502thereof, includes an upper tooling assembly550and a lower tooling assembly552. The upper tooling assembly550and a lower tooling assembly552for multiple stations502are, in an exemplary embodiment, unitary or coupled and support the dies, punches and other elements of each station. In this configuration, the upper tooling assemblies550for the stations move at the same time and are driven by a single drive assembly (not shown). For the purpose of identifying specific components, elements of a tooling assembly are also identified as parts of a specific station502. That is, for example, the upper tooling assembly550at the bubble station512, discussed below, is also identified as the bubble station upper tooling assembly560. It is understood that any specifically identified upper tooling assembly550or lower tooling assembly552, e.g. a “first rivet station upper tooling assembly,” are generally part of the upper/lower tooling assemblies550/552, respectively and the identifier/name merely indicates the nature of the station.

The conversion press500further includes a frame554and a drive assembly. In an exemplary embodiment, the lower tooling assembly552is fixed to the frame554and is substantially stationary. The upper tooling assembly550is movably coupled to the frame554and is structured to move from a first position, wherein the upper tooling assembly550is spaced from the lower tooling assembly552, and a second position, wherein the upper tooling assembly550is closer to, and in an exemplary embodiment, immediately adjacent, the lower tooling assembly552. The lower tooling assembly552is, in an exemplary embodiment, coupled, directly coupled, or fixed to the frame554.

It is understood that, generally, the belt506moves when the upper tooling assembly550is in (or moving toward or away from) the first position. Conversely, the belt506is stationary when the upper tooling assembly550is in the second position. As is known, the drive assembly is structured to, and does, move the upper tooling assembly550between the first and second positions. Further, and as is known, the upper tooling assembly550and the lower tooling assembly552include separately movable elements, e.g., punches, dies, spacers, pads, risers and other sub-elements (collectively hereinafter “sub-elements”), that are structured to, and do, move separately from each other. All elements, however, generally move with the upper tooling assembly550between first and second positions. That is, generally, the motions of the sub-elements are relative to each other but as a whole, the upper tooling assembly550moves between the first position and the and second position as described above. Further, it is understood that the drive assembly includes cams, linkages, and other elements that are structured to move the sub-elements of the upper tooling assembly550and the lower tooling assembly552in the proper order. That is, selected sub-elements of the upper tooling assembly550and the lower tooling assembly552are structured to move independently of other selected sub-elements and a specific selected sub-element. For example, one selected sub-element is structured to move into, and dwell, at the second position while another sub-element moves into and out of the second position. Such selective motion of the sub-elements is known in the art.

For the sake of this disclosure, it is assumed that a blank shell20, i.e., a blank including a central panel30, an annular countersink32, a chuck wall34, and a curl36, as shown inFIGS.1and2, is provided to the conversion press500. As is known, conversion generic press stations502(as shown in the Figures, known stations are generically identified by reference number502) perform forming operations on the shell blank20that are not relevant to this disclosure. For the purpose of this application, the following stations are identified: a bubble station512(FIG.3), a first rivet station514(FIG.5), a second rivet station516(FIG.7), a score station518(FIG.9), a panel station520(FIG.10), and a stake station522(FIG.11). In an exemplary embodiment, the first rivet station514is a “coining” rivet station514that is structured to, and does, form a “coined rivet button”14that becomes a “coined rivet”12. Initially, the shell blank20is moved into the bubble station512,FIG.3, that includes a bubble station upper tooling assembly560and a bubble station lower tooling assembly562. Generally, the bubble station lower tooling assembly562includes a die563having an annular generally planar portion564and a central domed portion565. The bubble station upper tooling assembly560includes a punch566having an annular generally planar portion567and a domed portion568. A blank20with a generally planar central panel30(not shown) is disposed between the bubble station upper tooling assembly560and the bubble station lower tooling assembly562. When the bubble station upper tooling assembly560moves to the second position, a bubble38is formed thereon, as shown inFIG.4. As shown inFIG.4, a bubble38is generally arcuate, or generally curvilinear, when viewed in cross-section. The bubble38includes an outer periphery39and a “rivet portion”40. As is known, and in an exemplary embodiment, the outer periphery39is coined during the formation of the bubble38. As used herein, the “rivet portion”40is that portion of the bubble38that becomes the rivet button14and then the rivet12. Further, the rivet portion40includes a sidewall portion42and a top portion44. The rivet portion sidewall portion42becomes the rivet button sidewall16and then the coined rivet sidewall16. Similarly, the top portion44becomes the coined rivet button top portion18and then the coined rivet top portion18. Stated alternately, the outer periphery39is disposed concentrically about the sidewall portion42. Further, the sidewall portion42is disposed concentrically about the top portion44. In an exemplary embodiment, the outer periphery39is disposed concentrically about and immediately adjacent the sidewall portion42, and, the sidewall portion42is disposed concentrically about and immediately adjacent the top portion44.

As noted, when the bubble38is formed, the outer periphery39thereof is coined. The bubble outer periphery39subsequently becomes the area of the central panel30disposed about (encircling) the rivet12. In an exemplary embodiment, the bubble outer periphery39has a thickness of between about 0.005 inch and 0.008 inch, or about 0.0065 inch. Further, the bubble outer periphery39is, in an exemplary embodiment, thicker than the thickness of the coined top portion18, discussed below. That is, if the coined top portion18is at the upper end of its thickness range, the outer periphery39is also at the upper end of its thickness range. If the coined top portion18is at the lower end of its thickness range, the outer periphery39is anywhere in its thickness range, so long as the coined outer periphery39is thicker than the coined top portion18. Further, as noted above, the un-coined portions of the central panel30disposed about the outer periphery39have a thickness equal to the base thickness of the sheet material22, i.e., the average thickness.

The shell blank20is then moved to the coining rivet station514. The coining rivet station514,FIG.5, is structured to, and does, form the bubble38into a coined rivet button14. The coining rivet station514includes a coining rivet station upper tooling assembly570and a coining rivet station lower tooling assembly572. Generally, the coining rivet station lower tooling assembly572includes a die573having an annular generally planar portion574and a central punch575. The coining rivet station upper tooling assembly570includes a central punch576, and an outer annular punch577disposed about (encircling) the central punch576. Pads (not numbered) structured to hold the blank20are disposed about the coining rivet station lower tooling assembly die573and coining rivet station lower tooling assembly central punch575, as well as the coining rivet station upper tooling assembly punches576,577.

The coining rivet station upper tooling assembly central punch576defines a first coining surface578(hereinafter, “first coining surface”578, or, “upper tooling assembly first coining surface”578). In an exemplary embodiment, the first coining surface578is substantially planar. Similarly, the coining rivet station lower tooling assembly central punch575defines a second coining surface579(hereinafter, “second coining surface”579or “lower tooling assembly second coining surface”579). In an exemplary embodiment, the second coining surface579is also substantially planar. The coining rivet station lower tooling assembly planar portion574is disposed opposite the coining rivet station upper tooling assembly annular punch577. Further, the coining rivet station lower tooling assembly central punch575is disposed opposite the coining rivet station upper tooling assembly central punch576. The coining rivet station lower tooling assembly central punch575and the coining rivet station upper tooling assembly central punch576operatively engage, and coin, the rivet portion top portion44. That is, the first coining surface578is structured to, and does, move between a first position, wherein the first coining surface578is spaced from the second coining surface579, and a second position, wherein the first coining surface578is a coining distance from the second coining surface579. As used herein, a “coining distance” is a distance between two surfaces sufficiently close so as to coin material disposed between the two surfaces. Thus, when the first coining surface578and the second coining surface579are in the second position, the first coining surface578and the second coining surface579are structured to, and do, form a rivet coined top portion18. Hereinafter, the “top portion18” is identified as the “coined rivet top portion18” both because it is part of the coined rivet button14(or coined rivet12) and because the metal thereof is “coined.” Conversely, the sidewall16is still identified hereinafter as the “sidewall16.” That is, while the sidewall16is part of the coined rivet button14, the metal of the sidewall16is not coined and the term “coined rivet sidewall portion” may imply that the sidewall16is also coined.

That is, the coining rivet station lower tooling assembly central punch575and the coining rivet station upper tooling assembly central punch576operatively engage the outer periphery of the bubble38and return the outer periphery of the bubble38to the plane of the central panel30while the coined rivet top portion18is being formed. The coined rivet top portion18is not in the same plane as the central panel30; thus, the rivet portion sidewall portion42is formed over the coining rivet station lower tooling assembly central punch575, as is generally known. The rivet portion sidewall portion42is not coined.

That is, the rivet portion top portion44is coined and becomes the thinner and more rigid top portion18. At the same time, a portion of material from the rivet portion top portion44flows into the sidewall portion42as that portion becomes the sidewall16. In an exemplary embodiment, the top portion18has a first thickness and the sidewall16has a second thickness. The first thickness is less than the second thickness, as shown inFIG.1A. Moreover, the sidewall16is not coined and is therefore more ductile than the coined rivet top portion18or the coined portion of the central panel30(formerly the coined outer periphery39as described above). In an exemplary embodiment, the top portion18first thickness is between more than 0.003 inch and less than 0.0082 inch or about 0.004 inch. In another embodiment, the top portion18first thickness is between about 0.004 inch and less than 0.008 inch or about 0.006 inch. In another exemplary embodiment, the top portion18first thickness is less than 0.0082 inch.

In an exemplary embodiment, the plane of the coined rivet top portion18extends generally parallel to the plane of the central panel30. The sidewall16, when viewed in cross-section, has an angle (α) of between about 70° and 90° or about 90° relative to the plane of the central panel30, as shown inFIG.6. In another exemplary embodiment, the sidewall16, when viewed in cross-section, has an angle (α) of less than 90° but more than 80°. A coined rivet button14uses less material than a non-coined rivet button and therefore solves the problems noted above. Further, as used herein, a coined rivet button14that is initially formed with a coined top portion18at the first rivet station514is, as used herein, an “initially coined rivet button.” Coining the top portion18at a first rivet station reduces the amount of metal that flows into the top portion18during subsequent forming operations thereby solving the problems stated above. In an alternate embodiment, the second rivet station516is the “coining” rivet station.

Further, as shown inFIG.6A, it is noted that in the prior art, formation of a rivet button A included deforming the rivet portion sidewall portion B over, i.e., in contact with, the lower tooling C. As shown inFIG.6B, the coining rivet station514is structured to, and does, allow the rivet portion sidewall portion42to gap, i.e., be spaced from, the lower tooling572. This configuration is also generated because the top portion18and the bubble outer periphery39is coined. A press station502, i.e., an upper tooling assembly550and a lower tooling assembly552, that is structured to cause a rivet portion sidewall portion42that is disposed between two areas of coined material to be spaced from the tooling assemblies550,552, is, as used herein, an “gapped press station” and the tooling assemblies thereof are each a “gapped tooling assembly.” Thus, in an exemplary embodiment, the coining rivet station514is a “gapped” coining rivet station514and the tooling assemblies570,572thereof are “gapped” tooling assemblies570,572. Use of a gapped coining rivet station514allows for the thickness of the rivet portion sidewall portion42, and the subsequently formed sidewall16, to be thicker than the coined top portion18. solving the problems stated above. That is, having a sidewall16that is thicker than the coined top portion18reduces the chance of a failure at the coined rivet12solving the problems stated above.

In an exemplary embodiment, the blank20is then moved to a second rivet station516, as shown inFIG.7. The second rivet station516includes an upper tooling assembly that is generally similar to the coining rivet station514, but does not include the equivalent to a coining rivet station upper tooling assembly central punch576. In this configuration, there is nothing that opposes a second rivet station lower tooling assembly central punch585. Thus, as a second rivet station upper tooling assembly outer annular punch587moves downwardly, the coined rivet button14is further formed over the second rivet station lower tooling assembly central punch585so as to have a generally perpendicular sidewall16. The cross-sectional view of the blank shell20following formation in the second rivet station516is shown inFIG.2.

That is, when viewed in cross-section, the sidewall16is generally perpendicular to the plane of the central panel30. The transition between the sidewall16and the coined rivet top portion18is, as used herein, the “peripheral upper edge”19. Because the top portion18is coined, the peripheral upper edge19is structured to have a sharper bend than prior art transitions between a rivet button sidewall and the rivet button top portion. In an exemplary embodiment, the peripheral upper edge19has a radius of between about 0.012 inch and 0.031 inch. A transition between a rivet button sidewall and a rivet button top portion with a radius of between about 0.012 inch and 0.031 inch is, as used herein, a “reduced radius” peripheral upper edge19. That is, the reduced radius peripheral upper edge19has, a radius of between about 0.012 inch and 0.031 inch, when viewed in cross-section, as shown inFIG.2. A coined rivet button14in this configuration, i.e., a button with a generally perpendicular sidewall16and a coined rivet top portion18, is, as used herein, a “square coined rivet button”14′, as shown inFIG.8. A square coined rivet button14′ is structured to collapse, when staked, with an enhanced overlap of a tab body47, as described below.

The score station518,FIG.9, creates a number of scores (not shown) that define a tear panel as is known in the art. The panel station520,FIG.10, forms any additional formations, e.g., recessed portions, on the blank20as is known. In an exemplary embodiment, there are a number of panel stations520. These stations are not relevant to the present disclosure.

The final station relevant to the present disclosure is the stake station522,FIG.11, that is structured to couple a tab46to the coined rivet button14. The cross-sectional view of the blank shell20following formation in the stake station522is shown inFIG.1. The stake station522includes the elements described in U.S. Pat. No. 5,755,134 and operates in a similar manner and the description of the staking process and the upper tooling assembly550and lower tooling assembly552described therein is incorporated by reference. It is generally noted that the stake station522includes an upper tooling assembly590with a staking punch594and staking adjustment spacer596, and, a lower tooling assembly592with a primary anvil598. The stake station lower tooling assembly primary anvil598has a smaller cross-sectional area than the coined rivet button14(or square coined rivet button14′). It is noted that the stake station upper tooling assembly staking adjustment spacer596has an enhanced cross-sectional area. As used herein, an “enhanced cross-sectional area” for a stake station upper tooling assembly staking adjustment spacer596means that the cross-sectional area is structured to form a staked coined rivet12with an enhanced overlap of a tab body47, as described below.

As shown inFIG.1, the tab46, shown schematically, includes an elongated, generally planar body47that defines a coupling opening48. As is also known, the tab46is disposed over the coined rivet button14(or square coined rivet button14′; hereinafter, it is understood that the discussion of the coined rivet button14also applies to the square coined rivet button14′). That is, the coined rivet button14extends through the tab coupling opening48. When a stake station upper tooling assembly staking punch594and the stake station upper tooling assembly staking adjustment spacer596move to their second position, the stake station upper tooling assembly staking punch594engages the coined rivet button top portion18thereby deforming the sidewall16. Accordingly, the coined rivet button14is structured to be, and is, deformed to be a coined rivet12.

Thus, the coined rivet button14has a first configuration, wherein the tab46is not captive on a coined rivet12, and a second configuration, wherein the coined rivet button14is formed into a coined rivet12and wherein the tab46is captive on the coined rivet12. Further, the coined rivet button14has a first maximum cross-sectional area, a first height, and sidewall16has a first thickness. The coined rivet12, i.e., the coined rivet button14following staking/deformation, has a second maximum cross-sectional area, a second height, and the sidewall16has a second thickness. The coined rivet12second maximum cross-sectional area is greater than the coined rivet button14first maximum cross-sectional area, the coined rivet button14first height is greater than the coined rivet12second height, and the sidewall16second thickness is an enhanced thickness relative to the sidewall16first thickness. As used herein, an “enhanced thickness” means that the thickness of the sidewall16is greater than the base thickness of the sheet material.

Moreover, because the un-coined sidewall16is disposed between the coined metal of the central panel30and the coined rivet button top portion18, the sidewall16deforms to a greater degree relative to a prior art rivet wherein the top portion is not coined. Thus, when deformed during the staking operation, the coined rivet button14, and the sidewall16, form a coined rivet12with an “enhanced overlap” of the tab body47. As used herein, an “enhanced overlap” of a tab body means that the deformed sidewall16was formed from a square rivet button14′. As used herein, a “square” rivet button14′ is a rivet button having a sidewall16which, when viewed in cross-section, has an angle (α) of between about 70° and 90° or about 90° relative to the plane of the central panel30. Further, to be a “square” rivet button14, the peripheral upper edge19has a reduced radius. In an exemplary embodiment, the coined rivet12overlaps the sides of the tab coupling opening48by a minimum of 0.008 inch. This solves the problems stated above. A tab body47coupled to a can end10by a coined rivet12with an enhanced overlap of the tab body47is less likely to be decoupled from the can end10thereby solving the problems stated above. Further, the amount of metal of the sidewall16that deforms outwardly is increased when the sidewall16extends generally perpendicular to the plane of the central panel30. Thus, a square coined rivet button14′, when deformed as described above, forms a “very enhanced overlap.” That is, as used herein, a “very enhanced overlap” means the overlay of a tab46created when a square coined rivet button14′ is used to couple a tab46to a can end10. This also solves the problems stated above.

Accordingly, as shown inFIG.12, a method of forming a can end10with a coined rivet12includes: providing1000a sheet material22with a base thickness, performing1002preliminary forming operations on the sheet material to form a shell blank, forming1004a coined rivet button14on the shell blank20, staking1005a tab46to the coined rivet button14and performing1006finishing operations on the can end10. Performing1002preliminary forming operation on the sheet material to form a shell blank20includes forming a central panel30, an annular countersink32, a chuck wall34, and a curl36, as is known. Alternately, the method of forming a can end10with a coined rivet12includes providing1001a shell blank20having a central panel30, an annular countersink32, a chuck wall34, and a curl36. As used herein, “finishing operations” include, but are not limited to, scoring the shell blank20, paneling the shell blank20, inspection of the shell blank20, or applying coatings and/or other surface treatments to the shell blank20.

In an exemplary embodiment, forming1004a coined rivet button on the shell blank20includes forming1010a bubble including a rivet portion top portion44, forming1020the bubble with a rivet portion top portion44into the coined rivet button14, and/or forming1022the bubble into a coined rivet button having a sidewall16, a generally planar top portion18and a peripheral upper edge19, forming1024a coined rivet button top portion with a thickness that is one of between more than about 0.003 inch and less than 0.0082 inch or about 0.004 inch, or, between about 0.004 inch and less than 0.0082 inch or about 0.006 inch, and/or forming1026the coined rivet button peripheral upper edge19to have a radius of between about 0.012 inch and 0.031 inch forming1026a coined rivet button top portion with a thickness that is one of between more than about 0.003 inch and less than 0.0082 inch or about 0.004 inch, or, between about 0.004 inch and less than 0.0082 inch or about 0.006 inch.

Further, in an exemplary embodiment, staking1005a tab46to the coined rivet button1includes providing1030a tab46with a body47, the tab body47including a coupling opening48, positioning1032the tab46over the coined rivet button14with the coined rivet button14extending through the tab coupling opening48, forming1034the coined rivet button14into the coined rivet12, and wherein the coined rivet12has an enhanced overlap of the tab body47.