Title of Invention

"METHOD AND APPARATUS FOR PRODUCING COUNTAINER BODY END COUNTERSINK"

Abstract

An annular groove of a can end with a reduced radius is disclosed. In one embodiment, this is by a method and apparatus which reworks the can end to increase the strength of the can end by reducing the radius of the annular groove of the can end. This method includes the step of reworking the annular groove of the can end to reduce a magnitude of the annular groove from a first radius to a second radius by exerting an inwardly-directed force on at least part of the annular groove and relative to the annular groove and collapsing at least part of the annular groove inwardly relative to the annular groove. The apparatus used in this reworking may include inner and outer die surfaces, wherein at least one of which engages a lower portion of the annular groove, and a punch, opposing and axially movable relative to the annular groove and die surfaces, for engaging the annular groove to exert inwardly-directed forces on the. lower portions of the annular groove to collapse the lower portions of the annular groove inwardly, toward the punch. The reduced radius may also be achieved in a blank and form station where an axially-directed force is exerted on a flange such that portions of the blank flex into engagement with a generally concave die surface.

Full Text

The present invention generally relates to a method of reforming a container end piece which is attachable to an open end of a container body, and to an apparatus for reforming such a container end piece. Metal containers typically have at least one end piece which is separately attached to the container to seal the same. In a two-piece design, the container body is drawn and ironed to have an integrally formed bottom and sidewall such that only a single end is necessary to seal the container body. In a three-piece design, a sheet of metal is rolled into a cylindrical configuration and joined along a seam which extends along the entire length of the container body such that there are two open ends, each of which is sealed by separately attaching an end thereto. Metal container designs must meet some types of strength requirements. For instance, in the case of beverage containers, which are typically of the two-piece design, often the containers are subjected to relatively high internal pressures. Moreover, the container must be able to withstand handling during shipping when containers are often dropped. The or each end which is separately attached to the container body is one part of the container which must meet these types of strength requirements. Balanced with the need for stronger containers, and including container ends, are economic and environmental considerations, such as reducing the amount of metal used to manufacture container ends which reduces material and transportation costs and the amount of raw materials used in can manufacture. Even a slight change in the gauge or thickness of the container or container end can result in significant economic and material usage savings due to the enormous volume of containers and container ends produced yearly. As such, there is a continued need to utilise thinner and thinner materials to form container bodies and container ends which still meet specified strength requirements. A first aspect of this invention relates in particular to a method of reforming a container end piece which is attachable to an open end of a container body and which comprises a central panel, an annular groove disposed about a perimeter of the central panel and having a curved portion extending between and integrally joining a chuckwall and an inner panel wall of the annular groove, the curved portion being located at the bottom of the annular groove, and a flange disposed about the annular groove, the method comprises the steps of: placing the end piece between a punch and inner and outer die surfaces of at least one reworking tool; and exerting with the reworking tool a force on the annular groove which is inwardly-directed relative to the annular groove so that at least part of the annular groove collapses inwardly relative to the annular groove to reduce the radius of the curved portion of the annular groove, and so that portions of the chuckwall and the inner panel wall are engaged between the punch and the inner and outer die surfaces. Such a method is known from patent document US-A-5356256. In that known method, the inner panel wall is engaged between the punch and the inner die surface, the chuckwall is engaged between the punch and the outer die surface, and the punch is moved between the inner and outer die surfaces so as to stretch or tension the annular groove into conformity with the shape of a nose of the punch. The method of the first aspect of the present invention is characterised in that, during the exerting step, the curved portion of the annular groove becomes engaged between the punch and at least one of the inner and outer die surfaces. It will therefore be appreciated that the curved portion of the annular groove can be collapsed inwardly to reduce its radius by being pushed by at least one of the die surfaces, so that the reduced radius can be achieved without substantial stretching or tensioning of the annular groove, thus resulting in reduced thinning of the material forming the annular groove. The exerting step preferably includes applying annular diametrically-opposed forces, which are inwardly-directed relative to the annular groove, on at least part of the annular groove, and also preferably includes exerting an axial force on the container end. The exerting step also preferably includes moving the punch relative to the annular groove and the inner and outer die surfaces to push at least one unsupported concave portion of the curved portion of the annular groove inwardly toward the punch, and more particularly preferably includes forcing the or each unsupported concave portion inwardly against and in generally conforming relation with a corresponding portion of the punch. In the case where the reworking tool has a vertical working surface adjacent the inner die surface, the exerting step preferably includes: engaging the vertical working surface against an upper portion of the annular groove provided by the inner panel wall, and exerting an inwardly-directed force toward the punch thereon; and engaging an intermediate portion of the annular groove provided by the inner panel wall, and exerting an outwardly-directed force away from the punch thereon. Also, in the case where the punch has a nose portion for engaging the curved portion of the annular groove, and an inner curved part disposed above the nose portion, the exerting step preferably includes: engaging an upper portion of the annular groove provided by the inner panel wall, and exerting an inwardly-directed force toward the punch thereon; and engaging the inner curved part of the punch against an intermediate portion of the annular groove provided by the inner panel wall, and exerting an outwardly-directed force away from the punch thereon. As a result, it is possible to inhibit substantial bowing of the central panel during the reforming operation and to assist the translation of the curved portion of the annular groove towards the die surfaces. The method preferably further includes the step of exerting an inwardly-directed force toward the punch on one of the chuckwall and the inner panel wall to form a second curved portion, separate from the first-mentioned curved portion, on the annular groove. The centre panel has a diameter which is preferably substantially unchanged by the reforming method. The annular groove has a depth which is preferably increased by the reforming method. The flange has a height which is preferably increased by the reforming method. A second aspect of the present invention is more particularly concerned with a complementary apparatus for reforming a container end piece having a central panel, an annular groove disposed about a perimeter of the central panel and having a lower curved portion, and a flange disposed about the annular groove, the apparatus comprising: inner and outer die surfaces for engaging the annular groove; and a punch, opposing and axially movable relative to the inner and outer die surfaces and the annular groove positioned therebetween, for engaging the annular groove against the inner and outer die surfaces to reduce the radius of the curved portion of the annular groove, wherein at least one of the inner and outer die surfaces exerts forces toward the punch and inwardly-directed relative to the annular groove on the annular groove as the punch is moved relative to the annular groove and the inner and outer die surfaces so that the curved portion of the annular groove collapses toward a corresponding portion of the punch. Again, such an apparatus is known from patent document US-A-5356256. The apparatus of the second aspect of the invention is characterised in that: at least one of the inner and outer die surfaces is arranged for engagement with the curved portion of the annular groove; and the punch is arranged to cause the curved portion of the annular groove to engage against that die surface, so that that die surface exerts a force toward the punch and inwardly-directed relative to the annular groove on the curved portion of the annular groove, as the punch is moved relative to the annular groove and the inner and outer die surfaces. In the case where the apparatus is to be used for reforming such a container end in which the annular groove comprises a chuckwall and an inner panel wall, the curved portion extending therebetween, and the annular groove comprises concave inner and outer segments adjacent the curved portion, the punch is preferably configured such that portions of the inner and outer segments are unsupported relative to and displaced from the punch and/or the inner and outer die surfaces are preferably configured to engage against portions of the inner and outer segments, respectively, to exert diametrically-opposed inwardly-directed forces on the inner and outer segments to push the inner and outer segments inwardly, toward the punch. The inner and outer die surfaces are preferably each angled between about 30 degrees and 60 degrees relative to a vertical reference axis. The apparatus preferably further includes a generally vertical working surface which is engageable on an upper portion of the annular groove to exert an inwardly-directed force, toward the punch, thereon, and the generally vertical working surface is preferably adjacent to and extends above the inner die surface. The apparatus preferably further includes an inclined surface adjacent and extending above the outer die surface and slidably engageable with the annular groove. The punch preferably has a nose portion for engaging at least the curved portion of the annular groove to push the annular groove against at least the inner and outer die surfaces. In this case, the punch preferably has inner and outer inclined surfaces adjacent the nose portion for supporting the annular groove in substantial conforming relation therewith upon collapse of the curved portion of the annular groove. These inner and outer inclined surfaces of the punch are preferably generally angularly oriented to correspond with the inner and outer die surfaces, respectively, and may thus preferably each be inclined at an angle of between about 30 degrees and 60 degrees relative to an axis of the punch. The punch preferably has an inner curved part disposed above the nose portion for engaging the annular groove to exert an outwardly directed force, away from the punch, on the annular groove. In accordance with a third aspect of the present invention, there is provided a method of reforming a container end piece which is attachable to an open end of a container body and which comprises a central panel, an annular groove disposed about a perimeter of the central panel and having a curved portion located at the bottom of the annular groove, and a flange disposed about the annular groove, the method comprising the step of: exerting a force on the annular groove which is inwardly-directed relative to the annular groove so that at least part of the annular groove collapses inwardly relative to the annular groove to reduce the radius of the curved portion of the annular groove; characterised in that the centre panel has a diameter which is substantially unchanged by the reforming method. Specific embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of an apparatus for reworking a can end according to principles of the present invention; Figs. 2A and 2B show the annular groove of a can end prior to and after reworking, respectively; Figs. 3A to 3C are progressive, fragmentary cross-sectional views of the annular groove of the can end and part of the apparatus of Fig. 1 prior to, during, and after reworking of the can end; and Figs. 4A and 4B are fragmentary cross-sectional views of a can end and part of a modified form of the apparatus of Fig. 1 prior to and after reworking, respectively. DETAILED DESCRIPTION Fig. 1 illustrates a container end in accordance with principles of the present invention. Such container ends may be attached to an open end of a container body to seal the contents therein. These container ends may be used in both two-piece and three piece designs. In the present invention, and as illustrated in Figs. 1 and 2A-2B, the container end 10 generally includes a substantially planar central panel 16, an annular groove 22 disposed about a perimeter of the central panel 16, and a flange 28 disposed about the annular groove 22. The annular groove 22 includes a first curved portion 34 (i.e., countersink) at the bottom of the annular groove 22. The annular groove 22 also includes a chuckwall 40 and an i nn«»r panel wall 46, the first curved portion 34 extending between and integrally joining the chuckwall 40 and the inner panel wall 46. The chuckwall 40 extends between and integrally joins the flange 28 and the first curved portion 34 and the inner panel wall 46 extends between and integrally joins the central panel 16 and the first curved portion 34, as illustrated in Figs. 1-2. Of importance, the first curved portion 34 of the annular groove 22 has an initial radius R,. The annular groove 22 has an initial depth De and a reworked depth De' . The flange 28 has an initial height H and a reworked height H'. According to one embodiment of a method in accordance with principles of the present invention, the container end 10, and specifically the annular groove 22, may be reworked to decrease the radius R, of the first curved portion 34, for instance, to R,', such that the first curved portion 34 is generally v-shaped. Such a decrease in the radius Rj of the first curved portion 34 provides increased resistance to buckling c-f the annular groove 22. In another embodiment of a method in accordance with principles of the present invention, the diameter Di of the central panel 16 before and after reworking remains generally constant. In this regard, the diameter Di of the central panel 16 initially and after reworking is substantially the same. •a..' Fig. 1 and 3A-3C illustrate a reworking tool 54 which is used according to a method in accordance with principles of the present invention. The purpose of the reworking tool 54 is to reduce the radius R1 of the first curved portion 34 to yield increased strength and buckle resistance of the annular groove 22. The reworking tool 54 accomplishes such a reduction in the radius of the first curved portion 34 by exerting inwardly-directed forces (i.e., toward the interior of the annular groove 22) on at least part of the annular groove 22 such that portions of the annular groove 22 are pushed inwardly, toward the interior of the annular groove (e.g., toward a center of curvature of the first curved portion 34), against corresponding segments of the reworking tool 54, as will be described in more detail below. In the illustrated embodiment of Figs. 1 and 2A-2B, the reworking tool 54 comprises a reform punch 70 and inner and outer dies 90, 110. The punch 70 includes a nose portion 74 for engaging an interior surface of the annular groove 22, and specifically, the first curved portion 34 of the annular groove 22, the nose portion 74 having a radius R2 and comprising inner and outer working surfaces 77, 79. The inner and outer working surfaces 77, 79 of the nose portion 74 terminate into inner and outer curved parts 76, 78 having radii R3 and R4, which terminate into substantially inclined and vertical surfaces 80, 82, respectively. The radius of the nose portion 74 of the punch 70 substantially corresponds to the radius of a reformed/reworked annular groove 22, and specifically, a reformed, generally v-shaped first curved portion 34. In this regard, the radius Rj of the nose portion 74 may be between about 0.003 inches and 0.007 inches, and preferably, less than about 0.010 inches. The radii of R3, R,, of the inner and outer curved parts 76, 78 of the nose portion 74 may be between about 0.028 inches and 0.032 inches each, and preferably, about 0.030 inches each. The inner and outer working surfaces 77, 79 are substantially symmetrically inclined relative to each other to achieve the reduced generally v-shaped radius Rt of the first curved portion 34. In this embodiment, the inner working surface 77 is inclined at an angle of about 45° relative to the vertical surface 80 and the outer working surface 79 is also inclined at an angle of about 45° relative to the surface 80. However, it is believed that these surfaces 77 and 79 may be disposed at an angle ranging from about 30° to about 60°. For purposes of engaging the chuckwall 40 of the annular groove 22, the inclined surface 82 is substantially oriented such that the inclined surface 82 corresponds to and is substantially parallel with an upper surface of the outer die 110, which will be described below. In the illustrated embodiment, the inclined surface 82 is oriented substantially 33° relative to the outer working surface 79. As illustrated in Figs. 1-3, the reworking tool 54 includes a punch 70 and chamfered inner and outer die surfaces 98, 114. In the illustrated embodiment, the inner and outer die surfaces 98, 114 are part of inner an^ outer dies 90, 110. The inner and outer die surfaces 98, 114 cooperate with the punch 70 to reduce the radius R! of the annular groove 22 positioned therebetween to R/. As shown in Figs. 3A-3C, the inner die 90 of the reworking tool 54 includes the annular chamfered inner die surface 98, a generally vertical working surface 96 and a convex working surface 92 having a radius R7. The inner die surface 98 is engageable with and against part of the unsupported (e.g., concave shaped or having a gap between the punch and the corresponding portion of the annular groove) inner segment 36 of the first curved portion 34 and has an inclination substantially corresponding to the desired reworked radius of the first curved portion 34 and the nose portion 74 of the punch 70. In this regard, the function of the inner die surface 98 is to engage part of the inner segment 36 generally normal thereto and to push or collapse the unsupported inner segment 36 of the first curved portion 34 inwardly, toward the punch 70, such that the unsupported inner segment 36 is pressed in substantially supported or conforming engagement against the corresponding surface of the nose portion 74 of the punch 70. The inner die surface 98 is preferably inclined at a matching angle with surface 77, which as noted above is between about 30° and about 60° relative to a vertical reference axis, and more typically at an angle of between about 42° and about 48° relative to the vertical reference axis, and in the illustrated embodiment at an angle of about 45° relative to the vertical reference axis shown. The generally vertical working surface 96 extends between and integrally joins the inner die surface 98 and the convex working surface 92. The vertical working surface 96 functions to frictionally engage or "catch" the annular groove 22, and in particular,, an upper portion (e.g. , point or band) 102 of the inner panel wall 46, during reworking operations with the punch 70 to substantially inhibit bowing of the central panel 16 of the container end 10 and to assist in the reduction of the radius of the annular groove 22 and the translation of the tip 48 of the annular groove 22 downwardly, toward the vertex of the inner and outer die surfaces 98, 114. In this regard, the inner die surface 98 and the vertical working surface 96, together with the punch 70, may cooperate to reduce the radius of the first curved portion 34 by exerting an inwardly-directed force (i.e., toward the punch 70) on the inner segment 36 of the annular groove 22 to collapse the inner segment 36 and exerting an inwardly-directed force (i.e., towards the punch 70) on the upper portion 102, as the inner curved part 76 of the punch 70 exerts an outwardly-directed force (i.e., away from the punch 70) on the annular groove 22 therebetween, at an intermediate portion (e.g., point or band) 104. The vertical working surface 96 and/or the inner curved part 76 may be structured to apply the radially outwardly-directed and radially inwardly-directed forces, respectively, annularly about the annular groove 22, or, alternatively, at selected portions about the circumference of the annular groove 22. The outer die 110 illustrated in Figs. 3A-3C, with which the punch 70 and inner die 90 cooperate to rework the annular groove 22, includes annular chamfered outer die surface 114 and inclined surface 116, which are substantially engageable against the annular groove 22, and specifically, the outer segment 38 and the chuckwall 40, respectively. It is believed that having a slidable engagement between the outer die 110 and the chuckwall 40 and the outer segment 38 substantially inhibits thinning of the chuckwall 40 during reworking operations. The outer die surface 114 is engageable with the unsupported (e.g., concave or having a gap between the punch and the corresponding portion of the annular groove) outer segment 38 of the first curved portion 34 and has an inclination substantially corresponding to the desired reworked radius of the first curved portion 34 and the nose portion 74 of the punch 70. In this regard, the function of the outer die surface 114 is to engage part of the outer segment 38 generally normal thereto and to push or collapse the unsupported outer segment 38 of the first curved portion 34 inwardly, toward the nose portion 74 of the punch 70, such that the outer segment 38 is pressed in substantially supported and conforming engagement against the corresponding surface of the nose portion 74 of the punch 70. The outer die surface 114 of the outer die 110, which is positionable proximate (i.e., with a gap therebetween or adjacent thereto) the inner die surface 98 of the inner die 90 for reworking operations, may be symmetrically inclined relative to the inner die surface 98 to form a substantially v-shaped annular groove 150. The outer die surface 114 is inclined at a matching angle with surface 79, which as noted above is between about 30° and about 60° relative to a vertical reference axis, and which is more typically at an angle of between about 42° and about 48° relative to the vertical reference axis, and in the illustrated embodiment is at an angle of about 45° relative to the vertical reference axis. The inclined surface 116 is oriented at an angle substantially corresponding to the inclined surface 82 of the punch 70 to facilitate slidable engagement with the annular groove 22, and specifically, the chuckwall 40 therebetween. In the illustrated embodiment of Figs. 3A-3C, the inclined surface 116 is oriented at an angle of about 33° relative to the outer die surface 114. As shown in Figs. 3A-3C, the inner and outer die surfaces 98, 114 of the inner and outer dies 90, 114, respectively, substantially form a gapped v-shaped groove 150 which accommodates and corresponds to the reworked first curved part 34 and the nose portion 74 of the punch 70. The depth of the v-shaped groove 150 and gap between the inner and outer dies 90, 110 are sufficient to allow reformation of the first curved portion 34 of the annular groove 22 as inwardly-directed forces (i.e.. toward the interior of the annular groove 22) are exerted on unsupported portions (e.g., parts of inner and outer segments) of the annular groove 22 and relative to the annular groove 22. In this regard, as the inner and outer segments 36, 38 of the first curved portion 34 are collapsed inwardly relative to the annular groove 22, the v-shaped groove 150 accommodates the resulting downward translation of the tip 48 of the annular groove 22. Referring to Figs. 3A-3C, in order to reduce the radius of the annular groove 22, and specifically, the first curved portion 22 (i.e., countersink) to increase the strength of the container end 10, the container end 10 is receivable between the punch 70 and the inner and outer dies 90, 110. In particular, the container end 10 may be initially positioned between the punch 70 and the inner and outer dies 90, 110 such that at least a portion of the annular groove 22 is received within at least part of the v-shaped groove 150 formed by the chamfered inner and outer die surfaces 98, 114 of the inner and outer dies 90, 110, as illustrated in Fig. 3A. In this regard, prior to reworking the annular groove 22 having a first radius, the annular groove 22 may be initially positioned between the punch 70 and the inner and outer dies 90, 110. In this initial configuration, the inclined surface 116 engages a portion of the chuckwall 40 and the outer die surface 114 engages part of the outer segment 38 of the first curved portion 34 generally normal thereto. Furthermore, the inclined surface 80 and the inner curved part 76 of the punch 70 engage the portions of the chuckwall 40 and the inner panel wall 46, respectively, and the tip 75 of the nose portion 74 of the punch 70 engages the first curved portion 34. In addition, the inner die surface 98 engages part of the inner segment 36 of the first curved portion 34 generally normal thereto and the vertical working surface 96 engages an upper portion of the inner panel wall 46. Of importance, the inner and outer segments 36, 38 of the first curved portion 34 are unsupported prior to reworking operations such that portions of the inner and outer segments 36, 38, are displaced from the inner and outer inclined working surfaces 77, 79 of the punch 70. In addition, there is a gap or space between the tip 48 of the annular groove 22 and the inner and outer dies 90, 110, as well as a gap between the vertical surfaces 99, 117 of the inner and outer dies 90, 110, respectively. In this regard, the punch 70 engages the annular groove 22 in three areas, namely, at the tip 75 of the nose portion 74 of the punch 70, at the inner curved part 76 of the punch 70 and along the inclined working surface 80, upwardly from the outer curved part 78. As noted above, the radius of the first curved portion 34 may be reduced by exerting an inwardly-directed force (i.e., toward the punch 70) on at least part of the annular groove 22 and relative to the annular groove 22 and by collapsing at least part of the annular groove 22 inwardly, toward the punch 70, as shown in Figs. 3A-3C. This is substantially accomplished by moving the container end 10, and, in particular, the annular groove 22 relative to the inner and outer dies 90, 110. In one embodiment, the punch 70 is moved axially relative to the annular groove 22 and the inner and outer dies 90, 110 such that an axial force is exerted on the annular groove 22 to drive the annular groove 22 against the inner and outer dies 90, 110. In this regard, and as illustrated in Figs. 3A-3C, annular inwardly-directed forces are applied against the unsupported inner and outer segments 36, 38 of the first curved portion 34 of the annular groove 22 and relative to the annular groove 22 as an axial force is exerted thereon. In one embodiment, diametrically opposed inwardly-directed forces (i.e., toward the interior of the annular groove 22) are applied generally normal to and against the unsupported inner and outer segments 36, 38 and relative to the annular groove 22, as shown in Fig. 3A. In this regard, the forces are symmetric and diametrically opposed as the inner and outer dies 90, 110 each push "in" on the first curved portion 34 of the annular groove 22. Due to the magnitude of inwardly-directed forces exerted on the inner and outer segments 36, 38, and the unsupported nature of the inner and outer segments 36, 38, such inwardly-directed forces applied against the inner and outer segments 36, 38 collapse the inner and outer segments 36, 38 progressively inwardly relative to the annular groove 22, such that the inner and outer segments 36, 38 collapse against the punch 70, and specifically, the inner and outer inclined working surfaces 77, 79 of the punch 70, respectively, in substantial conforming engagement therewith, resulting in a reduction in radius of the first curved portion 34, as shown in Figs. 3B-3C. In one embodiment of a method in accordance with principles of the present invention, wherein the initial radius of the first curved portion 34 is about 0.020 inches and the wall thickness of the annular groove 22 is about 0.0086 inches, inwardly-directed linear circumferential forces having a magnitude of between about 110 Ibs. and about 170 Ibs. (circumferential) may be applied on and relative to each of the inner and outer segments 36, 38 to collapse the unsupported inner and outer segments 36, 38 against the inner and outer inclined working surfaces 77, 79 of the punch 70. An axial force of between about 1000 Ibs. and about 1500 Ibs. may be exerted on the annular groove 22 to obtain such inwardly-directed forces on the inner and outer segments 36, 38. In order to facilitate reworking of the annular groove 22 as an inwardly-directed force (i.e., toward the punch 70) is exerted on the inner segment 36 to collapse the inner segment 36 inwardly, a method in accordance with principles of the present invention may also include exerting an inwardly-directed force (i.e., toward the punch, and generally away from the central panel) on the upper portion 102 and exerting an outwardly-directed force (i.e., away from the punch, generally toward the central panel 16) on an intermediate portion 104, above the inner segment 36. The radially outwardly-directed force may be exerted on the upper part of the annular groove 22 at the upper portion 102 by the vertical surface 96 during reworking operations to frictionally engage the inner panel wall 46. The outwardly-directed force (i.e., away from the punch 70, generally toward the central panel 16) may be exerted on the inner panel wall 46 at the intermediate portion 104 by the inner curved part 76 of the punch 70 during reworking operations. It is believed that exerting such forces on the annular groove 22 substantially inhibits bowing of the central panel 16 of the container end 10 and contributes to reformation of the annular groove 22 (i.e., reducing the radius of the annular groove 22) . It is also believed that exerting such forces on the annular groove 22 substantially retains the diameter Di of the central panel 16 of the container end 10, which is indicative that there has been no substantial thinning of the end 10. It is further believed that exerting such forces on the inner panel wall 46, coupled with the slidable interface between the outer die 110, chuckwall 40 and the punch 70, contributes to "directing" the tip 48 of the first curved portion 34 downwardly as the inner and outer segments 36, 38 collapse such that a substantially v-shaped first curved portion 34 results. The resulting reworked radius of the annular groove 22, and specifically, the reworked radius R1' of the first curved portion 34, is less than about 0.010 inches, and preferably less than about 0.007 inches, and even more preferably about 0.004 inches. The resulting reworked annular groove 22 also has an increased depth De' and flange height H' , each of which further increases the strength of the annular groove 22. In this regard, the described methodology can increase the annular groove depth between about 5% and about 8%, and can increase the flange height between about 1.5% and about 3%. In another embodiment, shown in Figs. 4A-4B, the punch 270 includes a nose portion 274 having a radius of R5 and an inner curved part 276 for engaging the annular groove 222 proximate the inner panel wall 246, the inner curved part 276 having a radius R6. The punch 270 also includes an inclined working surface 277 for engaging a portion of the annular groove 222 and a substantially linear inclined outer surface 280 for engaging the annular groove 222 proximate the chuckwall 240. Such a punch 270 is capable of reforming the annular groove 222 such that a substantially v-shaped first curved portion 234 is achieved to increase the strength thereof. In order to achieve a substantially v-shaped radius of the first curved portion 234 of the annular groove 222, the inclined working surface 277 may be angled between about 30° and about 60° relative to a vertical surface 282 of the punch 270, and in the illustrated embodiment at about 45° relative to the vertical surface 282, and the inclined outer surface 280 may be angled between about 11° and about 14° relative to a vertical surface 282 of the punch 270, and preferably, about 12.5° relative to the vertical surface 282. The inner and outer dies 290, 310 shown in Figs. 4A-4B are substantially similar to those shown in Figs. 3A-3C. However, in order to cooperate with the punch 270 to yield a substantially v-shaped reworked annular groove 222 of reduced radius, the inner die surface 298 of the inner die 290 and the outer die surface 330 of the outer die 310 substantially correspond to the inclined inner working surface 277 and the inclined outer surface 280 of the punch 270. In this regard, the inner die surface 298 of the inner die 290 is preferably disposed at a matching angle with the inner working surface 277, which as noted is between about 30° and about 60° relative to a vertical surface 299 of the inner die 290, and in the illustrated embodiment is at about 45° relative to the vertical surface 299; and the outer die surface 330 of the outer die 310 is disposed at a matching angle with the outer surface 280, which as noted is between about 11° and about 14° relative to a vertical surface 317 of the outer die 310, and preferably, at about 12.5° relative to the vertical surface 317. Referring to Figs. 4A-4B, the annular groove 222 is positionable between the punch 270 and the inner and outer dies 290, 310. In this embodiment, the punch 270 and inner die 290 engage the inner segment 236 and inner panel wall 246 substantially as described above with respect to Figs. 2A-2C. In this regard, an annular inwardly-directed force (i.e., toward the interior of the annular groove 222) may be applied on the unsupported inner segment 236 adjacent the first curved portion 234 and relative to the annular groove 222 to collapse the inner segment 236 against the inner inclined working surface 277 of the punch 270 to achieve a first curved portion 234 of reduced radius. According to this embodiment, the resulting reworked radius of the annular groove 222 is less than about 0.010 inches, and preferably, less than about 0.007 inches, and even more preferably, about 0.005 inches. Furthermore, the resulting reworked depth De of the annular groove 222 may increase from about 0.090 inches to about 0.095 inches, yielding an increase in the depth of the annular groove 222 of between about 4% and about 6%, and preferably, about 5%. In addition, the height H of the flange 228 may increase from about 0.270 inches to about 0.275 inches, yielding an increase in the height H of the flange 228 of between about 1.5% and about 2.0%, and preferably, about 1.8%. The above-described embodiments pertain to reworking an annular groove of a previously formed container end. First the annular groove is formed (e.g., at a blanking and forming station), and thereafter the container end is exposed to additional processing to at least reduce the radius of the annular groove and to also- potentially modify the configuration of the annular groove and/or adjacent container end structure. This reworking of the annular groove in accordance with the above may be done at a variety of locations in a production setting. For instance, reworking operations could be performed at a flange precurl or final curl station in the press used to form the container ends. These reworking operations could also be performed on a separate press than that used to produce the container ends (e.g., a conversion press). Container ends having an annular groove with a radius within the desired range of less than about 0.010 inches, and preferably from about 0.003 inches to about 0.007 inches, may also be produced directly from the container end forming process. Specifically, a container end having an annular groove within the noted range may be produced as the annular groove of the container end itself is being formed, as opposed to reforming or reworking the annular groove of an end piece. For instance, a container end with the noted desired radius may be produced in the blank and form stage of a container end press. One embodiment of a method and apparatus for directly achieving a container end with an annular groove of a radius of less than about 0.010 inches, and preferably from about 0.003 inches to about 0.007 inches, is illustrated in Figs. 5A-F. These figures progressively illustrate the formation of a container end having this type of radius in what is commonly characterized and a blank and form station. In the blank and form station 400, a generally circular blank or disk-like member is blanked out from a metal sheet 430 or othei. appropriate feed stock. This blank 434 is then drawn into a container end by the interaction of various dies discussed below. An annular groove with the above-described desired radius is achieved directly from this drawing procedure. Referring to Figs. 5A-5F, the blank and form station 400 includes first and second blanking dies 560, 570 and a support base 600 which is disposed radially outwardly of the blanking dies 560, 570. The metal sheet 430 is disposed on the support base 600 and below the first blanking die 560 and above the second blanking die 570. Subsequent axial movement of the blanking die 560 in the direction of the arrow A illustrated in Fig. 5A and relative to the stationary support base 600 produces the blank 434 from the metal sheet 430. As illustrated in Fig. 5A, the blank 434 is disposed above the second inner die 550 at this time. The second blanking die 570 is movable in the direction of the arrow A but is biased in a direction which is generally toward the first blanking die 560 or opposite to the direction of arrow A. This may be affected by having the second blanking die 570 be spring loaded and this spring (not shown) would then be compressed during the noted movement of the first blanking die 560 such that the second blanking die 570 would also move in the direction of the arrow A during this blanking operation. Other "movably biased" mechanisms could be used, such as an air system. Although the outer perimeter 442 of the blank 434 is disposed between the first and second blanking dies 560, 570 at this time, the blank 434 is able to "slide" or move relative to the first and second blanking dies 560, 570 which facilitates the formation of the flange 412 of the can end piece 410 (e.g., the blank 434 is able to slide between the first blanking die 560 and the second blanking die 570 during formation of the flange 412). The flange 412 is formed during a first portion of the drawing procedure in which the blank and form station 400 further utilizes first and second outer dies 510, 520 and first and second inner dies 530, 550. The first blanking die 560 continues to move in the direction of the arrow A as illustrated in Fig. 5A. The blank and form station 400 also exerts an annular, axially-directed force on an outer portion 438 of the blank 434 with the first outer die 510. In this regard, the first outer die 510 is moved axially relative to the blank 434 in the direction of the arrow B illustrated in Fig. 5A. The second outer 520 is movable in the direction of the arrow B, but is biased in a direction which is generally toward the first outer die 510 or opposite to the direction of the arrow B. This may be affected by having the second outer die 510 die be spring loaded and this spring (now shown) would then be compressed such that the second outer die 520 would also move in the direction of the arrow B illustrated in Fig. 5A. Other "movably biased" mechanisms could be used, such as an air system. After a certain amount of movement of the first and second outer dies 510, 520 and the first and second blanking dies 560, 570 relative to the support 600, the central portion of the blank 434 engages the second inner die 550 which is illustrated in Fig. 5B. Once this engagement is established, further movement of the first and second outer dies 510, 520 in the direction of the arrow A and of the first and second blanking dies 560, 570 in the direction of the arrow B causes a certain amount of sliding-like movement of the blank 434 relative to both the blanking dies 560, 570 (e.g., by sliding between the dies 560, 570), a certain amount of sliding-like movement between the blank 434 and the outer dies 510, 520 (e.g., by sliding between the dies 510, 520), and/or a stretching of the blank 434. Achieving the noted sliding-like movement is facilitated by having the first inner die 530 compressively engage the blank 434 against the second inner die 550 which has occurred prior to the position illustrated in Fig. 5B. About the time that the blank 434 is about to become disengaged with the blanking dies 560, 570 by the sliding-like movement as illustrated in Fig. 5B, further movement of the first blanking die 560 and therefore the second blanking die 570 in the direction of the arrow B is terminated. The movement of the outer dies 510 and 520 in the direction of the arrow A continues for a time after the blank 434 becomes disengaged with the blanking dies 560, 570 and results in corresponding portions of the blank 434 being forced to generally conform to the shape of the surfaces 512 and 514 of the first outer die 510 as illustrated in Fig. 5C. This is provided by sliding-like movements of portions of the blank 434 within the gap between the second blanking die 570 and the first outer die 510 and within the gap between the first outer die 510 and the second inner die 550. Once the first outer die 510 reaches its bottom dead center position which is shortly after the position illustrated in Fig. 5C, the flange 412 is completely formed. As can be seen in Fig. 5C, while the outer dies 510 and 520 continue their movement in the direction of the arrow B, some time after becoming disengaged with the blank 434 the blanking dies 560 and 570 move in the direction of the arrow C as a result of the bias of the second blanking die 570. The annular groove 420 is formed after formation of the flange 412 utilizing, inter alia, a first die surface 540 of the first inner die 530 which engages at least a part 450 of an intermediate portion 436 of the blank 434, the second die surface 514 of the first outer die 510 which cooperates with the first die surface 540, and the second outer die 520 which conformingly engages the flange 412. The first die surface 540 and the second die surface 514 are both inclined relative to a vertical reference axis. In one embodiment, the first die surface 540 is inclined at an angle ranging from about 30° to about 60° relative to this vertical reference axis and in the illustrated embodiment is about 45° relative to vertical, while the second die surface 514 of the first outer die 510 is inclined at an angle ranging from about 10° and about 15° relative to this vertical reference axis. The vertical portion of the first inner die 530 has a length of about 0.060 inches in the illustrated embodiment, and the first surface has a length of about 0.045 inches in the illustrated embodiment. In order to form the annular groove 420 from the intermediate portion 436 of the blank 434, an annular, axially-directed force is exerted on the newly formed flange 412 to effectively flex the intermediate portion 436 into the annular groove 420. Referring to Fig. 5D, the second outer die 520, as a result of its bias, exerts an axially-directed force on flange 412 generally in the direction of the arrow D as its associated spring transmits a force on the die 520. This may be due to the driving force on the first outer die 510 being disengaged or reversed so as to axially drive the first outer die 510 in the direction of the arrow D, or alternatively to simply removing the force from the die 510 which initially drove the die 510 in the direction of the arrow B as described above. Note that the first outer die 530 remains in a substantially fixed position to forcibly retain the central portion of the drawn blank 434 against the second inner die 550. As a result of this retention of the drawn blank 434 and the fcrce being exerted on the flange 412 by the second outer die 520 due to its expanding spring or other biasing mechanism, the intermediate portion 436 begins to flex away from the surface of the second inner die 550 as illustrated in Fig. 5D. Continued application of the noted axially-directed forces on the flange 412 by the second outer die 520, as well as the interaction of the second die surface 514 of the first outer die 510 with the blank 434, forces the intermediate portion to flex into conformance with the first die surface 540 of the first inner die 530 and for the base of the annular groove 420 to be disposed in the gap between the first inner die 530 and the first outer die 510, all as illustrated in Fig. 5E. As illustrated in Figs. 5A-5F, for purposes of accommodating formation of the annular groove 420 from the intermediate portion 436 of the blank 434, a gap 460 exists between the first outer and first inner dies 510, 530. In addition, formation of the annular groove 420 is accommodated by the second die surface 514 of the first outer die 510, which exerts an inwardly-directed force on and relative to the intermediate portion 436 during formation of the annular groove 420. In this regard, as the biased (e.g., spring-loaded) second outer die 520 pushes the flange 412 upwardly relative to the first and second inner dies 530, 550, the intermediate portion 436 of the blank 434 is further flexed into the gap 460 to form a generally concave groove 420. As shown in Fig. 5E, as the second outer die 520 continues to exert an axial force on the flange 412 to push the flange 412 upwardly, a part 450 of the intermediate portion 436 engages and is pushed against the first die surface 540 of the first inner die 530. In this regard, the first die surface 540 exerts an outwardly-directed force on and relative to the part 450 of the intermediate portion 436 as the flange 412 is moved upwardly relative to the first die surface 540. Thus, as the second outer die 520 continues to apply an axial force on the flange 412 to move the flange 412 upwardly relative to the first die surface 540 and the part 450, the second die surface 514 of the first outer die 510 and the first die surface 540 of the first inner die 530 cooperate to form the annular groove 420 as the upper portion 424, adjacent the part 450, is flexed therebetween, wherein the part 450 substantially conforms to the first die surface 540. In this regard, an annular groove 420 having a radius in the upper portion 424 of less than about 0.010 inches, and more preferably ranging from about 0.003 inches to about 0.007 inches, is formed in the blank and forming stage. The gap 460 is approximately 0.20 to about 0.03 inches wide at least at a point located above the first die surface 540. Once the first outer die 510 becomes disengaged from the container end 410, the first inner die 530 may be moved in the direction of the arrow E illustrated in Fig. 5F such that the end 410 may be removed from the station 400. EXAMPLE 1 End pieces formed according to principles of the present invention were tested in order to determine whether end pieces formed according to principles of the present invention exhibited improved strength characteristics (e.g., resistance to buckling). In this regard, end pieces configured according to the present invention having a gauge of 0.0088 inches and 0.0086 inches (formed group) were tested and compared to conventional end pieces having a gauge of 0.0088 inches and 0.0086 inches (control group). End pieces configured according to principles of the present invention exhibited improved strength characteristics. Formed group end pieces having a gauge of 0.0086 inch buckled at an average of 102.2 psi, while control group end pieces having a gauge of 0.0086 inches buckled at an average of 94.7 psi. Similarly, the formed group end pieces having a gauge of 0.0088 inches exhibited improved strength characteristics over the control group. Formed group end pieces having a gauge of 0.0088 inches buckled at an average of 106.4 psi, while control group end pieces having a gauge of 0.0088 buckled at an average of 99.2 psi. The container ends in accordance with principles of the present invention thereby clearly exhibit increased strength. This allows for a reduction in the thickness of the sheet metal used to form the container ends which not only reduces material costs, but also preserves our natural resources. Although reducing the gauge of the sheet metal typically dictates a loss of strength, by utilizing principles of the present invention at least some of this strength is recovered such that the container ends will still meet the various container body strength specifications. The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art. WE CLAIM: 1. A method of reforming a container end piece which is attachable to an open end of a container body and which comprises a central panel, an annular groove disposed about a perimeter of the central panel and having a curved portion extending between and integrally joining a chuckwall and an inner panel wall of the annular groove, the curved portion being located at the bottom of the annular groove, and a flange disposed about the annular groove, the method comprising the steps of: placing the end piece between a punch and inner and outer die surfaces of at least one reworking tool; and characterised by the steps of; exerting with the reworking tool a force on the annular groove, which force is inwardly-directed relative to the annular groove whereby at least part of the annular groove collapses inwardly relative to the annular groove thus reducing the radius of the curved portion of the annular groove, and whereby portions of the chuckwall and the inner panel wall are engaged between the punch and the inner and outer die surfaces; and engaging the curved portion of the annular groove between the punch and at least one of the inner and outer die surfaces during the exerting step. 2. A method as claimed in claim 1, wherein the exerting step comprises applying annular diametrically opposed forces, which are inwardly directed relative to the annular groove, on at least part of the annular groove. 3. A method as claimed in claim 1 or 2, wherein the exerting step comprises exerting an axial force on the container end. 4. A method as claimed in any preceding claim, wherein the exerting step comprises moving the punch relative to the annular groove and the inner and outer die surfaces to push at least one unsupported concave portion of the curved portion of the annular groove inwardly toward the punch. 5. A method as claimed in claim 4, wherein the exerting step comprises forcing the or each unsupported concave portion inwardly against and conforming to a corresponding portion of the punch. 6. A method as claimed in any preceding claim, where in: the reworking tool has a vertical working surface adjacent the inner die surface; and the exerting step comprises: engaging the vertical working surface against an upper portion of the annular groove provided by the inner panel wall, and exerting an inwardly-directed force toward the punch thereon; and engaging an intermediate portion of the annular groove provided by the inner panel wall, and exerting an outwardly-directed force away from the punch thereon. 7. A method as claimed in any preceding claim, where in: the punch has a nose portion for engaging the curved portion of the annular groove, and an inner curved part disposed above the nose portion; and the exerting step comprises: engaging an upper portion of the annular groove provided by the inner panel wall, and exerting an inwardly-directed force toward the punch thereon; and engaging the inner curved part of the punch against an intermediate portion of the annular groove provided by the inner panel wall, and exerting an outwardly-directed force away from the punch thereon. 8. A method as claimed in any preceding claim, comprising the step of exerting an inwardly directed force toward the punch on one of the chuckwall and the inner panel wall to form a second curved portion, separate from the first-mentioned curved portion, on the annular groove. 9. A method as claimed in any preceding claim, wherein the centre panel has a diameter which is substantially unchanged by the reforming method. 10. A method as claimed in any preceding claim, wherein the annular groove has a depth which is increased by the reforming method. 11. A method as claimed in any preceding claim, wherein the flange has a height which is increased by the reforming method. 12. An apparatus for reforming a container end piece in accordance with the method as claimed in any one of claims 1 to 11, said apparatus having a central panel, an annular groove disposed about a perimeter of the central panel and having a lower curved portion, and a flange disposed about the annular groove, the apparatus comprising: inner and outer die surfaces for engaging the annular groove; and a punch, opposing and axially movable relative to the inner and outer die surfaces and the annular groove positioned therebetween, wherein the annular groove is engaged against the inner and outer die surfaces to reduce the radius of the curved portion of the annular groove, at least one of the inner and outer die surfaces exerts inwardly-directed forces toward the punch on and relative to the annular groove as the punch is moved relative to the annular groove and the inner and outer die surfaces whereby the curved portion of the annular groove collapses toward a corresponding portion of the punch; at least one of the inner and outer die surfaces is arranged for engagement with the curved portion of the annular groove; and the punch is arranged to cause the curved portion of the annular groove to engage against that die surface, said die surface exerting a force toward the punch and inwardly-directed relative to the annular groove on the curved portion of the annular groove, as the punch is moved relative to the annular groove and the inner and outer die surfaces. 13. An apparatus as claimed in claim 12, for reforming such a container end in which the annular groove comprises a chuckwall and an inner panel wall, the curved portion extending there between, and the annular groove comprises concave inner and outer segments adjacent the curved portion, wherein the punch is configured whereby portions of the inner and outer segments are unsupported relative to and displaced from the punch. 14. An apparatus as claimed in claim 13,wherein the inner and outer die surfaces are configured to engage against portions of the inner and outer segments, respectively, to exert diametrically-opposed inwardly-directed forces on the inner and outer segments to push the inner and outer segments inwardly, toward the punch. 15. An apparatus as claimed in any of claims 12 to 14, wherein the inner and outer die surfaces are each angled between 30 degrees and 60 degrees relative to a vertical reference axis. 16. An apparatus as claimed in any of claims 12 to 15, having a vertical working sur face which is engageable on an upper portion of the annular groove to exert an inwardly-directed force, toward the punch, thereon. 17. An apparatus as claimed in claim 16, wherein the vertical working surface is adjacent to and extends above the inner die surface. 18. An apparatus as claimed in any of claims 12 to 17, having an inclined surface adjacent and extending above the outer die surface and slidably engageable with the annular groove. 19. An apparatus as claimed in any of claims 12 to 18, wherein the punch has a nose portion for engaging at least the curved portion of the annular groove to push the annular groove against at least the inner and outer die surfaces. 20. An apparatus as claimed in claim 19, wherein the punch has inner and outer inclined surfaces adjacent the nose portion for supporting the annular groove in substantial conforming relation therewith upon collapse of the curved portion of the annular groove. 21. An apparatus as claimed in claim 20, wherein the inner and outer inclined surfaces of the punch are angularly oriented to correspond with the inner and outer die surfaces, respectively. 22. An apparatus as claimed in claim 20 or 21, wherein the inner and outer inclined surfaces of the punch are each inclined at an angle of between about 30 degrees and 60 degrees relative to an axis of the punch. 23. An apparatus as claimed in any of claims 19 to 22, wherein the punch has an inner curved part disposed above the nose portion for engaging the annular groove to exert an outwardly directed force, away from the punch, on the annular groove.

Documents:

164-del-1997-abstract.pdf

164-del-1997-claims.pdf

164-del-1997-correspondence-others.pdf

164-del-1997-correspondence-po.pdf

164-del-1997-description (complete).pdf

164-del-1997-drawings.pdf

164-del-1997-form-1.pdf

164-del-1997-form-13.pdf

164-del-1997-form-19.pdf

164-del-1997-form-2.pdf

164-del-1997-form-26.pdf

164-del-1997-form-3.pdf

164-del-1997-form-4.pdf

164-del-1997-form-6.pdf

164-del-1997-gpa.pdf

164-del-1997-petition-137.pdf

164-del-1997-petition-138.pdf