Method and apparatus for preventing buckle of beer cans during pasteurization
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of co-pending application Ser. No. 940,563, filed Sept. 8, 1978. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the processing of canned beer, and is particularly directed to eliminating the problem of buckling of the top and bottom of a beer can during the pasteurization of beer. 
     It is conventional to pasteurize canned beer by conveying filled and sealed cans of beer to a heat treatment station at which the beer is pasteurized. This heat treatment is intended to inactivate whatever yeasts remain in the beer to prevent further fermentation. 
     During such heat treatment, carbon dioxide is released from the beer and adds to that already at the headspace of the can, thereby raising the internal pressure on the can to the greatest degree it will normally experience. This high pressure can buckle the shape of the can, particularly its top and bottom which are the weakest areas of the can in this respect. To prevent such buckling, a much thicker metal sheet is used to strengthen the can&#39;s top and bottom, compared to the sidewall. However, this increases the cost of the can. 
     Similar problems with can buckling have long been known in industries other than beer canning. In some instances, a food-containing can is mated with at least two and up to four shape-retaining pieces which are held by vice-like members during the heat treatment. Such a solution has not found acceptance in the beer canning industry, however, because it would require major changes within the existing conventional pasteurizer, such as: new equipment for placing, holding, and conveying all the close-fitting, shape-retaining pieces over each beer can, and; new heat transfer equipment for heating beer cans that are surrounded by these pieces. Such changes are not conveniently adaptable to the conventional pasteurizer which is designed to heat and convey each beer can as part of a several-foot-wide, standing group by using overhead hot-water sprays and walking beam conveyors, respectively. 
     Thus, prevention of can buckling has only been achieved by using a much thicker gauge metal sheet for the ends of beer cans, an undesirable solution. 
     OBJECTS OF THE INVENTION 
     Accodingly, it is an object of the invention to provide a method and apparatus for preventing buckling of filled beer cans during the beer&#39;s pasteurization. 
     It is a more specific object of the invention to provide such a method and apparatus which is usable with the equipment of conventional pasteurizers and which is relatively inexpensive. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The above and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings of which: 
     FIG. 1 illustrates a conventional beer can with its top partially broken away to reveal its double seam; 
     FIG. 2 is a perspective view of an anti-buckle ring for inhibiting buckle in the top of a beer can; 
     FIG. 3 is a cross-sectional view of the anti-buckle ring shown in FIG. 2; 
     FIG. 4 is a cross-sectional view illustrating approximately one-half of the seamed top of a beer can and the way in which the double seam and related areas are captured by the anti-buckle ring of FIG. 2; 
     FIG. 5 is a schematic illustration of a beer canning method utilizing the anti-buckle ring of FIG. 2; 
     FIG. 6 is a top plan view, somewhat schematic, of a can/ring assembler for use with the method depicted in FIG. 5; 
     FIG. 7 is a sectional view taken along lines 7--7 of FIG. 6; 
     FIG. 8 is a cross-sectional view of an alternate embodiment of the anti-buckle ring; 
     FIG. 9 is a cross-sectional view illustrating approximately one-half of the seamed top of a beer can and the way in which its double seam is captured by the anti-buckle ring of FIG. 8; 
     FIG. 10 illustrates a conventional beer can with its bottom partially broken away to reveal the construction of the base area of the can; 
     FIG. 11 is a perspective view of an anti-buckle ring for inhibiting buckle in the bottom of a beer can; 
     FIG. 12 is a cross-sectional view of the ring shown in FIG. 11; 
     FIG. 13 is a cross-sectional view illustrating approximately one-half of the bottom of a beer can and the way in which it mates with the anti-buckle ring shown in FIGS. 11 and 12; 
     FIG. 14 is a cross-sectional view of a modified anti-buckle ring for inhibiting buckle in the bottom of a beer can; and 
     FIG. 15 depicits a beer can mated with the anti-buckle rings of FIGS. 2 and 11. 
    
    
     SUMMARY OF THE INVENTION 
     As disclosed in said co-pending application Ser. No. 940,563, buckling of beer-can tops during the beer&#39;s heat treatment in the pasteurizer is prevented by, prior to entering the pasteurizer, capturing the top of the can within an anti-buckle ring means which encircles and braces the seamed top of the can from radial displacement. With the ring means and the can mated, the combination is transported through the pasteurizer. After pasteurization, the ring means is automatically removed from the can for further use with another can. By this method, the seamed top of each beer can is held by the ring means from radial displacement which may otherwise occur during the heat treatment within the pasteurizer, and buckling of the top of the can is prevented by virtue of the seamed top being held from radial displacement. 
     According to the invention of the prevent application, the bottom of a beer can is also prevented from buckling by utilizing another anti-buckle ring of a somewhat different configuration. Prior to a beer can entering the pasteurizer, the bottom of the can is captured by an anti-buckle ring which braces the base area of the can&#39;s bottom from substantial radial displacement, while permitting the can&#39;s bottom panel to bulge outwardly. With the latter ring and the can mated, the combination is transported through the pasteurizer. After pasteurization is completed, the anti-buckle ring is automatically removed from the bottom of the can. 
     Preferably, each can enters the pasteurizer with its top mated to one anti-buckle ring and its bottom mated with another anti-buckle ring. In this manner, key portions of a can&#39;s top and bottom are held from radial displacement and buckling is prevented in each end of the can. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown a conventional beer can 10 having a bottom 12, a top 14, and a circumferential sidewall 16. Typically, the bottom 12 and the sidewall 16 of the can body are formed from a single piece of metal sheet and the top 14 is formed from a separate piece of metal sheet. To join the top 14 to the sidewall 16, the top is interlaced with the sidewall to form a double-hook interlock called a &#34;double seam&#34; as indicated at 18. Voids in the double seam 18 between the top 14 and the sidewall 16 are sealed by a rubber-resin-based compound that is applied on the inside flange of the top after the top has been formed. 
     During pasteurization of the beer, the can and its contents are subjected to high temperatures, usually by subjecting the can to a hot-water spray. As a result of the high temperature to which the beer rises, carbon dioxide is released from the beer and adds to that already in the headspace in the can. If the pressure of the carbon dioxide becomes greater than the beer can top 14 and the double-seam 18 can resist, the double-seam becomes distorted radially outward and the top buckles upwardly. In the past, a relatively thick metal sheet has been used to fabricate the top 14 to resist such buckling. 
     In order to use a thinner gauge and, hence, less expensive material for the top 14, an anti-buckle means preferably in the form of a ring 20, which may be constructed as shown in FIGS. 2 and 3, is slipped over the top of the can before pasteurization of the beer, all as described in said co-pending application. 
     Specifically, the ring 20 has a central aperture 22 surrounded by a circumferential extending outer flange 24. The flange 24 includes a relatively thick base portion 26 extending radially toward the aperture 22 and a narrower top portion 28, the latter of which meets the base portion 26 at an interface 30. Disposed in the flange 24 is a circularly extending groove 32 defined by a bottom wall 34, an outer wall 36 and an inner wall 38, as best shown in FIG. 4. Extending upwardly from the base portion 26 is a circumferentially extending inner flange 40 bounded by the inner wall 38, a rounded top wall 42, a rounded fillet 44, and an innermost wall 46. 
     As shown in FIG. 4, the outer flange 24 and the base portion 26 are dimensioned such that the ring is adapted to slip onto the top of a beer can with the base portion of the ring at least closely adjacent the top of the double seam and the outer flange 24 holding the double seam from radial displacement. More specifically, the double seam 18 is received within the groove 32 is shown, whereby the wall 36 is closely adjacent or in contact with the outer circumferential portion of the double seam 18 as at the seaming wall radius 48. Further, the bottom wall 34 is in contact with or closely adjacent to the bottom or seaming panel 50 of the double seam 18, and the wall 38 of the inner flange 40 is in contact with or closely adjacent to the inner circumferential portion of the double seam 18, preferably at the so-called chuck wall 52 of the can. The top wall 42 is contoured to conform to the contour of the chuck wall radius 54 and is in contact with or closely adjacent thereto. The rounded fillet 44 is likewise contoured to conform to the contour of the can&#39;s panel radius 56 and is in contact with or closely adjacent thereto. 
     The reasons for including the inner flange 40 are to brace the double seam 18 from radial displacement, to prevent buckling at chuck wall radius 54, panel radius 56, and panel 58 that can occur if the panel is permitted to bulge unsymmetrically, and to prevent separation between the chuck wall 52 and the body wall 60 of the can body, particularly for cans having deep aluminum tops. It has been found that increased pressure within the beer can causes the domed center portion of the beer can top to bulge away from the contents. This bulging action concurrently increases the angle between the chuck wall 52 and the body wall 60. The points along the chuck wall 52 which resist this tendency to separate become the weakest points and become distored radially outward, adjacent points being distored radially inward. This also causes distortion of the chuck wall radius 54, the panel radius 56 and, of course, the domed top of the beer can. Because of the inclusion of the inner flange 40 and the contact or at least close proximity between mutually conforming portions of the can&#39;s top and the ring&#39;s inner flange, the buckling of the beer can top and the distortion of the double seam is prevented. 
     A beer processing method utilizing the anti-buckle ring 20 is illustrated schematically in FIG. 5. The conveying path for the beer cans only is illustrated by the line having small rectangles thereon, the conveying path for the anti-buckle ring only is illustrated by the lines having circles thereon, and the conveying path for the beer cans when mated with the anti-buckle ring is shown by the heavy solid lines. 
     Near the bottom of FIG. 5 there is shown schematically a beer filler 62 which is conventional in construction for filling each can with beer. The filled beer cans are then conveyed to a conventional double seamer 64 which forms seams such as the double-seam 18 in the top of the beer cans. After the seams are formed, the cans are conveyed to an inverter indicated schematically at 66 for inverting the beer cans so that their top is facing downwardly. Following their inversion, the beer cans are conveyed, top down, along the path 68 to an assembler 70 which mates each beer can with an anti-buckle ring. 
     The conveyance path for the anti-buckle ring begins at a collection/dispersement hopper 72 from which the rings are conveyed via a path 74 to the assembler 70. A return conveyor path 76 returns rings to the hopper 72 which are in excess of the number of beer cans conveyed to the assembler 70. 
     At the assembler 70, described in more detail hereinafter, an anti-buckle ring is mated with the downwardly facing top of each beer can and then the combination of the beer can and its anti-buckle ring are conveyed along a path 78 to a pasteurizer 80. The pasteurizer 80 may be of conventional design, wherein the cans are heat treated by an overhead spray, in which case the anti-buckle rings, because of their small geometry and their minimum covering of the cans, do not substantially hinder the heating of the cans or their contents. Moreover, the fact that the rings do not substantially interfere with the pattern of spray allows their use with conventional pasteurization processes, especially when the cans are inverted during pasteurization. 
     When pasteurization is complete, the cans leave the pasteurizer 80 in single file, their tops facing downwardly and resting on their anti-buckle rings. Thus disposed, the cans and rings are conveyed along a path 82 to a can/ring separator indicated schematically at 84. At the separator 84, the cans are separated from their respective rings so that the rings may be returned via path 86 to the hopper 72 for reuse. The cans are preferably inverted by the separator 84 and conveyed along a path 88 with their tops facing upwardly for further processing or shipment. 
     Separator 84 may be of the type which first inverts the cans and then passes them under an overhead magnetic conveyor which lifts the rings away from the cans. The rings are then conveyed to the path 86 for further use and the cans are conveyed to the path 88. When this type of separator is used, the rings 20 are, of course, constructed with a magnetically attractable material. 
     In a preferred embodiment of the separator 84, the cans from the pasteurizer 80 are transferred onto a flat top, two-belt conveyor where they are spaced at fixed intervals by a feed screw, for example. Two L-shaped, metal side strips, with horizontal ledges pointing the center of the can travel path and vertical ledges downward, guide the rings and hold them during the separation. Cam driven pusher rods, attached to a conveyor within the two flat top belts, are moved in synchronism with the screw conveyor such that they enter the anti-buckle ring openings 22 from the bottom and push the beer cans away from the rings, lifting the beer cans onto another level to be conveyed to the path 88. After the pusher rods withdraw from the cans, they are lowered to exit from the ring&#39;s opening 22 so that the rings may be conveyed back to the hopper 72 via the path 86. 
     Referring now to FIG. 6, there is shown a preferred embodiment of the can/ring assembler 70. The assembly 70 includes a feed conveyor 90 for the beer cans 10, a feed conveyor 92 for the anti-buckle rings 20, a turret assembly 94 for mating the rings 20 with the beer cans 10, and a rotating disc 96 for removing the mated beer cans and rings from the turret assembly 94 and for placing them on a conveyor 98. 
     The feed conveyor 90 includes a driven belt 100 for carrying the cans 10 toward the turret assembly 94 and a feed screw 102 for spacing the beer cans at fixed intervals on the belt 100. 
     The turret assembly 94 includes a rotating pocket turret 104 (partly broken away) having semi-circular pockets 106 spaced around its outer periphery for capturing the beer cans 10 as illustrated. Thus, as a beer can reaches the end of the belt 100, it is grabbed by a pocket 106 and moved in an arcuate path as indicated by the arrow 108. 
     Spaced below and rotating in synchronism with the pocket turret 104 is a starwheel 110 for grabbing the anti-buckle rings 20 as they arrive from the conveyor 92. The starwheel 110 includes a plurality of finger-like protrusions 112 spaced around the periphery of the starwheel 110. Between adjacent protrusions 112, there are gaps 114 into which the rings 20 are urged by the protrusions 112. Thus, as the turret assembly 94 rotates, the beer cans are urged into the pockets 106 of the pocket turret 104 and the anti-buckle rings 20 are captured by the gaps 114 in the starwheel 110. The gaps 114 are equal in number to the pockets 106 and vertically aligned therewith so that each ring 20 is in vertical alignment with its associated beer can as the two are rotated in the direction of the arrow 108. 
     The turret assembly 94 also includes a separator plate 116 which is located between the starwheel 110 and the pocket turret 104. As shown, the separator plate 116 has a pair of parallel, arcuate edges 118 and 120 which extend from a leading edge 122 of the plate 116 to its trailing edge 124. Separator plate 116 is spaced beneath the pocket turret 104 by a distance such that the bottoms of the beer cans 10 rest on the upper surface of the separator plate 116 while the cans 10 are being conveyed from the leading edge 122 of the plate 116 to its trailing edge 124. This arrangement is shown more clearly in FIG. 7. As shown at the right of FIG. 7, a beer can 10 is carried by the pocket turret 104 with its top resting on the separator plate 116. Below the separator plate 116 is a ring 20 held in a gap 114 in the starwheel 110 between adjacent starwheel protrusions 112. As the turret assembly 94 rotates the can 10 and its associated ring 20 beyond the trailing edge 124 of the plate 116, the beer can 10 falls by gravity into the ring 20, as illustrated in the leftmost portion of FIG. 7. In this condition, the side wall of the can 10 is still held by the turret 104 but the top of the can 10 is now in a gap 114 between adjacent starwheel protruberances 112. 
     Also shown in FIG. 7 is a plate 126 (omitted from FIG. 6 for clarity) which extends circularly beneath the starwheel 110 for supporting the rings 20 during their arcuate conveyance by the starwheel 110. When the can 10 drops into the ring 20, both the can and the ring 20 are supported by the plate 126. 
     As the cans and rings are conveyed in mating relationship, they eventually are urged onto the rotating disc 96 by a guide rail 128 which is supported by means not shown for engaging the side wall of a can and for directing it onto the rotating disc 96, the latter of which then rotates the cans and their mating rings in the direction of the arrow 130. The conveyor 98 which is disposed beneath the disc 96 receives cans and their mating rings from the disc 96 for conveyance to the pasteurizer 80. Although not shown in FIG. 6, a guide rail similar to guide rail 128 may be disposed above the rotating disc 96 and the conveyor 98 for urging the beer cans 10 onto the conveyor 98. 
     The anti-buckle ring described above and in said co-pending application provides superior anti-buckle protection, particularly for beer cans having deep tops, i.e., cans whose tops extend approximately one-quarter inch below their seaming panel. To prevent buckling of cans whose tops are more shallow, an alternate anti-buckle ring 132 may be employed, as shown in FIGS. 8 and 9. 
     As shown in cross-section, the ring 132 has a central aperture 134 surrounded by a substantially flat base portion 136. The outer radial portion of the ring 132 comprises an outer, vertically extending flange 138 having a relatively thick bottom portion 140 and a narrower top portion 142 meeting the bottom portion 140 at an interface 144. The base portion 136 and the flange 138 are dimensioned such that the ring 132 is adapted to slip onto the top of a beer can with the base portion 136 engaging or at least closely adjacent the top of the double-seam and with the flange 138 engaging or closely adjacent the double-seam. With this arrangement, the flange 138 holds the double-seam from outer radial displacement during heat treatment or pasteurization of the beer, thereby preventing the top of the can from buckling in response to high internal pressure on the can. To mate the ring 132 with a beer can, the ring 132 is slipped over the top of the beer can with the top portion 142 extending toward the bottom of the can. 
     FIG. 9 is an enlarged view of one side of the double-seam of the can illustrating the way in which the ring 132 preferably engages the can. As shown, the top of the can is facing downwardly so that the double seam 18 rests on the base portion 136 of the ring. In addition, the bottom portion 140 of the flange 138 completely encircles the double-seam 18 and is closely adjacent to or in contact with a portion 146 of the double seam 18. The upper portion 142 of the flange 138 encircles the sidewall 16 of the can and is in contact therewith or at least closely adjacent to it. The upper portion 142 of the flange does not extend all the way to the bottom of the can; preferably, it extends only about one inch beyond the top of the can to make insertion of the can into the ring easy and to reduce the expense of the ring. 
     With the arrangement shown in FIG. 9, it is the bottom portion 140 of the flange 138 which holds the double-seam 18 from radial displacement. The horizontal portion 136 and the top portion 142 of the flange function to locate the bottom portion 140 with respect to the double-seam 18 but do not have any substantial buckle-resisting function. The ring 132 may be used with the apparatus illustrated in FIGS. 5-7 as described above. 
     By virtue of the above described method and apparatus for processing beer cans, it is possible to use thinner gauge or different alloys for the beer can top, thereby reducing the cost of a beer can and yet preventing buckle of the beer can during heat treatment. Moreover, the anti-buckle ring described herein is adapted for fast feeding characteristics during can/ring assembly and separation and remains stably mated with a beer can during high-speed can travel. In addition, the use of the anti-buckle ring requires no changes in conventional pasteurization techniques. 
     In some instances, a beer can is made of three pieces of metal, one piece for the can body and the other two pieces for the can&#39;s top and bottom. With such three piece beer cans, both the top and the bottom of the can may have a double seam, in which case the anti-buckle rings described above may be used to capture either the top of the can, the bottom of the can, or both. Hence, when reference herein is made to a can&#39;s double-seamed top of a conventional two piece beer can, it is intended to also include the double-seamed bottom of a three piece beer can. 
     According to the invention of the instant application, a beer can need not have a double-seamed bottom in order to utilize the anti-buckle principles described above. Beer cans whose bottoms include a conventional bottom panel and base area are also inhibited from buckling by employing another type of anti-buckle ring. Such a beer can 200 is illustrated in FIG. 10 and is depicted in the inverted position it normally assumes prior to pasteurization. 
     As shown, the can 200 has a bottom 202, a top 204, and a circumferential sidewall 206. Typically, the bottom 202 and the sidewall 206 of the can body are formed from a single piece of metal sheet. The top 204 is joined to the sidewall 206 by the usual double seam, as indicated at 208. 
     The bottom 202 of the can includes a base area 210 and a bottom panel 212. The bottom panel covers the bottom center of the can and may extend by curving into the can as shown at 214. Prior to meeting the sidewall 206, the bottom panel curves toward the bottom of the can to form a curved radius portion 216 which constitutes the beginning of the base area 210. 
     Extending substantially vertically from the radius portion 216 toward the bottom of the can is an inner base wall 218 which may be either straight or frusto-conical. The wall 218 curves outwardly toward the sidewall 206 to form a curved base radius 220. 
     Joining the sidewall 206 to the base radius 220 is an outside base wall 222 which may also be straight or frusto-conical. 
     With the illustrated can structure, the base area 210 acts primarily as a support for the can 200 and its contents in most of the canning process and all subsequent phases leading toward consumer use. The base area 210 and the panel 212 are designed to co-operatively resist internal can pressures that would buckle the bottom 202, causing an unstable base area. 
     As stated above, the can 200 and its contents are subjected to high temperatures during pasteurization, usually by subjecting the can to hot-water spray. As a result of the high temperature to which the beer rises, carbon dioxide is released from the beer and adds to that already in the headspace of the can. If the pressure of the carbon dioxide becomes greater than the beer can bottom 202 can resist, the outward bulge of the bottom panel 212 distorts the inside base wall 218 radially inward to ultimately yield a buckle. In the past, a relatively thick metal sheet has been used to fabricate the bottom 202 to resist such buckling. 
     In order to use a thinner gauge and, hence, less expensive material for the bottom 202, an anti-buckle means, preferably in the form of a ring 224 which may be constructed as shown in FIGS. 11 and 12, is slipped over the bottom of the can 200 before pasteurization of the beer. 
     As shown, the ring 224 has a central aperture 226 which is surrounded by a circumferentially extending, U-shaped member comprising an inner circumferential flange 228, a substantially horizontal base portion 230, and a circumferential outer flange 232, together defining a groove 234 for receiving the base area 210 of the can. Radially inward of the flange 228, the central aperture 226 is formed to permit the bottom panel of the can to bulge outwardly when the ring 224 is mated with a can as described below. 
     Referring now to FIG. 13, the mating relationship between the bottom of the can 200 and the ring 224 is illustrated in detail. As shown, the ring&#39;s flanges 228 and 232 and a base portion 230 are mated with most portions of the can&#39;s base area 210. The most important support is provided at the inner base wall 218 and radius 216 that connects the panel 212 and the inner base wall. The flange 228 includes a support radius 238 which either abuts or is closely adjacent to the can&#39;s radius 216, and an inside base support wall 240 which either abuts or is closely adjacent to the can&#39;s inner base wall 218 to provide this important support to prevent radially inward displacement at this section. 
     It should be noted that an angular gap exists between the panel 212 near the radius 216 and a lower wall 242 on the flange 228 so that panel bulge will not push the ring out of its mated position with the can bottom. The central aperture 226 also permits the dome-shaped bottom panel 212 to bulge outward without pushing the ring 224 out of its mated position with the can&#39;s bottom. The central aperture 226 also permits a rod to enter through it to contact the bottom panel 212 so the can may be separated from the ring 224. It should be noted, however, that a central aperture 226, while preferable, is not a mandatory feature. Sufficient space may be incorporated in a ring to allow the bottom panel 212 to bulge. Where a ring is constructed without a central aperture, such a ring may be lifted from the can by a vacuum cup or any other suitable means. 
     The base radius 220 of the can is abutted by or is at least closely adjacent to a base-radius support radius 244 on the ring to hold the base radius from inward radial displacement. The radius 244 merges into a ring wall 246, followed by an inclined ring wall 248 and a substantially vertical ring wall 250, all of which approximately conform to the contour of the can&#39;s outside base wall 222 to provide mating stability between the ring 224 and the can. The requirement of closeness between the can&#39;s base wall 222 and ring walls 246, 248 and 250 cannot, however, be critical due to manufacturing tolerances in the outside diameter of the can, as by tooling wear in fabricating the can&#39;s sidewall 206. 
     Use of the ring 224 is similar to the above described use of the anti-buckle ring for the tops of beer cans. Specifically, after a double seam has been formed in each filled can, the can is inverted. The purpose of such inversion is to use the internal can pressure developed during pasteurization to force beer out of faulty double seams or fractures in the top of the can. Such faulty cans are detected and removed by a fill detector located downstream of the pasteurizer. 
     After inversion, each can proceeds to a conventional assembling machine such as described above for mating a ring 224 with a can. The mated can and ring are conveyed to a pasteurizer in which they are conventionally conveyed en masse in a group several feet wide. 
     In the pasteurizer, water from overhead sprays fills the central aperture 226 to form a pool bounded by the bottom panel 212 and an inner wall 252 on the flange 228. The water flows outward over an upper ring wall 254 and outer ring walls 256 and 258. The surface tension of the water causes it to move from the wall 258 to the sidewall 206 where heat transfer occurs as water flows down the sidewall. 
     Upon exit from the pasteurizer, the ring 224 may be separated from the can by a mechanical lifter, vacuum, or a magnetic device if the ring is made of a magnetically attractable material, depending on the brewer&#39;s preference. 
     As for dimensions of the ring 224, its outside diameter as defined by the wall 258 need be no more than the outside diameter of the anti-buckle ring described above which may mate with the top of the can. However, if only the ring 224 is employed and no ring is simultaneously used to prevent buckle of the top of a can, the outside diameter of the ring 224 may be reduced. For example, FIG. 14 illustrates a modified anti-buckle ring 224a for the bottom of a beer can. The ring 224a is similar to the ring 224 except that its outer flange 232a has been shortened. With this modification, the outside diameter of the ring 224a is no greater than the outside diameter of the can with which it mates. Hence, ring-to-ring contact between adjacent cans in the pasteurizer is avoided and the cans are conveyed through the pasteruizer in a more stable manner. 
     The ring 224a may be constructed of metal, plastic, or a combination of metal and plastic which are compatible with brewery conditions and overall requirements. The mating stability of ring 224a can be enhanced by including a magnetic material on the ring for steel beer cans or a pressure-sensitive adhesive at the radius 216 or inner base wall 218 of aluminium beer cans. 
     Although a brewer may elect to use only an anti-buckle ring on the top of a beer can or only an antibuckle ring on the bottom of a beer can, both rings can be used simultaneously. In the latter case, the top and bottom of a can may be made of thinner gauge metal in order to minimize the can cost. FIG. 15 illustrates the beer can 200 mated with the top anti-buckle ring 20 and the bottom anti-buckle ring 224. 
     Although the invention has been described in connection with a specific processing method and preferred ring construction, it will be obvious to those skilled in the art that many alterations and modifications thereto may be made without departing from the invention. Accordingly, it is intended that all such alterations and modifications be included within the scope of the invention as defined by the appended claims.