Abstract:
An improved can end, and method for making a can end, for pressurized beverage containers with a stay on tab. The tab incorporates a raised region with a hole. The raised region is positioned to receive the vapor vented from the can upon initial lifting of the tab. The raised region and hole are sized and shaped to discharge the vapor from the region, through the hole, and into the surrounding environment, appearing as a mist or cloud. Among other configurations, the raised region can be shaped as the top half of a bubble or a crescent, and the opening can be circular or elongated.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to beverage cans having easy-open ends, and particularly to pressurized beverage containers for products such as beer and soft drinks. The invention particularly includes an improved can end that provides a visible, directed vent discharge. 
     Most consumers are familiar with metallic beverage containers having easy-open ends and containing soft drinks or beer. And, most consumers are equally familiar with the associated marketing efforts, including the use of various decorations, trademarks, markings, colors, shapes and other indicia on the cans used to differentiate among the contained products and the producers. Producers are constantly searching for ways to differentiate their product from those of others. In addition to the product, the package often serves as a significant feature of this differentiation. 
     Many of the metallic cans for holding beverages or other products are provided with easy-open can ends having attached pull tabs. The pull tab is attached to the can end by an integral rivet. The can end has a tear strip defined by a score. The pull tab is lifted and then pulled or torn to provide an opening defined by the tear strip through which the contents can then be poured. Consistent with ecological and safety considerations, the tear strip and tab, under normal conditions, remain connected to the can end. 
     When opening a carbonated or pressurized can, the consumer typically hears a venting from the can on lifting of the tab, and is aware that continued movement forces the tear strip, defined by the score, downwardly into the can. The score used in most cans today includes the formation of a vent region adjacent the rivet. Although it may appear to the consumer to be a single action of lifting and pulling the tab, basically this can end construction provides an initial opening of the score at the vent region in response to the lifting of the rivet by the tab. This action is followed by further fracture of the score line as a nose of the tab presses downwardly on the tear strip. In the can industry, this is often referred to as an initial “pop” followed by a “push.” During the initial pop, pressure contained within the can is vented. This involves the venting of gas, typically carbon dioxide or nitrogen, which disperses broadly from the vent region generally laterally along the surface of the can end beneath the tab and into the surrounding environment. A purpose of the initial venting is to relieve pressure and avoid what is referred to as “missiling” of the tear panel. Accordingly, it has been desired to broadly dissipate the vented gas. A typical easy-open can end construction, including an anti-missile feature, is taught in U.S. Pat. No. 5,738,237, incorporated herein by reference. Further, the industry has viewed the discharge from a container as an undesirable feature, as discussed in U.S. Pat. No. 4,928,845 which teaches a throttle device as a safety feature against spraying from the can. U.S. Pat. No. 4,741,451 discloses another structure wherein a closure block on the interior of a can holds a lever portion of a pull tab which is pulled away from an aperture to allow venting from the can. 
     Although beverage cans are quite common and used throughout the world every day, the manufacturing technology involved is far from simple, and the capital investment in manufacturing machinery and tooling to manufacture the cans and can ends is substantial. It is not uncommon, for example, to use a 13 station die set to produce merely the tab. Exemplary methods of tab construction are taught in U.S. Pat. No. 4,465,204, the contents of which are incorporated herein by reference. Once in operation at the large volumes and high speeds of the can making industry, the can makers prefer to avoid major changes to the manufacturing systems, equipment and tooling. 
     While use of easy-open cans is widely and well received, it is desirable to provide a can including an improved can end which not only functions in the easy-open manner described above, but which also provides an additional method of product differentiation. It is further desirable to provide such improved cans without excessive modification of existing can manufacturing processes, equipment and tooling. 
     SUMMARY OF THE INVENTION 
     This invention provides a can having an improved easy-open can end, and method of manufacturing the end, which discharges a visible mist on opening of a pressurized can. It provides this feature through structure which does not require excessive modifications of the can end or the can end manufacturing processes, equipment and tooling. 
     In preferred form merely the tab is modified. A typical tab includes a rearward finger portion and a forward nose portion. As is typical in the art, the tab is mounted to the can end by a rivet and positioned such that the nose extends over the tear strip which is defined by the score. The score includes a vent region which is positioned adjacent the rivet. A typical tab includes a face portion extending between the rivet and the nose. Accordingly, the face portion extends over the vent region of the score. In accordance with the invention, the face portion is provided with a raised section having an opening such as a circular hole. The raised section extends over the vent region such that upon lifting of the tab, most of the gas discharged from the vent region is directed generally upwardly into the volume defined by the raised section, and then through the opening in the raised section. The raised section and opening are sized and shaped to cause the gas to discharge through the opening as a visible mist. 
     While many configurations are possible, such as a hemispherical bubble having a circular hole, a preferred raised section is a semi-circular or crescent shaped structure having an opening which is elongated, circular or oval. 
     The modification of a typical prior art tab forming process can readily involve the addition of steps during or at the end of the tab forming manufacturing process whereby the raised section and opening are formed. As desired, new tabs can be specifically configured and positioned to provide a raised section which receives the vented gas and an opening through which it will be dispersed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages, nature and additional features of the invention will become more apparent from the following description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a plan view of a prior art easy-open can end; 
     FIG. 2 is a plan view of a portion the prior art can end of FIG. 1 showing additional detail of the tab and showing score and contour lines in phantom; 
     FIG. 3 is a perspective view showing a can body with an attached can end; 
     FIG. 4 is a plan view of a tab in accordance with the invention; 
     FIG. 5 is an elevational cross section view taken at V—V of FIG. 4; 
     FIG. 6 is another plan view of a tab in accordance with the invention; 
     FIG. 7 is an elevational cross section view taken at VII—VII of FIG. 6; 
     FIG. 8 is another plan view of a tab in accordance with the invention; 
     FIG. 9 is an elevational cross section view taken at IX—IX of FIG. 8; 
     FIG. 10 is another plan view of a tab in accordance with the invention; 
     FIG. 11 is an elevational cross section view taken at XI—XI of FIG. 10; 
     FIG. 12 is yet another plan view of a tab in accordance with the invention; 
     FIG. 13 is an elevational cross section view taken at XIII—XIII of FIG. 12; 
     FIG. 14A is an elevational cross section view of the central region of a can end in accordance with the invention; 
     FIG. 14B is a view similar to FIG. 14 showing a seal on the can end; 
     FIG. 15 is a schematic cross section view illustrating a vent mist in accordance with the invention; 
     FIG. 16 is a layout of a prior art pull-tab manufacturing sequence; and 
     FIG. 17 is a layout of a pull-tab manufacturing sequence in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 and 2 there is shown an exemplary prior art can end  10 . Can end  10  has an end panel  12  of generally circular shape which includes a circumferentially extending raised edge  14  for attaching the can end  10  to a suitable cylindrical beverage can or the like. The can end  10  is preferably manufactured of a relatively ductile metal such as aluminum, but may be made from other materials. Can ends  10  of the prior art or of the inventive type herein described are attachable to a can body  8  as shown schematically in FIG.  3 . Within the can is a beverage  6  and a head space  4  above the beverage  6 . 
     A retained tear strip  16  extends across can end  10  from a position spaced inwardly of raised edge  14  to approximately the center of can end  10 . Tear strip  16  is defined by a generally U-shaped or V-shaped score  18  with open end  20  of the V or U shape positioned toward the center of the can end  10 . The score  18  is interrupted so that the tear strip  16  will be captively retained on the underside of the can end  10  when opened. 
     An integral rivet  22  is positioned adjacent open end  20  of score  18 , and a graspable ring-like pull tab  24  is secured to can end  10  by rivet  22 . Pull tab  24  includes a forward nose portion  26  and a rearward finger portion  28 . Pull tab  24  also includes a face portion  30  between the rivet  22  and the nose  26 . As is well known in the art, the periphery of the tab  24  is typically formed by rolling the edges, and thus the periphery, such as the nose portion  26 , is more rigid than the face portion  30 . The face portion typically includes a profile  31  for added strength in this region. 
     As shown best in FIG. 2, in addition to the main score  18  forming the boundary of the tear strip  16 , there is included an anti-fracture score  32  and an anti-missile score  34 . A vent region  38  of the main score  18  adjacent rivet  22  is also shown. It is evident that the vent region  38  is covered by the face  30 . Upon lifting of the finger portion  28  of the tab  24 , the vent region  38  of the score  18  opens as the rivet  22  is initially lifted. A gaseous vapor is released from within the can and disperses laterally under the tab  24  and then into the surrounding environment. The face portion  30  of the tab  24  is thinner and not as rigid as the periphery of the tab  24 , and bends in this face portion  30  as the tab  24  is lifted. 
     Referring now to FIG. 4 there is shown a tab  24  in accordance with the invention, having a nose portion  26 , finger portion  28 , and face portion  30 . As formed, the tab  24  includes a rivet hole  40 , a forming cavity or tongue  42 , a finger cavity  44  and a gripper rise  46 . All of these features are well known in the art, as is the fabrication process by which the tab  24  is attached to the can end  10 . The inventive embodiments include a raised section  48  rising from the face portion  30 . The raised section or store  48  includes an opening  50  therethrough as shown in FIG.  4  and FIG.  5 . The raised region  48  defines a volume for receiving and then discharging a vented vapor, as described further below. 
     Alternative configurations of the raised section  48  and opening  50  are shown in FIGS. 6 through 13. FIGS. 6 and 7 show a raised section  48  generally round in cross section, being generally hemispherical, and having a round or circular opening  50 . This appears as a portion of a round bubble rising from the face  30  and having a circular opening. FIGS. 8 and 9 show an elongated raised section  48  being generally rectangular in cross section and having a round opening  50 . FIGS. 10 and 11 show a raised section  48  being in the shape of a half-moon bubble and having an elongated opening  50 . Here the raised section  48  extends to the rolled edge of the nose  26 , which has been found to be desirable as it aids in maintaining the strength of the face portion  30  of the tab  24  and sufficiently contains the vapor discharged into the raised portion  48 . Generally, the raised portion, if not overly large, may provide to the face  30  a strengthening similar to that of the profile  31  (FIG.  2 ). FIGS. 12 and 13 show a raised section  48  generally round in cross section, as a hemisphere, and having an opening  50  which is a plurality of round opening holes  52 . It has been found that an elongated raised section  48 , as compared to a round raised section  48 , tends to better retain vapor within the raised section with less lateral discharge that bypasses passing through the opening  50 . The raised portion  48  is preferably vertically aligned above at least a portion of the vent region  38 , as shown in FIG.  2 . 
     Referring now to FIG. 14A, there is shown a schematic of the central portion the inventive can end  10 . At this stage of operation, the tab  24  has been lifted sufficiently to fracture the score  18  at the vent region  38 . Pressurized gas or vapor  54  is discharged from the head space  4  in the interior of the can body  8  through the open vent region  38 , communicates into the raised portion  48  and through the opening  50  into the surrounding environment. The discharge of the vapor along this path forms an ejection mist  58  of the type shown in FIG.  15 . The appearance of the mist  58  will vary depending on a number of variables, including the type of vapor and its temperature and pressure within the interior  56  of the can, the conditions of the ambient environment, the volume and configuration of the raised portion  48 , and the configuration and area of the opening  50 . It has been found, however, that by use of the raised section  48  and opening  50  to control the discharge as compared to prior art systems, the discharge can be sufficiently focused under anticipated conditions to create a visible mist. From an aesthetic standpoint, it is deemed to be desirable that the mist  58  be visible and form a cloud or a fan or wedge shape. Where the product contained within the can is a carbonated soft drink or beer, the mist is anticipated to contain carbon dioxide, with or without some vaporous form of the product. Typically the mist  58  is initially visible, and then dissipates into the surrounding environment. A residue may remain on the can end  10 . Also illustrated in FIG. 14A is an inner bead  59  which functions for the nose  26  to react against on initial opening, which is typical of many prior art can end designs. 
     It has been found that the area of the discharge opening  50  is one of the most important factors in controlling the appearance and formulation of the mist  58 . If the opening  50  is too small and restrictive, either the mist  58  is discharged as too narrow and harsh a stream, or the venting is overly constrained and no mist is formed. If the opening is too large, the vapor vents quickly and a visible mist is not formed. It has also been found that if the raised section  48  is too large compared to the face portion  30 , it may excessively weaken the tab which could fail upon lifting. It is also desirable that the face portion  30  of the tab  24  fit snugly against the end panel  12 , to create a loosely sealed area from which the raised portion  48  rises. As shown in FIG. 14B, a seal  88 , such as a polymer, can be included to enhance the containment of the vapor within the raised portion  48  and alleviate discharge other than through the opening  50 . The seal  88  preferably extends approximately 180° about the nose  26  of the tab  24  and is affixed to the bottom of the pull tab  24  prior to attachment of the tab  24  onto the can end  10 . The process of fixing the tab  24  onto the can end  10  is well known to those skilled in the art, and includes actual formation of the rivet  22  from a rivet button on the end panel  12  such that the tab  24  is captured through the rivet hole  40 . 
     A visible mist on opening can function as one feature to differentiate the product within the can from the product of others, and provides a pleasing alternative to the consumer. 
     Referring now to FIG. 16 there is shown a typical three out prior art manufacturing sequence for formation of a pull tab  24  in accordance with manufacturing machinery and tooling of Stolle Machinery, Inc. of Sidney, Ohio. As shown, it involves 13 sequential tooling die stations. Tab sheet stock  60  of aluminum, for example standard alloy 5182 of 0.010 to 0.011 inches thick, is passed through the sequence. In the first station tab stock pilot holes  62  and carry strip holes  64  are pierced. In the second station additional carry strip holes  64  and the finger cavities  44  are pierced. In the third station the forming cavity or tongue  42  is pierced. In the fourth station the outside contour  70  of the tab is lanced. In the fifth station the tongue  42  is reformed as indicated at reference numeral  72 . In the sixth station the tab contour is precurled  74  and the finger hole is precurled as indicated at numeral  76 . In the seventh station the area around the rivet location is formed downward, into a panel form indicated at reference numeral  78 . In the eighth station the outside contour  70  and precurled finger hole  76  get a 90 degree wipedown and a panel form  78  restrike. The ninth station is idle. In the tenth station the outside contour  70  and finger hole  44  get curled. In the eleventh station a rivet hole  80  is pierced. In the twelveth station the tab reform and tip up operation is performed, indicated respectively by reference numerals  82  and  84 . And, in the thirteenth station the rivet hole  80  is reformed, indicated at reference numeral  86 . 
     In accordance with the inventive method, this manufacturing sequence is improved to include formation of the raised portion  48  and opening  50 . One contemplated implementation of this improvement as shown in FIG. 17 is piercing of the face portion at the third station to form the opening  50 , and forming the raised portion  48  in the sixth station. Other sequences can be utilized, including modification of the existing stations or providing one or more additional stations. If a seal  88  is utilized, it can be added after formation of the tab  24  and prior to connection of the tab  24  to the can end  10 . 
     A series of tests was performed to compare various sizes and configurations for the raised portion  48  and opening  50 . Beverage can bodies  8  of the 12 ounce size were filled and various embodiments of the inventive can end  10  were sealed onto the bodies  8 . Some of the cans were filled with beer, and some with carbonated beverage. Several tab designs presently in use on the commercial market were utilized, and the results did not vary among these types. The results are presented in Table I. In Table I, “Small bubble raised portion” is a bubble or hemispherical style raised portion  48  (as shown in FIGS. 6 and 7) ⅛ inch diameter at its widest cross section, and ⅛ inch deep (rising ⅛ inch from the face  30 ); “Large bubble raised portion” is a bubble or hemispherical style raised portion  48  (as shown in FIGS. 6 and 7) {fraction (3/16)} inch diameter at its widest cross section and ⅛ inch deep; “Half moon raised portion” is a raised portion  48  of the type shown in FIGS. 10 and 11, {fraction (5/16)} inch long, {fraction (5/32)} inch wide and ⅛ inch deep. “Double slit” refers to a hemispherical bubble style having two parallel slits; “Single slit” refers to a hemispherical bubble style having a slit across the raised bubble; and, “Radius slit” refers to semi-circular opening. “Small hole” refers to a {fraction (1/32)} inch diameter opening; “Large hole” refers to a {fraction (1/16)} inch diameter opening; “Elongated hole” refers to an opening {fraction (1/32)} inch by {fraction (5/32)} inch. The test tabs were made by taking standard commercial machine-made tabs and through a hand process, forming into these tabs the raised portion  48  and opening  50 . The results column of Table I is a subjective determination of the degree to which the mist was aesthetically acceptable. 
     
       
         
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 ITEM 
                 DESCRIPTION 
                 RESULTS 
               
               
                   
               
             
             
               
                 A 
                 Large bubble raised portion/multi holes 
                 VERY POOR 
               
               
                 B 
                 Small bubble raised portion/multi holes 
                 VERY POOR 
               
               
                 C 
                 Small bubble raised portion/large hole 
                 POOR 
               
               
                 D 
                 Small bubble raised portion/small hole 
                 VERY POOR 
               
               
                 E 
                 Large bubble raised portion/elongated hole 
                 GOOD 
               
               
                 F 
                 Large bubble raised portion/small hole 
                 FAIR 
               
               
                 G 
                 Large bubble raised portion/large hole 
                 GOOD 
               
               
                 H 
                 Half-moon raised portion/large hole 
                 VERY GOOD 
               
               
                 I 
                 Half-moon raised portion/elongated hole 
                 VERY GOOD 
               
               
                 J 
                 No raised portion/elongated hole 
                 NO MIST/ 
               
               
                   
                   
                 SOLID STREAM 
               
               
                 K 
                 No raised portion/large hole 
                 NO MIST/ 
               
               
                   
                   
                 SOLID STREAM 
               
               
                 L 
                 Large bubble raised portion/double slit 
                 POOR 
               
               
                 M 
                 Large bubble raised portion/double small 
                 POOR 
               
               
                   
                 hole 
               
               
                 N 
                 Small bubble raised portion/single slit 
                 VERY POOR 
               
               
                 O 
                 Small bubble raised portion/radius slit 
                 POOR 
               
               
                 P 
                 Large bubble raised portion/single slit 
                 FAIR 
               
               
                 Q 
                 Large bubble raised portion/radius slit 
                 FAIR 
               
               
                   
               
             
          
         
       
     
     Items J and K were tabs that included merely an opening, with no raised portion. Other opening shapes on tabs without a raised portion were tried and the results did not generate an aesthetically acceptable mist or were very inconsistent and less controlled. Test samples with tabs of the various sizes and shapes represented in Table I were also prepared with still water and pressurized liquid nitrogen in the cans. The results were similar to those presented in Table I, but were somewhat less intense than the response from cans filled with beer or carbonated beverages. In other terms, there was a somewhat less visible, but still acceptable, mist formation. 
     It is thus evident that can ends can be manufactured including inventive structure which provides a visible mist or cloud upon initial opening. This feature can be utilized to differentiate among producers and products, and to provide consumers with a desirable vision upon opening of a pressurized container. Many alternatives are possible. For example, the size, configuration and position of the raised region or receiving reservoir and of the opening can be of numerous variations, provided that the raised reservoir receives the initial vent discharge through the vent region of the score. And, the manufacturing sequence to provide the raised region and opening can be adjusted consistent with minimizing the impact on existing systems and tooling.