Patent Publication Number: US-2006010957-A1

Title: Method and apparatus for making a can lid shell

Description:
CLAIM OF PRIORITY  
      This application is a continuation of U.S. patent application Ser. No. 10/107,941, entitled “METHOD AND APPARATUS FOR MAKING A CAN LID SHELL,” filed on Mar. 27, 2002 on behalf of inventor Martin Hubball. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to the manufacture of can lids for use on metal beverage containers. More particularly, the invention relates to a novel method and apparatus for making a shell for a can lid requiring significantly less force during the forming process than current manufacturing methods.  
     BACKGROUND OF THE INVENTION  
      Aluminum cans are widely used as containers for retail sale of beverages in individual portions. Annual sales of such cans are in the billions and consequently, over the years, their design has been refined to reduce cost and improve performance. Additional refinements have been made in the production process and equipment used for manufacturing such containers to further reduce costs and eliminate scrap and waste.  
      The method and apparatus of the present invention are particularly adapted for making a shell for a can lid using current single-action or double-action mechanical presses, with redesigned tooling. Presently, a shell for a beverage can lid has a center panel, a countersink, and a seaming panel, which consists of an outer seaming portion and a connecting portion, although many variations of the basic can lid can be found in use. In some arrangement of can lids, the connecting portion is almost vertical. In more recent designs of can lids, the connecting portion has been formed at more of an angle from vertical. Beverage can lids are usually formed from relatively thin sheet metal materials. The formation of a can lid shell is a metal drawing operation. If the shell is made from round blanks of sheet metal, a single-action press is used to form and shape the lid. If the lid is made from a preformed cup, a double-action press is used for completion of forming and shaping the lid.  
      In the effort to reduce costs and improve performance, the sheet material used to manufacture cans and lids has become progressively thinner, and the alloys used stronger. Currently, the materials have an initial thickness of 0.0088 inches or less, this thickness being projected to continue to decrease with technological developments. As the sheet material used to form lids has become thinner, the forming of can lids has become more difficult, because the thinner materials are more prone to wrinkling and cracking of the sheet material during forming. This is especially true in can lids in which the connecting portion is at a greater angle. It is not uncommon, with current materials, to use forces of up to 1100 pounds to secure such lids in the tooling during the shell forming operation, while lids with essentially vertical connecting portions may be formed using forces of approximately 400-500 pounds. The increased force required during the forming process accelerates wear on tooling, requires increased energy to generate the needed force, and requires increased support during forming to prevent distortion.  
      Therefore, what is needed is a method for forming can lid shells that enables better control of high strength, thin gauge material while forming can lid shells that decreases material failures, and requires a decreased load on the presses and tooling, thus prolonging the life of the equipment. Additionally, what is needed is apparatus that can achieve the desired method for forming can lid shells.  
     SUMMARY OF THE INVENTION  
      To these ends, the present invention contemplates a novel tooling structure and method for making a can lid shell, for use in both single-action and double-action presses. The tooling of this invention comprises upper and lower die sets mounted in a conventional die press. The upper and lower die sets are movable with respect to each other for making the formed can lid shell. The tooling of this invention comprises the addition of a forming ring within the die set. By adding a forming ring inside the die set, the force exerted on the metal during the drawing operation is reduced significantly. Sufficient force only needs to be exerted to prevent wrinkling of the can lid shell material, particularly in the area of the seaming panel, and to withstand panel-forming forces. The invention will be more readily understood from a consideration of the following detailed description of the drawings illustrating the prior art and a preferred embodiment of the invention.  
      The invention disclosed is a process or apparatus for making a shell for a can lid having a central panel, a countersink, and a seaming panel comprising clamping material in a tool die between a die core ring and a draw pad using a clamping force of less than 1100 pounds, the die core ring having an outer portion against which the material is clamped, a connecting surface profile, and an inner diameter. A portion of the material that will form the central panel is engaged against a die center in the tool die that has an outer diameter that is less than the inner diameter of the die core ring. The die center, and a forming ring between the draw pad and die center are moved in a direction to form both the central panel and the seaming panel. These portions of the shell are formed between the die center, the forming ring and the die core ring, with the forming ring supplying support and applying force to the material between the forming surface of the forming ring and the connecting surface profile of the die core ring.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings are incorporated into and form a part of the specification to assist in explaining the present invention. The drawings are intended for illustrative purposes only and are not intended as exact representations of the embodiments of the present invention. The drawings further illustrate preferred examples of how the invention can be made and used and are not to be construed as limiting the invention to only those examples illustrated and described. The various advantages and features of the present invention will be apparent from a consideration of the drawings in which:  
       FIG. 1  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components at stage  1  of the lid forming operation.  
       FIG. 2  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components at stage  1  of the lid forming operation.  
       FIG. 3  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components at stage  2  of the lid forming operation.  
       FIG. 4  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components at stage  2  of the lid forming operation.  
       FIG. 5  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components at stage  3  of the lid forming operation.  
       FIG. 6  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components at stage  3  of the lid forming operation.  
       FIG. 7  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components at stage  4  of the lid forming operation.  
       FIG. 8  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components at stage  4  of the lid forming operation.  
       FIG. 9  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components at stage  5  of the lid forming operation.  
       FIG. 10  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components at stage  5  of the lid forming operation.  
       FIG. 11  is a side elevation view in cross-section, of the tooling structure of the prior art during a lid forming operation, illustrating the position of the various operative components during the formation of the annular countersink of the lid.  
       FIG. 12  is a side elevation view in cross-section, of the tooling structure during a lid forming operation, illustrating the position of the various operative components during the formation of the annular countersink of the lid.  
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The present invention is described in the following text by reference to drawings of examples of how the invention can be made and used. The drawings are for illustrative purposes only and are not necessarily exact scale representations of the embodiments of the present invention. In these drawings, the same reference characters are used throughout the views to indicate like or corresponding parts. The embodiments shown and described herein are exemplary. Many details are well known in the art, and as such are neither shown nor described. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present invention have been described in the drawings and accompanying text, the description is illustrative only, and changes may be made, especially in matters of arrangement, shape and size of the parts, within the principles of the invention to the full extent indicated by the broad general meaning of the terms used in the claims. The words “up,” “upward,” “down,” and “downward” as used in this document, are used in reference to a can lid shell as it would appear when it is in the final position on top of a beverage can.  
       FIG. 1  illustrates one embodiment of a known tool die apparatus  10  for making a can lid from metallic material  22 . Those skilled in the art will be acquainted with the various methods of forming can lids to provide the general configuration and geometry of the can lid  10  as described herein. The apparatus  10  consists of a die core ring  12 , a draw pad  14 , and a die center  16 . The outer portion of the die core ring  12  that clamps the material  22  against the draw pad  14  has a radius of curvature R 1  on the inner curve. Radius R 1  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. The material  22  is held between the die core ring  12  and the draw pad  14  by means of force F 1 , a force of approximately 1000 to 1200 pounds, exerted on the draw pad  14  for lids in which the connecting portion is at an angle, and a force of approximately 400 to 500 pounds exerted on the draw pad  14  for lids in which the connecting portion is approximately vertical. The force F 1  is applied to the material  22 , holding the material  22  in place between the die core ring  12  and the draw pad  14  at a force area FA 1 . The inner diameter of the die core ring  12  has a radius of curvature R 3  on the outwardly curving portion. Radius R 3  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. The die core ring  12  has a radius of curvature R 7  on the connecting surface profile portion. Radius R 7  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. The die center  16  has a radius of curvature R 2  at the edge of the die center  16  that comes in contact with the material  22 . Radius R 2  is the machining radius typically used to achieve the desired radius for redrawing the lid panel. The die center  16  has a radius of curvature R 4  at the edge of the die center  16  that is closest to the draw pad  14 . Radius R 4  is the obverse of radius R 7  on the die core ring  12 . Radius R 4 , in combination with Radius R 7 , forms the desired seaming panel radius on the can lid.  
       FIG. 2  illustrates one embodiment of the tool die apparatus  110  of the current invention for making a can lid from metallic material  22 . The apparatus  110  of the present invention consists of a die core ring  12 , a draw pad  14 , a die center  116  and a forming ring  118 . The outer portion of the die core ring  12  that clamps the material  22  against the draw pad  14  has a radius of curvature R 1  on the inner curve. Radius R 1  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. For example, in materials that have a thickness of 0.0088 inches or less, a desired seaming panel radius is typically in the range of 0.055-0.080 inches. The material  22  is held between the die core ring  12  and the draw pad  14  by means of force F 2 , a force of approximately 200 to 300 pounds, exerted on the draw pad  14 . The force F 2  is applied to the material  22 , holding the material  22  in place between the die core ring  12  and the draw pad  14  at a force area FA 2 . The inner diameter of the die core ring  12  has a radius of curvature R 3  on the outwardly curving portion. Radius R 3  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. The connecting surface of the die core ring  12  has a radius of curvature R 7  on the inwardly curved portion of the profile. Radius R 7  is the machining radius typically used to achieve the desired seaming panel radius on the can lid. The die center  116  has a radius of curvature R 6  at the edge of the die center  116  that comes in initial contact with the material  22 . Radius R 6  is the machining radius typically used to achieve the desired radius to reform the material  22  into the panel wall. The forming ring  118  is located between the draw pad  14  and die center  116 . The forming ring  118  provides a support surface for the connecting portion of the seaming panel during the drawing process, reducing the amount of force required, and reducing the probability of wrinkles in the can lid, especially in can lids that have a connecting portion formed at an angle. The forming ring  118  also helps prevent distortion of critical angles and radii formed in the shell drawing process. The forming ring  118  has a radius of curvature R 5  at the corner that is closest to the draw pad  14  and material  22 . Radius R 5  is the obverse of radius R 7  on the die core ring  12 . Radius R 5 , in combination with Radius R 7 , forms the desired seaming panel radius on the can lid. The die center  116  and forming ring  118  move towards the material  22  together to achieve the configuration shown in  FIG. 2 . The use of a forming ring results in the lid forming process being a draw/redraw process, as opposed to the draw process of the prior art. In one embodiment of the invention, a plurality of upper and lower die sets are installed together in a cooperative matrix or pattern for making a plurality of the formed can lids simultaneously.  
       FIG. 3  illustrates the second stage of forming a can lid known in the prior art using apparatus  10  for making a can lid from metallic material  22 . The material  22  continues to be held between the die core ring  12  and the draw pad  14  by means of force F 1  exerted on the draw pad  14 . The die center  16  continues to move against the material  22 , applying a counter-force which starts the formation of the center panel  24  and the seaming panel  26  of the can lid shell by drawing the material  22  at radius R 2  on the die center  16 , and at radius R 1  on the die core ring  12 . As can be seen, no support is provided for the part of the material  22  that will form the connecting portion of the seaming panel  26  at this stage of the process.  
       FIG. 4  illustrates one embodiment of the apparatus  110  of the current invention at the second stage of forming a can lid from metallic material  22 . The material  22  continues to be held between the die core ring  12  and the draw pad  14  by means of force F 2  exerted on the draw pad  14 . The die core ring  116  is exerting a counterforce to the material  22 , starting the formation of the center panel  24  by drawing the material  22  at radius R 6  on the die center  116 . At the point of formation shown in  FIG. 4 , the forming ring  118  has come in contact with the material  22 , and is exerting a counterforce F 3 , of approximately 200 to 400 pounds at force area FA 3 , on the material  22 , starting the formation of the connecting portion of the seaming panel  26  of the can lid.  
       FIG. 5  illustrates the third stage of forming a can lid known in the prior art using apparatus  10  for making a can lid from metallic material  22 . The material  22  continues to be held between the die core ring  12  and the draw pad  14  by means of force F 1  applied to the draw pad  14 . At the point of formation shown in  FIG. 5 , the die center  16  has moved against the material  22 , continuing the formation of the center panel  24  and the seaming panel  26  of the can lid shell. One portion of the die center  16  has moved up to and slightly beyond the inner diameter of the die core ring  12 , continuing to draw the material  22  at radius R 2  on the die center  16 , and at radii R 1  and R 3  on the die core ring  12 . As can be seen, no support is provided for the part of the material  22  that will form the connecting portion of the seaming panel  26  at the third stage of the process of forming a lid in the prior art.  
       FIG. 6  illustrates one embodiment of the apparatus  110  of the current invention at the third stage of forming a can lid from metallic material  22 . The material  22  continues to be held between the die core ring  12  and the draw pad  14  by means of force F 2  exerted on the draw pad  14 . At the point of formation shown in  FIG. 6 , the force F 2  is believed to provide only sufficient force to prevent formation of wrinkles in the seaming panel  26 . Force F 2  is not believed to provide force for the purpose of drawing the material  22  during lid formation. The die center  116  and forming ring  118  have moved against the material  22 , for further formation of the center panel  24  and the seaming panel  26  of the can lid shell. The force F 3  exerted by forming ring  118  on the material  22 , has forced the material  22  against the inner diameter and connecting surface of die core ring  12 . The material is drawn at radius R 6  on the die center  116 , at radius R 5  on the forming ring  118 , and at radii R 1 , R 3  and R 7  on the die core ring  12 .  
       FIG. 7  illustrates the fourth stage of forming a can lid known in the prior art using apparatus  10  for making a can lid from metallic material  22 . The material  22  continues to be held between the die core ring  12  and the draw pad  14  by means of force F 1  exerted on the draw pad  14 . At the point of formation shown in  FIG. 7 , the die center  16  is drawing the material  22 , forming the center panel  24  and the seaming panel  26  of the can lid shell. The die center  16  has continued to move further beyond the inner diameter of the die core ring  12 , drawing the material  22  at radius R 2  on the die center  16 , and at radii R 1  and R 3  on the die core ring  12 , and is just starting to contact the material  22  at radius R 4  on the die center  16 . The primary force for drawing and securing of the material  22  is being proved by means of force F 1 . At this point in the forming process, the material  22  is subject to tremendous stress and shear, and is prone to buckling or wrinkling, especially in the areas of the material  22  that are not supported.  
       FIG. 8  illustrates one embodiment of the apparatus  110  of the current invention at the fourth stage of forming a can lid from metallic material  22 . The material  22  is held between the die core ring  12  and the draw pad  14  by means of force F 2  exerted on the draw pad  14 . At the point of formation shown in  FIG. 8 , the force F 2  is believed to be primarily providing force to prevent formation of wrinkles in the seaming panel  26 . Force F 2  is not believed to be serving the purpose of providing draw force for lid formation. The die center  116  is drawing the material  22 , forming of the center panel  24  and the seaming panel  26  of the can lid. The force F 3  exerted by forming ring  118  on the material  22  continues to provide the draw pressure for the formation of the center panel  24  and the connecting portion of the seaming panel  26  of the can lid shell. The die center  116  has moved further beyond the inner diameter of the die core ring  12 , continuing to draw the material  22  at radius R 6  on the die center  116 , and at radius R 3  on the die core ring  12 .  
       FIG. 9  illustrates the fifth stage of forming a can lid known in the prior art using apparatus  10  for making a can lid from metallic material  22 . The material  22  is held between the die core ring  12  and the draw pad  14  by means of force F 1  exerted on the draw pad  14 . At the point of formation shown in  FIG. 9 , the die center  16  is drawing the material  22 , forming the center panel  24  and the seaming panel  26  of the can lid shell. The die center  16  has moved to its furthest point beyond the inner diameter of the die core ring  12 , drawing the material  22  at essentially all points between the die center  16  and the die core ring  12 . The magnitude of the force for drawing and securing of the material  22  is being provided primarily by means of force F 1 . At this point in the forming process, the forming of the center panel  24  and the seaming panel  26  are essentially complete.  
       FIG. 10  illustrates one embodiment of the apparatus  110  of the current invention at the fifth stage of forming a can lid from metallic material  22 . The material  22  is held between the die core ring  12  and the draw pad  14  by means of force F 2  exerted on the draw pad  14 . At the point of formation shown in  FIG. 10 , the force F 2  is believed to be providing force to prevent formation of wrinkles in the seaming panel  26 . Force F 2  is not believed to be serving the purpose of providing draw force for lid formation. The force F 3  exerted by forming ring  118  on the material  22  continues to provide the draw pressure for the formation of the center panel  24  and the connecting portion of the seaming panel  26  of the can lid shell. At the point of formation shown in  FIG. 10 , the die center  116  has moved to its furthest point beyond the inner diameter of the die core ring  12 , essentially completing the formation of the center panel  24  and the seaming panel  26  of the can lid shell.  
       FIG. 11  illustrates the formation of the annular countersink  28  of a can lid known in the prior art using apparatus  10 . The material  22  is held between the die core ring  12  and the draw pad  14  primarily by means of force F 1  exerted on the draw pad  14 . During formation of the annular countersink as shown in  FIG. 11 , the die center  16  has reversed direction of movement, beginning to move away from the die core ring  12 . A panel forming punch  38  moves across the side of the material  22  opposite the die center  16 , toward the die core ring  12 , pressing the material  22  toward the die core ring  12 , forming the annular countersink  28 . Although this step in the forming process is described and shown here as occurring after the forming of the can lid shell, in some forming processes, based on the manufacturing equipment used, the formation of the annular countersink occurs at other points in the forming process, although the method is the same as described.  
       FIG. 12  illustrates the formation of the annular countersink  28  of a can lid in one embodiment of the apparatus  110  of the current invention. The material  22  is held between the die core ring  12  and the draw pad  14  primarily by means of force F 2  exerted on the draw pad  14 , and between the forming ring  118  and the die core ring  12  primarily by means of force F 3  exerted on the forming ring  118 . Force F 3  supports the outer wall of the annular countersink during formation. This substantially prevents the distortion of countersink  28  and also enables the formation of a greater variety of seaming panel wall  26  shapes with a wider variety of radii of curvatures during forming and reforming of the can lid. During formation of the annular countersink  28  as shown in  FIG. 12 , the die center  116  has reversed direction of movement. A panel forming punch  38 , which has an outer diameter D 1  that is less than the outer diameter D 2  of the die center  116 , moves across the side of the material  22  opposite the die center  116 , toward the die core ring  12 , pressing the material  22  toward the die core ring  12 , forming the annular countersink  28 . Although this step in the forming process is described and shown here as occurring after the forming of the can lid shell, in some forming processes, based on the manufacturing equipment used, the formation of the annular countersink occurs at other points in the forming process, although the method is similar to the one described here.  
      The embodiments shown and described above are exemplary. Many details are often found in the art and, therefore, many such details are neither shown nor described. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present invention have been described in the drawings and accompanying text, the description is illustrative only, and changes may be made in the detail, especially in matters of shape, size, and arrangement of the parts within the principles of the invention to the full extent indicated by the broad meaning of the terms of the attached claims.  
      The restrictive description and drawings of the specific examples above do not point out what an infringement of this patent would be, but are to provide at least one explanation of how to use and make the invention. The limits of the invention and the bounds of the patent protection are measured by and defined in the following claims.