Abstract:
An apparatus for forming a container body from a metal blank has a ram, a blank holder, an annular die, an annular die holder, an insert and a plurality of ironing rings. The ram is centered about a longitudinal axis. The blank holder has an aperture through which the ram passes, The annular die is substantially axially aligned with the ram and adapted to allow the ram to pass therethrough. The annular die holder has a recessed portion adapted for receiving the annular die therein. The recessed portion has an annular, arcuate concave surface. The insert is located within the recess between the annular, arcuate concave surface and the annular die. The insert has a support surface for supporting the annular die thereon opposite an annular, arcuate, convex surface in operative engagement with the annular, arcuate concave surface and swivelable thereon. The plurality of ironing rings is substantially axially aligned with the ram.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    N/A 
       FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       TECHNICAL FIELD 
       [0003]    The invention relates the production of can bodies for beverage containers; more particularly, the invention relates to a draw and iron apparatus for producing the sidewall and bottom profile of a can body for a two-piece beverage container. 
       BACKGROUND OF THE INVENTION 
       [0004]    Two-piece cans are by far the most common type of metal containers used in the beer and beverage industry. They are usually formed of aluminum or tin-plated steel. The two-piece can consists of a first cylindrical can body portion having an integral bottom end wall and a second, separately-formed, top end panel portion which, after the can has been filled, is double-seamed thereon to close the open upper end of the container. 
         [0005]    The can body is formed in a body making apparatus which draws and irons a metal blank (sometimes a preformed cup) into a deep, cylindrical cup. In a first step, the metal blank is fed into the apparatus, and a metal cup is formed in a drawing process. The cup typically has a sidewall diameter that is generally equal to the sidewall diameter of a finished can body. The sidewall at this point is generally unchanged from a sidewall of the metal blank and does not have a finished height. Additionally, the sidewall at this point has a thickness greater than that of a finished can body. In subsequent steps, the drawn cup is passed through ironing tools. These tools lengthen the cup sidewall without changing the diameter of the cylindrical sidewall. The metal needed to lengthen the sidewall comes from the thickness of the sidewall. Accordingly, as the cup passes through the ironing tools, a height of the cylindrical sidewall becomes greater (it is lengthened) and the thickness of the sidewall is decreased. In a final step, the bottom of the cup is shaped by a forming tool. The resultant unfinished can body has a cylindrical sidewall and a domed bottom profile. In a subsequent manufacturing step, the upper portion of the sidewall is necked in so that a reduced diameter neck is formed. 
         [0006]      FIG. 1  shows a typical existing body making apparatus  10  which carries out the process described above. The apparatus  10  is centered about a longitudinal axis  50 . A ram  14  and punch assembly  15  (collectively referred to herein as the ram) is axially aligned with the longitudinal axis and is generally adapted, as in sized and shaped, to pass through a central cavity  16  of the apparatus  10 . The cavity  16  is at least partially formed by a plurality of annular tools, each having an aperture substantially axially aligned with the longitudinal axis  50 . 
         [0007]    A redraw sleeve  18  is positioned to the right of the ram  14  as shown in  FIG. 1 , assuming a conventional horizontally oriented apparatus  10  and a rightward thrust of the ram  14  through the cavity. The redraw sleeve  18  applies a force to a base or bottom portion of a blank. The ram  14  forces the blank through an annular redraw ring  22  to reduce the diameter of the cup and form the metal cup described previously. After the drawing step, the punch  12  maintains the diameter of the cup substantially constant as subsequent tools lengthen the sidewall as described above. 
         [0008]    As an aside, the assumed orientation is for purposes of describing the prior art and, later, the invention, and in no way limits the invention to the orientation other than in terms of the relative positioning of the elements of the prior art and the invention. 
         [0009]    The redraw ring  22  includes a carbide insert  26  which operatively engages the metal cup. The redraw ring  22  is supported in the apparatus  10  by a housing  28 . The housing  28  includes a recess  30  in which the redraw ring  22  is supported in the apparatus  10 . 
         [0010]    Ironing rings  34  are located axially beyond the redraw ring  22 . In the apparatus  10  shown, there are three ironing rings  34 . Again, the purpose of the ironing tools  34  is to lengthen and thin the metal in the sidewall of the can body as the blank passes between the ironing tools  34  and the ram  14 . Second rings  35  associated with the first two ironing rings  34  and located axially beyond are for guiding the ram  14 . 
         [0011]    A domer  38  is located at the end of the apparatus  10  after the ironing tools  34 . The domer  38  is provided for reshaping the bottom profile of the can body after the sidewall has been fully formed. 
         [0012]    One can body defect that is associated with the draw and iron process results in a top edge of the can body sidewall having unequal heights about the circumference of an open end of the can body opposite the reformed bottom end. This can be caused by unequal pressure applied by the redraw sleeve  18  on the metal blank against the redraw ring  22 . Machine operators will often shim the apparatus to adjust the clearance between the ram  14  and the tooling  22 , 34  to counteract the effect of the uneven pressure. 
         [0013]    For instance, in an attempt to achieve equal pressure around the blank, the operator will place shims in the tool pack. This can change the angle of the entire tool pack, including not only the redraw sleeve  18  and redraw ring  22 , but also the ironing rings  34 . The shim is typically placed at position A, as shown in  FIG. 1 . If the operator determines that there is excessive variation in the top edge of the container body height, he/she would add a shim at position A on  FIG. 1  to correctly reposition the redrawing ring  22 . However, the operator does not know the thickness of the shim that is needed. Therefore, he/she must use trial and error to determine the correct thickness of the shim. 
         [0014]    One of the problems with shimming is that the operators must place them consistently. If there is a jam, the operators have to remove the tooling. When the operator replaces the tooling, he/she is supposed to ensure the can quality is good, and add shims as necessary. Moreover, the shims often do not stay in place and must be reinserted when variability arises. Additionally, shims are stuck to the apparatus using grease, and the shims fall out easily. 
         [0015]    The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior draw and iron can body apparatuses of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings. 
       SUMMARY OF THE INVENTION 
       [0016]    One aspect of the present invention is directed to an apparatus for forming a container body from a metal blank. The apparatus comprises a ram, a blank holder, an annular die, an annular die holder, an insert, and a plurality of ironing rings. The ram is centered about a longitudinal axis. The blank holder has an aperture through which the ram passes. The annular die is substantially axially aligned with the ram and adapted to allow the ram to pass therethrough. The annular die holder has a recessed portion adapted for receiving the annular die therein. The recessed portion has an annular, arcuate concave surface. The insert is positioned within the recess and is located between the annular, arcuate concave surface and the annular die. The insert supports the annular die thereon opposite an annular, arcuate, convex surface in operative engagement with the annular, arcuate concave surface and swivelable thereon. The plurality of ironing rings are substantially axially aligned with the ram and positioned in sequential order. 
         [0017]    The apparatus of the first aspect of the invention may include one or more of the following features, alone or in any reasonable combination. The annular die may have a support surface in operative engagement with a support surface of the insert. The support surface of the annular die may be substantially planar. The support surface of the insert may be substantially planar. The annular die may have a generally circumferential outer wall which is substantially at a right angle to the support surface. The annular, arcuate convex surface of the insert and the support surface of the insert may converge as the annular, arucate convex surface and the support surface extend radially outwardly wherein the annular, arcuate convex surface and the support surface merge at point adjacent a generally circumferential wall of the annular die holder. The apparatus may further comprise a locating ring located between the annular die holder and the generally circumferential outer wall of the annular die. The insert may be produced from a material having a Rockwell scale hardness less than a Rockwell scale hardness of the annular die. The insert may be integrally formed with the annular die to form a one-piece unit therewith. 
         [0018]    A second aspect of the present invention is also directed to an apparatus for forming a container body from a metal blank. The apparatus comprises a ram, a blank holder, an annular die, an annular die holder, an insert, and a plurality of ironing rings. The ram is centered about a longitudinal axis. The blank holder has an aperture through which the ram passes. The annular die is substantially axially aligned with the ram and adapted to allow the ram to pass therethrough. The annular die holder has a recessed portion adapted for receiving the annular die therein. The recessed portion has an annular, arcuate concave surface. The insert is positioned within the recess and located between the annular, arcuate concave surface and the annular die. The insert supports the annular die opposite an annular, arcuate, convex surface. A means for reducing a coefficient of friction is between the annular, arcuate concave surface and the annular, arcuate convex surface of the insert. The plurality of ironing rings is substantially axially aligned with the ram. 
         [0019]    The apparatus of the second aspect of the invention may include one or more of the following features, alone or in any reasonable combination. The annular die may have a support surface in operative engagement with a support surface of the insert. The support surface of the annular die may be substantially planar. The support surface of the insert may be substantially planar. The annular die may have a generally circumferential outer wall which is substantially at a right angle to the support surface. The annular, arcuate convex surface of the insert and the support surface of the insert may converge as the annular, arucate convex surface and the support surface extend radially outwardly wherein the annular, arcuate convex surface and the support surface merge at point adjacent a generally circumferential wall of the annular die holder. The apparatus may further comprise a locating ring located between the annular die holder and the generally circumferential outer wall of the annular die. The insert may be produced from a material having a Rockwell scale hardness less than a Rockwell scale hardness of the annular die. The means for reducing the coefficient of friction may comprise producing the annular, arcuate convex surface of the insert and the annular, arcuate concave surface of the insert from dissimilar metallic materials. The means for reducing the coefficient of friction may comprise a fluid pressure between the annular, arcuate convex surface of the insert and the annular, arcuate concave surface of the insert. The fluid pressure may be provided by a gas. The fluid pressure may be provided by a liquid. The insert may be integrally formed with the annular die to form a one-piece unit therewith. 
         [0020]    Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: 
           [0022]      FIG. 1  is cross-sectional side view of a prior art apparatus for drawing and ironing the sidewall of a container body; 
           [0023]      FIG. 2  is cross-sectional side view of an apparatus of the present invention; and 
           [0024]      FIG. 3  is a cross-sectional side view of an annular die holder having a recess for receiving an annular insert and an annular die therein 
           [0025]      FIG. 4  is a cross-sectional side view of an annular die holder having a recess for receiving an annular insert and an annular die therein; 
           [0026]      FIG. 5  is a perspective view of a die holder of the present invention; 
           [0027]      FIG. 6  is a perspective view of an insert for the die holder of the present invention; and 
           [0028]      FIG. 7  is a perspective view of an alternative embodiment of the inset of the present invention integrally formed with an annular die to form a one-piece unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
         [0030]    The present invention is directed to a method and apparatus for drawing and ironing a metal blank into a semi-finished can body having a generally cylindrical sidewall, an open end, and an opposite enclosed bottom. The metal blank may be a flat sheet of metal strip, typically aluminum, or more preferably a shallow preformed cup formed from a flat metal sheet. More specifically, the invention described herein pertains to the first stage in such a draw and iron process wherein the metal blank undergoes a deep drawing step to produce a cylindrical sidewall having a diameter, substantially equal to the finished diameter of the semi-finished can body. Subsequent ironing steps elongate the sidewall without appreciable change in the diameter thereof. 
         [0031]    The present invention eliminates the need for an operator to shim the tool pack as described in the Background. Accordingly, the invention saves time in setting up a can body making apparatus by eliminating the need for shimming as described above. The invention automatically positions the redraw ring  22  in the correct position. Thus, variability (length and waviness) of the sidewall along a top edge of the open end of the semi-finished can body is reduced or eliminated. This reduces metal waste as a variable top edge must be trimmed to make it uniform in subsequent manufacturing steps. 
         [0032]    Referring to the figures, a draw and iron apparatus  100  incorporating the principles of the present invent is illustrated in  FIG. 2 . The apparatus  100  which carries out the process described in the Background with the exception that it provides an improved redraw ring assembly as will be described in great detail below. 
         [0033]    The apparatus  100  is centered about a longitudinal axis  50 . A ram  114  and punch assembly  115  (collectively a ram) is axially aligned with the longitudinal axis and is generally adapted, as in sized and shaped, to pass through a central cavity  116  of the apparatus  110 . The cavity  116  is at least partially formed by a plurality of annular tools, each having an aperture substantially axially aligned with the longitudinal axis  50 . 
         [0034]    A redraw sleeve  118  is positioned about the ram  114  an extent of the apparatus, assuming a conventional oriented apparatus  100  and axial thrust of the ram  114  through the cavity. The redraw sleeve  118  applies a force to a base or bottom portion of a blank. The ram  114  forces the blank through an annular redraw ring  122  to reduce the diameter of the cup and form the metal cup described previously. After the drawing step, the ram  114  maintains the diameter of the cup substantially constant as subsequent tools lengthen the sidewall as described above. 
         [0035]    The assumed orientation for purposes of describing the present invention in no way limits the invention to the assumed orientation other than in terms of the relative positioning of the elements of the prior art and the invention. The inventors contemplate that the draw and iron apparatus could be rotated through a complete 360 degrees with the relative positioning remaining the same. 
         [0036]    A first annular die or redraw ring  122  includes an annular carbide insert  126  which operatively engages the metal cup. The redraw ring  122  has an outer surface  200  including an annular cut out  204  in which the carbide insert is seated. The metal blank is drawn against the carbide insert  126  as the ram  114  forces the metal blank downwardly into the apparatus cavity  116 . Radially outwardly from the cutout  204 , the outer surface  200  has a substantially planar portion  208  which terminates at a circumferential wall  212  and is perpendicular thereto through a circumferential radiused corner. The wall  212  extends from the corner and terminates at a substantially planar bottom surface  216  and is perpendicular thereto through a circumferential radiused corner. The bottom surface  216  extends radially inwardly from the corner to an opening which is axially aligned with the longitudinal axis  50 . 
         [0037]    The redraw ring  122  is supported in the apparatus  100  by a housing or annular die holder  128 . The die holder  128  includes a recess  130  in which the redraw ring  122  is supported in the apparatus  100 . The die holder  128  of the present invention is substantially bowl-shaped wherein the recess  130  has an inwardly concave surface  300  and a center opening  304  axially aligned with the longitudinal axis  50 . The inwardly concave surface  300  is preferably annular and arcuate, more preferably annular and semi-spherical or a truncated sphere. An annular, vertical circumferential wall  304  extends from a radially outermost edge of the concave surface  300  and terminates at a generally planar surface  306 . An O-ring or locating ring  308  may be seated within a circumferential recess  312  within the die holder  128  or the redraw ring  122  to position the O-ring  308  between the wall  304  of the holder  128  and the wall of the redraw ting  212  to aid in centering the redraw ring  122 . 
         [0038]    An insert  400  is seated within the recess  130 . The insert  400  is located within the recess  130  between the inwardly concave surface  300  and the redraw ring  122 . Accordingly, the redraw ring  300  is supported in the recess  130  by the insert  400 , preferably atop the insert  400  as shown. The insert  400  has a surface  404  on which the redraw ring  122  sits or is supported. This surface  404  is generally planar. Opposite the surface  404  is an outwardly convex surface  408 . The convex surface  408  operatively engages the concave surface  300  of the recess  122 . It follows that the convex surface  408  has a complimentary shape to the concave surface  300 , in this case annular and arcuate, preferably semi-spherical or a section of a sphere. Thus, in the insert  400 , the annular, arcuate convex surface  408  and the surface  404  converge as the annular, arucate convex surface  408  and the surface  404  extend radially outwardly wherein the annular, arcuate convex surface  408  and the surface  404  merge at a point  412  adjacent the generally circumferential wall  304  of the annular die holder  128 . The point  412  preferably has a radius of curvature to limit wear on the wall  304 . 
         [0039]    The insert  400  allows the redraw ring  122  to achieve a swiveling motion within the die holder  128 . The clearances between the tooling restrict the swiveling motion to a desirable degree. For example, a desirable amount of movement of the redraw ring  122  relative to the die holder  128  may be no more than about 0.0019 ins (0.05 mm), and an undesirable amount of the such movement may be more than 0.0035 ins (0.89 mm), measured as a maximum height of a radially outer edge  200   a  of the outer surface  200  of the redraw ring  122  above a radially inner edge  306   a  of the surface  300  of the die holder  128 . Thus, it is aspect of the invention to restrict such movement and height differential to between 0.0019 ins and 0.0035 ins. 
         [0040]    The swiveling motion allows the redraw ring  122  to self-correct relative to the ram  114  and the redraw sleeve  118  to adjust the center position of the redraw ring  122  and provide automatic centering of the redraw ring  122  without the use of shims as discussed above. 
         [0041]    Further, the insert  400  is produced from a material that is dissimilar from the material used to produce the die holder  128 . For example, the die holder  128  may be produced from AISI-H13 tool steel whereas the insert  400  is produced from a softer material, such as a brass or bronze alloy, for example the brass and bronze alloys produced by Ampco Metals, such as Ampco 18. Generally, the insert  400  will have a hardness on the Rockwell C scale that is less than a hardness of the redraw ring  122  and the die holder  128 . Additionally, if the insert  400  was produced from a like tool steel to that of the die holder  128 , the inventors believe that the coefficient of friction between the parts produced from the tool steel would be too high. Therefore, one aspect of the invention is to reduce the coefficient of friction between the insert  400  and the die holder  128 , preferably by varying the material used to produce the insert  400 , for example producing it from a brass alloy, although the coefficient of friction may also be lowered by other means such as polishing the engagement surfaces of the insert  400  and the die holder  128  or by providing a fluid pressure between the engagement surfaces such that the engagement surfaces ride or float on a lubricating, coefficient of friction reducing film or fluid pressure  440 . However, the preferred method of reducing friction has the advantage of not requiring a source of fluid pressure or precise polishing of the engagement surfaces to each a desired amount of movement of the insert  400  relative to the die holder  128 . 
         [0042]    A group ironing tools  134  are located axially beyond/downstream the redraw ring  122 . In the apparatus  100  shown, there are three ironing tools  134 . In a process well known in the art of beverage can body manufacturing, the ironing tools  134  are used to lengthen and thin the metal in the sidewall of the can body as the blank passes between the ironing tools  134  and the ram  114 . 
         [0043]    A domer  138  is located below the ironing tools  134 . The domer  138  is provided for reshaping the bottom profile of the can body after the sidewall has been fully formed. 
         [0044]      FIG. 7  shows an alternative arrangement wherein The insert  400  is integrally formed with the redraw ring  122  to form a one-piece unit therewith. In other words, the support surfaces  216 , 404  of the redraw ring  122  and the insert  400  are eliminated or merged as to be non-existent. 
         [0045]    The terms “first,” “second,” “upper,” “lower,” “top,” “bottom,” “above,” below,” etc. are used for illustrative purposes to associate relative positioning of elements to other elements only and are not intended to limit the embodiments in any way. The term “plurality” as used herein is intended to indicate any number greater than one, either disjunctively or conjunctively as necessary, up to an infinite number. The terms “joined,” “attached,” and “connected” as used herein are intended to put or bring two elements together so as to form a unit, and any number of elements, devices, fasteners, etc. may be provided between the joined or connected elements unless otherwise specified by the use of the term “directly” and/or supported by the drawings. 
         [0046]    While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.