Abstract:
Aerosol cans, more particularly, aluminum aerosol cans made from disks of aluminum coil feedstock, are provided. A method for necking aerosol cans of a series 3000 aluminum alloy is also provided. The method prevents the cans from sticking in the necking dies and produces a can with a uniquely shaped profile. The aluminum aerosol cans that are produced have the attributes of strength and quality, while being produced at a cost that is competitive with steel aerosol cans.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This case is a divisional of U.S. application Ser. No. 10/224,256 filed 20 Aug. 2002 and entitled Aluminum Aerosol Can and Aluminum Bottle and Method of Manufacture. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention is directed to aerosol cans and, more particularly, to aerosol cans constructed of aluminum.  
           [0004]    2. Description of the Background  
           [0005]    Traditionally, beverage cans begin as disks of aluminum coil feedstock that are processed into the shape of a beverage can. The sides of these cans are approximately 0.13 mm thick. Generally, the body of a beverage can, excluding the top, is one piece.  
           [0006]    In contrast, aerosol cans are traditionally made one of two ways. First, they can be made from three pieces of steel, a top piece, a bottom piece, and a cylindrical sidewall having a weld seem running the length of the sidewall. These three pieces are assembled to form the can. Aerosol cans may also be made from a process known as impact extrusion. In an impact extrusion process, a hydraulic ram punches an aluminum slug to begin forming the can. The sides of the can are thinned to approximately 0.40 mm through an ironing process that lengthens the walls of the can. The rough edges of the wall are trimmed and the can is passed through a series of necking dies to form the top of the can. Although aerosol cans made of steel are less expensive than aerosol cans made by an impact extrusion process, steel cans are aesthetically much less desirable than aerosol cans made with an impact extrusion process.  
           [0007]    For a variety of reasons, aluminum aerosol cans are significantly more expensive to produce than aluminum beverage cans. First, more aluminum is used in an aerosol can than in a beverage can. Second, the production of aluminum cans by impact extrusion is limited by the maximum speed of the hydraulic ram of the press. Theoretically, the maximum speed of the ram is 200 strokes/minute. Practically, the speed is 180 slugs/minute. Beverage cans are made at a rate of 2,400 cans/minute.  
           [0008]    One problem facing the aerosol can industry is producing an aluminum aerosol can that performs as well or better than traditional aerosol cans but is economically competitive with the cost of producing steel aerosol cans and aluminum beverage cans. Another problem is producing an aerosol can that has the printing and design quality demanded by designers of high-end products. Traditional beverage cans are limited in the clarity of printing and design that can be imprinted on the cans. Beverage cans are also limited in the number of colors that can be used in can designs. Thus, a need exits for an aluminum aerosol can that has the attributes of strength and quality, while being produced at a cost that is competitive with steel aerosol cans.  
           [0009]    Producing aluminum cans of a series 3000 aluminum alloy coil feedstock solves some of these problems. Series 3000 aluminum alloy coil feedstock can be shaped into a can using a reverse draw and ironing process, which is significantly faster and more cost effective than impact extrusion, aluminum can production. Additionally, series 3000 aluminum alloy is less expensive, more cost effective, and allows for better quality printing and graphics than the use of pure aluminum.  
           [0010]    Unfortunately, certain obstacles arise in necking a series 3000 aluminum alloy can. Series 3000 aluminum alloy is a harder material than pure aluminum. Therefore, cans made from series 3000 aluminum alloy are stiffer and have more memory. This is advantageous because the cans are more dent resistant, but it poses problems in necking the cans by traditional means because the cans stick in traditional necking dies and jam traditional necking machines. The solution to these obstacles is embodied in the method of the present invention.  
           [0011]    Summary of the Present Invention  
           [0012]    This invention relates to a method for making and necking an aluminum aerosol can from a disk of aluminum alloy coil feedstock where the method is designed to, among other things, prevent the can from sticking in the necking dies. Additionally, this invention relates to the aluminum aerosol can itself, which has a uniquely shaped profile and is made from aluminum alloy of the 3000 series.  
           [0013]    The aluminum can of the present invention is comprised of a generally vertical wall portion having an upper end and a lower end, where the upper end has a predetermined profile. A bottom portion, extending from the lower end of the can, has a U-shaped profile around its periphery and a dome-shaped profile along the remainder of the bottom portion. Preferably, the generally vertical wall portion is approximately 0.20 mm thick, and the bottom portion is approximately 0.51 mm thick in the area of the U-shaped profile.  
           [0014]    The present invention is also directed to a method of forming a neck profile in an aluminum can made of a series 3000 aluminum alloy, where the can is processed with at least 30 different necking dies. This invention solves the problems of necking a series 3000 aluminum alloy can by increasing the number of necking dies used and decreasing the degree of deformation that is imparted with each die. A traditional aerosol can, made from pure aluminum, which is 45 mm to 66 mm in diameter, requires the use of 17 or less necking dies. A can made by the present invention, of similar diameters, made from a series 3000 aluminum alloy requires the use of, for example, thirty or more necking dies. Generally, the number of dies that are needed to neck a can of the present invention depends on the profile of the can. The present invention processes the aluminum can sequentially through a sufficient number of necking dies so as to effect the maximum incremental radial deformation of the can in each necking die while ensuring that the can remains easily removable from each necking die.  
           [0015]    There are several advantages of the can and method of the present invention. Overall, the process is faster, less expensive, and more efficient than the traditional method of impact extrusion, aerosol can production. The disclosed method of production uses a less expensive, recyclable aluminum alloy instead of pure aluminum. The disclosed can is more desirable than a steel can for a variety of reasons. Aluminum is resistant to moisture and does not corrode or rust. Furthermore, because of the shoulder configuration of a steel can, the cap configuration is always the same and cannot be varied to give customers an individualized look. This is not so with the present invention in which the can shoulder may be customized. Finally, aluminum cans are aesthetically more desirable. For example, the cans may be brushed and/or a threaded neck may be formed in the top of the can. Those advantages and benefits and others, will be apparent from the Description of the Preferred Embodiments within. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    For the present invention to be easily understood and readily practiced, the present invention will now be described, for purposes of illustration and not limitation, in conjunction with the following figures, wherein:  
         [0017]    [0017]FIG. 1 is a view of one example of an aluminum can formed by the method of the present invention, partially in cross-section;  
         [0018]    [0018]FIG. 2 is a cross-sectional view of the bottom portion of the aluminum can of FIG. 1;  
         [0019]    [0019]FIG. 3 is one example of a coil of aluminum alloy feedstock used for this invention;  
         [0020]    [0020]FIG. 4 is one example of the coil of aluminum alloy feedstock of FIG. 3 showing metal disks punched from it;  
         [0021]    [0021]FIG. 5 is a single metal disk of FIG. 4 made of a series 3000 aluminum alloy;  
         [0022]    [0022]FIG. 6 illustrates the disk of FIG. 5 drawn into a cup;  
         [0023]    [0023]FIGS. 7A-7C illustrate the progression of the cup of FIG. 6 undergoing a reverse draw process to become a second cup having a narrower diameter after completion of the reverse draw process;  
         [0024]    [0024]FIG. 8 illustrates one example of a shaped bottom formed in the second cup of FIG. 7C;  
         [0025]    [0025]FIGS. 9A-9D illustrate the progression of the second cup of FIG. 7C or of FIG. 8 through an ironing and trimming process;  
         [0026]    [0026]FIG. 10A shows the resulting shoulder profile of an aluminum can after the can of FIG. 9D has passed through thirty-four necking dies used according to one embodiment of the present invention;  
         [0027]    [0027]FIG. 10B illustrates the resulting shoulder of the can of FIG. 10A after it passes through the last necking die used according to one embodiment of the present invention;  
         [0028]    [0028]FIGS. 11A-11D are a sequence of views, partially in cross-section, of the aluminum can of FIG. 10B as it undergoes one example of a neck curling process;  
         [0029]    [0029]FIG. 12A is an aluminum can of FIG. 11D having a tapered shoulder;  
         [0030]    [0030]FIG. 12B is an aluminum can of FIG. 11D having a rounded shoulder;  
         [0031]    [0031]FIG. 12C is an aluminum can of FIG. 11D having a flat shoulder;  
         [0032]    [0032]FIG. 12D is an aluminum can of FIG. 1 ID having an oval shoulder;  
         [0033]    [0033]FIG. 13-FIG. 47 are a sequence of cross-sectional views illustrating thirty-five necking dies used according to one embodiment of the present invention;  
         [0034]    [0034]FIG. 48 shows a cross-sectional view of the center guides for the first fourteen necking dies used according to one embodiment of the present invention;  
         [0035]    [0035]FIG. 49 shows a cross-sectional view of the center guides for necking dies number fifteen through thirty-four used for one embodiment of the present invention;  
         [0036]    [0036]FIG. 50 illustrates one example of a die holder with a compressed air connection according to the present invention;  
         [0037]    [0037]FIG. 51 shows an aluminum can of the present invention having a brushed exterior, partially in cross-section;  
         [0038]    [0038]FIG. 52 shows an aluminum can of the present invention having a threaded aluminum neck, partially in cross-section; and  
         [0039]    [0039]FIG. 53 shows an aluminum can of the present invention having a threaded plastic outsert over the can neck, partially in cross-section. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]    For ease of description and illustration, the invention will be described with respect to making and necking a drawn and ironed aluminum aerosol can, but it is understood that its application is not limited to such a can. The present invention may also be applied to a method of necking other types of aluminum, aluminum bottles, metal containers and shapes. It will also be appreciated that the phrase “aerosol can” is used throughout for convenience to mean not only cans, but also aerosol bottles, aerosol containers, non-aerosol bottles, and non-aerosol containers.  
         [0041]    The present invention is an aerosol can and a method for making aluminum alloy cans that perform as well or better than traditional aluminum cans, that allow for high quality printing and design on the cans, that have customized shapes, and that are cost competitive with production of traditional aluminum beverage cans and other steel aerosol cans. The target markets for these cans are, among others, the personal care, energy drinks, and pharmaceutical markets.  
         [0042]    A one piece, aluminum aerosol can  10 , as seen in FIG. 1, has a generally vertical wall portion  12 . The generally vertical wall portion  12  is comprised of an upper end  14  and a lower end  16 . The upper end  14  has a predetermined profile  18 , and a neck  19  that has been curled. Alternatively, the neck can be threaded (see FIGS. 52 and 53). The aluminum can  10  also has a bottom portion  20  extending from the lower end  16 . As shown in FIG. 2, the bottom portion  20  has a U-shaped profile  22  around the periphery of the bottom portion  20  and a wrinkle-free, dome-shaped profile  24  along the remainder of the bottom portion  20 . The U-shaped profile  22  is preferably 0.51 mm thick.  
         [0043]    The aluminum can  10  of the present invention is made from aluminum alloy coil feedstock  26  as shown in FIG. 3. As is known, aluminum alloy coil feedstock  26  is available in a variety of widths. It is desirable to design the production line of the present invention to use one of the commercially available widths to eliminate the need for costly slitting processes.  
         [0044]    The first step in a preferred embodiment of the present invention is to layout and punch disks  28  from the coil feedstock  26  as is shown in FIG. 4. It is desirable to layout the disks  28  so as to minimize the amount of unused feedstock  26 . FIG. 5 shows one of the metal disk  28  punched from a series 3000 aluminum coil feedstock  26 . The disk  28  is drawn into a cup  30 , as shown in FIG. 6, using any of the commonly understood methods of making an aluminum cup, but preferably using a method similar to the method of U.S. Pat. Nos. 5,394,727 and 5,487,295, which are hereby incorporated by reference.  
         [0045]    As shown in FIG. 7A, the cup  30  is then punched from the bottom to begin to draw the bottom of the can through the sidewalls (a reverse draw). As shown in FIG. 7B, as the stroke continues, the bottom of the cup  30  is drawn deeper so that the walls of the cup develop a lip. As shown in FIG. 7C, the completion of the stroke eliminates the lip altogether resulting in a second cup  34  that is typically narrower in diameter than the original cup  30 . The second cup  34  may be drawn one or more additional times, resulting in an even narrower diameter. The resulting cup  34  has the vertical wall portion  12  and the lower end  16  with the bottom portion  20 . The bottom portion  20  may be shaped as shown in FIGS. 8 and 2. Although other configurations may be used, the domed configuration illustrated herein is particularly useful for containers that are pressurized.  
         [0046]    As shown in FIGS. 9A through 9D, the vertical wall portion  12  is ironed multiple times until it is of a desired height and thickness, preferably 0.21 mm thick. The vertical wall portion  12  should be of sufficient thickness to withstand the internal pressure for the intended use. For example, some aerosol products require a can that withstands an internal pressure of 270 psi or DOT 2Q. The ironing process also compacts the wall making it stronger. The upper end  14  of the vertical wall portion  12  is trimmed to produce an aluminum can  10 , as shown in FIG. 9D.  
         [0047]    According to one embodiment of the present invention, the can  10  is attached to a first mandrel and passed through a first series of necking dies. Subsequently, the can  10  is attached to a second mandrel and passed through a second series of necking dies. In the embodiment illustrated, the can  10  will pass through up to more than thirty necking dies. These necking dies shape the can  10  as shown in FIGS. 10A and 10B. Each die is designed to impart a desired shape to the upper end  14  of the generally vertical wall portion  12  of the can  10 , so that by the end of the necking process (FIG. 10B), the upper end  14  has the desired profile  18  and the neck  19 .  
         [0048]    The can  10 , partially shown in FIG. 10B, is shown in full in FIG. 11A. As shown in FIGS. 11A through 11D, the neck  19  of the can  10  is curled through a series of curling steps. The resulting aerosol can  10  of the present invention (as shown in both FIG. 11D and FIG. 1) has the predetermined shoulder profile  18 , the curled neck  19 , and is adapted to receive an aerosol-dispensing device. As shown in FIGS. 12A through 12D, the predetermined shoulder profile  18  can be a variety of shapes including, that of a tapered shoulder, a rounded shoulder, a flat shoulder, and an oval shoulder, respectfully. The resulting aluminum can may be between 100 and 200 mm in height and 45 and 66 mm in diameter. The aluminum can may be customized in a variety of ways. One way would be to add texture the surface of the can, for example, by brushing the surface of the can as shown in FIG. 51. Additionally, the predetermined shoulder profile can be adapted to receive an aerosol-dispensing device. The predetermined shoulder profile can also extend into or carry a neck, threaded or not (see FIGS. 52 and 53). An aluminum neck without threading can carry a threaded plastic outsert, as shown in FIG. 53.  
         [0049]    The present invention also encompasses a method of forming a shoulder profile in an aluminum can made of a series 3000, e.g. 3004, aluminum alloy. The first step of this method entails attaching the aluminum can to a first mandrel. The can is then passed sequentially through a first series of up to and including twenty-eight necking dies that are arranged on a necking table in a circular pattern. The can is then transferred to a second mandrel. While on the second mandrel, the can is sequentially passed through a second series of up to and including twenty-eight necking dies which are arranged in a circular pattern on a second necking table. This method includes trimming the neck after the can passes through a certain predetermined number of necking dies. That is, one of the necking dies is replaced with a trimming station. Trimming eliminates excess material and irregular edges at the neck of the can and helps to prevent the can from sticking in the remaining necking dies. A sufficient number of necking dies will be used so as to effect the maximum incremental radial deformation of the can in each necking die that is possible while ensuring that the can remains easily removable from each necking die. Effecting the maximum incremental radial deformation is desirable for efficient can production. A problem arises when the deformation is too great, thus causing the can to stick inside the necking die and jam the die necking machine. Generally, at least 2° of radial deformation can be achieved with each die after the first die, which may impart less than 2° of the deformation.  
         [0050]    The shape and degree of taper imposed by each die onto the can is shown in FIGS. 13 through 47. The method of the present invention may use a stationary center guide as shown in FIG. 48 for each of the first fourteen necking dies. FIG. 49 shows the center guides for the necking dies  15  through  34 . Compressed air can also be used to aid the removal of the can from the first several necking dies. For other shoulder profiles, movable guides and compressed air can be used on all necking positions. FIG. 50 shows a general die holder with a compressed air connection.  
         [0051]    The necking dies used in the method and apparatus of the present invention differ from traditional necking dies in several ways. Each die imparts a smaller degree of deformation than the necking dies of the prior art. The angle at the back of the first necking die is 0° 30′0″ (zero degrees, thirty minutes, zero seconds). The angle at the backs of dies two through six is 3° instead of the traditional 30°. The necking dies of the present invention are also longer than those traditionally used, preferably they are 100 mm in length. These changes minimize problems associated with the memory of the can walls, which memory may cause the can to stick in traditional necking dies. Additionally, in the test runs, the top of the can was pinched and was sticking on the center guide of traditional dies. Therefore, the first fourteen necking dies have non-movable center guides. Finally, the present invention uses compressed air to help force the cans off and out of each necking die. The compressed air also helps to support the can walls.  
         [0052]    While the present invention has been described in connection with preferred embodiments thereof, those of ordinary skill in the art will recognize that many modifications and variations may be made without departing from the spirit and scope of the present invention. The present invention is not to be limited by the foregoing description, but only by the following claims.