Abstract:
An apparatus for reducing the diameter of an open end of a container is claimed. The apparatus comprises a housing having a longitudinal axis. A die is supported in the housing about the longitudinal axis. A radially expandable pilot member is also supported in the housing. The radially expandable pilot member is selectively moveable between a contracted position and an expanded position relative to the longitudinal axis. The radially expandable pilot member comprises a plurality of forming members. A method which utilizes the apparatus is also claimed.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates generally to a method and apparatus for necking containers and, more particularly, concerns a solid, expandable pilot member for supporting the interior surface of a two-piece beverage can during a necking operation.  
         BACKGROUND OF THE INVENTION  
         [0002]    Two-piece cans are the most common type of metal containers used in the beer and beverage industry and also are used for aerosol and food packaging. 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.  
           [0003]    An important competitive objective is to reduce the total can weight as much as possible while maintaining its strength and performance in accordance with industry requirements. For pressurized contents such as soft drinks or beer, the end panel must be made of a metal thickness gauge that is on the order of at least twice the thickness of the side wall. Accordingly, to minimize the overall container weight the second end panel should be diametrically as small as possible and yet maintain the structural integrity of the container, the functionality of the end, and also the aesthetically-pleasing appearance of the can.  
           [0004]    In the past, containers used for beer and carbonated beverages had an outside diameter of 2{fraction (11/16)} inches (referred to as a 211-container) and were reduced to open end diameters of (a) 2{fraction (9/16)} inches (referred to as a 209-neck) typically in a single-necking operation for a 209 end; or, (b) 2{fraction (7.5/16)} (referred to as a 207½-neck) typically in a double-necking operation for a 207½ end; or, (c) 2{fraction (6/16)} (referred to as a 206-neck) in a triple-or quad-necking operation.  
           [0005]    More recently, the open ends of beverage containers have been necked to 2{fraction (2/16)} (referred to as a 202-neck). The 202-neck is created using ten to sixteen separate, sequential operations. Further, different can fillers use cans with varying neck size. Hence, it is very important for the can manufacturer to quickly adapt its necking machines and operations from one neck size to another.  
           [0006]    Years ago, the process used to reduce the open end diameter of two-piece containers to accommodate smaller diameter second end panels typically comprised a die necking operation wherein the open end was sequentially formed by one, two, three or four die-sets to produce respectively a single-, double-, triple- or quad-necked construction. Examples of such proposals are disclosed in U.S. Pat. Nos. 3,687,098; 3,812,896; 3,983,729; 3,995,572; 4,070,888; and 4,519,232. For these patents, it should be noted that in each die necking operation, a very pronounced circumferential-step or rib is formed. This stepped rib arrangement was not considered commercially satisfactory by various beer and beverage marketers because of the limitations on label space and fill capacity.  
           [0007]    In an effort to offset the loss of volume or fill capacity resulting from the stepped rib configuration of the container, efforts have been directed towards eliminating some of the steps or ribs in a container neck. Thus, U.S. Pat. No. 4,403,493 discloses a method of necking a container wherein a taper is formed in a first necking operation. A second step or rib neck is then formed between the end of the tapered portion and the reduced cylindrical neck.  
           [0008]    U.S. Pat. No. 4,578,007 also discloses a method of necking a container in a multiple necking operation to produce a plurality of ribs. The necked-in portion is then reformed with an external forming roller to eliminate at least some of the ribs and produce a frustoconical portion having a substantially uniform inwardly curving wall section defining the necked-in portion.  
           [0009]    However, beer and beverage marketers prefer a neck construction having a relatively smooth neck shape between, for example, the 206 opening and the 211 diameter can. This smooth can neck construction is made by a spin necking process, and apparatus as shown, for example, in U.S. Pat. Nos. 4,058,998 and 4,512,172.  
           [0010]    More recently, U.S. Pat. No. 4,774,839 disclosed a die necking apparatus for producing a smooth tapered wall between the container side wall and a reduced diameter neck. The apparatus includes a plurality of rotatable necking turrets, each having a plurality of identical necking substations with a necking die.  
           [0011]    The necking dies in the respective turrets include an internal configuration to produce a necked-in portion on the container. The necking substations also have a floating form control element or pilot member that engages the inner surface of the container to control the portion of the container to be necked. The necked-in portion is reformed in each succeeding turret by dies to produce a smooth tapered wall between the arcuate segments without the need for subsequent roll forming.  
           [0012]    The pilot member generally does not provide support or guidance from the moment the can edge contacts the die to the moment the can edge contacts the floating pilot member. Consequently, the can edge is susceptible to wrinkling or pleating.  
           [0013]    One way of overcoming the above problem is to reduce the clearance between the initial can contact with the necking die and the pilot member by increasing the number of necking operations. This is very expensive, however, because each necking operation requires a separate necking station.  
           [0014]    Further, even with an increased number of necking operations, small wrinkles may form on or near the open edge of the can. These wrinkles are ironed out during subsequent necking operations by forcing the edge of the can between the cylindrical upper portion of the necking die and the floating pilot member. The ironed out wrinkles create localized regions exhibiting increased work hardening that are generally more brittle than adjacent areas and may fail (i.e. fracture or crack) when the open end is flanged.  
           [0015]    Wrinkles become even more prevalent as the container sidewall is down-gauged from approximately 0.0062-0.0064 ins. to 0.0050-0.0054 ins. To avoid wrinkling, four to six additional necking operations may be required. Additional necking operations, however, require additional manufacturing space, pressurized air, electricity, and manufacturing time. Thus, adding additional necking operations is cost prohibitive.  
           [0016]    Despite these difficulties, producing a suitable 202-neck container from thinner gauge material remains a manufacturing goal. To produce such a 202-neck container while maintaining the current number of necking stations requires extreme dimensional control of both the necking die and pilot member diameters, and the force required to insert the edge of the can between the necking die and the pilot member tends to crush the body of the can or flatten the bottom of the can. Consequently, the can has to be pressurized to twenty to thirty or more psi prior to forming.  
           [0017]    To prevent loss of control of the can edge, the pilot member may be shaped over the entire inside profile of the die. Once the neck is formed, however, the can cannot be removed from the pilot member. Methods have been developed to expand the pilot member during the necking operation to keep the edge of the can in contact with the die and to return the pilot to its original size for can removal.  
           [0018]    One such apparatus is disclosed in U.S. Pat. No. 5,755,130. The apparatus includes a pilot having an elastomeric sleeve and a means for providing for lateral deformation of the sleeve. During necking, the sleeve is controllably deformed in a manner such that the lateral portion of the sleeve is placed into supporting engagement with the interior wall of the can, pressing the can against the transition zone of the die. This supporting action of the elastomeric material against the can wall during the reduction in diameter is aimed at avoiding the formation of localized pleats.  
           [0019]    Another such apparatus is disclosed in U.S. Pat. No. 6,032,502. The apparatus of this patent includes a die assembly having a cylindrical die for engaging the outer surface of the container and spinning pilot rollers which support the inner diameter of the portion of the container to be necked. The drawback of this method is that the inner surface of the container is only supported at the area where the roller contacts the inner surface.  
           [0020]    The present invention provides a rigid, expandable pilot member to eliminate the drawbacks of the current necking apparatuses.  
         SUMMARY OF THE INVENTION  
         [0021]    The present invention is directed to a method and apparatus for necking the open end of a container. The method disclosed herein overcomes the difficulties described above by using a rigid, expandable pilot member which provides a continuous surface for supporting interior surface of the container during a die-necking operation.  
           [0022]    An object of the invention is to reduce the thickness of the metal at the open end of the container while reducing the diameter of the container&#39;s open end. The apparatus replaces a conventional pilot member with an expandable metallic pilot member.  
           [0023]    The expandable pilot member comprises a plurality of segments which are individually expandable to form a continuous surface. In its unexpanded condition, some of the segments are retracted inwardly of other segments. Upon expansion during the necking operation, end portions of the individual segments mate to form a continuous surface. Thus, the entire circumference of the interior wall of the container is supported because there are no gaps between the individual segments of the pilot member. The pilot member is retracted after the necking operation is completed to facilitate removal of the necked-in container from the tooling.  
           [0024]    The pilot member is expanded by a rigid actuator which automatically pushes the segments into working position when the actuator is lifted. When the actuator is lowered, the pilot member is retracted by forces provided by four springs to each pilot member segment respectively.  
           [0025]    Other advantages and aspects of the invention will become apparent upon making reference to the specification, claims, and drawings to follow. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0026]    [0026]FIG. 1 is a plan view a necking and flanging apparatus incorporating the modular nature of the present invention;  
         [0027]    [0027]FIG. 2 is a fragmentary sectional view of a necking apparatus formed in accordance with the invention;  
         [0028]    [0028]FIG. 3 is an enlarged sectional view of the pilot member and die assembly;  
         [0029]    [0029]FIG. 4 is a perspective view of the fully expanded pilot member of the present invention (the pilot member retainer is not shown);  
         [0030]    [0030]FIG. 4 a  is a perspective view of a contracted pilot member of the present invention (the pilot member retainer is not shown);  
         [0031]    [0031]FIG. 5 is a cross-sectional view along  3 - 3  of FIG. 3;  
         [0032]    [0032]FIG. 6 is a cross-sectional view along  4 - 4  of FIG. 3 of a partially expanded pilot member of the present invention;  
         [0033]    [0033]FIG. 7 is cross-sectional view along  4 - 4  of FIG. 3 of an expanded pilot member of the present invention;  
         [0034]    [0034]FIG. 8 is a cross-sectional view of the external forming segments of a pilot member of the present invention;  
         [0035]    [0035]FIG. 9 is a cross-sectional view of the internal forming segments of a pilot member of the present invention;  
         [0036]    [0036]FIG. 10 is cross sectional split view of an expanded pilot member on the left and a contracted pilot member on the right;  
         [0037]    [0037]FIG. 11 is side view of an actuator of the present invention;  
         [0038]    [0038]FIG. 11 a  is a bottom view of an actuator of the present invention;  
         [0039]    [0039]FIG. 12 is an enlarged fragmentary sectional view showing the beginning of the first necking operation;  
         [0040]    [0040]FIG. 13 is a view similar to FIG. 12 showing the completion of the first necking operation;  
         [0041]    [0041]FIG. 14 illustrates the beginning of the second necking operation;  
         [0042]    [0042]FIG. 15 illustrates the beginning of the third necking operation;  
         [0043]    [0043]FIG. 16 illustrates the beginning of the fourth necking operation;  
         [0044]    [0044]FIG. 17 illustrates the beginning of the fifth necking operation;  
         [0045]    [0045]FIG. 18 illustrates the beginning of the sixth necking operation;  
         [0046]    [0046]FIG. 19 illustrates the beginning of the seventh necking operation;  
         [0047]    [0047]FIG. 20 illustrates the beginning of the eighth necking operation;  
         [0048]    [0048]FIG. 21 illustrates the beginning of the ninth necking operation; and  
         [0049]    [0049]FIG. 22 illustrates the beginning of the tenth necking operation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0050]    While this invention is susceptible of embodiment 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 embodiments illustrated.  
         [0051]    Referring to FIG. 1, a necking and flanging system  18  of the present invention is illustrated. The system  18  produces containers having a smooth-shaped neck profile and an outwardly-directed flange.  
         [0052]    As will be described more specifically below, the necking and flanging apparatus  18  includes a plurality of substantially identical modules comprising the necking stations that are positioned in a generally C-shaped pattern. A single operator can visually observe and control the operation of all modules from a central location. The plurality of individual modules are interconnected to provide the complete necking and flanging system or apparatus, as will be explained.  
         [0053]    [0053]FIG. 1 shows the apparatus  18  for necking and flanging a container  16  or beverage a can. The embodiment of FIG. 1 has container necking station modules  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38 , and  40  and a flanging station module  42 . Additional necking stations can be added to the apparatus  18  without departing from the spirit of the invention. Transfer wheels  21 ,  23 ,  25 ,  27 ,  29 ,  31 ,  33   a ,  33   b,    33   c,    35 ,  37 ,  39 ,  41 , and  43  move the containers  16  serially and in a serpentine path through the various necking stations.  
         [0054]    Each of the necking station modules  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38 , and  40  are substantially identical in construction so as to be interchangeable, and can be added to or subtracted from the system depending upon the type of container that is to be formed. Each of the necking station modules has a plurality of circumferentially-spaced individual, substantially identical necking substations (FIG. 2). The number of stations and substations can be increased or decreased to provide the desired necking operation for various sizes of containers. The details of the necking substations will be described in further detail later.  
         [0055]    An additional advantage of utilizing substantially identical modules is that many of the components of the modules are identical in construction, thus enabling a reduction of inventory of parts.  
         [0056]    [0056]FIG. 1 further shows cylindrical metal container bodies  16  which are made of conventional materials in any conventional manner, being fed sequentially by suitable conveyor means (not shown) into the necking and flanging apparatus  18 . The conveyor means feeds the containers  16  to a first transfer wheel  21 , as is known in the art. The containers  16  are then fed serially through the necking modules by the interconnecting transfer wheels.  
         [0057]    More specifically, the first transfer wheel  21  delivers containers to the first necking module, generally designated by reference numeral  22 , where a first necking operation is performed on the container  16 , as will be described later. The containers  16  are then delivered to a second transfer wheel  23  which feeds the containers  16  to a second necking module  24  where a second necking operation is performed on the container  16 . The container is then removed from the second module by a third transfer wheel  25  and fed to a third necking module  26  where a third necking operation is performed.  
         [0058]    The containers  16  are then sequentially moved through the subsequent necking modules  28 ,  30 ,  32 ,  34 ,  36 ,  38 , and  40  to complete the necking operation. The necked containers are then transferred by transfer wheel  41  to a flanging module  42  where an outwardly-directed flange is produced on the container, as is well known in the art, and is delivered to transfer wheel  43  for delivery to an exit conveyor.  
         [0059]    As will be explained in more detail below, each station is concurrently operating on, or forming, a number of containers  16  with each container  16  being in a different state of necking as it is being processed from the entry point to the exit point of each necking station module.  
         [0060]    All of the moving members in the necking and flanging apparatus  18  are driven by a single drive means  44  which includes a variable-speed motor connected to an output transmission  46 . Each of the transfer wheels, as well as the necking modules and flanging module, have gears in mesh with each other to produce a synchronized continuous drive means for all of the components.  
         [0061]    The variable-speed drive feature of drive means  44  allows the speed of the module apparatus to be regulated. The variable-speed drive also allows the operator to accurately index the components of the system relative to each other.  
         [0062]    The necking and flanging apparatus  18  includes a vacuum means associated with each of the modules and on each of the transfer wheels to assure that the containers  16  remain in the conveyor track. A suitable interconnecting and supporting framework  50  is provided for supporting rotatable turrets  70  that are part of the modules.  
         [0063]    Referring now to FIG. 2, a partial view of a necking module is illustrated. Each necking module of the necking apparatus includes a stationary frame  50  and a rotary turret assembly  70  which is rotatably mounted on the frame and which holds a plurality of identical necking substations  72  around the periphery thereof. The turret assembly  70  is rotatably supported on the stationary frame by upper bearings  73  and lower bearings (not shown).  
         [0064]    A lower turret portion  74  and an upper turret portion  76  are supported on a rotary drive shaft  78  The upper turret portion  76  is slidable axially on drive shaft  78  and is connected to the lower turret portion  74  for rotation therewith by a rod  80  which extends through a collar  82  on the lower turret frame.  
         [0065]    A container lifter pad  84  is mounted on a ram or piston  86  which is reciprocally mounted in a cylinder  88  which is secured to the lower turret portion  74 . The lower end of the ram  86  includes a cam follower which rides on a cam for raising and lowering the ram and the lifter pad  84 . The lifter pad  84  thereby moves a container or can  16  toward and away from the upper turret portion.  
         [0066]    [0066]FIG. 3 discloses an upper portion of the necking substation  72  in greater detail. The necking substation  72  includes an upper forming or necking portion  102 .  
         [0067]    The upper necking portion  102  includes a floating necking die element  130  that is secured to a retainer  132  by means of a threaded cap  134 . The retainer includes a central axis  135 . The cylinder  132  has an axial opening  136  in which a hollow actuator or shaft  137  is reciprocally mounted. A cam follower  138  is mounted on the upper end of actuator  137  and rollably abuts on an exposed camming surface of a fixed upper face cam  139  secured to the frame.  
         [0068]    The actuator  137  and the cam follower  138  are maintained in engagement with the cam  139  by a dual cam track mechanism which also centers the actuator  137  in the opening  136 . The lower end of actuator  137  is used to control expansion and contraction of a form control member or pilot member  140 , as explained in more detail below. Pressurized air may be introduced through the actuator  137  and the pilot member  140  into the container  16  during the necking operation.  
         [0069]    Referring to FIGS. 4 and 4 a,  as well as FIGS. 2, 3, and  5 - 7 , the pilot member  140  of the present invention generally comprises four forming segments  150   a - d  which are mounted for controlled relative radial movement within the pilot member retainer  132 . The forming segments  150   a - d  are generally produced from a durable, rigid material such as tool steel. Coatings can be added to the forming segments  150   a - d  to enhance surface properties. Biasing members bias the forming segments  150   a - d  inwardly in a contracted position. The biasing members are generally spring members  152   a - d  but the biasing can also be performed by elastic members, air pressure, or the like. (See FIG. 10). A first pair of the forming segments  150   a,b  is contracted inwardly of a second pair of the forming segments  150   c,d.  (See FIG. 6). The first pair of forming segments  150   a,b  have a comparatively smaller surface area than the second pair of forming segments  150   c,d.    
         [0070]    Each forming segment  150   a - d  has an outer surface  154  defining an external surface area and an inner surface  158 . The outer surface  154  comprises a container supporting surface  162 , a pair of guides  166   a,b,  and a sliding slab  170  located between the guides  166   a,b.  The combination of the two guides  166   a,b  and the slab  170  inhibit rotation of the forming segments  150   a - d  within the pilot member retainer  132 .  
         [0071]    The container supporting surface  162  generally follows the curvature of the open end of the container. The container supporting surface  162  includes an upper cylindrical portion  173  positioned at a first radial distance R 1  from the central axis  135  which transitions through an arcuate transition zone to an annular, arcuate, bulged entry portion  174  located at a second radial distance R 2  from the central axis  135 . The curvature of the bulged entry portion  174  is generally similar to the curvature of the upper portion of the necking die  130  and cooperates with the necking die during the operation to reform the upper portion of the container  16  as it is necked.  
         [0072]    The bulged entry portion  174  also provides a guide to the open end of the container. This bulge portion  174  prevents the open end of the container from folding over itself and wrinkling as the container is forced into the necking die  130 , and includes a lower tapered portion for centering the container and a straight portion for guiding the container. Thus, it allows for improved control over the metal flow during forming and allows for a greater clearance between the necking die  130  and the expanded pilot member  140 .  
         [0073]    Referring to FIGS. 8 and 9, the inner surface  158  of each forming segment  150   a - d  includes an angled step  178   a - d.  While each forming segment  150   a - d  includes an angled step  178   a - d,  the angled steps  178   a,    178   b  of the first pair of smaller forming segments are longer and positioned at a relatively increased height as compared to the height and length of the angled steps  178   c,    178   d  of the second pair of larger forming segments. The purpose of this aspect will become clear upon further description.  
         [0074]    The actuator  137  extends through the retainer  132  and selectively engages the inner surface  158  of each forming segment  150   a - d.  The actuator  137  has an opening  168  therethrough for delivering the air pressure to the interior space of the container.  
         [0075]    Referring to FIGS. 11 and 11 a,  the actuator  137  comprises a proximal end  184  and a distal end  186 . The distal end  186  is the working end of the actuator  137 . The distal end  186  includes inclined zones  188   a - d  which engage and cooperate with the angled steps  178   a - d  of the forming segments  150   a - d.  The inclined zones  188   a - d  are separated by splits  189  to prevent the over-tightening of the forming segments  150   a - d  against one another. The distal end  186 , therefore, acts like a series of flexible beams separated by the splits  189 .  
         [0076]    When the actuator  137  is moved upwardly, the inclined zones  188   c,d  push the second pair of forming segments  150   c,d  outwardly relative to the central axis  135  against the force provided by the springs  152   c,d.  As the actuator  137  continues moving upwardly, the inclined zones  188   a,b  push the first pair of forming segments  150   a,b  outwardly against the force provided by the springs  152   a,b.    
         [0077]    In the fully expanded position, the four forming segments  150   a - d  fit tightly together along peripheral edge portions  192 . The forming segments  150   a - d  fit together in such a way that very little or no transition gap exists between the forming segments  150   a - d.  When the segments  150   a - d  are fully expanded and the peripheral edges  192  of adjacent segments  150   a - d  are in contact with one another, a continuous circumferential forming surface  193  is formed by the adjacent container supporting surfaces  162 . (See FIG. 4). The reduction or elimination of the gaps between the forming segments  150   a - d  prevents marks or metal deformation caused by can material filling the gaps during the necking process.  
         [0078]    Referring again to FIG. 11 a,  the splits  189  in the actuator  137  prevent the forming segments from being over-tightened. When a predetermined amount of force provided by the distal end  186  of the actuator  137  to the forming segments  150   a - d  is reached, the inclined zones  188   a - d  of the distal end  186  flex inwardly to prevent over-tightening of the peripheral edges portions  192 .  
         [0079]    The die  130  is mounted with a small clearance. The die  130  is mounted in such a way that it will “float” or is capable of some movement within the retainer  132 . Thus, the die  130  can center itself about the open end of the container during the necking operation. In previous necking apparatuses, the die  130  was fixed while the pilot member  140  was mounted to “float.” 
         [0080]    Referring again to FIGS. 2 and 3, in operation of the module, shaft  78  is caused to rotate about a fixed axis on the stationary frame  50 . As the container  16  is moved upwardly into the die  130 , the shaft  78  is rotated and, therefore, the upper open end of the container is incrementally reformed. At about the time the upper edge of the container contacts the die  130 , pressurized air is introduced into the container from a source through the opening  141 . As the turret assembly  70  is rotated about 120° of turret rotation, the upper cam  139  is configured to move the actuator  137  upwardly and  30 . expand the pilot member  140  outwardly toward the die  130 .  
         [0081]    As mentioned above, the actuator  137  is biased downwardly and will move upwardly to the position shown in FIG. 3 as the turret assembly rotates. Thereafter, during the remainder of the 360° of rotation, the cam  139  is configured to return the pad  120  to its lower position and pilot member  140  to its contracted position at substantially matched speeds while the necked container  16  is removed from the die  130 . During this downward movement, the pressurized air in the container will force the container from the die  130  onto the pad  120 .  
         [0082]    Containers  16  are continually being introduced onto pad  120 , processed and removed as indicated in FIG. 1.  
         [0083]    The present invention provides a method whereby a container can be necked to have a smaller opening by utilizing a plurality of necking modules. The benefits derived from this method include reduced metal wrinkling and/or pleating and the ability to reduce the thickness of the metal blank used to form the container body. In the illustrated embodiment of FIG. 1, multiple necking operations and one flanging operation are performed on the neck of the container. The length of the necked-in or inwardly-tapered portion is increased during each of the necking operations.  
         [0084]    In each necking operation, a portion of the taper is reworked to extend its length. Small segments of reduction are taken so that the various operations blend smoothly into the finished necked-in portion. The resultant necked-in portion has a rounded shoulder on the end of the cylindrical side wall which merges with an inwardly-tapered annular straight segment through an arcuate portion. The opposite end of the annular straight segment merges with the reduced cylindrical neck through a second arcuate segment.  
         [0085]    The necking operation will be described by reference to FIGS.  12 - 22 . In the embodiment described, a “211” aluminum container is necked to have a “202” neck in ten operations. Assume that a container  16  carried by a conveyor, as indicated in FIG. 1, has been moved into position, such as shown in FIG. 2, and the necking operation is being initiated. FIGS.  12 - 22  depict the necking operation performed in ten necking station modules; however, sixteen or more necking station modules can be utilized.  
         [0086]    A trial was performed by inserting the pilot member  140  of the present invention into a manually operated press which was converted to be a necking station which was designed to simulate the fourth necking operation. The fourth stage is known to be pleat sensitive.  
         [0087]    Pilot member  140  dimensions were chosen corresponding to the fourth stage die dimensions, assuming the container to be necked would be a standard production beverage container having an initial varnished topwall thickness of 0.0066 ins. (0.167 mm). After the third stage, the topwall thickness of the container was measured at 0.0068 ins. to 0.0069 ins. (0.173-0.176 mm).  
         [0088]    The diameter of the pilot member bulge  174  was that of the inside of the container neck at the end of the third stage in the necking apparatus.  
         [0089]    An entry radius of the pilot member  140  was chosen arbitrarily. Subsequent trials indicated that the entry radius may be set to match the natural bending radius of the topwall of the container as it engages the die  130 .  
         [0090]    Angles located at the intersection of the peripheral edges of the support segment  150   a - d  were sharp to avoid any gap between the fully expanded pilot member  140 .  
         [0091]    Trials were conducted to determine the correct air pressure and the timing of the pressurized air application to neck a standard top wall thickness (0.0066 inches or 168 μm) container. Not having enough air pressure caused large numbers of containers to crush while improper timing for the application of the pressurized air pushed the containers out of the dies before the pilot member collapsed, and the containers unnecked.  
         [0092]    The following procedure was established, and it was controlled as a function of the press. The containers were placed in the apparatus. The air pressure was opened to pressurize the container. Next, the pressurized container was necked. The air pressure was removed as soon as the container forming was complete. Another blast of pressurized air was then provided to eject the container after the pilot member was contracted.  
         [0093]    The results from this trial were mixed. Few of the containers were crushed with the air pressure at 3 bars or lower. Other than the few crushed containers, none of the containers exhibited pleats. Containers that were not crushed or pleated were obtained by increasing the air pressure above 3 bars, and the time to pressurize the container before forming.  
         [0094]    The trials were repeated with containers having a topwall thickness of 0.0054 inches (138 μm). The air pressure was reduced to 3 bars or less with the same tooling. All of the containers were necked successfully.  
         [0095]    Results of the trials are summarized in Table 1.  
                                             TABLE 1                                   Varnished   Varnished           Containers   Containers                                        No. of Containers   30   30           Thickness of Topwall   173-176 μm   138 μm           Properly Necked Containers   27   30           Pleated Containers    0    0           Crushed Containers    3    0                      
 
         [0096]    The method of the present invention is less sensitive to tight tolerances than conventional die necking. In a conventional necking apparatus, tight tolerances are necessary to form the neck prior to the container reaching the die exit radius and partially above the die exit radius after the neck is formed. With the expandable pilot member, the die and sleeve exit diameters do not need to be closely dimensioned to each other because tightening at the neck formation is done by the forming segments on the expanded pilot member diameter. Thus, an additional 35 μm of clearance coming from the thickness of the top wall (from 176 μm to 138 μm) is achieved.  
         [0097]    While a specific embodiment has 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