DOMER ASSEMBLY FOR FORMING CONTAINER END WALL

Abstract: A domer assembly includes a domer pad (50) and an annular forming element (52) with biasing means between the pad, the annular forming element and the base. The biasing means for the annular forming element includes an annular chamber divided into spaced segments (177, 179) that each have a piston (188, 190) reciprocated therein and a pressurized fluid source connected thereto, while the domer pad is supported on a post (150) that extends through a tubular column forming part of the base and has an enlarged pad (152) at the opposite end which also is in communication with the pressurized fluid source to produce an end wall configuration that has a center dome (20), a generally U-shaped annular portion (22) connected by two arcuate portions (36, 38) to the side wall of the container.

Description: DOMER ASSEMBLY FOR FORMING CONTAINER END WALL DESCRIPTION Technical Field The present invention relates generally to the formation of drawn and ironed containers having a cylindrical shell and an integral end wall and, more particularly, to a forming apparatus for the reforming of the end wall of a drawn and ironed container and the resultant container. Background Prior Art One type of machine that has been utilized for producing container shells of the above type is manufactured by Ragsdale, Inc., and is identified as a Model CR-24 Can Wall Drawing and Ironing Press. This machine includes a plurality of axially-spaced die assemblies that cooperate with the movable punch to convert the shell cup into a finished container shell. At the end of the stroke, the punch cooperates with the domer assembly for producing the final configuration of the integral end wall of the container. This dome configuration for the end wall has a very critical configuration which allows the container to withstand substantial internal pressures during the filling and handling operations, and also to withstand considerable stresses or resistance to buckling and inversion when the container is dropped after being filled. Another type of machine that has found a remarkable degree of commercial success for producing container shells of the above type is manufactured by Standun, Inc. and is generally disclosed in U.S. Patent o. 3,735,629. The Standun machinery, in its present commercial form, as modified by the Assignee of the present invention, has been proven to be capable of producing container shells at a rate of more than 200 per minute under strenuous operating conditions and, thus, the time for reforming the end wall to its final complicated configuration is extremely limited and the container end wall must be free of any wrinkles after such reforming process. In an effort to reduce the cost of finished containers, manufacturers are constantly striving to reduce the thickness of the initial stock material, thereby decreasing the overall metal cost of each container. Since the end wall (bottom) of the container essentially represents the initial thickness of the can stock, new bottom profiles are required to maintain the pressure performance of thinner guage of stock materials. Purchasers and users of such containers, particularly the beer and beverage industry, have very stringent requirements which require that the finished and filled container be capable of maintaining internal pressures above 100 psi minimum without any significant distortion, and to provide such capability, rather elaborate dome or end configurations have been developed. Another more recent requirement for such drawn and ironed containers is that the container must have a minimum resistance to the reversal of the end wall when the container is inadvertently dropped after it has been filled and is ready for sale and that the end wall have a buckle resistance of more than 100 psi. However, as the thickness of the stock material decreases, the problem of wrinkling the container shell wall becomes more acute, particularly when attempting to produce the more elaborate configurations in the end wall. One problem that has recently received some attention is the handling of the containers, particularly during shipment, storage and display. With the increased use of the reduced end necked portion on the upper end of the container, allowing for the use of smaller ends as part of the package, one of the problems that has been encountered is stability of the containers, particularly when several six-packs of individual containers are stacked upon each other. This has created a problem in displayng the goods on shelves. While this has to some degree been a problem in the industry, no particular attention has been given to solutions for accommodating proper stacking and interlocking of a plurality of containers on a shelf. Thus, while numerous types of domer assemblies have been proposed and have been utilized on a commercial basis, manufacturers of drawn and ironed containers are constantly striving the enhance the machinery for forming such drawn and ironed containers so that it will be more reliable, can easily be maintained and can also be changed to change the configurations of the container end walls, if desired. Summary of the Invention According to the present invention, a unique domer assembly has been developed which is capable of producing substantially wrinkle- free reformed end walls in drawn and ironed containers using minimum thickness of stock material that has heretofore not been possible. The domer assembly, in cooperation with a conventional punch of a drawing and ironing machine, is designed such that the forming elements can easily be removed and replaced without disassembly of the entire unit. More specifically, the domer assembly of the present invention is designed for use with an ironing machine having a punch reciprocable along a path on the frame of the ironing machine which cooperates with the domer to reform the end wall of a container shell. The punch cooperates with a center domer element and an annular forming element which are resiliently biased to a first position and are movable from said first position in response to forces applied by the movement of the punch to absorb the shock loads developed during the can manufacturing operation and also to insure that there is uniform conformity of the end wall of the container shell with the domer and the punch without any wrinkles. In the embodiment disclosed, the center domer element is mounted on a post that extends through a tubular column which forms part of the base or frame and the post has an enlarged pad or surface on the opposite end thereof that is located within a sealed chamber defined in the base or frame. The sealed chamber is adapted to receive pressurized pneumatic fluid, such as air, to act as a shock- absorbing member, as will be described later. The doming element is likewise biased to a first position through a pneumatic pressurized fluid source that cooperates with a pair of axially-spaced annular pistons which surround the tubular column and have adjacent ends in engagement with each other, while one end of one piston is engageable with the annular forming element, preferably through a plurality of circumferentially-spaced pins. More specifically, the biasing means comprise first and second axially-spaced annular pistons that are located in separate chambers with the second piston having an annular flange surrounding the support column that has a free end which is engageable with the first piston so that the two pistons move as a unit and are separately enclosed in sealed chambers. Thus, large forces can be developed in a very confined space. Furthermore, the structural arrangement of the supporting elements for the domer pad and the annular-forming or doming element are at all times exposed for easy access and are held in the assembled position through an annular collar, which can readily be removed so that the components can be replaced in a minimum period of time, reducing the down¬ time for the machinery in the event such is necessary. The particular configuration of the domer elements and the punch, along with biasing means that result in large holding pressures on the container end wall during the reforming process, allows the end wall of a container formed from stock material of 0.0130 inches or less into a configuration that is capable of resisting buckling pressure greater than 100 psi. The end wall is free of any wrinkles and is formed to the rigid configuration that is capable of resisting dome reversal when filled with a product and inadvertently dropped. According to a further aspect of the present invention, the container produced by the above apparatus can be formed using reduced thickness stock material- without increasing the diameter of the disc-shaped stock material. The new container has excellent column strength, buckle strength and resistance to harsh handling, while at the same time incorporates a nesting feature for allowing the bottom profile wall to nest with the end attached to the reduced neck portion of the container. More specifically, the drawn and ironed beer and beverage container includes a cylindrical side wall having a reduced neck surrounding an upper open end with an outwardly- directed flange adapted to be seamed to a reduced diameter end. The bottom profile is designed to nest on the reduced diameter end to provide a peripheral support around the entire perimeter between the end and the bottom of two adjacent containers. The bottom profile includes a spherically, inwardly-domed portion surrounded by a generally U-shaped annular segment defining a lower support for the container with the annular segment having a diameter of about 80% of the diameter of the side wall. A specifically configured annular joining segment is integral with the side wall and the U-shaped annular segment with the joining segment including a first annular arcuate portion having an interior radius and a second annular arcuate portion having an exterior radius to produce an annular support point for nesting with an end on an adjacent container. The particular domed profile is configured to eliminate the need of any metal reversal during the formation of the bottom profile at the end of a drawing and ironing operation, and the profile incorporates specifically-dimensioned radii and segments that simplify the metal-deforming process so that the containers can be manufactured at acceptable production rates. Brief Description of Drawing FIG. 1 is a fragmentary cross- sectional view of the container having the present ivnention incorporated therein; FIG. 2 is an enlarged fragmentary cross-sectional view of the container shown in FIG. 1, along with the tooling for forming the bottom profile; FIG. 3 is an enlarged fragmentary segment of the container bottom profile; FIG. 4 is a perspective view of a container having an end seamed thereto; FIG. 5 is a fragmentary cross- sectional view showing two containers in nesting relation to each other; and, FIG. 6 is cross-sectional views of a 5 fragmentary portion of a domer assembly and punch that forms part of a drawing and ironing machine. Detailed Description 10 FIG. 1 of the drawings discloses a fragmentary portion of a container, generally designated by reference numeral 10, having a generally cylindrical side wall 12 and an integral end wall 14. Container 10 is what is - 1 - 5 commonly known as a "drawn and ironed container" wherein a flat circular metal disc is converted into a shallow cup in a press, commonly referred to as a "cupper". The shallow cup is then delivered to a drawing and 2 o ironing machine, commonly referred to as a "bodymaker" wherein the cup is reformed to reduce the diameter thereof and increase the height by reducing the thickness of the side wall. The end wall is subsequently reformed at 5 the end of the stroke of the punch that forms part of the press or bodymaker. After the end wall or bottom has been reformed to the particular bottom profile, the container has a reduced neck 16 formed around the open end and 0 an outwardly-directed flange 18 with the flange being utilized for double-seaming an end thereto.. With the increased attention in reduction of metal costs, many manufacturers are now utilizing what is referred in the industry as a "206 End" rather than the prior, most common "209 End", the numerical values indicating the effective diameter of the end, which also dictates the amount of metal required for forming the end. With the use of the "206 End" and a substantially reduced neck on the upper end of the container, the problem of stacking several groups of containers upon each other has become more acute. Most commercially-available containers use a bottom profile having an outwardly-convex peripheral annular segment surrounding a reduced diameter lower support surface and an inwardl -domed central portion inside the annular support surface. According to the present invention, the bottom profile of the drawn and ironed container is configured such that the bottom of one container will nest within the end of an adjacent container attached to the reduced neck and the container is still capable of withstanding internal pressures on the order of 100 psi and also has a column strength of approximately 350 pounds or greater. Moreover, the present container has exhibited excellent results in drop-tests that have recently become a criteria in the beer and beverage industry. According to the present invention, the lower end 14 of the container 10 includes a center domed portion 20 (FIG. 3) surrounded by an annular U-shaped portion 22 and an annular joining segment 24 integral with the side wall 12 and the U-shaped portion 22. As shown in FIG. 3, the center domed portion 20 has a spherical radius Rl and is joined to the U-shaped portion by an arcuate segment 26 having a radius R2. The U-shaped portion 22 includes an annular, substantially vertical wall 28 and an outer annular wall 30 interconnected by an annular arcuate lower segment 32 having an interior radius R3. The lower segment 32 defines an annular support surface 34 for the container 10. The inner annular wall 28 is substantially vertical and defines an included angle with respect to a vertical axis (not shown) through the container which is as close to zero as possible, while the outer annular wall 30 defines an angle A. The joining segment 24 includes a first annular arcuate portion 36 having an exterior radius R4 and a second annular arcuate portion 38 having an interior radius R5. The particular radii and dimensions of the various parts that form the integral lower end 14 of the container are important to the overall performance of the container when filled with pressurized contents and also incorporates a nesting feature which will preclude "wobbling" when two filled containers are stacked on each other. A specific set of parameters will now be described with the understanding that some of these parameters may be varied without departing from the spirit of the present invention. A container having a cylindrical side wall diameter Dl of 2.597 inches (64.93 mm) was for ed from a flat circular disc having a diameter of 5.495 inches (137.38 mm) and a thickness of 0.0128 inch (.32 mm). The disc was first converted into a cup and then converted to a finished drawn and ironed container using tooling shown in FIG. 2, to be described later. The container center dome 20 has a spherical radius Rl of 2.120 inches (53.85 mm) with the radius R2 of segment 26 being 0.050 inch (1.25 mm). The lower annular arcuate support had a radius R3 of 0.040 inch (1.00 mm) and the angle A for wall segment 30 was 27°30* and the angle for wall segment 28 was less than 5°, preferably as close to vertical as possible. The exterior radius R4 was 0.100 inch (2.80 mm), while the interior radius R5 was 0.200 inch (5.00 mm). The support diameter D2 for the container was 2.000 inches (50.00 mm), while the diameter D3 for the center of the radius R4 was 2.365 inches (59.13 mm) and the diameter D4 for the center of the radius R5 as 2.187 inches (54.68 mm). This type of container was then filled with beverage and an end 40 was seamed to the reduced neck portion 16 by a double seam 42 (FIG. 4). The end was a standard commercial 206 End. This container was tested extensively and was found to meet or exceed all minimum requirements for the beer and beverage industry. Furthermore, filled containers, when stacked upon each other, had a good snug fit with continuous contact around the entire periphery. Actual tests were conducted on this and it was found that the bottom profile nested snuggly into a "206 End" double seamed to the opposite end of the container after it was filled with a product and did not "rock". Dome reversal tests were then conducted using a bottom profile having a dome height of 0.390 inch, measured from the lower center of the dome to the bottom edge of the container, and it was determined that it withstood pressures of 99.5 psi before dome reversal occurred. This figure is well above the minimum requirements for this container. FIG. 5 of the drawings shows the nesting relation between two containers stacked upon each other. It should be noted that the annular arcuate segment 36 has continuous extended contact with the double seam 42 and the U-shaped annular segment 22 is partially wedged into the double seam to prevent tilting of the upper container with respect to the lower container. While the relative dimensions and their relation have not been fully explored, it is believed that some of the relationships are critical to the overall success in performance of the container. For example, in the specific container described, the diameter D2 was less than 80% of the diameter Dl of the container. The relationship between the diameter of the support surface 34 and the spherical radius Rl of dome 20, along with the vertical annular wall 28, is believed to add strength characteristics. Also, the fact that the joining segment has two arcuate segments 36 and 38 having significantly different radii, with radius R5 being about twice the radius R4, provides excellent internal pressure resistance. FIG. 2 of the drawings shows the tooling used for forming the bottom profile of the present invention. The tooling includes a center dome pad 50, an outer annular forming element 52 and a punch 54. The center dome pad 50 has an upper spherical surface 56 having a radius Rl and a peripheral edge having a radius R2, along with a peripheral vertical surface 58. The outer annular forming element 52 has an inclined flat surface 60, a convex annular surface 62 having a radius R4, and a concave annular surface 64 having a radius R5. The punch 54 has a lower nose 70 configured to produce the U-shaped portion 22 and an outer surface 72 conforming to the surfaces 62 and 64. Containers constructed in accordance with the present invention exhibited more than adequate resistance to buckling, internal pressure and column strength. It has also been noted that the stock material thickness could be reduced to 0.0125 inch, and possibly as low as 0.0120 inch, which significantly reduces the raw material cost for these containers. It should also be noted that the tapered upper end 16 of the container is a -In¬ constantly-reducing taper from the cylindrical sidewall to the upper flange 18. This constantly-reducing tapered smooth neck is produced in a spin-necking operation and tests have shown that this results in significantly increased crush strength for the container, in fact, these tests show that the upper edge of the neck will actually curl rather than having the tapered portion wrinkle. As indicated above, one of the problems encountered in forming container shells from reduced thicknesses of aluminum stock material and reforming the end wall of the configuration described above is that the metal has a tendency to wrinkle, particulary in the reformed juncture area, which renders the finished container unacceptable. According to the present invention, the domer 50 and annular forming element 52 are biased with unique biasing means that produce greater pressure in a confined space to insure that the container shell is accurately reformed around the punch 54 without wrinkling of the very ductile aluminum. FIG. 6 discloses a domer assembly, constructed in accordance with the teachings of the present invention, generally designated by reference numeral 110 that cooperates with punch 54 for reforming the end wall 14 of drawn and ironing container shell 10 to the configuration described above. The domer assembly 110 consists of a base or frame structure 120 that has a central domer 50 and an annular forming or doming element 52 surrounding the central domer or pad 50. The center axes of the domer pad 50 and the annular forming element 52 are coaxial with each other and with the axis of the punch or ram 54. The base or frame 120 consists of a generally circular housing 130 at the lower end which has a tubular or circular support column 134 extending therefrom which is held in a fixed position with respect to the lower housing 130 through a plurality of bolts 136 and an annular collar 138. A generally circular chamber 140 is defined on the lower end of the housing 130 and is closed by a lower cover plate 142 to define a sealed chamber that is in communication with the center support column 134. The center domer element ' 50 is supported by a domer pad support element 146, with the pad secured to the element 146 through a center screw 148. The support element 146 rests on a center post 150 that extends through the tubular column 134 and has an enlarged pad 152, which is located within the sealed chamber 140, and is secured to the lower end of post 150 by a bolt 153. The pad 152 defines an enlarged continuous surface 154 which is substantially greater than the exposed surface area of domer 50 and is exposed within the chamber 140 to a pressurized pneumatic source of fluid that is delivered into the chamber through an opening 156 in the cover plate. The center support post 150 is preferably in the form of two members 150a and 150b, which are interconnected with each other through a bolt 150c, with a plurality of anti¬ friction elements 160, such as brass bushings, supported on reduced portions at the opposite ends of members 150a and 150b and separated by a spacer 161 to provide a friction-free movement of the post 150 with respect to the tubular support column 134. The annular forming element 52 has a peripheral flange 168 and is retained on the upper end of a circular housing 180 through a support collar 170 and a plurality of circumferentially-spaced bolts 172. The lower end of the annular-forming element 52 rests on the upper end of a plurality of circumferentially-spaced pins 174 that extend through openings in the element 146. The lower ends of the pins 174 are exposed within an annular chamber 176 that is defined between the outer circular housing 180 and the center tubular column 134. The annular chamber 176 is divided into first and second chamber segments 177 and 179 through an annular ring 182 that has an outer peripheral flange 184 directed towards collar 138. Thus, the upper chamber segment 177 is separated from a lower chamber segment 179 through the annular ring 182 and first and second pistons 188 and 190 are respectively located within the upper and lower annular chamber segments 177 and 179. The second annular piston 190 has an upwardly-directed flange 192 integral therewith, the free end of which is adapted to be maintained in engagement with the lower surface of the first piston 188. In the specific embodiment illustrated, the circular housing 180 has its lower end attached to annular collar 138 through bolts 193 and its upper end attached to support collar 170 through bolts 172 so that the circular housing 180, collar 138 and lower housing 130 define a one-piece or basic frame 120. This one-piece fixed frame 120 is designed to be received into a confined space in either a Ragsdale bodymaker or a Standun bodymaker without any modification thereof. For this purpose, an upper annular support collar 210 and a lower annular support collar 212 are threaded and received onto the threaded outer surface of circular housing 180. Collars 210 and 212 are utilized in supporting the entire dome assembly 110 in either a frame element 230 that forms part of a commerσially- available Ragsdale drawing and ironing machine or a commercially-available Standun machine having a frame element 232. If the domer assembly is used with a Ragsdale bodymaker, the enlarged collars 210 and 212 abut opposed surfaces of frame element 230 and are clamped with one or more bolts 233 to hold the assembly in the fixed position with respect to the punch assembly 54. If the unit is designed to be utilized with a Standun machine, a spacer sleeve 240 is utilized as part of the support member, along with collars 210 and 212 to fix the domer assembly on frame element 232 using a bolt 233. Pressurized pneumatic fluid is supplied to the chamber 176 through conduit means that may be formed directly in the one- piece fixed frame and connected to a pressurized pneumatic fluid source or means, such as air (not shown). Thus, as shown in FIG. 6, collar 138 has one or more counterbores 250 extending from the periphery thereof and in communication with an axial bore 252 in circular housing 180 which in turn is in communication with chamber segments 177 and 179 through bores 254 and 256, respectively. The source (not shown) is connected to the open end of counterbore 250 and may have an accumulator (not shown) associated therewith. The same or a different pressurized fluid source is connected to inlet 156. Suitable seals 260 are provided where necessary. As is apparent from an inspection of FIG. 6, the internal opening in circular housing 180 is stepped to provide a shoulder 272 for ring 182 resulting in different volumes for chamber segments 177 and 179 and different surface areas on pistons 188 and 190 exposed to the pressurized fluid. Thus, chamber segments 177 and 179 could be pressurized to different levels to initially provide a lower holding force in annular forming element which would be increased as the forming element moves. The provision of two axially-spaced pistons in the separate chambers, which may be considered primary and secondary biasing means. both in communication with a pressurized fluid • source, produces greater holding pressures between the annular element 52 and the punch 54 during the forming process in a very confined space, which minimizes the possibility of wrinkles developing in the reformed end wall of the container shell. Also, as can be seen from the drawing, the surface area of the pad 152 is extremely large in relation to the surface area of the domer pad so that extremely large reaction forces can be absorbed without significant movement of the- domer element and, at the same time, the domer element can still move a limited amount without destruction of the tooling in case a misfed container shell is introduced into the system. If desired, a sensor 258 may be provided to sense the extent of movement of pad 152 and interrupt the machine in the event of excessive movement of the domer 50, such as when two container shells are on punch 54 simultaneously. Also, vent openings 270 may be provided through circular housing 180 to vent the unpressurized side of chamber segments 177 and 179 to atmosphere. A further advantage of the above arrangement of the domer assembly is that the domer 50 and/or annular forming element 52 can easily be replaced merely by removal of bolts 172 and collar 170. After the collar 170 is removed, the domer 50 and/or annular forming element can be withdrawn and replaced.

Claims: CLAIMS 1. Apparatus for reforming an end wall of a container shell comprising a punch reciprocable along a path with said container shell thereon, a base at the end of said path having a center tubular column with a central domer supported on said column and aligned with said punch, and an annular forming element surrounding said central domer with biasing means between said base and said annular forming element, the improvement of said biasing means including first and second axially-spaced annular pistons around said column and engageable with said annular forming element and pressurized pneumatic fluid means in communication with said first and second pistons to bias said annular forming element to a first position and accomodate constrained movement of said annular forming element in response to forces applied by said punch. 2. Apparatus as defined in Claim 1, in which said base has an annular chamber surrounding said column with a divider in said chamber to form first and second chamber segments respectively having said first and second pistons therein and said pressurized pneumatic fluid means is in communication with both chamber segments so that a large reaction force is developed on said annular forming element in a confined annular space. 3. Apparatus as defined in Claim 2, in which said first piston has a first surface engageable with said annular forming element and an opposite surface exposed to said pressurized pneumatic fluid means and in.which said second piston has an annular flange extending from a first surface engageable with said opposite surface and an opposite surface exposed to said pressurized pneumatic fluid means. 4. Apparatus as defined in Claim 1, in which said column has a center post telescoped therein with said central domer supported on one end of said post and an enlarged reaction pad on an opposite end of said post and in which said base has an enlarged sealed chamber receiving said reaction pad and in communication with said presssurized pneumatic fluid means to produce a substantially larger reaction force on said central domer in relation to forces on said annular member. 5. Apparatus as defined in Claim 1, in which said annular forming element has a lower inclined flat annular surface, a convex annular surface above said flat annular surface and a concave annular surface above said convex annular surface, and in which said punch has an annular nose and a surrounding annular surface corresponding to said concave annular surface and said convex annular surface and cooperating with said central domer and said annular forming element to produce a bottom profile having a central spherical dome surrounded by a generally U-shaped portion having flat walls and an arcuate annular convex portion and an arcuate annular concave portion between said U- shaped portions and a side wall of said container. 6. A drawn and ironed beer and beverage container of the 8-ounce and also the 12-ounce and 16-ounce variety and having a bottom profile adapted to nest with an end of the 206 variety seamed to an open end of another container comprising a cylindrical side wall having an integral bottom having a first arcuate annular portion integral with said side wall and having an interior radius of approximately 0.200 inch, a second arcuate annular portion integral with a lower end of said first arcuate annular portion and having an exterior radius substantially less than the radius of said first arcuate annular portion, a generally U-shaped annular portion integral with said second arcuate annular portion and having inner and outer flat portions defining an acute angle of substantially less than 45° interconnected by an arcuate segment defining a lower annular support for said container, and an inwardl -domed spherical disc having a radius greater than the diameter of said lower annular support and less than the diameter of said cylindrical side wall, said second arcuate annular portion defining a peripheral contact point with said end. 7. A drawn and ironed beer and beverage container as defined in Claim 1, in which said diameter of said lower annular support is about 80% of the diameter of said cylindrical side wall. 8. A drawn and ironed beer and beverage container as defined in Claim 2, in which said exterior radius is about 0.100 inch. 9. A drawn and ironed beer and beverage container as defined in Claim 3, in which said interior radius is about twice the dimension of said exterior radius.

Inventors: MIKAS RAYMOND, PULCIANI SAM C, SZCZERBA ROBERT M, WYLETA ROBERT M, MIKAS, RAYMOND, PULCIANI, SAM, C., SZCZERBA, ROBERT, M., WYLETA, ROBERT, M.
Applicants: NAT CAN CORP, NATIONAL CAN CORPORATION
Application year: 1985
Main classification: B21D22
IPC codes: B21D22, B65D1