Patent Publication Number: US-6658911-B2

Title: Method and apparatus for forming container end shells

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/324,897 filed Sep. 25, 2001, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates to a method and apparatus for forming end shells for metal containers, and particularly to forming the end shell with an annular reinforcing rib and a peripheral curl. Even more particularly, the invention relates to forming the reinforcing rib and peripheral curl on the end shell in a single press cycle in which the end shell is formed from a starting blank of sheet material. 
     2. Background Information 
     In the metal container art, containers usually consist of a body formed of lightweight metals such as an aluminum, and a separate end shell for closing the container, also formed of lightweight metal from strip material. It is desirable in forming the end shells to form a peripheral curl to enable the end shells to be stacked and transported between work stations without the end shells nesting too tightly together and sticking, hampering their movement through various production stages until they are ultimately seamed onto the finished container. This peripheral curl may also facilitates the seaming of the end shell on the open top of the container. 
     Various types of tooling has been developed for forming this peripheral curl, most of which requires a separate machine and tooling station separate from that of the press in which the end shell is formed. One common tooling uses curling rolls such as shown in U.S. Pat. No. 4,116,361. However, these prior art curl forming machines involve transporting the end shells from the forming press to a second station for the curling operation which requires additional equipment for handling the end shells. 
     Other types of tooling have attempted to form the peripheral curl on the end shell in the same press or tooling station in which the end shell is formed to avoid this transfer problem and expense. Examples of such single station tooling for forming the end shell and peripheral curl are shown in U.S. Pat. Nos. 4,031,836, 4,372,720, 4,574,608, and 6,290,447. In this type of tooling, the initial disc blank and final end shell having the peripheral curl thereon is formed and ejected from the press at the same level in the press. It has been found that production speed can be increased by performing several of the forming operations, such as blanking of the initial disc blank and forming a preliminary cup-shaped blank at a first level, and then final forming the end shell at a second level, at which level the shell is then ejected from the press. Examples of such multi-level end shell production type presses are shown in U.S. Pat. Nos. 4,903,521 and 4,977,772. However, none of these multilevel presses form a peripheral curl on the end shell. 
     It is also desirable to form an annular reinforcing rib in the end shell to provide strength and rigidity thereto. Various types of tooling have been developed for forming an annular reinforcing rib in the end shell between the central panel and peripheral edge. However, certain types of tooling use a die having a male portion which engages and forces the metal into an opposed complementary female die providing a positive engagement between the tooling and metal. This die contact can cause thinning and wrinkling of the metal due to the pressure exerted by the dies against the metal trapped therebetween. Examples of such tooling are shown in U.S. Pat. Nos. 4,516,420, 4,587,825, 4,713,958, 4,715,208, 4,716,755, 4,808,052, and 4,977,772. Another type of tooling pushing the metal into an enlarged cavity without a male or positive female die component, such as shown in U.S. Pat. Nos. 4,109,599 and 4,571,978. Since the cavity is enlarged, it does not form a true radius for the reinforcing rib, which can reduce to strength of the resulting rib. 
     Thus, the need exists for an apparatus and method for forming container end shells with an annular reinforcing rib and a peripheral curl in a single press cycle wherein the blanking and partial forming of the end shell is carried out at a first level and the formation of the final end shell, reinforcing rib and peripheral curling is carried out prior to ejection of the end shell from the press at the second level in order to increase the speed of production. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for forming an end shell for use on a container body which is formed in a single press cycle at a single work station wherein a portion of the end shell is produced at a first level and the final forming of the end shell, including forming an annular reinforcing rib and peripheral curl, is formed at a second level in the press, from which level the finished end shell is ejected. 
     Another aspect of the present invention provides for the forming of the end shell without complicated and expensive modifications for retrofitting existing presses and which eliminates the need for expensive and complicated transfer mechanisms for transferring the end shell to an adjacent curling station. 
     A further aspect of the invention preferably provides an apparatus and method for forming a plurality of the end shells in a single cycle of the press wherein the reinforcing rib and peripheral curl are formed on the end shell during the upward movement of an inner ram, and in which a curl forming outer die ring also functions as the lift ring for moving the completed end shell back to the second level for subsequent ejection from the press. 
     Still another feature of the invention is to form the annular reinforcing rib in the end panel of the shell just prior to forming the end curl during upward movement of an outer die core ring and aligned outer punch shell. 
     Another feature of the invention is forming the peripheral curl by increasing the overall outer diameter of the end shell in contrast to the heretofore methods and apparatus which reduce the diameter of the end shell to form the peripheral curl. 
     A further feature of the invention is to provide an apparatus and method for forming an end shell having an annular reinforcing rib and a peripheral curl which avoids any thinning of the metal and which prevents wrinkling of the metal by maintaining a portion of the frustro-conical chuckwall portion of the end shell in a secure clamped position between an inner pressure member and an inner die core ring during formation of the reinforcing rib and peripheral curl. 
     The present invention forms the peripheral curl by pivotally moving an outer portion of an elongated chuckwall of an end shell blank during reverse movement of an outer die core ring and outer punch sleeve by providing a slip-fit clamping engagement of the outer periphery of the chuckwall therebetween. 
     The present invention also forms an annular reinforcing rib in the end shell by pushing metal from the chuckwall into an annular groove or female die component formed in the punch core during reverse movement of an outer die core ring and outer punch sleeve wherein the groove matching the desired radius of the reinforcing rib and functions as the female die component, but without a male die component engaging the metal. 
     The foregoing advantages, construction, and operation of the present invention will become more readily apparent from the following description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention, illustrative of the best modes in which applicant contemplates applying the principles of the invention, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims. 
     FIG. 1 is a partially schematic sectional view of the apparatus of the present invention mounted in a press and showing the blanking of a flat disc-shaped blank from the strip material; 
     FIG. 2 is an enlarged view of a portion of FIG. 1 showing formation of the cup-shaped blank from the flat disc-shaped blank; 
     FIG. 3 is further enlarged fragmentary sectional view showing the formed cup-shaped blank moving to the second level of the press; 
     FIG. 4 is a view similar to FIG. 3 showing the start of forming of an elongated chuckwall of an end shell blank; 
     FIG. 5 is a sectional view similar to FIG. 4 showing the continued formation of the elongated chuckwall; 
     FIG. 6 is a view similar to FIGS. 4 and 5 showing the partially formed end shell at the bottom of the press down stroke; 
     FIG. 7 is a view similar to FIG. 6 showing the start of forming the reinforcement rib in the end shell upon the return up stroke of the press; 
     FIG. 8 is a view similar to FIG. 7 showing completion of the annular reinforcement rib just prior to formation of the peripheral curl; 
     FIG. 8A is an enlarged view of the encircled portion of FIG. 8; 
     FIG.  8 AA is an enlarged view similar to FIG. 8A showing a modified punch shell configuration; 
     FIG. 9 is a view similar to FIG. 8 showing the start of forming the peripheral curl; 
     FIG. 9A is an enlarged view of the encircled position of FIG. 9; 
     FIG.  9 AA is a view similar to FIG. 9A utilizing the modified punch shell; 
     FIG. 10 is a view similar to FIGS. 8 and 9 showing completion of the peripheral curl; 
     FIG. 10A is an enlarged view of the encircled position of FIG. 10; 
     FIG.  10 AA is a view similar to FIG. 10A utilizing the modified punch shell; 
     FIG. 11 is a view similar to FIG. 10 showing the formed end shell being moved back to the second level for subsequent ejection from the press; 
     FIG. 12 is a view similar to FIG. 11 showing the end shell being ejected from the press at the second level; 
     FIG. 13 is an enlarged sectional view of the flat disc-shaped blank produced by the tooling as shown in FIG. 1; 
     FIG. 14 is an enlarged sectional view showing the cup-shaped blank produced by the tooling as shown in FIG. 2; 
     FIG. 15 is an enlarged sectional view showing the partially formed end shell produced by the tooling as shown in FIG. 6; 
     FIG. 16 is an enlarged sectional view of the finished end shell having the peripheral curl as shown in FIG. 10; 
     FIG. 17 is a view similar to FIG. 2 showing a modified apparatus and method for forming the end shell with the peripheral curl; 
     FIG. 18 is a view similar to FIG. 3 of the modified apparatus showing the cup-shaped blank at the second level; 
     FIG. 19 is a view similar to FIG. 4 showing the modified apparatus starting the elongation of the chuckwall of the end shell blank; 
     FIG. 20 is a sectional view similar to FIG. 6 showing the modified apparatus at the bottom of the down stroke; 
     FIG. 21 is a sectional view similar to FIG. 7 showing the start of forming the reinforcement rib in the end shell by the modified apparatus; 
     FIG. 22 is a view similar to FIG. 8 showing the modified apparatus at the start of forming the peripheral curl on the partially formed end shell; and 
     FIG. 23 is a view similar to FIG. 11 showing the formed end shell with the peripheral curl raised to the second level prior to ejection from the press. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The method and apparatus of the present invention preferably is utilized in conjunction with a double action press, some examples of which are shown and described in U.S. Pat. Nos. 3,902,348, 5,626,048, and 5,628,224. However, if desired the method and apparatus can also be utilized in conjunction with a single action press without affecting the concept of the invention. The main features of press  1  are shown in FIG.  1  and are described briefly below and include an inner ram  3  and an outer ram  5 , only portions of which are shown in FIG.  1 . 
     A usual punch core  8  also referred to as a draw horn, is connected to the lower end of a punch riser  4  which is reciprocated by inner ram  3 . An inner pressure sleeve  9  (FIG. 2) and a concentrically located outer punch shell  10  surround punch core  8  and are reciprocated by inner ram  3  and independently moved by pneumatic cylinders  6  and  7 , respectively. An outer pressure sleeve  12  extends concentrically about punch shell  10  and is reciprocally moved by a piston  13  controlled by movement of outer ram  5 . A cut ring  15  is mounted on outer ram  5  by a cut ring retaining sleeve  16  secured to outer ram  5 , by a plurality of bolts  17 . 
     A blank and draw die  20  is mounted by bolts  21  on a fixed base which is indicated generally at  23 . A stock plate  24  is resiliently mounted by springs  25  or other type of cushioning means on base  23 , for supporting a strip of material  26  as it is fed into the press for forming flat disc-shaped blanks  27  therefrom. When stock plate  24  is at its normal at-rest position aligned with annular top clamping surface  29  of blank and draw die  20 , it will define a first level indicated by plane  30  (FIG.  1 ). A die core, indicated generally at  32 , is fixedly mounted on base  23  and includes a flat planar top surface  33  which defines a second level indicated by plane  35 . Blank and draw die  20  is formed with a die opening  36  which is in vertical alignment with top surface  33  of die core  32 . An air passage  37  is formed in base  23  generally aligned with second level  35 , and is connected to a source of pressurized air for ejecting finished end shells, indicated generally at  39 , from the press as shown in FIG.  12 . Inner and outer die core rings  40  and  41  respectively, are concentrically mounted about die core  32  and are independently moveable with respect to each other and to die core  32  by pneumatic cylinders  42  and  43  respectively. 
     In carrying out the method steps of the present invention, a strip of sheet material  26 , such as lightweight aluminum, is fed into the press in the direction of arrow A (FIG.  1 ). Outer ram  5  moves cut ring  15  downwardly to sever a flat blank disc  27  from sheet  26  without requiring any prior clamping pressure being applied to the sheet material. Blank  27  is releasably clamped between outer pressure sleeve  12  and top surface  29  of blank and draw die  20 . Inner ram  3  then moves downwardly in the direction of arrow B (FIG. 2) whereby punch shell  10  draws disc blank  27  through die opening  36  to form a shallow cup-shaped blank  45  which includes a cylindrical sidewall  46  and a flat bottom wall or panel  47  as shown in FIGS. 2 and 14. 
     Inner ram  3  continues to move punch shell  10 , inner pressure sleeve  9 , and punch core  8  downwardly through die opening  36  carrying cup  45  to second level  35  as shown in FIG.  3 . Pressure sleeve  9  is carried downwardly by upper annular edge  34  thereof engaging an outwardly extending shoulder  28  formed on punch shell  10  until sleeve  9  and shell  10  reach the bottom of their stroke as shown in FIG.  6 . Upon reaching second level  35 , a rounded nose  50  of punch shell  10  will press annular outer corner  51  of cup  45  toward an annular curl forming groove  52  formed in an upper end of outer die core ring  41 . Groove  52  has a considerably greater radius of curvature than rounded nose  50  as discussed below. As shown in FIG. 4, bottom panel  47  of cup  45  is moved against top surface  33  of die core  32  and clamped against surface  33  by an annular flat surface  53  formed on the outer end of punch core  8 . Continued downward movement of punch shell  10  and inner pressure sleeve  9  will move outer and inner die core rings  41  and  40 , respectively, downwardly as shown by arrows C and D (FIG.  5 ). This downward movement of inner pressure sleeve  9  and punch shell  10  will form an end shell blank having an elongated chuckwall  54  formed from portions of cylindrical sidewall  46  and outer portions of bottom panel  47  of cup  45  against a tapered surface  49  of nose  50 . End shell blank  55  (FIG. 15) is formed upon pressure sleeve  9 , punch shell  10 , and inner and outer die core rings  40  and  41  reaching the bottom of the inner ram down stroke as shown in FIG.  6 . Blank  55  includes elongated chuckwall  54  which terminates in a partially curled peripheral edge  57 . 
     After reaching the bottom of the down stroke as shown in FIG. 6, inner and outer die core rings  40  and  41  reverse their direction of movement and begin to move upwardly as shown in FIG. 7 by actuation of pneumatic cylinders  42  and  43  (FIG.  2 ), moving inner pressure sleeve  9  and punch shell  10  upwardly therewith as shown by arrows D. Punch core  8  remains in its lowermost position and maintains clamping pressure against bottom panel  58  of shell blank  55  against top surface  33  of die core  32 . As shown in FIG. 8, an inwardly extending annular shoulder  31  of pressure sleeve  9  engages a stop ring  38  mounted on punch core  8  providing a positive stop and accurate positioning of sleeve  9  for the subsequent forming of curl edge  66 . 
     In accordance with one of the features of the invention, a portion of the metal, which is indicated at  62  and located in the unclamped portion of elongated chuckwall  54  between inner die core ring  40  and annular rib  53  of punch core  8  (FIG.  6 ), is pushed into a female die component formed in the outer periphery of punch core  8  which forms an annular outer groove  60 . Upon completion of the upward movement of inner die core ring  40  as shown in FIG. 8, an annular reinforcing rib  61  is formed in bottom panel  58  of shell blank  55  by movement of the unclamped metal into groove  60  which functions as a female die component. This formation of rib  61  without the use of a mating male die component prevents thinning and wrinkling of the metal. Also, this female die component or groove exactly matches the desired contour, shape, size, etc. of rib  61  in contrast to other rib forming grooves which do not provide this exact matching feature. 
     Outer die core ring  41  continues its upward movement as shown by arrow E (FIG.  8 ), moving punch shell  10  with it as shown by arrow F, while rounded nose  50  of punch shell  10  maintains a releasable clamping engagement with the partially curled peripheral edge  57  of shell blank  55  in curl forming groove  52  of outer die ring core  41 , as shown in FIG.  8 A. Inner die core ring  40  and pressure sleeve  9  remain in position by engagement of shoulder  31  with stop ring  38 . 
     In accordance with another feature of the invention, continued upward movement of outer die core ring  41  in the direction of arrow E (FIG. 8) forms the desired peripheral curl on shell blank  55  as shown in FIGS.  9  through  10 AA and described below. As outer die core ring  41  continues to move upwardly, an annular area  63  of elongated chuckwall  54  (FIGS. 8A,  9 A, and  10 A) is maintained in a secure clamped position between opposed stationary curved outer surfaces  56  and  59  of inner pressure sleeve  9  and inner die core ring  40  respectively, which causes the unclamped outer portion of chuckwall  54  to pivot about a curved area  64  from the position of FIG. 8A to that of FIG.  10 A. During this pivoted movement the material passes through the releasably clamped area between rounded nose  50  and curl forming groove  52  as shown in FIGS. 9A and 10A, whereby partially curled edge  57  will follow the general contour of groove  52  which will cause the metal to curl back upon itself until it reaches the desired final peripheral curl configuration  66  as shown in FIG.  10 A. 
     As punch shell  10  and die core ring  41  move upwardly, the natural inherent tendency of the metal in partially curled edge  57  is to continue to turn inwardly as it moves about the larger radius of surface  52  to form the desired peripheral curl  66 . Since the chuckwall is securely clamped at area  63  between pressure sleeve  9  and inner die core ring  40 , this upward movement of punch shell  10  and die core ring  41  requires the metal to move outwardly which results in the formation of curl  66 . Outer die core ring  41  continues to move upwardly in the direction of arrow E as shown in FIGS. 10 and 11 after formation of peripheral curl  66 , continuing to move punch shell  10  upwardly as shown by arrow F. 
     Immediately after completion of forming peripheral curl  66 , punch core  8 , and inner pressure sleeve  9  will also move upwardly in the direction of arrows G and H as shown in FIG. 11, which will release the clamping engagement of end shell  39  with die core  32  and inner die core ring  40 . This enables outer die core ring  41  to raise the formed end shell  39  to discharge level  35  at which location in the stroke cycle, a blast of pressurized air indicated by arrow  68  (FIG.  12 ), is released through air passage  37  to discharge end shell  39  from press  1  at level  35 . Preferably shell  39  is discharged from the press in the same direction as is the incoming material feed direction. The finished end shell can then be deposited into a hopper, conveyor, or other equipment for transportation to storage or additional processing. 
     Another feature of the invention, as shown in FIGS. 15 and 16, is that the overall outer diameter D 1  of preliminarily formed end shell blank  55  is increased when forming the peripheral curl as shown by larger diameter D 2  of end shell  39 . In all known prior edge curl forming apparatus, the preliminarily formed curl is moved inwardly to form the final peripheral curl, decreasing the overall diameter of the end shell. In the present invention, this increase in overall diameter is achieved by the rotation of the outer portion of the elongated chuckwall  54  about a pivot area  64  as shown in FIGS. 8A,  9 A, and  10 A and discussed above. 
     A slightly modified punch shell  10 A is shown in FIGS.  8 AA- 10 AA. In this embodiment, modified punch shell  10 A is formed with a more rounded nose  50 A than nose  50  described above, and is void of the tapered surface  49 . Most importantly, a shoulder  50 B is formed in an outer edge  10 B of punch shell  10 A. Shoulder  50 B provides a positive stop for controlling the curvature and amount of pivotal movement of the metal during formation of peripheral curl  66 . As the metal moves about nose  50 A and along curl forming groove  52 , it will engage shoulder  50 B, as shown in FIG.  10 AA, which provides for the desired configuration of the peripheral curl to insure consistency therein as the curls are formed in the end shells. 
     Thus, the improved apparatus and method of the present invention enables an end shell to be formed with a peripheral curl at a single station of a press and in a single press cycle by forming a partially formed end shell  55  (FIG. 15) upon completion of the downstroke of the inner ram, with the final peripheral curl being formed upon the upstroke of the inner ram and reverse movement of the inner and outer die core rings. Futhermore, disc-shaped blanks  27  are formed at first level  30  and then moved to second level  35  for subsequent formation of the peripheral curl and ejection from the press providing increased production speed by eliminating the need to raise the finished end shell back to the first level for ejection. This two level feature also avoids any contact or coordination with the movement of the incoming sheet material  26 . 
     A slightly modified form of the apparatus of the present invention is shown in FIGS. 17-23. A main difference in this modified apparatus is providing punch core  70  with an annular groove  71  that is spaced inwardly from the outer periphery of the punch core and the elimination of inner pressure sleeve  9 . Groove  71  forms an outer rounded nose  72  which has a similar contour and functions in a similar manner as did inner die sleeve  9  of the first embodiment described above. As particularly shown in FIG. 22, outer rounded nose  72  of die core  70  clamps area  63  of chuckwall  54  against the upper rounded surface of inner die core ring  40  in the same manner as inner pressure sleeve  9  and retains a clamping engagement therewith as outer die core ring  41  moves upwardly in the direction of arrow E to form peripheral curl edge  66 . 
     In the same manner as shown in FIGS. 8A-10A, outer reinforcing rib  61  is formed in annular groove  71  as inner and outer die core rings  40  and  41  move upwardly as shown in FIGS. 20 and 21. The finished end shell  39  is ejected in a similar manner by pressurized air from air passage  37  as the shell is raised to the second level  35  as shown in FIG. 23 after punch shell  10  has been raised out of clamping engagement with the peripheral curl and punch core  70  moves out of clamping engagement against panel  58 . 
     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.