Abstract:
A method and apparatus for making a container lug lid which minimizes scrap waste is described. The blanks for forming container lug lids therefrom comprise an odd number of dissimilar lugs with one or more of the lugs comprising a male lug. Circumferential bases are formed between each lug, with one or more of the circumferential bases having a female complementary shape for receiving a male lug of an adjacent blank. The blank pattern for cutting the blanks from a sheet of material, which is preferably scrolled, comprises arranging the blanks in a closely spaced arrangement with the male lugs positioned for alignment with an adjacent female or complementary shaped circumferential base.

Description:
This application is a divisional of application Ser No. 09/066,019 filed on Apr. 24, 1998 now U.S. Pat. No. 6,065,628. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains generally to lid closures for use with cylindrical containers. More particularly, the invention pertains to metal lid closures having a plurality of lugs which are crimped for closing and sealing the ends of a pail or container, and to a method for making the same. 
     BACKGROUND OF THE INVENTION 
     Many types of prior art container lids have been devised for closing pails or containers. These container lids are generally applied to an open ended pail or container which has a curled annular rim formed about an open end. Prior art lids are generally disc-shaped and have a downwardly facing annular groove or channel adapted to receive the annular rim of the container. A series of lid lugs project downwardly from the annular channel of the lid for attaching the lid to the container rim. For example, lug lids for use with two and one half to seven gallon containers generally contain an even number of lugs on the order of 16 to 20 lugs, which are formed along a circumferential edge of the lid with spaces formed between the lugs. The lid is sealed to the container by use of a crimping tool to crimp the lugs about the annular rim of the container in a sealing arrangement. 
     These metal container lids are generally manufactured by blanking or punching a rectangular or square sheet of metal with a pattern comprising a plurality of unfolded container lids or blanks. For example, a typical prior art punch pattern is shown in FIG. 1, and comprises four closely spaced unfolded container lids which are symmetrical in shape. One major disadvantage of the prior art container lid design and punch pattern is that costly material is wasted in between the holes (i.e., the scrap skeleton) even though the blanks are closely spaced together. In addition, a larger sheet of material is required than necessary in order to produce a given number of container lids. This waste is a function of the container lid design and the amount of spacing allotted for adjacent blanks. Scrap material represents an expensive loss which is only partly recoverable and which requires additional resources to convert into a usable form. Another disadvantage of the prior art is that more time is wasted in gathering and transporting the scrap to recycling centers. Yet another disadvantage of the prior art is that paint used to coat the sheet prior to punching is wasted as well as the additional energy required to cure the paint on a larger sheet. 
     It is therefore desirable to provide an improved container lid design and blank pattern layout which reduces the amount of scrap material generated and thus results in considerable cost savings with very few drawbacks. It is further desirable to provide an improved container lid design and blank pattern layout which reduces the sheet size of the material while producing an equivalent number of lids. 
     SUMMARY OF THE INVENTION 
     In accordance with the teaching of this invention a container lid is provided, together with a process for making the same in which the container lid is capable of beings inexpensively manufactured with minimal material waste being generated and while having the advantages enjoyed by prior art container lids. 
     The invention provides in one aspect a lug lid for sealing a container having an annular curved rim, the lug lid comprising a planar surface having an annular channel on the peripheral edge of said lid; a plurality of lugs projecting downwardly from an outer wall of the channel; one or more of said lugs being asymmetrically shaped relative to the other lugs; and a plurality of circumferential bases formed between adjacent lugs. 
     The lug lid provides in another aspect a lug lid comprising a planar surface having an annular channel on a peripheral edge of said lid; an odd number of lugs projecting from an outer wall of the channel with one or more of said lugs comprising a male lug; and a plurality of circumferential bases formed between adjacent lugs with one or more of said circumferential bases comprising a female mating gap. 
     The lug lid provides in yet another aspect of the invention an odd number of lid lugs having at least some of those lugs formed in a different shape than other lugs on that lid. The ends of the lugs maybe bent or curled to facilitate removal of the lid from the container. 
     The invention provides in another aspect a method for making a plurality of container lids comprising the steps of forming one or more lid blanks, each blank comprising a plurality of lugs on a peripheral edge of said blanks, a plurality of circumferential bases formed between each of said lugs, one or more of said lugs comprising a male lug, and one or more of said circumferential bases having a complementary female shape for mating with said male lug; arranging the lid blanks upon a sheet of material such that each of said male lug of an adjacent lid blank is aligned and positioned within said mating circumferential base of an adjacent lid blank; cutting the lid blanks from a sheet of material; and forming a container lid from each of said blanks. 
     The invention provides in yet another aspect a method for making container lids comprising the steps of: forming two or more lid blanks having a plurality of lugs on the peripheral edge of the blank, with a plurality of circumferential bases formed between each of said lugs, arranging the lid blanks upon said sheet of material such that one or more of said lugs of a lid blank art interlocked with respect to lugs of an adjacent blank; cuttingi a plurality of lid blanks from a sheet of material; and forming a container lid from each of said blanks. 
     The invention provides in still another aspect a container lid prepared by the method comprising the steps of forming a plurality of lid blanks, each said blank comprising a plurality of lugs on a peripheral edge of said lid, a plurality of circumferential bases formed between each of said lugs, one or more of said lugs comprising a male lug, and one or more of said circumferential bases having a complementary shape for mating with said male lug; arranging the lid blanks patterns upon a sheet of material such that said male lug of an adjacent lid blank is positioned within said complementary shaped circumferential base of an adjacent lid blank; cutting the arranged lid blanks from a sheet of material; and forming a container lid from each of said blanks. 
     The method in another aspect of the invention utilizes a specially configured sheet of material designed in conjunction with the configuration of the lid blanks substantially to maximize utilization of the sheet material. In one form, the sheet material has rectangular aligned end sections with an offset center portion, the offset being formed by a trapezoid of material being added to and extending outwardly from one margin of the sheet while a trapezoidal recess of the same size and shape is provided on the other margin. This material shape permits at least three rows of lid blanks to be positioned on the material, with the center row offset from the top and bottom rows to permit adjacent lug blanks in the rows to be more closely spaced to one another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a plan view of the prior art scroll layout of container lid blanks; 
     FIG. 2 is a perspective view of the container lid design of the present invention adapted to be received on a prior art container; 
     FIG. 2A is a perspective view of a portion of the container lid design showing the other side of the lid in FIG. 1; 
     FIG. 3 is a cross section of the container lid of the present invention taken in the plane  2 — 2  as shown in FIG. 1; 
     FIG. 4 is a plan view of the layout of contain,r lid blanks of the present invention; 
     FIG. 5 is a plan view of a single container lid blank of the invention; 
     FIG. 6 is a greatly enlarged portion of FIG. 4 showing the interface of mating lugs of adjacent container blanks; 
     FIG. 7 is a plan view of an alternative embodiment of the pattern layout of container lid blanks of the present invention; and 
     FIG. 8 is a plan view of an alternative embodiment of the pattern layout of container lid blanks of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to the Figures, and more particularly to FIGS. 2 through 3, there is illustrated a new and improved container lid  10  for use in conjunction with prior art containers  20  typically made of plastic or metal. These prior art containers  20  are suitable for the storage and transportation of paint, liquids, and other flowable materials in a sealed airtight condition. These prior art containers or buckets  20  are generally formed from steel sheets or other resilient material and comprise a cylindrical container body  22  having sidewalls, a conventional closed lower end (not shown), and an open upper end  24  which cooperate to define a storage chamber. The open upper end  24  generally has a curled annular rim  26  which is formed from a curl of rolled metal or other suitable material and is adapted to receive a lug lid  10 . 
     The lug lid  10  of the invention generally comprises a planar surface  30  preferably having a circular or disk-like shape having a plurality of annular strengthening ribs  11  and an annular downwardly facing channel  32  comprising a raised and inverted U-shaped cross section forming an outer peripheral edge  34  of the lug lid  10 . The annular channel  32  is adapted to fit over and seat upon the annular rim  26  of the container  20 , with the annular rim  26  being received in the annular recess of the channel  32 . An optional gasket (not shown) may be seated and affixed by conventional means in the annular channel. Once the lid  10  is seated upon the container rig, a plurality of lugs  40  are crimped along the annular rim  26  of the container  20  such that the lid is in sealing engagement with the container  20 . 
     The lugs  40  are formed about the periphery of the lug lid  10 , projecting downwardly from an outer wall  42  of the annular channel  32 . The lug lid  10  of the invention preferably has an odd number of lugs  40 , typically in the range of 13 to 17 and preferably 15 lugs, many of which are uniquely shape. In contrast, prior art lug configurations (not shown) generally provide an even number of identically shaped lugs, on the order of  18  to  20  lugs per lid. The lugs  40  of the invention overlap the rim  26  of the container  20  when the lid  10  is seated upon the rim  26 . The shapes of most of the lugs  40  generally are rectangular with curved or rounded e edges  43  terminating in a flat edge  44 . However, many other lug shapes would work for the invention. 
     An optional tabular end  45  may be formed on the flat edge  44 , which may be formed or bent into an upward curl  46  in order to facilitate opening of the crimped lugs  40 . The optional curl  46  may be utilized to pry the crimped lugs open in order to release the lid  10 . Interspaced between each of the lugs  40  are circumferential bases  48  which exist between each lugs,  40  in order to assist in the crimping of the lugs around the rim curl  26  of the container  20 . 
     In contrast to the prior art however, not all of the lugs  40  are identical in shape. Almost all of the lugs  40  have different shapes and varying widths. As shown in FIG. 5, the blank lid design  50  has one plane of symmetry  52  due to the odd number of lugs and the unique shape of each lug. Beginning with lug  54  in the 9 o&#39;clock position, lug  54  has a curved edge  43 , a tabular end  45  and a truncated upper edge  55  connected to an elongated circumferential base  56  formed between lug  60  and lug  54 . A truncated edge  58  of lug  60  is connected to the elongated circumferential base  56  formed between lug  60  and lug  54 . These truncated edges  55 , 58  in combination with the elongated circumferential base  56  form a female mating base  51  which is used to facilitate the interlocking of the lid blanks  50  as shown in FIG. 4, and as explained in more detail, below. The design of lug  60  is thus the mirror image of lug  54 , each of which further comprises a tabular end  45  connected to the truncated edge  55 , 58  and a rounded end  43  adjoining the tabular end  45 . 
     Lugs  64 ,  68 ,  72 ,  76  and  80  are all very similarly shaped as a rectangle with rounded or radiused edges  43  with a tabular end  45  formed on the outer peripheral edge. Formed between adjoining lugs are circumferential bases  48  of varying widths. Lugs  64  and  68  are slightly canted towards each other, while lugs  76  and  80  are canted away from each other such that interdigitization is facilitated, as explained in more detail, below. Lug  84  is also approximately rectangular in shape with a radiused edge  43  on one end and a edge  85  that is partially radiused and partially truncated closest to the circumferential base formed between lugs  84  and  88 . Lug  88  is pyramidal in shape, i.e., two inclined edges  89  joined to a circumferential edge  90  there between and forming a male lug for production purposes. Lugs  94  through  114  because of the plane of symmetry, are the mirror image of lugs  84  through  60 , respectively. For example, lug  94  is the mirror image of lug  84 , lug  98  is the mirror image of lug  80 , etc: 
     The punching pattern of conventional lid blanks as shown in FIG. 1 demonstrates that the container lid blanks are sufficiently spaced apart such that the blanks do not touch each other at any place and are disposed about the same distance from each other. Punching out the lids from the material therefore necessarily results in the production of a residual punching grid or scrap skeleton which can be utilized only as scrap. Moreover, for a given lid size, a larger material surface area is required for the same number of container lids for the prior art design as compared to the design and layout of the invention. 
     FIG. 4 shows the punching pattern of six container lid blanks  50  of the invention from a scrolled sheet of metal. FIG. 4 illustrates three rows of container lid blanks comprised of 2 lid blanks in each row, with the center row being offset from the top and bottom rows. In each row, the male lug  88  of the container lid blank is aligned with, and placed between the female circumferential base  51  formed between the lugs of the adjacent container lid blank, leaving a very thin scrap skeleton as shown in FIG.  6 . The container lid blank lugs in the adjacent rows are aligned with and placed closely between the circumferential bases of the adjoining container lid blanks. Thus the container lid lugs are interdigitated or interlocked with the lugs in the adjacent rows, analogous to gear teeth between mating gears. 
     This relationship between the respective lid blanks and lid rows minimizes the amount of material between the lid blanks and thus minimizes the scrap skeleton remaining when the lids have been removed from the sheet material. The design of the odd number of specially configured lid lugs, the layout of the lid blanks and offset lid blank rows and the shape of the sheet material contribute to the efficiency of the process. In the preferred form the scrolled sheet material, indicated generally at  120 , has two rectangular ends  122  and  124  and an offset central section, indicated generally at  126 . The offset central section  126  is formed by a trapezoidal piece  128  being added to and extending outwardly from one side or margin of sheet material  120  and a similarly shaped and sided trapezoidal recess  130  being provided on the other side. 
     In an alternative embodiment of the invention, the container lid blank  50  may comprise three or more female circumferential bases  51  and three or more male shaped lugs  88 , such as shown in FIG.  7 . The male lugs  88  and the female circumferential oases  51  are alternated on a container lid blank  50 . Thus as shown, the layout of the container blanks  50  in the middle row are such that the female circumferential bases  51  and the male lugs  88  are positioned for alignment with the adjacent male lugs  88  and female circumferential bases  51 . 
     In yet another alternative embodiment of the invention as shown in FIG. 8, the container lid blank  140  comprises an odd number of symmetrically shaped lugs  143  with circumferential bases  144  formed between each lug. Preferably, the blank has  15  lugs, with each lug having the same angular displacement α. It is additionally preferred that the circumferential bases  143  be the same. Lug  146  is symmetrically shaped, but has a narrower tabular extension  148  than the tabular extensions  150  of the other lugs  142 . Directly opposite lugs  146  are two adjacent lugs  144 , which are canted away from each other to allow lug  146  to be disposed between, or interlocking with respect to, the adjacent lugs  144  on an adjacent blank when the blanks are layed out. In addition, lugs  142  are additionally interlocking with respect to lugs  142  on an adjacent blank on the locations identified with the letter “B”. Thus, the container blanks  140  air probably arranged upon a scrolled sheet of material  120  as described above, with the blanks arranged in two or more rows in a tightly spaced configuration. The middle row is offset from the outer rows to allow closer spacing of the blanks  140 . In addition, each row has the blank lug  146  interlocking with respect to the adjacent blank lugs  144 . 
     Although the invention has been disclosed and described with respect to certain preferred embodiments, certain variations and modifications may occur to those skilled in the art upon reading this specification. For example, the invention could be utilized on a cover that is not round nor which contains a annular channel or an annular rim section. Any such variations and modifications are within the purview of the invention notwithstanding the defininig limitations of the accompanying, claims and equivalents thereof.