Abstract:
The neck of a container has a smooth seal surface engaged by the inner skirt or plug of a cap. Such surface is free of trim and parting line flaws which are characteristic of blow-molded jars because the surface is formed in such a way that the seal surface is not in contact with mold parting lines and further the trim of the neck (excess plastic) is located away from the sealing surface. In one form of the disclosure, above the sealing surface the neck wall slants outward and then bends upward-inward in a short, tapered stretch about 18° to the horizontal which engages the underside of the cap disk to compress against the disk or a liner or foil. In another form of the invention, above the seal surface the neck extends outward and then upward and then inward in a flange which is trimmed along a line which has a circumference no less than the circumference of the seal surface. The exterior of the neck is formed with shoulders which engage over locking beads on the interior of the outer skirt of the cap.

Description:
This is a division of application Ser. No. 08/847,928, filed on Apr. 28, 1997, U.S. Pat. No. 5,964,362, which was a file wrapper continuation of Ser. No. 08/385,808 filed Feb. 9, 1995, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a new and improved blow molded neck construction for bottle or other container, a cap therefor and method of forming said neck. More particularly, it relates to the neck finish for a blow molded plastic bottle characterized by the fact that when used with a cap having a plug (i.e., inner skirt) the surface of the neck against which the plug seals is a seal surface without parting lines and a portion above the seal surface comprises an inward directed thin flexible flange. 
     2. Description of Related Art 
     An exemplar of the prior art is U.S. Pat. No. 4,691,834 which shows an upward inward directed flexible flange sealing against the corner of the intersection of the outer wall of the plug and the underside of the top of the cap. The neck sealing surface is, inherently, somewhat uneven and ragged since the neck is cut or sheared adjacent this sealing surface. In the present invention, however, the neck is trimmed at the edge of the upper flexible flange but such edge is not the portion of the neck which seals against the cap plug. 
     The references cited against said U.S. Pat. No. 4,691,834 are likewise distinguishable. 
     U.S. Pat. Nos. 4,625,876 and 4,798,301 show curved plug contacting surfaces but these are of substantially the same diameters as the inner edge of the flanges which engage the underside of the top of the cap. 
     SUMMARY OF THE INVENTION 
     The bottle of the present invention is blow molded in a split mold by techniques well known in the art. The surfaces of the mold which define the neck structure cause the neck shape hereinafter described. An upper portion of the parison above the neck is trimmed or cut from the neck according to conventional practice (e.g. pull-up trim, spin trim, etc.) The circle at which the upper portion of the parison is severed from the neck is the inner edge of an inward upward slanted flange. The other end of the flange merges into a curved surface which extends inward a greater distance than the aforesaid edge to merge with an internal sealing surface of lesser diameter than said edge. The neck structure above the neck sealing surface has rapidly changing diameters which form a flexible membrane due to parison stretching in the blow molding process. Below the sealing surface the exterior of the neck structure slants downward outward to a horizontal shoulder and then extends downwardly and then outwardly to a second or lower shoulder. 
     The cap with which the neck is used has a top having a depending central plug or inner skirt, the outer surface of which seals tightly against the sealing surface of the neck. The cap also has an outer skirt having internal sealing beads which engage the upper and lower shoulders of the neck to hold the cap in place. The lower portion of the outer cap skirt may be removed by the user engaging and pulling a pull tab which causes the lower part of the skirt to disengage at a circumferential score line. Until such lower skirt is removed, the cap and neck are tamper-evident. 
    
    
     The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a neck portion of a jar in accordance with the present invention partially broken away to reveal structure. 
     FIG. 2 is an enlarged sectional view of the neck structure and a portion of a blow dome superimposed thereabove. 
     FIG. 3 is a side elevational view of a cap with which the neck is used, the cap being partially broken away in section to reveal internal construction. 
     FIG. 4 is an enlarged sectional view of a portion of FIG.  3 . 
     FIG. 5 is a further enlarged fragmentary bottom plan view of a portion of the cap showing a top view of the pull tab. 
     FIG. 6 is a fragmentary sectional view taken substantially along the line  6 — 6  of FIG.  5 . 
     FIG. 7 is an enlarged sectional view showing schematically the seating of the cap on the neck. 
     FIG. 8 is a view similar to FIG. 7 of a prior art device. 
     FIG. 9 is a view similar to FIG. 7 of a modification. 
     FIG. 10 is a view similar to FIG. 7 of another modification. 
     FIG. 11 is a view similar to FIG. 7 showing possible distortion of the cap top if pressure is applied to the container. 
     FIG. 12 is an enlarged view of the neck structure showing an alternate seal area. 
     FIG. 13 is a view similar to FIGS. 9 and 10 showing modified sealing surface positions. 
     FIG. 14 is a vertical sectional view through a modified container neck and portions of the mold and blow pin forming same. 
     FIG. 15 is a view of similar to FIG. 14, showing the blow pin in raised position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Neck  11  is formed on a thin-walled jar or other container and has a curved primary seal surface  12  which is very smooth and is distinguished by the absence of parting lines inasmuch as it is formed by air pressure or other mechanical means during the blow molding process and is not formed by the mold halves and thus does not have a mold parting line formed therein. As shown in FIG. 12, seal surface  12  may be vertical or it may be curved, as shown in FIG.  2 . Further, the primary sealing surface has minimal ovality, by reason of the way it is formed. Above surface  12  the neck structure extends outwardly in a outward stretch  13  which terminates in an upward bend  14 . Above bend  14  is a thin, tapered upward-inward extending flange  16 , the inner edge of which is of greater diameter than the diameter of surface  12 . Below surface  12  the neck extends downwardly-outwardly in a slanted stretch  17  which terminates in a short vertical stretch  18 , there being an inward directed substantially horizontal upper shoulder  19  below surface  18 . Vertical stretch  21  extends downwardly from the inner edge of shoulder  19  terminating in an inwardly curved portion  22  which merges with an outward downward stretch  23 . An approximately vertical short surface  24  (of greater diameter than surface  18 ) terminates in a second or lower horizontal inward directed shoulder  26 . Vertical stretch  27  depends from the inner edge of shoulder  26 , merging with an outward stretch  30  which merges with an outward downward stretch  29 . The lower end of stretch  29  merges with an inward downward stretch  31 . 
     In accordance with one form of standard blow molding practice, a parison of the plastic material from which the container is to be formed is deposited in the split mold. Air is blown into the parison to expand it to fill the mold. In one form of the present invention, the mold has inserts which shape the finish of the neck of the container heretofore described and above these neck inserts the mold widens out to establish what is known as a blow dome of excess material. The blow dome is severed from the neck finish by well-known means. In accordance with the present invention, as distinguished from prior neck finishes, the blow mold is severed at the inner edge of flange  16 . Severing the edge of the neck from the blow dome may cause a rough surface. One of the advantages of the present invention is that the edge at which the blow dome is severed is not the primary sealing surface  12 . Thus directing attention to FIG. 2, blow dome  33  has an outward upward slanted stretch  34  merging into a curved stretch  36  which has an inward slanted stretch  37 . The cut line  38  is a circle wherein the stretch  34  is severed from the inner edge of flange  16 . By reason of the almost 180° bend  14 , and the rapid diameter changes within a relatively short vertical distance flange  16  is thin and flexible. 
     Another way to achieve the neck structure of the present invention is to employ what is commonly referred to as “pull-up” trim. In this case the cut line  38  is achieved by having a close diametrical fitting of a blow pin positioned internally within the parison and sets of shear steels mounted on the split mold. Diameters of the blow pin are typically 0.001 inch to 0.004 inch smaller than that diameter defined by the shear steels in closed position. After blowing of the neck and container, the portion of the parison above cut line  38  is severed from the neck portion below cut line  38  by upward movement of the blow pin relative to the shear steels. 
     It will be understood that the type plastic used to mold neck  11  may be any suitable relatively hard plastic such as polyethylene. 
     One form of closure or cap used with the present invention is shown in FIGS. 3-7. The closure of FIGS. 3-7 comprises an indented circular top  42  having a short peripheral cylindrical upward extending member  43  from which extends outwardly a stack rim  44 . The outer edge of rim  44  has a depending downward stretch  46  which merges into vertical, substantially cylindrical upper outer skirt  48 . The lower end of skirt  48  merges into an outward downward slanted stretch  55 . Below stretch  55  is the lower substantially cylindrical outer skirt  49 . An internal scoreline  51  separates stretch  55  from lower skirt  49 . Below lower skirt  49  the cap has an outward downward slanted flange  52  which, for practical purposes, rests against the surface  30  of neck  11 . Interrupted upper inner bead sections  53  engage under the shoulder  19 . Lower inner bead  54  at the lower end of skirt portion  49  engages under the shoulder  26 . When the cap is attached, the beads  53  and  54  prevent cap  41  from being removed from neck  11 . In order to enable the user to grip cap  41 , ribs  50  extend outwardly from member  48  merging with the outer surface of lower skirt portion  49  as best shown in FIG.  7 . Ribs  50  also impart columnar strength to the closure to transfer vertical force and prevent closure collapse during axial application of the closure to the finish. 
     At one portion of the circumference of lower skirt  49  (as best shown in FIGS.  5  and  6 ), spaced downwardly therefrom is a horizontal pull tab  57  having a curved connection  58  to skirt  49 . The interior of skirt  49  is formed with a notch  59  where tab  57  joins lower skirt  49 . Notch  59  forms a vertical line of weakness through skirt  49 . Enlargement  61  is formed on the distal edge of pull tab  57 . The flange  52  is formed thinner than the rest of flange  52  in the thin area  62  adjacent tab  57 . 
     As a downward extension of cylindrical member  43  the cap  41  is formed with a depending skirt extension  66 , the lower inner edge of which is formed with a radius  67 . The inner surface of member  43  seals against primary seal surface  12 . The vertical position of cap top  42  can be adjusted to provide for compression of surface  12  against the adjacent surface of member  43 . 
     Directing attention to FIG. 7 it will be seen that the surface  12  is the primary sealing surface against the member  43 . As has been noted, the surface  12  is very smooth and hence forms a very effective seal against the member  43 . 
     When the cap is applied, the beads  53  and  54  lock under the shoulders  19  and  26  to prevent removal of the cap and hence are tamper evidencing. When the user wishes to open the container, the user grips the enlargement  61  and bends the pull tab  57  outwardly and then pulls circumferentially, tearing the lower skirt  49  from the upper cap portion. The user may then grip under the surface  55  which, as shown in FIG. 7, is spaced from the bottle finish by a considerable gap, and pull upwardly causing the interrupted upper bead segments  53  to disengage from shoulder  19  so that the cap may be removed. The ribs  50  rigidify the upper portion of the cap to allow the forces necessary to push the cap onto the bottle from causing the cap to buckle. The portion of the cap above line  51  constitutes a reclosure cap and may be pressed back on the neck after portions of the contents of the jar are dispensed as frequently as required. 
     Comparison of FIG. 7 with prior art structure shown in FIG. 8 shows that in the present invention the very smooth surface  12  causes a tight seal against the exterior of member  43  and the flange  16  need not seal at all, whereas in the prior all the cut inner edge of the flange is a primary seal. The primary seal surface  12  has minimum deviation from ovality as compared to FIG. 8 where the primary seal is coincident with a trim surface. Bottles of this type of this invention and the prior art were molded. The ovalty of the two types was measured. The unexpected result of these experiments was that the current invention produced a significantly more circular primary seal area. Refer to Table A. for tabulated results. The stretch occurring on both sides of the primary seal  12  is primarily contributing to the superior ovality and differentiate it from prior art. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
             
           
               
                 TABLE A 
               
             
             
               
                   
               
               
                 STD BOTTLE STYLE 
                 PRESENT INVENTION 
               
             
          
           
               
                 Run 
                 Run 
                 Run 
                 Run 
                 Run 
                 Run 
                 Run 
                 Run 
               
               
                 A 
                 B 
                 C 
                 D 
                 A 
                 B 
                 C 
                 D 
               
               
                   
               
               
                 0.055 
                 0.020 
                 0.048 
                 0.028 
                 0.024 
                 0.058 
                 0.002 
                 0.015 
               
               
                 0.053 
                 0.002 
                 0.056 
                 0.015 
                 0.006 
                 0.010 
                 0.106 
                 0.030 
               
               
                 0.062 
                 0.000 
                 0.044 
                 0.010 
                 0.017 
                 0.002 
                 0.013 
                 0.010 
               
               
                 0.043 
                 0.010 
                 0.058 
                 0.003 
                 0.016 
                 0.004 
                 0.005 
                 0.027 
               
               
                 0.058 
                 0.029 
                 0.025 
                 0.009 
                 0.014 
                 0.013 
                 0.005 
                 0.034 
               
               
                 0.064 
                 0.016 
                 0.055 
                 0.003 
                 0.011 
                 0.060 
                 0.017 
                 0.017 
               
               
                 0.011 
                 0.005 
                 0.059 
                 0.002 
                 0.004 
                   
                 0.003 
                 0.017 
               
               
                 0.019 
                 0.013 
                 0.049 
                 0.005 
                 0.007 
               
               
                 0.042 
                 0.006 
                 0.045 
                 0.002 
                 0.013 
               
             
          
           
               
                 Average 0.028 
                 Average 0.016 
               
               
                   
               
             
          
         
       
     
     If the contents of the container are non-viscous (e.g., brine-packed pickles) or if the walls of the container are easily squeezed during transportation or handling, top  42  may be subjected to upward pressure causing it to become “domed” (outwardly convex). Such action may cause the inner skirt member  43  to pivot away from curved primary seal  12 , resulting in leakage. This effect is illustrated in FIG.  11 . 
     FIG. 9 shows one remedy for such leakage. Contrasting FIG. 9 with FIG. 7 it will be seen that top  42   b  is raised relative to stack rim  44   b  and that the contact of surface  12   b  with inner skirt member  43   b  is more closely opposite top  42   b.  In addition, reducing the vertical spacing between top  42   b  and stack rim  44   b  reduces the lever arm and corresponding mechanical advantage of the inward force component generated by internal pressure. Hence doming of top  42   b  does not result in pivoting of skirt  66   b  out of sealing contact with surface  12   b.  FIG. 11 shows how pressure applied to the container (as by squeezing the side wall) may cause top  42   b  to bow upward, pulling plug  66   b  away from such surface  12   b.    
     FIG. 10 shows another remedy for leakage due to doming of surface  42   c.  A plurality of angularly spaced, substantially radially gussets  71  are formed at the intersection of top  42   c  and cylindrical member  43   c.  Gussets  71  prevent member  43   c  from pivoting away from surface  12   c.  A similar result can be achieved by replacing gussets  7  with a continuous reinforcing bead or shoulder at the intersection of the exterior surfaces of top  42   c  and member  43   c.    
     FIG. 12 illustrates a shape wherein seal surface  12   d  is cylindrical rather than curved. 
     FIG. 13 shows a structure in which top  42   c  is closer to the level of rim  44   e.  Surface  12   e  engages the surface of cylinder  43   e  below the level of top  42   e.    
     Directing attention to the modification shown in FIGS. 14 and 15, formation of a modified container neck is shown. Such a neck may resemble that shown in U.S. Pat. No. 4,699,287, with an important modification, as hereinafter explained. In FIG. 14 the parison forming the neck is shown between a blow pin  86  and shear steel  76  and neck insert  21  as molding is being completed. 
     Shear steel  76  has an inward projector  77  terminating in a vertical inward shearing edge  78 . Blow pin  86  has a lower cylindrical portion  87  having an outward shearing edge  88  with a groove  89  thereabove. 
     As shown in FIG. 14, blow molding of the parison to the shape of shear steels  76  and neck insert  81  has just been completed. Edge  88  is located below edge  78 . Air blowing through hole  91  has formed vertical stretch  101  and inward horizontal stretch  102  as well as the portions thereabove. The smooth, vertical, lower cylindrical portion  87  has formed internal primary seal surface  12   f.    
     The blow pin  86  then moves from the position of FIG. 14 to the position of FIG.  15 . The neck structure is sheared between edges  78  and  88 . Inner flange edge  96  is formed where the edges  78 ,  88  have sheared the same and the parison sheared-off portion  94  thereabove is discarded. 
     It is noted that edge  96  is of a larger diameter than primary seal surface  12   f.  hence the hollow plug or inner skirt such as that shown in U.S. Pat. No. 4,699,287 seated on the container neck seals against surface  12   f  instead of surface  96 . Since blow pin  86  has no parting line surface  12   f  has no flash. Surface  12   f  is smooth and its diameter is always the same during repetitive molds and hence makes a superior seal with the cap plug. 
     In FIGS. 8,  9 ,  10 ,  12 ,  13  and  14  in general the same reference numerals are used for parts corresponding to FIG. 7, followed by subscripts a, b, c, d, e and f respectively. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.