Abstract:
A resealable anti back-off closure system that is substantially leak-proof and back-off resistant. A closure and container include mating screw threads. The closure includes recesses formed within the interior surface of the closure adapted to cooperate with protrusions formed on the neck of the container. The protrusions and recesses releasably lock together when the closure is screwed onto the container. The closure and container form at least two seals when coupled, including a flange seal and a land seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/194,432, filed Jul. 20, 2015, and titled BACK-OFF RESISTANT CLOSURE SYSTEM, which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to a container closure and container neck structure and more particularly to back-off resistant closure systems. 
       BACKGROUND 
       [0003]    Locking closures for use with containers, such as bottles or jars are well known. “Backing-off,” or loosening of non-locking closures, including for example, caps, is due in part to vibration incurred during shipping and handling, the self-lubricating properties of typical plastic container materials, and lubricating properties of stored liquids. Those skilled in the art recognize that backing-off can be a significant problem as it relates to shipping, often resulting in spoilage, spilling, or contamination. 
         [0004]    Various closure system designs have been used to solve the backing-off problem. One known locking closure system design employs outwardly projecting ratchet portions on a neck portion of a container to engage with corresponding interior ratchet formations on a frangible tamper-evident skirt of a cap. Once tightened into place, the ratchet formations are engaged such that the cap is locked into place and cannot loosen or back off of the container without first removing the frangible tamper-evident band from the cap. Although such a closure system is appropriate for consumer goods, such as drinking beverages where tamper evidence is a primary concern, a drawback of such a single-use prior art closure is that the closure is no longer back-off resistant once the tamper-evident band containing the locking mechanism has been removed. 
         [0005]    For uses where tamper evidence is of little concern, it can be desirable for a closure to maintain back-off resistance each time the closure is tightened. Thus recloseable back-off resistant closure systems, see e.g., U.S. Pat. No. 6,047,840, have been used to provide repeatable antiback-off functionality. Generally, such recloseable prior art closures consist of outwardly projecting ratchet formations on the container neck and recessed lugs extending radially inwardly from the cap so that the lugs engage the ratchet formations when the cap is screwed onto the container. The lugs provide additional resistance, or friction, to the closure thereby resisting backing off of the closure. While such antiback-off closures were an improvement over the prior art, some leakage could still occur, as sealing structures were not improved. 
         [0006]    For purposes such as oil sample analysis, a closure&#39;s ongoing and repeatable ability to avoid spoilage, spilling, or contamination by remaining tightly sealed is paramount. Oil samples are shipped from the field to laboratories and therefore must not only seal well, but must also be back-off resistant to prevent loosening of the containers during the shipping process. Oil sampling companies have reported leakage rates of around  30  percent for existing closure systems due to shipping alone. Because empty oil sample containers are sent to the field in a closed state to avoid contamination of the containers before filling and are also closed and re-opened often in laboratories, oil sample containers must also be reclosable while maintaining their sealing and anti back-off functionality. Notwithstanding the effort to address the tendency of container closures to back-off, the industry continues to search for a cap and neck finish which achieves such an objective, but which also provides a secure seal. Accordingly, it is an object of the present invention to provide a resealable anti back-off closure system that is substantially leak-proof and it will be appreciated that the present disclosure is an improvement over prior art closure systems. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    Other features and advantages of the present disclosure will be apparent from the following detailed description, the accompanying drawings, and the appended claims. 
         [0008]    The present disclosure comprises an improved closure system, including an improved closure and an improved container neck finish. The closure system includes a closure and container neck finish forming a neck-interior flange seal, a closure and neck finish forming a neck-interior land seal, and protrusions formed on one of the container neck and the cap&#39;s interior and corresponding recesses formed on the other of the container neck and the cap&#39;s interior skirt to releasably prevent back-off of the closure from the bottle. 
         [0009]    The closure and container neck are provided with mating threads. The threads may be continuous or interrupted. In accordance with the present disclosure, an illustrative thread for a blow-molded, high density polyethylene bottle is 6 threads per inch and a minimum of one full turn of thread. However, depending upon the desired application, it may be advantageous to design for higher or lower threads per inch and/or more leads. 
         [0010]    Another feature of the present disclosure is that the closure is provided with a flange or inner skirt which fits inside the container neck adjacent the container land area. The closure&#39;s flange or inner skirt engages the container neck as the closure is threaded onto the container. The flange seal contacts an interior area of the container neck, such that the interior of the neck and the flange seal form a tight seal. This feature prevents the leakage from the container. 
         [0011]    The interior surface of the closure member also includes a flat, land area within the cap. The land area within the closure contacts a land area at the top of the neck of the container such that the flat area and the land area form an additional seal. 
         [0012]    Still another feature of the disclosure is a shoulder connection formed beneath the threads by contact of the interior shoulder formed on the closure and the outer surface of the container neck. 
         [0013]    An additional optional shoulder connection is formed by contact of the shoulder formed on the container neck and with the closure skirt. 
         [0014]    The closure also includes a plurality of narrow recesses defined by the cap&#39;s interior skirt and extending longitudinally along a portion of the length of the interior skirt. 
         [0015]    Correspondingly, at least one outwardly projecting protrusion is formed below the threads on an exterior surface of the container neck. The mating recesses of the closure and container neck protrusions are engaged by the downward rotational threading of the closure relative to the neck. In other words, the recesses and protrusions are brought into longitudinal and rotational alignment and engagement by rotating the closure relative to the neck. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of exemplary embodiments of the disclosure. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
           [0017]      FIG. 1  illustrates a perspective view of a resealable anti back-off cap, that is substantially leak-proof, in accordance with the present disclosure; and 
           [0018]      FIG. 2  illustrates a perspective view of a resealable anti back-off container that is substantially leak-proof, in accordance with the present disclosure. 
           [0019]      FIG. 3  illustrates a perspective view of a resealable anti back-off container cross-section that is substantially leak-proof, in accordance with the present disclosure. 
           [0020]      FIG. 4  illustrates a cross-section of a closure system in accordance with the present disclosure, including the cap of  FIG. 1  and the container of  FIGS. 2 and 3 , in a fully-engaged position. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    For the purposes of promoting and understanding the principals of the invention, reference will now be made to one or more illustrative embodiments illustrated in the drawings and specific language will be used to describe the same. 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. 
         [0022]    In a disclosed embodiment, a copolymer resin closure has been found to be desirable to prevent breakage of the closure in the event that the container is dropped. Specifically, the cap is manufactured from a high density polyethylene and the container is manufactured from a clarified polypropylene. 
         [0023]      FIGS. 1-4  show an illustrative embodiment of a cap  100  and container neck  200  having features that when coupled, provide a substantially leak-proof, resealable, anti back-off closure system.  FIG. 1  shows an illustrative embodiment of a cap  100 . The cap  100  has a generally flat top disk  110  from the periphery of which depends an upper skirt  140 . The lower edge of upper skirt  140  merges with the upper edge of lower skirt  120 . The lower skirt  120  has a generally horizontal, planar lower edge  122 . Upper skirt  140  and lower skirt  120  have vertical ribs  124  spaced therearound, for example, knurling to aid in gripping the cap  100 . The vertical ribs  124  are further defined by lower edges  126 . 
         [0024]    On the interior of upper skirt  140  is formed a thread  130 . At least one recess  150  is defined by the inside of lower skirt  120 . The recess(es)  150  include an recess inner surface  152 , first recess inner edge  154 , and second recess edge  156 , and extend in length to recess end  158 . A plurality of recesses  150  may be spaced or separated by a portion of the inside of lower skirt  120  and the plurality of recesses  150  may extend around the periphery of lower skirt  120 . 
         [0025]    An inner flange  112  extends downward from top disk  110 . The outer bottom edge  114  of flange  112  may be rounded or formed with a bevel. A circular land area  116  on the underside of disk  110  is located between flange  112  and skirt  140 . A radius  118  joins circular land area  116  and the upper edge of skirt  140 . 
         [0026]      FIG. 2  and  FIG. 3  show an illustrative embodiment of a finished neck  200 . Neck  200  has a central neck opening  210  and a first upper neck portion  214  terminating at land area  212 . 
         [0027]    Extending radially outward from the first upper neck portion  214  is a thread  230  which is selected to mate with thread  130  of cap  100 . The number of thread leads and linear thread density may be advantageously chosen. A second upper neck portion  220  is located below the thread  230  and extends downward to upper shoulder  222 , which extends radially outward from the neck  200  to form a horizontal surface. 
         [0028]    Below upper shoulder  222  is a vertical engagement wall  224 . Vertical engagement wall  224  terminates in middle shoulder  226  which extends approximately radially outward and, at its lower end, merges with a transition  240 . Outwardly of and below transition  240  is the main body  242  of the container. 
         [0029]    Projecting out from vertical engagement wall  224  are protrusions  250 . Protrusions  250  may be spaced and dimensioned to match the recesses  150  of cap  100 . Protrusions  250  may be further separated by a portion of vertical engagement wall  224  and the plurality of protrusions  250  may extend around the periphery of vertical engagement wall  224 . Protrusion(s)  250  may also consist of a single protrusion. Each protrusion has a top surface  258  which can be co-planar with the surface of upper shoulder  222 . Protrusion outer surface  252  is approximately vertical and terminates at middle shoulder  226 . Protrusions  250  are further defined by protrusion first edges  254  and protrusion second edges  256 . 
         [0030]    Referring now to  FIG. 4 , various features of cap  100  are dimensioned to match the features of neck  200  to provide releasable retention of the cap and neck, and sealing. Threads  130  of cap  100  are rotationally mated with thread  230  of neck  200 . Upon sufficient rotation, cap  100  is drawn downward onto neck  200  such that recesses  150  of cap  100  are engaged with protrusions  250  of neck  200 . The engagement of the recesses  150  and protrusions  250  provide resistance to turning (antiback-off) and thus reopening (unscrewing) that requires a greater torque on cap  100  relative to the neck  200  than would be experienced in normal shipping and handling. The size, depth of engagement, and other features of recesses  150  and protrusions  250  can be modified to provide the level of resistance to turning that is desired for the application. Alternatively, protrusions  250  can be located on the cap  100  and the recesses  150  defined on the neck  200 . 
         [0031]    A flange seal is formed by inner flange  112  of cap  100  and the inner surface  216  of the central opening  210  of neck  200 . A land seal is formed by land area  116  of cap  100  and land area  212  of neck  200 . An optional shoulder connection can be formed by lower edge  122  of cap  100  in contact with the middle shoulder  226  of neck  200  and can provide an additional seal and/or anti back-off feature. Each of these seals and connections is made upon the cap  100  being drawn fully downward onto neck  200  and each can be designed to contribute to the sealing and anti back-off features of the closure system. Alternative embodiments of the closure system can include any combination of a subset of the disclosed seals and connections in addition to other closure seals known in the art. 
         [0032]    It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.