BACK-OFF RESISTANT CLOSURE SYSTEM

[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.

[0002] This invention relates to a container closure and container neck structure and more particularly to back-off resistant closure systems.

[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'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.

[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's interior and corresponding recesses formed on the other of the container neck and the cap'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'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'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.

[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.