US 3295708 A
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Description (OCR text may contain errors)
Jan; 3, 1967 J. M. WATHEN, JR 3,2953% THREADED CLOSURE Filed April 26, 1965 /fl INVENTQR. Jaw/V M055 W4 mag Je.
United States Patent 3,295,708 THREADED CLOSURE John Moss Wathen, .lr., Shelbyville, Tenm, assignor to American Can Company, New York, N.Y., a corporation of New Jersey Filed Apr. 26, 1965, Ser. No. 450,728 6 Claims. (Cl. 215-43) The present invention relates to threaded closures, and more particularly to an improved closure for containers of thermoplastic material.
Containers of thermoplastic materials, such as collapsible tubes and bottles made of polyethylene, polyvinyl chloride, and like materials are inherently resilient. Where the container is provided with a threaded neck which is closed by a threaded screw cap, customarily of a more rigid material than the neck of the container itself, this natural resiliency creates a minor yet troublesome problem of maintaining the desired tightness between cap and neck. Ordinarily, the caps are assembled to the necks of these containers in mass production by special equipment adjusted to provide the desired tightness (in terms of torque required to unscrew the cap) specified by the packers whose products are vended in these containers. The resiliency of the necks which receive the screw caps make absolute control of this specified torque extremely difficult, and after handling, shipping and storage, incidences occur where the closure has lost some of the tightness applied at the time of initial assembly.
A principal object of this invention is to provide a threaded closure construction which overcomes the above mentioned problem.
Another object of this invention is the provision of a threaded closure construction for plastic containers, such as collapsible tubes, bottles and the like, which enables greater positive control of the tightness of the closure.
These and other objects and advantages of this inven tion will become apparent from the following description which, taken in connection with the accompanying drawings and appended claims, disclose a preferred embodiment thereof.
Referring to the drawings:
FIGURE 1 is an elevational view of a collapsible plastic tube container embodying this invention.
FIGURE 2 is a top view of this container.
FIGURE 3 is a sectional view taken substantially along line 2-2 of FIGURE 2.
FIGURE 4 is an enlarged, fragmentary view in prespective showing the structure of the preferred form of this invention in greater detail.
FIGURE 5 is a sectional view, similar to FIGURE 3, showing the complete closure including the threaded neck of the container and a conventional screw cap assembled thereto.
In its preferred or exemplary form as illustrated in the drawings, the present invention is embodied in a collapsible squeeze-tube having an integral end member 11 on which is disposed a hollow, externally threaded neck generally designated 12.
Containers of this type are well known and may be of metal, plastic or laminated construction. The end member 11 and neck 12 may be afiixed to the body of tube It in a number of well known Ways, but preferably the end and neck portions are molded directly to the tube in the manner taught in United States Patent 2,673,374 to Andre Strahm. Of course, the neck may be separately molded and then affixed to the container, or, as is customary in the manufacture of plastic bottles, the neck may be shaped and molded in the same molding operation which forms the bottle,
Neck 12 is provided with an external, helical thread 3 ,295,708 Patented Jan. 3, 1967 13 of conventional configuration which meshes with a corresponding internal thread 14 of a screw cap 15. Neck thread 13 terminates slightly below the outer end of the neck in a rounded, lead-in end 13a which gradually merges into the cylindrical wall of the neck. A corresponding lead-in end is provided on cap thread 14 to facilitate assembly of the cap onto the threaded neck. The extreme outer end of the neck 13 is planar and normal to the axis of the tube, thereby providing an an nular sealing surface 16 against which the roof portion 17 of the cap tightly engages when the latter is fully threaded onto the neck.
A small projection or lug 18 is formed on the upper surface of thread 13 adjacent its lead-in end 13a, at about the position where the thread begins to diminish from its normal size. Preferably, lug 18 has a narrow angular width of only a few degrees (about 5 to 20 on the neck circumference), projects radially outwardly from the wall of the neck to about half the height (or depth) of thread 13, and extends from the upper surface of the thread to and flush with surface 16 of the end of the neck. As shown, lug 18 is Wedge-shaped (having an included angle at its apex of about 60), and its apex edge is slightly tapered as at 19 from its outermost point inwardly to the upper surface of thread 13.
The purpose of lug 18 is to provide a slight but deliberate interruption on thread 13 which, when cap 15 is fully threaded onto neck 13, will be deformably engaged by a recessed, interior surface of the cap. This interior surface, for example, may be the inner terminus 14b of cap thread 14, which normally rides over the upper surface of neck thread 13 in the region of lead-in end 13a. As shown in FIGURE 5, this engagement causes lug 18 to deform downwardly, thus providing a predetermined amount of resilient engagement between the neck and cap in excess of what normally would be present if lug 18 were omitted. This predetermined frictional interference between lug 18 and surface 14b provides a positive hold to prevent back-off slippage of the cap 15 after its threaded assembly onto neck 13. Also, this slight interference enables closer control of the assembly torque of the cap and neck, thus minimizing the field problems associated with cap tightness and removal.
Although in the invention above described the lug 18 is shown on the container neck, or male portion of the threaded closure, it will be understood that the arrangement may be reversed and the lug placed on the interior thread of the cap. Ordinarily, however, the cap is formed of much harder material than that of which neck 13 is formed. Therefore, in this instance it is preferable that the lug 18 be formed on the softer and more resilient of the two closure members.
It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction, and arrangement of the parts Without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.
What is claimed is:
1. A closure for a container comprising an upstanding hollow neck, a cap rotatably engaged on said neck, coacting threads on said neck and cap securing them in rotational engagement and for enabling their disengagement upon relative rotation thereof, and a projection formed integrally on one of said threads adjacent the upper end of said neck providing interfering frictional engagement with the other said thread when said cap and said neck are fully engaged.
2. The construction of claim 1 wherein said projection is on the lead-in end of the thread on said neck.
3. The construction of claim 2 wherein said thread on said neck is on the exterior of said neck and said projection is a small lug-like formation on the upper surface of said lead-in end, said formation being deformed and frictionally engaged by a recessed annular wall portion of said cap.
4. The construction of claim 3 wherein said lug-like formation extends from the upper surface of said lead-in end substantially to the upper end of said neck and said cap has a roof portion overlying said neck, the peripheral region of which makes frictional, deforming engagement with said formation.
5. A closure for a plastic tube comprising a hollow neck of resilient thermoplastic material, an integral thread formed on the exterior of said neck, a screw cap having an interior thread rotatably engaged with the thread on said neck, and a lug-like projection formed integrally on the lead-in end of said neck thread and extending from the upper surface of said lead-in end to substantially the upper end of said neck, said lug-like formation being deformably engaged by an interior wall surface of said cap when said threads are fully engaged.
6. A collapsible tube of thermoplastic material comprising a tubular body and an integrally formed headpiece having an upstanding hollow neck, a thread on the exterior surface of said neck for rotatably receiving an interiorly threaded screw cap, and a narrow lug-like formation formed integrally on the upper surface of the lead-in end of said neck thread, said lug-like formation being positioned to make deformable engagement with an interior surface of the screw cap upon full engagement of the latter on said neck.
References Cited by the Examiner UNITED STATES PATENTS 2,827,193 3/1958 Martin 21531 LOUIS G. MANCENE, Primary Examiner.
THERON E. CONDON, Examiner.
J. B. MARBERT, Assistant Examiner.