US 3272369 A
Description (OCR text may contain errors)
United States Patent 3,272,369 CONTAINER CLOSURE Arvid Kjellsen Grimsley, Rockaway, N.J., assignor to American Can Company, New York, N.Y., a corporation of New Jersey Filed Oct. 7, 1964, Ser. No. 402,127 3 Claims. (Cl. 215-43) This invention relates to threaded closures for containers, and particularly to a thermoplastic screw cap having improved seal characteristics.
In the art of threaded closures, particularly those made of so-called soft thermoplastics, the problem of providing an effective seal is exaggerated by such factors as the style or design requirements of the cap, and the materials of which both the cap and container neck are made and structural irregularities in the closure elements-particularly the container neck. These considerations do not always permit reliance on customary design standards such as heavier construction or tighter and greater thread engagement to provide the necessary seal. The consumer is conscious of and objects to excessive force and twisting required to open and close a container. Impairment of the intended seal may occur due to distortion of the cap resulting from excessive force. Also, higher sealing torques and increased thread engagement generally dictate additional material with attendant increased cost.
The primary object of the present invention is the provision of a low cost, easily manipulated threaded closure of high sealing efficiency.
Another object of this invention is the provision of a threaded plastic cap for a threaded closure, having a special resilient construction providing improved seal efficiency with ordinary thread engagement and material weight.
These and other objects and advantages of this invention Will be apparent from the following description which, taken in connection with the accompanying drawings and appended claims, discloses a preferred embodiment thereof.
Referring to the drawings:
FIGURE 1 is a sectional view, showing the closure of this invention in a position of less than full engagement.
FIGURE 2 shows the closure in a position of full engagement.
FIGURE 3 is a fragmentary view, partly in section, depicting the efficiency of the closure seal even when the neck element of the closure is not true.
FIGURE 4 is a fragmentary sectional view showing a modified form of cap.
The closure illustrated comprises an upstanding, hollow neck member generally designated 10, which may be formed integrally with a container, such as a plastic bottle or collapsible tube, or may be a separate piece which is constructed to snap onto or otherwise be mounted to a container. Neck member includes an intermediate wall portion 11 the periphery of which is formed with helical threads 12, and a smooth-surfaced cylindrical portion 13 extending upwardly from the threads and terminating in a lip 14 which defines an aperture 15. The exterior corner of the lip 14 is slightly rounded or tapered, as at 16, in the customary fashion. Neck member 11 may be of any suitable material, such as metal or either thermosetting or thermoplastic material.
The other member of the closure is an internally threaded cap, generally designated 20, made of one of the soft or resilient thermoplastic materials, such as polyethylene. It comprises a generally cylindrical skirt portion 21 having threads 22 formed on its interior surface adjacent one end thereof, an upstanding extension portion 23, and a transversal wall 24 of planar configuration disposed within the extension portion and integrally connected to the up- 3,272,369 Patented Sept. 13, 1966 per region of the skirt portion by an annular membrane 25. In the form illustrated in FIGURE 1, membrane 25 is an upwardly and inwardly tapered member of uniform thickness substantially less than the thickness of planar wall 24 and skirt 21 and in its normal position prior to full thread engagement projects slightly inwardly over the lip 14 of the container neck 11. The thinness of membrane 25 with respect to planar wall 24 and skirt 21 enables the membrane to flex and readily conform to the neck lip, as will be described. Preferably the angle of taper of membrane 25 is less than 45 to the longitudinal axis of the cap, with the result that with full thread engagement a substantial portion of the interior surface of the membrane conforms to the smooth exterior surface of neck portion 13.
The spacing of planar wall 24 with respect to threads 22 and the geometry and disposition of annular membrane 25 are, obviously, important to the efficiency of the seal. Upon full thread engagement, as illustrated in FIGURE 2, planar wall 24 is drawn downwardly into contiguous or contacting engagement with neck lip 14, and membrane 25 is caused to flex between its points of joinder with the relatively thick planar wall and skirt and thereby snugly conform to the corner 16 of the lip and the exterior surface of neck portion 13. Since the diameter of planar wall 24 is slightly less than that of neck portion 13, the angle of taper of annular membrane 25 and its inherent resiliency enables it to be drawn tightly around the lip corner 16 and downwardly into tight conformity with the surface of neck portion 13, thus providing an improved and highly efficient seal which is neither difficult to engage and disengage, nor inclined to cause distortion of the cap skirt upon the application of high sealing forces.
Cap skirt extension 23 enclosing planar wall 24 and membrane 25 is primarily an aesthetic feature but contributes to the strength of the cap as well as its appearance. Obviously, this member could be dispensed with entirely or modified in numerous ways to achieve different desired aesthetic results.
FIGURE 3 depicts a principal advantage of the present invention in providing a good seal efficiency even though the neck of the container is not formed completely true. In the manufacture of many types of threaded neck containers today, the neck is first formed as an integral part of the container and later trimmed to desired length. This trimming operation occasionally results in a surface irregularity at the lip of the neck, in the form of burrs or an uneven or angular cut such as shown in FIGURE 3. This means that the lip 14 of the neck-ordinarily the prime sealing surface, is not square with the axis of the neck and thus not a perfect sealing seat. This imperfection in the neck lip 14 is immaterial in the present invention, however, since the angular disposition and flexibility of thin membrane 25 enables it to flex and effectively seat completely and continuously about the lip with substantially the same sealing engagement and pressure at every point.
FIGURE 4 depicts an alternate embodiment of a screw cap generally designated 20 having skirt 21 extension 23 and planar wall 24 like that of the preceding embodiment and being otherwise identical except for the configuration of annular membrane 25 In this instance the membrane 25 is of arcuate cross-section which gradually increases in thickness from a minimum where it joints with skirt 21 to a maximum where it joins with planar wall 24 At this latter point the thickness of the membrane 25 is equal to that of planar wall 24 but its average thickness is substantially less than the thickness of either the planar wall or skirt 21 Thus, membrane 25 is relatively more flexible and capable of being drawn into tight conformity with the end surfaces of the con- 3 tainer neck when the cap and neck threads are fully engaged.
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 plastic screw cap for attachment to the cylindrical threaded neck of a container which is formed with a smooth cylindrical exterior side wall at its upper end which merges into a smooth transverse sealing lip wall to form a relatively sharp sealing corner extending 360 around the neck, said cap being made of a relatively soft, resilient plastic material and comprising a cylindrical wall having threads formed in its internal surfaces for engagement with the threads of the container neck, a transversely extending end wall disposed above said threads, and an upwardly and inwardly inclined resilient sealing wall thinner than and connecting said cylindrical wall and said transversely extending end wall, said sealing wall at its bottom end having an internal diameter greater than the external diameter of the upper end of the container neck and at its top end having an internal diameter smaller than the external diameter of the upper end of the container neck, said sealing wall being adapted to be engaged intermediate its top and bottom ends by the sealing corner of said container neck in a driving fit and to be indented under tension around the sealing corner of the neck and into sealing engagement with the cylindrical side wall of the container neck when the cap is seated on the container neck.
2. The cap of claim 1 wherein said connecting Wall is straight in radial cross-section and is inclined less than 45 to the axis of the cap.
3. The cap of claim 1 wherein said connecting wall is arcuate in radial cross-section.
References Cited by the Examiner UNITED STATES PATENTS 2,617,553 11/1952 Lay 215-41 3,144,154 8/1964 Puse et al. 215-43 3,160,303 12/1964 Healy 21543 FOREIGN PATENTS 823,993 12/ 1951 Germany. 161,961 1/1958 Sweden.
r JOSEPH R. LECLAIR, Primary Examiner.
R. PESHOCK, Assistant Examiner.