US 3405831 A
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Description (OCR text may contain errors)
Oct. 15, 1968 J. E. HLIJDSON 3,405,831
CONTAINER Filed Sept. 19, 1966 v 2 Sheets-Sheet 1 INVENTOR.
J' E. HUDSON BY I ATTORNEYS Oct. 15, 1968 J E, HUDSON 3,405,831
CONTAINER Filed Sept. 19, 1966 2 Sheets-Sheet 2 INVENTOR.
J. E. HUDSON U QP M' A T TORNEVS United States Patent 3,405,831 CONTAINER Jimmie E. Hudson, Bartlesvilie, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Sept. 19, 1966, Ser. No. 580,304 8 Claims. (Cl. 215-43) ABSTRACT 0F THE DISCLOSURE A plastic bottle is formed with flexible protrusions extending radially outward from the thread section which cooperate with a smooth surface on a cap so as to form a reusable locking device. These flexible protrusions may take the form of a plurality of tabs projecting outwardly from the ridges of the threads or may take the form of a Web extending across the threads.
This invention relates to plastic containers with screw caps.
The advent of tough, chemically resistant plastics has made possible packaging many materials in plastic containers which were formerly packaged in containers of glass, metal, and the like. With the availability of clear bottles made of poly (vinyl chloride), oriented polypropylene, polycarbonate, and the like, plastics have taken on a renewed importance as a container material. Many of these plastic materials which are otherwise desirable materials for the fabrication of containers exhibit a very low coefiicient of friction. Indeed such plastic materials as polyethylene, polypropylene, and nylon are frequently used as self-lubricating bearings because of their natural slippery nature. Thus it is not surprising that this property creates a problem with containers using screw-on caps in that the caps tend to unscrew during shipping or handling. The prior art discloses means to combat this problem but these means have generally been complex and cumbersome. Furthermore they have frequently been of such a nature that when the cap is first unscrewed the locking device is broken and thus is not effective to prevent the cap from coming unscrewed when it is replaced on the container.
It is an object of this invention to provide a plastic container with a simple means which allows a cap to be screwed on easily and yet which resists any tendency of the cap to come unscrewed.
It is a further object of this invention to provide a plastic container with a means which allows a cap to be screwed on easily and yet which resists any tendency of the cap to come unscrewed, wherein said means is equally effective after the cap has been removed repeatedly.
It is a still further object of this invention to provide a container with a locking means which also serves as a seal.
In accordance with this invention a bottle is formed with flexible protrusions, extending radially outward from the thread section, which cooperate with a smooth surface on a cap so as to form a reusable locking device.
In the drawings forming a part hereof, in which like reference characters indicate corresponding parts in all views:
FIGURE 1 is a perspective view of the upper portion of a container made in accordance with one embodiment of this invention;
FIGURE 2 is a sectional view taken on line 22 of FIGURE 1;
FIGURE 3 is a sectional view of the thread section of a container made in accordance with this invention similar to FIGURE 2 except that a cap is affixed to the container;
3,405,831 Patented Oct. 15, 1968 FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 3;
FIGURE 5 is a perspective view of the upper portion of a container made in accordance with an alternate embodiment of this invention, and
FIGURE 6 is a perspective view of the upper portion of a container made in accordance with an alternate embodiment of this invention.
Referring now to the drawings, a container 1 has a body portion 2 and a thread section 3, said thread section having screw threads 4 provided with flexible tabs or protrusions 6 extending radially outward from the ridges of said threads.
FIGURES 3 and 4 illustrate the way the flexible tab is folded back against thread 4 when cap 7 is screwed into place. Cap 7 has a downwardly projecting annular skirt or wall 8 and thread grooves 9 which cooperate with thread ridges 4.
FIGURE 5 illustrates an alternate embodiment in which the outwardly extending protrusion is in the form of a web 10 which projects radially outward from the thread sect-ion of the container. This web extends over the ridges of the threads as does tab 6 but also extends across the grooves of the threads.
FIGURE 6 illustrates an alternate embodiment in which the threads are in the form of discontinuous lugs 14.
As the cap is screwed onto the container the flexible tabs 6 are folded back against the threads 4 providing little resistance to the turning of the cap; however, after the cap is screwed on any attempt to unscrew it will result in the flexible tabs buckling and thus forming a wedge which resists further unscrewing. Since the locking is partially effected by the wedging of the buckled tab between the thread sections of the container and the cap, notches or catches do not have to be present on the cap. Thus these bottles can use standard caps, and said caps can have a smooth inner surface.
The degree of resistance to unscrewing can be controlled by varying the length and/or thickness of the protrusions either alone or in combination with varying the tolerance between the cap and the container neck. Generally the protrusions will extend radially outward a distance equal to between 5 and percent of the depth of the threads, preferably between 15 and 30 percent; the thickness of the protrusions will generally be from 5 to 50 percent of the radial length, preferably from 15 to 25 percent.
The act of unscrewing the cap does not destroy the locking mechanism; thus, as often as it is desired to replace the cap, the locking mechanism is effective to resist the caps being unscrewed. In instances where it is desired to provide the locking feature only up to the time the cap is first removed, the flexible project-ions can be trimmed off after the initial removal of the cap.
The containers of this invention are preferably fabricated by a blow molding technique, for instance by blowing a freshly extruded parison out against a mold or by forming parison blanks which are reheated and blown out against a mold. Alternatively they can be made by any conventional molding means such as injection molding or powder molding.
The flexible locking projections are preferably formed as the container is made thus avoiding the necessity of any extra steps. When using the blow molding techniques the projections can be formed by the action of a split sleeve which forms the neck. This split sleeve pinches out a portion of the parison between the two halves at the parting line. This split sleeve may be a separate entity or it may be an integral part of a split mold. Or in embodiments where a mandrel is inserted into the parison to force the plastic to conform to the shape of the thread forming sleeve, this mandrel may also force the plastic into recesses in the inner surface of the thread forming means to form the protrusions. In this latter instance the protrusions do not necessarily have to be at the parting line. In injection molding or powder molding the mold simply has the appropriate recesses to form the protrusions. It is apparent that in embodiments where the protrusions are formed by pinching part of the parison between the split sleeve parts, with a sleeve having two halves either one or two sets of protrusions are possible. With a sleeve split into three parts a maximum of three sets of protrusions are possible. With other means of forming the protrusions any number of sets of protrusions are possible; furthermore, the protrusions can be in a vertical row one above the other on each successive thread or they can be spaced at random around the circumference on the various threads. The protrusions may be provided on all the threads, on only part of the threads, or on only one thread.
The caps used in conjunction with this invention can be formed by injection molding, vacuum forming, powder molding, or any other conventional molding means. They may be formed in the same manner as the container on which they are used or they may be formed in a different manner; for instance, an injection molded cap will frequently be used on a blow molded container.
The threads can be single or multiple lead. The term thread is meant to include all types of lugs or catches which are engaged with a cap by rotating the cap relative to the container whether continuous or discontinuous.
While this invention is primarily concerned with bottles and jars, it is applicable to any type of container having a closure which is engaged by rotating the cap relative to the container.
Any plastic material can be utilized in fabricating the container. Examples of suitable materials include: olefin polymers, particularly polymers and copolymers of ethylene, propylene, and l-butene; nylon; poly (vinyl chloride); polycarbonates; acetal resins; fluorocarbon polymers; rubber; and the like. The cap can be fabricated from any material used in the fabrication of caps such as plastics, metal, and the like.
In the alternate embodiment shown in FIGURE the outwardly extending protrusion is in the form of a web across both the ridges and grooves of the threads. This arrangement not only provides a locking means but also aids in sealing the container to prevent the passage of liquids or gases into or out of the container.
The outwardly extending protrusion can be formed in its final state in the initial forming of the container. Alternatively it can be formed in a rough form in the initial forming of the container and trimmed to its final form in a subsequent operation.
EXAMPLE A polypropylene homopolymer of 0 .905 density (ASTM D1505-60 I) and 4 melt flow (ASTM D1238- 62T Condition L) was extruded into a parison 0.970 inch in diameter. This was programmed so as to give a parison wall thickness of 90 mils in the area to be formed into the thread section and 150 mils in the section to be for-med into the body of a bottle. This parison was immediately passed into a water cooled quench sleeve one foot long. The parison was pulled out against the inside of this sleeve by a vacuum. The cooled parison was then transferred to a heating chamber andheated to a temperature just below the melting point of the polypropylene over a period of 18 minutes. The parison was then removed from the heating chamber by a clamp aflixed to the bottom end of the parison. Split sleeves with a contoured inner surface to form the threads were brought together around the top part of the parison. A portion of the outer surface of the parison was squeezed between the two halves of the sleeve at the parting line to form the flexible projections. A mandrel was then inserted into this top part of the parison; this mandrel forced the plastic to conform more completely to the shape of the inner surface of the split sleeve thus forming the threads and neck portion of the bottle. The bottom of the parison was pinched simultaneously with the formation of the threads. The parison was then transferred into a split cavity mold, the mold closed and fluid pressure introduced into the mold to force the parison out against the mold surfaces, thus producing a 12 ounce oriented polypropylene bottle with flexible projections on the threads.
While this invention has been described in detail for the purpose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope of the invention.
1. A plastic container adapted to be closed with a screw cap, comprising: a body; and a thread section, said thread section having at least one thread and at least one outwardly extending flexible protrusion in the form of a web which extends across the thread ridges and grooves.
2. A container according to claim 1 wherein said at least one thread is continuous.
3. A container according to claim 1 wherein said web extends radially outward from a ridge of said at least one thread a distance equal to between 5 and percent of the depth of the threads.
4. A container according to claim 1 wherein the material comprising the container is a polymer of at least one monomer selected from the group consisting of ethylene, propylene, and l-butene.
'5. A container according to claim 1 wherein the material comprising said container is polypropylene.
6. A container according to claim 1 in combination with a cap. i
7. A container according to claim 6 wherein said cap has a smooth inner surface.
8. A plastic container adapted to be closed with a screw cap, comprising: a body; a thread section, said thread section having at least one thread; a plurality of flexible integrally molded protrusions extending outwvardly from a ridge area of said at least one thread.
References Cited UNITED STATES PATENTS 1,365,884 1/1921 Bayne 28-592 2,169,686 8/1939 Fabrice 215' 44 2,355,486 8/1944 Tinnerman 15114 2,886,089 5/1959 Schlage l5l--25 3,158,553 11/1964 Carski 215-44 3,295,708 l/ 1967 Wathen 215-43 WILLIAM T. DIXSON, IR., Primary Examiner.