US 3189208 A
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Description (OCR text may contain errors)
June 15, 1965 G. E. JOWETT 3,189,208
CLOSURES, MORE ESPECIALLY FOR CONTAINERS Filed March 16 1964' Inven+or G. E. JowETT M'oi'neys United v. States Patent 0 3,189,268 CLUSURES, MURE ESPEHALLY FGR (IQNTAlNl-ERS George Edward .ioweit, ll llumbles, Fawansea, Glamorgan,
Wales, assignor to Viscose Beveloprnent Company Limited, London, England, a British company Filed Mar. to, wed, er. No. 352,22ll Claims priority, application Great Britain, Mar. 19, 1963, 10,884/ 63 4 (Ilaims. (El. Zl5-38) This invention concerns improvements in and relating to closures, more especially for containers.
It has been proposed to form so-called secondary closures for bottles and the like from synthetic plastics tubing which has been stretched in such a manner that it can be caused to shrink by heating it to an elevated temperature. The proposed method of applying such closures is to cut the tubing into conveniently short lengths, to place these lengths of tubing over the necks of bottles which have been closed by stoppers orthe like and then to subect the neck ot" the bottle to heat so that the tubing shrinks The present invention provides a shaped structure for the production in situ of a closure for a container, said structure consisting of a tube of heat-shrinkable thermoplastic material which has been heat sealed at one end, and being of such dimensions in relation to the container to be closed thereby that it can be placed over an opening of the container and shrunk by heat to conform to the outline of the container. The structure according to the invention has the advantage that it provides a complete closure for a container such as a bottle, being capable of extending continuously over the top of the container. It is also inexpensive and surprisingly neat in appearance when shrunk into place. It may be used as a secondary closure, or may itself form a primary closure, if necessary being provided with an inner sealing wad. It may also be used as a primary closure for means other than containers, for example as a temporary closure for apertures in machines, engineering components and the like.
Preferably the heat sealed end of the structure is generally concave towards the interior thereof. The heat seal may, for example, extend in the form of a curved line across the end of the tube, said line having a radius of curvature which is smaller towards the ends than in the middle. By this means a greater neatness in the appearance of the finished closure may be obtained.
Advantageously the structure is of such thickness and rigidity that when applied to a container of which the said outline is in the form of a screw thread, and shrunk thereon, it can be removed from the container by an unscrewing movement and subsequently replaced thereon as required. It can thus form a simple and inexpensive screw cap useful as a primary closure, In a modified dorm this structure may comprise a ring with open top capable of forming a closure with a cap, wad or the like and being removeable and replaceable as specified. If desired the structure may have a skirt portion divided by a line of weakness from a main closure portion. When the structure is applied to a screw threaded container of suitable configuration, the arrangement can then be such that the skirt portion is held by a corresponding portion of the container against rotation with the main closure portion when the latter is unscrewed from the container so that the skirt portion is parted from the cloto fit closely over the bottle and the stopper or primary sure portion and remains on the container. Thus an indication may be obtained that the closure portion has been removed. The skirt portion can alternatively be secured in position by means of adhesive. a The invention is illustrated by way of example in the accompanying drawings, in which:
FIG. 1 is an elevation of a shaped structure according to the invention before it has been applied to a container, FIG. 2 is a sectional elevation of a threaded bottle neck with a closure formed by means of a shaped structure as shown in FIG. 1, and FIG. 3 is a plan view corresponding to FIG. 2.
Referring to FIG. 1 of the drawings a shaped structure 1 for application to a bottle neck having an external diameter of approximately 1% inches isfcrmed from 2" Wide flat tubing of thermoplastic material which has been molecularly orientated by internal information under the influence ofheat, and subsequently cooled to re, tain it at the inflated dimension. The tubing thus has the property of being heat-shrinkable, that is to say that when heated it will tend to to inflation.
heat seal extending in a curve concave towards the interior of the tube. The curve comprises a central arcua ate portion a which has a centre of curvature at a point P on the central axis of the fiat tube, and a radius of curvature of 2 /2 inches, and two symmetrical arcuate end portions b having centres of curvature Q on the radii to the ends of the are a, and radii of curvature of 1 inch each. The are a extends over an angle of approximately 25.
The structure is open at the lower end, and has a lower skirt portion 3, which is partially separated from the body of the structure by a line of perforations 4.
In order to apply the structure to a container as a closure, it is opened out at the lower end, placed over the open mouth of the container and then subjected to heat so that it shrinks to conform to the closure.
As shown in FIGS. 2 and 3 the structure hasbeen applied in this manner to a threaded bottle neck 5. The structure thus takes the form of a cap, beneath which a sealing wad 6 has been applied to the mouth of the bottle. Owing to the shape of the heat sealed end 2 of the structure, this end has now shrunk to conform closely to the flat sealing wad 6, while the remainder of the structure has the same shape as the profile of the bottleneck. As shown, the perforations 4 are located adjacent the lower terminus of the threaded portion 5a of the bottle neck, so that the skirt portion 3 is located on an unthreaded portion 5b of the neck. The portion 5!) is provided with radial pips 7 to prevent the skirt portion 3 from turning relatively thereto. If desired, the: pips 7 may be dispensed with and the skirt portion 3 secured by means of an adhesive.
If the structure 1 is formed of material of sufiicient thickness and rigidity, it can be removed together with the sealing wad 6 from the bottle neck 5, by unscrewing in the manner of a normal screw cap. In this operation, the skirt portion 3 will remain on the bottle neck, being (separated from the structure 1 at the line of weakness formed by the perforations 4. The structure can then be replaced on the bottle as desired, the separated skirt 3 serving as an indication that it has once been removed.
According to a modification of the above embodiment of the invention, the structure 1 may be applied to the bottle neck 5 in the form of a ring instead of a cap, the closure in its final form would then be similar to that shown in FIG. 2 except that instead of extending fully over the top of the sealing wad 6 the structure 1 would terminate in the form of an inturned flange extending to the dotted lines X.
return to its dimension prior.
Suitable material for the structure 1 of the above described embodiments is polystyrene tubing of 0.01 inch thickness (or 0.02 inch when folded fiat to form a double Wall), which has been inflated during orientation at a blow ratio of 5:1, that is to say the inflated tube has a diameter which is 5 times the diameter of the tube before inflation. This material is convenient to handle during formation of the shaped structure of FIG. 1, while still having a sufiicient measure of stability to allow it to be removed and replaced on the screw top bottle in the manner described.
According to a further modification of the above embodiment of the invention, the structure 11 may be adapted for use as a secondary closure or a disposable primary closure, more especially for a container of other than threaded form. In this case the structure is not provided with perforations 4, and may be made of less rigid material, for example polystyrene of less wall thickness, or polyvinyl chloride. Advantageously, using the same profile of the heat sealed end, the material is polystyrene of 0.006" double wall thickness.
Shaped structures as described above may be formed in a continuous operation from fiat heat shrinkable tubing by heat sealing the tube in conventional manner, using a shaped heated bar, and simultaneously cutting the tube by means of separate cutter blades. It is important, however, that the time and pressure of application of the bar to the material of the structure, and also the tem perature of the bar, should be carefully controlled to avoid substantial shrinkage of the material during the heat sealing operation. For example when sealing polystyrene having a double wall thickness of between 0.003 and 0.020 inch, the bar should have a temperature of 130 C.-150 C., the pressure per inch of the bar should be from 60-120 lbs. and the time of contact should be less than 0.1 second. Equivalent figures for polyvinyl chloride are: temperature 180 C.-210 0; pressure per inch of bar, 60l20 lbs.; time less than 0.3 second.
The material of the structure adjacent the seal may be cooled, if desired, by means of an air blast, suitable shielding then being interposed between the air blast and the heat bar. The material of the tube is preferably supported on a resilient base during heat sealing thereof.
1. A shaped structure for the production in situ of a closure for a container, said structure consisting of a length of heat-shrinkable thermoplastic tubing in flat form and closed at one end by means of a line heat-seal extending across the full width of the fiat tubing, the tubing being of such transverse dimension in relation to the container to be closed that the said structure can be placed over an opening of the container and shrunk to fit the same, and the profile of the heat sealed end of the tubing being generally concave towards the interior thereof so that when the structure is so shrunk the closed end thereof will conform to the outline of the container.
2. A shaped structure as claimed in claim 1, in which the profile of the heat sealed end has a radius of curvature which is smaller towards the ends than in the middle.
3. A shaped structure as claimed in claim it of such thickness and rigidity that when applied to a container of which the said outline is in the form of a screw thread, and shrunk thereon, it can be removed from the container by an unscrewing movement and subsequently replaced thereon as required.
4. A shaped structure for the production in situ of a closure for a container, said structure consisting of a length of heat shrinkable thermoplastic tubing in flat form and closed at one end by means of a line heat seal extending across the full width of the tubing, the profile of the heat seal being concave towards the interior of the tubing so that when the structure is placed over an opening in the container and shrunk to fit the same the closed end of the structure will present a substantially flat surface extending over said opening, a line of weakness extending across the Width of the tubing to define, at the open end of the tubing, a skirt portion partially divided from the main closure portion, and the tubing being of such thickness and rigidity that, when the container is provided at said opening with a screw threaded upper neck portion and an irregular lower neck portion, the main closure portion of the shrunk-on structure can be removed from said upper neck portion by an unscrewing movement and subsequently replaced, while the skirt portion will part from the main closure portion rather than be removed from said lower neck portion.
References Cited by the Examiner UNITED STATES PATENTS 2,328,845 9/43 Pike et al. 2l5---38 2,331,794 10/43 Mallory 21538 2,790,286 4/57 Snyder 21538 2,954,139 9/60 Owens 21538 GEORGE O. RALSTON, Primary Examiner.
FRANKLIN T. GARRETT, Examiner.