GB1570637A

GB1570637A - Dispensing closures

Info

Publication number: GB1570637A
Application number: GB281977A
Authority: GB
Original assignee: Silgan Dispensing Systems Slatersville LLC
Current assignee: Silgan Dispensing Systems Slatersville LLC
Priority date: 1976-03-11
Filing date: 1977-01-24
Publication date: 1980-07-02
Also published as: FR2343660A1; DE2649631A1

Description

(54) IMPROVEMENTS IN OR RELATING TO DISPENSING CLOSURES 171) We, POLYTOP CORPORATION, a corporation organised under the laws of the State of Massachusetts, United States of America, of 110 Graham Drive, Slatersville, Rhode Island 02876, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment:- This invention relates to dispensing closures.

The term "dispensing closure" has been adopted by the closure industry to designate various differently constructed closures having a part which is movable between a closed position in which an opening through the closure is closed off and an open position in which material may pass through the opening from within the interior of the closure to the exterior of the closure. Com- monly such dispensing closures have been two-piece structures constructed so as to utilize a spout capable of being assembled upon a cap by temporarily deforming the cap so that the spout is mounted for rotational movement between the open and closed positions.

Previously such two-piece dispensing closures have commonly been constructed utilizing both a cap and a spout formed of a common polyolefin polymer composition.

These ,parts have previously been formed by injection molding polyethylene or polypropylene since these polyolefins are inert, present a relatively neat surface appearance, and are physically capable of the degree of distortion necessary for the assembly of a spout upon a cap in the manner mentioned above. Very early in the history of twopiece, snap-together dispensing closures it was recognized that these polyolefins are rather difficult materials to mold to precise dimensions as are required in dispensing closures.

For a dispensing closure to be commercially acceptable the external dimensions of the closure should be of a uniform character corresponding to the dimensions of a mold or the molds used in producing the closure. Preferably, for a closure to look satisfactory as used, it should be substantially free from surface distortion, but such distortion is apt to be caused by undesired dimensional changes in a polyolefin polymer as a closure part formed in a die physically cools.

In a sense the absence of surface imperfections such as surface warpage or shrinkage is secondary to the criticality of the dimensions of the co-operating operative parts of the dispensing closure which are used to achieve a valve action to open and close the opening through the closure. If those parts, such as the bearings or equivalents, the trunions or the like contacting the bearings, the base of the spout and the sealing ring which contacts the base of the spout in a dispensing closure, are not precisely formed the closure is apt to leak. The industry recognizes that it is more difficult to form leakproof closures for use with certain types of fluids than with other types.

The need for dispensing closures which can be utilized with various hard-to-seal types of fluids has resulted in various specialized sealing structures which will form an adequate seal in a dispensing closure in even those cases where precise control of molding conditions has made it difficult to provide satisfactory dispensing closures.

One known method of controlling the dimensions of polyolefin closure parts is to control as precisely as reasonably possible the molding conditions and cycles used in the formation of such parts. Such precise control is comparatively difficult and furthermore is comparatively expensive from a manufacturing standpoint. Fr'om an economic point of view it is extremely desirable to produce dispensing closure parts utilizing comparatively rapid injection molding machine cycles. In general the shorter the molding cycle employed in forming 'such parts the more difficult it is to produce parts within a very close range of tolerances. A factor complicating the production of parts for dispensing closures to precise tolerances relates to the fact that there is usually some variation in the physical properties of a polyolefin used for the manufacture of such parts.

In accordance with this invention there is provided a dispensing closure comprising a cap having means for connection to a container, an opening leading through the cap, and sealing means extending around said opening on the exterior of said cap, and a valve member mounted on the cap for movement between a closed position in which the valve member co-operates with the sealing means and closes off the opening and an open position in which the valve member permits material to pass from within the interior of the container to the exterior of the closure through the opening, wherein at least the cap is formed of a structural polyolefin polymer foam having a solid polyolefin outer skin and a closed cellular core surrounded by said skin.

A dispensing closure in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is an isometric view of the dispensing closure, and Figure 2 is a cross-sectional view on an enlarged scale illustrating the internal structure of the closure shown in Figure 1.

In Figure 2 the internal structure is illustrated in an essentially diagrammatic manner and not to scale, so that the nature of the material used may be conveniently visualized.

The closure 10 is formed so as to include a cap 12 and a spout 14 serving as a valve member.

This spout 14 is provided with aligned trunions 16 extending on opposite sides of a cylindrical centre part 18. These trunions 16 are adapted to be snapped through restricted entrances 20 into bearing openings 22 serving to hold the trunions 16 so that the part 18 engages an upwardly extending, resilient, comparatively small sealing ring 24 of a shape having a "thin" V-shaped crosssectional configuration located about an opening 26 leading through the cap 12, from a container (not shown), into a cavity 30 located generally within the top 32 of the cap 12.

When in a closed position as indicated the spout 14 extends from the cavity 30 along a groove 34 in the top 32 to adjacent a decorative skirt 36 located so as to surround the skirt 28. A tip 38 on the spout 14 is adapted to be manually engaged for use in rotating the spout 14 from a closed position as shown to a vertically extending open position in which a passage 40 in the spout 14 is in alignment with the opening 26.

Except when the spout 14 is in such an open position the opening 26 is sealed off by the sealing ring 26 engaging the member 18.

The precise manner of such engagement will be dependent upon the price type of sealing ring or sealing member used. Preferably the sealing member will be constructed as shown and described in U.S. Patent Specification No. 3,495,745. The sealing ring 24 can however be formed in a number of manners known in the dispensing closure industry.

At least the cap 12 and preferably also the spout 14 are formed of a rigid structural, polyolefin polymer foam structure consisting of a solid, continuous polyolefin outer skin or surface 42 and a closed cellular core 44 surrounded by this surface or skin 42. The core 44 differs from the skin or surface 42 primarily in that it consists of a plurality of comparatively minute closed pores or cells 46 dispersed in a matrix of the same material as is present in the skin or surface 42. This matrix is considered to act so as to exhibit what may be referred to as a "bridging effect" serving to provide rigidity to the interiors of the cap 12 and the spout 14. The sizes of these pores or cells 46 will vary somewhat within the cap 12 and the spout 14 in accordance with the thickness in crosssection of the cap 12 and the spout 14 in any particular location.In general the thinner the cross-section of a part the smaller the pores or cells 46 present. Thus, in the particular closure 10 illustrated the pores or cells 46 within the skirt 36 will tend to be somewhat smaller than the pores or cells in the area of the cap 12 at the top 32 generally above the skirt 28 where comparatively large masses of material are present.

It is of course known to form various types of articles such as children's blocks, brush handles and the like of a rigid structure polyolefin polymer foam structure consisting of a solid, continuous polyolefin outer skin or surface and a closed cellular core surrounded by this skin or surface. In such utilizations of polymer foam materials the polymer structures employed are usually utilized primarily because of their weight savings. In such structures dimensional criticality is not as important as in dispensing closures. In dispensing closures, surface uniformity is a matter of importance and in addition the tolerances of internal dimensions can be critical.

The skin or surface 42 is preferably sufficiently thick so that the appearance of this skin or surface 42 is not significantly or materially affected by the presence of the cells or pores 46 beneath the skin and is sufficiently thick so that the skin is continuous and provides sufficient physical strength to resist damage during assembly of the closure 10 and/or during installation and/or use of the closure. It is presently considered that the skin or surface should normally be at least about 0.015 inches (0.038 cm.) thick in order to possess the physical characteristics and properties referred to above.

It is also considered that this skin or surface 42 should preferably be no thicker than about 0.060 inches (0.152 cm.) thick.

If the skin or surface 42 is thicker than about this value there may be a tendency for surface deformation to occur in the skin 42 during the formation of the cap 12 or the spout 14 using commonly known injection molding equipment operated in accordance with known practice at a comparatively rapid cycle rate. Any such deformation would tend to affect surface appearance and/or surface dimensions. Both of these matters are important in a dispensing closure.

The actual formation of a cap 12 and a spout 14 so as to have a skin or surface 42 surrounding a closed cellular core 44 as described in the preceding is comparatively simple. A mixture of polyolefin polymer pellets and at least one conventional blowing agent is supplied to a known injection molding machine in the established manner.

If desired the blowing agent used may be incorporated within such pellets or the blowing agent may be merely mixed with such pellets in known manner. Under no cricumstances should be the amount of the blowing agent and other extraneous non-polymer material used be sufficiently great so as to significantly detract from the physical properties of the polymer material employed.

Normally this is no problem.

The amount of the blowing agent used will, of course, depend upon the effectiveness of the agent as well as the manner in which the agent is caused to release gas as the result of the process conditions employed during the formation of parts from a mixture as described. Since various blowing agents differ significantly in their effective- ness and since the manners in which injection molding machines are operated will differ significantly it is considered that it would be meaningless to specify herein a precise amount of blowing agent which should be used with any particular polymer composition. Furthermore, the effectiveness of a blowing agent will also vary somewhat in dependence upon the particular polymer with which it is employed.

It is believed that those skilled in the injection molding field will be easily able to determine in any specific application the amount of a specific blowing agent required to produce a structure as described through the use of simple, routine experimentation.

As a guide to such experimentation it is noted that it is presently believed that from about 2% to about 3% by weight of the most commonly known polyolefin blowing agents (based upon the weight of the polymer material present) should be used in conjunction with a conventional injection molding machine operated in accordance with normal parameters for the production of foam polyolefin polymer parts of a known external shape used in dispensing closures.

One advantage of the above-described closure is that the ram pressures used with an injection molding machine operated to produce the closure parts can be significantly decreased from the ram pressures required to produce solid polyolefin parts for conventional dispensing closures using the same machine and the same molds. Since an injection molding machine is operated with the molds or dies in such a machine held tight together a mixture as described is, of course, forced under heat and pressure into the die cavities.

As the material enters the die cavities the pressure on the material will be somewhat relieved and the temperature of the material will be adequate so that the blowing agent will act to form the pores or cells 46 described. As this occurs the chilling action at the walls of the die cavities will automatically tend to form the previously described surface or skin 42. As the blowing agent used exercises its action the pores or cells 46 will form so as to have dimensions which can be best described as varying from sub-microscopic to microscopic in accordance with the thickness or cross-section of the material present at any specific location. In general the more "massive" the material at a specific location within a die cavity the larger the pores or cells will tend to be which form in such a location.A number of factors, however, influence the size of the pores or cells that form.

Because of the manner in which the skin or surface 42 forms the density within a part of the dispensing closure will vary significantly from one area to another within the interior of that part. In general there will be a gradation of the internal density with the density of material within a part being the highest within the skin or surface 42 and gradually decreasing to a minimum value in such area or areas within a part where the material is present in a "massive" area or volume. Within such massive areas it is considered that probably the density will be from about 60% to 80% of the density of the polymer material in a skin or surface 42.

It is interesting to note that the structure d a part formed as described is determined prior to such a part being completely formed, that is before the part is ready to be removed from a die cavity and used.

The pores or cells 46 are formed in the polymer material as this material is in what may be referred to as a viscous or plastic state as the result of gas released by the blowing agent used. This gas will be under pressure during molding. As a consequence of the gas pressure within the pores or cells 46 the skin or surface 42 will be held or forced outwardly into direct, intimate contact with the die cavity during molding.

This holding action will prevail until such time as the parts formed in this manner are internally cooled within the die to a sufficient extent so they are dimensionally stable. In the formation of parts of the above-described closure the mold or dies should not be opened until such time as substantially all of the material within these die cavities is cooled past what may be regarded as a "critical" temperature. This is the highest temperature at which the gas present within the pores or cells 46 is incapable of exerting sufficient pressure to cause a dimensional change. Such a critical temperature will vary depending upon the specific polymer used and the specific blowing agent employed.

By forming parts in the manner indicated it is possible to produce parts as described which are substantially free from surface irregularities caused by the shrinkage of a polyolefin during cooling and which are within very close dimensional tolerances.

Further, there is a somewhat unusual aspect relating to the sealing ring or member 24 in the cap 12 formed as described. Because of the comparatively thin and/or small dimension of this sealing ring or member 24 when the cap 12 is produced as described this sealing member 24 will be substantially free from any internal cells or pores 42. As a consequence of this within the closure 10 the necessary flexibility considered to be required in order to obtain adequate sealing action through the use of the ring or member 24 will not be interfered with. Further, internal shrinkage within the cap 12 will not tend to distort this ring or member 24 from a desired configuration.

It will be appreciated that although one specific form of dispensing closure has been described the invention is applicable to dispensing closures of different forms and configurations.

The cap and spout of the above-described closure are of such a nature as to be capable of being molded with comparatively minimal difficulty to reasonably precise tolerances as are required in satisfactory dispensing closures. The closure is substantially without various imperfections such as are caused by the shrinkage of a polyolefin or the like. The individual parts of the closure are of lighter weight than the parts previously utilized in dispensing closures and are relatively resistant to physical damage. Although the weight savings achieved in an individual dispensing closure are comparatively small these weight savings are in fact significant because of the tremendous numbers of such closures manufactured and use and because of the price of the polymer material used in forming the closures.

The parts of the above-described closure can be easily and conveniently manufactured using known injection molding equipment at a relatively rapid cycle rate and using molding conditions and cycle control which are relatively easy to manage in connection with high speed or rapid production of such parts.

The closure parts may be more easily produced than known parts and are more satisfactory than such known parts in that they possess an increased resistance to damage during assembly, during installation on a container, and during use of the container.

The above-described dispensing closure differs from previously proposed dispensing closures primarily as to the material employed in creating one or more parts of the closure.

WHAT WE CLAIM IS:- 1. A dispensing closure comprising a cap having means for connection to a container, an opening leading through the cap, and sealing means extending around said opening on the exterior of said cap, and a valve member mounted on the cap for movement between a closed position in which the valve member co-operates with the sealing means and closes off the opening and an open position in which the valve member permits material to pass from within the interior of the container to the exterior of the closure through the opening, wherein at least the cap is formed of a structural polyolefin polymer foam having a solid polyolefin outer skin and a closed cellular core surrounded by said skin.

2. A dispensing closure according to claim 1, wherein the sealing means comprises an upstanding, resilient ring extending outwardly from the cap and surrounding the opening, the sealing ring being substantially free from the closed cells in the core.

3. A dispensing closure according to claim 1 or 2, wherein the skin is at least about 0.015 inches thick.

4. A dispensing closure according to claim 1 or 2, wherein the skin is from about 0.015 to about 0.060 inches thick.

5. A dispensing closure according to any of claims 1 to 4, wherein the density of material of the closed cellular core varies from about 60% of the density of the polymer within the interior of the core to about the density of the polymer adjacent the skin.

6. A dispensing closure according to any of claims 1 to 5, wherein the valve member comprises an elongate spout having

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. may be referred to as a viscous or plastic state as the result of gas released by the blowing agent used. This gas will be under pressure during molding. As a consequence of the gas pressure within the pores or cells 46 the skin or surface 42 will be held or forced outwardly into direct, intimate contact with the die cavity during molding. This holding action will prevail until such time as the parts formed in this manner are internally cooled within the die to a sufficient extent so they are dimensionally stable. In the formation of parts of the above-described closure the mold or dies should not be opened until such time as substantially all of the material within these die cavities is cooled past what may be regarded as a "critical" temperature. This is the highest temperature at which the gas present within the pores or cells 46 is incapable of exerting sufficient pressure to cause a dimensional change. Such a critical temperature will vary depending upon the specific polymer used and the specific blowing agent employed. By forming parts in the manner indicated it is possible to produce parts as described which are substantially free from surface irregularities caused by the shrinkage of a polyolefin during cooling and which are within very close dimensional tolerances. Further, there is a somewhat unusual aspect relating to the sealing ring or member 24 in the cap 12 formed as described. Because of the comparatively thin and/or small dimension of this sealing ring or member 24 when the cap 12 is produced as described this sealing member 24 will be substantially free from any internal cells or pores 42. As a consequence of this within the closure 10 the necessary flexibility considered to be required in order to obtain adequate sealing action through the use of the ring or member 24 will not be interfered with. Further, internal shrinkage within the cap 12 will not tend to distort this ring or member 24 from a desired configuration. It will be appreciated that although one specific form of dispensing closure has been described the invention is applicable to dispensing closures of different forms and configurations. The cap and spout of the above-described closure are of such a nature as to be capable of being molded with comparatively minimal difficulty to reasonably precise tolerances as are required in satisfactory dispensing closures. The closure is substantially without various imperfections such as are caused by the shrinkage of a polyolefin or the like. The individual parts of the closure are of lighter weight than the parts previously utilized in dispensing closures and are relatively resistant to physical damage. Although the weight savings achieved in an individual dispensing closure are comparatively small these weight savings are in fact significant because of the tremendous numbers of such closures manufactured and use and because of the price of the polymer material used in forming the closures. The parts of the above-described closure can be easily and conveniently manufactured using known injection molding equipment at a relatively rapid cycle rate and using molding conditions and cycle control which are relatively easy to manage in connection with high speed or rapid production of such parts. The closure parts may be more easily produced than known parts and are more satisfactory than such known parts in that they possess an increased resistance to damage during assembly, during installation on a container, and during use of the container. The above-described dispensing closure differs from previously proposed dispensing closures primarily as to the material employed in creating one or more parts of the closure. WHAT WE CLAIM IS:-

1. A dispensing closure comprising a cap having means for connection to a container, an opening leading through the cap, and sealing means extending around said opening on the exterior of said cap, and a valve member mounted on the cap for movement between a closed position in which the valve member co-operates with the sealing means and closes off the opening and an open position in which the valve member permits material to pass from within the interior of the container to the exterior of the closure through the opening, wherein at least the cap is formed of a structural polyolefin polymer foam having a solid polyolefin outer skin and a closed cellular core surrounded by said skin.

a passage therein which communicates with the opening when the spout is in the open position, and wherein the spout can be snapped into place on the cap with the spout being movably mounted on said cap in engagement with the sealing means.

7. A dispensing closure according to any of claims 1 to 6, wherein the valve member is formed of a structural polyolefin foam having a solid polyolefin outer skin and a closed cellular core surrounded by the skin.

8. A dispensing closure constructed and arranged substantially as herein described with reference to the accompanying drawing.