Plastic Container

Abstract

A package for containing liquid is provided. The package includes a plastic container, a fluid tight membrane sealingly engaged thereto, said membrane having a tear tab portion, extending completely around its periphery, and a closure engaged to the container over the membrane. A method for sealing the package is also provided.

Description

SUMMARY OF THE INVENTION

This invention relates to a package formed primarily of thermoplastic material and to a method of sealing such package by adhering a membrane having a peripheral tear tab to the container portion thereof. The package of the present invention is provided with a closure member which may be readily snapped over the container finish. The closure holds the membrane in position on the container finish during the sealing operation. Thus, the design of the package permits it to be sealed rapidly and efficiently using induction heating to effect the seal between the membrane and the container while the closure is engaged to the container. Furthermore, the design permits such sealing to be accomplished while at the same time leaving a peripheral portion of the membrane unsealed to function as a tear tab. The package of the present invention is especially well suited for packaging paints or other liquids which require a liquid-proof seal during shipment and, yet, require a reseal feature to temporarily close the container after removal of the liquid-proof seal. It is not necessary that the reseal closure be capable of holding the contents in a liquid-type relationship.

Accordingly, it is an object of the present invention to provide a package capable of containing liquids without leaking during shipment from the processor to the ultimate user, but which after opening by removal of the membrane can be reclosed.

It is a further object of the present invention to provide a package for containing liquids in which the liquid-tight seal is effected by means of a membrane sealingly adhered to the container finish while the closure member is positioned thereover.

It is another object of the present invention to provide a package in which the membrane portion giving the liquid-tight seal is provided with tear tab means extending completely around the periphery of the container mouth.

Finally, it is an object of the present invention to provide a method for sealing a membrane on a container while leaving a peripheral portion thereof unsealed to provide a tear tab extending completely around the periphery.

It is an additional object of the present invention to provide a method of induction heat sealing a membrane on a container in a manner to provide a tear tab extending completely around the periphery thereof and yet to avoid burning or otherwise adversely affecting the tear tab during the sealing operation.

Other objects and advantages of the present invention will become obvious in the following detailed description taken in conjunction with the annexed sheets of drawings on which:

FIG. 1 is an exploded perspective view of the package of the present invention.

FIG. 2 is an enlarged fragmentary sectional view of the sealed package showing the induction coil member utilized to effect the seal between the membrane and the container.

FIG. 3 is a top plan view of the package and coil shown in FIG. 2.

FIG. 4 is an enlarged fragmentary sectional view showing the container with the membrane sealed thereto, but with the closure removed therefrom.

FIG. 5 is a fragmentary sectional view showing the prior art method of sealing.

Although other means may be utilized for adhering the membrane portion of the present package to the plastic container, it is especially well suited for sealing by means of an induction heater. Such heater induces an eddy current in the metallic foil portion of the membrane in the area to be sealed thus causing the plastic film portion of the membrane to become sealed to the plastic container. The coil utilized to induce such heat is tailored to the specific container size and configuration so that the heat is concentrated in the specific area to be sealed without excessive heat flowing to the unsealed peripheral portion to be utilized as the tear tab.

Referring now to the drawings, there is provided a package, generally designated by the numeral 10, comprising a container 12, a disc sealing membrane 26, and a closure member 16. If desired, the closure 16 may be provided with a tab 17. The container 12 has a body portion 18 which terminates at its upper end in a neck or finish portion 19. An annular groove 20 is formed between the neck 19 and the body portion 18. The finish 19 includes a generally inwardly and slightly upwardly inclined flange portion 22. The outer portion 22a of the flange 22 is generally horizontal while the inner portion 22b tapers inwardly and upwardly at an angle approximately 15.degree. from horizontal when the container is in an upright position. The inner upwardly inclined portion 22b of flange 22 terminates at its innermost area in an upstanding annular bead 23 which defines the periphery of the container mouth 24. Although the angle A at which the inner portion 22b of the flange 22 is preferably approximately 15.degree. from horizontal, when the container is in an upright position, the angle could be as small as 10.degree. or as large as 25.degree. to 30.degree..

Adhered to the annular bead 23 is a laminated disc sealing membrane 26 which is comprised of various layers of material. Although various types of laminates could be used, it is preferred that the membrane disc 26 include a thermoplastic bonding material layer 27 and a metallic foil layer 28. Additionally, a support layer 29 of kraft paper or synthetic plastic material or the like may be provided if the metallic foil layer is not of a strength or thickness to properly retain the contents of the container 12. The thermoplastic bonding layer 27 may be formed of any desired plastic material which is capable of being heat sealed to the plastic container. For example, if the container 12 is formed of high density polyethylene, the thermoplastic bonding layer 27 may be formed of a polyester film, polyethylene or polypropylene. A membrane disc which has been utilized having the three layers of polyester, foil, and pulp is one produced by the Film and Allied Products Division of 3M Company and sold as its "Safe-Gard" 456 Closure Liner.

As can be noted from FIGS. 2 and 4, te membrane disc 26 is adhered to the container only at the annular bead portion 23 thereof. A peripheral portion of the disc 26 extends radially outwardly from the annular bead 23 and forms a tear tab 31 which may be readily grasped for ease in removing the disc from the container. The tear tab 31 extends completely around the periphery of the disc thus providing, in effect, a 360.degree. tear tab. Although a shorter tear tab would obviously be suitable from the standpoint of simply removing the membrane disc from the container, the 360.degree. feature for the tear tab 31 is desirable to permit the use of induction heating for sealing the membrane disc to the container.

If a shorter tear tab were utilized with an induction heating unit to effect the sealing of the membrane disc to the container, excessive heat would build up in the short narrow tab area causing burning of the support layer 29 and possible melting of the metallic foil layer 28 thus, rendering the package unsuitable. However, by utilizing a tear tab 31 which extends completely around the periphery of the disc, the heat which is built up during the sealing step by the induction heater is successfully dissipated without causing burning or other adverse effects to the tab 31. Additionally, the configuration of the container by virtue of the upwardly raised annular bead 23 and the upwardly inclined taper of the inner portion 22b of the flange 22 causes the peripheral portion of the disc 26 defining the tear tab 31 to be held out of contact with the plastic container at all times thus insuring that such tab portion 31 does not become inadvertently sealed during the induction heating step even if it becomes hot enough to start melting the bonding layer 27. As will be seen, the configuration of the closure member 16 also assists in maintaining the peripheral portion of the disc out of contact with the flange.

The closure 16 comprises a top panel portion 34 and an annular skirt 35 depending therefrom. The skirt 35 has an inwardly extending bead 36 at the lower portion thereof which engages the annular groove 20 of the container 12 thereby securing the closure to the container. At the juncture between the skirt 35 and the top panel 34, the closure is provided with a horizontal stop or shoulder 38 which is positioned to engage the outer portion 22a of the flange 22 and thereby limit the downward extent to which the closure 16 may be telescoped over the container finish 19. A short vertical wall portion 39 extends upwardly from the inner portion of the shoulder 38 and connects with the top panel 34. If desired, an annular ridge 40 extending upwardly from the periphery of the top panel 34 as an extension of the wall 39 may be provided to give added rigidity to the closure 16 and to provide means for stabilizing a package which is stacked thereupon.

As can be seen from viewing FIG. 2, the height of the wall 39 depends upon the height of the annular bead 23 above the outer portion 22a of flange 22 as determined by the radial extent of inner portion of 22b, the angle at which it is disposed, and the magnitude or size of the annular bead 23. Thus, as will become apparent from a description of the sealing operation, the height of the wall 39 should be such that the top panel 34 urges the membrane disc 26 snugly and firmly against the annular bead 23 when the closure is engaged with the container, i.e. with the annular bead 36 engaged in groove 20. Thus, upon engagement of the closure 16 to the container 12, the top panel 34 will function to urge the disc 26 against the annular bead 23 forcing the inner portion 22b of flange 22 downwardly slightly. However, the amount of downward movement of the flange inner portion 22a is limited by the shoulder 38 positioned to engage the outer portion 22a of the flange 22 to insure that the peripheral portion 26a of the membrane disc 26 is at all times in a spaced relationship with the flange 22. Such spaced relationship between the peripheral portion 26a and the flange 22 insures that peripheral portion 26a does not become inadvertently sealed thereto during the sealing operation.

It is desirable from the standpoint of efficiency of operation to effect the step of sealing the membrane disc 26 to the annular bead 23 after the closure 16 is in position on the container. Such procedure permits the membrane disc 26 to be supplied to the packer as an insert to the closure 16 so that both the disc and the closure can be applied to the container in one operation. Such procedure also permits the closure to hold the disc in proper position relative to the container 12 during the sealing operation. With the closure 16 and the membrane disc 26 thus positioned on the container 12, the seal between the thermoplastic bonding layer 27 of the disc and the annular bead 23 of the container finish 19 may be effected by an induction heating operation which causes the metallic foil layer 28 to be heated sufficiently to bring the thermoplastic bonding layer 27 to a temperature at which it will become sealed to the annular bead 23.

The fusing or other sealing of a thermoplastic layer incorporated as part of a membrane disc having a metallic layer by induction heating is disclosed in U.S. Pat. Nos. 2,937,481 and 3,460,310, the teachings of which are incorporated herein by reference. Because of the presence of the 360.degree. tear tab and the problems resulting from an excessive build up of heat in the tear tab area using previously known induction heating techniques, it became necessary to make significant changes in the induction heating method utilized to seal the package of the present invention.

Referring now to FIG. 2, the method by which the present package can be sealed by induction heating without adversely affecting the tear tab will be described and compared with the prior art as shown in FIG. 5. As shown in FIG. 2, there is provided an induction coil 45 having several turns or loops identified for purposes of illustration as shown as 45a being the outermost loop and progressing inwardly with 45b, 45c, and the innermost loop being identified as 45d. As is well known in the art, the coil 45 has terminals 46 connected to an appropriate source of power, for example a 2 1/2 KW generator, manufactured and sold by Lepel High Frequencies Laboratories, Inc. The coil is preferably formed of hollow, electrically conductive tubing to permit the circulation of cooling fluid such as water therethrough. The maximum heat in a disc subjected to induction heating such as the membrane disc 26 is developed beneath the innermost turn 45d of the induction coil. Refernce is made to FIG. 5 which identifies the area beneath the innermost turn 45d as the "Maximum Heat Area."

Attempts were made to seal the package of the present invention using the conventional sealing method under which the innermost turn of the coil was positioned directly over or slightly outside of the periphery of the membrane disc. These attempts were unsuccessful in that excessive heat was generated in the tear tab area with the result that the tear tab 31 became scorched or burned rendering the package unsatisfactory. Attempts were also made to seal membrane discs having tear tabs which extended only a short arcuate distance, for example, 30.degree., rather than completely around the periphery. Again these attempts were unsuccessful because in changing the disc from a circular configuration to a non-circular configuration, the heat generated became concentrated in the tab area. Such concentration of heat in the relatively small tab area resulted in one of two problems. First, the disc would be sealed to the container in all areas around the periphery except in the area adjacent the small tab which was not sealed at all. Secondly, attempts to correct this by increasing the heat generated caused burning of the tear tab.

Accordingly, a coil 45 was fabricated as illustrated in FIG. 2 so that its innermost turn 45d conformed in size as closely as possible with the diameter of the annular bead 23 of the container. The innermost turn of the coil is, of course, a portion of a spiral and, hence, not a precise circle; however, it proved to be close enough to a circle to function as desired. Thus, using a coil in which the innermost turn 45d substantially overlay the annular bead 23 resulted in the effective sealing of the membrane disc 26 to such annular bead without damaging the 360.degree. tear tab 31.

It is well known that induction heating generally causes the heat to flow outwardly to the outermost periphery of the metallic foil layer 28 of the disc being sealed. Despite this inherent tendency the method of sealing as previously described using a coil in which the innermost turn 45d substantially overlay the annular bead 23 was successful because, the annular bead 23 apparently acted as a heat sink to dissipate the heat in that area while the portions of the disc 26 in the tab area 31 remained out of contact with the container flange 22. By virtue of remaining out of contact, the tab area did not adhere thereto even though the thermoplastic bonding layer 27 in such tab area may have become heated to the softening point of the plastic.

The present invention provides a package and a method of sealing in which the package may be readily sealed in an efficient operation with a minimum of handling of the closure and membrane disc components and yet provides a package which may be readily opened by a consumer who simply grips the tear tab at any place throughout the 360.degree. periphery and tears the membrane disc off. The package can, upon removing a portion of the contents, be temporarily reclosed simply by reapplication of the closure 16. Although the container has been illustrated as having a snap on type closure 16, it could, of course, be engaged to the container 12 by means of conventional threads.

Claims

I claim:

1. A package comprising

a. a container having a body portion terminating at its upper end in an inwardly directed flange defining a mouth for removing the contents therefrom, said flange having an annular bead extending upwardly therefrom adjacent said mouth, the top of said annular bead forming the highest point of said container and means on said container for retaining a closure.

b. a membrane extending across said mouth and adhered to said annular bead to seal said container, said membrane having a peripheral portion extending outwardly from said annular bead and overlying said flange, said outwardly extending peripheral portion being in unsealed relation to said container, and

c. a closure engaged to said container, said closure having a top panel, an annular skirt depending therefrom and a shoulder positioned at the juncture between said top panel and annular skirt, said shoulder being spaced downwardly from said top panel in a position to engage the upper end of said container outwardly from said annular bead to limit the downwardly movement of the closure on the container.

2. A package comprising

a. a container having a body portion, a neck portion extending upwardly therefrom, a flange extending inwardly and upwardly from the top of said neck defining an open mouth, the uppermost portion of said flange being an upwardly extending annular bead,

b. a membrane member extending across said mouth and sealed to said annular bead, said membrane member having a tear tab capable of being grasped extending radially outwardly beyond said annular bead, and

c. a closure engaged to said container, said closure having a top panel portion, a wall portion extending downwardly from the periphery of said top panel portion, a shoulder extending outwardly from said wall portion, an annular skirt extending downwardly from said shoulder, and means for retaining the closure on the container, said shoulder engageable with the top of said neck to limit the downward movement of the closure on the container, said top panel urging the membrane member against the annular bead while permitting the tear tab portion thereof to remain out of contact with said flange.

3. The package as defined in claim 2 wherein said tear tab extends completely around the periphery of the annular bead.

4. The package as defined in claim 6 wherein said flange is disposed at an angle greater than 10.degree. from horizontal when the container is in an upright position.

5. A package comprising

a. a container formed of flexible material, said container having a body portion terminating at its upper end in a neck portion having means thereon for retaining a closure, a flange extending inwardly and upwardly from said neck, said flange having an annular bead extending upwardly therefrom adjacent said mouth, the top of said annular bead forming the uppermost portion of said container.

b. a membrane extending across said mouth and adhered to said annular bead to seal said container, said membrane having a peripheral portion extending outwardly from said annular bead, said outwardly extending portion being in unsealed relation to said container and of sufficient radial extent to permit grasping, and

c. a closure engaged to said container, said closure having a top panel, an annular skirt depending therefrom, and means engageable with the retaining means of said container, the application of said closure to said container causing said membrane to first engage the annular bead of the flange and then to deflect said flange downwardly to a position at which said bead remains as the highest point of the container, said closure having a shoulder at the juncture between the top panel and the annular skirt, said shoulder being spaced downwardly from said top panel in a position to engage the top of said container neck to limit the downward movement of the closure on the container.