Patent Application
20080283529
The present invention relates to containers sealed with flexible lids formed from materials such as polymer film, aluminum foil, paper, and the like.
It is known to seal a container with a lid formed from a heavy-gauge aluminum foil having a heat-sealable material on its underside. The lid is shaped to include a cylindrical skirt that extends upwardly from an outer periphery of a center panel of the lid, such that the heat-sealable material is on the radially outwardly facing side of the skirt. The skirt is heat-sealed to a generally cylindrical inner surface of the container body adjacent the open end of the container, the center panel of the lid thus being recessed below a top edge of the container body. The lid includes a line of weakness such that the center panel can be torn free of the skirt, at least part of which remains attached to the container body. A pull tab is attached to the top surface of the center panel to aid the user in tearing out the center panel. The pull tab typically is heat-sealed to the center panel. For example, a container and lid generally as described above are disclosed in U.S. Pat. No. 4,744,484 to Grabher.
A difficulty associated with such container lids arises because of inevitable variations in the strength of the bond between the tab and the center panel. Such variations are due to mechanical process and material variations that are difficult to control or eliminate. Additionally, it has been found that the tab bond strength tends to diminish with aging of the lid. Accordingly, it can be expected that some proportion of the lids produced according to the conventional process will have a tab bond strength that is less than the force required to detach the center panel from the skirt. When the user pulls on the tab of such a lid, the tab will tend to come off the center panel and the user will then have to resort to other means to open the container, such as puncturing the lid with a sharp implement and then tearing out the lid in pieces. This is inconvenient for the user.
The present invention addresses the above needs and achieves other advantages, by providing a lid formed as a laminate having a built-in opening feature. In accordance with one embodiment of the invention, a lid for a container comprises an upper layer of flexible sheet material laminated by an adhesive to a lower layer of flexible sheet material to form a laminate. The laminate includes an adhesive-free region in which the adhesive is absent between the upper and lower layers. The upper layer includes a pair of spaced cut lines defining an integral pull strap in the upper layer. Each of the cut lines extends from a first end to a second end. The first ends of the cut lines define a first end of the strap at which the strap is integrally joined to the rest of the upper layer; similarly, the second ends of the cut lines define an opposite second end of the strap that is integrally joined to the rest of the upper layer. At least a middle portion of the strap's length is within the adhesive-free region. In some embodiments, the laminate is shaped to have depressions adjacent the opposite edges of the strap to facilitate grasping the strap.
In some embodiments, the first ends and the second ends of the cut lines are outside the adhesive-free region in an adhesively laminated area of the laminate. When the strap is pulled to detach the lid, the pulling force is exerted on the adhesively laminated area. Thus, the strap has the strength of the adhesive bond, and the tear-resistance of the strap is not a limiting factor. As a result, the upper layer of the laminate can be thinner than would otherwise be needed if the tear-resistance of the upper layer were the limiting factor.
Alternatively, the first ends and/or the second ends of the cut lines can be within the adhesive-free region.
The laminate in some embodiments can include at least one line of weakness radially inward of the outer edge of the laminate, the line of weakness delineating a removable portion of the laminate that is severable along the line of weakness from an outer peripheral portion of the laminate. In some embodiments, the laminate is shaped to form a generally cylindrical skirt that includes the outer peripheral portion. The skirt can be adhered to an inner surface of a container to close the container. Pulling on the pull strap causes the laminate to sever along the at least one line of weakness for detaching the removable portion so as to open the container.
In one embodiment, a pair of radially spaced concentric lines of weakness are formed in the laminate, an outer one of the lines of weakness being formed in the upper layer and an inner one of the lines of weakness being formed in the lower layer. Each line of weakness comprises a cut extending partially or entirely through the thickness of the respective layer, and allows the layer to sever along the line with little or no force. An annular region is thus defined between the lines of weakness. The upper and lower layers outside the annular region are laminated together with an adhesive providing a bond with a sufficient peel strength to keep the layers from separating when the lid is pulled to detach it from the container, and hence the lower layer severs along the inner line of weakness and the layers then separate from each other in the annular region until the outer line of weakness is reached. The upper layer then severs along the outer line of weakness so that the lid comes free of the container.
The separability of the layers in the annular region in some embodiments can be provided by disposing a readily peelable adhesive in the annular region between the layers. In other embodiments, the separability is achieved by providing no adhesive in the annular region. Thus, the layers are adhered to each other outside the annular region but are not adhered in the annular region.
The upper layer of the lid can be a monolayer or a multilayer structure. For instance, the upper layer can be a single layer of polymer film such as polyester (e.g., PET). Alternatively, the upper layer can be a laminate of a polymer film such as polyester and a barrier layer such as aluminum foil.
In embodiments employing adhesive in the annular region, the adhesive preferably is a pressure-sensitive adhesive (PSA). Outside the annular region a different adhesive, such as a conventional laminating adhesive, is employed. The PSA “bridges the gap” between the lines of weakness. Preferably, the PSA also extends somewhat outward of the outer line of weakness and somewhat inward of the inner line of weakness so that slight errors in the locations of the lines of weakness because of manufacturing tolerances will not result in either line of weakness being in a location where the stronger laminating adhesive is present.
In operation, the strap is pulled upwardly, which exerts a pulling force having an upward component and a component generally radially inwardly away from the skirt on each end of the strap. Initially, a portion of the skirt adjacent one or both of the ends of the strap begins to detach from the container body until the at least one line of weakness is reached, and then the laminate begins to sever along the at least one line of weakness, eventually resulting in the removable portion of the lid coming free of the portion that remains affixed to the container body. In those embodiments having the radially spaced inner and outer lines of weakness formed respectively in the lower and upper layers, the lid first severs along the inner line of weakness. Further pulling of the strap away from the skirt causes the upper layer to begin separating from the lower layer in the annular region between the lines of weakness. In those embodiments in which no adhesive is present in the annular region, the upper layer will immediately separate from the lower layer up to the outer (upper) line of weakness. In other embodiments in which PSA is present in the annular region, the PSA allows the layers to readily peel apart. When the outer (upper) line of weakness is reached, the upper layer begins to sever along the outer line of weakness, and the removable portion finally is completely detached from the outer peripheral portion of the laminate, which remains attached to the container body.
The invention also provides a container having a lid as described above.
In an alternative embodiment of the invention, the laminate for forming the lid includes an inner line of weakness in the lower layer as described above, but the outer line of weakness is omitted. The upper and lower layers are adhered over their entire surfaces with an adhesive such as a low bond-strength adhesive or PSA. The lid is formed such that the skirt terminates at its top end on the inner surface of the container body. In operation, the strap is pulled upwardly causing a portion of the skirt adjacent each end of the strap to begin to detach from the container body until the inner line of weakness is reached, and then the lower layer begins to sever along the inner line of weakness. Further pulling of the strap causes the upper layer to peel away from the lower layer until the top end of the skirt is reached, at which point the removable portion of the lid comes free of the container.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
A container 10 in accordance with one embodiment of the invention is illustrated in
The lid 16 is formed from a laminate of flexible sheet materials. As further described below, the laminate is die-cut to produce a disk-shaped laminate or lid blank that is subsequently shaped by suitable tooling into a form as best seen in
With reference to
In one embodiment, a lower surface of the upper layer 28 that faces the lower layer is pattern-printed with an adhesive 34. The adhesive 34 is a laminating adhesive formulated to bond the layers together with a relatively high bond strength such that the layers bonded together by the adhesive are not readily peelable from each other. The laminating adhesive can be, for example, a two-component polyurethane adhesive system, such as Tycel 7900/7283 available from Henkel. The laminating adhesive 34 is applied to the upper layer in such a manner that a sufficiently large proportion of the surface is covered by the adhesive to permit the upper layer to be adhesively attached to the lower layer 26 at a downstream laminating station. The laminating adhesive 34 is not applied to an annular region 36 of the upper layer. In this embodiment, the annular region 36 is free of adhesive. The annular region 36 is dimensioned to occupy the area of the skirt 20 of a lid fashioned from the laminate 30. The adhesive 34 is applied to those areas outside the annular region 36, except that a region 38 that lies within the interior of the annular region 36 is kept free of adhesive for reasons soon to become apparent. Thus, the laminating adhesive must be applied by an apparatus capable of accurately applying the adhesive in a predetermined pattern, in registration with the pressure-sensitive adhesive but not covering it. A suitable adhesive application device can be a gravure roll.
In another embodiment, a lower surface of the upper layer 28 that faces the lower layer is pattern-printed with a first adhesive 32 as well as with a second adhesive 34. The first adhesive 32 is applied to the annular region 36 of the upper layer. The second adhesive 34 is applied to those areas outside the annular region 36, except that a region 38 that lies within the interior of the annular region 36 is kept free of adhesive as in the prior embodiment above. The first adhesive 32 is formulated to allow the layers bonded together by the adhesive to be readily peeled apart with relatively low peel force. The first adhesive advantageously can comprise a pressure-sensitive adhesive (PSA). Pressure-sensitive adhesives are often based on non-crosslinked rubber adhesives in a latex emulsion or solvent-borne form, or can comprise acrylic and methacrylate adhesives, styrene copolymers (SIS/SBS), and silicones. Acrylic adhesives are known for excellent environmental resistance and fast-setting time when compared with other resin systems. Acrylic pressure-sensitive adhesives often use an acrylate system. Natural rubber, synthetic rubber or elastomer sealants and adhesives can be based on a variety of systems such as silicone, polyurethane, chloroprene, butyl, polybutadiene, isoprene, or neoprene. When the laminate of the invention is to be used for food packaging, the pressure-sensitive adhesive generally must be a food-grade composition. Various pressure-sensitive adhesives are approved by the U.S. Food and Drug Administration for use in food packaging, as regulated by 21 CFR Part 175. A preferred food-grade pressure-sensitive adhesive for use in the present invention is Jonbond 743 available from Bostik Findley. Additives (e.g., particulates or the like) can be added to the pressure-sensitive adhesive to reduce the tenacity of the bond, if desired. The second adhesive can comprise a laminating adhesive as previously described.
As evident from
The laminate is then advanced to a cutting station (not shown) at which a pair of lines of weakness are formed in the laminate. More specifically, an inner line of weakness 42 is formed in the lower layer 26. The inner line of weakness 42 comprises a cut extending partially, or preferably entirely, through the thickness of the lower layer, and can be formed by mechanical technique such as die-cutting (so-called “kiss” cutting). Alternatively, the line of weakness can be formed by use of a laser. The use of lasers for scoring through polymer films and laminates is generally known, for example as described in U.S. Pat. No. 5,158,499, incorporated herein by reference. The depth of the score line formed by the laser can be regulated by regulating the power output or beam intensity of the laser beam, the width or spot size of the laser beam, and the amount of time a given spot on the film surface is irradiated by the beam. These factors generally are selected based on the characteristics of the material being scored. Some materials are more readily scored by lasers than other materials, as known in the art. At any rate, the line of weakness 42 weakens the lower layer so that severing of the lower layer will occur preferentially along the line of weakness. The inner line of weakness extends in a closed loop about a center point of the annular region 36. Preferably, the inner line of weakness 42 is circular and is concentrically positioned with respect to the annular region 36, and is slightly greater in radius than the radially innermost extent of the annular region 36.
An outer line of weakness 44 is formed in the upper layer 28. The outer line of weakness 44 comprises a cut extending partially, or preferably entirely, through the thickness of the upper layer, and can be formed by mechanical technique such as die-cutting or by use of a laser. The line of weakness 44 weakens the upper layer so that severing of the upper layer will occur preferentially along the line of weakness. The outer line of weakness 44 extends in a closed loop about the center point of the annular region 36, and advantageously is circular and is concentrically positioned with respect to the inner line of weakness 42 and larger in radius than the inner line of weakness. The outer line of weakness 44 preferably is slightly smaller in radius than the radially outermost extent of the annular region 36.
Additionally, at the cutting station, preferably the upper layer 28 is die-cut or laser-cut along a pair of generally parallel cut lines 46 that extend through the full thickness of the upper layer, so as to form an integral pull strap 48 in the upper layer. At least the majority of the lengths of the cut lines 46 are located in the adhesive-free region 38 of the laminate so that the strap 48 can be lifted away from the lower layer 26 and grasped and pulled to open the container. Proper registration of the lines of weakness 42, 44 and cut lines 46 with respect to the adhesive-free or PSA region 36 and the adhesive-free region 38 is achieved through the detection of the eye marks 40 on the laminate with an optical detector (not shown) and suitable control of the cutting equipment based on signals from the optical detector, as would be understood by one of ordinary skill in the art.
After the cutting station, the laminate is die-cut to cut out the individual lids from the laminate. For each lid, the laminate is cut along a circular cut line that is greater in radius than the outer line of weakness 44 and is concentric with respect thereto.
With reference to
Alternatively, the lid shaping can be accomplished concurrently with placing the lid onto the container.
The skirt 20 is heat-sealed to the inner surface of the container body side wall, which typically includes an impervious liner (not shown) whose inner surface has a heat-sealable material. If desired, the shaping of the lid to form the skirt and the heat-sealing of the skirt to the side wall can be accomplished substantially simultaneously. Preferably, the full axial extent of the skirt is heat-sealed to the container body side wall, including a portion 50 of the skirt extending below the inner line of weakness 42.
In operation, as illustrated in
Accordingly, the opening mechanism of the lid relies on the separation of the layers 26, 28 in the adhesive-free or PSA region 36. The force needed to separate the layers in the region 36 is low enough so that the lid will open reliably, eliminating or at least greatly reducing the incidence of opening failures caused by inadvertent tab detachments or the like. The provision of an integral strap 48 further aids in preventing such failures, and saves on material and process costs ordinarily required for making and attaching a separate tab.
As noted, with reference to
Polymer films tend to tear easily, and hence there is a risk that when the strap 48 is pulled to detach the lid from the container, one end of the strap may tear away from the lid, or even both ends of the strap may tear away from the lid. It would then be more difficult to remove the lid because there would not be any easily graspable part of the lid. The user may have to resort to using a tool to puncture and tear through the lid in order to remove it. This is undesirable.
To address this potential problem, a lid in accordance with a further embodiment of the present invention is generally similar to the lid 16 of
When the upper layer 28 comprises a polymer film and the lower layer 26 comprises a metal foil with a heat seal slip coat on its lower surface, the inner line of weakness 42 advantageously can be omitted. The outer line of weakness 44 can extend through nearly the entire thickness of the laminate. When the strap is pulled to open the container, the lid severs along the line of weakness 44, leaving a portion of the laminate above the line 44 still attached to the container, the remainder of the lid coming free of the container.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, while the lid 16 shown and described above has a circular peripheral shape, the present invention also encompasses lids of other shapes such as oval, rectangular, etc. In this regard, terms used herein such as “annular”, “radial”, “concentric”, and the like, are intended to apply to all such shapes rather than being restricted to circular lids. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
The present application is related to U.S. patent application Ser. No. 11/289,006 filed on Nov. 29, 2005, currently pending, and U.S. patent application Ser. No. 11/560,041 filed on Nov. 15, 2006, currently pending, the entire disclosures of which are incorporated herein by reference.
