The new approach provides opportunities for expanding the range of materials that can be used to construct lids for single use cups and offers benefits for single use container manufacturers and the material recovery industry.
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The invention relates to the method used to fit a disposable lid into a cup, thus expanding the choice of materials that can be used for the purpose.
Disposable cups and lids are widely used in the beverage industry, thus presenting a constant flow of recyclable matter to material recovery facilities. The typical disposable lid is made of plastic and usually coupled with a cup made of polyethylene coated paper or of polystyrene. Plastic, paper and polystyrene are directed in the material recovery facilities to separate processing streams, but prior to that they would have to be sorted apart from each other. Sorting is often difficult, costly and ineffective, especially when the lid has not been separated from the cup at the moment of disposing of it by the consumer.
Sorting challenges result in large percentage of recoverable material being rejected and directed to landfills, or ending up in the wrong stream thus polluting the batch. The economic dimensions of reduced recoverability or lowered batch quality of post-consumer cups and lids are significant. One way to mitigate the material sorting challenges is pairing up cups and lids of the same basic material—paper cup with paper lid, polystyrene cup with polystyrene lid, etc.
The ability to make disposable lids from material other than plastic also creates an advantage for cup manufacturers, who can utilize the same manufacturing process and material inventory for both cups and lids (paper, polystyrene, etc).
Attempts in the industry to manufacture lids of material other than plastic have not been successful because they have been largely based on replicating the same approach used for plastic lids, but with materials like paper or polystyrene. The physical properties of the latter materials cannot support a design relying on a peripheral groove that clamps around the rim of a cup, as they are lacking in the required elasticity. Therefore, a different shape and method of mounting is required for paper and polystyrene in order to construct lids with matching or superior liquid-tight sealing effect, sturdiness and reliability.
The inventive idea is that instead of mounting the lid on top of the cup by clamping around the outside of the rim, this new lid is shaped and sized to slide on the inside of the cup and grip onto the inner surface of the cup by way of peripheral tension force.
A basic lid of that type would have an inverted frustum shape, similar to the cup, but with much smaller wall height and varying shape of lid top (FIG. 1/11, showing a lid with semi-spherical top). The shape of the top is independent of the fundamental principle this lid works (wall going inside the cup) and can only be limited by manufacturing constraints or design preference.
The sealing tension produced by inserting the lid into the cup comes from the delta between the circumference of the cup inner wall and the circumference of the lid's outer wall. This delta could be equal, for instance, to the thickness of the material used for cup and lid, but could also be controlled through appropriate sizing of the lid, if material thickness is either too little to achieve the desired sealing effect or too much to insert the lid comfortably into the cup.
This method of constructing and mounting disposable lids onto cups harnesses the symmetry of force applied uniformly against all points of frustum shaped objects inserted into each other, combined with minimal material flexibility which is sufficient in paper and polystyrene to produce the desired sealing tightness in the area of contact between cup and lid.
This invention presents a different approach to the construction of lids for disposable beverage cups, as well as method of mounting of the lid on a cup. The new lid slides into the cup, relying on the pressure between the outer wall of the lid and the inner wall of the cup for liquid-tight seal.
Conventional cup lids employ an elastic peripheral groove to clamp around the cup rim. The need for elasticity in this design limits the choice of lid material to various forms of plastic.
In order to use other materials for lids, such as paper (non-elastic and soft) or polystyrene (non-elastic and brittle), the lid will have to fit the cup by going on the inside of the cup, instead of the outside.
FIG. 1/11—Lid shape and dimensions relative to cup's shape and dimensions. Lid wall slope, defined by angle matches that of the cup's . The lid rim size is such that works with the cup's rim to prevent lid from sliding further into the cup than necessary. The lid top is semispherical in this illustration, but could have other shapes.
FIG. 2/11—Lid as fully inserted into the cup. Liquid-tight sealing is achieved at the areas where the lid's outer wall presses against the cup's inner wall
FIG. 3/11—Lid top as attached to the inner wall of the lid.
FIG. 4/11—Lid top as attached to the outer wall of the lid.
FIG. 5/11—Lid top is rolled into the lid rim through bending or thermoforming
FIG. 6/11—Lid top is attached by its own rim to the lid rim
FIG. 7/11—Lid top is continuous with lid rim and walls
FIG. 8/11—Stack of lids, illustrating the benefit of a groove between lid walls and top
FIG. 9/11—Lid with semi-spherical (dome) shape
FIG. 10/11—Lid with flat top
FIG. 11/11—Lid with frustum shaped top
The lid slides inside the cup until a tight fit is achieved between the inner wall of the cup and the outer wall of the lid
The lid has similar conic angle as the cup it seals (FIG. 1). The angle of the lid wall can vary slightly from the angle of the cup in order to fit different size cups with same rim size, but varying height—hence slightly varying conic angle.
The height of lid walls may vary, depending on desired strength of fit or manufacturing constraints
The lid has the basically the same outer circumference (a) as the cup it seals (FIG. 1/8). The outer circumference of the lid may vary slightly from that of the cup in order to compensate for thickness of material (too thin or too thick) that may compromise the sealing effect
The lid has a rim (b) similar to that of the cup to prevent it from sliding into the cup further than intended (FIG. 1/8, FIG. 2/8). The rim can be either rolled (e.g. paper) or extruded (e.g. polystyrene)
The lid is mounted on the cup by positioning the lid horizontally level into the cup opening and pressing onto the lid rim until a tight fit is achieved between the inner wall of the cup and the outer wall of the lid (FIG. 2/8)
The lid top can be manufactured flat (FIG. 10/11) or bulging upwards in a choice of shapes to provide additional benefits such as overflow control and drinking comfort—e.g. semi-spherical (FIG. 9/11) or in the shape of a frustum (FIG. 11/11).
The lid top can be attached to the lid walls in various manners—e.g. attached to the inside wall of the lid (FIG. 3/11), the outer wall of the lid (FIG. 4/11), rolled into the lid's rim (FIG. 5/11), flat pressed onto the lid's rim (FIG. 6/11) or made of one continuous piece together with lid's walls and rim (FIG. 7/11). The variety of methods is intended to address design and manufacturing preferences.
For stacking lids together, the method of attachment of lid top to lid wall makes provision of an up-facing groove that accepts the bottom of the upper lid in the stack. (FIG. 8/11)
For stack-ability of lids, the lid top size is generally smaller than lid walls so that the top of the lower lid can be manipulated in and out of the walls of upper lid in a stack. (FIG. 8/11)