Spillage Preventing Cup Lid

Field of the Invention

This invention relates to devices for alleviating spills from lidded cups.

Background of the Invention The paper cup of coffee, tea, hot chocolate, or fancy drinks such as lattes and cafe au lait, has become practically ubiquitous. Equally ubiquitous is the lid on top of the cup with a small hole for allowing the consumer to drink the beverage within. However, the lid does not make the cup spill proof; rather it merely alleviates spilling and makes it possible to for the consumer to enjoy the beverage while walking or driving. It does not prevent the beverage from spilling through the little drinking hole if the consumer or the consumer's vehicle comes to a sudden stop, nor does it prevent the beverage from spilling all over the consumer's lap, newspaper, or computer if the cup is tipped over. Thus, it is desirable to have a cup lid that enables the consumer to drink from the cup while preventing spills.

Summary of the Invention

In one aspect, the invention is a lid for covering a cup. The lid includes a first opening through which liquid is dispensed from the cup, and a mesh is disposed in the first opening that prevents significant liquid flow through the first opening when the exterior surface of the mesh is substantially dry. The mesh material may have an opening size between 5 and 100 microns, for example, between 20 and 30 microns. The material may be concave with respect to the exterior of the cup to provide a path for liquid on an exterior of the mesh to flow off the mesh under the influence of gravity.

The mesh may be fabricated from a hydrophobic material. The mesh may be woven, for example, from a monofilament material. The mesh may be fabricated from polytetrafluoroethylene (PTFE), polystyrene, a polyamide, a polyester, a polyetheretherketone, or a polypropylene. The mesh may be coated with a hydrophobic material, for example, a PTFE-based waterproofing material or a silicone-based waterproofing material. The mesh may prevent significant liquid flow

through the first opening when the exterior surface of the mesh is substantially dry and when the liquid has a temperature between 50°C and 9O ⁰ C. The lid may include a plurality of grooves and the mesh may be attached to the lid via a complementary fit of a portion of the mesh with the grooves. The mesh may be etched, cut, or punched into the lid material. The mesh may be welded to the lid. The the lid and the mesh may both be polymeric materials, and an interface between the mesh and the lid may include cross-links between the lid material and the mesh material. The mesh may be glued to the lid, for example, with a plastic cement, epoxy, or cyanoacrylate resin.

In another aspect, the invention is a lid for covering a cup. The lid includes a first opening through which liquid is dispensed from the cup, and a double layer of mesh is disposed in the first opening. There is a gap between the two layers.

In another aspect, the invention is a lid for covering a cup. The lid includes a first opening through which liquid is dispensed from the cup, and a double layer of mesh is disposed in the first opening. An inner layer of the mesh is hydrophilic and an outer layer of the mesh is hydrophobic. There may be a gap between the hydrophilic layer and the hydrophobic layer.

Brief Description of the Drawing

The invention is described with reference to the several figures of the drawing, in which, Figure 1 is a schematic of the interaction of a liquid drop with a surface that is

(A) not wet and (B) wet by the liquid.

Figure 2 is a schematic of the behavior of a liquid behind a mesh that is (A) not wet and (B) wet by the liquid.

Figure 3 is a schematic of exemplary meshes for use with various embodiments of the invention.

Figure 4 is a schematic of (A) a prior art lid and (B) a lid configured according to an exemplary embodiment of the invention

Figure 5 is a schematic of (A) an upturned cup of fluid incorporating a prior art lid and (B) an upturned liquid-containing cup incorporating a lid according to an exemplary embodiment of the invention.

Figure 6 is a schematic of a double mesh layer according to an exemplary embodiment of the invention.

Detailed Description of Certain Preferred Embodiments

In one embodiment, a lid is provided for covering liquids in a cup such that it is easy to drink from the cup but that spillage from the cup will be prevented or reduced if the cup is tilted or liquid is splashed onto the lid from within. The lid is constructed from a solid material and a fine mesh material. The mesh material prevents or reduces the flow of liquid from the lid when the cup is tilted or when the liquid splashes against the lid. However, when the user wants to dispense the liquid from the cup, for example, when drinking from the cup, the mesh material allows the liquid to flow freely. This "controlled" dispensing of the liquid is achieved by exploiting the surface tension of the liquid. Without being bound by any particular theory, it is thought that the surface tension pressure created by utilizing a fine mesh, e.g., a grid, can prevent the liquid from flowing through the mesh when the cup is tilted or when liquid is splashed against it. By making the mesh size small enough, the surface tension pressure will be high enough to retain a column of liquid in high acceleration conditions. However, when a sufficiently high differential pressure is applied over the mesh, e.g., when a consumer applies a vacuum on one side of the lid, the surface tension will not be sufficient to prevent flow of the liquid through the mesh. Once the liquid passes through the mesh, there is no more surface interface between air and the liquid to create surface tension, allowing the liquid to flow freely through the mesh. This will allow the user to easily dispense the liquid in the desired quantity. After the user finishes dispensing the liquid, air on one side of the mesh will reestablish surface tension with the liquid and prevent accidental dispensing. The mesh may also be sized to reduce the size of a liquid droplet that can flow though it without touching the mesh material. The size of the area covered by the mesh is large enough that the speed of the liquid flowing through the mesh during dispensing may be kept low while maintaining a high volume rate of flow. This will result in low flow losses over the mesh so that the liquid can easily be dispensed once the surface tension is overcome.

Figure 1 shows the effect of wetting 16 and non- wetting 12 materials on the angle that a liquid 13 droplet forms with the surface of the material. Material 12 has a very low surface tension coefficient with liquid 13 (Figure IA). This repels the liquid off the surface so that the liquid makes an angle 11 greater than 90° with the surface. Similarly, a wetting surface 16 is fabricated from a material that has a high surface tension coefficient with the liquid 13 (Figure IB). This results in the liquid wetting the surface, e.g., the angle 15 between the liquid and the surface is less than 90°. As used herein, the term "hydrophilic" is used to describe materials on which a drop of water forms a contact angle less than 90°, while the term "hydrophobic" is used to describe materials on which a drop of water forms a contact angle of greater than 90°.

Figure 2 shows the mechanism of surface tension applicable to certain embodiments of the invention. A cross-sectional view of meshes fabricated from non- wetting material 21 and wetting material 30 are shown. Liquid 22 is confined by three materials: the mesh, the container wall, and outside air. The fluid above the mesh exerts a pressure that, in Figure 2, is sufficient to force the liquid through the mesh. The tension at surfaces 24 and 28 of the liquid opposes this pressure. Without being bound by any particular theory, it is thought that the absence of liquid molecules on both sides of the surface results in a stronger bond between the molecules at surfaces 24 and 28, creating surface tension. The mesh will restrain the liquid as long as this bonding force is larger than the product of the pressure from liquid 22 and the area over which the pressure is imparted, e.g., surfaces 24 and 28. In the case of the non- wetting material 21, the liquid tends to bead 23 on the material. This beading prevents the surface 24 and bead 23 from coming in contact with each other. The effective area over which the pressure is imparted is a function of the square of diameter 26. When wetting material 30 is used, spreading of the liquid on the material 27 causes the surface 28 of the liquid behind the mesh to come into contact with liquid outside the mesh, e.g., at 29. This combination results in a greater effective surface area of water, e.g. defined by diameter 31, for the pressure from the liquid behind the mesh to act on. The wetting material thus causes the force at the surface of the liquid to be higher than for non- wetting materials. If the force from the liquid behind the mesh is larger than the bonding force of the surface molecules (e.g., the surface tension), the surface will break, allowing the liquid to flow through the

mesh. Figure 2 shows that, for the same hole size, the non-wetting material will be able to contain a larger pressure than the wetting material.

Figure 3 shows a number of mesh constructions that are available on the market. Figure 3A shows a flat mesh 35, in contrast with woven mesh 36 (Figure 3B). The size of the mesh, e.g., the shortest "hole" dimension, for the different constructions is shown. For a square mesh the size is 31 ; for a diamond mesh (Figure 3C) the size is 32. The width of the "bars" and thickness 34 of the material may also be optimized. For many commercially available meshes, this thickness and width are about the same as the size of the mesh opening. The mesh opening may be between 5 and 100 microns, for example, between 5 and 20 microns, between 20 and 30 microns, between 30 and 40 microns, between 40 and 50 microns, between 50 and 60 microns, between 60 and 70 microns, between 80 and 90 microns, or between 90 and 100 microns. Both flat and woven meshes may be employed. The mesh may be formed from a variety materials, e.g., polytetrafluoroethylene (PTFE), polyetheretherketones (PEEK), polyamides (e.g., nylon), polyesters, polystyrene, or polypropylene. Other suitable materials will be familiar to those of skill in the art. If the material is insufficiently hydrophilic, it may be coated with a hydrophobic or waterproofing material such as a PTFE based or silicone based coating. One skilled in the art will recognize that the optimal mesh opening will depend in part on the hydrophobicity of the material.

Lid 41 is a prior art lid used for covering a cup filled with a beverage (Figure 4A). Opening 42 allows for the user to dispense the liquid by drinking it. Air hole 43 allows air to flow into the cup to prevent formation of a vacuum inside the cup due to the reduction in fluid volume. The opening 42 allows liquid to leave the cup when the consumer drinks it but also when the cup is tilted or when liquid splashes against the lid.

Figure 4B illustrates an exemplary embodiment of the invention. Lid 44 also has an opening for dispensing the liquid, but the opening is covered with mesh 45. This mesh also allows for the free dispensing of the liquid when the user sucks it through the mesh, but prevents or reduces the discharge of the liquid when the cup is tilted or when the liquid splashes against the lid. In some embodiments, the mesh is not flat but is integrated into the bowed geometry of the lid. This allows any liquid

that beads on the outside of the mesh to roll off the mesh and onto the lid and increases the flow area for the liquid during dispensing.

One skilled in the art will recognize that the cup may hold a wide variety of beverages, including but not limited to coffee, tea, hot chocolate, and specialty coffee drinks. In some embodiments, the beverage may have a temperature between about 50° and about 90°C. Cold beverages, e.g., fountain drinks, may also benefit from various embodiments of the invention. Of course, hot beverages are often not served "neat" but with added milk or cream (indeed, many hot chocolates are served as a mixture with milk, not water). Dairy liquids may have higher viscosities and lower surface tensions than aqueous beverages. The mesh size and materials may be further optimized to provide specific spill protection for water-based and dairy-based beverages, or to optimize the spill protection for all types of beverages.

Figure 5B shows one embodiment of the invention in use. Cup 50 and lid 51 (Figure 5A)/56 (Figure 5B) contain liquid 52 and some air 53. Figure 5A shows the cup tilted over on a surface 56 so that liquid 52 presses against opening 54. Without a mesh over opening 54, liquid 52 is free to flow out and spills 55 onto surface 56. When the same cup 50, but with a mesh 57 integrated into lid 56, is tilted over, liquid 52 does not flow out.

For the mesh to stop the flow from a tilted cup or splashing, it needs to be dry on the outside. If the mesh is wet, there will be liquid on both sides of the mesh and thus no surface tension to oppose the column pressure. This will allow the liquid to flow out freely and will not prevent the accidental discharge of the liquid. Use of a hydrophobic mesh material can prevent wetting of the mesh material. Figure 1 illustrates the difference between a low surface tension material 12 and a high surface tension material 16. The liquid 13 tends to bead on the low surface tension materials, i.e. the angle 11 is greater than 90°, while the high surface tension materials gets wetted (angle 15 is less than 90°).

The mesh may be fabricated using any method known to those skilled in the arts of plastics forming and fabrication. For example, the mesh may be glued to the lid, for example, with a plastic cement, epoxy, or cyanoacrylate resin. The glue should be stable at the temperatures expected for the beverages being dispensed. It is not necessary that the uncured glue be suitable for consumption so long as it sets

completely. In other embodiments, heat is used to integrate the mesh with the lid. For example, the mesh may be welded to the lid, or heat may be used to facilitate chemical cross-links between the polymers in the lid and the mesh. Alternatively or in addition, the lid may be formed with grooves, and the mesh may have projections that fit into the grooves. The mesh may also be integrated with the lid; for example, it may be etched, cut, or punched into the lid.

Without being bound by any particular theory, the discussion below explains a theoretical basis for adjusting and optimizing the different characteristics of the mesh. All liquids have a specific surface tension between it and other liquids. The following relation gives the pressure for a liquid to overcome the surface tension between it and another fluid:

AP - — m

where λ is the surface tension coefficient between two fluids (air and water) and d is the diameter or opening size of the mesh. In the case of a woven mesh, d is the length of one of the sides of the mesh (31, 32 Figure 3). Mesh opening sizes are usually given in microns and this is the value used in the calculation for d.

In one embodiment, the surface tension pressure is higher than the pressure exerted on the mesh by a fluid column when the cup is tilted or the pressure on the mesh when the liquid strikes it when the liquid splashes in the cup. The liquid column pressure is given by:

" Fluid Column where p is the density of the fluid, g is the acceleration of the liquid (gravity in normal conditions), and h is the height of the fluid column. The pressure exerted on the mesh due to a splashing liquid is related to the speed of the liquid Fas:

The mesh prevents the liquid from flowing through it when the surface tension pressure is larger than the combination of the liquid column pressure and the splashing pressure, e.g.:

—> pgh + -pV ² (4) a 2

For this equation to apply, the liquid must be in contact with the mesh. If, in the case of splashing, the liquid drop size is smaller than the mesh size d, the liquid will flow through the mesh unobstructed. Thus, the mesh size should be optimized for the expected drop size.

As soon as the surface tension is overcome, liquid flows through the mesh, placing liquid on the other side of the mesh and removing the liquid/air interface, thus negating the surface tension.

When the mesh has the same fluid on both sides, the pressure required to allow flow through the mesh, e.g., the pressure imparted by the user to drink from the cup, is sufficient to overcome the friction through the mesh and is given by the following equation:

δ^ _c , _/ , = KV ¹ (5) where K is the coefficient of friction of the mesh, and V is the velocity of the fluid through the mesh. The pressure drop over the mesh is related to the speed of the liquid V through the mesh. The rate of volume flow of liquid though the mesh is calculated by:

Q = VA _Eff (6) where A _Bff is the effective flow area through the mesh. A _Eff is the difference between the total area covered by the mesh and the area taken up by the mesh material, e.g., the open area of the mesh. From the above equation, it can be seen that, to increase the amount of liquid that is dispensed from the cup in a given time, either the speed through the mesh or the effective area of the mesh may be increased. If the velocity is increased, it will result in a higher pressure drop over the mesh. A more efficient option is to increase the effective area of the mesh.

In summary, the flow through the mesh is governed by the effective free area of the mesh and the pressure differential over the mesh. To reduce the pressure required from the user while allowing the user to drink at a comfortable rate, the effective area may be increased and the velocity through the mesh reduced. In

addition, the mesh opening, d, is preferably small enough for the surface tension of the fluid to oppose the pressure from the column of fluid in the cup and to stop splashing liquid from penetrating the mesh. These are conflicting needs. A low pressure-drop over the mesh is correlated with large values of d. However, the human mouth has the ability to build up a large suction pressure. Thus, the mesh opening can be very small. For a 5 micron mesh, the pressure required to draw water through the mesh is about 26,000 Pa, equivalent to the pressure at the bottom of a 2.7 m column of water. For a 25 micron mesh, the pressure to draw water through the mesh is about 5,280 Pa, equivalent to about 0.54 m of water, while for a 100 micron mesh, the pressure required is about 1,264 Pa, equivalent to about 0.13 m of water. The last value is of course shorter than a restaurant drinking straw, but even the higher levels of suction may be easily achieved by a person. Hot liquids have lower viscosities and may be extracted from the cup with lower levels of suction for the same mesh size. In another embodiment, a double mesh is disposed across the opening of the Hd (Figure 6). In one embodiment, two meshes with a small (e.g., about 1 mm or less) gap between them can increase the flow resistance between the meshes and to create a fluid layer in the mesh. This fluid layer will tend to pull the fluid from the upper surface of the top mesh into the fluid layer, thereby reducing the wetting of the top layer. In another embodiment, two meshes, an outer hydrophobic material and an inner hydrophilic material, may be used to accomplish the same effect. A small gap between the two meshes may further increase the fluid withdrawing effects of the inner mesh. The openings may be aligned, partially aligned, or offset.

Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

What is claimed is: