Patent Publication Number: US-2015059079-A1

Title: Liquid Covering Disks and Systems

Description:
BACKGROUND 
     The present disclosure relates generally to liquid covering disks and systems. In particular, this disclosure describes floating disks including a shape and a structure that provide stability to the disks and adherence to the surface when the disks are deployed on a surface of a body of liquid. 
     Ponds, reservoirs, and open tanks are often used to store and treat liquids. Liquids having large open surfaces are common in the fields of chemical production, anodizing, galvanizing, plating, dying, sewage treatment, oil waste storage, and other such fields. In many of these fields, unimpeded access to the liquid is desired. However, having large open liquid surfaces may lead to evaporation of the stored liquid, unintended plant and organism growth on the liquid surface, emission of noxious fumes, and exposure to wildlife. 
     Reducing fluid loss, toxic vapors emission, and heat loss are major environmental and financial concerns. Reducing evaporation and heat transfer is influenced by a variety of factors, such as wind conditions above the liquid surface, liquid temperature, environment temperature, liquid density, and the concentration of the substance evaporating in the air. Reducing evaporation will also reduce noxious fumes. 
     Some liquid covers presently understood in the art are polygonal shaped covers designed to be placed on the surface in concert, covering the liquid body. Examples of references describing such covers include U.S. Pat. Nos. 4,270,232 and 8,342,352 and European Patent No. 1,697,234. The complete disclosures of these patents and patent applications are herein incorporated by reference for all purposes. 
     In high velocity wind conditions, however, known liquid covers tend to be blown off the surface of the ponds, leaving significant surface on the liquid body exposed. Heavier designs that are less affected by the wind suffer from high shipping costs. 
     As a result, known liquid covering disks are not entirely satisfactory for the range of applications in which they are employed. Specifically, there exists a need for liquid coverings that protect against the harms listed above, while being wind resistant, easily adaptable to various liquid bodies, and of limited cost to manufacture. Examples of new and useful liquid covering disks relevant to the needs existing in the field are discussed below. 
     SUMMARY 
     The present disclosure is directed to liquid covering disks and systems. In some examples, a disk configured to float on the surface of a body of liquid includes a body, a plurality of ribs projecting from the body, and a sidewall protruding at the periphery of the body. The body has a top surface, a bottom surface, and an aperture at a periphery of the body. The aperture is configured to allow a liquid to pass through. A portion of the body, a portion of the plurality of ribs, and a portion of the sidewall define a cavity allowing a volume of a gas to be trapped in the cavity when the disk is deployed on the surface of the body of liquid and providing buoyancy to the disk. 
     In some embodiments, the body may include a polygonal shape. In other embodiments, the plurality of ribs radiate outward from the center of the polygonal shape towards the edges of the polygonal shape. In some embodiments, the plurality of ribs extend from the top surface and from the bottom surface of the body. In further embodiments, the ribs have a height above the body that decreases from a center of the body towards the periphery of the body. 
     In some embodiments, the body includes a cross-sectional profile that decreases from a center of the body to the periphery of the body. In other embodiments, the sidewall protrudes from the top surface and from the bottom surface. The sidewall may include a concave portion and/or a convex portion. In further embodiments, the aperture is positioned adjacent the sidewall. In some embodiments, the sidewall includes a sigmoidal curvature along the periphery of the body. In other embodiments, the aperture follows a contour of the curvature. 
     The inventive subject matter further contemplates a system for covering a surface of a body of liquid, including a plurality of disks configured to float on the surface of the body of liquid. The plurality of disks unite when floating on the surface of the body of liquid to form an arrangement of floating disks. Each of the plurality of disks includes an interlocking element configured to interact with a complementary interlocking element at an adjacent disk to assist in keeping the arrangement of floating disks together. 
     The interlocking elements may include a portion of the sidewall, a curvature of the sidewall, and/or a sigmoidal curvature of the sidewall extending from the bottom surface of the body and an inverse curvature extending from the top surface at a corresponding location of the body. 
     In further embodiments, a system for covering a surface of a body of liquid includes a plurality of disks configured to float on the surface of the body of liquid, each disk including a body having a substantial polygonal shape in the horizontal floating plane, the body including a top surface and a bottom surface, a plurality of ribs projecting from the top surface and the bottom surface of the body, each rib having a height above the body that decreases from the center of the body towards the periphery of the body, a sidewall protruding from the top surface and from the bottom surface at the periphery of the body and coupled to at least some of the plurality of ribs. 
     A portion of the body, a portion of the plurality of ribs, and a portion of the sidewall define a cavity allowing a volume of a gas to be trapped in the cavity when the disk is deployed on the surface of the body of liquid. The plurality of disks unite when floating on the surface of the body of liquid to form an arrangement of floating disks. Each of the plurality of disks includes an interlocking element configured to interact with a complementary interlocking element at an adjacent disk to assist in keeping the arrangement of floating disks together. 
     The foregoing embodiment may further include a plurality of apertures at the periphery of the body, the aperture allowing a liquid to pass through the top surface and the bottom surface. In some embodiments, the plurality of ribs are arranged in a pattern that is substantially identical at the top surface and at the bottom surface of the body. In other embodiments, the body includes a cross-sectional profile that that decreases from a center of the body towards the periphery of the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an arrangement of liquid covering disks. 
         FIG. 2  is a perspective view of a liquid covering disk. 
         FIG. 3  is an exploded perspective view of a portion of the liquid covering disk shown in  FIG. 2 . 
         FIG. 4  is a close up view of the texture of the material forming the liquid covering disk shown in  FIG. 1 . 
         FIG. 5  is a top plan view of the liquid covering disk of  FIG. 2 . 
         FIG. 6  is a cross-sectional view of the liquid covering disk of  FIG. 2  along line  6 - 6  in  FIG. 5 . 
         FIG. 7  is a cross-sectional view of the liquid covering disk of  FIG. 2  along line  7 - 7  in  FIG. 5 . 
         FIG. 8  is a side elevation view of the liquid covering disk of  FIG. 2 . 
         FIG. 9  is a cross-sectional perspective view of the arrangement of liquid covering disks of  FIG. 1 , illustrating interlocking features between disks. 
         FIG. 10  is an exploded cross-sectional view of interlocking features of liquid covering disks of  FIG. 9 . 
         FIG. 11  is top plan view of a second embodiment of a liquid covering disk. 
         FIG. 12  is a side view of the liquid covering disk of  FIG. 11 . 
         FIG. 13  is a top plan view of a third embodiment of a liquid covering disk. 
         FIG. 14  is a side view of the liquid covering disk of  FIG. 13 . 
         FIG. 15  is a top plan view of a fourth embodiment of a liquid covering disk, which includes spherical chambers. 
         FIG. 16  is a side view of the liquid covering disk of  FIG. 15 . 
         FIG. 17  is a top plan view of a fifth embodiment of a liquid covering disk. 
         FIG. 18  is a side view of the liquid covering disk of  FIG. 17 . 
         FIG. 19  cross-sectional view the embodiment of a liquid covering disk shown in  FIG. 17  along line  19 - 19 . 
         FIG. 20  is a perspective view of a sixth embodiment of a liquid covering disk, which includes cylindrical chambers. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed liquid covering disks and systems will become better understood through review of the following detailed description in conjunction with the figures. The detailed description and figures provide merely examples of the various inventions described herein. Those skilled in the art will understand that the disclosed examples may be varied, modified, and altered without departing from the scope of the inventions described herein. Many variations are contemplated for different applications and design considerations; however, for the sake of brevity, each and every contemplated variation is not individually described in the following detailed description. 
     Throughout the following detailed description, examples of various liquid covering disks are provided. Related features in the examples may be identical, similar, or dissimilar in different examples. For the sake of brevity, related features will not be redundantly explained in each example. Instead, the use of related feature names will cue the reader that the feature with a related feature name may be similar to the related feature in an example explained previously. Features specific to a given example will be described in that particular example. The reader should understand that a given feature need not be the same or similar to the specific portrayal of a related feature in any given figure or example. 
     The inventive subject matter provides systems and liquid covering disks that reduce evaporation, heat loss, reduce foam formation and emission of noxious or toxic fumes from an open liquid surface by forming a floating arrangement of liquid covering disks. The liquid covering disks include a body, a plurality of ribs projecting from the body, and a sidewall protruding at the periphery of the body. A portion of the body, a portion of the plurality of ribs, and a portion of the sidewall define a cavity. 
     A liquid covering disk including a number of such open cavities allows a volume of a gas to be trapped in the cavity when the disk is deployed on the surface of the body of liquid thereby providing buoyancy to the disk. Additionally, cavities with an open side facing the surface of the body of liquid provide the disks with a tendency to stick to the surface of the body of liquid. Furthermore, disks that are generally similar in shape tend to unite edge to edge when floating on the surface of the body of liquid to form an arrangement of floating disks that covers a major portion of an open liquid body. Complementary interlocking elements assist in keeping the arrangement of floating disks together. 
     The liquid covering disk has a polygonal shape in the horizontal floating plane, for example a triangular, quadrangular or hexagonal shape. The liquid covering disks may be hollow or solid. Some embodiments are made using a plastic having a gravity which is approximately one half the specific gravity of the liquid to provide the disk with the desired buoyancy. 
     With reference to  FIGS. 1-10 , a first example of a system for covering a surface of a body of liquid and liquid covering disk will now be described. Liquid covering disk  100  includes a body  120  having a top surface  112 , a bottom surface  114 , and apertures  132  at a periphery  122  of body  120 . Apertures  132  are configured to allow a liquid and debris to pass through. Disk  100  further has a sidewall  116  protruding vertically at periphery  122  of body  120  and a plurality of ribs  124  projecting vertically from body  120 . 
     A plurality of channels  126  are formed by portions of body  120 , portions of ribs  124 , and portions of sidewall  116 . The channels are formed by ribs  124 , protuberance  148 , sidewall  116 , and top surface  112 . Each rib  24  has two surfaces which define faces of channels  126 . 
     On each major side of disk  100 , channels  126  slope downwards towards apertures  132  proximate sidewall  116 . Channels  126  serve to direct water and other debris towards apertures  132  to allow the water and debris to exit channels  126  through apertures  132  on whatever side of disk  100  is oriented upwards. Of course, the channels on the side of disk  100  oriented downwards will be wholly or partially submerged in the liquid body. 
     As can be seen in  FIGS. 2 ,  5  and  6 , disk  100  includes a set of cavities  118  and cavities  144 . Cavities  118  are disposed along the periphery of disk  100  whereas cavities  144  are located at the center of disk  100 . Cavities  118  are defined by a portion  136  of body  120 , portions  138  and  140  of ribs  124 , and portion  141  of sidewall  116 . Cavity  144  is defined by a substantially cylindrical protuberance  148  that projects from body  120  at the center of the hexagonal shaped body  120 . 
     When floating on the surface of a body of liquid a volume of a gas, such as air, may be trapped in cavities  118  and  144  between the surface  128  of the body of liquid  130  and the surfaces of the cavities. The trapped volume of gas imparts increased stability and buoyancy to disk  100 . Trapping air below the bottom surface of the disk in the cavities increases the buoyancy of the disk. 
     Cavities  118  and  144  increase the stability of liquid covering disk through pressure equilibrium principles. When a pocket of air is trapped in cavities  118  and  144  by the surface of a liquid, the pressure of that pocket of air will be in equilibrium with the local atmospheric pressure. Attempts to separate the disk from the surface of the liquid will have the effect of increasing the volume of the chamber of air sealed in the cavities. Increasing the volume of the sealed chamber will decrease the air pressure within the sealed chamber and create a pressure imbalance with the ambient air pressure. The net result is that disk  100  will resist separating from the surface of the liquid in response to wind or other forces because the ambient air will act on the liquid and the disk to maintain the pressure of air sealed in cavities  118  and  144  in equilibrium with the ambient air pressure. 
     When an arrangement of liquid covering disks is used, wind may push upon the rib faces and push the liquid covering disks more closely together and reduce gaps in the coverage between them. The liquid covering disks may unite as an arrangement  142  of floating disks disposed in edge to edge relationship with generally like disks to cover at least a major portion of a body of liquid. For example, a system  190  for covering a surface of a body of liquid including a plurality of disks  100  is shown in  FIG. 1 . 
     Liquid covering disk  100 , or a collection thereof, function to reduce heat loss and evaporation, suppress waves, reduce foam formation, and prevent the emission of noxious or toxic fumes from a body of liquid on which liquid covering disk  100  is deployed. In operation, liquid covering disk  100  floats with top surface  112  approximately above surface  128  of a body of liquid  130  and bottom surface  114  approximately below surface  128  of body of liquid  130 . Of course, the disk may flip over from time to time, reversing the orientation of the top and bottom surfaces. 
     Body  120  of disk  100  has a substantially hexagonal shape in a horizontal plane. Top surface  112  includes a substantially cylindrical protuberance  148  that projects from body  120  at the center of the hexagonal shaped body  120 . Although protuberance  148  is substantially cylindrical in shape with a substantially flat top, this disclosure also contemplates protuberances that implement different designs as well. 
     A plurality of ribs  124  radiate from protuberance  148  extending from body  120 . In particular, twelve trapezoidal ribs  124  on each side of disk  100  radiate out from protuberance  148  towards periphery  122  of body  120  where they merge with sidewall  116 . As one can see in  FIG. 2 , the height of ribs  124  gradually descends as they approach sidewall  116  and merges with the sidewall at equal height. The outer edges of the ribs, i.e., the end of the ribs away from the top/bottom surface, defines the contours of the disk, for example contour  134  of disk  100 . 
     Liquid covering disk  100  further includes a sidewall  116 , formed by a projection of the hexagonal periphery of top surface  112  and bottom surface  114 . In some embodiments, sidewall  116 , top surface  112 , and bottom surface  114  are coupled such that they form a unified body. 
     Sidewall  116  generally follows periphery  122  of hexagonal shaped body  120 . However, at each side of the hexagonal shape, sidewall  116  includes a curvature, for example sigmoidal curvature  152 . Curvature  152  includes a concave portion  154 , where the sidewall deviates slightly inward, relative to the side of the hexagonal shape, towards the center of the body, and a convex portion  156 , where the sidewall deviates slightly outward, relative to the side of the hexagonal shape, towards the center of the body. 
     Apertures  132  serve as a port that allows an amount of liquid to pass through freely. For example, apertures  132  are formed in body  120  proximate sidewall  116  and allow water and debris to flow through back into the main liquid body. Additionally, apertures  132  along the periphery reduce or prevent water from being trapped on the top surface of the disk. 
     Aperture  132  allows for a gap in body  120  and sidewall  116  so that when a collection of liquid covering disks are used in concert and are nested in a closed, packed pattern, liquid is allowed to easily pass through aperture  132 , whereas other liquid covering disks in the tightly packed pattern may otherwise substantially restrict such flow. In some embodiments, disks may be provided with additional apertures or ports. 
     Bottom surface  114  is substantially similar to top surface  112 , including a similar shape, size, and topography, except for a shift in the curvature along the sides of the hexagonal shape, i.e., concave portions at the top surface align with convex portions at the bottom surface, and vice versa. 
     For the sake of brevity, the elements of bottom surface  114  will not be described in detail. However, bottom surface  114 , like top surface  112 , includes a central protuberance and ribs that are substantially the same shape and size as the corresponding parts on top surface  112 . Sidewall  116 , however, along the sides of the polygonal shaped body includes a portion wherein the curvatures are the opposite of the curvatures at the top surface. In particular, at top surface  112  sidewall  116  includes sigmoidal curvature  152  whereas at bottom surface  114 , sidewall  116  includes sigmoidal curvature  158 , which is positioned as the inverse to sigmoidal curvature  152 . 
     For example,  FIG. 1  shows a split in sidewall  116  where a concave portion  160  curves inward below convex portion  156  of curvature  152  and a convex portion  162  curves outward below concave portion  154  of curvature  152 . Although the patterns formed by the ribs  124  of top surface  112  and bottom surface  114  are substantially similar, this is not specifically required, and liquid covering disks with different top surfaces and bottom surfaces are equally within this disclosure. 
     Additional openings  164  and  166  are provided in the portions of body  120  where sidewall  116  curves outward, i.e., in top surface  112  and bottom surface  114  at the convex portions  156  and  162 , respectively, of side wall  116 . Openings  164  and  166  assist the disk in settling into a substantially flat position on the surface of the body of liquid and to communicate fluid between channels  126  and the body of liquid on which disk  100  floats. In some embodiments, the body, ribs, and sidewall may include additional openings. 
     Body  120  has a cross-sectional thickness that decrease from the center to edge  146  to facilitate dispersion of rain water and to avoid standing water. For example, the center of top surface  112  is at a higher elevation relative to its lateral periphery  122 . However, in some embodiments liquid covering disks may include a substantially flat top surface and/or bottom surface. In other embodiments, either the top surface, bottom surface, or both, may include a depression, or lowers in elevation as one approaches the center, for example in combination with an opening. 
     The outer contours of the ribs follow a similar profile. Ribs  116  create channels which guide rain to the edges of the disks. Ribs  116  provide structural support to the disk and provide resistance to wind. The contour of the disk is determined by the height of the ribs and the sidewall. 
     The dimension of the cavities may depend on the application and wind resistance that is desired. The cavities can be sized to provide additional stability and buoyancy. In some embodiments, the size of the cavities is selected to allow the disks to float at a predetermined depth below the surface of the body of liquid. 
     In one example, a body has a diameter of about 8 inches and a height of at least about 0.5 inches. In another example, three liquid covering disks may cover about 1 square foot of surface of body of liquid. In some embodiments, the sidewall may have a height between 40% and 60% of the overall height of the disk. 
       FIG. 5  illustrates the position of the channels  126  created by the body, ribs, and sidewall. Disk  100  has a total of 48 channels, 24 channels at the top surface side of the body and 24 channels at the bottom surface side. Each side has a middle cavity at the center of the polygonal shape and 6 cavities at the peripheral edges. 
     Cavities  118  and  144  may capture a given amount of a gas when a liquid covering disk is placed in water or other liquid. The size and volume of the cavities may be selected to create desired buoyancy and surface adhesion characteristics. For example, the size and volume of the cavities may be selected to cause the buoyant force of the gas enclosed in cavities  118  and  144 , combined with any buoyant force created by the density of the disk&#39;s construction material, to be sufficient to maintain the disk afloat on the body of liquid with its lower contours at a predetermined depth below the surface of the body of liquid. 
     In some embodiments, the disk may have cavities that are enclosed. In other embodiments, the disk may have cavities that are enclosed and filled with foam and other solids that are generally understood to include pockets of trapped gas. Further example embodiments may include cavities that are enclosed and partially filled with a fluid. In some examples, dense substances may be added to the body to provide more stability to the disk while positioned in a liquid body. 
     Liquid covering disks may hold differing quantities of gas into the cavities. By adjusting the shape of the body and the pattern of the ribs and sidewall, the size of the cavities is modified and the liquid covering disks may be designed to float at different depths, for example from about 10% to about 60% submerged when deployed on a body of liquid. These modifications may also be useful in adapting liquid covering disks for use in liquids of varying densities. 
       FIGS. 9 and 10  illustrate details of an interlocking mechanism  172  as used in an arrangement  142  of floating disks disposed in edge to edge relationship. Interlocking mechanism  172  includes portions of substantially identical disks  100  with curvatures on the sides of adjacent disks complementing and overlapping each other. 
       FIGS. 9 and 10  show disks  100 , here referred to as a first disk  174  and a second disk  176 , having interlocking elements  168  and  170 , respectively. Interlocking element  168  is formed, for example, by the concave portions  54 ,  60  and convex portions  56 ,  62  of sidewall  116 , as described above, on disk  168 . Complementary interlocking element  170  is formed of similar concave portions  54 ,  60  and convex portions  56 ,  62  of a sidewall  116  of adjacent disk  176  which is oriented such that curvatures of each respective disk complements the other. 
     The interlocking elements are symmetrically positioned over the polygonal body and include protruding and recessing portions formed by alternating concave and convex portions. The concave and convex portions are designed to overlap with similar but inverse interlocking elements of adjacent disks. 
     Liquid disk covering  100  is shown in  FIGS. 1-10  with a specific rib pattern and a hexagonal shape, but this shape is not explicitly required in every embodiment of liquid disk coverings. For example, the disk may take a wide variety of shapes, including, but not limited to, polygonal, elliptical, or non-polygonal shapes. Certain shape examples include interlocking elements, such as complimentarily configured projections and recesses positioned around the liquid covering disk&#39;s perimeter when viewed from above. 
     Turning attention to  FIGS. 11-19 , additional examples of a liquid covering disks are described. The liquid covering disks described hereafter includes many similar or identical features to liquid covering disk  100 . Thus, for the sake of brevity, each feature of liquid covering disks  200 ,  300 ,  400 , and  500  will not be redundantly explained. Rather, key distinctions between liquid covering disks  200 ,  300 ,  400 ,  500  and liquid covering disk  100  will be described in detail and the reader should reference the discussion above for features substantially similar between the liquid covering disks. 
       FIGS. 11 and 12  illustrate a second example of a liquid covering disk. Liquid covering disk  200  has a body  220 , a sidewall  216 , a plurality of channels  226 , and plurality of ribs  224 . Body  220  is substantially triangular shaped. Sidewall  216  projects around periphery  222  of body  220  similar to sidewall  116 , described above, and including interlocking mechanism  272  having sigmoidal curvatures  252  and  258  along the sides of the substantially triangular shaped body  220 . Ribs  224  radiate from a center cavity  244 . 
       FIGS. 13 and 14  illustrate a third example of a liquid covering disk. Disk  300  has a body  320 , a sidewall  316 , a plurality of cavities  318 , a plurality of channels  326 , and plurality of ribs  324 . Body  320  is substantially rectangular shaped. Sidewall  316  projects around periphery  322  of body  320 , similar to sidewall  116  described above. 
     Disk  300  includes interlocking mechanism  372  having sigmoidal curvatures  352  and  358  along the sides of the substantially rectangular shaped body  320 . Ribs  324  radiate from a center of disk  300 . A central cavity may be formed at the center of the disk in addition or alternatively to the periphery cavities  318 . 
       FIGS. 15 and 16  illustrate a fourth example of a liquid covering disk. Disk  400  has a body  420 , a sidewall  416 , a plurality of channels  426 , and a plurality of ribs  424 . Sidewall  416  projects around periphery  422  of body  420 , similar to sidewall  116  described above, including interlocking mechanism  472  having sigmoidal curvatures  452  and  458  along the sides of the substantially hexagonal shaped body  420 . Ribs  424  radiate from a center of disk  400 . The pattern of the ribs  424  of disk  400  is similar to the pattern of ribs of disk  100  described above with reference to  FIGS. 1-10 . 
     A key difference between liquid covering disk  400  and liquid covering disk  100  lies in the placement of six spherical chambers  492 ,  493 ,  494 ,  495 ,  496 ,  497  at the vertices of the hexagonal shaped disk  400 . Spherical chambers  492 ,  493 ,  494 ,  495 ,  496 ,  497  are positioned on, or form part of body  420 , with symmetrical halves being part of top surface  412  and bottom surface  414 . In some embodiments, spherical chambers may be filled with a gas or any suitable material that assists with buoyancy of disk  400 . In further embodiments, spherical chamber may be filled with a dense material and contribute to the stability of the disk on the surface of the body of liquid. 
       FIGS. 17-19  show a fifth example of a liquid covering disk. Disk  500  has a body  520 , a sidewall  516 , a plurality of periphery vertices  518 , a pair of central cavities  544 , and a plurality of ribs  524 . Ribs  524  radiate from central cavities  544 . The pattern of ribs  524  is similar to the pattern of ribs of disk  100 , described above with reference to  FIGS. 1-10 . 
     A key difference between liquid covering disk  500  and liquid covering disks described above is that vertices  518  are solid as opposed to hollow cavities or chambers. In the present example, vertices  518  are made from the same material as the other components of disk  500 . However, the material forming vertices may be selected to impart desired buoyancy characteristics, such as a variety of structural foams. 
     The profile of disk  500  is conducive to stacking disks on top of each other during manufacturing and installation. Further, the profile of disk  500  is conducive to the disks sliding past each other when deploying the disks into a body of liquid. 
     Interlocking mechanism  572 , having sigmoidal curvatures  552  and  558  along the sides of the substantially hexagonal shaped body  520 , is substantially identical to interlocking mechanism  172  described above. 
       FIG. 20  shows a sixth example of a liquid covering disk, namely, liquid covering disk  600 . Liquid covering disk  600  is substantially similar to liquid covering disks described above, including to liquid covering disk  400 , and includes a plurality of channels  626 . As the reader can see in  FIG. 20 , however, liquid covering disk  600  cylindrical chambers or cavities  696  instead of the spherical chambers included in liquid covering disk  400 . Cylindrical chambers  696  may be open or unplugged, as shown in  FIG. 20 , or closed off or plugged to trap a volume of air within the cylindrical chamber. Plugging or unplugging the chambers will change the buoyancy of the liquid covering disk, with disks having plugged chambers being more buoyant. 
     The disks may be made of a material which resists chemicals, UV, and abrasion from friction between adjacent disks.  FIG. 4  shows an example of a suitable material, an engineered micro-structure  180 , which may be used for the body of the liquid covering disk. 
     In some embodiments, liquid covering disk  100  and all of its components are made of an ultraviolet stabilized material, such as ultraviolet stabilized high density polyethylene (HDPE). The use of ultraviolet stabilized high density polyethylene helps maintaining the disk&#39;s material integrity during outdoor use over an extended period of time. In liquid covering disk  100 , for example, adding carbon black to the polyethylene, for example a ratio of about 2%, provides ultraviolet light protection and stabilization. In other embodiments, ultraviolet light protection or stabilization may be achieved by adding carbon black to the main constituent of the disk, such as high density polyethylene or polypropylene, for example in a ratio of about 2% to about 10%. 
     Examples of suitable constructions materials for disks include expanded polypropylene, high density polyethylene, and an expanded polypropylene using a blowing agent with UV stabilization. An expanded HDPE using a blowing agent with UV stabilization may also be used. 
     In some examples, an expanded polypropylene is used that was created using a process that expands plastics while in the solid state as opposed to conventional foaming techniques. Conventional foaming techniques can inadequately control bubble size in the plastic piece and require the use of potentially harmful foaming agents. One suitable solid state plastic expansion process is the Ad-air® process utilized by MicroGREEN Polymers, Inc. 
     Other suitable materials include an expanded polypropylene using a glass bubble or an expanded HDPE using a glass bubble. 
     In some embodiments, the disk may be formed in one piece but using a different materials and/or different color for the main body and ribs. Other embodiments may be formed as an assembly of parts, for example, a body provided with distinct ribs and a sidewall. Further example embodiments may be made by joining a top portion and a bottom portion to form disks as described above. In many examples, many features at the top surface and the bottom surface of the disks are identical, which simplifies manufacturing. 
     Some example embodiments of liquid covering disks may be made by injection molding techniques. For example, each half of a liquid covering disk may be made by an injection molding technique. The molded halves are then fused together using a hot plate, which allows for a “perfect weld” when working with high-density polyethylene. Other joining techniques can also be used, such as ultrasonic welding, high frequency welding, friction welding, spin welding, laser welding, hot gas welding, free-hand welding, and the like. 
     Other embodiments of liquid covering disks may be made by blow molding techniques. Blow molding may be desirable where high speed fabrication is required. Using blow molding techniques, disks can be made in one simple operation, removing the need for welding two halves. 
     Other example embodiments of liquid covering disks may be made by a combination of injection molding with air injection technologies which reduce the original polymer density and improve insulation properties. 
     Blow molding agents and glass spheres may be added to reduce density and improve physical properties. Some rib patterns may increase the disk&#39;s rigidity and thereby offset the increased elasticity and softness resulting from the use of the blowing agent. Because the ribs can be added separately from the body, a different material can be used where no blowing additive has been introduced. Adding the ribs separately can be done, for example, in one step by using a two material injection molding method where two types of thermoplastic resin are successively injected into the mold by respectively different injection cylinders, thereby producing a product with two types of resins and colors. 
     Liquid covering disks in this disclosure are often recited using terms such as “top” and “bottom” to better illustrate disks&#39; relative vertical orientation. However, many liquid covering disks according to this disclosure, specifically including liquid covering disks  100 ,  200 ,  300 ,  400 , and  500  may be turned over 180 degrees and be capable of substantially the same functionality. This may be particularly useful in windy conditions, in which a liquid covering disk may be flipped unintentionally. 
     The disclosure above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in a particular form, the specific embodiments disclosed and illustrated above are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed above and inherent to those skilled in the art pertaining to such inventions. Where the disclosure or subsequently filed claims recite “a” element, “a first” element, or any such equivalent term, the disclosure or claims should be understood to incorporate one or more such elements, neither requiring nor excluding two or more such elements. 
     Applicant(s) reserves the right to submit claims directed to combinations and subcombinations of the disclosed inventions that are believed to be novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of those claims or presentation of new claims in the present application or in a related application. Such amended or new claims, whether they are directed to the same invention or a different invention and whether they are different, broader, narrower or equal in scope to the original claims, are to be considered within the subject matter of the inventions described herein.