SELF-CLOSING LID

Abstract

A self-closing lid that can be applied to a container and which provides a screen to prevent oversized debris from entering an inlet. The self-closing lid preferably includes a pair of flaps that rotate into an open position when material is being applied to the inlet and which rotate closed—preferably via a counterbalance, when material is no longer being applied to the inlet. The autonomous self-closing lid is preferably configured to not open in response to rainwater falling into the inlet and has shapes and/or features which direct the rainwater away from the inlet and outside of the lid.

Description

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to a self-closing lid, which can be added to a container. More particularly, embodiments of the present invention relate to a self-closing lid which can screen material as it goes into the container and which can channel and/or otherwise direct water away from an inlet of the container. Embodiments of the present invention can be particularly useful for large containers of granulate and/or power material, including for example proppant that is typically used when performing hydraulic fracturing of subsurface formations in a well (including but not limited to a frac sand box). The use diversity of the present invention can include but is not limited to sand (which can include for example wet, dry, frac, beach, construction, play, combinations thereof and the like), dirt, agricultural (including for example grains, nuts, fruits, vegetables, and the like—including but not limited to tobacco, soybeans, peanuts, wheat, and the like), plastics and polymer materials (including for example pellets), as well as rocks, cement, aggregate, gravel, and other rocks when loaded into boxes, containers, bins, conveyers, transport mechanisms, grinders, blenders, sifters, and any other storage or separation into storage mechanisms. Such storage and transport containers, mechanisms, and structures generally referred to herein as a “container”.

With currently known container lids that are disposed atop a large container, workers are forced to climb up onto the top of containers via a ladder to open the box top to allow facilities to load. This scenario puts the workers at risk of falling from heights that can cause catastrophic injury and potentially be fatal. There is a present need for a container lid that avoids the necessity for workers to climb on any equipment. Applicant has thus developed the self-opening and closing lid, which uses a counterweight design that opens under the weight of the material being loaded and closes at the lack thereof, thus avoiding the need for workers to climb atop the container.

Another area of concern is the fact that over time, for various reasons, current lids go missing. This can be a result of aged hinge points, or the result of the operator not properly closing and securing them, causing them to come off in transit due to the winds at high speed. There is thus a present need for a container lid that is permanently affixed to the container, and the hinge points are such that there is zero possibility of a lid coming off due to weather, age, or neglect. Should a hinge point wear out, regardless of circumstance, the counterweight prevents components from dropping into the container and because the lid is preferably wider on the inside than the opening, this prevents the lid from leaving the box. This configuration thus mitigates the risk of contaminated products in the box, and the risk to the public that is posed by a lid coming off in transit and falling into oncoming or surrounding traffic.

Safety is also important when recognizing that the lid has become open because of excess material or for any other reason. Embodiments of the present invention address this issue by optionally providing visually-observable indicia of an open and/or closed condition of the lid.

Conventional container lid designs also suffer the risk of contamination when material is being loaded, as there is nothing to keep debris from entering the container. Embodiments of the present invention address this with the implementation of a built-in screen to screen debris from entering.

BRIEF SUMMARY OF EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention relate to a self-closing lid having a lid frame with an opening, a pair of counterbalanced flaps, each of the pair of counterbalanced flaps hingedly coupled to the lid frame and positioned such that the pair of counterbalanced flaps are disposed on opposing sides of the opening such that the pair of counterbalanced flaps rotate between an open configuration and a closed configuration, wherein the pair of counterbalanced flaps are counterbalanced such that the pair of counterbalanced flaps are biased into a closed configuration due to counterbalancing, and a screen is positioned to screen material passing through the opening. The opening can be a lid opening through which material preferably passes when a user is filling a container. The self-closing lid can also include at least one water discharge opening disposed in the lid frame. The pair of counterbalanced flaps can be sized such that at least one of the pair of counterbalanced flaps has an end portion that overlaps an end portion of the other of the pair of counterbalanced flaps. A portion of each of the pair of counterbalanced flaps passes through a respective opening in the frame. The pair of counterbalanced flaps can each have a counterbalance weight disposed thereon in a location that is outside of the lid frame. The pair of counterbalanced flaps can each have sidewalls that extend upward when in a closed configuration.

In one embodiment, the pair of counterbalanced flaps are pitched when closed such that a terminal end portion of each respective flap is elevated higher with respect to a hinge location. Each of the pair of counterbalanced flaps can be pitched to shed water to a first side and/or to a second side. The screen can be disposed within the opening in the lid frame. The lid frame can be hingedly coupled to a container, which can optionally be a frac sand box. The self-closing lid can be disposed on a frac sand box.

Optionally, the self-closing lid can include a mesh disposed above the opening of the lid frame. The mesh can be convex such that a center portion of the mesh is higher than an edge portion of the mesh. In one embodiment, the mesh can be concave such that a center portion of the mesh is lower than an edge portion of the mesh. At least one wiper can be communicably coupled to at least one of the pair of counterbalanced flaps such that the at least one wiper moves across at least a portion of the mesh in response to movement by at least one of the pair of counterbalanced flaps. The mesh can be disposed within a mesh-holding frame the mesh-holding frame can be movable with respect to the lid frame.

Embodiments of the present invention relate to a method for automatically opening and closing a lid in response to a material being applied thereto, the method including forming an opening in a lid, forming a frame around the opening, counterbalancing a pair of flaps and positioning them such that the pair of flaps is biased into a closed position with respect to the formed opening when weight of material is not applied to them, and positioning a screen above the pair of flaps. The method can also include hingedly coupling the lid to a container. Optionally, hingedly coupling the lid to a container can include hingedly coupling the lid to a frac sand box.

Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or can be learned by practice of the invention. The objects and advantages of the invention can be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more embodiments of the invention and are not to be construed as limiting the invention. In the drawings:

FIG. 1A is a perspective view of a lid in a closed configuration according to an embodiment of the present invention;

FIG. 1B is a perspective view of a lid with mesh in a closed configuration according to an embodiment of the present invention;

FIG. 2 is a perspective view of a lid in an open configuration according to an embodiment of the present invention;

FIGS. 3A and 3B are drawings which illustrate perspective views looking up toward an underside of the lid wherein the flaps are in a closed configuration (3A) and in an open configuration (3B);

FIG. 4 is a perspective view of a lid in an open configuration, wherein the lid is configured to hingedly attach to a container;

FIG. 5 is a view of the configuration of FIG. 2, looking up toward an underside of the lid;

FIG. 6 is a perspective view of a flap of a lid having an angle or otherwise convex shape to direct water toward sidewalls thereof;

FIG. 7 is a view if an underside of a lid in a closed configuration that is configured to hingedly attach to a container;

FIG. 8 is a perspective view of a lid with a concave mesh according to an embodiment of the present invention;

FIG. 9 is a view of a lid in a closed configuration and having an elongated water discharge opening disposed in a sidewall thereof;

FIG. 10 is a perspective view of a lid in an open configuration with a concave mesh according to an embodiment of the present invention;

FIG. 11 is a perspective view of a lid in an open configuration with a convex mesh according to an embodiment of the present invention;

FIG. 12 is a perspective view of a lid with wiper brushes in an open configuration according to an embodiment of the present invention; and

FIG. 13 is a perspective view of a lid with wiper brushes in a closed configuration according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures generally and FIGS. 1A through 4 in particular, embodiments of the present invention relate to self-closing lid 10 having a pair of hingedly closing flaps 12 attached to a lid frame 14 via hinge pin 16 which passes through hinge opening 18 of each of flaps 12. Of course, flaps 12 can alternatively include or have hinge pin 16 on them with hinge opening being disposed in or otherwise attached to lid frame 14. In one embodiment, terminal end portions of flaps 12 preferably at least slightly overlap one another. A pair of flaps 12 are preferably provided and are configured such that they pass through a respective opening that is formed in opposing sidewalls 26 of lid 12. Each of the hinge flaps 12 also preferably comprise or are otherwise attached to counterweight 20. The weight and position of counterweight 20 is preferably such that flaps 12 will return to their closed position when material is not applied directly to them. In one embodiment, the weight of the material that is required to overcome the effect of counterweight 20 is preferably at least two pounds, more preferably at least 5 pounds.

Lid frame 14 preferably includes inlet 24, which is an opening therethrough. Inlet 24 can optionally include one or more side walls 26. In one embodiment, screen 28, which can comprise a grate, can be disposed or otherwise positioned within, on, over or under inlet 24. Screen 28, if provided, preferably prevents large objects from entering a container to which lid 10 is attached. As best illustrated in FIG. 5, lid 10 can include attachment hinge 30, which can optionally include hinge pin 32 and hinge opening 34. Optionally, hinge pin 32 can be welded (spot, seam, or stitch-welded), bolted, or otherwise attached to a container. Of course, the opposite configuration can also be provided such that hinge pin 32 is attached to lid 10 and instead hinge opening 34 can be attached or otherwise provided on the container. Attachment hinge 30 enables the entire lid 10 to be rotated away so that it is not covering an opening of the container, and to be rotated back such that it is again covering the top of the container.

In one embodiment, screen 28 can be made to be placed within a boundary formed by sidewalls 26. Optionally, screen 28 can be locked into place via one or more fasteners and/or otherwise bolted or secured on lid frame 14. As such, screen 28 can be substituted for another screen having larger or smaller openings-or can be easily replaced with a like screen if the original screen becomes damaged or otherwise wears out.

As best illustrated in FIG. 6, one or both flaps 12 can be bent or otherwise curved such that they have a slanted or convex shape which causes water, that lands on a top surface thereof, to roll down to the base of flap sidewalls 40, when flaps 12 are in a closed configuration. For example, a bend 60 can be put into flaps 12 to allow water and other materials to roll down to the base of flap sidewalls 40. The thus-directed water can then travel along the base of flap sidewalls 40 where the water can then run or drip onto internal catch channel 42 (see FIG. 7), which has a curved, notched or cup-shaped cross section such that water is directed along the top of it.

In one embodiment, lid 10 is preferably configured such that when it is attached to a container, the upper surfaces of the lid and/or the upper surfaces of flaps 12, when in a closed configuration, will be pitched such that rainwater is directed to run off of lid 10 in a predetermined location with respect the sidewalls 26. For example, in one embodiment, lid 10 is preferably configured to be pitched such that when a container, with lid 10 thereon, is transported, oncoming wind that is encountered during transport pushes water down the sloped upper surfaces of flaps 12 and causes most of the water to exit the lid without entering the container. This eliminates the risk of wet material that customers currently contend with in the current market due to lids being open in transit, which wet material tends to clump together, which makes removal difficult.

Water discharge opening 44 (see FIG. 8) is preferably disposed in one or more sidewalls 26 at the top of catch channel 42. This allows water (including for example rainwater) that falls into inlet 24 to land on a top surface of flaps 12 when they are in a closed configuration, before the water is directed such that it is discharged out of discharge opening 44. This configuration causes the water to then be moved to the exterior of inlet 24 where the water is then forced to run down the outside of the container—thus preventing or greatly reducing the amount of water that is allowed to enter the interior of the container when the lid is in a closed configuration. This can be especially beneficial for large containers which are typically left in an uncovered, outdoor environment. In one embodiment, the lid is attached to, or is configured to be attached to a container and more particularly to a frac sand box. In one embodiment, lid 10 is welded to a top portion of a frac sand box. In one embodiment, attachment hinge 30 is welded and/or bolted onto a container.

Lid 10 addresses multiple issues surrounding the safety, functionality, and product contamination issues that known lids of containers—especially frac sand box lids, currently encounter. In known frac sand box lids, workers must climb on top of boxes via a ladder to open the box top to allow facilities to load. This scenario puts the worker at risk of falling from heights that could potentially be fatal. With lid 10, there is no need to climb on any equipment because lid 10 is self-opening and closing, utilizing a counterweight configuration that opens under the weight of the material being loaded and closes in response to a lack of sufficient material to overcome the effects of counterbalances 20.

Optionally, lid 10 can have mesh 50, as shown in FIG. 1B, which can optionally be replaceable. Mesh 50 can be disposed above screen 28 or can be used without screen 28. Mesh 50 preferably comprises openings that are at least one square inch and more preferably are at least two square inches. In one embodiment, mesh 50 can be made from a material the same as or similar to chain link fencing. Mesh 50 can comprise frame 54. Mesh 50, if provided, preferably prevents or otherwise impedes objects of a size larger than its openings from entering a container to which lid 10 is attached. Mesh 50 can be secured to lid 10 via any desirable manner—most preferably which is removable or at least can be opened to dump debris off of mesh 50 which failed to pass therethrough, mesh 50 and frame 54 can be held in place via fastener 56, which can optionally comprise a latch, catch bolt, or any other desirable fastener. In one embodiment, a plurality of layers of mesh 50 and a respective frame 54 can optionally be stacked atop one another.

Hinge 58 can optionally comprise a spring-loaded hinge or a non-spring-loaded hinge. Latch 56 can be released, thus allowing frame 54 and thus mesh 50 to pivot about hinge 58, exposing lid frame 14 and sidewalls 26, as well as screen 28 (if provided). Mesh 50 can be seen fastened to lid frame 14 and in a closed position in FIG. 2. In one embodiment, frame 54 can be connected to the rest of lid 10 such that it is spring loaded and such that if latch 56 is opened, frame 54 pops up while latch 56 again closes before frame 54 lands back onto the now closed latch, thus helping hold frame 54 in a slightly open position.

Embodiment of the present invention can thus provide visually-observable indicia of an open lid. For example, a flagging system can be implemented by painting or otherwise applying indicators (which can include, but is not limited to, for example, red paint) on an upper portion of flap 12 that is lifted up (and/or counterweight 20) when loading material. The flag system also shows when the lid is open for any reason after loading and can be visible from the ground without the need for an employee to climb atop the container. Overpouring material is also something considered by using the same red flag system, which allows for dividing the material that can have been accidentally poured on top of the lid to not interfere with the lid closing. In one embodiment, counterweight 20 is preferably formed into a wedge shape—for example with a triangle cross-section. This shape can allow counterweight 20 to push down through any sand that is atop sand or other granular material and which has thus built up under counterweight 20. Thus, the wedge-shape of counterweight 20 can help flaps 12 to close even when sand is piled up under counterweight 20.

In one embodiment, counterweight 20 can be triangle-shaped such that it is pointing down when closed. With this configuration, counterweight 20 will drop and more easily push through material that is in its way and which may have accumulated on top of the container.

This mesh 50 and/or screen 28 can be adapted to a customer specific size to allow material to flow freely during the loading process, while still catching any foreign material that can have been introduced to the material, thus preventing costly downtime on the job. The mesh 50 and/or screen 28 can optionally be affixed permanently to lid frame 14 and/or sidewalls 26, just as the lid is to the container, so that the right material goes into the container. For example, frac sand can be wet or dry and flow through a larger holed screen easily without getting caught thereon. Without a flow of material, lid 10 will stay closed, maintaining safety from large rocks, debris, animals, and even the limbs or workers people. Lid 10 is sized so that it fits under the safety of stacking poles on the corners of the container (if provided), so that it is not sheared off or otherwise crushed into the container. Lid 10 can be attached in multiple ways to any desired container, including via a hinge, which allows the entire lid to flop open if the container is being emptied from the top or a side.

Because lids for containers can, for various reasons, become separated from the container—for example as a result of aged hinge points, or the result of the operator not properly closing and securing them. If the container is being transported at high speed, this can cause such known lids to come off in transit due to the winds at high speed. In one embodiment, lid 10 is preferably configured to open simply by the flow of material into the container, and to close when material ceases to flow into the container, thus providing a lid which can open and close without a user needing to manually open and close the lid. In one embodiment, lid 10 is preferably welded or otherwise bolted to the container to provide a lid which is permanently affixed to the container. In one embodiment, should hinge pin 16 or the material around opening 18 wear out, regardless of the reason, counterweight 20 on an end portion of flap 12 is preferably made to be larger than an opening in sidewall 26 where hinge pin 16 is provided such that if flap 12 falls down, counterweight 20 will catch on an opening formed in a sidewall 26 through which flap 12 passes and will thus prevent flap 20 from falling clear of the rest of lid 10. This mitigates the risk of contaminated products in the box, or public risk of a lid coming off in transit and falling into oncoming or surrounding traffic.

In one embodiment, screen 28 can reduce the risk of contamination when material is being loaded into a container. Screen 28 can be made to a customer-specific size and configuration to allow material to flow freely during the loading process, while still catching any larger foreign material that can inadvertently be introduced, thus preventing costly downtime on the job. In one embodiment, screen 28 is preferably affixed permanently—for example by welding or bolting, so that the right material goes into the storage and transportation. For example, in one embodiment, frac sand can be potentially wet or dry and flow through larger openings in screen 28 without getting caught. Without flow of material, flaps 12 of lid 10 will stay closed, maintaining safety from large rocks, debris, animals, and people. In one embodiment, lid 10 is preferably sized such that it fits under the safety and stacking poles on the corners of a container when lid 10 is attached to the container. This prevents lid 10 from being sheared off of the container or otherwise crushed.

In one embodiment, as best illustrated in FIG. 9, elongated opening 46 can be provided along a lower portion of sidewall 26 such that water, which falls into opening 24 and atop flaps 12 (when they are in a closed configuration), can easily be discharged out of inlet 24 of lid 10. This is particularly useful when flaps 12 have a curved shape as illustrated in FIG. 6. Elongated opening 46 allows water to spill out if heavy rain is encountered while the container is in transit at high speed. In this embodiment, water piles up against flap sidewalls 40 and then spills over them and exits directly out through elongated opening 46. Discharge opening 44 allows water to weep out of when it is raining, and the container is not being transported at speed.

In one embodiment, mesh 50 can be flat, concave (as shown in FIGS. 8 and 10), convex (as shown in FIG. 11), or any other desired shape for a particular application. Regardless of whether mesh 50 is flat, concave, convex, or other, it can optionally be removable via fastener 56. Frame 54 can optionally be disposed around mesh 50 to stiffen it and help hold it in its shape and prevent deformation of mesh 50 or to otherwise facilitate attachment to the rest of lid 10. Optionally, frame 54 can be constructed to any desired height such that it also optionally functions as sidewalls to help retain material being poured through mesh 50. If mesh 50 is convex and if frame 54, is not of significant height, the mesh 50 can thus direct debris to fall away from opening 24, and prevent it from entering (for example things like rocks). Mesh 50 can optionally be attached to a top portion of frame 54, a middle portion of frame 54 and/or a bottom portion of frame 54. If mesh 50 is concave, it can assist in guiding material into a central portion of mesh 50 to help funnel material into the container and help avoid the material spilling out of lid 10 while it is being poured into the container.

In one embodiment, wiper brushes 90 can be provided on lid 10, as illustrated in FIGS. 12 and 13. Wiper brushes 96 are urged to move across mesh 50 or screen 28 each time flaps 12 open or close. In one embodiment, this can be achieved by positioning push bar 92 such that it is pushed by an upper top side of one or more flaps 12 being rotating in response to opening or closing of the lower portion of flaps 12. Because push bar 92 is preferably communicably coupled to brush 96 (for example via arms 94, when push bar 92 is urged by the upper portion of flap 12, brush 96 is caused to translate across at least a portion of mesh 50 or screen 28. FIG. 12 illustrates the positioning of a pair of brushes on opposing ends of mesh 50 when flaps 12 are in an open configuration, while FIG. 13 illustrates the positioning of brushes 96 near the center of mesh 50 when flaps 12 are in a closed configuration. Wiper brushes 96 sweep remaining debris off mesh 50 or screen 28 to keep them clean. In one embodiment, push bar 92 runs parallel to the side of lid 10 where hinge pin 16 and hinge opening 18 are located. Arms 94 are connected and run perpendicular to push bar 92. Arms 94 can run up to the length of opening 24. As flap 12 moves from a closed position to an open position (and vise-versa), push bar 92 is pushed/pulled by flap 12 which pushes/pulls brush 96 along the surface of mesh 50 or screen 28. Optionally, a plurality of standoffs 98 can be provided to accommodate any height difference between the end portion of flaps 12 when in an open and closed configuration. Of course, numerous other configurations, devices, and methods can be used to remove sand from atop mesh 50 or screen 28 when desired or otherwise in response to flaps 12 opening and/or closing.

In one embodiment, lid 10 can be incorporated into new builds of containers or an existing lid can be removed and replaced with lid 10. In one embodiment, lid 10 can be welded or bolted onto the container. For containers which are rounded, welding of lid 10 thereon is preferred to maintain the seal. Spot or stitch welding can be used for faster attachment. While seam welding can be used when ensuring dryness or sealing of container with product being transported.

The terms, “a”, “an”, “the”, and “said” mean “one or more” unless context explicitly dictates otherwise. Note that in the specification and claims, “about”, “approximately”, and/or “substantially” means within twenty percent (20%) of the amount, value, or condition given. When referring to an “open” and/or a “closed” configuration of the lid or the flaps of the lid, it is to be understood that the “closed” configuration can be an at least mostly closed configuration such that an air-tight seal is not required—for example, “closed” can mean that an opening is at least 95% closed as compared to its “open” configuration, such that small gaps, cracks, and/or spaces can still be present in a “closed” configuration. Likewise, in an “open” configuration, a 100% unrestricted opening is not required for an “open” configuration. Rather, an “open” configuration can be at least substantially “open”—even if a small amount of blockage or restriction is caused by a lid or a flap.

Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been described in detail with particular reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and this application is intended to cover, in the appended claims, all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, none of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguring their relationships with one another.

Claims

1. A self-closing lid comprising: a lid frame having an opening;a pair of counterbalanced flaps, each of said pair of counterbalanced flaps hingedly coupled to said lid frame and positioned such that said pair of counterbalanced flaps are disposed on opposing sides of said opening such that said pair of counterbalanced flaps rotate between an open configuration and a closed configuration, wherein said pair of counterbalanced flaps are counterbalanced such that said pair of counterbalanced flaps are biased into a closed configuration due to counterbalancing; anda screen positioned to screen material that passes through said opening.

2. The self-closing lid of claim 1 further comprising at least one water discharge opening disposed in said lid frame.

3. The self-closing lid of claim 1 wherein said pair of counterbalanced flaps are sized such that at least one of said pair of counterbalanced flaps comprises an end portion that overlaps an end portion of the other of said pair of counterbalanced flaps.

4. The self-closing lid of claim 1 wherein a portion of each of said pair of counterbalanced flaps passes through a respective opening in said frame.

5. The self-closing lid of claim 1 wherein said pair of counterbalanced flaps each comprise a counterbalance weight disposed thereon in a location that is outside of said lid frame.

6. The self-closing lid of claim 1 wherein said pair of counterbalanced flaps each comprise sidewalls that extend upward when said pair of counterbalanced flaps are in a closed configuration.

7. The self-closing lid of claim 1 wherein said pair of counterbalanced flaps are pitched when closed such that a terminal end portion of each respective flap is elevated higher with respect to a hinge location.

8. The self-closing lid of claim 1 wherein each of said pair of counterbalanced flaps are pitched to shed water to a first side and/or to a second side.

9. The self-closing lid of claim 1 wherein said screen is disposed within said opening in said lid frame.

10. The self-closing lid of claim 1 wherein said lid frame is hingedly coupled to a container.

11. The self-closing lid of claim 1 wherein said self-closing lid is configured to attach to a frac sand box.

12. The self-closing lid of claim 1 wherein said self-closing lid is disposed on a frac sand box.

13. The self-closing lid of claim 1 further comprising a mesh disposed above said opening of said lid frame.

14. The self-closing lid of claim 13 wherein said mesh is convex such that a center portion of said mesh is higher than an edge portion of said mesh.

15. The self-closing lid of claim 13 wherein said mesh is concave such that a center portion of said mesh is lower than an edge portion of said mesh.

16. The self-closing lid of claim 13 further comprising at least one wiper communicably coupled to at least one of said pair of counterbalanced flaps such that said at least one wiper moves across at least a portion of said mesh in response to movement by at least one of said pair of counterbalanced flaps.

17. The self-closing lid of claim 13 wherein said mesh is disposed within a mesh frame and wherein said mesh frame is movable with respect to said lid frame.

18. A method for automatically opening and closing a lid in response to a material being applied thereto, the method comprising: forming an opening in a lid;forming a frame around the opening;counterbalancing a pair of flaps and positioning them such that the pair of flaps is biased into a closed position with respect to the formed opening when weight of material is not applied to them; andpositioning a screen above the pair of flaps.

19. The method of claim 18 further comprising hingedly coupling the lid to a container.

20. The method of claim 18 wherein hingedly coupling the lid to a container comprises hingedly coupling the lid to a frac sand box.