Gravity ring

Abstract

A disaster shelter for mounting under ground. The shelter includes an entranceway having at least one air vent and a substantially hollow paraboloid shaped shelter cell. The shelter cell includes a paraboloid focus portion attached to the entranceway and paraboloid base portion disposed opposite the entranceway. A gravity ring is attached to the paraboloid base portion and is dimensioned such that the shelter is constrained within the ground when the water table reaches ground level.

Description

CLAIM OF PRIORITY

[0001] This application is a Continuation in Part of co-pending U.S. patent application Ser. No. 09/408,706, filed on Sep. 30, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of underground enclosures such as disaster shelters and, in particular, to means for retaining an enclosure within the ground, regardless of the level of a surrounding water table.

BACKGROUND OF THE INVENTION

[0003] History has shown that hurricanes, sudden tornadoes, and devastating earthquakes, can cause a significant loss of property and, more importantly, of human life. There are many ways to protect oneself from such catastrophic events. For example, cellars that are covered with concrete slabs or other sturdy rigid foundations may remain intact when in a worst-case scenario the upper housing structure is destroyed or blown away. However, there is no guarantee that the structures above these cellars will not crash downward into the cellar. Further, modular or mobile homes are built upon slabs and, accordingly, offer no protection against the devastating forces of a hurricane, tornado or earthquake.

[0004] A tornado may have swirling winds forces that can reach speeds of over 200 MPH. This kind of wind force creates a type of suction force that has a tendency to pick up all sorts of structures to transport the same to a different location. Accordingly, it is important that people have strong shelters available within a short distance or in close proximity to where they live.

[0005] A number of underground shelters have been developed to protect inhabitants in the event of a hurricane or tornado. U.S. Pat. No. 5,829,208 issued Nov. 3, 1998 describes a steel reinforced cylindrical structure having a bell-shaped end at one end and a spigot at the other end. It is of a size to comfortably protect up to 10 people within its interior. One end of the structure is closed by a concrete end wall while the other end is partially closed by a slanting concrete deflector wall. The deflector wall at its upper end may or may not be fastened to the top of the cylindrical structure.

[0006] Although this structure could protect individuals from minor inclement weather, the design creates inherent problems during a disaster. First, concrete will leak while under ground for a long period of time. Thus, during a hurricane, the structure will leak, and the porous character inherent in concrete will only be augmented by winter freezing. Second, the cylindrical structure will not provide protection from a tornado, or strong hurricane winds. While cylinders provide protection from an evenly distributed force, a point force will crush the structure. Third, the structure is designed to be only partially underground which makes it vulnerable to heavy winds and complete exposure during a tornado, which would render the structure useless, and would crumble in the event of an earthquake. Fourth, this structure does not provide a life support system to provide fresh air in the event the disaster lasts longer than a few hours. Fifth, there are no communications devices in the event of a medical emergency, or inability to escape from the shelter because of heavy debris. Sixth, this shelter contains no structural elements that would prevent uplifting during times of high ground water. Finally, this shelter provides a single means of entry and egress, creating a possibility that inhabitants will be trapped by fallen debris.

[0007] U.S. Pat. No. 4,615,158 issued Oct. 7, 1986 describes a tornado shelter, specially adapted for use with mobile home lots. The shelter is an underground enclosure defined by an annular sidewall and a top and bottom. The top enclosure has an entrance and egress passageway in communication with both the enclosure and the bottom of a mobile home.

[0008] Although this shelter may provide protection from a low force tornado which lasts for a short period of time, or a short lived weak hurricane, this shelter is not suited to protect inhabitants from a Force 5 tornado, forceful hurricane or earth quake. The invention has a cylindrical shape, which only acts to disperse forces evenly over the entire structure when the force acts upon the structure evenly. If a hard force hits just one area of the structure, it will tend to buckle and destroy its integrity. The shelter is constructed from steel cylinder sidewalls and a concrete floor, which has a tendency to leak over time. This shelter provides an entranceway made of a removable board from the floor of the mobile home, followed by a tube connecting the mobile home to the shelter. Therefore, if the mobile home is pulled off its foundation, the entrance tube will be openly exposed to the forceful winds of a tornado or hurricane. Since this tube is not in the ground, the result will most likely be a complete destruction of the entrance tube, and therefore full exposure of the inside of the shelter to the forceful winds and rain. Finally, this shelter also lacks all life sustaining mechanisms.

[0009] U.S. Pat. No. 4,955,166 issued Sep. 11, 1990 describes a generally spherical tornado shelter for safely housing and protecting people and things underground in the form of a truncated globe that is formed from a curved sidewall and terminates in the floor at the lower end thereof. The spherical shelter is preferably made of fiberglass and has a generally rectangular entrance formed in spaced relation to the central axis and provides a doorway into the interior of the structure. A plurality of steps lead from the entrance down the floor and enables people to conveniently walk through the entrance, down the steps, into and back up from the shelter.

[0010] Although this invention may provide protection from a low force tornado, this shelter has a structural design which will render the invention vulnerable in the event of a high force tornado or hurricane. Although made of fiberglass and virtually leak proof, the spherical shape is inherently weak when acted upon by point forces. The entrance is rectangular in shape and therefore susceptible to destruction by heavy force winds. Finally, even if the entrance remains intact through the disaster, a large amount of debris may become packed against the doorway, trapping the inhabitants inside.

[0011] In response to the above reference problems with existing shelters, the inventor of the present invention has developed a shelter that utilizes a fiberglass shell in the form of a partial or full parabaloid, which is buried within the-earth with one parabaloid focus facing upward toward the level of the earth. This type of shelter is structurally superior to the shelters noted above and, because they are not intended to provide shelter from nuclear fallout, can be buried fairly close to ground level. However, the combination of the watertightness of the shelter, burial close to ground level, and the small amount of surface area of the shelter upon which the earth extents its force, created the need for a means for retaining the shelter within the ground when the surrounding water table rises to ground level.

[0012] Prior art shelters have dealt with this problem in two distinct ways. The first is to utilize concrete, either as part of the structure or as an “anchor” for the structure, to hold the structure in place. As noted above, concrete structures are notoriously leaky and, therefore, are not preferred. Further, the use of concrete anchors requires the use of cables or other ties from a point on the shelter to the anchor, creating point forces upon the shelter, which can reduce its structural integrity. Finally, the need to pour concrete at the shelter site dramatically increases the cost of installation of the structure. Accordingly, concrete is not an acceptable means for retraining a shelter within the ground.

[0013] The second way that prior shelters have been restrained has been to bury the shelter deeply within the ground and at such an orientation so as to provide a large surface area upon which the earth may bear, effectively counterbalancing the upward buoyancy forces upon the shelter. This method has been very effective in applications, such as nuclear fallout shelters, where deep burial is desirable. However, where weather is of primary concern, deep burial is unnecessary and adds significantly to the cost of installation. Further, the need to increase the structural strength of the shelter in order to accommodate the increased ground force, and the need to provide a separate sealed entranceway in order to access the shelter, significantly increases the cost of the shelters themselves.

[0014] Therefore, there is a need for a disaster shelter that provides protection from a tornado, hurricane, earthquake, chemical or biological disaster, that will not leak while under ground for a long period of time, that will not be crushed by a point force upon the structure, that will not be lifted from the ground in the event of high water table, that does not require the use of concrete anchors or concrete integral to the shelter itself, and that does not need to be buried deeply within the ground.

SUMMARY OF THE INVENTION

[0015] The present invention is a gravity ring and a disaster shelter upon which the gravity ring may be mounted. The combined gravity ring and disaster shelter may be shallowly buried under ground such that shelterists are protected from natural disasters such as tornadoes and hurricanes, and from human made disasters, such as bombs, armed invasions or the like.

[0016] In its most basic form, the gravity ring of the present invention has a second surface that is dimensioned for attachment to an underground enclosure such that the downward force of the earth upon the gravity ring is transferred to the enclosure. The gravity ring also includes a first surface that extends outward from the enclosure and is dimensioned such that a force exerted upon the second surface by the earth is sufficient to constrain the enclosure within the ground when a water table reaches a level of the ground. As will be discussed in detail below, although the present invention is referred to as a “gravity ring”, it is understood that the invention is not limited to conventional “rings”, but rather refers to any means for counterbalancing a buoyancy force upon an enclosure utilizing the weight of the earth surrounding the enclosure. Accordingly, the term “gravity ring” should not be read as being so limited.

[0017] In the preferred embodiment, the gravity ring is not fixedly attached to the enclosure, but includes a second surface that is an inner surface of a substantially cylindrical ring and is dimensioned to create and interference fit with the top portion of a parabaloid shaped enclosure, or with an extended ridge extending from a cylindrical enclosure. The first surface of the preferred gravity ring extends outward and upward in the shape of a partial dome in order to increase the surface area acted upon by the earth and to provide increased structural integrity over flat, flange-like, surfaces. However, in other embodiments, the first surface may be a flat surface and the gravity ring may be of a non cylindrical shape and be permanently or removably attached to the shelter using art recognized means.

[0018] In embodiments where a full parabaloid is not utilized, the gravity ring preferably does not include an inner surface, but rather the first and second surfaces are portions of a continuous top surface of the ring. In these embodiments, the sidewalls of the enclosure are attached to the top surface of the ring along its second surface, and the portion of the ring that extends beyond the outside of the sidewall of the enclosure forms the first surface upon which the ground bears.

[0019] In the preferred embodiment, the gravity ring is dimensioned to restrain a disaster shelter within the ground. However, it is recognized that the gravity ring of the present invention has broader application to other types of subterranean enclosures. For example, in some embodiments, the gravity ring is dimensioned to restrain an underground fuel storage tank, while in others it is dimensioned to restrain a septic tank. Further, it is recognized that the gravity ring may be dimensioned to take different shapes than those dimensioned to engage the full and partial parabaloid shaped disaster shelters disclosed herein. Accordingly, the gravity ring of the present invention should not be limited to application in connection solely with the particular embodiments of the disaster shelters described herein.

[0020] In its most basic form, the disaster shelter includes an entranceway having at least one air vent and a substantially hollow shelter cell. The shelter cell includes a entrance portion attached to the entranceway and base portion disposed opposite the entranceway. A gravity ring extends from, and exerts a downward force upon, the base portion and is dimensioned such that the shelter is constrained within the ground when the water table reaches ground level.

[0021] The preferred disaster shelter includes a life support system made up of an air intake duct, an air filter, a blower and at least one battery. The air filter is preferably a highly efficient particulate air filter that filters particles from the air. The preferred blower includes an exhaust disposed within said shelter cell and wherein said exhaust is positioned to create cyclonic air movement within said shelter cell. The preferred battery comprises is a one twelve volt deep cycle battery having sufficient electrical energy, when fully charged, to power the blower to supply between 40 and 60 cubic feet per minute of air for six days. In some embodiments a battery charger, such a solar panel, charges the battery.

[0022] The preferred entranceway includes a substantially cylindrical manway attached to the focus portion of the shelter cell. A hatch dome ring is disposed about, and extends outward from, the manway and a hatch dome cover is removably attached to the hatch dome ring such that the hatch dome cover forms a weather resistant seal with the hatch dome ring The preferred manway includes an air inlet and an air outlet, while the preferred hatch dome ring includes at least one inlet vent opening and at least one outlet vent opening. In such an embodiment, it is preferred that inlet vent opening and outlet vent opening be dimensioned and disposed relative to the air inlet and air outlet such that rain is prevented from entering the air inlet and air outlet. The preferred hatch dome cover is hatch dome ring form a substantially continuous surface having an angle of incidence of less than twenty degrees in order to protect the shelter from damage due to flying debris.

[0023] The preferred disaster shelter is manufactured of structural fiberglass that is capable of withstanding up to ten pounds per square inch of overpressure and an earthquake of an intensity of up to 8.5 on a Richter scale. An emergency escape manway is disposed through a sidewall of the preferred shelter cell to allow egress in the event that the hatch dome cover cannot be opened. Finally, the preferred shelter includes a communications device, such as a two-way radio, for communicating with the outside world. In this preferred shelter, the two-way radio includes a retractable antenna to avoid damage during a tornado or other disaster.

[0024] Therefore, it is an aspect of the invention to provide a disaster shelter that provides protection from a tornado, hurricane, earthquake, chemical or biological disaster.

[0025] It is a further aspect of the invention to provide a disaster shelter that will not leak while under ground for a long period of time.

[0026] It is a further aspect of the invention to provide a disaster shelter that will not be crushed by a point force upon the structure.

[0027] It is a further aspect of the invention to provide a disaster shelter that includes a life support system for maintaining breathable air within the shelter.

[0028] It is a further aspect of the invention to provide a gravity ring that allows an enclosure to remain restrained in the ground in areas of high water tables without the need for cables or other wires that can damage the enclosure during an earthquake or other ground shock.

[0029] It is a further aspect of the invention to provide a gravity ring that allows an enclosure to avoid the use of concrete as part of the structure of the enclosure.

[0030] It is a further aspect of the invention to provide a gravity ring that allows an enclosure to be buried a short distance from the surface of the ground.

[0031] These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a side view of one embodiment of the gravity ring of the present invention attached to a disaster shelter.

[0033] FIG. 2 is a side view of the preferred embodiment of the gravity ring of the present invention attached to a full parabaloid disaster shelter.

[0034] FIG. 3 is a top view of the preferred embodiment of the gravity ring of the present invention

[0035] FIG. 4 is a cut-away side view of one embodiment of the disaster shelter of the present invention.

[0036] FIG. 5 is a top isometric view of the preferred hatch dome ring.

[0037] FIG. 6 is a cut away isometric view of the preferred embodiment of the disaster shelter of the present invention.

[0038] FIG. 7A is an end view of an underground storage tank utilizing an alternative embodiment of the gravity ring.

[0039] FIG. 7B is an end view of the embodiment of FIG. 7A.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Referring first to FIG. 1, a side view of one embodiment of the disaster shelter 10 is shown. The disaster shelter 10 includes a substantially hollow paraboloid shaped shelter cell 12 and an entranceway 14 having at least one air vent opening 22 disposed therethrough. The shelter cell 12 is preferably manufactured of structural fiberglass and is oriented such that the paraboloid focus portion 16 is attached to entranceway 14 and the paraboloid base portion 18 is disposed opposite of the entranceway 14. The preferred shelter shell is a paraboloid bell having a 1:1.7 elliptical ratio. This paraboloid shape optimizes the structural integrity of the fiberglass, as it will not buckle or be destroyed by strong point forces.

[0041] In the embodiment of FIG. 1, the gravity ring 20 is attached to, and surrounds the paraboloid base portion 18. The gravity ring 20 allows the system to remain constrained within the ground, even in areas where the water table reaches ground level, without the need for separate tie-downs or bulky concrete footings, where the water table, below which the ground is completely saturated with water. Under this circumstance, the disaster shelter 10 displaces water creating approximately 28,900 lbs. of hydrostatic pressure or upward “buoyancy” force, but is held stable in the ground by the gravity ring 20, which generates approximately 35,650 pounds of downward “gravity” force. Such a positive gravity force allows the disaster shelter 10 of the present invention to be restrained underground without the need for separate restraining cables, as are commonly used to restrain underground tanks. The elimination of these cables is a significant benefit as they create very localized stress, which may damage the structure during ground shock from heavy traffic or earthquakes. Conversely, the gravity ring 20 creates uniform stresses around the disaster shelter 10, effectively eliminating local stresses.

[0042] Although the gravity ring 20 of FIG. 1 is shown as being attached to the base portion 18 of a partial parabaloid shelter cell 12, there are a number of different ways in which the gravity ring 20 may be utilized. As shown in FIGS. 2 and 3, a separate and removable gravity ring 120 forms an interference fit with a full parabaloid shelter cell 122. The gravity ring 120 of FIGS. 2 and 3 includes a second surface 130 that forms a cylinder having a diameter D, which is dimensioned to engage the outer surface of the shelter cell 122. As shown in FIG. 2, the preferred diameter D is equal to approximately ninety nine percent (99%) of the maximum diameter of the parabaloid shelter cell 122. However, the second surface 130 may take any dimension, so long as it will allow the gravity ring to engage the enclosure.

[0043] In some embodiments, such as those in which a cylindrical tank (not shown) is buried on its end, the tank may include a flange or series of shelves disposed about the outside surface and the diameter D may be dimensioned to be slightly larger than the diameter of the tank. In these embodiments, the first surface is not the inside cylindrical surface, but is part of the bottom surface of the ring 120 that engages the flange. Similarly, gravity rings may be dimensioned to engage flanges or shelves disposed upon the outsides of other non-cylindrical tanks in substantially the same manner. Accordingly, the gravity ring 120 should not be seen as being limited to interference fit rings or rings that are substantially cylindrical.

[0044] The gravity ring of FIGS. 2 and 3 also includes a first surface 128 that extends outward from the shelter cell 122 and is dimensioned such that a force exerted upon the second surface 128 by the earth is sufficient to constrain the shelter cell 122 within the ground when a water table reaches a level of the ground. In the preferred embodiment, the surface area of the first surface 128 is designed to exert one hundred and twenty percent (120%) of the upward buoyancy force exerted upon the shelter, given a ground density of seventy pounds per cubic foot. This calculation provides an adequate factor of safety, and meets the requirements of current underground enclosure standards. However, it is recognized that a calculation using a smaller percentage relative to buoyancy, or a higher ground density, may be utilized, provided the total is at least equal to the total buoyancy force exerted when the water table reaches ground level.

[0045] The gravity ring of FIGS. 2 and 3 is preferably manufactured of structural fiberglass and is dimensioned such that the first surface 128 extends upward in the form of a dish. In the preferred embodiment, the radius R formed by the first surface 128 is equal to one half of the diameter D of the second surface 130 of the gravity ring. This is preferred as it provides a structurally stable member having increased surface area upon which the ground may bear. However, it is recognized that gravity rings 120 having different cross sections may be substituted to achieve similar results.

[0046] As noted above, it is preferred that the gravity ring and disaster shelter be manufactured of structural fiberglass. Although other materials, such as stainless steel and the like, may be utilized, structural fiberglass is preferred for a number of reasons. First, fiberglass provides extremely high resiliency and corrosion resistance and has a tendency to remain intact if overstressed. Second, it may be easily shaped into the hollow compound curved structure that makes up the paraboloid shelter cell 12. Third, fiberglass forms a complete vapor barrier, which provides a dry atmosphere when placed below ground, and it has proven to be sound in the underground storage tank industry. Fourth, structural fiberglass is a poor thermal conductor so there is little to no “sweating” on the inside walls during occupancy. Finally, structural fiberglass does not conduct electricity. This is important as hurricanes and tornadoes commonly have severe and numerous lighting strikes often topple power poles and above ground structures leaving live electrical wires sparking on the ground. Accordingly, a disaster shelter 10 manufactured from structural fiberglass is safe to use even if in direct contact with live power lines or directly struck by lightning.

[0047] Referring now to FIG. 4, the inside of one embodiment of the disaster shelter 10 is shown. This embodiment includes a life support system 24 that provides breathable air to the occupants of the shelter 10. The life support system 24 includes an air intake duct 26 in fluid communication with an air vent (not shown). An air filter 28 is in fluid communication with the air intake duct 26 and acts to filter the incoming air. A blower 30 is in fluid communication with the outlet of the air filter 28 and circulates the air within the shelter cell 12. Finally, at least one battery 32 is placed in electrical communication with the blower 30, providing power to allow the blower to operate.

[0048] As shown in FIG. 4, the air intake duct 26 enters the shelter cell 12 through an opening in the shelter cell 12. However, in other embodiments, such at the embodiment of FIG. 5, the air intake duct 26 is disposed entirely within the shelter cell 12 and is in communication with the air vent via an air inlet 27 disposed through the entranceway 14. The air intake duct 26 is preferably manufactured of corrugated plastic smooth bore hose. However, other art recognized duct materials may be substituted to achieve similar results.

[0049] The air filter 28 receives the incoming air from the air intake duct 26 and filters it in a predetermined manner. In the preferred embodiment, the air filter 28 is a highly effective particulate air filter (hereafter HEPA filter) that is capable of removing 99.99% of particles, larger than 0.3 microns in size, from the air. Accordingly, the HEPA filter will remove all physical particles such as dust, aerosols, and pollen, from the incoming air. In other embodiments, however, the air filter 28 also includes a carbon filter (not shown) for filtering chemical and biological contaminants from the air. Such a carbon filter would preferably include both an activated carbon filter medium and a whetlerite carbon filter medium and would be disposed at the outlet of the HEPA filter.

[0050] The blower 30 is in fluid communication with the outlet of the air filter 28. The The preferred blower is a battery-powered reverse curve motorized impeller. This preferred blower has a 60,000 hour life and supplies an air stream of 40 cubic feet per minute (CFM) into the interior of shelter cell 12. Given an interior volume of 474 cubic feet in the preferred shelter cell 12, the preferred blower 30 provides an air change within the shelter cell 12 every twelve minutes. The exhaust of the blower 30 is preferably positioned such that it creates cyclonic air movement within the shelter. The warm spiraling spent air rises up to vent out around the hatch dome. This air may be exhausted through the same air vent 27 through which incoming air is taken. However, as shown in FIGS. 4 and 5, exhaust air may also be vented through a dedicated air outlet 29. The air supply rate and positioning of the preferred blower 30 places the shelter under positive pressure and has proven to work extremely well at maintaining constant oxygen, carbon dioxide, and moisture levels.

[0051] The preferred blower 30 includes an on/off switch that allows the blower 30 to be disengaged when ground fires, or other airborne contaminants, are present around the hatch dome. During such a time, the shelterists must breathe in a sealed shelter atmosphere. The safe duration time for sealed operation is based on a 3% carbon dioxide limit and, therefore, is a function of the number of shelterists, degree of physical activity of the shelterists, and the volume of the shelter cell 12 above the floor 34. In the preferred embodiment, six shelterists who are mildly active can be in the shelter cell 12 for approximately 4 hours before reaching the 3% CO2 limit.

[0052] The battery 32 provides power to the blower 30, as well as to other electrically powered devices, such as lights, two-way radio's, scanners or the like, that are utilized within the shelter cell 12. In the preferred embodiment, the battery 32 is made up of three, twelve volt-110 amp deep cycle marine batteries contains sufficient electrical energy, when fully charged, to power the blower for up to six days at air flow rates of 40 and 60 cubic feet per minute. However, other batteries, having different power levels and providing different useful lives, may be utilized to achieve similar results. During non-disaster time, the battery 32 will suffer a very minor loss of charge. Accordingly, the preferred disaster shelter 10 also includes a battery charger 36 for recharging the battery. In some embodiments, a solar panel (not shown) made up of photovoltaic cells is disposed above the level of the ground 42 and are wired to the battery 32. In this manner, the battery 32 is allowed to trickle charge via the electrical energy generated by the solar panel 38. However, in other embodiments, different battery chargers 36 may be utilized. For example, the battery 32 may be charged by an automobile and a heavy-duty set of jumper cables run from the automobile through the entranceway 14 to the battery 32.

[0053] The embodiment of FIG. 4 also includes an emergency escape manway 44 disposed through the side wall 46 of the shelter cell 12 to provide a means of egress from the shelter in the event that the entranceway 14 is unable to be opened due to heavy debris or damage. If a heavy object, such as a car, comes to rest on top of the entranceway 14, the emergency escape manway 44 provides the shelterist with the ability to dig upwards and sideways to get around the object. Accordingly, it is preferred that crushed stone be used to backfill around the emergency escape manway 44 if the disaster shelter 10 is installed in cold climates where the ground freezes.

[0054] The preferred embodiment of the emergency escape manway 44 includes a manway cover 48 that may be unbolted from the inside of the shelter cell 12 to allow shelterists to dig upwards to the level of the ground 42. After an emergency exit, the preferred manway cover 48 may be re-bolted and backfill material can be taken up to the surface using a five-gallon bucket and rope and re-backfilled.

[0055] In the embodiment of FIG. 4, the entranceway 14 is made up of a substantially cylindrical manway 50 attached to said focus portion 16 of said shelter cell 12. A hatch dome ring 52 is disposed about, and extends outward from, the manway 50. Finally, a hatch dome cover 54 is removably attached to the hatch dome ring 52 such a weather resistant seal is formed between the hatch dome cover 54 and the hatch dome ring 52. The hatch dome cover 54 is preferably of a dome shape and is dimensioned to sit within a groove 56 in the hatch dome ring 52. In some embodiments, a common gasket is applied between the groove 56 and hatch dome cover 54 to enhance leak protection. When mounted to the preferred hatch dome ring 52, the preferred hatch dome cover 54 and hatch dome ring 52 form a dome having an angle of incidence A of approximately twenty degrees (20°). This low angle of incidence A prevents the shelter 10 from being displaced by high winds and allows the hatch dome cover 54 and hatch dome ring 52 to deflect flying debris during a tornado or hurricane without damage.

[0056] The preferred hatch dome cover 54 and hatch dome ring 52 are made of an intumescent laminate material called COMBAT COMPOSITE™ material, which is a structural fire-and bullet-resistant laminate developed by Radius Defense Inc. of Northwood, N.H. The hatch dome is also designed to protect the shelter from a fire reaching 1700° F. for one hour while maintaining its structural integrity in compliance to A.S.T.M. E119. This design and material makes the preferred shelter 10 very stealthy. It produces little or no thermal signature, little or no metallic signature, and little or no radar signature, making it almost impossible to be detected by modern target acquisition equipment. Although the hatch dome cover 54 is not impenetrable, it is manufactured according to The National Institute of Justice (NIJ) standards from Class 0 up to Class IV to resist penetration by various threats, and is specifically designed to resist seven basic assaults from people trying to break into the shelter.

[0057] As shown in FIG. 4, the hatch dome cover 54 may be secured from the inside of the shelter cell 12 via a locking mechanism 58, such as a pivot hinge 59. The preferred pivot hinge 59 is a stainless steel vertical pivot hinge that mounted inside of the entranceway 14 and is capable of lifting the hatch dome cover 54 even when it is covered with up to six tons of debris. In another embodiment, the locking mechanism 58 utilizes an external hinge that fits within a pocket (not shown) in the hatch dome ring 52 and an integral locking bar, which secures the hatch dome cover 54 to the hatch dome ring 52. The combination of the integral hinge and locking bar allows the hatch dome cover 54 to be quickly closed and locked in the event that a shelterist is pursued by an intruder, and to resist pressures of negative 5 PSIG created by a blast or tornado. In the preferred embodiment, the hatch dome cover 54 is connected to the hatch dome ring by an external recessed hinge which allows the hatch dome cover 54 to open 160 degrees. This allows fast and easy submarine type entry. Three self-positioning forged hatch clamps secure the hatch dome cover 54. In this preferred embodiment, each hatch clamp is designed to resist 5000 lbs. of uplifting force caused by the negative pressure of a tornado or explosion. Once the hatch dome cover 54 is pulled closed, the three spring-loaded hatch clamps are rotated by hand 90 degrees and the wing nut on each hatch clamp is tightened by hand.

[0058] Referring now to FIG. 5, an isometric view of the preferred hatch dome ring 52 is shown. As noted above, the hatch dome ring 52 is disposed about, and extends outward from, the manway 50. In this manner, the hatch dome ring 52 and acts to shield the air inlet 27 and air outlet 29 from the elements. The preferred hatch dome ring 52 is mounted with its bottom rim 60 disposed at ground level to prevent high winds from hitting the underside of the hatch dome ring 52. Thus, the top surface 62 of the hatch dome ring 20 includes at least one inlet vent opening 64 and at least one outlet vent opening 66 to allow gasses to enter and exit the area between the hatch dome ring and the manway 50. The top surface 62 of the preferred hatch dome ring 52 also includes a recessed groove 56 disposed about the open top for mating with the hatch dome cover (not shown) and at least one notch 74 that is sized to allow a hinge to be utilized to attach the hatch dome cover to the hatch dome ring 20. In addition, a number of rain gullies 76 may be utilized to drain trapped water from the area surrounding the recessed groove 56.

[0059] In the preferred embodiment, multiple small vent openings 64, 66 are utilized to provide sufficient airflow to and from the air inlet 27 and air outlet 29. These vent openings 64, 66 are preferably sized to prevent sabotage by an intruder utilizing an implement, such as a grappling hook. The vent openings 64, 66 on the top surface 62 of the hatch dome ring 52 are preferably not disposed directly above the air inlet 27 and air outlet 27. This arrangement causes a venturi effect, where the air and rain pass through the openings 64, 66 at high velocity and immediately slow upon entering the area under the hatch dome ring 52, effectively dropping to the rain to the ground prior to entering either the air inlet 27 or air outlet 29. The bottom surface 68 of the preferred hatch dome ring 20 includes a pair of baffles 70, 72. These baffles 70, 72 are disposed in predetermined locations relative to the air inlet 27 and air outlet 29 in order to prevent gasses exhausted through the air outlet 29 from being sucked into the air inlet 27.

[0060] In some embodiments of the invention, an entranceway such as that disclosed in the Applicant's co-pending application Ser. No. 09/330,870, titled ENTRANCEWAY AND DISASTER SHELTER UTILIZING THE SAME, and incorporated herein by reference, is utilized. In still other embodiments, a variation of the entranceway of the Applicant's co-pending application is utilized. This alternative entranceway 14, shown with reference to FIGS. 5-7, includes a leaching septic tank 102 a vertically oriented HEPA filter 104, and a plunger valve 118 disposed between the air inlet 27 and HEPA filter 104.

[0061] As shown in FIG. 6, the preferred septic tank 102 is an extruded half-paraboloid tank that is designed to withstand external pressure of at least 50 PSIG, such as is generated by a nuclear blast or heavy traffic over the shelter. The septic tank 102 includes a plurality of openings 106 that allow solid waste to collect within the tank 102, while allowing liquid waste to leach out into the surrounding soil. The septic tank 102 includes a pump port 108 that allows the solid and liquid wastes to be manually pumped from the tank 102. The pump port 108 is preferably disposed upon the top of the tank 102 and, when installed, is located approximately twelve inches below the level of the ground and must be excavated prior to pumping. However, in other embodiments, an extension pipe (not shown) between the pump port 108 and ground level may be included to eliminate this need to excavate. The preferred septic tank 102 also includes a septic vent 110 that passes from the tank 102 and terminates under the hatch dome ring 52 and allows gasses, such as methane, generated during decomposition to vent through the outlet vent opening 66 to the surrounding atmosphere. The vertically oriented HEPA filter 104 conserves space around the entranceway 14 and allows a clear twenty-four inch diameter manway opening to be utilized.

[0062] Referring again to FIG. 6, the shelter 10 is dimensioned to allow a shelterist 80 to comfortably stand within the shelter cell 12. In addition to the features discussed above, the preferred disaster shelter 10 also includes a communication device 82 and a light 84 in electrical communication with the battery 32. It is preferred that that light 84 be flourescent light, due to the low power requirements and low heat generation of such lights. However, incandescent lights 84 may be utilized to achieve similar results. The preferred communication device 82 includes a pair of radios, such as a 12-volt CB/weather band radio and scanner.. The CB/weather radio allows shelterists to keep track of tornado activity and allows two-way communications to local people. The optional scanner allows monitoring of all AM, FM, search and rescue, fire, police, aircraft, weather, and numerous other frequencies in the local area.

[0063] Referring now to FIGS. 7A and 7B, an alternative embodiment of the gravity rings is shown. In this embodiment, adapted for use with a cylindrical underground storage tank 222 mounted horizontally within the ground, the gravity ring is made up of two semi-cylindrical extensions 220 that are attached to, and project outward from, either end 224 of the tank 222. As was the case with the gravity rings discussed above, these extensions 220 each include a first surface 230 that is dimensioned to transfer a downward force generated by the ground to the tank in order to counterbalance the upward buoyancy force created when the water table reaches ground level.

[0064] The gravity ring of FIGS. 7A and 7B is preferably mounted to the bottom of a storage tank via art-recognized means. In cases where the tanks are manufactured to metal, this may be via welding or bolting. In cases where fiberglass tanks are utilized, the extensions 220 may be laminated directly to the bottom of the tank or formed integral thereto.

[0065] Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

Claims

1. A gravity ring for restraining an enclosure below a quantity of earth, wherein said quantity of earth forms a ground level, and wherein said gravity ring comprises:

a first surface that extends outward from an outer surface of said enclosure, said second surface being dimensioned such that a force exerted upon the second surface by said quantity of earth disposed upon said first surface is sufficient to constrain said enclosure below said ground level when a water table reaches said ground level; and

a second surface in communication with said first surface, wherein said second surface is dimensioned for engagement with said enclosure such that said downward force exerted upon said first surface by said quantity of earth is transferred through said second surface to said enclosure.

2. The gravity ring as claimed in claim 1 wherein said second surface is an inner surface of a substantially cylindrical ring.

3. The gravity ring as claimed in claim 2 wherein said enclosure comprises a parabaloid shaped top portion and wherein second surface is dimensioned to create an interference fit with said outer surface of said enclosure.

4. The gravity ring as claimed in claim 2 wherein said first surface is dimensioned to form a curved inner surface extending upward towards said ground level.

5. The gravity ring as claimed in claim 4 wherein said enclosure comprises a parabaloid shaped top portion and wherein second surface is dimensioned to create an interference fit with said outer surface of said enclosure.

6. The gravity ring as claimed in claim 1 wherein said gravity ring is manufactured of a fiberglass composite material.

7. The gravity ring as claimed in claim 6 wherein said enclosure is manufactured of a fiberglass composite material and wherein said gravity ring is attached to said enclosure.

8. The gravity ring as claimed in claim 7 wherein said gravity ring is substantially permanently attached to said enclosure.

9. The gravity ring as claimed in claim 7 wherein said enclosure is removably attached to said enclosure.

10. A disaster shelter for mounting below a quantity of earth, wherein said quantity of earth forms a ground level, and wherein said disaster shelter comprises:

an entranceway;

a shelter cell, said shelter cell having an entrance portion attached to said entranceway and base portion disposed opposite said entranceway; and

a gravity ring disposed about said base portion, said gravity ring comprising;

a first surface that extends outward from an outer surface of said shelter cell, said second surface being dimensioned such that a force exerted upon the second surface by said quantity of earth disposed upon said first surface is sufficient to constrain said shelter below said ground level when a water table reaches said ground level; and

a second surface in communication with said first surface, wherein said second surface is dimensioned for engagement with said shelter cell such that said downward force exerted upon said first surface by said quantity of earth is transferred through said second surface to said shelter cell.

11. The disaster shelter as claimed in claim 10 wherein said entrance portion of said shelter cell is dimensioned to form a partial parabaloid having a paraboloid focus portion attached to said entranceway.

12. The disaster shelter as claimed in claim 11 wherein said entrance portion and said bas portion of said shelter cell to form a substantially full parabaloid shaped shelter cell.

13. The disaster shelter as claimed in claim 11 wherein said entranceway further comprises a substantially cylindrical manway attached to said focus portion of said shelter cell, a hatch dome ring disposed about, and extending outward from, said manway, and a hatch dome cover removably attached to said hatch dome ring such that said hatch dome cover forms a weather resistant seal with said hatch dome ring

14. The disaster shelter as claimed in claim 10, wherein said shelter cell is manufactured of structural fiberglass.

15. The disaster shelter as claimed in claim 10 further comprising an emergency escape manway disposed through a sidewall of said shelter cell.

16. An underground enclosure for mounting below a quantity of earth, wherein said quantity of earth forms a ground level, and wherein said enclosure comprises:

a substantially hollow tank portion; and

a gravity ring disposed about said tank portion such that said gravity ring applies a downward force upon said tank portion, said gravity ring comprising;

a first surface that extends outward from an outer surface of said tank portion, said second surface being dimensioned such that a force exerted upon the second surface by said quantity of earth disposed upon said first surface is sufficient to constrain said tank portion below said ground level when a water table reaches said ground level; and

a second surface in communication with said first surface, wherein said second surface is dimensioned for engagement with said tank portion such that said downward force exerted upon said first surface by said quantity of earth is transferred through said second surface to said tank portion.

17. The underground enclosure as claimed in claim 16, wherein said tank portion comprises a substantially cylindrical tank portion and wherein said gravity ring comprises a first extension portion extending outwardly from a first end of said tank portion and a second extension portion extending outwardly from a second end of said tank portion.

18. The underground enclosure as claimed in claim 17 wherein at least a portion of said tank portion and said gravity ring are manufactured of structural fiberglass.