Prefabricated emergency shelter

An emergency shelter to be used under the floor of a residential or commercial structure. In the preferred embodiment, a prefabricated acrylic shelter is sized to accommodate at least one individual in a crouching or sitting position. The shelter is placed prior to the pouring of a slab foundation or the building of the floor in a pier and beam foundation. The unit is sealed to prevent moisture infiltration and provides the benefits of a relatively pleasant surface without the accumulation of moisture. Additional advantages are the relative lower expense, light weight, and ease of installation of the prefabricated shelter. Other uses of the shelter include security and storage.

FIELD OF INVENTION
 This invention relates to prefabricated storm shelters.
 BACKGROUND
 Underground storm shelters have proven to be effective shelters for
 tornados in many parts of the country. Buried or partially buried storm
 shelters have been used for many years. The difficulties of incorporating
 buried storm shelters in residential constructions and neighborhoods
 include the expense, the lack of space associated with the standard lot,
 and the presence of shallow bedrock in many areas. The fabrication of
 traditional storm shelters is also relatively expensive.
 The recommended procedure for tornado alerts in many parts of the country
 is for the residents to move to the center part of their house, such as an
 interior bathroom or closet. While this strategy is generally effective,
 there are cases of extremely high winds where residents are not safe in
 any part of the house and where the only practical effective shelter is
 one that is below the foundation of the home or buried in the vicinity of
 the home.
 The most common material of construction of existing storm shelters is
 concrete, which may either be prefabricated in one or more sections for
 site assembly; or poured in place structures. Although the concrete
 shelters are strong, there are several disadvantages to that material
 including difficulty and expense of installation, weight, long-term water
 resistance, and interior moisture condensation.
 An object of the current invention is to provide a storm shelter to be
 installed below the floor level of a home for use in an emergency. Another
 object of the invention is to provide a shelter that can be installed
 without limitations of lot size or easement restrictions.
 It is a further object of the present invention to provide a shelter that
 requires limited excavation.
 It is a further object of the present invention to provide such a shelter
 in a relatively inexpensive prefabricated form.
 It is a further object of the present invention to provide a material of
 construction which is water resistant, which will minimize condensation on
 the interior of the shelter, and which will provide a shelter that is
 relatively impervious to water seepage from the outside.
 It is a further object of the present invention to provide a shelter with
 interior surfaces which are smooth, sturdy, corrosion-free, and pleasant.
 It is a still further object of the invention to provide an underground
 emergency shelter system that accomplishes all or some of the above
 objects in combination.
 It is an object of the present invention to provide a prefabricated shelter
 of a material which is lighter and easier to install than precast
 concrete. It is a further object of the present invention to provide a
 shelter which can be built into new construction in a manner which permits
 entry from the interior of the home. In the current invention it is
 desirable to place the unit below the floor lever for maximum safety and
 security.
 It is an object of the preferred embodiment of the invention to provide a
 lightweight underground emergency shelter system and may be anchored by a
 house foundation without requiring a separate and elaborate anchoring
 apparatus.
 An object of the present invention is to provide a prefabricated shelter
 which can be constructed with materials such as acrylic which is used in
 conventional tubs and spas, and which can be fabricated by vendors such as
 tub and spa vendors. It is a further object of the present invention to
 provide prefabricated units which can be handled without special equipment
 such as cranes.
 An object of the present invention is to provide a pleasant interior
 surface in a single unit without requiring an exterior support frame.
 One object of the present invention is to provide a smaller and more
 affordable emergency shelter which does not require elaborate anchoring.
 U.S. Pat. No. 4,955,166 for a "Tornado underground shelter" issued on Sep.
 11, 1990 to Steve M. Qualline and Louis R. Dunnam describes a large,
 generally spherical tornado shelter with a seat member is attached to the
 sidewall and floor which forms a structural member that strengthens the
 globe. The patent describes disadvantages of concrete structures
 shrinkage, cracking, and becoming saturated with moisture such that the
 interior is unsuitable for habitation or storage. The shelter provides
 standing headroom for its occupants. The '166 patent references a second
 embodiment of incorporating the large spherical structure into the floor
 of a home with the entrance above the floor level of the home. The patent
 also references placing the structure under a patio with the stairway
 extending at least three steps above the top surface of the patio, thereby
 precluding someone inadvertently falling through the open door thereof. An
 object of the present invention is to provide a relatively inexpensive
 prefabricated structure of more practical size that can be incorporated
 more readily into conventional home designs without increasing the
 foundation size of home.
 SUMMARY OF THE INVENTION
 In the preferred embodiment of this invention, a prefabricated storm
 shelter with a top entrance of approximately 28 inches square is installed
 below the foundation or floor of a residence. Fabrication of the unit is
 preferably in a top section and a bottom section with the unit sealed
 along its side surfaces to prevent moisture intrusion. The unit is
 typically composed of a material such as acrylic upon a reinforced
 fiberglass to provide structural integrity and a relatively pleasant
 interior finish. The shelter is designed to be placed so that the entrance
 way is at the floor level of first floor of a residential or commercial
 structure having a concrete slab foundation. Alternately, the unit may be
 placed so that the hatch is at the floor level of a pier and beam
 foundation.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 The preferred embodiment of the shelter is designed for installation below
 a concrete slab foundation of a residential structure.
 Referring now to FIG. 1 which is a top view of the preferred embodiment,
 and to FIG. 2, which is a side view of the preferred embodiment, the
 shelter 10 is approximately 6 feet in width and 6 feet in length and has a
 height of at least 36 inches. Greater lengths and widths may be used in
 cases where additional space is required. Greater heights may by used, and
 a height of 42 inches is an approximate height to permit a relatively
 convenient crouching or sitting for a temporary stay during an event such
 as a tornado or thunderstorm. These dimensions are smaller than a typical
 storm shelter in order to provide a practical and affordable emergency
 shelter. The dimensions permit the shelter to be installed within the
 foundation area of a home with low additional excavation costs. In
 addition to lower installation costs, the smaller dimensions permit the
 shelter cost to be lower than other types of larger shelters. The shelter
 is preferably composed of a top section 20 and a bottom section 30. The
 top section has a lip 21 which is fastened to the bottom section lip 31
 during assembly to create a single unit. The top section contains a hatch
 40 which is typically located near a side wall so that a prefabricated
 step 101 may be used to assist a person in entering and exiting the
 shelter. The opening of the hatch is preferably at least 28 inches by 28
 inches. The hatch includes a riser section 41 that is typically about 5"
 above the top of the upper section. This height allows room for a layer of
 sand and the thickness of a typical concrete slab.
 The unit is preferably assembled at the factory or dealer, but it can also
 be assembled on site as described in the alternate embodiment.
 Referring now to FIG. 3, the unit is preferably installed so the top of the
 hatch is located at the floor level of a slab. The floor 80 is poured
 level around the hatch 40. This hatch is typically located in a closet
 near an exterior wall 90. The reason for locating the hatch in a closet is
 for cosmetic purposes. One reason for locating the hatchway near an
 exterior wall is the ability to vent the unit through an exterior wall. An
 additional benefit to placing the unit near an exterior wall is to permit
 easier reference points for placing and aligning the unit within a
 foundation.
 Referring now to FIG. 2 which is a cross section of the preferred
 embodiment, the shelter is preferably fabricated with a vacuum molding
 process similar to the process for fabricating tubs and spas. The bottom
 section is preferably fabricated in a female mold where a hot acrylic
 sheet with a thickness of approximately 1/8" is placed over the mold, and
 a vacuum drawn on the mold to form the hot sheet to conform to the bottom
 section mold. The bottom edges are beveled 32 to avoid sharp comers and
 edges in order to support this vacuum forming process, to avoid stress
 points on the completed section, and to provide improved comfort within
 the shelter. Alternate resin materials may be used including ABS, PVC,
 polyethylene, and fiberglass reinforced gel coat.
 The top section is preferably fabricated in a male mold where a hot acrylic
 sheet is placed over the mold, and a vacuum drawn on the mold to form the
 hot sheet to conform to the top section mold. The top edges are beveled 22
 to avoid sharp corners and edges in order to support this vacuum forming
 process and to avoid stress points on the completed section. Both the top
 section and the bottom section can be fabricated in either a male mold or
 a female mold.
 The vacuum forming process produces thin shells of the upper and lower
 shelter sections. These shells are reinforced by applying a fiberglass
 resin material to a thickness of about 1/4", with additional material
 provided at stress points. The preferred method of applying the fiberglass
 reinforcement is to spray a cut fiberglass/resin composition to the back
 side of the shells. The preferred composition is 18% glass, 1.5% catalyst,
 and 80.5% resin. Structural coring can be placed within the laminated
 fiberglass to add structural strength.
 Referring now to FIG. 5 which is a side view of the top section showing the
 molded hatchway area, the top hatch is formed as a closed section
 approximately seven inches above the top of the upper section. In order to
 form the hatchway 40, the hatched top is cut approximately two inches
 below this extension. Hinges 43 are used to mount this cut away section 45
 so that it opens by swinging downward into the shelter. In the preferred
 embodiment, a step is formed on the bottom shell, and the hinges are
 mounted on the opposite side of the hatch from where the step is located
 so that the hatch can be fully opened without obstruction. There are
 several advantages to and inward opening door including resistance to
 suction and the ability to open the door if debris falls over the door
 opening.
 Referring now to FIG. 6 which is a side view of the top section showing the
 installed hatch lid 45, the lid is mounted with two hinges 43. The lid is
 latched by spring loaded latch bolts 53 which extend into recesses in the
 hatch opening. The lid is recessed 51 for a diameter of about 4-5"
 diameter and 1 to 1.5 inch deep for a handle 52, which is preferably a
 garage door-type mechanism. The spring loaded latch bolts 53 are moved
 into a retracted position when the handle is turned, thereby permitting
 the hatch to be opened. A lock 54 is typically provided to restrict entry
 into the shelter.
 Referring now to FIG. 7, the preferred dimensions of the hatch opening is
 28 inches by 28 inches. The hatch comers 48 are beveled to permit
 construction by the vacuum molding process. The top hatch extension is
 formed with a draft angle of approximately five degrees to permit the top
 lid section 45 to be removed from the mold. This draft angle causes the
 hatch to be slightly smaller in dimension than the hatch opening, and a
 gasket is provided for sealing the hatch. After the vacuum forming
 process, a foam or wood backing is placed for reinforcement upon the
 acrylic before the fiberglass application. This reinforcement adds
 strength to the Hatch lid so that the lid will withstand a static or
 dynamic load. The reinforcement also provides a depth that permits the
 handle to be recessed. Similar reinforcement may be placed at other
 portions of the upper and lower section.
 The lid is typically placed under a cut away section of carpet with clear
 markings so that the occupants or residents can locate the shelter in a
 time of necessity.
 Referring now to FIG. 8A and 8B, which are side and top views of the
 preferred installation, ventilation is provided through a vent pipe 60 and
 through an optional fan 62 which is vented through an external foundation
 wall 90. In some embodiments, a battery will be provided which will supply
 temporary power for ventilation and lighting. The preferred embodiment
 includes a conduit 64 to route lines to a junction box 63 which contains
 cable, electrical, and telephone outlets. It is desirable to place
 rechargeable flashlights and other electrical devices in the shelter, and
 to have a ground fault interrupt receptacle in the shelter. In the typical
 installation, conduit is supplied into the chamber so that wiring may be
 performed to support electricity for television, a telephone line, and a
 panic button type of signal device.
 For the preferred shelter dimensions of 6' by 6' by 42" high, the
 foundation area is excavated to a depth of about 52" for an area
 approximately 7.5' square. The bottom of the excavation is then backfilled
 with about 5-6 inches of sand 71. The sides of the excavations are
 typically 1 to 2 feet wider than the main unit, and the sides are
 backfilled with a sand and gravel mix 72. Before the unit is place in the
 hole, the sand at the bottom of the pit is compacted and leveled. The
 grade is then taken to determine if sand should be added or removed to
 achieve the desired height and level of the bottom of the excavation pit.
 The grade will normally require at least 4 shots to determine consistency
 of the reading in order to verify that the bottom is level. Once the
 proper level and height have been obtained, the unit can be lowered into
 place. The preferred shelter dimensions result in a unit weight of about
 300 to 350 pounds, and the unit can be positioned by 4 workmen without
 special equipment. After the unit is set, it is once again checked for
 level, and for the height of the hatch. Once the level is correct, the
 side fill is poured into place and compacted, and a layer of sand 71 up to
 1/2" in thickness is placed on top of the unit. This top layer of sand
 permits the concrete slab to move freely. The slab is reinforced per
 standard design with reinforcement rods or cables.
 Referring now to FIG. 4, the preferred method of attaching the upper and
 lower sections is to bolt the sections together with stainless steel bolts
 and nuts at a spacing of approximately a spacing approximately 18 inches
 apart. At least one bead of silicon caulk is placed upon the lower section
 lip prior to assembly. The preferred assembly technique is to temporarily
 clamp the sections together while drilling at least one hole on each side
 of the unit. After the bolts are installed in each hole, then the
 temporary clamps may be removed, and the remaining holes may be drilled.
 When used as a storm shelter, the occupants of a residence or other
 structure will move to the shelter hatch, open the lid by rotating the
 handle 90 degrees, and climb into the shelter. A step integral to the
 lower section of the shelter is used during ingress and egress. The
 occupants move away from the hatch area to permit additional persons to
 enter. Some shelters may be equipped with power ventilation and emergency
 power for monitoring radio or television for weather updates, and a
 telephone. After the last person has entered the shelter, the lid may be
 closed and secured by rotating the handle 90 degrees or pushing up on the
 lid until the spring loaded latches snap into place.
 After danger has passed, the occupants open the lid by rotating the handle
 90 degrees and exit the chamber.
 The unit may be used as a storm shelter for tornado, hurricanes, and other
 severe weather; a security shelter; as an isolation chamber; as a storage
 compartment with relatively constant temperature; as an earthquake
 shelter; and as a mobile home type shelter.
 ALTERNATE EMBODIMENT--SECURITY SHELTER
 The unit may also serve as a temporary security shelter. In some
 installations, the presence of the unit may not be noticed by intruders to
 a home. Occupants may seek short periods of safety in the shelter by
 locking the door from the inside of the shelter. In some installations, a
 telephone will be available inside the shelter, and the phone can be used
 to call for assistance. A panic button may also be provided to permit an
 audible alarm to be activated from within the shelter.
 ALTERNATE EMBODIMENT--STORAGE
 The unit may also serve partially as a storage unit for occasionally used
 items or for items such as wine that may require a relatively constant,
 cool temperature.
 ALTERNATE EMBODIMENT--VERTICAL EXTENSION
 Referring now to FIG. 2B, in cases were additional head room is desired,
 one or more vertical extension sections 102 may be provided. Each
 extension will typically be about 18" high with a lip on the top and
 bottom which will mate with the lips on the upper and lower sections.