WO1990012940A1

WO1990012940A1 - Sun tent

Info

Publication number: WO1990012940A1
Application number: PCT/GB1990/000530
Authority: WO
Inventors: John Kay
Original assignee: John Kay
Priority date: 1989-04-14
Filing date: 1990-04-06
Publication date: 1990-11-01

Abstract

The sun tent is a temporary shelter in which people out of doors can bathe in and be warmed by direct and reflected solar radiation in sunny but cold or cold and windy weather. The sun tent is deployed by air inflation to the interior by a fan (5) and power source (6) housed within the tent wall. The wall is principally structured of: a base that is a reflective, thermally insulating, mechanically cushioning flexible sheet, composed principally of expanded plastic closed-cell foam; a top (1) of thin plastic film which is an efficient window to the sun's radiation; and an entrance/exit mouth (8) which otherwise self seals against the escape of the pressurizing air. In the undeployed sun tent, the base, top (1), mouth (8) and other parts lie together as one sheet which is rolled into a compact pack.

Description

SUN TENT

BACKGROUND AND SUMMARY OF INVENTION

This invention relates to sunbathing aids, to treatment for seasonal affective disorder or S.A.D. syndrome, to solar energy collection devices and to inflatable structures and survival shelters. The impetus to design this invention was the gratification brought by sunshine in the short days of winter and the fact that even on the coldest days direct sun light from a clear sky has abundant energy. The power of the solar energy is principally related to the angle of the sun above the horizon and for a given angle and clarity of atmosphere, is similar for winter or summer. It was apparent that if cold surfaces and cold breezes could be excluded, basking in winter sunlight could be very pleasurable. People suffering from S.A.D. syndrome are treated by exposure to bright light and it is reasonable to expect that sunlight is the most therapeutic. There are many devices designed to serve the sun bather with shelter, enhanced irradiation by reflection and convenient positioning of the body, but in studying the prior art it was apparent that the convenience and effectiveness in practical usage and the economy of manufacture were limitations for all inventions to date as compared with what was sought by this inventor. What was sought at the outset was a device where a user, contending with the vagaries of the weather, could spontaneously or at their whim, with a minimum of effort, sunbathe in comfort and warmth at about any location out of doors in cold weather when the sun appeared. Within these goals the prior art was replete with shortcomings. Any device similar to the many versions of wind breakers and reflectors would not completely prevent cold air driven by wind from reaching the sun bather. Any structure which did not completely surround the sun bather would be unsuitable. Any device which used exotic or expensive materials, for example special glass or teflon film transparent to ultra violet light as a window of the structure, would not be in line with the goal of economy. Any portable structure, as simple for example as a camping tent but with frame and material to set up, would deter from the sought after spontenaity of use. Any device which was not compact in storage and weighed more than a few pounds was similarly unsuitable. All prior art patents show one or more problems when viewed with these goals: including - too much bulk, weight and complexity, lack of flexibility in use, use of exotic or expensive materials, incomplete protection from the undesirable environment, and incomplete exposure to solar radiation. What was arrived at by design in the sun tent was functionality of the goals and the economic use of economical and lightweight materials. The sun tent is a tent whose wall is supported by air pressure supplied by a fan and power source housed within the wall. The wall is principally structured of: a base that is a reflective, thermally insulating, mechanically cushioning flexible sheet, composed principally of expanded plastic closed-cell foam; a top of similar area to the base, of thin plastic film which is an efficient window to the sun's radiation; and an entrance mouth which otherwise self seals against the escape of the pressurizing air. The base and top are joined at the edge and in the undeployed tent lie together with the mouth as one sheet which is rolled into a compact pack. A deployed sun tent exhibits rounded and flexible surfaces which allow a multiplicity of orientations with respect to the ground and the sun, concentration of the reflected radiation and protective non-rigid suspension of the potentially fragile top. The sun tent can also be used as a general purpose shelter from an adverse environment. Within the scope of the basic design, minor changes can change its uses. Metalizing for reflectivity of the top sheet would provide a shelter against desert sun. Other coatings could provide selective transmission of solar radiation, i.e. radiant heat and blocking of ultra violet for alpine or arctic environments.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 is a perspective view of one embodiment of the invention with a visibly transparent top. The sun tent is deployed and in use by a reclined female person. Fig 2 is a view of the section AA in Fig 1 and without occupant. Fig 3 is an elevation in the direction B of Fig 1 and shows the mouth end. Fig 4 shows a vertical section in the same direction as Fig 3 but with the sun tent cambered to one side to face radiation from the sun. Fig ^*5 is a plan view of the same sun tent uninflated and unrolled. Fig 6 is a side elevation of Fig 5 to show the flat and planar aspect. Fig 7 is an underside view of Fig 5 and shows the edge attachment of the top to the base. Fig 8 is a perspective of the sun tent rolled and packed in its groundsheet/cover 3 for storage and portability. Fig 9 is a cross section of Fig 8 showing the roll of the materials. Fig 10 is a schematic cross section of the wall of the sun tent having a double film top. Fig 11 is an enlarged schematic cross section of the mouth end in Fig 2 and illustrates the fastening of parts. The groundsheet/cover 3 is omitted. Fig 12 is a schematic of a section CC in Fig 6. The groundsheet/cover 3 is omitted. forming a hinge.

16. Inner plastic tape adhered to lips and together with 15 forming a hinge.

17. Flexible and resilient reinforcing rod of fiberglass and resin.

18. Adhesive layer from adhesive transfer tape.

19. Adhesive layer of adhesive tape.

20. Thin plastic film inner layer.

21. Air bleed hole inner.

22. Air bleed hole outer.

23. Snap connector female with gripping tab.

24. Snap connector male.

25. Rivet for reinforcing joint between base and groundsheet/cover.

26. Cut away of top 1 around perimeter of fan air passage.

27. Arrows symbolizing air pressure on faces of lips of mouth.

28. Grommeted hole for anchoring.

29. Sliding air control valve.

Fig 13 is an elevation of the mouth end of Fig 5 to show the closed flat aspect in contrast to Fig 14. The groundsheet/cover 3 is omitted. Fig 14 is an elevation of the mouth end as in Fig 13 but with the lips parted for access to the interior. The groundsheet/cover 3 is omitted.

LIST OF NUMBERED PARTS

1. Top sheet of thin plastic film.

2. Base sheet of closed-cell plastic foam.

3. Groundsheet and cover for compacted sun tent.

4. Slab of plastic foam for housing fan, battery and connections and reinforcing straight aspect to upper lip of the mouth.

5. Air pump/fan.

6. Battery.

7. Switch and electrical link recessed in slit in plastic foam.

8. Entrance and exit mouth.

9. Fold in base sheet absorbing or folding material excess to the deployed geometry.

10. Upper lip.

11. Lower lip.

12. Air bleed end reinforcement plastic foam slab.

13. Air bleed hole.

14. Overlap of edge of top laid on band of adhesive on underside perimeter of base sheet.

15. Outer plastic tape adhered to lips and together with 16 DETAILED DESCRIPTION

Referring to the drawings, Fig 1 shows one preferred embodiment of the invention, a cold weather sun tent with the capacity for one or two persons. Its body wall supported by internal air pressure approximates very generally a cylindrical tube with closed hemispherical ends. Gravity and reinforcing spars modify on that shape. Figs 2 through 14 elaborate on this same embodiment. The sun tent is comprised of a visibly transparent top 1 of thin plastic film and a base 2 of closed-cell plastic foam. The two are joined together by an overlap of the top 1 onto a band of adhesive applied to the underside perimeter of base 2, shown as 14 in Fig 7. This joint 14 is continuous except where it is replaced by the mouth 8 or entrance to the sun tent which appears as a slot in Fig 1. Mouth 8 consists of an upper lip 10 and a lower lip 11 as in Fig 2 and which normally seal against the escape of air out through the mouth. Fig 11 shows a larger scale schematic view of mouth 8 in Fig 2. Lips 10 and 11 are rectangles of flexible flat sheet closed-cell plastic foam similar to the base 2 material but of thinner guage and about one quarter of an inch thick. Top 1 is fastened to upper lip 10 in joint 14 by a band of adhesive laid along the underside outer edge of lip 10. Lower lip 11 is joined with base 2 along the length of their common outside border by strong adhesive or welding. Included in this joint is a reinforcing rod 17 of a material such as resin and fiberglass composite. The elasticity of the plastic foam allows the rod to embed. The two lips 10 and 11 are fastened to each other face to face as shown in Fig 12 by two side hinges -of adhesive plastic tape. Each hinge consists of an outer tape 15 and an inner tape 16 adhered to the lips. The mutual contact line of tape 15 and tape 16 is the pivot of the hinge which allows the internal faces of the lips to be pushed apart into a tunnel as in Fig 14. A tape suitable for the hinges is made of polyester with a high-strength acrylic adhesive. In an alternate construction, the hinge could be formed of a contact weld between the lips, or hinges could be welded to the lips. Upper lip 10 extends inwardly beyond lower lip 11 by about one inch, sufficient to provide a handle for an occupant of the sun tent to grasp and lift upper lip 10.' A slab 4 of closed-cell polyethylene plastic foam is adhered directiy on the face of top 1 next to mouth 8 and adjacent and parallel with top lip 10. Towards one end of slab 4 a hole through the slab provides an interference fit housing for an electric air pump-fan 5, and towards the other end a similar hole accomodates. with an interference fit, a battery 6. A cable and switch 7 recessed in the slab connects fan 5 and battery 6. Adjacent to fan 5, top 1 has a section 26 in Fig 11 cut out for free passage of air through fan 5 to the interior of the sun tent. At the opposite end of the sun tent to fan 5, base 2 is provided with air vents. A small grommeted hole 13 bleeds air out for a minimum safe through ventilation for breathing. A sliding valve 29 is adjustable from the interior or the exterior and allows the release of more air for temperature and humidity control and for deflating the sun tent for storage. As shown in Fig 1, below and surrounding mouth 8 is a groundsheet/cover 3 of thin, rugged, waterproof material such as woven polyethylene. It is permanently fastened along one edge to base 2 between the rivets 25 in Fig 5 by an adhesive strip or weld strip. The rivets 25 serve to reinforce the ends and highest stress points of the joint. Groundsheet/cover 3 is fitted with male 24 and female 23 snap connectors for securing the roll of the compacted sun tent, as in Fig 8. Small finger tabs fastened to the groundsheet/cover 3 by the riveted type female snap connectors 23 allow for easier location and release of the connectors. A slab 12 of the same material as slab 4 is adhered to base 2 at the end opposite to the mouth and parallel and close to the joint of top 1 and base 2. Slab 12 braces this edge of the base against buckling and maintains symmetry with the-mouth end.

OPERATION AND DESCRIPTION

The sun tent is constructed largely of flat sheet but flexible materials and naturally lies flat with very little profile as shown in Fig 6. For storage and portability, it is rolled up with top 1 facing inward and protected by base 2, starting with slab 12 as the core of the roll. Groundsheet/cover 3 becomes the cover and female snap connectors 23 are located on and fastened to male snap connectors 24. The side edges of groundsheet/cover 3 are tucked into the hollow center of the roll. Fig 8 shows a perspective of the resulting compact pack. Fig 9 shows a cross section of this rolled pack. Lips 10 and 11 are pulled into the curve with top 1 and base 2, but slabs 12 and 4 remain substantially uncurved. To deploy a sun tent from its pack, a user releases snap connectors 23 and 24. The elasticity of base 2 and the lip material commence a partial unravelling which first exposes the groundsheet/cover 3 and then slab 4. The sun tent may not completely unravel to the position as shown in Fig 6 due to a set taken on by the various materials and especially base 2. This set is partly affected by the time the sun tent has been compacted into a ^"roll, but is of little consequence as the complete unravelling is air pressure powered. Typically the user can now kneel or sit on groundsheet/cover 3 and switch on fan 5 at switch 7. Air input from fan 5 separates and raises top 1 away from base 2. According to this embodiment, fan 5 is of the type used in electronic cooling applications. It independently weighs 3.5 oz. and measures 2.36" square by 1" deep. It runs with little noise with an electrical consumption of 160 milliamps from battery 6. Battery 6 is a rechargeable lead acid gel of 0.8 amp hours, capacity at 12v and weighs 10 oz. with dimensions similar to fan 5. Fan 5 has an initial air delivery of 20 cubic feet per minute at minimum pressure. The pressure required to separate and initially raise top 1 from base 2 is less than 0.001" of water. The pressure inside the sun tent rises only very slowly until the fully inflated position as shown in Fig 1 is approached. Full inflation is reached when top 1 and base 2 become taut and the sun tent as a whole is comparatively rigid. Fan 5 then quickly achieves its maximum pressure differential of approximately 0.3" of water and continues to run with its blades in a partial aerodynamic stall. With stall., the rotational speed of fan 5 increases a little and its electrical current consumption drops a little. An audible change of note in the gentle sound from fan 5 accompanies the blade stall and signals the full inflation of the sun tent. Fan 5 continues to supply a comparatively small amount of fresh air to replace that leaving bleed hole 13, adjustable valve 29 if open, and any small leakage past the seal between lips 10 and 11. In fact fan 5 can accomodate large losses of air below its maximum 20 cubic feet per minute and still keep the sun tent deployed. This is the case when the user, positioned on groundsheet/cover 3, enters the sun tent. Because top 1 is so light and requires so little pressure to keep it buoyant and aloft, lips 10 and 11 can be parted without a total deflation of the sun tent. With the lips parted as in Fig 14, the escape of air out through the tunnel created is larger than the supply of fan 5 which would eventually cause top 1 to collapse onto base 2. However, the entry of a user through the tunnel partially blocks and slows the escape of the low pressure air. In this particular embodiment, the user enters mouth 8 either head or feet first and slides through as one might get into or out of a sleeping bag. Once upper lip 10 is no longer supported by hand or a part o ' the user's body, lip 10 falls down and closes with bottom lip 11, as shown in Fig 2. The sun tent quickly regains full inflation and the structural stability that comes from having the material of its body wall taut. In the inflated sun tent some space exists between lips 10 and 11 towards their outer edges and can be seen in Fig 1 as a slot or gape of mouth 8. This space is at atmospheric pressure and as shown in Fig 11, internal air pressure 27 pushes lips 10 and 11 together creating the seal towards and at the internal edge of lower lip 11. Under full inflation the sun tent can resist deformation by light outdoor winds. Stronger winds can

^• create deformation to the symmetry of the shape shown in Fig 1, but the human body apart from adding ballast to the very light structure, also adds longitudinal reinforcement through base 2. Higher pressure fans could be employed for more rigidity in more adverse conditions. Prototypes of this

-embodiment of the two person capacity sun tent weigh only 3.5 pounds, are robust in normal wind conditions and stay deployed for up to five hours on the self-contained battery power. Supplementary power could be used for longer or permanent deployment. As this embodiment is used in sunny conditions, it would be convenient to use a solar cell panel for supplementing power. With the pressure of a breeze, deployment is facilitated by allowing the sun tent to unroll downwind or unfurl assisted by the wind. Parting the lips of an uninflated sun tent into a brisk breeze causes the sun tent to immediately plump up with air and so reduces the time to taut deployment. Fan 5 always has to complete the final inflation to taut deployment and thus an entrance into the sun tent can be made at any stage of inflation. Undisturbed, this particular embodiment self inflates from partially rolled or flat, to taut deployment in approximately two minutes. Lips 10 and 11 tend to lie against base 2. Breaking the seal from inside to open mouth 8 to form an exit tunnel is simply a matter of lifting a center portion of the protruding edge of upper lip 10. - In the fully inflated sun tent with adjustable valve 29 closed, the small air input from fan 5 leaves the fan face radially, due to centrifugal action and the stall condition of the fan blades. The very low air current through the sun tent to bleed hole 13 cannot be felt by an unclad body, but insures of air replacement, for respiration in particular. A further oxygen and carbon dioxide exchange of small but significant effect takes place due to centrifugal action in the stalled fan. The fan blades rotate at over 5,000 revolutions per minute and throw out air radially on both sides of the fan face. This is replaced by air moving in from the center or axis line of the fan on both sides. Mixing by turbulance takes place between the blades of the fan. Opening adjustable valve 29 lowers the internal pressure a little and allows fan 5 to pump, with less stall, a larger flow of air through the tent for cooling or dehumidifying. The very light sun tent is usually ballasted against the influence of wind by the user's body, but a hole and grommet 28 in groundsheet/cover 3 provides for tethering or staking of the sun tent. Without a ballast, a sun tent tethered from gro πtet hole 28 aligns downwind with any significant breeze. Once inside the sun tent, a user has further control over the positioning of the sun tent. As shown in Fig 4, positioning the body to one side or the other of the center cambers the sun tent to that side. The sun tent can also be swiveled around given the flexible nature of base 2, as one could move in a sleeping bag. Given this positioning control, the user has control over the amount of solar radiation entering the sun tent. Base 2 acts as an efficient reflector and diffuser of solar radiation and, as shown in Fig 4, collecting and concentrating the radiation on the user if so desired. In the case of base 2 consisting of a plastic foam of closed cells of expanded polyethylene, each cell is a partial reflector with its own orientation. Radiation that passes through the thin membrane walls of one cell can be reflected at another membrane when striking that membrane at less than the angle of refraction. The result is a diffusion reflector of radiation which is more efficient than some aluminized fabrics. This was found to be true for ultra violet A and ultra violet B radiation where reflectivity of the foam sheet approached 50%. Together with the polyethylene foam appearing very white, it was also found to be a good reflector of infra red radiation. .In Contrast to some solar collecting devices and shelters, no part of this embodiment of the sun tent is designed to absorb solar radiation, given the exception of solar cells for electric power if included. The only net absorber of solar radiation in the sun tent is the user or items of color introduced by the user. In cold weather, mild air temperature in the sun tent is largely the result of conduction and convection from the user's body and clothing. The thin plastic foam cell membranes of base 2 in contact with the user's body have virtually no heat capacity and the small gas cells are efficient thermal insulators. In the lowest temperatures of winter, the plastic foam surface always feels warm to unclad skin. The inhabitant of the sun tent feels warm by virtue of solar radiation received and has control over the amount received. Extremely low outside temperatures provide no discomfort to unclad skin in full sunlight. The slow movement of the minimum ventilation air through the interior cannot be felt and the energy in sun light from a clear sky is abundant even at low sun angles. In cold sunny weather, the resulting micro environment of the sun tent can mimic a perfect summer day. An important aspect of the sun tent design is its use of, and the fastening manner for, the thin film plastic top 1. This embodiment uses a high clarity polyolefin of approximately a one thousandth of an inch thickness. The fragility of such a thin film would present a problem for any structure using solid spars or solid attachment points and especially where wind gusts are experienced. In the sun tent, top 1 responds to pressure fro the wind or a solid contact by flexing with a large margin of freedom of movement. Base 2, which anchors top 1, is itself flexible and follows the movement of top 1 and so dissipates any local increase in stress. The result is that this structure is very rugged for its intended purpose. The advantages of being able to use a polyolefin for top 1 are: I (_-

(i) it can have a lower static electric build-up than many plastics and attracts little dust; (ii) by virtue of high plasticity it ca have less tendancy to tear than do most plastic films when nicked; (iii) similarly, it can show less craze and crease marks when folded; (iv) it can have a low co-efficient of friction which makes for ease of user movement and packing; and (v) it offers excellent economy. In the very thin films that are employed, the polyolefins can have excellent transparency to_ all wavelengths of light, including ultra violets A and^"B.^' Measured transparency to erythemic ultra violet or UVB exceeded 95% for a high clarity thin film polyethylene. ^'In contrast, prior art structures using of necessity heavier guage materials for their solar window, could be limited to less efficient radiation transmission or the use of more exotic or expensive materials. Polyolefins have limited life expectancy when exposed to ultra violet light as compared with for example fluoropolymers, but this is not a limiting factor given the short period intermittent use of this device where the mechanical properties are of higher priority. In this embodiment, the nature of joint 14 has important aspects. The adhesive used can be applied as a transfer tape onto the underside edge of base 2. It can provide an adherence to top 1 which is ultimately stronger in shear than top 1 and yet distributes the load on the thin film with elasticity and plasticity. In contrast, a welded or sewn joint could create high stress points and tears in such a thin material. With the correct formulation of adhesive, top 1 can be peeled off base 2 to be replaced by a new top. Since this top material is of flat sheet, such a replacement can be very _ economic. A variation on configuration of the top is shown schematically in Fig 10. A thermal insulation layer of air is created to prevent moisture from respiration and perspiration from condensing on the inner roof surface when outside temperatures are very low. Here, in addition to top 1, another similar gossamer sheet 20 is adhered to the inner upper edge of base 2. The flat dimensions of sheet 20 are slightly smaller than top 1 by two times the thickness of base 2. It is supported by air pressure in the inflated sun tent and lies parallel to but separated from top 1 by a distance equal to the thickness of base 2. To support top 1 and maintain the separation, air bleeds through a few small holes 21 distributed in sheet 20 near fan 5 and applies pressure to the inner surface of top 1. This very small flow of air is allowed to bleed out from top 1 through holes 22 distributed near the opposite end of the sun tent to holes 21. Holes 22 have an area equal to holes 21 and allow a pressurization of the gap between top 1 and sheet 20 to be about one half the pressurization of the interior of the sun tent. The through flow of air starts with air sourced close to fan 5. It is unhumidified by occupants of the sun tent and is a negligible portion of fan 5 output. Another significant refinement to the sun tent could be the inclusion of a low battery condition alarm, or a low air pressure alarm to warn users of an imminent deflation. Without much departure from the essential features of the invention described so far, the sun tent can find a wider practical usage and an example would be simply as a portable shelter from wind and rain. For a full night or full sleeping term it can have a longer fan running time than the embodiment described by a small reduction in electrical consumption of the fan or a small increase in battery capacity. Radiation reflective coatings on or radiation absorptive inclusions on or in the plastic of top 1 can provide utilitarian changes and without any weight penalty. Examples are the exclusion of the shorter or all of the ultra violet radiation, the exclusion of heat radiation, and the exclusion or reduction of visible light. For interior privacy, the top 1 can be transmitting but diffusive with no optical clarity. A metalized or aluminized coating of top 1 can provide reflective and complete protection from the sun for use in a hot desert climate. In this case the occupants could obtain evaporative cooling from air flow from fan 5 with valve 29 open. An interior metalized coating of top 1 or plastic film inner layer 20 can provide reflection of body heat for night or cold conditions. As the last of many possible examples of utility which could be listed, the sun tent can be used on expeditions for solar radiation drying or warming of equipment, or heating of water in dark containers.

Claims

hat is claimed is:

1. A lightweight portable shelter which is deployed semi automatically from a compact pack by self-generated air pressure, comprising a bottom which is planar, flexible and largely air impermeable; a top which is planar, flexible, largely air impermeable and less mechanically rugged than^' said bottom; a mouth to provide entrance and exit way for solid bodies, with means to normally seal against the escape of air when said shelter is deploying or deployed; an air pump and power source for said pump; said bottom and said top being joined together near their edges except for a length where they are joined to said mouth, together forming the wall of a cavity which can be filled with pressurized air through said wall and from said pump; an air replacement means for inside said cavity of the fully deployed shelter; a damage limiting and prevention means for said top in contact with solid objects and wind gusts where said top is non-rigidly anchored by its attachment to the flexible said bottom and can move in the direction of force from said contact; a second damage limiting and prevention means for said top in contact with solid objects and wind gusts where said top is allowed a range of freedom of movement by being supported on air in an arch over said air and can move in the direction of force from said contact and alter the curvature of said arch ; said bottom showing a generally convex undersurface when said cavity is inflated; said generally convex undersurface providing means for a multiplicity of orientations against a supporting undersurface; said bottom and said top can lie together without inflation of said cavity and be rolled into said compact pack with said top as the inner layer, protected against damage by said bottom; said damage limiting and prevention means for said top and the protection afforded by said bottom in said compact pack provides a means to improve the portability of said shelter by reducing the mass of said top required to be sufficiently rugged.

2. The structure of claim 1 wherein said bottom includes the means to be thermally insulating and mechanically cushioning by containing gas within a plastic membrane; said air pump is a fan and has a volumetric cut off at a given pressure; said means for air replacement comprises an adjustable air release valve located in said wall where air released is replaced by said air pump; is included a means to impress a symmetry of shape on said cavity and a straight aspect to said mouth by semi-rigid spars attached to and within said wall and parallel with the axis of roll of said compact pack.

3. The structure of claim 2 wherein said mouth is a flexibly edged slot which can be closed by a generally airtight zipper.

4. The structure of claim 2 wherein said mouth is comprised of two inwardly pointing semi-flexible planar lips which self seal against the escape of said pressurized air which acts to press said lips together, said bottom or said top can fulfill the function of one of said lips, said lips are hingedly joined at two side edges and can be pushed apart into a short tunnel, said lips lie parallel with said top and/or said bottom for rolling into said compact pack.

5. The structure of claim 4 wherein said top transmits solar radiation incident upon it.

6. The structure of claim 5 wherein said top transmits efficiently said solar radiation by virtue of the thinness of the section presented as medium to said radiation and permits the use of materials that would otherwise not be considered efficient transmitters of certain wavelengths of said radiation.

7. The structure of claim 6 wherein said fan is axial flow, said volumetric cut off occurs by aerodynamic stall of blades of said fan, said stall and part stall conditions produce a second means of air replacement by mixing between said blades of air in axial to radial circulation across both faces of said fan; is provided a means to lessen condensation in cold weather of water transpired from occupants of said shelter onto the inner surface of said top by inducing a laminar flow of lower humidity fresh air spread radially from inner face of said fan along said inner surface; said flow of air along said inner surface provides means to prevent discomfort of cold air impinging directly on occupants of said shelter. ;8. The structure of claim 7 wherein said energy source is a battery.

9. The structure of claim 8 wherein said battery is rechargeable.

10. The structure of claim 9 wherein a solar panel provides energy to. said battery and said fan.

11. The structure of claim 8 wherein said bottom has means to reflect and generally concentrate ultra violet, visible and infra red radiation generally towards the center of said shelter, said means to concentrate resulting from the concave curve of _^~aid bottom. 12. The structure of claim 11 wherein said plastic membrane of said bottom is optically clear to said radiations and said plastic membrane forms the walls of a multitude of closed cells, said means to reflect occurs at the two surfaces of said plastic membrane when said radiations strike said membrane at large angles of incidence, said radiations passing through any one part of said plastic membrane have a high probability-of striking another part at a large angle of incidence and being reflected.

13. The structure of claim 11 wherein is provided a second means to prevent condensation onto said inner surface by said top including a thermally insulating gas layer held between two or more plastic films.

14. The structure of claim 13 wherein said top comprises two plastic films positioned parallel and held taut in the deployed sun tent by differential air pressure which bleeds from said cavity with holes in both said films.

15. The structure of claim 11 wherein said top incorporates dyes or filtering agents to block the transmission of certain wavelengths of said radiations.

16. The structure of claim 8 wherein the interior surface of said bottom has means to absorb infra red radiation and serves to heat the interior by conduction.

17. The structure of claim 11 including a means for lowering isolated stresses in the joints between said top and other parts of said shelter where said joints are composed of a plastic viscous adhesive which can flow at overstressed points before failure of the joint or top, said stresses in the joints being in particular the result of uneven distribution of said top against said bottom in manufacture of said shelter; a means for lowering isolated stresses in said top due to said uneven distribution of said top and inadvertent harsh contact where the material of said top has a high plasticity and stretches to dissipate said stresses.

18 The structure of claim 13 wherein said top is a one gas cell thick multi-celled plastic sheet akin to bubble wrap.

19. The structure of claim 4 wherein said top is a metalized but largely plastic film capable of efficient solar radiation reflection and said shelter provides protection in sun-baked desert conditions and air flow from said fan can provide evaporative cooling to occupants of said shelter.

20. A lightweight portable cold weather shelter and collector of solar radiation which is deployed semi automatically from a compact roll pack by self-generated air pressure and comprising a bottom which is a planar, flexible, mechanically cushioning, thermally insulating sheet comprised largely of plastic and expanded plastic closed-cell foam; a top of one or two layers of planar flexible plastic film transparent to solar radiation and having a high transmission efficiency for ultra violet, infra red and visible light by virtue of the thinness of section presented to said light, said film can carry filtering agents to selectively block specific unwanted radiation; a mouth to provide entrance and exit way for users, comprised of two inwardly pointing semi-flexible rectangular planar lips which seal against the escape of pressurized air which acts to press said lips together into a seal, said lips are hingβdly joined at their side edges, can be pushed apart into a short tunnel, can lie flat and parallel with said top and said bottom for rolling into said compact roll pack; said bottom and said top being joined together near their edges, except for a length where they are each joined to the outer edge of a different said lip, together form the wall of a cavity which can be filled with said pressurized air when said wall freely curves and takes on tension to oppose the pressure; semi-rigid reinforcement spars attached to or within said cavity wall parallel to the axis of roll of said compact roll pack impress a straight aspect to said outer edge of each said lip and a symmetry of shape to said cavity; an axial fan mounted in said cavity wall supported by one of said reinforcement spars to supply said pressurized air, having a maximum pressure output suitable to tension said cavity wall against external environmental wind pressures, blades of said fan supply air to rapidly deploy said shelter and then, at said maximum pressure, operate in a partial aerodynamic stall and supply a reduced flow of air radially and generally parallel to said fan inner face for ventilating and to sweep inner surface of said cavity to reduce condensation in cold weather of water transpired by occupants of said shelter, potentially cold said air avoids impinging directly on and causing discomfort to said occupants; a rechargeable battery to supply energy to said fan, mounted with switch and wiring in said spar supporting said fan; an air venting valve, adjustable inside and outside said shelter, fitted through said base near joint with said top in the end of said shelter opposite to said mouth and adding control to the air exchange of the enclosed micro environment; damage limiting and prevention means for potentially fragile said film of said top in contact with solid objects and wind gusts where said top is non-rigidly anchored by its attachment to the flexible edge of said bottom and can move in the direction of force from said contact, and where said top is given a range of freedom of movement by being supported on air in an arch over said air and can move in the direction of force from said contact and alter the curvature of said arch; said bottom, when said cavity is inflated showing a generally convex undersurface, which when ballasted by occupants of said cavity allows a multiplicity of orientations for said shelter with respect to the sun; the interior face of said bottom is a diffuse reflector of said solar radiation and when said cavity is inflated, said face is generally concave and concentrates said solar radiation towards the center of said cavity; a means to secure said shelter as said compact roll pack and protect it in an aesthetic cover where said cover is attached to said base and wraps around said compact roll pack to fasten to itself, said cover also serves as a flat ground sheet surrounding said mouth when said shelter is deployed, said cover/ground sheet can be staked or fastened to anchor said shelter when deployed.