Collapsible pop-open lightweight solar heating system

A collapsible pop-open solar heating system having a heating enclosure with an open configuration and a collapsed configuration. The enclosure is made of substantially opaque flexible fabric having reflective interior surfaces, and it includes a region of transparent flexible material for the passage of light. When placed in an open configuration, the enclosure is shaped so as to reflect and focus light into a focal region in the interior space defined by said enclosure. To facilitate rapid erection, preferred embodiments include a collapsible flexible spring frame contained within at least one sleeve in the fabric enclosure. The sleeve confines the spring frame and when the enclosure is unrestrained, the spring frame urges the enclosure into an open configuration. A door in the enclosure permits placement and removal of heating and cooking vessels in the enclosure.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 through 15 , wherein like reference numerals refer to like components in the various views, FIG. 1 is a front axonometric view of a first preferred embodiment of the collapsible pop-open lightweight solar heating system (or pop-open solar oven) of the present invention, while FIGS. 2 and 3 are a cross-sectional side view in elevation and a front view in elevation thereof. FIG. 4 is a side perspective view showing an alternative collapsible pop-open oven shape. FIG. 5 shows the first and second embodiments of the pop-open oven in its collapsed configuration ready for transport and storage. These views collectively show the principles, operation, and construction of the first preferred embodiment 10 of the collapsible pop-open lightweight solar heating system of the present invention. The inventive apparatus may be accurately characterized as a collapsible pop-up solar-powered oven. The oven structure is a self-supporting and self-expandable portable structure including a first and second side panel, 12 , 14 , a back panel 16 , a top panel 17 , a floor panel 18 , and a transparent front panel 20 . The side, floor and back panels are preferably fabricated of lightweight flexible opaque material, and even more preferably of rip stop nylon. The front panel may be fabricated from any of a number of transparent, lightweight plastic materials. The panels are sewn together at their edges, and the seams form either continuous or discrete sleeves 22 into which either a single loop or a combination of loops of flexible spring steel, plastic, or other material with a spring-like memory are slidably inserted to form a frame 24 . The sleeve confines the loops forming the frame and when unrestrained causes the flexible spring or springs to urge the panels into a separated relationship, or to deploy the pop-up apparatus into a tautly open configuration, as shown in FIGS. 1 - 4 . The combination of the spring material in the sleeves and the shape of fabric results in the panel planes of the oven taking on compound curve shapes which collectively form a parabolic shape, a “rocker” as viewed from the side. The parabolic shape of the unit increases its efficiency in focusing sunlight on an identifiable focal point or focal area to heat a container and any substances contained therein. Frame spring or springs 24 are made of a flexible coilable material, including, but not limited to steel or plastic strips, preferably having a rectangular cross-section to facilitate self-expandability. The frame also facilitates the collapsibility of the structure into overlaying loop assemblages or loops, as shown in FIG. 5 . The front panel includes a zipper 26 or functionally equivalent means of access and secure closure. This closure preferably runs along a portion of the intersection of the front, floor, and one side panel. This provides access to the oven interior so that an object or vessel may be positioned at the focal point for a number of purposes, including, cooking, pasteurizing liquids, heating a shower water bladder, melting snow and ice, steam generation, warming batteries, sterilizing instruments, cooking and heating food, emergency signaling, and radar locating (depending upon materials). The interior side of each side panel and the back panel is preferably coated and/or covered with or includes a silverized, reflective, flexible material. Thus, the only inlet for sunlight 28 ( FIG. 3 ) to enter the oven chamber is through front panel 20 . Referring now to FIG. 3 , it can be seen that sunlight entering the front panel is thereafter focused and reflected into a focal point (or intersections of reflected solar energy forming a small focal area) where a vessel or container 30 may be positioned on a lightweight stand 32 of appropriate dimensions. Because in most instances the most efficient focusing system brings the focal point or focal points to a location above the ground, it is preferable that the cooking container be supported by a stand 32 , though materials that are self-supporting may not need a stand. Other features of the preferred embodiment include a plurality of grommets or gusset and tabs 34 positioned along the seams of the panels, thus providing anchor and tie points for guying strings or lines 36 . Although FIGS. 1 - 3 depict the inventive oven as having a substantially tetrahedral shape (tipped on one side), the configuration may be varied dramatically while preserving the functional principles embodied. Virtually any shape may be employed, as long as the shape lends itself to collapsibility with a spring frame and defines an interior space in which energy from the Sun's radiation can be focused at a specific area within the interior space. Thus, a cylindrical oven would be an obvious variation, said oven having a portion of its side transparent to light, and all other portions having reflective interiors. FIG. 4 shows a design variation 40 on the design of FIGS. 1 - 3 , in this instance comprising a combination of two arcuate panels 42 , 44 , and a third transparent front panel 46 . This simple assembly allows for a single spring to form the entire frame structure without any overlap in the seams at the panel intersections. This is accomplished by threading the spring into seam 22 commencing at point 48 and proceeding first forward parallel to the zipper 26 immediately above the base portion of panel 44 , and proceeding continuously until terminating at point 50 . While a single spring design is not essential to the proper functioning of any embodiment of the pop-up oven of the present invention, it advances the interest of keeping the apparatus lightweight. FIG. 6 shows a third preferred embodiment 60 of the collapsible pop-open solar heating system of the present invention, while FIG. 7 shows detail of the cooking compartment access of this embodiment. In this embodiment, the inventive apparatus is configured to include first and second solar energy collecting compartments, 62 and 64 , respectively. The first solar collecting compartment is formed by six panels which angle outwardly from the second compartment. The panels include a front panel 66 , a rear panel 68 , and side panels 70 , 72 , 74 and 76 , each of said panels joined to adjoining panels at a dedicated contiguous sleeve 66 a , 68 a , 70 a , 72 a , 74 a , and 76 a , into which a dedicated spring is inserted and contained. Adjoining sleeves are either permanently sewn together or, alternatively, may be selectively fastened with fastening means, such as hook and loop material. The entire first solar collecting compartment is covered by a selectively attachable and flexible transparent front cover 78 . This cover fastens to the outside of the first compartment panels with fastening means such as hook and loop material. As in the first and second preferred embodiments described above, the panels of the first compartment of the third preferred embodiment are preferably fabricated of lightweight flexible material, such as rip stop nylon; and, as above, the panels have silverized or other reflective interior surfaces for focusing solar energy to a region within the collection compartment. The third preferred embodiment includes a second solar collection compartment 64 which also functions as the cooking compartment. This compartment is defined by six side panels 80 , 82 , 84 , 86 , 88 , and 90 , which depend downwardly from the lower end 92 of the first solar collecting compartment. The sixth, or rear, side 90 , is comprised of first and second flaps 90 a , 90 b , which selectively open and close to form a door sealed with mating hook and loop material 92 . The base portion 94 of the cooking compartment includes a flat panel 96 substantially parallel with the front cover, which allows the oven to be positioned optimally for collecting solar radiation coming from a substantially overhead position in the sky (see FIG. 10 ); and an angled panel 98 , which permits the oven to be tipped and angled toward the sun as it moves across the sky either toward or away from a generally overhead position (see FIG. 9 ). Each of the panels comprising the cooking compartment may be fabricated of flexible material pulled taut by springs, as described above, or may be fabricated of lightweight material having sufficient rigidity to hold the apparatus upright without a frame structure. The compartment panels preferably including fastening means that allow for selective connection of the panels to form the closed compartment. Hook and loop material is ideally suited to this purpose. Unlike the panels of the first compartment, those of the second compartment include blackened interior surfaces to maximize heat collection and retention. Also, to minimize heat loss when opening the compartment door to place or remove a cooking vessel 100 , the two compartments are separated by a second flexible transparent panel 102 . FIG. 8 shows the apparatus of FIGS. 6, 7 , 9 and 10 in its fully collapsed configuration. As will be readily appreciated, this configuration is suited for both storage and transport and gives the pop-open heating apparatus of the present invention significant advantages over existing art. FIG. 11 is a front perspective view of a fourth preferred embodiment 110 of the collapsible pop-open solar heating apparatus of the present invention, while FIG. 12 is a cross-sectional side view in elevation thereof. In this embodiment, as in the third embodiment, the solar heating apparatus is comprised of first and second solar energy collecting compartments, 112 and 114 , respectively. The first solar collecting compartment, having an inverted and truncated tetrahedral shape, is formed by four panels which angle upwardly and outwardly from the second compartment. The panels include a front panel 116 , a rear panel 118 , and side panels 120 and 122 , each of said panels connected to adjoining panels at a dedicated contiguous sleeve 116 a , 118 a , 120 a , and 122 a , into which a dedicated spring is inserted and contained. Adjoining sleeves are either sewn together or selectively fastened with hook and loop material, or similarly easy-to-use fastening means. The first solar collecting compartment is covered by a flexible transparent front cover 124 , which selectively fastens to the outside of the first compartment panels, preferably with hook and loop material. The inside surfaces of the first compartment panels are highly reflective. The fourth preferred embodiment includes a second solar collection compartment 114 , which functions as the cooking or heating compartment. Four sides form this compartment, 126 , 128 , 130 , and 132 , each depending downwardly from the lower portion of the first solar collecting compartment. The rear side 128 is comprised of two fabric or thin material flaps 128 a and 128 b , which may be closed by approximating complementary fastening devices. As illustrated, particularly in FIG. 12 , the front side 126 of the cooking compartment extends vertically to a height less than that of the rear side 128 . Consequently, the first or upper compartment is always angled, and the surface contacting base portion 134 need not include an angled region to enable tilting toward a setting or rising sun. The first solar collection compartment is separated from the heating compartment with a transparent plastic barrier 136 that permits direct and reflected solar radiation to be focused onto a cooking vessel 138 . The compartment temperature increases as the energy is absorbed by the compartment gasses, the cooking vessel and its contents, and the blackened interior sides of the compartment panels, 126 , 128 , 130 , 132 . FIG. 13 is a rear perspective view of the apparatus of FIGS. 9 - 12 , showing the access to the cooking/heating compartment 114 . Flaps 128 a and 128 b are simply separated and opened to reveal the internal compartment. This figure illustrates that the closure is accomplished with complementary hook and loop material 140 . This view also shows that the transparent barrier 124 of the first compartment is attached to front and rear panel sides, 118 and 116 , with hook and loop material 140 . If desirable, the barrier could be attached to all four panel sides for increased stability and rigidity. FIG. 14 is a perspective view of the apparatus of FIGS. 9 - 13 , shown in a fully folded or collapsed configuration. FIG. 15 is a perspective view of the apparatus of FIGS. 9 - 14 , showing the folding and fastening schedule for collapsing and erecting the apparatus. All of the flaps that are preferably detachable are shown detached so as to enable full folding of the flexible structure. Selected positioning of hook and loop fastening material facilitates rapid collapse, just as it facilitates rapid erection. It will be appreciated that the upper compartment panels, framed and made rigid by loop spring material, will collapse and then fold onto one another so that two corners of one side extend outwardly. All of the flaps of the compartment panels may then be folded and tucked into the layers of the collapsed structure. In this configuration the system is highly portable and easily stored in small spaces. Distilled to its most essential aspect, and characteristic of each of the embodiments, the present invention may be described as a collapsible pop-open solar heating system, comprising a heating enclosure having an open configuration and a collapsed configuration, the enclosure being made of substantially opaque flexible fabric having reflective interior surfaces, and including a window of flexible material for the passage of light. When in the open configuration, the enclosure is shaped so as to reflect and focus light entering the enclosure through the transparent window into a focal region in the interior space defined by the enclosure. In the pop-open embodiments, aa collapsible flexible spring frame is contained within at least one sleeve in the flexible fabric, and the sleeve confines the spring frame. When unrestrained the spring urge the enclosure into an open configuration. Access means are provided for opening the enclosure for placement and removal of heating and cooking vessels. While the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment(s) of the invention, it will be apparent to those of ordinary skill in the art that many modifications thereof may be made without departing from the principles and concepts set forth herein, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use. Accordingly, the proper scope of the present invention should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications as well as all relationships equivalent to those illustrated in the drawings and described in the specification.