Collapsible pop-open lightweight solar heating system

Abstract

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.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

[0003] Not applicable.

TECHNICAL FIELD

[0004] The present invention relates generally to solar heating devices, and more particularly to collapsible pop-open lightweight solar heating system adapted for use by backpackers, campers, climbers, scouts, military personnel, third world countries and relief organizations, and in emergency kits.

BACKGROUND INFORMATION AND DISCUSSION OF RELATED ART

[0005] Collapsible and portable solar heating devices are known in art. For instance, U.S. Pat. No. 4,612,914 to Dogey, issued Sep. 23, 1986, teaches a portable solar powered oven, distiller, heater and light directing survival apparatus fabricated of light weight, flexible materials. The device is formed by concentrating incident solar radiation by means of a funnel shaped reflector into a transparent container which concentrically surrounds a solar heat exchanger. The reflector, transparent container and heat exchanger are constructed in such a way as to permit the heating of food, water, air or desalination reactants to temperatures in excess of 400.degree. F., yet when collapsed, can all fit within the portable transparent container.

[0006] However, the solar heating device of the '914 patent is formed in a particular shape and is comprised of semi-rigid materials. The heating device is in the shape of a cylindrical, transparent container with a removable, sealable closure, and a concentric, inner solar absorbing container. The transparent container and inner absorbing, heat exchanging container lie on the major axis of a surrounding, funnel shaped reflector, which is constructed of a flexible, yet semi-rigid reflective material. The reflector is held in a fixed position relative to said transparent container by mechanical fasteners that create frictional forces at the reflector's base about the transparent container's closure and whose other function is to define the geometry of the reflector by connecting sections together by the mechanical fasteners. The reflector is constructed in sections so when disassembled, will roll up and fit within the containers for portability. The closure will have an optional mechanical fastener, which penetrates the center point of the closure, attaching the solar absorbing container to the closure and an exterior mounted two-axis swivel that can be attached to a fixed base for manually or electro-mechanically directing the major axis of said reflector at the sun for optimum performance.

[0007] The Dogey device is ill-suited for backpackers and hikers as it is neither lightweight nor particularly portable. It requires a swivelable rigid stand for effective orientation to the sun, and it is also fabricated from semi-right materials which limit its portability and make it cumbersome to carry.

[0008] As is readily appreciated by anyone who has carried food and cooking utensils in a backpack, the apparatus taught in Dogey would not serve their needs, as weight and space are critical concerns to hikers and backpackers; it eliminates the need to carry heavy fuel, but it substitutes a heavy oven. Thus, there long remained a need for an efficient solar oven device with features that would enable the user to hike in and out of an area without the need to carry a heavy stove and fuel containers.

[0009] Accordingly, the present inventors devised an apparatus to provide a solution to the foregoing problems and further solve the problems presented by, e.g., the solar cooking devices in the art. Specifically, U.S. Pat. No. 5,893,360 to Stoumen, et al., issued Apr. 13, 1999 teaches an inflatable solar oven comprised of two sheets of flexible material which are sealed at their edges to form an enclosure. The top sheet is clear and the bottom sheet has a reflective layer. The two sheets can be inflated to form a spherical enclosure by passing air through an edge opening that is also large enough to access a water or food holding receptacle which can be placed with the inflated enclosure. Extended portions of the sheets that form the opening can be rolled up to form a closure for it. The inflated enclosure can be secured to the ground in an appropriate position to receive the sun's rays which pass through the clear sheet and reflect from the bottom sheet to heat the receptacle therein.

[0010] While the above-described inflatable solar oven has many advantages over any prior art portable solar cooking devices, it would nonetheless be desirable to have means to define the open oven space more rapidly than is possible with the inflatable oven. Furthermore, it would be desirable to have a portable, collapsible solar oven more durable, abrasion resistant, and adapted for use in more extremely rugged environments, including high altitude and high wind environments, rocky terrain, and other hostile environments that would tax the structural and functional integrity of a lightweight inflatable fabric solar cooking apparatus.

[0011] Various means for quickly erecting portable fabric structures are known. For example, a lightweight tent which can be quickly erected and quickly collapsed is disclosed in U.S. Pat. No. 3,675,667, which teaches a tent of the type generally referred to as quickly erecting or self erecting which can be folded down without taking its components apart. U.S. Pat. No. 5,038,812 to Norman, issued Aug. 13, 1991, teaches a quickly erectable, quickly collapsible, self supporting portable structure that is self-expandable with little or no effort by the user, which in their fully expanded upstanding configuration are self-supporting. The fully expanded upstanding structure can be quickly collapsed into a stack of side members and coiled into a pack. The structures are adapted for use as tents, shelters, pavilions and automobile carports. In general the portable structures have a set of at least three side members each having a flexible frame, a side panel, a pocket joined to the panel by stitching. The frame causes the side members to be self expandable. Side members are hinged together by stitching. A floor member sewn to the bottom of each side member holds the structure in the upstanding position.

[0012] The '812 patent references several of its predecessors, including, U.S. Pat. No. 3,960,161; U.S. Pat. No. 3,990,463, and U.S. Pat. No. 4,825,892, and U.S. Pat. No. 4,815,784.

[0013] There is no known portable, lightweight solar powered oven that combines the foregoing technologies; namely, that provides a quickly erecting and quickly collapsible oven structure adapted for collecting solar rays.

BRIEF SUMMARY OF THE INVENTION

[0014] Accordingly, it is an object of the present invention to provide a lightweight solar heating system that can be quickly erected and quickly collapsed, and which provides a solar oven made of flexible material which can be folded into a small, relatively light package and yet can be quickly and easily erected for use to expose a large reflective surface that will direct the sun's rays onto a container for food, water, or snow to be cooked, heated, and/or pasteurized.

[0015] Another object of the invention is to provide a durable lightweight pop-open oven compartment made of rip stop nylon or other sturdy flexible material, that is substantially self-erecting and self-supporting by means of a flexible spring steel or ribbon plastic frame.

[0016] Still another object of the invention is to provide a flexible, highly portable solar heating device that is particularly well adapted for ease and economy of manufacture.

[0017] Yet another object of the present invention is to provide a device suitable for use by the world's poor, refugees in refugee camps, displaced persons generally, relief workers, and military personnel or others living in a permanently or temporarily nomadic condition.

[0018] These and additional objects are accomplished by the present invention, whereby a solar heating system is fabricated of flexible material having a loop spring frame. The system may be collapsed for storage and transport into a substantially flat shape, but it may be rapidly and easily popped open to a form a fully erect structure having a combination of at least one transparent side for allowing solar radiation to enter the structure, and a plurality of opaque sides having highly reflective interior surfaces capable of capturing and focusing the solar energy onto heating and cooking containers. In selected embodiments, the system includes bifurcated compartments to increase heating efficiency.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0019] FIG. 1 is a front axonometric view of a first preferred embodiment of the collapsible pop-open lightweight solar heating system of the present invention;

[0020] FIG. 2 is a cross-sectional side view in elevation of the solar oven of FIG. 1;

[0021] FIG. 3 is a front view in elevation of the solar oven of FIGS. 1 and 2;

[0022] FIG. 4 is a side perspective view showing an alternative collapsible pop-open oven shape;

[0023] FIG. 5 shows a pop-open oven in its collapsed configuration ready for transport and storage;

[0024] FIG. 6 shows a third preferred embodiment of the collapsible pop-open solar heating system of the present invention;

[0025] FIG. 7 shows detail of the cooking compartment access of the apparatus of FIG. 6;

[0026] FIG. 8 shows the apparatus of FIGS. 6 and 7 in its fully collapsed configuration;

[0027] FIG. 9 is a cross-sectional side view in elevation of the apparatus of FIGS. 6-8, shown supported on an angled surface to tip the apparatus;

[0028] FIG. 10 is a cross-sectional side view in elevation of the apparatus of FIGS. 6-9, shown fully upright;

[0029] FIG. 11 is a front perspective view of a fourth preferred embodiment of the collapsible pop-open solar heating apparatus of the present invention;

[0030] FIG. 12 is a cross-sectional side view in elevation of the apparatus of FIG. 11;

[0031] FIG. 13 is a rear perspective view of the apparatus of FIGS. 9-12, showing the access to the cooking compartment;

[0032] FIG. 14 is a perspective view of the apparatus of FIGS. 9-13, shown in a fully folded or collapsed configuration; and

[0033] FIG. 15 is a perspective view of the apparatus of FIGS. 9-14, showing the apparatus panels poised for folding into a collapsed configuration.

DETAILED DESCRIPTION OF THE INVENTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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).

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 66a, 68a, 70a, 72a, 74a, and 76a, 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.

[0044] 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.

[0045] 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 90a, 90b, 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 116a, 118a, 120a, and 122a, 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.

[0050] 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 128a and 128b, 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.

[0051] 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.

[0052] FIG. 13 is a rear perspective view of the apparatus of FIGS. 9-12, showing the access to the cooking/heating compartment 114. Flaps 128a and 128b 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.

[0053] FIG. 14 is a perspective view of the apparatus of FIGS. 9-13, shown in a fully folded or collapsed configuration.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

Claims

1. A collapsible pop-open solar heating system, comprising: a heating enclosure having an open configuration and a collapsed configuration, said enclosure made of substantially opaque flexible fabric having reflective interior surfaces, and including a region of transparent flexible material for the passage of light, wherein when in said open configuration said enclosure is shaped so as to reflect and focus light entering said enclosure through said transparent flexible material into a focal region in the interior space defined by said enclosure; a collapsible flexible spring frame contained within at least one sleeve in said flexible fabric, wherein said sleeve confines said spring frame and when unrestrained causes said spring frame to urge said enclosure into an open configuration; and access means for opening said enclosure for placement and removal of heating and cooking vessels in said enclosure.

2. The solar heating system of claim 1, wherein said access means comprises a fabric flap formed in said enclosure selectively secured by fastening means.

3. The solar heating system of claim 2, wherein said fastening means comprises portions of complementary hook and loop material.

4. The solar heating system of claim 2, wherein said fastening means is a zipper.

5. The solar heating system of claim 1, wherein said heating enclosure is substantially tetrahedral in shape and comprises: first and second side panels, a back panel, a top panel, and a floor panel, said panels affixed to immediately adjoining panels and fabricated of flexible opaque material, said panels each including sleeves along their respective edges, and a transparent panel attached at its edges to said first and second side panels, said top panel, and said floor panel.

6. The solar heating system of claim 5, wherein said spring frame comprises a plurality of flexible and coilable springs having memory, said springs slidably inserted into said panel sleeves, wherein said sleeves confine said springs such that when said springs are unrestrained, said panels are urged into a separated relationship to deploy said heating enclosure into an open configuration.

7. The solar heating system of claim 5, wherein said enclosure includes access means when in an open configuration.

8. The solar heating system of claim 5, further including a plurality of tabs and grommets to serve as tie points for guying lines.

9. The solar heating system of claim 1, wherein said heating enclosure comprises a combination of two arcuate panels and a transparent front panel, and wherein said spring frame comprises a single spring inserted into a continuous sleeve to form said spring frame.

10. A collapsible solar heating apparatus having a collapsed configuration and an open configuration, said apparatus comprising: a first solar energy collecting compartment, said first compartment having a plurality of sides with reflective interior surfaces and forming a polyhedron having a first opening and a second opening smaller than the first opening; a second solar energy collecting compartment extending downwardly from said second opening of said first solar energy collecting compartment and comprising a plurality of panels forming a polyhedron having an opening contiguous with the second opening of said first solar energy collecting compartment and a base for placement on a substantially flat surface; and a transparent panel covering the first opening of said first solar energy collecting compartment.

11. The solar heating apparatus of claim 10, wherein said first and said second compartments are separated by a transparent panel.

12. The solar heating apparatus of claim 10, wherein each of said sides of said first solar energy collecting compartment is made of flexible fabric and includes an integral sleeve around the edges of said side, said sleeve containing a frame spring.

13. The solar heating apparatus of claim 10, wherein said sides of said second solar energy collecting compartment are non-reflective.

14. The solar heating apparatus of claim 10, wherein each of said sides of said first solar energy collecting compartment are made of flexible fabric and each of said sides is joined to adjoining sides at a dedicated contiguous sleeve into which a dedicated spring is inserted and contained.

15. The solar heating apparatus of claim 10, wherein said sides are fastened to adjoining sides in the open configuration by strips of hook and loop material.

16. The solar heating apparatus of claim 10, wherein said second solar energy collecting compartment includes an access door comprised of selectively sealable overlapping flaps.

17. The solar heating apparatus of claim 10, wherein said solar energy collecting compartments each have six sides.

18. The solar heating apparatus of claim 17, wherein said second solar energy collecting compartment has a base with a flat portion and an angled portion for tipping said apparatus at an angle.

19. The solar heating apparatus of claim 10, wherein each of said solar energy collecting compartments has four sides.

20. The solar heating apparatus of claim 19, wherein said second solar collecting compartment has a front side and a rear side, said front side extending vertically to a height less than that of said rear side, such that said first solar energy collecting compartment always angled relative to the surface on which said apparatus is placed.