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FIELD OF THE INVENTION  
         [0001]    This invention relates to the field of portable structures. More particularly this invention relates to the field of mobile, expandable structures containing one or more rooms, that can easily be transported and assembled and conversely being equally as quick and convenient to disassemble for relocation. The expansion of these units is in both the horizontal and the vertical directions and provides for full support of the roof and upper walls without the need for hydraulics or other supports to keep the roof and upper portions elevated during use. These structures may or may not be permanently affixed to a framework with wheels to be towed by a motor vehicle. The unique method of erecting and supporting will be fully described within body of this patent.  
         BACKGROUND OF THIS INVENTION  
         [0002]    There are many designs of mobile structures but most are burdened with a flimsy structure or are limited in the area into which they can expand, while others are cumbersome, awkward to transport, and labor intensive to assemble. Such portable light structures are usually in the trailer style and used for private accommodations while the larger units are designed to fulfill government contracts. The device as herein described and disclosed, will fully meet the structural requirements of a mobile commercial or military accommodation of one or more rooms while being low profile, light weight and easy to transport. It uniquely provides for full support of the upper portions upon lower portions and thus increases the load-bearing ability of the upper portions.  
           [0003]    The need for adequate accommodations for disaster relief structures, that can be stored in a relatively small area and quickly dispersed to be set up as office space, medical room, temporary storage, maintenance and repair rooms, etc., has been made vary apparent recently. In the past there was a requirement that everything used for housing and relief had to travel over rough terrain to get to a desired activity site. With the development of the roads throughout the developed areas of the world, and the use of large air transport planes capable of vehicle transport, there is almost no place that is not accessible by some form of road system. With government and military requirements for portable structures, there has also not been a great deal of concern with weight because large vehicles usually transport units of this kind with the primary concern being, making them indestructible.  
           [0004]    Problems arise when mobile structures of this kind become too heavy to be moved around easily in urban environments, often requiring a lot of heavy equipment for assembly. One of the many unique features of this invention is the capability of maintaining a lightweight solid structure while almost doubling the square footage of internal protected floor area. Additional problems arise in the time involved to assemble conventional cumbersome mobile structures.  
           [0005]    The unique device herein disclosed describes a structure that is equipped with all the mechanisms required to easily erect and be fully assembled by one or two people in less than ten minutes, with the same time required for disassembly. An additional feature of this structure is that the floor inside the erected structure is completely flat and provides a large working area. The erected structure features a roof and upper sides and ends that are fully supported by a translateable lower endwall thus elevating the stress on conventional hydraulic and screw extensions during long term use. Also paramount to the development of the disclosed device was to provide a portable housing unit of this kind, keeping the weight down while being structurally solid enough to meet the stringent structural requirements of government and military contracts.  
           [0006]    U.S. Pat. No. 2,890,498. of Floyd E. Bigelow relates to a portable building, and more particularly to a house or cabin structure made up of separate parts which may be easily assembled and disassembled and which disassembled may be formed into a compact assemblage for covenant storage or transportation. This structure does not have a central framework, and would not be convenient to transport over the highway to a disaster site, or work well for portable offices.  
           [0007]    U.S. Pat. No. 3,866,365 of Michael L. Honigman describes expandable structural modules for space enclosures that incorporate a number of sophisticated mechanisms to assemble a device used as cabin trailers or camper units. This device cannot achieve extended lengths and would not be practical for a commercial of government enclosure.  
           [0008]    U.S. Pat. No. 4,603,518 of Walter Fenns describes a collapsible building, which is mounted on the platform of a conveyance that has a first elongated unit mounted on a platform, and a pair of collapsible elongated units, which flank the first unit when the building is fully erected. This is a large heavy structure requiring a semi truck to transport and it does not present a low profile when towing.  
           [0009]    U.S. Pat. No. 4,850,268 of Kenichiro Saito et al, describes a multi-purpose laboratory room for mobile applications. The room comprises a housing structure having an airtight laboratory unit, an entrance unit and an air-conditioning system. This is a specialized structure, not easily transported or used for other applications.  
           [0010]    U.S. Pat. No. 4,958,874 of Leslie J. Hegedus discloses a mobile unit comprises a lorry trailer having sidewall portions, which pivot down to form a large floor and upwardly slideable panels or frames from which unfold side roof portions. This invention discloses a trailer-mounted structure that is very complicated and time-consuming to erect. It does not supply a low profile when towing.  
           [0011]    U.S. Pat. No. 5,345,730 of Bruce A. Jurgensen teaches of an expandable structure, which may be expanded on a selected site into a composite structure incorporating the core structure and a contiguous expanded section. This is another patent that discloses a device that will only expand laterally and cannot be lowered to create less wind resistance when being towed.  
           [0012]    U.S. Pat. No. 5,761,854 of Brian D. Johnson et al, describes a container with fold down sides to create an expanded structure. This again is another patent that discloses a device that will only expand laterally and cannot be lowered to create less wind resistance when being towed.  
           [0013]    U.S. Pat. No. 5,797,224 of Ray R. Gunthardt describes a multitude of structures composed of many intricate parts and mechanism, all of which would create a great deal of weight and be very complicated to erect.  
           [0014]    U.S. Pat. No. 5,815,988 of Jose Raymon Molina teaches of an expandable retractable portable structure having a movable portion hingedly connected to a stationary portion. This patent is similar to the Fennes U.S. Pat. No. 4,603,518 having a complete side unit hinge out from a central unit producing a high profile when towing.  
           [0015]    U.S. Pat. No. 5,964,065 of Tomasz K. Migurski et al, discloses an advanced vehicle-transportable field emergency medical system, comprising surgical suites deployed from a core module, each expanding to form an enclosed surgical treatment room with perimeter tenting space. This patent relates to a complicated, specialized structure with a specific purpose taking a great deal of time to erect by people who were familiar with the intricacies of the device.  
           [0016]    U.S. Pat. No. 5,596,844 of Juan R. Kalinowski describes a foldable portable building that be collapsed to fit within the outside dimensions of an internationally standardized (ISO) goods container. This patent describes a very heavy unit when it is in the collapsed state and very complicated to erect.  
           [0017]    U.S. Pat. No. 5,966,956 of Leland M. Morris et al, teaches of a portable unit which is foldable to be shipped and transported as a standard cargo shipping container. This is another patent that describes a heavy structure that is cumbersome and heavy to transport.  
           [0018]    As such, there is a need for a structure that is fixated on a central framework and easy to transport by towing or trucking. Such a device should have a low profile to facilitate movement where low passage height exists. Such a device should be compact yet an expandable structure that is easily erected in a minimum amount of time by a minimum number of people. Further, such a device should be structurally sturdy and self supporting of the upper structure by the lower portion of the structure to alleviate stress on hydraulic or similar expansion means during long term use of the expanded unit.  
         SUMMARY OF THE INVENTION  
         [0019]    The invention herein disclosed relates to a new and unique system for assembling and supporting mobile, expandable structures that accommodate one or more rooms. More specifically, these structures will expand on both length and width outwardly at the same time and then elevate all the roof members together in a secondary operation to a desired height, which in the current best mode is substantially eight feet. Once so elevated, the roof and upper wall portions are structurally supported in their elevated position by lower walls which translate into a position to register in line with the upper walls and thereby support the upper half of the structure securely during the expanded mode.  
           [0020]    The expanding and elevating of the roof members is provided by a central means to elevate the roof member and a means to expand the sides which in the current best mode is provided by hydraulic cylinders communicating with pressurized fluid from motor energized pumps. However those skilled in the art will realize that other common mechanical means, such as screw jacks or cables and motors and similar come along type devices could be used and such are anticipated. A secondary manual back-up expansion system will achieve all the same results in the event that there is not enough power in the batteries to operate the preferred hydraulic system.  
           [0021]    The structures may be mounted on a variety of vehicles or on fixed foundations and could even be dropped on site by a helicopter or large truck. Because of the large area of unobstructed floor space yielded by the expanded device and unique folding floor elements, the internal configuration can consist of a single large room, two or more smaller rooms with a kitchen and restrooms being other additional options.  
           [0022]    When transporting the structure all components which expand to the erected structure will be best transported in the retracted positions. Upon arrival at the desired erecting sight, when vehicle mounted as in the current preferred mode, the structure base will first be leveled and stabilized by actuating the hydraulic levers in a hydraulic control box on the tongue at the front of the structure. Four of these controls operate the hydraulic jacks at the four corners of the central frame forming the base, which are the means used to initially level the base of the device. Next, the hydraulic motor energizes the hydraulic rams or cylinders that extend the two opposing side sections can be activated with another lever in the hydraulic control box. This provides the means to laterally translate the side sections from a first retracted position inside the interior cavity of the central structure, formed between the central top unit and the central bottom unit, to the extended position. The length of the expandable side sections is described, but not limited to the full length of the interior cavity of the mobile, expandable structure. Each side section may vary in length and location on the mobile, expandable structure and still be covered within the scope of this patent. When the side sections are fully extended the central roof section and the side section roof panels are interlocked together to form a watertight seal. Then the support legs on the corners of the side sections are manually extended to the ground to fully stabilize the complete structure.  
           [0023]    The next operation is to activate the hydraulic lever in the hydraulic control box as a means to raise all the roof elements at the same time with the central hydraulic cylinder. The roof elements must be raised above their fixed position preferably at least two inches allowing a gap for the front and back bottom wall panels to be repositioned before lowering. Telescoping guide cylinders at the four corners of the central frame align the top and bottom sections. The top and bottom wall panels at the front and back are aligned with a means for cooperative in-line engagement currently provided by alignment pins and bushings. This unique interlocking feature allows that when bottom sections of both end wall panels are relocated from their position in the interior cavity and under the top sections of the end wall panels, and the roof elements are lowered into their fixed position, the top sections will be fully supported by the bottom sections and form a seal thereon combining to a solid wall section, both in the front and back of the structure. A means to translate the bottom wall panel of the end wall panel assemblies, from a first position out of line with the centerline of the top wall panels to a secondary position registered with inline with the centerline of the top wall panel provides this unique function which in the current best mode is two or more beveled locating pins extending from the top edge of the bottom wall panel to engage within orifices in bushings located along the bottom edge of the top wall panel. This registered sealed engagement is combined with a slide or hinged translation of the bottom section. By translating the bottom sections into cooperative sealed registered engagement with the top sections of the endwalls, the primary load of the roof component of the locked side section roofs and central roof section and the upper portions of the wall attached thereto is removed from the central hydraulic cylinder and translated to the end walls. During long term use of the device, this provides relief to the hydraulic cylinder or other elevation means from the constant weight of these sections. It also provides added safety to the inhabitants of the structure since the potential for collapse of the upper section onto the bottom is elevated by the bottom endwalls supporting all the weight inline. In the event that the roof is covered with snow or ice or soil increasing the weight of the upper section, the support scheme provided by the engagement of the lower endwalls inline and sealed with the upper endwalls provides extra load bearing and safety to the occupants.  
           [0024]    At least one door but preferably two doors with one in both the front and back end wall panels are preferably formed of two sections and operate like a common Dutch door. By using the two piece endwalls with half the door on each, the door handle and lock on the lower section and a second lock on the upper section, both swing independently. However, a registered and permanently engaged door of two sections might also be used. Windows in the doors and wall panels will be at the option of the customer requirements.  
           [0025]    In the preferred embodiment the floor panels for the side sections will be lowered and raised automatically with straps that are attached to the lower edges of the top sections. When the top section is raised, the strap communicating between the top section and the floor section slackens and both side section floor panels are lowered into position flush with the center floor section thus creating a completely flat floor. The straps are then disconnected and stored. In this preferred embodiment, the floor panel hinge will attach on the outermost lower edge of the bottom section on each of the side sections to result in a completely flat floor surface when the device is in the fully extended position with both sides extended.  
           [0026]    A second embodiment would feature the same center section arrangement but the floor panels will have the floors of the side sections hinging on the inner edge attached to the central frame structure to be manually lowered to form a completely flat floor.  
           [0027]    A third preferred embodiment would again use essentially the same center section arrangement but will have the complete bottom side section with the floor included, hinging on the inner edge attached to the central frame structure. This will form area with sealed containment area to keep equipment and supplies in a clean environment when being transported or stored. This embodiment of the invention will also have a completely flat floor surface. The preferred embodiment of the top section of the side sections will be constructed of, but not limited to a one-piece fiberglass section. The top section will consist of a front and rear end panel, a pair of side panels and a roof panel. Both top and bottom sections will have side panels that may or may not have one or more windows to be determined by the customer&#39;s requirements.  
           [0028]    In an additional preferred embodiment to reduce weight should that be desired, the top sections of the side sections will be a tubular framework covered with a waterproof fabric. Not only covering the ends, sides and top of the side sections, the fabric may extend past the side wall to create a retractable awning. The fabric used for covering the top sections of the side sections may incorporate flexible photovoltaic cells for generating operating power for the structure.  
           [0029]    An alternate preferred embodiment of the structure will have one each of the end wall panels of two separate structures replaced with header units to accommodate the mating together of two or more structures when placed back-to-back thus forming twice the open flat floor area of a single structure.  
           [0030]    An object of this invention is to provide a mobile, expandable structure that when retracted or assembled will pass the rigid structural specifications and requirements of commercial and government contracts.  
           [0031]    Another object of this invention is to provide a mobile, expandable structure that is not excessively heavy.  
           [0032]    A further object of this invention is to provide a mobile, expandable structure that can be extended and setup in less than ten minutes.  
           [0033]    An additional object of this invention is to provide a mobile, expandable structure that when fully extended will be close to twice the retracted size.  
           [0034]    Still another object of this invention is to provide a mobile, expandable structure that when extended will have an eight foot ceiling and completely flat floor with vertical walls.  
           [0035]    A further object of this invention is to provide a mobile, expandable structure with wall, end panels and doors that can be equipped with glass windows.  
           [0036]    Yet another object of this invention is to provide a mobile, expandable structure with a two-part front and back wall panel system that interlocks to form two rigid end wall units with the weight of the top half of the structure fully supported by the bottom endwalls.  
           [0037]    Another object of this invention is to provide a mobile, expandable structure that the two top sections of the side sections can be covered with a waterproof photovoltaic material that will generate electrical power.  
           [0038]    Still another object of this invention is to provide a mobile, expandable structure with expandable side sections that may be rotated in and out of place and form a sealed compartment with the central floor area.  
           [0039]    An additional object of this invention is to provide a mobile, expandable structure that can be retracted to have a narrow low profile, to be easily towed behind a motor vehicle on the street.  
           [0040]    These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0041]    Accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.  
         [0042]    [0042]FIG. 1 depicts a perspective view of the disclosed mobile, expandable structure in the retracted state ready for transporting.  
         [0043]    [0043]FIG. 2 depicts a perspective view of the mobile, expandable structure, in the expanded condition  
         [0044]    [0044]FIG. 3 depicts a top view of the mobile, expandable structure in the expanded state showing a portion of the roof cut away to display the floor areas. A portion of the side floor panel has been cut away to display the frame members.  
         [0045]    [0045]FIG. 4 is a section through the mobile, expandable structure illustrating the top and bottom front wall panels in the erecting position.  
         [0046]    [0046]FIG. 5 is a section through the mobile, expandable structure illustrating the top and bottom front wall panels in the interlocked position descended from the erecting position of FIG. 4.  
         [0047]    [0047]FIG. 6 is a detail of the two piece endwall segments in the erecting position.  
         [0048]    [0048]FIG. 7 is a detail of the two piece endwall segments in the in the interlocked and load supporting position.  
         [0049]    [0049]FIG. 8 is a section through the expanded mobile, structure, viewing the typical wall panels, illustrating the preferred embodiment of the side section floor panel.  
         [0050]    [0050]FIG. 9 is a section through the mobile, expandable structure with the roof panels and upper section lowered, and illustrating the operation of the preferred embodiment of the side section floor panels.  
         [0051]    [0051]FIG. 10 is a section through the mobile, structure with the side section top in the lowered position, illustrating the operation of the second embodiment of the side section floor panels.  
         [0052]    [0052]FIG. 11 is a section through the mobile, structure with the roof panels lowered, depicting the operation of the third embodiment of the side section floor panels.  
         [0053]    [0053]FIG. 12 is a section through expanded mobile, structure with one side and the roof in the extended position, illustrating the second preferred embodiment of the side section top section with fabric cover and awning. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0054]    Referring now to the drawing FIG. 1 shows the mobile, expandable structure  10 , in the retracted position. The central structure  12  consists of a top unit  14  shown covering a central structure bottom unit and having one-piece central roof section  18 . At the distal ends of the central structure  12  is a top wall panel  24  and a bottom wall panel  26  which translates inline and inter locks to form the rigid end wall panel assembly  20 . Typical end wall panel assemblies  20  at both ends of the central structure  12  will incorporate a Dutch style door with  28  as the top door member  28  and bottom door member  30 . The door members in the current best mode will operate independently, both having separate locking capabilities, also being able to interlock together working as a single door unit.  
         [0055]    A means to translate the bottom wall panel  26  of the end wall panel assembly  20 , from a first position out of line with the centerline of the top wall panel  24  to a secondary position inline with the centerline of the top wall panel  24  is provided to allow such separation. This is done by translating the bottom wall panel  26  toward the interior of the central structure  12  and out of line with the top wall panel  24  to allow the endwall assembly  20  and attached central roof section  18  to collapse to the contracted position of FIG. 1 for transport. Also provided is a means for cooperative registered engagement between the bottom edge of the top wall panel  24  and the top edge of the bottom wall panel  26  in the form of two or more beveled locating pins  82  extending from the top edge of the bottom wall panel to engage within an orifice  84  in bushings  86  located along the bottom edge of the top wall panel  24 .  
         [0056]    The base of the central structure  12 , provided here by the frame assembly  70 , has four hydraulic elevating jacks  32  built in at each corner providing a means to level the base of the central structure. An interior cavity is defined in the central structure  12  by the area below the central roof section  18  and between the two endwall assemblies  20 . At the front of the central structure  12  is a towing tongue  34  with a towing ball receiver  36  thereby allowing the device to be towed on the wheels attached to the frame assembly  70 . As noted above, in some instances the disclosed device  10  might be used without wheels  35  where it is transported on the back of a truck or in an airplane and just moved to position with a forklift or the like. The current best mode does feature wheels  35  since they ease the transport of the device  10  no matter what manner it is transported. Portable steps  42  will be available to be placed in front of the doors at either end of the central structure  12 . Mounted on the tongue  34 , the preferably watertight hydraulic control box  38  houses the hydraulic actuating levers  40 . By operating the hydraulic control levers  40 , the structure cannot only be leveled on the desired site, but the expandable first side section  48 A and the expandable opposing second side section  48 B can be extended into the extended position from the retracted position from the same control location. Although two expandable side sections  48 A and  48 B are shown it must be understood that the mobile expandable structure could incorporate only a single side section  48 , and while not yielding as much floor space would still be anticipated within the scope of this patent and using the two piece supporting endwall assemblies  20  described above, would be a great improvement in portable structures.  
         [0057]    The two expandable side-sections  48 A and  48 B are typical in their basic configuration with two alternate embodiments of the top section  50 A and  50 B and bottom side wall section  52 . In the embodiment of the expandable side sections  48 A and  48 B, top section  50 A is composed of a roof panel  54 , a first upper end panel  56  and second upper end panel  58 , and upper side panel  60 . The side sections, when extended from their retracted position inside the central cavity  71 , will be supported at their distal ends by side section support legs  62  that are manually positioned while raising the central structure  12  with the hydraulic leveling jacks  32  at the four corners. Optional windows  64  can be added in any of the upper side panels  60  or either of the top wall panels  24  of the endwall assembly  20  or to the top door member  28  optionally and to improve viewing from inside.  
         [0058]    [0058]FIG. 3 displays a plan view of the mobile, expandable structure  10  in the expanded condition with a portion of the central roof section  18  cut away along with a portion of the side roof panel  54 , to reveal the central floor panel  66  and the preferred embodiment of the side floor panels  68 A. Also the floor panels  66  and  68  have been cut away to display the frame assembly  70  forming the base. Extending the guide rails  72  and the expansion activating rails  74  facilitates the expansion of the side sections&#39;  48 A and  48 B from the retracted position with the side sections  48   a  and  48   b  and roof panel  54  inside the central cavity  71  to the expanded position projecting from the sides of the central structure  12 . A means to translate the expandable side sections  48 A and  48 B from a first retracted position inside the interior cavity of the central structure  12 , formed between the central top unit  14  and the central bottom unit  16 , to the extended position is provided in the current best mode by the hydraulic cylinders communicating elongation and contraction to the activating rails  74  which move the entire side section in and out of the interior cavity  71  as needed. The maximum length of the expandable side sections  14  and  16  is described, the full length of the interior cavity  71  between the endwall assemblies  20 . Each of side sections  14  and  16 , may vary in length and location on the mobile, expandable structure  10  and still be covered within the scope of this patent. The width of the side sections  14  is dictated by the width of the interior cavity  71  in that they must substantially retract therein consequently one half the width of the interior cavity  71  would be the best maximum width to achieve maximum compaction in the retracted position. However a larger mobile expandable structure  10  could be achieved by allowing the side sections  14  to overhang the sides of the central cavity  71  if desired in some applications.  
         [0059]    The central roof section  18  is cooperatively engaged with the two side top sections  50 A or  50 B and the roof panels  54  of the sides such that they will raise and lower as a single unit. Centrally located within the structure  12  is a means to raise and lower the central roof section  18  and the two side sections&#39;  50 A or the alternate embodiment sections  50 B along with the communicating roof panels  54 , which in the current best mode is the hydraulic jack cylinder  76 . Thus, as the hydraulic jack raises and lowers the central roof section  18  all the other aforementioned cooperatively engaged parts raise and lower with it. Also, in the current best mode, as the central hydraulic jack  76  raises the roof, four telescoping guide cylinders  78  at the corners locating the central structure top  14  and the central structure bottom  16  aligned in registered engagement with each other.  
         [0060]    [0060]FIG. 4 is a section view through the expanded mobile structure  10 , viewing the end wall assembly  20  in the erecting position where top wall panel  24  is rigidly attached to the top of the central structure  12  and the bottom wall panel  26  is adjustably attached to the frame assembly  70  providing the base. As shown, the bottom wall panel is positioned inside of the top wall panel  24  during expansion and contraction of the upper section during set up. This allows the top wall panel  24  and thus the central roof section and attached side roof sections  54  to drop down much more compact for transport by allowing the top wall panel  24  to laterally translate by the bottom wall panel  26 .  
         [0061]    [0061]FIG. 5 is a section through the mobile, expandable structure  10  illustrating the top wall panel  24  and the bottom wall panel  26  in alignment forming a rigid wall panel  20  when in the expanded or fully erected position. FIG. 6 further illustrate the panels  24  and  26  in the erecting position with the wall panel alignment pin  82  located on the top edge of the bottom wall panel  26  thereby providing a registration means between the two. A bushing  84  with an alignment orifice  86  is located on the lower edge of the top wall panel  24 . A means to translate the bottom section of the endwall from a first position out of line with the center line of the upper endwall to a position inline with the center line of the upper endwall is provided as depicted by relocating linkage  88  located on the bottom edge of bottom wall panel  26  attached to the frame assembly  70 , facilitating the adjustment of the wall panel  26  directly under top wall panel  24  by rotating it on the relocating linkage  88 . Another such means could be provided by sliding mechanism and thus achieving the same results that will be covered within the scope of this patent, however the current best mode features the relocating linkage  88  to simply rotate the bottom wall panel  26  out of the way of the top wall panel  24  to allow them to laterally translate in relation to each other during lowering of the upper section.  
         [0062]    [0062]FIG. 7 illustrates the wall sections  24  and  26  in the interlocked position in registered engagement with each other. As noted, a great advantage is gained by translating the bottom wall panel  26  in line with the top wall panel  24  by communicating the weight of the central roof section  18  and the engaged side roof sections  54 , upper side panels and upper end panels  56  all engaged with to central roof section  18 , to the bottom wall panels  24  when the top and bottom wall panels are so engaged and thereby become a rigid weight bearing element of the structure.  
         [0063]    [0063]FIG. 8 is a section through the expanded mobile structure  10  illustrating the preferred embodiment of the side floor panels&#39;  68 A pivoting on the floor panel hinge mechanism  80 , with the floor panel lifting straps  89  and the attaching means  92 . This strap mechanism provides a means to automatically raise and lower the floor panels  68 A when the top section  50 A is raised and lowered, in this case by the hydraulic jack cylinder  76 . Each lifting strap is attached to a lower edge of the expandable side top section  50 A and hooked to the attaching means  92  on the end of the floor panel  68 A opposite the hinge  80  so that when the side section top  50 A is raised the strap  89  translates over the edge of the side section bottom lowering the side section floor panel  68 A. This operation acts in reverse raising top section  50 A raises all the parts cooperatively engaged and raises the side section floor panel  68 A when the side section top  50 A is raised illustrated in FIG. 9.  
         [0064]    [0064]FIG. 10 is a section through the mobile, expansible structure  10  with the side section top  50 A in the lowered position, illustrating the operation of the second embodiment of the side section floor panels&#39;  68 B, pivoting on the floor panel hinge mechanism  80  mounted on the opposite side. The same strap means noted above can be used for automatic raising and lowering if a pulley (not shown) were affixed above the hinge  80 .  
         [0065]    [0065]FIG. 11 is another section through the mobile from one end, showing the expandable structure  10  depicting the operation of the third preferred embodiment with the side section  48 A attached to the side floor panel  68 C pivoting into the central cavity  71  for transport. This embodiment would function the same in all other aspects except that the side floor panels  68   a  would be attached to the bottom side wall section  52  and the lower side end panels  59  as a complete lower side unit and it would rotate in and out of the central cavity  71  on a hinge  70 .  
         [0066]    [0066]FIG. 12 is a section through the mobile, expandable structure  10  illustrating another preferred embodiment of the expandable side section top section  50 B with a waterproof fabric covering  94 . The waterproof fabric covering  94  is held in place with a tubular framework  92  and also incorporates an awning extension  98  with an awning framework  96 . The awning extension  98  will have a hingeable support mechanism  100  to make angular adjustments in the awning. This embodiment would work well with the embodiment of the rotating lower section of FIG. 11.  
         [0067]    While the present invention has been described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended in the foregoing disclosure, and will be appreciated that in some instance some features of the invention will be employed without a corresponding use of other features without departing from the scope of the invention as set forth in the following claims.

Summary:
A low profile, expandable, mobile rigid structure with unique a unique assembly and support system, that can easily be transported by an average sized vehicle. The structure features a central structure with a central roof section, a pair of endwall assemblies, and a central floor mounted to a base. The endwalls are two pieced having a bottom endwall panel and a top endwall panel. From the side of the central structure one or more side sections are retractable and expandable to increase the size of the floor space inside. The two pieced endwalls allow for compaction of the structure for travel by translating the lower portion of the endwall from supporting the upper portion. A two pieced door allows entry into the structure when it is expanded.