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BACKGROUND OF THE INVENTION 
     The invention relates to a mobile accommodation unit in container form. The mobile accommodation unit comprises a box-shaped main box element which has a floor element and a ceiling and normally end and side walls. The main box element may have the standardized dimensions of a conventional container, though this is not necessary, and the dimensions of the main box element may be different from the standardized container dimensions. At least one secondary box element of smaller cross sectional area is provided. In a transport state, this secondary box element is retained within said main box element. This secondary box element can be pulled out of the main box element through a lateral opening of the main box element, in order to provide an accomodation unit of enlarged space and floor area for living or working. 
     Accommodation units in container form can be used for various purposes. Container can easily and quickly be transported to any desired location by truck, boat, rail, helicopter, airplane or other transport means. Their capacity of quickly providing rooms make the particularly adapted for emergency missions. Container can easily be used as mobile hospital with surgery facilities or as control center for catastrophe or emergency missions. They may also be used, for example, as a command center for military missions. Other applications are work rooms on construction sites, temporary classrooms or simply rooms to live in. 
     In order to be able to transport containers with conventional transport equipment, the containers are usually made with standardized dimensions. Often, the space available within such containers is not sufficient. It is well known, to place a plurality of such containers side-by-side or one on top of the other. It is possible to connect such containers. To this end, individual side walls of the containers may be removed. This procedure suffers from the disadvantage that a separate vehicle is required for the transport of each container. In some cases, for example if a mobile operating room or a mobile control center is to be established, a rather large, continuous floor area is required, which permits equipment to be installed easily accessible. Such floor areas are not provided by the dimensions of a standardized, mobile container. Often, such continuous floor areas cannot be obtained by modular combination of a plurality of separate containers. Firstly, errecting a construction with a plurality of containers requires quite some time. In addition, such construction will not yield a continuous floor surface of the desired size. 
     German patent 44 29 927 discloses a mobile accommodation unit in container form, which consists of a main box element and at least one secondary box element, which can be pulled out of the main box element on an open side thereof. A lifting device permits the secondary box element to be lowered, after it has been completely pulled out of the main box element, such that the floor of the secondary box element is lowered to the level of the floor of the main box element. Correspondingly, when retracting the secondary box element, the secondary box element has to be lifted to permit pushing it into the main box element. 
     A similar design is disclosed by German utility model 0 94 08 060.7. There, a lifting rail is provided, which can be extended from the main box element parallel to the secondary box element and permits the secondary box element to be lowered, in order to bring the floor of the secondary box element to the level of the floor of the main box element. 
     These prior art mobile accommodation units; suffer from the disadvantage that they are difficult to seal. In order to bring the floors to a common level, the secondary box element has to be removed completely from the main box element, and the the secondary box element has to be lowered as a whole. This results in rather large gaps between main box element and secondary box element. Such gap is difficult to seal. Such seal is, however, imperative, for example, for a sterile operation room. Furthermore, always the whole secondary box element has to be lifted or lowered. This necessitates an expensive an high-power lifting device. This is particularly true, if the secondary box element has heavy equipment such as an operating table fixedly installed therein. 
     U.S. Pat. No. 3,719,386 has an expansible caravan with a main box element and a secondary box element. The secondary box element is larger than the main box element mounted on a chassis and has no fixed floor. Thereby, the secondary box element can be pushed over the main box element, in the transport state. In the expanded state of use, the secondary box element is pulled laterally from the main box element. A floor for the secondary box element consists of two articulated halves and is folded up, in the transport state. In the state of use, the two halves are straight and close the secondary box element at the bottom. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the invention to provide an accommodation unit in container form of the type mentioned in the beginning which permits a continuous floor level to be established after expansion of the secondary box element. 
     It is another object of the invention to provide an accommodation unit in container form of the type mentioned in the beginning wherein a continuous floor level can be achieved with a minimum of expenditure of equipment or power. 
     Furthermore, it is an object of the invention to provide an accommodation unit in container form of the type mentioned in the beginning which can easily be sealed. 
     To this end, the main box element, as means for equalizing the floor levels, has a movable floor element in addition to its basic floor element and means for lifting and lowering this movable floor element. 
     With such an arrangement, the secondary box element need not be lowered after being pulled out of the main box element. Rather remains the floor of the secondary box element at its floor level, which is higher because the secondary box element has to be movable into the main box element. The floor levels are equalized by appropriate lifting of the movable floor element of the main box element. There is no need, as with the prior art, to completely pull the secondary box element out of the main box element, in order to permit it to be lowered. Instead it is possible to retain the main box element-side edge of the secondary box element within the main box element. This facilitates sealing. 
     In order to further enlarge the floor area of the mobile accommodation unit in its expanded state, one embodiment of the invention provides a second secondary box element of smaller cross sectional area than that of the first secondary box element. In the transport state, the first secondary box element is retracted into the main box element on one side thereof through a first opening, and the second secondary box element is retracted into the first secondary box element on the opposite side through a second opening of the main box element. The first secondary box element has also a movable floor element which is vertically movable relative to a basic floor element such that the floor levels of both the main box element and of the first secondary box element can be equalized with the floor level of the second secondary box element by appropriate adjustment of the heights of the movable floor elements. 
     Also here, the floor level of the whole accommodation unit is determined by the highest floor level. Here, this is the floor level of the smallest, second secondary box element which has to be pushed into the first secondary box element, in the transport state. The floor levels of both the main box element and of the first secondary box element are equalized wit this highest floor level by appropriate adjustment of the respective movable floor elements. 
     Sealing means may be provided between the main box element and each of the secondary box elements. As already explained above, this is facilitated by the fact that main box element and secondary box element retain their relative positions in vertical and lateral direction and are only telescoped into or out of each other. 
     The sealing may be effected by providing seals between the edges of each lateral opening of the main box element and the secondary box element open towards the main box element along the edges of the secondary box element, such seals sealing the secondary box element in the expanded state relative to the main box element. Cooperating sealing members may be provided on the floor element or movable floor element of each secondary box element and on the movable floor element of the main box element, such sealing members providing a seal between the movable floor element of the main box element and the respective floor elements of the secondary box elements, when the movable floor element has been lifted to the level of the floor element or movable floor element, respectively, of the secondary box elements. 
     In another embodiment of the invention, again, a second secondary box element of smaller cross sectional area than the first secondary box element is provided. In the transport state, the first secondary box element is retracted into the main box element on one side through a first opening of the main box element, and the second secondary box element is pushed into the first secondary box element on the opposite side through a second opening in the main box element. Here, however, the first secondary box element has a floor element which can be coupled and de-coupled thereto or therefrom, respectively, and the floor level of which in its coupled state is identical with the floor level of the second secondary box element. In the transport state, the de-coupled floor element of the first secondary box element is supported by the movable floor element of the main box element. The movable floor element of the main box element is movable into a fully lowered position, into an intermediate position and into an extended or upper position. In the fully lowered position, the de-copled floor element of the first secondary box element supported thereby is positioned below the floor element of the second secondary box element. In the intermediate position of the movable floor element, the floor element of the first secondary box element is lifted to the floor level of the second secondary box element and can be coupled to the first secondary box element. In the extended or upper position, after both secondary box elements have been expanded or pulled out, the movable floor element of the main box element is lifted to the common floor level of the two secondary box elements. 
     The height-adjustable movable floor element of the main box element has two functions: Firstly, it forms the floor of the main box element at the same floor level as the floors of the two secondary box elements. Secondly, it serves for lowering the de-coupled floor element of the first, larger secondary box element, such that the second, smaller secondary box element can be shifted into the first secondary box element for the transport state. This permits providing the floor levels of the two secondary box elements in one plane from the beginning. 
     In the transport state, the secondary box elements are telescoped into the main box element. The floorelement of the first secondary box element is de-coupled therefrom and is supported by the movable floor element of the main box element, the movable floor element being in its fully lowered position. Therefore, the second secondary box element could betelescoped into the first-floor-less-secondary box element without being impeded by the floor element thereof. In order to erect the accommodation unit, at first, the second secondary box element is retracted from the central main box element. The second secondary box element determines the floor level of the accommodation unit. Then, the movable floor element of the main box element is moved by appropriate lifting means into its intermediate position. In this intermediate position, the floor element of the first secondary box element engages the lower edge of the first secondary box element. In this position, the floor level of the first secondary box element is identical with that of the second secondary box element. The floor element is coupled with the first secondary box element. The first secondary box element with the floor element coupled thereto is retracted out of the main box element. Finally, the movable floor element is moved into its extended or upper position, in which the movable floor also is at the floor level of the two secondary box elements. 
     With such an arrangement, only one hight-adjustable floor element needs be provided, even if two secondary box elements are used. 
     The coupling of the floor element with the first secondary box element can be effected in the following way: Downwards extending locking bolts having tapered tips are provided along the lower edges of the end walls of the first secondary box element and are vertically movably guided in bushings. Locking balls are retained in lateral openings of the bushings. The floor element of the first secondary box element, which is adapted to be coupled and de-coupled to the first secondary box element, has annular looking members, which have recesses in their inner wall. When the floor element is lifted to engage the first secondary box element, the locking members are shifted over the bushings and locking bolts. The locking bolts can be displaced downwards in the bushings by means of a cam structure, which extend along the lower edges of the first secondary box element. The locking balls are urged radially outwards by the locking bolts and partially extend into the recesses of the locking members. The de-coupling is effected by means of the cam structure in reverse. 
     The floor elements of the box elements may be guided by rollers, when they are contracted or expanded. 
    
    
     Two embodiments of the invention are described hereinbelow with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, vertical sectional view of a first embodiment of an accommodation unit in container form. 
     FIG. 2 is a schematic, vertical sectional view of the accommodation unit of FIG. 1 in expanded state. 
     FIG. 3 is a plan view of the accommodation unit of FIGS. 1 and 2 in its expanded state. 
     FIG. 4 is a perspective illustration of a main box element wit a guiding system for a secondary box element being in ist operative position. 
     FIG. 5 is a vertical sectional view of a second embodiment of an accommodation unit in container form, in its transport state. 
     FIG. 6 is a vertical sectional view of the accommodation unit similar to FIG. 5 after the smaller, second secondary box element has been moved out, the floor element of the first secondary box element still being supported by the movable floor element of the main box element, the latter floor element being in its lowered position. 
     FIG. 7 is a vertical sectional view similar to FIG. 6, with the movable floor element of the main box element being lifted to its intermediate position and the floor element of the larger, first secondary box element engages the lower edges of the first secondary box element, such that the floor element of the first secondary box element can be coupled with these lower edges. 
     FIG. 8 is a vertical sectional view similar to FIG. 7 with the larger, first secondary box element, after its floor element has been coupled therewith, being moved out of the main box element. 
     FIG. 9 is a vertical sectional view of the accommodation unit in its expanded state of use, the movable floor element of the main box element has been lifted to its expanded or upper position and is at the same floor level as the two secondary box elements. 
     FIG. 10 is a perspective view of the locking mechanism, by means of which the floor element of the first secondary box element can be coupled with the end walls of this secondary box element. 
     FIG. 11 is a perspective view of the locking mechanism similar to FIG. 10 with lifted and coupled floor element. 
     FIG. 12 shows a detail “X” of FIG. 8 at an enlarged scale, and illustrates the sealing with fully extended first secondary box element. 
     FIG. 13 shows a detail “Y” of FIG. 5 at an enlarged scale. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, numeral  10  designates an accommodation unit in container form. In its transport state, the accommodation unit  10  is a box-like unit, which is shown in FIG. 1 in a vertical sectional view. In its retracted state as shown in FIG. 1, the accommodation unit has the dimensions of a conventional, standardized container. The accommodation unit  10  consists of a main box element  12 , a large, first secondary box element  14  and a small, second secondary box element  16 . The secondary box elements  14  and  16  are open on one side towards the main box element  12  and are also box-like. The main box element and the secondary box element may have doors, windows, locks and the like. These elements are not shown in FIG. 1 for clarity. The main box element  12  and the secondary box elements  14  and  16  are marked by different types of hatching. The main box element  12  has rectangular openings  20  and  22  in opposite side walls. The secondary box element  14  and  16  can be moved out of the main box element  12  through the openings  20  and  22 , respectively, by means of a guiding system  18 , as illustrated in FIG.  2 . In FIGS. 1 and 2, only rollers  19  of the guiding system can be seen. 
     Numerals  24  and  26  designate the rims of the openings  20  and  22 , respectively. The inner edges of the rims  24  and  26  sealingly engage the respective side walls, ceilings and floor elements  32  and  34 , respectively, of the secondary box elements  14  and  16 , respectively. In the retracted transport state, Flanges  40  and  42  of the secondary box elements  14  and  16 , respectively, engage the outer surfaces of the rims  24  and  26 , respectively, and provide an additional seal for the whole retracted container. 
     A further, movable floor element  38  is ürovided above the floor element  36  of the main box element  12 . Also the larger, first secondary box element  14  has a movable floor element, which is height-adjustable relatibe to the floor element  32  of the secondary box element  14 . 
     In FIG. 2, the secondary box elements  14  and  16  are expanded or moved out of the main box element  12 . To this end, the secondary box elements  14  and  16  are guided by the guiding system  18 . The guiding system  18  includes guide rails  46  and  48 , which are provided in pairs and can, for example, retracted into or pulled out from housings (not shown) of the main box element  12 . Furthermore, the guiding system  18  has supporting beams  50  and  52 , which can be attached, at their one ends, to the side walls of the main box element  12  in the area of the rims  24  and  26 , respectively, and, at their other ends, to the outer ends of the guide rails  46  and  48 , respectively. When the secondary box elements  14  and  16  are expanded or moved out, they roll on the guide rails  46  and  48  through the rollers  19 . The pairs of guide rails  46  and  48  are interconnected by a longitudinal string piece  54  (FIG. 4) each. The rollers of the secondary box elements  14  and  16  engage a detent device (not shown) to limit their outward movement. 
     In the present embodiment, the floor element  34  of the small secondary box element  16  has the highest floor level. Both the movable floor element  38  of the main box element  12  and the movable floor element  56  of the large secondary box element  14  are lifted to the floor level of the floor element  34  of the small secondary box element by means of lifting devices  58  and  60 , respectively. Thereby, a continuous, plane floor is obtained throughout the whole floor area of the accommodation unit  10 . 
     FIG. 3 is a plan view of the accommodation unit  10 . The movable floor element  38  of the main box element  12  is idicated by a cross  62 . The spacing  64  between the end walls  66  of the small secondary box element  16  is selected such that the small secondary box element  16  can be telescoped directly between the end walls of the large secondary box element  14 . The spacing  70  between the end walls  68  of the large secondary box element  14  is dimensioned accordingly. The main box element  12  may have areas  72  and  74  which are not covered by the movable floor element  38 . These areas  72  and  74  may, for example, be used for the drive unit  76  driving the movable floor element  39  or for a air conditioning installation  78 . In FIG. 3, these elements are illustrated merely as boxes. 
     It can be seen from FIG. 3, that fixedly installed furniture such as control panels, medical cupboards or the like can be mounted substantially only on the side walls  82 . Operation tables or desks can be accommodated in the small secondary box element  16 . 
     FIG. 4 is a schematic, perspective view of the main box element  12  with the guiding system  18 . 
     In the transport state, the support beams  52  are unhooked from the guide rails  46  and are accommodated in housing recesses  84  of the side wall  86  of the main box element. 
     FIGS. 5 to  12  illustrate a second embodiment of an accommodation unit in container form with expandable secondary box elements. 
     FIG. 5 shows the accommodation unit in its transport state, two secondary box element being telescoped in a main box element. 
     Referring to FIG. 5, numeral  100  designates a container-like main box element. The main box element  100  has a roof  102  and a floor element  104 . Roof  102  and floor element  104  are interconnected by end walls parallel to the plane of the paper of FIGS. 5 to  9 . In FIGS. 8 and 9, only one end wall  106  with a door is visible. Rectangular openings  114  and  116  are provided in opposite side walls  110  and  112 , respectively. 
     A larger, first secondary box element  118  is telescoped in the main box element  100 . The secondary box element  118  has a roof  120 , end walls  121  and  123 , of which only the rear end wall  121  is visible in FIG. 5, and a side wall  122 . In FIG. 5, side wall  122  closes the opening  116 . The first secondary box element  118  is open on the side opposite the side wall  122  and defines an opening  124 . In the transport state of FIG. 5, the first secondary box element also has no floor. 
     A smaller, second secondary box element  126  is telescoped in the first secondary box element  118 . The second secondary box element  126  has a roof  128 , a floor element  130 , end walls, of which only the rear end wall  131  is visible in FIG. 5, and a side wall  132 . In the transport state of FIG. 5, the side wall  132  closes the opening  124  of the first secondary box element  118 . 
     The main box element  100  has a movable floor element, which can be lifted relatve to the “basic” floor element  104  by a lifting device (not shown). The lifting device may comprise one or more hydraulic jacks or my other type of lifting device well-known to a person skilled in the art. The movable floor element  134  can be moved to a lowered position by the lifting device, as illustrated in FIG. 5, to an intermediate position and in an extended or upper position. A floor element  136  appertaining to the first secondary box element  118  is supported on the lowered movable floor element  134 . This floor element  136  can be coupled with the lower edges of the end walls of the—in FIG. 5 floor-less—first secondary box element  118 , as will be described below. 
     As can be seen from FIG. 5, the floor element  136  is supported on the movable floor element  134  through rollers  138 . 
     In this transport state, the accommodation unit has the standardized dimensions of a container and can be transported by conventional transport equipment such as a truck. 
     In order to set up the expanded accommodation unit, at first, the smaller, second secondary box element  126  ist pulled out to the left in FIG. 5, as illustrated in FIG.  6 . The floor element  130  with its inner or upper surface  140  determines the floor level of the whole accommodation unit. The lower edges  142  of the end walls  121  and  123  of the first secondary box element  118  lie in the plane of the inner surface  140 . 
     As the next step, the movable floor element  134  of the main box element  100  is lifted to its intermediate position. Thereby, the movable floor element  134  also lifts the floor element  136  supported thereon and brings it into engagement with the lower edges  142  of the end walls  121 ,  123 . The floor element  136  is coupled with the end walls  121  and  123  by a locking device to be described below. 
     In this state, the inner surface of the floor element  136  of the first secondary box element  118 , i.e. the floor level, lies in the same plane as the inner surface  140  of the second secondary box element  126 . 
     Then the first secondary box element  118  is telescoped to the right in FIG.  7 . This is illustrated in FIG.  8 . 
     In a final step, the movable floor element  134  of the main box element  100  is then lifted to its extended or upper position. In this position, the surface  144  of the movable floor element  134  lies at the same floor level as the inner surfaces  140  and  142  of the floor elements  130  and  136  of the two secondary box elements  126  and  118 , respectively. 
     FIGS. 10 and 11 illustrate the coupling of the floor element  136  to the end walls  121  and  123  of the first secondary box element  118 . 
     Downwards extending bushings  146  are provided at the lower edges of the end faces  121 ,  123  of the first secondary box element  118 . Downwards extending locking bolts  148  are slidably guided in the bushings  146 . The locking bolts  148  have tapering tips  150 . The bushings have lateral openings  152 . Locking balls  154  are guided in the lateral openings  152 . 
     The floor element  136 , adapted to be coupled to or de-coupled from the secondary box element  118  has annular locking elements  156  in alignment with the bushings  146 . The annular locking elements  156  form a bore  158  with an inner wall. The bushings  146  can be inserted into the bore  158 . In their inserted states, the bushings  146  are laterally guided in the bores  158 , as can be seen best from FIG.  11 . The inner wall of each bore  158  has a circumferential groove  160 . When the bushing  146  has been inserted into the bore  158 , the lateral openings  152  of the bushing  146  lie at the level of the circumferential groove  160 . 
     The locking bolts  148  have an enlarged head  162 . The head  162  is guided in a groove of a cam structure  164 . The cam structure  164  is adjustable along the lower edge  142  by means of an adjusting spindle  166 . In the position of FIG. 10, the locking bolt  148  is retracted. The tapering tip  150  permits the locking balls to yield radially inwards. Then the bushing  146  can be inserted into the annular locking element  156 . If the cam structure  164  is shifted to the front left in FIGS. 10 and 11, the locking bolt  148  will be pushed downwards. The the locking bolt  148  urges the locking balls  156  radially outwards partly into the circumferential groove and prevents yielding of the locking balls  156  radially inwards into the openings  152 . In this way, the floor element  136  is coupled with the lower edges  142  of the end walls  121  and  123  of the first secondary box element  118 . 
     As can be seen from FIG. 11, a sealing profile  168  of the floor element  136  extends longitudinally to the first secondary box element  118 , i.e. from front right to the rear left in FIGS. 10 and 11, is caused, thereby, to engage a sealing profile complementary thereto of the first secondary box element  118 . 
     FIG. 12 illustrates the guiding and sealing of the first secondary box element  118  in the main box element  100 , when the secondary box element  118  has been fully expanded. 
     The floor element  136  of the first secondary box element  118  is guided on rollers  172 , which are provided on the main box element  100  at the lower edge of the opening  116 . A profile  174  extending into the main box element  100  is integrally provided at the inner edge of the first secondary box element  118 . This profile  174  forms a sealing ledge  176 . The sealing ledge cooperates with a sealing ledge  178  complementary thereto of the movable floor element  134 . Thereby, the floor elements  136  and  134  engage sealingly. 
     An all-around profile  180  at the inner end of the first secondary box element  118  cooperates with a seal  182  extending also all around the opening  116 . The seal is provided on a profile  184  of the man box element  100  extending all around the opening  116 . This profile also carries bearings for the rollers  172 . As the secondary box element  118  is telescoped out of the main box element  100  without relative change of hight, the sealing between main box element  100  and first secondary box element  118  around opening  116  presents no problems. 
     FIG. 13 shows a detail “Y” of FIG. 5 at an enlarged scale. FIG. 13 shows virtually the same location as FIG. 12, however in the transport state with retracted first secondary box element  118 . A profile  196  extending all around the side wall  122  is provided at the outer end of the first secondary box element  118 . The profile  186  holds a seal  188  also extending all around the side wall  122 . In the transport slate, this seal sealingly engages the profile  184  of the main box element  100 . In addition, the profile  186  bas a horizontal bracket  190 , on which roller  172  is supported.

Summary:
A mobile accommodation unit in container form for use as mobile hospital or mobile control or command center or the like has a box-shaped main box element and at least one secondary box element. In a transport state, the secondary box element is telescoped into the main box element. For setting up an accommodation unit of increased floor area, the secondary box element can be pulled out of a lateral opening of the main box element. In order to provide a continuous floor surface, after the secondary box element has been pulled out, the main box element has a movable floor element, which can be lifted relative to a basic floor element so as to equalize the floor levels of the main box element and the secondary box element.