Abstract:
Prefabricated foldable building units are described that have one or more of the following advantages. They are more easily prefabricated, more easily transported to building sites without requiring special permits, unloadable and unfoldable at the building sites without using cranes (they can be unloaded using ground-level lifting rigs and unfolded using, for example, a cable mechanism), allow precise and fast completion at the building site, and allow significant reduction in the scope of work to be completed on-site, where costs and scheduling are far less manageable. Further, methods for unloading and unfolding foldable building units are described that obviate the need for one or more cranes that can be expensive and project-complicating, thereby opening up a significant percentage of building sites for placement of prefabricated foldable building units.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/245,162, filed Sep. 23, 2009, U.S. Provisional Application No. 61/371,524 filed Aug. 6, 2010, U.S. Provisional Application No. 61/371,540, filed Aug. 6, 2010 and U.S. Provisional Application No. 61/371,513, filed Aug. 6, 2010. The entire teachings of the above applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Architectural structures, particularly residential buildings, are typically built on-site with each stage of the building process requiring to transport necessary materials and specific skilled labor to the site. The inherent cost inefficiency of this approach is well known in the art. 
         [0003]    Thus, alternative approaches have been described aimed at providing economically priced housing. Some of these alternatives included prefabricating various parts of a building at a central facility, transporting the parts to a building site and then completing the assembly on-site. Other alternatives included prefabricating foldable building units at a central facility, transporting the foldable building units to a building site, unloading and unfolding the foldable building units on-site using cranes, and then completing the assembly on-site. However, it has been described that for a number of reasons, the installation cost of prefabricated non-foldable building units was substantial and, when added to the cost of manufacture and delivery, caused the total cost of these prefabricated non-foldable building units to rise to levels detrimental for competition with conventional construction. Previously described foldable building units have one or more of the following disadvantages. They require substantial work at the building site, substantial time for finishing at the building site, they are difficult to prefabricate, they do not allow precise unfolding and finishing at the building site, and they require cranes for unloading and unfolding at the building site. Cranes can be very expensive to employ, difficult to schedule, and are not even suitable for a significant percentage of building sites, thus, excluding these building sites for a substantial number of prefabricated foldable building units and often requiring home owners or developers of respective building sites to use conventional construction. 
         [0004]    There is, therefore, a need for foldable building units that cost less, allow improved precision at the building site, are easier to prefabricate, transport, and unfold and finish quickly at the building site, and can be placed at building sites that were previously not suitable for placement of prefabricated foldable building units. 
       SUMMARY OF THE INVENTION 
       [0005]    One embodiment of the present invention is a foldable building unit. The foldable building unit includes a structural frame that at least in part is made of frame elements that are foldably connected with metal hinges. It further includes interior finish materials with indirect connection to the frame elements to reduce direct contact of the interior finish materials with the frame elements. The frame elements are at least in part made of metal and the metal hinges are attached to a metal part of the frame elements. 
         [0006]    Another embodiment of the present invention is a foldable building unit that includes a structural frame that at least in part is made of frame elements that are foldably connected with offset hinges. The offset hinges are attached to metal parts of the frame elements and the offset hinges are adapted and positioned on the frame elements such that when folded, interior finish materials connected to the frame elements are offset from each other. 
         [0007]    Another embodiment of the present invention is a foldable building unit that includes a structural frame that at least in part is made of frame elements that are foldably connected with metal hinges, wherein the frame elements are at least in part made of metal, the metal hinges are attached to a metal part of the frame elements, and the metal hinges are adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0008]    Another embodiment of the present invention is a foldable building that includes foldably connected finished wall panels, foldably connected finished floor panels, and foldably connected finished ceiling and/or roof panels. The foldable building in unfolded configuration is substantially in finished condition. 
         [0009]    Another embodiment of the present invention is a foldable building having a structural frame adapted to be connected to ground-level lifting rigs to lift or lower the foldable building. 
         [0010]    Another embodiment of the present invention is a method for unloading a foldable building unit from a transport vehicle. The method includes (a) placing ground-level lifting rigs next to the transport vehicle in positions adapted to allow attaching lifting members of the ground-level lifting rigs to the foldable building unit and to allow lifting of the foldable building unit; (b) attaching lifting members of the lifting rigs to the foldable building unit; (c) operating the lifting rigs to lift the foldable housing module off the transport vehicle; and (d) driving the transport vehicle to a location to remove the loading area of the transport vehicle from underneath the foldable housing module. 
         [0011]    Another embodiment of the present invention is a method for unfolding a folded building unit. The method includes unfolding folded frame elements that are part of a structural frame of the folded building unit from a folded configuration to an unfolded configuration using one or more of a cable mechanism, hydraulic mechanism or air actuation mechanism. 
         [0012]    Another embodiment of the present invention is a foldable building comprising a core structure made of first frame elements in fixed connection, and second frame elements hingedly connected, directly or indirectly, to the core structure. The second frame elements are made of metal members, and the core structure and the second frame elements are part of the structural frame of the foldable building. 
         [0013]    Another embodiment of the present invention is a foldable building unit comprising (a) a structural frame that at least in part is made of frame elements that are foldably connected with offset hinges, and (b) interior finish materials with indirect connection to the frame elements to reduce contact of the interior finish materials with the frame elements, wherein the frame elements are at least in part made of metal, the offset hinges are attached to a metal part of the frame elements, and the offset hinges are adapted and positioned on the frame elements such that when folded, interior finish materials connected to the frame elements are offset from each other. 
         [0014]    Another embodiment of the present invention is a foldable building unit comprising (a) a structural frame that at least in part is made of frame elements that are foldably connected with metal hinges, and (b) interior finish materials with indirect connection to the frame elements to reduce contact of the interior finish materials with the frame elements, wherein the frame elements are at least in part made of metal, the metal hinges are attached to a metal part of the frame elements, and the metal hinges are adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0015]    Another embodiment of the present invention is a foldable building unit comprising (a) a structural frame that at least in part is made of frame elements that are foldably connected with offset hinges, and (b) interior finish materials with indirect connection to the frame elements to reduce contact of the interior finish materials with the frame elements, wherein the frame elements are at least in part made of metal, the offset hinges are attached to a metal part of the frame elements, the offset hinges are adapted and positioned on the frame elements such that when folded, interior finish materials connected to the frame elements are offset from each other, and the offset hinges are metal hinges adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0016]    Another embodiment of the present invention a foldable building comprising (a) a core structure made of first frame elements in fixed connection, (b) second frame elements hingedly connected, directly or indirectly, to the core structure, wherein the second frame elements are made of metal members, and the core structure and the second frame elements are part of the structural frame of the foldable building; and (c) interior finish materials with indirect connection to the second frame elements to reduce direct contact of the interior finish materials with the frame elements, wherein one or more of the second frame elements are hingedly connected with offset hinges attached to the frame elements, and the offset hinges are adapted and positioned on the frame elements such that when folded, interior finish materials connected to the frame elements are offset from each other. 
         [0017]    Another embodiment of the present invention is a foldable building comprising (a) a core structure made of first frame elements in fixed connection, (b) second frame elements hingedly connected, directly or indirectly, to the core structure, wherein the second frame elements are made of metal members, and the core structure and the second frame elements are part of the structural frame of the foldable building; and (c) interior finish materials with indirect connection to the second frame elements to reduce direct contact of the interior finish materials with the frame elements, wherein one or more of the second frame elements are hingedly connected with metal hinges attached to the frame elements, and the metal hinges are adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0018]    Another embodiment of the present invention is a foldable building comprising (a) a core structure made of first frame elements in fixed connection, (b) second frame elements hingedly connected, directly or indirectly, to the core structure, wherein the second frame elements are made of metal members, and the core structure and the second frame elements are part of the structural frame of the foldable building; and (c) interior finish materials with indirect connection to the second frame elements to reduce direct contact of the interior finish materials with the frame elements, wherein one or more of the second frame elements are hingedly connected with offset hinges attached to the frame elements, and the offset hinges are adapted and positioned on the frame elements such that when folded, interior finish materials connected to the frame elements are offset from each other, and the offset hinges are adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0019]    Another embodiment of the present invention comprises a combination of two or more, including all, of the above embodiments. 
         [0020]    The foldable building units of the present invention have one or more of the following advantages. They are more easily prefabricated, allow more flexibility in building shapes including higher ceilings and larger spaces, reduce or eliminate material damage due to, for example, shipment, structural deflection, thermal flexure and contraction, and structural aging, more easily transportable to building sites without requiring special permits, unloadable and unfoldable at the building sites often without using cranes (they can be unloaded using ground-level lifting rigs and unfolded using, for example, a cable mechanism) and allow significant reduction and increased speed of work to be completed on-site, where typically costs and scheduling are far less manageable. 
         [0021]    Additionally, as mentioned above, the methods for unloading and unfolding foldable building units of the present invention can obviate the need for cranes that can be expensive and project-complicating, thereby opening up a significant percentage of building sites for placement of prefabricated foldable building units. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
           [0023]      FIG. 1  is a perspective view of a foldable building in unfolded configuration without interior and exterior finishing. 
           [0024]      FIG. 2  is a perspective view of a foldable building in unfolded configuration without interior and exterior finishing. 
           [0025]      FIG. 3  is a perspective view of the foldable structural frame of the foldable building shown in  FIG. 1  in unfolded configuration, and further provides detail views of some of the structural features of the structural frame. 
           [0026]      FIG. 4  is a perspective view of an unfolding sequence of the foldable structural frame of the foldable building of  FIG. 1  from the folded configuration on the left-hand side to the unfolded configuration on the right-hand side. 
           [0027]      FIG. 5  is a perspective view of a frame element made of four hollow structural steel sections and intermediate elements attached to the frame element. 
           [0028]      FIG. 6  is a cross-sectional view illustrating a powder actuated fastener connection of a lumber sill to the hollow structural steel section of  FIG. 5 . 
           [0029]      FIG. 7  is a perspective view of a finished wall panel or section. 
           [0030]      FIG. 8  is a cross-sectional view illustrating indirect connection of interior finish materials with a respective frame element. 
           [0031]      FIG. 9  provides a perspective view of four folding configurations of a three-axis step-out hinge. 
           [0032]      FIG. 10  provides a front (at top of figure) and top view (at bottom of figure) of two frame elements that are foldably connected with a three-axis step-out hinge. 
           [0033]      FIG. 11  is a top view of the hinge area of the two foldably connected frame elements shown in  FIG. 10  for four folding configurations. 
           [0034]      FIG. 12  is a perspective view of a fixed-axis offset hinge. 
           [0035]      FIG. 13  is a cross-sectional view of two foldably connected hollow structural steel sections in which the seam or fold between the hollow structural steel sections as well as the hinge(s) are covered with a flexible polymer gasket. 
           [0036]      FIG. 14  is a cross-sectional view of part of a finished wall panel or section. 
           [0037]      FIG. 15  is a perspective view of four ground-level lifting rigs holding the folded structural frame of a foldable building. 
           [0038]      FIG. 16  is a perspective view illustrating steps of the uploading (from left to right) or unloading (from right to left) of a foldable building unit on a transport vehicle. 
           [0039]      FIG. 17  is a perspective view of an unfolding sequence of the foldable structural frame of the foldable building of  FIG. 2  from the folded configuration on the left-hand side to an unfolded configuration on the right-hand side. 
           [0040]      FIG. 18  is a cross-sectional view of a folding wall corner in unfolded configuration and substantially finished condition. 
           [0041]      FIG. 19  is a cross-sectional view of the folding wall corner of  FIG. 18  in finished condition. 
           [0042]      FIG. 20  illustrates the use of a cable mechanism in unfolding and folding of a foldable floor section of a foldable building unit. 
           [0043]      FIG. 21  is a cross-sectional view of a hinged wall detail in unfolded configuration and substantially finished condition. 
           [0044]      FIG. 22  is a cross-sectional view of the hinged wall detail of  FIG. 21  in finished condition. 
           [0045]      FIG. 23  is a perspective view of an unfolding sequence of one embodiment of a clerestory-shaped single-story foldable building of the present invention 
           [0046]      FIG. 24  is a cross-sectional view of a fixed-axis offset hinge in an unfolded configuration with each hinge leave attached to a structural member. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    A description of example embodiments of the invention follows. 
         [0048]    Although the teachings of the present invention are applicable to a wide variety of structures of different weight, size, shape and materials for a variety of diverse uses, for purposes of the following description, the present invention will be described in the context of prefabricated foldable building units. 
         [0049]    The foldable buildings (and, more generally, foldable building units) of the present invention can be prefabricated such that the foldable buildings, after unfolding on the building site, are substantially in finished condition. That is, they do not require or significantly reduce the addition of further building sections such as wall panels, floor and roof sections, or the addition of interior and exterior finish materials with the exception of minor, non-structural finishing in areas required for folding movement. However, the prefabrication process can be reduced substantially, even to the extent that merely a foldable structural frame of the present invention is prefabricated and unfolded at the building site. 
         [0050]    Further, all necessary mechanical and electrical systems for the residential or commercial foldable building, for example, all the required appliances and plumbing fixtures, can be installed in a core structure (i.e., a part of the structural frame of the foldable building that is made of frame elements that are not unfolded at the building site, typically, frame elements that share at least one fixed seam connection with another frame element) of the foldable building at the time of its prefabrication. At this point, the foldable building has been brought into finished condition and only requires connection to the local utilities, e.g. electricity and sewerage, and seam connections for it to be completed. 
         [0051]      FIG. 1  is a perspective view of a foldable building  100  in unfolded configuration without interior and exterior finishing. The foldable building contains a structural frame that includes interconnected frame elements  110  made of hollow structural steel sections and wooden intermediate elements  120  attached thereto. Selected frame elements are foldably connected with hinges  130  that can be of various designs described herein. For ease of illustration, interior and exterior finishing materials are not shown. Such materials are preferably attached (e.g., glued, nailed, screwed, welded and/or bolted, or otherwise fastened) to the intermediate elements  120 . 
         [0052]    Use of appropriately dimensioned metal sections, more typically, hollow structural steel sections as shown in  FIG. 1 , as part of a foldable structural frame of a foldable building unit, and, particularly, foldably connected frame elements made of hollow structural steel sections, have been found to be advantageous for a number of reasons including the following: Fewer and/or smaller hinges (typically, metal hinges) can be used to foldably connect frame elements, reducing labor and material cost in the prefabrication process, reducing the cost of on-site finishing, and increasing the precision of the folding and unfolding of foldably connected frame elements thereby further reducing the labor and material cost of on-site finishing by enabling prefabrication of interior and exterior materials that fit into the unfinished areas (e.g., seams of foldably connected frame elements) after unfolding (see, e.g.,  FIGS. 18 and 19  with regard to finishing material that is desired and can be prefabricated to complete a typical folding wall corner with minimal on-site labor). Large frame geometries as part of the structural frame, for example, rectangular frame elements spanning the entire side of a foldable building can be employed (see, e.g., the wall frame element  450  in  FIG. 4 ), reducing prefabrication cost and/or simplifying the unfolding. 
         [0053]    Further, foldable structural frames substantially made of metal frame elements (e.g., made from hot-formed steel, for example, from hollow structural steel sections) can be prefabricated to superior tolerances such that a respective foldable building unit in substantially finished condition upon unfolding exhibits reduced or no gaps in the seam areas between foldably connected frame elements thereby reducing the work associated with on-site finishing of these seam areas. 
         [0054]      FIG. 2  is a perspective view of a further foldable building  200  in unfolded configuration without interior and exterior finishing. The foldable building contains a structural frame that includes interconnected frame elements  110  made of hollow structural steel sections and wooden intermediate elements  120  for attachment of finish materials (not shown). Selected frame elements are foldably connected with hinges  130 . The foldable building includes frame elements that are unfolded during unfolding and others that remain fixed. The roof of the foldable building includes a fixed roof section  210  and a foldable roof section  215  which is foldably connected with hinges  130  to the fixed roof section  210 . The floor of the foldable building includes a fixed floor section  220  foldably connected to a foldable floor section  225 . Further, the fixed roof section  210  and fixed floor section  220  are in fixed connection with fixed wall sections  230 ,  232  and  234 . Fixed wall section  232  is foldably connected with the foldable wall section  240  which itself is further foldably connected to foldable wall section  242 . Fixed wall section  234  is foldably connected with the foldable wall section  244  which itself is further foldably connected to foldable wall section  246 . Foldably connected sections are connected with hinges (not all hinges shown) attached to the frame elements of the respective sections. 
         [0055]    Foldable building units, for example, the foldable buildings shown in  FIGS. 1 and 2 , can further include a number of prefabricated interior walls (not shown) that can be fixed, foldably connected, or panelized and form one or more rooms in the unfolded building. 
         [0056]    The foldable buildings of the present invention can be several stories high. With the use of a crane, multi-story structures can be built on-site by stacking separate foldable building units with a crane. In this arrangement, ceiling frame elements of the lower unfolded foldable building unit lie directly below floor frame elements of the upper foldable building unit. During prefabrication, appropriate openings can be included in the ceiling of the lower foldable building unit and in the floor of the upper foldable structure to accommodate a staircase, which can be installed in the lower foldable building unit during prefabrication. 
         [0057]      FIG. 3  is a perspective view of the foldable structural frame of the foldable building shown in  FIG. 1  in unfolded configuration, including detail views of some of the structural features of the structural frame. 
         [0058]      FIG. 4  is a perspective view of an unfolding sequence of the foldable structural frame of the foldable building of  FIG. 1  from the folded configuration  400  on the left-hand side to the unfolded configuration  300  on the right-hand side. The unfolding sequence is shown for the foldable structural frame; however, the same unfolding sequence can be used for a respective substantially finished foldable building. The roof frame elements  410  and  420 , and the clerestory truss frame element  430  are lifted (e.g., with a cable mechanism) to provide unfolding space for the floor frame element  440  which is foldably connected to the wall frame element  450 . Floor frame element  440  is folded downward to the ground and wall frame element  450  upward to establish a wall (e.g., front wall) of the foldable building, Then, the roof frame elements  410  and  420  can be lowered onto and connected to the wall frame element  450 , followed by the unfolding of the wall frame elements  460 ,  470  and  480  (note that wall frame element  480  is foldably connected and part of the structural frame  400  but only shown in for the foldable building in unfolded configuration  300 ). It is to be understood, that the above unfolding sequence is not the only possible sequence for unfolding the foldable building  400 . For example, the wall frame elements  460  and  470  could be unfolded, at least partly, prior to unfolding or completing the unfolding of roof frame elements  410  and  420 . The core structure of the structural frame is provided by the frame elements that are not moved during unfolding to the unfolded configuration  300 . 
         [0059]    Foldable building units of the present invention can unfold from one side of a core structure of the structural frame of the foldable building unit as shown, for example, in  FIG. 4 , but can also be designed to unfold from a plurality of sides. For example, a foldable building of the present invention can be adapted to unfold in two opposite directions. 
         [0060]      FIG. 5  is a perspective view of an unfinished wall section or panel  500  that includes a frame element made of four structural steel sections  510  and intermediate elements attached to the frame element. The intermediate elements are a lumber sill  520  (i.e., a wooden bottom plate element) and a lumber header  530  (i.e., a wooden top plate element), both fastened to the frame elements with powder actuated fasteners or other suitable fasteners  540  (fasteners connecting the lumber header  530  to the frame element are not visible in this perspective view). Lumber studs  550  (i.e., stud elements) are fastened between the lumber header  530  and the lumber sill  520 . Interior finish materials can be attached (e.g. nailed, screwed, fastened and/or glued) to the intermediate elements (here, lumber) to connect indirectly to the frame element. 
         [0061]    Steel frame elements can be combined with wooden intermediate elements as shown in  FIG. 5  to form lightweight steel and wood hybrid structures in which the frame elements provide structural stability and the wooden intermediate elements provide substantial lateral structural resistance and are used to attach interior and exterior finishing material using standard construction approaches, reducing labor training and associated costs. Use of these strong and lightweight structures (and, in particular, the use of the foldable structural frames of the present invention) substantially reduces the amount of required building material, and also allows reduced weight of the frame elements and, thus, reduced weight of the foldable building unit, which in turn facilitates the transport of larger folded building units for a given maximal allowed weight according to given road regulations. Further, a reduced weight of foldably connected frame elements can facilitate the unfolding of these frame elements without the use of a crane. 
         [0062]      FIG. 6  is a cross-sectional view illustrating a powder actuated fastener or other suitable fastener connection of the lumber sill  520  to the structural steel section  510  of  FIG. 5 . The lumber sill  520  is positioned and dimensioned to provide a wood offset  610  from the steel of the hollow structural steel section  510 . The wood offset  610  can reduce or prevent contact of interior finish material (not shown; e.g. drywall attached to the lumber sill  520 ) with the steel. It can also reduce heat transfer and/or reduce or prevent contact of potential condensate formed on the steel with interior finish material. 
         [0063]    It has been found that the use of powder actuated fasteners allows establishment of a strong connection between wooden intermediate elements and steel frame elements (in particular, made of hollow structural steel sections) quickly, reducing the prefabrication cost and providing significant connection strength. 
         [0064]      FIG. 7  is a perspective view of a finished wall panel or section  700 , which can be obtained by attaching interior finish material, such as gypsum wall board  710  and a baseboard  720 , to an unfinished wall panel. The finished wall panel  700  includes interior finish material, such as gypsum wall board  710  and a baseboard  720 , with indirect connection to the respective frame element. The indirect connection is further illustrated in  FIG. 8 . 
         [0065]      FIG. 8  is a cross-sectional view illustrating indirect connection of interior finish materials with a respective frame element. Interior finish material, such as a gypsum wall board  710 , is attached to a bottom plate (here, a wood sill plate  520 ) which in turn is fastened using a powder actuated fastener or other suitable fastener  540  to the hollow structural steel section  510 . A baseboard  720  is attached to the gypsum wall board  710  and optionally a plywood backer board  810  fills the wood offset gap. 
         [0066]    The indirect connection shown in  FIG. 8  is one of a number of possible connections that allow reduction of structural stress transfer from the structural frame to interior finishing materials, reduce heat loss, and improve moisture control. A further indirect connection is shown in  FIGS. 18 and 19 . 
         [0067]    Indirect connections of interior and/or exterior finishing materials to metal frame elements (particularly, frame elements made of structural steel sections) are one aspect of a “multi-tolerance” building approach that disaggregates and cushions brittle or otherwise fragile finish materials from the vibrational, kinetic and settling forces applied to the structural frame during shipping, setting, unfolding and settling of the prefabricated foldable building units. A second aspect of a multi-tolerance building approach is provided by the offset hinges of the present invention which are specifically engineered to safely nest hingedly (i.e., foldably connected with one or more hinges) connected frame elements at a designed distance away from its neighboring frame element, allowing, for example, for thicker wall depths and thus the prefabricated inclusion of finish materials. This is associated with a significant reduction in the scope of work to be completed on-site, where costs and scheduling are far less manageable. Thus, foldable building units of the present invention can include final interior finishing, such as trim, gypsum board, paint or wallpaper. 
         [0068]      FIG. 9  is a perspective view of four folding configurations of a three-axis step-out hinge  900  (e.g., a type of offset hinge). Hinge leaves  910  extend into hinge knuckles  920  surrounding hinge pins  930 . Center hinge leaves  940  extend in two directions into hinge knuckles  920  surrounding hinge pins  930 . The folding configurations can be part of a folding and/or unfolding sequence. 
         [0069]    The three-axis step-out hinges provide folding flexibility and can increase the packing/folding degree of a foldable building unit. 
         [0070]      FIG. 10  provides a front view (at top of figure) and top view (at bottom of figure) of two frame elements  110  that are foldably connected with a three-axis step-out hinge  900 . 
         [0071]      FIG. 11  is a top view of the hinge area of the two foldably connected frame elements  110  shown in  FIG. 10 , providing four folding configurations that can be part of an unfolding sequence from an unfolded configuration (for example, the folding configuration shown on the left-hand side) to the folded configuration shown on the right-hand side. One of the frame elements  110  is connected to one of the hinge leaves  910  of the three-axis step-out hinge through a spacer element  1110  dimensioned and positioned such that a planar surface is jointly formed by the two foldably connected frame elements in the unfolded configuration shown on the left-hand side of the figure. As can be seen for the folded configuration, a three-axis step-out hinge can provide an offset  1120 . Thus, interior finish materials (not shown) attached to the frame elements can be offset from each other. 
         [0072]      FIG. 12  is a perspective view of a fixed-axis offset hinge. Hinge leaves  910  with extended hinge knuckles  1210  surrounding a hinge pin  930  can be rotated around the axis provided by the hinge pin  930 . In completely folded configuration (not shown) the offset hinge provides an offset which increases with the length of the extension  1220  of the extended hinge knuckles  1210 . Thus, interior finish materials (not shown) attached to the frame elements can be offset from each other. 
         [0073]      FIG. 13  is a cross-sectional view of two foldably connected hollow structural steel sections  510  in which the seam or fold between the hollow structural steel sections  510  as well as the hinge(s)  1310  are covered with a flexible polymer gasket  1320  which is attached (for example, glued) to the hollow structural steel sections. 
         [0074]      FIG. 14  is a cross-sectional view of part of a finished wall panel or section illustrating indirect connection of the of interior and exterior finish materials to a structural steel section of a frame element. Two intermediate elements, a wood face plate  1410  and a wood plate  1420  (e.g., lumber sill) are attached to a rectangular structural steel section  1430 . A wood stud  1440  is further attached to the wood plate  1420 . Interior finish material  1460  (for example, gypsum board) is attached to the wood plate  1420 . Exterior finish material  1450  (for example, plywood or OSB sheating) is attached to the wood face plate  1410 , the wood plate  1420 , and/or the wood stud  1440 . 
         [0075]      FIG. 15  is a perspective view of four ground-level lifting rigs  1510  holding a folded steel assembly  1520  of a foldable building. Only the steel assembly is shown; however, foldable building units in various finished conditions, can be held, lifted and lowered using ground-level lifting rigs such as the ones that are shown. Each lifting rig  1510  includes a hoist  1530  (e.g., manual or electric) and a lifting member  1540  (e.g., chain with hook for connection to a solid stock steel rig). Connection members  1550  (e.g., a solid stock steel rig) are connected to the lifting members  1540  of the ground-level lifting rigs  1510 . Connection members can be part of the folded steel assembly and extendable into an extended position as shown, or they can be separate parts that are inserted into the folded steel assembly (e.g., into hollow structural steel sections of a floor frame element). 
         [0076]      FIG. 16  is a perspective view illustrating the steps of uploading (from left to right) or unloading (from right to left) of a foldable building unit (here, the folded foldable building unit is illustrated in terms of its folded steel assembly  1520 ) on a transport vehicle  1610 . For uploading, the ground level lifting rigs are placed next to the foldable building unit (which is folded sufficiently to comply with transport regulations). The folded steel assembly  1520  and lifting members of the ground-level lifting rigs are attached to the folded building unit. Then the lifting rigs are operated to lift the folded building unit up to a height sufficient to allow the transport vehicle  1610  to drive its loading area  1620  under the folded steel assembly. On the left, four ground-level lifting rigs  1510  are holding the folded steel assembly  1520  at a height sufficient to allow the transport vehicle  1610  to drive its loading area  1620  under the folded steel assembly  1520 . The transport vehicle  1610  moves its loading area  1620  under the folded steel assembly as shown in the middle and on the right of the figure. After the loading area  1620  has been placed appropriately under the folded building unit as shown at the right, the lifting rigs can be operated to lower it onto the loading area. The ground-level lifting rigs can then be disconnected, and, if desired, also transported to a building site for use in unloading of the foldable building unit. 
         [0077]      FIG. 17  is a perspective view of an unfolding sequence of the foldable structural frame of the foldable building of  FIG. 2  from the folded configuration  1700  on the left-hand side to an unfolded configuration  1710  on the right-hand side. The unfolding sequence is shown for the foldable structural frame; however, the same unfolding sequence can be used for the respective substantially finished foldable building. First a floor  1720  and/or roof panel  1730  is unfolded, then two separate pairs of hingedly connected wall panels  1740  and  1750  are unfolded to complete the building envelope. 
         [0078]      FIG. 18  is a cross-sectional view of a folding wall corner in unfolded configuration and substantially finished condition. A hinge  1810  is attached to members  1820  (typically, hollow structural steel sections) of two foldably connected frame elements. Intermediate elements  1830  (e.g., lumber) are attached to the members  1820 . Interior finish materials, such as drywalls  1840 , are attached to intermediate elements  1830 . Exterior finish materials such as sheathing  1850  (e.g., Advantech® sheathing), housewrap  1860 , siding  1870  (e.g. wood or corrugated steel siding), and plywood  1880  are directly or indirectly attached to the intermediate elements  1830  in a manner that leaves unfinished areas  1890  dimensioned to accommodate folding of the frame elements. 
         [0079]      FIG. 19  is a cross-sectional view of the folding wall corner of  FIG. 18  in finished condition. Additional interior finish material such as drywall  1910  is attached (e.g., drywall glued and/or screwed) to the intermediate element with tape  1920  at the seams. Further, foam  1930  and exterior finish material such as wood trim  1940  is added to finish the exterior unfinished area. 
         [0080]      FIG. 20  illustrates the use of a cable mechanism in unfolding and folding of a foldable floor section  2000  of a foldable building unit. For ease of illustration, merely part of a structural frame of a foldable building unit in cross-sectional view is provided. A cable  2010  of an electric winch  2020  (attached, for example, to a fixed part of the structural frame) is guided through appropriately selected frame elements to a position that is suitable for folding (here lifting) or unfolding (here lowering) of the foldable floor section  2000 . If the cable is attached to the clerestory truss, the cable mechanism can be used to raise or lower the clerestory truss. 
         [0081]      FIG. 21  is a cross-sectional view of a hinged wall detail  2100  in unfolded configuration and substantially finished condition. A hinge  2110  foldably connects a first structural member  2120  (typically, a structural steel section) of a first substantially finished panel (only part of which is shown in the cross-sectional view) with a second structural member  2130  (typically, a structural steel section) of a second substantially finished panel (only part of which is shown in the cross-sectional view). Intermediate elements  2140  and  2150  (e.g., here lumber) are attached to the members  2120  and  2130 , respectively. Interior finish materials, such as drywall  2160 , are attached to the intermediate elements  2140  and  2150 . Exterior finish materials such as sheathing  2170  (e.g., Advantech® sheathing), siding  2180  (e.g. wood or corrugated steel siding), and plywood  2190  are directly or indirectly attached to the intermediate elements  2140  and  2150  in a manner that leaves unfinished areas  2195  dimensioned to accommodate folding of the frame elements. 
         [0082]    A foldable connection between two substantially finished wall panels can include one or more, typically, at least two hinges, that can be configured and positioned as shown, for example, in  FIG. 21 . 
         [0083]      FIG. 22  is a cross-sectional view of the hinged wall detail of  FIG. 21  in finished condition  2200 . Additional interior finish material such as foil backed drywall  2210  is attached (e.g., glued and/or screwed) to the intermediate element with tape  2220  at the seams. Further, foam  2230  and exterior finish material such as wood (e.g. cedar) trim  2240  is added to finish the exterior unfinished area. 
         [0084]    The hinged wall detail of  FIGS. 21 and 22  separates the structural members from direct contact with the finish-grade materials which are more brittle and would tend to degrade if forces from the structural members were substantially transferred to them. Moreover, the hinged wall detail does not provide a direct metal pathway between the exterior and interior of the structure in order to prevent undesirable transfer of heat between the interior and exterior of the structure. 
         [0085]      FIG. 23  is a perspective view of an unfolding sequence for one embodiment of a clerestory-shaped single-story foldable building of the present invention from the folded configuration  2300  to an unfolded configuration  2310 . The folded building is very compact and properly dimensioned to allow for efficient transport to the building site. The unfolding sequence can be used with one or more, and, more typically, all of the panels (fixed and foldable connected ones) in substantially finished condition; even windows  2320  and doors  2330  can be part of the folded building. Firstly, a floor panel  2340  hingedly connected to a core structure  2350  of the foldable building is unfolded. The floor panel  2340  is further hingedly connected to a wall panel  2360 , which typically is unfolded after the floor panel  2340  has been unfolded. Further wall panels  2370  and  2380  hingedly connected to the core structure are unfolded and fastened to the unfolded wall panel  2360 . Then the roof panel  2390  is unfolded and fastened to one or more of the unfolded wall panels. 
         [0086]      FIG. 24  is a cross-sectional view of a fixed-axis offset hinge  2410  with each hinge leave  2420  attached to a structural member (typically, structural steel member) shown in an unfolded configuration. Typically, fixed-axis offset hinges such as the one shown in the drawing are attached to the structural members so that a tolerance  2420  (e.g., ⅛″) is provided. In completely folded configuration (not shown) the offset hinge provides an offset, which allows sufficient clearance for finish and other materials. Further, the interior finish materials (not shown) attached to the frame elements can be sufficiently offset from each other to avoid direct and potentially damaging contact, for example, during transport. 
         [0087]    The foldable building units of the present invention can be adapted to accommodate unfolding using a robust, cost-effective cable mechanism enabling the smooth and facile unfolding of prefabricated homes, on-site, without the need for a crane or cranes which can be expensive and project complicating. 
         [0088]    Specifically, foldable structural frames of the present invention can include frame elements made at least in part of materials with point load strengths adapted for point loading arising from pulling the respective frame elements with a device such as a cable hoist. 
         [0089]    The use of ground-level rigs of the present invention can have several advantages compared to the use of cranes for unloading foldable building units including the following. Ground-level lifting rigs can be used for unloading foldable building units on building sites that are not suited for the use of cranes or even accessible by cranes. Further, ground-level rigs can be transported along with the folded building unit on the transport vehicle, thus, allowing unloading at any desired time without advance scheduling (as is typically required if cranes are used). 
         [0090]    A “foldable building unit” as used to herein, is a part of a building or an entire building, wherein the part or entire building are foldable, that is, can be folded from an unfolded configuration to a folded configuration and vice versa. For example, a foldable building unit can be one or more foldable rooms of a building, a foldable story of a building, or an entire foldable building. Preferably, the foldable building unit is an entire foldable building. A foldable part of a building or an entire foldable building can be several stories high in unfolded configuration, typically, however, more typically, one or two stories high. A foldable building unit in “unfolded configuration” is a foldable building unit in which the foldably connected frame elements have been unfolded into positions that can be maintained in the finished condition of the foldable building unit. A foldable building unit in “folded configuration” is a foldable building unit in which foldably connected frame elements are folded into positions suitable for uploading, transport, and/or unloading of the building unit. The foldable building or foldable building unit can be a commercial or residential building. 
         [0091]    The present invention also encompasses buildings that are more than two stories high. Such buildings can be built from one unfolding building unit or from a plurality of foldable building units, for example, each foldable building unit being typically one or two stories of the final multi-story building. Typically, in many locations, use of a crane is not desirable due to associated cost and possible crane scheduling difficulties. However, if buildings with more than two stories are to be set up on the building site, more typically, a crane can be employed. 
         [0092]    Foldable buildings of the present invention can have one or more rooms. 
         [0093]    A “structural frame” as used herein, refers to the totality of members of a foldable building unit that are primarily responsible for providing structural stability of the foldable building unit in folded, partially unfolded and unfolded configuration, and which transmit loads (e.g., static, dynamic, and/or vibrational loads) to the ground. A structural frame of a foldable building unit can be made at least in part of frame elements that are foldably connected. Other parts of the structural frame can be connected in fixed relative positions. Typically, a structural frame can comprise both, foldably connected frame elements and frame elements in fixed relative positions. However, the structural frame can also consist entirely of foldably connected frame elements. Structural frames can include members that are made of a plurality of materials in various forms and dimensions. Suitable materials that can be used include but are not limited to wood, metal (e.g., aluminum or steel) and polymers. Suitable forms include but are not limited to I-beams, wide-flange beams, angles, hollow structural sections and channel sections. The selection of a material, form and dimension for a given structural part or member of a structural frame is interdependent and depends on factors such as the position of the structural part or member in the structural frame, and whether the member is part of a frame element that is foldably connected. 
         [0094]    A “frame element” as used herein, refers, to an element of a structural frame of a foldable building unit that includes a plurality of members that form a closed or open frame. Typically, the members form a closed frame. However, the members can also form an open frame, or have additional members as shown attached thereto. Typically, frame elements that are foldably connected through hinges are made at least in part of metal, wherein the hinges are attached to metal parts, for example, a metal member, of the frame elements. Frame elements can include one or more members made of metal, typically, at least the member to which a hinge is attached is made of metal. Suitable metals include but are not limited to aluminum and steel. Preferably, the metal members are made from hot-formed steel. Suitable hot-formed steel includes hollow structural steel sections, I-beams and steel channels (typically, C-shaped cross-section). Typically, the hot-formed, steel is a hollow structural steel section or a steel channel. Steel members can be connected, for example, by welding to form a steel frame element. 
         [0095]    Frame elements can include parts or have elements attached to them that enable automatic guidance of the relative movement of foldably connected frame elements during folding and/or unfolding. 
         [0096]    Frame elements can further include parts or have elements attached to them that enable automatic locking or bolting of foldably connected frame elements in selected folding configurations. 
         [0097]    Interior and exterior finish materials can be attached to the structural frame, and, specifically, frame elements of the structural frame. Interior finish materials include but are not limited to wall finishing (for example, gypsum board and Advantech® sheathing), ceiling finishing and floor finishing (for example, Advantech® sheathing with Bamboo flooring on top. Exterior finishing elements include but are not limited to siding and roofing. 
         [0098]    For finish materials, and, in particular, interior finish materials, it has been found that “indirect connection” to the frame elements to reduce contact, partially or entirely, of the interior finish materials with the frame elements is advantageous for one or more of the following reasons. Reduced contact can (a) reduce the transfer of structural stresses from one or more frame elements of the structural frame to the often fragile and brittle interior finish materials thereby reducing or eliminating significant damage (such as dry wall cracking) of the interior finish materials, in particular, during folding, uploading, transporting, unloading and/or unfolding of the foldable building unit, (b) reduce or eliminate the exposure of the interior finish materials to water, for example, water that can condensate on metal parts of the frame elements, and (c) reduce heat transfer between the inside of the finished building unit to the outside of the finished building unit. 
         [0099]    Thus, generally, it is preferred to use indirect rather than direct connections of finish materials, particularly, interior finish materials with respective frame elements. However, even though indirect connections are typically preferred, not all connections between interior finish material and a respective frame element have to be indirect. 
         [0100]    Indirect connections are particularly preferable for frame elements made entirely from metal, that is, metal frame elements. However, even though “indirect connections” are favorable, direct connections (e.g., glue, screws, nails etc.) can also be present, even to metal parts of the frame elements. 
         [0101]    Indirect connections can be provided through intermediate elements. Intermediate elements can be made of a plurality of materials. Preferably, intermediate elements are made, at least in part, of materials that have a force cushioning effect, that is, force cushioning elements such as, for example, wood, sprayed foam, and light-gauge aluminum studs. Typically, an intermediate element is positioned and dimensioned such that it can connect or can be connected (e.g., using powder-actuated fasteners or self-tapping screws) to the frame element through one area of the intermediate element (e.g., through one side of the intermediate element) and that it can be connected to the finish material, particularly, the interior finish material (for example, using nails or screws) through another area of the intermediate element (e.g., through another side of the intermediate element). Even more preferably, intermediate elements are entirely made of force cushioning materials such as wood. Foldable building units of the present invention can include wall panels, roof and floor sections that are in substantially finished condition, that is, with the exception of unfinished areas dimensioned to accommodate folding of the frame elements, and unfinished areas due to wall connection seams (i.e., seams between walls that are not connected but upon unfolding jointly form a wall), these wall panels, roof and floor sections are finished. 
         [0102]    “Finished panels” as referred to herein, are panels that include frame elements and interior finish materials connected (typically, indirectly) to them, and can also include elements such as doors and windows. Finished panels can be, for example, finished wall panels, finished floor panels, finished ceiling panels and finished roof panels. 
         [0103]    “Metal hinges” as referred to herein, refers to hinges in which at least the load bearing parts (including hinge leaves, hinge knuckles and hinge pin(s)) are made of metal. Preferably, the entire hinge is made of metal. Preferably, the metal is steel. 
         [0104]    “Offset hinges” as referred to herein, are hinges that include at least two hinge leaves that are foldably connected and provide an offset between the two hinge leaves in folded configuration. Offset hinges can include two hinge leaves that are foldably connected around one, two, three or more axes. An offset set hinge that provides for one axis of rotation is hereinafter also referred to as a “fixed-axis hinge.” Preferably, fixed-axis hinge is made of two hinge leaves that have extended hinge knuckles attached thereto, wherein the extended hinge knuckles extend around a hinge pin to foldably connect the hinge leaves. For an offset hinge, the extension provided by each of the extended hinge knuckles can be of the same length or they can be different. Typically, the extension provided by each of the extended hinge knuckles of an offset hinge is the same. Extended hinge knuckles of different extension lengths can be desired if, for example, the thicknesses of two frame element that are to be foldably connected is different. The larger the extensions provided by the extended hinge knuckles of an offset hinge are, the larger can be the offset between interior finish materials connected (typically, indirectly) to the frame elements. 
         [0105]    Typically, at least the load bearing parts (including hinge leaves, extended hinge knuckles, and hinge pin(s)) of offset hinges are made of metal. Preferably, the entire offset hinge is made of metal. Preferably, the metal is steel. 
         [0106]    An offset hinge that provides for two, three or more axes of rotation is hereinafter also referred to as a “step-out hinge.” With increasing number of axes that are being provided by the step-out hinge, the degrees of freedom for folding increase, however, at the same time controlling the folding process becomes increasingly difficult. Preferably, step-out hinges provide for three axis of rotation (i.e., three-axis step-out hinge). More preferably, a step-out hinge includes a first hinge leaf, a second hinge leaf, a first center hinge leaf and a second hinge leaf, wherein the first hinge leaf is foldably connected to the first center hinge leaf, the first center hinge leaf is foldably connected to the second center hinge leaf, and the second center hinge leaf is foldably connected to the second hinge leaf. It has been found that step-out hinges with a plurality of axes provide advantageous folding flexibility relative to single axis hinges. Typically, at least the load bearing parts (including hinge leaves, extended hinge knuckles, and hinge pin(s)) of step-out hinges are made of metal. Preferably, the entire step-out hinge is made of metal. Suitable metals include steel. Hinges can be attached via their respective hinge leaves to frame elements to foldably connect the frame elements. In the preferred case of metal hinges that are to be attached to metal parts of frame elements, for example, metal members or entire metal frame elements, the hinges can be attached, for example, by welding. Typically, hinge leaves of metal hinges are welded to frame elements using methods known in the art. 
         [0107]    Hinges and, in particular, offset hinges and step-out hinges (which can also be offset hinges) allow for a plurality of folding configurations associated with respective relative positions of the hinge leaves and respective attached frame elements. Typically, the step-out hinges suitable in the present invention provide an offset. For example,  FIG. 9  provides a perspective view of four folding configurations of a three-axis step-out hinge providing an offset in the folded configuration. Typically, for a three-axis step-out hinge the folded configuration is as shown at the bottom of  FIG. 9 . If interior finish materials are connected (typically, indirectly) to the frame elements such that they face each other in the folded configuration, the three-axis step-out hinge provides an offset in the folded configuration, that is, it offsets the interior finish materials from each other. If the hinge is used to foldably connect two frame elements that jointly form a flat surface, for example, a floor in the finished building unit, the folding configuration as shown at the top can correspond to the unfolded configuration. If the hinge is used to foldably connect two frame elements that jointly form, for example, a 90 degrees wall corner in the finished building unit, the third folding configuration from the top shown in  FIG. 9  can correspond to the unfolded configuration. If the two foldably connected frame elements are desired to be placed at different angles in the finished building unit, other folding configurations of the three-axis step-out hinge can correspond to the unfolded configuration. 
         [0108]    Hinges and/or frame elements can further include spacer elements (see, e.g., Feature  1110  in  FIG. 11 ) that are sandwiched between the hinge leaves and frame elements such that a desired unfolded configuration of the foldably connected frame elements is achieved. In addition or alternatively, hinge leaves, parts of a member of a frame elements, members of a frame element or entire frame elements can have different dimensioned to achieve a jointly formed planar surface. 
         [0109]    The hinges used in the foldable building units of the present invention can be adapted and positioned to remain within the building unit in unfolded configuration and finished condition. 
         [0110]    A spacer element can be part of the three-axis step-out hinge, in particular, one of the hinge leaves of the three-axis step-out hinge can have a thickness that obviates the spacer element. The spacer element can also be part of the frame element, for example, the frame element may have a thickness in the area to which the hinge leave is to be attached that obviates the need for a spacer element. Alternatively, the spacer element can be a separate element that can be attached to the hinge leave and frame element. Typically, a spacer element is made of metal, preferably, of steel. 
         [0111]    For foldable building units that are pre-fabricated to include interior finish material, it is desirable that the foldable building unit in folded configuration can be uploaded, transported and unloaded without significant direct contact of finish materials of the folded panels. It has been found that contact can be reduced or entirely prevented by using appropriately dimensioned offset hinges to foldably connect frame elements that have interior finish materials attached to them. 
         [0112]    The foldable building units of the present invention can be unfolded on a building site to provide part of or an entire building. Generally, after unfolding of the foldable building unit some finishing work at the building site is required. 
         [0113]    A foldable building unit in “finished condition” refers to a building unit that is ready for commercial or private use. 
         [0114]    An advantage of the foldable building units of the present invention is that they can be prefabricated to the extent that these building units are substantially in finished condition after unfolding, requiring significantly less labor after unfolding on the building site than ones previously described. 
         [0115]    The foldable building units of the present invention are foldable to facilitate transport of the pre-fabricated building units. Preferably, the foldable building units in folded configuration are dimensioned such that transport with a transport vehicle, preferably, a semitrailer does not require a special transport permit. Regulations pertaining to the operation of trucks and trailers vary from country to country, and, in some instances from state to state. For example, currently, in at least one state of the United States of America, the length of a semitrailer including a foldable building unit can be up to 53 feet without requiring a commercial drivers license, the width of a semitrailer including a foldable building unit can be up to 102 inches without requiring a commercial drivers license, and the height of a semitrailer including a foldable building unit can be up to 13 feet, 6 inches without requiring a commercial drivers license. 
         [0116]    A “transport vehicle” as referred to herein, is a vehicle that is suited for transporting a foldable building unit along roads to a building site. Typically, the transport vehicle is a semitrailer. 
         [0117]    A “ground-level lifting rig” as referred to herein, is a device that is adapted to move a load, typically, lift a load and contains at least one lifting member that can be connected to a foldable building unit. A ground-level lifting rig is designed with regard to its structural stability and lift power such that it can be used in lifting of a foldable housing module without structural damage to the lifting rig. Ground-level lifting rigs are typically portable. Also, they are preferably small for ease of transport along with the foldable building unit, for example, on the transport vehicle that transports the foldable building unit. Ground-level lifting rigs can be manually powered (e.g., a manual hoist) or use another source of energy (e.g., electrical energy used with an electric hoist, electric hydraulic system, air power lift, etc.). Ground-level lifting rigs can be adapted such that they can be placed on various types of surfaces that can be even, uneven, and/or with or without slope. 
         [0118]    A “lifting member” as referred to herein, is a part of a ground-level lifting rig that can be connected to connection members or directly to a foldable building unit and is moved during lifting of the foldable housing module. A lifting rig can have one or more lifting members. Typically, it has one lifting member. The lifting member can be any part that can be temporarily contacted or attached to a connection member or directly with a foldable building unit and is adapted to maintain contact or attachment during lifting and/or lowering of the foldable building unit. 
         [0119]    A “connection member” as referred to herein, is a part that is either part of the structural frame or can be attached to the structural frame, and can be connected to the lifting member of a ground-level lifting rig and is adapted to maintain connection between the foldable building unit and the lifting member of the ground-level lifting rig during lifting and/or lowering of a the foldable building unit. 
         [0120]    Polymer gaskets can be used to cover seams or folds of foldably connected members (e.g., hollow structural steel sections) of respective frame elements as well as hinges (including offset and step-out hinges). Suitable polymer gaskets are sufficiently flexible to prevent tearing of the polymer gasket during folding and unfolding, do not hinder folding and unfolding and are preferably not permeable for water. An example is shown in  FIG. 13 . 
         [0121]    Seams or folds of foldably connected frame elements, and preferably all boundaries of folded components, can be sealed with polymer gaskets at the time of prefabrication to reduce or remove the need for time-consuming and error-prone on-site weatherproofing. 
         [0122]    While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.