Abstract:
Embodiments of the present invention provide a building construction with specially designed light gage metal studs, concrete slabs, and other prefabricated components. In one embodiment, a building construction for a wall structure comprises one or more wall panels; and at least one wall holding track connected to an edge of one of the wall panels, the at least one wall holding track having two flanges connected to a web to form a generally U-shaped track to receive the edge of the wall panel, the web including a plurality of integrally formed threaded nuts to receive threaded fastening members, the integrally formed threaded nuts being disposed at preset locations along the web. The invention gives a solution to modularize buildings, especially for residential homes which makes the building construction more assembly like.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to building construction using prefabricated components and, more particularly, to energy efficient building construction using light gage metal studs, concrete slabs, and other prefabricated components designed to provide an assembly building construction that makes efficient use of materials and labor. 
       BACKGROUND ART 
       [0002]    Prefabricated building panels and associated components have been used to form the walls, floors, and roofs of a building structure for many years. The prefabricated building panels and associated components act as structural components of the building. Construction utilizing prefabricated panels and components offers many advantages, including more rapid construction and standardization, than traditional on-site construction. The prefabricated building panels and components can be constructed on-site or off-site, and then moved into position to form the panel structures. There continues to be a need for improved prefabricated building panels and components to meet the demand for lower labor and material costs, as well as energy efficiency. 
       SUMMARY OF THE INVENTION 
       [0003]    Embodiments of the present invention provide a building construction with specially designed light gage metal studs, concrete slabs, and other prefabricated components that eliminate most conventional beams and that integrate wall panels, floor slabs, and roof decks into a well-connected skeletal structure. Compared to traditional metal studs frames, the usage of steel can be greatly reduced. The assembly procedure to build a wall section can be applied to various types of structures, such as wooden frame buildings, metal (heavy or light) frame buildings, or concrete frame buildings. The present system will not only greatly reduce material and labor cost, but can provide a more cost effective and energy efficient building in terms of energy savings, building materials recycling, reduced maintenance needs, cost effectiveness, much shorter construction time, and adaptability to different architectural designs. The building construction assembly process is analogous to the furniture assembly process. 
         [0004]    In accordance with an aspect of the present invention, a building construction for a wall structure comprises one or more wall panels; and at least one wall holding track connected to an edge of one of the wall panels, the at least one wall holding track having two flanges connected to a web to form a generally U-shaped track to receive the edge of the wall panel, the web including a plurality of integrally formed threaded nuts to receive threaded fastening members, the integrally formed threaded nuts being disposed at preset locations along the web. 
         [0005]    In some embodiments, the web includes one or more access holes that allow access to one or more hollow interior portions of the wall panel. The one or more access holes of the web are open to allow air flow into the one or more hollow interior portions of the wall panel. A filling material is introduced via the one or more access holes of the web into the one or more hollow interior portions of the wall panel. The filling material fills the one or more hollow interior portions of the wall panel to provide solid touch between bearing surfaces of a lower edge and an upper edge of the wall panel which is disposed generally vertically. The web is slanted with respect to two generally parallel flanges. Each wall panel has a lower edge connected to a lower wall holding track and an upper edge connected to an upper wall holding track. 
         [0006]    In specific embodiments, at least one of a floor, a roof, a bearing header, or a column is connected to the web of the wall holding track by fastening members threadingly coupled to the integrally formed threaded nuts of the web. Two wall holding tracks are disposed parallel to each other and spaced by a gap to form a double layer wall holding track to hold two wall panels spaced by the gap. 
         [0007]    In accordance with another aspect of the invention, a wall holding track comprises two flanges connected to a web to form a generally U-shaped track to receive an edge of a wall panel. The web includes a plurality of integrally formed threaded nuts to receive threaded fastening members, the integrally formed threaded nuts being disposed at preset locations along the web. The web includes one or more access holes that allow access to the edge of the wall panel received into the generally U-shaped track. 
         [0008]    In some embodiments, two additional flanges are connected to another web to form a second generally U-shaped track to receive an edge of another wall panel. The web of the second generally U-shaped track includes a plurality of integrally formed threaded nuts to receive threaded fastening members, the integrally formed threaded nuts being disposed at preset locations along the web. The web of the second generally U-shaped track includes one or more access holes that allow access to the edge of the wall panel received into the second generally U-shaped track. The two generally U-shaped tracks are disposed generally parallel to each other and connected by a connecting member between the two webs that are coplanar with each other. 
         [0009]    In accordance with another aspect of the present invention, a wall supporting structure comprises a first floor panel and a second floor panel which are generally coplanar and disposed at a distance spaced above a ground; a first generally U-shaped beam connected to an edge of the first floor panel, the first generally U-shaped beam having a web connected to two flanges; and a second generally U-shaped beam connected to an edge of the second floor panel, the second generally U-shaped beam having a web connected to two flanges. The web of the first generally U-shaped beam and the web of the second generally U-shaped beam are aligned with each other and attached together. 
         [0010]    In some embodiments, a first bearing header is provided at an opposite edge of the first floor panel from the first generally U-shaped beam, and a second bearing header is provided at an opposite edge of the second floor panel from the second generally U-shaped beam. An upper wall is disposed above and aligned with the first and second generally U-shaped beams. The first and second generally U-shaped beams are spaced above the ground without a lower wall aligned with the first and second generally U-shaped beams. 
         [0011]    These and other aspects of the invention are described in further detail below and shown in the accompanying drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic perspective view of different concrete slabs or panels; 
           [0013]      FIG. 2  is a schematic diagram of a double-layer wall or combination wall; 
           [0014]      FIG. 3  is a schematic view of a bearing wall section; 
           [0015]      FIG. 4  shows schematic views of (a) a bearing header with floor slab, (b) a front view thereof, (c) a top plan view thereof, (d) a back view thereof, (e) a right side view thereof, (f) a left side view thereof, (g) a bolt therefor, and (h) a wall holding track having holding nuts; 
           [0016]      FIG. 5  shows a preferred embodiment for use of a bearing header and wall holding track when coupling two walls together at a wall corner; 
           [0017]      FIG. 6  shows schematic views of (a) a roof panel, (b) a cross-sectional view thereof, (c) a bolt therefore, (d) a wall holding track therefor, and (e) a wall holding track therefor with air circulating holes. 
           [0018]      FIG. 7  shows schematic views of (a) an upper wall holding track having holding nuts, (b) an upper wall holding track, and (c) a bottom wall holding track. 
           [0019]      FIG. 8  is a schematic perspective view of a double-layer wall holding track. 
           [0020]      FIG. 9  is a schematic perspective view of a structure including wall holding tracks for a double-layer wall and upper floor panel and bearing header. 
           [0021]      FIG. 10  is a schematic perspective view of the components of a bearing wall section. 
           [0022]      FIG. 11  is a schematic view of a building skeleton formed of columns and light-gage metal studs. 
           [0023]      FIG. 12  shows schematic views of (a) a front view of a washer, (b) a back view thereof, (c) a side view thereof, (d) a sectional view thereof, (e) a front view of a rivet-type bolt, (f) a left side view thereof, (g) a right side view thereof, (h) a front view of a screw-type bolt, (i) a left side view thereof, (j) a right side view thereof, (k) a front view of a screw-type nut, (l) a left side view thereof, (m) a right side view thereof, and (n) a sectional view thereof. 
           [0024]      FIG. 13  shows schematic views of (a) a structure for supporting floor slabs with U-shaped beams and a 2-U beam member supporting an upper story wall, and (b) a close-up view of the 2-U beam member. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]      FIG. 1   a - d  present schematic perspective views of different types of concrete slabs or panels in accordance with a preferred embodiment of the present invention. As shown,  FIG. 1   a  presents a sandwich panel  10  having an insulation core  12 . The insulation core  12  includes any suitable insulation material. The hollow panel  20  in  FIG. 1   b  has a plurality of hollow channels  22 . The hollow channels  22  can be left hollow or can be filled with a filling material which can be any suitable construction material. The shape of the hollow channels  22  can be circular, elliptical, square, rectangular, triangular, or the like.  FIG. 1   c  shows a solid panel  30 .  FIG. 1   d  shows a reinforced panel  40  having side reinforcements in the form of metal studs  42 ,  44  to provide additional strength for a load bearing wall. Although the reinforced panel  40  in  FIG. 1   d  is a solid panel, other reinforced panels may include a sandwich panel or a hollow panel with side reinforcements. The panels can be used for building wall sections in various types of structures, such as wooden frame buildings, metal (heavy or light) frame buildings, and concrete frame buildings. The concrete slabs, regular or light-weight, used in walls can be classified as bearing walls for load bearing and non-bearing walls. The non-bearing walls may also be referred to as curtain walls for exterior use or partition walls for interior use. 
         [0026]    The different wall panels can be selected to build an energy efficient structure. Depending on the local climate and structure location, one may select to use hollow slabs or panels, sandwich slabs or panels, or solid slabs or panels. Sandwich panels  10  are more heat preserving or insulating, and is suitable for use in cold climate as both inner and outer walls as shown in  FIG. 2 . For hot climate, the use of hollow panels  20  as outer walls is beneficial by aligning the hollow channels  22  to provide good ventilation from near the ground to near the roof and ensuring that other members used to assemble the outer wall (such as wall holding tracks as discussed below) do not block the ventilation paths through the hollow channels  22 . Sandwich panels  10  are desirably used as inner walls. 
         [0027]      FIG. 2  is a schematic diagram of a double-layer wall or combination wall  50  which includes an inner wall  52  and an outer wall  54  spaced by a gap or air space  56 . The double-layer wall  50  can be a combination of two bearing walls, two curtain walls, or a bearing wall and a curtain wall. 
         [0028]      FIG. 3  is a schematic view of a typical wall section. Columns  60  and bottom holding tracks  62  are attached to the base  64 . For the first story, the top of the footing is the base. For an upper story, the top of the story just below is the base. Wall panels  66  are mounted on the bottom holding tracks  62 . The wall panels  66  may be comprised of solid slabs or panels, sandwich slabs or panels, or hollow slabs or panels. Top holding tracks  68  are fastened at the top of the wall panels  66 . A bearing header  70  is placed on top of the top holding tracks  68  and supported by the columns  60 . Optional U-shaped side holding tracks  72  are coupled to the vertical sides of the wall panels  66  to provide additional strength against buckling. The side holding tracks may further be attached to the columns or the like. The top, bottom, and side holding tracks are U-shaped with a pair of flanges connected to a web or bearing face, and these U-shaped tracks are sized to match the thickness of the wall panels to be disposed between the pair of webs. 
         [0029]    If the wall section is a bearing wall section that is load bearing, all wall panels  66  are vertically installed and each wall panel  66  is a factory-made whole piece. No structural damage on any wall panel is allowed before and during the installation. It is important for a bearing wall section to have solid touch between the wall panels  66  and the bearing faces of the bottom holding track  62  and top holding track  68 , and between the holding tracks and the bearing header  70 . Solid touch is achieved by filling any open cores, channels, or gaps between the bearing surfaces of the bearing wall section to eliminate open spaces or gaps. Further, side holding tracks  72  installed along the vertical edges of the wall panels  66  are desirable for providing strength against buckling. Optionally, on each wall slab or panel, a side reinforcement metal stud  42  or  44  ( FIG. 1 ) that is poured with the concrete panel can be fixed with upper and lower wall holding tracks by self-drilling screws. 
         [0030]    For a non-bearing wall section, solid touch is not required and reinforcement using side holding tracks is not necessary. Further, the filling of any hollow channels or cores of the wall panels can be eliminated. 
         [0031]      FIG. 4   a  shows a bearing header with floor slab structure  80 . If the floor slab  81  is on top of the bearing wall directly, the bearing header  82  will serve as the holding end for the floor slab  80  and is poured with the floor slab  81 .  FIGS. 4   b - 4   f  show various views of the bearing header  82 . The bearing header  82  includes a plurality of pipes or channels  84  for receiving bolts  86  in  FIG. 4   g  for attaching wall holding tracks or the like to the bearing header  82 . 
         [0032]      FIGS. 4   h ( 1 ) and ( 2 ) show different views for a preferred embodiment of a wall holding track  90  which includes a web or bearing face  92  and two spaced flanges  94 . In a preferred embodiment, the web  92  of the wall holding track  90  includes integrally formed or built-in positioning or holding nuts  96  for coupling with the bolts  86  to fasten the wall holding track  90  to other structural components such as the matching pipes or channels  84  of the bearing header  82 . The web  92  may further include access holes  98  that match the hollow channels or openings  22  of the hollow panel  20  in  FIG. 1   b  to provide ventilation or allow filling or serve as conduits for wiring, tubing, and the like. The holes  98  of the wall holding track  90  can be large holes or small holes, and can even be replaced by a wire mesh. The holes  98  facilitate construction and checking or inspecting, allow air flow when ventilation is desired in the wall panels, and allow filling of hollow spaces in the wall panels when solid touch or insulation is desired. 
         [0033]    The nuts presumably are integrally formed with the tracks to receive bolts or threaded rods for fastening the tracks to other structural components such as floor slabs, roofs, and the like. For example, a bearing header with floor slab can include matching holes to receive bolts or threaded rods that are connected to the corresponding nuts of the track to fasten the bearing header to the track. 
         [0034]    If the same structural idea is applied into wall corners, use of a metal stud column may be eliminated by vertically installed bearing headers.  FIG. 5  shows a preferred embodiment for use of a bearing header and wall holding track when coupling two walls together at a wall corner. As shown in FIG. a, the bearing header  82  is coupled to the edge of the first wall and the wall holding track  90  is coupled to the edge of the second wall such that the holding buts  96  match up with the holes/channels  84  in the bearing header in a vertical fashion such that the bolts  86  can then be used to couple the two walls together. 
         [0035]      FIGS. 6   a  and  6   b  show a roof panel  100  having holes or apertures  102  for roof holding or fastening. The roof panel  100  may include a layer of insulation sandwiched between layers of concrete. As shown in  FIGS. 6   b  and  6   c , each hole  102  receives a bolt  104  for attaching the roof panel  100  to another structural component such as the wall holding track  110  of  FIG. 6   d . The wall holding track  110  has a slanted web  112  for an inclined roof and a pair of flanges  114 . In a preferred embodiment, the web  112  includes integrally formed or built-in positioning or holding nuts  116  for coupling with the bolts  104  to fasten the wall holding track  110  to other structural components such as the roof panel  102 , a floor, a bearing header, or a column (for side wall holding tracks that are disposed generally vertically). The web  112  may further include holes  118  that match the hollow channels or openings  22  of the hollow panel  20  in  FIG. 1   b  to provide ventilation or allow filling or serve as conduits for wiring, tubing, and the like. The holes  118  of the wall holding track  110  can be large holes or small holes, and can even be in the form of a wire mesh. The holes  118  facilitate construction and checking or inspecting, allow air flow when ventilation is desired in the wall panels, and allow filling of hollow spaces in the wall panels when solid touch or insulation is desired. 
         [0036]      FIG. 6   e  shows a wall holding track  120  having a slanted web  122 , a pair of flanges  124 , and preferably with integrally formed nuts  126  and holes  128 . The wall holding track  120  further includes a horizontal web  130  with air circulating holes  132  that match the hollow channels or openings  22  of the hollow panel  20  in  FIG. 1   b  for air circulation. In the case where hollow panels  20  are used as the outer wall, the air circulating channels  22  can make the building more energy efficient. The wall holding track  120  can be used just under the roof. 
         [0037]      FIG. 7  shows examples of wall holding tracks, including an upper wall holding track  140  having built-in holding nuts  142  and access holes  144  for air flow, checking, or filling.  FIG. 7   b  shows an upper wall holding track  150  with holes  152  for air flow, checking, or filling.  FIG. 7   c  shows a lower wall holding track  160  with holes  162  for air flow, checking, or filling. 
         [0038]      FIG. 8  is a schematic perspective view of a double-layer wall holding track  170  which includes two wall holding tracks  172  spaced by an air layer spacer or gap  174 . The two wall holding tracks  172  hold a pair of spaced wall panels to form a double wall structure. The wall holding tracks  172  desirably include access holes  176  at the webs or bearing faces for air flow, checking, or filling. In some embodiments, the wall holding tracks  172  include built-in nuts (not shown). A connecting member  178  in the gap  174  connects the two wall holding tracks  172  which include coplanar webs. 
         [0039]      FIG. 9  is a schematic perspective view of a structure including a double-layer wall holding track for a double-layer wall and upper floor panel and bearing header. A double-layer wall holding track  170  serves as a bottom track for the lower edges of the double walls. An upper wall holding track  180  is disposed to receive the upper edge of one of the walls. The upper wall holding track  180  is disposed below and connected to a bearing header  182  for a floor panel. A second double-layer wall holding track  184  serves as bottom tracks for wall panels of an upper floor, and is aligned with the first double-layer wall holding track  184  for the double walls. The second double-layer wall holding track  184  is connected to the bearing header  182 . A second upper wall holding track  186  is connected below the second double-layer wall holding track  184  to receive the upper edge of the other wall. 
         [0040]      FIG. 10  is a schematic perspective view of the components of a bearing wall section  190 . A pair of columns  192  are connected to a bottom wall holding track  194 , and they are mounted on a base  196 . A plurality of wall panels  198  are disposed between the pair of columns  192  and are supported on the bottom wall holding track  194 . An upper wall holding track  200  is disposed between the columns  192  and connected to the upper edges of the wall panels  198 . A bearing header  202  is disposed above the upper wall holding track  200 . Optionally, side wall holding tracks  204  are disposed next to the columns  192  and are fixed on columns  192 . The side wall holding tracks  204  are disposed vertically to increase the buckling strength of the wall panels  198 . Another option is to add a side reinforcement metal stud  42  or  44  ( FIG. 1 ) which is poured with the concrete panel  198 . Then each metal stud  42  or  44  on the panel can be fixed with upper and lower wall holding tracks  200  and  204  by self drilling screws to have a much stronger wall. 
         [0041]      FIG. 11  is a schematic view of a building skeleton  210  formed of columns  212  and light-gage metal studs or wall holding tracks  214  that are connected together. The columns and tracks  214  will function as the skeleton and/or tendons. Concrete slabs will function as the muscles and meat of the building. External walls, floors, and roofs will represent the skin of the building.  FIGS. 9-10  illustrate how the various wall holding tracks meet all the wall construction needs of a building. 
         [0042]      FIG. 12  shows examples of fastening members. The first is (a) a front view of a washer  220 , (b) a back view thereof, (c) a side view thereof, and (d) a sectional view thereof. The second is (e) a front view of a rivet-type bolt  230 , (f) a left side view thereof, and (g) a right side view thereof. A tiny hole in the head of the bolt provides better rivet. The third is (h) a front view of a screw-type bolt  240 , (i) a left side view thereof, and (j) a right side view thereof. The fourth is (k) a front view of a screw-type nut  250 , (l) a left side view thereof, (m) a right side view thereof, and (n) a sectional view thereof. 
         [0043]      FIGS. 13   a  and  13   b  show a structure for supporting floor slabs with U-shaped beams and a 2-U beam member supporting an upper story wall. The structure includes exterior walls  300 , bearing headers  302  for two floor slabs  304 , and two U-shaped beams  306  connected to respective edges of the two floor slabs  304 . The U-shaped beams  306  each include two flanges connected to a web. The webs of the two U-shaped beams  306  are aligned with each other, desirably in contact with each other, and connected together to form a 2-U beam member supporting an upper story wall  308 . The 2-U beam member can support the upper story wall  308  with no lower story wall below the 2-U beam member in the longitudinal direction. 
         [0044]    One procedure of constructing a wall section is described herein. The standard dimensions of wall panels are summarized in the following table, as provided by the National Standard Construction Drawing 05J910-1 that is approved by the Department of Construction of P.R.C. and published in 2006. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Dimension (mm) 
               
             
          
           
               
                   
                 Item 
                 Thick 
                 Width 
                 Length 
               
               
                   
                   
               
             
          
           
               
                   
                 Solid Panel (SOP) 
                 60 
                 600, 1200 
                 2100-3000 
               
               
                   
                 Sandwich Panel 
                 60 
                 600, 1200 
                 2100-3000 
               
               
                   
                 (SWP) 
                 90 
                 600, 1200 
                 2100-3300 
               
               
                   
                   
                 120 
                 600, 1200 
                 2100-4200 
               
               
                   
                 Hollow Wall Panel 
                 90 
                 600, 1200 
                 2100-3300 
               
               
                   
                 (HWP) 
                 120 
                 600, 1200 
                 2100-4200 
               
               
                   
                 Hollow Floor Panel 
                 120 
                 600, 1200 
                 4200 
               
               
                   
                 (HFP) 
               
               
                   
                   
               
             
          
         
       
     
         [0045]    According to the procedure, columns are constructed using light-gage cold-formed metal studs in a conventional manner. Using self-drilling screws and/or concrete nails, upper and lower wall holding tracks are connected to the columns and the base. In each wall section, the outer side web of the lower wall holding track is cut off to the length about 1.25 times of the wall panel width at the place the last piece of wall panel will be installed. Optionally, to increase the buckling strength of the wall, side wall holding tracks can be installed vertically on the respective sides of the columns. The upper edges of the wall panels are inserted into the upper wall holding track, and the lower edges of the wall panels are inserted into the lower wall holding track. The last wall panel is cut to fit to finish the installation of the wall panels. Self-drilling screws can be used to fix reinforcing metal studs on the wall panel to the wall holding tracks. The fastening parts of  FIG. 12  can be used to close the opening of the wall holding tracks, which is on the right side of  FIG. 9 . If the vertical or side wall holding tracks are used, fastening parts of  FIG. 12  can be used as well to fasten the side wall holding tracks. Gaps between the upper wall holding track and the wall panels can be filled with cement or any other approved construction material to ensure solid touch for bearing walls. This completes a typical bearing wall panel. 
         [0046]    To install the fasteners such as those shown in  FIG. 12 , holes of about 1/16″ to ⅛″ inch or about 2 mm larger than the bolt diameter are drilled on the wall panels. Using the same center, the wall panel surface is drilled to a size just enough to hold the washer. If the holes are prefabricated in the factory, the holes on the wall holding tracks and the holes on the wall panels are aligned during manufacturing. The bolts and washers are put in place and are either riveted or screwed to tighten. 
         [0047]    The floor slabs are hollow slabs with reinforcements in the bottom side (tension side) of the slabs. For floor slabs with end(s) connected with walls, it is preferable to cast the bearing header with the slab and hook up reinforcement with fixing pipes of bearing header. If steel reinforcements are used in the floor slabs when connecting them to the bearing header using a bolting pipe, a stronger structure will be obtained. To preserve energy, sandwich panels are preferably used for roof deck construction. Similar to floor panels, the sandwich panels are preferably reinforced to take designed loads. The construction of the roof decks is similar to the construction of floor slabs but with special design as shown in  FIG. 6 . 
         [0048]    The same composition column used in metal stud buildings can be used in the present construction. In addition, steel columns, wooden columns, or concrete columns may be used. As for the beams, most beams in conventional structures are replaced by bearing header for floor slab ( FIG. 4   a ). For beams supporting upper walls, one may use traditional beams or 2-U beams ( FIG. 13 ). 
         [0049]    As seen in  FIG. 11 , the skeleton of the building includes columns (bones) and light gage metal stud or wall holding tracks (tendons). Some general principles should be followed. Major bearing walls should continue from bottom to top. Columns may be designed at each exterior wall corner and three or four wall joints. As the tendons of a building, columns are connected by wall holding tracks. 
         [0050]    The following is an assembly building construction procedure. Footing with anchor bolts are poured in place for columns and shearing walls. Columns and wall holding tracks are installed to form the skeleton of the building. The above-described procedure is used to install the wall panels of the first story (for a double wall construction, only the inner wall is installed and the outer wall is installed after electrical and plumbing lines are in place). The gaps between the top of the bearing wall panel and the wall holding tracks are filled. All floor slabs of the second story are installed. All wall holding tracks on the second story are installed, and the bottom wall holding tracks are fastened to bearing headers. The wall panels of the second story are installed. Any additional stories are constructed following the same procedure for the second story. After the top story is formed, the wall holding tracks for the roof and the roof panels are installed. Electric wiring and plumbing piping lines are installed in air gaps or access holes in the wall panels. All support parts for heavy hanging needs are also installed. The outer walls from the bottom story to the top story are installed one by one to complete the construction of the building. 
         [0051]    Although preferred embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.