Patent Publication Number: US-2006000177-A1

Title: Frame assembly and environmental enclosure

Description:
RELATED APPLICATION  
      This application claims priority to Provisional Patent Application Ser. No. 60/579,410 filed in the U.S. Patent and Trademark Office on Jun. 14, 2004. 
    
    
     FIELD OF THE INVENTION  
      This invention relates to an environmental or contaminant shield or enclosure which prevents airborne contaminants from contacting a part received within or transmitted through the environmental or contaminant enclosure. More particularly, this invention relates to a frame assembly for an environmental or contaminant shield or enclosure and the shield or enclosure.  
     BACKGROUND OF THE INVENTION  
      Environmental or contaminant shields or enclosures, commonly referred to as “clean tunnels,” are utilized by many industries to prevent airborne contaminants from contacting a part received within or transmitted through the environmental or contaminant shield or enclosure. Such enclosures are used, for example, in an automotive paint facility, wherein the vehicle body is conveyed through clean tunnels between the several steps performed in the paint shop including, for example, sanding, tack-off (typically performed by feather dusters), paint booths and ovens to prevent airborne contaminants, including particulate and waterborne contaminants, from contacting the vehicle body following sanding, cleaning, tack-off and painting. A typical automotive paint facility may include over a mile of clean tunnels. As will be understood, however, other manufacturing and assembly facilities also use clean tunnels or enclosures during assembly or manufacture, including downtime. A typical clean tunnel or enclosure includes a frame assembly comprised of like channel-shaped frame members formed from sheet metal, typically steel, each having an open end, including an end or bottom wall and opposed side walls having opposed inwardly projecting end portions, wherein an end cap is received in the opening end of the channel-shaped frame members which secures a flexible film stretched over the frame members forming the clean tunnel as disclosed, for example, in U.S. Pat. Nos. 4,860,778 and 5,906,078.  
      As disclosed in such patents, the like channel-shaped frame members are then interconnected in end to end relation into a rectangular frame and the flexible sheet is stretched over the frame members and the rectangular frame members are then interconnected in side to side or end to end relation to form a U-shape clean tunnel or enclosure, preventing airborne contaminants from contacting a part received in the clean tunnel or enclosure. In a typical application, the frame members are first interconnected in end to end relation to form a rectangular frame, a flexible film is stretched over the rectangular frame and secured by end caps and the rectangular frame members with the flexible film are then interconnected in end to end and side to side relation with fasteners or clips. However, because the open ends of the channel-shaped frame members are closed by the end caps which secure the flexible film, assembly of the rectangular frame members with the end caps and flexible film require special clips or fasteners which penetrate the channel-shaped frame members making assembly of the frame members difficult, requiring special tools or parts and potentially reducing the structural integrity of the frame assembly.  
      It would also be desirable to easily remove and replace damaged flexible film after assembly, which comprises a majority of the surface area of the clean tunnel or enclosure, without special tools and to form the frame members from extruded aluminum to form a light weight, more rigid rugged construction. The environmental enclosure and frame assembly of this invention solves the problems associated with the prior art described above, including frame members which may be easily and securely assembled and wherein the flexible film may be easily assembled on the frame members or removed and replaced if damaged.  
     SUMMARY OF THE INVENTION  
      The frame assembly for an environmental enclosure of this invention includes a plurality of interconnected channel-shaped frame members, wherein each of the frame members includes a first end wall, opposed spaced side walls extending generally perpendicular to and integral with the first end wall and an opening opposite the first end wall adapted to receive and retain an end cap for retaining a film over the frame assembly. As thus far described, the channel-shaped frame members may be generally similar to the frame members disclosed in the above-referenced U.S. patents. However, the frame members of this invention further include an integral internal retainer channel within the channel-shaped frame members including a retainer wall integral with and extending generally perpendicular to one of the side walls, spaced from the end wall, for receiving a connector element interconnecting the channel-shaped frame members into a rectangular frame or for interconnecting abutting transverse frame members for braces or the like. In a preferred embodiment, the internal retainer wall is generally L-shaped, including a first portion integral with and extending generally perpendicular to the side wall and an end portion extending toward the first end wall of the channel-shaped frame member and in the disclosed embodiment, the first end wall further includes an internal retainer wall extending toward the end portion of the generally L-shaped retainer wall, forming an integral internal channel for receiving a retainer element as described. In a preferred embodiment, the channel-shaped frame members are formed from extruded aluminum, forming a light weight rigid construction.  
      In one of the disclosed embodiments of the channel-shaped members, the first side wall which includes the internal retainer channel, has a second end wall extending from and integral with the first side wall and the opening which receives the end cap is adjacent the second side wall and the opening is defined by parallel enlarged bead-shaped portions to receive and retain the end cap which retains a film overlying the frame assembly. In the other disclosed embodiments, the end portions of the side walls are U or hook-shaped each having an enlarged bead-shaped portion extending toward the first end wall.  
      In one of the preferred embodiments of the frame assembly of this invention, the channel-shaped frame members further include an L-shaped retainer portion including an end wall portion integral with a side wall, preferably a side wall opposite the integral internal channel described above, extending parallel to the first end wall and preferably aligned with the first end wall, and an end portion integral with and extending generally perpendicular to the end wall portion of the retainer portion forming a channel-shaped retainer or connector portion for interconnecting adjacent channel-shaped members in side to side relation, wherein the channel-shaped frame members of the frame assembly include a first plurality of channel-shaped members each having a generally L-shaped connector portion extending from one side wall and a second plurality of channel-shaped members which are a mirror image of the first channel-shaped members, and wherein the L-shaped retainer portions are aligned in side to side abutting relation and a fastener interconnects the first and second channel-shaped members.  
      The channel-shaped frame members of this invention are first assembled into rectangular frame assemblies, wherein the ends are preferably mitered or cut at a 45 degree angle and an L-shaped connector element having a first leg portion is received in the internal retainer channel of one frame member and a second leg portion is received in an internal channel of a perpendicular second channel-shaped frame member forming a rectangular frame assembly. The rectangular frame assembly is then covered with a thin, preferably transparent film and secured by end caps, such that each rectangular frame assembly is covered by a thin transparent film. In the disclosed embodiment of the frame assembly of this invention having a generally L-shaped retainer portion, the rectangular frame assemblies are then secured in side to side relation by a fastener, such as a clip, rivet or the like. In a preferred alternative embodiment, the frame assemblies are interconnected in side to side relation by a U-shaped retainer member having end portions received around the adjacent channel-shaped frame members and secured by suitable fasteners, such as screws, bolts, or the like. The frame assemblies may be rectangular or square. In one preferred embodiment, a rectangular frame assembly is first formed having a height equal to the desired height of the environmental enclosure and the rectangular frame assemblies include cross members having end portions secured to the rectangular frame assembly by U-shaped retainer members received within the cross members having slots received in the opposed end portions of the internal retainer channel, forming a light weight rigid assembly. The preferred alternative embodiment of the frame assembly has the advantage that the frame assembly is more rigid and does not require mirror image channel-shaped frame members and is thus less expensive to manufacture and assemble.  
      In a preferred embodiment of the frame assembly of this invention, the channel-shaped frame members are extruded, preferably extruded aluminum, forming a rigid lightweight frame assembly which is easily assembled or disassembled, as required. Further, the thin flexible film may be easily secured to or replaced on the frame assemblies by end caps which, in a preferred embodiment, includes a planar end portion and projecting generally parallel outwardly bowed legs which are received between the parallel enlarged bead-shaped portions defining the opening to the channel-shaped frame members, securely retaining the flexible film.  
      As will be understood, the disclosed embodiments of the frame assembly and channel-shaped frame members is provided for illustrative purposes only and various modifications may be made to the frame assembly and channel-shaped frame members within the purview of the appended claims as described further below.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side perspective view of one embodiment of an environmental enclosure of this invention;  
       FIG. 2  is a partial exploded view of the ends of two frame members, a connector channel, end caps and flexible film illustrating the assembly of the frame members shown in  FIG. 1  in end to end relation;  
       FIG. 3  is a side view of a rectangular frame assembly, which is a component of the environmental enclosure shown in  FIG. 1 ;  
       FIG. 4  is a side cross-sectional view of  FIG. 3  in the direction of view arrows  4 - 4  with the end cap and film;  
       FIG. 5  is a partially exploded top perspective view of two rectangular frame assemblies shown in  FIG. 1  illustrating one means of interconnecting the frame assemblies further illustrated in  FIG. 6 ;  
       FIG. 6  is an end cross-sectional view of two frame members shown in  FIG. 1  interconnected in side to side relation;  
       FIG. 7  is a side cross-sectional view similar to  FIG. 5  with an alternative fastener interconnecting the frame members;  
       FIG. 8  is a partial side view of an alternative embodiment of the environmental enclosure of this invention;  
       FIG. 9  is a partial side cross-sectional view of  FIG. 8  in the encircled area  9 ;  
       FIG. 10  is a cross-sectional view of  FIG. 9 , in the direction of view arrows  10 - 10 ;  
       FIG. 11  is a perspective view of one embodiment of the corner connector element illustrated in  FIGS. 9 and 10 ;  
       FIG. 12  is a partial side cross-sectional view of  FIG. 8  in the direction of view arrows  12 - 12 ;  
       FIG. 13  is an end cross-sectional view of  FIG. 8  in the direction of view arrows  13 - 13 ;  
       FIG. 14  is a side cross-sectional view of  FIG. 8  in the encircled area  14 ;  
       FIG. 15  is as end cross-sectional view of  FIG. 14  in the direction of view arrows  15 - 15 ;  
       FIG. 16  is a perspective view of the connector element shown in  FIGS. 14 and 15 ; and  
       FIG. 17  is an end cross-sectional view of  FIG. 8  in the direction of view arrows  17 - 17 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      As will be understood, the embodiments of the frame assembly and environmental enclosure of this invention disclosed in the figures are for illustrative purposes only and various modifications may be made to the frame assembly and environmental enclosure of this invention with the purview of the appended claims as described further below.  
      The embodiment of the environmental enclosure or clean tunnel  20  shown in  FIG. 1  and FIGS.  2  to  7  includes a plurality of interconnected rectangular frame assemblies  24  interconnected in side to side relationship, each including four frame members  26  or  26 A interconnected in end to end and side to side relation having a flexible film  28  preferably stretched between the frame members  26  and  26 A. The flexible film  28  may be formed of any suitable material, including a transparent polymeric film, such as polyethylene, having a thickness of for example about 0.18 mm and preferably formed of a polymer, such as polyethylene or a polyethylene resin which shrinks upon heating, such that the flexible film  28  may be stretched between the frame members  26  and  26 A when heated, providing a smooth and regular surface. As will be understood, the shape or configuration of the environmental enclosure or clean tunnel  20  will depend upon the application of the environmental enclosure. For example, the environmental enclosure  20  may be in the form of a clean tunnel, as shown in  FIG. 1 , for enclosing a conveyor (not shown) for conveying a vehicle body (not shown) between the various work stations in a paint shop and may include access doors  30 . Alternatively, the environmental enclosure  20  may be in the form of a housing having closed ends (not shown) for storage of manufactured parts in a manufacturing facility to prevent contamination of the parts prior to subsequent manufacturing operations. The disclosed embodiment of the environmental enclosure  20  and frame assembly of this invention may be sufficiently rigid to be a free standing structure supported by the floor or may include additional reinforcement (not shown in  FIG. 1 ) again depending upon the application.  
       FIG. 4  is a cross-section of one preferred embodiment of a channel-shaped frame member  26  which includes a channel-shaped portion  32  and an integral connector portion  34 . The channel-shaped portion  32  includes a first end wall portion  36 , a first side wall  38  extending generally perpendicular to and integral with the first end wall portion  36  and a second side wall portion  40  spaced from the first side wall  38  extending perpendicular to and integral with the first end wall portion  36  forming a channel-shaped portion  32  having an opening  39  opposite the first end wall  36  as shown in  FIG. 4 . In a preferred embodiment, the first side wall  38  includes an end portion  42  at or adjacent the opening  39  at the open end of the channel-shaped portion  32  extending toward the second side wall  40  and the second side wall  40  includes an end portion  44  extending toward the first side wall  38  for receiving and retaining an end cap  64  as described below. In one preferred embodiment, the second side wall  40  also includes a second end portion  46  extending away from the first end portion  44  and overlying the end wall  48  of the connector portion  34 . The disclosed embodiment of the connector portion  34  includes an end wall portion  48  which is integral with the second side wall  40  and generally aligned or continuous with the first wall portion  36 . The connector portion  34  further includes a leg portion  50  which is spaced from the second side wall  40  and preferably extends generally perpendicular to and is integral with the end wall portion  48  of the connector portion  34  as shown in  FIG. 4 . In a preferred embodiment, the leg portion  50  has a shorter length than the side walls  38  and  40  of the channel-shaped portion  32 . In a preferred embodiment of the frame members  26 , the end portions  42 ,  44  and  46  include an enlarged bead-shaped cap retainer portion  52  which are generally parallel to the side walls  38  and  40  and extend toward the first end wall  36  and the end wall  48  of the connector portion, respectively, having an enlarged bead-shaped cross-section and an arcuate outer exterior surface to receive and retain end caps as described below.  
      As set forth below, the frame members  26  are preferably interconnected in end to end relation to form rectangular frame assemblies  24  as shown in  FIGS. 1 and 3 . In a preferred embodiment, the channel-shaped portion  32  of each of the frame members  26  includes an internal integral channel  55  configured to receive corner connectors  54 , also shown in  FIG. 2 . In a preferred embodiment, the internal channels  55  include a generally L-shaped portion  56  integral with the first side wall  38  having an end portion  58  extending toward the first bottom portion  36  and the internal channel  55  may include a second wall portion  60  which extends generally perpendicular to and is integral with the first bottom wall portion  36  generally aligned with the end portion  58  of the generally L-shaped web portion  56 , forming an integral internal channel  55  in the channel-shaped portion  32  having an opening opposite the second side wall  40  as best shown in  FIG. 4 . The generally L-shaped web portion  56  may also be arcuate or J-shaped to receive an arcuate corner connector channel  54 . As discussed further below, the frame members  26  (and  26 A described below) may be formed of aluminum and extruded forming a light weight relatively rigid structure at reduced cost. As shown in  FIG. 3 , the ends of the frame members  26  may be mitered or cut at a 45 degree angle, such that the abutting ends interfit as shown in  FIG. 3  to form the rectangular frame assemblies  24  as best shown in  FIG. 2 . The corner connectors  54  in this embodiment are preferably L-shaped having leg portions  62  which are telescopically received in the internal channels  55  in the channel-shaped portions  32  of the frame members  26  to complete the assembly of the rectangular frame assemblies  24 . The flexible film  28  may then be received over the inwardly projecting end portions  42  and  44  of the side walls  38  and  40 , respectively, and secured in place by a first end cap  64  as shown in  FIGS. 2 and 4 . Alternatively, as described below, the entire frame assembly may be assembled before application of the flexible film  28  and end caps  64 .  
      In one preferred embodiment, the first end caps  64  include a planar end portion  66  and projecting generally parallel outwardly bowed legs  68 . As best shown in  FIG. 4 , the legs  68  may include an arcuate outer surface  70  and the distal ends  70  of the leg portions  68  may be bowed slightly outwardly to interfit with the arcuate cap retainer portions  52  of the end portions  42  and  44  of the side walls  38  and  40 , respectively, to securely retain the flexible film  28 . The first end caps  64  may be formed from an extruded polymer, such as polyethylene or polypropylene, and the flexible film  28  is preferably formed of a heat shrinkable polymer, such as polyethylene, and the flexible film  28  is then preferably heated following assembly to stretch the film  28  over the rectangular frame assemblies  24  and  24 A.  
      Once the rectangular frame assemblies  24  and  24 A are assembled, as described above, the embodiments of the rectangular frame members  24  and  24 A may be interconnected in side to side relation by the connector portions  34 , as now described, with reference to  FIGS. 6 and 7 . First, however, it should be noted from  FIGS. 6 and 7  that the frame members include frame members  26  as just described and frame members  26 A which are substantially a mirror image of the frame members  26 , but may be otherwise identical. That is, the frame members  26 A may be identical to the frame members  26  except that the channel-shaped connector portion  32 A is on the right in  FIGS. 6 and 7  and the connector portion  34 A is on the left in  FIGS. 6 and 7 , whereas the channel-shaped portion  32  of frame member  26  is on the left in  FIGS. 6 and 7  and the connector portion  34  of frame member  26  is on the right in  FIGS. 6 and 7 . Thus, no further description of the frame members  26 A is required for a complete understanding and the elements of the frame members  26 A are numbered the same as the frame members  26  with the suffix “A.” The rectangular frame assemblies  24  and  24 A formed from the frame members  26  and  26 A are then assembled in side to side abutting relation as shown in  FIGS. 6 and 7 , with the leg portions  50  and  50 A of the connector portions  34  and  34 A in abutting relation and the leg portions are then secured together by suitable fasteners.  
      In an embodiment of the frame assembly shown in  FIGS. 5 and 6 , the rectangular frame members  24  are retained by a U-shaped clip  74  having parallel leg portions  76  received over the leg portions  50  and  50 A of the frame members  26  and  26 A, respectively, retaining the rectangular frame members  24  and  24 A in side to side abutting relation. The U-shaped clips may be formed of a metal, such as aluminum, but are preferably formed of a relatively rigid extruded plastic, such as polypropylene. The frame assembly shown in  FIG. 6 , may thus be assembled without tools or skilled labor. As will now be understood, the leg portions  50  and  50 A preferably have a length less than the length of the side walls  38 ,  40 ,  38 A and  40 A to provide easy access to the connector portions  34  and  34 A, respectively, for securement of the frame members  24  and  24 A together as described.  FIG. 5  also illustrates the assembly of two rectangular frame members  24  and  24 A with the U-shaped clip  74 , wherein the leg portions  50  and  50 A are first aligned and moved into abutting relation and the U-shaped clip  74  is then received over the abutting leg portions  50  and  50 A.  FIG. 7  illustrates an alternative means of securing the leg portions  50  and  50 A using conventional rivets  78  received through openings  80  in the abutting leg portions  50  and  50 A. The assembly of  FIG. 7  is otherwise identical to the assembly shown in  FIG. 6  and thus no further description is required.  
      The embodiment of the frame assemblies shown in  FIGS. 6 and 7  may then be finished and sealed with second end caps  82 , which are identical to the first end cap  64 , except for size. That is, the second end caps  82  include a planar end portion  84  and generally parallel outwardly bowed legs  86  which are received between the opposed second end portions  46  and  46 A of the second side walls  40  and  40 A, respectively, as shown in  FIGS. 5, 6  and  7 . Although the second end caps  82  are optional, they prevent the accumulation of dust or debris in the connector portions  34  and  34 A and provide a more finished assembly.  
      It is important to note that the embodiment of the frame assembly of this invention shown in  FIG. 1  and the frame assemblies described below may be assembled before application of the film  28  which would be difficult, if not impossible, with the frame assemblies for environmental enclosures disclosed in the above referenced prior art. That is, the channel-shaped frame members  26  may first be assembled into rectangular frame assemblies  24 , as described above, and the rectangular frame assemblies may then be assembled into an enclosure, such as the clean tunnel  20  shown in  FIG. 1 , before application of the flexible film  28 . This is an important advantage over the prior art because the flexible film  28  may be damaged during assembly. Following assembly of the rectangular frame assemblies  24  and  24 A, the flexible film  28  is cut to size and applied over the opposed end portions  42  and  44  or  42 A and  44 A, and secured in place by the first end cap  64  and preferably heated to stretch the film in place over the rectangular frame assemblies  24  and  24 A. This is a particular advantage where the flexible film  28  is transparent because this method of assembly provides a clear view of the interior of the environmental enclosure  20 . Further, the clear film may be damaged or coated with debris during use and the configuration of the frame members  26  and  26 A makes replacement of the flexible film easy and simple without requiring tools. The first end caps  26  are simply removed and the flexible film  28  may be easily replaced. It is also important to note that the frame assemblies of this invention may also be easily disassembled and changed or stored without special tools, particularly where the rectangular frame assemblies are secured in side to side relation with a clip, such as shown at  74  in  FIG. 6 .  
      The alternative preferred embodiment of the environmental enclosure or clean tunnel  120  shown in  FIG. 8  also includes a plurality of interconnected frame assemblies  124  interconnected in side to side relation as described below and the rectangular frame members  124  are covered with a flexible film  128  which is preferably stretched over the frame assemblies as described above. However, in this embodiment of the environmental enclosure  120 , the rectangular frame members  124  preferably have a height equal to the desired height of the environmental enclosure and may include cross members  122  for rigidity as described below. As set forth above, the shape or configuration of the environmental enclosure  20  will depend upon the application of the environmental enclosure. The embodiment of the rectangular frame assemblies  124  shown in  FIG. 8  are formed from a plurality of channel-shaped frame members  132  best shown in cross-section in  FIG. 10 .  
      As shown in  FIG. 10 , this embodiment of the channel-shaped members  132  each include a first end wall  136  and opposed first and second side walls  136  and  138  which are preferably integral with and extend generally perpendicular to the first end wall  136 . The channel-shaped members  132  further include an opening  139  opposite the first end wall  136  for receipt of an end cap  164  as described above. In this embodiment, however, the end portion or second end wall  142  of the side wall  138  opposite the first end wall  136  extends to the opening  139 , such that the opening  139  is spaced from the integral internal retainer channel  155  formed by the generally L-shaped wall  156  integral with the first side wall  138  and the wall  160  integral with the first end wall  136 . As described above, the end portion  158  of the L-shaped internal wall  156  preferably extends toward the first end wall  136  and the end wall  136  further includes an integral internal wall  160  which extends toward the end portion  158 , forming an integral internal channel  155  for receipt of a connector element  154  as described below. As also stated above, the L-shaped wall  156  may also be arcuate. In this embodiment of the channel-shaped frame members  132 , the opening  139  opposite the first end wall  136  includes parallel enlarged bead-shaped portions  152  and  153  having an arcuate outer surface, wherein the bead-shaped portion  152  at the end of the second end wall  142  extends toward the first end wall  136  and the enlarged bead-shaped portion  153  at the distal end of the second side wall  140  extends inwardly from the second side wall  140  as shown in  FIG. 10 . As described above, a preferred embodiment of the end cap  164  includes a planar portion  166  and generally parallel outwardly bowed leg portions  168  having an outer surface  170  and bowed end portions  172  which are securely retained between the parallel bead-shaped end portions  152  and  153 , securely retaining the flexible film  128 . As will be noted, the elements of the channel-shaped frame members  132  are numbered in the same sequence as the channel-shaped frame members  32  for ease of understanding.  
      As described above, the rectangular frame assemblies  124  may be formed by mitering the ends of the channel-shaped frame members  132  at a 45 degree angle as shown in  FIG. 9  and the connector element  154  is L-shaped, as best shown in  FIG. 11  having perpendicular end portions  155  preferably including a plurality of teeth  157  outwardly inclined from the distal ends in a “Christmas tree” configuration to securely retain the leg portions  155  in the integral internal channels  155  formed by the L-shaped wall  156  integral with the first side wall  138  and an opposed wall  160  integral with the first end wall  136 . The L-shaped connector element  154  may be an aluminum extrusion. As will be understood from the above description of the channel-shaped frame members  132 , this embodiment of the frame members does not include an L-shaped integral connector portion  34 , but this embodiment of the channel-shaped frame members  32  does not require a mirror image frame member as described above with reference to FIGS.  5  to  7  and thus results in less cost and a more rigid construction as described below.  
       FIG. 12  illustrates a suitable tie down of the environmental enclosure  120  to the floor  180 , such as the concrete floor of a manufacturing facility. In the disclosed embodiment shown in  FIG. 12 , an L-shaped tie down plate having a horizontal portion  182  is affixed to the floor  180  by a conventional concrete anchor bolt  184  having a nut  186 . The vertical leg  188  is attached to the first end wall  136  of the channel-shaped member  132  by a conventional machine screw  190  or the like, forming a rigid support for the environmental enclosure  120  shown in  FIG. 8 .  
       FIG. 13  illustrates a suitable interconnection between adjacent channel-shaped frame members  132  in side to side abutting relation with a U-shaped connector plate  192 . As shown in  FIG. 13 , the U-shaped connector plate  192  includes a planar central portion  194  having a width slightly greater than the combined width of the first end walls  136  of two abutting channel-shaped frame members  132  and transverse leg portions  196  which receive the second side walls  140  of the channel-shaped frame members  132  and the central portion  194  is affixed to the first end wall  136  by machine screws  198  or the like.  
       FIGS. 14 and 15  illustrate a suitable connection between the vertical channel-shaped members  132  and the cross members  122  shown in  FIG. 8 . In a preferred embodiment, the cross members  122  are identical to the channel-shaped frame members  132  and the horizontal cross members  122  are attached to the vertical channel-shaped frame members  132  by a U-shaped connector plate  200  best shown in  FIG. 16 . The connector plate  200  includes a planar central portion  202  having opposed transverse slots  204  adjacent to but spaced from one of the perpendicular leg portions  206 . As shown in  FIG. 14 , the central portion  202  of the U-shaped connector plate  200  is attached to the first end wall  136  of the vertical channel-shaped frame members  132  by machine screws  208  or the like. The transverse leg portions  206  of the U-shaped connector plate  200  are then received within the channel-shaped transverse brace member  122  and secured by machine screws  210 . In the preferred embodiment, the leg portion  158  of the L-shaped internal channel portion is received in one slot  204  and the opposed internal wall  160  is received in the opposed slot forming a very rigid construction as shown in  FIG. 15 .  
       FIG. 17  illustrates a suitable interconnection between the top transverse frame member  132  of the rectangular frame assembly  124  and a channel-shaped frame member  212  of a rectangular frame assembly which forms the top of the environmental enclosure  120  generally as shown in  FIG. 1 . In a preferred embodiment, the channel-shaped frame member  212  is identical to the channel-shaped frame member  132  and the rectangular frame assemblies which form the top of the environmental enclosure (not shown) may be identical to the rectangular frame assemblies  124  described above. In the disclosed embodiment, the top channel-shaped frame member  132  is attached to the channel-shaped frame member  212  by an L-shaped connector plate  214  which is received against the first side wall  138  of the channel-shaped frame members  132  and  212  and secured in place by machine screws  214  or the like as shown in  FIG. 17 . As set forth above, the channel-shaped frame member  212  may be identical to the channel-shaped frame members  132  and thus the components of the channel-shaped frame member  212  are numbered the same as the components of the channel-shaped frame member  132  in  FIG. 17 . As shown in  FIG. 17 , the machine screws  214  are received through the integral internal channels  155  formed by the opposed walls  158  and  160  and the flexible film  128  secured by end caps  164  are located on the inside of the environmental enclosure.  
      As will be understood from the above description of the preferred alternative embodiment of the environmental enclosure  120  shown in FIGS.  8  to  17 , the assembly of the environmental enclosure is similar to the environmental enclosure  20  shown in FIGS.  1  to  7 . That is, the rectangular frame assemblies  124  may be first assembled, as described above, and the rectangular frame members may then be covered with a flexible, preferably transparent film  128  and secured by end caps  164 . As described above, the flexible film  128  is then preferably heated to stretch the film over the rectangular frame assemblies  124  and the flexible film  128  may be easily replaced if damaged following assembly of the environmental enclosure. As set forth above, the embodiment of the environmental enclosure  120  and channel-shaped frame members  132 ,  202  and  212  have several advantages over the environmental enclosure  20  and channel-shaped frame members  26  described above, including reduced costs of manufacturing and assembly and increased rigidity. However, both embodiments provide important advantages over the prior art, including reduced weight, ease of assembly and easy replacement of the flexible film. As set forth above, the channel-shaped frame members may be formed from extruded aluminum making the environmental enclosure or clean tunnel  20 ,  120  light in weight and relatively rigid, but having sufficient flexibility for ease of assembly. The environmental enclosure or clean tunnel may be fixed directly to the floor, such as a concrete floor or steel platform using power actuated fastening systems, such as pins, anchor bolts or the like. The upper rectangular frame assemblies may also be supported by the building structure, using brackets, cables or the like.  
      As will be understood from the above description of the preferred embodiments of the frame assemblies and environmental enclosures of this invention, various modifications may be made within the purview of the appended claims. For example, the opening to the channel-shaped portion or channel-shaped members may be configured to receive other end caps as disclosed, for example, in the prior art. Further, any suitable fasteners may be utilized to interconnect the adjacent the channel-shaped frame members or the frame members to the connector plates described above., including machine screws, bolts or the like The frame assemblies shown in FIGS.  1  to  7  may be square, as shown, or rectangular with transverse bracing elements as disclosed in FIGS.  8  to  17 . Finally, as described above, the environmental enclosure or clean tunnel of this invention may have any configuration depending upon the application. That is, the enclosure may include end walls at various locations and venting may be provided, as required. Having described alternative embodiments of the environmental enclosure, frame assemblies and channel-shaped frame members of this invention, the invention is now claimed as follows.