Patent Publication Number: US-2022216676-A1

Title: Frame for an explosion-proof housing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage application of PCT/EP2020/062462, filed on May 5, 2020, which claims the benefit of German Application No. 102019113195.2, filed on May 17, 2019, the contents each of which are incorporated herein by reference thereto. 
    
    
     TECHNICAL FIELD 
     The invention relates to the field of explosion-proof housings. 
     BACKGROUND 
     Explosion-proof housings are known from the prior art. For example, DE 10 2017 112 159 A1 discloses a housing comprising a housing wall including inner cavities, which contribute, on the one hand, to pressure relief of the interior space and, on the other hand, to an increase in the deformation resistance of the housing wall. 
     A need exists for housings that have thin wall thicknesses as well as large housing dimensions, while also ensuring a flameproof enclosure. 
     BRIEF SUMMARY 
     Disclosed is a frame for an explosion-proof housing enclosing a housing interior space for accommodating operating equipment that can produce sparks, wherein the frame includes support elements, at least one of the support elements being a receiving support element and delimiting a support element interior space, and the receiving support element delimiting an opening by which the housing interior space is fluidically connected to the support element interior space. 
     Also disclosed is an explosion-proof housing comprising a frame, wherein the frame includes support elements, at least one of the support elements being a receiving support element and delimiting a support element interior space, and the receiving support element delimiting an opening by which the housing interior space is fluidically connected to the support element interior space. 
     Also disclosed is a method of making a frame, wherein the frame includes support elements, at least one of the support elements being a receiving support element and delimiting a support element interior space, and the receiving support element delimiting an opening by which the housing interior space is fluidically connected to the support element interior space, the method including the following steps: arranging the support elements to form the frame or at least a sub-structure of the frame, fastening the support elements, aligning the frame or the sub-structure of the frame, and connecting the support elements to fix an alignment of the frame or the sub-structure of the frame. 
     The explosion-proof housing for which the frame is intended is preferably designed according to the ‘flameproof enclosure’ explosion protection type. The housing encloses an interior space. Operating equipment can be arranged in the interior space. This equipment can produce sparks. In the event of an explosion occurring in the housing interior space, the housing is configured to release gas and/or particles from the housing if need be after having been cooled in such a way that the gas and/or the particles cannot ignite the atmosphere outside the housing. 
     The frame comprises support elements. The frame can be composed of elongated support elements, for example. Support elements of which the frame can be composed, for example, can be profiled sections, in particular hollow sections, such as square tubes. The support elements can in particular be horizontally arranged support elements, which form carriers or bars, and/or vertically arranged support elements, which form braces, and/or support elements which form struts and, for example, are diagonally arranged. At least some of the support elements preferably extend along the edges of the housing. Embodiments can comprise support elements that are frame-shaped themselves. These can, for example, be composed of hollow sections. 
     At least one of the support elements delimits a support element interior space. Such support elements can also be referred to as receiving support elements. The support elements are preferably hollow inside. At least one of the receiving support elements delimits an opening. As a result of the opening, the housing interior space is fluidically connected to the support element interior space of the receiving support element to reduce explosion pressure by venting burned and unburned gas from the housing interior space into the support element interior space. 
     The frame, which at least in embodiments can also be referred to as a skeleton carrier, on the one hand, has a supporting and stabilizing function for the entire housing design and, on the other hand, has the function of reducing pressure as a result of the support element interior space connected to the housing interior space. In this way, thin wall thicknesses as well as large housing dimensions are possible, while also ensuring the flameproof enclosure. 
     The frame preferably has a skeletal design composed of support elements and is three-dimensional. The frame can comprise lateral frame sections, which are assembled from elongated support elements, and, if necessary, elements for connecting the support elements, and which enclose a planar surface. In simple embodiments, these lateral frame sections can be formed of four elongated support elements which are oriented perpendicularly to one another and arranged in one plane. 
     Embodiments of the frame can be produced by means of embodiments of a modular system according to the invention. The modular system is characterized in that a plurality of (preferably three or more) frame types can be created using a certain number of different basic element types or basic module types, the frame types differing among one another in size. 
     The method according to the invention for producing the frame comprises the step of arranging support elements to form the frame or at least a sub-structure of the frame. The support elements are fastened, preferably to one another, so that subsequent alignment or iterative alignment with the attachment is possible. The frame or the sub-structure of the frame is aligned. The alignment of the frame or of the sub-structure is fixed by rigidly connecting the support elements. In this way, rough tolerances of the frame elements during the alignment can be compensated for. 
     Further preferred features or embodiments of the frame according to the invention, of the housing according to the invention, of the modular system according to the invention, as well as of the method according to the invention result from the following description: 
     In the frame, support element interior spaces of receiving support elements, that is, of the support elements that delimit a support element interior space, can be fluidically connected among one another. As a result of the connection, gas exchange is made possible between the support element interior spaces, preferably without the gas having to take a detour through the housing interior space, when flowing from one support element interior space to another support element interior space. 
     Support elements can be joined to form, with the support element interior spaces thereof, intermediate volumes that are contiguous in the support element interior spaces in the arrangement of connected support elements. 
     The connected support element interior spaces can form an unbranched channel or a channel that is branched once or multiple times, which serves as an absorption chamber for a pressure wave coming from the interior space of the housing. The channel can be used for the flameproof gas exchange between the housing interior space and the surrounding area of the housing. At least a portion of the channel cross-section is preferably free of porous material. This reduces the flow resistance through the channel so that, in the event of an explosion in the interior space of the housing, unburned gas or non-ignited gas is able to push, as a result of the expansion of ignited gas, from the interior space of the housing through the channel into the surrounding area, without resistance from material completely taking up the cross-section of the channel. Despite all this, the gas nonetheless has to be pushed out of the interior space against the resistance of the preferably flameproof elements that are used to close the openings to the interior space or the venting opening. 
     Not necessarily all of the receiving support elements have to delimit an opening by which the housing interior space is fluidically connected to the support element interior space. 
     The frame and/or the housing preferably establishes a venting opening by which the housing interior space is fluidically connected, preferably in a flameproof manner, if necessary indirectly via one or more support element interior spaces, or directly, to the surrounding area of the housing. In embodiments, the fluidic connection can only be open after a protective element has been destroyed or ruptured or released in another manner, for example a rupture disk or another protective body, which serves to shield the venting opening with respect to environmental influences such as dirt and/or moisture. When the venting opening is closed with a pressure relief body, the preferably present protective element can shield the pressure relief body against environmental influences to protect the pressure relief body from becoming clogged with dirt and/or moisture. While, in embodiments, the fluidic connection of the housing interior space via at least one support element interior space is always open to the surrounding area of the housing by way of the venting opening, the connection, in other embodiments, can be opened automatically during an explosion, for example as a result of a rupture disk being destroyed. In still other embodiments, the channel made of fluidically connected support element interior spaces is sealed with respect to the surrounding area of the housing, so that the channel absorbs gas in the event of an explosion, without giving it off to the surrounding area. 
     The venting opening can be closed in a flameproof manner by a pressure relief body, for example a grille or a grille system. A preferably present protective element can ensure that narrow pores of a flameproof pressure relief body also do not become clogged with dirt and/or liquid in a dirty, for example dust-laden, or moist environment. In embodiments, at least one support element, for example a support element that has one or no opening for the connection between the support element interior space and the housing interior space, can establish a venting opening. The venting opening established by the support element can, as described above, be closed by a pressure relief body, wherein the pressure relief body can be flameproof so as to close the venting opening in a flameproof manner. The venting opening established by the support element can be closed by a protective element, wherein the closure is opened in the event of an explosion in the interior space of the housing, or in the intermediate volume, as a result of the protective element being destroyed or ruptured due to the explosion, so as to expose the connection through the venting opening. 
     One or more support elements can comprise a, preferably flameproof, for example tubular, shell, by way of which the support element delimits the support element interior space, for example transversely to an extension direction, in particular a longitudinal extension direction, of the support element. 
     The opening in a receiving support element for the fluidic connection between the interior space of the housing and the support element interior space is preferably sealed with a gas-permeable pressure relief body. The pressure relief body does not necessarily have to close the opening in a flameproof manner. In embodiments, it is sufficient when the pressure relief body absorbs a portion of the kinetic energy and/or thermal energy of the gas flowing through the pressure relief body. The flameproof nature of a connection between the interior space of the housing and the surrounding area through the intermediate volume can be achieved by flameproof venting openings in such embodiments. 
     In other embodiments, the pressure relief body, however, can form a flame arrester in that the pressure relief body has open pores, for example, which form a flameproof gap. The opening in the receiving support element can be closed in a flameproof manner by such a pressure relief body. The pressure relief body can, for example, be formed by a grille or a grille system. As an alternative, the pressure relief body can, for example, be a random wire body, a metal or polymer foam, or the like. 
     When, in addition to the flameproof pressure relief bodies in the connection between the housing interior space and the intermediate volume, also the venting openings are closed in a flameproof manner, an explosion of the gas in the intermediate volume cannot completely roll over into the interior space of the housing, and also not into the surrounding area. When an explosion of the gas in the intermediate volume can be prevented, a flameproof nature of the venting openings may be dispensed with, if necessary, and only the connection between the interior space of the housing and the intermediate volume in the support elements can be flameproof. 
     “Closed in a flameproof manner” means that at least no gas or particles can pass through the flameproof closure, which have a temperature so that the gas or the particles can ignite an atmosphere behind the flameproof closure, in particular in the surrounding area of the housing. 
     The explosion-proof housing according to the invention comprises a frame according to the invention. Surface elements (these can also be referred to as closing elements) are preferably fastened to the frame to close the housing. The surface elements are preferably fastened to the outside of the frame. 
     Particularly preferably, plate-shaped surface elements are fastened to the housing to close the housing. 
     The surface elements can be welded and/or bonded to the frame, for example. Mutually abutting surface elements can be joined, in particular welded or bonded, to one another. In embodiments, the housing can, among other things, be closed in a flameproof manner in this way. 
     In preferred embodiments, at least two surface elements are seamlessly joined to one another in one piece. In preferred embodiments, the housing comprises at least one curved or folded plate for closing at least two sides of the housing. The sides preferably include an angle of 90°, for example. In this way, at least one elongated weld seam between two surface elements can be dispensed with. 
     The frame and the surface elements are preferably made of the same material. In this way, stresses due to changes in temperature can be avoided, since the frame and the plate material or the surface element material have the same thermal coefficient of expansion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantageous embodiments and features result from the dependent claims, the following description, and the figures. 
       In the drawings: 
         FIG. 1  shows an exemplary embodiment of a housing according to the invention; 
         FIG. 2  shows an exemplary embodiment of a frame according to the invention, for example of the housing according to the invention according to  FIG. 1 , in a perspective view; 
         FIG. 3  shows an exemplary embodiment of a support element according to the invention, as it can be used, for example, in the frame according to the invention according to  FIG. 2 , in a perspective view; 
         FIG. 4  shows the support element according to  FIG. 3 , comprising welded-on exemplary pressure relief bodies; 
         FIG. 5  shows a perspective view of the housing according to  FIG. 1 , with a view into the interior space with the cover removed; 
         FIG. 6  shows an exemplary embodiment of a cover by way of which the housing according to  FIG. 1  can be closed, in a perspective view; 
         FIG. 7  shows a cross-sectional view through another exemplary embodiment of a support element; 
         FIG. 8  shows a cross-sectional view through yet another exemplary embodiment of a support element; 
         FIGS. 9 a , 9 b    show illustrations of a method for producing surface elements of housings according to the invention; 
         FIGS. 10 a  to 10 d    show modules of an exemplary modular system; 
         FIG. 11 a    shows an example of a support frame, assembled from the modules according to  FIGS. 10 a    to  10   d;    
         FIG. 11 b    shows a sectional illustration through a section of the support frame according to  FIG. 11   b;    
         FIG. 12  shows an example of a housing comprising the support frame according to  FIG. 11   a;    
         FIGS. 13 a  to 13 d    show a modification of the modular system according to  FIGS. 10 a    to  10   d;    
         FIGS. 14 a  to 14 g    show another exemplary embodiment of a modular system according to the invention and an example of a support frame composed thereof; 
         FIG. 15 a    shows a frame according to another exemplary embodiment of a modular system; 
         FIGS. 15 b  to 15 d    show elements of the frame according to  FIG. 15 a    or of the housing according to  FIG. 15   e;    
         FIG. 15 e    shows a housing designed with the frame according to  FIG. 15 a   ; and 
         FIG. 16  shows a flow chart of one example of a method according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of the explosion-proof housing  10  according to the invention is shown in  FIG. 1 , which is configured for use in a surrounding area  11  at risk of explosions. The housing  10  is used to accommodate components, for example electronic or electrical components, which can form sources of ignition for an explosive gas mixture during operation. The housing  10  surrounds an interior space  12  (see  FIG. 5 ) in which the aforementioned components can be arranged. The housing  10  according to the invention is preferably designed according to the ‘flameproof enclosure’ protection type. This means that gas or particles do not necessarily have to be prevented from finding their way from the housing interior space  12  to the outside into the surrounding area  11  in the event of an explosion. However, gaps leading from inside the housing  10  to the outside have to be dimensioned in such a way that the gas cools, or the particles cool, sufficiently to prevent a potentially explosive atmosphere outside the housing  10  from being ignited. In the case of this ignition protection type, the surface temperature of the housing  10  also has to remain below the ignition temperature of the surrounding explosive atmosphere when an explosion occurs in the interior space of the housing  10  or when another (fault) event occurs. The housing  10  can in particular satisfy the standard EN 60079-1 (protection type Ex d) or, for example, a corresponding US standard. 
     As shown, the housing  10  according to the invention is preferably cuboidal. The housing comprises mutually opposing longitudinal sides  13 , mutually opposing end faces  14 , as well as a bottom  15  (or back), and a cover  16  (or front side). A venting opening  17  is preferably established in at least one side, for example the longitudinal side  13 , end face  14 , bottom  15  or cover  16 . In the illustrated exemplary embodiment, two venting openings  17  are established in an end face  14 . The exemplary embodiment according to  FIGS. 1, 2 and 5  is shown lying on the back  15 . When the housing  10  is set up vertically, the venting openings  17  are thus located at the top. The venting openings  17  are preferably each closed in a flameproof manner by a pressure relief body  18 , which can have a grille structure, for example. 
     The housing interior space  12  can comprise a volume of at least several liters, for example at least 100 liters or at least 500 liters or even at least 1000 liters. In principle, however, this housing concept can also be used for smaller housings  10 . 
     As is apparent by way of example from  FIGS. 2 and 5 , the housing  10  preferably comprises a skeletal frame  20 , which forms a framework of the housing  10 . The frame  20  is assembled from elongated support elements  21 . 
     The frame  20  can include multiple planes  22   a, b , for example a first, for example lower, plane  22   a  and a parallel second, for example upper, plane  22   b , which are formed by planar frame sections  22   a ,  22   b  assembled from support elements  21 . Intermediate planes are possible (not shown). In the illustrated exemplary embodiment, each side of the frame  20  is preferably formed by, preferably planar, frame sections, which each enclose a surface area. In other embodiments, at least one side is formed by a, for example flat, frame element. For example, the bottom of the frame can be formed by a flat frame element. As an alternative or in addition, support elements can be arranged on at least one side, for example forming a cross (not shown). 
     Support elements  21  can, in particular, be formed of one or more profiled sections. In the illustrated exemplary embodiment, rectangular hollow sections or square tubes are used as support elements. 
     The support elements can form horizontal bars  21   a  and vertical braces  21   b , which extend parallel along the edges of the housing  10 , as  FIGS. 2 and 5  illustrate. In addition or as an alternative, it is also possible, in principle, to provide a frame  20  comprising diagonal support elements (struts) (not shown). 
       FIG. 3  shows an exemplary embodiment of a support element  21 , here by way of example a support element  21  that forms a brace  21   b  in the illustrated exemplary embodiment according to  FIGS. 1, 2 and 5 , which is arranged parallel to a longitudinal side  13  of the housing  10 . 
     The support elements  21  each comprise a tube having a rectangular or square cross-section. The illustrated support elements accordingly comprise four longitudinal sides  24  and two end faces  25  (end sides). Instead of using the rectangular tube as the base body of the support element  21 , it is also possible to provide different tubes having a polygonal cross-section, for example a triangular cross-section, a pentagonal cross-section, a hexagonal cross-section, and the like. The support elements  21 , which form the longitudinal sides  13  as well as the end faces  14  of the frame  20  or of the housing  10 , preferably each delimit a support element interior space  26 . In the support element  21   a  according to  FIG. 3 , elongated, for example rectangular, openings  27  are distributed across the length of the support element  21   a . Gas can flow from the housing interior space  12  into the support element interior space  26  via these openings  27 . The support element  21  moreover includes end-face connection openings  28 . The end-face connection openings  28  are used to connect the support element  21  to a respective further support element  21  of the same plane  22   a ,  22   b . The support element  21   a  is joined, for example bonded or welded, to abutting support elements  21   b  via the end-face connection openings  26  in the manner of a miter joint. The connection openings  26  can, of course, also be arranged in such a way that two support elements  21   a  of a plane  22   a ,  22   b  of the frame oriented transversely to one another are butt joined. In such an embodiment, which is not illustrated, a support element includes an end-face connection opening and abuts against a longitudinal side  24  of a further support element, where this has a corresponding connection opening. The end-face opening thereof, however, should be closed in a flameproof manner. Overall, a miter joint is thus preferred, since in this case a flameproof closure of the end-face opening can be dispensed with. The reason is that a flameproof connection is preferably obtained when establishing the joint between the support elements  21   a  across the corners. Support elements  21   a  for the end faces of the housing  10  or frame  20  can likewise include multiple openings, or, as shown ( FIGS. 2 and 5 ), one opening  27  for the fluid exchange between the housing interior space  12  and the support element interior space  26 . 
     The support element  21   a  shown in  FIG. 3  furthermore includes longitudinal-side connection openings  29 , which due to the orientation in the illustrated exemplary embodiment are upper-side or bottom-side connection openings. The longitudinal-side or upper-side or bottom-side connection openings  29  are used to connect the support element  21   a  to a further, vertically oriented support element  21   b  to establish a fluidic connection between the support element interior space  26  and the further support element  21   b . In the illustrated exemplary embodiment, the end-face support elements  21   a  do not include any longitudinal-side connection openings for the connection to vertical support elements  21   b , although this is also possible. 
     In the illustrated exemplary embodiment, vertically oriented support elements  21   b , for connecting the two planes  22   a ,  22   b , include end-face connection openings  28 , which are arranged at the longitudinal-side connection openings  29  of the longitudinal-side support element  21   a  for connecting the support element interior spaces  26 . 
     The support elements  21 , which are connected in such a way that the support element interior spaces  26  thereof, in principle, are able to exchange gas, if necessary only after a rupture body, for example, has been destroyed, overall form an intermediate volume  30 . Consequently, the receiving support elements  21  include those whose support element interior spaces  26  are joined to form an intermediate volume  30 . The intermediate volume  30  is an unbranched flow channel, or a flow channel branched once or multiple times, which leads from the housing interior space  12  through the openings  27  in the support elements and the venting openings  17  to the outside. 
     The frame  20  or the housing  10  can comprise further support elements  21  which, even though they can delimit a support element interior space  26 , do not form part of the intermediate volume  30  or do not have to form part of the intermediate volume  30 . In the illustrated exemplary embodiment according to  FIG. 2 , these are arranged on the bottom side, for example. 
     To form the intermediate volume  30 , the connecting site between the support elements  21  is preferably flameproof. The support elements  21  can be bonded and/or welded to one another, for example, wherein the adhesive and/or weld seam is preferably flameproof. 
     The openings  27  in the support elements  21  to the housing interior space  12  are preferably closed by pressure relief bodies  31 , as is apparent from  FIGS. 2, 4 and 5  by way of example. This means that at least a majority of the gas has to pass through the pressure relief body  31  when passing through the opening  27 . The pressure relief bodies  31  for the openings  27  to the housing interior space  12  can be identical to or different from the pressure relief bodies  18  for the venting openings  17 . The pressure relief bodies  31  can be flameproof. After passing the pressure relief body  31  and reaching the intermediate volume  30 , the gas from the housing interior space  12  has cooled in such a way that it is already no longer able to ignite the atmosphere in the intermediate volume  30 . The receiving support elements  21  consequently preferably comprise a flameproof shell, by way of which the receiving support element  21  delimits the support element interior space  26  transversely to the longitudinal extension direction L of the support element  21 , or radially, wherein the shell can be formed by a wall  33  of the support element and/or, at least in sections, by a flameproof pressure relief body  31 . 
     A pressure relief body  31  for an opening  27  to the housing interior space  12  and/or a pressure relief body  18  for a venting opening  17  can, for example, be composed of sintered metal spheres, metal powders, one or more woven wire cloth or laid scrim layers situated on top of one another or the like. 
     A pressure relief body  18 ,  31  preferably has open pores, the width of which is so small and the length of which is so large that flames from the housing interior space  12  cannot reach the intermediate volume  30  of the frame  20 , or from the intermediate volume  30  of the frame  20  cannot reach the surrounding area. It is also not possible for any particle embers to reach the intermediate volume  30  in this way. 
     A pressure relief body  18 ,  31  can be made of metallic or non-metallic material. The particular material, such as metal, ceramic, glass, or the like, in the form of particles, spheres, threads, or foam can be shaped into a stable body by sintering, bonding or mechanical joining. Pressure relief bodies  18 ,  30  can in particular be designed as planar plates. The pressure relief bodies  18 ,  30  preferably form flame proofing filters, which have gas passage openings in the form of pores that are so narrow and so long that flames and particle embers cannot pass through. 
     In the exemplary embodiment according to  FIGS. 3 and 4 , openings  27  to the housing interior space  12  are only provided on a longitudinal side  24 . As the cross-sectional illustration of one exemplary embodiment of a further elongated support element  21  according to  FIG. 7  of one example of a frame shows, embodiments of support elements  21  can include openings  27  for the gas exchange between the housing interior space  12  and the intermediate volume  30  or the surrounding area  11  of the housing  10 , on at least two, or in particular in the case of vertical support elements  21   b  for example three, longitudinal sides  24  arranged at an angle with respect to one another, which abut the housing interior space  12 . These openings  27  can be closed, preferably closed in a flameproof manner, by pressure relief bodies  31 . 
     Embodiments of the frame can comprise at least one support element  21 , in which a body of the support element  21  itself forms a framework-like or skeletal frame as a carrier for pressure relief bodies  31 , in particular plate-shaped pressure relief bodies  31 . 
     Embodiments of the frame  20  can comprise at least one support element  21 , which is a profile-shaped or tubular open-pored pressure relief body  31 . A corresponding exemplary embodiment is illustrated in  FIG. 8  in a cross-sectional view. The pressure relief body  31  can be assembled from open-pored plates, for example, which can be welded or bonded to one another, for example. 
     Other exemplary embodiments of support elements (not shown) alone do not form a shell, in particular flameproof shell, if necessary with one or more pressure relief bodies. Rather, lateral openings of the support elements are only closed when connected to surface elements, so that the support elements delimit a support element interior space with the surface elements. 
     Support elements  21  may be present that, even though these, with the support element interior space  26  thereof, contribute to the intermediate volume  30 , do not have any direct openings  27  to the housing interior space  12 . These are arranged, for example, in the lower plane  22   a  at the end faces  14  in the exemplary embodiment according to  FIG. 2 . However, similarly to the end-face support elements  21  arranged in the upper plane  22   b  of the exemplary embodiment, these can include recesses  36  to establish venting openings  17  of the housing  10 . 
     The frame  20  forms a framework for the housing  10 . Surface elements  37  to  40  can form the outer planking of the frame. The surface elements  37  to  40  for the longitudinal sides  13 , end faces  14 , bottoms  15 , and covers  16  can be fastened to the frame  20 . In principle, exemplary embodiments in which the surface elements  37  to  40  are arranged in the frame  20  and fastened to the frame  20  are also possible. The frame then forms an outer skeleton (not shown). 
     The housing according to  FIG. 1  is closed by plate-shaped surface elements  37  to  40 , which can be fastened to the frame  20 .  FIGS. 1 and 5  show the exemplary frame  20  according to  FIG. 2  including planking made of plates  37 ,  38 , which close the housing on the longitudinal side and on the end face. A further plate  39  closes the housing  10  on the bottom side. In particular the plates  37 ,  38  that close the housing on the longitudinal side and on the end face can be fastened to the frame  20 . The plates  37 ,  38  can, in particular, be connected to the support elements  21  in a punctiform or linear manner, for example by means of punctiform or linear weld seams or spots  41 . In the illustrated exemplary embodiment, the plates  37 ,  38  for the longitudinal sides  13  and end faces  14  according to  FIGS. 1 and 5  are connected to the support elements  21  by means of spot welding joints  41 . 
     Plates, in particular the plates  37  to  39  for the longitudinal sides  13  and end faces  14  and the bottom  15 , can be joined among one another, for example welded and/or bonded to one another. The plates  37  to  39  can be joined to one another, for example, so that a flameproof gap or a sealing seam  42  is formed between the plates  37  to  39  to limit an explosion to the interior space of the housing. The plates  37  to  39  do not necessarily have to establish a flameproof gap with the frame or with the support elements  21 , but can do so in embodiments, wherein then, if necessary, explosion-proof sealing seams  41  can be dispensed with. 
     Mutually abutting plates  37  to  39  can be seamlessly joined to one another in one piece. One option for producing the housing  10  is shown in  FIGS. 9 a , 9 b    by way of example. There, a sheet metal-like basic material is bent along the dotted lines to form three abutting plates  37 ,  39 , and thus a portion of the shell of the housing  10 . The formation of elongated weld seams, which have to be tight, is dispensed with along the dotted line. In exemplary embodiments, a sheet metal material may, of course, also only be bent along a line to form surface elements for closing sides of the housing  10  designed transversely to one another. 
     The frame  20  and the surface elements  37  to  40 , preferably at least the surface elements  37 ,  38  for the end faces  14  and the longitudinal sides  13  of the housing  10 , are preferably made of the same material. For example, both the frame  30  and the surface elements  37  to  40  can be made of aluminum, steel, or plastic, or composite material. When the frame  30  and the surface elements  37  to  40  are made of the same material, the thermal coefficients of expansion are comparable, which avoids stresses. 
     To establish at least one venting opening  17 , one or more surface elements  37  to  40  can include at least one recess  43 . 
     The pressure relief bodies, by means of which the venting openings  17  can be closed, can, as shown, be arranged in the support element interior space  26 . As an alternative, the pressure relief body  18  can be fastened to the outside of the surface element  38  to close the venting opening  17  in a flameproof manner. 
     Electrical feedthroughs for contacting the components in the interior space  12  of the housing  10 , or mechanical feedthroughs for transferring a movement, can be arranged in one or more of the surface elements  37  to  40 . These feedthroughs (not shown) are flameproof to prevent an explosion in the interior space of the housing from rolling over into the surrounding area at a location of the surface element  37 - 40  at which a feedthrough is arranged. 
     It is possible to render the connection between the housing interior space  12  and the surrounding area  11  of the housing  10  through the intermediate volume  30  flameproof by closing, in a flameproof manner, the openings  27  in the support elements  21  for connecting the support element interior spaces  26  to the housing interior space  12 . As an alternative or in addition, the at least one venting opening  17 , which establishes a connection between the intermediate volume  30  and the surrounding area  11  of the housing  10 , can be closed in a flameproof manner. 
     In the illustrated exemplary embodiment, both the openings  27  in the support elements  21  are closed in a flameproof manner, and the venting openings  17  are closed in a flameproof manner. When gas in the intermediate volume  30  is ignited, for example since walls of the support elements  21  reach the ignition temperature, the gas is able to exit the venting opening  17 , if need be, in such a cooled state, as a result of the flameproof closure of the venting opening  17 , that it cannot ignite the atmosphere outside the housing  10 . If the flameproof closure of the venting opening  17  is dispensed with, care must be taken to ensure, for example, that gas in the intermediate volume  30  cannot be ignited. 
     As an alternative or in addition to forming a flameproof shell of the support elements  21  by way of the flameproof pressure relief bodies  31 , which delimits the support element interior space  26  transversely to the longitudinal extension direction L of the support element  21 , the connection between the housing interior space  12  and the intermediate volume  30  may not be flameproof. Only the one or more venting openings  17  are closed in a flameproof manner. 
     In still other embodiments, no venting openings  17  are present. The interior space openings  27  in the receiving support elements  21  can then be partially closed by pressure relief bodies  31 , which can be flameproof, but in embodiments do not have to be flameproof. By closing the interior space opening  27  at least partially, or across the entire surface area, with a pressure relief body  31 , it is ensured that the gas cools as it passes through the interior space opening  27  and enters the intermediate volume  30 , wherein heat absorption by the pressure relief body  31  and, if necessary, expansion upon the entry from the pressure relief body  18  into the intermediate volume  30  can contribute to cooling. For example, the Joule-Thomson effect may come into play. 
     The intermediate volume  30  or the channel and/or each support element interior space  26  preferably has a greater surface-to-volume ratio than the interior space  12  of the housing  10 , so that penetrating gases from the interior space  12  are cooled better than in the interior space  12  of the housing  10 . 
     For a flameproof closure of the venting opening  17 , as illustrated in  FIG. 5 , the end-face plate  38 , due to the pressure relief body  18  arranged in the support element  21  in the illustrated exemplary embodiment, has to be connected around the venting opening  17  to the end-face support elements  21   a ,  21   b  in such a way that gases, which are so hot that they can ignite the atmosphere outside the housing  10 , are prevented from exiting. This is possible, for example, by forming a flameproof gap between the plate  38  and the support element  21   a ,  21   b  or by way of a sealing seam joining the plate  38  to the end-face support elements  21   a ,  21   b.    
     Possible exit paths from the housing interior space  12  into the surrounding area  11  are preferably limited to those that lead through the intermediate volume  30 . In particular the surface elements  37 ,  38 ,  39 ,  40  are preferably free of such openings that establish a gas connection between the interior space  12  of the housing  10  and the surrounding area  11 , without the gas having to take a path through an intermediate volume  30  formed by the receiving support elements  21  of the frame  20 . 
     The advantage of interposing an intermediate volume between the interior space  12  of the housing  10  and the surrounding area  11  is that the gas, in the event of an explosion, is able to enter the intermediate volume  30  in a plurality of locations inside the housing interior space  12 , and the actual connection to the surrounding area  11  can be arranged in a central location. In embodiments, only the closure of the venting opening  17  or of the venting openings  17  has to be flameproof and must not exceed a maximum surface temperature, to avoid that atmosphere at the closure ignites. Moreover, the intermediate volume  30  forms an absorption chamber for a pressure wave coming from the interior space  12  of the housing  10 . A portion of the kinetic energy and thermal energy released by the explosion can be taken up by the plurality of pressure relief bodies when the gas passes through the pressure relief bodies into the intermediate volume  30 . 
     As is apparent by way of example from  FIG. 5 , the housing  10  can comprise a frame-shaped flange  45  for fastening the cover  16 . The flange  45  is preferably welded and/or bonded to the longitudinal-side plates  37  and the end-face plates  38 , so that the weld seam and/or bonded seam is flameproof. As an alternative or in addition to the formation of a sealing seam between the flange  45  on the one hand, and the longitudinal-side and end-face surface elements  37 ,  38  on the other hand, a flameproof gap can be established between the flange  45  on the one hand, and the longitudinal-side and end-face plates  37 ,  38  on the other hand. 
     The establishment of flameproof gaps between the support elements  21  and the surface elements  37 ,  38  can be dispensed with. Otherwise, it could be sufficient to also establish a flameproof gap, in particular a flat gap between the flange  45  and the support elements  21  of the upper plane  22   b , so as to design the housing to be flameproof at this location. 
     The flange  45  can include threaded holes  46  or other devices to connect the cover  16  to the flange  45 . The threaded holes  46  can form flameproof gaps with the fastening pins for fastening the cover  16 . A flameproof gap, in particular a flat gap, can be established between the flange  45  and the cover  16 . 
     A cover  16 , as it can be used for the exemplary housing  10  according to the invention, is apparent by way of example from  FIG. 6 . The cover  16  comprises a plate-shaped surface element  40 . The cover  16  can comprise a stabilizing intermediate plate  47 , which can include recesses. The cover  46 , however, can also make do without the intermediate plate  47 . The cover plate  40  comprises an edge region  49  in which openings for fastening pins are arranged, which cooperate with the threaded holes  46  of the flange. The edge region  49  is configured to form a flameproof gap, in particular a flat gap, with the flange  45 . 
     A bracing frame  16   a  can be arranged on the inner side of the cover  16 . The bracing frame elements  16   b  of the bracing frame, however, do not contribute to the intermediate volume  30 . The same applies to the bracing frame elements  15   b  of the bracing frame  15   a  of the bottom  15  in the illustrated exemplary embodiment. In other embodiments, the bracing frame elements  15   b  of the bottom  15  can likewise be support elements  21  of the frame  20  and form part of the intermediate volume  30 . This means that the support element interior spaces  26  of the bracing frame elements  15   b  are fluidically connected to the end-face and longitudinal-side support elements  21  of the lower plane  22   a.    
     During use, the cover  16  is fixedly connected to the remaining housing body shown in  FIG. 5 , wherein corresponding connecting means, such as clamps, screws (as in the illustrated exemplary embodiment) or the like are used for this purpose. Components that can form ignition sources, such as relays, transistors, resistors or similar elements that can heat up during operation, are present in the housing interior space  12 . When the housing  10  is located in an explosive atmosphere, combustible or explosive gases can reach the housing interior space  12 . If they are ignited there, the deflagration that occurs results in an expansion of the involved gases. The intermediate volume, formed by the support element interior spaces, is preferably free of electrical or electronic components, which can form ignition sources. If components are arranged at all in the intermediate volume, these are preferably designed to be intrinsically safe. 
     These flow, while cooling, through the openings  27  in the support elements  21  into the intermediate volume  30 , and from there via the venting openings  17  to the outside. As a result of the explosion, possibly present rupture disks can be destroyed. In any case, at the latest then the fluidic connection between the housing interior space  12  and the support element interior space  26  is open. Gas can now flow from the housing interior space  12  into the support element interior space  26 . 
     The gas cools upon entering the support element interior spaces  26 . When the openings  27  into the support element interior spaces  26  are closed by open-pored pressure relief bodies  31 , this results in even more cooling, in particular due to heat transfer to the pressure relief body  31 . In embodiments of the housing  10 , the pressure relief bodies  31  closing (covering) the openings  27  may not be flameproof themselves, but can still result in a certain degree of cooling of the gas, for example due to the absorption of thermal energy, when the gas passes through the openings  27  into the intermediate volume  30 . 
     When the pressure relief body  31  closes the opening  27  in a flameproof manner, the gases or particles, as they pass through the pressure relief body  31 , are cooled to such an extent that the gases making their way into the intermediate volume  30 , which is a channel, if necessary a channel branched multiple times, no longer represent an ignition source for explosive gas in the intermediate volume  30  or in the surrounding area  11  of the housing  10 . 
     When the pressure relief body  18  closes the venting opening  17  in a flameproof, the gases, as they pass through the pressure relief body  18 , are cooled to such an extent that the gases or particles making their way from the intermediate volume  30  or the housing interior space  12  through the venting opening  17  no longer represent an ignition source for explosive gas in the surrounding area of the housing. 
     The excess pressure as a result of the explosion is consequently reduced by the gas, during an explosion, being able to enter from the interior space  12  of the housing through the one or more openings  27  in the support elements  21  into the intermediate volume  30 , whereby it can already experience initial cooling. The pressure wave can consequently be partially absorbed by the intermediate volume. Excess pressure in the intermediate volume  30  is reduced via the venting openings  17 , if any are present. 
     If the openings  31  in the support elements  21  are not closed in a flameproof manner, or if the gas in the intermediate volume  30  is at risk of exploding for another reason, for example because the inner surface of the support elements  21  can potentially become so hot that gas ignites therein, the at least one venting opening  17  is preferably closed in a flameproof manner. 
     Preferably, at least a portion of the cross-section of the channel  30  formed by the support element interior spaces  26  connected among one another is free of porous material to provide minor resistance to the gas inside the channel  30 . In the event of an explosion, for example in a corner of the large-volume housing  10 , it is thus possible for gas that, for example, has not ignited, to be pushed, for example from an opposite corner, with overall minor resistance through the openings  27  from the interior space  12  of the housing  10 , the channel  30 , and out of the venting openings  17 . 
     Modular systems according to the invention are suitable for producing in particular large housings  10  having a housing interior space  12  with a volume of greater than or equal to 100 liters, greater than or equal to 500 liters, or even greater than or equal to 1000 liters, although modular systems according to the invention can also be used for smaller volumes. 
       FIG. 10  shows modules of an exemplary embodiment of a modular system  100  according to the invention for producing frames  20  of varying sizes.  FIG. 11 a    shows an example of a frame  20 , composed of the modules of the modular system  100 , and  FIG. 12  shows an example of a housing  10  composed by means of the frame  20  according to  FIG. 11 a   . Potential differences compared to the exemplary embodiments according to  FIGS. 1 to 9 , in addition to the essential difference that  FIGS. 10 to 12  relate to a modular system  100  or a frame  20  and a housing  10  composed thereof or therewith, can be derived from the following description. Otherwise, the description regarding the exemplary embodiments according to  FIGS. 1 to 9  can be used for the description of details of possible exemplary embodiments of the modular system  100  or a frame  20  and a housing  10  composed thereof. 
     A first module  101  of the modular system  100  is a receiving support element  21 , which delimits a support element interior space  26  and an opening. In specimens of the first module  101 , this opening can serve as the interior space opening  27  of the fluidic connection of the housing interior space  12  to the support element interior space  26 . The opening is preferably closed by a pressure relief element  31  in a flameproof manner. 
     A second module  102  of the modular system  100  is used to connect two adjoining receiving support elements  21 , which are arranged behind one another in a longitudinal direction, in one plane. 
     A third module  103  of the modular system  100  is used to connect two adjoining receiving support elements  21 , which are arranged across the corners, in one plane. The second module  102  and the third module  103  likewise form support elements  21  of the frame  20 . The second module  102  and the third module  103  can comprise first connecting channel sections  50   a  to connect the support element interior spaces  26  of adjoining support elements  21  of a plane to one another. The connection between adjoining support element interior spaces  26  is preferably flameproof with respect to the interior space  12  of the housing  10 , so that an explosion in the intermediate volume  30  cannot roll over into the interior space  12  of the housing  10 . The connected receiving support elements  21  of a plane form a planar, two-dimensional first frame section  22   a . Using the same second and third modules  102 ,  103 , further receiving support elements  21  can be connected in a flameproof manner via second connecting channel sections  50  in a further parallel plane to a planar, two-dimensional second frame section  22   b . The second and third modules  102 ,  103  comprise connecting webs  51 . In a second or third module  102 ,  103 , a connecting web  51  rigidly connects the first connecting channel section  50   a  to the second connecting channel section  50   b . The frame sections  22   a ,  22   b  are connected via the connecting webs  51  of the second and third modules  102 ,  103  to form a three-dimensional, skeletal frame  20 . The second and third modules  102 ,  103  can be joined by welding and/or bonding, for example, to the abutting receiving support elements  21  of the first module type  101 . 
     An elongated, web-like fourth module  104  of the modular system  100  is configured to connect opposing support elements of the second module type  102  inside the first frame section  22   a , so that a basket-shaped three-dimensional frame  20  is obtained, as it is illustrated in  FIG. 11 a   . The fourth module  104  and the opposite second modules  102  can each be connected by way of a screw joint, for example. The corresponding section of the second module for the screw joint is hidden in  FIG. 10 b   . A corresponding section for establishing the screw joint  52  is illustrated in  FIG. 14 c    based on another exemplary embodiment of a module of the modular system. 
     The planar first frame section  22   a  and the planar second frame section  22   b  of the basket-like frame  20  according to  FIG. 11 a    assembled from the modules  101 ,  102 ,  103 ,  104  of the modular system  100  each have a contiguous intermediate volume  30   a ,  30   b , formed of the support element interior spaces  26  of the receiving support elements  21  and the interior spaces of the connecting channel sections  50   a ,  50   b .  FIG. 11 b    shows a sectional view through the cutting plane S in  FIG. 11 a    for illustration. The intermediate volumes  30   a ,  30   b  are not directly connected among one another, so that gas flowing from an intermediate space  30   a  to the other intermediate space  30   b  would have to take the detour through the interior space  26  of the housing  10 . 
     The modular system  100  allows basket-like frames  20  having different lengths to be produced from the four basic types  101 ,  102 ,  103 ,  104  of modules, as illustrated in  FIGS. 10 a   - 10   d.    
     The second module  101 , the third module  103 , and the fourth module  104  can be provided in adapted lengths, and, if necessary, adapted in terms of the number of connecting sections  53  for the connection to surface elements  37  to  39 , to be able to produce frames  20  having different widths and/or different depths. It is preferably provided for the modular system  100  that the length of the first module  101  is not varied, but the module forms a common part, which is arranged in various quantities in a width direction and/or in a length direction to produce frames  20  having different widths and/or lengths. 
     The surface elements  37  to  40  can be connected to the frame  20  for closing the housing  10  by way of flat connecting sections  53 . The second module  102  and/or the fourth module  104  can, for example, comprise connecting sections  53 , as is illustrated in the exemplary embodiment according to  FIGS. 10 b  to 10 d   . The connecting sections  53  of the second module  102  of and of the fourth module  104  preferably each provide a planar, patch-like, for example rectangular, in particular square, connecting surface  54  so as to form patch-like connecting regions with the surface elements  37 ,  39 . The third module  103  comprises angled connecting sections  55 . As an alternative or in addition, connecting sections  53 ,  55  of the second, third and/or fourth modules  102 ,  103 ,  104  can be separate modules of the modular system  100 . A corresponding exemplary embodiment is shown in  FIGS. 14 c  and 14 d   . In such embodiments, the connecting web  51  of the second, third or fourth module  102 ,  103 ,  104  is arranged between the separate module, which provides the connecting surface  54 ,  56 , and the surface element  37 ,  38 ,  39 , when the connection has been established. 
     The connecting sections  53 ,  55  are accessible from the interior space  12  of the housing  10  or the frame  20 , so that a screw joint can be established with the surface elements  37  to  39  from the interior space  12 . As an alternative or in addition to a screw joint, connecting surfaces  54 ,  56  of the connecting sections  53 ,  55  can be bonded and/or welded to the surface element  37 ,  38 ,  39 . A pure screw joint is preferred over a pure weld and/or bonded joint due to the potentially higher strength. 
     The connecting surfaces  54 ,  56 , which are separate from one another, are planar in a patch-like manner, for example square, as in the illustrated exemplary embodiment, or angled. Compared to a variant including connecting surfaces that are contiguous, in the form of a strip, in the longitudinal extension of the second, third or fourth module  102 ,  103 ,  104 , this has the advantage that rough tolerances of the surface element  37 ,  38 ,  39  and/or of the module  102 ,  103 ,  104  can be more easily compensated for. 
     Even if a screw joint having bores that perforate the surface element  37 ,  38 ,  39  is provided between the connecting sections  53 ,  55  and the surface element  37 ,  38 ,  39 , the flameproof nature of the housing  10  nonetheless must be ensured. This can take place, as in the illustrated exemplary embodiment, by ensuring a sufficiently long thread gap between the external thread and internal thread in the bore. 
     The surface elements preferably comprise a base material  60  made of sheet metal having a constant thin wall thickness for this purpose, having dimensions that completely close the side of the housing  10 . Strip-shaped (as illustrated), or alternatively patch-shaped, reinforcement metal sections  61  are fastened to the outside of the metal sheet  60 , for example bonded and/or welded to the base material  60 . The thickness of the reinforcement metal metal section  61  alone, or together with the thickness of the base material  60 , is sufficiently dimensioned to provide a flameproof thread gap to ensure the flameproof nature. Attaching the reinforcement metal section  61  to the outside has the advantage that, in the event of an explosion in the interior space  12  of the housing  10 , the base material  60  is pushed against the reinforcement metal sections  61 . As a result, the strength of the connection between the reinforcement metal section  61  and the base material  60  is less important than if the reinforcement metal section  61  were arranged on the inside of the base material  60  in the interior space  12 . 
     A frame  20  according to the invention can be produced as follows, for example by means of the modular system  100  from  FIGS. 10 a  to 10 d   , wherein this is schematically represented in the flow chart of an exemplary embodiment of the method  200  according to the invention according to  FIG. 16 : Elements  101 ,  102 ,  103 ,  104 ,  21  can be fixed to one another (step  201 ) in such a way that an alignment of the frame  20 , or of a sub-structure of the frame  20 , is still possible. The frame  20  or the sub-structure can be aligned (step  202 ), and the alignment can be fixed (step  203 ). The fixing  201  of elements and alignment  202  can take place incrementally by first creating sub-structures of the frame by fixing the elements  201 , aligning the sub-structure, and fixing the alignment, and thereafter adding further elements, aligning the resulting sub-structure, and fixing the alignment. As an alternative, initially all elements can be fixed so as to form the frame. The frame is then aligned, and the alignment is fixed thereafter. In both instances, the alignment can compensate for relatively rough tolerances of the components of the frame  20 . After the frame sub-structures or the frame  20  has or have been aligned, the elements can be rigidly fixed to one another so as to fix the alignment of the frame sub-structure or of the frame  20 , and to ultimately complete the support frame  20 . 
     Thereafter, the surface elements  37 ,  38 ,  39  can be fastened to the connecting sections  53 ,  55 . The surface elements  37 ,  38 ,  39  are sealingly welded and/or bonded to one another along the edges of the housing  10 . A flange  45 , which is used to connect the surface elements  37 ,  38  to the cover  40 , is welded and/or bonded to the surface elements  37 ,  38 . Similarly to the exemplary embodiment according to  FIG. 5 , the flange  45  can, for example, be produced from elongated profiled sections, for example rectangular sections. A flat gap is preferably formed between the flange  45  and the cover  40  so as to ensure the flameproof nature at this location. 
     It shall be noted that, when a cover  16  is mentioned in the present application, this does not necessarily mean that the housing  10  is to be inserted in an orientation in which the cover  16  closes an opening toward the top. 
       FIG. 12 , for example, shows a housing  10  that comprises a frame  20  including modules  101 ,  102 ,  103 ,  104  from the modular system  100  according to  FIGS. 10 a  to 10 d    and planking made of the surface elements  37  to  39 . Feet  60  are arranged at a surface element  38 , on which the housing  10  can sit. The cover  16  of the exemplary embodiment according to  FIG. 5  can be used for closing the housing, as is described in connection with  FIG. 6 . 
     Venting openings  17  are provided in the upper side of the housing  10  according to  FIG. 12  to connect the first intermediate volume  30   a  and the second intermediate volume  30   b  to the surrounding area  11  of the housing  10 . The venting openings  17  can be closed by rupture disks. The modular system  100  can comprise a fifth module (not shown) in addition to the modules according to  FIG. 11 a   , which is a receiving support element  21  including an opening for forming a venting opening  17 . As an alternative or in addition, specimens of the first module  101  having an appropriate orientation of the opening  27  can form a receiving support element  21  including a venting opening. As an alternative or in addition, it may be provided, when using the modular system  100 , that venting openings have to be created, for example cut-out or exposed, in specimens of the first module  101 . 
     Embodiments of modular systems according to the invention comprise modules  101 ,  102 ,  103 ,  104  made of the materials steel, aluminum or plastic and can be used to produce a support frame  20  for planking made of steel, aluminum, or plastic plates. 
       FIGS. 13 a  to 13 d    illustrate a variant of the embodiment of the modular system  100  according to  FIGS. 10 a    to  12 . The first module  101 , similarly to the first module according to  FIG. 10 a   , comprises a hollow section as the base body and, in contrast to the exemplary embodiment according to  FIG. 10 a   , comprises welded-on and/or bonded-on flange sections  63 , which are configured for creating a screw joint of two adjoining receiving support elements  21  by means of openings. The advantage of the embodiment according to  FIGS. 13 a -13 d    is that the weld joint for fastening the flange sections  63  can be created without the receiving support elements  21  already having been assembled to form a frame  20 . The receiving support elements  21  can be pushed toward one another by means of the screw joint after the assembled receiving support elements  21  have been assembled and aligned, wherein a second module  102 , which essentially corresponds to the embodiment described in connection with  FIG. 10 b   , is clamped between adjoining receiving support elements  21 . In the process, sections of the first module  101 , of the second module  102 , or additional elements that can be referred to as sealing sections  64  or sealing elements  64 , are deformed so as to close gaps present between adjoining receiving support elements  21  at least in such a way that gas and/or particles can leave the intermediate volume through the gap in a non-ignitable state, at the most. Independently thereof, the second module  102  can be a casting. Designing the second module  102  (see also the exemplary embodiment according to  FIG. 14 c   ) exclusively with openings oriented in a single direction makes this possible, using a simple tool. 
       FIG. 14 a    shows a perspective view of a frame  20  according to the invention, produced with the aid of a modification of the modular system  100  according to  FIGS. 10 a    to  12 . Modules  101  to  104   b  are shown in  FIGS. 14 b  to 14 f   . Corner modules  103  comprising a connecting web  51 , as shown in  FIG. 10 c   , are not present in this modular system  100 . Instead, angular modules  103  (see  FIG. 14 b   ), which comprise a connecting channel section  50 , in a planar frame section  22   a  or  22   b  connect adjoining receiving support elements  21 , of which the frame  20  is composed, across the corners, without connecting the planar first frame section  22   a  and the planar second frame section  22   b  to one another. The second module  102  according to  FIG. 14 c    differs from the second module  102  shown in  FIG. 10 b    in that a connecting section  53  is absent in the second module  102  according to  FIG. 14 c   . As illustrated in  FIG. 14 d   , this is formed by a module  105  that is separate from the second and fourth modules  102 ,  104   a ,  104   b  ( FIGS. 14 c , 14 e , and 14 f   ) and that includes a slotted receiving section  65  in which the second or the fourth module  102 ,  104   a ,  104   b  is accommodated. 
     The fourth module  104  can be present in at least two variants  104   a ,  104   b , which connect specimens of second modules  102  located opposite one another in the longitudinal direction of the frame or in the transverse direction of the frame  20 . One variant  104   a  of the fourth module can be configured by means of form-fit sections  66  (such as notches) to establish certain positions for the specimens of the variant  104   b  of the fourth module oriented in the transverse direction along the length of the specimen of the fourth module  104   a , which is oriented in the longitudinal direction. 
     Otherwise, the description regarding the embodiment according to  FIGS. 1 to 12  with respect to the description of details of a frame  20 , composed as is apparent from  FIGS. 14 a  to 14 g   , can be used. In particular, the first module  101 , that is, the receiving support element  21 , can be designed as described in connection with the embodiment according to  FIGS. 10 a    to  12 . The modification according to  FIGS. 13 a  to 13 d    can also be used in an exemplary embodiment corresponding to  FIGS. 14 a    to  14   g.    
       FIGS. 15 a  to 15 e    illustrate an example of a modification of the frame  20  according to  FIGS. 14 a  to 14 g   , and an explosion-proof housing  10  of the ‘flameproof enclosure’ protection type formed therewith. The embodiment of the modular system  100  of which the frame  20  according to  FIG. 15 a    is composed does not require the fourth module  104 ,  140   a ,  104   b  for connecting opposing second modules  102  and does not require connecting sections  53 ,  55  for the screw joint to the surface element  37 ,  38 ,  39 . The cells or openings formed by two adjoining connecting webs  51  and interposed receiving support elements  21  are intended to be closed by sheet metal elements  67  (see  FIG. 15 b   ), in which the sheet metal is shaped to alternately form recessed beads  68  and raised beads  69 . The longitudinal extension direction of the recessed and raised beads  68 ,  69  is preferably oriented parallel to the longitudinal extension direction of the receiving support elements  21  or transversely to the longitudinal extension direction of the connecting webs  51 . The sheet metal elements  67  are preferably trapezoidal sheet metal elements, which, in sections, makes straight weld seams and/or bonded seams possible between the trapezoidal sheet metal and abutting connecting webs  51  of the specimens of the modules  102 . Each sheet metal element  67  is arranged in the cell or opening to which the sheet metal element  67  is assigned. The sheet metal element  67  is connected to the adjoining second modules  102 , which are illustrated by way of example in  FIG. 14 c   , and the parallel receiving support elements  21 , for example by means of a weld and/or bonded joint. 
     Similarly to the housing  10  according to  FIG. 12 , for example, the housing  10  can include venting openings  17  on the upper side and/or, as illustrated in  FIG. 15 e   , lateral venting openings  17 . These are formed by corresponding recesses in lateral receiving support elements  21  and the sheet metal element  67  that closes the cell, which delimit the receiving support elements  21 . 
     Even though the second modules  102  in the frame according to  FIG. 15 a   , similarly to what is shown by way of example in  FIG. 14 c   , can comprise devices  52  for creating a screw joint with the fourth modules  104 , these are preferably not required to stabilize the surface element  39  forming the rear wall. The surface element  39  is preferably not a planar sheet metal element, but a sheet metal element  70  comprising integrally formed recessed beads  68  and raised beads  69 , for example a trapezoidal sheet metal element (see  FIG. 15 c   ). The longitudinal extension direction of the recessed beads  68  and of the raised beads  69  is parallel to the longitudinal extension direction of the first frame section  22   a . The surface element  39  is preferably welded and/or bonded to the elements, in particular receiving support elements  21 , that form the first frame section  22   a , so as to close the opening established by the first frame section  22   a  in a flameproof manner. 
     The edge openings are closed by means of metal corner plates  71  (see  FIG. 15 d   ) forming an edge, which are welded and/or bonded to the corner modules  103  as well as the second modules  104 . 
       FIGS. 15 a  to 15 e    illustrate a modular system for producing a frame  20  or housing that, in embodiments, provides that lateral surface elements  37  are composed of individual, identical sheet metal elements  67 ,  71 . 
     A weld joint and/or bonded joint between elements can form a sealing seam, which closes all the gaps between the elements to be connected, so as to be able to dispense with a flameproof gap, in particular a flat gap, in this location when no ignitable gas or particles is ore are supposed to exit in this location. Sealing seams can, for example, be provided at the butt joints between support elements  21  when the interior space  12  of the housing  10  is to be separated in a flameproof manner from the intermediate volume  30 ,  30   a ,  30   b , that is, when the interior space openings  27  in the support elements  21  are closed by gas-permeable, but flameproof pressure relief bodies  31 . 
     While the figures show exemplary embodiments of frames  20  and housings  10  that are cuboidal, embodiments of frames  20  or housings  10  according to the invention can delimit interior spaces  12  across at least one corner. For example, a housing  10  according to the invention can enclose an L-shaped housing interior space  12 . Possible embodiments of modular systems  100  include those that enable the selective provision of housings having cuboidal interior spaces  12  or interior spaces  12  that are delimited across the corners by the housing  10 , for example L-shaped or U-shaped interior spaces  12 . 
     The illustrated embodiments of the frames  20  form endoskeletons since the surface elements are fastened to the outside of frame elements. As an alternative, the frame can form an exoskeleton or corset, in which the surface elements  37  to  39  close an interior space  12  and against which the surface elements  37  to  39  are pushed to the outside in the case of an explosion. 
     According to the invention, a frame  20  for explosion-proof housings  10  is provided. The frame  20  is assembled from support elements  21 . Preferably, square tubes are used as support elements  21 , which are provided with elongated rectangular openings  27 , which are preferably closed by flameproof grilles  31  that are welded on or fastened in another manner. The square tubes  21  of the embodiment are joined to form a skeletal frame  20 , which supports the housing structure (support frame). Preferably metal plates  37  to  40  (for example stainless steel or aluminum), or also plastic plates, are fastened to the outside of the frame  20  by bonding and/or welding so that the housing  10  is closed. Venting openings  17 , which can be closed by flameproof grilles  31 , are preferably provided in suitable locations of the housing  10 , such as at the bottom  15  or at the end faces  14 . According to the invention, thin wall thicknesses of the surface elements  37  to  40 , for example plates, as well as large housing dimensions, while ensuring a flameproof enclosure, are made possible by means of the supporting and stabilizing support frame  20 , which also helps to reduce the pressure. 
     LIST OF REFERENCE NUMERALS 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 10 
                 housing 
               
               
                 11 
                 surrounding area 
               
               
                 12 
                 housing interior space 
               
               
                 13 
                 longitudinal side 
               
               
                 14 
                 end face 
               
               
                 15 
                 bottom 
               
               
                  15a 
                 bracing frame 
               
               
                  15b 
                 bracing frame element 
               
               
                 16 
                 cover 
               
               
                  16a 
                 bracing frame 
               
               
                  16b 
                 bracing frame element 
               
               
                 17 
                 venting opening 
               
               
                 18 
                 pressure relief body 
               
               
                 20 
                 frame 
               
               
                 21 
                 support element 
               
               
                  21a 
                 brace 
               
               
                  21b 
                 bar 
               
               
                  22a 
                 first plane/first frame section 
               
               
                  22b 
                 second plane/second frame section 
               
               
                 24 
                 longitudinal sides 
               
               
                 25 
                 end faces 
               
               
                 26 
                 support element interior space 
               
               
                 27 
                 opening (interior space opening) 
               
               
                 28 
                 end-face connection opening 
               
               
                 29 
                 longitudinal-side connection opening 
               
               
                 30 
                 intermediate volume/flow channel 
               
               
                  30a 
                 intermediate volume 
               
               
                  30b 
                 intermediate volume 
               
               
                 31 
                 pressure relief body 
               
               
                 33 
                 wall 
               
               
                 36 
                 recess 
               
               
                 37 
                 surface element 
               
               
                 38 
                 surface element 
               
               
                 39 
                 surface element 
               
               
                 40 
                 surface element 
               
               
                 41 
                 seam, location 
               
               
                 42 
                 sealing seam 
               
               
                 43 
                 recess 
               
               
                 45 
                 flange 
               
               
                 46 
                 threaded bore 
               
               
                 47 
                 intermediate plate 
               
               
                 49 
                 edge region 
               
               
                 50 
                 connecting channel section 
               
               
                  50a 
                 connecting channel section 
               
               
                  50b 
                 connecting channel section 
               
               
                 51 
                 connecting web 
               
               
                 52 
                 section for screw joint 
               
               
                 53 
                 connecting section 
               
               
                 54 
                 connecting surface 
               
               
                 55 
                 connecting section 
               
               
                 56 
                 connecting surface 
               
               
                 60 
                 base material 
               
               
                 61 
                 reinforcement metal section 
               
               
                 62 
                 foot 
               
               
                 63 
                 flange section 
               
               
                 64 
                 sealing section 
               
               
                 65 
                 receiving section 
               
               
                 66 
                 form-fit section 
               
               
                 67 
                 sheet metal element 
               
               
                 68 
                 recessed bead 
               
               
                 69 
                 raised bead 
               
               
                 70 
                 sheet metal element 
               
               
                 71 
                 metal corner plate 
               
               
                 100  
                 modular system 
               
               
                 101  
                 first module 
               
               
                 102  
                 second module 
               
               
                 103  
                 third module 
               
               
                 104  
                 fourth module 
               
               
                 104a 
                 first variant 
               
               
                 104b 
                 second variant 
               
               
                 105  
                 fifth module 
               
               
                 200  
                 method 
               
               
                 201  
                 step 
               
               
                 202  
                 step 
               
               
                 203  
                 Step 
               
               
                 L 
                 longitudinal extension direction