Abstract:
The invention relates to a heating device for installation in a switchgear cabinet, having a support and a heating body, wherein the support replaceably accommodates the heating body in a holder. Simple and secure mounting of the heating body on the support is achieved in that the holder has a contact surface to which limiting elements are attached, in that the limiting elements immobilize the heating body in a form-fitting manner transversely to the contact surface plane, and in that one or a plurality of locking elements are provided in the region of the holder, which immobilize the heating body in a form-fitting manner perpendicularly to the contact surface.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a heating device for installation in a switchgear cabinet, having a support and a heating body, wherein the support replaceably accommodates the heating body in a holder, according to the preamble part of claim  1 . 
     Heating devices of this type are in particular used when switchgear cabinets are arranged in outdoor areas. Depending on weather conditions, it may be needed for reliable operation of the electronics accommodated in the switchgear cabinet to raise the thermal level by utilizing heating devices. Another application results when the risk of formation of condensate in the interior of the switchgear cabinet is given. The heating device is fixed in the interior of the switchgear cabinet such that the available heating power may be used accordingly. 
     Various heating elements having the respectively needed power are available for different applications. Commonly, the heating devices are fixed to top head rails by means of mounting brackets. The mounting brackets are, on the one hand, connected with heating bodies and comprise screw bores to screw them to a top head rail or a chassis mounted within the switchgear cabinet. 
     Heating devices of this type are known from company brochure “Rittal-Handbuch 31, Seiten 654 and 655”. 
     A heating device according to the preamble part of claim  1  is known from US 2005/0006053 A1. A support replaceably receives a heating body within a holder, wherein limiting elements are arranged spaced apart from another such that they form guiding rails for the heating body. When the heating body is completely inserted into the guiding rails, it is locked in that position by means of snap-lock elements. The snap-lock elements are arranged in transverse direction of the limiting elements, so that they define a final mounting position in which the heating body is firmly retained. 
     EP 0 002 660 A1 discloses a heating device of a switchgear cabinet consisting of a base plate which is U-shaped in cross-section and which accommodates a heating body together with a thermostat. The base plate is provided with a continuous fixing double-web into which a screwing groove is formed so that self-tapping fastening screws may be screwed at any location therein. 
     A switchgear cabinet heater is described in DE 92 17 778 U1, wherein a heating body is screwed onto a thermostat housing. 
     Finally, also GB 2 140 260 A shows a heating body which can be screwed to a support. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to create a heating device of the type mentioned in the introductory, which may be quickly and easily installed in the interior of a switchgear cabinet and which ensures reliable fixing of the heating body. 
     This object is solved by a heating device according to claim  1 . The holder has a contact surface which is arranged upright between limiting elements spaced apart from another, wherein one or a plurality of snap-lock elements are provided in the region of the holder which immobilize the heating body within the holder such that the limiting elements immobilize the heating body in a form-fitting manner transversely to the contact surface plane. The limiting elements are discontinuous in an end region of the holder to form the snap-lock elements. In this way, a geometry of the support results which is open in longitudinal direction of the heating bodies and allows utilization of heating bodies of varying length. 
     This heating device can be mounted in the interior of the switchgear cabinet such that firstly the support is coupled to a desired fixing site, for example a top head rail. Subsequently, the heating element can be inserted into the holder of the support and snapped into the snap-lock elements. Thus, toolless assembly is possible. In a locked state, the heating device is supported on the contact surface on the one hand and by the limiting elements on the other hand. Thereby, the heating body is reliably secured against translation transverse to the contact surface plane in a form-fitting manner. Reliable fixing of the heating element can be effected by this snap-lock element. 
     Since it is provided to arrange a support in the region of the holder which comprises a guiding slope inclined at an angle with respect to the contact surface, guiding the heating body into the holder during assembly, the heating body may be obliquely inserted into the holder during assembly, the guiding slope guiding the insert motion. Subsequently, the heating body is pivoted into the holder while locking with the snap-lock element. That assembly is unique and may be performed in a simple manner. 
     A possible variant of the invention is such that the snap-lock elements immobilize the heating body perpendicularly to the contact surface in a form-fitting manner. Further, it is provided that the holder comprises a protrusion engaging a recess of the heating body. A variant may be that the snap-lock element engages a recess of the heating body. 
     According to a preferred embodiment of the invention, it may be provided that the holder comprises an interface for heating bodies of varying length which are embodied as profiled sections. Thus, the user is provided with a kit, wherein heating bodies having different heating power may be selectively attached to a holder. The heating bodies may be cut to length as profile sections from a semi-finished product at low cost. 
     The limiting elements may in particular be embodied as parallel webs, the heating body abutting thereto via mounting bars formed thereon. By this measure, the number of different parts may be further reduced. 
     According to a preferred variant of the invention, it may be provided that the holder comprises a protrusion engaging a recess of the heating body or that the snap-lock element engages a recess of the heating body. 
     In a heating device according to the invention, the snap-lock elements may be arranged such that they are locked with the mounting bar which is integrally formed with the heating body and is embodied as a heat exchanger fin. On the one hand, the number of parts is reduced. On the other hand, the heating body is configured efficiency-optimized, since heating energy can also be dissipated via the mounting bars. 
     A conceivable variant of the invention is such that two assembled bodies are attached to the holder, which are spaced apart from another and delimit a cable duct, that the cable duct provides access to an electrical terminal of the heating body and that one or both assembled bodies enclose an air-duct, which is spatially connected with an air-guiding region of the heating body. On the one hand, the two assembled bodies serve to shield the electrical terminal of the heating body. On the other hand, the assembled bodies provide the air duct to allow target-oriented air flow to the air guiding region of the heating body. 
     The cable duct may be closed by means of a removable cover which is snap-locked to the support. The cover being removed, the electrical terminal of the heating element may easily be accessed for installation purposes. 
     A particularly preferred variant of the invention is such that the heating body is embodied as extruded profile with integrally molded heat exchanger fin and that the heating body comprises a base part having a heating element receptacle into which the heating element is inserted. By this measure, a particularly simple and cost-effective construction for the heating body to be produced will result. In particular, the heating body may be fabricated from an extruded aluminum profile which guarantees good heat exchange characteristics. The heating element may be pressed into the heating element receptacle to allow a good heat transfer between the heating body and the heating element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in detail below with the aid of an exemplary embodiment illustrated in the drawings. It is shown in: 
         FIG. 1  a support in a perspective front view; 
         FIG. 2  a heating body in a perspective side view; 
         FIG. 3  a further variant of embodiment of a support in a perspective front view; 
         FIGS. 4 and 5  a heating body in various views; 
         FIG. 6  a further variant of embodiment of a heating body in a front view;  FIG. 7  is a front view of an assembly of the support of  FIG. 3  with the heating body of  FIGS. 4 and 5 ; 
         FIG. 8  is a sectional view taken through the line  8 - 8  of  FIG. 7 ; and 
         FIG. 9  is a perspective front view of the assembly of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a support  10  which is embodied as an injection-molded part made of plastic. It comprises a holder  11  which possesses a contact surface  12 . In the center of contact surface  12 , a protrusion  15  which is rectangular in cross-section rises above the contact surface plane. Bores  19 , are machined into contact surface  12  which give access to the rear face of support  10 . Fixing screws may be guided through bores  19  serving for coupling to a support in the interior of the switchgear cabinet. For example, a top head rail or a mounting chassis may be used as support. 
     Contact surface  12  is bordered on both sides by two limiting elements  13 . Limiting elements  13  are embodied as rib-shaped webs which are parallel spaced apart. Limiting elements  33  are discontinuous in the end region of contact surface  12  such that snap-lock elements  14  are formed. Snap-lock elements  14  are resiliently integrally coupled to support  10 . They comprise an inclined deflecting slope which merges into a steep locking face arranged parallel to contact face  12 . 
     Supports  16  are connected to limiting elements  13  facing away from snap-lock elements  14 . Supports  16  are embodied such that they protrude beyond limiting elements  13  in direction of the plane of contact surface  12 . In this way, an undercut is formed. The undercut merges into a guidance slope  16 . 1  inclined at an angle &lt;90° with respect to the surface contact plane. Two assembly bodies  17  are formed to support  10  at the end of contact surface  12  facing away from snap-lock elements  14 . Assembly bodies  17  are spaced apart from another such that they laterally delimit a cable duct  18 . Each of the assembly bodies  17  encloses an air duct  17 . 1 . On the one hand, air duct  17 . 1  is open in a longitudinal direction of contact surface  12 . On the other hand, air duct  17 . 1  is open towards the rear side of support  10  as may be clearly recognized in  FIG. 1 . Furthermore, air duct  17 . 1  is also open at the bottom face at the bottom of  FIG. 1 . 
       FIG. 2  illustrates a heating body  20  which can be mounted to support  10 . The heating body  20  is embodied as an extruded aluminum profiled section. It comprises a base part  21 , to which heat exchanger fins  22  are integrally formed. Base part  21  is penetrated by a heating element receptacle  25  which is a continuous recess in a longitudinal direction of heating body  20 . At the bottom side thereof, heat exchanger fins  22  of heating body  20  are embodied such that they form laterally protruding mounting bars  24 . A recess  23  in form of a milling groove is machined into heating body  20  between mounting bars  24 . Recess  23  is dimensioned such that protrusion  15  of support  10  can be accommodated therein. An electrical heating element, not illustrated in  FIG. 2 , can be pressed into heating element receptacle  25 . The press process is configured such that heat transfer faces of the heating element are in direct contact with limiting faces of the heating element receptacle  25 , so that a good heat transfer is ensured. 
     For mounting heating element  20 , mounting bars  24  are brought to the guiding slopes  16 . 1  of support  16 . The longitudinal center axis of heating body  20  is at an angle of &lt;90° with respect to the plane of contact surface  12 . 
     Heating body  20  can be inserted into holder  11  such that mounting bars  24  slide along guiding slopes  16 . 1  until they reach the region of undercut of supports  16 . Then, the heating body  20  may be folded down until its center longitudinal axis is parallel to contact surface  12 . When folding down, protrusion  15  engages recess  23 . Simultaneously, snap-lock elements  14  reach mounting bars  24  with their deflecting slopes. Resiliently suspended snap-lock elements  14  are then deviated in opposite direction, until mounting bars  24  have passed the deviating slopes. Snap-lock elements  14  then snap inwardly, wherein snap-locked faces of snap-lock elements  14  catch behind mounting bars  24 . Heating body  20  is thus attached to the limiting elements  13  in transverse direction in a form-fitting manner. In longitudinal direction of the limiting elements  13 , heating body  20  is held at protrusion  15  in a form-fitting manner. Offsetting the heating body  20  is prevented in a direction perpendicular to contact surface  12  by snap-lock elements  14  and undercut of supports  16 . In this way, heating body  20  is reliably secured to support  10 . 
     The electrical terminal of the heating element is, in an assembled state of heating body  20 , held in the region of cable duct  18 . Thus, the electrical connection can be made in a simple way. Finally, cable duct  18  can be covered by a cover (which is not illustrated). 
     During operation, the heating element transfers its heating power to heating body  20 . That heating power is dissipated at heat exchanger fins  22  mainly by convection processes into the interior of the switchgear cabinet. Convection is supported by the chimney effect of air ducts  17 . 1 . 
       FIG. 3  shows a further variant of embodiment of support  10 . Support  10  corresponds essentially to the embodiment features of support  10  according to  FIG. 1 . In particular, it comprises a holder  11  having a contact surface  12  which is laterally bordered by two web-like limiting elements  13 . Furthermore, support  10  possesses two assembled bodies  17  respectively enclosing an air duct  17 . 1  and laterally merging to a cable duct  18 . Also in so far, support  10  of  FIG. 3  is similar to support  10  of  FIG. 1  so that reference may be made to the relevant explanations above. For support  10  according to  FIG. 3 , two supports in form of protrusions are formed to each limiting element  13 . Supports  16  of both limiting elements  13  are opposite by pairs and thus form sliding guides for heating body  20 . In the region of the two assembled bodies  17 , a tongue-shaped spring element is exposed from contact surface  12  which carries a snap-lock element  14 . 
       FIGS. 4 and 5  show a variant of embodiment of a heating body  20  which is configured for mounting at support  10 . Heating body  20  according to  FIGS. 4 and 5  essentially corresponds to the heating body of  FIG. 2 . 
     Different from the heating body of  FIG. 2 , heating body  20  of  FIGS. 4 and 5  possesses a recess  23  which is positioned in the region of an end side of heating body  20 . Recess  23  serves as a locking receptacle for snap-lock element  14  of support  10 . For mounting heating body  20 , it is put  17  with its mounting bars  24  on that end of contact surface  12  facing away from the assembled bodies. Now, heating body  20  can be moved on contact surface  12 , while mounting bars  24  pass below supports  16 . Thus, supports  16  prevent lifting of heating body  20  perpendicular to contact surface  12 . While inserting heating body  20 , front end of heating body  20  comprising recess  30  leads snap-lock element  14 . The tongue-shaped tap of snap-lock element  14  is deviated downwardly. Deviating is supported by an approach slope which is oblique with respect to contact surface  12 . As soon as recess  23  reaches the region of snap-lock element  14 , snap-lock element  14  locks into recess  23  and immobilizes heating body  20  undisplaceably in axial direction. Consequently, heating body  20  is reliably attached to support  10 . As may be recognized in  FIG. 5 , recess  23  is embodied as a milled groove. 
       FIG. 6  illustrates a further variant of embodiment of a heating body. In place of the milled groove, recess  23  is produced such that heat exchanger fins  22  are finally sawed into recess  23   b  and are bent laterally. Two parallel cuts are made for each heat exchanger fin  22 , the cuts being spaced apart from another such that the width of recess  23  indicated in  FIG. 4  results. 
     As may be further recognized in  FIGS. 5 and 6 , each heating body  20  comprises two screw channels  24 . 1  extending in longitudinal direction. If needed, heating body  20  can additionally be screwed to support  10 .