Abstract:
A power connection device, in particular for power connections of safety containers, is provided. To improve the operational safety, the power connection device includes two cascaded current feedthroughs, whereby the electrical connections between the conductors of the feedthrough are arranged in conduits of reduced volume so that the interstices between the conductors are at least partially filled.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit under 35 U.S.C. §119(a) of German Patent Application No. 10 2009 011 277.4, filed Mar. 5, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates power connection devices, in particular the invention relates to electrical feedthroughs, by which high currents, particularly in the low and middle voltage range are led through or into containers. 
     2. Description of Related Art 
     In the case of containers for storing or conveying combustible dangerous goods, it is often necessary to lead high electrical power into the container. For example, submerged pumps arranged in the interior of the container are used in plants for piping and/or conveying fluidized natural gas. Connection arrangements with sealing electrical feedthroughs are used for leading the power necessary for the pumps into the interior of the container. For doing so, a feedthrough is typically flanged on a flange of the pressure container. 
     In particular with pressure containers of combustible gases and fluids it thereby is important that the current feedthrough stays leak-proof for a long time. Just in the case of storing combustible material, which may form explosive gas mixtures, there is additionally the risk that even in the case of very small leaks being uncritical in itself gas mixtures may be formed in closed areas of the feedthrough. Such areas may be formed in fitted protective housings. If a deflagration then takes place, the feedthroughs may be damaged such that the combustible material now leaks quickly. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is the object of the invention to form an electrical feedthrough with increased operational safety, in particular for tanks or pressure containers, in particular for storing and transporting material forming explosive gas mixtures. This object is solved by the subject matter of the present application. 
     According to the invention, a power connection device, in particular for power connections of pressure containers is provided for doing so, the device comprising two cascaded power feedthroughs, or generally electrical feedthroughs respectively, wherein the electrical connection between the conductors of the power feedthrough are guided in conduits so that the interstices between the conductors are at least partially filled. 
     In more detail, the invention provides A power connection device for a container, in particular for a pressure container, including: first and second electrical feedthroughs, each having a metal flange, each having at least an opening filled for sealing by an insulation body in axial direction, in which body at least one conductor electrically insulated to the flange, and protruding from the insulation body is arranged, wherein the electrical feedthroughs have several conductors each, and wherein a conductor of the first feedthrough is each electrically contacted with a conductor of the second electrical feedthrough, and forms an electrical connection, wherein the contacted with each other conductor ends of the electrical connections are arranged in conduits, and the conduits of different electrical connections are separated from each other so that the interstices between the conductor ends of different electrical connections are at least partially filled, wherein the two current feedthroughs are sealing connected with each other so that the conduits form chambers between the insulation bodies, the chambers being sealed against the surrounding of the power connection device. Thereby, the chambers may separately be sealed, or also communicate with each other for example via conduits or other connections. In both cases, the entirety of the chambers, however, is sealed against the surrounding. 
     Even in case of a malfunction of one of the sealing insulating bodies of the feedthroughs, no content of the container may still escape, due to the two power feedthroughs. If, on the other hand, an insulating body of the electrical feedthrough facing the container becomes leaky, explosive gas mixtures may be formed. Particularly because an electrical discharge is possible due to the voltage applied to the conductors during operation, there is in principle the risk of a deflagration or explosion. This could damage the insulating bodies such that the power connection device becomes leaky overall. 
     Such a malfunction of the power connection device is thus avoided that the conductors between the feedthroughs proceed in single conduits whose individual volumes are smaller than the volume of a common chamber. Preferably, the individual chambers have a volume being as small as possible, taking the electrical and mechanical requirements into account. By doing so, the sealed volume formed in the interstice between the two feedthroughs is reduced to a minimum. Since also the amount of explosive gas in case of a leak is accordingly reduced, the pressure generated thereby is not sufficient any more for damaging the feedthroughs. Therefore, a considerably increased operational safety is achieved by the combination of the cascaded feedthroughs with conductors proceeding in conduits between the insulating bodies of the feedthroughs. 
     In order to be able to test the leak tightness of the power connection device, at least one testing conduit connected with the conduits from the outside is provided in an advantageous further development of the invention. Preferably, two testing conduits connected with the conduits from the outside are provided. A testing arrangement may then be connected with the one or several testing conduits, by which arrangement it is determined, whether gases from the container or from the surrounding arrived or escaped respectively into the interior of the interstice formed by the conduits between the two current feedthroughs. With containers for natural gas for example, a gas detector may be connected. Alternatively, the internal space may be flushed and rendered inert through the conduit system. 
     In order to ensure the functionality of a double sealing of the container by means of the two cascaded current feedthroughs, it furthermore is purposeful to provide the testing conduits with a valve, which may be opened for the purpose of testing the feedthrough. Alternatively, a permanently operational flushing or monitoring system may also be connected. 
     In order to further improve the capability of resistance of the current feedthroughs against the pressure occurring in case of deflagration, it is moreover advantageous, if at least with one of the two electrical feedthroughs each a conductor is arranged in a separate insulating body. Preferably, both feedthroughs are assembled in such a manner. 
     The conduits may also be formed as separately sealed interstices. Preferably, the conduits may communicate with each other. The latter offers the advantage that testing the leak tightness may already take place by testing at a single testing conduit. 
     According to a still further embodiment of the invention, at least one sleeve-shaped insulation element surrounding the conductor protruding from the insulation body, and being pressed against the insulation body is provided. The conductors are in principal electrically insulated against the metal flange of the feedthrough due to the spacing apart to the inner wall of the conduit surrounding the conductors as we as due to insulation by means of the insulation body. But the electrical insulation may considerably improved by means of the insulation elements mentioned above, and is thereby as much as possible impassible to introduced contaminations consisting of particularly conductive material. By pressing the insulation element onto the respective insulation body of the feedthrough, an intimate contact of the insulation element with the insulation body of the feedthrough is particularly achieved, also. For this reason, creepage currents between the conductor and the wall of the opening in the metal flange, in which the insulation body is arranged, may be avoided or at least inhibited. When doing so, it furthermore is of particular advantage, if the insulation element is pressed onto the insulation body or its surface by means of a spring element or by spring force respectively. Even if the spring element relaxes a little bit due to subsiding of the insulation element, a sufficient pressing force is still kept preserved. If the insulation element is only screwed in contrast, solving the screwing or a deformation or a shrinking of the insulation element could result in an at least local loss of pressing force. Generally, the insulation elements may have a knuckle or an overhanging edge, to which the spring element acts for equally distributing the pressing force along the circumferential direction of the insulation element. In particular, highly insulating plastic materials like for example PVC, silicone, or fluorinated polymers are suitable materials for these insulation elements. Particularly in case of cryogenic gases, polytetrafluorethylen (PTFE) is particularly suited. 
     Flat spiral springs, tension springs, disk springs, or leaf springs as well as elastomer springs come into consideration as spring elements. For example, a pressure plate may be used as leaf spring, which plate has openings, through which the sleeve-shaped insulation elements are guided. If the pressure plate is affixed to the feedthrough by means of screwings spaced apart from the insulation elements, and rest on the knuckles of the insulation elements, bending stress is applied to the plate, and the spring force generated hereby presses the insulation elements onto the insulation bodies of the electrical feedthrough. 
     Insulation elements affixed in such a manner are preferably used on the outer side of a feedthrough, thus the side of the flange, facing the side the other feedthrough is affixed. Preferably, insulation elements surrounding the protruding conductors are bilaterally provided on the outer sides of the electrical feedthrough. 
     In order to establish an efficient and space-saving insulation inside the conduits, two insulation elements each arranged in the conduits, and plugged into each other may be provided, which elements are pushed apart by a spring so that the ends of the insulation elements are pressed against facing insulation bodies of the first and the second electrical feedthroughs. 
     The conduits, in which the conductors proceed, may be inserted in a separate spacer piece or also internal piece between the two electrical feedthrough. According to a further embodiment of the invention, the conduits, however, are inserted in one of the metal flanges of the first or second feedthrough. By this means, a separate connecting piece is avoided, and the assembly is thereby made easier. 
     In order to ease assembling, also lock bush connections may particularly be provided, by which the conductors belonging to an electrical feedthrough are electrically contacted with each other, when the feedthroughs are attached to each other, or affixed. Thereby, the power connection device may be mounted in a particularly easy manner, because a laborious internal cabling can be omitted. Additionally, considerably less space is needed for the individual connections, compared with a connection by means of a lug. On the other hand, this also allows a corresponding reduction of the conduit volume, having the above mentioned advantages concerning an improved reliability in case of a deflagration of explosive gas mixtures. 
     Also on the outer side of the arrangement of the two electrical feedthroughs, a plug connection is advantageous which is formed when assembling. Thereto, developing the invention further provides that at least one connection flange is connected with one of the electrical feedthroughs, wherein a plug body having plug elements is arranged in the connection flange so that the plug elements are electrically contacted with the conductors of the electrical feedthroughs by attaching the feedthrough on the connection flange. Preferably, the arrangement of the two electrical feedthroughs is connected with corresponding flanges, in which plug bodies are inserted, on both sides, thus container-sided as well as connection-sided. Alternatively, the usual connection by means of lugs in a connection box is possible. 
     If sleeve-shaped insulation elements resting on an insulation body of a feedthrough are used for improving the electrical insulation as described above, it is then furthermore favourable, if the insulation elements overlap with the plug body in axial direction for improving the electric strength. According to further development of the invention, the sleeve-shaped insulation elements thereto extend into openings of the plug body, in which openings a plug element is arranged each. 
     In a preferred embodiment of the invention, the sealing insulation bodies is form as glass fusion. Highly tight and pressure resistant connections to the metal flange and to the fused in conductor may be produced by means of glass fusions. Additionally, such an insulation body has a very low porosity due to the glass structure. The glass structure avoids diffusion through the insulation body. Even after long operating time, aggregation of methane in the interstice between the insulation bodies, formed by the conduits, for example, is avoided with containers for natural gas. Alternatively, ceramic insulation bodies, however, may be used also. 
     In the following, the invention is described in more detail by means of exemplary embodiments and with reference to the enclosed figures. Thereby, same reference signs refer to same or corresponding elements. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view through a power connection device; 
         FIG. 2  is an enlarged view of electrical feedthroughs of the power connection device in  FIG. 1 ; 
         FIG. 3  illustrates a filling body having conduits of the power connection device of  FIG. 1 , and 
         FIG. 4  illustrates spacer piece with conduits of the power connection device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cross-sectional view of an embodiment of a power connection device according to the invention is shown in  FIG. 1 .  FIG. 2  additionally shows details of the arrangement with the two electrical feedthroughs  3 ,  5  screwed together. 
     The power connection device  1  comprises a first electrical feedthrough  3  and a second electrical feedthrough  5  screwed together with the first electrical feedthrough  3 , each having a metal flange  35  or  55  respectively. In the feedthroughs  3 ,  5 , there are openings  30 ,  50  in axial direction, each sealing filled by insulation bodies  31  or  51  respectively. A conductor  32  or  52  respectively electrically insulated to the flange  35 ,  55  and protruding from the insulation body  31 ,  51  is arranged in each of the openings. The protruding ends of the conductors  32 ,  52  are referred to by the reference signs  33 ,  34  as well as  53 ,  54 . 
     The electrical feedthroughs  3 ,  5  each have several conductors, wherein only one conductor each may be seen in the cross-sectional view of  FIG. 1 . For example, the power connection device may overall have three conductors for connecting a submerged being in the container, or another electrical device. 
     The two conductors  32 ,  52  are electrically contacted with each other, so forming an electrical connection  16 . Thereby, the conductor end  34 ,  54  of the electrical connection, contacted with each other are arranged in a conduit formed by the opening  50  of the flange  55 . The further electrical connections are also guided in own conduits, wherein the conduits of different electrical connections are separated from each other so that the interstice between different electrical connections is at least partially filled. 
     The two current feedthroughs  3 ,  5  are sealing connected with each other by means of a sealing inserted between the flanges  35 ,  55 , and a screwing  21  so that the opening  50  forms a sealed chamber between the insulation body  32 ,  52  with respect to the surrounding of the power connection device  1 . Thereby, the further, not shown openings may also communicate with the opening  50 . 
     A testing conduit makes connecting a gas detector possible, by means of which is can be determined, whether materials arrived from the container in the interstice formed by the opening  50  through a leak in the container-sided feedthrough. Likewise, the other feedthrough may also be tested concerning tightness, for example by feeding a test gas on the outer side. If the openings communicate with each other, one single testing conduit is sufficient for testing the tightness of the whole arrangement consisting of the first and the second feedthrough  3 ,  5 . The testing conduit is preferably provided with a valve not shown for being able to seal the opening  50  with respect to the surrounding. 
     Two insulation elements  10 , 11  are arranged in the conduit formed by the opening  50  of the feedthrough  5 . Since these elements are arranged in the sealed interior between the feedthroughs  3 ,  5 , these insulation elements  10 ,  11  are also referred to as inner insulation elements. Preferably, the insulation elements are made from highly insulating and heat-resistant material. PTFE is a particularly suited material. 
     The insulation elements  10 ,  11  are formed pipe-shaped or sleeve-shaped, and have an overhanging edge  100  or  110  respectively, wherein one of the overhanging edges each rests on one of the insulation bodies  31  or  51  respectively. A spiral spring  12  is inserted under pretension, and rests with its ends on the overhanging edges  100 ,  110  so that spring simultaneously acts on the edges  100 ,  110  and presses the insulation elements  10 ,  11  onto the surface of the insulation bodies  31 ,  51  in the flanges  35 ,  55 . 
     Furthermore, the insulation elements  10 ,  11  have different diameters so that they may be plugged into each other, and may be shifted against each other in axial direction along the conductors. Due to the overlapping of the insulation elements  10 ,  11  in axial direction, thereby achieved, a complete insulation is achieved. 
     On the outer side, thus on the sides of the flanges  35 ,  55  which point to the container and to the connection side of the power connection device  1 , there are pipe-shaped insulation elements  17 ,  18  affixed, also. Spring elements are here also provided in order to firmly press the insulation elements  17 ,  18  at their overhanging edges  170  or  180  respectively onto the insulation bodies  31 ,  51  in the flanges  35 ,  55  of the electrical feedthroughs  3 ,  5 . 
     Especially, a pressure plate  15  is here provided as spring element, which plate is affixed to the flanges  35  or  55  respectively of the electrical feedthroughs  3 ,  5  by means of screwings  150  spaced apart from the openings, through which the sleeve-shaped insulation elements are plugged. A bending moment is generated in the pressure plate  15  by the spaced apart screwing and the rest of the pressure plate  15  on the overhanging edge  170  or  180  respectively of the sleeve-shaped insulation elements  17 ,  18  so that the pressure plate  15  acts as leaf spring. Therefore, a permanent pressing force between the insulation bodies  31 ,  51  and the insulation elements  17 ,  18  is ensured in this case, also. 
     The electrical connection between the two protruding ends  34 ,  54  of the conductors  32 ,  52  is established by means of a lock bush connection, as it may be seen best by means of the detailed view of  FIG. 2 . Exemplarily, both ends  34 ,  54  of the conductors  32 ,  52 , facing each other are formed as lock bushes in the example shown in  FIG. 2 , wherein a rod is inserted into both lock bushes. 
     Since the conductors  32 ,  52  are arranged axially aligned, the electrical connection is established simultaneously with resting the electrical feedthroughs  3 ,  5  onto each other during assembling. 
     Connection flanges  7 ,  9  with pipes  70 , 90  are flanged to the metal flanges of the feedthroughs  3 ,  5 . One of the connection flanges  7 ,  9  is a connection flange of the container, while the exterior connection lines are led in through the pipe at the other at the other flange. In case of the shown exemplary embodiment, both flanges are of similar type so that the flange  7  as well as the flange  9  may principally be the container-sided flange as construction is concerned. Inter alia, the pipe at the facing flange serves as protection housing. A sealing  20 , or a sealing connection is provided at least between the container-sided flange, and the feedthrough  3 ,  5  flanged thereon, preferably at both connection flanges  7 ,  9 . 
     Plug bodies  40  with plug elements  41  are inserted into the pipes  70 ,  90  of the flanges  7 , 9 , with which elements the connection cables  42  in the pipes  70 ,  90  are connected. The plug elements  41  are in turn formed for a lug connection for achieving a contact with the assigned conductor  32 ,  53  upon attaching. In case of the shown example, the plug elements  41  are lock bushes, into which the conductors  32 ,  52  are inserted when attaching the flanges  7 ,  9  or the feedthroughs  3 ,  5  respectively. 
     For improving the insulation, the sleeve-shaped insulation elements  17 ,  18  and the plug bodies  40  intertwine. In case of the shown example, the plug elements  41  are thereto arranged in openings  44  in the plug body, wherein the insulation elements  17 ,  18  extend into the openings  44 . 
     In case of the example described above, the conduits are arranged in one of the flanges. But further configurations are still self-evidently possible, too, with which the enclosed inner volume between the two feedthroughs is essentially reduced to conduits, in which single electrical connection proceeds. 
     One possibility is a filling body with conduits, with which the inner volume between the feedthroughs is filled.  FIG. 3  shows such an example. In this example, the feedthrough  5  has a cap-shaped flange. An inner volume  56  is defined by the cap-shape. This inner volume is at least partially filled by a filling body  57 , wherein this filling body has separate conduits  58 , in which each a single electrical connection is arranged, here again established by the conductor ends  34 ,  54  with lock bushes connection. 
     In case of the examples shown so far, the two feedthroughs are furthermore directly flanged onto each other. It is possible as well to insert a spacer piece having the conduits, and which the two feedthroughs are flanged onto.  FIG. 4  shows such an example. Here, a spacer piece in form of a flange is provided. Conduits  61  are inserted into the spacer piece  60  so that the interstice between the conductor ends  34 ,  54  of the electrical connections is at least partially filled. 
     For flanging the two feedthroughs  3 ,  5  to the interstice  60 , channel bores  62  may be provided in the spacer piece  60 , through which bores the screws of the screwing connection  21  are plugged. Therefore, the two feedthroughs  3 , 5  are simultaneously flanged to the spacer piece  60 , consequently. In case of the example shown in  FIG. 4 , the testing conduit  14  is arranged in the spacer piece  60 , too. 
     The example shown by means of  FIG. 4  is advantageous to that effect that two identically or similarly constructed electrical feedthroughs  3 ,  5  may be inserted. 
     It is apparent to the person skilled in the art that the invention is not limited to the examples described above, but may in fact be varied in manifold ways within the scope of the claims hereinafter. In particular, the feature of the exemplary embodiments may combined with each other, as meaningful. 
     LIST OF REFERENCE SIGNS 
     
         
           1 : Power connection device 
           3 ,  5 : Electrical feedthrough 
           7 ,  9 : Connecting flange 
           10 ,  11 : Inner surface insulation elements 
           12 : Spring 
           14 : Testing conduit 
           17 ,  18 : Outer surface insulation elements 
           20 : Sealing 
           21 : Screwing of  3 ,  5   
           30 ,  50 : Openings for conductors in  3 ,  5   
           40 : Plug body 
           41 : Plug element in  40   
           42 : Connecting cable 
           44 : Opening in  40   
           31 ,  51 : Conductor of  3 ,  5   
           33 ,  34 : Ends of  31   
           35 ,  55 : Flanges of  3 ,  5   
           56 : Inner volume in  55   
           57 : Filling body 
           58 : Conduits in  57   
           60 : Spacer piece 
           61 : Conduits in  60   
           62 : Channel bores for screwing in  60   
           53 ,  54 : Ends of  51   
           70 ,  90 : Pipes at  7 ,  9   
           100 ,  110 : Overhanging edges of  10 ,  11   
           170 ,  180 : Overhanging edges of  17 , 18