Patent Publication Number: US-2010108376-A1

Title: Connection box for solar panel

Description:
FIELD OF THE INVENTION 
     The present invention relates to a connection box. More particularly this invention concerns a connection box for a solar panel. 
     BACKGROUND OF THE INVENTION 
     A typical connection box, in particular for solar panels, comprises a cover that upwardly closes a base that is itself attached to the back of a solar panel. The base has a first opening for at least one output conductor or cable from the panel and at least one opening for a feed cable exiting from the panel and going to the network using the solar-generated electricity. The base also has a compartment that holds circuit elements for connecting the panel-output cable to the feed cable. 
     A connection box of this type is disclosed, for example, in 10 2005 008 123 A1. The base of the connection box here has a strip-conductor structure that is provided with cable clamps. The cable clamps function to connect the feed cables and the panel-output cables to the strip-conductor structure. 
     In US 2005/0230140 screw-type terminals are provided to which the panel-output cables and feed cables are electrically connected by strip-conductor structures. 
     U.S. Pat. No. 7,444,743 discloses a strip-conductor structure inside a connection box in which the feed cables and panel-output cables are connected by crimping to the strip-conductor structure. For bridge diodes, the strip-conductor structure forms forked-spring-contact-type contact clips. 
     DE 20 2005 018 884 describes a connection box whose opposite side walls has holes through which panel-associated panel-output cables and feed cables are routed into the connection box. Bridge-like clamping components are placed between the cables to be connected and are analogous to the strip-conductor structures. At their ends, these clamping components have clamp springs to make the contact of the cables and provided with contact openings in which the bridge diodes can be inserted. 
     In the case of all of the above-referenced publications, the installation cost of producing the electrical connection of the panel-associated panel-output cable and feed cable is significant. The connection-clamping terminals presented in numerous variants must in each case be spread by a tool, then the appropriate leads must be inserted, after which the tool must then be removed. In some cases, the terminal clamps must also be closed by the tool. The same is true for the installation of bridge diodes. In addition, fitting the bases of the connection boxes with the appropriate circuit elements also involves a significant cost. The connection box itself must be formed with various retaining elements for attachment of the strip conductors, and the strip conductors must be stamped, shaped, inserted into the connection box, and attached there. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved connection box for solar panel. 
     Another object is the provision of such an improved connection box for solar panel that overcomes the above-given disadvantages, in particular that simplifies the electrical connection of panel-output and feed cables. 
     SUMMARY OF THE INVENTION 
     A box for connecting an output conductor from a solar panel to a feed cable. The box has according to the invention a cover, a base securable to a solar panel, closable by the cover, and formed with a first opening for the output conductor and at least one second opening for a feed cable, and means in the base for securing the conductor directly in electrical conduct to the cable. 
     The direct electrical contact between of the panel-output cable and the feed cable eliminates the need for the disadvantageous strip-conductor structures and contacts of the prior art and the need to manipulated them with tools. As a result, the material cost, as well as production and installation costs are significantly reduced. 
     Thus the invention uses a direct electrical contact between the panel-output cable and the feed cable so long as the panel-output cable is near the region of the end of the feed cable. 
     A preferred embodiment of the invention is characterized in that the panel-output cable is engaged with an electrically conductive and mechanically reinforced end of the feed cable. The mechanical reinforcement of the end of the feed cable, in particular, of the stripped conductors, enables the panel-output cable and feed cable to be connected in a secure and fixed manner using appropriate means. 
     Provision is made whereby the end of the feed cable is stripped and mechanically reinforced by a cable end sleeve. Attaching a cable end sleeve is a simple and appropriate measure for mechanically reinforcing a lead composed of multiple conductors, that is stranded wire. A mechanical reinforcement can also be effected just as well by solder, that is tinning the stranded-wire bundle. Additionally, a massive single conductor is mechanically stiff enough to use as is within the scope of the invention. 
     Within the scope of the invention, what is then also involved is a direct engagement of panel-output cable on the feed cable when the leads are enveloped by a reinforcing means as long as the panel-output cable is fitted in the region of the core of the feed cable. 
     From the point of view of installation, the panel-associated panel-output cable can be engaged with the feed cable in a simple manner by a contact clip, in particular, if the contact clip is designed as a spring having an approximately Ω-shaped cross-section. 
     In an especially preferred embodiment of the invention, the contact along with the panel-output cable and the feed cable form a self-supporting connection assembly. This means that the assembly composed of the panel-output cable, feed cable, and contact clip do not require any additional support for securely establishing a permanent electrical connection between the cable and the panel conductor. 
     From the point of view of assembly, it is especially advantageous for the contact to be provided on the bottom face of the cover facing the base component. In this type of design of the invention, closing the box and making an electrical connection of panel-output cable and feed cable are effected in a single operation. 
     In another embodiment, provision is made whereby the connection box is of multipolar design, thus accepting at least two panel-output cables and two feed cables, joinable by two clips, or more. In connection boxes of this type, it often happens that a diode bridging two panel-output cables is provided. In order to connect this bridge diode to two panel-output cables, provision is made whereby the bridge diode makes contact with each contact clip that are each mounted on the cover of the connection box and support the diode. 
     A significant problem of the prior art is posed by the heat emitted by the various functional components placed inside the connection box. One example in particular here is the currently widely used shunt diodes that can reach temperatures of up to 180° C. However, active or passive switching components provided in the future are also emitters of heat. 
     This waste heat negatively affects the cables of the solar cells on a solar panel. A solution to remedy the heat problem must be provided both for crystalline-type solar panels as well as for the increasingly used thin-film panels. 
     One embodiment of the invention therefore proposes that the cover have a heat-conducting material on its bottom face facing the base, in particular, that is in contact through thermal bridges with the heat-emitting components inside the box. 
     The waste heat is passed through the proposed heat-conducting material directly away from the panel to the cover of the box. This is typically ventilated from outside, thereby allowing the heat to be effectively dissipated. 
     In a first embodiment, provision is made whereby the heat-sink is in contact with heat-emitting components inside the box by spring-elastic pressure elements functioning as thermal bridges, in particular, flexible tongues formed by the heat-conducting plate. 
     The especially preferred approach, however, is one where the contact for fitting the panel-output cable on the feed cable functions as thermal bridge. 
     Fabrication is significantly simplified if the contact is formed by the heat-conducting plate. 
     Dissipation of the heat from the diode can be done especially effectively if the body of the diode constituting the heat-emitting component is mounted directly on the heat-conducting material, in particular, the heat-conducting plate. This obviously also applies in the case of every other heat-emitting circuit element inside the connection box. 
     Identified as circuit elements are all those elements that affect the conduction of electrical current from the solar panel into the electrical network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which: 
       FIG. is a perspective view from below of the cover of the box according to the invention; 
         FIG. 2  is a perspective view from above of the cover box; 
         FIG. 3  is a view from above of an inverted alternate cover box in accordance with the invention; and 
         FIG. 4  is a section taken along line IV-IV of  FIG. 2 . 
     
    
    
     SPECIFIC DESCRIPTION 
     As seen in  FIGS. 1 and 2  a connection box  10  according to the invention has a base  11  ( FIG. 2 ) with a generally rectangular and planar floor  12  and an annular side wall  13  that define a compartment  14  serving to hold circuit elements. On two opposing sides at its outer surface, the side wall  13  is provided with guides  15  and projecting locking lugs  16 . Below the locking lugs  16 , the guides  15  have tool-guide slots  17 . (The references to “up” and “down” being purely for convenience of description, since the box is often mounted inverted on the generally downwardly facing back face of a solar panel.) 
     An inner wall  18  parallel to the outer side wall  13  is provided inside the compartment  14  such that it is spaced relative to side wall  13  by a circumferential gap  19  from the wall  13 . The side wall  13  and inner wall  18  each have aligned cable guide cutouts or holes  20  through which a feed cable  21  passes. The feed cable  21  conducts the electricity generated by the solar panel into an electricity network, optionally through additional technical equipment. 
     The base  12  has a hole or opening  22  through which panel-output cables  23  are routed into compartment  14  of connection box  10 . These panel-output cables  23  are strip conductors whereas the feed cable  21  is a standard cable with conductors held in an outer insulating sheath. 
     The feed cable  21  has a stripped end  24  where its conductors are mechanically reinforced by a cable end sleeve  25 . A crimp ring  26  inward therefrom in the end  24  functions as part of a strain-relief assembly. The floor  12  of the connection box  10  has two approximately U-shaped ridges  27  extending perpendicular upward from the floor  12 . These ridges  27  form a holding seat  28  that is centrally grooved. This groove receives the crimp ring  26  to take up strain in the feed cable  21 . 
     The end  24  provided with the cable end sleeve  25  of the feed cable  21  extends across the opening  22  of the floor  12  and is anchored at least on the opposite side in the compartment  28  of the opening  22 . To this end, two U-forming lugs  29  on the floor  12  form a snap-in support for the cable end sleeve  25 . In this case, the cable end sleeve  25  also rests on a support ridge  40  extending across the opening  22 . 
     The panel-output cable  23  coming from the solar panel passes through the opening  22  into the connection box  10  and over the end  24  of feed cable  21  such that it is partially wrapped around the cable  11  end sleeve  25  in electrical contact therewith. 
     The floor  12  of the base  11  of the connection box  10  is secured by its face turned away from the cover  30  to the solar panel shown schematically at  55 , in particular, by an adhesive bond  56 . The opening  22  is in the region of a cutout in the solar-panel housing through which panel-output cables  23  are routed to the outside. 
     A cover  30  the of connection box  10  is shown in  FIG. 1 . It has a planar top wall  31  normally extending parallel to but space from the floor  12  and provided with an essentially circumferential collar  32  directed toward the base  11 . 
     At opposite sides, locking lugs  33  facing the base  11  project from the cover  30  and each define a snap-in-locking opening  34 . A circumferential overhanging rim  35  projecting from the cover wall  31  opposite the collar  32  is formed near the locking lugs by a tool-engagement formation  36 . Similarly, the collar  32  has a cable guide cutout  37 . This corresponds in terms of its position with cable guide cutouts  20  of the inner and outer side walls  13  and  18 . 
     The bottom face of the cover wall  31  facing the base  11  is provided with a contact  38  in the form of a clip spring  39  having an approximately Ω-shaped cross-section. 
     When the box  10  is closed, that is, when cover  30  is mounted on the base  11 , the collar  32  fits in the base-section-associated ring gap  19 . To effect a gas-tight seal of connection box  10 , a seal (not shown), is provided. The lug guides  15  receive the locking lugs  33  that are pushed over the wedge-shaped locking lugs  16  and grasp these from behind while locking the connection box  10  closed. The cable end sleeve  25  overlaps the clamping springs  39 , which engage in the overlap region of the panel-output cable  23  and the end  24  of the feed cable  21 , and are provided on the cover wall  31 , when everything is closed. This ensures that panel-output cable  23  is held in a securely clamped fashion on the cable end sleeve  25 . 
     The tool-engagement formations  17  and  36  function to allow spreading and release of the snap-in-locking connection between the locking lugs  33  and locking lugs  16 , so as to allow the cover to be removed from base  11 . 
       FIG. 4  shows on the right the snap-in-locking connection between the cover  30  and the base  11  by the locking lugs  33  grasping behind the locking lugs  16 . Also shown is the insertion of the collar  32  in the annular gap  19  is formed between the inner side wall  18  and the outer side wall  13 . The cable end sleeve  25  surrounds the core  41  composed of multiple conductors in the embodiment and mechanically reinforces this core  41 . The panel-output cable  23  exiting the solar panel passes around the cable end sleeve  25 . This cable end sleeve  25  itself rests on a lower support ridge  40  bridging the opening  22 . The spring  39  grips the panel-output cable  23  on the cable end sleeve  25 , and holds the panel-output cable  23  on the cable end sleeve  25  securely so as to form a good electrical connection. 
       FIG. 4  clearly shows that only the cable end sleeve  25  of the contact  39  functions as a support. The spring  39 , panel-output cable  23 , and cable end sleeve  28  consequently form a self-supporting connection arrangement. 
     It is within the scope of the invention that the clip  38  can be mounted detachably on the panel-output cable  23  and cable end sleeve  25 . 
     In sum, a connection box  10  has been described that advantageously provides an installation-friendly, secure electrical connection between the panel-output cable  23  and the feed cable  21 . The need for tool to work on conductor elements and strip-conductor structures inside the connection box has been eliminated. The simple arrangement of the panel-output cable  23  directly on an electrically conductive region of the feed cable  21  and the secure connection by a contact that only needs to be fitted in place have significant time and cost advantages for installing the connection box, in particular, if the clip  38  is mounted on the cover  30  of box  10  and the connection between panel-output cable  23  and feed cable  21  are locked together by closing the box  10 . 
       FIG. 3  shows a cover  50  of another embodiment of the invention that corresponds with another base (not shown). The connection box  10 , not shown in its entirety, of this second embodiment is of multipolar design. This means that multiple panel-output cables  23  exiting the solar panel are connected to two feed cables  21  inserted into the connection box  10 . In this case, this involves a two-pole connection box  10  in which, analogously to the previous description, one panel-output cable  23  is fitted on each electrically conductive and mechanically reinforced end  24  of a respective feed cable  21 . Contacts  38  provided in the cover  50 , which here too are designed as clamping springs  39  with an approximately Ω-shaped cross-section, ensure the good electrical connection of the panel-output cables  23  and the ends  24  of the respective feed cables  21 . 
     In the case of multipole connection boxes  10 , panel-output cables  23  are typically provided with shunt diodes  51 . These prevent the solar panel from heating up, whenever solar cells are not operating in the case of parallel operation, for example, due to shading, by preventing undesired current from flowing. 
     Unlike the prior art referenced in the introduction, the shunt diodes are not inserted in the base using connection clamping terminals, but are instead integrated in the cover  50  and electrically connected to clamping springs  39  through their leads  52 . 
     Since shunt diodes  51  in current applications are the main cause of waste heat, the arrangement of the shunt diode in the cover has significant advantages in thermal terms alone. The diode is thus mounted directly adjacent the usually well-ventilated end wall  31  of the cover  50  such that the waste heat can be effectively dissipated. Dissipation of the waste heat can also be significantly improved further by disposing large-area heat-sink plates, or at least one heat-conducting plate  53  on the bottom side of cover wall  31 . These cooling plates—also identified as heat sinks—are connected through thermal bridges in this example leads  52 , to the body  54  of the diode  51 , thereby further improving heat dissipation. 
     In one development, not illustrated here, the diode body  54  rests directly on the cooling plate  53 , diode body  54  then preferably providing as large a support area as possible. 
     It is also conceivable for the cover itself to be designed as the cooling body or cooling plate  53 . To this end, this can be fabricated out of an efficiently-heat-conducting material, in particular, a metal such as aluminum. 
     If the goal is to provide additional heat-emitting circuit elements inside the base of connection box  10 , these can be connected to cooling plates  53  through flexible tongues functioning as thermal bridges. 
     In sum,  FIG. 3  shows an extremely advantageous development of the invention by which problems caused by waste heat from circuit elements supported inside the connection box  10  can be eliminated.