Abstract:
The invention relates to a fuse holder for a fuse-link in which a fuse status indicator having a printed circuit board and a glow lamp is fitted. The necessary connecting lines are made of conductive plastic from the top and base contacts of the fuse-link to the printed circuit board of the status indicator. The conductive plastic is injected in channels which are provided therefor and are situated in the housing of the fuse holder.

Description:
TECHNICAL FIELD 
     The invention relates to a fuseholder having a fuse status indicator according to the precharacterizing clause of Patent claim  1 . Such a fuseholder is known from DE 41 27 214.5 A1. 
     BACKGROUND OF THE INVENTION 
     Electrical fuse assemblies having a fuseholder for insertion into a fuse housing are in widespread use. The fuse link or fuse, the actual protection element, is accommodated in the fuseholder such that it can be replaced. The fuseholder may, for example, be in the form disclosed in DE 34 06 815 A1, or the form disclosed in DE 37 41 743.6 A1. According to Application DE 197 34 234.5, the latter is preferably equipped with a coding tongue, which rests elastically against the foot contact of the fuse link. 
     A flashing status indicator according to DE 41 27 214.5 A1, which was mentioned above, is in each case fitted in the fuseholder. This status indicator comprises a glow lamp, which is arranged behind a window in the upper part of the fuseholder, and a small board in the vicinity of the glow lamp, with the electronic components such as capacitors, diodes and resistors required to actuate the glow lamp. The status indicator is electrically connected via connecting lines to the head contact and foot contact of the fuse link and, when the glow lamp flashes, this indicates whether the fuse link has been tripped and has blown. 
     In the past, the electrical connection between the head contact and foot contact of the fuse link and the board of the status indicator was produced by means of small pieces of wire, which were soldered at one end to the board and at the other end to the contact elements which are connected in the fuseholder to the head contact and foot contact of the fuse link. 
     This arrangement has the disadvantage that the steps for insertion of the pieces of wire into the fuseholder and their soldering during the production of the fuseholder can be carried out only manually. The production process is thus rather complex. 
     DE 35 13 833 C2 discloses a melting fuse link which has a high cylindrical insulating-material body, in the interior of which a melting conductor is provided between two contact caps arranged at the ends of the insulating body, with a series circuit comprising a high-value resistor and an optoelectronic display device being connected in parallel with the melting conductor. The high-value resistor may comprise an electrically conductive, high-resistance layer or an electrically conductive, high-resistance plastic insert, which extends from one contact cap to the other and rests against the inner surface of the hollow-cylindrical insulating-material body. This arrangement also has the disadvantage that the plastic insert must be inserted in and attached to the insulating-material body separately, although this can be done manually or automatically. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of refining the fuseholder with the built-in status indicator so that the production process is simple. In order to achieve this object, the invention provides a fuseholder having the features of claim  1 , and a method for producing a fuseholder having the method steps of claim  7 . 
     According to the invention, this object as stated in the patent claims is achieved in that the connecting lines for the status indicator are no longer composed of wire, but of a conductive plastic for which channels which have accurately predetermined dimensions are provided in the fuseholder, the rest of which is composed of insulating plastic. 
     The connecting lines for the status indicator can thus easily and quickly be configured by means of so-called two-component injection molding during the process of molding the plastic fuseholder. 
     The conductive plastic may make contact with the head contact and/or foot contact of the fuse link directly, or indirectly via the metallic connections for the fuse link in the fuseholder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the fuseholder according to the invention and having an integrated connecting line for a status indicator are explained in more detail in the following text with reference to the drawing, in which: 
     FIG. 1 shows a section view of a first version of a fuseholder having a built-in status indicator; 
     FIG. 2 shows a section view of a second version of a fuseholder having a built-in status indicator; and 
     FIG. 3 shows a side view of the second version of the fuseholder. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a section view from the side of a fuseholder  10 , as is used in conventional fused switches. In fused switches of this type which are described, for example, in the abovementioned DE 34 06 815 A1, the fuseholder  10  is used in conjunction with the fuse link or fuse  20  which is located in it and, in general, is a melting fuse, not only to protect the load side against short circuits, but also to isolate the load side from the power supply, as is required, for example, when working on the electrical installation. To this end, when the fuseholder  10  is inserted into the housing of the fused switch, it can tilt from a switched-on position to a switched-off position. 
     The fuseholder  10  has an operating handle  11 , in which the board  25  and the glow lamp  26  of a fuse status indicator are accommodated. The glow lamp  26  is fitted behind a window  12  at the front, visible end of the operating handle  11 . The electrical circuit of the status indicator, having the diodes, capacitors, resistors, etc. for actuating the glow lamp  26 , is essentially located on the board  25  in such a manner that the glow lamp  26  flashes when the fuse link  20  has blown. 
     The fuse link  20  has a metallic head contact  22  and a metallic foot contact  23 . The head contact  22  of the fuse link  20  is connected to a metallic holding and connecting element  14  of the fuseholder  10 , and the foot contact  23  of the fuse link  20  is connected to a metallic holding and connecting element  15  of the fuseholder  10 . The metallic holding and connecting elements  14 ,  15  are used firstly to fix the fuse link  20  elastically in the fuseholder  10  such that it can be replaced, for which purpose, for example, the upper holding and connecting element  14  may include a compression springs  14   a  and, secondly, to produce the electrical contact between the fuse link  20  and the corresponding connections in the fused switch when in the switched-on position. 
     Apart from the metallic holding and connecting elements  14 ,  15 , the broad  25  and the glow lamp  26  of the status indicator and the window  12 , the fuseholder  10  (except for the fuse link  20 ) is composed of plastic, which is molded by injection molding. A channel is provided in the electrically insulating plastic, of which the housing of the fuseholder  10  is essentially composed, in one of the walls of the housing, which runs between the board  25  and the holding and connecting element  15  for the foot contact  23 , and this channel is filled with an electrically conductive plastic, forming a first connecting line  16 . The connecting line  16 , which is composed of the conductive plastic, is formed by means of two-component injection molding; this produces the connection between the board  25  and the holding and connecting element  15  for the foot contact  23  of the fuse link  20 . 
     In the same way, a further channel is provided in another wall of the housing, which runs between the board  25  and the holding and connecting element  14  for the head contact  23 , and this channel is filled with the conductive plastic, forming a second connecting line  17 . The connecting line  17  produces the connection between the board  25  and the holding and connecting element  14  for the head contact  22  of the fuse link  20 . 
     Instead of the connecting lines  16 ,  17  making contact with the holding and connecting elements  14 ,  15 , they may alternatively make direct contact with the head and foot contacts  22 ,  23  of the fuse link  20 , for example via projecting tabs, which are formed on the housing of the fuseholder  10  such that, when the fuse link  20  is inserted, they are connected to its head contact  22  and foot contact  23 . 
     The connecting lines  16 ,  17  are preferably connected to the board  25  via appropriately positioned contact pieces  18 , in such a manner that the board  25  need be inserted only into the cavity provided for this purpose in the operating handle  11 , with the electrical contact between the board  25  and the connecting lines  16 ,  17  then being produced automatically. 
     The channels for the connecting lines  16 ,  17  may be of such a size that they result in a specific conductivity and a specific resistance by virtue of the channel length and the channel cross section together with the type of conductive plastic provided in each case. The circuit on the board  25  may thus be simplified. Typical resistance of the connecting lines  16 ,  17  are 10 3  to 10 4  ohms. 
     In order to obtain particular resistance values, different plastics may also be used for the two connecting lines  16 ,  17 , that is to say plastics with different conductivity. 
     The connecting lines  16 ,  17  may also be formed only partially from conductive plastic, in particular if the other part of the connecting lines  16 ,  17  can be formed, for example, by a spectral configuration, for example, of the holding and connecting elements  14 ,  15 . 
     The connecting lines  16 ,  17  are, of course, routed or covered such that it is impossible to touch any live parts. 
     FIGS. 2 and 3 show a second version of the fuseholder, which is denoted by the reference symbol  30 . The version is intended for a fuse which has a separate on/off switch. Like the fuseholder  10 , the fuseholder  30  also accommodates a fuse link  20  having a head contact  22  and a foot contact  23 . 
     In this version of the fuseholder, only the head contact  22  of the fuse link  20  is connected to a holding and connecting element  34  of the fuseholder  30 ; the foot contact  23  of the fuse link  20  is, in contrast, free, and is directly connected to a corresponding contact in the fused switch. 
     However, a coding tongue  35  rests elastically against the foot contact  23  of the fuse link  20  and projects to a different extent from the housing of the fuse link  20  depending on the rating of the fuse, and thus the diameter of the foot contact  23 , as is disclosed in Application DE 197 34 234.5. 
     The board  25  and the glow lamp  26  of the fuse status indicator are once again accommodated in the upper part  31  of the fuseholder  30 , with the fuse status indicator being arranged behind a window  32 . 
     As in the first version of the fuseholder, apart from the metallic holding and connecting element  34 , the board  25 , the glow lamp  26  of the status indicator and the window  32  (excluding the fuse link  20 ), the fuseholder  30  is once again composed of injection-molded plastic. In the electrically insulating plastic for the housing of the fuseholder  30 , a channel is provided in the coding tongue  35 , which rests elastically against the foot contact  23 , and this channel is filled with an electrically conductive plastic, forming a first connecting line  36 . The connecting line  36 , composed of the electrically conductive plastic, is formed by means of two-component injection molding, as in the first version of the fuseholder. As can be seen from the section view in FIG.  2  and the view of the narrow side of the fuseholder  30  with the coding tongue  35  in FIG. 3, the connecting line  36  runs from the contact point between the coding tongue  35  and the foot contact  23  along the length through the coding tongue  35 , and further onwards through the housing of the fuseholder  30  as far as the board  25 . 
     Furthermore, another channel is provided in the housing of the fuseholder  30  between the board  25  and the holding and connecting element  34  for the head contact  22 , and this channel is likewise filled with conductive plastic, forming a second connecting line  37 . 
     Instead of making contact with the holding and connecting element  34 , and connecting line  37  may in this case as an alternative also make direct contact with the head contact  22  of the fuse link  20 . 
     The connecting lines  36 ,  37  are preferably once again connected to the board  25  via contact pieces  38 , in such a way that, when the board  25  is inserted into the cavity in the upper part  31  provided for this purpose, this at the same time produces the electrical contact between the board  25  and the connecting lines  36 ,  37 . 
     In this embodiment, the channels for the connecting lines  36 ,  37  may also be of a size such that they produce a specific electrical resistance, preferably between 10 3  and 10 4  ohms. Apart from this, various plastics may also be used for the two connecting lines  36 ,  37  for the fuseholder  30 ; and the connecting lines  36 ,  37  may be only partially composed of conductive plastic. 
     In both the described embodiments, the external shape of the fuseholder  10 ,  30  with the built-in status indicators corresponds exactly to the shape of fuseholders without status indicators, so that the fuseholders  10 ,  30  with the integrated connecting lines for the built-in status indicators can also be replaced by fused plugs without any status indicators even in already existing systems, without any work being required to the wiring and connections of the fused switch. 
     The electrically conductive plastics used may be plastics composed of polyphenylenesulfite which are mixed with carbon fibers in such a way as to comply with the requirements for the mechanical, thermal and electrical characteristics demanded of such electrically conductive, thermoplastic construction materials.