Connecting device at a bus bar
BACKGROUND OF THE INVENTION 
     The present invention relates to a connecting device for connecting an electric wire to a bus bar, with a longitudinal groove between two walls which form together a U-shaped section. 
     In racks with plug-in units placed above each other feeding of electric power with different tensions and frequencies as well as grounding is usually achieved with bus bars, which are vertically arranged at the gables of the rack. The bus bars have sockets for electric power, often structured as a number of out-bent tabs, or as a number of holes in the bars where a terminal wire provided with cable clips may be connected. It is common for the connections to these bus bars hitherto used to be material and space consuming, while connection to the bus bar can only be made at places determined and prepared in advance. 
     SUMMARY OF THE INVENTION 
     With the device of the invention electric wires can be connected anywhere on the bus bar without previous punching. Compared with earlier known connecting devices, the device according to the invention gives as a result lower labour costs, less consumption of material and less space requirement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the following an example of a connecting device according to the invention is described, whereby reference is made to the accompanying drawing where 
     FIG. 1 shows a perspective drawing of the connecting piece and the bus bar, 
     FIG. 2 shows an end view of the connecting piece and the bus bar, 
     FIG. 3 shows a longitudinal section through the connecting piece, 
     FIG. 4 shows a plan view of the connecting piece. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In a connecting device, as shown in FIG. 1, there is included, among other things, a connecting piece 1, which is arranged in order to be connected to a bus bar 2, which has at least one groove 3 between two walls 4, which together with the groove 3 form a U-shaped section. The connecting piece 1 is, for that reason, provided with two inwardly sloping connecting surfaces 5. 
     Furthermore, in the connecting device a screw 6 is included (see also FIG. 2) which is inserted through a hole in the connecting piece shown in FIGS. 3 and 4. The screw 6 is a screw with a triangular thread, the diameter of which is chosen so that its threads cut into the walls of the bus bar 4 when the screw is screwed through the connecting piece. The hole 7 for the screw is, as appears from FIG. 3, to its outermost part, made with a diameter less than the rest of the hole. 
     When tightening the screw 6, the inwardly sloping surfaces 5 of the connecting piece 1 will press the walls of the bus bar 4 towards each other, whereby it is guaranteed that the threads of the screw will have a solid grip in the walls of the bus bar. 
     To prevent the walls of the bus bar to be pressed too close to each other, the connecting piece has two guiding prongs 8, which on one hand extend alongside the screw 6 and steer it perpendicularly to the bus bar, and on the other hand, prevent the walls of the bus bar from pressing too close to each other. 
     Furthermore, the connecting piece 1 is provided with a recess 9 wherein an electric wire can be soldered. 
     The material of the bus bar is tinned copper and of the connecting piece tinned brass. The size of the device may, as measured by the width of the groove 3 between the walls of the bus bar 4, be 2.3 mm.