You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fastening element for fitting parts according to the preamble of patent claim 1, to a spring ring according to claim 9 and to a fitting according to claim 10. 
     2. Summary of the Invention 
     The object of the invention is to provide a fastening element for fittings or fitting parts which is relatively uncomplicated and makes simple mounting possible. 
     This object is achieved by means of a fastening element having the features specified in patent claim 1. 
     Further advantageous embodiments of the invention are as specified in the dependent claims. 
     The invention is explained in more detail below by way of example., with reference to drawings in which: 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a diagrammatic illustration of two fitting parts which are connected to one another by means of an installed fastening element according to the invention; 
     FIG. 2 shows an enlarged partial illustration of such a fastening element; 
     FIG. 3 shows a side view of a spring ring for such a fastening element; 
     FIG. 4 shows a top view of such a spring ring; 
     FIG. 5 shows an illustration of a detail to explain the operation of such a spring ring, and 
     FIG. 6 shows an enlarged cross section of the edge of such a spring ring. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows two fittings, parts  1  and  2 , which may be, for example, a housing, a tubular piece, a hydraulic appliance, etc., said figure illustrating, in particular, preferably a wide fitting part  1  in the form of a housing part of a water fitting with an at least approximately cylindrical outer contour and a lateral fitting part  2  in the form of an outflow pipe with an outflow  3  for water or another liquid. The term “hydraulic” refers, within the meaning of the invention, to any liquid. The outflow pipe  2  has an axial cavity or passage  4  which communicates with an orifice forming the outflow  3 . The fitting parts  1  and  2  have in each case axially symmetric axes  5  and  6 , which are located in one and the same plane, and are connected in close contact to one another by means of a fastenings element  7 . One end ( 30  in FIG. 2) of the fittings, part  2  is in contact with the outside of the cylindrical wall  8  of the fitting part  1  which has the larger diameter. The cylindrical wall  8 , the shape of which is not appreciably impaired by this contact, is thus in contact with a sectional plane of the fitting part  2 , said sectional plane being designed for this purpose in the special form of what is known as a penetration, so that the shape of this end ( 30  in FIG. 2) of the fitting part  2  is matched to the outer surface of the cylindrical wall  8  of the fitting part  1 . The tubular fitting part  2 , which has the smaller diameter, can thereby be joined, flush, to the fitting part  1  at a predetermined angle. A sharp contact edge is thereby formed, as seen from outside, between the fitting parts  1  and  2 . 
     The fastening element  7  according to FIGS. 1 and 2 comprises a plurality of parts, to be precise: a connecting insert  9 , a threaded shank  10  with a nut  11 , a spring ring  12  (FIGS. 3 to  6 ), a sealing ring  13  and a special seal  14 . The connecting insert  9  has a circular cross section and is provided with an axial continuous bore  15 . The connecting insert  9  itself may consist of one, two or more parts; it is preferably of one-piece design, and it is therefore also referred to as a pipe connection piece. 
     FIG. 2 shows further details of the fastening element  7  according to the invention. A region  16  at one end of the pipe connection piece  9  is likewise designed as a penetration so that it can be added flush to the fitting part  1 . The other end of the pie connection piece  9  is delimited by an end face  17  formed perpendicularly to the axis  6 . The pipe connection piece  9  has a cylindrical outer surface  18 , so that it can be introduced slideably with only a little play into a bore  19  at one end of the fitting part  2  as far as a shoulder  20 . The pipe connection piece  9  also has a relatively wide and deep groove  21  for the spring ring  12  and a smaller groove  22  for the sealing ring  13 . The grooves  21  and  22  are designed to be parallel to the end face  17 . In the region of the end  16  of the pipe connection piece  9 , there is formed by a widened inner bore  23 , as far as a shoulder  24 , an air gap where the special seal  14 , for example a silicone seal, is accommodated. The end portion of which is preferably likewise designed as a penetration, so that it can be added, flush, to the fitting part  1 . The nut  11  presses against the end face  17  via a curved washer  25 . 
     The threaded shank  10  has a coaxial inner bore  26  and, on the outside, is provided with a middle smooth outer surface between a first region  27  having an external thread for the nut  11  at one end and a second region  28  likewise having an external thread at the other end. The cylindrical wall  8  of the fitting part  1  has a continuous oblique internally threaded wall  29  which is formed coaxially to the axis  6 . The end region  28  is screwed into this bore  29 . The end of the threaded shank of this side is shaped at least approximately according to the inner contour of the fitting part  1 . 
     FIG. 3 shows the lateral shape of the spring ring  12  which, as may be gathered from FIG. 4, is not completely annular since it has a cutout at an angle w from about 30° to 110°. A resilient clamping piece may also otherwise serve as a spring ring  12 . 
     The fitting, part  2  (FIG. 2) has, adjacent to its oblique end a widened inside diameter, so that there is an air gap  31  as far as a transitional ramp  32 . Between the ramp  32  and the end face  17  of the pipe connection piece  9 , in the mounted state, there is, on the inside of the fitting part  2 , a peripheral groove  33  which is designed to have the spring ring . 12  clamped in it in such a way that the pipe connection piece  9  can be held firmly on the fitting part  2  and be pressed against the latter. 
     Preferably, as illustrated in FIG. 5, that wall or flank  34  of the groove  33  which faces the fitting part  1  is preferably designed to be inclined inward. Moreover, as illustrated in FIG. 5 and 6, the edge region of the cross section of the spring ring  12  is in the shape of a symmetrical trapezium, the small unequal side being located at the outer edge between two preferably oblique or inclined flanks  35  and  36  which, in particular, may also be designed symmetrically, and the flank  34  and  35  having the same inclination. 
     The fastening element according to FIGS. 1 to  6  functions as follows: 
     First, the oblique end region  28  of the threaded shank  10  is screwed into the threaded bore  29  of the wall  8 , until the inner end of said threaded shank is at least approximately in alignment with the inner contour of the fitting part  1 . The pipe connection piece  9 , if appropriate with the seal  14  mounted, is then pushed over the threaded shank  10 , until said pipe connection piece comes to bear at least approximately with one end face against the fitting part  1  in a suitable rotary position and the threaded end region  27  of the threaded shank  10  projects from the bore  15 . Finally, the nut  11  on the portion  27  is screwed down and preferably tightened via the curved washer  25 , in order to retain the pipe connection piece  9  against the wall  8  of the housing  1 . 
     Once the pipe connection piece  9  is firmly fixed to the wall  8  the fitting part  1  in the correct rotary position with respect to the angle between the axes  5  and  6  and the sealing ring  3  is introduced into the groove  22  and the spring ring  12  into the groove  21 , the fitting part  2  to be fastened can then be slipped over the pipe connection piece  9 . The trapezoidal edge, that is to say the radial outer end region of the flank  36 , of the elastic spring ring  12  slides over the ramp  32  and is pressed into the groove  21 , until, when the fitting part  2  moves further on, said spring ring spreads into the groove  33  of this fitting part  2 , so that the flanks  34  and  35  are in contact with one another in the manner of wedge surfaces. The selected dimensions are such that, in the correct rotary position of the fitting part  2 , the end region  30  is in contact all-round with the outer surface  8  of the fitting part  1 . This spring ring  12  therefore makes a firm connection which can no longer be pulled off. Since the shoulder or flank  34  (FIG.  5 ), nearer to the fitting part  1 , of the groove  33  inside the fitting part  2  is designed obliquely, specifically with the same angle of incidence as in the case of the trapezoidal edge  35  of the spring ring  12  with which it comes into contact, radial bracing occurs, which ensures a play-free connection between the fitting parts  1  and  2 . The small angle of incidence at the flank also brings about selflocking. 
     According to the present invention, therefore, the pipe  2  is pressed against the fitting part  1  by means of the spring ring  12 . The spring ring  12  may also, in a known way, have, for example, circular cross section if a releasable connection is to had instead. Preferably, however, the spring ring  12  has at least one flank  35  which is inclined with respect to a plane lying at right angles to the axis of the groove, preferably the spring ring being designed radially on the inside with a rectangular cross section ( 35 ) and radially on the outside with a symmetrically trapezoidal ( 36 ) cross section. 
     The connection between the fitting parts  1  and  2  thereby becomes unreleasable, so that a complete unit, as a replacement for a corresponding one-piece structure is obtained. The two unreleasably connected fitting parts prove to be particularly advantageous with regard to their surface treatment. This is because a corresponding one-piece structure would be relatively difficult to clean, grind, polish, chromium-plate, lacquer, etc., particularly along the sharp contact edge between the two tubular parts. However, such surface treatments can be carried out satisfactorily in the case of the originally separate fitting parts according to the invention. 
     It is unimportant for the present invention whether the cross sections of the fitting parts  1  and  2  are circular or have another, for example elliptic shape 
     The cylindrical wall  8  is therefore to be understood, in general, as the outer wall of the fitting part  1 . 
     The connecting insert  9  is preferably designed in one piece. It may also consist of two parts, such as would be obtained, for example, by a cut along the plane of the flat wall  37  (FIG. 5) of the groove  33 , because the two parts would then anyway be retained by the nut  11 . In this case, a sealing ring could be inserted between the ramp  32  and the spring ring  12 .

Summary:
The fastening element is intended for two hydraulically communicating fitting parts ( 1, 2 ). In order to fasten a lateral fitting part ( 2 ) on the end face to an outer wall ( 8 ) of a wide fitting part ( 1 ) at a predetermined angle, the lateral fitting part ( 2 ) has, in one end region, a cavity ( 4 ) in which an inner peripherally formed groove for a spring ring ( 12 ) is located. The fastening element ( 7 ) comprises a connecting insert ( 9 ) which is mounted in this cavity ( 4 ) of the lateral fitting part ( 2 ) and which carries a threaded shank ( 10 ) with a bore ( 15 ), in order to allow hydraulics communication between the two fitting parts ( 1, 2 ). The connecting insert ( 9 ) has an outer peripherally formed groove such that a spring ring ( 12 ) is mounted unreleasably between these two grooves.