Abstract:
A device for connecting two tubular piping parts, in particular piping parts in a motor vehicle exhaust system, has two connector pieces with a sealing device being mounted between the connector pieces. The connector pieces are stressed against each other in axial direction by a spring device. The spring device has a wire spring which surrounds one connector piece at least partially with two spring branches and is supported by this connector piece. The wire spring is stressed against a stop on the other connector with the spring branches or another area of the wire spring.

Description:
FIELD OF THE INVENTION 
     The present invention concerns a device for connecting two tubular piping parts, and in particular, a device for connecting piping parts in a motor vehicle exhaust system. 
     RELATED TECHNOLOGY 
     A device for connecting two tubular piping parts of the generic type is known from German Patent Application No. 44 44 550 A1. The spring device for generating a pre-stress force between the two connector pieces has a curved washer which supports itself on one connector piece and another curved washer that is mechanically attached to the other connector piece. The two curved washers are pre-stressed against each other by clamps. The previously known device is relatively complicated in structure and in addition requires a relatively large additional space. 
     A similar device with which a motor vehicle engine exhaust system can also be decoupled from vibration generated by the engine is known from French Patent 2 360 028. In the French patent, a spiral spring which presses the two piping parts apart in the axial direction is stressed between the two connector pieces. This piping connection has the disadvantage that it inadequately decouples engine vibrations. 
     In German Patent Application No. 196 53 906.4, which is not necessarily prior art to the present application, a device is described for decoupling piping parts in the motor vehicle exhaust system in which a spring device with two spring branches is inserted into slots in a connector piece of a piping part and the spring branches are supported on part of an end section. However, this older device is also relatively complicated. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to create a device for connecting piping parts, in particular for use in a motor vehicle exhaust system. Decoupling of engine vibrations can be achieved in a simple and cost-effective manner using as little space as possible. 
     The present invention therefore provides a device for connecting two tubular piping parts, in particular piping parts in the motor vehicle exhaust system, the piping parts having connector pieces, between which a sealing device is mounted and the connector pieces being stressed against each other in axial direction by a spring device. The spring device contains a wire spring ( 5 ), which surrounds one of the two connector pieces ( 1   a ,  2 ,  3   a ,  3   c ) at least partially with two spring branches ( 5   a ,  5   b ) and is supported by this connector piece ( 3   a ,  3   c ) while it is stressed with the same spring branches ( 5   a ,  5   b ) or another area of wire spring ( 5 ) against a stop on the other connector piece ( 2 ,  1   a ). 
     With the device according to the present invention, two exhaust pipes in a motor vehicle exhaust system can be connected in an optimum manner so that they are gas tight and the vibration generated in the exhaust system by the engine can be decoupled from the vehicle body. 
     In contrast to previous solutions, the device according to the present invention can achieve space requirement, manufacturing feasibility, cost and assembly goals. In particular, the spring device made from a wire spring, in particular from round wire, can be produced especially cost-effectively. In addition, this connection requires very little space with simultaneously very simple shaping at the pipe ends and/or simple design of the connector pieces. 
     Additional decoupling elements in the exhaust system can be omitted because of the connecting device according to the present invention, since the separating point between front part and rear part of the exhaust system can also take on the function of decoupling element in the usual manner. This both saves costs and decreases the exhaust system weight. Advantageous designs and further developments of the invention are described below. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     Embodiments of the present invention are explained below with reference to the drawings; in which: 
     FIG. 1 shows a view of a first embodiment of the present invention from the front; 
     FIG. 2 shows a cross-section along Line II—II in FIG. 1; 
     FIG. 3 shows a side view of the embodiment according to FIG. 1; 
     FIG. 4 shows a top view of the embodiment according to FIG. 1; 
     FIG. 5 shows a front view of a second embodiment; 
     FIG. 6 shows a side view of the second embodiment; 
     FIG. 7 shows a front view of a third embodiment; 
     FIG. 8 shows a side view of the embodiment according to FIG. 7; 
     FIG. 9 shows a lengthwise section through a fourth embodiment; 
     FIG. 10 shows a side view of a fifth embodiment; 
     FIG. 11 shows a front view of the embodiment according to FIG. 10; 
     FIG. 12 shows a face view from arrow direction A in FIG. 10, opposite the view according to FIG. 11; 
     FIG. 13 shows a sixth embodiment in side view; 
     FIG. 14 shows a front view of the embodiment according to FIG. 13; 
     FIG. 15 shows a seventh embodiment in front view; 
     FIG. 16 shows a side view of the embodiment according to FIG. 15; and 
     FIG. 17 shows a cross-section along Line XVII—XVII according to FIG. 15, without a wire spring. 
    
    
     DETAILED DESCRIPTION 
     For the sake of uniformity and better understanding, the description which follows of the embodiments using the individual figures identifies corresponding parts with the same reference numbers. 
     As shown, for example, in FIGS. 1-4, in order to connect two exhaust pipes  1  and  3  to each other, provide sealing, and at the same time decouple from vibrations generated by an engine that is not shown, a sealing ring  4  is inserted between the two pipe ends. Wire spring  5  as a spring device, which is manufactured of round wire, presses the two ends of exhaust pipes  1  and  3  against each other. Exhaust pipe  1  that extends into exhaust pipe  3  as an internal pipe has on its end bead  2  as a connector piece, which wire spring  5  having an appropriately bent shape contacts on two opposite sides. 
     Exhaust pipe  3  extends with connector piece  3   a  over sealing ring  4  in the axial direction and is provided with slots  6  on two opposite points. Wire spring  5  has a stirrup shape with two side branches  5   a  and  5   b  and one cross part  5   c  connecting the two side branches to each other. It can be seen from FIGS. 2 and 3 that two side branches  5   a  and  5   b  contact two points  7   a  and  7   b  on each side on one wall of slot  6  of outer pipe  3 , i.e., its connector piece  3   a . With opposite convexity  7   c  on wire spring  5 , which is located between two points  7   a  and  7   b , the wire spring also contacts each side on bead  2  of exhaust pipe  1 . 
     FIG. 1 shows that wire spring  5  surrounds inner pipe  1  on both sides with slight outer convexities  8   a  and  8   b . At the same time, this centers wire spring  5  and secures it against slipping out. In the upper area, wire spring  5  also fits flush on outer pipe  3  with a slight internal convexity  9 . Because of internal convexity  9 , a stop is also produced for wire spring  5  which aids is assembly. 
     A press-in plate  10  (see side view in FIG.  1  and top view in FIG. 4 in dotted lines) may be mounted on wire spring  5  on upper cross part  5   c , which facilitates assembly. The connection of press-in plate  10  with wire spring  5  can be in any desired manner, e.g., by welding, soldering or gluing. 
     In FIGS. 5 and 6, as well as in FIGS. 7 and 8, further designs of wire spring  5  are described, which have a structure that is otherwise the same. So that wire spring  5  may have a contact point on each side on outer pipe  3 , i.e., its connector piece  3   a , brackets  11   a  and  11   b  may be pressed out of outer pipe  3  on each side. As a result, wire spring  5  has a contact point on each side on bead  2  of inner pipe  1  and on brackets  11   a  and  11   b  of the outer pipe. As can also be seen in FIGS. 5 and 6, wire spring  5  has double spring branches on each side with two inner spring branches  5   a  and  5   b  and two outer spring branches  5   d  and  5   e . The two inner spring branches  5   a  and  5   b  contact bead  2  while outer spring branches  5   d  and  5   e  contact brackets  11   a  and  11   b.    
     The embodiment shown in FIGS. 7 and 8 corresponds to the embodiment shown in FIGS. 5 and 6 with respect to the support of wire spring  5  with two double spring branches  5   a  to  5   e . However, to reinforce the spring force, the spring is here provided with a spiral winding  12  in the intermediary area between the inner and outer spring branches. The number of windings in spiral winding  12  can be selected depending on the characteristic curve of wire spring  5  and the space available. This means a spiral wire spring  5  can be designed with one or several windings. Also the exact shape of wire spring  5  depends on the respective spring characteristic curve and the space available, so that other shapes and designs of wire spring  5  are also conceivable. 
     For the pipe connection to have not only a vibration decoupling effect but also a damping effect, a wire cushion  13  can be inserted between the inner pipe and outer pipe  3 . This embodiment is shown in FIG.  9 . For this purpose, connector piece  3   a  of outer pipe  3  is provided with cylindrical extension  3   b . Ring-shaped damping cushion  13  bridges the intermediate space between extension  3   b  and inner pipe  1 . Damping cushion  13  made of wire can be designed in one or more parts and may cover the entire circumference of inner pipe  1 . However, it is possible to use damping cushion  13  only in segments on the circumference. A spring damper system is obtained with the resulting possibility of tuning due to damping cushion  13 . Additionally, a guiding and bearing function between two pipes  1  and  3  results. By using damper cushion  13 , the two pipes can also be used at points at which the exhaust system would sag with standard spring-loaded pipe connections. 
     FIGS. 10,  11  and  12  show a fifth advantageous pipe connection embodiment. As can be seen from these drawings, wire spring  5  is designed in such a way that outer pipe  3  need not clearly project beyond inner pipe  1  but only has a connector piece  3   a  with a small extension in contact with bead  2  of inner pipe  3 . 
     The design of the pipe connection according to FIGS. 10,  11  and  12  makes it possible to connect both pipes directly to each other with a very simply shaped single-piece wire spring  5  without one of the pipes having to be slit. On one side, wire spring  5  is form fit with pipe  3  (see FIGS. 10 and 12) and the pipe is surrounded almost 180° in an arc shape  14   a . In this manner, wire spring  5  is centered and simultaneously secured against slipping out. On opposite sides, side branch  5   a  or  5   b  is connected to arch  14   a  with counter-arch  14   b . Then on each side, each side branch  5   a  or  5   b  contacts contact point  7   d  at a point on bead  2  of pipe  1  (see FIGS.  10  and  11 ). 
     FIGS. 13 and 14 show a modification of the embodiment shown in FIGS. 10 to  12 . Shaping wire spring  5  with an intermediate branch  5   f  on each side between counter-arch  14   b  and side branch  5   a  produces three contact points on ring bead  2 , namely  15   a  and  15   c  on each side and  15   b  in an area between the two sides, e.g., on the top. In this manner, a uniform distribution of spring force over pipe bead  2  on sealing ring  4  is obtained. With this structure of wire spring  5 , it is also possible to leave both ends of the wire spring, i.e., the two spring branches  5   a  and  5   b , open or connect them mechanically to each other. Spring branches  5   a  and  5   b  can thus be not only connected to each other, but also to outer pipe  3  through arc shape  14   a . Of course, however, separation of wire spring  5  is also possible by elimination of arc shape  14   a . In such an embodiment, because of outer convexities  8   a  and  8   b , wire spring  5  is held securely on outer pipe  3 . 
     Instead of two ( 7   d ) or three ( 15   a ,  15   b , and  15   c ) contact points on bead  2 , an even multiple of the respective number of contact points is also possible i.e., 4, 6, 8×9, etc. To this end, it is only necessary to design wire spring  5  appropriately. 
     FIGS. 15 to  17  show an embodiment of the pipe connection in which the connector pieces can be designed in a spherical form  1   a  and/or  3   c  on both pipes  1  and  3  (see FIG. 17, which shows a cross-section without a wire spring). Connector piece  3   c  of pipe  3  is designed as a pipe bell and the opposing piece, connector piece  1   a , as a pipe bead, to which an additional cylindrical part  1   b  is connected. Seal ring  4  is inserted in this case between cylindrical part  1   b  and pipe bell-shaped extension  3   c  of pipe  3 . 
     Because of this spherical shape of the two pipe ends, wire spring  5  can be designed to be fully symmetrical as can be seen in FIGS. 15 and 16. This prevents wire spring  5  from being incorrectly installed. As can be seen, arc shape  14   a  of wire spring  5  is repeated on the other pipe piece, namely pipe  1 , by arc shape  14   c  formed in the same way. Depending on the requirement, wire spring  5  can be left open at both ends or mechanically connected. 
     Because of the multiple possibilities of suspension and damping properties using wire spring  5 , the exhaust system can be better tuned to the particular vibration problems of a vehicle. 
     Since wire spring  5  is only inserted, both initial assembly by the vehicle manufacturer and replacement in repairs is free of problems and cost-effective.