Abstract:
A device for connecting pipes in a heavy truck exhaust system includes a flexible sleeve joined to both connecting pipes and a flow guide connected or formed to an upstream pipe and extending through the flexible sleeve into the downstream pipe. The flow guide may have a frustoconical shape converging toward an outlet end with an outlet rim that flares radially outward. An inlet rim of the downstream pipe converges radially inward to prevent backflow into the joint region.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
       [0001]    The invention relates to exhaust systems for vehicles, in particular heavy trucks. More particularly, the invention relates to a flexible coupling for an exhaust system for a heavy truck that allows liquid to pass through the coupling without leakage. 
         [0002]    Exhaust systems in truck tractors conduct exhaust gases along a relatively long path from the engine rearward of the cab to a stack or tail pipe. The pipes are subject to vibrations from the flowing gases and vibrations and bending movements imparted by the moving vehicle. To accommodate vibration and flexing, the pipe joints are joined with resilient, movable couplings. 
         [0003]    U.S. Pat. No. 5,145,215 to Udell shows one such resilient coupling. The device includes two sleeve members  16 ,  17  that join in an overlapping manner. The end edges of the sleeves are turned outward and inward, respectively, to retain a spacer member  48  between the sleeves. The sleeves are surrounded by a bellows  10 , which is, in turn surrounded by a braided wire fabric  23 . The ends of the assembly are received in end caps. The end caps are mounted to the adjacent pipe ends to provide the coupling. 
         [0004]    With the increasing use of exhaust after-treatment devices and with stricter controls on exhaust products, truck exhaust systems may in the future be called on to carry liquid material to treat the combustion products or to clean or regenerate exhaust after-treatment devices, such as diesel particulate filters, oxidizers, or catalyzers. The liquid material may be as a condensate or atomized form, and may include automotive or diesel fuel, urea, ammonia, or some other combustive, oxidizing or catalyzing agent. 
         [0005]    The present invention provides a flexible pipe coupling system that eliminates components and associated cost and complexity of known devices, while providing a coupling allowing liquid to pass without leakage. 
         [0006]    According to the invention a flexible sleeve joins an upstream pipe to a downstream pipe. A guide tube extends from an outlet end of the upstream pipe through the flexible sleeve into an inlet end of the downstream pipe. The guide tube carries flow through the flexible sleeve area and allows the flow to exit into the downstream pipe. An outlet of the guide tube is disposed within the downstream pipe of the coupling, and is spaced from the internal walls of the downstream pipe. This ensures that all flow passes the joint area into the downstream pipe and isolates the guide tube from the downstream pipe to prevent the transmission of vibration. 
         [0007]    According to an aspect of the invention, the guide tube may be shaped as a straight cylinder. Alternatively, the guide tube has a frustoconical shape that converges at an outlet end. This second embodiment allows the upstream pipe and the downstream pipe to have the same diameter, the convergence of the guide tube providing the spacing between the guide tube and downstream pipe inlet. 
         [0008]    According to another aspect of the invention, an outlet of the guide tube may include a radially outwardly flaring mouth to improve the pressure loss at the outlet of the guide tube. 
         [0009]    According to another aspect of the invention, an inlet end of the downstream pipe may be shaped with a rim that converges radially inwardly. The rim of the downstream pipe helps prevent backflow of liquid into the flexible sleeve area. 
         [0010]    According to one embodiment, the guide tube is a separate component fastened to the outlet end of the upstream exhaust pipe. According to an alternative embodiment, the guide tube is a formed extension of the upstream pipe. 
         [0011]    The invention provides a low cost, reliable device. The flexible sleeve allows the upstream exhaust pipe and downstream exhaust pipe to move relative to one another, but the sleeve does not need to be liquid tight. The internal guide tube carries liquid and exhaust gas flow through the coupling joint without leakage. 
         [0012]    The invention is particularly applicable to newer exhaust systems which may carry liquids for regenerating exhaust after-treatment devices, such as particulate filters, oxidizers, and catalyzers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will be better understood by reference to the following detailed description read in conjunction with the appended figures, in which: 
           [0014]      FIG. 1  is sectional view of an exhaust pipe coupling in accordance with the invention; 
           [0015]      FIG. 2  is a sectional view of an exhaust pipe coupling according to an alternative embodiment; 
           [0016]      FIG. 3  is a sectional view of an alternative embodiment of a guide tube of the invention; 
           [0017]      FIG. 4  is a sectional view of an alternative embodiment for an inlet to a downstream exhaust pipe; and, 
           [0018]      FIG. 5  is a sectional view of another alternative embodiment for an inlet to a downstream exhaust pipe. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  shows a longitudinal sectional view of an exhaust pipe coupling device in accordance with a first embodiment of the invention. The device connects an upstream exhaust pipe  10  with a downstream exhaust pipe  20 . The normal flow direction of exhaust gas is shown by arrow A. In addition to carrying gas combustion products, truck exhaust systems are or may in the future be called on to carry liquid material to treat the combustion products or to clean or regenerate exhaust after-treatment devices, such as diesel particulate filters, oxidizers, or catalyzers. The liquid material may be as a condensate or atomized form, and may include automotive or diesel fuel, urea, ammonia, or some other combustive, oxidizing or catalyzing agent. The device according to invention assures that liquid material passes the joint areas in the exhaust piping without leakage. 
         [0020]    A flexible sleeve  30  receives the outlet end  12  of the upstream pipe  10  and the inlet end  22  of the downstream pipe  20 . Clamps  40 ,  42  secure the flexible sleeve  30  to the outer surfaces of the upstream pipe  10  and downstream pipe  20 . The flexible sleeve  30  in a preferred embodiment is a metal spiral wound tube that provides resilient bending in a plane perpendicular to the gas flow direction A, and accommodates compression and tension in the flow direction. The spiral forms rings that are interlocked to provide a closed surface. The sleeve is preferably stainless steel. A flexible sleeve as described is available, for, example, from Federal Hose, Inc. of Painesville, Ohio, Riker Products of Toledo, Ohio and Tru-flex Metal Hose Corp. of West Lebanon, Ind. Other similarly functional flexible sleeves could be substituted. 
         [0021]    A guide tube  50  extends from the outlet end  12  of the upstream pipe  10  into the inlet  22  of the downstream pipe  20 . The guide tube  50  is spaced radially from the downstream tube  20  to prevent the transmission of vibration therebetween. The guide tube  50  may be formed a cylinder, which is illustrated and described in connection with  FIG. 2 . In the preferred embodiment of  FIG. 1 , the downstream tube  20  is formed with a larger diameter to accommodate the end of the guide tube. The upstream tube  10  may be formed with the same diameter as the guide tube  50 . Alternatively and preferably, the guide tube  50  has a frustoconical shape that converges in the flow direction A, that is, narrows from an upstream end  52  to a downstream end  54 . This shape allows the guide tube  50  to be fitted to an upstream pipe  10  having the same diameter as the downstream pipe  20  and provide spacing between the outlet  54  of the guide tube  50  and the inlet  22  of the downstream pipe  20 . 
         [0022]    Preferably, the downstream end  54  of the flow guide  50  is shaped with a radially outward flaring rim  56  that aids flow in exiting from the flow guide. 
         [0023]    Preferably also, the inlet end  22  of the downstream pipe  20  is shaped with a radially inwardly converging rim  24  to help prevent liquid backflow into the flexible sleeve  30  area. The bend in the rim should be enough to act as a catch to prevent liquid backflow, but not interfere with the free movement of the outlet of the guide tube. 
         [0024]    Other means for preventing backflow into the sleeve area may be substituted. For example, a ring  26  may be secured inside the inlet of the downstream pipe as shown in  FIG. 4 . Alternatively, the inlet of the downstream pipe may be provided with a trough  28  to collect liquid before it reaches the sleeve area as shown in  FIG. 5 . Other means as will occur to those skilled in the art may be used. 
         [0025]    As illustrated in  FIG. 2 , the guide tube  51  may be formed as a cylinder, in the view shown, being an extended portion of the upstream pipe  11 . Of course, the guide tube  51  may also be formed as a separate component attached to the upstream pipe  11 . In the embodiment of  FIG. 2 , the upstream pipe  11  and guide tube  51  have a diameter smaller than the diameter of the downstream pipe  20 , which provides the spacing between the outlet  55  of the guide tube and the inlet  22  of the downstream pipe. An adapter  60  is mounted on the upstream pipe  11  to accommodate the difference in diameter with the downstream pipe  20  for mounting the flexible sleeve  30 . As in the embodiment of  FIG. 1 , the flexible sleeve  30  is secured to the upstream pipe  11  and downstream pipe  20  by clamps  40 ,  41  or other suitable devices. 
         [0026]    The downstream pipe  20  is also formed with the preferred inlet rim  24  converging radially inward. The guide tube  51  shown in  FIG. 2  has a straight outlet, but may be formed with the flared outlet rim shown in  FIG. 1 . 
         [0027]    In the embodiment illustrated in  FIG. 1 , the flow guide  50  is a separate component attached to the upstream pipe  10 , which can be done by any convenient method, including welding. Alternatively, as shown in  FIG. 2 , a flow guide  50 ′ may be an extension of an upstream pipe  10 ′, and drawn down in diameter if a frustoconical section is desired. 
         [0028]    The invention has been described in terms of principles and preferred embodiments and components. Those skilled in the art will understand that the invention may be practiced with substitutions for preferred components without departing from the spirit and scope of the invention as defined in the appended claims.