Abstract:
A muffler includes three or more concentric pipes which convey exhaust gases from an input end of the muffler to an output end of the muffler. The exhaust gases reverse direction as they pass from a first pipe into a second pipe, and again as they pass from the second pipe into the third pipe. After the exhaust gases have reversed direction twice, they exit the muffler. Perforated portions of the three concentric pipes can be used to allow exhaust gases to pass from one pipe into another.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to mufflers which are used to reduce sound levels. Such mufflers can be used on internal combustion engines, and with other devices which produce exhaust gases. 
         [0003]    2. Background of the Related Art 
         [0004]    Internal combustion engines used in vehicles and in other applications typically employ some type of a muffler device to deaden the sound of the exhaust gases exiting the external combustion engine. In a typical muffler, baffles are arranged in the interior of the muffler to force the exhaust gases to reverse direction one or more times before they exit the muffler. However, forming a muffler with multiple baffles requires a significant amount of physical space. As a result, it is difficult to construct an effective muffler which can be used in applications which require a very small muffler volume, such as on motorcycles. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter. 
         [0006]    In a muffler embodying the invention, three or more concentric pipes are connected together. Portions of the smallest diameter and the intermediate diameter pipes are solid walled, and portions have perforations. The perforated sections of the pipes allow exhaust gases to pass from one pipe to another. As the exhaust gas moves from a first pipe into a second pipe, the exhaust gas is forced to reverse its flow direction. By providing three or more concentric pipes, the muffler can cause the exhaust gases to reverse direction at least twice before exiting the muffler. 
         [0007]    In some embodiments of the invention, more than five pipes could be used to form the muffler. In addition, the concentric pipes could have any cross-sectional shape including circular, oval, rectangular, or other shapes. 
         [0008]    In other embodiments of the invention, the perforated portions of the pipes could be completely eliminated such that gases flowing out of one pipe simply reverse direction and flow into the other pipe. 
         [0009]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements, and wherein: 
           [0011]      FIG. 1  is a perspective view of a muffler embodying the invention; 
           [0012]      FIG. 2  is a longitudinal cross-sectional view of a muffler embodying the invention; 
           [0013]      FIG. 3  is a cross-sectional view of a muffler embodying the invention taken along section line III-III in  FIG. 1 ; 
           [0014]      FIG. 4  is a cross-sectional view of a muffler embodying the invention taken along section line IV-IV in  FIG. 1 ; 
           [0015]      FIG. 5  is a cross-sectional view of a pipe which can be used in a muffler embodying the invention; 
           [0016]      FIG. 6  is a cross-sectional view of another muffler embodying the invention; and 
           [0017]      FIGS. 7   a - 7   d  are cross-sectional views of mufflers embodying the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    A perspective view of a muffler embodying the invention is shown in  FIG. 1 . As shown therein, the muffler includes three concentric pipes connected together. The smallest diameter pipe  30  can serve as either an input or an output end of the muffler. The largest diameter pipe  20  can serve as the other of the input and output ends of the muffler. An intermediate diameter pipe  40  is located between the smallest diameter pipe  30  and largest diameter pipe  20 . 
         [0019]    A longitudinal cross-sectional view of the muffler shown in  FIG. 1  appears in  FIG. 2 . In this embodiment, the smallest diameter pipe  30  acts as an input end of the muffler. The right side of the smallest diameter pipe  30  has a plurality of perforations. The perforated section  32  of the smallest diameter pipe  30  allows exhaust gas entering the muffler to flow from the first pipe into the intermediate diameter pipe  40 . The right ends of both the smallest diameter pipe  30  and the intermediate diameter pipe  42  are closed off. As a result, exhaust gas flowing into the muffler inside the smallest diameter pipe  30  is forced to reverse its flow direction as it flows from inside the smallest diameter pipe  30  into the intermediate diameter pipe  42 . This reversal of the flow direction is shown by the arrows appearing in  FIG. 2 . 
         [0020]    The left side of the intermediate diameter pipe  42  is also perforated. The perforated section  44  of the intermediate diameter pipe  40  allows exhaust gases to pass from within the intermediate diameter pipe  42  into the largest diameter pipe  20 . In passing from inside the intermediate diameter pipe  42  to the largest diameter pipe  20 , the exhaust gases must again reverse their flow direction. The reversal of the flow direction is also depicted by the arrows appearing in  FIG. 2 . The exhaust gas then passes down the length of the largest diameter pipe  20  and outside the muffler at the outlet end on the right side of the muffler. 
         [0021]      FIG. 3  is a cross-sectional view of the muffler shown in  FIGS. 1 and 2  taken along section line III-III in  FIG. 1 . As shown therein, on the left side of the muffler, the smallest diameter pipe  30  has a solid wall, as does the largest diameter pipe  20 . However, the intermediate diameter pipe  40  is perforated at this location. 
         [0022]      FIG. 4  shows a cross-sectional view of the muffler of  FIGS. 1 and 2  taken along section line IV-IV in  FIG. 1 . As shown therein, at this location on the muffler, the smallest diameter pipe  30  is perforated, while the intermediate diameter pipe  40  and the largest diameter pipe  20  are solid walled. 
         [0023]    A round, flat piece of metal  52  closes off the right ends of the smallest diameter pipe  30  and the intermediate diameter pipe  40 . As shown in  FIG. 4 , small tabs  50  can be used to attach the circular end plate, or the intermediate diameter pipe  40  to the largest diameter pipe  20 . This serves to keep the smallest and intermediate diameter pipes centered within the largest diameter pipe  20 . 
         [0024]    A torus shaped plate  54  is attached to the left ends of the intermediate diameter pipe  40  and the largest diameter pipe  20  to seal off the left ends of these two pipes. The smallest diameter pipe  30  would pass through the torus plate  54 . 
         [0025]    In the embodiments shown in  FIGS. 1-4 , the smallest and intermediate diameter pipes have a portion of their length perforated. The remaining portions are solid walled. In alternate embodiments, each of these pipes could be constructed from two separate pieces of pipe having the same diameter that are joined together at their ends, one piece being solid and the other perforated. In still other embodiments, each pipe could be formed of two separate pipes having slightly different diameters. As shown in  FIG. 5 , a first solid walled pipe  60  could be located inside a perforated pipe  70 . The solid walled pipe would be shorter than the perforated pipe  70 , such that a portion of the perforated pipe  70  extends beyond the solid walled pipe  60 . In additional embodiments, although the slightly different diameters could be arranged as shown in  FIG. 5 , the larger diameter pipe  70  might be shorter than the solid walled pipe  60 , such that only small portions of the two pipes overlap. Also, the perforated pipe could have a smaller diameter than the solid walled pipe, which would reverse the orientation shown in  FIG. 5 . 
         [0026]    In still other embodiments of the invention, the perforated portions of the smallest and intermediate diameter pipes could be completely eliminated. This would mean that the smallest diameter pipe  30  would not extend all the way down to the right side of the muffler, and the intermediate diameter pipe would not extend all the way to the left side of the muffler. 
         [0027]    In some embodiments of the invention, as shown in  FIG. 6 , a fiber filling material  82  can surround the largest diameter pipe of the muffler. A shell  80  can then be formed around the three concentric pipes and the fiber filling material to enclose the muffler. With this type of construction, the largest diameter pipe could be perforated, which would allow some of the gases to pass into the fiber filling material  82 . 
         [0028]    The fiber filling material  82  can be fiberglass or any other similar material which can be used to dampen sound vibration to further quiet the muffler. In addition, the fiber filling material  82  can be used to help reduce the amount of heat which passes from within the muffler to the exterior shell  80  of the muffler. 
         [0029]    Although the above embodiments are illustrated with three circular cross-sections, other cross-sectional shaped pipes could be used. For instance, as shown in  FIG. 7   a , all three of the pipes could have an oval cross-section. In addition, mixtures of oval and circular cross-sectional pipes could also be used. For instance,  FIG. 7   b  shows the smallest diameter pipe  30  and the intermediate diameter pipe  40  having an oval cross-section, whereas the largest diameter pipe  20  has a circular cross-section.  FIG. 7   c  shows an embodiment of the invention where the smallest diameter pipe  30  and the intermediate diameter pipe  40  have circular cross-sections, while the largest diameter pipe  20  has an oval cross-section.  FIG. 7   d  shows an embodiment wherein the smallest diameter pipe has a circular cross-section, the intermediate diameter pipe has an oval cross-section, and the largest diameter pipe has a circular cross-section. Of course, any other combination of different cross-sectional shapes could also be used. For instance, the muffler could be constructed using rectangular, square, or other geometric cross-sectional shaped pipes. 
         [0030]    In addition, although the embodiments described above show the smallest diameter pipe being used as the input end, and the largest diameter pipe being used as the output end of the muffler, the flow direction of the exhaust gases could be reversed. As a result, each of the arrows shown in  FIGS. 2 and 6  could be oriented in the opposite directions so that exhaust gases enter into the largest diameter pipe, reverse direction and pass into the intermediate diameter pipe, and then reverse direction again and pass into the smallest diameter pipe. The smallest diameter pipe would then be used as the output of the muffler. 
         [0031]    Furthermore, although the embodiments of the invention illustrated in the drawings comprise three concentric pipes, more than three concentric pipes could be used. For instance, the muffler could be constructed with five concentric pipes which would require the exhaust gases to reverse direction a total of four times before exiting the muffler. In fact, the muffler could have more than five concentric pipes so that the direction of the exhaust gases is reversed multiple times before exiting the muffler. 
         [0032]    The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.