Abstract:
A muffler is described with a housing having an input and an output. At least one plate is disposed within the housing to divide it into at least a first and a second internal expansion chamber. At least one tube is disposed through the plate, the tube having first and second ends with a bend therebetween, the bend altering an orientation of the second end of the tube so that the second end faces an interior surface of the housing. The housing, the plate and the tube establish a path for the exhaust between the input and the output. In addition, the first and second internal expansion chambers cooperate to attenuate sound, and the tube assists in sound attenuation and/or affects the path of the exhaust to arrest the discharge of sparks from the output.

Description:
[0001]    This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 60/259,702, which was filed on Jan. 5, 2001, the contents of which are incorporated by reference in their entirety. 
     
    
     
       1. FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to the field of muffler systems for internal combustion engines. More particularly, the present invention relates to a combined muffler and spark arrester for attenuating sound and for reducing or eliminating the discharge of glowing hot carbon particles that typically become entrained in the exhaust gases produced by an engine.  
         2. DESCRIPTION OF RELATED ART  
         [0003]    The by-products produced by internal combustion engines as a result of burning fossil fuels, such as gasoline, include exhaust gases (typically, water, carbon dioxide, and other gases) and carbon particles. Due to the extreme heat produced during the combustion reaction, the carbon particles that become entrained in the exhaust gases usually are glowing hot and, as a result, are referred to as sparks.  
           [0004]    If these sparks are discharged from the exhaust system, they might initiate a fire, especially if an operator drives the vehicle through a wooded area. As a result, it is not uncommon for designers to incorporate structures in their exhaust systems to delay and substantially prevent the expulsion of sparks until after the carbon particles have cooled sufficiently so that they no longer present a risk of fire. For example, in accordance with USDA Standard 5100, at least 80% of the carbon particles should be maintained within the arrester, with only small non-harmful, particles being released. Structures incorporated into an exhaust system that perform this function are referred to as “spark arresting” because of the function performed.  
           [0005]    As the name suggests, mufflers attenuate the sound of the engine to reduce the ambient noise levels generated thereby. The structures that muffle sound also may function to attenuate sparks discharged by the engine.  
           [0006]    One prior art example is illustrated in FIG. 1. The muffler shown incorporates structures that combine both sound muffling and spark arresting functions.  
           [0007]    As FIG. 1 illustrates, after combustion, exhaust gases and carbon particles (sparks) are discharged by the engine and directed to the muffler  100 . After entering the muffler  100  through inlet port  101 , the exhaust and sparks pass through a series of expansion chambers  102   a - 102   f . The expansion chambers  102   a - 102   f  cause the exhaust gases to expand and contract repeatedly, thereby attenuating the sound of the engine. One or more pipes  112  (often referred to as “tune pipes”) also are incorporated into muffler  100  to assist in attenuating the sound of the engine.  
           [0008]    Muffler  100  also includes a plate  104  separating expansion chamber  102   c  from expansion chamber  102   d . A number of perforations  105  (FIG. 2) pass through plate  104 . A plate portion  105   b  (shown in detail in FIG. 2) extends at an angle from a point adjacent to each perforation  105 . Plate portions  105   b  are angled to direct the exhaust stream in a circular direction within exhaust chamber  102   d.    
           [0009]    Additionally, after passing through plate  104 , as a result of the centrifugal force established by the circular motion of the exhaust gases, the majority of the carbon particles are thrown against the side walls of exhaust chamber  102   d  and become trapped specifically in chamber  102   e  of the muffler  100 . This reduces or eliminates almost all of the carbon particle sparks directed to the exit of muffler  100 .  
           [0010]    Also as illustrated in FIG. 1, muffler  100  includes a tuning chamber  103  that assists in reducing exhaust noise. Tuning chamber  103  typically houses an insulation material, such as glass wool or other similar acoustically absorbent material. The acoustically absorbent material assists in attenuating the sound produced by the engine and also may function to trap the carbon sparks.  
           [0011]    Acoustically absorbent materials, however, are not the only materials that may be positioned along the travel path of the exhaust gases as they travel from the inlet (such as inlet  101 ) to the discharge end of a muffler. As recognized by those skilled in the art, metal screens may be disposed at intervals in the exhaust travel path to help attenuate sound and trap carbon particles in the mesh. However, such screens may become clogged with carbon particles and create a significant back pressure that may adversely affect the operation of the engine. Therefore, the screen must be removable and checked periodically, e.g., every 100 hours, thereby increasing the manufacturing cost to the manufacturer and maintenance cost to the owner of the machine.  
           [0012]    As made apparent by the drawings, muffler  100  establishes a convoluted travel path through expansion chambers  102   a - 102   f . Not only does the convoluted path attenuate sound, it also lengthens the travel time of the carbon particles (sparks) through muffler  100 . As a result, muffler  100  both attenuates sound and also reduces or eliminates the discharge of sparks.  
           [0013]    U.S. Pat. No. 5,627,351, issued on May 6, 1997 to Okuma et al. and assigned to Honda Giken Kogyo Kabushiki Kaisha of Japan, describes an alternative approach to the prevention of spark discharge. Okuma et al. discloses a spark arrester that includes a filter structure with a cylindrical body disposed in an expansion chamber of a muffler assembly. Carbon particles (sparks) are filtered from the exhaust stream as the exhaust travels from one chamber in the muffler to another. The cylindrically shaped, metal mesh screen acts as the filter for the carbon particles in this muffler design.  
           [0014]    While the prior art provides several examples of mufflers that effectively attenuate sound and reduce the emission of sparks, they usually rely on a number of exhaust chambers (such as chambers  102   a - 102   f  illustrated in FIG. 1) to accomplish these functions. The division of a muffler into many separate chambers increases the overall weight of the muffler. In addition, the greater the number of chambers in the muffler, the greater the cost to manufacture that muffler.  
           [0015]    Accordingly, a need has developed for a muffler system with few internal chambers that can attenuate noise and reduce or eliminate the emission of sparks so that the muffler will be both lightweight and more economical to manufacture.  
           [0016]    Finally, a need has developed for more compact (in size) mufflers that perform the functions discussed above. Smaller mufflers save space, thereby providing more room for other components in the host vehicle, such as an automobile or a recreational vehicle.  
         SUMMARY OF THE INVENTION  
         [0017]    It is, therefore, one aspect of the present to improve the noise attenuation and spark arresting capabilities of mufflers by comparison with those in the prior art.  
           [0018]    Another aspect of the present invention is to reduce the number of chambers within a muffler without sacrificing the muffler&#39;s ability to attenuate sound and reduce or eliminate the discharge of sparks.  
           [0019]    Another aspect of the present invention is to provide an All Terrain Vehicle (“ATV”) with a muffler system that minimizes risk of fire to minimize environmental damage caused by the use of ATVs in woodland terrain.  
           [0020]    According to one preferred embodiment of the present invention, a muffler is described with a housing having an input and an output. At least one plate is disposed within the housing to divide it into at least a first and a second internal chamber. At least one tube is disposed through the plate, the tube having first and second ends with a bend therebetween, the bend altering an orientation of the second end of the tube so that the second end faces an interior surface of the housing. The housing, the plate, and the tube establish a path for the exhaust between the input and the output. In addition, the first and second internal chambers cooperate to attenuate sound, and the tube affects the path of the exhaust to arrest the discharge of sparks from the output.  
           [0021]    These and other aspects of the present invention will be revealed by the discussion that follows. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and, together with the description, explain aspects, advantages, and principles of the invention. In the drawings:  
         [0023]    [0023]FIG. 1 illustrates a cross-sectional view of a prior art muffler system and its associated muffler chamber;  
         [0024]    [0024]FIG. 2 illustrates a cross-sectional view of a perforated plate of the prior art assembly of FIG. 1;  
         [0025]    [0025]FIG. 3 illustrates a side view of an exemplary ATV that embodies the present invention;  
         [0026]    [0026]FIG. 4 is a schematic view of an exemplary engine muffler system in accordance with the present invention;  
         [0027]    [0027]FIG. 5 is a perspective view of a partitioning member and separating tubes in accordance with the present invention;  
         [0028]    [0028]FIG. 6 is a side view of one of the separating tubes of FIG. 5; and  
         [0029]    [0029]FIG. 7 is a plan view of the partitioning members and the tubes illustrated in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0030]    The following detailed description refers to the accompanying drawings that illustrate exemplary embodiments consistent with the present invention. Other embodiments are possible and modifications may be made to the embodiments without departing from the spirit and scope of this invention. Therefore, the following detailed description is not meant to limit the invention solely to the embodiments described.  
         [0031]    [0031]FIG. 3 is a perspective view showing an all-terrain vehicle (ATV)  100 . The ATV  100  includes a frame  120  from which a pair of front wheels  102  and a pair of rear wheels  103  are operatively suspended. Handlebars  110  operatively connect to wheels  102  to provide steering for ATV  100 . Also, a seat  104  is disposed in frame  120  to accommodate a rider of the ATV  100 . A suitable power unit, e.g., an internal combustion engine  150 , is carried by frame  120  and provides drive power for (either or both of) the front and rear wheels  102  and  103  through a suitable transmission (not shown). Exhaust from the engine  150  is conducted to a muffler  1  constructed in accordance with the present invention.  
         [0032]    [0032]FIG. 4 provides a detailed view of the muffler  1  in which exhaust from the engine  150  enters through an inlet, e.g., inlet port  4 . As discussed above, the engine exhaust is hot and may contain sparks that are formed of hot carbon particles. The exhaust is channeled through the inlet port  4  and provided to a first expansion chamber  6 . The first expansion chamber  6  is provided as a first stage of noise reduction for the engine exhaust, reducing the noise by alternately compressing and expanding the hot gases in the engine exhaust. The first expansion chamber  6  may be configured to filter noises within a first predetermined frequency range. The first predetermined frequency range could include, for example, low frequency noises. For example, as shown in FIG. 4, the first expansion chamber may include a first screen  7  with a double-walled structure having a first wall  7   a  with holes or perforations and a second wall that is substantially solid. A sound absorbing material, e.g., stainless steel wool, may be provided between the first and second walls  7   a  and  7   b  for alternating sound.  
         [0033]    A first end of the first expansion chamber  6  is connected with the inlet port  4  and configured to receive the exhaust from the inlet port  4 . The other end of the first expansion chamber  6  is connected with a first end of a cylindrical housing  8 . As shown in FIG. 4, the first expansion chamber  6  forms a partial coaxial connection with the cylindrical housing  8 .  
         [0034]    Next, a disc-shaped partitioning member  10  is provided for partitioning the cylindrical housing  8  into a first portion  8   a  and a carbon accumulation section  8   b . The partitioning member  10  may be connected to the housing  8 , e.g., by welding. The first portion  8   a  defines a second expansion chamber. The partitioning member  10  includes a number of apertures  11  for placement of a corresponding number of tubular pipes  12  therethrough. FIG. 5 provides a more detailed view of the partitioning member  10 , the apertures  11 , and the tubular pipes  12 .  
         [0035]    In FIG. 5, the apertures  11  are shown to be positioned near a peripheral edge of the partitioning member  10 . Each pipe  12  has a proximal end  12   a  and a distal end  12   b  portion, as illustrated more clearly in FIG. 6. Additionally, when placed within the cylindrical housing  8 , each pipe  12  is positioned such that its proximal end  12   a  is positioned between the partitioning member  10  and the first expansion chamber  6 . Further, as illustrated in FIG. 6, each pipe  12  is straight at its proximal end  12   a  and has a bend  12   c  at its distal end  12   b . Further, as illustrated in FIG. 4, a longitudinal axis  12 ′ of the pipes  12  is shown to be aligned with a longitudinal axis  9  of the cylindrical housing  8 , although the axis  12 ′ could be angled with respect to the axis  9 .  
         [0036]    The positioning of the partitioning member  10  within the cylindrical housing  8 , and the insertion of the tubular pipes  12  through the apertures  11  of the partitioning member  10 , facilitate the separation of the carbon particles from the exhaust gases. During operation, the hot gases of the engine exhaust flow through the first expansion chamber  6  and into the second expansion chamber  8   a . While the gases flow completely through the tubular pipes  12  and through the carbon accumulation section  8   b  of the cylindrical housing  8 , the carbon particles are extracted from the exhaust gas at least in part by the tubular pipes  12  and are then trapped in the carbon accumulation section  8   b . Specifically the bends  12   c  (FIG. 6) in the distal end portions  12   b  of the pipes  12  direct the carbon particles into a carbon trap  14  of the carbon accumulation section  8   b . The carbon trap  14  could include a screen  20 .  
         [0037]    The length of the pipes  12 , the angle of the bends  12   c , and the precise angular orientation of the distal end portions  12   b  are determined based upon the degree of desired carbon particle arresting and other desired performance characteristics of the muffler system  1 , such as frequency attenuation. For example, the length, the angle of the bends and/or other dimensions (e.g., the diameter) of the pipes  12  can be selected to attenuate sound at a predetermined frequency. Similarly, a diameter and/or cross-section of the tubes  12  also is chosen based upon desired operational characteristics.  
         [0038]    [0038]FIGS. 6 and 7 illustrate angles associated with the pipes  12 . FIG. 6 shows an angle (α) associated with each pipes  12  and formed by the intersection of the axis  12 ′ and an axis  12 ″. Each angle (α) may be within a range of angles, e.g., from 5 to 90 degrees, depending on desired muffler characteristics. Of course, the angle (α) could be more than 90° or less than 5°, if desired. Angle (α), shown in FIG. 7, is formed from an intersection of an axis  10 ′ or an axis  10 ″ of the partitioning member  10 , with the axis  12 ″ of one of the pipes  12 . The angle (α) may be within a range of angles from 0 to 90 degrees, depending on the desired muffler characteristics. Of course, the angle (β) could be less than 0° or greater than 9° if desired. In the example shown, the angle (β) is  65 °, the angle y is 85°, and the angle Ø is 55°.  
         [0039]    The bends  12   c  are structured and arranged to channel the carbon particles in the direction of the carbon trap  14 . A combination of factors, such as the velocity of the carbon particles, their direction of travel, and gravity, cause the particles to accumulate in the carbon trap  14 . The carbon particles enter the tubular pipes  12  at the proximal end  12   a  and flow through the pipe  12 . The movement of the exhaust causes the particles to exit the pipes through the distal end  12   b . Since the distal ends  12   b  are angled, the particles exit the tubes  12  and enter the carbon trap  14  in a rotating manner, creating centrifugal motion. The centrifugal motion of these rotating particles causes the particles to accumulate along the inside of the carbon trap  14 . Although the apertures  11  in the positioning member  10  are shown to be symmetrically arranged with respect to one another, this symmetrical arrangement is not required.  
         [0040]    Since the carbon particles from the engine exhaust become trapped in the carbon trap  14 , over time these trapped particles begin to accumulate. In order to remove these accumulated particles, a plug  16  is provided. A user of the muffler system  1  can remove the plug  16  in order to release the accumulated carbon particles from the carbon accumulation section  8   b.    
         [0041]    Next, a noise absorption section  18  is provided in the carbon accumulation section  8   b  for reducing the noise associated with the engine exhaust gases. Finally, an outlet port  26  is provided adjacent to the noise absorption section  18  to permit the engine exhaust gases to escape into the atmosphere. A second screen  24 , which may be similar in construction to the first screen  7 , is provided in an outlet of the muffler  1 , e.g., a port  26 , to provide filtering of noises within a second predetermined frequency range. The second screen  24  could be filled with, for example, stainless steel wool. The second frequency range may include, for example, higher frequency noises.  
         [0042]    As seen in the illustration of FIG. 4 and the discussion above, the carbon particle arresting function and the tuning function are performed in only a few chambers, unlike prior art systems that require many chambers to perform the separation and tuning functions. Therefore, a muffler system constructed and arranged in accordance with the present invention can be manufactured more easily and provided in a smaller muffler housing. Also, a muffler system in accordance with the present invention is capable of performing the same functions as conventional muffler systems in larger housings.  
         [0043]    The foregoing description of the preferred embodiments provides an illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible consistent with the above teachings or may be acquired from practice of the invention.