Abstract:
A marine muffler adapted with an internally tunable sound suppression structure is adaptable to different configurations thereby allowing for structural adjustments to optimize sound suppression and minimize backpressure for particular engine and exhaust conditions. A muffler housing defines an interior volume and includes an exhaust inlet and outlet. The outlet has a reduced diameter as compared with the inlet such that the exhaust gas accelerates through the muffler. An inclined baffle partitions the interior volume into a lower chamber in communication with the exhaust inlet and an upper chamber in communication with the exhaust outlet. Exhaust ducts attached to each side wall penetrate the baffle thereby placing the upper and lower chambers in fluid communication. A corrugated partition divides each exhaust duct into a plurality of non circular conduits. The muffler may be tuned by selectively capping one or more conduit outlets.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/885,538, filed on Oct. 2, 2013. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all rights whatsoever. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to marine exhaust systems for use with internal combustion marine engines, and more particularly to an improved marine muffler having an inclined baffle assembly and tunable pulse attenuation exhaust conduits that provide improved exhaust noise silencing. 
     2. Description of Related Art 
     Marine vessels are typically configured with a propulsion system powered by an internal combustion engine mounted within the vessel hull. Exhaust generated by the engine is commonly combined with cooling water and routed through exhaust conduit to the stern of the vessel via one or more exhaust ducts where the exhaust is discharged through one or more exhaust ports formed in the transom. One or more mufflers are installed within the exhaust duct(s) to silence noise associated with the engine and exhaust gases. 
     A variety of structures are known in the background art for use in silencing marine exhaust noise. The present inventor has invented a number of novel marine exhaust components that have greatly improved the silencing and efficiency of marine exhaust systems. Among those inventions developed by a named inventor for the present invention are the following: 
     
       
         
               
               
             
           
               
                   
               
               
                 U.S. Pat. No. 
                 Entitled 
               
               
                   
               
             
             
               
                 4,918,917 
                 Liquid Cooled Exhaust Flange 
               
               
                 5,196,655 
                 Muffler for Marine Engines 
               
               
                 5,228,876 
                 Marine Exhaust System Component Comprising a Heat 
               
               
                   
                 Resistant Conduit 
               
               
                 5,262,600 
                 In-line Insertion Muffler for Marine Engines 
               
               
                 5,444,196 
                 In-line Insertion Muffler for Marine Engines 
               
               
                 5,504,280 
                 Muffler for Marine Engines 
               
               
                 5,616,893 
                 Reverse Entry Muffler With Surge Suppression Feature 
               
               
                 5,625,173 
                 Single Baffle Linear Muffler for Marine Engines 
               
               
                 5,718,462 
                 Muffler Tube Coupling With Reinforcing Inserts 
               
               
                 5,740,670 
                 Water Jacketed Exhaust Pipe for Marine Exhaust Systems. 
               
               
                 6,564,901 
                 Muffler for Marine Engine 
               
               
                 7,581,620 
                 Marine Muffler with Angularly Disposed Internal Baffle 
               
               
                 7,905,322 
                 Marine Muffler with Angularly Disposed Internal Baffle 
               
               
                 7,942,238 
                 Marine Muffler with Angularly Disposed Internal Baffle 
               
               
                 8,246,403 
                 Marine Water Drop Muffler 
               
               
                 8,651,907 
                 Water Jacketed Marine Exhaust Components Having 
               
               
                   
                 Multiple Stream Spray Ring Configurations 
               
               
                   
               
             
          
         
       
     
     In U.S. Pat. No. 5,262,600, the first named inventor herein disclosed an in-line insertion muffler for marine engines employing a first housing encompassing a second housing which is partitioned by an angularly disposed inner planar baffle that has proven extremely effective in reducing engine noise. In U.S. Pat. No. 5,444,196, the first named inventor herein disclosed an improved version of the in-line muffler having a corrugated sleeve disposed between in the first and second housings. In U.S. Pat. No. 5,625,173, the first named inventor herein disclosed a single baffle linear muffler with an angularly disposed baffle that may be planer, convex, or concave. In U.S. Pat. No. 7,581,620, the first named inventor herein disclosed a marine muffler comprising an elongate cylindrical housing having an inlet and an outlet, and an internal volume partitioned by an angularly disposed internal baffle into a lower chamber in communication with the inlet and an upper chamber in communication with the outlet. A centrally disposed duct passes through the baffle to allow exhaust gas and exhaust cooling water to flow from the lower inlet chamber to upper outlet chamber. 
     The various linear mufflers made in accordance with the above-referenced patents have achieved tremendous success and widespread acceptance within the marine industry. Such muffler systems have been successfully installed on a wide variety of marine vessels having engines in excess of 1,000 horsepower. Due to the myriad engine packages and exhaust configurations, there exists a need for advancements in marine mufflers that allow for structural adjustments to the muffler to optimize sound suppression and minimize backpressure for specific engine makes and models. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention overcomes limitations present in the art by providing an improved muffler for marine engines having an internal tunable sound suppression structure that is adaptable to different configurations thereby allowing for structural adjustments to the muffler to optimize sound suppression and minimize backpressure for particular engine and exhaust conditions. A marine muffler in accordance with the present invention comprises a housing defining an interior volume and including an exhaust inlet and outlet, and an inclined baffle partitioning the interior volume into a lower chamber in communication with the exhaust inlet and an upper chamber in communication with the exhaust outlet. Both the inlet and outlet are preferably formed by generally tubular/cylindrical structures, with the outlet having a reduced diameter as compared to the inlet such that the exhaust gas accelerates through the muffler. The housing preferably defines a generally rectangular cross-section that includes generally planar opposing side walls. Generally vertically disposed exhaust ducts, attached to each side wall, penetrate the baffle thereby placing the upper and lower chambers in fluid communication. Each exhaust duct preferably includes a corrugated partition that divides the exhaust duct into a plurality of non-circular conduits. Each exhaust duct is preferably positioned such that a plurality of conduit inlets are positioned below the baffle in proximity to the bottom of the housing, with a plurality of conduit outlets positioned above the baffle in proximity to the top of the housing. A significant aspect of the present invention involves selectively closing or capping the top portions of one or more conduits thereby modifying exhaust flow dynamics through the muffler resulting corresponding changes in sound suppression and backpressure. A further significant aspect of the present invention involves adapting the caps with relatively small apertures which has proven effective in reducing noise and backpressure. By selectively capping one or more conduits in this manner the muffler can be tuned for maximum performance and silencing. 
     Accordingly, it is an object of the present invention to provide an improved marine muffler configured to accelerate exhaust gas passing therethrough. 
     Still another object of the present invention is to provide such a marine muffler wherein the baffle partitions the muffler into a lower inlet chamber and an upper outlet chamber. 
     Yet another object of the present invention is to provide such a muffler wherein the baffle is adapted with tunable exhaust ducts in communication with said inlet and outlet chambers. 
     Still another object of the present invention is to provide such a muffler wherein the duct is partitioned into a plurality of sub-passages, at least some of which are capped such that the muffler may be tuned for a particular engine/exhaust configuration. 
     In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an inlet end perspective view of a marine engine muffler in accordance with the present invention; 
         FIG. 2  is a side view thereof; 
         FIG. 3  is a sectional side view thereof taken along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a sectional top view taken along line  4 - 4  of  FIG. 1 , to reveal internal structure; and 
         FIG. 5  is perspective sectional view thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention may be understood more readily by reference to the following detailed description taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Any and all patents and other publications identified in this specification are incorporated by reference as though fully set forth herein. 
     Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. 
     With reference now to the drawings,  FIGS. 1-5  depict a preferred embodiment of a muffler, generally referenced as  10 , in accordance with the present invention. Muffler  10  is primarily characterized as having a generally hollow muffler housing  12  formed about a longitudinal axis with opposing ends forming a generally cylindrical inlet  14  and a generally cylindrical outlet  16 . Inlet  14  is preferably larger in diameter (e.g. larger cross-sectional area) than outlet  16  so as to cause exhaust gas flowing therethrough to accelerate such that exhaust gas exits outlet  16  with a greater velocity than the velocity if measured at inlet  14 . In a preferred embodiment, housing  12  is fabricated from a composite material such as temperature resistant fiberglass, however, any suitable material is considered within the scope of the present invention. Housing  12  preferably includes generally planar opposing side walls, each referenced as  20 , a top  22  and a bottom  23 . Housing  12  preferably comprises a generally rectangular cross-section. In an alternate embodiment, top  22  and bottom  23  may define arcuate interior surfaces which may be either convex or concave when viewed from the interior of housing  12 . Providing the housing with arcuate top and bottom surfaces has been found to provide improved strength/stiffening and thus reduce vibration of the top and bottom surfaces thereby reducing housing vibration generated noise. These arcuate surfaces may be formed by curved inserts affixed to the top and bottom of the housing interior or may be integrally formed as the top and bottom surfaces. Housing  12  is preferably elongate. More particularly, the length of the housing (as measured from inlet to outlet) is larger than the housing width (as measured from side-to-side) and housing height (as measured from top to bottom). The present invention is suitable for use with housings having various shapes and thus should not be construed as being limited to the housing configuration disclosed above. 
     As best depicted in  FIG. 3 , muffler housing  12  defines an internal volume and includes an angularly disposed/inclined baffle  24 , having a peripheral edge in sealing engagement with the inner surface of housing  12  so as to divide the internal volume into a lower/inlet chamber  26  (e.g. the volume disposed below the baffle) and an upper/outlet chamber  28  (e.g. the volume disposed above the baffle). In a preferred embodiment baffle  24  is generally planar, however, any suitable shape, such as concave or convex (about either a longitudinal axis or alternatively a transverse axis when viewed from above), is contemplated and considered within the scope of the present invention. Baffle  20  is angularly disposed or inclined as illustrated in  FIG. 3 . As should be apparent, the angle of inclination will vary depending on the dimensions of the muffler housing, however, in the preferred embodiment the angle of inclination is dictated by the length and height of the housing as the baffle preferably divides the housing interior into roughly equal upper and lower chambers. More particularly, baffle  20  extends angularly downward from in proximity to the top of housing  12  proximal muffler inlet  14  to in proximity of the bottom of housing  12  proximal muffler outlet  16 . As should be apparent, the exact terminus of baffle  20  is not considered particularly important so long as the interior of housing  12  is divided into a lower chamber at the inlet side and an upper chamber at the outlet side. While baffle  20  is preferably disposed so as to define upper and lower chambers of generally equal volumes, the baffle may be configured to form chambers of different sizes and/or dimensions in accordance with the present invention. Accordingly, exhaust entering the muffler enters the inlet chamber  26 , which chamber is defined by the lower surface of baffle  24  and the inner surfaces of opposing side walls  20  and bottom  23 . 
     An exhaust duct, generally referenced as  30 , has edges attached in sealing engagement to the inner surface of each opposing side wall  20  and extends through baffle  24 . Each exhaust duct  30  includes an open bottom end  32 , and an open top end  33  disposed above the bottom end  32 . Exhaust ducts  30  are generally vertically disposed and penetrate baffle  24  thereby placing the upper and lower chambers,  26  and  28 , in fluid communication. Each exhaust duct  30  is preferably defines a generally rectangular cross section, and may terminate in laterally outwardly flared ends  31 , as best seen in  FIG. 4 . Each exhaust duct  30  preferably includes a corrugated partition  34  that divides the exhaust duct into a plurality of non-circular exhaust conduits, referenced as  36 . Exhaust duct  30  and corrugated partition  34  further function to stiffen the generally planar housing side walls  20 , thereby reducing the tendency of (non-reinforced) side walls to vibrate in response to exhaust gas pulsation. This reduction in housing side wall vibration results in a quieter muffler by reducing the transmission of vibration related noise external to housing  12 . Exhaust ducts  30  are preferably sized and positioned such that the bottom ends thereof place the conduit inlets in proximity to the bottom  23  of the housing  12 , and the top ends thereof place the conduit outlets in proximity to the top  22  of housing  12 . 
     As best seen in  FIGS. 3 and 4 , a significant aspect of the present invention involves selectively closing-off or capping the top portions of one or more conduits, by affixation of one or more cap(s) referenced as  38 A and  38 B. Caps  38 A are attached in sealing engagement with the top  33  of duct  30  so as to seal off one or more exhaust conduits  36  thereby modifying exhaust flow dynamics through the muffler resulting corresponding changes in sound suppression and backpressure. By selecting the number and location of conduits  36  to cap, the muffler may be tuned to maximize sound suppression and backpressure. By way of example,  FIG. 3  illustrates capping four ( 4 ) conduits at each end of duct  30 . As should be apparent, the number and location of capped conduits may vary depending upon the exhaust flow characteristics and dynamics for a given application. Thus, any suitable capping arrangement, including the non-use of caps  38 A and  38 B, is considered within the scope of the present invention. In a preferred embodiment cap  38 A is affixed in sealing engagement with the top portion  33  of duct  30  on the inlet side of muffler  10  so as to substantially seal off one or more exhaust conduits  36  disposed toward at the inlet end of duct  30 . Similarly cap  38 B is affixed in sealing engagement with the with the top portion  33  of duct  30  on the outlet side of muffler  10  so as to substantially seal off one or more exhaust conduits  36  disposed toward at the outlet end of duct  30 . Further, the preferred positioning of caps  38 A and  38 B is as shown in  FIG. 3 , namely cap  38 A fixed in covering relation with one or more exhaust conduits  36  on the inlet end of duct  30 , and cap  38 B fixed in covering relation with one or more exhaust conduits  36  on the outlet end of duct  30 , with the remaining exhaust conduits therebetween left open (e.g un-capped). Accordingly, muffler  10  may be adapted with a single cover, e.g.  38 A, while not employing the second cover  38 B. The use of both caps  38 A and  38 B is preferred, but considered optional. 
     A further significant aspect of the present invention involves the ability to further tune the muffler by forming relatively small apertures  39  in one or more of the caps  38 A and/or  38 B. Apertures  39  allow for limited exhaust flow through the otherwise capped conduits and thereby further allow the muffler to be tuned for a specific application. By varying the number, location, and radius of apertures  39  the performance of the muffler may be further tuned and refined. Apertures  39  are preferably ⅛″ in diameter, however, the size may be adjusted to any suitable diameter within the scope of the present invention. 
     As best illustrated in  FIG. 3 , exhaust gas and exhaust cooling water enter the inlet chamber  26  of muffler  10  via inlet  14 . Under certain conditions wherein the engine is operating at relatively low RPM&#39;s, it is expected that exhaust gas cooling water will begin to pool on the housing floor or bottom  23  within inlet chamber  26 . As the water level rises, it will eventually begin to choke the flow paths to the exhaust conduit inlets at the lower portion  32  of duct  30 . As a result, the exhaust gas velocity will naturally increase thereby causing entrainment of the water with the exhaust gas and as the exhaust gas flows upward through the un-capped, generally centrally disposed conduits  36 . The exhaust gas and water exit duct  30  through the top portion  33  of duct  30  via the exhaust conduits  36  into outlet chamber  28  whereafter the exhaust gas and entrained cooling water are allowed to exit via muffler outlet  16 . A muffler in accordance with the present invention may be fabricated from composite material, such as heat resistant fiberglass, or any other suitable material. 
     The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.