Patent Publication Number: US-6341664-B1

Title: Exhaust muffler with stamp formed internal assembly

Description:
TECHNICAL FIELD 
     The subject invention relates to vehicular exhaust mufflers having an outer shell surrounding a stamp formed internal assembly and end caps and inlet and exhaust tubes at opposed ends of the outer shell. More particularly, the subject invention is directed to an improved stamp formed internal assembly for decreasing manufacturing costs and increasing the muffler useful life. 
     BACKGROUND OF THE INVENTION 
     Vehicular mufflers are today very commonly constructed using stamp formed sheet metal outer shells as well as internal assemblies. The internal assemblies quite often incorporate and form baffles, exhaust tubes and other components utilized in attenuating and decreasing the apparent sound generated by the vehicle engine. By stamp forming, the various muffler component parts manufacturing costs can be significantly decreased. Several such mufflers which have been constructed using various stamp formed component parts are, for example, shown and described in Gerber, U.S. Pat. No. 5,816,361, Gerber et al., U.S. Pat. No. 5,717,173, Wilcox, et al., U.S. Pat. No. 4,941,545 and Wolfhugel, U.S. Pat. No. 4,396,090. 
     The Gerber, U.S. Pat. No. 5,816,361, for example, discloses a muffler constructed with a tubular outer shell and end caps attached thereto at each end thereof An internal cartridge or assembly is provided and constructed of stamp formed component parts. These assemblies or cartridges are constructed using two identical stamp formed plates which have been placed in mirror relation with respect to one another forming baffles at each end thereof and tubes extending therebetween. Each of the tubes include perforations. Although this muffler and the stamp formed assembly therein provide for a generally inexpensive means of manufacturing, it has shortcoming and drawbacks. For example, the stamp formed plates are assembled by spot welding and, as a consequence, the coating of the sheet metal as well as the sheet metal itself is weakened thereat thereby causing premature deterioration thereof by the acidic water which typically condenses within the muffler. Additionally, this condensate of acidic water is not readily removed from the central chambers between the baffles causing accumulation thereof and furthering premature deterioration of the stamp formed plates and assembly. Further yet, most prior mufflers tend to be limited in their application to only certain vehicles or with only certain exhaust engines. 
     Accordingly, a need exists for a muffler constructed using stamp formed sheet metal component parts which decreases manufacturing costs and which is more resistant to deterioration and which is, further, more universal for use on different vehicles and exhaust engines. 
     SUMMARY OF THE INVENTION 
     It is the principal object of the present invention to overcome the above-discussed disadvantages associated with prior mufflers constructed using stamp formed sheet metal components. The present invention overcomes the disadvantages associated with prior mufflers by providing a muffler having a tubular outer shell and end caps connected to opposed ends thereof. A pair of stampings or stamp formed sheet metal plates are connected to each other in a face to face relationship and forming an assembly which includes a least three tubes extending between baffles. The sheet metal stampings are identical to one another and are also located in mirror image relation with respect to one another for forming the assembly. The assembly is received within the muffler outer shell and an inlet tube extends through one of the end caps and communicates with one of the assembly tubes. At the other end of the muffler, an outlet tube extends through that end cap and communicates with another one of the assembly tubes. As constructed, the assembly baffles divide the volume within the outer shell for providing a first chamber between the muffler inlet end and a baffle, a second chamber between the outlet end and the other baffle and a central chamber between the baffles. Preferably, the stampings portions forming the assembly between the baffles extend to the inner surface of the outer shell thereby dividing the central chamber into upper and lower central chambers. 
     Each of the stampings or plates include baffle portions at opposing ends and further include valley portions and semicircular portions extending longitudinally between the baffle end portions. The valley portions are located between the semicircular portions so that, when the stampings are located in mirror image relation and face to face to one another with the valley portions of one stamping located adjacent the valley portion of the other stamping and the semicircular portions of one stamping located adjacent the semicircular portions of the other stamping, the resultant assembly includes longitudinally extending tubes formed by the semicircular portions extending between the end baffle portions. 
     The sheet metal stampings or plates are attached to one another by rivets which are provided at the valley portions of the stampings. Preferably, the stampings are provided with alternating rivet holes and annular protrusions in each of the stamping valley portions such that, when two stampings are placed in mirror image relation with respect to one another and face to face, the annular protrusions of one stamping are received within the rivet holes of the other stamping. After the stampings are place in mirror image relation with respect to one another and with the annular protrusions of one of the stampings extending through the rivet holes of the other stamping, the annular protrusions are deformed radially outwardly thereby clamping or fixedly attaching the stampings together thereat. With this rivet type attachment, the protective coating of the sheet metal is not damaged or otherwise compromised except for the cut surfaces of the rivet holes and annular protrusions. Additionally, the deforming or bending over of the sheet metal over the rivet holes further reinforces the attachment providing additional mass unlike, for example, spot welding. 
     So as to further decrease deterioration of the stampings and increase the life of the muffler, each of the baffles are provided with an impression whereby, upon insertion of the assembly within the outer shell and locating the baffles therein, the impressions form weep holes between the upper and lower chambers and the first and second chambers. Thus, the acidic water which condenses within the upper and lower central chambers readily and easily exits through these weep holes and to the first or second chambers wherefrom the water can be expelled through a hole provided in the muffler outer shell or end cap. By only providing an impression along the outer edge of the stamping portion which forms the baffle, the sheet metal coating is again not removed or otherwise compromised thereby preventing rapid deterioration thereof and lengthening the life of the muffler. 
     The muffler is further improved by providing a design which is substantially more universal and usable on different vehicles and exhaust engines. In this regard, each of the assembly tubes are provided with one or more rows of openings for providing communication between the assembly tubes and the upper and lower central chambers. The openings are louver shaped and, preferably, one-half of the row of louvers open longitudinally generally toward the inlet end of the muffler and the other one-half of the row of louvers open generally longitudinally in the opposite direction toward the exhaust end of the muffler. It has been found that, most preferably, two rows of louvers identical to the first and wherein each row includes ten louver shaped openings, five of which open in the direction of the inlet end and the other five opening in appositive direction toward the exhaust end, advantageously cause exhaust noise to be attenuated in the upper and lower central chambers for many different vehicles and exhaust engines. Yet more preferably, each of the two rows of louver shaped openings are located on each stamping semicircular portion less than forty-five degrees radially from each other around the semicircular portion which forms the assembly tubes. 
     In one form thereof, the present invention is directed to a muffler including a outer shell having an inlet end and an exhaust end. A pair of stampings are provided and form an assembly which includes a least three tubes extending between baffles. The assembly is received within the outer shell and therewith forms a first chamber between the inlet end and a baffle, a second chamber between the outlet end and a baffle and a central chamber between the baffles. An inlet tube extends through the inlet end and communicates with one of the assembly tubes. An outlet tube extends through the outlet end and communicates with another one of the assembly tubes. A plurality of openings are provided between at least one of the assembly tubes and the central chamber. The stampings are provided with an impression for thereby forming weep holes between the central chamber and the first and second chambers whereby water may travel between the central chamber and the first and second chambers. The assembly tube openings are louver shaped. Each of the stampings are identical to one another and include valley portions between semicircular portions. The stampings are located in mirror image relation with respect to one another with the valley portions of one stamping located adjacent the valley portions of another stamping and the semicircular portions of one stamping located adjacent to the semicircular portions of the other stamping thereby forming the assembly. A rivet assembly is provided at the valley portions for retaining the stampings together. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of a muffler constructed in accordance with the principles of the present invention; 
     FIG. 2 is an exploded perspective view of the muffler shown in FIG. 1 generally showing the method of assembly of the various components thereof; 
     FIG. 3 is a side elevation view of the muffler shown in FIG. 1 with the outer shell cut away and showing the stamping assembly received therein; 
     FIG. 4 is a perspective view of a stamping assembly constructed and assembled in accordance with the principles of the present invention; 
     FIG. 5 is an end view of the stamping assembly shown in FIG. 4; 
     FIG. 6 is a side elevation view of the stamping assembly shown in FIG. 4 ; 
     FIG. 7 is a cross-sectional view taken generally along line  7 — 7  in FIG. 4; 
     FIG. 8 is a cross-sectional view taken generally along line  8 — 8  in FIG. 5; 
     FIG. 9 is a cross-sectional view taken generally along line  9 — 9  in FIG. 5; 
     FIG. 10 is a top plan view of a stamping constructed in accordance with the principles of the present invention; 
     FIG. 11 is a cross-sectional view taken generally along line  11 — 11  of FIG. 10; 
     FIG. 12 is a cross-sectional view taken generally along line  12 — 12  of FIG. 10; 
     FIG. 13 is a cross-sectional view taken generally along line  13 — 13  of FIG. 10; 
     FIG. 14 is a cross-sectional view similar to FIG. 11 but depicting another embodiment of a second stamping in accordance with the principles of the present invention; and, 
     FIG. 15 is a cross-sectional view taken generally along line  15 — 15  and depicting the second embodiment stamping assembly. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     The exemplifications set out herein illustrate preferred embodiments of the invention in one form thereof and such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Referring initially to FIGS. 1-4, there is shown a muffler generally depicted by the numeral  10  and having an outer shell  12  having a generally oval shape and defining an inlet end  14  closed off with an inlet end cap  16  and an outlet end  18  closed off with an outlet end cap  20 . A stamping assembly generally depicted by the numeral  22  is constructed of two generally identical stampings or plates  24  located on top of one another and in mirror image relation with respect to one another. The stamping assembly  22  is received within the muffler outer shell  12  preferably centered or equidistant from each of the inlet and outlet ends  14  and  18 . 
     Each of the stampings  24  include valley portions  26  between semicircular portions  28  such that when a set of stampings  24  are located in mirror image relation with respect to one another the valley portions  26  of one stamping are located adjacent the valley portions  26  of the other stamping and the semicircular portions  28  also located adjacent one another thereby forming three longitudinally extending tubes or openings  30 . The stampings  24 , at each longitudinal end thereof, are also provided with baffle portions  32  extending radially outwardly to a perimeter area  34  formed with an oval shape similar to the oval shape of the inner surface of outer shell  12 . In this manner, when two stampings  24  are assembled to one another in a mirror image relation with respect to one another, baffles which are shown and generally depicted by the numeral  36  are formed having a cross-sectional shape and size so as to fit within the outer shell  12  as shown. Essentially, the perimeter areas  34  of portions  32  engage the inner wall of the outer shell  12  thereby dividing the muffler outer shell  12  into a first chamber  38  between the inlet end  14  or end cap  14  and a baffle  36  and a second chamber  40  between the outlet end  18  or end cap  20  and a baffle  36 . The stampings  24  further include side edges  42  such that when the assembly  22  is received within the outer shell  12 , the side edges  42  extend substantially to the inner wall of the stamping  12  thereby further dividing the central chamber located between the baffles  36  into an upper central chamber  44  and a lower central chamber  46 . 
     An inlet tube  48  extends through a hole in inlet end cap  16  and communicates with one of the assembly tubes  30 . An outlet tube  50  extends through a hole in the outlet end cap  20  and communicates with another one of the assembly tubes  30 . Thus, in operation, exhaust gases entering the inlet tube  48  are directed past the first chamber  38  and through one of the assembly tubes  30  to the second chamber  40 . As the outlet tube  50  communicates with and is blocking one of the assembly tubes  30 , the exhaust gases are directed from the second chamber  40  through the remaining tube  30  (that tube not directly connected to either the inlet tube  48  or outlet tube  50 ) and back to the first chamber  38 . At the first chamber  38  the exhaust gases then travel back through the tube  30  connected to or communicating with the outlet tube  50  thereby exiting the muffler  10 . As more fully discussed hereinbelow, the stampings  24  and the assembly  22  are constructed in accordance with the principles of the present invention so as to resist corrosion and be generally long lasting and, further, so as to attenuate the sound from the exhaust engine generating the exhaust gases. 
     So as to resist corrosion of the muffler components as a result of the acidic condensation which accumulates within the muffler, the various components thereof including stampings  24 , outer shell  12 , end caps  16  and  20 , and inlet and outlet pipes  48  and  50  are all preferably made of cold-rolled low carbon steel with an aluminized coating. Additionally, each of the stampings  24  are formed with an impression  52  in each of the perimeter areas  34  of baffle portions  32 . The impressions, as shown, are formed by bending the metal thereat so as to form an elongate longitudinally extending channel in the perimeter areas  34  such that, when the assembly  22  is received within the outer shell  12 , a weep hole generally depicted by the numeral  54  is formed between the inner wall of the outer shell  12  and the impression or channel  52 . Thus, acidic condensation forming within either the upper or lower central chambers  44  or  46  may travel out through the weep holes  54  to either first or second chambers  38  or  40  and out of the muffler  10  through a hole in one of the end caps  16  or  20  (not shown) which is commonly used on all mufflers. 
     As shown in the figures, the perimeter area  34  is provided with some width and does not end with an abrupt edge at the inner surface of the outer shell  12 . Additionally, the impression  52  extends across the entire width of the perimeter area  34  and by merely bending the metal to form the channel, the aluminized coating of the cold-rolled sheet metal is retained. Thus, only the perimeter edge  56  whereat the stampings  24  have been cut are not covered with the corrosion resistant aluminized coating and only that perimeter edge is not protected from oxidation as a result of the acidic condensation. It is further noted that by providing the weep holes  54  at each of the baffles  36 , the acidic condensation may also travel from either of the first and second chambers  38  and  40  across either of the upper or lower central chambers  44  and  46  to wherever the water exhaust port hole may be located at either the inlet or outlet end caps  16  or  18 . As best seen in FIG. 6, the perimeter edge  56  of each of the stampings  24  is bent or “broken” radially inwardly. In this manner, when the stamping assembly  22  is “stuffed” or inserted longitudinally into the outer shell  12 , the perimeter edge  56  is more readily located properly for sliding the stamping assembly  22  longitudinally into the outer shell  12 . 
     As best seen in FIGS. 4,  7 , and  13 , the stampings  24  are preferably attached or retained together by rivet assemblies via the same sheet metal material as that of the stampings themselves. In this regard, at each of the valley portions  26 , the stampings  24  are provided with alternating rivet holes  58  and annular protrusions  60 . The annular protrusions  60  extend vertically downwardly as seen in FIG.  13  and have an outer diameter slightly smaller than the diameter of the rivet holes  58 . Additionally, the rivet holes  58  and annular protrusions  60  are located in the valley portions  26  in a pattern such that, when stampings  24  are located adjacent and in mirror image relation with respect to one another as depicted in FIGS. 2 and 4, the annular protrusions  60  of one stamping  24  are received through adjacent rivet holes  58  of the other stamping  24 . This also essentially locates the stampings  24  so as to form the stamping assembly  22  as shown in FIG.  4 . The annular protrusions  60  are thereafter stamped or otherwise deformed radially outwardly forming a rivet annular lip  62  so as to thereby retain the stampings  24  together. As seen in FIGS. 4 and 7, at each valley portion  26 , preferably, there are a total of five rivet connections with the rivet annular lip  62  of each alternating in direction vertically upwardly and downwardly. In this manner, any acidic condensation that may accumulate in either the upper or lower central chambers  44  or  46  and regardless of the position of the muffler (right side or upside down) the acidic water readily flows through the holes  64  extending through the annular protrusions  60  and thereafter out of the upper and lower central chambers  44  and  46  through weep holes  54 . As can be appreciated by alternating the location of the rivet annular lips  62  up and down, any acidic condensation is prevented from “puddling” or accumulating on the surface of the valley portions  26  by the height of the annular protrusions and lips  62 . Further yet, the aluminized coating is, for the most part, retained and the carbon steel thereunder does not become exposed other than at the outermost perimeter edge of the annular protrusions  60  which form the annular lip  62 . Nevertheless, because the rivet holes  58  are essentially wrapped by the metal forming the annular protrusion  60 , the overall connection between the stampings  24  is solid and a substantial amount of corrosion must occur to deteriorate the metal forming the protrusion  60  and to thereby cause the stampings  24  to separate from one another. 
     As best seen in FIG. 10, the pattern of alternating rivet holes  58  and annular protrusions  60  in the valley portions  26 a and  26 b preferably includes three rivet holes  58 , two of which are located at the proximal ends of the valley portions near the baffle portions  32 , and one of which is centrally located between the annular protrusions  60 . This pattern is repeated in valley portions  26   c  and  26   d  except that the rivet holes  58  and annular protrusions  60  are reversed. In this manner, as also discussed hereinabove, when the stampings  24  are located in mirror image relation with respect to one another as depicted in FIGS. 2 and 4, the opposing annular protrusions  60  of each stamping  24  match the pattern of the rivet holes  58  of the opposing stamping so as to be received therein as shown in FIGS. 4 and 7. It is noted that the side edges  66  of each of the stampings  24  extend generally linearly and are located radially outwardly such that they come in contact with the inner wall of the outer shell  12 . In this manner, the upper and lower central chambers  44  and  46  are better defined and separated from one another. 
     During use of muffler  10 , exhaust gases, in general, do not flow through the upper and lower central chambers  44  and  46  but, rather, those chambers attenuate or otherwise decrease the apparent sound emitted by the exhaust engine. In this regard, a plurality of openings  68  are provided in each of the semi-circular portions  28  forming the tubes  30 . These openings  68  provide communication between the flowing exhaust gases traveling through the tubes  30  and the upper and lower central chambers  44  and  46 . Openings  68  are made by stamping a lance or louver-shape portion  70  of the metal radially outwardly as best seen in FIGS. 9 and 11 so as to thereby form louver-shaped openings  68  as shown. Preferably, two rows of ten louver-shaped openings  68  are provided on each of the semi-circular portions  28  as shown in FIG. 10, thereby providing a total of four rows and forty louver-shaped openings in each of the tubes  30 . As best seen in FIG. 9, in each row of openings  68 , five or one-half of the louver-shaped openings open longitudinally toward one of the baffle portions  32  whereas the other five or one-half of the louver-shaped openings  68  open longitudinally in the opposite direction or toward the other baffle portion  32 . As best seen in FIG. 11, each of the rows of louver-shaped openings  68  are located at an angle α radially from each other about the central longitudinal axis of the tube  30 . Preferably, angle α is about 20 to 70 degrees and no greater than about 45 degrees. Very importantly, because one-half of the louver-shaped openings open longitudinally opposite the direction of the other one-half of the louver-shaped openings, regardless of the direction of travel of the exhaust gases, the upper and lower central chambers  44  and  46  operate and attenuate the sound substantially identically. Thus, the inlet tube  48  and outlet tube  50  can be connected for communication with any one of the formed tubes  30  so long as a serpentine exhaust flow pattern is achieved and the muffler  10  will, nevertheless operate generally identically and regardless of how the operator may install the muffler  10 . That is, the muffler can be installed upside down from the position shown in FIGS. 1 and 2 and will, nevertheless, operate the same. Indeed, muffler  10  could even be installed for directing the exhaust gases opposite the direction depicted by the arrows in FIG.  1  and muffler  10  will, nevertheless, operate substantially identically. As can be appreciated, this provides for a generally universal muffler capable of installation on many different vehicles and in different ways and locations. Further yet, it has been advantageously found that the louver-shaped openings  68  made by stamped lower shaped portions  70  as provided and as described hereinabove, provide attenuation in the upper and lower central chambers  44  and  46  sufficient for properly decreasing the apparent sound on many different exhaust engines and vehicles. Thus, muffler  10  can be used on many different exhaust engines and vehicles. 
     In another embodiment depicted in FIGS. 14 and 15, only a single row of ten louver-shaped openings  72  are provided at the apex of the semi-circular portions  28 . These louver-shaped openings  72  are somewhat larger than those of the embodiment of FIGS. 1-13 and are  9  formed by stamping a lance or louver-shaped portion  74  of the semi-circular portions  28 . As shown in FIG. 15, one-half or five of these louver-shaped openings  72  similarly open longitudinally toward one baffle portion  32  whereas the other one-half or five louver-shaped openings open in an opposite direction longitudinally toward the other baffle portion  32 . In this embodiment, a total of twenty such openings  72  are thus provided in each of the tubes  30 . Similarly, this design is also believed to be generally universal in nature for operation with various patterns of locations of the inlet and outlet tubes  48  ad  50  and for use with various different exhaust engines and vehicles. 
     While the invention has been described as having specific embodiments, it will be understood that it capable of further modifications. This application is, therefore, intended to cover any variations, uses or adaptations of the invention following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and fall within the limits of the appended claims.