# Patent

## Title
Muffler attachment system

## Abstract

A muffler for an internal combustion engine includes a first shell includes a flexible portion, an intake conduit, and a second shell coupled to the first shell. The intake conduit extends outwardly from the first shell and is configured to be inserted into an exhaust port of an engine. The flexible portion surrounds the intake conduit. Upon attachment to the engine, compression force is stored via elastic deflection of the flexible portion of the first shell, thereby pressing the intake conduit into the exhaust port such that a seal is formed.

## Background
This is a continuation of application Ser. No. 12/508,424, filed Jul. 23, 2009, which is incorporated herein by reference in its entirety.


BACKGROUND
The present invention relates generally to the field of combustion engines. More specifically the present invention relates to a system for attaching a muffler to a combustion engine configured for use with power equipment, such as lawn mowers, pressure washers, secondary generators, and the like.
The combustion process associated with internal combustion engines can be quite loud. As such, combustion engines are typically equipped with mufflers to reduce noise emissions. The muffler on a small engine is typically attached directly to the exhaust outlet of the cylinder block or cylinder head, and includes a resonating chamber or chambers designed to dissipate sound. Some mufflers include perforations on the housing for exhaust gases to exit, while others include an outlet tube.
In a typical multiple-chambered, tube-outlet muffler for a small combustion engine, exhaust gases and noise enter the muffler through a conduit attached to the cylinder block. The noise is directed into a resonating chamber, where the noise is dissipated. Typically, the chamber walls are formed from the muffler housing and internal separators or baffles. The separators are perforated, such that exhaust gases and noise pass through the perforations into another chamber of the muffler, where the noise is further dissipated. Exhaust gases exit the muffler through the outlet tube. Other mufflers use a perforate outlet formed from a series of perforations in the muffler housing.
SUMMARY
One embodiment of the invention relates to a muffler for an internal combustion engine including a first shell includes a flexible portion, an intake conduit, and a second shell coupled to the first shell. The intake conduit extends outwardly from the first shell and is configured to be inserted into an exhaust port of an engine. The flexible portion surrounds the intake conduit. Upon attachment to the engine, compression force is stored via elastic deflection of the flexible portion of the first shell, thereby pressing the intake conduit into the exhaust port such that a seal is formed.
Another embodiment of the invention relates to an engine including a muffler including an intake conduit extending therefrom, an exhaust port formed in at least one of a cylinder head and a cylinder block, the intake conduit of the muffler coupled to the exhaust port, a boss extending outwardly from the cylinder head or the cylinder block and spaced apart from the exhaust port, and a fastener coupling the muffler to the boss such that the boss provides a separation between the muffler and the cylinder head or the cylinder block.
Another embodiment of the invention relates to an engine including an exhaust port, a boss spaced apart from the exhaust port, a muffler including a first shell having an intake conduit, a flexible portion surrounding the intake conduit, and a first coupling surface surrounding the flexible portion and a second shell having a second coupling surface coupled to the first coupling surface to couple the first shell to the second shell, and a fastener. The intake conduit is coupled to the exhaust port by way of an interference fit, such that the flexible portion of the first shell is deflected to a deflected position. The fastener couples the muffler to the boss with the flexible portion in the deflected position, thereby biasing the intake conduit into the exhaust port to form a seal.
Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.



BRIEF DESCRIPTION OF THE FIGURES
The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which:
FIG. 1 is a perspective view of a combustion engine according to an exemplary embodiment.
FIG. 2 is a side view of the combustion engine of FIG. 1.
FIG. 3 is a perspective view of a cylinder block and a cylinder head according to an exemplary embodiment.
FIG. 4 is an exploded view of the cylinder head of FIG. 3 and a muffler according to an exemplary embodiment.
FIG. 5 is a perspective view of the muffler coupled to the cylinder head of FIG. 4 with a muffler guard, according to an exemplary embodiment.
FIG. 6 is a sectional view taken generally along line 6-6 of FIG. 5.
FIG. 7A is a front view of a muffler according to an exemplary embodiment.
FIG. 7B is a sectional view taken generally along line 7B-7B of FIG. 7A.
FIG. 7C an enlarged view taken generally within the encircled region 7C of FIG. 7B.
FIG. 8A is a sectional view of a fitting according to an exemplary embodiment.
FIG. 8B is a sectional view of a fitting according to another exemplary embodiment.
FIG. 8C is a sectional view of a fitting according to yet another exemplary embodiment.



DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.
Referring to FIG. 1, an internal combustion engine 110 includes a blower housing 112 covering a top of the engine 110, with an air intake 114 and a fuel tank 116 mounted to a side of the engine 110. A recoil starter 126 is attached to the top of the blower housing 112.
The engine 110 further includes a crankcase 120 and a sump 122 fastened to the underside of the crankcase 120. The crankcase 120 supports internal components of the engine 110, such as a piston, a connecting rod, a camshaft, and other components. The sump 122 forms a base of the crankcase 120, and holds a pool of oil lubricant within the crankcase 120. A vertical crankshaft 124 extends from the crankcase 120, through the sump 122, and may be used to drive power equipment, such as a rotary lawn mower, a pressure washer pump, a secondary generator, or other equipment. In other embodiments, the engine may include a horizontal crankshaft, an automatic starter, and the crankcase 120 and sump 122 may be integrally cast.
FIG. 2 shows a side view of the engine 110, with various engine components not shown to better display the engine 110 structure. For example, the blower housing 112 is omitted to show components on the top of the engine 110, including a base 130 of a blower scroll, an ignition armature 132, and a rocker cover 118. The base 130 guides air from a blower fan to cool parts of the engine 110 heated as a result of the combustion process. The ignition armature 132 produces a timed electric charge used by a spark plug 144 to ignite the fuel.
The rocker cover 118 is mounted to a side of the engine 110, and encases rockers 138 (see FIG. 5) that drive intake and exhaust valves. Beneath the rocker cover 118 and rockers 138 is a cylinder head 142 covering a cylinder block 140. The cylinder head 142 caps the cylinder block 140, forming a combustion chamber. Intake and exhaust valves are controlled by the rockers, and control the flow of air in and exhaust out of the combustion chamber.
Also shown in FIG. 2, a muffler 128 is attached to a side of the engine 110. The muffler 128 reduces noise emissions from combustion processes occurring within the engine 110. The muffler 128 includes a housing 136 having a generally rectangular body formed from two shells crimped together. In other embodiments, the body may be generally circular, square, octagonal, or other shapes. The housing 136 includes mounting apertures 156, with the muffler 128 fastened to the cylinder head 142 with fasteners 134 extending through the mounting apertures 156. In the center of the muffler 128 are a series of perforations 160 on the housing 136. Exhaust gases exit the muffler 128 through the perforations 160.
While FIG. 2 shows the muffler 128 according to an exemplary embodiment, other types and forms of mufflers may also use the teachings disclosed herein. For example, in other embodiments the muffler 128 is attached to a cylinder block instead of a cylinder head. In some embodiments, the muffler 128 may be coupled to the engine 110 with other types of fasteners, such as self-tapping screws, hooks, pins, bars, welds, etc., and combinations thereof. Also, in some embodiments, the muffler 128 is attached with different numbers of fasteners. For example, in at least one embodiment, a muffler includes a loop to be engaged by a hook extending from a cylinder block. In some embodiments, the perforations 160 of the outlet are not in the center of the muffler housing. In other embodiments, the muffler outlet includes a tube through which exhaust gases exit. Muffler geometries and dimensions vary depending upon the particular frequency and amplitude of sound to be dissipated and other factors, such as an intended application.
In an exemplary embodiment, the engine 110 is a four-stroke engine. An exhaust conduit 150 (see FIG. 6) extends within the cylinder head 142. In other embodiments the exhaust conduit extends within the cylinder block 140. The exhaust gases exit the cylinder head 142 through the exhaust port 146, and into the muffler 128.
FIG. 3 shows the cylinder head 142, an exhaust port 146, and structure to attach the muffler 128 to the exhaust port 146 (with various engine components not shown to better display the structure). The exhaust port 146 is shown as a round aperture on a side of the cylinder head 142. Exhaust gases are directed from the combustion chamber, past the exhaust valve 164, and to the exhaust port 146. While FIG. 3 shows the exhaust port 146 as an aperture, in other embodiments the exhaust port is a tube or conduit extending from the engine.
Two bosses 148 extend from the cylinder head 142. The bosses 148 are positioned to the sides of the exhaust port 146, and include tapped apertures 166 to receive the fasteners 134. In an exemplary embodiment, the bosses 148 are positioned such that the centers of the bosses 148 are more than one inch from the center of the exhaust port 146 (e.g., about two inches). Placement of the bosses 148 away from the exhaust port 146 reduces heat transfer from exhaust gases exiting through the exhaust port 146. For example, sufficient distance between the bosses 148 and the exhaust port 146 allows for general purpose, self-tapping screws to be used—as opposed to specialty bolts designed to handle high temperatures without much thermal expansion. With embodiments employing self-tapping screws, the apertures 166 are cored, not tapped.
FIG. 4 shows an exploded view of the cylinder head 142 and the muffler 128, with fasteners 134 (e.g., screws, bolts, etc.) for attaching the muffler 128 to the cylinder head 142. When the muffler 128 is attached to the cylinder head 142, exhaust gases are directed out of the exhaust port 146 and into an intake pipe 168 of the muffler 128. As shown in FIGS. 2 and 4, the fasteners 134 pass through the apertures 156 in a flat portion 152 along an edge 154 of the muffler housing 136. Use of the flat portion 152 along the edge 154 reduces the surface area of the interface between the fasteners 134 and the muffler 128, further reducing heat transfer to the fasteners 134.
FIG. 5 shows a perspective view of the muffler 128 fastened to the cylinder head 142 via the fasteners 134 of FIG. 4. Also shown in FIG. 5, a muffler guard, in the form of a cage 162, surrounds the muffler 128. In some exemplary embodiments, the cage 162 is made of metal bars (e.g., steel, iron, aluminum, etc.) welded together in a matrix. The cage 162 is spaced apart from the housing 136 of the muffler 128 to reduce heat transfer to the cage 162, and to limit access to the muffler 128. The cage 162 also helps prevent foreign objects, such as dry leaves or an operator, from contacting the housing 136, which may get quite hot. In other embodiments, the muffler guard is a second perforated housing, formed from a high-temperature plastic or composite shell. Still other embodiments employ other forms of commercially available muffler guards.
According to an exemplary embodiment, the cage 162 is attached to the engine 110 via the fasteners 134. For example, the fasteners 134 pass through mounting loops 170 of the cage 162. The fasteners 134 then pass through the mounting apertures 156 of the muffler 128, and into the bosses 148. In other embodiments, the fasteners first pass through the mounting apertures 156 of the muffler, then through the mounting loops 170 of the cage 162, and then into the bosses 148. Placing the bosses 148 away from the exhaust port helps to reduce heat transfer to the cage 162. Accordingly, the fasteners 134 that attach the muffler 128 may simultaneously be used to attach the cage 162. In other embodiments, different types or numbers of fasteners are used to attach the cage 162.
Referring to FIG. 6, the exhaust conduit 150 is shown extending within the cylinder head 142 to the intake pipe 168 of the muffler 128. The exhaust conduit 150 is chamfered proximate to where the exhaust conduit 150 contacts the intake pipe 168 of the muffler 128. Exhaust gases entering the muffler 128 enter a first resonance chamber 172. One side of the chamber 172 is formed from a separator 174 (or baffle) within the muffler 128. The separator includes a dome-like structure 176. The other sides of the chamber 172 are formed from the housing 136. Exhaust gases pass from the first chamber 172 through a series of perforations in the separator 174, into a second chamber 178. As shown in FIGS. 2 and 6, exhaust gases exit the second chamber 178 through the perforations 160 on the housing 136. Engine noise is dissipated in the first chamber 172, and further dissipated in the second chamber 178. Other embodiments include mufflers with different numbers of chambers and separators. In some embodiments employing tube outlets, a spark arrester may be coupled to the end of the tube.
Still referring to the exemplary embodiment shown in FIG. 6, the intake pipe 168 of the muffler is tapered. The cross-sectional area of the intake pipe 168 decreases with distance away from the muffler 128. In some embodiments, the rate of decrease is linear, while in other embodiments, the rate of decrease is non-linear and not continuous. During attachment of the muffler 128 to the engine 110, the intake pipe 168 is inserted into the exhaust port 146, such that the end of the intake pipe 168 contacts chamfered walls of the exhaust conduit 150.
When the engine 110 is running, heat transfers from hot exhaust gases passing through the exhaust conduit 150 and into engine components, such as the intake pipe 168 of the muffler 128. The engine components expand, with different materials expanding at different rates and to different extents. In a preferred embodiment, the intake pipe 168 is designed so that thermal expansion of the materials will improve the seal between the intake pipe 168 and the exhaust conduit 150.
FIGS. 7A, 7B, and 7C show a muffler 210 according to another exemplary embodiment. The muffler 210 is formed from a front shell 212 and a back shell 214 crimped together around edges 216. The front shell 212 includes an intake pipe 218 extending outward from the front shell 212.
A flexible portion 220 of the front shell 212 surrounds the intake pipe 218 and has an outwardly extending curvature. When the intake pipe 218 is inserted through an exhaust port 222 and into an exhaust conduit 224, resistance from contact at an interface 226 between the intake pipe 218 and the exhaust conduit 224 generates a compressive force that is transferred through the intake pipe 218 to the flexible portion 220 of the front shell 212. The flexible portion 220 deflects, storing the force like a spring. Fasteners 236 hold the flexible portion 220 of the front shell 212 in the deflected position, and the force holds the end of the intake pipe 218 tightly against the exhaust conduit 224 under pressure such that an airtight seal is formed. In other embodiments, the intake pipe 218 itself is flexible, and stores compression force when pressed into the exhaust port 222.
The exhaust conduit 224 shown in FIGS. 7B and 7C includes a bevel 228 proximate to the exhaust port 222. The bevel 228 is angled outward to facilitate positioning of the intake pipe 218 into the exhaust port 222 during assembly. Additionally, the intake pipe 218 is coupled to the shell 214 with a rounded fillet 230. The fillet 230 reduces stress concentrations between the shell 214 and the intake pipe 218. When coupled, the fillet 230 fits the space provided by the bevel 228.
Further referring to FIG. 7B, the exhaust conduit 224 further includes a backstop. The backstop is in the form of an annular step 232 or a shoulder at an end of a chamfered portion 234 of the exhaust conduit 224. When the intake pipe 218 is inserted into the exhaust conduit 224, the step 232 blocks the intake pipe 218 from deeper insertion. Also, the step 232 may increase the surface area of contact 226 between the intake pipe 218 and the exhaust conduit 224, providing a stronger seal. Further, the step 232 guides exhaust gases into the intake pipe 218, away from leaking between the intake pipe 218 and the exhaust conduit 224. In other embodiments, the backstop is in the form of protrusions, hooks, crossing bars, or other structures that limit the ability of the intake pipe 218 to be further inserted into the exhaust conduit 224.
Referring to FIG. 7C, in an exemplary embodiment, the angle of taper θ′ of the intake pipe 218 is less than a chamfer angle θ′′ of the exhaust conduit 224. In some embodiments, the difference of relative angles θ′, θ′′ is approximately between two to twenty degrees, preferably between five to ten degrees, such as about seven degrees. A meeting of two angled surfaces is intended to increase the surface area of the contact 226, producing a better seal.
FIG. 8A shows a fitting arrangement 310, with an intake 312 of a muffler and an exhaust port 314 of an engine. The intake 312 includes an intake pipe 318 having a uniform cross-section. The exhaust port 314 is formed at the end of an exhaust conduit 320. The exhaust conduit 320 has a chamfered portion 322 with a widening cross-sectional area leading to the exhaust port 314. The intake pipe 318 may be inserted into the chamfered portion 322, where an end of the intake pipe 318 contacts walls of the exhaust conduit 320. As the intake pipe 318 is inserted, some of the insertion force compresses an interface between the intake pipe 318 and the chamfered portion 322, producing an airtight seal.
FIG. 8B shows a fitting arrangement 410, with an intake 412 of a muffler and an exhaust port 414 of an engine. The intake 412 has a chamfered aperture 416 with a cross section that narrows into the muffler. An engine exhaust conduit 418 includes an outwardly extending pipe 420, with the exhaust port 414 formed at an end of the exhaust pipe 420. The exhaust pipe 420 may be inserted into the chamfered aperture 416 of the muffler intake 412. As with the fitting 310 shown in FIG. 8A, a coupling force, which holds the muffler to the engine, produces a compression force at an interface between the intake 412 and the exhaust pipe 420.
FIG. 8C shows a fitting arrangement 510, with an intake 512 of a muffler and an exhaust port 514 of an engine. The intake 512 includes an intake pipe 516 having a rounded end 518 with a cross-sectional area narrowing away from the muffler. In some embodiments, the rate of narrowing is not constant. The exhaust port 514 is formed at the end of an exhaust conduit 520. The exhaust conduit 520 has a cross-sectional area that widens away from the engine. In some embodiments, the rate of widening is not constant. The exhaust conduit 520 further includes a step 522 that serves has a backstop to limit a distance of insertion of the intake pipe 516 into the exhaust conduit 520.
The construction and arrangements of the muffler attachment, as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. In some embodiments, fitting attachments taught herein may be applied to fittings between components in power equipment that do not include a muffler. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

## Claims

1. A muffler for an internal combustion engine, the muffler comprising:
a first shell formed in part by a flexible portion;
an intake conduit; and
a second shell coupled to the first shell;
wherein the intake conduit extends outwardly from the first shell and is configured to be inserted into an exhaust port of an engine;
wherein the flexible portion surrounds the intake conduit; and
wherein, upon attachment to the engine, compression force is stored via elastic deflection of the flexible portion of the first shell, thereby pressing the intake conduit into the exhaust port such that a seal is formed.

2. The muffler of claim 1, further comprising:
an outlet formed in the second shell for allowing exhaust gases to exit the muffler.

3. The muffler of claim 2, wherein the intake conduit is tapered with respect to distance from the first shell.

4. The muffler of claim 1, further comprising:
an outlet at least partially formed in the second shell for allowing exhaust gases to exit the muffler.

5. The muffler of claim 4, wherein the intake conduit is tapered with respect to distance from the first shell.

6. The muffler of claim 4, wherein the flexible portion of the first shell comprises an outwardly extending curvature.

7. The muffler of claim 6, wherein the outwardly extending curvature is arcuate in a lateral cross-section of the muffler.

8. An engine, comprising:
a muffler including an intake conduit extending therefrom and an interior chamber in fluid communication with the intake conduit;
an exhaust port formed in at least one of a cylinder head and a cylinder block, the intake conduit of the muffler coupled to the exhaust port;
a boss extending outwardly from the at least one of a cylinder head and a cylinder block in which the exhaust port is formed, the boss spaced apart from the exhaust port; and
a fastener coupling the muffler directly to the boss such that the boss provides a separation between the muffler and the cylinder head or the cylinder block;
wherein the fastener extends through the muffler external to the interior chamber.

9. The engine of claim 8, wherein the muffler further includes a first shell having a first coupling surface and a second shell having a second coupling surface coupled to the first coupling surface to couple the first shell to the second shell.

10. The engine of claim 9, wherein the fastener extends through the first coupling surface and the second coupling surface.

11. The engine of claim 10, further comprising:
a muffler guard fastened to the boss by the fastener.

12. The engine of claim 11, wherein the fastener comprises a fastener suitable for use at low temperatures.

13. The engine of claim 8, further comprising:
a second boss extending outwardly from the cylinder head or the cylinder block and spaced apart from the exhaust port and opposite the first-mentioned boss; and
a second fastener coupling the muffler to the second boss such that the second boss provides a separation between the muffler and the cylinder head or the cylinder block, wherein the second fastener extends through the muffler exterior to the interior chamber.

14. The engine of claim 8, wherein the muffler further includes a first shell having a first coupling surface and a second shell having a second coupling surface coupled to the first coupling surface to couple the first shell to the second shell; and
wherein the fastener extends through the first mating surface and the second mating surface.

15. The engine of claim 8, further comprising:
a second boss extending outwardly from the cylinder head or the cylinder block and spaced apart from the exhaust port and opposite the first-mentioned boss; and
a second fastener coupling the muffler to the second boss such that the second boss provides a separation between the muffler and the cylinder head or the cylinder block.

16. An engine, comprising:
an exhaust port;
a boss spaced apart from the exhaust port;
a muffler including a first shell formed in part by a flexible portion, an intake conduit surrounded by the flexible portion, and a first coupling surface surrounding the flexible portion and a second shell having a second coupling surface coupled to the first coupling surface to couple the first shell to the second shell; and
a fastener;
wherein the intake conduit is coupled to the exhaust port by way of an interference fit, such that the flexible portion of the first shell is deflected to a deflected position; and
wherein the fastener couples the muffler to the boss with the flexible portion in the deflected position, thereby biasing the intake conduit into the exhaust port to form a seal.

17. The engine of claim 16, wherein the muffler further includes an outlet formed in the second shell for allowing exhaust gases to exit the muffler.

18. The muffler of claim 16, wherein the muffler further includes an outlet at least partially formed in the second shell for allowing exhaust gases to exit the muffler.

19. The engine of claim 16, wherein the muffler further includes an interior chamber in fluid communication with the intake conduit; and
wherein the fastener extends through the muffler exterior to the interior chamber.