BACKGROUND OF THE INVENTION [0002] The present invention relates to exhaust mufflers for watercraft, and more particularly to an improved marine muffler of a design that is more compatible with other equipment to be fitted within the interior of the watercraft.

[0003] Marine vessels that utilize internal combustion engines typically use mufflers to attenuate exhaust noise generated by operation of the engines. In the past, such mufflers typically consisted of large main bodies which often were twice the diameter of the associated inlet and outlet pipes. The large sizes of the mufflers restricted designers in their efforts to include other features and equipment that might be placed where the mufflers were situated. There remains a need in the art for smaller mufflers capable of levels of noise attenuation comparable to those achieved by larger current models.

SUMMARY OF THE INVENTION [0004] This need and others are addressed by apparatus in accordance with the present invention. In accordance with a first embodiment of the invention, an exhaust muffler for a marine engine comprises a housing or canister, an inlet baffle and an outlet baffle. The housing preferably is cylindrical and defines an axis, an inlet and an outlet. The inlet and outlet baffles are positioned in the housing such that the inlet baffle communicates with the inlet and the outlet baffle communicates with the outlet. The inlet defines a first internal port transverse to the axis. The outlet baffle defines a second internal port transverse to the first internal port.

[0005] Most preferably, the inlet and outlet baffles are substantially in the form of surfaces of revolution, each enclosed by the preferred housing in alignment with the axis. The inlet baffle defines a first internal port normal to the axis. It includes a converging inlet baffle intake section communicating with the inlet of the housing; a diverging inlet baffle exit section adjacent the first internal port; and an inlet baffle intermediate section connecting the converging inlet baffle intake section with the diverging inlet baffle exit section. The outlet baffle includes an end cap transverse to the axis ; a gradually diverging outlet baffle intake section adjacent to the end cap; and a sharply diverging outlet baffle exit section communicating with said outlet. The gradually diverging outlet baffle intake section defines a second internal port and a third internal port opposite the second internal port. The second and third internal ports are each oblique to the axis, the second internal port having a second internal port length in a direction parallel to the axis and the third internal port having a third internal port length greater than the second internal port length in the direction parallel to the axis.

[0006] The preferred muffler is highly compact. Most preferably, the housing consists of a cylinder having the same, or nearly the same, external dimensions as inlet and outlet pipes which conduct exhaust gases and water to and from the inlet and outlet of the housing. The inlet and outlet baffles, in turn, preferably are in the form of surfaces of revolution which fit within the cylindrical housing. The compactness of the housing as compared with the housings of known mufflers allows more room for other equipment within a boat's interior spaces. l0007] In accordance with a second embodiment of the invention, an exhaust muffler for a marine engine comprises a housing, a baffle plate and a plurality of lift tubes. The housing preferably is cylindrical and defines an axis, an inlet and an outlet. The baffle plate comprises a center piece, a first end piece transverse to the center piece and a second end piece transverse to the center piece. The baffle plate is positioned within the housing so as to define a first chamber within the housing in communication with the inlet and a second chamber within the housing in communication with the outlet. The lift tubes extend through the center piece of the baffle plate in communication with both the first and second chambers.

[0008] Most preferably, the housing is cylindrical and defines an axis. The center piece, and the first and second end pieces, are substantially planar. The center piece of the baffle plate preferably lies along the axis, while the first and second end pieces extend at approximately 45'angles to the axis. The first and second end pieces are arcuate or elliptical in shape so as to facilitate sealing the baffle plate against the interior of the housing so as to provide a substantially gas-tight separation between the first and second chamber.

[0009] Optionally, a plurality of bypass tubes extend through at least one of the first and second end pieces of the baffle plate in communication with both the first and second chambers.

[0010] Therefore, it is one object of the invention to provide a marine muffler of a design that is more compatible with other equipment to be fitted within the interior of the watercraft, but which nonetheless is capable of significantly reducing noise in an exhaust gas-and-water flow from an internal combustion engine. Other objects and advantages of the invention will be apparent from foregoing and following descriptions, and the accompanying drawings and claims.

BRIEF DESCRIPTION OF DRAWINGS [0011] Fig. 1 is a schematic view of an engine room of a watercraft including an exhaust system having a marine muffler in accordance with the invention; [0012] Fig. 2 is a side elevational view of a first embodiment of a marine muffler in accordance with the invention; [0013] Fig. 3 is a sectional view of the marine muffler of Fig. 2, taken along the line 3-3 in Fig. 2; [0014] Fig. 4 is a side elevational view of an inlet baffle for the marine muffler of Fig. 2; [0015] Fig. 5 is a front elevational view of the inlet baffle of Fig. 4; [0016] Fig. 6 is a side elevational view of an outlet baffle for the marine muffler of Fig. 2; [0017] Fig. 7 is a bottom plan view of the outlet baffle of Fig. 6; [0018] Fig. 8 is a top plan view of an alternative outlet baffle for the marine muffler of Fig. 2; [0019] Fig. 9 is a side elevational view of a second embodiment of a marine muffler in accordance with the invention; [0020] Fig. 10 is a side sectional view of the marine muffler of Fig. 9, taken along the line 10-10 in Fig. 9; [0021] Fig. 11 is a side sectional view of the marine muffler of Fig. 9, taken along a line coincident with the line 10-10 in Fig. 9 so as to illustrate an alternative interior configuration; and [0022] Fig. 12 is a cut-away view of the marine muffler of Figs. 9 and 11.

DESCRIPTION OF PREFERRED EMBODIMENT [0023] Referring initially to Fig. 1 of the drawings, an engine room 20 of a boat (not shown) includes wet marine exhaust systems 22 for conducting exhaust gases away from internal combustion engines 24. The wet marine exhaust systems 22 preferably cool the exhaust gases with water drawn from the exterior of the boat (not shown); attenuate noise by passing the exhaust gases and water (not shown) through one or more mufflers including marine mufflers 26 in accordance with the invention; and conduct the exhaust gases and water (not shown) in exhaust pipes 28 through the hull 30 to the exterior of the boat. The configurations of the wet marine exhaust systems 22 are not critical to the present invention.

[0024] As suggested by Fig. 1, space within the engine room 20 is limited.

Care must be exercised in designing the components to be placed there so as to leave adequate space both for the components themselves and for necessary maintenance and repair activities which must be conducted in the engine room 20.

[0025] Turning now to Fig. 2, a first preferred marine muffler 26 in accordance with the invention includes a housing or canister 40 which is secured to an inlet or inlet pipe 42 and an outlet or outlet pipe 44 by means of sleeves 41 and 43. The inlet 42 preferably receives exhaust gases with residual entrained water from the upstream portion of the wet marine exhaust system 22 (Fig. 1) while the outlet 44 discharges the exhaust gases and residual water to the exhaust pipe 28 (Fig. 1). The housing 40 preferably is cylindrical and of substantially the same external dimensions as the inlet 42 and the outlet 44. The housing 40 likewise preferably is of substantially the same external dimensions as the exhaust pipe 28 (Fig. 1). As such, the muffler 26 is highly compact, allowing significant space for other equipment within the boat 10 (Fig. 1). Most preferably, as suggested in Fig. 1, the exhaust pipe 28 and the muffler 26 are removable and replaceable as a unit, if necessary, from the exterior of the boat (not shown) through a hole cut through the hull 30 around the area where the exhaust pipe 28 passes through the hull 30.

[0026] As shown in Fig. 3, the inlet 42 is located near a first end 46 of the housing 40. The outlet 44 is located near a second end 48 of the housing 40 opposite said first end 46.

[0027] The preferred housing 40 defines an enclosed interior space 50 containing an inlet baffle 52 and an outlet baffle 54. The inlet and outlet baffles 52, 54 are disparate in the sense that they are separate and do not abut, communicating with one another only through the medium of the interior space 50. The housing preferably defines an axis 56 which extends from the first end 46 of the housing 40 to the second end 48 of the housing. The inlet baffle 52 and the outlet baffle 54 preferably align with each other along the axis 56. The baffles 52,54 are supported inside the interior space 50 of the housing 40 by tube supports or support rings 60 and 62, respectively.

[0028) As shown in Fig. 4, the preferred inlet baffle 52 comprises a sharply converging inlet baffle intake section 70, a diverging inlet baffle exit section 72 and a gradually converging inlet baffle intermediate section 74. The gradually converging inlet baffle intermediate section 74 connects the converging inlet baffle intake section 70 with the diverging inlet baffle exit section 72, forming a flow constriction 76 where it and the diverging inlet baffle exit section 72 meet. The preferred inlet baffle 52 defines an inlet port 78 which communicates with the inlet 42 (Fig. 2) and a first internal port 80 which communicates with the interior space 50 of the housing 40. As shown in Fig. 5, which is an elevational view of the inlet baffle 52 in which the viewer faces the first internal port 80, the preferred inlet baffle 52 is in the form of a surface of revolution centered on the axis 56. This shape facilitates the positioning of the inlet baffle 52 within the preferably cylindrical housing 40.

[0029] As shown in Fig. 6, the preferred outlet baffle 54 comprises a gradually diverging outlet baffle section 90 and a sharply diverging outlet baffle exit section 92. The outlet baffle 54 defines a first internal port 94 and a second internal port 96 opposite the first internal port 94. An impermeable end cap 98 is positioned over an exposed axial end of the gradually diverging outlet baffle section 90 facing the first internal port 78 (Fig. 4) of the inlet baffle 52 (Fig. 4) when the inlet and outlet baffles 52,54 (Fig. 3) are positioned in the housing 40 (Fig. 3) as shown in Fig. 3.

[0030] Without wishing to be bound by any theory of operation, exhaust gases (not shown) with entrained water (not shown) flow into the inlet baffle 52 (Figs. 3-5) through the inlet port 78 (Figs. 4-5); pass through the sections 70,74 and 72 (Fig. 4), in that order; and exit into the interior space 50 (Fig. 3) of the housing 40 (Fig. 3) axially through the first internal port 80 (Figs. 4-5). The flow constriction 76 (Figs. 4-5) in the inlet baffle 52 (Figs. 3-5) tends to increase flow velocity which serves to attenuate exhaust noise in the exhaust gas-and-water flow.

[0031] As the mixture of exhaust gases and entrained water (not shown) moves into the interior space 50 (Fig. 3) of the housing 40 (Figs. 2-3), the water falls to the bottom of the interior space 40 (Figs. 2-3). The water (not shown) collects in the interior space 50 (Fig. 3) and preferably stabilizes at a level near the second internal port 94 (Figs. 6-7).

[0032] The exhaust gases (not shown) enter the outlet baffle 54 (Figs. 3 and 6-7), through the second and third internal ports 94,96 (Figs. 6-7). The water collected in the interior space 50 (Fig. 3) of the housing 40 (Figs. 2-3) restricts the flow of exhaust gases into the second internal port 94 (Figs. 6-7), thereby increasing the velocity of the exhaust gases as they enter the port 94 (Figs. 6-7). The increase in velocity enables the exhaust gases (not shown) to carry water (not shown) in the form of small droplets from the interior space 50 (Fig. 3) into the outlet baffle 54 (Figs. 3 and 6-7) and out of the muffler 26 (Figs. 1-3). The mixing of the exhaust gases and water (not shown) results in extreme turbulence. The net effect is that acoustical energy in the exhaust gases is absorbed by the small droplets of water.

[0033] As shown in Fig. 7, the second and third internal ports 94,96 are preferably elongated in shape, with the third internal port 96 longer than the second internal port 94. This geometry promotes the lifting of water (not shown) into the outlet baffle 54 and the generation of turbulence in the flow.

[0034] The preferred housing 40 (Fig. 3), inlet baffle 52 (Figs. 3-5) and outlet baffle 54 (Figs. 3 and 6-7) are formed from any suitably impermeable, corrosion- resistant material such as stainless steel or a suitable polymer, such as fiber reinforced thermoset plastic. Most preferably, the housing 40 (Fig. 3), the inlet baffle 52 (Figs. 3-5) and the outlet baffle 54 (Figs. 3 and 6-7) comprise fiber- reinforced thermoset plastic. The preferred end cap 98 is affixed to the gradually diverging outlet baffle intake section 90 (Figs. 6-7) of the outlet baffle 54 (Figs. 3 and 6-7) by any suitable means, such as welding, or with a suitable adhesive.

[0035] As shown in Fig. 8, the shape of the end cap 98'on the outlet baffle 54'is not critical to the invention. For example, in the marine muffler 26'of Fig. 8, the end cap 98'forms planar surfaces oblique with respect to the axis 56'.

[0036] Turning now to Fig. 9, a second preferred marine muffler 126 in accordance with the invention includes a housing 140 which is secured to an inlet or inlet pipe 142 and an outlet or outlet pipe 144. The inlet 142 preferably receives exhaust gases with residual entrained water from the upstream portion of the wet marine exhaust system 22 (Fig. 1) while the outlet 144 discharges the exhaust gases and residual water to the exhaust pipe 28 (Fig. 1). The housing 140 preferably is cylindrical, sealed on opposite ends thereof by end caps 145 and 147.

[0037] As shown in Fig. 10, the housing 140 of the marine muffler 126 defines an enclosed interior space 150 and a central axis 156. The interior space 150 contains a baffle plate 158. The preferred baffle plate 158 defines a center piece 164, a first end piece 166 and a second end piece 168. The preferred center piece 164 is substantially planar and lies along the central axis 156. The preferred first and second end pieces 166,168 are also substantially planar, but lie at approximately 45 ° angles to the center piece 164. The outlines of the preferred first and second end pieces 166,168 are arcuate or elliptical such that, when the edges of the baffle plate 158 are secured to the housing 140, as by welding, or suitable adhesives, the baffle plate divides the interior space 150 into enclosed first and second chambers 182 and 184.

[0038] The interior space 150 of the muffler 126 further contains a plurality of cylindrical lift tubes 204,206 and 208 which extend through the center piece 164 of the baffle plate 158 and communicate between the first chamber 182 and the second chamber 184. The number of lift tubes 204,206, 208 is not critical to the invention.

[0039] Without wishing to be bound by any theory of operation, exhaust gases and entrained water (not shown) enter the first chamber 182 through the inlet 142. The entrained water (not shown) collects in the first chamber 182 and preferably stabilizes at a water level near openings of the lift tubes 204,206, 208.

The water collected in the first chamber 182 restricts the flow of exhaust gases (not shown) into the lift tubes 204,206, 208, thereby increasing the velocity of the exhaust gases (not shown) as they move between the first and second chambers 182, 184. The increase in velocity enables the exhaust gases (not shown) to carry water (not shown) in the form of small droplets from the first chamber 182 into the second chamber 184 and out of the muffler 126. The mixing of the exhaust gases and water (not shown) results in extreme turbulence. The net effect is that acoustical energy in the exhaust gases is absorbed by the small droplets of water.

[0040] As shown in Figs. 11 and 12, the housing 140'of an alternative marine muffler 126'having an exterior appearance as shown in Fig. 9 defines an enclosed interior space 150'and a central axis 156'. Analogously to the muffler 140 of Fig. 10, the interior space 150'contains a baffle plate 158'defining a center piece 164', a first end piece 166'and a second end piece 168'. The interior space 150'of the muffler 126'further contains a plurality of cylindrical lift tubes 204', 206'and 208'which extend through the center piece 164'of the baffle plate 158'and communicate between the first chamber 182'and the second chamber 184'.

[0041] As best shown in Fig. 12, in addition to the lift tubes 204', 206', 208', the muffler 126'also includes a plurality of cylindrical bypass tubes 210', 212', 214' and 216'which extend through the first and second end pieces 166', 168'in communication with both the first chamber 182'and the second chamber 184'. Most preferably, end portions of the bypass tubes 210', 212', 214', 216'facing bounding surfaces of the interior space 150'of the housing 140'are angled so as to terminate in planes parallel to that of the center piece 164'. The number and arrangement of the bypass tubes 210', 212', 214', 216'is not critical to the invention.

[0042] From the foregoing, it will appear to those of ordinary skill in the art that the preferred mufflers 26 (Figs. 2-8), 126 (Figs. 9-10) and 126' (Figs. 9 and 11- 12) are designed so as to be compatible with other equipment to be fitted within the limited space available in an engine room or other such interior space of a water craft while providing noise attenuation to a degree similar to that of prior art mufflers.

Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims.