US3967446A
Expired / Lapsed
US
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Exhaust relief silencing apparatus for marine propulsion systems
Assignee: Brunswick Corp
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Filing: 1974-08-26
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Granted: 1976-07-06
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Expires: 1994-08-26
Abstract
Abstract A tuned exhaust gas relief system for marine propulsion systems, for example an outboard motor, includes a lower drive shaft housing coupled to a two stroke engine by a pair of intermediate stacked exhaust extension plates. The housing directs the exhaust gas downwardly to a through-the-hub exhaust propeller for exit therethrough. With the unit in reverse or idling, exhaust gases are trapped within the housing. A pair of tuned exhaust relief passageways may be formed by cavities in the mating faces of the two extension plates with a pair of inlet openings in the lower wall of the bottom plate. A baffle member may overlie the inlet openings. The passageways define constant cross-sectional area channels which terminate in exhaust openings in the rear wall of the drive shaft housing. A resonant cavity, which may be integrally formed by mating recesses in the opposed faces of the extension plates, is in close spaced relation to each idle exhaust passageway. Connecting openings are distributed along the length of the common wall between the cavity and passageway. An exhaust housing within the drive shaft housing forms an exhaust expansion chamber of high acoustical impedance between the lower ends of the exhaust pipe means and the upper wall extension plate assembly. The idle exhaust passageways have a low acoustical impedance, so that the acoustical impedance mismatch between the chamber and the passageways attenuates the high frequency sounds. The idle exhaust passageways may transmit the half wave frequency and even multiplies thereof. The resonator cavity is selected to attenuate the particular half wave frequency, or an even multiple thereof, which because of physical space requirements may be present and not attenuated by the idle exhaust passageway means.
Inventors
- 👤 Joseph H. Harralson
- 👤 William F. Wurzbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:26
CPC Classifications
F; F01; F01N; F01N13/00; F01N13/12; B; B63; B63H; B63H20/00; B63H20/24; B63H20/245; F02; F02B; F02B61/00; F02B61/04; F02B61/045
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
139 words
In an outboard propulsion unit including an exhaust housing means having a main exhaust passageway means terminating in a main exhaust nozzle means for discharging of exhaust gases, said main exhaust nozzle means being below the idle water line whereby water moves into the main exhaust passageway means and creates a back pressure condition in said exhaust passageway means at idle, an idle exhaust passageway means communicating with the main exhaust passageway means and terminating in exhaust port means to provide essentially unrestricted flow therefrom, said idle exhaust passageway means including silencing means having a resonator cavity means located adjacent to said idle exhaust passageway means and connected thereto by at least one opening and operable to modify the flow of exhaust gases through the idle exhaust passageway means and limit the pressure waves therein caused by engine operation.
Claim 2
Dependent Claim
139 words
In an outboard propulsion unit including an exhaust housing means having a main exhaust passageway means terminating in a main exhaust nozzle means for discharging of exhaust gases, said main exhaust nozzle means being below the idle water line whereby water moves into the main exhaust passageway means and creates a back pressure condition in said exhaust passageway means at idle, an idle exhaust passageway means communicating with the main exhaust passageway means and terminating in exhaust port means to provide essentially unrestricted flow therefrom, said idle exhaust passageway means including silencing means having a resonator cavity means located adjacent to said idle exhaust passageway means and connected thereto by at least one opening and operable to modify the flow of exhaust gases through the idle exhaust passageway means and limit the pressure waves therein caused by engine operation.
Claim 3
Dependent Claim
27 words
The propulsion unit of claim 1 wherein the silencing means includes baffle plate means located in overlying relationship to the entrance to said idle exhaust passageway means.
Claim 4
Dependent Claim
17 words
The propulsion unit of claim 1 wherein said idle exhaust passageway means has an essentially constant cross-section.
Claim 5
Dependent Claim
27 words
The propulsion unit of claim 3 wherein said idle exhaust passageway means has a rectangular cross-section including a narrow extending passageway to attenuate high frequency pressure waves.
Claim 6
Dependent Claim
54 words
The outboard propulsion unit of claim 1 having a multiple cylinder engine with a pair of said idle exhaust passageway means with individual silencing means and wherein each of said silencing means includes a resonator cavity means located adjacent to said exhaust passageway means and connected thereto by a plurality of restricted flow openings.
Claim 7
Dependent Claim
59 words
The outboard propulsion unit of claim 1 wherein said housing means has an upper exhaust passageway wall assembly located above the water line and said idle exhaust passageway means is located within said wall assembly and includes an inlet opening to the upper portion of said main exhaust passageway means, said silencing means being located in said wall assembly.
Claim 8
Dependent Claim
86 words
The outboard propulsion unit of claim 6 having a tuned exhaust system including main exhaust pipe means terminating within said exhaust housing in downwardly spaced relation to said upper wall assembly, the housing defining an expansion chamber of high acoustical impedance between the lower ends of the exhaust pipe means and the upper wall assembly, and said idle exhaust passageway means forming a finite length low acoustical impedance passage, so that an impedance mismatch is created in the idle exhaust system to minimize sound power transfer.
Claim 9
Dependent Claim
56 words
The propulsion unit of claim 7 wherein said idle exhaust passageway means has a uniform, narrow width to reduce the resonant frequency and increase attenuation of high frequencies, said idle exhaust passageway means having negative attenuation at half-waves and multiples thereof, said resonator cavity means being tuned to a low even multiple of said half-wave frequency.
Claim 10
Dependent Claim
19 words
The propulsion unit of claim 8 wherein said resonator chamber is tuned for a resonance frequency of 1000 hertz.
Claim 11
Dependent Claim
133 words
The outboard propulsion unit of claim 6 wherein said wall assembly includes a top and a bottom plate means mounted in abutting relation upon the upper end of said exhaust housing means, said top plate means being adapted to support an internal combustion engine having an exhaust manifold means terminating in the upper face of said top plate means, said plate means having a centrally located exhaust extension opening means and said bottom plate means having a depending exhaust pipe means, said idle exhaust passageway means being located at the interface of said plate means, and extending about the outer side of said exhaust extension opening means, said resonator cavity means being located adjacent the one side of said idle exhaust passageway means and coupled thereto by a plurality of lateral opening means.
Claim 12
Dependent Claim
186 words
The outboard propulsion unit of claim 10 wherein said exhaust manifold means and extension opening means and pipe means include a pair of side-by-side main exhaust passageways defining a tuned exhaust system, said idle exhaust passageway means includes a pair of idle exhaust passageways correspondingly located to the opposite sides of said main exhaust passageways, each of said idle exhaust passageways including an inlet opening located in the bottom surface of the bottom plate means and generally in alignment with the outer side of the extension opening means, said idle exhaust passageway extending rearwardly from said inlet opening in close-spaced relation to said extension opening means and terminating behind said extension opening means in alignment with the inlet opening, a separate resonator cavity means for each idle exhaust passageway means located immediately outwardly of the corresponding idle exhaust passageway means, each of said cavity means including an enlarged forward portion located adjacent the forward portion of the idle exhaust passageway means and a narrow portion located adjacent the portion laterally aligned with the extension opening means, coupling openings located in the wall adjacent the narrow portion.
Claim 13
Dependent Claim
186 words
The outboard propulsion unit of claim 6 including a lower unit having an exhaust nozzle means and secured to the lower end of the housing means and an internal combustion engine mounted on said upper wall assembly, a tuned exhaust pipe means secured to the upper wall assembly and extending downwardly through said exhaust housing and terminating in upwardly spaced relation to said lower unit to discharge the exhaust gases into the housing for discharging of the exhaust gases through said nozzle means below the water from the lowermost end of the unit, the lower end of said exhaust pipe means extending below the idle water line of the housing, said idle exhaust passageway means including an inlet opening forwardly of the pipe means and extending rearwardly about the pipe means and then downwardly through said housing and terminating in said exhaust port means located above the idle water line of the unit, said resonator cavity means coupled by restricted opening means to the idle exhaust passageway means to reduce the pulsation of the pressure waves at the exhaust ports as a result of engine operation.
Claim 14
Dependent Claim
21 words
The outboard propulsion unit of claim 12 including a baffle plate located in overlying downwardly spaced relation to said inlet opening.
Claim 15
Dependent Claim
95 words
In the outboard propulsion unit of claim 1 wherein said exhaust housing means includes a lower drive shaft housing secured to a lower propeller unit having an exhaust nozzle concentrically of the propeller unit for discharging of the exhaust gases through the propeller unit, said housing means having an upper wall assembly including a pair of plates including mating cavities forming said idle exhaust passageway means, said cavity means located adjacent the idle exhaust passageway means and coupled thereto by a plurality of longitudinally spaced openings spaced in the direction of the exhaust gas flow.
Claim 16
Dependent Claim
25 words
The outboard propulsion unit of claim 14 includes a pair of said idle exhaust passageway means, each of said passageways having a similar cavity means.
Claim 17
Dependent Claim
43 words
The outboard propulsion unit of claim 14 wherein said idle exhaust passageway means is an elongated passageway and said resonator cavity means is a parallel narrow cavity coupled to the central portion of said idle exhaust passageway means by said plurality of openings.
Claim 18
Dependent Claim
52 words
The apparatus of claim 16 having a pair of tuned exhaust systems and a pair of said idle exhaust passageway means including separate resonator cavities, each of said cavities having a volume of approximately 1.2 cubic inches and coupled to the exhaust passageway means by three openings of about 1/8 inch diameter.
Claim 19
Dependent Claim
28 words
The outboard propulsion unit of claim 16 wherein the silencing means includes baffle plate means located in overlying relationship to the entrance to said idle exhaust passageway means.
Claim 20
Dependent Claim
113 words
In a marine propulsion unit including an engine, a propelling element, a drive train connecting said engine and propelling element and a housing for said drive train including a main exhaust passageway therethrough, said housing and the main exhaust outlet therein normally extending below the water, means for relieving exhaust pressure within said main exhaust system primarily where said unit is at idle or in reverse comprising a channel of preselected cross-sectional area and length venting said main exhaust passageway to the atmosphere, the dimensions of said channel being selected to attenuate selected audio frequencies, and a side branch resonating cavity connected to said channel having dimensions selected to attenuate selected audio frequencies.
Claim 21
Dependent Claim
113 words
In a marine propulsion unit including an engine, a propelling element, a drive train connecting said engine and propelling element and a housing for said drive train including a main exhaust passageway therethrough, said housing and the main exhaust outlet therein normally extending below the water, means for relieving exhaust pressure within said main exhaust system primarily where said unit is at idle or in reverse comprising a channel of preselected cross-sectional area and length venting said main exhaust passageway to the atmosphere, the dimensions of said channel being selected to attenuate selected audio frequencies, and a side branch resonating cavity connected to said channel having dimensions selected to attenuate selected audio frequencies.
Claim 22
Dependent Claim
29 words
The device of claim 18 wherein said main exhaust passageway includes an expansion chamber and the inner end of said exhaust pressure relieving channel is open to said chamber.
Claim 23
Dependent Claim
19 words
The device of claim 19 including a plurality of said channels and connected cavities each of substantially identical dimensions.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-07-06 | 1980-01-05 | 1980-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-06 | 1984-01-05 | 1984-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-06 | 1988-01-05 | 1988-07-06 | $7700.00 | Window Closed / Lapsed |