Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2001-09-12
2003-08-26
Hsieh, Shih-Yung (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S264000, C181S270000, C181S277000, C181S278000
Reexamination Certificate
active
06609590
ABSTRACT:
BACKGROUND
This invention relates generally to exhaust systems, and specifically to exhaust systems for marine and other limited-space environments, for controlling and disposing of engine exhaust gases while attenuating the engine noise associated with exhaust gases expelled from the engine.
Historically, society has gradually increased restrictions on the amount of noise which is tolerated from vehicles driven by internal combustion engines. Restrictions have been placed on automobile noise emissions. Restrictions have also been placed on aircraft noise emissions. More recently, restrictions have been imposed in some localities on boat noise emissions.
The difficulty with sound attenuation in the context of boats is that there is typically more limited room in a boat or boat engine compartment, thus precluding use of an expansive e.g. automobile-style muffler where the exhaust gases typically make two or more 180 degree turns inside the muffler. Existing designs of water craft typically do not provide adequate space, given the engine design contemplated for the water craft, to accommodate an automotive-style muffler of sufficient size to suitably control sound emissions from the engine.
A further complication is that consumers prefer increasingly larger size engines in marine vehicles, which emit greater volumes of exhaust gases, and are accompanied with greater levels of the sound which must be attenuated as the gases travel between the engine exhaust ports and the exhaust tip of the exhaust system.
Conventional high performance marine exhaust systems have routinely run the exhaust gases out the rear of the boat, with the only sound attenuation being whatever attenuation is incidentally developed by a spray of water injected into the exhaust pipe just behind the exhaust header.
Thus, there is a requirement for a sound-attenuating exhaust system, especially an exhaust system effective in marine applications, which is compact in size, effective in attenuating sound, and cost effective.
This invention relates generally to an in-line exhaust system which operates in an exhaust pipe generally sized to handle the exhaust gases, with conventional sound-attenuation treatment in a conventional sound attenuation cannister, from a respective size engine, whereby desired levels of sound attenuation can be accomplished while operating within, or substantially close to, the external dimensions of an exhaust pipe suitable for use with such engine while using conventional sound attenuation devices. Thus, the invention achieves sound attenuation while adding little or no space requirements in additional to the conduit requirements for conveying the exhaust gases to the rear of the boat for expulsion to ambient.
It is an object of the invention to provide a suitable sound attenuating exhaust system which utilizes an in-line sound attenuation design which continually passes the exhaust gases toward an exit tip of the exhaust pipe.
Another object is to provide an in-line sound-attenuating exhaust system wherein at least a first apertured baffle plate, having substantial gas-deflecting surface area, extends across the gas flow channel of an exhaust pipe at an oblique angle to the longitudinal axis of the exhaust pipe.
It is a further objective to provide a sound-attenuating exhaust system, and a baffle for use in such sound-attenuating exhaust system, wherein the baffle has multiple baffle plates, first and second such baffle plates having aperture configurations different and distinct from each other.
It is another objective to provide an exhaust system, and a baffle, including first, second, and third baffle plates, and wherein at least one such baffle plate defines a plate angle, relative to a longitudinal axis of such baffle, different from another such plate angle.
Yet another objective is to provide an exhaust system comprising an internally-carried baffle having a length of no more than 36 inches, wherein the exhaust system is effective to reduce sonic intensity by at least 3 decibels.
It is still another objective to provide an exhaust system, including an exhaust pipe and a baffle inside the exhaust pipe, wherein the baffle and exhaust pipe define a friction fit therebetween, and wherein force exerted on the exhaust receiving surface of the first, input baffle plate increases the intensity of the friction fit.
Still another objective is to provide an in-line sound-attenuating exhaust system wherein baffle plates, in combination with the internal surface of the exhaust pipe, define sound attenuation chambers having longitudinal cross-sections, and wherein no cross-section configuration represents more than 50 percent of the cross-sections in the baffle.
It is still another object of the invention to provide an in-line exhaust system wherein each baffle plate defines a different angle or angle pattern with a longitudinal axis of the baffle.
Still another object is to provide an in-line sound-attenuating exhaust system wherein first and second elliptical, apertured baffle plates are joined to each other and cross each other in a gas flow channel of an exhaust pipe.
Yet another object is to provide an in-line sound-attenuating exhaust system wherein at least first and second substantially planar baffle plates extend across substantially the full cross-section of the gas flow channel of the exhaust pipe, at oblique angles, spaced from each other and parallel to each other.
SUMMARY
In a first family of embodiments, this invention comprehends in-line sound attenuating exhaust systems for use in combination with internal combustion engines. Such exhaust system comprises an exhaust pipe having first and second ends, and a length between the first and second ends, an inner surface, an outer surface, a gas flow channel, and a longitudinal axis. Such exhaust system further comprises a sound-attenuating baffle disposed in the exhaust pipe. The baffle comprises at least a first baffle plate extending across the gas flow channel at an oblique angle to the longitudinal axis of the exhaust pipe. The baffle plate has an exhaust receiving surface defining substantial gas-deflecting surface area, an exhaust discharging surface, and an array of apertures extending between the exhaust receiving surface and the exhaust discharging surface.
The baffle preferably includes a second baffle plate having a second array of apertures, the second baffle plate being joined to the first baffle plate, preferably in edge-to-edge relationship with the first plate, thus preferably forming an included angle with the first baffle plate, and extending across the gas flow channel at a second oblique angle to the longitudinal axis. The second oblique angle is preferably different from the first oblique angle, and can be a mirror image of the first oblique angle.
In some embodiments, the baffle further comprises a backwash valve secured over one of the baffle plates.
Where the baffle is comprised of first and second plates, the plates in some embodiments form a fixed included angle therebetween of about 100 degrees to about 130 degrees. Where more than two plates are used, the magnitude of the first plate angle with respect to the longitudinal axis is preferably different from the magnitude of the second plate angle and included angles between the plates are typically no more than 90 degrees.
In preferred embodiments, the magnitudes of the first and second plate angles with respect to the longitudinal axis cooperate with each other in attenuating different sonic frequencies of exhaust gases passing through the baffle.
In some embodiments, at least one of the first and second arrays of apertures comprises individual apertures each defining a like projected aperture area and wherein the apertures in the aperture configuration are uniformly spaced from each other.
In other embodiments, at least one of the first and second arrays of apertures comprises respective ones of the apertures in the given array which define different projected aperture areas and wherein the apertures in the aperture configurations are not uniformly spaced
Hsieh Shih-Yung
Wilhelm Thomas D.
Wilhelm Law Service
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