Sound attenuator for a supercharged marine propulsion device

Acoustics – Sound-modifying means – Muffler – fluid conducting type

Reexamination Certificate

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Reexamination Certificate

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06752240

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally related to a compact, low resistance, effective sound attenuator and, more particularly, to a sound attenuator intended for use with a marine propulsion device, such as an outboard motor and tuned for a selected range of frequencies.
2. Description of the Prior Art
Many types of devices produce sound at frequencies and amplitudes that can be annoying or discomforting to human beings in the vicinity of the device when it is operating. For example, automobile engines use mufflers to reduce the level of sound emanating from the internal combustion engine of the automobile. Many applications of compressors use mufflers, or sound dampers, to limit the magnitude of sound emanating from the compressor. When a compressor or Roots blower is used as a supercharger in conjunction with an internal combustion engine, significant sound naturally emanates from the compressor or blower. It is therefore useful to provide a sound attenuation device in combination with a compressor.
U.S. Pat. No. 4,192,401, which issued to Deaver et al on Mar. 11, 1980, describes a complete louver flow muffler. A muffler for reducing the audible noise level of exhaust gases emitted by combustion engines has an inlet tube with a patch of louvers or perforations and is arranged so that all or substantially all of the gas flowing through the muffler is forced through the patch into an expansion chamber from which it flows by either cross bleeding through a patch of louvers or perforations into an outlet tube or to a chamber opening into the inlet end of the outlet tube. A splitter partition may be used to control flow through the louvers and provide additional attenuation. An imperforate portion of the inlet tube is used as a driven tuning tube with a resonator chamber to form a Helmholtz low frequency attenuation system, the performance of which may be improved in some cases by use of an orifice in a wall of the resonator. Also disclosed is a muffler in which all of the gas flows through a louver patch in the outlet tube and an imperforate part of the outlet tube is used as a part of an aspirating type Helmholtz system.
U.S. Pat. No. 3,993,160, which issued to Rauch on Nov. 23, 1976, describes a silencer for a heat engine. An outer return tube is provided outside an exhaust silencer case and forms part of means for interconnecting the downstream end of an upstream tube and the upstream end of a downstream tube with respect to the direction of travel of the exhaust gases through the silencer. The upstream tube and downstream tube are perforated and extend in the case. At least a fraction of the exhaust gas stream travels through the outer return tube.
U.S. Pat. No. 6,408,832, which issued to Christiansen on Jun. 25, 2002, discloses an outboard motor with a charge air cooler. An outboard motor is provided with an engine having a screw compressor which provides a pressurized charge for the combustion chambers of the engine. The screw compressor has first and second screw rotors arranged to rotate about vertical axes which are parallel to the axes of crankshaft of the engine. A bypass valve regulates the flow of air through a bypass conduit extending from an outlet passage of the screw compressor to the inlet passage of the screw compressor. A charge air cooler is used in a preferred embodiment and the bypass conduit then extends between the cold side plenum of the charge air cooler and the inlet of the compressor. The charge air cooler improves the operating efficiency of the engine and avoids overheating the air as it passes through the supercharger after flowing through the bypass conduit. The bypass valve is controlled by an engine control module in order to improve power output from the engine at low engine speeds while avoiding any violations of existing limits on the power of the engine at higher engine speeds.
U.S. Pat. No. 6,405,692, which issued to Christiansen on Jun. 18, 2002, discloses an outboard motor with a screw compressor supercharger. An arrangement similar to that described above in relation to U.S. Pat. No. 6,408,832, is provided.
U.S. Pat. No. 6,382,931, which issued to Czabala et al on May 7, 2002, describes a compressor muffler. A muffler assembly for muffling noises associated with a compressor is described. The muffler assembly is mounted on the compressor such that the two move as a single body. The muffler assembly includes an intake having a hollow interior adapted to receive a first flow of gas from the ambient environment. A baffle disposed in the hollow interior of the intake restricts the flow of gas through the intake. In one embodiment, the baffle defines at least a portion of a plurality of fluid portals that separate the first flow of gas into a plurality of flows of gas as the gas passes from a first side of the baffle to a second side of the baffle. As a result, the first flow of gas is disturbed and noise from the compressor is thereby attenuated. In another embodiment, a plurality of baffles are disposed in the hollow interior of the intake to define a tortuous path for the flow of gas through the intake for attenuating noise.
U.S. Pat. No. 6,361,290, which issued to Ide on Mar. 26, 2002, describes a suction muffler for a hermetic compressor. The invention provides a suction muffler comprising component portions formed by injection forming a thermoplastic synthetic resin and joined to each other by induction welding, and also provides a hermetic compressor including the suction muffler. The suction muffler having this configuration is superior to conventional suction mufflers having joint portions joined by ultrasonic welding and vibration welding in the uniformity of the welding strength at the whole joint portion thereof and in minimizing the occurrence of fins.
U.S. Pat. No. 6,287,098, which issued to Ahn et al on Sep. 11, 2001, describes a muffler for a rotary compressor. A rotary compressor including a main bearing having a discharge passage for discharging compressed gas and a boss for inserting a motor shaft is described. The main bearing forms a component of a compression chamber and a muffler has a boss hole for passing the boss of the main bearing and a discharge opening for discharging the compressed gas. The muffler is mounted on the main bearing, wherein the discharge opening in the muffler is formed at least one in number inside of the discharge passage in the main bearing, whereby attenuating a noise generated in operation of the rotary compressor is effectively accomplished.
U.S. Pat. No. 6,129,522, which issued to Seo on Oct. 10, 2000, describes a suction muffler for a compressor. The suction muffler has a body and suction pipe. The body has an expansion chamber for expanding gaseous refrigerant flowing from an evaporator, a suction chamber for drawing the refrigerant expanded in the expansion chamber, and a resonance chamber in which the refrigerant drawn into the suction chamber resonates. The suction pipe is assembled with the body and connects the suction chamber with a cylinder head of the compressor. The suction pipe provides a passage that the refrigerant in the suction chamber flows into the cylinder head. The refrigerant flows into the suction chamber after being expanded in the expansion chamber, so the noise caused by the pulsation of pressure is reduced and the refrigerant resonating in the resonance chamber can reduce the noise of a specific frequency. Further, since the suction muffler has a simple construction having a small number of components, the leakage of noise through the gaps between the components can be reduced.
U.S. Pat. No. 5,996,731, which issued to Czabala et al on Dec. 7, 1999, describes a compressor muffler. A muffler assembly for muffling noises associated with a compressor is described. The muffler assembly includes an air intake having a hollow interior for receiving air from the ambient environment when the compressor is operating. A baffle is located within the interior of the intake for restricted passage of the air through the intake.

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