Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2002-09-24
2003-11-25
Nappi, Robert E. (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S212000, C181S275000
Reexamination Certificate
active
06651773
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to exhaust control systems for internal combustion engines, and more specifically to a sound attenuation device including multiple flow paths therein, for reducing exhaust noise throughout the audio frequency range. The present invention is properly considered an exhaust sound attenuation and control system, as it not only reduces sound levels, but may reduce emission levels as well by means of internal coatings of emissions reduction material which provide catalytic reaction of exhaust pollutants passing through the device.
2. Description of the Related Art
While the internal combustion engine has proven to be a reasonably good power source for motor vehicles, it is not without its drawbacks. One of the chief drawbacks of the internal combustion engine is the noise output which results from the rapid burning of fuel in the combustion chambers of the engine, and the rapid expulsion of the hot exhaust gases into the atmosphere. As a result, legislation in virtually every area of the world requires motor vehicles to have equipment which reduces sound output.
Accordingly, mufflers, resonators and other such sound attenuating devices have been known for many years, since shortly after the very earliest development of the internal combustion engine. These two types of sound control devices, i.e., mufflers and resonators, have generally not been combined into a single unit due to conflicting characteristics and physical requirements.
Mufflers are generally installed near the output end of an exhaust system, where the exhaust gases have cooled somewhat, and are adapted to attenuate the sound level of the exhaust through a wide range of frequencies. Relatively low temperature, mild steels are acceptable for such use, with the primary consideration for durability being corrosion resistance. Mufflers operate by passing the exhaust gases through a series of pipes within the muffler shell, with the pipes generally having a series of smaller passages or orifices in their side walls. The exhaust gases are forced through these side passages by the pressure developed by the operating engine, with the muffler serving to attenuate the exhaust sound through a relatively wide range of frequencies.
Many exhaust systems also incorporate a resonator. Resonators are also sound attenuation devices, but operate on a completely different principle than that of the muffler. The resonator is adapted to pass the exhaust gases therethrough with little or no impedance, while canceling or absorbing sounds within a certain relatively narrow and well defined frequency range. This range is generally relatively high, with the muffler being relied upon for the attenuation of lower exhaust frequencies.
The resonator may be placed either upstream or downstream from the muffler, and is used to quiet any noises not damped by the other components of the exhaust system.
While the present invention is primarily directed to various embodiments of an exhaust sound attenuating device which serves the function of both muffler and resonator in a single unit, the present invention may also include means for treating exhaust emissions as well. By the time of the 1950s, it was becoming apparent that the ever increasing volume of automobile and truck traffic was generating exhaust emissions which were adversely affecting the environment. This was particularly true in urban areas and other areas where geographic and meteorological conditions combined to create areas where such emissions do not readily dissipate. Accordingly,. by the late 1960s, various regulations were being implemented to require equipment to reduce exhaust emissions output from automobiles, particularly in California and other urban areas.
While early emissions control efforts provided some relief, standards have become increasingly strict in order to keep pace with the ever increasing volume of automobile and truck traffic throughout the U.S.A. With the development of the catalytic converter, which uses one or more noble metals such as platinum, rhodium, and/or palladium to produce an oxidizing and/or reducing catalytic reaction with the exhaust products and heat generated by the exhaust, a real breakthrough was achieved in the control of vehicle emissions. An automobile equipped with one or more catalytic converters was capable of meeting most, if not all, of the exhaust emissions standards of the time, and the use of catalytic converters became commonplace on automobiles and light trucks powered by spark ignition engines in the U.S.A. More recently, catalytic converters have been developed which incorporate rare earth elements with the noble-metals to increase the efficiency of the catalytic converter.
Catalytic converters require relatively high heat in order to efficiently perform the catalytic chemical reactions necessary to convert exhaust pollutants into relatively innocuous gases. Accordingly, catalytic converters are conventionally installed as closely as possible to the exhaust manifold of the engine itself, and are customarily constructed of relatively high temperature tolerant materials, e.g., corrosion resistant steel. While the present inventor has developed devices which combine the function of the catalytic converter and resonator in a single device, he knows of no single device which combines the functions of the muffler and resonator in a single unit, and which may also include at least some limited catalytic conversion function as well. Such a device would be desirable, as it would save space beneath the vehicle, would reduce weight, and would likely reduce exhaust backpressure in comparison to a series of separate devices. Manufacturing costs for the production of a single device incorporating all of the functions heretofore provided in a series of separate devices would be reduced as well, as would labor costs during vehicle assembly and repair.
The present invention responds to this need by providing a system which combines the functions of the muffler and the resonator in a single device, and which may also incorporate emissions reduction material in order to perform some relatively limited treatment of the exhaust as it passes through the present sound attenuation device. While the present attenuation device will generally be installed somewhat downstream of the conventional catalytic converter, it may be constructed of materials adapted to resist higher temperatures and may be installed somewhat further upstream in the exhaust system, where more efficient catalytic reactions will occur within the device. The present exhaust sound attenuation and control system may be constructed to have any practicable external configuration as desired, and may be constructed as a single unit or as plural, generally parallel units joined by one or more crossover pipes, as desired.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,541,240 issued on Sep. 17, 1985 to John H. Munro, titled “Exhaust System For Internal Combustion Engines,” describes a device having a series of removable foraminous chambers providing sound attenuation, spark and moisture control, and catalytic emission control. While the function of the Munro device is similar to that of the present system, the Munro device has a different internal configuration with exhaust flow having a straighter path. The present system is considerably more compact.
U.S. Pat. No. 5,014,510 issued on May 14, 1991 to Franz Laimbock, titled “Exhaust System, Particularly For Two-Stroke Cycle Internal Combustion Engines,” describes an exhaust assembly having a relatively wider expansion area which includes a primary catalytic converter therein. A longitudinal divider is installed upstream of the primary catalytic converter element, with the divider also being coated with catalytically reactive material. It is well known that two stroke cycle exhaust systems are relatively limited in their configur
Colon-Santana Eduardo
Litman Richard C.
Nappi Robert E.
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