Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2000-11-14
2002-07-09
Nappi, Robert E. (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S224000, C181S267000
Reexamination Certificate
active
06415887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an exhaust muffler and more particularly to such a muffler with baffle for reducing sound output without significant increase in back-pressure developed within the muffler.
2. Description of the Related Art
Exhaust gas flow from an internal combustion engine is made up of a train of high pressure zones interspersed with low pressure zones as the exhaust valves of the engine open and close. The zone train moves through an exhaust pipe to atmosphere. The size of the exhaust pipe is important because it must be small enough to keep the high pressure zones from expanding too rapidly in order to retain thermal and kinetic energy, and it must be large enough to not restrict gas flow which would cause excessive back-pressure. When the exhaust pipe is properly designed, the low pressure zones in the exhaust gas exert a drawing action on the combustion chamber which helps to purge expended gas from the chamber. Mufflers attenuate sound by gradually dissipating the latent energy remaining in the exhaust gas but this also tends to reduce the drawing action by building back-pressure. The exhaust gases have a range of longitudinally propagated sound frequencies (waves) due to the high state of molecular motion within the gases as they are expelled from the combustion chamber. Some of these sound frequencies can support or assist expulsion of the exhaust gases while other frequencies will not. Attenuating all sound, as in a conventional muffler, reduces power because of loss of the potentially supportive sound frequencies. Neutralizing reverse waves, i.e., those traveling upstream within the exhaust pipe is important for reducing power loss. Thus, anti-reversing exhaust system designs exist in the art, and these attempt to cancel substantial amounts of echoing and reverse wave propagation. Tuning an exhaust system is considered to be a complex process of sizing exhaust tubes, determining the length of components and possibly combining multiple tubes to synchronize gas pulses with sound waves for the lowest power loss within a selected RPM range for a given engine. The present invention provides a novel approach to sound attenuation by canceling reverse waves so as to achieve least power loss and maximum engine power. It attenuates noise by focusing sound waves, nullifying unwanted frequencies while amplifying reciprocal waves in conjunction with exhaust gas pulses to reinforce exhaust gas exit flow and maximize the scavenging effect in the combustion chamber to increase power.
The following art defines the present state of this field:
Wirt, U.S. Pat. No. Re. 31,275 describes a broadband sound attenuating, acoustically lined, duct of varying cross-sectional shape but in the usual case having a constant cross-sectional area, and wherein the duct liner is configured to maintain an essentially constant acoustic existence and scaled acoustic reactance throughout provided by means of changes in the effective depth of the liner. Design tradeoffs permit some variation in the cross-sectional area of the duct with concomitant changes in liner properties. In all cases, the duct is designed so that every section along its major axis is optimally tuned to absorb most efficiently some part of the frequency spectrum of interest. The device is particularly suitable for sound suppression of jet aircraft engines.
Emmons, U.S. Pat. No. 1,400,350 describes a muffler, including a body portions, inlet and exhaust pipes connected to said body portion, a plate positioned adjacent the inlet end of the muffler, and provided with a centrally disposed cone shaped projection extending toward and in alignment with the inlet pipe, and adapted to deflect gases radially outward, said plate being formed with radially disposed curved slots, and vanes attached to said plate adjacent each of said slots or imparting a whirling motion to fluid passing through said slots.
Lathers, U.S. Pat. No. 2,473,103 describes a muffler comprising a tubular casing having inlet and outlet openings at opposite ends thereof and adapted to receive through its inlet opening the exhaust gases from an internal combustion engine or the like, said casing including a first section the inner wall of which gradually diverges from the inlet end of the casing toward the outlet end of said casing to form a substantially conical first section; and imperforate, elongated member of substantially conical configuration within said first section having its apex disposed adjacent the inlet opening of said casing and its base extending beyond the large end of said first section; an imperforate, elongated member of substantially conical configuration within said first section having its apex disposed adjacent the inlet opening of said casting and its base extending beyond the large end of said first section; a second section adapted to receive the exhaust gases from the first section and being of bulbous or barrel-shaped configuration, said section enclosing the base portion of said conical member and having a maximum diameter greater than the maximum diameter of said conical section and a minimum diameter corresponding substantially to the maximum diameter of said first section, the outer surface of said conical member being spaced from the inner surfaces of said first and second sections to provide therebetween a flow path of constantly increasing area for the exhaust gases as they pass through said sections; a spiral vane positioned between said spaced surfaces to impart a spiral movement to the exhaust gases as they pass through said flow path; a third section having a baffle therein, said baffle including two substantially flat perforated plates arranged in parallel spaced relation and extending longitudinally throughout substantially the length of said section, and at least two other substantially flat perforated plates arranged in parallel spaced relation and being coextensive with the first mentioned plates, said first mentioned plates and said second mentioned plates being disposed in cross-like or honeycomb formation within said third section; and a fourth section having a baffle secured therein, said baffle extending longitudinally throughout substantially the length of said third section and having two perforated portions arranged in a V formation with the apex of the V directed toward the inlet of the fourth section and the total area of the perforations in said V formation being greater than the total area of the perforation in the baffle in said third section.
Backman, U.S. Pat. No. 2,708,006 describes a muffler for silencing the exhaust of an internal combustion engine, said muffler comprising; intercommunicating inlet intermediate and outlet sections disposed in axially aligned series relationship, each of said sections comprising a hollow cylindrical casing portion for confining exhaust gases within said muffler; said inlet section comprising an upstreamwardly disposed portion adapted for connection to the exhaust duct of an internal combustion engine; an insert element disposed within said casing portion of said inlet section and including a plurality of radially inwardly extending webs each provided at its radially outwardly disposed end portion with an axially upstreamwardly directed extension, said webs being arranged to cause effective uniform distribution of exhaust gases flowing toward said intermediate section; a plurality of coaxially nested tubular member disposed in laterally spaced relationship within said casing portion of said intermediate section each of said tubular member which is located intermediate said intermediate section casting portion and the innermost of said tubular members being formed of perforated sheet metal; a plurality of spaced substantially uniformly peripherally disposed spacing member formed of perforated sheet metal and interconnecting said intermediate section casing portion and adjacent ones of said tubular members for maintaining said tubular members and said casing portion in said spaced coaxial relationship, said spa
Asher Rodney Lee
Moran Clay
Rhode Judy
CR Patents, Inc.
Gene Scott-Patent Law & Venture Group
Martin Edgardo San
Nappi Robert E.
Rhode Judy
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