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Publication numberEP1929132 A1
Publication typeApplication
Application numberEP20050794344
PCT numberPCT/US2005/031408
Publication date11 Jun 2008
Filing date2 Sep 2005
Priority date2 Sep 2005
Also published asEP1929132A4, WO2007030099A1
Publication number05794344, 05794344.1, 2005794344, EP 1929132 A1, EP 1929132A1, EP-A1-1929132, EP05794344, EP1929132 A1, EP1929132A1, EP20050794344, PCT/2005/31408, PCT/US/2005/031408, PCT/US/2005/31408, PCT/US/5/031408, PCT/US/5/31408, PCT/US2005/031408, PCT/US2005/31408, PCT/US2005031408, PCT/US200531408, PCT/US5/031408, PCT/US5/31408, PCT/US5031408, PCT/US531408
InventorsBob A. Seastrom
ApplicantBob A. Seastrom
Export CitationBiBTeX, EndNote, RefMan
External Links: Espacenet, EP Register
Exhaust silencer
EP 1929132 A1 (text from WO2007030099A1) 
The present invention lowers the noise output from an engine while increasing performance. The present invention's shape allows the bores (20) to push exhaust backwards, away from a motorized device without combining the air streams. The rifling (30) of the bores (20) creates a vortex of each exhaust stream, further lowering the decibels and increasing engine performance.
Claims  (OCR text may contain errors)
CLAIMSI claim:
1. A silencer, comprising: a conical main body; and bore holes within said main body; wherein said bore holes are arranged to exhaust air so that the air does not intersect upon exhaustion.
2. The silencer of claim 1, wherein said bore holes are arranged along the sides of said main body.
3. The silencer of claim 1, wherein said bore holes have a short side and a long side.
4. The silencer of claim 1, wherein said bore holes have a short side distal of said main body.
5. The silencer of claim 1, wherein said bore holes have a long side medial of said main body.
6. The silencer of claim 1, wherein said bore holes have rifling.
7. The silencer of claim 1, wherein one of said bore holes is at the tip of said main body.
Description  (OCR text may contain errors)


The present invention relates to an improvement in exhaust silencers. More particularly, the present invention relates to an exhaust silencer that quiets vehicles to 96 decibels or less, and is designed to be attached to a standard muffler, as stock or after market, and fits in a mount that has a spark arrestor.


As is well known, exhaust silencers are devices capable of reducing unwanted noise. Many motorized vehicles produce unwanted noise, and exhaust silencers are the conventional way to prevent such noise from reaching undesirable levels.

There are some silencers that open alternative passageways to vent the exhaust to quell noise. U.S. Patent No. 6,546,722 issued to Sagara et al. on April 15, 2003, shows an engine exhaust assembly for a motorcycle having a valve partition that opens when the engine has high revs. Sagara' s et al.'s device is designed so that at low revs, the valve partition does not open to produce less sound. Unlike the present invention, Sagara' s device reduces sound via use of partitions and valves that variably open and close.

There are other devices that change the angle of discharge of exhaust, and they act both as silencers and engine performance boosters. U.S. Patent No. 3,949,829, issued to Honda et al. on April 13, 1976, shows an exhaust silencer for a motorcycle that has a pair of exhaust silencer tubes extending along the lengthwise direction of the body of the motorcycle. Honda et al.'s device has the exhaust silencer tubes arranged so that there is increased volumetric capacity - the rationale being that increased capacity means that gases can expand and provide a greater silencing effect before being release from the motorcycle. Unlike the present invention, Honda's device works by channeling exhaust gas along a longer volumetric path prior to release.

Some devices aim to slow the movement of air from the combustion chamber of the engine, and thus, prevent the violent noisy collision of air from the exhaust with the ambient air around a motorcycle. PCT Publication No. WO 03/048532 Al by Piccaluga et al. published on June 12, 2003, shows an apparatus for reducing sound nuisance of spark ignition exhaust. Piccaluga' s device recognizes that there are many silencers that try to reduce Shockwaves associated with sound nuisance. Piccaluga's device claims to go beyond such silencers by reducing the speed differential between the combustion chamber and the exhaust, acting as a piston, with modified pressure by preventing the gas from the combustion chamber to strike violently against the stationary air, by allowing the gas to expand in an expansion chamber attached to a cylinder block. The pressure is exerted on different axes which cancel the Shockwave. Unlike the present invention, Piccaluga's device forces the air in multiple internal directions before exhausting it through one port.

U.S. Patent No. 5,441,023 issued to Ma on August 15, 1995, is quite similar to Piccaluga's device because it also forces the air in multiple internal directions. Ma's device also has an acoustic reflector to reflect sound waves propagating along a branch section leading to an engine port. Unlike the present invention, Ma's device does not separate the exhaust upon its release from the vehicle into the atmosphere.

In the past it has been hard to obtain both goals of increased engine efficiency and noise lessening at the same time. There is a need for an improved device that not only acts as an effective silencer, but moreover, is capable of increasing engine performance. Further, there is a need for an improved device that fits easily with a spark arrestor while silencing engine noise and increasing engine performance.

The following references are publications in the different fields, which help to explain the underlying technology incorporated in the present invention.


G. Wilfert, L. Fottner, "The Aerodynamic Mixing Effect of Discrete Cooling Jets with Mainstream Flow on a Highly Loaded Turbine Blade", ASME 94-GT-235 (1994), Journal of Turbomachinery Vol. 118 No. 3 (1996) pp 468-478

Th. Hildebrandt, L. Fottner, "Durham Low Speed Turbine Cascade - Test Case 3", ERCOFTAC Workshop 08-11 January 1996, Courchevel (1996)

W. Jahnen, L. Fottner, "A New Multi-Stage Compressor Test Facility for Inlet Distortion Investigations", 13th Symposium on Measuring Techniques for Transonic and Supersonic Flow in Cascades and Turbomachines, Zurich, September 1996 2. BOUNDRY LAYER REFERENCES

Shear Stress Behavior on Complex Rough Surfaces, J A. Gillies and W G.


Submitted at Wind Erosion: An International Symposium/Workshop, January 27,


(see also

Bradley, E. F.: 1968, "A Shearing Stress Meter for Micrometeorological Studies", Quarterly Journal of the Royal Meteorological Society 94, 380-387.

Butterfϊeld, G.R.: 1991, "Grain Transport in Steady and Unsteady Turbulent Air Flows", Acta Mechanica Suppl. 1, 97-122.

Butterfϊeld, G.R.: 1993, "Sand Transport Response to Fluctuating Wind Velocity", in Turbulence: Perspectives on Flow and Sediment Transport, Clifford, N. J., French, J.R. and Hardisty, J. (Eds.), John Wiley & Sons, Chichester, pp. 305-336.

Garratt, J. R.: 1980, "Surface Influence Upon Vertical Profiles in the Atmospheric Near Surface Layer", Quart. J. Roy. Meteorol Soc. 106, 803-819. Gillies, J. A.: 1994, "A Wind Tunnel Study of the Relationships Between Complex Surface Roughness Form, Flow Geometry and Shearing Stress", Ph.D. Thesis, University of Guelph, 231 p.

Hardisty, I: 1993, "Frequency Analysis of Sand Transport in a Turbulent Air Flow", in Turbulence: Perspectives on Flow and Sediment Transport, Clifford, NJ., French, IR. and Hardisty, J. (Eds.), John Wiley & Sons, Chichester, pp. 295-304.

Huang, C.-h. and Bradford, J. M.: 1992, "Applications of a laser scanner to quantify soil microtopography", SoilSci. Soc. Am. Journal 56, 1, 14-21.

Huang, C.-h., White, I., Thwaite, E. G. and Bendelli, A: 1988, "A Noncontact Laser System for

Measuring Soil Surface Topography", Soil Science Society of America Journal 52,


Iversen, J. D., Wang, W.P., Rasmussen, K.R. and Mikkelsen, H.E.: 1991, "Roughness Element Effect on Local and Universal Saltation Transport", Acta Mechanica (Suppl.2), 65-75. Krogstad, P.-A.3 Antonia, R.A. and Browne, L.W.B.: 1992, "Comparison Between Rough- and Smooth-wall Turbulent Boundary Layers", J. Fluid Mechanics 245, 599- 617.

Krumbein, W.C. and F.J. Pettijohn: 1988, Manual of Sedimentary Petrography, SEPM Reprint Series No. 13, Soc. of Economic Palaeontologists and Mineralogists, Tulsa OK3 549 p.

Lee, B. E. and Soliman, B. F.: 1977, "An Investigation of the Forces on Three Dimensional Bluff Bodies in Rough Wall Turbulent Boundary Layers", Transactions of the ASME, Journal of Fluids Engineering, 503-510.

Levi, E.: 1983, "Oscillatory Model for Wall-bounded Turbulence", Journal of Engineering Mechanics 109 (3), 728-740.

McKenna-Neuman, C. and Nickling, W. G.: 1994, "Momentum Extraction with Saltation: Implications for Experimental Evaluation of Wind Profile Parameters", Boundary-Layer Meteorol. 68, 35-50.

Middleton, G. V. and Southard, J.B: 1984, "Mechanics of Sediment Movement", SEPM Short Course Number 3, SEPM3 Tulsa, OK. Mulhearn, PJ. and Finnigan, JJ.: 1978, "Turbulent Flow Over a Very Rough Random Surface", Boundary-Layer MeteoroL 15, 109-132.

Nickling, W. G. and Gillies, J. A.: 1993, "Dust Emission and Transport in Mali, West Africa", Sedimentology 40 (5), 859-868..

Nickling, W. G. and McKenna-Neuman, C: 1995, "Development of Deflation Lag Surfaces", Sedimentology, 42, 403-414

Prandtl, L.: 1932, "Zw turbulenten Stromung in Rohren und langs Platten", Ergebn.

Aerodyn. Versuchsanst 4, 18-29.

Rao, K.N., Narashima, R., and Narayanan, M.A.B.: 1971, "Bursting in a Turbulent

Boundary Layer", Journal of Fluid Mechanics 80, 401-430.

Raupach, M.R.: 1981, "Conditional Statistics of Reynolds Stress in Rough-wall and

Smooth-wall Turbulent Boundary layers", Journal of Fluid Mechanics 108, 363-382.

Raupach, M.R., Antonia, R.A., and Rajagopalan, S.: 1991, "Rough-wall Turbulent Boundary Layers", Applied Mechanics Reviews 44 (1), 1-25. Raupach, M.R., Coppin, P. A., and Legg, BJ: 1986, "Experiments on Scalar Dispersion within a Model Plant Canopy Part I: The Turbulence Structure", Boundary-Layer Meteorol. 35, 21-52.

Raupach, M.R., Thom, AS., and Edwards, L: 1980, "A Wind Tunnel Study of Turbulent Flow Close to Regularly Arrayed Rough Surfaces", Boundary-Layer Meteorol. 18, 373-397.

Taylor, P. A.: 1988, "Turbulent Wakes in the Atmospheric Boundary Layer", in Flow and Transport in the Natural Environment: Advances and Applications Steffen, W. L. and Denmead, O. T. (Eds.), Springer- Verlag, Berlin, 270-292.

Tippens, P.E.: 1978, Applied Physics, McGraw-Hill, Toronto, 758 p.

Williams, JJ., Butterfield, G.R., and Clark, D.G.: 1994, "Aerodynamic Entrainment

Threshold: Effects of Boundary Layer Flow Conditions", Sedimentology 41 (2),


Wolfe, S. A.: 1993, "Sparse Vegetation as a Surface Control on Wind Erosion" , Ph.D. Thesis, University of Guelph, 257 p.

SUMMARY OF THE INVENTION A silencer is provided that forces exhaust air through rifled passages. The rifled passages cause the exhaust air to spin at high velocity. The spinning air in each rifled passage leaves the present invention via an angled end of each rifled passage. The angled ends force the exhaust air stream to bend outward and away from a line directly behind the present invention. The bending outward and away helps to quickly dissipate any loud sound in various trajectories.

Further, the spinning air in each rifled passage forces hot air exhaust and particulate matter exhaust to separate from cooler air exhaust. Thus, upon release from the angled ends, a stream of cooler air exhaust fires out, contained within a hot air exhaust and particulate matter exhaust "cylinder" - the "cylinder" formed by the hot air exhaust and the particulate matter exhaust. Sound from the engine exhaust is also contained by the cylinder, such that the hot air exhaust and particulate matter exhaust cylinder around the cooler air and engine exhaust sound packages noise leaving the present invention. The engine exhaust sound is dissipated in various trajectories because of the angled ends above, but moreover, the engine exhaust sound remains contained within the cylinder well after leaving the present invention. Because the engine exhaust sound remains contained so, unless someone is in the direct path of the trajectory of the engine exhaust sound contained within the cylinder, that someone will not perceive the engine exhaust sound.

While there are many designs for silencers, none use bore passages with rifling in combination with a conical body, nor the use of the roughness of the inside of the bore passages as stated herein. One object of the present invention is to lower the noise output from an engine while increasing performance and fitting easily with a spark arrestor. There is nothing known that accomplishes these three goals together as well as the present invention. The present invention's shape allows bored passages to push exhaust away from a motorized device without combining hot and cold air streams. The rifling of the bored passages creates a vortex of exhaust stream within each bored passage, further lowering the decibels and increasing engine performance. The roughness of the surface of the bored passages forms a boundary layer lowering wind friction and increasing efficiency. The internal formation of the present invention provides a space for a vacuum to form that increases engine efficiency while sound reduction is achieved. The present invention also has baffling that increases the sound reduction.


Figure 1 is an environmental view drawing of the present invention.

Figure 2 is an environmental view photograph.

Figure 3 is a side cross sectional view.

Figure 4 is a bottom cross section cut away view drawing.

Figure 5 is a Dyno Comparison Test.

DETAILED DESCRIPTION In Figure 1, the present invention (10) is shown in its preferred embodiment having eight bores (20) through a cone (22). The bores (20) are arranged so that they open into the surface of cone (22). The bores (20) end at an angle as they intersect the surface of cone (22), and this is important because as exhaust flows from bores (20), the exhaust encounters a longer sidewall (27) of each of bores (20) that is medial and a shorter sidewall (28) of each of bores (20). The longer sidewall (27) for ensures that exhaust moves in a straight line out of each of bores (20), while the shorter sidewall (28) of each of bores (20) ensures that exhaust moves out laterally away from a straight line out of each of bores (20).

The overall effect of longer sidewall (27) and shorter sidewall (28) is that exhaust moving out of each of bores (20) moves at an angle lateral from a direct line behind cone (22). The overall effect of longer sidewall (27) and shorter sidewall (28) is that each stream of exhaust moving out of each of bores (20) moves so as not to intersect another stream of exhaust, and therefore the exhaust streams do not combine their sound nor lower the efficiency of the engine. If the exhaust streams were allowed to combine, then unintended resistance would be transferred back to an engine because the exhaust streams would repel one another with force against the force of the exhaust stream.

Each bore (20) has preferably four rifles (30) cut into the interior wall of each bore (20). The rifles (30) are 0.02 inches deep and form a helix; each helix, if allowed to continue long enough to complete, would be three inches. In other words, the rifles (30) have a 3 inch pitch. Each bore (20) is preferably 0.312 inches in diameter. It should be further noted that the machining inside each bore (20) is specifically designed to be rough such that the interior wall of each bore (20) is rough between the rifles (30). Bore sizes will vary depending on the displacement of the engine.

Cone (22) has a tip (40) that is preferably flat with a diameter of 0.61 inches. The surface of cone (22) depends from tip (40) at a 36 degree angle from the horizontal plane. It is the surface of cone (22) with its 36 degree angle that makes each of bores (20) have a longer sidewall (27) that is medial and a shorter sidewall (28) that is lateral. The largest diameter of the surface of cone (22), and this includes tip (40), is 2.73 inches. Lower sidewall (24) of cone (22) depends from the surface of cone (22) at a 15 degree angle from the vertical plane.

Threads (50) allow the present invention (10) to attach to a conventional exhaust pipe (200), shown in Figure 2. A conventional spark arrestor (71) fits conventionally inside exhaust pipe (200) so that arrestor lip (72) will touch threads (50) when the present invention (10) is attached to exhaust pipe (200).

Also, Figure 1 shows the outside plate (60), depending roughly 15 degrees from the horizontal plane, with three screw holes (70), which are used to attach the present invention (10) to exhaust pipe (200) (seen in figure 6). It is believed that three screw holes (70) are necessary to keep the present invention (10) attached to the exhaust pipe (200), however more screw holes (70) would certainly work. The present invention (10) will take on whatever characteristics are necessary as conventionally available with exhaust systems to make sure the present invention (10) fastens securely to exhaust systems. The present invention (10) may also be integrated straight into or as a part of an exhaust system.

Additionally, attached to the inside of the present invention (10) and extending into the exhaust pipe (200) is spark arrestor (71). Spark arrestor (71) is conventional and known and is often used in the woods when off-roading in order to protect from the danger of fire.

Figure 3 is a side cross section view of the present invention (10). Figure 3 shows the bore (20) going straight down into the body of the present invention (10) and opening into the main chamber (160). Conventional baffling can be present at the bottom of each bore (20) and within each bore (20). It should be understood that the baffling is not necessary for the present invention (10) to function, and that it merely adds sound deadening capabilities, and is present in the current embodiment.

Figure 4 is a bottom cross section cut away view of the present invention (10). The bores (20) are placed evenly around the tip (40), which in this embodiment, does not contain a bore (20); but in one of the alternative embodiments of the present invention, tip (40) might contain a bore. Additionally the screw holes (70) are also placed evenly around the center in the plate (60).

The Rifling

Each of the rifles (30) forces the exhaust stream into a vortex motion. Gaseous substances (such as the exhaust in the case at hand) being ejected from a device in a vortex motion has many effects which are known, though the vortex has never before been used in this manner and for this purpose.

As the exhaust gases are forced through each of the bores (20), they are further compressed. The rifles (30) cause the gases to spin in a vortex. Molecules of air in the exhaust gases at the outside of the vortex are slowed by friction with the interior wall of each bore (20) that is rough between the rifles (30). Because slow- moving molecules are more affected by centrifugal force, the molecules of air in the exhaust gases at the outside of the vortex tend to fall toward the center of the vortex. The fast-moving molecules of the exhaust gases, located just inside the outer layer of the vortex, transfer some of their energy to the center of the vortex by bombarding some of its slow-moving molecules and -speeding them up. This results in the accumulation of slow-moving molecules in the center of the stream and of fast- moving molecules around the outside. Therefore the stream consists of a core of cold air surrounded by a rim of compressed hot air. This compressed stream of hot air creates a sort of air tube around the colder internal air even after it has left the bore (20). The affect of this air tube is that it holds the sound internal to it with the cold air allowing said sound to be dispersed more slowly and therefore at a lower decibel. Further, the creation of a vortex coming out of an engine sucks the gasses away from the engine. The design of the current invention (10) creates a partial vacuum in the invention's chamber (160) — see Figure 3 ~ thereby deadening the sound therein and at the same time, at sufficient speeds, will create a partial vacuum in the vehicles combustion chamber (not shown) which of course makes the engine more efficient. The Rough Surface

The rough surface (not shown) in each bore (20) is also designed to allow ease of airflow. The influence of surface structure on airflow has been the subject of considerable discussion and research. In the case at hand the surface is not so rough as to create substantial obstructions in the airflow such as the rifling (30) but is sufficient to create a boundary-layer on the outside of the vortex while still inside the bore (20). A boundary layer is where a layer of air is created by the movement of a gaseous substance over an uneven surface. This layer allows all other gasses to pass over an object with less (in fact almost no) friction then if in direct contact with said object. Boundary layers are ~= J111T" determined in accordance with the Prandtl equation. Currently, the roughness is created in the milling process by having the tool chatter. The surface finish is currently @ 500. Further experimentation for the most efficient roughness and therefore wind friction (t0 =r α2) is underway and will be modified in accordance with the engine and other factors discussed herein.

A review of Figure 5 shows four Dyno tests comparing the horse power, torque and RPM's of a straight pipe (100), a stock silencer (110), the present invention (10) as the embodiment shown in Figure 1, and an alternative embodiment of the present invention (120) with a ninth bore (20) placed in the tip (40). As can be seen, horsepower for the present invention (10) and alternative embodiment of the present invention (120) — with a ninth bore (20) ~ is greater than a straight pipe (100) and substantially more the stock silencer (110) with similar results on torque.

Other embodiments have been envisioned. Already discussed was the use of multiple bores (20), however the use of less bores (20) has also been discussed. The more bores (20) used the greater the exhaust outflow, the closer to mimicking a straight pipe. If less bores (20) are used there will be the possibility of back flow. The present invention (10) can be modified, and less bores (20) can be used in order to increase the pressure. At the same tim, the bores (20) could be lengthened (shortened, widened, narrowed) and the rifling could be tightened (loosened). This would increase the cohesiveness and speed of the exhaust streams allowing them to project further out away from the vehicle before breaking up. But then too tight an exhaust stream could theoretically push the stream at sonic speeds thereby creating other sound problems. Further, a faster stream would evacuate the devices chamber and the engines combustion chamber that would have additional affects on both the sound deadening capabilities and the efficiency of the engine. It is therefore understood that the different elements of the present invention (120): rifling, shape of the device, number of bore holes, roughness of the bore holes, bore hole placement, internal baffles in the main chamber of the device, and size of the main chamber will all affect the sound dampening and engine efficiency created by the invention.

In the following the invention has be described in its preferred embodiments. It should be understood that these embodiments are but few renditions of the present invention, and so long as the primary objectives of the invention are met through the elements claimed that many other embodiments are possible.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
CN2240616Y *28 Oct 199420 Nov 1996曾志成Improved vehicle exhaust pipe
DE3237417A1 *8 Oct 198212 Apr 1984Laszlo LevayTubular exhaust end piece for motor vehicles
GB428257A * Title not available
GB656552A * Title not available
GB191226560A * Title not available
US4354573 *17 Feb 198119 Oct 1982Sankei Giken Kogyo Kabushiki KaishaSilencer for motorcycle
Non-Patent Citations
1 *See also references of WO2007030099A1
International ClassificationF01N1/08, F01N13/08
Cooperative ClassificationF01N1/12, F01N1/086, F01N13/082
European ClassificationF01N1/12, F01N1/08H, F01N13/08B
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