Patent Application
20230279797
The present disclosure relates generally to sound absorbing elements and more particularly to a sound absorbing panel or tube structure having micro-louver sound attenuating slits which can be used to attenuate noise in various environments, and in particular, exhaust noise in muffler assemblies.
Slotted or perforated sheet materials are known for use in attenuating sound in various industries and environments, such as acoustic enclosures for machinery, etc., and in connection with the present disclosure, in attenuating exhaust noise in mufflers.
In enclosure structures, the sheet materials may be utilized as flat sheets lining the interior of an enclosure.
In connection with an exhaust environment, the slotted or perforated sheets are rolled into a tube and may be used as an inner exhaust conduit within a muffler structure. A concentric outer tube enclosure may be provided in spaced relation to the inner tube, and one or more layers of fiberglass insulation may be layered between the inner tube and the outer tube to form the basic muffler structure.
Previous sound absorbing elements have attempted to balance material composition, material weight, thickness, perforation/slit size (width, length, height), density, perforation/slit pattern and perforation percentage (i.e. the ratio of open to closed area per square unit of measure) in order to maximize performance and utility. Generally, it has been thought that increasing the perforation percentage, i.e. providing a larger open area per square inch, would improve sound attenuation, but performance has not been significantly improved over the years. Additionally, a known drawback to increasing the perforation ratio is that it exposes the surrounding fiberglass insulation to excessive heat and exhaust gas chemistry which degrades the fiberglass insulation, allows fiberglass particles to leak into the exhaust stream and ultimately allows the particles to be expelled into the environment.
There is therefore believed to be a need for an improved sound attenuating material which both maintains or improves sound attenuation as well as protecting the fiberglass insulation from heat and gas and acting to retain the fiberglass material within the muffler.
The present invention provides a novel sound absorbing sheet material with a unique combination of micro-louver slit parameters and patterns which provide both superior noise attenuation and a reduced perforation area to better protect fiberglass insulation when used in a muffler assembly.
The present invention further provides a novel muffler assembly incorporating the novel sound absorbing sheet as the inner exhaust conduit.
Exemplary embodiments will now be described further by way of example with reference to the following examples and figures, which are intended to be illustrative only and in no way limiting upon the scope of the disclosure.
Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the device and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. Further, in the present disclosure, like-numbered components of the embodiments generally have similar features, and thus within a particular embodiment each feature of each like-numbered component is not necessarily fully elaborated upon. Additionally, to the extent that linear or circular dimensions are used in the description of the disclosed systems, devices, and methods, such dimensions are not intended to limit the types of shapes that can be used in conjunction with such systems, devices, and methods. A person skilled in the art will recognize that an equivalent to such linear and circular dimensions can easily be determined for any geometric shape. Further, to the extent that directional terms like top, bottom, up, or down are used, they are not intended to limit the systems, devices, and methods disclosed herein. A person skilled in the art will recognize that these terms are merely relative to the system and device being discussed and are not universal.
Referring to
The materials from which the sound absorbing sheets 10 may be manufactured are preferably metals. Examples may include stainless-steel, stainless-steel alloys, aluminum, aluminum alloys, aluminized steel, austenitic alloys and ferritic alloys, as well as other metals and metal alloys.
In an exemplary embodiment, the sheet material may comprise 0.012 inch (0.3048 mm) thick Annealed Ferritic Stainless Steel. This is roughly half the thickness of previous sheet materials. The thinner sheet material is lower in weight and cost and allows a shallower perforation depth to pierce the material. This in turn allows easier manufacturing, consumes less energy during the manufacturing process and provides a lower micro-louver height (h) perpendicular to the material plane. The lower profile micro-louvers also improve (reduces) turbulence within the exhaust gas flow over the surface thereof.
The thinner metal material is also easier to handle and roll into tubular form or other forms and is also easier to weld.
Furthermore, the thinner material allows the micro-louver openings 12 to be formed with the same total cross-sectional perforation area but having a smaller louver height (h) and a smaller cross-sectional slit height (x) (see Prior Art
The micro-louver slits 12 in the illustrated embodiments may be accomplished with suitable shearing pressure perpendicular to the material plane whereby the louver edge is partly pressed out of the plane and the slit created with a shallow height (
As previously seen in
Referring to
As noted above, the relationship between the slits is largely dependent on how large a percentage of the surface the slits form, i.e. the perforation ratio or open area percentage. In this regard, the Applicant has found through extensive testing that with the above noted dimensional parameters, the perforation ratio “P” can be much lower than found in the prior art, and in this regard can be lower than 3.5% open area, and more preferably can be about 2% open area.
In this regard, the ranges of these dimensional parameters are laid out in the table below. The identified parameters are meant to serve as guidelines and the invention should not be limited by these exemplary ranges.
The pattern formed by the slits 12 constitutes just one example of a variety of possible placements and orientations of the slits and in this regard,
Each of the noted louver patterns in
Turning now to
Generally, the muffler assembly 20 comprises an inner micro-louver sheet tube 22 (as described above) rolled with the perforations 12 extending from inside to outside and welded longitudinally in a cylindrical configuration (see also
The outer tube 24 may include an inner annular flange 32 to create an annular gap 34 between the outer surface of the outer fiberglass layers 26 and the inner surface of the outer tube housing 24.
A further muffler assembly 50 is illustrated in
While the exemplary muffler embodiments are illustrated with round tubular exhaust tubes, some exemplary muffler embodiments may use alternative non-round shapes for the exhaust gas flow. Examples may include oval tubular, elliptical tubular, square tubular or rectangular tubular shapes. Generally, it should be understood that the micro-louver blank material can be formed into any desired shape which is appropriate for the end use and air flow pattern in any application.
It can therefore be seen that the exemplary embodiments described herein provide unique and novel sound absorbing structure having micro-louver sound attenuating slits which can be used to attenuate exhaust noise in muffler assemblies. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit.
While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 63/316,561, filed Mar. 4, 2022, the entire contents of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63316561 | Mar 2022 | US |
