Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2000-12-29
2003-11-04
Lockett, Kimberly (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
Reexamination Certificate
active
06640926
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the field of acoustic duct silencers, and more particularly, to modular elbow silencers.
BACKGROUND OF THE INVENTION
The use of high-performance Heating Ventilation and Air Conditioning (HVAC) systems has resulted in unacceptably high noise levels in buildings. Obtrusively loud noise from ducts used in an HVAC system can effect the overall environment in a building by transmitting unwanted sound throughout the building. Additionally, air flowing through abrupt changes in the cross-sectional dimensions of a duct can also produce sound. Accordingly, there has been a longstanding problem with the amount of sound transmitted through the ducts of an HVAC system.
Various attempts have been made to minimize the sound propagation in straight air ducts. One such attempt provides a sound attenuating silencer lined on the inside of the straight air duct.
Sound attenuating silencers have also been used in elbow ducts to reduce noise propagation. Elbow silencers currently used in the industry are modified standard linear silencers which are typically bent at an angle of approximately ninety degrees.
FIG. 1A
illustrates a conventional one-piece elbow silencer
110
currently used in industry which typically includes a casing having a baffle
120
which defines two flow channels or paths
130
and
140
. With this construction, each air or sound flow channel or path
130
and
140
defined by the baffle
120
has a different length, making pressure loss, self generated noise and sound attenuation unpredictable and unreliable.
Another conventional arrangement of elbow silencers is illustrated in FIG.
1
B. The arrangement shown in
FIG. 1B
uses two elbow silencers
150
and
160
which are positioned in a nested relationship. The air or sound flow channels
130
and
140
of the two elbow silencers
150
and
160
are similar to the flow channels of the elbow silencer
120
shown in
FIG. 1A
because each defines a different length which, again, makes pressure loss, self generated noise and sound attenuation unpredictable and unreliable.
Turning vanes have also been used in an attempt to minimize the sound propagation in existing elbow air ducts. Turning vanes are baffles that are inserted into a single duct which define flow channels for the air flow. However, turning vanes are impractical because they require insertion of multiple baffles into an existing single duct. Turning vanes are also inconsiderate of space constraints and it is time consuming and expensive to insert the baffles into a single duct.
SUMMARY OF THE INVENTION
The present invention provides a modular acoustic elbow silencer which is configured to attenuate sound and is capable of being nested with another, complementary elbow silencer. According to one embodiment, an elbow silencer for attenuating noise associated with a fluid medium passing through said elbow silencer comprises a casing and a baffle. The casing includes sides that define an inlet end and an outlet end. The baffle is disposed within the casing and defines a flow channel through which the fluid medium passes. The elbow silencer is capable of being nested with a complementary elbow silencer having substantially the same flow channel.
REFERENCES:
patent: 5563382 (1986-10-01), Choyce
patent: 6024189 (2000-02-01), Heuser
patent: 6464036 (2002-10-01), Yenner
Industrial Acoustics Company, Inc.
Lockett Kimberly
Morgan & Finnegan , LLP
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