Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2001-10-15
2003-09-23
Lockett, Kimberly (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S238000, C181S249000, C181S264000, C181S277000
Reexamination Certificate
active
06622819
ABSTRACT:
FIELD OF THE INVENTION
The present invention provides a sound attenuator for pneumatic exhaust.
BACKGROUND OF THE INVENTION
Sound attenuators are used to reduce the noise produced by pneumatic exhaust discharged from various devices such as, for example, air operated diaphragm pumps, pneumatically powered piston or plunger pumps, air cylinders, pneumatic directional control valves, and air motors. Conventional sound attenuators typically include a housing containing porous media such as wrapped or rolled layers of metal or plastic screens and/or other filter materials that control the rate of expansion of the decompressing pneumatic exhaust. Such conventional sound attenuators may also include one or more rigid baffles or fins that force the pneumatic exhaust to flow in tortuous paths within the housing before exiting the housing through a plurality of slits or openings. Conventional sound attenuators of this type are disclosed in, for example, Trainor, U.S. Pat. No. 3,561,561, and Boretti, U.S. Pat. No. 4,316,523.
Those of skill in the art will readily appreciate that conventional sound attenuators for pneumatic exhaust tend to clog easily and/or become plugged during use for a variety of reasons. For example, the rapidly decompressing gas can lead to the formation of ice on various surfaces within the sound attenuator. Ice crystals can clog or plug pathways within a conventional sound attenuator resulting in a decrease in the efficiency and capacity and/or a complete plugging of the device. For this reason, conventional sound attenuators also typically include a pressure relief means such as a blow-out plug to allow for the venting of pneumatic exhaust in the event of a clog or plug. It will be appreciated that if the sizing of the pressure relief means is not sufficient to handle the volume and/or pressure of pneumatic exhaust and/or system fluid (i.e., pumped product) presented, a catastrophic failure of the sound attenuator device or the pneumatic device can occur. In either event (i.e., the blow-out plug operates or a catastrophic failure of one or both of the devices), pneumatic exhaust and, in some cases, system fluid can be discharged into the environment in an uncontrolled and non-sound attenuated manner.
Another problem presented by conventional sound attenuators is that the use of porous filter media to control the rate of expansion also tends to create excessive back pressure, which can reduce the operational efficiency of the pneumatic device. Moreover, it is difficult to maintain a constant back pressure using conventional sound attenuators because of their tendency to become progressively clogged over time.
Another limitation in conventional sound attenuator designs is that pattern of the pneumatic exhaust discharged from such devices is generally random in nature like a sprinkler. Thus, the pneumatic exhaust exiting the sound attenuator is discharged in many directions, which can adversely affect the work environment in the affected area surrounding the sound attenuator.
A sound attenuator is needed that can effectively attenuate the noise produced by pneumatic exhaust while also providing the least amount of constant back pressure necessary for the efficient operation of the pneumatically powered device. Such a sound attenuator should not clog or freeze easily, and should not adversely affect the work environment surrounding the equipment on which it is installed.
SUMMARY OF THE INVENTION
The present invention provides a sound attenuator for pneumatic exhaust that attenuates the sound of pneumatic exhaust to safe levels, does not easily clog or plug, does not create excessive back pressure, resists freezing and icing, and provides a controlled discharge pattern of pneumatic exhaust. The sound attenuator according to the invention can be used to attenuate the sound of pneumatic exhaust from air operated diaphragm pumps, pneumatically powered piston or plunger pumps, air cylinders, pneumatic directional control valves, air motors, and any other type of device or equipment providing a source of pneumatic exhaust.
A sound attenuator according to the invention comprises a body having an open end and an inner cavity defined by an inner wall. An inlet port is provided in the body. The inlet port is adapted to establish fluid communication between a source of pneumatic exhaust and the inner cavity. A cap is releasably connected to the body to cover the open end. The sound attenuator further comprises at least one exit port in fluid communication with the inner cavity. A plurality of baffles are arranged within the inner cavity so as to define a series of sequential closed chambers between the inlet port and the exit port. A deflector is positioned proximal to the exit port to redirect the flow of pneumatic exhaust at least 90°. The deflector cooperates with an exterior surface of the body to define an expansion zone. Each of the baffles has a periphery in contact with the inner wall and is adapted to flex under a predetermined pneumatic pressure load to permit the pneumatic exhaust to flow between the periphery and the inner wall of the body.
In the preferred embodiment of the invention, the sound attenuator further comprises a diffuser that is mounted to the exterior side of the body. The diffuser has an ellipsoidal-section surface portion that is positioned proximal to the deflector to redirect the flow of pneumatic exhaust passing through the expansion zone at least 90°. The diffuser also preferably comprises a finger portion in contact with the exterior surface of the body that can be positioned with respect to the deflector to adjust the dimensions of the expansion zone.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
REFERENCES:
patent: 771070 (1904-09-01), Hewitt
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patent: 1109702 (1914-09-01), Reetz
patent: 1289750 (1918-12-01), Hauman
patent: 2198021 (1940-04-01), Wood
patent: 3507353 (1970-04-01), Murphy
patent: 3561561 (1971-02-01), Trainor
patent: D220165 (1971-03-01), Trainor
patent: 3779340 (1973-12-01), Hoffman et al.
patent: 4079809 (1978-03-01), Visnapuu et al.
patent: 4316523 (1982-02-01), Boretti
patent: 4341283 (1982-07-01), Mazzanti
patent: 4749058 (1988-06-01), Trainor
patent: 5500494 (1996-03-01), Ligman
patent: 5909016 (1999-06-01), Sterling
Lockett Kimberly
Rankin, Hill Porter & Clark LLP
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