US20090142212A1

US20090142212A1 - Rotary blower with noise abatement jacket enclosure

Info

Publication number: US20090142212A1
Application number: US11/998,893
Authority: US
Inventors: Paul Xiubao Huang; Sean William Yonkers
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-12-03
Filing date: 2007-12-03
Publication date: 2009-06-04

Abstract

A rotary blower with noise abatement jacket enclosure having multiple interconnected and synchronized parallel multi-lobe rotors with the same number of lobes for propelling flow from a suction port to a discharge port of an inner casing without internal compression. The noise abatement jacket enclosure is shaped to surround the blower and to conform generally to its body contours, but is oversized to provide adequate cooling spaces with outer skin of the blower. It comprises a forced air cooling jacket comprising an inner and outer cover, a sound absorbent layer comprising an inner and outer surface, the inner surface in contact with the blower outer cooling cover, and a sound barrier layer comprising an inner surface in contact with the outer surface of the sound absorbent layer.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to the field of mechanical vacuum pumps and blowers used in industrial and municipal applications, and more particularly relates to double rotor multi-lobe type blowers commonly known as positive displacement rotary blowers or simply Roots blowers, and more specifically relates to a Noise Abatement jacket enclosure for reducing noise transmission from rotary blowers.
2. Description of the Prior Art
Rotary blowers are widely used in industrial and municipal applications such as for loading a bulk truck by pneumatic conveying bulk materials or for cleaning municipal sewer lines by vacuum suction. They are desired because of its unique performance characteristics inherent from its rotary positive displacement nature: it delivers an almost constant flow at varying vacuum levels. The ability of varying pressure or vacuum at constant flow makes rotary blowers the ideal tools for pneumatic conveying applications where material clogging can be quickly cleared with the increase of the discharge pressure or suction vacuum while maintaining the transfer capability.
Rotary blowers for use in municipal sewer cleaning applications, especially when used in residential areas, are required to meet stringent noise level requirements, such as those prescribed by OSHA. Rotary blowers tend to be very noisy, sometimes as high as 90-105 dBA if untreated, because of the sharp discharge flow pulsations and engagement of timing gears at high speed. The later is generally of high frequency and radiates from blower body. From a system point of view, the primary source of noise generation in a blower package is the rotary blower. In addition to the Rotary blower, there is an array of secondary sources of noise, such as the motor, the valves, and the silencer body. But they are all about 10-20 dBA less than the noise level of the blower.
Noise generated by the aforementioned sources is propagated either by air or by structure. By introducing upstream and downstream silencers, been widely used in the industry, air borne noise transmitted through air stream is greatly reduced. Effort are also made to reduce the noise level by lowering the pulsation inside the blower, such as the method disclosed in U.S. Pat. No. 4,215,977 to Weatherston by self-cancelling a portion of the pulsation with de-phasing. The commercial application of this technology is, for example, Roots WhispAir as explained in publication “Roots Whispair Blowers”. However, its effectiveness is limited, only achieving 5-10 dBA reduction. Moreover, to reduce the structure borne noise and the air borne noise radiated from blower surface itself, one way is to increase the mass and stiffness of the blower. Such modification of the structure of the blower is expensive and can affect manufacturability of the blower. Another way is to enclose the blower system in a room-like sound enclosure usually consisting of 6 sided wall panels with sound absorbent material and hard reflection surfaces. Sound enclosure built in this fashion is generally very effective, reducing the noise levels up to 25 dBA, but it is expensive, heavy and bulky, especially not practical for mobile applications.
What is therefore needed is a device capable of achieving a high damping and reduction of noise emitted from blower surfaces while being kept light in mass, small in size and suitable for mobile application. It would further be preferable if the device could also serve to enhance the heat transfer from the blower outer surfaces, so that they could operate more quietly, reliably and be used for mobile applications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a noise abatement jacket enclosure, with a shape generally conforming to blower outer contours, for reducing noise transmission from a rotary blower while maintaining small size, light weight and suitable for mobile application.
It is a further object of the present invention to provide a noise abatement jacket enclosure for a rotary blower which comprises a forced air cooling jacket with a shape generally conforming to blower outer contours to enhance the heat transfer from the blower outer surfaces, so that they could operate more quietly, reliably and be used for mobile applications.
It is a further object of the present invention to provide a noise abatement jacket enclosure for a rotary blower which comprises a sound absorbent layer comprising an inner and outer surface, the inner surface in contact with the blower outer surface, and a sound barrier layer comprising an inner surface in contact with the outer surface of the sound absorbent layer.
It is a further object of the present invention to provide a noise abatement jacket enclosure for a rotary blower which comprises a forced air cooling jacket comprising an inner and outer cover, a sound absorbent layer comprising an inner and outer surface, the inner surface in contact with the blower outer cooling surface, and a sound barrier layer comprising an inner surface in contact with the outer surface of the sound absorbent layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section front view of a preferred embodiment of the noise abatement Jacket enclosure of the present invention with a forced air cooling layer;

FIG. 2 is a cross-section side view of a preferred embodiment of the noise abatement Jacket enclosure of the present invention with a forced air cooling layer;

FIG. 3 is a cross-section top view of a preferred embodiment of the noise abatement Jacket enclosure of the present invention with a forced air cooling layer;

FIG. 4 is a cross-section front view of an alternative embodiment of the noise abatement Jacket enclosure of the present invention with a forced air cooling layer;

FIG. 5 is a cross-section side view of an alternative embodiment of the noise abatement jacket enclosure of the present invention with a forced air cooling layer;

FIG. 6 is a cross-section top view of an alternative embodiment of the noise abatement jacket enclosure of the present invention with a forced air cooling layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.
As a brief introduction, the present invention rotary blower with a noise abatement jacket enclosure includes an inner enclosed casing having a flow suction port and a flow discharge port and an internal bearing support structure, and an outer multi-layered cover, the noise abatement jacket enclosure, comprising a forced air cooling jacket layer, a sound absorbent layer, the inner surface in contact with the blower outer cooling layer, and a sound barrier layer comprising an inner surface in contact with the outer surface of the sound absorbent layer. The noise abatement jacket enclosure is shaped to surround the blower and to conform generally to its body contours, but is oversized to provide adequate cooling spaces between outer skin and the blower.
The present invention rotary blower with noise abatement jacket enclosure also includes two parallel multi-lobe rotors mounted on two parallel rotor shafts respectively, where the rotor shafts are supported by the internal bearing support structure of the inner casing and interconnected through a set of timing gears to rotate the rotors in synchronization for propelling flow from the suction port to the discharge port. Cooling fans are mounted on one of the two rotor shafts at locations adjacent to the inlet and outlet openings of the outer cover for circulating cooling air through the space between the outer cover and the inner casing.
It is therefore an object of the present invention to teach the construction of a noise abatement jacket enclosure for reducing the radiation noise from blower outer surfaces. More specifically, the noise abatement jacket enclosure of the present invention is a multi-layered apparatus constructed to engage in contact with a rotary blower so as to both reduce noise propagation and to act as a cooling path on the blower outer surfaces. The present invention rotary blower with noise abatement jacket enclosure is capable of achieving lower noise level while maintaining being effectively cooled, light weight and compact size, thereby improving the blower application range for mobile and residential areas.
Referring to FIGS. 1 to 3, there is shown a typical arrangement of a preferred embodiment of the rotary blower 10 with noise abatement jacket enclosure 50. Typically, the rotary blower 10 has two parallel rotors 12 mounted on rotor shafts 14 and 16 respectively, where rotor shaft 14 is driven by an external rotational driving mechanism (not shown) and through a set of timing gears 18 rotate the rotors 12 in synchronization without touching each other for propelling the flow from a suction port 36 to a discharge port 38 of the blower 10. The rotary blower 10 also has an enclosed casing 20, wherein the rotor shafts 14 and 16 are mounted on an internal bearing support structure 22 with bearings 24 and seals 26. The casing structure further includes an outer cover 28 with a space maintained between the inner casing 20 and the outer cover 28 as cooling air passage 52 as indicated by the arrows for cooling flow direction in FIG. 1 to 3. In FIG. 2, the large arrows show the direction of the internal flow as propelled by the rotors 12 from a suction port 36 to a discharge port 38 of the blower 10.
As an important novel and unique feature of the present invention, a noise abatement jacket enclosure, is conformingly surrounding the rotary blower 10 of the present invention, and its cross-section is illustrated in FIG. 1 to 3. In the embodiment illustrated, noise abatement jacket enclosure 50 is comprised of three layers. A first layer is comprised of forced air cooling path layer 52. A cooling fan 40 is employed on one side of the blower to provide positive cooling air for the blower 10. The cooling fan is mounted on the extended shaft 14, adjacent to the air inlet openings 42 of the outer cover 28 for bringing in cooling air, which is in turn guided by the outer cover 28 to pass around the inner casing 20 through the space between the outer cover 28 and the inner casing 20 and exits from the air outlet openings 44 of the outer cover 28, as shown by the arrows in FIGS. 1 and 3. The second and third layer, a preferably prefabricated combination of sound absorbent layer and a sound barrier layer, is located in contact with the outer surface of forced air cooling jacket layer 52. The sound barrier layer 56 is used to reduce sound transmitted to the ambient. The sound absorbent layer 54 is preferably glued onto the sound barrier layer 56. In one embodiment, forced air cooling path layer 52 is in contact with sound absorbent layer 54 which is itself attached to sound barrier layer 56 such that the entire assembly comprising noise abatement jacket enclosure 50 may be fastened to rotary blower 10 and conforming to its outer contours.
When a rotary blower 10 is surrounded by the noise abatement jacket enclosure 50 of the present invention comprised of the forced air cooling layer 52 in contact with the sound absorbent layer 54 which is in contact with the sound barrier layer 56, there exists both a reduction in the noise transmitted from the rotary blower to ambient as well as an improvement in the cooling provided to the rotary blower.
The theory of operation underlying the noise abatement jacket enclosure 50 of the present invention is as follows. The vibrating inner surfaces 20 of the rotary blower 10 first is reflected by the cover 28, which is also used to guide the cooling air around the blower outer contours. Then the vibrating surfaces 28 of the rotary blower 10 sets the sound absorbent layer 54 in vibration and the vibration induced mechanical energy is turned into heat. It is of note that sound absorbent layer 54 exhibit low stiffness, and as such, act as a decoupler between the sound barrier layer 56 and the rotary blower casing 28. It is the purpose of the sound barrier layer 56 to again reflect sound waves back and forth between the sound barrier layer 56 and the rotary blower 28 thereby increasing the dissipation of sound energy.
In the event that the rotary blower 10 outer surface 20 temperature is not very high (typically lower than 120° F.), there is no need to have the forced air cooling layer 52 to carry the heat away. In that case, the forced air cooling layer 52 is not needed and the rotary blower 10 outer surface 20 is immediately followed by a sound absorbent layer layer 54 which is itself surrounded by a sound barrier layer 56. In such an instance, the combination of the sound absorbent layer 54 and the sound barrier layer 56 is sufficient to achieve the goal of the present invention.
FIGS. 4 to 6 show a typical arrangement of another preferred embodiment of the rotary blower 10 with noise abatement jacket enclosure 50. In this embodiment, the forced air cooling layer 52 is comprised of an inlet filter 62, a cooling fan 40, a cooling flow passage formed between the outer cover 28 and the inner casing 20, manifold 64 and injection ports 66 and 68. The cooling air from fan 40, is guided by flow passage 52 to the manifold 64, gathering for injection onto rotors 12 through openings 66 and into discharge port 38 through induction openings 68, exiting at discharge port 38, as shown by the arrows in FIGS. 4 to 6.
It is apparent that there has been provided in accordance with the present invention a noise abatement jacket enclosure for reducing noise transmission in rotary blower. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.

Claims

1. A rotary blower with noise abatement jacket enclosure, comprising:

a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between, and an inner enclosed casing and an outer cover with a hollow space there-between;

b. two parallel multi-lobe rotors having the same number of lobes and rotatably mounted on two parallel rotor shafts respectively inside said inner casing and interconnected through a set of timing gears to rotate in synchronization for propelling flow from said suction port to said discharge port;

c. a cooling layer comprising said space between outer cover and said inner casing and at least one cooling fan mounted on one of said two rotor shafts for circulating cooling air through said layer;

d. a sound absorbent layer comprising an inner and outer surface, said inner surface in contact with said outer surface of said cooling layer;

e. and a sound barrier layer comprising an inner surface in contact with said outer surface of said sound absorbent layer;

f. whereby said high rotary blower is capable of achieving a high damping and reduction of noise emitted from said blower surfaces while being kept light in mass and small in size, and at the same time enhancing the heat transfer from said blower outer surfaces, so that said blower operates more quietly, reliably and be used for mobile applications.

2. The noise abatement jacket enclosure of claim 1, wherein said cooling layer has a centrifugal cooling fan mounted on one of said two rotor shafts for circulating cooling air through said layer.

3. The noise abatement jacket enclosure of claim 1, wherein said sound absorbent layer is comprised of a material selected from the group consisting of expandable Urethane foam.

4. The noise abatement jacket enclosure of claim 1, wherein said sound barrier layer is comprised of hard materials such as metal or plastic.

5. A rotary blower with noise abatement jacket enclosure, comprising:

a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between;

c. a sound absorbent layer comprising an inner and outer surface, said inner surface in contact with said outer surface of said blower housing;

d. and a sound barrier layer comprising an inner surface in contact with said outer surface of said sound absorbent layer;

e. whereby said high rotary blower is capable of achieving a high damping and reduction of noise emitted from said blower surfaces while being kept light in mass and small in size, and at the same time enhancing the heat transfer from said blower outer surfaces, so that said blower operates more quietly, reliably and be used for mobile applications.

6. The noise abatement jacket enclosure of claim 5, wherein said sound absorbent layer is comprised of a material selected from the group consisting of expandable Urethane foam.

7. The noise abatement jacket enclosure of claim 5, wherein said sound barrier layer is comprised of hard materials such as metal or plastic.

8. A rotary blower with noise abatement jacket enclosure, comprising:

a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between, and an inner enclosed casing and an outer cover with a hollow space there-between leading to a manifold with injection ports towards rotor near discharge port;

c. a cooling layer comprising said hollow space between said outer cover and said inner casing and at least one cooling fan on each side mounted on one of said two rotor shafts for circulating cooling air through said layer;

9. The noise abatement jacket enclosure of claim 9, wherein said cooling layer has a centrifugal cooling fan mounted at each side on one of said two rotor shafts for circulating cooling air through said layer.

10. The noise abatement jacket enclosure of claim 9, wherein said sound absorbent layer is comprised of a material selected from the group consisting of expandable Urethane foam.

11. The noise abatement jacket enclosure of claim 9, wherein said sound barrier layer is comprised of hard materials such as metal or plastic.