APPARATUS FOR MINIMISING NOISE IN A FAN UNIT

Abstract: The present invention is a system of symmetric guides (25A, 25B) and baffles (26, 28) for directing and diffusing the external air drawn from a fan blower (12) before distributing the flow evenly to the outlet of a fan filter unit (32). This arrangement not only reduces the turbulence and minimizes pressure loss within a fan filter unit (32) but also maintains the even distribution of air when discharged through the same system. Furthermore, the present invention is implemented in dimensions substantially similar to that of the fan blower (12) in terms of heights. As such, the present invention minimises noise of a fan filter unit (32) even in low clean room ceiling height. Finally, the present invention's guides (25A, 25B) and baffles (26, 28) are symmetrical surrounding the fan blower (12), which allows either the clockwise fan or the anti-clockwise fan to be used for the same fan filter unit (32) for user's convenience.

Description: APPARATUS FOR MINIMISING NOISE IN A FAN UNIT The present invention relates to an apparatus for minimising noise from air moving devices, such as fans, air blowers etc. In particular, the present invention relates to a fan unit which may be used with a filter. It is common to control the number of particles in the air in a modern production and/or testing facility in order to ensure the quality of its output. Whether be it for wafer dies, compact discs or memory disk drives, effective fan filter units are needed to not only keep the particles contents within the clean room at acceptable levels but also to circulate the air to maintain a pleasant working environment for the clean room workers. However, such powerful fan filter units create excessive noise. It is known to use insulation materials to line along a conduit to or within the fan filter units to reduce noise. However, over time, the particles or fiber from the insulation material are dislodged from the surface and contaminate the clean room facility. The problem associated with fan filter noise is particularly exacerbated in confined spaces or enclosures such as a multi-story water fabrication plant. By confined space, the present invention envisages the height of the ceiling to be less than three meters. Low ceilings cause noise from fan filter unit to be particularly pronounced. Previously, an apparatus which minimises noise from a fan filter unit has been suggested by the current applicant in WO 99/11984. However, the S-shaped baffles of this earlier design only allow the design to be used with fans which rotate with a predetermined orientation, i.e. either only clockwise or anti-clockwise. The present invention attempts to address the above problem of reducing noise associated with a fan unit, without increasing contamination caused by the unit The present invention also attempts to increase the power efficiency of such a fan unit The invention also can be used regardless of whether the fan rotates in an anti-clockwise or clockwise direction In a first aspect, the present invention provides a fan unit comprising a fan blower configured to emit air in a plurality of directions in an air flow plane, and a pair of guides disposed on opposite sides of said fan in the said air flow plane to guide the flow of air between the two guides, each guide having an indent opposite said fan to accommodate said fan and each guide being symmetric about a symmetry plane perpendicular to the air flow plane and formed through the centre of the fan and an indent The symmetric shape of each guide with respect to the fan allows the guides to be used in the same positions regardless of the direction of orientation of the fan In addition to the indent, the guides are preferably provided with protrusions on either side of the indent, wherein the protrusions extend towards the opposite guide Thus, each guide has a substantially "W"-type shape Preferably, the guide has a smoothly varying profile at the indent and, more preferably at the protrusions However, the noise-reduction -properties may be partially achieved, using a guide with straight sections The configuration of the guides reduces the noise from the fan unit Also, the configuration of the guides enhances the velocity of air circulating m the unit Hence, a more efficient fan unit can be produced as a lower power can be used to dπve the fan to achieve the same circulating air velocity The air in the fan filter unit moves between the two guides. Baffles are preferably located at either end of the guides The baffles are provided to direct the air away from the fan and out of the fan unit Ideally, there are a pair of baffles at each end of the guides. There is an upper baffle and a lower baffle which are arranged vertically above one another. The vertical direction is taken to be the direction which is perpendicular to the plane of air emitted from the fan. The baffles are preferably inclined with respect to one another, such that the distance between the baffles decreases in a direction away from the fan. Preferably, the upper baffles are disposed at an angle of at least 40° and at most 60° to the direction of the plane of air. More preferably, they are arranged at an angle of about 45° to the air flow plane. The lower baffles are preferably arranged at an angle of at least 5° and at most 15° to the direction of the plane of air more preferably at about 10° to the plane of air. The baffles are located such that as the air leaves the guides, the air is reflected by the upper baffle onto the lower baffle, the lower baffle is positioned to direct the air out of an outlet. Preferably, the fan unit comprises a housing which has a base plate and an upper housing located'-above the base plate, the fan and guides being located between the upper housing and lower base plate, the unit having side sections which may be integral with the upper housing. The side sections being located at opposite ends of the guides, such that the baffles lie between the side sections and the ends of the guides. In the above configuration, the base plate will preferably be located relative to the housing such that the separation between the base plate and the upper surface of the upper housing is smaller than the distance which the side sections protrude from the upper surface of the housing. There is also a gap between the side sections and the base plate to form the outlet of the fan unit. The gap between the side sections of the housing and the base plate should, ideally be large enough to accommodate at least a part of the lower baffle in this gap The fan unit of the present invention is primarily intended for use in a clean room Therefore, the unit preferably compπses a filter Generally, this filter will be located below the base plate of the umt The guides and/or the baffles of the present invention will preferably be made from a solid mateπal, more preferably a metal The guides and/or baffles may also be perforated The present invention will now be descπbed with reference to the following non- hmiting embodiments which Figure 1 is a exploded, πght side, perspective elevational view of an embodiment of the present mvention, Figure 2 is a front, cross sectional elevational view of the embodiment of Figure 1, Figure 3 is a top, plan elevational view of section A-A in Figure 2, Figure 4 shows \the locations in the fan filter umt where the airflow velocities were measured for Figure 5, Figure 5 is a chart compaπng the average velocity of airflow and noise level of a fan filter umt with and without the present invention over a range external static pressures (measured m mAq) for different airflow condition Figure 1 shows an exploded view of the fan filter unit For clarity, the filter is not shown A rotatable fan blower 12 is located on a base plate 14 A mounting plate 20 for the fan blower 12 is located on an opposing side of the base plate 14 to the fan blower 12. The fan blower 12 is located within a housing which is formed from the base plate 14, an upper housing 16 and end sections 22 The upper housing 16 has an air inlet 18 located in its centre. Such that in use, the air inlet is located above fan blower 12 Fan blower 12 is a conventional type blower It is configured to be rotated by a motor (not shown) which will be located on opposing side of base plate 14 to the fan blower 12 As the fan blower rotates, it air is drawn through inlet 18 and expelled air in direction tangential to the rotation direction of the fan blower 12. The fan blower is also provided with guides 24A and 24B which are located on either side of the fan blower 12 and are disposed within the stream of emitted air from fan blower 12. Each guide is provided with an indent 25 A and 25B which, when the guide is in position, accommodate the shape of the fan blower 12. On either side of the indent are protrusions 27A and 27B. Each of the protrusions extends towards the opposite guide 24. Upper baffles 26A and 28B and lower baffles are provided at either end of the umt, such that the baffles are disposed between fan blower 12 / guides 24 A and 24B and the end section 22. The guides 24A, 24B are inclined with respect to one another such that the distance between the guides 24A, 24B decreases away from the fan blower Essentially, the guides from a substantially V-shaped structure where the apex of the V is pointing towards the end sections 22. Figure 2 shows the direction of air flow within the fan filter of Figure 1 As previously described, air is drawn in through inlet 18 by the rotation of fan blower 12 Fan blower 12 is located on base plate 14 The rotation of the fan blower forces air away from the fan blower and into the baffles 26A and 26B and 28A and 28B The direction of the baffles turns the air from traveling away from the blower which is located on the base plate to traveling out of the outlet 19 which is located beneath the base plate 14 The air then travels through filter 32 which is located underneath opening 19 Figure 3 shows a plan view of the constructed fan filter umt of Figures 1 and 2 It can be clearly seen that the fan blower 12 is located between guides 24 A and 24B and is accommodated within indents 25A and 25B of the guides 24A and 24B The shape of the protrusions 27A and 27B which extend towards the complementary protrusions in the opposite guide should also be noted The guides 24A, 24B are contoured to receive the discharged air from the fan blower 12 (shown in dotted circle) and guide the flow of air with minimum amount of turbulence towards the baffles 26 and 28. As this is a top View, the lower baffle 28 is not clearly shown. The upper baffles 26 are disposed at angles of about 45° to the plane of air which is emitted from blower 12, to diffuse air from the guides 24 The lower baffles 28 are disposed at an angle of about 10° to the airflow plane to redirect the flow of air below the base plate 14 The plan view of Figure 3 is symmetric about both an axis which traverses the centre of the indents and the centre of the fan and an axis which runs through the centre of the fan and the centre of baffles 26 and 28. This symmetric arrangement allows a fan to be accommodated which can rotate in either direction. Figures 4 and 5 shows results from the fan unit Figure 5 shows a plot of the average air velocity taken at 15 different points in the fan unit The 15 locations within the fan unit are shown in Figure 4 It can be seen that far superior results are provided when the air guide and baffle are present Thus, the present invention allows a higher air velocity which provides enhanced air circling action with the same amount of dπving power to the fan Hence, the present invention provides considerable energy advantages to that of the pπor art Figure 5 also shows the noise level measured 1 metre away from the fan in decibels for a fan filter unit with the air guide and baffle and without the air guide and baffle It can be seen that the noise is greatly reduced for the case where the air guide and baffle are present

Claims: o CLAIMS 1 A fan unit comprising a fan blower configured to emit air in a plurality of directions in an air flow plane and a pair of guides disposed on opposite sides of said fan in the said air flow plane to guide the flow of air between the two guides, each guide having an indent opposite said fan to accommodate said fan and each guide being symmetric about a symmetry plane peφendicular to the air flow plane formed through the centre of the fan and an indent 2 A fan unit according to claim 1, wherein each guide is formed such that there is a protrusion on either side of the indent on each guide, each protrusion extending towards the opposite guide 3 A fan unit according to claim 2, wherein the guides have a smoothly varying profile at the protrusions 4 A fan umt according to any preceding claim, wherein the guides have a smoothly varying profile at the indents 5 A fan umt according to any preceding claim, wherein the guides are arranged symmetrically with respect to one another on either side of the fan 6 A fan unit according to any preceding claim wherein said guides compπse a solid mateπal, preferably a metal 7 A fan unit according to any preceding claim, wherein the umt further compπses baffles located at each end of the pair of guides, to direct air our of the umt at 8 A fan umt according to claim 7, wherein there is an upper baffle and a lower baffle at each end of the guides, the baffles being arranged above one another, perpendicular to the direction of the plane of air, the baffles being inclined with respect to one another, such that the distance between the baffles decreases in a direction away from the fan 9. A fan unit according to either of claims 7 or 8, wherein said baffles comprise a solid material, preferably metal. 10. A fan unit according to claim 9, wherein the baffles comprise a perforated material. 1 1. A fan unit according to any of claims 8 to 10, wherein said upper baffles are disposed at an angle of from 40 degrees to 60 degrees, and preferably 45 degrees to the plane of air flow. 12. A fan unit according to any of claims 8 to 11, wherein said bottom baffles are disposed at an angle of from 5 degrees to 15 degrees and preferably 10 degrees to the plane of air flow. 13. A fan unit according to any preceding claim, wherein the fan and guides are disposed on a base plate. 14. A fan unit according to claim 13, wherein the unit further comprises a top housing coupled, to said base plate with an inlet for drawing air into the fan, and side sections for enclosing the fan, an air outlet being formed by a gap between the base plate and the side sections. 15. A fan unit according to claim 14, where dependent on claim 8, wherein the lower baffles are at least partially located in the gap between the side sections and the base plate. 16. A fan unit according to any preceding claim, comprising a filter. 17. A fan unit as substantially hereinbefore described with reference to any of the accompanying drawings.

Inventors: LEE ZONG TANG, LEE, ZONG, TANG
Applicants: KYODO ALLIED IND PTE LTD, LEE ZONG TANG, KYODO-ALLIED INDUSTRIES PTE LTD, LEE, ZONG, TANG
Application year: 1999
Main classification: F04D29
IPC codes: B01D46, F04D17, F04D29, F24F1, F24F7