Title of Invention

''SIROCCO FAN''

Abstract

A sirocco fan which reduces abnormal noise and improves air flow includes: a scroll 2 with an inlet wall 8 and a closed endwall 9, the inlet wall a having an inlet and the endwall 9 being opposed to the inlet wall 8; and an impeller 3 provided in tile scroll 2, for suctioning and exhausting air, wherein a cutoff 7 of the sirocco fan 1 is inclined so as not to allow entire sections of a blade 10 of the impeller 3 to be simultaneously met entire sections of the cutoff 1 when the blade 10 of the impeller 3 passes through the cutoff 7, thereby, achieving stable air flow.

Full Text

SIROCCO FAN BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a sirocco fan, and more particularly, to a cutoff which divides an inlet and outlet side of the sirocco fan. Discussion of the Related Art Generally, a sirocco fan is kind of blower which is used for air-conditioning and ventilating, and is used in an air-conditioner or fan-coil heater. Also, the sirocco fan is called a multi -blade fan because it has about 30 to 50 blades. In this respect, the sirocco fan is compared differently with the radial fan having blades smaller than those of the sirocco fan. Figs. 1 and 2 are perspective and side views illustrating a related art sirocco fan. The related art sirocco fan will be described with reference to Figs. 1 and 2. The sirocco fan 1 includes a scroll 2 which acts as air passage, and an impeller 3 which is provided in the scroll 2 and used for inlet and outlet of the air by the driving force of a motor(not shown). The impeller 3 includes a pair of rims 3a and a plurality of blades 10 which are parallel to the rims 3a. The scroll 2 is divided into a circular main bodv 2a where I * the impeller 3 is located and a dittuser 20 connected with the main body 2a. And the main body 2a includes an inlet, wall H having an inlet 4 and a closed endwall 9 which is opposed to the inlet wall 8. A front end of the dithiser 20 acts as an outlet- There fore, in the sirocco fan 1, the air is sucked from the inlet 4 at the inlet wall 8 of the scroll 2 and exhausted out through the outlet 5 of the diffuser 20 . A reference numeral 6 which is nor, described is a bell -mouth which is located at the inlet 4 and fitted into the scroll 2 to guide sucking air and at the same time to shield the impel ler 3. In addition, the starting point in the diffuser 20 of the scroll 2 is a cutoff 7. The cutoff 7 is the standard point of the expansion radius of the scroll 2 and Lhe important part to divide '_he inlet and outlet side. Tn other words, since the cutoff 7 is the starting point which changes dynamic pressure into static pressure, it acts as the starting point of air outlet and quick change of pressure periodically occurs therein. As shown in Fig. 2b, in the related art sirocco fan 1, the cutoff 7 is parallel to the blade 10 of the impeller 3 or it is tapered at about 2° or less so as to easily separate the scroll 2 from the mold when producing the scroll 2. Referring to Figs. 2a and 2b, the operation of the related art sirocco fan will be described below. Once the impeller 3 which is located in tho scroll 2 is rotated by the driving force of the motor, suction power occurs • by the rotation of: the impeller 3, so that the air is sucked into the scroll 2 through the inlet 4 termed in the inlet wall 8 of the scroll 2. The sucked air is exhausted out of the scrol I .? through the outlet 5 formed in the scroll 2 while flowing inside Che scroll 2 by the continuous rotation of the impeller 3. However, the related art sirocco fan has the following problems. First, since the cutoff 7 is parallel to the blade 10 of the impeller, abnormal noise occurs significantly due to the blade passing frequency(BPF). The reason is, when the blade 10 of the impeller 3 meets the cutoff 7 by the rotation of the impeller 3, the blade 10 is parallel to the cutoff 7 and at the same time the entire sections of the blade 10 meet the enr.ire seer, ions of nhe cutoff 7 so that there occurs abnormal noise due to the BPF in the entire length direction of the blade. Second, as shown in the Fig. 3, the speed of the incoming air does not decrease until it hits the endwall 9 of the sirocco fan 1. Therefore the incoming air retains the ajtidl speed component until the time it passes through the blade ln of the impeller 3. For this reacon, the air that has hit the endwall 9 is re-circulated along the side of the scroll 2. Also, since the scroll 2 cannot transfer the dynamic pressure into static pressure, the flow speed of the point close Co the endwall 9 at the outlet 9 is comparatively fast and at the inlet wall 8 the flow speed is rather slow, thereby causing flow of the exhausting air to be irregular. Moreover, counterflow A may sometimes occur. In summary, in the related art---sirocco fan, there is a problem that the air flow is poor due to abnormal, noise. SUMMARY OF THE INVENTION Accordingly, Che present invention is directed to a sirocco an that substantially obviates one or more of the problems due r.o limitations and disadvantages of the related art. An object of the present invention is to provide a sirocco fan which reduces abnormal noise due to the BPF. Other object of the present invention is to a sirocco fan which increases air flow rate and enables stable air flow. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice oE the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. To achieve these and other advantages and in accordance with Lhe purpose of the present invention, as embodied and broadly described, a sirocco fan according to the present invention includes: a scroll with an inlet wall and a closed endwall, the inlet wall having an inlet and the endwall being opposed to the inlet wall; and an impeller provided in the scroll, for suctioning and exhausting air, wherein a cutoff of the sirocco fan is inclined so as not to allow entire sections of the blade of the impeller to be simultaneously met entire sections of the cutoff when the blade of the impeller passes through the cutoff, thereby achieving stable air flow. It is preferable that the cutoff is inclined towards the endwall from the inlet wall' of the scroll and it may have a Straight lined shape or a curved shape. Also, the cur.off has preferably an inclined angle in the range of 20' between 50', more preferably in the range of 30° between 40". Therefore, the sirocco fan of the present invention can reduce abnormal noise and also achieve high air flow race and stability of air flow. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included Lo provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: Fig. 1 is an exploded perspective view illustrating a background art sirocco fan,- Fig. 2a is a perspective view illustrating a background am airocco fan; Fig. 2b is a side view illustrating a background art sirocco Pan in view of an outlet side; Fig. 3 is a state view illustrating air flow in a background art sirocco fan,- Fig. 4 is a perspective view illustrating a sirocco fan according to the first embodiment of the present invention,- Fig. 5 is a side view of Fig. 4; Fig. 6 is a side view illustrating a sirocco fan according to the second embodiment of the present invention; Fig. 7 is a side view illustrating a sirocco ran according Co the third embodiment of the present invention; Fig. 8 is a state view illustrating air flow in a sirocco tan according to the present invention; and Fig. 9 is a graph illustrating noise to an inclined angle of a cutoff in a sirocco fan according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Fig. 4 is a perspective view illustrating the first embodiment of the present invention and Fig. 5 is a side view of Fig.4. A sirocco fan according to the present invention will be described with reference to Figs. 4 and 5. The same terms and reference numerals are given to the same elements as those of the related art sirocco fan and their description is omitted. In the same manner as the related ;irt, the sirocco fan 1 ot the present invention includes a scroll 2 and an impeller 3 located within the scroll 2. These scroll and impeller include the same elements as those of the related art. The sirocco fan of the related art is different from that of the present invention in that the cuLoff 7 of the related art sirocco fan 1 is parallel to the blade 10 of the impeller 3 while the cutoff 7 of che present invention crosses the blade 10 of Che impeller 3 each other. In other words, the cutoff V rs inclined with a predetermined angle towards the endwall 9 from the inlet wall 8. In this case, the blade 10 of the impeller 3 does not simultaneously meet the entire sections of the cutoff 7 but crosses the cutoff 7, when the blade 10 passes through the cutoff 7 by its rotation. Therefore, it is resulted in better air flow and noise reduction. The cutoff 7 is preferably inclined to be down from the inlet wall 8 to the endwall 9. Meanwhile, as shown in the Figs.6 and 7. the cutoff 7 may be formed with a curved line having a predetermined curvature. The curved line of the cutoff 7 may be formed with a convex shape upwards or downwards. The operation of the aforementioned sirocco fan according rn the present invention will be described below. The air sucked through the inlet 4 of the scroll 2 by rotation of the impeller 3 circulates inside the scroll 2 and then LS exhausted out of the sirocco fan 1 through the out lot: 5, i.e. the front end of the diffuser 20 in the scroll 2. AL this time, unlike the related art, in the present invention, the cutoff 7 formed in the outlet 5 of the scroll 2 is inclined with a predetermined angle, so that the air sucked into the sirocco fan 1 is smoothly exhausted out. To explain in more detail, the blade 10 of the impeller 3 13 inclined with a predetermined angle against the cutoff 7, GO that the entire sections of the blade 10 do not meet the entire . sections of the cutoff 7 at the same time. That is, since the blade 10 and the cutoff 7 cross each other, fluctuation oC pressure generated when the blade 10 passes through the cutoff could be reduced. In view of any one of the blade, one side of the blade 10 starts to contact from inlet wall 8 and another side of the blade 10 starts to contact from the endwall 9 so that the blade 10 passes through the cutoff 7, thereby resulting in slowness in the pressure fluctuation due to interference between the blade 10 and the cutoff 7. In other words, when the blade -10 and the cutoff 7 cross each other, there is a partial phase difference so that the pressure fluctuation naturally goes to the blade direction and the air flow goes on smooth. Also, even the distance between the blade 10 and the cutoff 7 is getting closer, discrete frequency sound due to the BPF can effectively be restrained. In accordance with the present invention, the cutoff 7 is downwards inclined to the endwall 9 so that it is resulted in the area of the endwall 9 is comparatively getting larger while the area in the inlet wall 8 is getting smaller. In other words, the outlet area ot the endwall 9, where the outlet speed is relatively is fast and the air flow is comparatively stable, is getting larger, on the contrary, the outlet area of the inlet wall 8 where the outlet speed is slow and apt to be unstable air flow is getting smaller. As a result, the entire air flow rate is getting increased and the air flow is getting stabilized. Furthermore, as compared with the related art, the length of the scroll 2 where the real diffusing occurs is getting increased so that it is good for the recovery of the star.ic pressure and the air flow is getting stable and the air flow rate 13 increased. Meanwhile, it" may be expected that the best, preferred inclined angle a can be obtained provided the inclined angle of the cutoff 7 is defined as tana = H/L (where, H is the width of the scroll and L is the width of the cutoff.). If the inclined angle reaches a maximum value, i.e. 90°, there exists no incline. Therefore, the best preferred inclined angle a can be obtained between 0° and 90°. The measure of noise to variation of the inclined angle a of the cutoff 7 are shown in Fig. 9. Fig. 9 shows test results of two sirocco fans with different curvatures of bell-mouth. In Fig. 9, it can be identified that noise can be reduced when the cutoff 7 is inclined with a predetermined angle. If the inclined angle a is 0°, that is, in the related arL sirocco fan, noise is about 45.2dB. On the other hand, if the inclined angle a is about 35°, the noise is about 41.2dB. II is noted that the noise can significantly be reduced when the inclined angle a is in the range of 20° between so". Particularly, it is noted that the noise can more efficiently be reduced when the inclined angle a is in the range of 30° between 40V The aforementioned sirocco fan according to the present invention can be used in a package type air-conditioner, a window type air-conditioner, a ceiling type or ceiling buried type air conditioner, and the like. Furthermore, the sirocco fan can be used for the purpose of radiating indoor fan coil unit: or office machineries, or utensil instruments. The sirocco ran can alternatively be used in the commercial sirocco blower and the other sirocco fans/blowers. As aforementioned, the sirocco £an according to the present invention has the following advantages. First, since it is possible to reduce abnormal noise caused by the BPF which occurs when operating the sirocco fan, stable operation .can be realized when the sirocco fan is used in the air-conditioner. Further, it is possible to efficiently reduce abnormal noise due to the BPF even if the distance between the cutoff and the blade of the impeller becomes shorter. This increases free design of the sirocco fan. Final ly, since air flow rate ot Lhe sirocco fan can be increased and stable air flow can be achieved, performance of the sirocco fan can be improved. It will be apparent to those skilled in the art that various modifications and variations can be made in the sirocco fan according Lo the present invention without departing from r.he spirit or scope of the invention. Thus, it is intended that r.hc present invention cavers the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents. We Claim: 1. A sirocco fan comprising: a scroll (2) with an inlet wall (8) and a closed endwall (9), the said; let wall having an inlet (4) and the said endwal! being opposed to the said iniet wall; and an impeller (3) provided in the said scroll, for suctioning and exhausting air wherein cutoff (7) of the said sirocco fan is inclined downwards from said inlet wall so as not to allow entire sections of a blade (10) of the said Impeler to be simultaneously met entire sections of the said cutoff when the said blade of the said impeller passes through the said cutoff, thereby achieving stable air flow. 2. The sirocco fan as claimed in claim 2, wherein said cutoff has an inclined angle in the range of 20° between 50°. 3 The sirocco fan as claimed in claim 3, wherein said cutoff has an inclined angle in the range of 30° between 40°. 4 The sirocco fan as claimed n claim 2, wherein said cutoff has s curved shape with a predetermined curvature. 5. The sirocco fan as claimed in claim 5, wherein the cutoff has a curved shape which is convex downwards. 5. The sirocco fan as claimed in claim 5, wherein said cutoff has a curved shape which is convex upwards. 7. The sirocco fan as claimed in claim 6 or 7, wherein an inclined angle between a straight line, which connects a start point of said cutoff with its end point, and a horizontal line, is in the range of 20° between 50°.

Documents:

106-DEL-1999-Abstract.pdf

106-del-1999-assignment.pdf

106-DEL-1999-Claims.pdf

106-del-1999-correspondence-others.pdf

106-del-1999-correspondence-po.pdf

106-DEL-1999-Description (Complete).pdf

106-DEL-1999-Drawings.pdf

106-DEL-1999-Form-1.pdf

106-del-1999-form-19.pdf

106-DEL-1999-Form-2.pdf

106-del-1999-form-26.pdf

106-del-1999-form-3.pdf

106-DEL-1999-Form-4.pdf

106-del-1999-form-6.pdf

106-del-1999-petition-137.pdf