Title of Invention

"AIRFLOW GUIDE STATOR VANE"

Abstract

An airflow guide stator vane for an axial flow fan and a tihruuded axlal flow fan aasembly having sach slator vanon are disclosed. Tho airflow guide stator vane has a lealing edge line, a trailing edge line, and an airflow guide surface extending from the leading edge line to the trailing edge line. Tho stator vane is radially positioned in an axial flow Ian and is curved so that its leading edge lino is perpendicular to oblique velocity componanta of an airflow each of which is a sum vector of a rotation-directional velocity component and a radius-directional component of an air particle of the airflow. The axial flow fan assembly comprises an axial flow fan and a shroud. The axial flow fan consists of a circular central hub connected with a driving shaft of a motor and a plurality of blades radially arranged along the circumference of the hub. The shroud consists of a housing surrounding the peripheral ends of said axial flow fan and forming an airflow passage, a motor support being positioned at its center portion and holding a motor for driving said axial flow fan, and the above-described stator vanes.

Full Text

AIRFLOW GUIDE STATOR VANE FOR AXIAL FLOW FAN AND SHROUDED AXIAL FLOW FAN ASSEMBLY HAVING SUCH AIRFLOW GUIDE STATOR VANES BACKGROUND OF THE INVENTION Field of the invention The present invention relates, in general, to axial flow fans and, more particularly, to an airflow guide stator vane for an axial flow fan capable guiding air having dimensional velocity components along the axial direction, and a shrouded axial flow fan assembly having such airflow guide stator vanes. Description of the Prior Art As well known to those skilled in the art:., an axial flow fan is a kind of fluid machinery and serves to blow air in the axial direction by the rotation of a plurality of radially arranged blades. Generally, the axial flow fan is used in conjunction with a shroud, the shroud surrounding the blades and guiding air toward the axial direction. Such a shrouded axial flow fan assembly is used to ventilate a room and promote the heat radiation of" an alr cooled heat exchanger, such as a radiator or a condenser of an automobile. The shrouded axial flow fan assembly may promote heat radiation by blowing air to or drawing air from the heat exchanger. The ahroudod axial flow fan may be claim fied into a pusher-type axial flow fan assembly and a puller-type axial flow fan assembly. The pusher-type axial, flow fan assembly serves to blow air from a position in front of a heat exchanger to a position behind the heat exchanger. Since such a puaher-typo axial flow fan assembly has a low blowing efficiency/ it is used only when the space, formed behind the heat exchanger in an engine room, is significantly limited. The puller-type axial flow fan asaembly so.i vus to allow air to paas through the heat exchanger by drawing air from a position in front of the hnat exchanger to a poslltion behled the loo exchanger. Since such a puller-type axlal flow fan the asswenbly has a high blowing efficiency, it is usnd In moat automobiles, recently. Meanwhile, in the shrouded axial flow fan assembly, the shroud of the fan assembly may have a plurality of airflow guide stator vanes so as to improve a blowing efficiency. The airflow guide stator vanes are radially arranged around a center portion with the center of the center portion lying on the central axis of the fan assembly. The airflow guide stator vanes serve to improve static pressure by converting the kinetic energy of the air blown by the blades of the fan to the pressure energy of the air, thus improving the blowing efficiency of the fan. Fig. 1 is a rear view showing a conventional puller-type ahrouded axial flow fan assembly provided nth airflow guide stator vanes. As shown in Fig. 1, the axial flow fan asscanbly comprlses an axial flow fan 10 and a shroud 30, The axial flow fan 10 consists of a central hub (not shown in the drawing) connected with the driving shaft of a motor (not shown) and a plurality of bladeu 12 extending radially outwardly from the hub. The axial flow fan 10 is mounted in the rear of a heat exchanger/ and serves to draw air from the front of the heat exchanger, pass the air through the heat exchanger and discharge the air to the rear of the axial flow fan 10. In'the process of the movement of the air, the heat exchanger La deprived of heat by the drawn air and is cooled. The axial flow fan is generally made of Mynthotic rosin and integrated with the blades 12 into a single body. The shroud 30 surrounds the blades 12 and is fixed d to the heat exchanger. The shroud 30 serves to guide air drawn Jby the axial flow fan to the rear and to support the axial flow fan 10 and a motor 10. The shroud 10 consists of a rectangular houaing 31, a motor support 32 positioned in the center portion of u plune and a plurality of airflow guide stator vanou 33 arranged radially between the housing 31 and the motor sport 32. The housing 31 has an inlet opened toward the face of tho heat exchanger and has a flaring airflow guide structure gradually diminished to its outlet. Its airflow guide structure allows the heat exchanger to be cooled sufficiently and blows air aiong the axial direction, thus improving the efficiency of the fan. The housing 31 is provided at its uppar and lower portions with mounting brackets 34 that, are used to mount the housing 31 to the heat exchanger by bolts. The stator vanes 33 extend radially from the housing 31 to the motor support 32 and connect the motor support 32 to rho housing 31. Additionally, as'shown in Fig, 2, each of the stator vanes is arcuated toward the direction of rotation and forms a guide surface 33a having a certain width, thus guiding air moved by the axial flow fan 10 toward the axial direction and improving the blowing efficiency of the fan. The motor support 32 holda the axial flow tan 10 mid a motor 20 for driving the axial flow fan 10. The motor support 32 is circular band-shaped in accordance with the shape of the hub of the axial flow fan 10 and the shape of the motor 20. In the shrouded axial flow fan assembly, as shown in Fig. 1, the stator vanes 33 are extended straightly from the circumference of the motor support 32 to the housing 31, and, as shown in Fiq. 2, the airflow guide surface 33a of each of the stator vanes is arcuated so that one end aide of the stator vanes 33 serve to increaao the uKiti-diroctiouai. velocity by converting the rotation-directional velocity component to the axis-directional velocity component, thas improving the blowing efficiency of the fan. That, since airflow generated by the axial flow fan 10 has rotation-directional velocity component Uth as well as the axis-diractioiwU velocity component U2 and blowing nf!t,ici«nuy of the fan is reduced when the rotation-directional velocity component U,h is left alone, the axis-directional velocity is increased by converting the rotation-directional velocity component to the axis-directional velocity component, uo thai the blowing efficiency of the fan ia iioproved. The function of the airflow guide surface 33a of the aieflow gnide state vanes i3 described in more detail in the following. In the airflow field inside of the housing 31, an air particle ia moved to the direction curved toward the direction of rotation and the radial direction. That is, as shown in Fig. 2, since the air particle, passing through the position spaced apart from the axial line of the axial How fan by a distance r alonu. the radial 'direction, has a rotation-directional velocity component UUs genuratud by the roUst.icm of the blades 12 of the axial flow fan 10 ao wed3. as an axis-airar.tlon.aJ velocity component U,,f t.h« nit: pmrsclii in moved toward the leading edge 33b of the stator vane 33 in the direction that is bent to the direction of rotation at Or with respect to the axial direction. Under the consideration of the actual airflow direction, the airflow guide surface 33a of each stator vane 33 is arcuated so that the leading edge aide of the guide surface 33a forms an oblique angle Gt (0t £ QT) with the axial line A.L. Therefore, the guide surface 33a reflects the air having oblique flow directio i toward the axial direction and, thus, increases the axis-directional yelocity AS a result,the blowing efficiency of the fan is Improved due to the increase of the axis-directional velocity. U.S. I'nl. No. 4,510,540 dlsclosea a fun and housing whom In the obliqun angle of the airflow guido Mit.clt.ico of each atator vane is defined with respect to the axial line so as to improve the blowing efficiency of the fan. The velocity vector A of air at the position, which is spaced apart from thw control line f rotation by a dlstnce r In the pleld nirt'iow, has oth an axls directional valocity compone A and a rotation-directional velocity component R. The velocity vector Ao forms an oblique angle T of Tan"1 (R/A) with the axial line. Each vane of the fan is positioned so that the width-directional tangent at the center of its width forms an ngle T/2 with a lino parallel to the airflow discharge direction with Ihe uii.flow yuido aurface of ouch vnno of the ian being arcuated in its cross section. Therefore, the guide surface; receives the air at the oblique angle T/2 and, thereafter, reflects axially at the angle T/2. As a result, the axis- directional velocity component is increased in proportion to the axially reflected rotation-directional velocity, thereby improving the airflow rate of the fan to the extent proportional t*.0 the axially reflected, rotation dl.r.yctlonui velocity. In U.S. Pat. No. 4,971,143, there J.a diadosed u ton stator assembly for heat exchangers wherein a plurality of vaimti extend rudirtlly from a motor support, to bonatug, with the leading edge side of each stator vane being oriented parallel to the direction of an entering air flow and the trailing edge side of each stator vane being oriented to be parallel to an axial line. The fan stator assetsibl y suppresses the generation of vortices at the airflow guide surface of the vane to curve the airflow smoothly, thereby improving the blowing efficiency of the axial flow fan. However, since the conventional axiaJ. flow fan assemblies Including t ho ;shroud«d ?txJal [low f«n niuuernbly deiicr.1 bod In Fig.l, the fan and housing described in U.S. Pat. No. 4,548,548 and the fan stator assembly for heat exchanger described in U.S. Pat. No. 4,971,143 are designed without; the consideration of the radius-directional component of air, they have a limitation in the improvement of blowing efficiency. As shown in Fig. 1, since the conventional axial flow fan aaboiiibliey control. only the axiy 'directional. velocity component Uz and the rotation-directional velocity component Uth except the radius -directional velocity component Ur notwithstanding that the air moved by the axial flew fan must have the radius-directional velocity component Ur as well as the axis-directional velocity component Uz and rotation-directional velocity component Uth , the blowing efficiency is low due to the existence of the radius-directional velocity component. Therefore, since the axial flow fan of the conventional shrouded axial flow fan assembly should be highly rotated so as to obtain a required airflow rate, a high power motor is required in the fan assembly. As a result, the conventional axial flow fan assemblies have defects in that their consumed electric power per required airflow rate and the noise of the fan assemblies are increased. The document DE-A 199 48 074 discloses as axial fan for transmitting air through the cooler of a motor vehicle. The fan comprises a rotor, an electrical motor and a vane element having a plurality of vane radially extending perpendicularly to the air flow generated. The document US-A 5,246,339 relates to a guide vane for an axial fan formed in the end portion facing towards the fan with a web between the radially outer and inner portions of the guide vane. SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an airflow guide stator vane for axial flow fans and a shrouded axial flow fan assembly having such airflow guide stator vanes, capable of improving the blowing efficiency by converting the radius-directional velocity components as well as the rotation- directional velocity components of airflow generated by an axial flow fan to the axis-directional velocity components by ifs airflow guide surface, thus allowing a low out-put motor to be used for the fan and reducing the consumed power for driving the axial flow fan and noise generated by the driving of the axial flow fan. In order to accomplish the abovp object, the present invention provides an airflow guide stator vane comprising a leading edge-line, a trailing edge line, and an air flow guide surface extending from the leading edge line to the trailing edge line, the stator vane being radially positioned in an axial flow fan characterged in the stator vane is curved so that its leading edge line is perpendicular to oblique velocity components of an airflow each of which is a sum vector of a rotation-directional velocity component and a radius directional component of an air particle of the airflow. In addition, the present invention provides an axial flow fan assembly, comprising an axial flow fan consisting of a circular central hub connected with a driving shaft of a motor and plurality of blades radially arranged along the circumference of the hub; and shroud consisting of a housing surrounding the peripheral ends of said axial flow fan and forming an airflow passage, a motor support being positioned at its center portion and holding a motor for driving said axial flow fan, and a plurality of airflow guide stator vanes being radially arranged between said housing and said motor support wherein said plurality of airflow guide stator vanes is curved so that its leading edge line is perpendicular to oblique velocity components of an airflow each of which is a sum vector of a rotation-directional velocity component and a radius-directional component of an air particle of the airflow. In accordance with the present invention there is disclosed an airflow guide stator vane comprising a leading edge line, a trailing edge line and an airflow guide surface extending from the leading edge line to the trailing edge line, the stator vane being radially positioned in an axial flow fan and being curved so that its leading edge line is perpendicular to oblique velocity components of an airflow each of which is a sum vector of a rotation-directional velocity component and a radius-directional component of an air particle of the airflow. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a rear view showing a conventional piller-type shrouded axial flow fan assembly provided with a plurality of airflow guide stator vanes; Fig. 2 is a cross section showing the vane and blade of the conventional fan assembly; Fig. 3 is a rear view showing a shrouded axial flow fan assembly according to a first embodiment of the present invention; Fig. 4 is the side cross section of Fig. 3; Fig. 5 is a cross section showing the vane and blade of the shrouded axial flow fan assembly according to the first embodiment; Fig. 6 is a graph showing variations in directional velocity components with respect to the position of an air particle in the radial line; Fig. 7 is a perspective view showing the directional velocity components of an air particle situated at the position spaced apart from the central axis of the fan assembly by the distance of r; fig. B is an enlarged perspective view allowing the uhapes of the stator vanes of the fan assembly of the first embodiment; Fig. 9ft in on enlarged view Hhowing the nUitor vane of the prnaent Invention and the velocity of an al r-parUclo; Fig. 9b is an enlarged view showing the conventional stator vane and the velocity of an air particle; Fig. 10 is a graph showing variations in incident angle and obliquo angle of the leading edge aide with respect to positions of each vane in the radial direction; Fig. 11 Is a graph comparing consumed power variations of the fan assemblies of the prior art and the present invention with regard to airflow rates; Fig. 12 is a graph comparing noise variation.'! of the fan assemblies of the prior art and' the present invention with regard to airflow rates; Fig. 13 is a noise spectrum comparing noise varlations of the fan asaeiablies of the prior art and the present invention with regard to frequencies'; Fig. 14 is a front view showing a ahrouded axcial flow fan assembly according to a second embodiment of the present invention; a partially exploded cr.otiB auction showing thu second embodiment; and Fiq. 16 is a rear view showing a shrouded axial flow fan assembly according to the second embodiment of the present invention, DESCRIPTION OF THE PREFERRED EMBODIMENTS for ease description, the dcuciviptioh on the same elements as those of the prior art is omitted and the same elements as those of the prior art are designated by the same reference characters as the reference characters of the prior art. Additionally, the flow of an air particle, which is a basic datura for the design of stator vanes according to the present invention, Is varied at positions in an air passage due to the resistance of a shroud housing, a heat exchanger, the shape of un automobile body, etc. that affect airflow. However, in the practical design of stator vanes according to the present invention, it is convenient to assume that the mean velocity is uniformly continued along the radial direction, the mean velocities with reapect to the rvdial distances being calculated from the velocities of air at various positions equally spaced apart from the central axis of a wind tunnel obtained from wind tunnel tests etc. That is, in the practical design, it is assumed that in spite of the difference in resistance generated by factors including the shroud housing, the heat exchanger, the shape of the automobile body, etc., which is moved by an axial flow fan, flows at the same relative velocity at positions situated on the concentric circle within the air passage when viewed from the basis of a polar coordinate system that has an origin in the central axis of the air passage. [EMBODIMENT 1] As shown in Figs. 3 and 4, an axial flow fan assembly according to Embodiment 1 comprises an axial flow fan 10 and a shroud 30. In this embodiment, the axial flow fan 10 consists of a circular central hub 11 positioned at its center portion and plurality of blades 12 radially arranged along the circumference of the hub 11. The shroud 30 consists of a motor 32 holding the axial flow fan 10 and a motor 20 for driving the axial flow fan 10, a plurality of air flow guide stator vanes 33 radially arranged along the circumference of the motor support 32, and a rectangular housing 31 surrounding the peripheral ends of the axial flow fan 10 and the stator vanes 33. In the axial flow fan 10 of this embodiment, the central hub 11 is connected with the driving shaft of a motor 20. The blades 12 are radially arranged along the circumference of the hub 11, are rotated together with the hub 11 and generate air flow. Incidentally, the axial flow fan 10 may be provided with an outer band 13 to which the peripheral ends of the blades 12 are fixed and which improves the blowing efficiency of the fan by suppressing the generation of vortices at the peripheral ends of the blades 12. The axial flow fan is generally made of synthetic resin and formed into a single body. However, the axial flow fan is sometimes made of lightweight aluminum. The outer band 13 shown in Fig. 4 has a flaring mouth like a bell mouth and covers an air guide portion 31b extended from the downstream end of the housing 31 toward the up-stream direction, so as to maximizing its function. In the shroud 30 of this embodiment, the housing 31 has a rectangular shape in accordance with the shape of a heat exchanger so as to cover the entire face of the heat exchanger, is projected at its upstream side end toward the upstream direction so as to ensure the space for airflow, and has a bell mouth-shaped cross section that grows smaller toward the downstream direction and finally forms a circular outlet 31a. The motor support 32 is positioned at the center portion of the outlet 31a and holds the axial flow fan 10 and the motor 20 for driving the axial flow fan 10. The motor support 32 is circular band-shaped in accordance with the shape of the hub 11 of the axial flow fan 10 and the shape of the motor 20. As shown in Fig. 3 the stator vanes 35 are radially arranged between the motor support 32 and the housing 31 and connect the motor support 32 to the housing 31. The stator vanes 35 serve to guide the three directional airflow generated by the axial flow fan 10 to the axial direction, thereby improving the blowing efficiency of the fan and reducing blowing noise. As shown in Fig. 5, the cross s?ction of each of the stator vanes 35 extending from a leading edge 35b to a trailing edge 35c is curved with respect to the axial direction, thereby allowing airflow to be bent along the airflow guide surface 35a of each of the stator vanes 35. In addition, shown in Fig. 3, the stator vanes 35 are curved with respect to the radial direction to introduce three-directional airflow effectively and guide the airflow toward the axial direction, thus improving the blowing efficiency of the fan and reducing noise. The structure and function of the stator vanes 35 is described in the following in more detail. (1) First of all, each of the stator vanes 35 is curved with respect to the radial direction so as to introduce drawn airflow. Therefore, the leading edge line defined by the line joining the leading edges of each vane is curved with reaped: to the radial lino defined by tin.: radiall", atraightly extended line. A3 shovm in Fig. 7, the air particle that pusses through the position P spaced apart from the axial line of the axial tan by the vatanca r along the radial direction in moved, by the axlal low fan 10 and has axisi-dlrectlenal velocity cojuponont U,, a rotafcioivdlrectionhl velocity component U12. and a radius-directional velocity component Ur. to showa In Fig. 6, the magnitudes of the velocity components depend upon the design of the blades of the axial flow fan. ha described above, since the airflow moved by the axial flow fan 10 kshould have the radiuf-dllrocUonal velocity component Uc as well as the axis-directional velocity component Uz and the rotation-directional velocity component Utiw the velocity vector U of the air particle of the u:lrfjow at the position P is the sum vector of the axia-direct.i.ona.l velocity- component uV,, the rotation'directlonaI velocity component Ut.t, and the radius-directional velocity component Ui:j. as shown in Fig. 7. When the sum vector of the radius-directional velocity component Ur and the rotation-directional velocity component Unrip UB, the velocity vector U of the air particle forms the angle 6 of Ton"1 (Ua/U7) with the axial line .A..L. This means that the ain.ee the air particle at the position P has the velocity component UH, the air particle is moved in the direction oblique toward the rotatior al direction and the radial direction with respect to the axial line A„i», Coping with the situation, each of the a to tor vuncy 3!.i la curved so that its individual leading edge is perpendicular to the oblique velocity component Ua, so as to receive oblique airflow effectively. That is, as shown in Fig. 0, each of stator vanes 35 is curved so that a tangent line at each of positions in the leading edge line forms the angle 0„ of Tan" J(U,/UU>) with the radiui, lino H.L., the obl.louo velocity cojnponent U^- forming the angle 0^ of Tan"'1 (Ur/Ut;l) with the rotation-directional velocity component Ur.h- As a whole, each of the stator vanes 35 is curved, with its middle portion protruding toward the direction of rotation. As nhown in Fig. 9a, since the stator vanes 35 are curved in such a way, the vanes 35 may receive air particles at each of the positions of the leading edge line effectively, thuy improving tho blowing efficiency of the axial flow fail 10. This effect is well underytood from Fig. 9b in which tho oblique velocity component U« of an air particle does not. form a right angle with the leading edge of the convontioiu.il. varus 33 because each of the conventional ctator vanoo 33 oxtondu jjtruJ ghl, 1 y along the radial direction. Tho angle 0U, which is formed by a tangent wt a .Loading odge and a radial lino passing through Lite leading odgu, muy be referred to as a leading edge oblique angle. On the other hand, differing from that of this embodiment, the blade 12 of the axial How fan 10 may him a forward curvature or a rearward curvature, thereby causing the radius-directional velocity component to have a minus value, that is, generating airflow moved toward the radially inward direction. in such a case, the stator vane 3 5 should bo designed to allow the leading edge line L.E.L to .form the leading edge oblique angle 85 of a" negative value, so that the guide stator vane has a rearward curvature. Meanwhile, the portion of the stator vane 35, situated within a predetermined radial area around the central axis, is not curved but is extended straightly in the radial direction. In the predetermined radial area around th« central axis, the velocity of the airflow in small and, consequently, the loading «dyw oblique miyU portion ol the atator vane in the area ahould be designed to bo curved. (2) Next, the airflow guide ourface 3ba oi the stator blade of this invention arcuated in its cross section is described in the following. TVs shown in Fig. 5, the airflow guide mirfae© 3ba of tho stator van© 35 of this invention serves to curve the entering air having the oblique velocity component toward the axial direction. To this end, the airflow guide surface 35a is doslgned to be arcuated BO that the incident angle Au, of tlw guide surface 3ba is equivalent to the discharge angle £W of airflow from the fan blade 12 and the projection angle IW of the guide surface 35a is zero (that is, Aout=-0) . The airflow guide surface 35a of each of the stator vanes 35 ia circulary arcuated from the loading edge 35b to the trailing edge 35c in its cross section. For example, as shown in Fig. 5, airflow discharged by the axial flow fan 10 ante re tho loading edge 35b of the atator vane 35b_, which is spaced apart from the central axis by the distance r, at a discharge angle Bol,t of Tan"1 CUUA7Z) that the velocity vector of the discharged air forma with tho axial line A.L. Therefore, the leading edge side of the stator vane 35 1 s oriented so aa to form an angle Ait, equivalent to the discharge angle EW with the axial line A.I,, while the trailing edge side of the stator" vane 35 ia oriented so as to be parallel to the axial line A.L. The airflow guide surface 35a between the leading edge 35b and the trailing edge 35c has the same curvature as that of the circle, the circle having as its center a point e at which the normals or tiie leatuny cage* 35b and the trailing edge 35c meet and having as its radius the distance between the point P and the leadiiu edge 35b. This curvature of the guide surface 35a minimizes the generation of vortices, thereby allowing air to flow smoothly along the guide surface 35a. in brief, I'ha airflow guide aurfaca 35a of the stator vanes according to the present invention receives the air parallel, curves it smoothly and discharges it in the axial direction. As described above, accoxding to the above-described structure of the stator vanes 35, the air generated by the axial flow fan 10 is introduced parallel to the airflow guide surface 35a, is smoothly curved toward the axial direction along the airflow guide surface 35a and is blown through the trailing edge 35c, h'ince the airflow generated by the axial flow fan 10 may come to flow in an axial direction due to the conversion of its' rotation-directional velocity components Uti, and its radius-directional velocity components Ur to the axis-directional velocity components by means of the stator vanes 35, the flow rate of the air in the axial direction is improved and, consequently, the blowing efficiency of the fan la improved. Especially, with regard to the puuher-l.ype Can positioned in front of the heat exchanger, the flow-through rate of the air with regard Lo thy radiation fins of the heat exchanger is high, Lhus improving the blowing efficiency more. According to the results of experiments, as shown in Figs. 11 and 12, the consumed electric power per airflow rate is reduced by 12-15% and the magnitude of noise per airflow rate is reduced by l-1.5dB, compared with the conventional shroud. Additionally, referring to the experimental data of Fig. 13 regarding noise spectrum, the noise with respect to each frequency is smaller compared with the conventional shrouded axial flow fan assembly. In brief, according to the shrouded axial flow fan assembly, the consumed electric power per the flow rate may be reduced largely and reduce noise, also. [EMBODIMENT 2] Fig. 14 illustrates a shrouded axial flow fan assembly according to Embodiment 2. The shrouded axial flow fan assembly is provided with a detachable stator 40. The detachable stator vanes 40 and the other parts are assembled together into the shrouded axial flow fan assembly illustrated in Figs. 14 and 15. The shrouded axial flow fan of this embodiment is like that of the previous embodiment except that the shrouded axial flow fan assembly is provided with the detachable stator 40 as a separate part. That is, as shown in Fig. 16, the detachable stator 40 is a distinct part separated from a shroud 40 with the radially inner ends of the vanes 41 of the stator 40 being fixed to the center ring 42 of the stator 40 and the radially outer ends of the vanes 41 of the stator 40 being fixed to the outer frame 43 of the stator 40. The stator 40 is detachably fitted into a mount groove 31c that is formed in the housing 31 of a shroud 30. In the meantime, each of the vanes 41 of the stator 40 is curved so that its middle portion is protruded toward the circumferential direction and has an airflow guide surface arcuated from its leading to its trailing edge, in outer ends of the vanes 41 of the stator: 40 being fixed to the outer tmsm A3 of the stator 40, The eta tor 40 iM detochably fitted Into a mount groove 31c that is formed in tho housing 31 of a shroud 30. In the meantime, each of the vanes 41 of the stator 40 is curved so that itc middle portion is protruded toward the ciircuinferential direction and ha a an airflow guide surface arcuated from its leading edge to its trailing edge,, in the some manner at? that, of the previous embodiment. At> u i.e;nU.l., tho prwieut oiribod;Wncn! \nm the tuning i off oct. a a that of thu provlouu ombodimunl. Additionally, the ufnt'.or As described above, the present invention provided an airflow guide iitutor wane for axial flow luim and 'a shrouded . axial flow fan" assembly having such airflow guide stator vanes, capable of improving the blowing efficiency by converting tho radiua-directional velocity component:, aa well as the rotation-directional velocity coauponouta o!: air (Mow generated by an axial flow fan to the axis-directional i velocity components by its airflow guide surface, thus allowing a low output motor to be used for the fan and reducing the consumed power for driving' tho axial flow fan and noise generated by the driving of the axial flow fan. According to another embodiment, the present invention. provides a shrouded axial flow fan assembly having detachably airflow guide stator vanes, allowing its stator to be attached to and detached from its shroud as occasion demands and producing the same effect as that of a slngle utruelure shroud. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the arl will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. We Claim: 1. An airflow guide stator vane (33,35) comprising a leading edge (35b) line, a trailing edge (35c) line and an airflow guide surface (35 a) extending from the leading edge (35b) line to the trailing edge (35c) line, the stator vane (33,35) being radially positioned in an axial flow fan (10), characterized in that the stator vane (33,35) is curved so that its leading edge (35b) line is perpendicular to oblique velocity components of an airflow each of which is a sum vector of a rotation-directional velocity component and a radius-directional component of an air particle of the airflow. 2. The vane (33,35) as claimed in claim 1, wherein said airflow guide surface (35a) is arcuated so that the incident angle of the guide surface (35a) is equivalent to a discharge angle of the airflow from the blade (12) and the projection angle of the guide surface (35a) is zero. 3. The vane as claimed in claim 1 or 2, wherein said airflow guide surface (35a) is arcuated circularly from its leading edge (35b) to its trailing edge (35c). 4. An axial flow fan (10) substantially as herein described with reference to the foregoing description and the accompanying drawings.

Documents:

1585-del-1999-abstract.pdf

1585-del-1999-claims.pdf

1585-del-1999-complete specifcation (granted).pdf

1585-del-1999-correspondence-others.pdf

1585-del-1999-correspondence-po.pdf

1585-del-1999-description (complete).pdf

1585-del-1999-drawings.pdf

1585-del-1999-form-1.pdf

1585-DEL-1999-Form-19.pdf

1585-DEL-1999-Form-2.pdf

1585-del-1999-form-3.pdf

1585-del-1999-form-5.pdf

1585-del-1999-gpa.pdf

1585-del-1999-petition-137.pdf

1585-del-1999-petition-138.pdf