AU8849191A

AU8849191A - Blade unit for producing a radial current of air and electric fan using same

Info

Publication number: AU8849191A
Application number: AU88491/91A
Authority: AU
Inventors: Keon Seok Moon
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-10-23
Filing date: 1991-10-22
Publication date: 1992-05-20
Also published as: WO1992007192A1; JPH06502469A; KR920008358A

Description

BLADE UNIT FOR PRODUCING A RADIAL CURRENT OP AIR AND ELECTRIC FAN USING SAME

Field of the Invention

The present invention relates to a blade unit for use in an electric fan; and, more particularly, to a novel blade unit designed to convert axially existing ambient air into a radially outward current of air. The present invention is also directed to an improved electric fan employing such a blade unit.

Description of the Prior Art

A variety of radial flow fans for producing a radial current of air to provide cooling effect have heretofore been proposed in the art. For example, Korean Utility Model Application No. 82-5631 filed on July 16, 1982 teaches a blade structure which consists of a cylindrical hub and a plurality of plate-like rectangular blades fixedly secured to the outer circumference of the hub. Although the blade structure was conceived to produce a radial current of air, it has been found disadvantageous at least in terms of the following two aspects. First of all, since the plate-like blades employed in the afore-mentioned blade structure are designed to extend a short distance radially, they lack the ability to suck a sufficient amount of axially present ambient air. As a result, it is not possible for the blade structure to produce a satisfactory amount of radial air current with a high flow rate. Secondly, the plate-like blades are subject to a strong air resistance as the blade structure rotates about its axis, consequently creating a great deal of mechanical vibration and operational noise. Korean Utility Model Application No. 83-1808 filed on

August 24, 1983 discloses a combined heater and blower apparatus housed within a cylindrical casing wherein the heater is disposed on the bottom of the casing to radiate thermal energy and the blower is located immediately above the heater to blow the heated air toward the top of the casing. The cylindrical casing has an array of inlet slots formed at its lower periphery and an array of outlet slots defined at its upper periphery. When the apparatus begins to operate, the ambient air is introduced into the cylindrical casing through the inlet slots and then optionally heated to a given level of temperature. Subsequently, the heated or unheated air will be directed to the casing top before it is discharged as a radial current of air through the outlet slots. In this type of heater/ blower apparatus, the upward air stream necessarily impinges against the casing top, which leads to a loss of flow velocity for the most part, if not all. Therefore, the apparatus discussed above functions merely as a heater rather than a combined heater and blower because it fails to produce a practical level of radial air current.

Korean Utility Model Application No., 84-6161 filed on June 29, 1984 discloses an electric fan which comprises a support, an electric motor pivotably mounted on the support, a rotor operatively connected to the electric motor and triple rows of blades. The blade rows comprise a first row of twisted blades, a second row of twisted blades arranged as a mirror image of the first blade row and a third intermediate row of flat blades. In such an electric fan, forward rotation of the rotor produces a radially outward current of air whereas reverse rotation of the rotor creates an axial air current in the opposite directions. However, this electric fan is not suitable for the practical use because of its inability to produce a sufficient intensity of axial or radial air current. Further, the individual blade is often subject to a severe vibration when the fan is in operation.

Summary of the Invention

Accordingly, it is an object of the present invention to provide a novel blade unit which is designed to produce a radial air current with a high flow rate and with a reduced blade vibration.

Another object of the present invention is to provide an improved electric fan which employs the blade unit to convert axially existing ambient air into a radial air current of higher flow rate. In accordance with one aspect of the present invention, there is provided a blade unit rotatably driven by an electric motor ^' to convert the axially existing ambient air into a radially outward current of air, which comprises: a rotor operatively connected to said electric motor for rotation about its axis; at least two upper blades extending upward from said rotor in an inclined relationship with the axis of said rotor, said upper blades circumferentially spaced apart with each other at a substantially equal pitch; and at least two lower blades extending downward from said rotor in an inclined relationship with the axis of said rotor, said lower blades circumferentially spaced apart with each other at a substantially equal pitch, said upper and said lower blades being so shaped and arranged that they can aerodynamically cooperate with each other to produce said radially outward current of air when said blade unit is caused to rotate.

Another aspect of the present invention resides in a fan comprising a base, a support bar vertically extending from said base, an electric motor carried by said support bar and a blade unit operatively connected to said electric motor for producing a radially outward current of air when said motor is energized, said blade unit including: a rotor operatively connected to said electric motor for rotation about its axis; at least two upper blades extending upward from said rotor in an inclined relationship with the axis of said rotor, said upper blades circumferentially spaced apart with each other at a substantially equal pitch; and at least two lower blades extending downward from said rotor in an inclined relationship with the axis of said rotor, said lower blades circumferentially spaced apart with each other at a substantially equal pitch, said upper and said lower blades being so shaped and arranged that they can aerodynamically cooperate with each other to produce said radially outward current of air when said blade unit is caused to rotate. Brief Description of the Drawings

The above and other objects and features of the present invention will become apparent from the following description and the accompanying drawings wherein like reference numerals refer to like parts in different views.

Fig. 1 is a front elevational view showing a first embodiment of the blade unit in accordance with the present invention; Fig. 2 is an enlarged plan view of the rotor constituting the blade unit shown in Fig. 1, with the blades removed for simplicity; Fig. 3 is an enlarged view illustrating one of the blades which forms a part of the blade unit as shown in Fig. 1;

Figs. 4(A), (B) and (C) are cross-sectional views taken along lines IVA-IVA, IVB-IVB and IVC-IVC of Fig. 3, respectively; Fig. 5 is a cross-sectional view taken along line V-V of

Fig. 2;

Fig. 6 illustrates the principle under which the blade unit produces a radial current of air;

Fig. 7 is a front elevational view showing a second embodiment of the blade unit in accordance with the present invention; Fig. 8 shows a modification of the blade unit shown in Fig. 7;

Fig. 9 depicts another modification of the blade unit shown in Fig. 7; Fig. 10 is a front elevational view showing a third embodiment of the blade unit in accordance with the present invention; Fig. 11 is an exploded view of the electric fan employing the blade unit shown in Fig. 7, with a portion thereof cut away for clarity; and

Fig. 12 is a perspective view of the improved electric fan with the blade unit surrounded by a safety cage.

Detailed Description of the Preferred Embodiments

Referring now to Fig. 1, there is shown a first embodiment of the blade unit in accordance with the present invention. As shown, the blade unit 10 comprises a rotor 12 which can be operatively connected to, e.g., an electric motor for rotation about its axis. The rotor 12 carries at its upper conical surface a pair of upper blades 14 that are spaced apart with each other along the circumference of the rotor at a substantially equal pitch and, at its lower conical surface, a pair of lower blades 16 that are arranged as mirror images of the upper blades 14. Each of the upper blades 14 has a longitudinal center line extending at an angle of l with respect to the axis of the rotor 12. Moreover, the individual lower blade 16 has a longitudinal center line which extends at an angle of 2 with respect to the axis of the rotor 12. Although it is preferable to make angles a l and 2 equal to one another, angle l may be greater than angle a z and vice versa. In order to maximize the flow rate of the radial air current, angles a l and α 2 can be set to a range, e.g., from 30 to 60° , and more preferably to 45° as long as the first embodiment shown in Fig. 1 is concerned. Additionally, each of the upper and the lower blades 16 is twisted along the longitudinal center line with respect to the rotor plane in a given fashion as set forth later. As used herein,, the "rotor plane" is meant by a reference plane on which the axis of the rotor 12 lies along with the longitudinal center line of a particular blade. For the blade unit to operate efficiently, it is of importance to have the upper blades 14 arranged as mirror images of the lower blades 16.

Turning to Figs. 2 through 4, there are shown by way of example the structural details of a rotor and a blade which may be advantageously used in the instant invention. As best shown in Fig. 3, the blade 14 consists of a proximal fixed end 18, a distal free end 20 and a medial transition point 22 bisecting the blade into a proximal region and a distal region. The width of the blade increases gradually from the proximal end 18 to the medial transition point 22 and then decreases from the medial transition point 22 to the distal end 20, finally becoming zero. Thus, the blade 14 has a curvilinear contour which is open at the proximal end 18 and closed at the distal end 20. It is preferable that the blade 14 have a concave front surface and a convex rear surface in order to maximize the flow rate of the radial air current, although this is not limitative in the invention.

As known to the person of ordinary skill in the art, it is of paramount importance to optimize the twist angle of a blade inasmush as it often has a critical effect on the flow rate of the radial air current and the level of operational noise. In the preferred embodiment, the twist angle of the blade with respect to the rotor plane is set to become largest at the proximal end 18 and to decrease gently toward the distal end 20. More specifically, twist angle β l at the proximal end 18 can be within a range from 30 to 40° ; for instance, ^2 at line IVA-IVA of Fig. 3 being 20 to 30° ; β 3 at line IVB-IVB being 10 to 20° ; and lastly the twist angle at line IVC-IVC being zero. It should be appreciated that the configuration or geometry of the blade explained above is not limitative in the invention but is presented for the illustrative purpose only. Unlike the blade design shown and described herein¬ before, the contour defining a blade may be either rectilinear or curvilinear. Furthermore, the twist angle may be constant along the longitudinal center line of the blade. It may be also possible to use non-twisted blades without unduely deteriorating the performance characteristics of the inventive blade unit.

Fig. 5 is a cross-sectional view of the rotor taken along line V-V of Fig. 2. As shown, the rotor 12 has a vertical cross- section of substantially rhombic shape and a horizontal cross-section of circular configuration. In the preferred embodiment, the rotor 12 consists of a body 24 and a top cap 26 seated on the fattened top surface of the body 24. The body 24 is formed with a frusto-conical upper half 24a and a frusto-conical lower half 24b, each extending in the opposite directions from a medial plane. Moreover, the body 24 has a countersinked axial bore 28 through which can be inserted an output shaft 32 of the electric motor. The output shaft 32 has at its free end a male thread 34. As a component of the rotor 24, the top cap 26 is of conical shape and has a female thread 30 engageable with the male thread 34 of the output shaft 32. When assembled, the top cap 26 cooperates with the frusto-conical upper half 24a to provide an aerodynamic rotor surface. Making the vertical cross-section of the rotor substantially rhombic as explained above assures that the axially existing air can flow without interruption toward the inter-blade region along the surface of the rotor. While a particular type of rotor has been described with reference to Fig. 5, the present invention is not limited to the afore-mentioned rotor and, therefore, a variety of modified rotors such as cylindrical hub may be utilized in the novel blade unit.

The principle under which a radially outward current of air is produced in accordance with the present invention will now be described with reference to Fig. 6. As shown and described above, the upper blade 14 is arranged as a mirror image of the lower blade 16 about the medial plane of the rotor 12. In addition, the upper and the lower blades 14 and 16 are twisted in the opposite directions to one another about their longitudinal center lines. Consequently, the spacing Hi between the leading edges 14a and 16a is greater than the spacing H2 between the corresponding trailing edges 14b and 16b when measured for each pair of the upper and the lower blades 14 and 16. Rotation of such blade unit in the clockwise direction will enable the individual blade to push the axially existing ambient air toward the radially outward direction, thereby producing an intensive radial current of air. The conical rotor surface ensures that the air should flow in a laminar pattern without creating any turbulent flow. Since the annular edge of the rotor is protruded to the inter-blade region, it is possible to avoid a so-called "cavitation" which would otherwise occur in the innermost inter-blade region. The flow rate of the radial air current can be regulated by way of either increasing or decreasing the rotational speed of the electric motor. Further, the thickness of the radial air current depends on the relative angle between the upper blade 14 and the lower blade 16 as well as the blade length.

Fig. 7 shows a second embodiment of the blade unit made in accordance with the present invention. This blade unit comprises a rotor 12 of the same construction as explained in conjunction with the first embodiment, four upper blades 14 extending upward from the rotor in an inclined relationship with the rotor axis and four lower blades 16 arranged preferably as mirror images of the upper blades 14. In accordance with the second embodiment, thanks to the increased number of blades, it is possible to produce a radial current of air at a much higher flow rate even if the rotational speed of the electric motor is somewhat low. While the blade unit has been described to have four upper or lower blades in the second embodiment, the exact number of blades is not critical in the present invention and, therefore, may be greater or fewer.

Fig. 8 is a top view showing a modification of the blade unit of Fig. 7 wherein the upper blades 14 are arranged alternately with respect to the lower blades 16 along the circumference of the rotor 12. In accordance with the modified blade unit, a certain amount of the air current produced by the upper blades 14 passes between the lower blades 16 and then flows in a radially downward direction. Likewise, the air current produced by the lower blades 16 moves radially upwardly between the upper blades 14. This will increase the thickness of the radial air current as compared to the blade units of the preceding embodiments. Another modified blade unit is shown in Fig. 9 wherein a given pair of the upper and the lower blades are axially offset by distance D from the adjacent pair of the upper and the lower blades. Use of the offset blades will expand the thickness of the radial air current from Ti to T2. Referring to Fig. 10, there is shown a third embodiment of the blade unit. The rotor 36 consists of an upper conical surface 38 and a lower conical surface 40, each extending in the opposite directions from a medial plane. Unlike the preceding embodiments, the rotor 36 is modified to have a radius at the medial plane greater than one half of the blade length. Attached at the top of the rotor 36 are a pair of upper blades 42, each forming an angle of γ 1 with respect to the rotor axis. The rotor 36 also carries at its bottom a pair of lower blades 44, each forming an angle of γ 2 with respect to the rotor axis. It is preferred that angles γ 1 and γ 2 be equal to one another and should range from 45 to 90° . In the third embodiment, the blade unit may employ even the conventional blades extensively used in the prior art axial flow fans as well as those blades shown and described above. This is possible because the rotor 36 plays a key role in producing the radial current of air. In operation, if the blade unit rotates in the clockwise direction, the upper and the lower blades 42 and 44 cooperate aerodynamically with the corresponding rotor surfaces 38 and 40 to thereby produce the radial current of air as clearly shown in Fig. 10.

Fig. 11 is an exploded view showing an electric fan which employs the blade unit set forth above in conjuction with the second embodiment. As shown, the electric fan comprises a base 50 having a hollow upstanding post 52. As is highly conventional, a control switch board 54 is installed on the base 50 so as to enable the user to control the operation of the electric fan. The upstanding post 52 slidably accommodates a support bar 56 in a height-adjustable manner. Additionally or alternatively, a spring 58 is retained within the upstanding post 52 to bias or urge the support bar 56 in an upward direction. Sliding movement of the support bar 56 is restrained by means of a set screw 60. The support bar 56 is provided with, at its top end, a flange 62 on which an electric motor 64 is fixedly secured by a number of bolts 66. As explained above with reference to Fig. 5, the electric motor 64 includes an output shaft 32 having at its free end a male thread 34. Finally, the blade unit 10 is fixed to the output shaft 32 by way of threadedly engaging the top cap 26 of the rotor with the output shaft 32. Fig. 12 is a perspective view of the electric fan made in accordance with the present invention. As shown, the blade unit is surrounded by an optional safety cage 70 so as to prevent the user from inadvertent access to the blade unit when the electric fan is still in operation. If the electric motor is energized by way of manipulating the control switch, the blade unit will be caused to rotate in the clockwise direction, thereby converting the axially existing ambient air into a radially outward current of air. The radial air current radiates simultaneously to the entire azimuth angle at a higher flow rate. In case where the electric fan is located at the center of a closed indoor area, the ambient air around the electric fan will continuously circulate in one direction, providing a synergistic cooling effect.

While the present invention has been shown and descirbed with reference to particular embodiments, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.

Claims

What is claimed is:

1. A blade unit rotatably driven by an electric motor to convert axially existing ambient air into a radially outward current of air, which comprises: a rotor operatively connected to said electric motor for rotation about its axis; at least two upper blades extending upward from said rotor in an inclined relationship with the axis of said rotor, said upper blades circumferentially spaced apart with each other at a substantially equal pitch; and at least two lower blades extending downward from said rotor in an inclined relationship with the axis of said rotor, said lower blades circumferentially spaced apart with each other at a substantially equal pitch; said upper and said lower blades being so shaped and arranged that they can aerodynamically cooperate with each other to produce said radially outward current of air when said blade unit is caused to rotate.

2. The blade unit as recited in claim 1, wherein each of said upper and said lower blades has a longitudinal center line, said center line forming an angle ranging from 30 to 60° with respect to the axis of said rotor.

3. The blade unit as recited in claim 2, wherein said center line forms an angle of 45° with respect to the axis of said rotor.

4. The blade unit as recited in claim 2, wherein each of said upper and said lower blades has a proximal end, a medial transition point and a distal end, the width of each said blades being greatest at said medial point.

5. The blade unit as recited in claim 4, wherein each of said upper and said lower blades is .twisted at an angle, said twist angle being largest at the proximal end and smallest at the distal end of said rotor.

6. The blade unit as recited in claim 5, wherein each of said upper and said lower blades is defined by a leading edge and a trailing edge, the spacing between said leading edges being greater than the spacing between said trailing edges when measured for each pair of said upper and said lower* blades.

7. The blade unit as recited in claim 1, wherein said upper blades include three or more twisted blades and said lower blades include the corresponding, number of twisted blades.

8. The blade unit as recited in claim 7, wherein said upper blades are alternately disposed with respect to said lower blades along the circumference of said rotor.

9. The blade unit as recited in claim 7, wherein a given pair of said upper and said lower blades are axially offset from the adjacent pair of said upper and said lower blades.

10. The blade unit as recited in claim 7, wherein said rotor has a vertical cross-section of substantially rhombic shape and a horizontal cross-section of substantially circular configuration.

11. The blade unit as recited in claim 10, wherein said rotor comprises a body and a conical top cap, said body having a flat top end and an axial bore, said conical top cap being seated on the top end of said body to provide an aerodynamic flow surface.

12. The blade unit as recited in claim 10, wherein said rotor has a radius greater than one half of the blade length, said rotor including an upper conical surface and a lower conical surface, said upper blades carried by the top end of said rotor so as to direct the ambient air to said upper conical surface, said lower blades carried by the bottom end of said rotor so as to direct the ambient air to said lower conical surface, whereby said upper and said lower blades cooperate aerodynamically with said upper and said lower conical surfaces, respectively, to produce a radially outward current of air when said blade unit is caused to rotate.

13. A fan comprising a base, a support bar vertically extending from said base, an electric motor carried by said support bar and a blade unit operatively connected to said electric motor for producing a radial current of air when said motor is energized, said blade unit including: a rotor operatively connected to said electric motor for rotation about its axis; at least two upper blades extending upward from said rotor in an inclined relationship with the axis of said rotor, said upper blades circumferentially spaced apart with each other at a substantially equal pitch; and at least two lower blades extending downward from said rotor in an inclined relationship with the axis of said rotor, said lower blades circumferentially spaced apart with each other at a substantially equal pitch;

* said upper and said lower blades being so shaped and arranged that they can aerodynamically cooperate with each other to produce said radially outward current of air when said blade unit is caused to rotate.

14. The fan as recited in claim 13, wherein said support bar is coupled to said base in a height-adjustable manner.

15. The fan as recited in claim 13, wherein each of said upper and said lower blades has a proximal end, a medial transition point and a distal end, the width of each of said blades being ^' greatest in the vicinity of said medial point.

16. The fan as recited in claim 15, wherein each of said upper and said lower blades is twisted at an angle, said twist angle being largest at the proximal end and smallest at the distal end of said rotor.

5

17. The fan as recited in claim 13, further comprsing a safety cage surrounding said blade unit.

18. The fan as recited in claim 13, wherein said upper 10 blades are alternately disposed with respect to said lower blades along the circumference of said rotor.

19. The fan as recited in claim 13, wherein said rotor has a vertical cross-section of substantially rhombic shape and a

15 horizontal cross-section of substantially circular configuration.

20. The fan as recited in claim 19, wherein said rotor has a radius greater than one half of the blade length, said rotor including an upper conical surface and a lower conical surface, said

20 upper blades carried by the top end of said rotor so as to direct the ambient air to said upper conical surface, said lower blades carried by the bottom end of said rotor so as to direct the ambient air to said lower conical surface, whereby said upper and said lower blades cooperate aerodynamically with said upper and said lower - 25 conical surfaces, respectively, to produce a radially outward current of air when said blade unit is caused to rotate.