EP1629206B1

EP1629206B1 - Fan

Info

Publication number: EP1629206B1
Application number: EP04735529A
Authority: EP
Inventors: Young Bok Son; Kyoung Suk Lim; Kwang Won Lee; Jeong Hun Aircon Group Research Laboratory KIM; Sung Man Hwang
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2003-06-04
Filing date: 2004-05-31
Publication date: 2009-03-11
Anticipated expiration: 2024-05-31
Also published as: DE602004019912D1; EP1629206A1; ES2321102T3; ATE425368T1

Description

Technical Field

The present invention relates to a fan for a home appliance, such as an air conditioner, or other manufacturing equipment.

Background Art

In general, various kinds of fans are used in home appliances, such as air conditioners, or ventilating systems for manufacturing equipment. There are axial fans and centrifugal fans in the fans depending on air flow characteristics.
The axial fan, with an air flow parallel to a rotation shaft, has a high flow rate, but is at a low pressure.
Though the centrifugal fan has an air flow in a direction of the rotation shaft at an inlet to blades where the air is introduced into the fan, the centrifugal fan has an air flow in a radial direction, a direction perpendicular to the rotation shaft, at an outlet from the blades. Because a purpose of the centrifugal fan is a pressure increase by centrifugal force, the centrifugal fan has a low flow rate, and a high pressure.
Therefore, in the system the fan is applied thereto, a suitable fan is employed taking the characteristics of the fans into account. For an example, since an indoor unit of an air conditioner requires a high pressure, a centrifugal fan, such as a sirocco fan or a turbo fan, is employed. Since a purpose of a ventilating system is discharge of a large quantity of air within a short time period, the axial fan is mostly employed, which can provide a high flow rate.
Since the fans have their own characteristics, it is difficult to increase both the flow rate and air pressure at the same time. Therefore, if a fan is required, which meets requirements of high flow rate and high pressure, it is required to increase a size of the fan. In a case of the home appliance, the size increase of the fan increases an overall size of a product, to cause a limitation of a mounting position in the system.
For solving this problem, Japanese Laid Open patent No. H8-216229 (Laid Open on August 27, 1996) discloses an air conditioning fan, and a method for fabricating the same which can increase both the air pressure and the air flow rate while the air flow direction is axial by forming a plurality of blades along a cylindrical hub in a helical or screw form.
However, since the air conditioning fan has the blades overlapped with one another and continuous, fabrication of the fan is difficult by using a general injection molding, to require a special extrusion molding, that is unfavorable for mass production.
WO 02/075159 A1 and US 6,126,395 A each disclose an axial fan comprising a cylindrical hub and a plurality of helical blades formed on the outside circumferential surface of the hub. The blades do not overlap with one another when the blades are seen in the axial direction of the hub. Each blade straightly extends in a radial direction.

Disclosure of Invention

An object of the present invention designed to solve the foregoing problem is to provide a fan, of which fabrication is easy so as to be favorable for mass production, and which has an axial air flow direction, and can provide a high air flow rate and a high air pressure at the same time.
To achieve the object of the present invention, there is provided a fan including a rotation shaft rotatably coupled to a driving motor, a cylindrical hub fixed to the rotation shaft, a plurality of helical blades on an outside circumferential surface of the hub, such that the blades do not overlap with one another when the blades are seen from a direction of the rotation shaft, wherein the blade is extended from the outside circumferential surface of the hub with a constant radius of curvature in a radial cross-section.
Partition lines each connecting a top end of the blade to a bottom end of an adjacent blade formed in the outside circumferential surface at a time of injection molding with molds.
The partition line is a straight line connecting an outer edge of the top end of the blade to an inner edge of the bottom end of an adjacent blade.
The partition line connects an outer edge of the top end of the blade to an inner edge of the bottom end of an adjacent blade. The partition line includes a first horizontal part straightly extended from the inner edge of the top end of the blade in a horizontal direction, a second horizontal part straightly extended from an inner edge of a bottom end of an adjacent blade in a horizontal direction, and a vertical part connected between the first, and second horizontal parts.
In other aspect of the present invention, there is provided a fan including a rotation shaft rotatably coupled to a driving motor, a cylindrical hub fixed to the rotation shaft, a plurality of helical blades formed on an outside circumferential surface of the hub such that the blades do not overlap with one another when the blades are seen from a direction of the rotation shaft.
A top end of the blade and a bottom end of an adjacent blade are spaced a distance away from each other in a circumferential direction of the hub.
The blade is extended from the outside circumferential surface of the hub with a fixed radius of curvature. The blade has the radius of curvature of the bottom end formed different from the radius of curvature of the top end, particularly, the blade has the radius of curvature of the bottom end formed greater than the radius of curvature of the top end.
In the meantime, the blade is straightly extended from the outside circumferential surface of the hub. The hub has an opened top and an opened bottom.
An angle a side edge of the blade forms becomes the greater as it goes from the bottom of the hub to the top of the hub the farther. Preferably, the blade has an exit angle θe greater than an inlet angle θi, and more preferably, the blade has an inlet angle θi of 35°.
Preferably, a ratio t_h : t_b of thickness of the hub to the blade is 1 : 1.5, and the blade has a thickness formed the thinner as the blade is extended from the outside circumferential surface of the hub the farther.
Preferably, a ratio of a diameter Dh of the hub to a diameter Db of a circle a rotation a locus of the blade forms is 0.4 ∼ 0.8, and more preferably, 0.6.
The hub has a plurality of helical blades on an inside circumferential surface of the hub.
The top end of the blade is extended beyond the top end of the hub, and the bottom end of the blade is extended beyond the bottom end of the hub.
The blade is extended from the outside circumferential surface of the hub in a normal line direction, or the rotation shaft is fixed only to a lower part of the hub, and the lower part of the hub is formed thicker than the upper part of the hub for suppression of vibration.
In the meantime, the rotation shaft includes a plurality of hubs fixed thereto at regular intervals, each having a plurality of blades formed thereon.
The hub has the upper part and the lower part each shortened by a length, such that a vertical length Lh of the hub is shorter than a vertical length Lb of the blade.
A ratio of the vertical length Lh of the hub to the vertical length Lb of the blade is preferably 4:6. The upper part and the lower part of the hub preferably have lengths reduced by the same amount.
The hub includes a connection plate inside of the hub having a top end of the rotation shaft fixed thereto, and the connection plate includes a plurality of radial reinforcing ribs provided thereto.
The reinforcing ribs are preferably symmetry with respect to the connection plate in up/down direction.
The connection plate includes a metal bushing provided to a center of the connection plate to surround the rotation shaft, and the lower part of the blade is cut away from an inner edge of the blade in contact with the bottom end of the hub to the side edge of the bottom end.
The blade has a section changing from an "S" form to an arc form as it goes from the upper part to the lower part of the blades the farther, and the hub includes a connection plate inside of the hub having a top end of the rotation shaft fixed thereto.
The connection plate includes a plurality of radial reinforcing ribs provided thereto, and the reinforcing rib is symmetry with respect to the connection plate in an up/down direction.
The connection plate includes a metal bushing provided to a center of the connection plate to surround the rotation shaft.

Brief Description of Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.
In the drawings;

FIG 1 illustrates a perspective view of a fan in accordance with a first preferred embodiment of the present invention;
FIG 2 illustrates a diagram of a partition line in a fan of the present invention;
FIG 3 illustrates a diagram of another form of a partition line of the fan of the present invention;
FIG 4 illustrates a front view of the fan in FIG 1;
FIG 5 illustrates a plan view of the fan in FIG 1;
FIG 6 illustrates a perspective view of a fan in accordance with a second preferred embodiment of the present invention;
FIG 7 illustrates a front view of a fan in accordance with a third preferred embodiment of the present invention;
FIG 8 illustrates a perspective view of a fan in accordance with a fourth preferred embodiment of the present invention;
FIG 9 illustrates a perspective view of a fan in accordance with a fifth preferred embodiment of the present invention;
FIG 10 illustrates a perspective view of a fan in accordance with a sixth preferred embodiment of the present invention;
FIG 11 illustrates a perspective view of a fan in accordance with a seventh preferred embodiment of the present invention;
FIG 12 illustrates a perspective view of a fan in accordance with an eighth preferred embodiment of the present invention;
FIG 13 illustrates a front view of a fan in FIG 12;
FIG 14 illustrates a perspective view of a fan in accordance with a ninth preferred embodiment of the present invention;
FIG. 15 illustrates a diagram of structure of the fan in FIG 14;
FIG 16 illustrates a plan view of the fan in FIG 14; and
FIG 17 illustrates a graph showing comparison of noise measurement results of the fan in the eighth embodiment, and the fan in the ninth embodiment.

Best Mode for Carrying Out the Invention

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 1 illustrates a perspective view of a fan in accordance with a first preferred embodiment of the present invention.
Referring to FIG. 1, the fan includes a rotation shaft 1 rotatably coupled to a driving motor (not shown), a cylindrical hub 2 fixed to the rotation shaft 1, and one pair of helical blades 3 on an outside circumferential surface of the hub 2.
The blades 3 are formed not to have overlapped portion with each other when seen from a direction of the rotation shaft 1. For this, a top end 3b of one of the blades 3 and a bottom end 3a of an adjacent blades 3 are spaced a distance in a circumferential direction, or formed on the same vertical line when seen from a side of the hub 2.
That is, when the hub 2 is divided into halves, the two blades 3 are formed on the divided halves of the hub 2 respectively, to enable injection molding of the hub 2 with an upper mold and a lower mold (not shown).
The bottom end 3a of the hub 3 is a part where air introduced into the blade 3 passes at a first time, and the top end 3b of the blade 3 is a part where the air passes as the air is discharged from the blade 3. For convenience sake, it is assumed that the air is introduced into a bottom of the fan and discharged from a top of the fan when the drawing is seen from above.
The blade 3 extends from an outside circumference of the hub 2 with a fixed radius of curvature, to have a semicircular curved form.
It is preferable that the radius of curvature of the top end 3b of the blade 3 is different from the radius of curvature of the bottom end 3a, for smooth flow of air, and, particularly, it is preferable that the radius of curvature of the bottom end 3a is greater than the radius of curvature of the top end 3b.
Accordingly, the bottom end 3a of the blade with a greater radius of curvature enables smooth entrance of air, and the bottom end 3a of the blade with a smaller radius of curvature enables to increase both the air pressure and the air flow rate because the air is discharged, with the air gathered.
Of course, the blade 3 may have a variety of forms, such as blade 3 extends on a straight line from the outside circumferential surface of the hub 3.
Unexplained reference symbols 3c and 3d denote an inside surface and an outside surface of the blade 3, respectively.
In the meantime, the hub 2 has opened top and bottom. Therefore, because the air entering into the bottom of the fan is guided to the top of the fan along, not only the blades 3, but also an inside of the hub 2, the fan can have a high air flow rate. Of course, depending on an environment and conditions the fan is applied thereto, the top and the bottom of the hub 2 may be closed.
The hub 2 has four ribs 4 inside thereof at 90° intervals fixed to inside surfaces of the rotation shaft 1 and the hub 2 for supporting the rotation shaft 1.
In the meantime, the hub 2 has a partition line 5 in the outside surface thereof connected between the top end 3b of one of the blades and the bottom end 3a of an adjacent blade. The partition line 5 is formed in the outside circumferential surface of the hub 2 when the hub 2 is injection molded with the upper and lower molds.
The partition line 5 will be described in more detail. FIG. 2 illustrates a diagram of a partition line in a fan of the present invention.
Referring to FIG. 2, the partition line 5 connects an outside surface 3d of the top end of one of the blades and an inside surface 3c of the bottom end of an adjacent blade. The outside surface 3d of the top end of one of the blades and an inside surface 3c of the bottom end of an adjacent blade are positioned at the same vertical line. According to this, the partition line 5 is a straight line.
FIG 3 illustrates a diagram of another form of a partition line of the fan of the present invention.
Referring to FIG 3, the partition line may also be formed to connect the inside surface 3c of the top end of one of the blades to the inside surface 3c of the bottom end of an adjacent blade.
In this instance, the top end 3b of one of the blades and the bottom end 3 a of an adjacent blade are spaced a distance in a circumferential direction of the hub 2. Therefore, the partition line connecting the top end 3b of one of the blades and the bottom end 3a of an adjacent blade forms, no straight line, but a 'Z' form, substantially.
In more detail, the partition line 5 has a first horizontal part 5a straightly extended from the inside surface 3c of the top end of one of the blades horizontally, a second horizontal part 5b straightly extended from the inside surface 3c of the bottom end of an adjacent blade horizontally, and a vertical part 5c connected between the first, and second horizontal parts 5a, and 5b.
As described before, the partition line 5 is formed in the outside circumferential surface of the hub 2 when the hub 2 is formed by injection molding with molds, if forms of the molds change, a form of the partition line 5 is also changed.
FIG 4 illustrates a front view of the fan in FIG. 1.
Referring to FIG 4, an angle a side edge 3e of one of the blades forms is formed such that the angle becomes the greater as it goes from the bottom of the hub 2 to the top of the hub 2 for improvement of flow characteristics. The blade 3 is formed such that an exit angle θe is greater than an inlet angle θi.
The inlet angle θi is an angle a tangential line to the edge 3e of the blade and a horizontal line form at the part where the air enters, and the exit angle θe is an angle a tangential line to the edge 3e of the blade and a horizontal line form at the part where the air exits.
The inlet angle θi denotes an entering angle of the air entering into the bottom 3a of the blade, and the exit angle θe denotes an exit angle of the air leaving from the top end 3b of the blade.
It is preferable that the inlet angle θi is 35°. In more detail, as a result of experiment of noise measurement of the fan with varied inlet angle θi shows that the noise of the fan varies with the inlet angle θi.
That is, if the inlet angle θi is 35°, the noise of the fan is around 31dB, and is around 36dB at the other angles. This is because a stream line of the entering air is almost the same with the inlet angle θi in a case the inlet angle θi is around 35°, to minimize formation of turbulence.
FIG 5 illustrates a plan view of the fan in FIG. 1.
Referring to FIG 5, the hub 2 and the blade 3 have certain thickness t_h, and t_b influencing to a vibration characteristic of the fan. That is, vibration of the fan varies with the thickness t_h, and t_b, especially a thickness ratio t_h : t_b, of the hub 2 and the blade 3.
In more detail, as a result of experiment for measuring vibration of the fan while varying thickness of the hub 2 and the blade 3, it is verified that the thickness ratio t_h : t_b, of the hub 2 and the blade 3 has a great influence to the vibration characteristics of the fan. Especially, the vibration characteristics of the fan are the best when thickness ratio t_h : t_b, of the hub 2 and the blade 3 is 1 : 1.5.
It is preferable that the blade 3 is formed such that the thickness t_b becomes the thinner as the blade is extended from the outside surface of the hub 2 the farther. Such a blade structure shifts a center of gravity of the blade 3 inward, to reduce a moment generated at the time of rotation of the fan, and consequently, to reduce the vibration of the fan.
Moreover, it is preferable that the fan of the present invention is fabricated to have a hub ratio Dh/Db of 0.4 ∼ 0.8 so that the fan provides a high air flow rate and a high air pressure, more preferably, 0.6. The hub ratio Dh/Db is a ratio of a diameter Dh of the hub 2 to a diameter Db of a circle of a rotation locus of the blade 3.
In view of fluid dynamics, though it is known that a size of the blade gives a great influence to a performance of the fan, as a result of actual experiment with fans having a variety of hub ratios Dh/Db, the air flow rate and the air pressure are good when the hub ratio Dh/Db is in a range of 0.4 ∼ 0.8, and are optimum when the hub ratio is 0.6.
FIG 6 illustrates a perspective view of a fan in accordance with a second preferred embodiment of the present invention.
Referring to FIG 6, the fan includes a hub 22 with opened top and bottom, and two pairs of helical blades 23, and 24 on an inside circumferential surface and an outside circumferential surface of the hub 22.
Alike the blades 23 on the outside circumferential surface of the hub 22, the blades 24 on the inside circumferential surface of the hub 22 are formed not to overlap with each other when seen from a direction of the rotation shaft 21.
According to this, since the fan blows air, not only with the blades 23 on the outside circumferential surface of the hub 22, but also with the blades 24 on the inside circumferential surface of the hub 22, to blow air through the inside of the hub 22 too, the air pressure and the air flow rate increase further.
FIG 7 illustrates a front view of a fan in accordance with a third preferred embodiment of the present invention.
Referring to FIG 7, the fan includes a hub 32, a rotation shaft 31, and one pair of helical blades 33 on an outside circumferential surface of the hub 32.
Top ends of the blades 33 are extended beyond a top end of the hub 32, and bottom ends of the blades 33 are extended beyond a bottom end of the hub 32, to increase lengths and areas of the blades 33, that increase an air flow rate of the fan.
FIG 8 illustrates a perspective view of a fan in accordance with a fourth preferred embodiment of the present invention.
Referring to FIG 8, the fan includes three blades 43a, 43b, and 43c on an outside circumferential surface of the hub 42 at 120° intervals for increasing an air flow rate.
Alike foregoing embodiments, the blades 43a, 43b, and 43c are helical, and formed on an outside circumferential surface of the hub 42 without overlap with one another when seen from a direction of the rotation shaft 41. Since the three blades 43a, 43b, and 43c are formed on the outside circumferential surface of the hub 42, the fan requires three molds for injection molding.
Thus, the fan of the present invention may be formed to have three or more than three blades, with an increased number of molds for injection mold.
FIG 9 illustrates a perspective view of a fan in accordance with a fifth preferred embodiment of the present invention.
Referring to FIG 9, the fan includes blades 53 each extended along a normal line from an outside circumferential surface of the hub 52 to have a great curvature, such that the hub 52 and the blades 53 have a form of 'an eye of a typhoon' when seen from a direction of a rotation shaft 51.
Since this fan structure enables to increase areas of the blades 53 while keeping a rotation locus of the blades 53 the same, an air flow rate of the fan is increased. Of course, in this case too, the blades do not overlap with each other when seen from the direction of the rotation shaft 51.
FIG 10 illustrates a perspective view of a fan in accordance with a sixth preferred embodiment of the present invention.
Referring to FIG 10, the fan includes a rotation shaft 61, and one pair of helical blades 63 on an outside circumference of a hub 62. Different from above embodiments, the rotation shaft 61 fixed only to a bottom of the hub 62. This structure enables easy fabrication of the fan, and reduces an installation space since no structure for fixing a top end of the rotation shaft 61 is required. However, the fan is liable to cause heavy vibration during rotation because the rotation shaft hold only the bottom of the hub 62. Therefore, it is preferable that a lower part of the hub 62 is thick, and an upper part of the hub 62 is thin, to lower a center of gravity of the hub for suppressing the vibration.
FIG 11 illustrates a perspective view of a fan in accordance with a seventh preferred embodiment of the present invention.
Referring to FIG. 11, the fan includes a rotation shaft 71, two hubs 73, and 76 fixed to the rotation shaft 71, and helical blades 74, and 77 on the hubs 73, and 76 formed not overelap with each other, respectively. According to this, the fan has two staged hub in which two hubs 73, and 76 are mounted in an up/down direction spaced a distance away from each other. It is preferable that the hubs 73, and 76, and the blades 74, and 77 have the same structure. However, it is apparent that forms and the like of the blades 74, and 77 and the hubs 73, and 76 may be changed as required.
Moreover, it is apparent that three hubs are mounted on the rotation shaft 71 in up/down directions, such that the fan has a three or more than three staged hub structure. However, the fan with a three or more than three staged hub structure is difficult to fabricate, and makes an overall size of a system the having the fan applied thereto large. Moreover, since a fan with an excessively long length is liable to result in drop of performance, the user is required to employ an appropriate number of stages.
FIG 12 illustrates a perspective view of a fan in accordance with an eighth preferred embodiment of the present invention, and FIG 13 illustrates a front view of a fan in FIG. 12.
Referring to FIGS. 12 and 13, the fan includes a hollow hub 82, and one pair of blades 83 on an outside circumferential surface of the hub 82 so as not to overlap with each other. The hub 82 has a length having certain lengths reduced from an upper part and a lower part respectively, such that a vertical length of the hub Lh is shorter than a vertical length Lb of the blade. The hub 82 also has a connection plate 84 inside thereof fixed to the rotation shaft coupled to a driving motor 85.
In the meantime, it is preferable that a ratio of the vertical length Lh of the hub 82 to the vertical length Lb of the blade 83 is 4:6. Moreover, it is preferable that lengths of the upper part and the lower part of the hub 82 are shortened by the same lengths, to make length differences between the top and bottom ends of the hub 82 and the top and bottom ends of the blade 83 are the same.
In a case the fan has such a hub 82 having the upper part and the lower part shortened thus, the air introduced from the lower part of the hub 82 comes into contact with the blades 83 at first, and moves along outside circumferences of the blades 33 and the hub 82, to reduce an amount of air flowing toward and inner space of the hub 82, to reduce turbulence caused by the air introduced into the inner part of the hub 82, to reduce an overall noise from the fan while an air flow rate of the fan is kept the same.
FIG 14 illustrates a perspective view of a fan in accordance with a ninth preferred embodiment of the present invention, FIG 15 illustrates a diagram of structure of the fan in FIG 14, and FIG 16 illustrates a plan view of the fan in FIG 14.
Referring to FIGS. 14 ∼ 16, the fan includes a hollow hub 92, and one pair of blades 93 on an outside circumferential surface of the hub 92 not to overlap with each other. Alike the eighth embodiment, the hub 92 has a form having the upper part and the lower part thereof reduced by certain lengths respectively.
The hub 92 also has a connection plate 94 inside thereof for fixing a top end of the rotation shaft 91 coupled to a driving motor 97. The connection plate 94 has a part in contact with an inside surface of the hub 92 curved upward for strengthening.
The connection plate 94 also has a plurality of reinforcing ribs 95 formed in a radial direction from the connection plate 94, for further increasing a strength of the connection plate 94. To do this, it is preferable that the reinforcing rib 95 is symmetry with respect to an upper surface and a lower surface of the connection plate 94.
In the meantime, there is a bushing 96 of metal surrounding the rotation shaft 91 at a center of the connection plate 94 having the top end of the rotation shaft 91 fixed thereto. The bushing 96 prevents the rotation shaft 91 from coming into direct contact with the connection plate 94, to prevent wear down of the connection plate 94 caused by fast rotation, and to enable the connection plate 94 to hold the rotation shaft 91, securely.
The bushing 96 may be fixed to the connection plate 94 by insert injection molding. Or course, the bushing 96 may be fixed to the connection plate 94 by a separate bracket (not shown) and the like, or press fit.
In the meantime, a lower part of the blade 93 is cut away starting from an inner side of the blade 93 in contact with a bottom end of the hub 92 to a side edge 93e of the bottom end in a straight line, to form a pointed triangular lower part of the blade 93, substantially. As a section of the side edge 93e is flattened as it goes from the upper part to the lower part, the blade 93 changes from an "S" form to a simple arc.
FIG 17 illustrates a graph showing comparison of noise measurement results of the fans of the eighth embodiment, and the ninth embodiment.
Referring to FIG 17, since the ninth embodiment fan has the inner side of the lower part of the blade 93 that generates turbulence noise while supplying no energy to the fluid actually cut away, the ninth embodiment fan can reduce noise lower than the eighth embodiment when the fan is rotated.
The fan of the present invention has been described embodiment by embodiment with reference to the attached drawing. However, it is apparent that by combining features of the embodiments of the fan appropriately, the fan may be embodied to have an optimum performance.
Moreover, though the fan of the present invention is designed to be suitable to an indoor unit of an air conditioner, the fan can be applicable to all systems that require air flow in the same or similar fashion.
It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Industrial Applicability

The fan of the present invention has the following advantages.
The fan of the present invention has helical blades on an outside circumferential surface of a hub without overlap with each other, thereby enabling injection molding with molds, to permit easy fabrication, mass production in a various, and complicate forms.

Claims

A fan comprising:
- a rotation shaft (1) rotatably coupled to a driving motor;

- a cylindrical hub (2) fixed to the rotation shaft (1);

- a plurality of helical blades (3) formed on an outside circumferential surface of the hub (2) such that the blades (3) do not overlap with one another when the blades (3) are seen from a direction of the rotation shaft (1),
characterized in that the blade (3) is extended from the outside circumferential surface of the hub (2) with a fixed radius of curvature in a radial cross-section.
A fan as claimed in claim 1 comprising:
- partition lines (5) each connecting a top end of the blade (3) to a bottom end of an adjacent blade (3) formed in the outside circumferential surface.
The fan as claimed in claim 2, wherein the partition line (5) is a straight line connecting an outer edge of the top end of the blade (3) to an inner edge of the bottom end of an adjacent blade (3).
The fan as claimed in claim 2, wherein the partition line (5) connects an outer edge of the top end of the blade (3) to an inner edge of the bottom end of an adjacent blade (3).
The fan as claimed in claim 4, wherein the partition line (5) includes;
- a first horizontal part straightly extended from the inner edge of the top end of the blade in a horizontal direction,

- a second horizontal part straightly extended from an inner edge of a bottom end of an adjacent blade in a horizontal direction, and

- a vertical part connected between the first, and second horizontal parts.
The fan as claimed in claim 1, wherein a top end (3b) of the blade (3) and a bottom end (3a) of an adjacent blade are spaced a distance away from each other in a circumferential direction of the hub (2).
The fan as claimed in claim 1, wherein the fixed radius of curvature in a radial cross-section of the blade (3) is different at the bottom end (3a) from the fixed radius of curvature at the top end (3b).
The fan as claimed in claim 7, wherein the fixed radius of curvature at the bottom end (3a) is greater than the fixed radius of curvature at the top end (3b).
The fan as claimed in claim 1 or 2, wherein the blade (3) is straightly extended from the outside circumferential surface of the hub (2).
The fan as claimed in claim 1 or 2, wherein the hub (2) has an opened top and an opened bottom.
The fan as claimed in claim 1 or 2, wherein an angle a side edge of the blade forms becomes the greater as it goes from the bottom of the hub to the top of the hub the farther.
The fan as claimed in claim 1 or 2, wherein the blade (3) has an exit angle (θe) greater than an inlet angle (θi).
The fan as claimed in claim 1 or 2, wherein the blade (3) has an inlet angle (θi) of 35°.
The fan as claimed in claim 1 or 2, wherein the blade (3) has a thickness formed the thinner as the blade is extended from the outside circumferential surface of the hub the farther.
The fan as claimed in claim 1 or 2, wherein a ratio t_h : t_b of the thickness of the hub to the blade is 1 : 1.5.
The fan as claimed in claim 1 or 2, wherein a ratio of a diameter (Dh) of the hub (2) to a diameter (Db) of a circle a rotation a locus of the blade forms is 0.4 ∼0.8.
The fan as claimed in claim 1 or 2, wherein the ratio of the diameter (Dh) of the hub to the diameter (Db) of the circle a rotation the locus of the blade forms is 0.6.
The fan as claimed in claim 10, wherein the hub (2) has a plurality of helical blades on an inside circumferential surface of the hub (2).
The fan as claimed in claim 1 or 2, wherein the top end of the blade (83; 93) is extended beyond the top end of the hub (82; 92), and the bottom end of the blade (83; 93) is extended beyond the bottom end of the hub (82; 92).
The fan as claimed in claim 1 or 2, wherein the blade is extended from the outside circumferential surface of the hub in a normal line direction.
The fan as claimed in claim 1 or 2, wherein the rotation shaft is fixed only to a lower part of the hub, and the lower part of the hub is formed thicker than the upper part of the hub for suppression of vibration.
The fan as claimed in claim 1 or 2, wherein the rotation shaft (71) includes a plurality of hubs (73, 76) fixed thereto at regular intervals, each having a plurality of blades (74, 77) formed thereon.
The fan as claimed in claim 1 or 2, wherein the hub (82) has the upper part and the lower part each shortened by a length, such that a vertical length (Lh) of the hub (82) is shorter than a vertical length (Lb) of the blade (83).
The fan as claimed in claim 23, wherein a ratio of the vertical length (Lh) of the hub to the vertical length (Lb) of the blade is 4:6.
The fan as claimed in claim 23, wherein the upper part and the lower part of the hub (82) have lengths reduced by the same amount.
The fan as claimed in claim 23, wherein the hub (82; 92) includes a connection plate (84; 94) inside of the hub (82; 92) having a top end of the rotation shaft (81; 91) fixed thereto.
The fan as claimed in claim 26, wherein the connection plate (94) includes a plurality of radial reinforcing ribs (95) provided thereto.
The fan as claimed in claim 27, wherein the reinforcing ribs (95) are symmetry with respect to the connection plate (94) in up/down direction.
The fan as claimed in claim 26, wherein the connection plate (94) includes a metal bushing (96) provided to a center of the connection plate (94) to surround the rotation shaft (91).
The fan as claimed in claim 23, wherein the lower part of the blade (93) is cut away from an inner edge of the blade (93) in contact with the bottom end of the hub (92) to the side edge of the bottom end.
The fan as claimed in claim 30, wherein the blade (93) has a section changing from an "S" form to an arc form as it goes from the upper part to the lower part of the blades (93) the farther.
The fan as claimed in claim 31, wherein the hub (92) includes a connection plate (94) inside of the hub (92) having a top end of the rotation shaft (91) fixed thereto.
The fan as claimed in claim 32, wherein the connection plate (94) includes a plurality of radial reinforcing ribs (95) provided thereto.
The fan as claimed in claim 33, wherein the reinforcing rib (95) is symmetry with respect to the connection plate (94) in an up/down direction.
The fan as claimed in claim 32, wherein the connection plate (94) includes a metal bushing (96) provided to a center of the connection plate (94) to surround the rotation shaft (91).