EP0553598B2 - A fan with convex blades - Google Patents

A fan with convex blades Download PDF

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Publication number
EP0553598B2
EP0553598B2 EP19920830038 EP92830038A EP0553598B2 EP 0553598 B2 EP0553598 B2 EP 0553598B2 EP 19920830038 EP19920830038 EP 19920830038 EP 92830038 A EP92830038 A EP 92830038A EP 0553598 B2 EP0553598 B2 EP 0553598B2
Authority
EP
European Patent Office
Prior art keywords
fan
blades
blade
hub
rotation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19920830038
Other languages
German (de)
French (fr)
Other versions
EP0553598A1 (en
EP0553598B1 (en
Inventor
Alessandro Spaggiari
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Spal SRL
Original Assignee
Spal SRL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
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Application filed by Spal SRL filed Critical Spal SRL
Priority to ES92830038T priority Critical patent/ES2087501T5/en
Priority to DE1992609484 priority patent/DE69209484T3/en
Priority to EP19920830038 priority patent/EP0553598B2/en
Publication of EP0553598A1 publication Critical patent/EP0553598A1/en
Application granted granted Critical
Publication of EP0553598B1 publication Critical patent/EP0553598B1/en
Publication of EP0553598B2 publication Critical patent/EP0553598B2/en
Anticipated expiration legal-status Critical
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
    • F04D29/325—Rotors specially for elastic fluids for axial flow pumps for axial flow fans
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
    • F04D29/38—Blades

Definitions

  • the invention relates to a fan generating an axial flow and equipped with convex or backward-curved blades, that is, blades curved in the opposite direction to the rotation direction of the fan.
  • Fans in general comprise a plurality of blades radiating outwards from a hub, said blades moving in a perpendicular plane to the said hub which supports them.
  • Each blade has a transversal dimension which is practically flat, and is inclined in such a way as to form a certain angle with respect to the rotation plane of the said fan.
  • the inclination is such that, when the fan rotates, the blades generate an air flow which is parallel to the rotation axis of the hub.
  • the "simplest” fans have straight blades, that is with the central longitudinal line of each blade being straight in the sense that is develops radially with respect to the hub to which it is keyed.
  • the prior art teaches fans with curved blades having their median line curved in the rotation direction of the fan or in the opposite direction, realising in this way a gradual penetration of the fanning surface of the blades in the air.
  • Patent US-PS 4.358.245 teaches an axial fan whose blades are curved in the rotation direction of the fan, and have an angle which grows according to the diameter of the blade at a certain point with respect to the maximum diameter of the same blade. The blade angle increases in the final 30% of the blade itself.
  • Patent US-A 4,569,632 teaches a fan of the type described above, whose blades curve backwards, that is in the opposite direction to the rotation direction of the fan itself, and are oriented in an inclination ratio with respect to the rotation plane which ratio diminishes constantly as the radius of the blade increases in the final 30% of its length.
  • German utility patent DE-U-89 03 903 teaches another fan of the type described above, whose blades curve forwardly, and the projections, on a plane perpendicular to the axis of rotation of the fan, of the front edge and the rear edge are defined, starting from the hub of the fan, by a first straight radial section until the 25% of the radial length of the blade and then by a second section following two arcs.
  • the aim of the present invention is to structure an axial-flow fan of the convex-blade type or backward-curving type in which an efficacy-silence compromise is reached.
  • the invention as characterized in the claim solves the above-described problem by proposing an axial fan with convex blades or backwards-curved blades in which the maximum transversal dimension of the blades is constant along their entire longitudinal development that is considering the section of a blade as an airfoil profile, the chord of such profile is constant along the longitudinal axis of the blade, i.e.
  • the axial flow fan according to the invention is denoted by 1 and comprises a central hub 3 from which a plurality of blades 2 radiate out in angularly equidistanced radial directions.
  • the hub 3 is keyable on to a motor shaft (not illustrated)which places it in rotation about a common axis.
  • the blades 2 are of the convex type, curved backwards, that is, with their median lines curved in the opposite sense to the rotation direction of reciprocally connected by means of an external stiffening ring 4.
  • the blades 2 are also inclined with respect to the rotation direction of the fan 1 in such a way as to generate, during the said fan's 1 rotation, an air flow parallel to the common rotation axis.
  • the invention envisages that the maximum transversal dimension of the blades 2 is constant along their entire longitudinal development (see figures 3 and 4).
  • the twisting of the blades that is, the progressinve variation of the keying angle on the hub 3 starting from the said hub 3 towards the external ring 4, remains constant along the entire development of the blades 2 themselves, in the sense that the derivative calculated in successive points along the longitudinal development of the blade 2 defines a constantly varying angular coefficient at point after point.
  • each blade 2 is structured as if it had been cut out of a straight blade in which each of its transversal sections had been made to slide on to the immediately contiguous transversal section.
  • the present fan thus reaches the proposed aims of silence, thanks to the backwards curvature of the blades 2, and of high performance, thanks to the substantial conformation of the same blades 2 which is comparable to the performance of straight blades.

Description

The invention relates to a fan generating an axial flow and equipped with convex or backward-curved blades, that is, blades curved in the opposite direction to the rotation direction of the fan.
Fans in general comprise a plurality of blades radiating outwards from a hub, said blades moving in a perpendicular plane to the said hub which supports them.
Each blade has a transversal dimension which is practically flat, and is inclined in such a way as to form a certain angle with respect to the rotation plane of the said fan.
The inclination is such that, when the fan rotates, the blades generate an air flow which is parallel to the rotation axis of the hub.
The "simplest" fans have straight blades, that is with the central longitudinal line of each blade being straight in the sense that is develops radially with respect to the hub to which it is keyed.
Fans structured in this way have shown themselves to be extremely efficient and capable of reaching elevated performance levels.
One drawback they have, however, is that they are extremely noisy since the blades strike the air to be fanned with all their operative surface at once and the resulting impact is violent.
With the aim of eliminating this drawback of noisiness, the prior art teaches fans with curved blades having their median line curved in the rotation direction of the fan or in the opposite direction, realising in this way a gradual penetration of the fanning surface of the blades in the air.
Patent US-PS 4.358.245, for example, teaches an axial fan whose blades are curved in the rotation direction of the fan, and have an angle which grows according to the diameter of the blade at a certain point with respect to the maximum diameter of the same blade. The blade angle increases in the final 30% of the blade itself.
Patent US-A 4,569,632 teaches a fan of the type described above, whose blades curve backwards, that is in the opposite direction to the rotation direction of the fan itself, and are oriented in an inclination ratio with respect to the rotation plane which ratio diminishes constantly as the radius of the blade increases in the final 30% of its length.
The German utility patent DE-U-89 03 903 teaches another fan of the type described above, whose blades curve forwardly, and the projections, on a plane perpendicular to the axis of rotation of the fan, of the front edge and the rear edge are defined, starting from the hub of the fan, by a first straight radial section until the 25% of the radial length of the blade and then by a second section following two arcs.
Fans thus made have shown themselves to be very silent, but have the drawback of having only a modest efficiency in comparison with that of the straight-bladed fans.
The aim of the present invention is to structure an axial-flow fan of the convex-blade type or backward-curving type in which an efficacy-silence compromise is reached.
The invention as characterized in the claim solves the above-described problem by proposing an axial fan with convex blades or backwards-curved blades in which the maximum transversal dimension of the blades is constant along their entire longitudinal development that is considering the section of a blade as an airfoil profile, the chord of such profile is constant along the longitudinal axis of the blade, i.e. in substantially radial direction, and their anterior or entry edges and posterior or exit edges are defined with respect to their rotation direction and observing parallel to the fan's rotation axis, by two circular arcs which exend from the hub to the external stiffening ring, further characteristcs and advantages of the present invention will better emerge from the detailed description which follows, made with reference to the accompanying drawings which represent a preferred but non-limiting embodiment included by way of example, in which:
  • Figure 1 shows, in axial view, the axial fan object of the present invention;
  • Figure 2 shows, in schematic axial view, some construction lines of one blade of the fan of figure 1, with the aim of better evidencing the said blade's characteristics;
  • Figures 3 and 4 show section III-IIII and respectively section IV-IV of figure 2.
With reference to the drawings, the axial flow fan according to the invention is denoted by 1 and comprises a central hub 3 from which a plurality of blades 2 radiate out in angularly equidistanced radial directions.
The hub 3 is keyable on to a motor shaft (not illustrated)which places it in rotation about a common axis.
The blades 2 are of the convex type, curved backwards, that is, with their median lines curved in the opposite sense to the rotation direction of reciprocally connected by means of an external stiffening ring 4. The blades 2 are also inclined with respect to the rotation direction of the fan 1 in such a way as to generate, during the said fan's 1 rotation, an air flow parallel to the common rotation axis.
The invention envisages that the maximum transversal dimension of the blades 2 is constant along their entire longitudinal development (see figures 3 and 4).
Furthermore, observing the fan 1 along its axial direction, the anterior or entrance edges 5 and the posterior or exit edges 6 of the blades 2, with respect to the rotation direction of the fan 1, develop along circle arcs as evidenced by radii Ri and Re in figure 2.
The twisting of the blades 2, that is, the progressinve variation of the keying angle on the hub 3 starting from the said hub 3 towards the external ring 4, remains constant along the entire development of the blades 2 themselves, in the sense that the derivative calculated in successive points along the longitudinal development of the blade 2 defines a constantly varying angular coefficient at point after point.
From figure 2 it can be seen that each blade 2 is structured as if it had been cut out of a straight blade in which each of its transversal sections had been made to slide on to the immediately contiguous transversal section.
Still with reference to figure 2, in can be seen that these ideal slidings of the transversal sections can happen along concentric circumferences whose centre lies on the rotation axis of the fan 1, so that the maximum transversal dimension is measured along the said circumferences.
The present fan thus reaches the proposed aims of silence, thanks to the backwards curvature of the blades 2, and of high performance, thanks to the substantial conformation of the same blades 2 which is comparable to the performance of straight blades.

Claims (1)

  1. An axial fan with the blades curved in the opposite direction to the rotation direction of the fan, constituted by a hub (3) from which blades (2) radiate out wards to an external stiffening ring (4), the said blades (2) having a section which is an airfoil profile the chord (L) of each blade being constant along the radial direction of the fan,
    characterised in that
    the projections, on a plane perpendicular to the axis of rotation of the fan, of the blade (2) anterior or entry edges (5) and the blade (2) posterior or exit edge (6) are defined by two circular arcs which extend from the hub to the external siffening ring (4).
EP19920830038 1992-01-30 1992-01-30 A fan with convex blades Expired - Lifetime EP0553598B2 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
ES92830038T ES2087501T5 (en) 1992-01-30 1992-01-30 A FAN WITH CONVEX BLADES.
DE1992609484 DE69209484T3 (en) 1992-01-30 1992-01-30 Fan with convex blades
EP19920830038 EP0553598B2 (en) 1992-01-30 1992-01-30 A fan with convex blades

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19920830038 EP0553598B2 (en) 1992-01-30 1992-01-30 A fan with convex blades

Publications (3)

Publication Number Publication Date
EP0553598A1 EP0553598A1 (en) 1993-08-04
EP0553598B1 EP0553598B1 (en) 1996-03-27
EP0553598B2 true EP0553598B2 (en) 1998-11-25

Family

ID=8212062

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920830038 Expired - Lifetime EP0553598B2 (en) 1992-01-30 1992-01-30 A fan with convex blades

Country Status (3)

Country Link
EP (1) EP0553598B2 (en)
DE (1) DE69209484T3 (en)
ES (1) ES2087501T5 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100441881C (en) * 2004-07-06 2008-12-10 斯佩尔汽车有限公司 Axial fan

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2723408A1 (en) * 1994-08-03 1996-02-09 Licentia Gmbh Axial airflow fan for water cooling system of IC engine vehicle
CN1061417C (en) * 1997-08-19 2001-01-31 吴凤清 Method for generating natural wind and electric fan of natural wind
EP0945625B1 (en) * 1998-03-23 2004-03-03 SPAL S.r.l. Axial flow fan
EP0945627B1 (en) * 1998-03-23 2004-01-02 SPAL S.r.l. Axial flow fan
FR2781843B1 (en) 1998-07-28 2000-10-20 Valeo Thermique Moteur Sa OPTIMIZED COMPACT FAN PROPELLER
US7937775B2 (en) 2005-08-09 2011-05-10 Microtek Medical, Inc. Surgical protective head gear assembly including high volume air delivery system

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1218244A (en) * 1958-03-05 1960-05-09 Chip evacuation fan for machine tools
FR1315717A (en) * 1960-12-19 1963-01-25 Lyonnaise Ventilation Advanced axial fan
US4358245A (en) * 1980-09-18 1982-11-09 Bolt Beranek And Newman Inc. Low noise fan
DE3220574A1 (en) * 1982-06-01 1983-12-01 Siemens AG, 1000 Berlin und 8000 München STEEL-FREE AXIAL FAN, ESPECIALLY FOR ELECTRICALLY DRIVED MOTOR VEHICLE RADIATOR FANS
US4569632A (en) * 1983-11-08 1986-02-11 Airflow Research And Manufacturing Corp. Back-skewed fan
DE3724319A1 (en) * 1987-07-22 1989-02-09 Klifa Gmbh & Co Fan wheel for a cooling blower
IT214345Z2 (en) * 1988-04-01 1990-05-03 Magneti Marelli Spa AXIAL FAN PARTICULARLY FOR VEHICLES

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100441881C (en) * 2004-07-06 2008-12-10 斯佩尔汽车有限公司 Axial fan

Also Published As

Publication number Publication date
EP0553598A1 (en) 1993-08-04
DE69209484T3 (en) 1999-04-01
ES2087501T5 (en) 1999-04-16
DE69209484D1 (en) 1996-05-02
EP0553598B1 (en) 1996-03-27
ES2087501T3 (en) 1996-07-16
DE69209484T2 (en) 1996-09-05

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