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(11) | EP 0 086 785 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
PROPELLER PARTICULARY FOR PNEUMATIC BLOWER USE SCHRAUBE INSBESONDERE FÜR LÜFTER PROPULSEUR NOTAMMENT POUR SOUFFLANTES |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention concerns a propeller particularly for pneumatic blower use as defined in the preamble of the main claim.
[0002] The noisiness of blowers causes a problem in blowers difficult to solve. Endeavours have been made to eliminate the noise of propellers in blowers by means of mufflers, e.g. by trumpet-like sound insulating chambers and sound traps continuing in the flow direction behind the blower. Moreover, mufflers of prior art are not satisfactory. Trumpet-like (flared) or tubular sound insulating chambers require great space and in addition their manufacturing and mounting costs are high. Mufflers cannot be installed at nearly all necessary points. The mufflers reduce the output of the blower.
[0003] In addition, blowers known in the art are not satisfactory as to their output. Raising the output and input power of the blower and the pitch angle of the propeller and/or increasing the propeller diameter causes in most instances the noise level of the propeller to become intolerable.
[0004] From US-A-3,075,743 a propeller for a turbo-machine is known wherein each blade consists of e.g. two vanes forming a slot between them. The flow output (m3/h), the pressure difference (mm H20) and especially the noise level (dB) obtained with said known propeller are not satisfactory.
[0005] The object of the present invention is to eliminate the drawbacks mentioned. The object of the invention is to provide a propeller especially for blower use which is substantially more quiet than any propeller known in the art, that is, of which the sound level is substantially lower than that of propellers known in the art. It is a further object of the invention to provide a propeller particularly for blower use, which is more efficient referred to its size and noise level than those of prior art.
[0006] Regarding the characteristic features of the invention, reference is made to the claims part.
[0007] Compared with the propeller of US-A-3,075,743 the propeller of the present invention gives better output and pressure difference results at remarkably (30%) lower noise level (same diameter, same number of revolutions, same number of blades).
[0008] The invention is described in the following in detail with the aid of embodiment examples and referring to the drawing attached, wherein:-
Fig. 1 presents a blower according to the invention, reproduced in perspective and sectioned in part, and
Fig. 2 shows the section along line II-II of the vane of the propeller according to Fig. 1.
[0009] In Fig. 1 is depicted a blower provided with a propeller according to the invention. The propeller comprises a hub 1, centrally and rotatably carried in a trumpet-like frame 13, with vanes 2, 2'. The vanes 2, 2' project radially from the hub and have an oblique pitch a against the plane placed at right angles to the axis of the hub (visible in Fig. 2). The propeller has been disposed to rotate with the aid of an electrical motor 14 located on the extension of the hub 1 in the frame 13 centrally and carried by supports 15. With the propeller rotating in a fluid - in air in the present case - the side 3 of the vane which first meets the fluid is the leading edge 3 and the opposite side is the trailing edge 4. The side of the vane 2 which when rotating meets the fluid is the pressure side 5 and the opposite side is the vacuum side 6.
[0010] In front of each vane 2 of the propeller shown in Figs. 1 and 2, in the direction of rotation of the vane partly in front of its leading edge 3, has been disposed a front louver element 7, substantially parallelling the vane and vane-shaped. The front louver in part dips into the vacuum side 6 of the vane and it forms a slot 8 with the vane 2.
[0011] The front louver element 7 is thinner and more narrow in the cross section then the vane 2. The front louver element 7 guides the fluid which the vane meets partly behind the vane to the vacuum side thereof and strongly reduces the turbulent flow in the region of the leading edge 3 of the vane. The decrease of turbulent flow reduces the fluid resistance as the vane rotates in the fluid, simultaneously reducing the intensity (that is the power) of the noise generated.
[0012] In the embodiment presented, the front louver elements 7 are fastened to the hub of the propeller similarly as the vanes of the propeller. The front louver elements have substantially the same shape as the vanes 2 of the propeller, with a pitch angle smaller than the pitch angle of the propeller vane, positive or negative, e.g. in the range from 0 to 25°C. If desired, the front louver element 7 may be fastened exclusively to the vane 2, e.g. by pin attachment, and/or to a vane circle which may be provided, encircling the vane tips, together with the vanes and the sound suppressor fins to be mentioned below.
[0013] According to the invention, as shown in Figs. 1 and 2, partly behind the trailing edge 4 of each vane 2 has been disposed a sound suppressorfin 9, which extends radially from the hub and substantially parallel to the vane and forms a slot 10 with the vane. The sound suppressor fin is vane-shaped, substantially smaller in thickness and width than the vane. The sound suppressor fin is affixed to the hub 1 of the propeller in the manner of the vane 2. If desired, it is possible to use the pin attachment mentioned, as sole mounting of the sound suppressor fin, and/or the vane circle mentioned above.
[0014] In the present embodiment there has been disposed another sound suppressor fin 11 partly behind the trailing edge of the sound suppressor fin 9 of each vane 2, this fin 11 extending radially from the hub equally, substantially parallel to the vane and to the preceding sound suppressor fin, and each such fin forming a slot 12 with the preceding sound suppressor fin. The latter sound suppressor fin 11 is substantially smaller than the vanes in its dimensions (width and thickness) and in the embodiment depicted also smaller than the first sound suppressor fin. The latter sound suppressor fin 11 may be affixed by pin attachment to the preceding sound suppressor fin 9 or to the vane 2 or, like the vane, to the hub 1. Possibly, a vane circle may be used as sole or additional mounting, as mentioned above with reference to the vane, the front louver element and the preceding sound suppressor fin.
[0015] The placement with reference to each other of the propeller vane 2, front louver element 7 and sound suppressor fins 9, 11 according to Fig. 1 is best revealed in Fig. 2, according to which the front louver element, vane and sound suppressor fins constitute a vane configuration which is substantially concave as viewed from the pressure side 5. Furthermore, the front louver element 7, the vane 2 and the sound suppressor fins 9, 11 are each concave as viewed from the pressure side 5. The front louver element 7 is located mainly on the vacuum side 6 of the vane, the first sound suppressor fin on the pressure side 5 of the vane, and the second sound suppressor fin 11 on the pressure side of the vane 2 and of the preceding sound suppressor fin 9. The front louver element 7, the vane 2 and the sound suppressor fins 9, 11 have greater thickness in their part adjacent to the leading edge and taper down towards the trailing edge.
Example 1
[0016] In order to determine the properties of the propeller of the invention, a propeller as shown in Fig. 1 was tested side by side with propeller of equal size but of conventional design. The number of vanes on each tested propeller was 8, the propeller diameter about 30 cm, the area of the propeller vane was substantially the same. During the test both propellers were run at 1400 r.p.m. In the test, the quantity of air transported by the propeller was measured, as well as the over-pressure generated on the propeller's positive pressure side at a constant distance from the propeller; the noise level of the propeller was furthermore aurally assessed.
Example 2
[0018] In order to measure the efficiency of the propeller of the invention and the level of the noise generated by the propeller, a measurement was carried out. An axial blower as shown in Figs. 1 and 2 was used in the measurements. The propeller's speed of rotation was 1462 r.p.m., the temperature of the blown air was -8°C. The efficiency was calculated from the power drawn by the electromotor of type Str6mberg HXUR 208 C2 B3, 2.2 kW 1420 r.p.m. The principle of the test set-up was that of BSS 848: Part 1: 1982, connected to a duct, blowing free.
Example 3
[0019] In order to compare the noise levels of a propeller, intended for an axial blower, according to the invention and of that of a Woods axial blower with identical diameter, a measurement was carried out in which the sonic power level was determined in a duct-test set-up as in Example 2, propeller diameters 50 cm, speed 1480 r.p.m.
[0020] The power level of the propeller of the invention has been entered on line dB1 in the table and that of the referenced propeller, on line dB2.
[0021] It is possible, in a pneumatic blower, to use to advantage a second sound suppressor fin with 90° pitch angle known e.g. from centrifugal blowers, in which case the tubular frame of the blower may be outwardly flared at said second sound suppressor fin, in order to boost the blower's output. The sound suppressor fins may, if desired, be placed equally on the vacuum side of the vane; similarly, the front louver element may be placed mainly on the pressure side of the vane. Furthermore, the number of propeller vanes and accordingly of louver elements and sound suppressor fins may vary to be proper for instance for a propeller with 2, 3, 4, 5, 6, 7, 8 or more vanes. Furthermore, the vanes and preferably the front louver elements, and possibly the sound suppressor fins, belonging to a propeller according to the invention may be constructed each to be turnable about its axis, these axes being radial with reference to the hub of the propeller. Thus, the vanes and preferably the front louver elements and the sound suppressor fins, may all be turnable jointly and/or separately and placeable in desired position, towards controlling the pitch angles of the vanes, front louver elements and/or sound suppressor fins jointly and/or, if desired, separately.
1. A propeller particularly for pneumatic blower use, comprising a hub (1) and at
least two vanes (2) radially projecting from the hub and having an oblique pitch angle
(a), the side of the vane which, when the propeller is rotating, first meets the fluid
being the leading edge (3) and the opposite side being the trailing edge (4) and the
side of the vane which meets the fluid being the pressure side (5) and the opposite
side being the vacuum side (6), wherein, in the direction of rotation, partly in front
of the leading edge of each vane there is disposed a radially extending front louver
element (7) substantially parallelling the vane and being vane-shaped, dipping partly
into one side of the vane, and forming a slot (8) with the vane characterized in that,
partly behind the trailing edge (4) of each vane (2) there is disposed radially extending
suppressorfin (9) substantially parallelling the vane and being vane-shaped and forming
a slot (10) with the vane both the front louver element (7) and the sound suppressor
fin (9) being substantially smaller in thickness and width than the vane.
2. Propeller according to claim 1, characterized in that, partly behind the suppressor
fin (9) of each vane (1) there is disposed another, possibly several sound suppressor
fins (11), the latter extending radially and substantially parallelling the vane and
each forming a slot (12) with the preceding sound suppressor fin.
3. Propeller according to claim 1 and 2, characterized in that the sound suppressor
fins (9, 11) are disposed at least in part on the pressure side (5) of the vane (2).
4. Propeller according to any one of claims 1 to 3, characterized in that the front
louver element (7), the vane (2) and the sound suppressor fin (9) and next sound suppressor
fin (11), if any, form a vane configuration which is concave as viewed from the pressure
side (5).
5. Propeller according to any one of claims 1 to 4, characterized in that the vane
(2) is concave as viewed from the pressure side (5).
6. Propeller according to any one of claims 1 to 5, characterized in that the front
louver element is concave as viewed from the pressure side (5).
7. Propeller according to any one of claims 1 to 6, characterized in that the sound
suppressor fins (9, 11) belonging to the propeller are concave as viewed from the
pressure side.
1. Flügelrad insbesondere zur Verwendung in einem pneumatischen Lüfter mit einer Nabe
(1) und mindestens zwei Flügeln (2), die radial von der Nabe wegstehen und einen geneigten
Steigungswinkel (a) haben, wobei die Seite des Flügels, die bei sich drehendem Lüfter
zuerst auf das Fluid trifft, die führende Kante (3) und die entgegengesetzte Seite
die nachlaufende Kante (4) ist und die Seite des Flügels, die auf das Fluid trifft,
die Druckseite (5) und die entgegengesetzte Seite die Unterdruckseite (6) ist, wobei
in Umdrehungsrichtung teilweise vor der führenden Kante jedes Flügels ein sich radial
erstreckendes vorderes Jalousieglied (7) angeordnet ist, welches im wesentlichen eine
Parallele bildet zum Flügel und von Flügelgestalt ist, teilwise in eine Seinte des
Flügels eintaucht und einen Schlitz (8) mit dem Flügel bildet, dadurch gekennzeichnet,
daß teilweise hinter der nachlaufenden Kante (4) jedes Flügels (2) eine sich radial
erstreckende Schallunterdrückungsrippe (9) angeordnet ist, die im wesentlichen eine
Parallele zu dem Flügel bildet und von Flügelgestalt ist und einen Schlitz (10) mit
dem Flügel bildet, wobei sowohl das vordere Jalousieglied (7) als auch die Schallunterdrükkungsrippe
(9) eine im wesentlichen kleinere Dicke und Breite haben als der Flügel.
2. Flügelrad nach Anspruch 1, dadurch gekennzeichnet, daß teilweise hinter der Schallunterdrükungsrippe
(9) jedes Flügels (1) eine weitere, möglicherweise mehrere Schallunterdrückungsrippen
(11) angeordnet sind, wobei sich die letzteren radial erstrecken und im wesentlichen
eine Parallele zu dem Flügel bilden und jeweils einen Schlitz (12) mit der vorhergehenden
Schallunterdrückungsrippe bilden.
3. Flügelrad nach Anspruch 1 und 2, dadurch gekennzeichnet, daß die Schallunterdrückungsrippen
(9, 11) mindestens teilweise an der Druckseite (5) des Flügels (2) angeordnet sind.
4. Flügelrad nach Anspruch 1 bis 3, dadurch gekennzeichnet, daß das vordere Jalousieglied
(7), der Flügel (2) und die Schallunterdrückungsrippe (9) sowie die nächste Schallunterdrückungsrippe
(11), falls vorhanden, eine Flügelgestalt bilden, die von der Druckseite (5) gesehen
konkav ist.
5. Flügelrad nach einem der Anspruch 1 bis 4, dadurch gekennzeichnet, daß der Flügel
(2) von der Druckseite (5) gesehen konkav ist.
6. Flügelrad nach Anspruch 1 bis 5, dadurch gekennzeichnet, daß das vordere Jalousieglied
von der Druckseite (5) gesehen konkav ist.
7. Flügelrad nach Anspruch 1 bis 6, dadurch gekennzeichnet, daß die zum Flügelrad
gehörenden Schallunterdrückungsrippen (9, 11) von der Druckseite gesehen konkav sind.
1. Hélice, notamment destinée à être utilisée dans un ventilateur, comportant un moyeu
(1) et au moins deux pales (2) faisant saillie radialement sur le moyeu et possédant
un angle d'attaque oblique (a), le côté de la pale qui, lorsque l'hélice tourne, rencontre
en premier le fluide étant le bord d'attaque (3) et le côté opposé étant le bord de
fuite (4), et le côté de la pale, qui rencontre le fluide étant le côté sous pression
(5) et le côté opposé étant le côté en dépression (6), et dans laquelle disposé partiellement
en avant du bord d'attaque de chaque pale, dans le sens de rotation, se trouve un
élément frontal formant volet abat-son (7) en forme de pale, disposé radialement tout
en étant sensiblement parallèle à la pale et s'engageant partiellement d'un côté de
la pale en délimitant une fente (8) avec cette dernière, caractérisée en ce que, disposée
partiellement en arrière du bord de fuite (4) de chaque pale (2), se trouve une ailette
d'atténuation acoustique (9), s'étendant radialement, sensiblement parallèlement à
la pale, et réalisée en forme de pale tout en délimitant une fente (10) avec la pale,
l'élément frontal formant volet abat-son (7) et l'ailette d'atténuation acoustique
(9) possédant tous deux une épaisseur et une largeur nettement inférieures à celles
de la pale.
2. Hélice selon la revendication 1, caractérisé en ce qu'en partie disposée derrière
l'ailette d'atténuation acoustique (9) de chaque pale (1), se trouve une autre et
éventuallement plusieurs autres ailettes d'atténuation acoustique (11), qui s'étendent
radialement et sensiblement parallèlement à la pale, en délimitant chacune une fente
(12) avec l'ailette précédente d'atténuation acoustique.
3. Hélice selon les revendications 1 et 2, caractérisée en ce que les ailettes d'atténuation
acoustique (9, 11) sont disposées au moins en partie sur le côté sous pression (4)
de la pale (2).
4. Hélice selon l'une quelconque des revendications 1 à 3, caractérisée en ce que
l'élément frontal formant volet abat-son (7), la pale (2), l'ailette d'atténuation
acoustique (9) et l'ailette d'atténuation acoustique suivante (11), dans le cas où
elle est présente, forment un ensemble en forme de pale qui est concave lorsqu'on
le regarde depuis le côté sous pression (5).
5. Hélice selon l'une quelconque des revendications 1 à 4, caractérisée en ce que
la pale (2) est concave lorsqu'on la regarde depuis le côté sous pression (5).
6. Hélice selon l'une quelconque des revendications 1 et 5, caractérisée en ce que
l'élément frontal forment volet abat-son, est concave lorsqu'on regarde depuis le
côté sous pression (5).
7. Hélice selon l'une quelconque des revendications 1 à 6, caractérisée en ce que
les ailettes d'atténuation acoustique (9, 11) appartenant à l'hélice, sont concaves
lorsqu'on les regarde depuis le côté sous pression.