US2561840A - Centrifugal fan - Google Patents

Description

J. C. BUSQUET CENTRIFUGAL FAN Juy 24g9 195i Filed June 5, 19@` Patented July 24, 17951 2,561,840 F F I CE 2,561,840 CENTRIFUGAL FAN Jan C. Busquet, Hengelo, Netherlands, assigner to Machinefabriek Gebr. Stork & Co. N. V.,

Hengelo, erlands Netherlands, a company of the Neth- Application June 5, 1946, serial No. 674,560 In the Netherlands April 9, 1940 section 1, PublieLaw 690, August s, 1946 Patent expires April 9, 1960 1 claim.

This invention relates to a centrifugal fan in which the fluid to be propelled enters the irnpeller centrally at one or both sides thereof and i the inlet branch or branches of the fan casing being provided with a set of guide blades which are adjustable in such a manner that the passage area between said blades may be varied.

As in centrifugal fans of this kind the adjustable guide blades in a more closed position impart a greater swirl to the incoming air than in a more open position the blades should have a different shape for each position of adjustment. The entrance part of the blades must always be radially directed whereas their outlet portion at full load should be radially and at zero load should be tangentially directed, so that in said rst case the blades have to be straight throughout their length and in said second case must be bent across an angle of 90. In practice, therefore, an intermediate form between both said blade-forms is chosen, which is slightly curved and is the exact shape of the blades for one position of adjustment only.

In order to avoid said drawback and to obtain greater efficiency in connection with the deflection of the flow of the fluid in the guide apparatus according to the invention the adjustable guide blades as well as the impeller blades are of aerofoil form.

The invention will be described with reference to the accompanying drawings, Fig. 1 of which shows a longitudinal section of a fan according to the invention and Fig. 2 of which is a cross section taken on line II-II of Fig. 1.

The impeller I is keyed to the shaft 2 which is supported in bearing 3, 4 and is driven by an electric motor 5 directly coupled therewith. The impeller has eight blades 6 of aerofoil section which are welded to the backwall of the impeller and a supporting ring I.

As appears from Fig. 2 the length of the blades 6 is considerably smaller than their mean pitch and the blades are relatively thick.

The casing 8 of the fan is provided with a cylindrical inlet branch 9 to which a wall I0 is secured extending perpendicularly to the impeller shaft 2. Parallel to the wall I a wall II is provided which carries a cone-shaped piece I2 bounding the guide channel formed between the walls I0, I I and merging said channel into the axial portion 9- of the inlet branch of the fan casing. Between the walls I 0, II guide blades I3 are pivotally mounted by means of trunnions I4.

The trunnions I4 projecting out of the wall II each carry an arm I connected to a ring I6 so that upon rotation of said ring the blades I3 are adjusted about an axis extending parallel to the impeller shaft 2 and the passage area between the blades is varied.

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As shown in Fig. 2 the guide blades I3 on both sides are bounded by convex faces. The length I of the blades I3 is nearly equal to their mean pitch measured at the mean radius Tri-T2 2 in which r1 denotes the largest radius and ri is the smallest radius of the rim of blades. The blades I3 are relatively thick and their greatest thickness is at least 10% of their length I. Said form of the blades presents the advantage that the flow of the fluid not under any condition is released from the blade surface so that a very favourable efiiciency is obtained.

The invention may also be applied to a fan in which the fluid enters at both sides and which has a set of adjustable guide blades in each inlet branch. f

What I claim is:

A centrifugal fan comprising a fan casing, a rotatable shaft journalled in said casing, an impeller secured to said shaft in said casing and having a backwall, a supporting ring in said casing, a series of impeller blades secured to said backwall and said supporting ring adjacent the periphery of said impeller, a cylindrical mem ber secured to said casing providing an inlet branch to said impeller centrally thereof, a rst wall secured to said cylindrical member perpendicular to said rotatable shaft, a second wall spaced from said rst wall and forming therewith a guide channel, guide blades adjustably mounted between said walls and attaching said walls together, a coneshaped member secured to said second wall and merging said guide channel into said inlet branch of said casing, said impeller blades and said guide blades being of aerofoil form.

JAN C. BUSQUET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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