Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Patent
1992-02-25
1994-03-01
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
416223R, 416234, 416237, F04D 2938
Patent
active
052901491
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an impeller of an axial-flow type fan, in particular for appliances for drying and dressing hair, with a hub structure, a plurality of blades integrally formed with a circumferential outer surface of the hub structure and arranged on the hub structure in a rotationally symmetrical manner, each blade being offset relative to an adjacent blade by an angle of rotation, in which adjacent blades completely overlap each other in the area of the blade leading edge and the blade trailing edge over the radial extent of the blades, and in which an opening angle formed by a projection of the leading edge and the trailing edge of each blade on a a plane normal to the axis of rotation of the impeller satisfies the condition that the opening angle be smaller than or equal to the angle of rotation.
BACKGROUND OF THE INVENTION
An impeller incorporating these features is already known from FR-PS 1 326 701. This impeller is particularly provided to accomplish an improved pressure stability in dependence on the flow rate. The essential feature of the impeller is that the efflux surfaces of the blades have trailing edges curving inwardly in opposite direction. Impeller blades of such a profile produce a stable air stream on their trailing edges along the entire zone of pressure flow of the blower, in contrast to an unstable flow developing in blowers with a conventional blade profile in the presence of specific pressure relations and specific amounts of flow. Preferably, the trailing edges of the blades are arranged in parallel with the leading edges of the blades, satisfactory results being obtained also if the alignment of the leading edges departs from that of the trailing edges by as much as 15 degrees. The curvature in opposite direction of the trailing edges of the blades relating only to the last fourth of the efflux surfaces, it may nevertheless be advantageous in certain cases that this curvature in opposite direction begins directly after the area between the trailing and leading edge of the blades. The rotors may be integrally manufactured by casting, injection-molding or milling, and may be made of an aluminum alloy, stainless alloyed steel, plastic, or a similar material.
The teaching is essentially aimed at obtaining a blade geometry such that the direction vector of the leading and trailing edge of each blade extends largely in parallel. The design method selected for this purpose consists in projecting various profiles on concentric circles. This results in a type of surface for the description of the blade geometry which cannot be described by rulers. Generating and making a pattern of such a type of surface incurs increased expenditure in all stages of the design and manufacture of such an impeller, starting with the determination of the surface points in the design stage up to the manufacture of the tools or injection molds. Moreover, the design method as it appears from FR-PS 1 326 701 does not ensure that an impeller with a predetermined blade profile is in fact ejectable from the mold, that is, it does not ensure that a slide of the injection mold inserted between two blades is movable radially to the axis of rotation of the impeller without a collision occurring. Overall, FR-PS 1 326 701 does not suggest a design for the manufacture of an impeller in which it is ensured that the impeller is capable of being manufactured by injection molding in addition to being ejectable from the mold, with the individual blade profile being practically exclusively determined by fluidic or physical, rather than manufacturing or tool related, side constraints.
A further impeller is known from U.S. Pat. No. 4,678,410. The impellers described in this prior publication have shown excellent results in practice on account of their high efficiency, their particular engineering design lending itself to large-scale production applying injection-molding processes. It is especially this last-mentioned advantage of the known impeller which is remarkable in so far as the problem of ejecting such impeller
REFERENCES:
patent: 2339602 (1944-01-01), Hagen
patent: 2446552 (1948-08-01), Redding
patent: 4514618 (1985-04-01), Majthan et al.
patent: 4678410 (1987-07-01), Kullen
"Taschenbuch der Mathematik", pp. 214-218 (1969).
"Ventilatoren", p. 338, FIG. 327, New York, 1972.
Braun Aktiengesellschaft
Look Edward K.
Verdier Christopher
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