IMPELLER BLADE FOR CENTRIFUGAL FAN AND MANUFACTURING METHOD THEREOF

Abstract

A fan blade made of a solid extruded aluminum alloy having certain cross-section shapes. Also provided is a method of producing fan blade, which includes heating a portion of a stock aluminum alloy material and pushing it through an extrusion die having an aperture while drawing the extruded portion of the material. The aperture can be designed or configured so that the extruded material has a cross section suitable to be used as an impeller blade.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application No. 62/800,488, filed Feb. 2, 2019, the disclosure of which is incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to the technical field of a centrifugal fan, and in particular, to structure and manufacture of an impeller blade for a centrifugal fan.

BACKGROUND

Centrifugal fan assemblies include a plurality of impeller blades positioned in a scroll-shaped housing or volute. The housing can include an inlet through which air is drawn by the fan blades, and an outlet through which pressurized air is discharged. The plurality of blades pressurize and accelerate an incoming axial airflow, and discharge the air into a scroll portion of the housing in a substantial radial direction. The blades may be attached to a hub fixed on a rotating shaft of an electric motor, or mounted on an outer periphery of a wheel that rotates about such a hub.

Currently in the commercial or industrial centrifugal fans, impeller blades are usually made of metal materials, such as a ferrous metal (e.g., alloy structural steel sheet such as Q235), aluminum alloy sheet, and stainless steel. The choice of materials can depend on the requirements of specific applications and the environment where the fan is used.

The traditional fan manufacture creates a large amount of pollution and poses challenges for waste disposal. With the increased pressure by the government and public for more efficient manufacture of a variety of industrial products, there is higher demand for environment-friendly design and manufacture of commercial and industrial fans. For example, the industry calls for more sophisticated and lightweight design of impellers. The industry must upgrade the design standards and manufacturing levels.

As shown in FIG. 1 and FIG. 2, the centrifugal fan blade of the prior art is typically manufactured by punching, which results in sharp edges of the impeller blade. Such sharp edges cause the impeller blades to vibrate and generate noise as well as create eddy currents, reducing their service life and lowering the energy use efficiency.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an impeller blade for a centrifugal fan with reduced wind resistance, eddy currents, and vibration during use of the blades, thereby reducing the possibility of noise generation and prolonging the service life of the impeller blades.

A further object of the present invention is to provide a method for manufacturing an impeller blade for a centrifugal fan by hot drawing a stocking material through a die with particular shapes and cold working hardening of the outer surface of a blade, which produces a blade with high surface hardness and excellent overall strength and rigidity with improved wear resistance.

In one aspect, a fan blade made of an extruded aluminum alloy is provided. The fan blade has a width direction and a uniform and solid cross section perpendicular to the width direction. The cross-section has two major opposing sides, a first lateral end, and a second lateral end. The two opposing sides are both smooth curves generally, and together defining a thickness therebetween. In some embodiments, the two major opposing sides curving to opposing directions. In some embodiments, the two major opposing sides curving to a same direction, and wherein the thickness gradually increases from the first lateral end to the second lateral end. In some embodiments, the first end has a radius of about 1 mm. In certain of these embodiments, the second end has an elliptical shape. In some embodiments, the second end has a maximum thickness of between about 3 mm to about 8 mm.

In another aspect, the present disclosure provides a centrifugal fan assembly comprising at least one mounting disc having a center and a radius; and a plurality of fan blades each defined herein which are mounted on the at least one mounting disc. In some embodiments, the plurality of fan blades are arranged radially symmetrically with respect to the center of at least one mounting disc. In some embodiments, all of the plurality of fan blades are arranged with the first end positioned proximal to the center of the at least one mounting disc and the second end positioned distal to the center of the at least one mounting disc, and wherein the two major opposing sides of all of the plurality of fan blades are curving to a same rotational direction. In some embodiments, the centrifugal fan further includes an electrical motor operatively coupled with the at least one mounting disc, the electrical motor configured to rotate in a direction such that each of the plurality of fan blades are forward-curved.

In another aspect, a method for producing an extruded material is provided. The method comprises: positioning a stock of a metal alloy material such that a first end of the metal alloy material is proximate an extrusion die, the extrusion die having an aperture on an end face; heating at least a portion of the stock of the metal alloy material proximate the die to soften the portion of the metal alloy material; pushing the softened portion of the stock of the metal alloy material through aperture along a forward direction such that a portion of the metal alloy material is extruded out of the aperture; and drawing the portion of the metal alloy material that has been extruded out of the aperture along the forward direction, thereby producing an extruded metal alloy material having a cross section having substantially the shape of the aperture of the extrusion die.

In some embodiments, the metal alloy material comprises aluminum alloy. In some embodiments, the method further comprises cutting the extruded material into a plurality of pieces or segments along a direction perpendicular to the forward direction of the extrusion.

In some embodiments, the aperture has a cross-section shape comprising two major opposing sides defining a thickness therebetween, the two major opposing sides both curving in the same direction, wherein one of the sides has a length greater than the other of the sides. In some embodiments. In some of these embodiments, the thickness can gradually increase from the first lateral end to the second lateral end.

In some embodiments, wherein the aperture has a shape comprising two major opposing sides curving in opposite directions.

The present disclosure also provides an extruded metal alloy material or aluminum alloy material made by the method described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings are intended to illustrate certain features of certain embodiments of the present invention and are not necessarily drawn to scale.

FIG. 1 is a depiction of a cross section of a fan blade of prior art.

FIG. 2 is another depiction of a cross section of a fan blade of prior art.

FIG. 3 is an example cross section profile of a fan blade according to some embodiments of the present invention.

FIG. 4 is another example cross section profile of a fan blade according to some embodiments of the present invention.

FIG. 5A is another example cross section profile of a fan blade according to some embodiments of the present invention.

FIG. 5B is a fan blade having a cross section shown in FIG. 5A according to some embodiments of the present invention.

FIG. 6A is front view of an extrusion die having an aperture for producing an extruded material for fabricating a fan blade according to some embodiments the present invention.

FIG. 6B is a schematic view of an extrusion process for producing an extruded material for fabricating a fan blade according to some embodiments the present invention.

FIG. 7A is a schematic depiction of a mounting disc.

FIG. 7B is a schematic depiction of a portion of a centrifugal fan assembly including a plurality of fan blades installed on a mounting disc.

FIG. 7C is a photograph of a partially assembled centrifugal fan assembly where a plurality of fan blades have been installed on a mounting disc.

DETAILED DESCRIPTION

It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments.

As seen in FIGS. 1-2, in the prior art, the impeller blades 1P are typically cut by cutting/punching, and the edges of the blade body 1P can be sharp structures, which tend to produce eddy currents and disturbance to the air flow, producing vibration and instability for the blades.

As shown in FIGS. 3, 4, 5A and 5B, some example impeller blades of the present invention for a centrifugal fan can include: blade body 1, where edges of the blade body 1 are all rounded transitions. In contrast to prior art impeller blades (as shown in FIGS. 1-2), the impeller blades of the present invention include rounded or smooth transitions at the edge of the blade body. This can be accomplished through a drawing/stretching process which will be further described below. Such smooth transitions reduce wind resistance of the impeller blades, improves circumferential exhausting ability, reduces vibration during the use of the blade, thereby reducing noise generation and prolonging the service life of the impeller blade.

In one embodiment, as shown in FIG. 3, the cross section of blade body 1 can have a substantially bilaterally symmetrical shape (thus the body 1 has a symmetrical arcuate curved surface), with greater thickness in the middle, tapering on both lateral ends. This type of blade can be used in low-power and low air pressure applications which do not require high strength. For example, the maximum thickness of the cross section of the blade body 1 D_M can be about 2 to 10 mm, e.g., 5 mm, and the lateral length (or chord length) L_C of the blade body 1 can be from about 100 to about 300 mm, or from about 100 to about 200 mm, e.g., about 180 mm. The chord height of the cross section of the blade body 1 C_H can be about 10-20 mm; and the radius of the lateral edge of the blade body 1 can be between 0.5 and 3 mm, e.g., about 1 mm or about 2 mm. The cross section has two major opposing sides, i.e., a top side curve 31, and a bottom side curve 32, both curving toward the same direction (in other words, they are both convex or both concave). As shown in FIG. 3, the contour length of the top curve is greater than that of the bottom curve 32. The curves can be arc part of a circle, or can be of more complex curves (e.g., those that can be approximated by higher power polynomials).

In another embodiment, as shown in FIG. 4, the blade body 1 has a symmetrical curved surface and the two major opposing sides, top side curve 33 and bottom side curve 34, that curve in opposing directions. The center of the blade body 1 can have a greater thickness than both the lateral ends. For example, in some embodiments, the blade body 1 can have a maximum thickness D_M of about 5 mm in the middle of the cross section, a cross section length L_C of from about 100 to 300 mm, or from about 100 to about 200 mm, e.g., about 180 mm. The lateral side edge radius R1 can be between 0.5 and 3 mm, e.g., about 1 mm, or about 2 mm. The top side curve 33 can have a contour length greater than, equal to, or smaller than that of the bottom side curve 34.

In still another embodiment, as shown in FIG. 5A, the blade body 1 can have an asymmetrical arcuate curved surface. This design can meet the requirements of higher precision and higher air flow speed, further avoiding eddy currents, ensuring that the blade body 1 does not vibrate, thereby avoiding noise, and prolonging the service life of the centrifugal fan. In order to reduce eddy currents, the cross section of the blade body 1 can take a shape that is gradually enlarged from a first lateral (or front) end to a second lateral (or rear) end. In the embodiment shown in FIG. 5A, the blade body 1 includes a rotating windward surface 11 and a rotating leeward surface 12, wherein the windward surface 11 is a side of the blade body 1 that rotates against the wind. The rotating windward surface 11 can have a uniform arc shape, and the rotating leeward surface 12 can have a plurality of arcs smoothly joined. The plurality of circular arc transitions prevent the wind flow through the rotating leeward surface 12 from flowing toward the rotating windward surface 11, thereby preventing the formation of eddy currents.

In some embodiments, in order to reduce the design difficulty and the high process precision requirements, the rotating leeward surface 12 includes two smooth transitional arc surfaces, namely a front end leeward surface 121 and a rear end leeward surface 122. The radius of the arc surface of the front leeward surface 121 can be similar or about the same as the radius of the rotating windward surface 11 so that the air entering the axial direction of the centrifugal fan can enter adjacent centrifugal blade space more smoothly. In such a manner, a high working efficiency of the centrifugal fan can be attained.

As the front end leeward surface 121 extends toward the rear end leeward surface 122, it also further deviates away from the rotating windward surface 11. The rear end is larger in cross section, ensuring the strength of the blade to satisfy the operating needs. Also, since the centrifugal fan structure is usually designed as a circular structure, the rear end of the centrifugal blade is often installed in the circumferential direction of the circular structure (that is, the end that is distal from the central rotating axis). This difference in dimensions between the front end and rear end of the blade also helps reduce the space between adjacent centrifugal blades toward the circumference. Excessive space between adjacent blades can result in the formation of eddy currents, which in turn lead to noise and vibration defects.

In order to avoid excessive increase in the size of the curved blade, and to ensure that the wind flow can flow on a relatively gentle arc surface, the radius of the rear leeward surface 122 is larger than the radius of the front leeward surface 121, and the rear leeward surface 122 is extended away from the end of the front leeward surface 121. Preferably, the blade body 1 further includes a front end portion 101 and a rear end portion 102. In order to make the wind flow more uniform and smoother, the upper and lower sides of the front end portion 101 smoothly transition from the rotating windward surface 11 and the front end leeward surface 121, respectively. The cross section of the rear end surface 102 can have an elliptical shape, and the upper and lower sides of the rear end surface 102 smoothly transition with the rotating windward surface 11 and the rear end leeward surface 122, respectively. The maximum thickness of the rear end surface 102 D_R (which can be considered the “height” or length along the minor axis of an ellipse approximating the rear end cross section shape) can be about from 3 mm to about 8 mm, for example, about 5 mm. The front end portion 101 can have a radius from 0.5 mm to 3 mm, e.g., about 1 mm, or about 2 mm. The cross section length L_C can be about 100 to about 300 mm. In some embodiments, the cross section length L_C of the fan blade as shown in FIG. 5A can be about 8¾ inches (or 222.2 mm), D_R can be about ⅛ inch (or 3.2 mm), and the radius of the front end portion 101 can be about 1/32 inch (or about 0.8 mm).

FIG. 5B illustrates the relationship between the cross section Sc of a blade and its width direction which is perpendicular to the cross section Sc. Along the width direction, the shape of the cross section Sc remains the same (or uniform).

In another aspect of the invention, a process for producing an extruded material, e.g., a metal alloy, is provided. The extruded material can take a sheet-like shape, with cross section shape similar to those depicted in FIGS. 3, 4, and 5A/5B. The process can be a continuous process and the extruded material can be cut into pieces to make plurality of impeller blades of desired sizes.

An example extrusion die 60 useful for the process is illustrated in FIG. 6A. In this illustration, the aperture 65 on the front end face 60A takes the shape similar to the cross section shape of a blade depicted in FIG. 5A. The description of the geometry of the cross-section profile of the blade can be equally applicable to the aperture 65. In other embodiments, the aperture 65 can take the cross section shape of the blades as illustrated in FIGS. 3 and 4 (the description of geometry thereof are likewise applicable to that of the aperture in such instances).

As further illustrated in FIG. 6B, the extrusion process can include positioning a stock (e.g., a rod) of a metal alloy material 62 such that a first end of the metal alloy material is proximate the extrusion die 60. At least a portion of the stock of the metal alloy material proximate the die can be heated to soften the portion of the metal alloy material. In an example, an aluminum alloy rod stock material with a composition containing about 0.5% Si by weight (wt), about 0.8 wt % Mg, about 0.7 wt % Fe, about 0.2 wt % Cu, about 0.15 wt % Mn, and 0.25 wt % Zn (the remainder being Aluminum) is heated to between about 550° C. and 590° C. for softening before passing the die. The softened portion of the stock of the metal alloy material is pushed through aperture 65 in the extrusion die 60 in a forward direction, e.g., by an upper roller 67 and a lower roller 68, or other pushing mechanism of the extrusion machinery, such that a portion of the metal alloy material is extruded out of the aperture 65. The portion of the metal alloy material that has been extruded out of the aperture and exposed is drawn along the forward direction (e.g., by using a damper movable along the forward direction) without heating, e.g., at room temperature, thereby producing an extruded metal alloy material having a cross section having substantially the shape of the aperture of the extrusion die. The drawing helps produce extruded metal alloy material with smooth/rounded edges, as well as facilitate crystallization of the metal material, especially on the surface of the extruded material, which improves the surface hardness and wear resistance of the extruded material. The pushing and drawing may be performed simultaneously, and the speed of pushing of the stock material and drawing of the extruded material can be coordinated/adjusted to produce a drawn sheet of desired dimension, geometry and properties. The extruded metal material can be cut along a direction perpendicular to the forward direction, thus producing a plurality of pieces each suitable to be used as an impeller blade as described herein.

A plurality of fan blades 1 described herein can be integrated into a centrifugal fan assembly. The blades can be installed on at least one mounting disc 710 (or two or more mounting discs, as needed) having a rotational center 715, as shown in FIG. 7A. FIG. 7B shows a side view of the plurality of blades 720 (similar to what has been shown in FIG. 5A) installed near the outer circumference of the mounting disc 710. The centrifugal fan assembly can further include an electric motor operatively coupled with the mounting disc (or mounting discs), the electrical motor configured to rotate in a direction such that each of the plurality of fan blades are deemed forward-curved, as shown in FIG. 7B. FIG. 7C is a photograph of a partly assembled fan assembly where a plurality of fan blades have been installed on a mounting disc.

It is to be noted that the terminology used herein is for the purpose of describing particular embodiments, and is not intended to limit the exemplary embodiments. As used herein, the singular forms are also intended to include the plural, unless the context clearly indicates otherwise, and it is also understood that when the terms “include” and/or “include” are used in the specification.

The term “about” as used with reference to a certain given value or quantity herein means a range of up to 25% deviation from (greater or smaller than) the given value.

While illustrative embodiments of the invention have been disclosed herein, numerous modifications and other embodiments may be devised by those skilled in the art in accordance with the invention. For example, the various features depicted and described in the embodiments herein can be altered or combined to obtain desired scaffold characteristics in accordance with the invention. Therefore, it will be understood that the appended claims are intended to include such modifications and embodiments, which are within the spirit and scope of the present invention.

Claims

1. A fan blade made of an extruded aluminum alloy, the fan blade having a width direction and a uniform and solid cross section perpendicular to the width direction, the cross-section having two major opposing sides, a first lateral end, and a second lateral end, the two opposing sides being both smooth curves generally, the two opposing sides defining a thickness therebetween.

2. The fan blade of claim 1, wherein the two major opposing sides curving to opposing directions.

3. The fan blade of claim 1, wherein the two major opposing sides curving to a same direction, and wherein the thickness gradually increases from the first lateral end to the second lateral end.

4. The fan blade of claim 3, wherein the first end has a radius of about 1 mm.

5. The fan blade of claim 3, wherein the second end has an elliptical shape.

6. The fan blade of claim 5, wherein the second end has a thickness of between about 3 mm to about 8 mm.

7. A centrifugal fan assembly comprising:

at least one mounting disc having a center and a radius; and

a plurality of fan blades each defined according to claim 3 mounted on the at least one mounting disc.

8. The centrifugal fan assembly of claim 7, wherein the plurality of fan blades are arranged radially symmetrically with respect to the center of the at least one mounting disc.

9. The centrifugal fan assembly of claim 8, wherein each of the plurality of fan blades are arranged with the first end positioned proximal to the center of the at least one mounting disc and the second end positioned distal to the center of the at least one mounting disc, and wherein the two major opposing sides of all of the plurality of fan blades are curving to the same rotational direction.

10. The centrifugal fan assembly of claim 9, further comprising an electrical motor operatively coupled with the at least one mounting disc, the electrical motor configured to rotate in a direction such that each of the plurality of fan blades are forward-curved.

11. A method for producing an extruded material, comprising:

positioning a stock of a metal alloy material such that a first end of the metal alloy material is proximate an extrusion die, the extrusion die having an aperture on an end face;

heating at least a portion of the stock of the metal alloy material proximate the die to soften the portion of the metal alloy material;

pushing the soften portion of the stock of the metal alloy material through aperture along a forward direction such that a portion of the metal alloy material is extruded out of the aperture; and

drawing the portion of the metal alloy material that has been extruded out of the aperture along the forward direction, thereby producing an extruded metal alloy material having a cross section having substantially the shape of the aperture of the extrusion die.

12. The method of claim 11, wherein the metal alloy material comprises aluminum alloy.

13. The method of claim 11, further comprising cutting the extruded material into a plurality of pieces along a direction perpendicular to the forward direction of the extrusion.

14. The method of claim 11, wherein the aperture has a cross-section shape comprising two major opposing sides defining a thickness therebetween, the two major opposing sides both curving in the same direction, wherein one of the sides has a length greater than the other of the sides.

15. The method of claim 14, wherein the thickness gradually increases from the first lateral end to the second lateral end.

16. The method of claim 11, wherein the aperture has a shape comprising two major opposing sides curving in opposite directions.

17. An extruded metal alloy material or aluminum alloy material made by the method of claim 11.