Fan-motor assembly

Abstract

A fan assembly includes a base which couples to a motor assembly. A shroud couples to the base and encloses a fan therebetween. An airflow conduit is formed between the base and the shroud and is positioned circumferentially around the fan. The airflow conduit terminates at a horn and includes a cross-sectional area which varies circumferentially. The airflow conduit includes a width that varies circumferentially and is largest at the horn.

Description

TECHNICAL FIELD

The present invention is generally directed to motor assemblies. In particular, the present invention is directed to a shrouded tangential fan-motor assembly that increases motor efficiency and air flow characteristics. Specifically, the present invention is related to a shroud mountable to a fan end bracket that forms a circumferentially non-uniform cross-sectional area.

BACKGROUND ART

Vacuum motors employing a tangential bypass are used in many applications such as vacuum manipulators, packaging equipment, bag filling, cutting tables, appliances and exhaust air removal, to name just a few. Such vacuum motor designs generally include a cylindrical housing, or shroud, which encloses a motor-driven fan rotating about an axis. Air is drawn into the housing via an aperture at the top axial center of the housing above the fan. As the fan rotates, the air is accelerated in the circumferential and radially outward direction. The housing provides an outlet located on the side of the fan opposed to the aperture. The outlet is a generally cylindrical opening disposed tangentially on the radially outer edge of the housing so that air traveling circumferentially along the radial outer edge is expelled through the outlet in the tangential direction. Such fans are efficient and have a small profile which enables them to fit in apparatuses which require a thin fan motor assembly.

As with most fan designs, efficiency is an important concern. Current housing designs do not direct airflow in its most efficient path within the housing. Specifically, unwanted turbulence and dead zones are believed to be generated by the uncontrolled path of the airflow from where the air is expelled from the rotating fan to where the air exits the outlet. The fan creates significant kinetic energy in the air by imparting tangential speed. The air must be decelerated in a controlled manner in order to convert the kinetic energy back to pressure. Sudden changes in cross-section may cause eddies and turbulence which dissipates the kinetic energy as heat instead of recovering it as pressure. The total pressure (or vacuum) created by the motor/fan assembly is thus negatively affected by allowing air to exit the fan in an uncontrolled manner. Therefore, there is a need to better manage air flow in order to achieve greater fan efficiency. Further, there is a need to provide air flow management features that are integral to the fan shroud and end bracket. This allows cheaper production, faster assembly and greater reliability.

Therefore, there exists a need in the art for a shroud and end bracket assembly that directs airflow and increases efficiency.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a first aspect of the present invention to provide a fan end bracket and shroud that achieves improved efficiency.

Another aspect of the present invention is to provide a fan assembly comprising a base which couples to a motor assembly, a shroud which couples to the base, at least one fan rotated by the motor assembly and enclosed between the base and the shroud, an airflow conduit formed between the base and the shroud and positioned circumferentially around the fan, the airflow conduit terminating at a horn and including a cross-sectional area which varies circumferentially, and wherein the airflow conduit includes a width that varies circumferentially and is largest at the horn.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein:

FIG. 1 is perspective view of a fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 2 is a top elevated view of the fan/motor assembly;

FIG. 3 is a partial cross-sectional view of the fan/motor assembly;

FIG. 4 is a perspective view of the fan assembly;

FIG. 5 is an alternate perspective view of the fan assembly;

FIG. 6 is a top view of the fan assembly;

FIG. 7 is a bottom view of the fan assembly;

FIG. 8 is a top view of a shroud used with the fan/motor assembly according to the present invention;

FIG. 9 is a top view of an end bracket used with the fan/motor assembly according to the present invention;

FIG. 10 is an exploded view of the fan assembly;

FIG. 11 is an alternate exploded view of the fan assembly;

FIG. 12 is a side view of the fan assembly;

FIG. 13 is a sectional view of the fan assembly along lines 13-13 of FIG. 7;

FIG. 14 is a top view of the motor/fan assembly;

FIG. 14A is a sectional view of the fan assembly along lines 14A-14A of FIG. 14;

FIG. 14B is a sectional view of the fan assembly along lines 14B-14B of FIG. 14;

FIG. 14C is a sectional view of the fan assembly along lines 14C-14C of FIG. 14;

FIG. 14D is a sectional view of the fan assembly along lines 14D-14D of FIG. 14;

FIG. 14E is a sectional view of the fan assembly along lines 14E-14E of FIG. 14;

FIG. 14F is a sectional view of the fan assembly along lines 14F-14F of FIG. 14;

FIG. 14G is a sectional view of the fan assembly along lines 14G-14G of FIG. 14;

FIG. 14H is a sectional view of the fan assembly along lines 14H-14H of FIG. 14;

FIG. 14J is a sectional view of the fan assembly along lines 14J-14J of FIG. 14; and

FIG. 14K is a sectional view of the fan assembly along lines 14K-14K of FIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

A motor/fan assembly is generally indicated by the numeral 10 in the accompanying drawings. As best seen in FIGS. 1-3, the motor/fan assembly 10 includes a motor sub-assembly 12 and a fan sub-assembly 14. It should be appreciated that the motor sub-assembly 12 may be of any suitable conventional construction. In one particular embodiment, the motor-subassembly 12 includes a housing 16. The housing 16 may carry a concentrically positioned bearing 18 which receives a shaft 20 therein. The shaft 20 carries an armature 22 which is rotatably received within a commutator 24. Shaft 20 further carries a cooling fan 26, which is positioned on the end of shaft 20 proximate to fan/sub-assembly 14. Cooling fan 26 provides air flow over the internal motor components promoting heat dissipation. The motor sub-assembly further includes a plurality of field coils (not shown) as well as a plurality of brushes 30. As is known in the art, these motor components interact to cause shaft 20 to selectively rotate. As will be hereinafter described, shaft 20 drives the working components of the fan sub-assembly.

Referring now to FIGS. 4-7 and 10-14, fan sub-assembly 14 includes a base 32 coupled to the end of motor sub-assembly 12. Base 32 may be generally circular and separates the motor sub-assembly 12 from the various fan components by sealing around shaft 20 in such a way that airflow generated by fan sub-assembly 14 is not contaminated by air or other matter from motor sub-assembly 12. Base 32 may be provided with a plurality of ears 34 upon which an associated apparatus may be fastened. Further, one or more mounting projections 35 may extend toward motor sub-assembly 12 to enable coupling thereto.

Base 32 includes a curved outer flange 36 which defines the radially outer surface thereof. Outer flange 36 may be provided with a raised shoulder 38 that projects axially from and circumferentially around the end 40 of outer flange 36. Shoulder 38 is received in the circumferential groove 42 of a shroud 44. In this manner, shroud 44 is received by outer flange 36 forming a generally airtight seal. Shroud 44, in cooperation with base 32, forms an enclosed chamber 46 which receives the working fan components. The shroud may be frictionally retained, staked or otherwise secured by fasteners to the base 32.

Base 32 includes an inner plate 48 that extends radially inward from flange 36 and faces chamber 46. Inner plate 48 includes a shaft aperture 50 therethrough. A support ring 52 is provided at the center of inner plate 48 around shaft aperture 50. Support ring 52 extends axially from inner plate 48, defining a boss 54 that extends into chamber 46. A flange 56 extends inwardly from the axial end of boss 54. A bearing 58 is received inside support ring 52 and is adapted to receive and support shaft 20 which rotates therein. A seal 60 may be captured between bearing 58 and flange 56 to prevent contamination of the air passing through fan sub-assembly 14. Seal 60 may be in any number of forms and could utilize the teachings of U.S. Pat. Nos. 5,482,378 and/or 6,472,786, both of which are incorporated herein by reference.

Shroud 44 is provided with a cylindrical port 62 which is substantially concentric with the shaft 20. Port 62 is provided to allow working air to enter the fan sub-assembly 14. Shroud 44 encloses a fan 64 that includes a plurality of blades 66 that extend radially outwardly. Blades 66 may be straight, angled, curved, or oriented in a sunburst pattern. Blades 66 are retained between a disc 68 at a bottom edge of each blade and a ring 70 at a top edge of each blade, wherein disc 68 has a central bore 72 permitting the fan 64 to be mounted to the shaft 20. Ring 70 has an airflow aperture 74 aligned with and approximately the same size as port 62 and in fluid communication therewith.

Fan 64 is spaced and coupled to shaft 20 by a plurality of elements. A spacer 76 extends through aperture 50 and bears against an inner race of bearing 58. Spacer 76 may be generally cylindrical and is received around shaft 20. A first washer 78 is positioned between spacer 76 and disc 68. A second washer 80 is positioned on the opposed side of disc 68 and is secured thereto by a nut 82. Nut 82 may be provided at the end of shaft 20 and may be tightened against second washer 80 which in turn clamps together the inner race of bearing 58, spacer 76, first washer 78 and fan 64 so that all turn as one unit with the shaft 20 as it is driven by motor sub-assembly 12.

Shroud 44 includes a cap 86 that extends radially outward from port 62. Cap 86 is frustoconical and shaped to generally follow the upper profile of ring 70 resulting in minimal clearance therebetween. This prevents unwanted turbulence, leaking and/or bleeding of air moved by the fan 64. To further improve efficiency and prevent leaks, a chamfer 86 is provided at the radial inner edge of cap 86 that partially receives the upturned edge of ring 70.

A conduit wall 88 extends radially outwardly from cap 86 and terminates at a downwardly turned lip 90 that includes circumferential groove 42. It should thus be evident that conduit wall 88 of shroud 44 includes an outer profile that mirrors that of the outer profile of flange 36 of base 32. The area between conduit wall 88 and base 32 defines a conduit 92 through which working air travels during rotation of fan 64. As will become evident, the area of conduit 92 grows larger as a function of circumferential distance about base 32 from a minimum area (shown in FIG. 14A) to a maximum area (shown in FIG. 14J). Conduit 92 begins at the minimum area location and terminates at a horn 94, as shown sequentially in FIGS. 14A-14K. Horn 94 includes a lower half 96 formed by base 32 and an upper half 98 formed by shroud 44. Horn 94 is substantially circular in cross section and extends tangentially from base 32 and shroud 44. The cross-sectional area of conduit 92 increases because both the width and height increases as a function of circumferential location. Thus, the radial distance of flange 36 from shaft 20 is not constant about the circumference and instead is curvilinear. In other words, flange 36 varies from a minimum radial distance (shown in FIG. 14A), to a maximum radial distance (shown in FIG. 14 J). Further, conduit wall 88 includes a radiused or upwardly curved cross-sectional shape. From minimum point (shown in FIG. 14A) conduit 92 grows wider, as measured by the distance between cap 84 and flange 36. Further, the channel grows taller, as defined by the distance between inner plate 48 and the furthest point on conduit portion 88.

When shaft 20 rotates, air is drawn in by the fan 64 into chamber 46 via port 62. As fan 64 rotates, air is further drawn through airflow aperture 74 and is urged radially outwardly by blades 66. The air flow which is ejected radially from blades 66 has both a radial and tangential component. In other words, air particles travel radially outwardly while at the same time spin with the fan 64. Thus, when the air exits the fan 64, if the fan is traveling in a counter-clockwise direction (as envisioned in the present embodiment), the air correspondingly travels circumferentially in a counter-clockwise direction around conduit 92. Because of the pressure differential between the outside atmosphere and chamber 46, the air exits conduit 92 via horn 94. Thus, as described above, air is drawn into port 62 and out of horn 94 upon rotation of shaft 20. Such systems are particularly useful in common household vacuums, but may also find applications in many other fields.

By varying the cross-sectional area of conduit 92 in the manner discussed above, the kinetic energy stored in the moving air can be converted more completely into static pressure, rather than turbulence induced heat, due to the reduction of eddies as the air leaves the rotating fan.

Based upon the foregoing, the advantages of the constructions described above are readily apparent. In particular, the conduit 92 is configured to provide a more efficient path for air to travel within fan sub-assembly 14. In this manner fan efficiency is increased, thus requiring less energy to provide the same air flow. As a further result, motor life is extended. Thus, the invention disclosed represents a great improvement in the art of fan assemblies.

Thus, it can be seen that the objects of the invention have been satisfied by the structure presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.

Claims

1. A fan assembly, comprising:

a base which couples to a motor assembly;

a shroud which couples to said base;

at least one fan enclosed between said base and said shroud;

an airflow conduit formed between said base and said shroud and positioned circumferentially around said fan, said airflow conduit terminating at a horn and including a cross-sectional area which varies circumferentially; and

wherein said airflow conduit includes a width that varies circumferentially and is largest at said horn.

2. The fan assembly according to claim 1, wherein said airflow conduit includes a height that varies circumferentially and is largest at said horn.

3. The fan assembly according to claim 1, wherein said shroud includes a conduit wall and said base includes an inner wall, said airflow conduit being formed between said conduit wall and said inner wall, and wherein said conduit wall is curved in cross-section.

4. The fan assembly according to claim 3, wherein said conduit wall includes a constant cross-sectional radius.

5. The fan assembly according to claim 1, wherein said base includes an outer flange forming at least part of said conduit, said outer flange being curvilinear.

6. The fan assembly according to claim 1, wherein said base includes an outer flange forming at least part of said conduit, said outer flange including a radial distance from said fan that varies circumferentially and is largest at said horn.

7. The fan assembly according to claim 6, wherein said base includes a conduit wall that mates with said outer flange, said conduit wall including a generally curved cross-sectional shape.

8. The fan assembly according to claim 7, wherein said outer flange includes a raised shoulder and said conduit wall includes a circumferential groove, said raised shoulder is received in said circumferential groove.

9. The fan assembly according to claim 3 wherein said inner wall is substantially flat in cross-section.

10. The fan assembly according to claim 3 wherein said shroud includes a port adapted to receive working air, said shroud further including a cap extending radially outward from said port terminating at said conduit wall, said cap being frustoconical.

11. The fan assembly according to claim 10 wherein said cap includes a chamfer about a radial inner edge, said fan including a ring that is at least partially received in said chamfer.