US20070274827A1 - Multi-stage taper fan-motor assembly - Google Patents

Abstract

A motor-driven fan assembly includes a bracket which couples to a motor assembly and includes an outlet port. A shroud assembly defines a first chamber and a second chamber and includes an inlet port, the shroud assembly is received on the bracket. A bearing-supported shaft is driven by the motor assembly, and extends through the bracket and into the shroud assembly. A first fan is coupled to the shaft and positioned in the first chamber. A second fan is coupled to the shaft and positioned in the second chamber. The first and second fan include a plurality of curved blades positioned between a flat disc and a cap, the cap defining a non-linear cross section. Rotation of the fans by the shaft results in air flow through the fan assembly. Dust is generally prevented from settling on the fan blades during operation, thereby preventing non-uniform dust buildup or breakup which may cause excessive vibration and reduce bearing and brush life.

Description

TECHNICAL FIELD
• The present invention is generally directed to motor assemblies. In particular, the present invention is directed to the fan portion of a motor assembly which increases motor efficiency and air flow characteristics. Specifically, the present invention is related to a multi-stage fan assembly with working air fans having nonlinear tapers which promotes efficiency and resists contaminant buildup.
BACKGROUND ART
• Vacuum motors employing multi-stage tapered fans 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 vacuums designs generally include a cylindrical housing, or shroud, which encloses a pair of motor-driven working air fans rotating about an axis.
• As shown prior artFIG. 1, such designs draw air into a housing via an aperture A at the top axial center of the housing above a first stage fan B. The first stage fan includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap. Thus channels are defined between adjoining blades and, as the fan rotates, the air is accelerated through the channels in the circumferential and radially outward direction. The air is then directed into a second stage which includes a second stage fan C. The second stage fan is generally identical to the first stage fan and includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap. Air is again accelerated through the channels defined by adjoining blades in the circumferential and radially outward direction. The housing provides an outlet located proximal the fan opposed to the aperture. As is evident fromFIG. 1, such fans may employ a linear taper wherein the cross-sectional height of the fan becomes linearly smaller as a function of radial distance from the axis of rotation. This in turn results in a linear constriction in the channel volumes as a function of radial distance from the axis of rotation. This feature was provided to improve airflow properties and improve efficiency. While the linear taper of such fans have been found to improve airflow certain drawbacks persist. Specifically, assemblies of this nature tend to collect contaminates such as dust and debris in the rotating working air fans. This is particularly a concern when air drawn into the fan assembly carries a dust and water mixture such as would be seen in a wet/dry vacuum. It has been found that dust and other contaminates collect in the working air fans which, over time, leads to bearing damage and eventual fan and/or motor assembly failure. Thus, while such fans are efficient and have a small profile, the aforementioned drawbacks persist.
• Therefore, there exists a need in the art for a fan assembly which minimizes dust and contaminate collection on the working air fans and therefore extends the life of the fan assembly.
SUMMARY OF THE INVENTION
• In view of the foregoing, it is a first aspect of the present invention to provide a fan insert which achieves improved efficiency.
• Still another aspect of the present invention is to provide a motor-driven fan assembly, comprising a motor assembly, a bracket coupled to the motor assembly, the bracket including an outlet port, a shroud assembly which defines a first chamber and a second chamber and includes an inlet port, the shroud assembly adapted to be received on the bracket, a shaft rotated by the motor assembly, the shaft extending through the bracket and into the shroud assembly, a first fan coupled to the shaft and positioned in the first chamber, and a second fan coupled to the shaft and positioned in the second chamber, wherein the first and the second fan each include a plurality of curved blades positioned between a flat disc and a cap, each cap defining a non-linear cross section.
• Yet another aspect of the present invention is attained by a fan assembly associated with a motor assembly having a rotatable shaft, the fan assembly comprising a shroud assembly which includes a first shell and a second shell having a spacing bracket disposed therebetween, the first shell including a tapered wall and the second shell having a tapered wall, the tapered wall of the first shell being curved and substantially identical to a tapered wall of the second shell, the shroud assembly adapted to receive the rotatable shaft, a first fan adapted to be coupled to the shaft and positioned adjacent to the tapered wall of the first shell, and a second fan adapted to be coupled to the shaft and positioned adjacent to the tapered wall of the second shell, wherein the first and the second fan include a plurality of curved blades disposed between a flat disc and a cap, each cap being curved to match the curvature of the adjacent tapered wall.
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 a sectional view of a prior art fan/motor assembly;
• FIG. 2 is a sectional view of a fan/motor assembly made in accordance with the concepts of the present invention;
• FIG. 3 is an exploded sectional view of the fan/motor assembly made in accordance with the concepts of the present invention;
• FIG. 4 is a top plan view of an exemplary rotating fan; and
• FIG. 5 is a top plan view of a stationary fan.
BEST MODE FOR CARRYING OUT THE INVENTION
• Referring now to the drawings and more particularly toFIGS. 2 and 3, it can be seen that a motor/fan assembly made in accordance with the invention is designated generally by thenumeral10. The motor/fan assembly10 of the present invention includes amotor sub-assembly11 and afan sub-assembly12. It should be appreciated that this disclosure is generally directed towards the fan sub-assembly, and thus themotor sub-assembly11 may be of any suitable conventional construction. In one embodiment, themotor sub-assembly11 includes ahousing13. Themotor housing13 may carry a concentrically positioned bearing14 which receives ashaft15 therein. Theshaft15 supports anarmature16 and acommutator17 thereon, as well as a number of fans as will be hereinafter discussed. The motor sub-assembly further includes a plurality offield coils19 in a manner known in the art. As is known in the art, these motor components interact to causeshaft15 to selectively rotate. As will be hereinafter described,shaft15 drives the working components of the fan sub-assembly.
• Anend bracket30 is provided on the end ofmotor sub-assembly11 opposite themotor housing13.End bracket30 may be generally circular and is provided to enable fan components to be coupled to themotor sub-assembly11.End bracket30 includes anouter flange32 which defines the radially outer surface thereof.Outer flange32 may be provided with a raisedshoulder34 which projects radially from and circumferentially aroundouter flange32. At least oneoutlet36 is provided inend bracket30. While the outlet of the present embodiment is axially facing, it should be appreciated that other outlet designs may be employed. For example, a plurality of radially facing ports or a single tangential horn may be employed which achieve substantially the same results for exhausting air from the fan sub-assembly.
• Theshaft15, which is operatively coupled to the above mentioned motor elements, extends through and is supported byend bracket30. Accordingly,end bracket30 includes asupport ring38 which is formed with a generallycylindrical body40 and aflange42, which projects radially inward fromcylindrical body40.Flange42 defines an axially orientedopening44 which is sized to allowshaft15 to extend therethrough. Thecylindrical body40 is adapted to receive abearing46 therein.Bearing46 thus receives and supportsshaft15 which rotates therein. Aseal48 may be positioned betweenflange42 and bearing46 to prevent contaminates from reaching thebearing46. In such a manner,end plate30 supportsshaft15.
• Fan sub-assembly12, which is supported by theend bracket30, includes ashroud assembly52 which encloses a plurality of fans as will be hereinafter discussed. It should be appreciated that, while embodiments shown inFIGS. 2-5 employ two working air fans, more than two might be employed, and stacked in the manner disclosed below. Shroudassembly52 includes afirst shell54 which is positioned at the axial end offan sub-assembly12, opposite theend bracket30.First shell54 includes anouter wall56 which is substantially cylindrical and centered about the axis defined byshaft15.Outer wall56 terminates at aradiused edge58 which transitions to a flat axially facingwall60.Facing wall60 is annular and extends radially inwardly fromradiused edge58.Facing wall60 terminates at it's radially inner edge at an axially projectingstep62.Axial step62 is generally cylindrical and connects to atapered wall64 which extends radially inward and axially outwards, away frommotor sub-assembly11. As is evident fromFIG. 2, the angle of taperedwall64 varies with radial location. In other words, the cross-section of taperedwall64 is non-linear. In one or more embodiments tapered wall may be described geometrically as having a constant radius R. In one or more embodiments the radius R of taperedwall64 may be about four inches. It should, however, be appreciated that the taperedwall64 may include non-linear profiles which do not include a constant radius. For example, the taper may be described as a concave curvature. In any event, taperedwall64 terminates on its radially inner edge at aring66.Ring66 is axially facing and defines aninlet port68.Inlet port68 provides the opening through which working air entersfan sub-assembly12.
• Shroud assembly52 further includes aspacing bracket70. Spacingbracket70 includes anouter wall72 which is substantially cylindrical and centered about the axis defined byshaft15. As shown inFIG. 2,outer wall56 offirst shell54 is received over a portion ofouter wall72 and rests against astep74.Step74 acts as a stop, against which the rim ofouter wall56 rests. In this manner thefirst shell54 is stacked atop thespacing bracket70.Outer wall72 terminates at aradiused edge76 which transitions to an axially facingbase wall78.Base wall78 is generally disc shaped and projects radially inward fromouter wall72. Anopening80 is provided at the concentric center ofbase wall78. As is evident fromFIG. 2, thefirst shell54 andspacing bracket70 define afirst chamber82, access to which is provided atinlet port68 andopening80.
• Shroud assembly52 further includes asecond shell84 which is positioned betweenend bracket30 andspacing bracket70.Second shell84 includes anouter wall86 which is substantially cylindrical and centered about the axis defined byshaft15. The cylindricalouter wall72 ofspacing bracket70 is received over a portion ofouter wall86 and rests against astep88.Step88 acts as a stop, against which the rim ofouter wall72 rests.Outer wall86 terminates at aradiused edge90 which transitions to a flataxially facing wall92. Facingwall92 is annular and projects radially inwardly from radiusededge90. Facingwall92 terminates at it's radially inner edge at anaxially projecting step94.Axial step94 is generally cylindrical and connects to a taperedwall96 which extends radially inward and axially outwards, away frommotor sub-assembly11. As is evident fromFIG. 2, the angle of taperedwall96 varies with radial location. In other words, the cross-section of taperedwall96 is non-linear. In one or more embodiments taperedwall96 may be described geometrically as having a constant radius. In one or more embodiments the radius of taperedwall96 may be about 4 inches. It should, however, be appreciated that taperedwall96 may include non-linear profiles which do not include a constant radius. For example, the taper may be described as a concave curvature. In any event, taperedwall96 terminates on the radially inner edge at aring98.Ring98 is axially facing and defines aninlet port100. Thus it should be evident thatsecond shell84 andend bracket30 define asecond chamber102, access to which is provided atinlet port100 andoutlet36.
• As earlier discussed,shroud assembly52 encloses a plurality of fans.First chamber82 encloses a first workingair fan104, hereinafterfirst fan104.First fan104 includes a base106 in the form of a disc.Base106 is coupled toshaft15 and, to that end, is provided with acentral bore108 which is sized to receiveshaft15 therein. As shown inFIG. 4, a plurality ofblades110 are carried bybase106 and are disposed in a curved sunburst arrangement radiating outwardly towardsouter wall56. Eachblade110 includes aleading edge112 which is spaced fromshaft15, thus defining afan eye114. Eachblade110 terminates proximate to the outer radial edge ofbase106 at a trailingedge116. Whenshaft15 rotates in a clockwise direction, theblades110 ofFIG. 4 further define aleading surface118 and a trailingsurface120, as will be discussed later in more detail. In one or more embodiments, theblades110 may be coupled tobase106 along the bottom edge thereof by a plurality of stakes or rivets (not shown) which are received in corresponding holes alongbase106. Though the bottom edge ofblades110 are flat, atop edge128 is provided with a non-linear taper. In other words, the height ofblades110, as defined as the distance frombase106, varies nonlinearly corresponding to the radial distance fromshaft15. Each adjoiningblade110 defines achannel129 therebetween which provides a path for airflow during fan operation. Finally, acap130 is provided which, along withbase106 retains theblades110 therebetween.Cap130 matches the profile oftop edge128 ofblades110 along thetop edges128 ofblades110.Cap130 includes acentral aperture132 which corresponds with the leadingedges114 ofblades110. And thecap130 has an outerperipheral edge133 that is in close proximity to theaxial step62. Accordingly, there is minimal turbulence generated betweencap130 and an underside of the taperedwall64. In other words, parasitic airflow that would otherwise interfere with working air flow through the fan assembly is minimized. As is evident fromFIG. 2, thecap130 andcorresponding blades110 may substantially match the cross-sectional profile of taperedwall64 offirst shell54. Thus, in one or more embodiments the cross-section ofcap130 may be described geometrically as having a constant radius. In one or more embodiments theradius cap130 may be about 4 inches. In other embodiments,cap130 may include non-linear cross-sectional profiles which do not include a constant radius. For example, the cross-sectional profile may be described as a concave curvature.
• First chamber82 also encloses astationary fan134 which is carried by spacingbracket70. As seen inFIG. 5,stationary fan134 includes a plurality ofblades136 which may oriented in a sunburst arrangement radiating outwardly towardsouter wall56. Adisc138 is positioned along the top surface ofblades136 and includes acentral bore140 which allowsshaft15 to project therethrough.Blades136 extend radially inward from the outer radial edge ofdisc138 and end at thecentral opening80 ofspacing bracket70.
• Thecentral opening80 ofspacing bracket70 communicates with a second workingair fan142, hereinaftersecond fan142, which is inclosed withinsecond chamber102.Second fan142 may be substantially identical to first workingair fan104. Thus, second workingair fan142 includes a base144 in the form of a disc.Base144 is coupled toshaft15 and, to that end, is provided with acentral bore146 which is sized to receiveshaft15 therein. As shown inFIG. 4, a plurality ofblades148 are carried bybase146 and are disposed in a curved sunburst arrangement radiating outwardly towardsouter wall56. Eachblade148 includes aleading edge150 which is spaced fromshaft15, thus defining afan eye152. Eachblade110 terminates proximate to the outer radial edge ofbase144 at a trailingedge154. Whenshaft15 rotates in a clockwise direction, theblades148 further define aleading surface156 and a trailingsurface158 as will be described later in more detail. In one or more embodiments, theblades148 may be coupled tobase144 along the bottom edge thereof by a plurality of stakes or rivets (not shown) which are received in corresponding holes alongbase144. Though the bottom edge ofblades110 are flat, atop edge166 is provided with a non-linear taper. In other words, the height ofblades148, as defined as the distance frombase144, varies nonlinearly corresponding to the radial distance fromshaft15. Each adjoining blade defines achannel167 therebetween which provides a path for airflow during fan operation. Finally, acap168 is provided which, along withbase144 retains theblades148 therebetween.Cap168 matches the profile oftop edge166 ofblades148 along thetop edges166 ofblades148.Cap168 includes acentral aperture170 which corresponds with the leadingedges150 ofblades148. And thecap168 has an outerperipheral edge169 that is in close proximity to theaxial step94. Accordingly, there is minimal turbulence generated betweencap168 and an underside of the taperedwall96. In other words, parasitic airflow that would otherwise interfere with working air flow through the fan assembly is minimized. As is evident fromFIG. 2, thecap168 andcorresponding blades148 may substantially match the cross-sectional profile of taperedwall96 ofsecond shell84. Thus, in one or more embodiments the cross-section ofcap168 may be described geometrically as having a constant radius. In one or more embodiments theradius cap168 may be about 4 inches. In other embodiments,cap168 may include non-linear cross-sectional profiles which do not include a constant radius. For example, the cross-sectional profile may be described as a concave curvature.
• In the present embodiment, theaforementioned fans104 and142 are spaced and coupled to theshaft15 by a plurality of elements. A T-spacer172 extends inwardly through opening44 insupport ring38 and bears against an inner race of bearing46. T-spacer172 may have a generally T-shaped cross section to provide an enlarged transverse surface against which thebase144 ofsecond fan142 may bear. Positioned betweenfans104 and142 is asleeve spacer174 which is received onshaft15. Awasher176 is positioned aroundshaft15 and betweensleeve spacer174 and each working air fan. Anut178 may be provided at the end ofshaft15 which may be tightened against awasher180 which in turn bears againstbase106 of first workingair fan104. This in turn clamps together the inner race of thebearing46, T-spacer172,sleeve spacer174,washers176,fans104 and142 andwasher180 so that all turn as one unit with theshaft15 as it is driven by themotor sub-assembly11.
• In this manner, whenshaft15 rotates clockwise, air is drawn intofirst chamber82 viainlet port68. Air is drawn intoeye114 and is urged radially outward byblades110. Once the air is ejected radially outwardlypast blades110,blades136 of thestationary fan134 direct the air flow radially inward towardopening80. As is evident fromFIG. 2, opening80 directs the air flow intosecond chamber102. Assecond fan142 rotates,blades148 again urge the air radially outward. Because of the pressure differential between the outside atmosphere and thesecond chamber102, the air exitssecond chamber102 viaoutlet port36. Thus, as described above, air is drawn intoinlet port68 and out ofoutlet port36 upon rotation ofshaft15.
• Of particular concern in such fans is the collection of dust and other particles within the working air fans. The present invention solves this problem through the cooperation of two elements. First, the use of a multi-stage fan, i.e. one which employs two working fans and a stationary fan therebetween, produces increased airflow. This feature, in combination with the non-linear profile offan blades110 and148, greatly reduces contaminates from sticking to fan blades. In particular, it has been found that in conventional multi-stage fans, dust and debris sticks to the leadingsurface118 or156 as air travels radially outward from theeye114 or152 of the fan. By reducing the height of thecaps130 or168 non-linearly in the radially outward direction, the cross sectional area ofchannels129 and167 is thus reduced. The reduction in channel area of the present invention is thus reduced more quickly than in a prior art fan. This reduction of area in turn accelerates the particle. Consequently, the particles in the air are accelerated faster than a traditional fan. Because the air is accelerated faster as it travels radially outward, any particles or contaminates in the air are ejected from the fan and not given an opportunity to stick to the leadingsurface118 or156. Thus, when such a non-linear taper is employed with a multi-stage working air fan design, the incidence of fan contamination is greatly reduced. This in turn leads to increased fan and bearing life. Specifically, uneven contaminate buildup, or buildup which suddenly breaks away from the blades, can cause vibration, which degrades bearing life. By preventing contaminates from sticking to the blades, this vibration is limited and bearing life is increased.
• 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 (15)

1. A motor-driven fan assembly, comprising:

a motor assembly;

a bracket coupled to said motor assembly, said bracket including an outlet port;

a shroud assembly which defines at least a first chamber and a second chamber and includes an inlet port, said shroud assembly adapted to be received on said bracket;

a shaft rotated by said motor assembly, said shaft extending through said bracket and into said shroud assembly;

a first fan coupled to said shaft and positioned in said first chamber; and

a second fan coupled to said shaft and positioned in said second chamber, wherein said first and said second fan each include a plurality of curved blades positioned between a flat disc and a cap, each said cap defining a non-linear cross section.

2. The fan assembly according toclaim 1, wherein said blades are disposed on said disc in a curved sunburst arrangement radiating radially outwardly.

3. The fan assembly according toclaim 1, wherein each said blade extends from said disc to said cap.

4. The fan assembly according toclaim 1, wherein said blades are secured to said cap and said disc.

5. The fan assembly according toclaim 1, wherein said shroud assembly further comprises:

at least a first shell and a second shell having a spacing bracket therebetween, said first shell includes a tapered wall having the same cross-sectional profile as said cap of said first fan and said second shell includes a wall having the same cross-sectional profile as said cap of said second fan.

6. The fan assembly according toclaim 5 further comprising a stationary fan, said stationary fan is coupled to said spacing bracket.

7. The fan assembly according toclaim 6, wherein said stationary fan comprises a plurality of curved blades and a disc, said blades are disposed between said disc and said stationary spacing bracket.

8. The fan assembly according toclaim 1, wherein said cap of said first fan includes a first fan aperture and said cap of said second fan includes a second fan aperture and when said shaft rotates air is drawn through said first and second fan apertures and radially outward across said blades.

9. A fan assembly associated with a motor assembly having a rotatable shaft, the fan assembly comprising:

a shroud assembly which includes a first shell and a second shell having a spacing bracket disposed therebetween, said first shell including a tapered wall and said second shell having a tapered wall, said tapered wall of said first shell being curved and substantially identical to a tapered wall of said second shell, said shroud assembly adapted to receive the rotatable shaft;

a first fan adapted to be coupled to the shaft and positioned adjacent to said tapered wall of said first shell; and

a second fan adapted to be coupled to the shaft and positioned adjacent to said tapered wall of said second shell, wherein said first and said second fan include a plurality of curved blades disposed between a flat disc and a cap, each said cap being curved to match the curvature of said adjacent tapered wall.

10. The fan assembly according toclaim 9, wherein each said blade is disposed on said disc in a curved sunburst arrangement radiating radially outwardly.

11. The fan assembly according toclaim 10, wherein each said blade extends from said disc to said cap.

12. The fan assembly according toclaim 10, wherein said blades are secured to said cap and said disc.

13. The fan assembly according toclaim 12, further comprising:

a stationary fan coupled to said spacing bracket.

14. The fan assembly according toclaim 10, wherein said stationary fan comprises a plurality of curved stationary blades and a stationary disc, said stationary blades are disposed between said stationary disc and said stationary spacing bracket.

15. The fan assembly according toclaim 10, wherein said cap of said first fan includes a first aperture and said cap of said second fan includes a second aperture and when said shaft rotates air is drawn through said first and second apertures and radially outward across said blades.

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