Compact and Self-Cooling Blower Assembly

This invention relates to blower assemblies, and more particularly relates to compact air blower assemblies, particularly for use as components to supply air to heating system burners.

Fuel burning heating systems in general use today frequently consist of a burner that is supplied with air for combustion from a motor-powered fan or blower assembly. Typically, the air suppliers for heating system burners may be radial airflow devices driven by conventional electric motors taking power from commercial electrical supply lines. In the United States, commercial electrical power is supplied typically at 110 and 220 volts at 60 cycles, and in many foreign countries electrical power is supplied typically at 220 volts at 50 cycles, and such electric power supplies operate the electric motors driving the air suppliers at speeds on the order of 2500 to 3500 rpm. At such low speeds, the size of the motor driven blower is large in order to supply the amount of air required for combustion of the fuel.

One type of blower which is commonly used is called a Sirocco blower in which air is drawn into the center of a cylindrical, cage-like air-moving wheel by its rotation and is forced radially outwardly from the center by curved vanes that extend along the axis of rotation at the cylindrical periphery of the air-moving wheel. A scroll-like casing surrounds the cylindrical periphery of the air-moving wheel to collect the air outflow and direct it tangentially through a peripheral outlet for delivery to the fuel burning chambers of a furnace. Operating at speeds of 2500 to 3500 rpm Sirocco blowers are large in size in order to deliver a sufficient air for fuel combustion in most heating systems. In addition, due to their poor aerodynamic shape, the efficiency of such blowers can be as low as 10 to 15 percent.

The invention provides an air blower assembly that is compact and operates efficiently at high speeds, and that can be inexpensively manufactured from a common set of blower parts to provide varied airflow capacities, and satisfy a variety of applications.

In the invention, a compact multi-use air blower assembly is provided by a high speed brushless electric motor comprising a stator and a rotor and rotatable shaft carried by a pair of shaft bearings, with the rotatable shaft including a shaft extension extending outwardly from one of the shaft bearings. A housing includes a first portion carrying the electric motor and shaft bearings and a second portion forming a blower enclosure about the shaft extension with a centrally located air inlet and a peripherally located air outlet. The blower enclosure encompasses a centrifugal blower wheel including a solid wall extending radially outwardly from a shaft-engaging hub and forming a plurality of air-moving blades projecting axially outward from the wall to edge portions that extend radially within the blower enclosure between the air inlet and the air outlet. The high speed brushless electric motor can rotate such a centrifugal blower wheel at high speeds, for example, 10,000 to 12,000 rpm to provide airflow more efficiently from a substantially more compact housing, occupying for example, from about 12 to about 50 percent of the volume of Sirocco type blowers of the same capacity.

The invention permits the manufacture of blower assemblies having a multiplicity of capacities and applications from a common set of parts by providing, in such blower assemblies, a centrifugal blower wheel in which the plurality of air-moving blades project a sufficient axial distance from the wall to their radially extending end portions that they permit reduction of their axial widths and a selectable location of the centrifugal blower wheel and its radially extending wall within the blower enclosure to provide a variety of air output capacities from operation of a single motor.

In addition, in preferred blower assemblies of the invention, the second portion of the housing can form a blower enclosure extending rearwardly from the centrifugal blower wheel and around the first housing portion carrying the electric motor to thereby provide a flow of cooling air for the electrical motor housing, permitting more power to be extracted from the electric motor for any given size by the resulting dissipation of the electric motor heat loss and/or a reduction of the temperature of the electric motor components.

Other features and advantages of the invention will be apparent from the drawings and the more detailed description of the invention that follows.

FIG. 1 is a cross-sectional view of a blower assembly of the invention taken at a plane through the axis of rotation;

FIG. 2 is a side view of the blower assembly of FIG. 1 as seen from the right of FIG. 1; and

FIG. 3 is a view of the blower assembly of FIGS. 1 and 2 with the part of the blower enclosure removed to illustrate the centrifugal blower wheel of the preferred embodiment.

FIGS. 1-3 illustrate a preferred embodiment 10 of the invention. As shown in FIG. 1, a preferred blower assembly of the invention includes a high speed brushless electric motor 11 carried by a first housing portion 12 driving a centrifugal blower wheel 13 within a second housing portion 14. In the invention, rotation of the blower wheel 13 at high speeds, such as 12,000 rpm, efficiently draws air into the blower assembly air inlet 15 as indicated by arrow 15a, and expels the air from air outlet 16, as indicated by arrow 16a. As explained further below, the invention permits blower assemblies to be matched to varied uses and applications with varied air delivery requirements with identical cast parts by merely machining a single blower wheel casting. For example, FIG. 1 indicates a centrifugal blower wheel 13a (shown in dashed lines), machinable from the same casting as blower wheel 13 (shown in solid lines), but in the blower assembly 10 providing a substantially reduced airflow from outlet 16 when driven by motor 11.

We may on occasion refer to an "axial direction" and use the word "axially" in this description and in doing so, we mean in a direction substantially parallel to the axis of rotation 17 of the blower assembly. In addition, for convenience in this description of the invention, we will refer to the side of the blower assembly 10 in which the air inlet 15 is located as being "forwardly", and in the "front" portion of the assembly and as representing a "forward" direction, and we will refer to the direction of the portion of the blower assembly 10 including the electric motor 11 and the first housing portion 12 as being "rearwardly", and in the "rear" portion and as representing a "rearward" direction. The application of this forward and rearward nomenclature to the blower assembly 10 is merely so that features may be conveniently described, and those skilled in the art will recognize this nomenclature has no other functional meaning and could easily be reversed in describing the invention.

As illustrated more specifically in FIG. 1, the first portion 12 of the housing carries the electric motor 11 within a circumferential wall portion 20 that extends axially along the axis of rotation 17 of the motor 11 and blower wheel 13, and includes an internal surface 20a for engaging and supporting the stator 21 of the electric motor 11. The stator 21 may be conveniently retained within the first housing portion 12 by a setscrew 22 which is positioned to engage the magnetic laminations of the stator 21. The first housing portion 12 further includes a radially inwardly extending forward wall portion 23 having a first circumferential surface 23a for engaging and supporting one bearing 24 of a pair of shaft bearings. The rearward portion of the first housing portion 12 includes a second circumferential locating surface 25 for engaging and supporting a separate end portion 26 which itself includes a circumferential locating surface 26a for engaging and supporting the other bearing 27 of the pair of bearings. The separate end bell 26 can be retained in the first housing portion 12 by, for example, a snap ring 28.

The bearings 24 and 27 are thus located and supported by the first housing portion 12 for carrying the rotatable shaft 30 and the rotor 31 of the electric motor within the electric motor stator 21 so that application of electric power to the stator 21 and a resulting rotating field created by the stator 21 acting on rotor 31 will drive the centrifugal blower wheel 13 in rotation at high speeds. As indicated in FIG. 1, bearings 24 and 27 are preferably ball bearings and axial loading for the ball bearings can be supplied by a spring 29.

As shown in FIG. 1, the rotatable shaft 30 includes a shaft extension 30a extending beyond the one bearing 24 of the pair of bearings where it is surrounded by the forwardmost portion of the second housing portion 14. As further illustrated in FIG. 1 the second housing portion 14 forms a blower enclosure and an air chamber 32 encompassing the centrifugal blower wheel 13. The walls of the second housing portion 14 forming the blower enclosure direct the air drawn through air inlet 15 by the rotating centrifugal blower wheel 13 (as indicated by arrow 15a) through the air chamber 32 and outwardly through air outlet 16 (as indicated by arrow 16a).

In the preferred embodiment of FIGS. 1-3, the second housing portion 14 includes a first blower enclosure wall 33 extending radially outwardly from the first housing portion 12 at a location adjacent the rearward end of the stator 21 carried by the first housing portion 12. The first blower enclosure wall 33 extends forwardly from this location in a portion 33a surrounding the centrifugal blower wheel 13. Thus, the second housing portion 14 forms the blower enclosure with an air chamber 32 surrounding the motor-carrying portion of the first housing portion 12 so that air circulating within the air chamber 32 will cool the first housing portion 12 that engages and carries the stator 21 of the electric motor 11, dissipating the heat losses of the electric motor 11 and reducing the temperature of the motor parts, permitting more power to be extracted from an electric motor of a given size and efficiency, and the size of the first housing portion 12 to be correspondingly reduced, and permitting motors of any given size and efficiency to be operated at lower temperatures. As indicated in FIG. 1, the axially extending circumferential part 20 of the first housing portion 12 between the air chamber 32 and the electric motor 11 can have a reduced thickness to facilitate heat transfer from the electric motor 11 to the air being urged through air chamber 32 by the rotating centrifugal blower wheel 13.

The front part of the second housing portion 14 is preferably a second separate element 34 which may be fastened to the wall portion 33a of the second housing portion 14 by a plurality of threaded fasteners 35 as shown in FIGS. 1 and 2. The front part 34 of the second housing portion 14 provides an inner air chamber wall 34a cooperating with the centrifugal blower wheel 13 and, in the preferred embodiment, a forwardly extending portion 34b forms the air inlet 15. In the preferred embodiment shown, the air outlet 16 is preferably formed by the periphery of wall portion 33a and the second separate element 34, and the wall portions 33 and 34 of the second housing portion 14 can be formed with a flange 36 including a plurality of openings 37 permitting the blower assembly to be mounted directly to a furnace casing where air can be delivered to its burner cavity to mix with atomized fuel for combustion. The outlet flange 36 is further illustrated in FIGS. 2 and 3. Because of their compact size and lightweight, blower assemblies of the invention may be conveniently mounted to a furnace assembly, or to any other apparatus needing a supply of air, by 2 or 3 threaded fasteners applied through holes 37 of the outlet flange 36.

As shown in FIGS. 1 and 3, the centrifugal blower wheel 13 includes a solid back wall 40 and a plurality of air-moving blades 41 projecting axially forwardly from the wall 40 and terminating in radially extending edge portions 41a that, in the preferred embodiment, can lie closely adjacent the inside surface 34a of the blower enclosure forming the air chamber 32. Wall 40 extends radially outwardly from a shaft-engaging hub portion 42 which is carried by the shaft extension 30a. The shaft-engaging hub 42 and centrifugal blower wheel 13 are clamped for rotation with the rotating shaft 30 by a nut 43 fitted on the end of the shaft extension 30a.

As indicated above, the invention permits blower assemblies to be provided with varied air capacities with a single set of parts. This is accomplished in the invention by providing a centrifugal blower wheel 13, which can be conveniently die cast from aluminum, with air-moving blades 41 that project axially forwardly from the wall 40 a distance greater than the distance between the forwardmost face of the front wall 23 of the first housing portion 12 and the rear facing surface 34a of the forward part 34 of the second housing portion 14. In addition, the cast blower wheel can have a shaft-engaging hub portion 42 extending rearwardly of the wall 40 a distance substantially equal to or greater than the axially extending width of the air-moving blades 41, as indicated generally by the dashed lines of FIG. 1. As further indicated in FIG. 1, the shaft-engaging hub 42 can extend forwardly of the wall 40 for a distance substantially equal to or greater than the axial width of the air-moving blades 41, as indicated generally by the solid lines of FIG. 1. Thus, by casting a part for the manufacture of the centrifugal blower wheel 13, which includes a plurality of air-moving blades 41 projecting from the wall 40 a distance substantially equal to or greater than that needed for their end portions 41a to be closely adjacent the forward inside wall portion 34a of air chamber 32 and which includes a shaft-engaging portion 42 extending forwardly and rearwardly of the wall 40 a distance substantially equal to or greater than the interval between the forwardmost surface of the first wall portion 23 and the rear facing surface 34a of the blower enclosure, the centrifugal blower wheel 13 may be selectively located within the blower enclosure formed by the second housing part 14 to provide blower assemblies having different air supply capacities. For example, by machining materials from the forward edge portions 41a of the air-moving blades 40 and the forward portion of the shaft-engaging hub 42 of such a blower wheel casting, a centrifugal blower wheel 13a (as shown by the dash lines of FIG. 1), can, for example, be provided and selectively located for reduced air requirements, and by way of further example, by removing material from the rearward portion of the shaft-engaging hub 42 and only enough material to finish the leading edges 41a of the air-moving blades 41 of such a blower wheel casting, a blower wheel 13 (as indicated in the solid lines in FIG. 1) can, for example, be provided and selectively located for higher air requirements. Thus, the invention can eliminate the need for different centrifugal blower wheel and enclosure castings for different air requirements, and the need for spacers, and permit a blower assemblies for multiple uses and applications and with varied air capacities to be inexpensively manufactured and with a minimum of parts and inventory. Of course, spacers can be used in the invention to clamp blower wheels to the rotating shaft if it is undesirable to provide an extended shaft-engaging hub portion on the blower wheel for machining as described above.

As indicated above, the blower assemblies of the invention are particularly adaptable for use on furnaces and other heating systems permitting a furnace manufacturer to inventory a common set of blower parts for installation on furnaces of various sizes and heating air requirements. For example, a blower assembly with the blower wheel as indicated in the dash lines 13a of FIG. 1 will be used with furnaces having a small air requirement whereas the blower assembly with the blower wheel as shown in solid lines in FIG. 1 will be used with furnaces requiring larger air requirements.

A blower assembly of the invention is compact and lightweight and can have a maximum outside dimensions of, for example, about 6 inches by 6 inches in its maximum dimensions and 3 inches thick. In preferred embodiments, the housing parts and centrifugal blower wheel may be die cast with aluminum to provide such an economical and lightweight construction.

While the invention has been described in a preferred embodiment, those skilled in the art will recognize that other embodiments may fall within the invention as defined by the scope of the claims that follow.