Patent Publication Number: US-7223070-B2

Title: Blower motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This non-provisional patent application claims priority under 35 U.S.C. § 119(a) from Patent Application No. 0328384.3 filed in Great Britain on Dec. 6, 2003. 
   FIELD OF THE INVENTION 
   This invention relates to a blower motor for a vacuum cleaner and the like and the improvement is applicable to both flow through and bypass type blower motors. 
   PRIOR ART 
   Blower motors for vacuum cleaners and the like are well known and fall generally into two types, the flow through type where working air is blown over and through the electric motor and the bypass type where the working air does not directly cool the motor, requiring a separate cooling system for the motor. However, the principle of operation is more or less the same. The motor, usually a universal motor but may be a d.c. motor, either with or without brushes, has a stator, a rotor, a motor body or housing and a diffuser plate. A fan cover is fitted to the motor. The motor drives a centrifugal type fan, known as the impeller, at high speed to create a vacuum at the inlet to the fan cover and expels the air through vents either in the fan cover in the case of the bypass blower or in the diffuser plate in the case of the flow through blower. 
   The efficiency of the blower depends on how efficiently the air can be moved from the inlet to the exhaust vents. Early designs used an impeller which was located axially separated from the diffuser plate within the fan cover. This has been improved by adding vanes to the diffuser plate which extend axially into the area along side or radially of the impeller to direct air flow from the impeller to the exhaust vents reducing swirling and turbulence in the void between the impeller and fan cover. 
   This increased the efficiency of the blower over all but complicated the assembly. As the motor operates at high speed, e.g. in some applications, up to 45,000 rpm, it is important that the motor and impeller are balanced to avoid severe vibrations. This is done by balancing the rotor during manufacture of the rotor and then by dynamically balancing the rotor and impeller combination when the impeller is fitted to the motor before the fan cover is installed. Balancing is effected by removing a small amount of material from an outer edge of the impeller at the correct location. However, with the additional vanes on the diffuser plate, the nibbing tool or cutter cannot gain access to the edge of the impeller to balance the rotor/impeller assembly. One solution is to leave a gap in the vanes to allow the tool access to the impeller, but this adversely affects the performance or efficiency of the air flow path. Another way, as shown in JP 2003-49799A and JP 2000-291592A by Toshiba Tec Corp., is to make the vanes a separate item which is installed after balancing and before the fan cover is fitted. This approach gives the best result but these two methods complicate the design and slow down the assembly of the final blower due to added parts which must be carefully fitted to the diffuser plate, otherwise the fan cover will not be properly seated. 
   BRIEF SUMMARY OF THE INVENTION 
   Accordingly, it is desired to have a blower for a vacuum cleaner or the like, in which air guide vanes are provided adjacent the impeller, which do not interfere with dynamic balancing of the rotor/impeller assembly and is easy to assemble (in either a flow through or bypass arrangement.) 
   The present invention achieves this by providing the air guide vanes as part of the fan cover. This is achieved preferably by use of a separate molded part fitted to the fan cover. The fan cover and vanes may or may not be keyed together, but there is no direct keying between the vanes and the diffuser although the fan cover could be keyed to the diffuser or a motor housing part. 
   Accordingly, the present invention provides a blower motor assembly comprising: a motor assembly, including a housing and having a stator and a rotor carried by the housing; and a working air fan assembly coupled to the housing and having an axial inlet and at least one exhaust outlet, the fan assembly having a cup shaped fan cover having a hole forming the inlet, a centrifugal fan fixed to the rotor for rotation therewith, a diffuser plate for guiding the working air to the at least one exhaust outlet and a vane plate for guiding the working air from the fan to the diffuser plate, the vane plate having an annular plate and a plurality of vanes located about the radial periphery of the fan; characterized in that the vane plate is fixed to the fan cover as a press fit against a circumferential wall of the fan cover and is nipped between the diffuser plate and a base of the fan cover to prevent axial movement. 
   Preferably, the base of the fan cover has at least one inwardly extending projection and the vane plate has a respective recess which engages the at least one projection to key the vane plate to the fan cover. 
   Preferably, the fan cover is keyed to a part of the motor assembly to circumferentially align the vanes of the vane plate with passages of the diffuser plate. 
   Preferably, the vane plate has an annular base portion from which the vanes depend axially, the base portion having a plurality of radially extending projections spaced about its peripheral edge which engage and grip the fan cover. 
   Preferably, the fan cover is a drawn metal part and the projections are stamped into the base forming blind holes in the outer surface of the fan cover, said blind holes not penetrating through the fan cover. 
   Preferably, the diffuser plate has a plurality of passageways for directing the working air from the vanes to the at least one exhaust outlet. 
   Preferably, wherein the passageways of the diffuser plate extend from one side of the diffuser plate to the other side and direct the working air from the fan cover and into the motor housing to cool the motor. 
   Preferably, the at least one exhaust outlet comprises a plurality of apertures formed in the cylindrical wall of the cup shaped fan cover and the passageways of the diffuser plate direct the working air towards and out the apertures. 
   Preferably, the apertures are axially spaced from the fan cover and the passageways direct the air axially and radially outward. 
   Alternatively, the vane plate could be integrally formed with the fan cover, preferably as a single monolithic molding. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
       FIG. 1  is an elevational view of a blower motor to which the present invention is applicable; 
       FIG. 2  is an exploded view of the motor of  FIG. 1 ; 
       FIG. 3  is a perspective view of a fan cover of the motor of  FIG. 2 ; 
       FIG. 4  is a plan view of a vane plate of the motor of  FIG. 2 ; 
       FIG. 5  is a view from below of the vane plate of  FIG. 4 ; 
       FIG. 6  is a view similar to  FIG. 2  of a blower motor according to a second embodiment; and 
       FIG. 7  is a perspective view of an alternative fan cover. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  illustrates a flow through blower motor  10  of the universal motor type as used, for example, in vacuum cleaners, garden blowers and other appliances requiring the creation of a vacuum or the movement of air under pressure. 
   The blower  10  has a motor which drives an impeller. In  FIG. 1 , the motor  11  and a fan cover  13  are visible.  FIG. 2  is an exploded view of the blower  10 . From the top of  FIG. 2 , the blower has a fan cover  13 , a vane plate  14 , an impeller  12 , a diffuser plate  15 , a rotor  16 , a stator  17 , brush assemblies  18  and a motor rear housing  19 . 
   The fan cover  13  is a drawn metal part having a cylindrical wall  20  and one closed end  21 . The closed end  21  has a central opening forming the inlet  22  for the blower. The closed end  21  is shown substantially flat with a series of raised rings  23  concentric with and adjacent the inlet  22 . The closed end  21  also has four equally spaced round depressions  25  formed by stamping. These depressions form closed or blind holes in the outer surface of the cover  13  and raised projections  24  on the inner surface of the end wall  21 . Being blind holes, the cover  13  does not lose its air tightness in this region. 
   The projections  24  form keys to align the vane plate  14  with the fan cover. A cutout  26  is formed in the free edge of the cylindrical wall  20  for keying the cover  13  to the body of the motor, e.g., to the motor housing  19  or the diffuser plate  15 . 
   The vane plate  14  is a plastics material molding, preferably of nylon. It has a plate like ring  27  with air guiding vanes  28  depending from the lower surface of the ring  27 . The ring  27  has four holes  29  which may be blind holes, which align with and receive the four projections  24  in the inner surface of the fan cover  13 . These serve to rotationally lock and key the vane plate  14  to the fan cover  13 . The ring  27  also has four radial projections  30  extending from the outer periphery of the ring  27  adjacent the holes  29 . These projections  30  form an interference fit within the fan cover  13  and hold the vane plate  14  to the cover  13 . A fifth projection  31  is also provided which is used during assembly to align the plate  14  with the fan cover  13 . Once the vane plate  14  is pressed into the fan cover  13 , the fan cover  13  and vane plate  14  become one part for final assembly. When assembled, the vanes  28  enclose the outer periphery of the impeller  12 . 
   The impeller  12  is a standard single stage centrifugal fan assembly used in blower motors. The impeller  12  has an inlet which is aligned with the fan cover inlet  22  and depending on the application, the impeller inlet may or may not engage a seal (not shown) fitted to the fan cover  13  about the inlet  22 . 
   The diffuser plate  15  forms an upper end of the motor housing and supports a bearing  32  for the motor shaft  33  as is commonly known. The diffuser  15  has a substantially flat upper surface  34  facing the impeller  12 . In this embodiment, the blower is of the flow through type and the diffuser  15  has an outer edge  35  which intermittently contacts the fan cover  13  at circumferentially spaced locations. In between the contact points are openings  36  between the fan cover  13  and the diffuser plate  15  forming outlets for passing the working air from the impeller  12  into the motor housing. 
   The motor housing comprises the diffuser plate  15  as mentioned above and a rear housing  19 . The diffuser plate  15  is attached to the motor housing  19  by four screws (not shown) passing through holes  37  (three only visible) in the diffuser plate  15  adjacent the outer periphery. In this embodiment, the rear housing  19  has a cup like appearance with an open end which mates with the diffuser plate  15  and a semi-enclosed end which supports a second bearing  38  for the motor shaft. The rear housing  19  supports the stator core  17  of the motor. One of two projections  34  for mounting the stator core is visible in  FIG. 2 . 
   The open end of the rear housing  19  has a flange  40 . The flange  40  abuts the diffuser plate  15  or more precisely, a plurality of air guide vanes  47  formed on the lower surface of the diffuser plate  15  and forming air passageways  46  for the working air. The flange  40  also receives the open end of the fan cover  13 . The fan cover  13  is pressed onto a wall or outer edge  41  of the flange  40  which has an axial extent sufficient to form a substantially air tight seal or seat between the flange  40  and the fan cover  13 . A ridge  42  is formed on the outer periphery of the flange to correctly position the fan cover  13  axially. Four recesses  43  in the flange wall  41  and ridge  42  allow the fan cover  13  to be crimped to the rear housing  19  to prevent removal and/or separation. A projection or alignment block  44  is formed on the wall of the flange  40  for mating with the cutout  26  in the open end of the fan cover  13  to circumferentially align the cover  13  with the motor housing  19 . This is only important if the design of the vane plate  14  is such that it should be physically aligned rotationally or circumferentially with the diffuser plate  15  as there is no provision to directly align the vane plate  14  with the diffuser plate  15 . 
   In assembling the blower, the rotor  16  is manufactured and balanced, the stator  17  and brush cage assemblies  18  are fitted to the rear housing  19 . The rotor  16  and bearings  38 ,  32  are fitted to the rear housing  19  and the diffuser plate  15  and the diffuser plate  15  is fixed to the rear housing  19 . The impeller  12  is then fitted to the motor shaft  22  and the motor is dynamically balanced. The fan cover  13 , complete with the vane plate  14  is fitted to the motor and crimped to the flange  40  completing the blower. 
   In fitting the cover  13 , the vane plate  14  is squeezed between or nipped by the fan cover  13  and the diffuser plate  15  preventing any movement of the vane plate. 
   Hence, the present invention provides an easy to assemble and dynamically balanceable blower with impeller guide vanes for a vacuum cleaner or the like. 
   A second embodiment is shown in  FIG. 6 . In this embodiment the blower is a bypass type blower in which the working air bypasses the motor section of the blower. The fan cover  13  has a plurality of apertures  45  forming the exhaust outlets formed in its cylindrical wall  20 . The diffuser plate  15  has a plurality of open passageways  45  which direct the working air axially downward and radially outward through the exhaust apertures  45 . The vane plate  14  is the same as in the first embodiment directing the air flow from the impeller  12  and into the passageways  46  formed in the diffuser plate  15 . The vane plate  14  is attached to the fan cover  13  in the same manner as used in the first embodiment. The two embodiments are essentially the same with the exception of the exhaust outlets or apertures  45  in the fan cover  13  and a slightly reconfigured diffuser plate  15 . A cooling fan (not shown) would be added to the motor shaft  33  to provide a separate flow of air to cool the motor. This type of motor is often used in wet and dry vacuum cleaners and carpet shampooing apparatus. 
   The embodiments described above are given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined in the appended claims. 
   For example, the fan cover  13  and the vane plate  27  could be formed integrally, preferably made as a monolithic molding, preferably of a heat resistant resin material such as BMC, nylon or the like. Such an alternative is shown in  FIG. 7  where the fan cover  13  has integrally molded air guide vanes  28  extending inwardly of the fan cover  13 , both from the base  21  and from the cylindrical wall  20  to provide rigid support for the individual vanes. As such, projections  24  and blind holes  25  are not required in this embodiment.