Patent Publication Number: US-2013251560-A1

Title: Blower

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201210081083.2 filed in The People&#39;s Republic of China on Mar. 22, 2012. 
     FIELD OF THE INVENTION 
     This invention relates to a blower as used in a vacuum cleaner or the like and in particular to an impeller and a diffuser of the blower. 
     BACKGROUND OF THE INVENTION 
     In a vacuum cleaner, air is moved to pick up dirt, dust and debris and deliver it to a dirt container, usually in the form of a filter bag supported within a canister. To cause the air flow, a blower is used to create a vacuum. Hence, the blower is also known as a vacuum blower. 
     The vacuum blower comprises a motor, an impeller creating the air flow and a diffuser. The impeller is fitted to and rotates with the shaft of the motor to generate high pressure air flow. The diffuser guides the air from the impeller through the motor where it is exhausted through openings in the motor housing after cooling the motor. 
     The construction of the impeller and the diffuser are very important as it affects the efficiency of the blower. A highly efficient blower can increase the volume of air being moved or reduces the power required to move the same volume of air. Hence, the desire for a more efficient blower is obvious. 
     SUMMARY OF THE INVENTION 
     Accordingly, in one aspect thereof, the present invention provides a blower comprising: a casing having an air inlet, an electric motor having a rotor and a stator, an impeller driven by the motor, and a diffuser for directing air from the impeller, the impeller and the diffuser being received in the casing, the impeller having a base and blades supported by the base, the diffuser having a plate like portion with diffuser vanes surrounding the impeller, wherein an inlet angle of the impeller blades is between 20˜30 degrees and an outlet angle of the impeller blades is between 26˜38 degrees. 
     Preferably, an inlet angle of the diffuser vanes is between 7˜11.5 degrees. 
     Preferably, an outlet angle of the diffuser vanes is between 15˜17.5 degrees. 
     Preferably, the rotor comprises a shaft, a rotor core fixed on the shaft, a commutator fixed on the shaft adjacent the rotor core, and rotor windings wound about poles of the rotor core and electrically connected to the commutator, the stator comprises an axially extending housing, at least one permanent magnet fixed to the inner surface of the housing, electrical terminals and at least one pair of brushes for making sliding contact with the commutator, the motor being operable by applying LVDC power to the rotor windings via the commutator. 
     Preferably, the stator has two magnetic poles, the rotor core has 5 slots, and the commutator has 5 commutator segments. 
     Preferably, the housing has an outer diameter of 35.7 mm±3%, the rotor core has an axial length of 25.1 mm±1%, and the permanent magnet has a thickness of 4.9 mm±3%. 
     Preferably, the casing has an outer diameter of 95 mm±3% 
     Preferably, the rotor is configured to rotate at a speed between 18,000˜22,000 rpm. 
     Preferably, the diffuser further comprises return guide vanes formed on one surface thereof remote from the impeller. 
     According to a second aspect, the present invention provides a blower comprising: a casing having an air inlet, an electric motor having a rotor and a stator, an impeller driven by the motor, and a diffuser for directing air from the impeller, the impeller and the diffuser being received in the casing, the impeller having a base and blades supported by the base, the diffuser having a plate like portion with diffuser vanes surrounding the impeller, wherein an inlet angle of the diffuser vanes is between 7˜11.5 degrees and an outlet angle of the diffuser vanes is between 1.5˜17.5 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labelled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. 
         FIG. 1  shows a blower in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a sectional view of the blower of  FIG. 1 ; 
         FIG. 3  shows an impeller being a part of the blower of  FIG. 1 ; 
         FIG. 4  shows an impeller and a diffuser being parts of the blower of  FIG. 1 ; 
         FIG. 5  shows a bracket being a part of the blower of  FIG. 1 ; 
         FIG. 6  is a top view of the impeller of  FIG. 3 , with a cover removed; and 
         FIG. 7  is a top view of the impeller and diffuser of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a blower  10  in accordance with a preferred embodiment of the present invention.  FIG. 2  is a sectional view of the blower  10 . The blower  10  comprises a casing  12 , a bracket  13 , an impeller  14 , a diffuser  16 , and an electric motor  18 . 
     Casing  12 , which is formed by drawing a sheet metal disc, is fitted over the bracket  13 , the impeller  14  and the diffuser  16  to define a working air chamber. An opening  20  in the casing  12  defines an air inlet for the blower. 
       FIG. 3  illustrates the impeller  14 , which comprises a curved cover  22 , a flat base  24  opposite the cover  22 , and a plurality of blades  26 . The cover  22  has an opening  28  formed at a center thereof and facing the opening  20  defined by the casing  12 . The opening  20  has an inwardly formed lip  30  which cooperates with the opening  28  in the cover  22  to restrict air recirculating within the air chamber across the impeller  14 . Preferably the lip extends into or through the opening  28 . The plurality of blades  26  are disposed between the cover  22  and the base  24 , extending in a curved manner and evenly distributed circumferentially to form a plurality of flow passages through which air passing through the opening  28  flows when the impeller  14  is rotating. Each blade  26  has a plurality of tabs  32  on each of the two long edges and holes corresponding to the tabs  32  are formed in the cover  22  and the base  24 . A tab  32  and a corresponding hole constitute a clamp structure. The blades  26  are firmly fixed between the cover  22  and the base  24  by crimping or otherwise deforming the tabs after they have been inserted into the holes to prevent their removal, in a manner generally known in the art. 
       FIG. 4  illustrates the impeller  14  and the diffuser  16 . The diffuser  16  has a central plate like portion  36  with diffuser vanes  38  on the upper surface and return guide vanes  40  on the lower surface. The diffuser vanes  38  and the return guide vanes  40  are integrally formed with the portion  36 . The diffuser vanes  38  are evenly arranged at the outer periphery of the upper surface of the portion  36 , facing the impeller  14  and surrounding the impeller  14 . The return guide vanes  40  are evenly arranged at the outer periphery of the lower surface of the portion  36 , facing the motor  18 . Passageways are formed between adjacent diffuser vanes and between adjacent return guide vanes  40 . 
     The motor  18  is preferably a low voltage direct current (LVDC) motor with a rotor and a stator surrounding the rotor. The rotor comprises a shaft  42 , a rotor core  44  fixed on the shaft  42 , a commutator  46  fixed on the shaft  42  adjacent the rotor core  44 , rotor windings  45  wound about poles of the rotor core  44  and electrically connected to the commutator  46 , and a cooling fan  48  fixed on the rotor core  44 . Outer surfaces of the rotor poles form a circle. Slots are formed between adjacent rotor poles for accommodating the rotor windings. The stator comprises an axially extending round housing  50  having an open end and a closed end, at least one permanent magnet  52  fixed to the inner surface of the housing  50  and an end cap  54  closing the open end of the housing  50 . Electrical terminals  56  for electrically connecting to an external power supply and brush cages  58  are supported by the end cap  54 . Brushes  59  are slidably received in the brush cages  58  for making sliding contact with the commutator  46 . Each electrical terminal  56  is electrically connected to a corresponding brush. Thus, a LVDC power, preferably between 12˜36 V, can be supplied to the rotor windings via the electrical terminals  56 , brushes and the commutator  46 . Preferably, the stator has two magnetic poles and two brushes, the rotor core has 5 slots, the commutator has 5 commutator segments, and the rotor windings are lap windings. The shaft  42  is rotatably supported by two bearings  60  received in bearing supports  62  at both ends of the motor. 
       FIG. 5  illustrates the bracket  13 . The bracket  13  has an inner ring  64  and an outer ring  66  connected to the inner ring  64  via bridges  68 . The inner ring  64  has a first recessed portion  70  and a hole  72  formed at the center of the first recessed portion  70 . The first recessed portion  70  is supported by one axial end surface of the housing at the closed end. The hole  72  is fitted to the bearing support  62  of the motor at the closed end. A flange  74  axially extends from the outer periphery of the outer ring  64 . The casing  12  is fitted to the outer surface of the flange  74  such that the casing  12  is firmly fixed to the bracket  13 . The central plate like portion  36  of the diffuser  16  has a second recessed portion  76  with a central hole. The second recessed portion  76  is fitted to the bearing support  62  and axially supported by the inner ring  64 . The return guide vanes  40  are axially supported by the outer ring  66 . The central plate like portion  36  and the bracket  13  are fixed to the housing  50  of the motor  18  by screws (not shown). The impeller  14  is coupled to a shaft  42  of the motor via a spacer  78  fitted to the shaft  42 . The spacer  78  has a plate portion  80  which supports the base  24  of the impeller  14 . The spacer  78  sits on the inner race of the bearing  60  at the closed end. A washer  82  is placed on top of the base  24  and a nut  84  screws into the end of the shaft  42  clamping the base  24  between the spacer  78  and the washer  82  so that the impeller rotates with the shaft. 
     In use, a LVDC power supply is connected to the motor  12  to cause the rotor to rotate. The impeller  14 , being fixed to the shaft  42 , is driven by the rotor causing air to be drawn into the impeller  14  through the inlet  20  in the casing  12  and expelled radially from the impeller  14  and through the passageways defined by the diffuser vanes  38  on the diffuser  16  and with the casing  12  directing the air flow from the upper surface of the diffuser around the outer edge of the diffuser into the passages formed between the return guide vanes  40  on the lower surface of the diffuser  16 . The return guide vanes  40  direct the air inwardly and axially through the openings in the bracket  13  and into the housing  50  where the air passes over the stator and rotor before being exhausted through apertures  86  in the lower portion of the housing  50 . 
     Preferably, the motor  18  is a 600 series LVDC motor. The LVDC power supplied to the motor is about 24V. The housing  50  has an outer diameter of 35.7 mm, the rotor core has an axial length of 25.1 mm, and the permanent magnet has a thickness of 4.9 mm, allowing a ±3% variation in these dimensions. 
     The blower in accordance with the present invention is particularly suitable for air processing apparatus such as hand dryers and vacuum cleaners. When it is used in vacuum cleaners, the motor  18  preferably operates at speed between 18,000 rpm and 22,000 rpm and the casing  12  has an outer diameter of 95 mm±3%. 
     As may be realized, the impeller  14  and the diffuser  16  play an important part in the efficiency of the air flow and in particular, in the turning and transferring of the air from, the impeller and into the housing. 
     Preferably, inlet angles α 1  of the impeller blades  26  are between 20˜30 degree. The angle α 1  means an angle formed by two lines L 1 , L 2 . Line L 1  represents the tangent to an imaginary circle touching inner ends of all blades  26  at the point A where it touches the blade  26 . Line L 2  represents the tangent to the curve of the blade  26  at point A. Outlet angles β 1  of the impeller blades  26  are between 26˜38 degree. The angle β 1  means an angle formed by two lines L 3 , L 4 , Line L 3  represents the tangent to an imaginary circle touching outer ends of all blades  26  at the point B where it touches the blade  26 . Line L 4  represents the tangent to the curve of the blade  26  at point B. The inlet angles α 1  and the outlet angles β 1  of the impeller blades  26  are shown in  FIG. 6 . 
     Inlet angles α 2  of the diffuser vanes  38  are between 7˜11.5 degree. The angle α 2  means an angle formed by two lines L 5 , L 6 . Line L 5  represents the tangent to an imaginary circle touching inner ends of all, vanes  38  at the point C where it touches the vane  38 . Line L 6  represents the tangent to the curve of the vane  38  at point C. Outlet angles β 2  of the diffuser vanes  38  are between 15˜17.5 degree. The angle β 2  means an angle formed by two lines L 7 , L 8 . Line L 7  represents the tangent to an imaginary circle touching outer ends of all vanes  38  at the point D where it touches the vane  38 . Line L 8  represents the tangent to the curve of the vane  38  at point D. The inlet angles α 2  and the outlet angles of the diffuser vanes  38  are shown in  FIG. 7 . 
     We have discovered that if the blower with above configuration is used in a small vacuum cleaner, such as a hand-held vacuum cleaner, an increase in efficiency can be achieved. The inlet angles α 1  and the outlet angles β 1  of the impeller blades  26  are especially important. Below table shows the efficiency changing when the angles α 1 , β 1  of the impeller blades  6  varies, under the test condition of air flow of the blower being 12.92 L/S and rotational speed of the rotor being 21,000 rpm. According to the table, an efficiency of about 71% or more can be achieved by using the angle α 1  in the range of 19° to 29° and the angle β 1  in the range of 25.5° to 37°. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 Q (L/S) 
                 α1 (°) 
                 β1 (°) 
                 ΔP (Pa) 
                 n (rpm) 
                 η (%) 
               
               
                   
                   
               
             
            
               
                   
                 12.92 
                 19.0 
                 30.0 
                 4222 
                 21000 
                 71.00 
               
               
                   
                   
                 22.5 
                 25.5 
                 4099 
                   
                 71.02 
               
               
                   
                   
                 24.8 
                 28.2 
                 4210 
                   
                 71.10 
               
               
                   
                   
                 24.3 
                 34.5 
                 4212 
                   
                 71.58 
               
               
                   
                   
                 26.0 
                 36.0 
                 4222 
                   
                 71.10 
               
               
                   
                   
                 27.0 
                 37.0 
                 4195 
                   
                 71.39 
               
               
                   
                   
                 29.0 
                 27.5 
                 4224 
                   
                 70.99 
               
               
                   
                   
                 32.0 
                 32.0 
                 4215 
                   
                 70.97 
               
               
                   
                   
                 34.0 
                 34.0 
                 4208 
                   
                 70.13 
               
               
                   
                   
                 36.0 
                 36.0 
                 4287 
                   
                 70.25 
               
               
                   
                   
               
            
           
         
       
     
     In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items. 
     Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.