Patent Publication Number: US-7896612-B2

Title: Blower unit and portable blower

Description:
The instant application should be granted the priority date of 10 Aug. 2006 the filing date of the corresponding German patent application, DE 10 2006 037 460.6. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a blower unit for a portable blower, and to a portable blower. 
     U.S. Pat. No. 4,413,371 discloses a portable blower having a blower unit. The fan is disposed in a cylindrical portion of the blower tube. The discharge nozzle is formed on the blower tube. The blower tube is made of metal thus increasing the weight of the blower, so that an operator quickly becomes fatigued when using the blower. Due to the geometry, manufacture of the blower tube of polymeric material is relatively expensive. Large, expensive molds are required. 
     It is therefore an object of the present invention to provide a blower unit and a blower that have a straightforward construction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This object, and other objects and advantages of the present application, will appear more clearly from the following specification in conjunction with the accompanying schematic drawings, in which: 
         FIG. 1  shows a side view of a blower unit, 
         FIG. 2  is a cross-sectional view taken along the line II-II in  FIG. 1 , 
         FIG. 3  is an exploded view of the blower unit of  FIG. 1 , 
         FIG. 4  is an enlarged view of a portion of  FIG. 2 , 
         FIG. 5  is a cross-sectional view taken along the line V-V in  FIG. 1 , 
         FIG. 6  is a cross-sectional view taken along the line VI-VI in  FIG. 1 , 
         FIG. 7  is a cross-sectional view taken along the line VII-VII in  FIG. 1 , 
         FIG. 8  is a cross-sectional view taken along the line VIII-VII in  FIG. 1 , 
         FIG. 9  is a cross-sectional view taken along the line IX-IX in  FIG. 1 , 
         FIG. 10  is a cross-sectional view taken along the line X-X in  FIG. 1 , 
         FIG. 11  is an end view of a fan wheel, 
         FIG. 12  is an end view of a guide wheel, 
         FIG. 13  is an end view of the blower unit taken in the direction of the arrow XII in  FIG. 1 , 
         FIG. 14  is a portion of a cross-sectional view taken along the line XIV-XIV in  FIG. 13 , 
         FIG. 15  is a portion of a cross-sectional view taken along the line XV-XV in  FIG. 13 , and 
         FIG. 16  is a schematic side view of a blower. 
     
    
    
     SUMMARY OF THE INVENTION 
     The blower unit of the present application comprises a rotatably driven drive shaft; a housing composed of at least two housing sections, wherein the housing is divided approximately parallel to the axis of the rotation of the drive shaft; and an axial fan that is disposed in the housing and is provided with at least one fan wheel driven by the drive shaft and at least one guide wheel fixedly disposed in the housing. The portable blower comprises a drive motor; a drive shaft rotatably driven by the drive motor; a blower unit that is provided with a housing, wherein the housing is composed of at least two housing sections and is divided parallel to the axis of rotation of the drive shaft; and an axial fan disposed in the housing and provided with at least one fan wheel driven by the drive shaft and at least one guide wheel fixedly disposed in the housing. 
     Constructing the housing from at least two housing sections simplifies manufacture of the housing. The housing shells can, for example, be easily manufactured in an injection molding process. By dividing the housing approximately parallel to the axis of rotation of the drive shaft, the blower can be easily assembled. The manufacture is simplified. Within manufacturing tolerances, the housing is advantageously divided exactly parallel relative to the drive shaft. However, it can also be advantageous for the division to deviate by several angular degrees from a parallel orientation relative to the drive shaft. 
     At least two housing sections advantageously have an identical configuration. The identical instruction of the housing sections represents an independent inventive concept that can also be realized with a blower unit where the housing sections are not divided parallel to the axis of rotation of the drive shaft. Due to the fact that the housing sections have an identical configuration, only a single tool is required. The storage space and the assembly are simplified. 
     Advantageously, two housing sections are provided that are embodied as half shells and are interconnected at a plane of separation. Due to the fact that the housing sections are embodied as half shells and are divided parallel to the axis of rotation of the drive shaft, the housing half shells can be formed without undercuts. As a result the manufacturing process can be simplified. The plane of separation in particular contains the axis of rotation of the drive shaft. As a result, the blower unit can be formed symmetrically relative to the axis of rotation. 
     To ensure a high stability of the housing, at least one guide wheel can support the housing sections in the interior of the housing. As a result, the wall thickness of the housing sections can be thin. Despite a greater stability, the weight of the blower unit is reduced. The guide wheel advantageously has an outer ring that rests on the inner periphery of the housing sections. The outer ring is in particular disposed in a recessed area of the housing sections that extends in the circumferential direction and secures the position of the guide wheel in the axial direction. The outer ring thus serves not only for the stabilization of the housing, but also for securing the position of the guide wheel. 
     The drive shaft is advantageously formed as a polygonal shaft. To achieve low bearing forces, the drive shaft can be mounted in at least two bearings, whereby in the axial direction of the drive shaft, at least one fan wheel is disposed between the bearings. Due to the fact that the drive shaft is mounted in two bearings and is not overhung mounted, the bearing forces can be reduced, and as a result the bearings can be made smaller. The weight of the blower unit is thus further reduced. A first bearing is advantageously disposed at the fan inlet, and a second bearing is advantageously disposed at the fan outlet. In this way, the bearing forces can be easily absorbed. At least one bearing is advantageously disposed on an inner ring of a guide wheel. In this connection, in particular the bearing disposed at the fan outlet is disposed on the inner ring of a guide wheel. By means of the bearing and the guide wheel, the bearing is secured relative to the housing. Due to the fact that the guide wheel serves for the mounting of the drive shaft, further components can be eliminated for mounting purposes. 
     Upstream of the fan inlet, the housing sections advantageously form a flow guide element, wherein the air that is drawn in flows along the outer periphery of the flow guide element. In the region of the flow guide element, the housing sections are expediently fixed in position on a guide tube of the blower. The first bearing of the drive shaft that is disposed at the fan inlet is in particular disposed on the flow guide element. To reduce the flow resistance at the fan outlet, a flow guide element can be disposed at the fan outlet, wherein air conveyed by the axial fan flows along the outer periphery of the flow guide element. 
     To achieve an adequate air throughout and an adequate flow velocity at the outlet out of the blower unit, the axial fan can be a multi-stage fan. The axial fan advantageously has three fan stages, each of which with a fan wheel and a guide wheel. The manufacture and assembly of the blower unit can be simplified if all of the fan wheels and all of the guide wheels of the axial fan respectively have an identical construction. This reduces the number of individual parts, that are required. 
     The guide wheels are advantageously angularly offset relative to one another about the axis of rotation of the drive shaft. It has been shown that by an angular offset of the guide wheels relative to one another the running noise of the blower unit can be reduced. The angular offset is advantageously approximately 360° divided by the number of guide wheel vanes divided by the number of fan stages. As a result, the guide wheel vanes are not aligned with one another. The angular offset between guide wheels disposed next to one another in the direction of flow can in this connection be a multiple of the given angular offset. However, the angular offset between the guide wheels is to be selected such that no guide wheel vane is aligned with the guide wheel vanes of another guide wheel. 
     To reduce the noise that results during operation, the number of the fan wheel vanes and/or the number of the guide wheel vanes can be an odd number. The number of guide wheel vanes is advantageously not the same as the number of fan wheel vanes. 
     The blower unit advantageously has an air outlet opening, whereby the flow cross-section in the air outlet opening is more than ¼ of a flow-through area of the fan wheel. The flow cross-section of the air outlet opening is in particular more than ⅓ of the flow-through area of the fan wheel. This results in good flow conditions that lead to a high cleaning effect of the blower unit. Favorable conditions are also achieved if the blower unit has a cylindrical portion, whereby the diameter of the cylindrical portion is approximate 0.3 to approximately 0.5 times the axial length of the cylindrical portion. The blower unit advantageously has an axial length that is approximately 2 to approximately 4 times the axial length of the axial fan. In comparison to known blower units, the overall length of the blower unit is comparatively short, and the axial fan extends over a considerable part of the axial length of the blower unit. As a result, the blower tube can be comparatively short. In this way, favorable flow conditions and at the same time low pressure losses can be realized in the blower tube. 
     Pursuant to the present application, a portable blower can have a drive motor, which rotatably drives a drive shaft, as well as a blower unit, whereby the blower unit has a housing in which is disposed an axial fan that is provided with at least one fan wheel driven by the drive shaft and at least one guide wheel fixedly disposed in the housing, whereby the housing is composed of at least two housing sections and is divided parallel to the axis of rotation of the drive shaft. 
     Due to the divided construction of the housing, the individual components can be easily positioned in the housing. A simple construction and an easy manufacture results. 
     At least two housing sections advantageously have an identical configuration. The two identically configured housing sections result in a simple construction of the blower. Due to the fact that the two housing sections are identical, the number of different components that have to be produced is reduced, and the storage space is simplified. 
     The blower expediently has an engine housing in which is disposed the drive motor. The blower in particular has a guide tube that extends from the engine housing to the fan housing. The housing sections are in particular fixed on the guide tube. 
     Further specific features of the present invention will be described in detail subsequently. 
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Referring now to the drawings in detail, the blower  40  shown in  FIG. 16  has an engine housing  41  in which is disposed a drive motor  43 , which is in particular embodied as a one-cylinder, two-cycle engine. A handle  42  is secured to the engine housing  41  for guiding the blower  40 . The blower  40  has a blower unit  1 , which is connected with the engine housing  41  via a guide  23 . 
     As shown in  FIG. 1 , the blower unit  1  has a housing  2 , out of which the guide tube  3  extends. The length i of that portion of the guide tube  3  that is formed on the blower unit  1  is advantageously more than 40 mm, in particular more than 50 mm. This enables a good connection with adjoining components, such as the housing  41  of the blower  40 . The housing  2  has a cylindrical main body that on that side that faces the engine housing  41  is provided with an air inlet opening  5 . The air inlet opening  5  is disposed concentrically relative to the guide tube  3 , and is covered by a cover grate  6 . On that side disposed remote from the engine housing  41 , a blower tube  10  is secured to the housing  2 ; a discharge nozzle  21  for the air stream is disposed on the blower tube  10 . The discharge nozzle  21  has an air outlet opening  9 , which is shown in  FIG. 2 . 
     As shown in  FIG. 1 , the housing  2  has a cylindrical portion  51  on which the cover grate  6  is disposed. The cylindrical portion  51  has an axial length e, which is advantageously approximately 300 mm to approximately 450 mm. The cylindrical portion  51  has a diameter f, which is advantageously approximately 90 mm to approximately 200 mm. The ratio of the diameter f to the length e is advantageously in the range of from about 0.3 to about 0.5. 
     The blower unit  1  has an axial length g, which is advantageously approximately 800 mm to approximately 1,200 mm. The axial length g of the blower unit  1  is advantageously approximately two to approximately four times an axial length h of the axial or axial-flow fan  11 . The length g is advantageously approximately three times the length h. 
     As shown in the cross-sectional view of  FIG. 2 , guided in the guide tube  3  is an input shaft  4  that is rotatingly driven about an axis of rotation  31  by the drive motor  43 . The input shaft  4  is connected to the drive shaft  28  in such a way that it is fixed against rotation relative thereto, so that the drive motor  43  drives the polygonal shaft  28  via the input shaft  4 . The drive shaft  28  is embodied as a hollow polygonal shaft. Disposed in the housing  2  is a three-stage axial fan  11 . The axial fan  11  has three fan wheels  12 ,  12 ′,  12 ″ as well as three guide wheels  13 ,  13 ′,  13 ″. Respectively paired up ones of the fan wheels  12 ,  12 ′,  12 ″ and the guide wheels  13 ,  13 ′,  13 ″ form in each case a fan stage. For a good cleaning result of the blower  40 , the axial fan  11  has a diameter from 90 mm to 200 mm, in particular from 140 mm to 170 mm. 
     Disposed upstream of the fan inlet  37  is a flow guide element  19 , around the outer periphery of which flows the air that is drawn into the axial fan  11 . Disposed on the flow guide element  19  is a first bearing  22  in which the drive shaft  28  is mounted. A second bearing  23  is provided at the downstream guide wheel  13 ″. Disposed downstream of the fan outlet  38  and of the guide wheel  13 ″ is a flow guide element  20 , along the outer periphery of which flows the air that is conveyed through the axial fan  11 . The flow guide element  20  extends centrally into the blower tube  10 . The fan inlet  37  designates the flow cross-section upstream of the first fan wheel  12  in the direction of flow, and the fan outlet  38  designates the flow cross-section downstream of the last guide wheel  13 ″ in the direction of flow. 
     As also shown in the enlarged illustration of  FIG. 4 , the fan wheels  12 ,  12 ′,  12 ″ have a sleeve portion  32  that has a cylindrical configuration and is arranged in the radial direction between the drive shaft  28  and the housing  2 . The guide wheels  13 ,  13 ′,  13 ″ have a cylindrical sleeve portion  33 , the diameter of which corresponds to the diameter of the sleeve portions  32 . The diameter of the flow guide element  19  at the fan inlet  37 , and the diameter of the flow guide element  20  at the fan outlet  38 , correspond to the diameter of the sleeve portions  32  and  33 . The sleeve portions  32  and  33  form a cylindrical chamber that is closed off at its ends by the flow guide elements  19  and  20 , and in the interior of which is guided the drive shaft  28 . The air conveyed by the axial fan  11  flows externally of the sleeve portions  32  and  33 . 
     The outer diameter c of the fan wheels  12 ,  12 ′,  12 ″ is advantageously approximately 140 mm to approximately 170 mm. The outer diameter d of the sleeve portions  32 ,  33  is advantageously approximately 70 mm to approximately 100 mm, whereby the ratio of the outer diameter d of the sleeve portions  32 ,  33  to the outer diameter c of the fan wheels  12 ,  12 ′,  12 ″ is at least approximately 0.5, whereby a value of greater than 0.5 is advantageous. A flow-through area  52  is formed between the wall of the housing  2  in the cylindrical portion  51  and the sleeve portions  32  and  33 . The ratio of the flow cross-section in the region of the air outlet opening  9  to the flow cross-section of the flow-through area  52  of the axial fan  11  is advantageously greater than 0.25. A ratio of greater than 0.3 is particularly advantageous. A value of about 0.37 has been established as expedient. 
     As shown in the exploded view of  FIG. 3 , the housing  2  is composed of a first housing section  7  and a second housing section  8 . The two housing sections  7 ,  8  are embodied as half sections or shells that are identical to one another. The housing  2  is divided in the longitudinal direction, in other words, parallel to the axis of rotation  31  of the drive shaft  28 . On sides that extend parallel to the axis of rotation  31  the housing sections  7 ,  8  rest against one another. The two housing sections  7 ,  8  are fastened to one another via screws  35 . A half of the flow guide element  19  is formed on each of the housing sections  7 ,  8 . The portions of the flow guide element  19  are connected to the respective housing section  7  and  8  via guide surfaces or fins  30 . 
     The input shaft  4  is mounted in the guide tube  3  via a support element  29  that centers the input shaft  4  in the guide tube  3 . The fan wheels  12 ,  12 ′,  12 ″ are provided with fan wheel vanes  14  on the periphery of the sleeve portions  32 . Guide wheel vanes  15  are disposed on the periphery of the sleeve portions  33  of the guide wheels  13 ,  13 ′,  13 ″. On the outer periphery of the guide wheel vanes  15  each guide wheel  13 ,  13 ′,  13 ″ is provided with an outer ring  34 . The flow guide element  20  at the fan outlet  38  is embodied as a monolithic component and is fixed to the downstream guide wheel  13 ″. The two housing sections  7  and  8  are secured in position on the guide tube  3 . As shown in  FIG. 3 , for this purpose a total of four screws  35  are provided in the region of the flow guide element  19 . 
     As shown in  FIG. 4 , the outer ring  34  of the downstream guide wheel  13 ″ is disposed in a recessed area  39  that extends on the periphery of the housing  2 . The recessed area  39  secures the position of the guide wheel  13 ″ in the direction of the axis of rotation  31  of the drive shaft  28 . Radially within the sleeve portions  32  the fan wheels  12 ,  12 ′,  12 ″ are provided with spokes  17  that extend radially inwardly to a hub  16 . The hub  16  has a polygonal profile, shown in  FIG. 11 , that cooperates with the polygonal profile of the drive shaft  28  and thus establishes a fixed connection between the fan wheels  12 ,  12 ′,  12 ″ and the drive shaft  28 . A respective spacer  24  is disposed on the drive shaft  28  between two hubs  16 ; the axial length of the spacers  24  corresponds to the distance between two fan wheels  12 ,  12 ′,  12 ″. The guide wheels  13  and  13 ′ are disposed radially outwardly of the spacers  24 . Each of the guide wheels  13 ,  13 ′,  13 ″ is provided with an inner ring  25  that is connected with the sleeve portions  33  via spokes  26 . The inner ring  25  has a lateral collar  27  that is radially spaced relative to the spacer  24 . The outer rings  34  of the guide wheels  13 ,  13 ′,  13 ″ are supported on the inner periphery of the housing  2 . The housing sections  7  and  8  are inter connected by the screws  35 . The securement via the screws  35  secures the outer rings  34  of the guide wheels  13 ,  13 ′,  13 ″ in the housing  2 . The outer rings  34  thereby reinforce the housing  2 . The downstream guide wheel  13 ″ supports the second bearing  23  for the drive shaft  28 . The second bearing  23  is disposed on the inner ring  25  and is supported in the axial direction against the collar  27 . 
       FIG. 5  shows the arrangement of the first bearing  22  in the housing sections  7  and  8  in the region of the flow guide element  19 . The interior of the flow guide element  19  is provided with struts  44  that support the bearing  22  and that reinforce the housing sections  7  and  8  in the region of the fastening effected by the screws  35 . As also shown in  FIG. 5 , four fins  30  are provided in each housing section  7 ,  8  that extend radially upwardly from the flow guide element  19  to the outer wall of the housing  2 . 
       FIG. 6  is a cross-sectional view through the upstream guide wheel  13 . The two housing sections  7  and  8  are inter connected by screws  35 . The two housing sections  7  and  8  rest against one another at a plane of separation  36 . The two screws  35  shown in  FIG. 6  are threaded in from opposite sides of the plane of separation  36 , so that in each case a head of one of the screws is disposed on the housing section  7  or the housing section  8  respectively, and each screw is threaded into the other housing section  7 ,  8 . The guide wheel  13  has an outer ring  34  that rests against the inner periphery of the housing  2  and supports the housing  2 . The guide wheel  13  is securely held in the housing  2  via the outer ring  34 . The outer ring  34  is connected to the sleeve portion  33  via guide wheel vanes  15 . The sleeve portion  33  is connected with the inner ring  25  via radially inwardly extending spokes  26 . The spacer  24 , which surrounds the drive shaft  28 , is disposed radially inwardly of the inner ring  25 . As shown in  FIG. 6 , the drive shaft  28  is embodied as a hollow shaft that has a polygonally profiled outer periphery. The inner periphery of the spacer  24  has a polygonal profile that corresponds to the drive shaft  28 . The inner ring  25  is radially spaced from the spacer  24 , so that the drive shaft  28 , with the spacer  24 , can rotate in an unobstructed manner in the guide wheel  13 . 
       FIG. 7  shows a further cross-sectional view through the guide wheel  13  downstream of the cross-section of  FIG. 6 . As shown in  FIG. 7 , the guide wheel  13  has nine guide wheel vanes  15 . That guide wheel vane  15  that is disposed at the top in  FIG. 7  and in a clockwise direction is disposed adjacent to the plane of separation  36  forms an angle α with the plane of separation  36 . The guide wheel  13 ′ of the second fan stage, which is disposed downstream of the guide wheel  13  of the first fan stage, has a configuration that is identical to the guide wheel  13 . That guide wheel vane  15  of the guide wheel  13 ′ that is disposed at the top in  FIG. 8  and in a clockwise direction is disposed adjacent to the plane of separation  36  forms an angle β with a plane of separation  36  that is greater than the angle α. The different between the angles α and β is a multiple of 13.3°. This offset results from 360° divided by the number of fan stages, namely three, and divided by the number of guide wheel vanes, namely nine. The mathematically determined value can be rounded off so that the actual offset corresponds approximately to the mathematically determined value. As shown in the cross-sectional view of  FIG. 9  through the downstream guide wheel  13 ″, that guide wheel vane  15  that is disposed at the top of  FIG. 9  and in the clockwise direction is adjacent to the plane of separation  36  is rotated by an angle γ relative to the plane of separation  36  that is between the angle α and the angle β. In the illustrated embodiment the difference between the angles β and α is twice the difference between the angles γ and α. The central guide wheel  13 ′ is thus offset relative to the upstream guide wheel  13  by twice the angle offset, and the downstream guide wheel  13 ″ is offset by the single angular offset. The selected angular offset ensures that none of the guide wheel vanes  15  of the guide wheels  13 ,  13 ′,  13 ″ are aligned with one another in the direction of the axis of rotation  31 . As a result, the development of noise during operation is reduced. All of the guide wheels  13 ,  13 ′,  13 ″ are identical. 
     As shown in the cross-sectional view of  FIG. 10 , the upstream end of the housing, in each of the housing sections  7 ,  8 , is provided with an outwardly directed raised portion  45  into which project correspondingly shaped raised portions  46  of the blower tube  10 . As a result, the position of the blower tube  10  is secured and the blower tube is held on the housing tube. Additional fastening means are not required for the blower tube  10 . 
       FIG. 11  shows an end view of a fan wheel  12 . As shown in  FIG. 11 , seven fan wheel vanes  14  are disposed on the fan wheel  12 . Adjacent fan wheel vanes  14  are spaced relative to one another by the distance a as measured in the circumferential direction. If the fan wheel  12  is made of polymeric material, removal from the mold can thus be easily ensured. The spacing a can, for example, be between 3 mm and 10 mm. 
     As shown in the end view of a guide wheel  13  in  FIG. 12 , nine guide wheel vanes  15  are disposed in a uniformly spaced-apart relationship between the sleeve portion  33  and the outer ring  34 . Adjacent guide wheel vanes  15  are spaced from one another by the distance b, measured in the circumferential direction, that can correspond to the distance a between adjacent fan wheel vanes  14  and is between 3 mm and 10 mm. 
       FIGS. 13 ,  14 , and  15  show the fixation of the cover grate  6  on the housing  2 . As shown in  FIG. 13 , the cover grate  6  is provided with latching elements  47  on which is disposed the inwardly projecting latching rim  48  that is shown in  FIG. 15 . The latching rim  48  cooperates with the housing  2  and thus fixes the cover grate  6  on the housing  2 . As shown in  FIG. 14 , additionally provided on the cover grate  6  are recessed areas  49  that extend into cutouts  50  of the housing  2  and thus fix the cover grate  6 . Thus also for the fixation of the cover grate  6  no additional components are required. 
     As shown in  FIG. 3 , each fan wheel  12 ,  12 ′,  12 ″ has seven fan wheel vanes  14 . Not only the number of fan wheel vanes  14  but also a number of guide wheel vanes  15  is not even. A different number of fan wheel vanes and guide wheel vanes is provided. Particularly advantageous for, reducing noise is having a number of fan wheel vanes  14  and/or a number of guide wheel vanes  15  that is a primary number. The fan wheels  12  can also be rotationally shifted relative to one another on the drive shaft  28 , so that no fan wheel vanes  14  are aligned with or overlap one another. In this connection the angular offset again advantageously corresponds to 360° divided by the number of fan wheel vanes divided by the number of fan stages. 
     The offset of the guide wheel vanes and/or of the fan wheel vanes relative to one another represents an independent inventive concept. Similarly an independent inventive concept is that the number of the fan wheel vanes and/or the number of the guide wheel vanes is an odd number, and in particularly a primary number, and also that the number of the fan wheel vanes and the number of the guide wheel vanes are different. 
     The specification incorporates by reference the disclosure of German priority document DE 10 2006 037 460.6 filed 10 Aug. 2006. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.