Patent Publication Number: US-6210109-B1

Title: Portable fluid blower

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to blowers using an impeller to draw in and centrifugally accelerate a fluid for controlled discharge thereof. 
     2. Background Art 
     Portable power blowers are widely used by homeowners and professionals, particularly in the landscape and maintenance industries. The most popular version of the power blower is a hand-holdable, gas powered unit which uses a forwardly projecting discharge conduit that can be conveniently oriented to control air discharge by an operator in use. An impeller, with a laterally extending rotational axis, draws air inwardly as it rotates. In one construction, the impeller has an unbladed core volume with radially projecting blades having upstream ends at the core volume and downstream ends located radially outwardly therefrom. Operation of the impeller causes air to be drawn into the core volume, picked up by the blades, centrifugally accelerated in a volute, and diverted at a point of separation from the downstream ends of the blades at high volume to the discharge conduit. 
     The assignee herein offers a line of such blowers which are lightweight and capable of producing a high volume air discharge. One significant problem with these gas powered blowers is that they generate a significant amount of noise during operation. Designers are constantly seeking ways to attenuate the noise generated at different locations throughout the unit to make it more environmentally compatible. 
     The assignee herein has done a substantial amount of research regarding noise generation in this type of blower. One noise source is where laterally/axially directed incoming air encounters the impeller and abruptly stops and changes direction to a radial flow. The radial flow is in turn abruptly halted and redirected to a curved flow path around the impeller axis in the volute as the radial flow encounters the surface bounding the volute. This abrupt halting and redirection of air flow produces unwanted noise. 
     Another problematic noise source is at a branching location where the accelerated flow in the volute divides to be either a) directed through the discharge conduit or b) redirected into the volute for recirculation. Directly between these divided flow paths, the accelerated air is abruptly halted, which may generate significant noise as the impeller blades travel past this location and shear the air. Also, the air re-entering the volute passes through a restriction, where the volute has its smallest volume. The noise generation thereat can be reduced by enlarging the volume of the volute at the re-entry point. However, by doing this, the efficiency of the unit may be compromised. Thus, designers in the past have generally opted to produce a more efficient unit while contending with a significant amount of operating noise. 
     Aside from the noise generated by the air flow and air shearing by the impeller blade in operation, the gas powered drives for these impellers generate noise that must be independently contended with. Conventional two cycle engines generate a significant amount of noise in operation. Communities are now legislating to restrict noise levels to below those which many existing two cycle engines used on power blowers operate at. Whereas, in the past, noise reduction in this field was desired, this noise reduction is now becoming a necessity. The search for solutions to the noise problem has, or is soon likely to, become a priority for most manufacturers of this type of equipment. 
     One manner of reducing noise generation is to use a motor to drive the impeller which operates off of an AC or DC power source. The use of AC power may be impractical where a source of AC power is unavailable or not readily accessible. 
     With respect to DC power sources, current technology is such that DC power sources, portable enough to be moved in a practical manner with the equipment that is powered, have a relatively limited life before recharging is required. Equipment efficiency is paramount in systems operating using a DC power supply. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a portable fluid blower having a housing defining an intake region for incoming fluid, an output region, and a fluid path for controllably communicating fluid entering the intake region to the output region at which fluid is discharged from the housing. An impeller on the housing is rotatable around a first axis and draws fluid into the fluid path through the intake region and accelerates fluid drawn into the fluid path so that the fluid drawn into the fluid path through the intake region is accelerated in the fluid path and discharged in an accelerated state at the output region. A drive rotates the impeller around the first axis. The fluid path has a first curved fluid path portion that extends at least partially around the first axis, and a second transition path portion through which fluid communicates from the input region towards the first curved fluid path portion. At least part of the second transition path portion is defined by a guide surface, that extends continuously around a central axis that is substantially coincident with the first axis, and has a diameter that increases progressively from the intake region axially relative to the central axis towards the first curved fluid path portion so that fluid moving from the intake region towards the first curved fluid path portion is guided progressively radially outwardly relative to the central axis through the part of the second transition path portion. 
     In one form, the impeller has an axial extent along the first axis and the guide surface extends over substantially the entire axial extent of the impeller. 
     The impeller may have a plurality of blades each having a length extending axially relative to the first axis. 
     In one form, one of the blades has a length that is less than the length of another of the blades. 
     The blades may be reversely curved along the lengths of the blades. 
     In one form, the plurality of blades includes a plurality of blades having a first length and a plurality of blades having a second length that is different than the first length, with there being a blade having the first length between two blades having the second length and a blade having the second length between two blades having the first length. 
     The blades having the first and second lengths may alternate around the entire circumference of the impeller. 
     In one form, each of the blades projects radially from the guide surface relative to the first axis and the amount of radial projection for each blade varies over the length of each blade. 
     In one form, each blade has an upstream edge and a downstream edge and the upstream edge of one of blades is substantially straight and orthogonal to the central axis. 
     The upstream edge of a second blade may be substantially straight and orthogonal to the central axis, with the upstream edges of the one and second blades being substantially parallel to each other and diametrically oppositely located relative to the central axis. 
     The downstream edge of one of the blades may be substantially straight and parallel to the central axis. 
     In one form, the impeller has a diameter and an edge at a location where the diameter of the impeller is the largest and the downstream edge of the blade is substantially flush with the edge at the location where the diameter of the impeller is the largest. 
     A cup-shaped element may be provided at the upstream end of the impeller and has a surface that blends into the guide surface. 
     In one form, the impeller rotates in a drive direction and the blades have a leading surface which is inclined in the drive direction. 
     The drive may be one of a gas powered drive, a drive operated by an alternating current power source, and a drive operated by a direct current power source. 
     The housing may have a surface with a funnel-shaped portion adjacent to the intake region. 
     In one form, the blades each have an edge that faces radially outwardly relative to the central axis and the housing has a wall with a surface that conforms to the radially outwardly facing edges over substantially the entire extent of the radially outwardly facing edges. 
     In one form, the radially outwardly facing edges have a serpentine shape. 
     In one form, the housing defines a volute which defines the first curved fluid a path portion, and the volute extends substantially fully around the central axis. 
     In one form, the housing has a discharge conduit defining the output region, the volute has an inlet portion and an outlet portion and fluid entering the intake region and communicating to the intake portion of the volute is centrifugally accelerated and moves through the volute to the output region and is discharged from the housing at the discharge conduit. 
     In one form, viewing the fluid blower axially relative to the central axis, the blades move in a path having a first diameter and the housing defines an intake opening at the intake region with a diameter that is less than the first diameter. 
     In one form, the diameter of the intake opening may be on the order of one-half the first diameter. 
     In one form, the housing has a first surface facing axially relative to the first axis toward the intake opening and a second surface facing radially outwardly relative to the first axis and the first and second surfaces meet to define an annular corner. The guide surface overlaps the annular corner in an axial direction relative to the first axis. 
     In one form, there is a transition wall between the inlet portion and outlet portion of the volute and the transition wall has a generally flat first surface which resides in a plane that is not parallel to the first axis. 
     The transition wall may have a generally flat second surface which defines a V shape in conjunction with the first surface. 
     The first and second surfaces may join along a line that is not parallel to the first axis. 
     The invention is also directed to a portable fluid blower having a housing defining an intake region for incoming fluid, an output region, and a fluid path for controllably communicating fluid entering the intake region to the output region at which fluid is discharged from the housing. An impeller on the housing is rotatable around a first axis and draws fluid into the fluid path through the intake region and accelerates the fluid drawn into the fluid path so that fluid drawn into the fluid path through the intake region is accelerated in the fluid path and discharged in an accelerated state at the output region. A drive rotates the impeller around the first axis. The housing and impeller have cooperating surfaces at the second transition path portion which guide fluid moving from the intake region towards the first curved fluid path portion progressively radially outwardly relative to the central axis through the second transition path portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary, perspective view of a conventional portable blower; 
     FIG. 2 is an enlarged, perspective view of the blower in FIG. 1 with part of the housing thereon removed; 
     FIG. 3 is an exploded, perspective view of a portable fluid blower, according to the present invention; 
     FIG. 4 is an enlarged, perspective view of a part of a housing on the blower in FIG. 3 with an impeller in operative position thereon; and 
     FIG. 5 is an enlarged, cross-sectional view of the fluid blower taken along line  5 — 5  of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In FIGS. 1 and 2, a conventional hand-holdable blower unit is shown at  10 . The blower unit  10  has a housing  12  defining an internal space  14  within which air is accelerated. More particularly, the blower unit  10  has a bladed impeller  16 , which rotates around a laterally extending axis  18  to draw air axially inwardly, as indicated by the arrow  20 , through a grill  22 . The impeller  16  directs the incoming air radially outwardly into a volute  24  in which the air is centrifugally accelerated and ultimately communicated to and through a discharge conduit  26 . In this embodiment, the impeller  16  is rotated by a gas powered motor  28  which is regulated by controls  30  on a carrying handle  32  for the blower unit  10 . 
     In FIG. 2, the precise air flow pattern into and through the blower unit can be seen. The motor  28  drives the impeller  16  in the direction of the arrow  34 . The impeller  16  has radially projecting blades  36  which are spaced uniformly around the axis  18  of the impeller  16 . Each blade has an upstream end  38  and a radially outwardly spaced downstream end  40 . Between the axis  18  and the upstream ends  38  of the blades  36 , a core volume  42  is defined. The core volume  42  does not have any air accelerating blades therewithin. 
     As the impeller  16  is driven, the blades  36  centrifugally propel air against the radially inwardly facing surface  44  of the volute  24 . A low pressure region is thereby developed in the core volume  42 , as a result of which intake air is drawn axially/laterally through the air intake grill  22  and into the core volume  42 . The arrows  46  indicate the air flow pattern. Initially, the air flows axially and at the impeller  16  abruptly changes direction to flow in a radial direction. The radial flow again abruptly changes direction upon encountering the radially inwardly facing surface  44 , whereupon the air moves in a curved path in the direction of the arrow  34  around the axis  18  through the volute. 
     The volute  24  has an inlet region  47  and an outlet region  48 , with the outlet region  48  communicating directly with the discharge conduit  26 . Air moving through the volute  24  from the inlet region  46  is accelerated and expanded, in a progressively increasing volume of the volute  24 , from where it communicates to the outlet region  48 . 
     The blower unit  10  has a number of areas at which noise generation is significant. At the point where the air flow changes from axial to radial flow at the impeller  16 , significant noise can be generated as the blades  36  “shear” the air. 
     There also may be significant noise generation where the air changes from a radial flow path to a centrifugal flow path in the volute  24 . 
     A further area of noise generation is at the cut-off point/juncture  50  where the air accelerated by the impeller  16  branches to either travel through the discharge conduit  26  or re-enter the volute  24  at the inlet region  47 . The cut-off point/juncture  50  is at the juncture of two generally flat surfaces  52 ,  54 . The planes of the surfaces  52 ,  54  are substantially parallel to the axis  18 . At the cut-off point/juncture  50  between the surfaces  52 ,  54  there is a stagnation point at which the accelerated air abruptly stops. The stagnated air is sheared by the blades  36 , which again may produce a significant amount of noise. 
     A portable fluid blower, according to the present invention, is shown in FIGS. 3-5 at  60 . The blower  60  has a housing  62  which defines an intake region  64  for incoming fluid, an output region  66 , at which a discharge nozzle  68  is provided, and internal fluid flow path/acceleration space  70  for controllably communicating fluid entering the intake region  64  to the output region  66  at which fluid is discharged from the housing  62 . The housing  62  has a handle  72 , which is shown schematically, but which may take any form convenient to hold the housing  62  in an operative orientation. 
     An impeller  74  is mounted on a shaft  76  for rotation around an axis  78  in the direction of the arrow  80 . A drive  82  rotates the impeller around the axis  78  to draw fluid towards and into the fluid path  70  through the intake region  64  and accelerate the intake fluid in the fluid path  70  for ultimate discharge in an accelerated state at the output region  66  in substantially a straight flow path that is transverse to the axis  78 . 
     The housing  62  is defined by first and second joinable parts  84 ,  86 , which cooperatively bound a chamber  88  within which the impeller  74  operates. 
     The fluid path  70  consists of a curved path portion at  90  around the axis  78  and a transition path portion  92  through which fluid communicates from the intake region  64  towards the curved path portion  90 . 
     The curved path portion  90  is defined by a volute  94  with an inlet region  96  and an outlet region  98 , corresponding to the inlet and outlet regions  46 ,  48  described for the blower unit  10 . The cross-sectional area, and thus the volume of the volute  94 , as seen clearly in FIG. 5, increases progressively from the inlet region  96  to the outlet region  98 . 
     The general operation of the fluid blower  60  is the same as that of the blower unit  10 , previously described. That is, fluid entering at the intake region  64  is directed through the transition path portion  92  into the curved path portion  90  defined by the volute  94  and centrifugally accelerated from the inlet region  96  to the outlet region  98  thereof at which point accelerated fluid is discharged through the nozzle  68  defining the output region  66 . 
     The impeller  74  has the same overall shape as a compressor wheel on a conventional turbocharger. The impeller  74  has a body  100  with a guide surface  102  that extends continuously, and is symmetrical, around a central axis that is coincident with the axis  78 . The guide surface  102  increases in radius progressively from an upstream end  104  to a downstream end  106 . The guide surface  102  has a concave curvature from the upstream end  104  to an axial location  108  adjacent to the downstream end  106 , at which point the curvature becomes convex. 
     The housing  62  has a mounting wall  110  through which the impeller shaft  76  extends. The mounting wall  110  has an axial facing, flat surface  112  which meets a radially outwardly facing surface  113  bounding a part of the volute  94  at an annular corner  114 . The guide surface  102  extends radially inwardly beyond the corner  114  and shrouds the corner  114  by axially overlapping the corner  114 . 
     The impeller  74  has a series of circumferentially spaced blades, including blades  116  of a first configuration and blades  118  of a second configuration which alternate around the entire circumference of the guide surface  102 . Each blade  116 ,  118  has a length extending around the axis  78 . The blades  116 ,  118  have the same general shape, however the blades  118  have both a lesser radial and axial extent than the blades  116 . 
     Exemplary blade  118 , as seen in FIG. 4, has a generally flat body  120  with an upstream edge  122  and a downstream edge  124 . The upstream edge  122  is substantially straight and is aligned to extend through the axis  78  substantially orthogonally thereto. The downstream edge  124  is substantially flush with the downstream end  126  (FIG. 5) of the guide surface  102  where the diameter of the impeller  74  is the largest, is straight, and extends substantially in a line that is parallel to the axis  78 . A radially facing edge  128  is reversely curved in the shape of an S between the upstream edge  122  and downstream edge  124 . The body  20  has a serpentine shape over its length. The body  120  is slightly curved along lines extending through a root edge  130 , where the blade  118  joins to the guide surface  102 , and the radially facing edge  128 . The radial projection of the radially facing edge  128  from the guide surface  102  decreases from the upstream edge  122  towards the downstream edge  124  up to a transition point  132  at which the downstream edge  124  and radially facing edge  128  meet. 
     In the embodiment shown, eight blades  116 ,  118  are provided on the impeller  74 . With this arrangement, the upstream edges  122  of two diametrically opposite blades  118  extend along a common line and through the axis  78 . 
     The blades  116  have the same general construction as the blades  118 , including flat, reversely curved bodies  134  with straight upstream and downstream edges  136 ,  138  having the same orientation as the upstream and downstream edges  122 ,  124 . The upstream edges  136  on diametrically opposite blades  116  have aligned lengths which extend through the axis  78 . The downstream edges  138  extend substantially parallel to the axis  78 . 
     The blades  116 ,  118  have leading surfaces  140 ,  142  which are inclined in the direction of rotation of the impeller  74 . 
     At the upstream end of the impeller  74 , an unbladed, cup-shaped element  144  is attached. The cup-shaped element  144  has a convex outer surface  146  which smoothly blends into the guide surface  102 . 
     As seen in FIG. 5, the first housing part  84  has a wall  147  with a surface  148  that conforms to the radially facing edges  128  of the blades  118 , and the corresponding edges  150  of the blades  116  over substantially the entire extent of the blade edges  128 ,  150 . A slight gap, on the order of ⅛th inch, is maintained between the radially facing edges  128  and wall surface  148 . 
     The wall  146  on the first housing part  84  has a substantially uniform diameter portion at  152  adjacent to the upstream blade edges  122 ,  136  and diverges axially outwardly therefrom to define a funnel-shaped portion at  154 . The diameter D of the intake opening  156  defined by the housing part  84  is on the order of ½ the diameter D 1  traced by the downstream edges  124 ,  138  of the blades  116 ,  118 . 
     In operation, intake fluid is funneled into the intake opening  156  at the intake region  64  and is directed by the guide surface  102  progressively radially outwardly through the transition path portion  92  to the path portion  90  defined by the volute  94 . Abrupt direction change for the fluid is avoided as the fluid enters the volute  94 . 
     At the same time, the configuration of the impeller  74  avoids the shearing action that occurs at a cut-off point/juncture  158 , corresponding to the cut-off point/juncture  50  in the blower unit  10 . The cut-off point/juncture  158  is at the apex of a V defined where two flat surfaces  160 ,  162  meet to define a transition wall. The planes of the surfaces  160 ,  162  are inclined from an axial alignment with the axis  78 . The line of the apex between the surfaces  160 ,  162  makes an acute angle with the axis  78 . 
     The drive  82  for the impeller  74  is shown as a motor  82  which is driven by a power supply  164  which may be an AC or DC power supply. 
     Alternatively, the impeller  74  can be driven by a gasoline-powered drive  166 , shown in FIG.  4 . 
     Regardless of the nature of the drive, it is desirable that the user have a readily accessible control  168  that is commonly provided directly on the handle  72 . 
     While the drive could take any form, the inherent efficiency of the impeller  74  having the above construction make it particularly suitable to be operated by a DC power supply. A motor with a DC power supply has the advantage that it can be made to operate at reduced noise levels compared to gasoline-powered drives with height efficiencies built in, the impeller  74  can be rotated at speeds to produce the same air volume as in some conventional impellers rotated at higher speeds. This translates into longer DC power supply life before recharge is necessary and lower levels of operating noise. 
     The foregoing disclosure of specific embodiments is intended to be illustrative of the broad concepts comprehended by the invention.