Patent Publication Number: US-9885370-B2

Title: Diffuser

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201410189647.3 filed in The People&#39;s Republic of China on May 7, 2014, the entire contents of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to a diffuser, as used in a blower or the like. 
     BACKGROUND OF THE INVENTION 
     Blowers are commonly used in appliances such as hand dryers and vacuum cleaners to provide airflow. A typical blower includes a housing with a motor, diffuser and impeller mounted therein. The impeller and the motor are respectively disposed at opposite sides of the diffuser. The motor rotates the impeller to produce the airflow. The airflow enters an air inlet of the impeller via an inlet of the housing. The diffuser guides the airflow from the impeller to the motor side where the air escapes through an outlet of the housing. 
     The design of the diffuser is of critical importance because it directly affects the efficiency of the blower. High efficiency diffusers can increase the amount of airflow or reduce the power consumed to provide the same amount of airflow. 
     Thus, there is a desire for a diffuser for a blower that can increase the efficiency of the blower. 
     SUMMARY OF THE INVENTION 
     Accordingly, in one aspect thereof, the present invention provides a diffuser comprising: a plate-shaped body, the body comprising an air inlet side and an air outlet side; a plurality of diffusion blades disposed at an circumferential edge of the body, each of the diffusion blades comprises an inclined guide surface, the guide surface having a starting end at the air inlet side of the body and a terminating end at the air outlet side of the body, the guide surface extending from the starting end to the terminating end along a circumferential path of the body and has a width gradually increasing from the starting end to the terminating end; and a plurality of air outlets at the terminating ends of the guide surfaces of the diffusion blades, each of the air outlets fluidly connects the terminating end of a corresponding one of the guide surfaces and the air outlet side of the body, wherein the body comprises an air inlet surface at the air inlet side, and the guide surface is inclined with respect to the air inlet surface at an inclination angle ranging between 18 to 25 degrees. 
     Preferably, each of the diffusion blades further comprises a curved connecting wall interconnecting an inner edge of the guide surface and the body, the curved connecting wall comprises a starting end connected with the starting end of the guide surface and a terminating end connected with the terminating end of the guide surface, and the connecting wall gradually departs from an outer edge of the guide surface to form the curved shape. 
     Preferably, the curved connecting wall comprises a plurality of curved sections having different radii of curvature. 
     Preferably, the curved connecting wall has an inlet angle ranging between 16 to 23 degrees. 
     Preferably, wherein the curved connecting wall has an outlet angle ranging between 28 to 36 degrees. 
     Preferably, the body comprises an air inlet surface at the air inlet side, an air outlet surface at the air outlet side, and an outer circumferential surface interconnecting circumferential edges of the air inlet surface and the air outlet surface, a projection of the outer circumferential surface along a center axis of the body is a circle in shape, and outer edges of the guide surfaces of the diffusion blades are located on the circle. 
     Preferably, the body comprises an air outlet surface at the air outlet side, the air outlet surface defines a cavity in flow communication with the air outlets. 
     Preferably, the diffuser further comprises a plurality of mounting posts disposed at the air outlet side. 
     According to a second aspect, the present invention provides a blower comprising: a motor having an output shaft; an impeller fixed to the output shaft to be driven to generate an airflow; and the diffuser of Claim  1  disposed downstream of the impeller in the direction of the airflow and an outer housing that houses the impeller and diffuser. 
     Preferably, the impeller comprises a plurality of fan blades, each of the fan blades having an outlet angle ranging between 22 to 35 degrees. 
     Preferably, the motor is mounted in a motor housing, one end of the housing is fixed to the outer housing, and the other end of the motor housing forms a pair of diametrically-opposed air ports. 
     Preferably, the motor is a universal motor comprising a pair of diametrically-opposed brushes, the brushes deviating from the air ports of the motor housing. 
     In view of the foregoing, the diffuser of the present invention is optimally configured to be well matched with the impeller. Each diffusion blade has an appropriately-sized flow passage with small flow resistance, thus achieving a good diffusion result. Therefore, the efficiency of the blower is greatly enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment 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 labeled 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  illustrates a diffuser according to the preferred embodiment of the present invention, viewed from the top; 
         FIG. 2  illustrates the diffuser of  FIG. 1 , viewed from below; 
         FIG. 3  is a vector diagram of a part of the diffuser of  FIG. 1 ; 
         FIG. 4  is a plan of the diffuser of  FIG. 1 ; 
         FIG. 5  illustrates a blower employing the diffuser of  FIG. 1 , in a partially assembled state; 
         FIG. 6  is a sectional view of the blower of  FIG. 5  with the motor removed; 
         FIG. 7  is a plan view of the blower of  FIG. 5  with an outer housing removed; and 
         FIG. 8  illustrates the blower of  FIG. 5 , complete with a motor housing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  and  FIG. 2 , a diffuser  10  according to the preferred embodiment, includes a plate-shaped body  12  and a plurality of diffusion blades  14  disposed along a circumferential edge of the body  12 . 
     The body  12  includes a first surface or air inlet surface  122 , a second surface or air outlet surface  124  opposite the air inlet surface  122 , and an outer circumferential surface  126  interconnecting circumferential edges of the air inlet surface  122  and the air outlet surface  124 . A side of the body  12  containing the air inlet surface  122  is called the air inlet side, and a side of the body  12  containing the air outlet surface  122  is called the air outlet side. Preferably, a projection of the outer circumferential surface  126  along an axial direction of the diffuser is a closed circle in shape. The axial direction of the diffuser is the axial direction of the blower to which the diffuser is to be fitted. 
     Each diffusion blade  14  includes a guide surface  142  and a connecting wall  144  disposed at an inner side of the guide surface  142  and connected with the body  12 . 
     The guide surface  142  is an inclined surface oriented toward the air inlet side of the body  12 , which has a starting end adjacent an outer edge of the air inlet surface  122  of the body  12  and a terminating end adjacent an outer edge of the air outlet surface  124 . The guide surface  142  extends from the starting end to the terminating end along the circumferential direction, with its width gradually increasing from the starting end to the terminating end. The guide surface  142  has an outer edge  146  located on the outer circumferential surface  126  of the body  12 . Each of the diffusion blades  14  further includes a sloping surface  143  extending from the terminating end of a corresponding one of the guide surfaces  142  toward the air inlet side of the body  12 . 
     The connecting wall  144  connects the inner edge of the guide surface  142  to the body  12 . Specifically, the connecting wall  144  extends from the air inlet surface  122  to the air outlet surface  124  of the body  12  in an axial direction of the diffuser. A starting end of the connecting wall  144  is connected with the starting end of the guide surface  142 , and a terminating end of the connecting wall  144  is connected with the terminating end of the guide surface  142 . From the starting end to the terminating end, the connecting wall  144  gradually departs from the outer circumferential surface  126  to form a curved shape and make the width of the guide surface  142  gradually increase. The curved connecting wall  144  may include multiple curved sections. In this embodiment, the curved connecting wall  144  is formed by two curved sections. However, the curved connecting wall may be made by three or four curved section. Each curved section has a different radius. The use of multiple curved sections allows the air channel to gently change the direction of the air while being easier to manufacture than a curve with a continuously changing radius. 
     The air outlet surface  124  of the body  12  is recessed to form a cavity  128  bounded by inner surfaces of the connecting walls  144 . 
     An air outlet  16  is formed between the terminating end of each connecting wall  144 , the terminating end of one corresponding guide surface  142 , the outer circumferential surface  126  of the body and the air inlet surface  122  of the body. Each air outlet  16  is in flow communication with the cavity  128 , such that air introduced from the starting end of the guide surface  142 , after flowing over the guide surface  142 , can enter the cavity  128  at the air outlet side of the body via the air outlet  16  adjacent the terminating end  16  of the guide surface  142 . 
     A plurality of mounting posts  130  is disposed on the air outlet surface  124  of the diffuser  10 , for mounting the diffuser  10  to another device, as described below. Each of the diffusion blades  14  further includes an outer wall  145  extending from a rim of one air outlet  16  along an outer edge of the guide surface  142 . 
       FIG. 3  illustrates an inclination angle of the guide surface of the diffuser of  FIG. 1 . In this disclosure, the inclination angle of the guide surface refers to an angle α between a projection of the inner edge of the guide surface  142  and a projection of the air inlet surface  122  on an axial plane on which the starting end A of the guide surface  142  and a center of the body  12  are located. Preferably, the inclination angle α of the guide surface ranges between 18 to 25 degrees. In this embodiment, the guide surface  142  is a flat surface inclined from the starting end A toward the terminating end B, with same height at the inner edge and outer edge thereof. It should be understood that the guide surface  142  may be slightly inclined inwardly or outwardly. Furthermore, the guide surface  142  is not intended to be limited to the flat surface. Rather, the guide surface  142  may for example be a slightly concave-curved or convex-curved surface. 
       FIG. 4  is a top plan view of  FIG. 1 . A tangent line L 1  of the inner edge of the guide surface  142  at the starting end A and a tangent line L 2  of a circle, formed by the diffuser, at the starting end A form an angle β, referred to as the inlet angle, wherein the circle has a center at a center O of the body  12  and a radius equal to the distance between the starting end A of the inner edge of the guide surface  142  and the body center O. Preferably, the inlet angle β ranges between 16 to 23 degrees. A tangent line L 3  of the inner edge of the guide surface  142  at the terminating end B and a tangent line L 4  of a circle at the terminating end B form an angle r, referred to as the outlet angle, wherein the circle has a center at the body center O and a radius equal to the distance between the terminating end B of the inner edge of the guide surface  142  and the body center O. Preferably, the outlet angle r ranges between 28 to 36 degrees. 
     In the diffuser exemplified above, each diffusion blade has an appropriately-sized flow passage with small flow resistance, thus achieving a good diffusion result. 
       FIG. 5  illustrates a blower employing the above-described diffuser. The blower is shown in a partially assembled state without motor windings and a motor housing, for ease of understanding.  FIG. 6  is a sectional view of the blower of  FIG. 5  with a motor removed.  FIG. 7  is a top view of the blower of  FIG. 5  with an outer housing and an upper plate of an impeller removed.  FIG. 8  illustrates the blower of  FIG. 5  complete with the motor housing assembled. 
     Referring to  FIG. 5  and  FIG. 6 , the blower includes a motor  30 , an impeller  50  fixed to an output shaft  32  of the motor  30 , a diffuser  10  fixed to the motor  30 , and an outer housing  70  that houses the impeller  50  and the diffuser  10 . 
     The impeller  50  includes a lower plate  52 , an upper plate  54  and blades  56  disposed between the lower plate  52  and the upper plate  54 . The lower plate  52  is fixedly mounted to one end of the output shaft  32  of the motor  30  by a screw nut or other known fastening means. A hole in the upper plate  56  centrally forms an air inlet  58 . The outer housing  70  forms an opening  72  corresponding to the air inlet  58  of the upper plate  56 , for entry of the airflow. 
     The diffuser  10  is disposed below the lower plate  52  of the impeller, i.e. on the side of the impeller  50  where the motor  30  is located. The body  12  of the diffuser  10  forms a center through hole  125 , and a bearing seat  127  is disposed at the air outlet side of the body  12 . A bearing  129  is mounted in the bearing seat  127 . Preferably, the bearing  129  is a ball bearing with an outer ring abutting against the air outlet surface  124  of the body  12  and an inner ring fitted to the output shaft  32 . The end of the output shaft  32  of the motor  30  extends through the through hole  125  to join with the impeller  50 . The mounting posts  130  are fixedly connected to a stator core of the motor  30 . An axial positioning structure  60  is further disposed between the diffuser  10  and the impeller  50 . Specifically, the positioning structure  60  is a positioning plate having a center through hole and a flange  62  formed around an edge of the through hole. The flange  62  of the positioning plate  60  is inserted into the through hole  125  of the diffuser  10  to abut against an inner ring of the bearing  129 . The lower plate  52  of the impeller is captured between the positioning plate and the screw nut fitted to the end of the output shaft. 
     Referring to  FIG. 7 , preferably, an outer edge of the lower plate  52  of the impeller  50  extends beyond the inner edge of the terminating end of the guide surface  142 , and an outlet angle θ of the blades  56  of the impeller  50  (i.e. the angle formed between a tangent line of the blade at a terminating end thereof and a tangent line of a circle at the terminating end of the blade, wherein the circle has a center at a center of the impeller and a radius equal to the distance between the terminating end of the blade and the impeller center) ranges between 22 to 35 degrees. This configuration allows the guide surface  142  of the diffuser  10  to be matched with the impeller  50 , such that the airflow out of the impeller  50  can smoothly flow over the guide surface  142  of the diffuser  10 , thus enhancing the efficiency of the blower. 
     Preferably, the motor  30  is a universal motor. During operation of the motor  30 , the impeller  50  is driven by the motor output shaft  32  to generate the airflow. The airflow enters the housing  70  via the opening  72 , enters the impeller  50  via the air inlet  58 , and flows out of the impeller  50  via passages formed between the blades  56 . The airflow in turn flows from the air inlet side (i.e. the near-impeller side) to the air outlet side (i.e. the near-motor side) of the diffuser  10  along the guide surface  142  of the diffuser  10 . 
     Referring to  FIG. 8 , the blower further includes a motor housing  80  for mounting the motor  30 . One end of the housing  80  is fixed to the outer housing  70 , and the other end forms a plurality of air ports  82 . Preferably, the motor housing  80  forms a pair of diametrically-opposed air ports  82  each including a pair of outwardly inclined sides  84 . The motor comprises a pair of diametrically-opposed brushes. The brushes do not align with the air ports of the motor housing. The airflow flowing over the motor  30  flows out of the housing  80  via the air ports  82 . The blower creates a vacuum at the inlet and pressurized airflow at the air ports. 
     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 or feature but do not preclude the presence of additional items or features. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
     The embodiments described above are provided by way of example only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims.