Patent Publication Number: US-10774487-B2

Title: Handheld blower having engine cooling flow

Description:
RELATED APPLICATION INFORMATION 
     This application is a continuation of U.S. patent application Ser. No. 14/034,104, filed Sep. 23, 2013, which claims the benefit of CN 201310054133.2, filed on Feb. 20, 2013, CN 201310108035.2, filed on Mar. 29, 2013, CN 201310109907.7, filed on Mar. 29, 2013, and CN 201310109908.1, filed on Mar. 29, 2013 the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE PRESENT DISCLOSURE 
     The present disclosure relates to electrical garden tools and, more particularly, to a handheld blower. 
     BACKGROUND 
     A garden handheld blower is mainly powered in two manners, i.e., by use of an external power supply or a battery pack. If an external power supply is used, the machine can only be used in applications with a power interface which greatly limits the application scope of the handheld blower. While using a battery pack can solve this problem, in the case of the battery pack the weight and the size of the battery pack is generally large in order to ensure sufficient usage capacity. As the capacity of the battery pack is increased, the whole weight of the handheld blower is also increased and the handling comfort of the device is accordingly decreased. Moreover, the arrangements for the members of most handheld blowers are unreasonable, which causes inflexible operation, and the operator needs to additionally provide a force to overcome the deflection of the handheld blower during operation which may cause operator fatigue after long periods of operation. 
     As for some garden handheld blowers, since the air needs to pass through the motor, the conducting wires of the motor may be fixed in two manners. In one manner, the wires are exposed in the airflow directly, thus it has a weak reliability, and the air trends to tear out the wires during a high-speed operation, so that the motor cannot be switched on. In the other manner, a fixation tool for installing the wires is arranged in the duct, which can facilitate the fixing and protection of the wires. However, due to the added members, on one hand the cost is increased and, on the other hand, the air resistance is also increased and the blowing efficiency of the whole machine is reduced. 
     Garden handheld blowers are mainly used to blow fallen leaves and small garbage on the ground. In order to blow plenty of fallen leaves on the ground and some relatively heavy garbage, the blowers are generally started to operate at the maximum speed. However, most of the current garden handheld blowers need to be operated by two hands for controlling the members so as to be rotated at the maximum speed and also to pressed the boost button for a long time so as to be operated continuously, thus the operation is inconvenient and the operator may feel fatigue during long times of operation. 
     Additionally, it is proved by experiments that in order to blow plenty of fallen leaves on the ground or some relatively heavy garbage, the blower needs a relatively large air flow rate. As for the handheld DC blower with a battery pack mounted to the housing currently in the market, the small capacity of the battery and the design limitations cause the blowing efficiency of the whole blower to be relatively low. The air flow rate of the blower is relatively small, and the working time is relatively short, and thus it cannot meet the requirements of the operator. 
     SUMMARY 
     The following describes a handheld blower with an improved air passage design and high efficiency. 
     In order to achieve the above objective, an exemplary handheld blower includes a housing, the housing including an air inlet and a duct assembly, the duct assembly including a duct connected with the housing, a motor and a fan mounted in the duct, a battery mounted on the housing, a handle, and a blowpipe connected to the housing by the duct assembly where the blowpipe defines a central axis. Along the direction of the central axis, the area of the flowing cross-section of an air passage at the rear end of the fan adjacent to the air inlet is larger than that of the flowing cross-section of an air outlet of the blowpipe. A flow-through area is formed between the inner wall of the housing and a hub of the fan, and the rate between the area of the flow cross-section of the air outlet of the blowpipe and the area of the flow cross-section of the flow-through area at the position of the fan is greater than or equal to 0.8. 
     The described handheld blower will also have a long working time and a large air flow rate. 
     In order to achieve the above objective, an exemplary handheld blower includes a housing, the housing including an air inlet and a duct assembly, the duct assembly including a duct connected with the housing, a motor and a fan mounted in the duct, a blowpipe connected to the housing by the duct assembly, and a battery mounted on the housing where the battery of the handheld blower has a capacity larger than 170 wh. 
     The described handheld blower with also have improved parameters of the axial fan and a large air flow rate. 
     In order to achieve the above objective, an exemplary handheld blower includes a housing, the housing including an air inlet and a duct assembly, the duct assembly including a duct connected with the housing, a motor and a fan mounted in the duct, and the fan being connected to the motor, a blowpipe connected to the housing by the duct assembly, a battery mounted on the housing where the fan is an axial fan having an outer diameter in the range from 85 mm to 140 mm. 
     The handheld blower defines a central axis on the blowpipe, and along the direction of the central axis, the area of the flowing cross-section of the air passage at the rear end of the fan adjacent to the air inlet is larger than that at the air outlet of the blowpipe. Such arrangement can effectively improve the flow characteristic of the airflow and enhance the blowing efficiency. Additionally, the rate between the area of the flow cross-section of the air outlet of the blowpipe and the area of the flow cross-section of the flow-through area at the position of the fan is larger than or equal to 0.8, which effectively reduces the air resistance caused by the airflow and the airflow loss on the wall of the air passage as well as the loss of the high-speed airflow in the blowpipe, thus the blowing efficiency of the whole machine may be increased. 
     The battery of the handheld blower has a capacity larger than 170 wh, which can provide sufficient power to the blower, thus it can increase the working time, enhance the air flow rate, and reduce the times of changing the battery pack, and the operation is more convenient. 
     The handheld blower uses an axial fan having an outer diameter in the range from 85 mm to 140 mm. Such arrangement enables the blower to have a large air flow rate sufficient to blow plenty of fallen leaves on the ground or some relatively heavy garbage thereby meeting the requirements of the operator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective schematic view of an exemplary handheld blower constructed according to the description which follows; 
         FIG. 2  is a front view of the handheld blower of  FIG. 1  with the housing removed; 
         FIG. 3  is a front view of the handheld blower of  FIG. 1 ; 
         FIG. 4  is a top view of the handheld blower of  FIG. 1 ; 
         FIG. 5  is a schematic view illustrating the connection between the air intake box and the duct assembly of the handheld blower of  FIG. 1 ; 
         FIG. 6  is a schematic view of the handle of the handheld blower of  FIG. 1 ; 
         FIG. 7  is a sectional view of the duct assembly of the handheld blower of  FIG. 1 ; 
         FIG. 8  is a perspective view of the duct assembly of the handheld blower of  FIG. 1  with a portion of the duct and the connecting pipe removed; and 
         FIG. 9  illustrates the curve of the functional relationship between the outer diameter of the blade of the fan and the blowing efficiency of the handheld blower of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     In order to better understand the technical content of the present invention, the following will describe preferred embodiments with reference to the drawings in detail. 
     Referring to  FIG. 1  and  FIG. 2 , in one embodiment of the present invention, the handheld blower  10  includes a housing  11 , an air intake box  12 , a handle  13 , a control assembly  14 , a battery  15 , a duct assembly  17  and a blowpipe  19 . The battery  15  and the duct assembly  17  are arranged on opposite ends of the housing  11  and the handle  13  is arranged on the housing  11 . The housing  11  is connected with the blowpipe  19  by the duct assembly  17 , and the air intake box  12  is arranged in the housing  11 . 
     Referring to  FIGS. 2 and 3 , the housing  11  includes an accommodating chamber  110 , a mounting portion  111 , a main air inlet  112 , a secondary air inlet  113 , a side air inlet  114  and a bending portion  115 . The accommodating chamber  110  is formed in the housing  11 , the air intake box  12  is mounted in the accommodating chamber  110 , and one end of the duct assembly  17  is fixedly mounted in the mounting portion  111 . The main air inlet  112  and the secondary air inlet  113  are arranged on the bottom of the housing  11 , and the side air inlet  114  is arranged on a side wall of the housing  11 . The airflow enters from the main air inlet  112  or the secondary air inlet  113 , and is guided by the bending portion  115  to flow into the duct assembly  17  from the mounting portion  111 . The side air inlet  114  can facilitate the entrance of the airflow and obtain a good entrance effect of the airflow. It should be noted that the side air inlet  114  may also be omitted. 
     Referring to  FIG. 5 , the air intake box  12  includes a bottom air intake portion  120 , a rear air intake portion  121 , a side air intake portion  122  and an air outlet  123 . The bottom air intake portion  120  and the rear air intake portion  121  are each configured as a grille structure and the rear air intake portion  121  is configured as a ramp structure corresponding to the bending portion  115  of the housing  11 . The air outlet  123  of the air intake box  12  is connected with an air intake end of the duct assembly  17 . As such, the air intake box  12  and the duct assembly  17  may form an independent working unit  18 , and the bottom air intake portion  120 , the rear air intake portion  121  and the side air intake portion  122  of the air intake box  12  form a plurality of blowing passages with the air outlet  123  respectively. Thus, as long as the independent working unit  18  can be mounted into the housing to form the blowing passages, the machine can effect a blowing function no matter how the housing  11  changes. In this way, the shape of the handheld blower may be changed quickly without changing the inner working units. In the illustrated embodiment, the main air inlet  112  of the housing  11 , the bottom air intake portion  120  and the air outlet  123  of the air intake box  12  cooperatively define a first blowing passage, the secondary air inlet  113  of the housing  11 , the rear air intake portion  121  and the air outlet  123  of the air intake box  12  cooperatively define a second blowing passage, and the side air inlet  114  of the housing  11 , the side air intake portion  122  and the air outlet  123  of the air intake box  12  cooperatively define a third blowing passage. 
     Referring to  FIGS. 1, 2, 4 and 6 , the handle  13  used to handle the handheld blower  10  is arranged on the bending portion  115  of the housing  11  and located above the housing  11  and the battery  15 . The handle  13  includes a gripping portion  130 , a battery mounting portion  131  and a speed adjusting portion  132 , wherein the gripping portion  130  is arranged between the battery mounting portion  131  and the speed adjusting portion  132 . 
     In the illustrated embodiment, a central axis L 1  is defined on the blowpipe  19  in the length direction. The gravity centre G of the whole blower is located in a plane P 1 , and the plane P 1  is substantially perpendicular to the working ground P 2  and parallel to the central axis L 1 . The housing  11 , the battery  15 , the duct assembly  17  and the blowpipe  19  are substantially arranged along the same line, and the gripping portion  130  of the handle  13  is arranged on opposite sides of the plane P 1 . Preferably, the gripping portion  130  of the handle  13  is symmetrically arranged on opposite sides of the plane P 1 . Thus, the machine has a compact structure, and the gravity centre is close to the gripping portion, which reduces the force needed to overcome the deflection of the handheld blower during operation, enhances the comfort of the handling and reduces the tiredness during long times of handling operation. It should be noted that the battery may also be arranged above or below the housing  11 . The housing  11 , the duct assembly  17  and the blowpipe  19  are substantially arranged along the same line. The gripping portion  130  of the handle  13  is arranged on opposite sides of the plane in which the gravity center is located. The plane is parallel to the axis of the blowpipe  19  and substantially perpendicular to the working ground P 2  which is defined as a horizontal plane. 
     The control assembly  14  is used to control the switching-on or switching-off and the rotating speed of the handheld blower. The control assembly  14  includes a trigger  140  for controlling the switching-on or switching-off of the handheld blower, a locking button  141  for preventing a mistaken startup of the handheld blower, a boost button  142  for controlling the handheld blower to rotate at the maximum rotating speed and a speed adjusting button  143  for adjusting the rotating speed of the motor  172  of the handheld blower. The speed adjusting button  143  is arranged on the speed adjusting portion  132 . For the sake of convenience, the trigger  140 , the locking button  141  and the boost button  142  are all arranged on the gripping portion  130 . With this positional arrangement, the operator can press the trigger  140  while operating the boost button  142  by his thumb. Additionally, if the machine needs to be operated under high-speed blowing condition for a long time, the operator can press the boost button  142  and the locking button  141  by his palm simultaneously while handling the gripping portion  130 , and can press the trigger  140  by his fingers. In this way, the handheld blower may be started by one-hand operation and kept to be operated at the maximum rotating speed, which reduces the tiredness of the hand during the operation and enhances the comfort of the handling. The locking button  141  is an assistant switch member for preventing the mistaken startup of the handheld blower. It may be appreciated that the locking button  141  may be omitted, and the operator can only use the trigger  140  and the boost button  142  to start up the handheld blower and keep a continuous operation. 
     The battery  15  is mounted to the housing  11  by the battery mounting portion  131 , and used to provide power to the handheld blower. The housing  11  is provided with an ejecting head  116  for cooperating with the battery  15  and a battery mounting base. The ejecting head  116  is connected with a spring  117  and may rotate relative to the housing. When the battery  15  is assembled to the housing  11 , the front end of the battery  15  pushes the ejecting head  116  to rotate against the elastic force of the spring  117  and deflect to a predetermined position. When the battery  15  is disassembled, the ejecting head  116  pushes the battery  15  towards the disassembling direction under the action of the spring  117 . 
     The battery mounting portion  131  is provided with a battery latch  1311  for locking the battery  15  on the housing  11 . The battery latch  1311  is further provided with a releasing button  1312  linked with it. By pressing or pushing the releasing button  1312 , the battery latch  1311  is disengaged from the battery  15 , and then the battery  15  may be removed conveniently under the action of the ejecting head  116 . Certainly, the battery mounting portion  131  may also be arranged on the housing  11  as long as it can lock the battery  15  to the battery mounting base arranged on the housing  11  when mounting the battery  15 . 
     Referring to  FIG. 7  and  FIG. 8 , the duct assembly  17  includes a connecting pipe  170  connected with the blowpipe  19 , a duct  171  connected to the housing  11 , a motor  172  and a fan  173 . The motor  172  is connected with the trigger  140  of the control assembly  14  by wires, and the connecting pipe  170  is locked with the duct  171 . A supporting ring  174  for accommodating the motor  172  is arranged in the connecting pipe  170  and the duct  171 . The motor  172  is mounted in the supporting ring  174  and the fan  173  is connected with the output shaft of the motor  172 . A plurality of radial air guiding ribs  175  are integrally formed in the connecting pipe  170  and the duct  171 . One end of each air guiding rib  175  is connected to the inner wall of the connecting pipe  170  or the duct  171 , and the other end is connected to the supporting ring  174 , wherein at least one air guiding rib  175  is provided with a channel  176  for the wires of the motor  172  to pass through. This arrangement can not only increase the reliability of positioning the wires and reduce the air resistance, but also eliminate the need of added members, thus the wires can be fixed easily, reliably and simply during the assembly. It may be appreciated that if the length of the duct  171  is sufficient, the connecting pipe  170  may be omitted, and the supporting ring  174  and the air guiding ribs  175  are directly arranged on the duct  171 . The duct  171  has an air intake portion  1711  which is configured as a lip edge structure for facilitating the guidance of air in order to reduce the noise at the air intake portion  1711  of the duct. The above lip edge structure may be formed with the duct  171  in one piece or may be formed as a single member to be mounted to the duct  171 . 
     In an embodiment of the present invention, the fan  173  is an axial fan, and the motor  172  is a brushless DC motor. The fan  173  is driven by the motor  172 , and includes a hub  1731  mounted to the rotating shaft of the motor and a plurality of blades  1732  mounted to the hub  1731 . The blades  1732  and the hub  1731  may be formed in one piece or may be formed separately and then assembled together. 
     One end of the fan  173  adjacent to the housing  11  is provided with a fairing  177 , and the other end of the fan  173  adjacent to the blowpipe  19  is connected with the motor  172 . Since the fan  173  is an axial fan, after passing through the first blowing passage, the second blowing passage, the third blowing passage and entering the fan  173 , the airflow axially passes through the air guiding ribs  175  under the action of the fan  173  and flows into the blowpipe  19 . In an embodiment of the present invention, the supporting ring  174  includes an accommodating portion  1741  for accommodating the motor  172  and an air guiding portion  1742 . The front end of the accommodating portion  1741  is provided with an opening, and the air guiding portion  1742  is a tapered structure integrally formed with the accommodating portion  1741 . The air guiding portion  1742  is arranged on one end of the supporting ring  174  adjacent to the blowpipe  19  and has a plurality of air intakes for the cooling airflows to pass through. During the blowing process, since the air pressure around the motor  172  is larger than that around the fan  173 , a secondary airflow is generated under the action of pressure differential. The secondary airflow passes through the air intakes of the air guiding portion  1742  and flows into the supporting ring  174  to cool the interior of the motor  172 , and finally flows out from the opening on the front end of the accommodating portion  1741 , thus the motor  172  may be cooled during the blowing process. 
     Still referring to  FIG. 3 , in order to facilitate the carrying of the machine, the handheld blower of the present invention further includes a strap with two ends connected to two hanging holes  118 ,  119  on the housing  11  respectively. The two hanging holes  118 ,  119  have the same distance from the center of the gripping portion  130 , and the center point of the connecting line between the positions of the two hanging holes  118 ,  119  is located around the gravity center line of the whole machine. 
     The handheld DC blower is mainly used to blow fallen leaves and small garbage on the ground. It is proved by research that, in order to blow plenty of the fallen leaves on the ground or some garbage, the air flow rate of the handheld blower generally needs to be larger than 395 cfm. The handheld DC blower in the current market with a battery pack mounted on the housing has a small battery capacity and a relatively low blowing efficiency, and thus cannot meet the requirement that the air flow rate is larger than 395 cfm and the working time is more than 5 min. Thus, in order to obtain relatively large air flow rate and relatively high blowing efficiency, it is required to optimize the battery capacity, the brushless DC motor, the parameters of the axial fan and the air passage design. 
     In order to obtain the desired air flow rate and working time, the capacity of the battery is generally larger than 170 wh. Typically, the capacity of the battery is proportional to the weight itself. As for the handheld blower, due to the requirement for the weight of the whole machine, the capacity of the battery pack is preferably in the range from 170 wh to 400 wh. On one hand, if the capacity of the battery pack is too small, the machine cannot meet the requirement for the air flow rate and the working time. On the other hand, if the capacity of the battery pack is too large, operator fatigue during operation may be increased, which is not convenient for long times of operation. 
     Table 1 lists the effective working time of the handheld blower operated at the maximum air flow rate and the minimum air flow rate when the capacity of the battery is 200 wh and 300 wh. It can be seen from table 1 that if the capacity of the battery is constant, the air flow rate is inversely proportional to the working time, that is to say, the larger the air flow rate is, the shorter the working time will be. In accordance with human engineering, through a number of simulation experiment analysis for the weight of the whole machine and the bearing degree of people, it can be determined that the performance parameters of the handheld blower suitable for most operators are as follows: the air flow rate is in the range from 385 cfm to 700 cfm and the working time is in the range from 20 min to 75 min. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Capacity of the battery 
                 Maximum air flow rate 
                 Minimum air flow rate 
               
               
                   
               
             
            
               
                 200 wh 
                 36 min 
                 120 min 
               
               
                 300 wh 
                 54 min 
                 180 min 
               
               
                   
               
            
           
         
       
     
     If the capacity of the battery is constant, in order to obtain a handheld DC handheld blower with an air flow rate larger than 395 cfm and higher blowing efficiency, it is required to optimize the brushless DC motor, the parameters of the axial fan and the air passage design. 
     Referring to  FIGS. 7 and 8  again, the motor  172  is accommodated into the supporting ring  174  arranged in the duct  171  and the connecting pipe  170 , and the hub  1731  of the axial fan  173  is mounted to the rotating shaft of the motor  172 . In accordance with the principle of aerodynamics, in order to reduce the air resistance and increase the air speed, the contours of the fairing  177 , the hub  1731  and the supporting ring  174  are designed with a streamlined shape, thus the diameter of the motor  172  may define the diameter of the hub  1731 . In addition, when designing the axial fan, the ratio of the root diameter to the top diameter of the blade, i.e., the ratio of the diameter of the hub of the fan to the outer diameter of the blade, hereinafter referred to as hub ratio, is an important parameter. With the same outer diameter of the blade and the hub, the smaller hub and the longer blades are more suitable for the axial flow blower having low pressure and high flow rate. It is proved by simulation analysis that the blowing efficiency of the blades is relatively high when the hub ratio is in the range from 0.25 to 0.45. Thus, if the diameter of the motor is relatively large, the diameter of the hub would be relatively large accordingly. In order to set the parameter of the hub ratio in the optimal scope so as to obtain a higher blowing efficiency, the diameter of the blade would be increased accordingly, and thus the volume of the duct is increased and the volume of the whole machine is increased. As a result, both the shape design and the operating comfort during the actual operation will be affected adversely. Thus, the diameter of the motor is preferably no larger than 35 mm. In this way, the whole machine is light in weight and occupies a smaller space. In accordance with the scope of the hub ratio, it can be further concluded that the scope of the outer diameter of the blade is in the range from 78 mm to 140 mm, thus the blowing efficiency is higher. As shown in  FIG. 9 , C 1  and C 2  are curves illustrating the functional relationship between the outer diameter of the blade and the blowing efficiency, which is obtained by simulation modeling and analysis when the air flow rate is 560 cfm and 500 cfm respectively. It can be seen from  FIG. 9  that the best blowing efficiency is obtained when the outer diameter of the blade is in the range from 85 mm to 140 mm. The blowing efficiency herein is defined as the ratio of the work caused by the flow of the airflow to the work consumed by the rotation of the blades of the fan. 
     Further, as the diameter of the motor is smaller than 35 mm and the ratio of the air flow rate to the diameter of the motor is larger than 12 cfm/mm, the handheld blower of the present invention can obtain higher blowing efficiency with a small motor as compared with the common handheld blower. 
     The following will describe the air passage design of the present invention in detail. Referring to  FIG. 2  again, along the direction of the axis L 1 , the flow cross-section S 1  of the air passage at the rear end of the fan  173  adjacent to the air inlet  112  is larger than the flow cross-section S 3  at the air outlet  191  of the blowpipe  19 , and a circular flow-through area is formed between the inner wall of the duct  171  and the hub  1731  of the fan. The ratio of the area of the flow cross-section S 3  of the air outlet  191  of the blowpipe  19  relative to the area of the flow cross-section S 2  of the circular flow-through area at the position of the axial fan  173  is preferably greater than or equal to 0.8. This arrangement can effectively improve the flow characteristic of the airflow, and enhance the blowing efficiency. Meanwhile, the air passage between the fan  173  and the air outlet  191  defines an outer contour line L 2  having an angle relative to the axis L 1 . Preferably, the angle between the axis L 1  and the outer contour line L 2  is smaller than 8° because a large angle can cause a certain air resistance against the airflow, so that the loss of the airflow in the wall of the air passage is increased and the loss of the high-speed airflow in the blowpipe  19  is also increased, which causes the reduction of the blowing efficiency of the whole machine. With the optimization for the above two parameters, a desired flow of airflow may be obtained, while a relative small pressure loss is obtained in the blowpipe  19 , which can effectively improve the blowing efficiency. 
     In order to obtain a sufficient air flow rate at the air outlet  191 , after being calculated by CFD (Computational Fluid Dynamics) and test data, it is desired to design a relatively large area of the air outlet. Preferably, the area of the cross-section of the air outlet  191  is configured to be larger than 4300 mm 2 . Certainly, the air speed will reduce as the blowing area increases, thus the area of the air outlet is preferably in the range from 4300 mm 2  to 8000 mm 2  according to the actual operation. 
     By optimizing the capacity of the battery, the brushless DC motor and the parameters design of the axial fan and improving the air passage design, when the capacity of the battery is in the range from 170 wh to 400 wh, the air flow rate of the handheld blower may be larger than 395 cfm, and the working time may be larger than 5 min, especially when the air flow rate is in the range from 430 cfm to 700 cfm. Meanwhile, it is also ensured that the ratio of the air flow rate to the input power is larger than or equal to 0.7 cfm/w when the blower is operated at the maximum air flow rate, thus the blowing efficiency can be improved significantly. 
     Although the above embodiments have disclosed the present invention, they are not intended to limit the invention. Various changes and modifications will occur to a person skilled in the art without departing the spirit and scope of the present invention. Thus, the protection scope of the invention shall be determined by the attached claims.