Blower / vacuum device tool

Abstract

A blower / vacuum device tool with reduced fan blade noise is provided. The tool includes a body extending between a first end and a second end and defining an airflow conduit therethrough; and a fan assembly. The fan assembly includes an axial fan having a plurality of fan blades nb and a motor rotatably connected to the axial fan. When nb is in the range of 17-45, the blade compactness of the axial fan is in the range of 0.0464 nb < = blade compactness < = 0.089 nb, the blade compactness is calculated by the equation blade compactness = c / s, c is the length of the chord line of the fan blade, s = 2 pi rm / nb, and rm is the average radius of the fan blade. Blade pass-through frequency BPF of a fan assembly greater than 6 KHz when the motor is operating at a speed of between 21000-38000 revolutions per minute RPM, blade pass-through frequency from equation

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 592,473, filed October 23, 2023, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates generally to outdoor tools, such as blowers, vacuum tools, and / or combination blower / vacuum tools, and more particularly to improved fan blade noise in such tools. BACKGROUND

[0004] Outdoor tools, such as blowers, vacuum tools, and combination blower / vacuum tools (collectively referred to as “blower / vacuum tools”), are commonly used to concentrate debris (e.g., leaves) using a blowing function and / or to collect debris using a suction function. Homeowners often use such blowers to clean their yards and outdoor spaces. Such battery-powered blower / vacuum tools are particularly popular due to their portability. However, there is a desire to improve various aspects of blower / vacuum tools, particularly handheld blower / vacuum tools.

[0005] One problem known with blower / vacuum tools is the level of noise generated by the fan assembly, particularly the fan blade noise generated by the blower / vacuum tool during operation. Due to the arrangement of the natural frequencies of the ear’s auditory canal, the range of human hearing is most sensitive between 2-6 KHz, with frequencies between 8-12 KHz being significantly less sensitive to human hearing, and frequencies of 16-20 KHz or higher being inaudible to humans. However, the typical fan blade pass frequency of an axial fan in a leaf blower is typically between 2.5-4 KHz, which is right in the range of human hearing that is most sensitive.

[0006] Accordingly, there is a need in the art for improved blower / vacuum tools. In particular, it would be advantageous to have a blower / vacuum tool with reduced fan blade noise. SUMMARY

[0007] Aspects and advantages of the disclosure will be set forth in part in the following description, or can be apparent from the description, or can be learned through practice of the technology.

[0008] According to one embodiment, a blower / vacuum tool is provided. The blower / vacuum tool includes a body extending between a first end and a second end, the body defining an airflow conduit therethrough; and a fan assembly disposed between the first end and the second end. The fan assembly includes a plurality of fan blades (n b) of the axial flow fan and a motor rotatably connected to the axial flow fan. When the motor is operated at a revolutions per minute (RPM) between 21,000 and 38,000, the fan assembly has a blade pass frequency (BPF) greater than 6 KHz, the blade pass frequency being calculated by the equation BPF = n / c, where n is the number of fan blades and c is the chord length of the fan blades. b The blade solidity of the axial flow fan is in the range of 0.0464n b ≤ blade solidity ≤ 0.089n b , the blade solidity being calculated by the equation blade solidity = c / s, where c is the chord length of the fan blades and s = 2πr m / n b , r m is the average radius of the fan blades.

[0009] According to another embodiment, a blower / vacuum tool is provided. The blower / vacuum tool includes a body extending between a first end and a second end, the body defining an airflow conduit therethrough; and a fan assembly disposed between the first end and the second end. The fan assembly includes an axial flow fan having a plurality of fan blades (n b ) and a motor rotatably connected to the axial flow fan. When the motor is operated at a revolutions per minute (RPM) between 21,000 and 38,000, the fan assembly has a blade pass frequency (BPF) greater than 6 KHz, the blade pass frequency being calculated by the equation BPF = n / c, where n is the number of fan blades and c is the chord length of the fan blades.

[0010] These and other features, aspects, and advantages of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the technology and, together with the description, serve to explain the principles of the technology. BRIEF DESCRIPTION OF DRAWINGS

[0011] A complete and enabling disclosure of the present application, directed to one of ordinary skill in the art, including the best mode of making and using the present system and method, is set forth in the specification, which makes reference to the drawings in which:

[0012] Figure 1 is a side view of a blower / vacuum tool according to an embodiment of the present disclosure;

[0013] Figure 2 is a side cutaway view of a blower / vacuum tool according to an embodiment of the present disclosure;

[0014] Figure 3 is a perspective view of an axial flow fan according to an embodiment of the present disclosure;

[0015] Figure 4 is a perspective view of an axial flow fan having an outer ring according to an embodiment of the present disclosure; and

[0016] Figure 5is a graphical representation of the blade solidity of an axial fan according to embodiments of the present disclosure versus the number of fan blades of the axial fan. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to embodiments of the present technology, one or more examples of which are illustrated in the drawings. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, unless otherwise contextually implied, each example is presented solely by way of explanation and is not meant to limit the technology in scope to that specifically shown. Indeed, modifications and variations that are obvious to those of skill in the art are intended to be within the scope of the technology. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a further embodiment. Thus, it is intended that this disclosure cover such modifications and variations as come within the scope of the appended claims and their equivalents. The detailed description uses numerical and letter designations to facilitate description of the drawings. Like reference numerals are used to indicate like parts throughout the several drawings.

[0018] As used herein, the terms "first", "second", and "third" can be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. A singular version of a word is intended to encompass a plural version of the word, unless the context clearly indicates otherwise. The terms "coupled", "fixed", "attached to" and the like are used to indicate either a direct or indirect connection, unless otherwise indicated by the context. As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article or apparatus that comprises a list of features is not necessarily limited only to those features but can include other features not expressly listed or inherent to such process, method, article or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0019] Approximating language, such as "approximately," "substantially," "about," or "near," as used herein, includes values that are within 10% of a stated value. When used in the context of an angle or direction, such terms include values that are within 10 degrees of the stated angle or direction. For example, "substantially perpendicular" includes any direction (e.g., clockwise or counterclockwise) that is perpendicular within 10 degrees.

[0020] The benefits, other advantages and problem solutions will be described below with respect to specific embodiments. However, the benefits, advantages, problem solutions, and any features that can cause any of the benefits, advantages, or solutions to occur or become more pronounced are not to be interpreted as critical, essential or necessary features of any or all the claims.

[0021] Generally, the present application is directed to a blower / vacuum tool having a fan assembly that produces reduced noise during operation. The fan assembly includes an axial fan and a motor. The axial fan includes a number and size of fan blades and operating characteristics of the motor, including rotational speed, that are optimized to reduce audible noise produced in the human hearing sensitive range (i.e., about 2-6 KHz) by increasing the blade pass frequency of the fan assembly to frequencies greater than 6 KHz.

[0022] Referring now to the drawings, Figure 1 A side view of a blower / vacuum tool 100 according to an example embodiment is shown. The blower / vacuum tool 100 is configured to produce an airflow along an airflow conduit 106 that extends between a first end 102 (e.g., an air inlet) and a second end 104 (e.g., an air outlet) of the blower / vacuum tool 100. The airflow conduit 106 can include a tube as shown.

[0023] As Figure 1 and Figure 2 shown, a housing 108 (e.g., a body of the blower / vacuum tool 100) can at least partially enclose components of the blower / vacuum tool 100, including an airflow generation assembly 110 that includes a fan 112 and a motor 114 that drives the fan 112, as well as various other components. For example, the airflow generation assembly 110 can be disposed between the first end 102 and the second end 104 of the airflow conduit 106. Electrical power to operate the airflow generation assembly 110 can be provided by a suitable power source, such as one or more batteries 116 that are removably coupled to the housing 108. The blower / vacuum tool 100 can be provided as a standard hand-held blower / vacuum tool having a wireless battery-powered power source. In other embodiments, the blower / vacuum tool can include a wired power source and / or a gas-powered power source. Further, the blower / vacuum tool according to the present disclosure can be a hand-held blower / vacuum tool as shown, or can be provided as a backpack blower / vacuum tool (not shown) that is adapted to be worn on the back of a user.

[0024] In example embodiments, the blower / vacuum tool can be a blower that utilizes a blowing function, e.g., generating airflow from the first end 102 as an inlet to the second end 104 as an outlet. In other example embodiments, the blower / vacuum tool can be a vacuum that utilizes a suction function, e.g., generating airflow from the second end 104 as an inlet to the first end 102 as an outlet. In other example embodiments, the blower / vacuum tool can be a combination blower / vacuum that can alternate between utilizing a blowing function and utilizing a suction function.

[0025] Still referring to Figure 1 and Figure 2 , the airflow generation assembly 110 can have an axial configuration that includes an axial flow fan 112. A motor 114 can be mounted within the housing 108. For example, the housing 108 can include a motor support 118 configured to support the motor 114 between the first end 102 and the second end 104. The motor 114 is oriented along a motor axis 120. The motor axis 120 coincides with a longitudinal axis 124 of the airflow conduit. Rotation of the motor 114 causes rotation of a main motor shaft 122 that extends along the motor axis 120. The motor shaft 122 is coupled to the fan 112, e.g., rotatably connected to the fan 112. In this way, rotation of the motor shaft 122 causes rotation of the fan 112. The motor 114 can be configured to operate at a rotational speed in a range of about 21,000 revolutions per minute (RPM) to about 38,000 RPM.

[0026] The fan 112 includes a hub 130 and a plurality of blades 132. The hub 130 can have a generally circular cross-sectional shape and can extend along the motor axis 120. The motor shaft 122 is coupled to the hub 130 and / or a fan drive shaft 134 to enable rotation to be transmitted from the motor 114 to the hub 130 or the fan drive shaft 134 and ultimately to the blades 132.

[0027] As shown in Figure 3 and Figure 4 , each respective fan blade 132 extends radially away from the hub 130. Each blade 132 extends from a root 140 and terminates at a tip 142, and has a first face 144 and a second face 146 opposite the first face 144. The root 140 contacts the hub 130 of the fan 112. The tip 142 contacts the hub 130 at a different angular position around the circumference of the hub 130 than the root 140. In another embodiment (not shown), the tip 142 can contact an adjacent blade 132 of the fan 112.

[0028] As shown in Figure 3 and Figure 4 , the fan 112 can have an inner radius r hand an outer radius r defined by the fan radius at the tips 142 of the blades t The fan 112 can include any suitable number of fan blades (also referred to herein as n b ), as further described below.

[0029] Figure 4 Embodiments of the fan 112 are shown that can include an outer ring 150 that surrounds the fan blades 132. For example, the outer ring 150 can contact the tips 142 of one or more fan blades 132 (e.g., all of the fan blades 132). In this manner, the outer ring 150 can rotate with the axial fan 112 and motor 114 during operation of the blower / vacuum tool 100.

[0030] In some aspects of the present invention, such as generally shown in Figure 2 the outer ring 150 can have an inner diameter 152 equal to 2r t The inner diameter 152 can be generally equal to the inner diameter of the first end 102 and / or the inner diameter of the second end 104. For example, the inner diameter 152 can be generally equal to the inner diameter of the first end 102 and the inner diameter of the second end 104. Further, the longitudinal axis 124 can extend through a center point of the first end 102, a center point of the outer ring 150, and a center point of the second end 104. In this manner, the airflow conduit can have a generally constant diameter along the length of the airflow conduit 106, thereby reducing disturbances to the flow within the airflow conduit.

[0031] The present inventors have discovered that the blade pass frequency of the blades of the blower / vacuum tool 100 can correspond to the sound frequency produced by the axial fan of the tool 100. The blade pass frequency can be calculated using the following equation: In this regard, the number of blades (also referred to herein as n b ) and the rotational speed of the fan can directly affect the sound frequency produced by the blower / vacuum tool 100. Since human hearing is most sensitive to sound frequencies between 2-6 KHz, and hearing sensitivity decreases and / or weakens above 6 KHz, the present inventors have discovered that achieving a higher blade pass frequency can therefore reduce the audible noise produced by the blower / vacuum tool 100. Based on the provided equation, the present inventors have discovered that in order to achieve a higher blade pass frequency above 6 KHz and therefore reduce the audible noise produced, the motor rotational speed can be increased, the number of fan blades 132 can be increased, or both the motor rotational speed and the number of fan blades 132 can be increased.

[0032] In the blower / vacuum tool 100 of the present utility model, as mentioned above, the motor can be configured to rotate at a speed between about 21,000 - 38,000 RPM. As human hearing is most sensitive to sound frequencies between 2-6 kHz, the present inventors have found that it can be desirable to provide a blower / vacuum tool 100 with a blade pass frequency greater than 6 kHz. Thus, when the blower / vacuum tool 100 can operate with a motor speed as low as 21,000 RPM, the present inventors have found that it can be desirable to implement a fan 112 with at least 17 fan blades 132.

[0033] Further, it can be desirable to increase the number of fan blades 132 provided on the fan 112. Blade solidity is a measure of fan blade spacing, which is directly affected by the number of blades provided on a given fan. Blade solidity is defined by the equation: Blade Solidity = c / s, where s = 2πr m / n b In this equation, c is the length of the chord line of the fan blade, r m is the average radius of the fan blade. The average radius r m of the fan blade is calculated from the equation

[0034] The present inventors have found that increasing the blade solidity of the fan 112 by increasing the number of blades can reduce the audible noise generated by the blower / vacuum tool 100 during operation. Further, as the number of blades n b increases, the blade solidity value can also increase. The present inventors have found that an ideal noise reduction can be achieved when the fan 112 of the blower / vacuum tool 100 satisfies the following condition: n b is in the range of 17 to 45, the blade solidity of the axial fan 112 can be in the range of 0.0464n b ≤ Blade Solidity ≤ 0.089n b .

[0035] The present inventors have found that the airflow generating assembly 110 of the present utility model with an axial fan 112 can be optimized when the dimensionless flow coefficient Φ is in the range of about 0.2 to about 0.6. The size and speed of the airflow generating assembly 110 are defined as a function of the optimal flow coefficient Φ. The flow coefficient is calculated by the equation:

[0036]

[0037] where q represents the flow rate (m 3 / s), A represents the cross-sectional area of the fan (m 2 ​), where ω represents the speed (rad / s) and R represents the fan tip radius (m) measured at the tip of the blade 142. In other words, the molecule q / (A) is the axial velocity of the fan (meters / second).

[0038] From the calculation of the flow coefficient Φ as shown above, the optimal size of the fan can be determined by rearranging the equation as shown below:

[0039]

[0040] By optimizing the blade solidity and flow coefficient of the airflow generating assembly 110 during operation of the blower / vacuum tool 100, the inventors have discovered that the blower / vacuum tool 100 can produce less audible noise while maintaining optimal airflow characteristics, thereby improving the overall experience of the user during operation of the blower / vacuum tool 100. For example, reducing the audible noise produced by the blower / vacuum tool 100 can be highly advantageous to the user, particularly for homeowners and other non-professional users. At the same time, maintaining optimal airflow characteristics can enable efficient battery life of the blower / vacuum tool 100, reducing the need for the user to charge or replace the power source without reducing the airflow power produced during operation.

[0041] To further reduce the audible noise produced by the blower / vacuum tool 100 during operation, the housing 108 can include an inlet muffler 160 disposed at the first end 102. For example, the inlet muffler 160 can be disposed within the airflow conduit 106 at the first end 102. In some embodiments, the inlet muffler 160 can include a sleeve 162 that surrounds at least a portion of the airflow conduit 106. The sleeve 162 can include sound absorbing material. In particular, the sound absorbing material can be configured to absorb noise in the 2-6 KHz frequency range to reduce audible noise in the human hearing frequency range. The sound absorbing material can include foam. Additionally or alternatively, the sound absorbing material can include foam, such as but not limited to a foam / film laminate, such as polyurethane foam. The sleeve 162 can encircle the entire circumference of the air conduit 106 and / or can encircle one or more portions of the circumference of the air conduit 106.

[0042] Further aspects of the present disclosure are provided by one or more of the following embodiments:

[0043] A blower / vacuum tool includes a body extending between a first end and a second end, the body defining an airflow conduit therethrough; and a fan assembly. The fan assembly includes an axial fan having a plurality of fan blades (n b ) and a motor rotatably connected to the fan. The blades of the fan assembly pass a blade passage frequency (BPF) greater than 6 KHz when the motor is operated at a speed between 21,000-38,000 revolutions per minute (RPM), the blade passage frequency being determined by the equation

[0044] The air blower / vacuum tool of any one or more embodiments, wherein the plurality of fan blades comprises 17 to 45 fan blades.

[0045] The air blower / vacuum tool of any one or more embodiments, wherein the axial fan comprises a hub and the plurality of fan blades extend from the hub at a root of each respective fan blade.

[0046] The air blower / vacuum tool of any one or more embodiments, wherein each of the plurality of fan blades terminates at a tip of each respective fan blade, the axial fan further comprising an outer ring in contact with the tip of each respective fan blade.

[0047] The air blower / vacuum tool of any one or more embodiments, wherein the outer ring rotates with rotation of the axial fan.

[0048] The air blower / vacuum tool of any one or more embodiments, wherein the outer ring comprises an inner diameter, wherein the inner diameter of the outer ring is approximately equal to the inner diameter of the first end and / or the inner diameter of the second end.

[0049] The air blower / vacuum tool of any one or more embodiments, wherein the longitudinal axis extends through a center point of the first end of the body, a center point of the outer ring, and a center point of the second end of the body.

[0050] The air blower / vacuum tool of any one or more embodiments, further comprising an inlet muffler disposed at the first end of the body, the inlet muffler comprising a bushing, the bushing comprising sound absorbing material configured to absorb noise in a frequency range of 2-6 KHz.

[0051] The air blower / vacuum tool of any one or more embodiments, wherein the sound absorbing material comprises foam.

[0052] The air blower / vacuum tool of any one or more embodiments, wherein the fan assembly has a dimensionless flow coefficient Φ calculated by the equation in the range of approximately 0.3 to 0.5 when the motor is operating at a rotational speed between 21,000-38,000 revolutions per minute (RPM), wherein q represents flow (m 3 / s), A represents a cross-sectional area at the fan (m 2 ), and ω represents a speed (rad / s), and R represents a fan tip radius (m) measured at the tip of the blade.

[0053] A blower / vacuum tool includes a body extending between a first end and a second end, the body defining an airflow conduit therethrough; and a fan assembly. The fan assembly includes an axial fan having a plurality of fan blades and a motor rotatably connected to the fan. When n b ≤ 0.089n b , the blade solidity of the axial fan is in a range of 0.0464n b ≤ blade solidity ≤ 0.089n b , the blade solidity is calculated by the equation blade solidity = c / s, where c is a length of a chord of the fan blades and s = 2πr m / n b , r m is an average radius of the fan blades. The blower / vacuum tool of any one or more embodiments, wherein the axial fan includes a hub and each of the fan blades extends from the hub at a root of each respective fan blade.

[0054] The blower / vacuum tool of any one or more embodiments, wherein each of the fan blades terminates at a tip of each respective fan blade, the axial fan further includes an outer ring in contact with the tip of each respective fan blade.

[0055] The blower / vacuum tool of any one or more embodiments, wherein the outer ring rotates with rotation of the axial fan.

[0056] The blower / vacuum tool of any one or more embodiments, wherein the outer ring includes an inner diameter, wherein the inner diameter of the outer ring is approximately equal to an inner diameter of the first end and / or an inner diameter of the second end.

[0057] The blower / vacuum tool of any one or more embodiments, wherein the longitudinal axis extends through a center point of the first end of the body, a center point of the outer ring, and a center point of the second end of the body.

[0058] The blower / vacuum tool of any one or more embodiments, further comprising an inlet muffler disposed at the first end of the body, the inlet muffler including a bushing including sound absorbing material configured to absorb noise in a frequency range of 2-6 KHz.

[0059] The blower / vacuum tool of any one or more embodiments, wherein the sound absorbing material includes foam.

[0060] The blower / vacuum tool of any one or more embodiments, wherein the fan assembly has a dimensionless flow coefficient Φ in a range of approximately 0.3 to 0.5, calculated by the equation when the motor is operating at a rotational speed between 21,000-38,000 revolutions per minute (RPM), wherein q represents flow (m 3A is the cross-sectional area at the fan (m2), ω is the speed (rad / s), and R is the fan tip radius measured at the tip of the blade (m). 2 A is the cross-sectional area at the fan (m2), ω is the speed (rad / s), and R is the fan tip radius measured at the tip of the blade (m).

[0061] This written description uses examples to disclose the application, including the best mode, and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A blower / vacuum tool characterized by, The blower / vacuum tool includes: a body defining an airflow conduit therethrough, the body extending between a first end and a second end; and a fan assembly disposed between the first end and the second end, the fan assembly including an axial fan having a plurality of fan blades and a motor rotatably connected to the axial fan; wherein the blade pass frequency BPF of the fan assembly is greater than 6 KHz when the electric motor is operating at a rotational speed of between 21,000 - 38,000 revolutions per minute (RPM), the blade pass frequency being defined by the equation limited.

2. The blower / vacuum tool of claim 1, wherein, the plurality of fan blades includes 17 to 45 fan blades.

3. The blower / vacuum tool of claim 1, wherein, the axial fan includes a hub, and the plurality of fan blades extend from the hub at a root of each respective fan blade.

4. The blower / vacuum tool of claim 3, wherein, each of the plurality of fan blades terminates at a tip of each respective fan blade, the axial fan further including an outer ring in contact with the tip of each respective fan blade.

5. The blower / vacuum tool of claim 4, wherein, the outer ring rotates with rotation of the axial fan.

6. The blower / vacuum tool of claim 4, wherein, the outer ring includes an inner diameter, wherein the inner diameter of the outer ring is equal to an inner diameter of the first end and / or an inner diameter of the second end.

7. The blower / vacuum tool of claim 4, wherein, a longitudinal axis extends through a center point of the first end of the body, a center point of the outer ring, and a center point of the second end of the body.

8. The blower / vacuum tool of claim 1, wherein, the blower / vacuum tool further includes an inlet muffler disposed at the first end of the body, the inlet muffler including a bushing, the bushing including sound absorbing material configured to absorb noise in a frequency range of 2-6 kHz.

9. The blower / vacuum tool of claim 8, wherein, the sound absorbing material includes foam.

10. The blower / vacuum tool of claim 1, wherein, When the motor operates at a speed between 21,000 and 38,000 revolutions per minute (RPM), the fan assembly has the property of... (The sentence is incomplete and requires more context to translate accurately.) The calculated dimensionless flow coefficient Φ, ranging from 0.3 to 0.5, is given, where q represents the unit in m³. 3 The flow rate is / s, where A represents the unit at the fan location as m³ / s. 2 The cross-sectional area, ω represents the velocity in rad / s, and R represents the fan tip radius in meters, measured at the blade tip.

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