Air blower and outdoor power tool

Abstract

The present disclosure provides a blower and outdoor power tool, such as for outdoor applications. The blower comprises an air inlet; an air outlet; and a fan assembly disposed between the air inlet and the air outlet. The fan assembly is provided with three stages of fans. A three-stage fan includes three axial fans mounted on a drive shaft, each axial fan including a plurality of blades, each blade having a blade tip, and three stator fans arranged in series with the axial fans. The three-stage fan has a dimensionless flow coefficient Phi in the range of about 0.3 to 0.5 calculated according to the formula Phi = (q / (A)) / Omega R, where q represents the flow (m3 / s), A represents the cross-sectional area (m2) of the fan, Omega represents the speed (rad / s), and R represents the fan tip radius (m) measured at the blade tip.

Description

Technical Field

[0001] This disclosure generally relates to blowers for outdoor applications (e.g., for blowing away leaves and other debris). In particular, this disclosure relates to a blower with optimized efficiency and airflow gain. Background Technology

[0002] Outdoor tools such as blowers are typically used to gather debris, such as leaves, using a blowing function. Battery-powered blowers are particularly ideal due to their portability. However, there is a need to optimize blower efficiency to extend blower runtime while maintaining blower performance (i.e., airflow rate).

[0003] Therefore, there is a need in this field for an improved blower tool. In particular, a blower that provides optimized efficiency and airflow gain is advantageous. Utility Model Content

[0004] As per this disclosure, aspects and advantages of the present invention will be set forth in part in the description which follows, or may be apparent from the description or learned by practice of the art.

[0005] According to one embodiment, a blower is provided. The blower includes an air inlet; an air outlet; and a fan assembly disposed between the air inlet and the air outlet. The fan assembly has a three-stage fan. The three-stage fan includes three axial fans mounted on a drive shaft and three stator fans arranged in series with the axial fans, wherein each axial fan includes a plurality of blades, each blade having a blade tip. The three-stage fan has a dimensionless flow coefficient Φ in the range of approximately 0.3 to 0.5, calculated according to the formula Φ=(q / (A)) / ωR, where q represents the flow rate (m³ / s). 3 / s), A represents the cross-sectional area of ​​the fan (m²). 2 ), where ω represents the velocity (rad / s) and R represents the fan tip radius (m) measured at the blade tip.

[0006] According to another embodiment, an outdoor power tool is provided. The outdoor power tool includes a power head having a power head housing, a power source, a motor powered by the power source, and a drive shaft extending from and rotatably driven by the motor. The power source and motor are arranged within the power head housing, and the drive shaft extends from the power head housing. The outdoor power tool also includes a blower having a blower housing with an air inlet, an air outlet, and a fan assembly. The drive shaft of the power head extends into the blower housing and is configured to drive rotation of the fan assembly.

[0007] These and other features, aspects, and advantages of the present invention will become more readily understood with reference to the description below and the 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. Attached Figure Description

[0008] The present invention will be fully and practically disclosed in this specification with reference to the accompanying drawings. This disclosure is intended for those skilled in the art and includes the best mode of making and using the system and method, as shown in the drawings:

[0009] Figure 1 This is a side cross-sectional view of a blower according to an embodiment of the present disclosure;

[0010] Figure 2 This is an exploded side view of a blower according to an embodiment of this disclosure;

[0011] Figure 3 This is a perspective view of the housing section of a blower including a stator fan, according to an embodiment of this disclosure;

[0012] Figure 4 This is a perspective view of the axial fan of the blower according to an embodiment of the present disclosure; and

[0013] Figure 5 This is a side perspective view of an outdoor power tool according to an embodiment of the present disclosure. Detailed Implementation

[0014] The present invention will now be described in detail with reference to embodiments thereof, one or more of which are illustrated in the accompanying 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 being more preferred or advantageous than other implementations. Furthermore, each example is provided by way of explanation rather than limitation of the technology. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made to the present technology without departing from the scope or spirit of the claimed technology. For example, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, this disclosure is intended to cover such modifications and variations within the scope of the appended claims and their equivalents. Numerical and alphabetic designations are used in the detailed description to denote features in the drawings. Similar or analogous designations in the drawings and specification are used to refer to similar or analogous parts in the present invention.

[0015] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another, rather than to indicate the position or importance of a single component. The singular expressions “a,” “an,” and “the” also include plural cases, unless the context explicitly specifies otherwise. The terms “coupled,” “fixed,” “connected to,” etc., refer to direct coupling, fixing, or connection, as well as indirect coupling, fixing, or connection through one or more intermediate components or features, unless otherwise specified herein. The terms “comprising,” “including,” “constituting,” “having,” or any other variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a set of features is not necessarily limited to those features, but may include features not expressly listed or other features inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, “or” is inclusive rather than exclusive. For example, any of the following satisfy conditions A or B: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0016] Terms indicating approximation, such as “approximately,” “roughly,” “approximately,” or “substantially,” include values ​​that are within 10% larger or smaller than the described value. When used in the context of angles or directions, these terms include values ​​that are within 10 degrees larger or smaller than the described angle or direction. For example, “roughly vertical” includes directions that deviate from vertical by within 10 degrees in any direction (e.g., clockwise or counterclockwise).

[0017] The benefits, other advantages, and solutions to problems are described below with reference to specific embodiments. However, the benefits, advantages, solutions to problems, and any features that may cause any benefit, advantage, or solution to occur or become more apparent should not be construed as key, necessary, or essential features of any or all claims.

[0018] In general, this invention relates to a blower with optimized efficiency and airflow. The blower includes a three-stage fan assembly having three axial fans and three stator fans arranged in series. The size of the fan assembly can be optimized based on the blower's ideal flow coefficient to optimize the blower's efficiency. This invention also relates to an outdoor power tool including a power head and a blower accessory removably coupled to the power head. The blower can be provided as a standard handheld blower with battery / electric or gas power, or as a blower accessory, or in other configurations.

[0019] Now refer to the attached diagram, Figure 1A cross-sectional side view of a blower 100, viewed along a central axis A according to an exemplary embodiment, is shown. The blower 100 is configured to generate airflow along an airflow duct extending between an inlet 102 and an outlet 104 of the blower 100. The blower 100 may define a central axis A extending between the inlet 102 and the outlet 104. An outlet duct 126 may extend parallel to the central axis A.

[0020] like Figure 1 As shown, the blower housing 108 may at least partially enclose components of the blower 100, such as a fan assembly 110 including multiple axial fans 112, and various other components. Power for operating the fan assembly 110 may be provided by a suitable power source, such as gas or one or more batteries (not shown). The blower 100 may be provided as a standard handheld blower with an electric (e.g., powered by a wired or wireless battery) or gas power source, as a blower accessory capable of being coupled to a tool or power source, or in any other configuration.

[0021] The fan assembly 110 can be a three-stage fan. In other words, the fan assembly 110 may include three axial fans 112, and may also include three compressor stages. Each compressor stage is formed by a stator fan 114. Each stator fan 114 is arranged in series with each axial fan 112 along a central axis A to form a configuration such that... Figure 1 The series axial fan assembly shown.

[0022] Fan drive shaft 116 extends along axis A through the center of each axial fan 112 and stator fan 114, and rotatably drives the axial fan 112. Fan drive shaft 116 is connected to the power head (see...). Figure 5 The coupling includes a motor and a power source, such as one or more batteries.

[0023] The blower housing 108 may have a multi-piece construction consisting of multiple main components coupled together to form the housing 108. For example, the blower housing 108 may include multiple stackable housing segments 118 connected in series to surround the fan assembly 110. Each stator fan 114 may be arranged in its respective stackable housing segment 118. For example, each stator fan 114 may be formed by a single-piece construction having a corresponding stackable housing segment 118. A first stator fan 114 is arranged in a first housing segment 118A, a second stator fan 114 is arranged in a second housing segment 118B, and a third stator fan 114 is arranged in a third housing segment 118C. The stackable housing segments 118 also surround each of the axial fans 112 to enclose the fan assembly 110.

[0024] Each stackable housing segment 118 includes one or more coupling features 120 configured to allow the stackable housing segments 118 to be stacked and fastened together. For example, the coupling features 120 may protrude or extend from the outer surface 122 of each housing segment 118. The coupling features 120 may include, but are not limited to, one or more orifices or openings for receiving fasteners, such as screws, passing through them.

[0025] In one aspect, the housing segment closest to the outlet 104 (i.e., the third housing segment 118C) may include an outlet cone 124 extending along axis A from the center of the third stator fan 114C toward the outlet 104. The outlet cone 124 may be formed as a single piece having the third housing segment 118C and the third stator fan 114C. The outlet cone 124 is capable of guiding a stable axial airflow toward the outlet 104, resulting in improved efficiency of the fan assembly 110.

[0026] The outlet pipe 126 may be arranged downstream of the fan assembly 110 to guide air from the fan assembly 110 to the outlet 104. The outlet pipe 126 may be coupled to the downstream end of the third housing section 118C. The outlet cone 124 may extend at least partially within the outlet pipe 126.

[0027] Figure 3 It shows Figure 2 A perspective view of the second housing section 118B and the second stator fan 114B. The stator fan 114B has a stator hub 150 and a plurality of stator blades 152. The stator hub 150 may have a diameter D. hub Diameter D hub The hub 130 of the axial fan 112 has a diameter approximately the same as that of the hub 130, as further detailed below. Stator blades 152 extend from the stator hub 150 to the inner surface 154 of the second housing section 118B. The stator fan 114B can be an example of all three stator fans 114A, 114B, and 114C. The outer surface 122 of the second housing section 118B includes one or more coupling features 120 extending therefrom. For example, three coupling features 120 may be arranged around the circumference of the outer surface 122; however, the present invention contemplates any suitable number and arrangement of coupling features.

[0028] Now go to Figure 4 The axial fan 112 is further described in detail below. Each axial fan 112 includes a circular hub 130 and a plurality of blades 132 extending radially outward from the hub 130 in a direction away from the central axis A. The hub 130 may have a diameter D in the range of approximately 55 mm to approximately 70 mm, for example, approximately 63 mm. hub .

[0029] The axial fan 112 also includes a drive shaft support 128 arranged radially inward from the hub 130 and configured to couple with the fan drive shaft 116. One or more support ribs 129 extend between the drive shaft support 128 and the hub 130 to connect the hub to the fan drive shaft 116, thereby enabling rotational transmission from the fan drive shaft 116 to the blades 132.

[0030] Each blade 132 extends radially outward from the hub 130 at the hub end 134 to the tip 136. The axial fan 112 can have a maximum diameter (D) extending to the tip of the blade 132. tip The blades are in the range of approximately 100 mm to approximately 140 mm, for example, in the range of approximately 110 mm to approximately 130 mm, such as approximately 120 mm. Each blade 132 extends axially along the hub 130 from the blade inlet side 138, which is arranged closer to the inlet 102, to the blade outlet side 140, which is closer to the outlet 104. Each blade has a chord length C extending axially along the hub 130 from the blade inlet side to the blade outlet side. The chord length C of each blade 132 can be in the range of approximately 30 mm to approximately 50 mm, such as approximately 40 mm.

[0031] Each blade 132 may have different angles at its inlet side 138 and outlet side 140. More specifically, the angle at the blade inlet side 138 at the hub (referred to as θ_hub,in or blade hub inlet angle) may differ from the angle at the blade inlet side 138 at the tip 136 (referred to as θ_tip,in or blade tip inlet angle). Similarly, the angle at the blade outlet side 140 at the hub (referred to as θ_hub,out or blade hub outlet angle) may differ from the angle at the blade outlet side 140 at the tip 136 (referred to as θ_tip,out or blade tip outlet angle).

[0032] The angle of each blade 132 at the blade inlet side 138 can be greater than the angle of each blade 132 at the blade outlet side 140. Furthermore, at any given location along the length of the blade 132, the angle of each blade 132 at the tip 136 can be greater than the angle at the hub end 134.

[0033] In one embodiment, the angle (θ_hub,in) of the blade inlet side 138 at the hub can be in the range of approximately 40 degrees to approximately 55 degrees, for example, approximately 47 degrees. The angle (θ_hub,out) of the blade outlet side 140 at the hub can be in the range of approximately 20 degrees to approximately 30 degrees, for example, approximately 26 degrees. The angle (θ_tip,in) of the blade inlet side 138 at the tip 136 can be in the range of approximately 58 degrees to approximately 70 degrees, for example, approximately 64 degrees. The angle (θ_tip,out) of the blade outlet side 140 at the tip 136 can be in the range of approximately 50 degrees to approximately 55 degrees, for example, approximately 52 degrees.

[0034] like Figure 4 As shown, in one aspect, the axial fan 112 may have seven (7) blades 132. However, the inventors have considered using any desired number of fan blades 132 to achieve the desired airflow characteristics as needed.

[0035] The inventors have discovered that the fan assembly 110 of this invention, featuring a three-stage axial fan, is optimal when the dimensionless flow coefficient Φ is in the range of approximately 0.3 to approximately 0.5. The dimensions and speed of the fan assembly 110 are defined as functions of the optimal flow coefficient Φ. The flow coefficient is calculated using the following formula:

[0036]

[0037] Where q represents flow rate (m 3 / s), A represents the cross-sectional area of ​​the fan (m²). 2 ), where ω represents the velocity (rad / sec), and R represents the fan tip radius (m) measured at 136 at the blade tip. In other words, the numerator q / (A) is the axial velocity of the fan (meters per second).

[0038] Based on the calculation of the flow coefficient Φ as shown above, the optimal fan size can be determined using a revised formula, as shown below:

[0039]

[0040] In one aspect of this invention, the fan assembly 110 may include three axial fans 112 having the following fan dimensions:

[0041] <![CDATA[D hub ]]> 62.8mm <![CDATA[D tip ]]> 119.0mm θ_hub,in 47.2° θ_hub,out 25.7° θ_tip,in 64.1° θ_tip,out 52° C 39.9mm Number of leaves 7

[0042] Now go to Figure 5The image illustrates an outdoor power tool 200 according to an exemplary embodiment. The outdoor power tool 200 includes a tool attachment 210 (e.g., a blower 100) and a power head 202. The power head 202 includes a power source 204 (e.g., a battery) and a motor 206. The power source 204 and the motor 206 may be arranged within a power head housing 208. The motor 206 is powered by the power source 204. When powered by the power source 204, the rotation of the motor 206 is configured to rotatably drive a drive shaft 212.

[0043] The power head drive shaft 212 is configured to extend from the power head housing 208. The power head drive shaft 212 may be disposed within an outer protective shaft 218. The power head drive shaft 212 and / or the outer protective shaft 218 may include one or more coupling features 214 configured to couple to a receiver 216 of the tool 210. The outer protective shaft 218 may also include a user input device 222 (e.g., a power switch) configured to control the operation of the power head 202 and a handle 224 configured to be held by a user.

[0044] In one aspect, tool 210 may be the blower 100 described herein. Receiver 216 may be coupled to the fan drive shaft 116 of the blower 100. Coupling feature 214 of the power head drive shaft 212 may be coupled or fastened to the receiver 216 of the blower 100, thereby coupling the power head drive shaft 212 and the fan drive shaft 116 together. For example, when coupled, the power head drive shaft 212 and the fan drive shaft 116 may extend coaxially along axis A. Rotation of the power head drive shaft 212 can be transmitted to the fan drive shaft 116, thereby causing rotation of the axial fan 112 of the blower 100.

[0045] Optionally, receiver 216 can be mounted on blower outer protective shaft 220, and fan drive shaft 116 can extend through outer protective shaft 220 to couple with power head drive shaft 212. The outer protective shaft 218 of power head 202 and blower outer protective shaft 220 can be configured to enhance the safety of outdoor power tool 200 by protecting the rotating drive shaft elements from contact with the user or bystanders.

[0046] Although Figure 5 The blower 100 is shown as a tool attachment 210 coupled to the power head 202 to form an outdoor power tool 200. However, the tool attachment 210 can be any desired outdoor tool selectively and removably coupled to the power head 202, including but not limited to rope trimmer attachments, edge trimmer attachments, hedge trimmer attachments, long-handled saw attachments, brush cutter attachments, broom attachments, brush attachments, tiller attachments, etc. Furthermore, the outdoor power tool 200 can be provided with multiple additional tool attachments 210 to form interchangeable tool kits that can be used in conjunction with the power head 202.

[0047] Other aspects of this utility model are provided by one or more of the following embodiments:

[0048] A blower includes an air inlet; an air outlet; and a fan assembly disposed between the air inlet and the air outlet. The fan assembly has a three-stage fan. The three-stage fan includes three axial fans mounted on a drive shaft and three stator fans arranged in series with the axial fans, wherein each axial fan includes multiple blades, each blade having a blade tip. The three-stage fan has a dimensionless flow coefficient Φ in the range of approximately 0.3 to 0.5, calculated according to the formula Φ=(q / (A)) / ωR, where q represents the flow rate (m³ / s). 3 / s), A represents the cross-sectional area of ​​the fan (m²). 2 ), where ω represents the velocity (rad / s) and R represents the fan tip radius (m) measured at the blade tip.

[0049] According to any one or more embodiments of the blower, each stator fan includes a stackable housing, wherein each of the stackable housings of the three stator fans is coupled together in series to form a blower housing, wherein the blower housing houses the three stator fans and the three axial flow fans.

[0050] A blower according to any one or more embodiments, wherein the blower housing has a diameter of less than about 140 mm.

[0051] The blower according to any one or more embodiments, wherein each axial fan includes a hub surrounding a drive shaft, wherein the hub includes a diameter ranging from approximately 50 mm to approximately 75 mm.

[0052] A blower according to any one or more embodiments, wherein each of a plurality of blades of each axial fan extends from a respective hub of each axial fan to a respective blade tip, wherein each axial fan includes a maximum diameter in the range of about 100 mm to about 140 mm.

[0053] According to any one or more embodiments of the blower, wherein the maximum diameter of each axial fan is in the range of approximately 115 mm to approximately 125 mm.

[0054] The blower according to any one or more embodiments, wherein each blade includes a chord length from the inlet side of the blade to the outlet side of the blade, the chord length being in the range of about 30 mm to about 50 mm.

[0055] The blower according to any one or more embodiments, wherein the chord length is in the range of about 35 mm to about 45 mm.

[0056] A blower according to any one or more embodiments, wherein the blade hub inlet angle at the hub is greater than the blade hub outlet angle of each blade at the hub.

[0057] The blower according to any one or more embodiments, wherein the blade hub inlet angle is in the range of about 40 degrees to about 55 degrees.

[0058] The blower according to any one or more embodiments, wherein the blade hub outlet angle is in the range of about 20 degrees to about 30 degrees.

[0059] A blower according to any one or more embodiments, wherein the blade tip inlet angle on the inlet side of the blade tip is greater than the blade tip outlet angle on the outlet side of the blade tip.

[0060] According to any one or more embodiments of the blower, the blade tip inlet angle is in the range of about 58 degrees to about 70 degrees.

[0061] According to any one or more embodiments of the blower, the blade tip exit angle is in the range of about 50 degrees to about 55 degrees.

[0062] An outdoor power tool includes a power head having a power head housing, a power source, a motor powered by the power source, and a drive shaft extending from and rotatably driven by the motor. The power source and motor are arranged within the power head housing, and the drive shaft extends from the power head housing. The outdoor power tool also includes a blower accessory having a blower housing with an air inlet, an air outlet, and a fan assembly. The drive shaft extends into the blower housing and is configured to drive rotation of the fan assembly.

[0063] An outdoor power tool according to any one or more embodiments, wherein the fan assembly includes a three-stage fan, the three-stage fan including three axial fans and three stator fans.

[0064] An outdoor power tool according to any one or more embodiments, wherein the fan assembly has a diameter of less than approximately 140 mm.

[0065] An outdoor power tool according to any one or more embodiments, wherein a blower is removably coupled to a drive shaft.

[0066] The outdoor power tool according to any one or more embodiments further includes at least one additional tool attachment configured to be removably coupled to the drive shaft, wherein the additional tool attachment is selected from the group consisting of a rope trimmer, a shank saw, a hedge trimmer, an edge trimmer, a brush cutter, a brush, and a broom.

[0067] This specification uses examples to disclose the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including making and using any device or system and methods of performing any combination. The patent scope of the present invention is defined by the claims, but may include other examples that would occur to a person skilled in the art. The scope of the claims covers such other examples if they include structural elements that are not distinct from the literal expression of the claims, or include equivalent structural elements that are not substantially different from the literal expression of the claims.

Claims

1. A blower, characterized in that: The blower comprises: Air intake; Air outlet; and a fan assembly disposed between the air inlet and the air outlet, wherein the fan assembly comprises a three-stage fan, wherein the three-stage fan comprises three axial flow fans mounted on a drive shaft and three stator fans arranged in series with the axial flow fans, wherein each axial flow fan and each stator fan comprises an inlet side and an outlet side, wherein the inlet side is arranged closer to the air inlet than the outlet side, and wherein the outlet side is arranged closer to the air outlet than the inlet side, Each axial flow fan includes a plurality of blades, each blade having a blade tip, and Wherein, the three-stage fan has the formula The dimensionless flow coefficient Φ was calculated in the range of 0.3 to 0.5, where q represents the flow rate (m 3 / s), A represents the cross-sectional area of ​​the fan (m 2 ), ω represents the speed (rad / s), and R represents the fan tip radius measured at the blade tip (m).

2. The blower according to claim 1, characterized in that: Each stator fan includes a stackable housing, wherein each of the stackable housings of the three stator fans are coupled together in series to form a blower housing, wherein the blower housing accommodates the three stator fans and the three axial flow fans.

3. The blower according to claim 2, characterized in that: The blower housing comprises a diameter of less than 140 mm.

4. The blower according to claim 1, characterized in that: Each axial flow fan comprises a hub surrounding the drive shaft, wherein the hub comprises a diameter in the range of 50 mm to 75 mm.

5. The blower according to claim 4, characterized in that: Each of the plurality of blades of each axial flow fan extends from a respective hub of each axial flow fan to each respective blade tip, wherein each axial flow fan includes a maximum diameter within a range of 100 mm to 140 mm.

6. The blower according to claim 5, characterized in that: The maximum diameter of each axial flow fan is in the range of 115 mm to 125 mm.

7. The blower according to claim 1, characterized in that: Each blade includes a chord length from an inlet side of the blade to an outlet side of the blade, the chord length being in a range of 30 mm to 50 mm.

8. The blower according to claim 7, characterized in that: The chord length is in the range of 35 mm to 45 mm.

9. The blower according to claim 4, characterized in that: A blade hub inlet angle at the hub is greater than a blade hub outlet angle of each blade at the hub.

10. The blower according to claim 9, characterized in that The blade hub inlet angle is in the range of 40 degrees to 55 degrees.

11. The blower according to claim 9, characterized in that: The blade hub outlet angle is in the range of 20 degrees to 30 degrees.

12. The blower according to claim 4, characterized in that: A blade tip inlet angle at an inlet side of the blade tip is greater than a blade tip outlet angle at an outlet side of the blade tip.

13. The blower according to claim 12, characterized in that The blade tip inlet angle is in the range of 58 degrees to 70 degrees.

14. The blower according to claim 12, characterized in that: The blade tip exit angle is in the range of 50 degrees to 55 degrees.

15. An outdoor power tool, characterized in that: The outdoor power tool comprises: a power head comprising a power head housing, a power source, a motor powered by the power source, and a drive shaft extending from and rotatably driven by the motor, wherein the power source and the motor are arranged in the power head housing, and the drive shaft extends from the power head housing; and A blower accessory, comprising the blower according to claim 1.

16. The outdoor power tool according to claim 15, characterized in that: The fan assembly includes a three-stage fan, and the three-stage fan includes three axial flow fans and three stator fans.

17. The outdoor power tool according to claim 16, characterized in that: The fan assembly has a diameter of less than 140 mm.

18. The outdoor power tool according to claim 15, characterized in that: The blower is removably coupled to the drive shaft.

19. The outdoor power tool according to claim 18, characterized in that: The outdoor power tool also includes at least one additional tool attachment configured to be removably coupled to the drive shaft, wherein the additional tool attachment is selected from the group consisting of a string trimmer, a long-handled saw, a hedge trimmer, an edger, a brush cutter, a brush, and a broom.

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