Patent Description:
In the related art (see for example <CIT>), a lawn edger, as a common garden tool, generally includes a long rod assembly for a user to operate, one end of the long rod assembly is connected to a working head, and the other end of the long rod assembly is connected to an operation assembly convenient for the user to operate. The lawn edger has relatively low overall performance. To improve the performance on this basis, the whole machine is required to be bigger and heavier. As a result, the machine is heavier and difficult to handle, and the user needs to move the machine forcefully for use and easily becomes fatigued during operation.

This part provides background information related to the present application, which is not necessarily the existing art.

The present application aims to solve or at least alleviate part or all of the preceding problems. Therefore, an object of the present application is to provide a lawn edger and a power tool.

To achieve the preceding object, the present application provides a lawn edger according to claim <NUM>. Preferred embodiments are provided in the dependent claims.

The present application has the following benefits: the electric motor drives the output shaft to rotate and thus can drive the blade to rotate, implementing a grass cutting function; when the electric motor is in the maximum-efficiency state, the ratio of the output power of the electric motor to the weight of the lawn edger is greater than or equal to <NUM> W/kg, which indicates that the electric motor has relatively large output power, a relatively small mass, and a relatively high power density so that machine performance is improved and the whole machine is kept in a relatively light state, thereby facilitating user operation.

In this application, the terms "up", "down", "left", "right", "front", and "rear" " and other directional words are described based on the orientation or positional relationship shown in the drawings, and should not be understood as limitations to the examples of this application. In addition, in this context, it also needs to be understood that when it is mentioned that an element is connected "above" or "under" another element, it can not only be directly connected "above" or "under" the other element, but can also be indirectly connected "above" or "under" the other element through an intermediate element. It should also be understood that orientation words such as upper side, lower side, left side, right side, front side, and rear side do not only represent perfect orientations, but can also be understood as lateral orientations. For example, lower side may include directly below, bottom left, bottom right, front bottom, and rear bottom.

In this application, the terms "controller", "processor", "central processor", "CPU" and "MCU" are interchangeable. Where a unit "controller", "processor", "central processing", "CPU", or "MCU" is used to perform a specific function, the specific function may be implemented by a single aforementioned unit or a plurality of the aforementioned unit.

In this application, the term "device", "module" or "unit" may be implemented in the form of hardware or software to achieve specific functions.

In this application, the terms "computing", "judging", "controlling", "determining", "recognizing" and the like refer to the operations and processes of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

Referring to <FIG>, the present application provides a power tool <NUM>, which is a mechanical tool for trimming a lawn, vegetation, or the like. The power tool may be a long-rod edger. An example in which the power tool <NUM> is a lawn edger is used for description.

Referring to <FIG>, the lawn edger includes an output shaft <NUM>, a front housing <NUM>, a rear housing <NUM>, a connection assembly <NUM>, an electric motor <NUM>, and a transmission assembly <NUM>. The output shaft <NUM> is used for mounting a blade <NUM> for cutting grass, the front housing <NUM> accommodates at least part of the output shaft <NUM>, the rear housing <NUM> is formed with a coupling portion <NUM> for coupling a battery pack <NUM>, the connection assembly <NUM> is used for connecting the front housing <NUM> to the rear housing <NUM>, and the electric motor <NUM> is mounted in the rear housing <NUM>. The transmission assembly <NUM> is used for transmitting power between the electric motor <NUM> and the output shaft <NUM> so that the electric motor <NUM> can drive the output shaft <NUM> to rotate and thus make the blade <NUM> rotate to implement cutting.

In some examples, the connection assembly <NUM> includes a connection tube <NUM>, the connection tube <NUM> is used for connecting the front housing <NUM> to the rear housing <NUM>, the transmission assembly <NUM> includes a drive shaft that is at least partially disposed in the connection tube <NUM>, and the connection tube <NUM> protects the drive shaft.

In some other examples, the connection assembly <NUM> includes the connection tube <NUM>, and the connection tube <NUM> is used for connecting the front housing <NUM> to the rear housing <NUM>. The transmission assembly <NUM> includes a first drive shaft <NUM>, a second drive shaft <NUM>, and a connection shaft <NUM>, the first drive shaft <NUM> is connected to the electric motor <NUM> and disposed at the rear end of the connection tube <NUM>, the second drive shaft <NUM> is used for driving the output shaft <NUM>, the connection shaft <NUM> connects the first drive shaft <NUM> to the second drive shaft <NUM>, and at least part of the connection shaft <NUM> is disposed in the connection tube <NUM>.

The first drive shaft <NUM> and the electric motor <NUM> are connected through a gear mechanism, a first gear is disposed on a motor shaft <NUM> of the electric motor <NUM>, a second gear is disposed on the first drive shaft <NUM>, and the first gear meshes with the second gear. The first gear and the second gear may be spur gears. The first drive shaft <NUM> and the connection shaft <NUM> are connected through a first joint, and the second drive shaft <NUM> and the connection shaft <NUM> are connected through a second joint. The second drive shaft <NUM> and the output shaft <NUM> are connected through a gear mechanism, a third gear is disposed on the second drive shaft <NUM>, a fourth gear is disposed on the output shaft <NUM>, and the third gear meshes with the fourth gear. The third gear and the fourth gear may be helical gears.

The lawn edger also includes a main handle <NUM> and an auxiliary handle <NUM>. The main handle <NUM> is mounted to the connection assembly <NUM> and used for a user to hold. The main handle <NUM> is disposed between the rear housing <NUM> and the auxiliary handle <NUM>. Both the main handle <NUM> and the auxiliary handle <NUM> are connected to the connection tube <NUM>. In this example, the auxiliary handle <NUM> extends to the upper side of the connection tube <NUM>. During operation of an operator, the main handle <NUM> is held with one hand and the auxiliary handle <NUM> is held with the other hand, facilitating holding.

In one example, at least part of the connection tube <NUM> extends curvedly so that the blade <NUM> is away from the operator, so as to ensure operational safety. Since the connection tube <NUM> is bent, the connection shaft <NUM> in the connection tube <NUM> also needs to be bent. Therefore, the connection shaft <NUM> is configured to be a flexible shaft, where torque is transmitted through the flexible shaft, and the flexible shaft can withstand greater torque.

As shown in <FIG> and <FIG>, the connection tube <NUM> includes a straight tube portion <NUM> and a curved tube portion <NUM> connected to each other, the straight tube portion <NUM> is connected to the rear housing <NUM>, and the curved tube portion <NUM> is connected to the front housing <NUM>. Both the main handle <NUM> and the auxiliary handle <NUM> are disposed at the rear end of the connection tube <NUM>. The setting where the straight tube portion <NUM> is behind the curved tube portion <NUM> facilitates the operation of the user at the rear end and makes the blade <NUM> at the front end away from the operator. Generally, the operator stands on the left side of the connection tube <NUM> to hold the main handle <NUM> and the auxiliary handle <NUM>. Therefore, the connection tube <NUM> is bent towards the right side of the connection tube <NUM> to make the blade <NUM> at the front end away from the operator.

The angle at which the curved tube portion <NUM> is bent relative to the straight tube portion <NUM> is greater than or equal to <NUM>° and less than or equal to <NUM>°. In some examples, the angle at which the curved tube portion <NUM> is bent relative to the straight tube portion <NUM> is greater than or equal to <NUM>° and less than or equal to <NUM>°. In some examples, the angle at which the curved tube portion <NUM> is bent relative to the straight tube portion <NUM> is equal to <NUM>°. Vibration and noise are reduced through gentle bending. The angle at which the curved tube portion <NUM> is bent relative to the straight tube portion <NUM> is denoted by α in <FIG>.

The radius of curvature of the curved tube portion <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the radius of curvature of the curved tube portion <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In one example, the radius of curvature of the curved tube portion <NUM> is <NUM>.

When the angle at which the curved tube portion <NUM> is bent relative to the straight tube portion <NUM> is equal to <NUM>° and the radius of curvature of the curved tube portion <NUM> is <NUM>, use requirements are met, and noise and vibration can be effectively reduced.

Along a direction parallel to the straight tube portion <NUM>, the length of the connection tube <NUM> is greater than or equal to <NUM>. A relatively great length makes the blade <NUM> farther away from the operator and can achieve a wider operation range. In one example, the connection shaft <NUM> can withstand a torque of at least <NUM> N·m. The diameter of the connection shaft <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the diameter of the connection shaft <NUM> may be <NUM>. The length of the connection shaft <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the length of the connection shaft <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>.

An axis of rotation of the output shaft <NUM> is basically perpendicular to an extension direction of the straight tube portion <NUM> so that the blade <NUM> is as far away from the operator as possible and the cutting of the blade <NUM> in a vertical plane is facilitated.

In some examples, the connection tube <NUM> may be a carbon fiber tube. A carbon fiber is an existing material. The carbon fiber tube has the advantages of high strength, a long lifetime, resistance to corrosion, a light mass, a low density, and the like so that the carbon fiber tube can not only reduce the weight but also maintain relatively high strength in a bent situation. In some other examples, the connection tube <NUM> includes an aluminum tube and a nylon tube, the nylon tube is inserted into the aluminum tube, and the connection shaft <NUM> is at least partially disposed in the nylon tube.

In some examples, referring to <FIG>, the lawn edger also includes a first communication unit <NUM> and a terminal device <NUM>. The first communication unit <NUM> is a wireless communication unit and can send information to the terminal device <NUM> or receive information from the terminal device <NUM>. The terminal device <NUM> includes a second communication unit <NUM>, the first communication unit <NUM> is connected to the second communication unit <NUM> by means of wireless communications, and the terminal device <NUM> is capable of displaying state information of the lawn edger. The terminal device <NUM> displays the state information of the lawn edger, making it convenient for the user to learn a working state of the lawn edger in time without being limited in position. The terminal device <NUM> enables the user to learn machine information on an APP, monitor the working state of the machine, and upgrade the machine. In some examples, the first communication unit <NUM> and the second communication unit <NUM> are each a Bluetooth unit. In some examples, the first communication unit <NUM> and the second communication unit <NUM> are each a Zigbee unit. In some other examples, the first communication unit <NUM> and the second communication unit <NUM> are each a Wi-Fi unit. The working principle of a wireless communication connection is the existing art, and the details are not repeated here. The terminal device <NUM> may be a mobile phone, a tablet, or a computer.

The lawn edger also includes a detection module <NUM> and a control module <NUM>. The detection module <NUM> is configured to detect an operating parameter or an electrical parameter of the electric motor <NUM>. The control module <NUM> is configured to determine, according to the operating parameter or the electrical parameter, whether the electric motor <NUM> is in a locked-rotor operating state and, when the electric motor <NUM> is in the locked-rotor operating state, control the electric motor <NUM> to stop rotating. The detection module <NUM> and the control module <NUM> collaborate to implement a brake protection function. After the blade <NUM> undergoes a locked rotor, the electric motor <NUM> can be immediately stopped in time, and the electric motor <NUM> is prevented from rotating with the flexible shaft, thereby avoiding a torsion of the flexible shaft.

The operating parameter may be a rotational speed, including, but not limited to, a rotational speed of the electric motor <NUM> and a rotational speed of the output shaft <NUM>. When the rotational speed of the electric motor <NUM> is greater than or equal to a first set value and the rotational speed of the output shaft <NUM> is less than or equal to a second set value, the control module <NUM> determines that the electric motor <NUM> is in the locked-rotor operating state. The electrical parameter may be a current of the electric motor <NUM>. The detection module <NUM> detects a present current value of the electric motor <NUM>, and the control module <NUM> determines whether the present current value is greater than a preset current threshold. If so, it is determined that the electric motor <NUM> is in the locked-rotor operating state.

As shown in <FIG> and <FIG>, the lawn edger also includes a display assembly <NUM> for displaying at least speed information of operating of the lawn edger. The user can acquire current speed information visually and conveniently. Even if the speed information changes due to an accidental collision, timely treatment can be made, providing operation convenience and improving working efficiency.

The speed information may be speed information of the output shaft <NUM>, facilitating the timely acquisition of a speed of the blade <NUM> by the user. The speed information may be speed information of the electric motor <NUM>, facilitating the timely acquisition of a state of the electric motor <NUM> by the user. It is to be understood that the lawn edger also includes a rotational speed sensor for detecting the speed of the electric motor <NUM> or the output shaft <NUM>.

In some examples, the display assembly <NUM> includes a display screen. Information is displayed on the display screen, facilitating visual observation. The display screen may be a touchscreen, facilitating speed regulation. In some other examples, the display assembly <NUM> includes a display light. Information is displayed by the display light, achieving a low fault rate. Light of different colors may represent different speed gears, for example, red represents a first gear, orange represents a second gear, and green represents a third gear. Alternatively, multiple speed display lights <NUM> may be disposed, and the number i of lights turned on among the multiple speed display lights <NUM> indicates that the lawn edger is in an i-th rotational speed gear. For example, in this example, the lawn edger has three speed gears: a low gear, an intermediate gear, and a high gear. Correspondingly, the display assembly <NUM> includes three speed display lights <NUM>, one speed display light <NUM> on indicates that the lawn edger is in the low gear, two speed display lights <NUM> on indicate that the lawn edger is in the intermediate gear, and three speed display lights <NUM> on indicate that the lawn edger is in the high gear. For example, in the low gear, the rotational speed of the blade <NUM> is greater than or equal to <NUM> rpm and less than or equal to <NUM> rpm; in the intermediate gear, the rotational speed of the blade <NUM> is greater than or equal to <NUM> rpm and less than or equal to <NUM> rpm; and in the high gear, the rotational speed of the blade <NUM> is greater than or equal to <NUM> rpm and less than or equal to <NUM> rpm.

In some examples, the speed information includes a speed gear or a speed value. The speed gears may be divided into the low gear, the intermediate gear, or the high gear.

In some examples, the display assembly <NUM> can display the remaining power of the battery pack <NUM>, facilitating timely charging. For example, the display assembly <NUM> includes a power display light <NUM>. Different colors of the power display light <NUM> represent different power levels. For example, red represents very little power, orange represents little power, and green represents sufficient power.

In some examples, the display assembly <NUM> can display the present efficiency or current or torque.

The display assembly <NUM> includes a display interface capable of displaying the speed information. For example, in this example, the three speed display lights <NUM> may be considered as the display interface. Of course, the display interface may also be considered as including the power display light <NUM> and the following Bluetooth display light <NUM>. A speed regulator <NUM> is disposed on a side of the display interface, and the speed regulator <NUM> is disposed relatively near the display interface, facilitating the simultaneous speed regulation and observation. Specifically, the distance between the speed regulator <NUM> and the display interface is less than or equal to <NUM>. The speed regulator <NUM> may be a speed regulation button that is pressed for speed regulation. The speed may be changed once every press, or the speed may be switched through presses of different durations. For example, in this example, the speed regulator <NUM> may be operated to switch the lawn edger between the low gear, the intermediate gear, and the high gear in turn.

The display assembly <NUM> is disposed on a housing of the main handle <NUM>. The housing of the main handle <NUM> is sleeved on the connection tube <NUM>, the display assembly <NUM> is disposed on the upper side of the housing of the main handle <NUM>, and the speed regulator <NUM> and the display assembly <NUM> are disposed on the same side of the main handle <NUM>, facilitating the simultaneous speed regulation and observation. Specifically, the speed regulator <NUM> is disposed at the rear end of the display interface, and the display interface is not blocked when the speed regulator <NUM> is operated.

Referring to <FIG>, a trigger <NUM> is further disposed on the housing of the main handle <NUM>, and the trigger <NUM> and the display assembly <NUM> are disposed on two opposite sides of the main handle <NUM>. The trigger <NUM> is disposed on the lower side of the housing of the main handle <NUM> and at the rear end of the main handle <NUM>. Generally, the main handle <NUM> is held with the right hand, the speed regulator <NUM> can be operated with a thumb of the right hand, and the trigger <NUM> can be operated with the remaining four fingers of the right hand. The speed regulator <NUM> and the trigger <NUM> are operated with a single hand.

The display assembly <NUM> also includes a display portion for displaying a connection state of the first communication unit <NUM>. For example, the display portion includes the Bluetooth display light <NUM>. When the Bluetooth display light <NUM> flickers, the first communication unit <NUM> is in a to-be-connected state. When the Bluetooth display light <NUM> is constantly on, the first communication unit <NUM> is in a connected state. The first communication unit <NUM> may be the Bluetooth unit or the Wi-Fi unit. The first communication unit <NUM> is configured to send information to the terminal device <NUM> or receive information from the terminal device <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, the lawn edger also includes a shield <NUM> surrounding at least part of the blade <NUM>. The shield <NUM> can not only prevent the blade <NUM> from injuring the operator but also prevent the grass from splashing.

Referring to <FIG>, the blade <NUM> rotates about an axis of rotation in a cutting plane, a guide protrusion <NUM> is circumferentially disposed on an outer peripheral surface of the shield <NUM>, and the guide protrusion <NUM> is in the cutting plane. The guide protrusion <NUM> is disposed in the cutting plane, making it convenient for the user to align the blade according to the guide protrusion <NUM> on the shield <NUM>, so that the user can align an edge of a road more clearly, and a cost and the weight can be reduced.

In an existing lawn edger, during the detachment and installation of the blade <NUM>, a gearbox needs to be clamped with a relatively large force, causing a crack of the gearbox.

Referring to <FIG>, a flange <NUM> is disposed on the output shaft <NUM>, the flange <NUM> is provided with a notch <NUM>, the shield <NUM> is provided with a shield hole <NUM>, and the shield hole <NUM> communicates with the notch <NUM>. During the detachment of the blade <NUM>, an end of a tool <NUM> passes through the shield hole <NUM> and is inserted into the notch <NUM> to fix the output shaft <NUM> so that the blade <NUM> can be conveniently detached. The tool <NUM> is clamped on the shield <NUM> rather than the gearbox, avoiding damage to the gearbox and protecting the gearbox from the crack.

Specifically, a limiting rib is disposed on the shield <NUM>, and the shield hole <NUM> is opened on the limiting rib, or the limiting rib surrounds the shield hole <NUM>. The tool <NUM> may use an existing wrench.

Referring to <FIG>, <FIG>, <FIG>, and <FIG>, the lawn edger also includes a support assembly including a walking wheel <NUM> for supporting the lawn edger on the ground. Specifically, the walking wheel <NUM> is rotatably disposed on the shield <NUM>. The walking wheel <NUM> supports the lawn edger. During use, the walking wheel <NUM> may be placed on the ground, and the lawn edger is pushed forward to implement cutting, thereby saving manpower.

The support assembly also includes a support plate <NUM> disposed on a side of the shield <NUM>. When the lawn edger is placed on the ground, the support plate <NUM> supports the lawn edger to prevent the lawn edger from turning to one side.

When the electric motor <NUM> is in a maximum-efficiency state, the ratio of output power of the electric motor <NUM> to the weight of the lawn edger is greater than or equal to <NUM> W/kg, which indicates that the electric motor <NUM> has relatively large output power, a relatively small mass, and a relatively high power density so that machine performance is improved and the whole machine is kept in a relatively light state, thereby facilitating user operation. In some examples, when the electric motor <NUM> is in the maximum-efficiency state, the ratio of the output power of the electric motor <NUM> to the weight of the lawn edger is greater than or equal to <NUM> W/kg. In some examples, when the electric motor <NUM> is in the maximum-efficiency state, the ratio of the output power of the electric motor <NUM> to the weight of the lawn edger is greater than or equal to <NUM> W/kg. In some examples, when the electric motor <NUM> is in the maximum-efficiency state, the ratio of the output power of the electric motor <NUM> to the weight of the lawn edger may be <NUM> W/kg, <NUM> W/kg, <NUM> W/kg, <NUM> W/kg, <NUM> W/kg, or <NUM> W/kg.

The output power of the electric motor <NUM> is greater than or equal to <NUM> W. In some examples, the output power of the electric motor <NUM> is greater than or equal to <NUM> W. In some examples, the output power of the electric motor <NUM> is greater than or equal to <NUM> W. In some examples, the output power of the electric motor <NUM> is <NUM> W, <NUM> W, <NUM> W, <NUM> W, <NUM> W, or <NUM> W.

The nominal voltage of the battery pack <NUM> is greater than or equal to <NUM> V, improving the machine performance and achieving suitability for more working conditions such as cutting harder stones. In some examples, the nominal voltage of the battery pack <NUM> is greater than or equal to <NUM> V. In some examples, the nominal voltage of the battery pack <NUM> is greater than or equal to <NUM> V.

As for the output power of the electric motor <NUM> when the electric motor <NUM> is in the maximum-efficiency state, a characteristic graph of the electric motor <NUM> is obtained through measurement, a maximum-efficiency point of the electric motor <NUM> is found from the characteristic graph, and output power corresponding to the maximum-efficiency point is the output power of the electric motor <NUM> in the maximum-efficiency state.

<FIG> is the characteristic graph of the electric motor <NUM>, and multiple curves are shown by using different lines in the figure, where the abscissa of each curve represents torque denoted as T and having a unit of N·m, and the ordinates of the curves are different. For ease of distinguishing, different lines and letters are used for representing the curves. The curves specifically represent the rotational speed denoted as N and having a unit of r/min, the output power denoted as Pout and having a unit of W, input power denoted as Pin and having a unit of W, a voltage denoted as U and having a unit of V, a current denoted as I and having a unit of A, and an efficiency percentage denoted as η. In the figure, η1 represents the maximum-efficiency point. In this example, efficiency at the maximum-efficiency point is <NUM>%, and the corresponding output power is <NUM> W.

The weight of the lawn edger is less than or equal to <NUM>. In some examples, the weight of the lawn edger is less than or equal to <NUM>. In some examples, the weight of the lawn edger is less than or equal to <NUM>. In some examples, the weight of the lawn edger may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

The weight of the lawn edger refers to the weight of a main part of the lawn edger excluding the battery pack <NUM> but including the blade <NUM> and the auxiliary handle <NUM>.

In another example, as shown in <FIG>, another lawn edger <NUM> has substantially the same structure as the lawn edger in <FIG>, which mainly differ in that a connection tube <NUM> extends along a straight line. Structures of the lawn edger in <FIG>, which are applicable to the lawn edger <NUM> in <FIG>, may all be applied to the lawn edger <NUM>. The details are not repeated here.

Claim 1:
A lawn edger (<NUM>, <NUM>), comprising:
an output shaft (<NUM>) for mounting a blade (<NUM>) for cutting grass;
a shield (<NUM>) surrounding at least part of the blade;
a front housing (<NUM>) accommodating at least part of the output shaft;
a rear housing (<NUM>) formed with a coupling portion (<NUM>) for coupling a battery pack (<NUM>);
an electric motor (<NUM>) mounted in the rear housing to drive the output shaft;
a connection assembly (<NUM>) for connecting the front housing to the rear housing; and
a transmission assembly (<NUM>) for transmitting power between the electric motor and the output shaft; characterized in that
the lawn edger (<NUM>, <NUM>) comprises a support assembly including a walking wheel (<NUM>) rotatably disposed on the shield (<NUM>) and supporting the lawn edger (<NUM>, <NUM>) during use; and
when the electric motor is in a maximum-efficiency state, a ratio of output power of the electric motor to a weight of the lawn edger is greater than or equal to <NUM> W/kg.