Patent Publication Number: US-2023148470-A1

Title: Lawn mower

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the Hong Kong Standard Patent Application No. 22020005367.0, filed on 6 Apr. 2020, the International Application No. PCT/CN2020/114671, filed on 11 Sep. 2020, and the International Application No. PCT/CN2020/119865, filed on 8 Oct. 2020, which are incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to a lawn mower. More particularly, the present disclosure relates to a power-assisted walk-behind lawn mower with an edge guide and a blade changing mechanism. 
     BACKGROUND 
     Lawn mowers are widely used outdoor power tools for cutting grass and maintaining the lawn surface. Electrically powered lawn mowers may be user-propelling or self-propelling with grass cutting blades rotatably driven by an electric motor above the grass and below the cutting deck of the lawn mower. A handle may be mounted at the rear of the lower housing and extended rearwardly and upwardly for the gardener or operator to control. 
     Generally, the cutting blades are enclosed within the housing of the cutting deck for preventing any accidental injury of the operator by the rotating blade. The side walls of the housing may extend below the plane of the cutting blade for minimizing the risk. However, this arrangement may limit the effective width of the cutting area. Vegetation growing beyond the effective width, such as along the width of the wheels, cannot be mowed. In the case of using the lawn mower near a walking path, a garden edge, a fence, a wall, or other structures, the cutting blade cannot reach the grass adjacent to the structure due to the distance between the cutting blade and the side wall of the housing. 
     Furthermore, the cutting blade of the mowing apparatus may wear out after repeated use for cutting shrubs or grass in a lawn and may need to be sharpened or replaced. However, the replacing process can be especially challenging and dangerous to an untrained user. The cutting blade is generally installed to rotate with an output shaft on a plane substantially in parallel to the ground surface. When replacing the cutting blade, the operator is required to hold the cutting blade firmly from rotating and unscrew a fastener carefully. As the cutting blade may be sharp, protective measures should be taken by the operator. 
     Accordingly, there is a need in the art for a power-assisted lawn mower that seeks to address at least some of the above issues. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure. 
     SUMMARY OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following summary, or may be obvious from the summary, or may be learned through practice of the invention. 
     In accordance with certain embodiments of the present disclosure, a power-assisted walk-behind lawn mower for cutting grass and maintaining the lawn surface is provided. The lawn mower comprises a mower deck, a cutting blade rotatably mounted to the mower deck, a motor for driving the cutting blade, and a blade changing mechanism. The blade changing mechanism includes a fastener for securing the cutting blade to the motor; a blade securement tool for limiting the cutting blade from rotating in at least one direction; and at least one opening at the mower deck for removably receiving the blade securement tool. 
     In accordance with a further aspect of the present disclosure, the blade securement tool limits the cutting blade from rotating in both directions. 
     In accordance with a further aspect of the present disclosure, the blade changing mechanism comprises two spaced apart openings. 
     Preferably, the blade securement tool comprises a U-shaped piece with two side pins, the U-shaped piece crosses the cutting blade when the two side pins are received in the two openings. 
     Preferably, the U-shaped piece comprises a horizontal member connected between the two side pins, wherein the horizontal member has a length larger than a width of the cutting blade. 
     In accordance with a further aspect of the present disclosure, the mower deck comprises a motor housing, the at least one opening is provided at the motor housing. 
     In accordance with certain embodiments of the present disclosure, the lawn mower comprises a mower deck, a cutting blade rotatably mounted to the mower deck, and an edge guide on the mower deck. The cutting blade defines a generally planar cutting area. The edge guide defines a channel extending from an area radially exterior to and below the cutting area to the cutting area. 
     In accordance with a further aspect of the present disclosure, the edge guide comprises a vertically extending outer guide, the outer guide is radially away from and extends lower than the cutting area. 
     In accordance with a further aspect of the present disclosure, the edge guide further comprises a combing structure at an inner side of the outer guide for combing and/or converging grass to the cutting area. 
     Preferably, the combing structure comprises one or more ribs, the one or more ribs divide the channel into two or more sub-channels. 
     Preferably, the one or more ribs extend at least partially in a radial direction. 
     Preferably, the two or more sub-channels are tortuous. 
     In accordance with certain embodiments of the present disclosure, a lawn mower is configured to be powered by one or more battery sources, and comprises a cutting blade, a motor for driving the cutting blade, and a dynamic power management system configured to adjust a rotation speed of the motor dynamically based on a duty condition of the cutting blade such that the rotation speed is a function of a current supplied to the motor. 
     In accordance with a further aspect of the present disclosure, the dynamic power management system comprises one or more current sensors configured to continuously or regularly measure the current of the motor. 
     In accordance with a further aspect of the present disclosure, the lawn mower further comprises a processor having a current consumption profile and is configured to determine the rotation speed of the motor by comparing the current of the motor with the current consumption profile. 
     Preferably, the current consumption profile comprises a plurality of predetermined current ranges or thresholds representing at least a high current consumption and a low current consumption. 
     In accordance with a further aspect of the present disclosure, the one or more current sensors are attached to a current path to the motor using a shunt resistor or a magnetic device. 
     In accordance with a further aspect of the present disclosure, the function is selected from a group consisting of: an increasing step function, a continuous monotonically increasing function, or a combination thereof. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Other aspects and advantages of the present invention are disclosed as illustrated by the embodiments hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended drawings contain figures to further illustrate and clarify the above and other aspects, advantages, and features of the present disclosure. It will be appreciated that these drawings depict only certain embodiments of the present disclosure and are not intended to limit its scope. It will also be appreciated that these drawings are illustrated for simplicity and clarity and have not necessarily been depicted to scale. The present disclosure will now be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG.  1    is a perspective view of the lawn mower m accordance with certain embodiments of the present disclosure; 
         FIG.  2    is a side view of the lawn mower of  FIG.  1   ; 
         FIG.  3    is a top view of the lawn mower of  FIG.  1   ; 
         FIG.  4    is a bottom view of the lawn mower of  FIG.  1   ; 
         FIG.  5    is a perspective view of the horizontal member of the handle of the lawn mower of  FIG.  1   ; 
         FIG.  6 A  is a side view of the horizontal member of the handle of the lawn mower of  FIG.  1    when the safety bail is pivoted to a higher position; 
         FIG.  6 B  is a side view of the horizontal member of the handle of the lawn mower of  FIG.  1    when the safety bail is pivoted to a lower position; 
         FIG.  7 A  is an exploded perspective view of the control assembly of the lawn mower of  FIG.  1   ; 
         FIG.  7 B  is an exploded top view of the control assembly of the lawn mower of  FIG.  1   ; 
         FIG.  7 C  is an internal view of the control assembly of the lawn mower of  FIG.  1   ; 
         FIG.  8 A  is an internal view of one of the tube connectors having a switch that can be triggered by the pivotal movement of the safety bail; 
         FIG.  8 B  is an exploded view of the safety bail and the tube connectors of the lawn mower of  FIG.  1   ; 
         FIG.  9    is a perspective view of the internal structure of the lawn mower of  FIG.  1    with the openable cover of the power module removed; 
         FIG.  10    is an internal perspective view of the power assembly and the cutting blade of the lawn mower of  FIG.  1   ; 
         FIG.  11    is an exploded view of the power assembly and the cutting blade of  FIG.  10   ; 
         FIG.  12 A  is a bottom front view of a mower deck of the lawn mower of  FIG.  1    with the blade securement tool mounted; 
         FIG.  12 B  is a rear view of the power assembly of the lawn mower of  FIG.  1    that can be mounted with the blade securement tool; 
         FIG.  12 C  is a bottom view of the lawn mower of  FIG.  1    when replacing the blade using the blade securement tool; 
         FIG.  13 A  is a bottom front view of an edge guide of the lawn mower of  FIG.  1   ; 
         FIG.  13 B  is a bottom view of the edge guide of  FIG.  13 A ; 
         FIG.  13 C  is a perspective view of the edge guide of  FIG.  13 A ; 
         FIG.  13 D  is a bottom perspective view of the edge guide of  FIG.  13 A ; 
         FIG.  13 E  is a perspective view of the edge guide of the lawn mower of  FIG.  1    with an extension portion below the outer guide; 
         FIG.  14 A  is a perspective view of the rear wheel; 
         FIG.  14 B  is an alternative view of the rear wheel of  FIG.  14 A  illustrating the gear driving mechanism; 
         FIG.  14 C  is an exploded view of the rear wheel of  FIG.  14 A ; 
         FIG.  15    is a front view of the propelling machine installed in the lawn mower of  FIG.  1   ; 
         FIG.  16    is a front internal view of the propelling machine of  FIG.  15    showing the structure of the actuator assembly; 
         FIG.  17    is an exploded internal view of the propelling machine of  FIG.  15   ; 
         FIG.  18    is an exploded view of the clutch assembly of the propelling machine of  FIG.  15   ; and 
         FIG.  19    is a schematic block diagram of the lawn mower in accordance with certain embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the disclosure or its application and/or uses. It should be appreciated that a vast number of variations exist. The detailed description will enable those of ordinary skilled in the art to implement an exemplary embodiment of the present disclosure without undue experimentation, and it is understood that various changes or modifications may be made in the function and structure described in the exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims. 
     The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all of the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued. 
     Terms such as “upper”, “lower”, “inner”, “outer”, “front”, “rear”, “top”, “bottom”, and variations thereof are used herein for ease of description to explain the positioning of an element, or the positioning of one element relative to another element, and are not intended to be limiting to a specific orientation or position. 
     The present disclosure relates to a structure of a lawn mower or a gardening tool, which is generally designated as  10 . More specifically, but without limitation, the present disclosure provides a power-assisted walk-behind lawn mower with a deck height adjustment mechanism. One having ordinary skill in the art would understand that the current disclosure is also applicable to various gardening tools and power equipment, such as blowers, cultivators, tillers, and lawn sweepers. 
     The lawn mower  10  is a walk-behind electric lawn mower arranged to operate on a lawn or a grass growing surface so as to cut the grass. This action is commonly known as “mow the lawn” and is often undertaken by gardeners and landscape workers, or referred to as the “operator”, to maintain a lawn surface. With reference to  FIGS.  1  and  2   , there is provided a lawn mower  10  comprising a mower body  200  and a handle  100 , wherein the mower body  200  is the tool body rest on an operating surface for cutting the grass. The mower body  200  comprises a mower deck  201  having a front end  201 A and a rear end  201 B. The handle  100  is coupled to the rear end  201 B of the mower body  200  comprising one or more mower joints  261 . The handle  100  is pivotable relative to the mower body  200  via the one or more mower joints  261 . The handle  100  comprises one or more tube assemblies  120  with a horizontal member  110  as a handgrip for the operator to control. The handle  100  is also slidable relative to the mower body  200 . As shown in  FIG.  10   , the lawn mower  10  further comprises a power module  210 , a motor  250 , and a cutting blade  521 , wherein the motor  250  is configured to drive the cutting blade  521 . In certain embodiments, the power module  210  is provided on top of the mower deck  201 . In certain embodiments, the power module  210  is formed integrally with the mower deck  201 . The mower body  200  further comprises a carry handle  220  coupled to the mower deck  201  with an actuator  230  thereon. This would be the most convenient for the operator to lift or lower the lawn mower  10  with the carry handle  220 . 
     As shown in  FIG.  2   , the mower body  200  defines a longitudinal axis B extending from rear to front of the mower body  200 . Furthermore, a vertical axis A that is substantially perpendicular to the longitudinal axis B is also defined. The handle  100  extends at an angle A 1  with respect to the longitudinal axis B in a work position. The lawn mower  10  is supported by a wheel arrangement comprising one or more front wheels  310  and one or more rear wheels  320 . In the illustrated embodiment, the wheel arrangement includes two front wheels  310  and two rear wheels  320 . Preferably, as is the case in this embodiment, the lawn mower  10  is switchable between self-propelling and user-propelling, with a propelling machine  600  arranged to propel the lawn mower  10  on an operating surface via the wheel arrangement. When the lawn mower  10  is switched to user-propelling, the operator pushes the handle  100  forward to move the lawn mower  10  on the operating surface via the wheel arrangement. It is apparent that the wheel arrangement may be formed from various types and combinations of wheels, including tracks (such as in tank tracks), chains, belts (such as in snow belts), or other forms of wheel arrangements. 
     In certain embodiments, a grass collector  400  may be removably attached to the rear portion of the mower deck  201  for collecting the clippings and debris ejected from the lawn mower  10 . The grass collector  400  may be essentially a box-like structure made of fabric, plastic, canvas, or other suitable materials. As illustrated in  FIG.  3   , the grass collector  400  may comprise a cover  411 , a collector handle  412 , and a capacity indicator. It is within the scope and spirit of the present disclosure that the grass collector  400  may have a different shape provided that the grass collector  400  can perform the function of collecting the clippings and debris ejected from the lawn mower  10 . The bottom of the grass collector  400  may have a sheet of metal as a support for carrying the debris. The grass collector  400  may be attached to the rear end  201 B of the mower deck  201  using one or more hooks, screws, clips, connectors, and/or other securing elements. 
       FIG.  4    illustrates the bottom side of the lawn mower  10 , which is opened for cutting the grass. A cutting blade  521  is provided in the mower body  200  and are rotatably housed within the cutting area  522  under the mower deck  201 . The cutting blade  521  is suspended above the ground at the lower end of an output shaft  254  arranged along the vertical axis A. The mower deck  201  comprises a motor housing  526  for housing the motor  250 . The cutting blade  521  is driven by the motor  250  to rotate above the ground and cut the grass. Therefore, the cutting blade  521  is rotatably mounted to the mower deck  201  and defines a generally planar cutting area  522 . The resulting grass clippings and debris are driven by airflow produced within the cutting area  522  by the rotation of the cutting blade  521  and an impeller  527 , through a discharge chute  550  underneath the mower deck  201 , to the grass collector  400 . 
     As shown in  FIG.  5   , the horizontal member  110  is at the distal end of the handle  100  away from the mower body  200 . Therefore, the tube assembly  120  as a telescopic tube assembly can be adjusted to position the horizontal member  110  at a height most comfortable to the operator. The horizontal member  110  comprises a crossbar  114 , a supporting bar  117 , and a control assembly  111  mounted to one or both of the crossbar  114  and the supporting bar  117 . Two tube connectors  115  are provided at a distal end of the tube assembly  120  for the supporting bar  117  is arranged horizontally therebetween. The crossbar  114  is substantially a U-shaped bar connected to both ends of the supporting bar  117  for the operator to grip onto, wherein the structure of the U-shaped bar may be raised in the middle, as evident from the drawings, or otherwise be lowered or straightened. In certain embodiments, the crossbar  114  may further be permitted to be pivotally rotated up and down about the supporting bar  117  by turning a pivotal joint (not shown) at the tube connectors  115 . In certain embodiments, the control assembly  111  comprises one or more of a safety bail  113 , a propelling actuator  116 , a cutting actuator  118 , and a control panel  112 . At least part of the control assembly  111  may be provided at the center of the crossbar  114  and, in certain embodiments, it may also be connected to the supporting bar  117 . On the upper surface of the control assembly  111  facing the operator, there may be provided the control panel  112 . The control panel  112  may provide indicators to indicate mower statuses, such as battery charge level, self-propelling speed, over current signal, blade change signal or others. The control panel  112  may also provide control buttons to change mower status, such as self-propelling speed adjustment, cutting speed adjustment, or others. The propelling actuator  116  comprises one or two bars extending laterally out of the main body of the control assembly  111 . The cutting actuator  118  may be in the form of a spring-loaded button at the main body of the control assembly  111 . The safety bail  113  may be pivotable by the operator and restores to its original position by a spring force or other pulling forces when released by the operator. In certain embodiments, only when the safety bail  113  is pivoted by the operator from a higher position as shown in  FIG.  6 A , to a lower position as shown in  FIG.  6 B , the lawn mower  10  can be operating by actuating the propelling actuator  116  to start self-propelling, or by actuating the cutting actuator  118  to start cutting. When the safety bail  113  is released, the lawn mower  10  is prevented from being operating. Other ways of configuring the functions of the safety bail  113 , the propelling actuator  116 , and the cutting actuator  118  are also within the contemplation of the present disclosure. 
     Referring now to  FIGS.  7 A and  7 B , the exploded view of the control assembly  111  is depicted. The control assembly  111  includes a control panel  112 , which may comprise a touch screen (not shown) or a plurality of switches  112 B and indicators, for selecting and indicating the mode of operation and the speed of each motor. A control circuit board  112 A, assembled within an upper housing  111 A and a lower housing  111 B, is provided to receive the signals from the control panel  112  and electrically connected to the main circuit board  216 . As shown in  FIG.  7 C , the cutting actuator  118  is a push button located on the control assembly  111 . The cutting actuator  118  is arranged to cause compression of a first spring  118 A, and has a protrusion  118 B on the bottom side of the cutting actuator  118  for engaging a first switch  119 A. When the cutting actuator  118  is actuated by the operator, it overcomes the resisting force from the first spring  118 A and the protrusion  118 B actuates the first switch  119 A within the main body of the control assembly  111 . When the propelling actuator  116  is actuated by the operator, it overcomes the resisting force from a second spring  116 A and actuates a second switch  119 B within the main body of the control assembly  111 . 
     Referring to  FIGS.  8 A and  8 B , the safety bail  113  has at least one end secured to the handle  100 , and preferably secured to at least one of the tube connectors  115 . A loop spring  113 C may be provided at a first pivotal end  113 D of the safety bail  113  to pivotally restore the position of the safety bail  113  when it is released. A tab  113 A is affixed or otherwise welded to the first pivotal end  113 D or the second pivotal end  113 E of the safety bail  113 , which is coupled with a third switch  113 B. When the safety bail  113  is pivoted down with respect to the pivotal ends  113 D,  113 E from a higher position to a lower position, the tab  113 A is pivoted up with respect to the pivotal ends  113 D,  113 E and actuates the third switch  113 . The pivotal movement of the safety bail  113  and the corresponding pivotal movement of the tab  113 A are indicated in  FIG.  8 B . 
       FIG.  9    depicts the structure of the lawn mower  10  around the mower deck  201 . It shows part of the power module  210 .  FIGS.  10  and  11    depict the internal structure and the exploded view of the power module  210 , the motor  250 , and the cutting blade  521  of the lawn mower  10 . The power module  210  comprises one or more battery receptacles  212  for accommodating one or more battery sources  211 , a main circuit board  216 , and a safety key receiver  217  for receiving a safety key  217 A. The power module  210  comprises an openable cover to allow operator&#39;s access to the one or more battery sources  211  and the safety key  217 A inside the power module  210 . The lawn mower  10  is configured to be powered by the one or more battery sources  211 . For instance, the electric power from the one or more battery sources  211  is supplied to the main circuit board  216  for driving and/or controlling the motor  250 , and/or the propelling machine  600 . In one embodiment, the battery source  211  may be a rechargeable lithium-ion battery configured to receive and store energy for powering the lawn mower  10 . In certain embodiments, a charging circuit may be included in the lawn mower  10 . But the batteries may also be removed from the lawn mower  10  for charging purposes. The one or more battery sources  211  can be installed to or removed from the one or more battery receptacles  212 . In certain embodiments, only when the one or more battery sources  211  are properly installed on the battery receptacles  212 , and/or the safety key  217 A is inserted, then the lawn mower  10  can operate. The mower deck  201  may have one or more air vents or openings for permitting ventilation such that the battery sources  211  can be cooled by air flows. In certain embodiments, at least some of the air vents or openings are provided at the bottom of the power module  210 . 
     The motor  250  may be an electric motor or other suitable engines for driving the cutting blade  521 , with or without transmissions. In certain embodiments, the motor  250  comprises an upper housing  251 , a stator with a rotor  252 , and a lower housing  253 . An output shaft  254  comprising a first end  254 A and a second end  254 B disposed opposite the first end  254 A is provided. The output shaft  254  may be supported by two bearings (not shown) respectively placed above and below the rotor  252 . the first end  254 A is a motor shaft portion configured to engage the motor  250 , and the second end  254 B is an output portion with a threaded end  254 C. The output shaft  254  is used for driving the cutting blade  521  to rotate. For convenience and simplicity, the electrical power and the respective electronic parts have not been shown in the figures. A heat sink  255  having a plurality of heat dissipating fins may be positioned adjacent to the battery sources  211  and the motor  250 . In certain embodiments, the heat sink  255  may comprise a plurality of air vents or openings for cooling air to pass through. The size and/or configuration of the air vents or openings is designed not to allow the passing of grass clippings and debris. 
     The output shaft  254  is coupled to the cutting blade  521  and the impeller  527 . The cutting blade  521  is rotatably mounted to the mower deck  201  for cutting the grass across an effective cutting width, which is equivalent to the longitudinal length of the cutting blade  521 . The impeller  527  rotates together with the output shaft  254 , and functions as an air pump to generate air flows within the cutting area  522 . In certain embodiments, such air flows cause cooling air to be drawn from above the mower deck  201 , optionally through the motor  250  and the heat sink  255 . In certain embodiments, the air flows cause the grass clippings to be directed through the discharge chute  550  to the grass collector  400 . The cutting blade  521  includes a body  521 A and a blade opening  521 B configured to receive the output shaft  254 , such that the cutting blade  521  is configured to rotate together with the output shaft  254  on a plane substantially in parallel to the ground surface and along the longitudinal axis B. The body  521 A may have a substantially rectangular shape having one or more cutting edges  521 C, or with teeth or curved structure. In certain embodiments, the lawn mower  10  may have more than one cutting blade  521  connecting to the output shaft  254  without departing from the scope and spirit of the present disclosure. 
     The impeller  527  is formed by a circular rotary disc  527 C with an impeller opening  527 A at the center, and a plurality of impeller blades  527 B arranged perpendicular to the circular rotary disc  527 C. The plurality of impeller blades  527 B are in an arcuate-shape and are evenly spaced apart circumferentially around the circular rotary disc  527 C. The output shaft  254  is first inserted into the impeller opening  527 A and then the blade opening  521 B, thereby the impeller  527  is positioned above the cutting blade  521 . Alternatively, it is also possible to have the cutting blade  521  placed above the impeller  527  without departing from the scope and spirit of the present disclosure. 
     On the second end  254 B, a clamp  525  and a fastener  523  are used to secure the cutting blade  521  and the impeller  527  to the motor  250 . In particular, the fastener  523  may include a nut and a washer that can be screwed into the thread end  254 C of the output shaft  254 , and is configured to axially secure the cutting blade  521 . On the opposite side of the circular rotary disc  527 C, there is provided one or more protrusions  527 D arranged to mate with the corresponding one or more mounting holes  521 D on the cutting blade  521 . The mating can limit the radial or circumferential movement of the cutting blade  521  relative to the impeller  527 . Therefore, the impeller  527  is configured to rotate together with the cutting blade  521  after securing with the clamp  525  and the fastener  523 . 
     Due to the repeated use of the cutting blade  521  for cutting shrubs or grass in a lawn, at least a certain portion of the cutting blade  521  may wear out. Therefore, there is a need to disassemble the cutting blade  521  from the mower for sharpening or replacement. However, the blade replacing process can be especially challenging and dangerous to the operator. Conventionally, the operator may need to hold the cutting blade  521  from rotating, and unscrew the fastener  523  with a tightening tool or a motorized tool. Protective gloves or certain tools are usually needed during the blade replacing process. This may cause the blade to be damaged in the process. 
     The present disclosure advantageously provides a blade changing mechanism that allows the operator to change the cutting blade  521  safely and conveniently. The blade changing mechanism comprises the fastener  523 , a blade securement tool  540 , and at least one opening  541  at the mower deck  201 . As shown in  FIG.  12 A , the blade securement tool  540  is mounted across the body  521 A of the cutting blade  521  for limiting the cutting blade  521  from rotating in at least one direction, and in the illustrated embodiment, the blade securement tool  540  limits the cutting blade  521  from rotating in both directions. The at least one opening  541  is provided for removably receiving the blade securement tool  540 , preferably on the motor housing  526 . Referring to  FIG.  12 B , the blade securement tool  540  comprises a U-shaped piece with two side pins  540 A and a horizontal member  540 B. The at least one opening  541  comprises two spaced apart openings arranged to receive the two side pins  540 A. The horizontal member  540 B is connected between the two side pins  540 A with a length larger than the width of the cutting blade  521 . The U-shaped piece crosses the cutting blade  521  when the two side pins  540 A are received in the two openings  541 . Therefore, the rotation of the cutting blade  521  can be limited by mounting the blade securement tool  540  across the cutting blade  521 . As illustrated in  FIG.  12 C , after securing the position of the cutting blade  521  with the blade securement tool  540 , the operator can use a tightening tool  542 , such as a spanner, a wrench, a screwdriver, or the like, to unscrew the fastener  523  from the threaded end  254 C. Similarly, the blade changing mechanism can also be used when assembling the cutting blade  521  to the lawn mower  10 . The operator first mounts the cutting blade  521  onto the output shaft  254  under the mower deck  201  by mating the one or more protrusions  527 D with the corresponding one or more mounting holes  521 D on the cutting blade  521 . Then the clamp  525  is used to secure the cutting blade  521 , and the blade securement tool  540  is used to limit the rotation of the cutting blade  521 . The operator can now easily screw the fastener  523  to complete the installation of the cutting blade  521 . 
     The lawn mower  10  of the present disclosure comprises one or more edge guides  510 , each edge guide  510  defines a channel extending from an area radially exterior to and below the cutting area  522  to the cutting area  522 . The edge guide  510  can improve the cutting of shrubs or grass outside the cutting area  522  of the lawn mower  10 , wherein the cutting area  522  is a generally planar area defined by the cutting blade  521 . This is particularly useful when the lawn mower  10  mows along a boundary, such as a walking path, a garden edge, a fence, a wall, or other structures. As shown in  FIGS.  13 A and  13 B , the edge guide  510  is located at each of the left and right sides of the lawn mower  10 , and is configured to guide the grass outside the cutting area into the cutting area  522 . The mower deck  201  may have different shapes with a side wall  202  surrounding the cutting area  522 . As shown in the illustrated embodiments, the mower deck  201  has a circular shape, and the edge guides  510  are positioned adjacent to the perimeter of the annular side wall  202 . The edge guide  510  extends tangentially from the periphery of the annular side wall  202  and generally in parallel with the longitudinal axis B. In certain embodiments, the mower deck  201  may be in the shape of a rectangular or a square, while the edge guides  510  may be provided adjacent to or within the side wall at the front corners (not shown). The edge guide  510  is formed integrally with the mower deck  201 . Alternatively, the edge guide  510  may also be a discrete element welded or otherwise affixed to the side wall  202  of the mower deck  201 . The edge guide  510  is operable to guide the grass outside the mowing area into the cutting area  522  under the mower deck  201  for the cutting blade  521  to cut. 
     In certain embodiments, the edge guide  510  comprises a vertically extending outer guide  511  and a combing structure  513  at an inner side of the outer guide  511  for combing and/or converging grass to the cutting area  522 . In certain embodiments, the outer guide  511  has a tapered protruding portion  511 B that extends further forward than the combing structure  513  for better converging the grass to the combing structure  513 . The combing structure  513  comprises one or more ribs  513 A built on a generally planar base  510 A. The planar base  510 A is extended from the base of the side wall  202 , which is better illustrated in  FIG.  13 C . In certain embodiments, the one or more ribs  513 A divide the channel into two or more sub-channels  512 , and may extend at least partially in a radial direction. In certain embodiments, the two or more sub-channels  512  are tortuous. When the lawn mower  10  moves forward to perform the cutting of the grass, the edge guide  510  can guide the grass near the left and right edges of the mower inward and into the cutting area  522  under the mower deck  201 . 
     Each of the two or more sub-channels  512  may include an opening  512 B between the outer guide  511  and the one or more ribs  513 A for easing the grass to pass through and guide to the cutting area  522 . Referring to the bottom perspective view in  FIG.  13 D , the sub-channel  512  may further comprise a bent channel  512 C and a cutout  512 A on the side wall  202 . As the edge guide  510  is built on the same planar base  510 A as the side wall  202 , the cutout  512 A provides an opening for the grass to enter into the cutting area  522 . 
     In an alternative embodiment, the outer guide  511  and the one or more ribs  513 A may protrude above and/or below the planar base  510 A. As shown in  FIG.  13 E , the outer guide  511  comprises an extension portion  511 A protruding below the planar base  510 A by an extension height H 3 . The extension portion  511 A may be a vertically extended guiding wall extending vertically along an axis perpendicular to or substantially perpendicular to the longitudinal axis B. Similarly, each of the one or more ribs  513 A may also has an extension protruding below the planar base  510 A (not shown). The two or more sub-channels  512  are above the ground surface by a first vertical height H 1 , whilst the outer guide  511  with the extension portion  511 A is above the ground surface by a second vertical height H 2 . The first vertical height H 1  is larger than the second vertical height H 2 , thereby the outer guide  511  is closer to the ground surface than the bottom of the mower deck  201 . With the difference between the first vertical height H 1  and the second vertical height H 2 , the two or more sub-channels  512  are defined and formed below the planar base  510 A, thereby cutout  512 A on the side wall  202  is not needed to comply with the safety standard required. 
     With reference to  FIG.  14 A , at least one of the rear wheels  320  has a tire  321 , a wheel rim  322 , and a hub  325 . The outer circumferential surface of the wheel rim  322  is configured to receive the tire  321 . The wheel rim  322  is mounted to the hub  325  through its inner circumferential surface. In certain embodiments, either or both of the tire  321  and the hub is formed integrally with the wheel rim  322 . The hub  325  has an axle hole  322 B at the center of the wheel rim  322  for receiving a wheel shaft  531 , wherein the rear wheel  320  is allowed to rotate freely about the wheel shaft  531 . The inner circumferential surface of the wheel rim  322  is further provided with internal gear teeth to form an internal ring gear  322 A. Referring to  FIG.  14 B , a pinion  324  engages the internal ring gear  322 A eccentrically from a central axis of the wheel shaft  531 . The external gear teeth of the pinion  324  are in mesh with the internal gear teeth of the internal ring gear  322 A, such that when the pinion  324  rotates about the driving shaft  533 , the wheel rim  322  is rotated about the wheel shaft  531  accordingly at a reduced speed than the pinion  324 . Therefore, the driving shaft  533  is configured to rotatably drive at least one of the pair of rear wheels  320 , which drives the lawn mower  10  forward. In certain embodiments, the pinions  324  are provided at both ends of the driving shaft  535 , therefore both rear wheels  320  can be driven to rotate around the wheel shaft  531 . 
       FIG.  14 C  shows an exploded view of the rear wheel  320  in accordance with the present disclosure. A back cab  323  (not shown in  FIGS.  14 A and  14 B ) is mounted on the internal side of the rear wheel  320  to cover the pinion  324  and the internal ring gear  322 A. The back cab  323  prevents grass clippings and debris from entering and blocking the meshing between the pinion  324  and the internal ring gear  322 A of the wheel rim  322 . Shaft openings are provided on the back cab  323  for the driving shaft  533  and the wheel shaft  531  to connect into the rear wheel  320 . A wheel hub cap  325 A is placed at the end of the wheel shaft  531 . 
     The propelling machine  600  in accordance with the present disclosure is shown in  FIG.  15   , which is installed to output the driving torque to the driving shaft  533 . As the driving shaft  533  is set to rotate together with the pinion  324 , the rear wheel  320  is driven by the pinion  324  when engaged with the internal ring gear  322 A. The propelling machine  600  comprises a driving motor  620 , a clutch assembly  630 , and an actuator assembly  610 . The propelling machine  600  is configured to be powered by the one or more battery sources  211 , which receives the electric power via the plural electric wires  213  from the main circuit board  216 . The driving motor  620  transfers the driving torque to the clutch assembly  630 . 
     In certain embodiments, the lawn mower  10  is switchable between self-propelling and user-propelling. This is achieved by the actuator assembly  610  by engaging or disengaging the clutch assembly  630 . The actuator assembly  610  may be an electromagnetic actuator, an electrical actuator having a solenoid, or a mechanical actuator having a pull wire. When the clutch assembly  630  is adjusted to an engaged configuration, the lawn mower  10  is in self-propelling mode. When the clutch assembly  630  is adjusted to a disengaged configuration, the lawn mower  10  is in user-propelling mode, and the rear wheels  320  are free to rotate. The actuator assembly  610  may also provide an enable signal for activating the driving motor  620  when the clutch assembly  630  is in the engaging configuration. By way of this arrangement, the actuator assembly  610  is operable to activate the driving motor  620  and clutch assembly  630  for driving the rear wheels  320 . 
     A mode selection wire  611  is an electric wire connected to the propelling machine  600  from the propelling actuator  116 , which is selectable by the operator to switch the lawn mower  10  between a self-propelling mode and a user-propelling mode. Therefore, the actuator assembly  610  receives a mode selection signal via the mode selection wire  611 . 
       FIG.  16    shows the internal structure of the actuator assembly  610  in accordance with the present disclosure. The actuator assembly  610  comprises an electromagnetic actuator  612 , a hook  615 , an actuator spring  614 , a locking member  616 , and a reset spring  617 . The mode selection wire  611  is connected to an electromagnetic actuator  612 , which comprises a cylindrical housing supported on the driving motor  620 , a solenoid, and a piston  613  movable between an extended position and a retracted position along the longitudinal length of the electromagnetic actuator  612  by an induced electromotive force. The piston  613  is connected to a hook  615  with an actuator spring  614  biasing and surrounding the piston  613  for restoring the piston  613  to an extended position when the electromagnetic actuator  612  is disabled. 
     When the electromagnetic actuator  612  receives an inoperative instruction, the piston  613  is in the extended position to push the hook  615  forward. When the electromagnetic actuator  612  receives an operative instruction, the electromagnetic actuator  612  is activated and the piston  613  is moved to the retracted position to pull the hook  615  rearward. The locking member  616  has a catch  616 B connected to the hook  615  on the upper side, which is rotatable about a pivot joint  616 D for locking or unlocking the clutch assembly  630 . On at least one of the fork end  616 A of the locking member  616 , a reset spring  617  is attached thereto for restoring the position of the locking member  616 . 
     As shown in  FIG.  17   , the locking member  616  comprises protrusions  616 C protruding out from the circumference of the fork end  616 A for interlocking the clutch assembly  630 . When the piston  613  is moved to the extended position, the catch  616 B is moved to a first direction to disengage the protrusion  616 C. When the piston  613  is moved to the retracted position, the catch  616 B is moved to a second direction to engage the protrusion  616 C. The clutch assembly  630  is adjustable between an engaged configuration and a disengaged configuration, wherein the driving torque is transferred from the driving motor  620  to the output shaft  533  in the engaged configuration, and wherein the driving torque is not transferred between the driving motor  620  and the output shaft  533  in the disengaged configuration. The clutch assembly  630  receives the driving torque from the driving motor  620 , and when in the engaged configuration, drives the output shaft  635  and the output gear  652  fixed co-axially and supported by a ball bearing  653 . The output gear  652  meshes with a shaft gear  651  on the driving shaft  533  so that the driving torque on the output gear  652  is transferred to the driving shaft  533 . In certain embodiments, the output gear  652  and the shaft gear  651  are the same in the number of teeth so that the gear ratio is 1 to 1. The shaft gear  651  is also supported by a plurality of ball bearings  654 , as shown in the illustration. 
       FIG.  18    illustrates the internal structure of the clutch assembly  630  in accordance with certain embodiments of the present disclosure. The clutch assembly  630  comprises a ring gear  631 , a first planetary gear set  632 , a planet carrier  633 , and a second planetary gear set  634 . The ring gear  631  comprises a circular detent track  636  having a plurality of circumferentially spaced detents  636 A. The first planetary gear set  632  comprises a sun gear  632 A and three planet gears  632 B in meshing relationship. The driving torque from the driving motor  620  is inputted from the motor shaft  622  to the clutch assembly  630  via the sun gear  632 A and coupled to the three planet gears  632 B. The ring gear  631  is driven by the first planetary gear set  632  to rotate and drive the second planetary gear set  634 , which in turn drives the planet carrier  633 . The planet carrier  633  is coupled to the output shaft  635  for transferring the driving torque to the driving shaft  533 . 
     When the operator activates the self-propelling mode by triggering the propelling actuator  116 , an operative instruction is received by the electromagnetic actuator  612 . The piston  613  is moved to the extended position by the electromagnetic actuator  612 , and pushes the hook  615  to the first direction. The locking member  616  is pivotable with respect to clutch assembly  530  to an unlocked position. At the unlocked position, each individual protrusion  616 C of the locking member  616  does not engage one of the detents  636 A of the circular detent track  636 , the ring gear  631  in moved by the driving motor  620 . 
     When the operator activates the user-propelling mode by triggering the propelling actuator  116 , an inoperative instruction is received by the electromagnetic actuator  612 . The piston  613  is moved to the retracted position by the electromagnetic actuator  612 , and pulls the hook  615  to the second direction. The locking member  616  is pivotable with respect to clutch assembly  530  to a locked position. At the locked position, the protrusion  616 C engages the circular detent track  636  and the ring gear  631  is not allowed to rotate. The reset spring  617  is configured to bias the locking member  616  the unlocked position. 
     Next, hereinafter is explanation and description on the driving circuit of the lawn mower  10  in accordance with certain embodiments of the present disclosure. 
       FIG.  19    is a schematic block diagram of the lawn mower  10  with a smart cutting mode. A processor  710 , or microcontroller, is configured to receive plural control signals and other status signals for controlling the operation of the motor  250  and the propelling machine  600 . 
     The processor  710  may be implemented by hardware, software, firmware (e.g., processor microcode), or any combination thereof. When implemented in software or firmware, the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a non-transitory storage medium. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. In certain examples, a microcontroller is used instead of the processor  710 , which may include an integrated circuit chip having a microprocessor, a read only memory (ROM), interfaces for peripheral devices, timers, analog-to-digital converters and digital-to-analog converters, and other functional units. 
     The processor  710  receives power from the one or more battery sources  211 , which are preferably rechargeable batteries provided in the lawn mower  10  and is described above in more detail with respect to  FIG.  9   . As the one or more battery sources  211  have limited battery capacity, a good power management is essential to ensure that the lawn mower  10  can effectively be used to mow the lawn without the need of recharging the battery sources  211  frequently. 
     As to provide an effective power management, the control panel  112  includes an operation mode selection. In certain embodiments, the lawn mower  10  is operable with two or more operation modes in associated with the motor  250 , wherein the two or more operation modes include a smart cutting mode and a normal mode. The normal mode may comprise at least one of an economy mode where the motor  250  has a relatively moderate output and a power mode where the motor  250  has a maximum output, and intermediate modes where the motor  250  has intermediate outputs. In certain embodiments, there is speed feedback for the propelling machine  600 . The control panel  112  may include a pace speed selector, which allows the operator to select the movement speed of the lawn mower  10  in self-propelling mode. Particularly, the speed of the propelling machine  600  is adjusted by applying a pulse width modulation (PWM) to the power supplied to the propelling machine  600 . The duty of the PWM is adjustable based on the pace speed selector. 
     Other control signals, such as the actuator  116 , the safety bail  113 , and the cutting actuator  118  are transmitted from the handle  100  to the processor  710  via a tube cable  730 . The processor  710  also receives a tilting signal from the tilt sensors  720  for determining whether the lawn mower  10  is raised to expose the cutting blade  521 , and a bag detection signal from the bag detectors  740  for determining whether the grass collector  400  is installed. The bag detectors  740  may include steel reeds for verifying the connections between the grass collector  400  and the rear end  201 B of the lawn mower  10 . The processor  710  also receives measurement data from the one or more temperature sensors  750  for determining whether the motor  250  and the propelling machine  600  are overheated. 
     In certain embodiments, the one or more tilt sensors  720 , including but not limited to, multi-axis accelerometers, gyroscopes, infrared sensors, motion sensors, or any combination thereof, are configured to detect the orientation of the lawn mower  10 . When the lawn mower  10  is raised to expose the cutting blade  521 , it is dangerous to have the cutting blade  521  rotating. The one or more tilt sensors  720  are configured to determine the tilt of the mower deck  201  to ensure that the electric power is supplied to the motor  250  and the propelling machine  600  when the cutting blade  521  is facing the ground surface. In other words, if the cutting blade  521  is not facing the ground surface, the electric power for the motor  250  is cut-off to prevent the cutting blade  521  from rotating. The movement of the handle  100  per se does not result in an electric power cut-off. 
     The operation modes in associated with the motor  250  are described in detail below. The economy mode is configured to reduce the motor&#39;s rotation speed. The power supplied to the motor  250  is smallest in the economy mode. As a non-limiting illustration, the motor  250  rotates at a low speed of 2,800 rotations per minute (RPM) in the economy mode. 
     The power mode is configured to increase the motor&#39;s rotation speed. The power supplied to the motor  250  is largest in the power mode. As a non-limiting illustration, the motor  250  rotates at a high speed of 3,300 RPM in the power mode. 
     The lawn mower  10  advantageously comprises a dynamic power management system for realizing the smart cutting mode. The dynamic power management system is configured to adjust a rotation speed of the motor  250  dynamically based on a duty condition of the cutting blade  521  such that the rotation speed R is a function F(IM) of a current IM supplied to the motor  250 . Operator control of the rotation speed is not required. The dynamic power management system comprises one or more current sensors  760  for detecting the current supplied. The one or more current sensors  760  are attached to the current path to the motor  250  using a shunt resistor, a magnetic device, or other equivalent structures. 
     In certain embodiments, the function is monotonically increasing with respect to the current. For instance, the function F(IM) is selected from a group consisting of: an increasing step function, a continuous monotonically increasing function, a combination thereof, or other increasing function known to an ordinary person skilled in the art. 
     The processor  710  is configured to dynamically adjust the speed of the motor  250  in response to the change in load and current supplied. In operation, the one or more current sensors  760  is configured to continuously or regularly measure the current of the motor  250 , and couple the measured current to the processor  710  or one or more operational amplifiers for comparing the measured current with a current consumption profile. The current consumption profile comprises a plurality of predetermined current ranges or thresholds representing at least a high current consumption and a low current consumption. Based on the current comparison, the processor  710  determines whether the current supplied to the motor  250  should be adjusted. 
     As a non-limiting illustration of the dynamic power management system, the motor  250  is first set to rotate at a low speed at 2,800 RPM. In a heavy duty condition, the load is increased and a higher current is required to drive the motor  250 . The current sensed by the one or more current sensors  760  is increased. When the current of the motor  250  is higher than a first threshold at 14 A, the processor  710  is configured to increase the power supplied to the motor  250  by increasing the voltage applied, thereby the speed of the motor  250  is increased to a higher speed of 3,300 RPM. Similarly, in a low duty condition, the load is decreased and a lower current is required to drive the motor  250 . The current sensed by the one or more current sensors  760  is decreased. When the current of the motor  250  is lower than a second threshold at lOA, the processor  710  is configured to decrease the power supplied to the motor  250  by lowering the voltage applied, thereby the speed of the motor  250  is decreased to a lower speed of 2,800 RPM. It should be noted that the numerals cited above are for illustrative purposes and are not meant to be a limitation of the present disclosure. It is also apparent that there may be more than two thresholds, and the thresholds are defined with hysteresis implemented. 
     This illustrates the fundamental structure and mechanism of the lawn mower in accordance with the present disclosure. It is apparent that the present disclosure may be embodied in other types of lawn mower or cutting apparatus without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the disclosure is indicated by the appended claims rather than by the preceding description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.