Patent Description:
Lawn mowers are often used as part of routine lawn care routines. Lawn mowers are traditionally powered by internal combustion engines which drive cutting blades at high speeds. As the lawn mower is advanced over the ground, the cutting blades trim the underlying grass to a desired height. In propelled, traditional lawn mowers, pulleys are utilized to transfer energy from the internal combustion engine to a drive wheel. Such pulleys are subject to wear and damage which can cause premature failure of the lawn mower.

Accordingly, improved lawn mowers are desired in the art. In particular, lawn mowers which provide enhanced operational capacity without compromising on functionality would be advantageous.

<CIT> describes a walk power mower having a cutting deck supported upon the ground by a front and rear wheel(s), wherein the mower includes a traction drive system incorporating a bidirectional transmission adapted to propel the mower alternatively in both forward and reverse directions. The mower may include a single bidirectional transmission powering only rear wheel(s) or only front wheel(s) of the mower, or two bidirectional transmissions may be provided to power both the front and the rear wheel(s).

Aspects and advantages of the invention in accordance with the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.

In accordance with one embodiment, a lawn mower is provided. The lawn mower includes: a mower deck; a cutting implement disposed below the mower deck; a handle coupled to the mower deck; a battery receiver configured to receive one or more batteries; a rear drive wheel; a forward drive wheel; a rear transmission coupled to the rear drive wheel and configured to receive power from the one or more batteries; a forward transmission coupled to the forward drive wheel and configured to receive power from the one or more batteries; and a controller configured to control the rear transmission and the forward transmission to selectively propel the lawn mower in a single-axle drive mode or an all-wheel drive mode, wherein the controller is configured to automatically revert to the single-axle drive mode when a power level of the one or more batteries drops below a critical threshold.

A full and enabling disclosure of the present invention, including the best mode of making and using the present systems and methods, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:.

Reference now will be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the drawings. Moreover, each example is provided by way of explanation, rather than limitation of, the technology.

The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive- or and not to an exclusive- or.

Terms of approximation, such as "about," "generally," "approximately," or "substantially," include values within ten percent greater or less than the stated value. When used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction. For example, "generally vertical" includes directions within ten degrees of vertical in any direction, e.g., clockwise or counter-clockwise.

Benefits, other advantages, and solutions to problems are described below with regard to specific embodiments.

In general, power tools described in accordance with one or more embodiments of the present disclosure can include lawn mowers driven by electric motors and having selectable drive modes. The selectable drive modes can include, for example, a single-axle drive mode and an all-wheel-drive mode. The operator can select between the various drive modes using a drive mode selector.

Referring now to the drawings, <FIG> illustrates a perspective view of a lawn mower <NUM> in accordance with an exemplary embodiment of the present disclosure. In accordance with one or more embodiments described herein, the lawn mower <NUM> may be reconfigurable between a plurality of operating modes, including, e.g., an all-wheel-drive mode and a single-axle drive mode (e.g., two-wheel-drive mode). The lawn mower <NUM> shown in <FIG> is depicted as including a mower deck <NUM>. The mower deck <NUM> may include a platform defining an upper surface and a lower surface. The mower deck <NUM> may thus delineate a cutting area from the surrounding environment so as to prevent flying debris from hitting the operator when in use.

The lawn mower <NUM> can further include a handle <NUM>. The handle <NUM> can extend in an upward and rearward direction from the mower deck <NUM> such that the handle <NUM> permits an operator to push or guide the lawn mower <NUM> over terrain. When the lawn mower <NUM> is in self-propel mode, the operator can use the handle <NUM> to guide the lawn mower <NUM>. When the lawn mower <NUM> is in unpropelled mode, the operator can use the handle <NUM> to push the lawn mower <NUM>.

The handle <NUM> can include a lower pivot assembly <NUM> which permits adjustment of the handle <NUM> in relation to the mower deck <NUM>. For instance, the pivot assembly <NUM> can permit the handle <NUM> to pivot between a plurality of in-use positions having different angular displacements relative to the mower deck <NUM>. By way of another example, the pivot assembly <NUM> can permit the handle <NUM> to pivot to a stored configuration whereby the handle <NUM> is, e.g., folded forward over the mower deck <NUM>.

An upper end <NUM> of the handle <NUM> can include one or more user interfaces <NUM> that allow the operator to adjust one or more parameters associated with operation of the lawn mower <NUM>. By way of non-limiting example, the user interfaces <NUM> can include any one or more of a power interface configured to power on the lawn mower <NUM>, a bail configured to prevent movement of the lawn mower <NUM> until the bail is depressed, a speed controller, an implement (e.g., blade) controller configured to selectively engage or disengage the implement from operation, a clippings release implement configured to selectively release a clippings container from the lawn mower <NUM>, or an auxiliary switch configured to operate an auxiliary component of the lawn mower <NUM> (e.g., one or more LED lights).

In an embodiment, the user interfaces <NUM> includes a drive mode selector <NUM> that is selectable between single-axis drive mode and all-wheel-drive mode.

In an embodiment, the drive mode selector <NUM> includes a push button. When the push button is depressed, the drive mode selector <NUM> is in a first operative state, e.g., all-wheel-drive mode. When the push button is not depressed, the drive mode selector <NUM> is in a second operative state different than the first operative state, e.g., a single-axle drive mode. The push button may be spring biased to return to the non-depressed state. The push button may be selectively retained in the depressed state by a detent or similar mechanism which selectively maintains the push button in the depressed state until the operator depresses the push button.

In another embodiment, the drive mode selector <NUM> includes a rotatable dial. The rotatable dial may be rotatable between a plurality of positions, including the aforementioned all-wheel-drive mode position and the aforementioned single-axle drive mode position. The rotatable dial may be selectively lockable in one or more of the plurality of positions. In certain instances, rotation of the rotatable dial may be prevented until the operator performs a secondary action other than rotation of the dial. For instance, prior to rotating the rotatable dial, the operator may be required to depress or lift the rotatable dial to unlock rotational movement.

In another embodiment, the drive mode selector <NUM> can include a switch can be pivotably toggled between a plurality of positions, including the aforementioned all-wheel-drive mode position and the aforementioned single-axle drive mode position. A lock may selectively prevent movement of the switch. Other drive mode selector interfaces are contemplated herein. The aforementioned list of drive mode selectors is meant to be illustrative; the disclosure is not intended to be limited to those drive mode selectors <NUM> described above.

Referring still to <FIG>, the lawn mower <NUM> can further include a forward drive wheel <NUM> including a first (e.g., left) forward drive wheel 114A and a second (e.g., right) forward drive wheel 114B. In certain instances, the left and right forward drive wheels 114A and 114B may be coupled together such that a common motive force provided to one of the left and right forward drive wheels 114A or 114B is also provided to the other of the left and right forward drive wheels 114A or 114B.

The lawn mower <NUM> can further include a rear drive wheel <NUM> including a first (e.g., left) rear drive wheel 116A and a second (e.g., right) rear drive wheel 116B (<FIG>). In certain instances, the left and right rear drive wheels 116A and 116B may be coupled together such that a common motive force provided to one of the left and right rear drive wheels 116A or 116B is also provided to the other of the left and right rear drive wheels 116A or 116B.

As described in greater detail below, the forward or rear drive wheels <NUM> and <NUM> can be powered by electric motors. The electric motors can be powered by one or more batteries. By way of non-limiting example, at least one of the one or more batteries can include lithium-ion batteries. In certain instances, the one or more batteries may share a common shape, size, power rating, or the like. In other instances, at least one of the one or more batteries may have a unique shape, size, or power rating as compared to the other(s) of the one or more batteries.

The one or more batteries can be receivable in a battery receiver <NUM> of the lawn mower <NUM>. The battery receiver <NUM> may be coupled with the mower deck <NUM>, for example, adjacent to an upper surface of the mower deck <NUM>. The battery receiver <NUM> can include one or more electrical interfaces, e.g., electrical contacts, configured to electrically couple with one or more electrical interfaces of the one or more batteries. The one or more batteries may be readily detachable from the electrical contacts of the lawn mower <NUM>. In one or more embodiments, the battery receiver <NUM> may define an interior compartment with a selectively closable cover <NUM> configured to selectively cover the interior compartment to prevent debris from contacting the one or more batteries. The cover <NUM> may be pivotally connected to the lawn mower <NUM> such that the operator can pivot the cover <NUM> between an open position, whereby the one or more batteries can be accessed, and a closed position, whereby the one or more batteries are protected. Alternatively, the cover <NUM> may include any one or more of a snap on cover, a sliding cover, or the like.

<FIG> illustrates a bottom view of the lawn mower <NUM> as seen in accordance with an exemplary embodiment of the present disclosure. As depicted, the forward and rear drive wheels <NUM> and <NUM> are disposed at forward and rear ends of the mower deck <NUM>, respectively, spaced apart from one another in a lateral direction by the mower deck <NUM>. A cutting implement <NUM> is disposed below the mower deck <NUM>. The cutting implement <NUM> includes a rotatable blade having one or more sharpened edges configured to cut through underlying material. Alternatively, the cutting implement <NUM> can include another type of cutting device, such as a cutting string, wire, or the like. The cutting implement <NUM> can be operatively coupled with a motor (not illustrated) that can rotatably drive the cutting implement <NUM>. The shape and size of the mower deck <NUM> may be selected to receive the rotating cutting implement <NUM> and prevent egress of debris from the cutting area.

Referring initially to the forward drive wheels <NUM>, a shaft <NUM> can extend between the left and right forward drive wheels 114A and 114B. The shaft <NUM> may be coupled to the left forward drive wheel 114A through a first drive gear and the shaft <NUM> may be coupled to the right forward drive wheel 114B through a second drive gear. By way of example, the left forward drive wheel 114A may be rotatable about a rotational axis. The first drive gear may be configured to provide motive force from the shaft <NUM> at a location radially spaced apart from the rotational axis. For instance, the left forward drive wheel 114A may include a gear interface along a peripheral location of the wheel. The first drive gear may mesh with the gear interface so as to drive the left forward drive wheel 114A. The right forward drive wheel 114B may be meshed with a second drive gear through a similar, or same, interface.

In the depicted embodiment, the left and right forward drive wheels 114A and 114B are each coupled to the shaft <NUM> through respective overrunning clutches 126A and 126B. The overrunning clutches 126A and 126B can permit the lawn mower <NUM> to turn when the shaft <NUM> is driving the forward drive wheels <NUM>. That is, the overrunning clutches 126A and 126B may selectively permit the forward drive wheels 114A or 114B, respectively, to slip relative to the shaft <NUM> such that the operator can turn the lawn mower <NUM> without binding the forward drive wheels <NUM> or cause damage to the lawn mower <NUM>.

The shaft <NUM> can be in operative communication with a forward transmission <NUM>. The forward transmission <NUM> can include an electronic transmission. The forward transmission <NUM> can be configured to provide motive force to the shaft <NUM> so as to rotate the shaft <NUM>. In certain instances, the shaft <NUM> can extend through the forward transmission <NUM>. The shaft <NUM> can be keyed with the forward transmission <NUM> to transfer rotational force into the shaft <NUM>. Rotational force transferred to the shaft <NUM> can rotate at least one of the forward drive wheels 114A and 114B through the respective overrunning clutch 126A or 126B to propel the lawn mower <NUM>.

In certain instances, the forward transmission <NUM> can be a dual-directional transmission configured to drive the shaft <NUM> in clockwise or counterclockwise rotation. That is, the forward transmission <NUM> can propel the lawn mower <NUM> in both the forward or rear directions. Affecting the direction of propulsion may be performed by the operator at the user interface <NUM>. In other instances, the forward transmission <NUM> may be a uni-directional transmission configured to drive the shaft <NUM> in only a single rotational direction. For example, the forward transmission <NUM> can be configured to propel the lawn mower <NUM> in only a forward direction. To reverse the lawn mower <NUM>, the operator can pull on the handle <NUM>.

The lawn mower <NUM> defines a centerline <NUM> extending from the front end of the lawn mower <NUM> to the rear end of the lawn mower <NUM>. In an embodiment, the forward transmission <NUM> is offset from the centerline <NUM>, e.g., laterally offset from the centerline <NUM>, by a distance. That is, the forward transmission <NUM> can be disposed closer to the first forward drive wheel 114A than the second forward drive wheel 114B. In a particular instance, the entire forward transmission <NUM> can be disposed on one side of the centerline <NUM>.

A shaft <NUM> can extend between the left and right rear drive wheels 116A and 116B. The shaft <NUM> may be coupled to the left rear drive wheel 116A through a first drive gear and the shaft <NUM> may be coupled to the right rear drive wheel 116B through a second drive gear. By way of example, the left rear drive wheel 116A may be rotatable about a rotational axis. The first drive gear may be configured to provide motive force from the shaft <NUM> at a location radially spaced apart from the rotational axis. For instance, the left rear drive wheel 116A may include a gear interface along a peripheral location of the wheel. The first drive gear may mesh with the gear interface so as to drive the left rear drive wheel 116A. The right rear drive wheel 116B may be meshed with a second drive gear through a similar, or same, interface.

In the depicted embodiment, the left and right rear drive wheels 116A and 116B are each coupled to the drive shaft <NUM> through respective overrunning clutches 134A and 134B. The overrunning clutches 134A and 134B can permit the lawn mower <NUM> to turn when the shaft <NUM> is driving the rear drive wheels <NUM>. That is, the overrunning clutches 134A and 134B may selectively permit the rear drive wheels 116A or 116B, respectively, to slip relative to the shaft <NUM> such that the operator can turn the lawn mower <NUM> without binding the rear drive wheels <NUM> or cause damage to the lawn mower <NUM>.

The shaft <NUM> can be in operative communication with a rear transmission <NUM>. The rear transmission <NUM> can include an electronic transmission. The rear transmission <NUM> can be configured to provide motive force to the shaft <NUM> so as to rotate the shaft <NUM>. In certain instances, the shaft <NUM> can extend through the rear transmission <NUM>. Rotational movement transferred to the shaft <NUM> can rotate at least one of the rear drive wheels 116A and 116B through the respective overrunning clutches 134A and 134B to propel the lawn mower <NUM>.

Similar to the aforementioned forward transmission <NUM>, in certain instances, the rear transmission <NUM> can be a dual-directional transmission configured to drive the shaft <NUM> in clockwise or counterclockwise rotation. That is, the rear transmission <NUM> can propel the lawn mower <NUM> in both the forward or rear directions. Affecting the direction of propulsion may be performed by the operator at the user interface <NUM>. In other instances, the rear transmission <NUM> may be a uni-directional transmission configured to drive the shaft <NUM> in only a single rotational direction. For example, the rear transmission <NUM> can be configured to propel the lawn mower <NUM> in only a forward direction. To reverse the lawn mower <NUM>, the operator can pull on the handle <NUM>.

In an embodiment, the rear transmission <NUM> is offset from the centerline <NUM>, e.g., laterally offset from the centerline <NUM>, by a distance. That is, the rear transmission <NUM> can be disposed closer to the first forward drive wheel 114A than the second forward drive wheel 114B. In a particular instance, the entire rear transmission <NUM> can be disposed on one side of the centerline <NUM>.

The forward or rear transmissions <NUM> and <NUM> can share any number of same or similar qualities, characteristics or functionalities as compared to one another. For instance, the forward or rear transmissions <NUM> and <NUM> can include a same or similar transmission design, same or similar gear ratio, same or similar relative displacements from the centerline, same or similar operational power ratings, or the like. In an embodiment, the forward or rear transmissions <NUM> and <NUM> can define one or more different qualities, characteristics or functionalities as compared to one another. For instance, the forward or rear transmissions <NUM> and <NUM> can have different gear ratios, different operational power ratings, or the like.

The forward or rear transmissions <NUM> and <NUM> can be in electrical communication with the aforementioned one or more batteries connected to the lawn mower <NUM>. The one or more batteries may thus selectively supply power to the forward or rear transmissions <NUM> or <NUM> when the operator engages the self-propel lawn mower <NUM> and initiates at least one of the forward or rear transmissions <NUM> or <NUM>. In some embodiments, in single-axle drive mode, the lawn mower <NUM> may be propelled by only the forward transmission <NUM>. In other embodiments, in single-axle drive mode, the lawn mower <NUM> may be propelled only by the rear transmission <NUM>. In some instances, the lawn mower <NUM> may be selectable between two different single-axle drive modes, i.e., using either of the forward transmission <NUM> or the rear transmission <NUM>. Selection between the different single-axle drive modes (e.g., forward drive or rear drive) may be performed using a selector input mechanism located, e.g., at the user interface <NUM>. In other instances, the lawn mower <NUM> may only be propelled in single-axle drive mode by a particular one of the forward transmission or the rear transmission <NUM>. That is, single-axle drive mode may be limited to, e.g., rear wheel drive. When the drive mode selector <NUM> is in the all-wheel-drive mode, both the forward or rear transmissions <NUM> and <NUM> can be used simultaneously to propel the lawn mower <NUM>.

In all-wheel-drive mode, the lawn mower <NUM> may exhibit increased traction, control, torque, or any combination thereof. However, operational range of the lawn mower <NUM> may be reduced in all-wheel drive mode. In all-wheel-drive mode, power distributed to the forward or rear drive wheels <NUM> and <NUM> may be equal, or approximately equal. In another embodiment, greater power can be distributed to either one of the forward or rear drive wheels <NUM> or <NUM> in the all-wheel-drive mode. For instance, the rear drive wheels <NUM> may provide at least <NUM>% of the propulsion, such as at least <NUM>% of the propulsion, such as at least <NUM>% of the propulsion, such as at least <NUM>% of the propulsion, such as at least <NUM>% of the propulsion. Meanwhile, the front drive wheels <NUM> can provide the remaining propulsion.

In single-axle drive mode, the lawn mower <NUM> may exhibit increased operational range. However, traction, control, torque, or any combination thereof may be reduced in single-axle drive mode. According to the present invention, the lawn mower <NUM> automatically reverts to single-axle mode when a power level of the one or more batteries drops below a critical threshold (e.g., less than <NUM>% charge remaining, such as less than <NUM>% charge remaining, such as less than <NUM>% charge remaining).

Referring again to <FIG>, the lawn mower <NUM> includes a controller <NUM>. The controller <NUM> illustrated in <FIG> is depicted in an interior volume <NUM> of the lawn mower <NUM>. Locating the controller <NUM> within the interior volume <NUM> may protect the controller <NUM> against, e.g., flying debris. In other embodiments, the controller <NUM> can be disposed in the handle <NUM> or at another location along the lawn mower <NUM>. The controller <NUM> is in communication with the forward transmission <NUM> and the rear transmission <NUM>, and optionally any one of more of the one or more batteries, a sensor disposed on the lawn mower <NUM>, or the user interface <NUM> (e.g., the drive mode selector <NUM>). The controller <NUM> can include, e.g., a memory unit <NUM> configured to store computer readable information and a processor <NUM> configured to execute the computer readable information.

According to the present invention, the controller controls the rear transmission <NUM> and the front transmission <NUM>. Optionally, the controller <NUM> can control at least one of the forward or rear transmissions <NUM> or <NUM> in response to inputs generated at the user interface <NUM>. For example, the controller <NUM> may receive a signal indicating engagement of the drive mode selector <NUM> between a first position corresponding with single-axle drive mode and a second position corresponding with all-wheel-drive mode. In response to the signal, the controller <NUM> can switch from single-axle drive mode to all-wheel drive mode.

With the lawn mower <NUM> in the all-wheel-drive mode, the controller <NUM> controls both the forward or rear transmissions <NUM> and <NUM> to propel the lawn mower <NUM>. With the lawn mower <NUM> in single-axle drive mode, the controller <NUM> controls only one of the forward or rear transmissions <NUM> or <NUM> to propel the lawn mower <NUM>. It should be understood that even in single-axle drive mode, the controller <NUM> may remain in communication with, or even control of, the other transmission (i.e., the non-driven transmission), however, propulsion forces may be generated by only one of the forward or rear transmissions <NUM> or <NUM>.

The controller <NUM> may be configured to control the relative speeds of the forward or rear drive wheels <NUM> and <NUM> to provide smooth all-wheel-drive propulsion to the lawn mower <NUM>.

In an embodiment, the forward drive wheels <NUM> define a first diameter and the rear drive wheels <NUM> define a second diameter different than the first diameter. For instance, the first diameter may be less than the second diameter. In an embodiment, a ratio of the first diameter to the second diameter is in a range of <NUM>:<NUM> and <NUM>: <NUM>. In a particular embodiment, the ratio of the first diameter to the second diameter is approximately <NUM>:<NUM>. By way of non-limiting example, the first diameter may be in a range of <NUM> inches and <NUM> inches, such as <NUM> inches, and the second diameter may be in a range of <NUM> inches and <NUM> inches, such as <NUM> inches.

To propel the lawn mower <NUM> in all-wheel-drive mode, the controller <NUM> can instruct the forward or rear transmissions <NUM> and <NUM> to operate at different relative speeds. That is, for example, the forward transmission <NUM> can rotate the shaft <NUM> at a faster rate (e.g., greater revolutions per minute (RPM)) than the rear transmission <NUM> so as to cause the effective displacement at the forward or rear drive wheels <NUM> and <NUM> to be equal to one another. In one or more embodiments, the controller <NUM> can instruct the forward or rear transmissions <NUM> and <NUM> to operate at different relative speeds from one another over the entire range of propulsion speeds of the lawn mower <NUM> so as to cause the displacement of the forward or rear drive wheels <NUM> and <NUM> to be equal at all times.

In another embodiment, the relative speeds of the forward and rear drive wheels <NUM> and <NUM> can be controlled by a component other than the controller <NUM>, such as by using different relative gearing ratios, or the like.

In certain instances, the controller <NUM> may include a plurality of control maps each defining a different operating characteristic of the lawn mower <NUM>. For instance, the plurality of control maps may include first and second control maps each configured to change an aspect of the propulsion experience of the lawn mower <NUM>-such as throttle response, maximum speed, acceleration curves, bail overrides, or the like. In certain instances, the control map utilized in all-wheel-drive mode is different than the control map utilized in single-axle drive mode. For instance, by way of non-limiting example, in all-wheel-drive mode the controller <NUM> may utilize a control map having a quicker acceleration curve or a higher maximum speed in response to enhanced traction created by driving all wheels of the lawn mower <NUM>. Similarly, in single-axle mode, the controller <NUM> may utilize a control map having a slower throttle response, e.g., an economical (eco) mode, to conserve battery power. In embodiments where the lawn mower <NUM> can be operated in single-axle mode by driving either the forward drive wheels <NUM> or the rear drive wheels <NUM>, the controller <NUM> may be reconfigurable between different control maps depending on which axle is being propelled. For instance, when the forward drive wheels <NUM> are driven in single-axle mode, the controller <NUM> may utilize a control map having a slower throttle response to mitigate wheel slip which might occur more easily than when propelling the lawn mower <NUM> using the rear drive wheels <NUM>.

In one or more embodiments, the controller <NUM> can utilize logic controls, e.g., feedback loops, to adjust rotational speeds of the forward or rear transmissions <NUM> and <NUM>, e.g., on the fly, to maintain a desired characteristic such as equal displacement of the forward or rear transmissions <NUM> and <NUM> in the event of installation of differently sized wheels, wheel wear, damage to the wheels, detected slip conditions at the wheels, or the like.

Advantageously, the lawn mower <NUM> can include features which allow the operator to quickly and effectively change the lawn mower <NUM> between a plurality of operating conditions without requiring the operator to manually adjust any pulleys, gears, or the like. Moreover, in certain instances the lawn mower <NUM> may be reconfigurable between single-axle drive mode and all-wheel-drive mode without requiring the lawn mower <NUM> be stopped. In this regard, the operator can adjust the lawn mower <NUM> on the fly, allowing the operator to adjust traction as needed based, e.g., on the varying terrain being traversed.

<FIG> illustrates an exemplary flow chart of a method <NUM> of operating a lawn mower. The method <NUM> includes a step <NUM> of operating the lawn mower with a first electronically controlled transmission. The first electronically controlled transmission is associated with a shaft coupled with one of a front drive wheel and a rear drive wheel. At step <NUM>, the lawn mower is operating in single-axle mode. Single-axle mode may enhance battery range, allowing the lawn mower to operate to utilize the lawn mower over a larger cutting area.

The method <NUM> further includes a step <NUM> of switching the lawn mower into an all-wheel-drive mode such that the first electronically controlled transmission is configured to drive the lawn mower and a second electronically controlled transmission is also configured to drive the lawn mower. The second electronically controlled transmission can be associated with a shaft coupled with the other one of the front drive wheel and the rear drive wheel. In certain instances, step <NUM> is performed with the lawn mower resting, i.e., stopped. In other instances, step <NUM> may be performed while the lawn mower is moving.

After step <NUM>, the lawn mower may be ready for all-wheel-drive mode. The method <NUM> can further include a step <NUM> of moving the lawn mower using the first and second electronically controlled transmissions. The first and second electronically controlled transmissions can each include motors that are configured to receive electrical power. Upon receiving electrical power, the first and second electronically controlled transmissions can propel the lawn mower. It is noted that the driven rotational speeds of the first and second electronically controlled transmissions can be different from one another. Such difference may be the result of, e.g., different wheel sizes of the forward or rear drive wheels. In certain instances, a controller can detect the rotational speeds or one or more other attributes of the lawn mower during step <NUM> and adjust the speed of either or both of the first or second electronically controlled transmission(s) accordingly.

In an embodiment, the steps <NUM> and <NUM> may be repeated in reverse order after step <NUM> to return the lawn mower to single-axle drive mode. In certain instances, the step of returning the lawn mower to single-axle drive mode can further include selecting which axle is to be powered in single-axle drive mode, i.e., whether the forward or rear drive wheels are to be powered.

Claim 1:
A lawn mower (<NUM>) comprising:
a mower deck (<NUM>);
a cutting implement (<NUM>) disposed below the mower deck (<NUM>);
a handle (<NUM>) coupled to the mower deck (<NUM>);
a battery receiver (<NUM>) configured to receive one or more batteries;
a rear drive wheel (<NUM>, 116A, 116B);
a forward drive wheel (<NUM>, 114A, 114B);
a rear transmission (<NUM>) coupled to the rear drive wheel (<NUM>, 116A, 116B) and configured to receive power from the one or more batteries;
a forward transmission (<NUM>) coupled to the forward drive wheel (<NUM>, 114A, 114B) and configured to receive power from the one or more batteries; and
a controller (<NUM>) configured to control the rear transmission (<NUM>) and the forward transmission (<NUM>) to selectively propel the lawn mower (<NUM>) in a single-axle drive mode or an all-wheel drive mode,
characterized in that
the controller (<NUM>) is configured to automatically revert to the single-axle drive mode when a power level of the one or more batteries drops below a critical threshold.