Mower with counterrotating cutting blades with different diameters

Abstract

The present invention relates to a mower (100) having at least one motor (102a, 102b) and a first blade (202) that is driven by the at least one motor (102a) to rotate about a first axis (106). The rotation of the first blade defines a first cutting circle. The mower includes a second blade (204) that is driven by the at least one motor (102b) to rotate about a second axis (108). The rotation of the second blade defines a second cutting circle smaller than the first cutting circle. The second axis (108) is offset in a longitudinal direction from the first axis (106). The mower includes a deck (114) covering the first and second blade (202, 204). In some embodiments, a third blade is used. In other embodiments, multiple electric motors are used to independently drive different blades.

Description

MOWER WITH MULTIPLE ROTARY CUTTING BLADESRELATED PATENT DOCUMENTS

[0001] This application claims the benefit of the following U.S. Provisional Application Numbers: 63 / 619,986, filed on January 11, 2024; 63 / 624,464, filed on January 24, 2024; 63 / 640,977, filed on May 1, 2024; 63 / 652,809, filed on May 29, 2024; and 63 / 693,322, filed on September 11, 2024, all of which are incorporated herein by reference in their entireties.SUMMARY

[0002] The present disclosure is directed to ground care machine platforms such as electric mowers. In one embodiment, a mower has at least one electric motor and a first blade that is driven by the at least one electric motor to rotate in a first direction about a first axis. The rotation of the first blade defines a first cutting circle. The mower includes a second blade that is driven by the at least one electric motor to rotate about a second axis in a second direction opposite the first direction. The rotation of the second blade defines a second cutting circle smaller than the first cutting circle. The second axis is offset in a longitudinal or downpath direction from the first axis. The mower includes a deck covering the first and second blades.

[0003] In another embodiment, a mower includes at least one electric motor and a pair of interchangeable blades that are driven by the at least one electric motor to rotate about a pair of first axes. The rotation of the pair of blades defines a pair of cutting circles. The mower includes a cleanup blade that is driven the at least one electric motor to rotate about a second axis. The rotation of the cleanup blade defines a cleanup cutting circle located between the pair of blades. The second axis is offset in a longitudinal or downpath direction from the pair of first axes. The mower includes a deck covering the pair of blades and the cleanup blade.

[0004] In another embodiment, a method involves rotating a first blade of a mower by a first electric motor and rotating a second blade of the mower by a second electricmotor. A slowed rotation speed of one motor of the first and second electric motors is determined, and a nominal rotation of another motor of the first and second electric motors is also determined. In response thereto, a rotation speed of the other motor is reduced or increased in response to the slowed rotation.

[0005] In another embodiment, a mower includes at least one motor and a first blade that is driven by the at least one motor to rotate about a first axis to define a first cutting circle. The mower includes a second blade that is driven by the at least one motor to rotate about a second axis to define a second cutting circle smaller than the first cutting circle. The second axis is offset in a longitudinal or downpath direction from the first axis. The mower includes a frame connecting the first and second blades. The frame is attached to or integrated with a deck. The mower includes a blade housing movably (e.g., pivotably, separably, removably) attached to the frame to transition between a deployed configuration and a stowed configuration. The blade housing includes a third blade that is driven by the at least one motor to rotate about a third axis. The rotation of the third blade defines a third cutting circle smaller than the first cutting circle. The third axis is offset in a lateral or crosspath or longitudinal direction from the first and second axes.

[0006] In another embodiment, a method involves rotating first and second blades of a mower by at least one motor to create respective first and second overlapping cutting paths as the mower moves along a work region. The method further involves moving a blade housing between a deployed configuration and a stowed configuration. The blade housing comprises a third blade that is driven by the at least one motor to create a third cutting path in the deployed configuration. The third cutting path overlaps at least one of the first and second cutting paths as the mower moves along the work region.

[0007] These and other features and aspects of various embodiments may be understood in view of the following detailed discussion and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The discussion below makes reference to the following figures, wherein the same reference number may be used to identify the similar / same component in multiple figures. The drawings are not necessarily to scale.

[0009] FIGS. 1 and 2 are top and bottom views of a mower according to various example embodiments;

[0010] FIG. 3 is a plot produced by a computational fluid dynamics model of the mower shown in FIGS. 1 and 2;

[0011] FIGS. 4 and 5 are top and bottom views of a mower according to other various example embodiments;

[0012] FIGS. 6-8 are top views of mower according to other embodiments;

[0013] FIG. 9 is a block diagram of functional modules of a mower according to an example embodiment;

[0014] FIG. 10 is a flowchart showing a method according to an example embodiment;

[0015] FIGS. 11 and 12 are top views of a mower according to other example embodiments;

[0016] FIG. 13 is a bottom view of the mower shown in FIGS 11 and 12;

[0017] FIGS. 14 and 15 are perspective views of the mower shown in FIGS. 11-13; and

[0018] FIGS. 16 and 17 are top views showing a single motor drive for a mower as shown in FIGS. 13-15;

[0019] FIG. 18 is a flowchart of a method according to another example embodiment;

[0020] FIGS. 19 and 20 are perspective views showing details of an expandable deck according to an example embodiment;

[0021] FIGS. 21 and 22 are perspective views showing details of an expandable deck according to another example embodiment;

[0022] FIGS. 23, 24, and 25 are perspective views showing details of a removably stowable blade housing according to another example embodiment; and

[0023] FIGS. 26 and 27 are top views showing details of a removably stowable blade housing according to another example embodiment.DETAILED DESCRIPTION

[0024] In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof. It is to be understood that other equivalent embodiments, which may not be described and / or illustrated herein, are also contemplated.

[0025] The present disclosure relates generally to ground care machines, which may be variously referred to herein as ground care vehicles, ground maintenance machines, ground maintenance vehicles, and the like. Ground care machines, such as lawn and garden machines, are known for performing a variety of tasks. For instance, powered lawn mowers are used by both homeowners and professionals alike to maintain turf areas within a property or yard. The same or different machines may be used for maintenance on the turf areas (and sometimes away from the turf), which may involve performing any combination of operations such as material collection (e.g., plant matter, dirt, golf balls), spraying, dethatching, edging, rolling, towing, snow / ice treatment and removal, etc.

[0026] Embodiments described herein include features of electrically powered mowers. Electrically powered mowers have some notable advantages over more widely- used internal combustion engine (ICE) powered mowers. An electric mower can be considerably quieter than an ICE mower and doesn’t emit combustion byproducts into the atmosphere. Also, electric mowers typically don’t require as much maintenance as ICE mowers, e.g., no need for oil and spark plug changes, don’t require fuel stabilizers for long storage periods, etc.

[0027] Electric mowers may have some disadvantages compared to ICE mowers, such being relatively more expensive. Also, in situations where swappable spare batteries are not available, recharging the mower’s battery may take much longer than refueling anICE mower. In order to mitigate these potential disadvantages, electric mower designs focus on energy efficiency of the devices, which can extend the operating time per charge. This can have other benefits, such as extending the usable life of the batteries.

[0028] One popular type of mower is a rotary blade mower, which uses an elongated blade or disk (both collectively referred to herein as a blade) that rotates around an axis that is normal to the ground. This type of mower is relatively simple compared to other types of mowers (e.g., reel mowers) because the blade is a simple structure that can be directly mounted to a motor shaft. This design also makes rotary blade mowers mechanically robust and relatively easy to service. The cut height can be controlled by changing a separation distance between the blade and the ground, e.g., by raising or lowering a deck on which the blade is mounted.

[0029] One factor that effects work efficiency of a mower (e.g., the area of turf that can be cut in a fixed unit of time) is the cut width. Cut width can be considered the width of a mowed strip of grass normal to the mower’s direction of forward motion. There are practical limits in increasing the cutting diameter of a single rotary cutting blade. Since the blade rotates in a circle, the mower deck must be large enough to cover the blade in both the cross-path and down-path directions of the mower. Therefore, an increase in cutting diameter increases both the crosspath and downpath dimensions of the mower deck, which is not always desirable. Large rotary blades may have other disadvantages compared to smaller blades, e.g., higher moment of inertia, higher stresses due to centrifugal forces, etc.

[0030] One solution to increase the cut width of a rotary blade mower is to use two cutting or more blades that each have a cutting diameter that is the appropriate fraction of the cut width (e.g., around Vi the cut width for two blades). This allows increasing the cross-path dimension of the mower without a corresponding increase in down-path dimension of the mower deck. A multiple cutting blade design will typically have overlap between the cutting circles of the multiple blades to ensure that grass between the cutting circles gets cut. In order to ensure that the blades don’t collide, a synchronization mechanism such as toothed drive belt may be used to keep the blades at an angular offset during operation such that they don’t collide in the overlapping region.

[0031] A common multiple blade rotary mower configuration has two blades of the same size. Both blades in such an arrangement can be interchangeable (e.g., the same part number), which reduces the number of unique parts needed for the mower. Even so, a multiple blade mower can still be more complicated than a single rotary blade design, and so this is one of the tradeoffs that may be considered when designing a mower with larger cutting circles, e.g., greater than 25”. For example, a typical two-blade mower has a mechanical coupling (e.g., belts and pulleys) to drive the multiple blades from a single motor.

[0032] Due to the small size of electric motors compared to gas engines, an electric mower can use a two or more motors to individually drive two or more respective rotary blades. This can eliminate the need for a belt drive or other mechanical coupling, and therefore can reduce the maintenance requirement, e g., lubricating idler wheel bearings, replacing belts. While two motors can be more expensive than a single motor, each motor in a multi-mower system can have lower performance (e.g., peak torque) than a single motor doing the same job. Thus the cost of two motors, for example, is not necessarily double that of the single motor setup, as each of the lower performance mowers will likely be cheaper than the single motor, even if not half as much. The use of multiple motors also eliminates mechanical losses (e.g., friction, turbulence, hysteresis, etc.) associated with mechanical couplings, thus can lead to increases in power efficiency.

[0033] In embodiments described below, multiple bladed electric mowers are described that include features that to increase energy efficiency, thereby maximizing the user of battery energy while working. This increase in efficiency can result in an increase in working time for a fully charged battery. In some embodiments, at least two blades are driven by dedicated motors. It will be understood that such designs can be adapted to include fewer motors than working blades, e.g., by adding a mechanical coupling, such that the same platform can be adapted for tradeoffs in power efficiency and cost. The blades in some embodiments can be arranged without overlapping each other on the mower deck, while still providing overlapping mowing paths (cut widths). Nonoverlapping cutting circles preclude the need for synchronization of the blades to avoid collisions, resulting in a simpler and more robust design.

[0034] In FIGS. 1 and 2, respective top and bottom views show features of an electric mower 100 according to an example embodiment. As seen in FIG. 1, the mower 100 includes at least one electric motor 102, which in this example includes two motors 102a, 102b. As best seen in FIG. 2, the mower 100 includes a first blade 202 that is driven by the electric motor 102a to rotate in a first direction 206 about a first axis 106. The rotation of the first blade 202, e.g., over a full rotation, defines a first cutting circle 104 (see FIG. 1).

[0035] A second blade 204 is driven by the electric motor 102b to rotate about a second axis 108 in a second direction 208 opposite the first direction 206. The rotation of the second blade 204 defines a second cutting circle 110 (see FIG. 1) smaller than the first cutting circle 104. As best seen in FIG. 1, the second axis 108 is offset 111 in a downpath direction 112 from the first axis 106, and a frame connects the first and second blades 202, 204. In this geometry, the downpath direction 112 also corresponds to a longitudinal direction and a crosspath direction 132 corresponds to a lateral direction. In this example, the frame is integrated with a deck 114 that covers the first and second blades 202, 204.

[0036] As used herein, the deck 114 refers to at least one or more shrouds, covers, housings, or the like that encompass part of the blades 202, 204, and may be tied together with a frame (e.g., space frame, truss) or other fabrication that provides structural support to various other components of the mower 100 as well as the shrouds, covers, etc. In other embodiments, the structural support may be provided by the deck shrouds themselves, e.g., a unibody construction to which other components are attached.

[0037] The mower 100 also includes wheels 113, a debris collector 115 (e.g., a bag), a handle 117, and a system controller 119. The mower 100 may include other features that are not shown in these figures, such as batteries, user interf ce / controls, wiring, etc. Note that the blades 202, 204 may turn in different directions than what is shown here, e.g., reversed or both in the same direction.

[0038] The first cutting circle 104 is non-overlapping with the second cutting circle 110, which prevents the first and second blades 202, 204 from touching during rotation. The first and second cutting blades 202, 204 and their respective cutting circles 104, 110 define respective first and second overlapping cutting paths 116, 118 while being movedalong a work region (e.g., turf). Region 123 indicates the amount of overlap between the cutting paths 116, 118, and may be around 1-4 inches. The first and second overlapping cutting paths 116, 118 define a mower cutting path 120, e.g., one that is greater than 25”. In some embodiments, the mower cutting path 120 may be on the order of 30”. For purposes of this disclosure, the reference numbers 116, 118, 120, and 123 may refer to both cutting paths and the widths of the respective cutting paths.

[0039] The second axis 108 is located closer to a leading edge 122 of the deck than the first axis 106, such that the smaller, second blade 204 leads the larger, first blade 202 in a forward cutting direction 125, which corresponds to a forward motion of the mower 100. As best seen in FIG. 2, the deck 114 includes a debris collection outlet 210 (also referred to a rear discharge opening) located at a trailing edge 124 of the deck. Rotation of the first blade 202 in the first direction 206 causes debris to be directed to the debris collection outlet 210 as indicated by arrow 213. The counter-rotation of the second blade 204 in the second direction 208 causes the debris to be directed to a region 211 between the first and second cutting circles 104, 110 where the debris moves in a direction 209 that is aligned with movement of the first blade 202. Shrouds 214, 216 surround parts of the blades 202, 204, and together with the overhanging perimeter of the deck 114, form airflow pathways to guide grass clippings and other debris to the debris collection outlet 210 as will be described below in relation to FIG. 3.

[0040] Note that while this and other mowers are illustrated as walk-behind mowers, these multiple blade concepts can be extended to stand-on and riding mowers as well. Stand on and riding mowers include zero turn mower configurations, which use differential rear steering of the rear wheels and front casters. Stand on and riding mowers include also include tractor mowers and the like, which include steered front wheels. These multiple blade concepts can also be used with remote controlled or autonomous mowers, which are designed to operate without an operator directly guiding or steering the mower.

[0041] The first and second blades 202, 204 are of different sizes. Notably, the second blade 204 is smaller than the first blade 202. In some embodiment a first diameter DI of the first cutting circle 104 (which corresponds to length of the first blade 202) is between 1.5 and 2.5 times than a second diameter D2 of the second cutting circle 110,(which corresponds to length of the second blade 204). The width W of the cutting path 120 of the mower can therefore be expressed as W = DI + D2 - O, where O is the overlap dimension 123. For example, if DI = 2*D2, 0 = 1, and W = 30, then D2 = (W +O) / 3 = 31 / 3 = 10.3 and DI = 20.6. Various adjustments can be made to overlap 123 and / or total cut width 120 such that one or both of DI and D2 correspond to sizes of part numbers of blades already in production, for example.

[0042] In some embodiments with two motors, the controller 119 is operable to selectively and independently modify respective first and second rotations speeds of the first and second electric motors 102a, 102b. For example, the controller 119 may be operable to detect that one of the first and second rotation speeds has slowed due to a high load (e g., tall or thick grass) at the respective one of the first and second blades 202, 204 and reduce another of the first and second rotation speeds to match the slowed rotation speed. In other cases, the other rotation speed may be increased, e.g., to speed the removal of grass clippings from around the cutting blade that has slowed.

[0043] In another example, one or both the blade’s speeds can be adjusted to reduce the effects of vibration at resonant frequency. As the mower 100 is used, surfaces of its parts may build up debris, moisture, etc., that causes a change in the resonant frequency of the blades, deck and the like. Blades may also get slightly damaged over time in a way that knocks them out of balance, and this can cause a significant change in vibration characteristics. Two more blades may also set up sympathetic vibrations at some frequencies. A change of speed, e.g., ±10%, of one or both of the blades 202, 204 may be sufficient to reduce the severity of vibrations at some frequencies while still being acceptable to the operator of the mower 100, particularly of the change is slowly made.

[0044] In another example, the combined aerodynamic performance of the blades 202, 204 may be improved in some conditions if one or both of their respective speeds are adjusted. Improvement of the aerodynamic performance may increase energy efficiency and / or increase debris collection efficiency. This may be due to heavier or lighter volume of debris (e.g., which can be sensed by changes in motor current), ambient conditions (e.g., temperature, humidity, precipitation), machine orientation (e.g., sloped ground), or other conditions of use. This could be adjusted dynamically via sensor and an open-loop orclosed-loop controller, as could the other embodiments described above. In other cases, the speeds may be set as user profiles that are selectable by an operator.[00451 The controller 119 may make other adjustments in response to a change in blade speed. For example, drive unit 212 shown in FIG. 2 may include a transmission coupled to one or more axles 215, which drive the rear wheels 113 in this example. The drive unit 212 includes or is coupled to an electric drive motor that is also controlled by the controller 119. This configuration is sometimes referred to as a walk-behind mower, in that the mower 100 is self-propelled, but is guided by the operator. The mower 100 may include features to prevent operation without an operator, e.g., a dead man’s switch on the handle 117 that will shut down the mower 100 if not activated by the operator. If blade speed is reduced due to loading of the blades as described above, then the mower speed can be adjusted accordingly by reducing the speed of the axles 215 (although an operator may decide to apply more force at the handle 117 if a slowdown is detected).

[0046] As noted above, the counter-rotation of the blades 202, 204 can lead to effective debris collection. In FIG. 3, a plot shows the results of a computational fluid dynamics (CFD) simulation of the mower configuration in FIGS. 1 and 2. Clippings are fed from the second blade 204 into the first blade 202 in region 211. The first blade 202 collects and directs the clippings to the debris collection outlet 210 and into the debris collector 115. This shows how the counter-rotating blades 202, 204 can efficiently divert debris for collection along an airflow path defined by the deck 114 and shrouds 214, 216.

[0047] In FIGS. 4 and 5, respective top and bottom views show features of an electric mower 400 according to another example embodiment. The mower 400 includes at least one electric motor 402, specifically three electric motors 402a-c in this example. As seen in FIG. 5, a pair 502 of interchangeable blades 502a, 502b are driven by the at least one electric motor 402 to rotate about first axes 406a, 406b. Rotation of the pair of blades defines a pair 404 of cutting circles 404a, 404b (see FIG. 4). Note that the blades 502a, 502b, 504b may turn in different directions than what is shown here, e.g., reversed or all three in the same direction.

[0048] The mower 400 includes a cleanup blade 504 that is driven by the at least one electric motor 402 to rotate about a second axis 408. Rotation of the cleanup blade 504defines a cleanup cutting circle 410 (see FIG. 4) located between the pair of blades 502. The second axis 408 is offset 411 in a downpath direction 112 from the first axes 406a, 406b. The location of the axes 406a-b, 408 results in the larger pair of blades 502 leading the smaller cleanup blade 504 in the forward cutting direction 125. A deck 414 covers the pair of blades 502 and the cleanup blade 504.

[0049] As seen in FIG. 4, the pair of cutting circles 404 and the cleanup cutting circle 410 are non-overlapping with each other, which prevents the pair of blades 502 and the cleanup blade 504 from touching during rotation. The pair of cutting circles 404 defines a pair 416 of non-overlapping cutting paths 416a, 416b, and the cleanup cutting circle defines a cleanup path 418 that overlaps the pair of non-overlapping cutting paths 416. The pair of non-overlapping cutting paths 416 defines outer bounds of a mower cutting path 420, e g., having a path width that is greater than 25”. For purposes of this disclosure, the reference numbers 416, 418, and 420 may refer to both cutting paths and the widths of the respective cutting paths.

[0050] The second axis 408 is located closer to a trailing edge 424 of the deck 414 (opposite leading edge 422) than the first axes 406a, 406b, such that the larger blades of the pair 502 cut the turf first before the smaller cleanup blade 504. In this way, the cleanup blade 504 only needs to cut a narrow swath 421 of turf left uncut between the pair of cutting circles 404. Because of this, the cleanup blade 504 and its driving motor / mechanism can be sized for a duty cycle that is less than what might normally be specified for a blade the size of the cleanup blade 504. This relatively low duty cycle might also allow using a different type of cutter for the cleanup blade 504, such as a disk, line, wire, etc.

[0051] In one embodiment, a first diameter D3 of each of the pair of cutting circles 404 (which corresponds to length of the blades 502a, 502b) is between 2.5 and 3 times than a second diameter D4 of the cleanup cutting circle 410 (which corresponds to length of the blade 504). The width W2 of the cutting path 420 of the mower can therefore be expressed as W2 = 2*D3 + G, where G is the dimension of the gap between the pair of blades 502, which also corresponds to the width of swath 421. For example, if G = 1, and W2 = 30, then D3 = (W2-G) / 2 = 29 / 2 = 19.5. The only size limitation on D4 is D4 > G.

[0052] The mower 400 may include a controller 419 operable similar to the controller 119 in FIG. 1. For example, the controller 419 may be operable to selectively and independently modify respective rotation speeds of the any two of the electric motors 402 or all three of the electric motors. For example, electric motors 402a and 402b may always be kept the same speed as each other for mowing, although their speeds can be reduced or increased together. In that case, the speed of the cleanup blade’s electric motor 402c can be selectively and independently modified relative to the speed-matched pair of electric motors 402a, 402b. As with previously described embodiments, the controller 419 may be further operable to detect that one of the three rotation speeds has changed (e.g., slowed) due to load at the respective one of the pair of blades and the cleanup blade. In response to detecting the changed rotation speed, the controller 419 may reduce or increase another of the three rotation speeds to match the changed rotation speed. The controller 419 may perform speed adjustments for other reasons described above, e.g., vibration reduction, aerodynamic performance, and increase debris collection rate by blades that are not slowed due to loading.

[0053] As noted above, the mowers may use fewer electric motors than rotating blades. In FIG. 6, a top view illustrates a mower 600 according to an alternate embodiment. The mower 600 may be configured with any features as described for mower 100 in FIGS. 1 and 2, as indicated by axes of rotation 106, 108 and cutting circles 104, 110. Unlike mower 100, mower 600 has a single electric motor 102 for driving the first and second cutting blades 202, 204 (not shown, see FIG. 2). Drive pulleys 602, 603, idler pulley 604, and belt 605 are shown coupling the first and second cutting blades 202, 204 in a way that results in the opposite rotation directions 206, 208 as shown in FIG. 2. Other mechanical coupling components may be used, e g., gears, chains, instead of or in addition to the belt and pulley components shown in FIG. 6. The mechanical coupling may not require synchronized rotation, e.g., to keep blades from colliding, and so may use a coupling mechanism that allows for slip such as smooth V-belts and pulleys.

[0054] In FIG. 7, a top view illustrates a mower 700 according to another example embodiment. The mower 700 may be configured with any features as described for mower 400 in FIGS. 4 and 5, as indicated by axes of rotation 406a, 406b, 408 and cutting circles404, 410. Unlike mower 400, mower 700 has a single electric motor 402a for driving the pair of cutting blades 502 (not shown, see FIG. 5). Drive pulleys 702, 704 and belt 706 are arranged to cause the pair of cutting blades 502 to rotate in the same direction as each other as shown in FIG. 5. The cleanup blade 504 continues to be independently driven by its own electric motor 402c in this example. The caveats and variations for the embodiment of FIG. 6 may apply here as well.

[0055] In FIG. 8, a top view illustrates a mower 800 according to another example embodiment. The mower 800 may be configured with any features as described for mower 400 in FIGS. 4 and 5, as indicated by axes of rotation 406a, 406b, 408 and cutting circles 404, 410. Unlike mower 400, mower 800 has a single electric motor 402a for driving the pair of cutting blades 502 and the cleanup blade 504 (not shown, see FIG. 5). Drive pulleys 802, 804, 808 and belt 806 are arranged to cause the pair of cutting blades 502 and the cleanup blade 504 to all rotate in the same direction as shown in FIG. 5. The caveats and variations for the embodiment of FIG. 6 may apply here as well. For any of these embodiments, a single electric motor may be replaced by an ICE motor, e.g., with appropriate additional coupling mechanisms such as clutches to enable disabling the brakes, drivetrain, and the like. Various embodiments may use a hybrid arrangement, e.g., an ICE motor to drive the pair of cutting blades 502 as shown in FIG. 7 and an electric motor to drive the cleanup blade 504.

[0056] In FIG. 9, a block diagram shows electrical components of a mower according to an example embodiment. These electrical components are applicable to any of the embodiments described herein. A system board 900 monitors and control various system functions. The system board 900 includes a controller 901 that may include one or more processors, e.g., central processing units, co-processors, etc. The controller 901 may be coupled to one or both volatile memory (e.g., dynamic random-access memory 902) and non-volatile memory (e.g., non-volatile random-access memory 903), which are referred to collectively as ‘memory.’ The controller 901 accesses and executes one or more computer programs or routines stored in the memory, as well as storing and retrieving other data to / from memory such as factory and user settings, logging data, etc.

[0057] The system board 900 may include sensors 904 for detecting board conditions such as temperature, voltages, etc., that that are monitored by the controller 901. The system board 900 also includes a power supply 907 that provides power to components on the board 900. The power supply 907 is shown being coupled to a power bus 908, however may also or instead have an alternate source of power, such as an onboard battery.

[0058] The controller 901 is coupled to one or more input / output (I / O) interfaces 905. The I / O interface 905 facilitates communications between the controller 901 and various functional modules 910, 920, 930, 940. Each of the functional modules 910, 920, 930, 940 may be coupled via separate lines (e.g., general input I / O, or GPIO lines) that send / receive analog and or digital signals that can be set and / or read by the controller 901. Some or all of the functional modules 910, 920, 930, 940 may be coupled to a common data bus, such as a controller area network (CAN) bus, inter-integrated circuit (I2C) bus, etc. The data bus 906 generally represents both commonly-coupled busses (e.g., with shared media access) or individual control lines.

[0059] The functional modules include a work unit 910 with one or more motors 911 to drive blades and may also include sensors 912, such as sensor for measuring shaft speed, electrical current, temperatures. The sensors 912 may also or instead be integrated into the motors 911 and / or the motors 911 may be operable to receive commands from the controller 901 (e.g., to set speed). Therefore, the motors 911 may be optionally coupled to the data bus 906 as shown, as well as being coupled to the power bus 908 to receive power. The work unit 910 is also shown with a retraction actuator 913, which may be a mechanical, electromechanical, electrohydraulic, or electric actuator that extends a third blade into cutting position as shown in the embodiments illustrated in FIGS. 11-17 and 19- 22. In some cases, the actuation may be purely mechanical, in which case no electrical components may be needed, or non-actuating electrical components may be used with mechanical components, e.g., a limit switch to shut off motor power in the event of a blade housing being manually moved out of a work position.

[0060] The functional modules include a drive unit 920 with one or more motors 921 to drive wheels or the like and may also include separate or motor-integrated sensors922, which include features described above for sensors 912. The motors 921 may be coupled to one or both of the data bus 906 and the power bus 908 similar to motors 911.[00611 The power unit 930 is a functional module that includes one or more main batteries 931 and a power conditioning circuit 932. The power conditioning circuit 932 may provide functions such as current limiting, fusing, battery charge control, voltage regulation, etc. The power unit 930 is a source of power for the power bus 908, and data may be communicated to and from the power unit 930 via the data bus 906. As shown the power conditioning circuit 932 is coupled to the batteries 931 via both one or more data lines 933 and power lines 934, although in some embodiments the batteries 931 may be directly coupled to one or both the data bus 906 and the power bus 908.

[0062] In one configuration, the mower may include a hybrid powertrain, in which an internal combustion engine 942 provides electrical power by way of a generator 944. This is shown coupled to the power conditioning circuit 932 via one or both of data lines 945 and power lines 946. The batteries 931 may be optional in such a configuration, or of reduced capacity. In the latter case, the batteries 931 may be included for engine starting and / or to provide a current boost to the power lines under heavy load. The internal combustion engine 942 may be coupled to a mechanical drive besides the generator, e.g., a traction unit. Generally, the hybrid configuration allows for some advantages of electrification such as reduction in mechanical drivelines, flexible control of torque, power, and speed, without the expense, weight, and recharging requirement of a fully electric unit.

[0063] A user interface 940 is also coupled to the data bus 906, in some cases may draw power from the power bus 908. The user interface 940 may include switches or other input devices that are usable by the operator activate the work unit 910 and drive unit 920. The user interface 940 may also include lights, displays, and the like that communicate mower status to the operator. For example, the operator may at least be interested in current state of battery charge which can be displayed via the user interface 940, e.g., via an LCD screen or indicator LEDs. The mower may have states, configurations, and settings that may be shown via the user interface 940, such as cutting mode, blade speed, hours of operation, etc.

[0064] The memory 902, 903 includes computer-readable instructions or applications that, when executed, e.g., by one or more processors, cause the controller 901 to perform various calculations and / or issue commands. That is to say, the controller 901 and memory 902, 903 may together define a computing apparatus operable to process input data and generate the desired output to one or more components / devices. For example,

[0065] In FIG. 10, a flowchart illustrates a method according to an example embodiment. The method involves rotating 1000 a first blade of a mower by a first electric motor and rotating 1001 a second blade of the mower by a second electric motor. The method involves determining 1002 a slowed rotation speed of one motor of the first and second electric motors and a nominal rotation of another motor of the first and second electric motors. For purposes of this example, “nominal” refers to a change within some expected operational limit, e.g., ±10%, ±5%, etc. In response to detecting the slowed rotation (block 1003 returns ‘yes’), a rotation speed of the other motor is changed (e.g., increased or decreased) 1004 in response to the slowed rotation. Optionally, a drive speed of the mower may be reduced 1005 in response to the slowed blade rotation. Note that other steps not shown may involve returning the motor and blade speeds to a set speed within the nominal range once the slowing due to outside influences has stopped. This method is applicable to mowers with more than two blades, e.g., by changing rotation of multiple other motors in response to a slowing of one.

[0066] In FIGS. 11 and 12 top views show features of a mower 1100 according to an example embodiment, and FIG. 13 shows a bottom view of the mower 1100. As seen in FIG. 11, the mower 1100 includes at least one motor 1102, which in this example includes three motors 1102a, 1102b, and 1102c which can be separately and independently speed- adjusted as in previous embodiments. As with other embodiments, the motors 1102 are shown as electric motors, however an ICE motor may be used in some case. As best seen in FIG. 13, the mower 1100 includes a first blade 1302 that is driven by the electric motor 1102a to rotate in a first direction 1306 about a first axis 1106. The rotation of the first blade 1302, e.g., over a full rotation, defines a first cutting circle 1104 (see FIG. 1).

[0067] A second blade 1304 is driven by the electric motor 1102b to rotate about a second axis 108 in a second direction 1308 opposite the first direction 1306. The rotation of the second blade 1304 defines a second cutting circle 1110 (see FIG. 11) smaller than the first cutting circle 1104. As best seen in FIG. 11, the second axis 1108 is offset 1111 in a downpath direction 1112 from the first axis 1106. A frame connects the first and second blades 1302, 1304. In this example the frame is attached to or integrated with a deck 1114 that covers the first and second blades 1302, 1304. The mower 1100 also includes wheels 1113, a debris collector 1115 (e.g., a bag, a clipping collection receptacle), a handle 1117, and a system controller 1119. The mower 1100 may include other features that are not shown in these figures, such as batteries, user interface / controls, wiring, etc.

[0068] The mower 1100 includes a third blade 1320 (see FIG. 13) that can be optionally deployed to increase a cut width of the mower 1100. A blade housing 1126 is pivotably attached to the deck 1114 to rotate between a deployed configuration (seen in FIG. 12) and a stowed configuration (seen in FIG. 11). In the stowed configuration, the blade housing 1126 fits within a pocket 1201 (see FIG. 12) formed in the deck 1114, which may be alternatively described as a hollow, indent, cavity, etc. Note that the deployed and stowed configurations may be alternatively referred to as wide and narrow, unfolded and folded, in-use and out-of-use, etc. Further, the blade housing 1126 may be referred to as an auxiliary deck, extendable deck, retractable deck, etc. Similarly, the blade housing 1126 in this and other embodiments may be considered a secondary blade housing, and the deck 1114 may be considered one or more primary blade housings.

[0069] The pocket 1201 allows the blade housing 1126 to be positioned substantially within the lateral width of the frame (defined by lateral limits of the deck 1114 in this example) of the mower 1100 when in the stowed configuration. The blade housing 1126 rotates around pivot 1128 (e.g., a piano hinge) that is attached to an outer edge of the deck 1114. The pivot 1128 has an axis normal to the plane of the ground, such that a bottom edge of the blade housing 1128 is at substantially the same height above ground in both the stowed and deployed configurations. The blade housing 1126 includes or houses the third blade 1320, which is driven by motor 1102c to rotate about a third axis 1130. In the deployed configuration shown in FIG. 12, the rotation of the third blade 1302defines a third cutting circle 1202 smaller than the first cutting circle 1 104. The third axis 1130 is offset 1208 in a crosspath direction 1206 from the first and second axes 1106, 1108. The third axis 1130 is also offset in the downtrack direction 1112 from the second axis 1108 and may be aligned with or slightly offset from the first axis 1106 in the downtrack direction 1112.

[0070] The first cutting circle 1104 is non-overlapping with the second cutting circle 1110, which prevents the first and second blades 1302, 1304 from touching during rotation. The third blade 1302 is in a separate blade housing 1126, which prevents collisions with the second blade 1304. As seen in FIG. 13, the first and second cutting circles 1104, 1110 define respective first and second overlapping cutting paths 1216, 1218. Region 1223 indicates the amount of overlap between the cutting paths 1216, 1218, and may be the same size as other embodiments described above.

[0071] The second and third cutting circles 1104, 1202 define respective second and third overlapping cutting paths 1218, 1220, with overlap region 1219 that may be similar in size to region 1223. The first, second, and third overlapping cutting paths 1216, 1218, 1220 define a maximum mower cutting path 1222, e.g., one that is greater than 25”. In some embodiments, the maximum mower cutting path 1222 may be on the order of 30”. For purposes of this disclosure, the reference numbers 1216, 1218, 1220, and 1222 may refer to both cutting paths and the widths of the respective cutting paths. In the stowed configuration shown in FIG. 11, the width of a minimum cutting path will be the sum of path widths 1216 and 1218 minus overlap 1223.

[0072] The deck 1114 includes a debris collection outlet 1310 located at a trailing edge 1124 of the deck. Rotation of the first blade 1302 in the first direction 1306 causes debris to be directed to the debris collection outlet 1310 as indicated by arrow 1313. The counter-rotation of the second blade 1304 in the second direction 1308 causes the debris to be directed to a region 1311 between the first and second cutting circles 1104, 1110 where the debris moves in a direction 1309 that is aligned with movement of the first blade 1302 and thereby passed to the first blade 1302. Shrouds 1314, 1316 surround parts of the blades 1302, 1304, and together with the overhanging perimeter of the deck 1114, form airflowpathways to guide grass clippings and other debris to the debris collection outlet 1310 as will be described below in relation to FIG. 3.[00731 The first and second blades 1302, 1304 are of different sizes, as are the first and third blades 1302, 1320. Notably, the both the second blade 1304 and third blade 1320 are smaller than the first blade 1302. The second and third blades 1304, 1320 may be the same or different sizes, and in the former case, may be interchangeable, although this may involve some other adaptations (e.g., reversible mounting), as these blades may be counterrotating as will be described below. The sizes of the blades may be similar to other embodiments, e.g., mower 100 shown in FIGS. 1 and 2.

[0074] As seen in FIG. 11, an inlet cover 1132 is biased to block a debris inlet 1134 of the deck 1114 in the stowed configuration. The blade housing 1126 has a debris outlet 1136 that aligns with the debris inlet 1134 when the blade housing 1126 is in the deployed configuration and allows debris to be passed from the third blade 1320 to the second blade 1304. The inlet cover 1132 may be biased to block the debris inlet 1134 by a spring, e.g., a coil spring (not shown) disposed on or near the inlet cover hinge 1133.

[0075] The inlet cover 1132 has a convex outer surface 1132a (see FIG. 12) that both seals against the curved debris inlet 1134 and rides against a curved outer surface of the blade housing 1126 when transitioning between stowed and deployed configurations. Arrows 1224 and 1225 indicate rotation of the blade housing 1126 and inlet cover 1132 respectively when moving from the stowed to the deployed configuration. This allows the blade housing 1126 to push the inlet cover 1132 out of the way upon deployment, thus only requiring a single actuator to both rotate the blade housing 1126 in and out of place and to open and close the inlet cover 1132. In FIGS. 14 and 15, perspective views show the mower 1100 in both the stowed and deployed configurations, respectively.

[0076] The movement of the blade housing 1126 between stowed and deployed configurations may be accomplished with mechanical linkages, e.g., cables, levers, springs, etc. In other embodiments, one or more electrical actuators may be used, e g., motors, drive screws, as shown in FIG. 9. As seen in FIG. 14, the debris outlet 1136 is uncovered in this embodiment when the blade housing 1126 is stowed, such that the third blade 1320 is accessible through the debris outlet 1136. In such a case, if the dedicated third motor 1102cis used, the third motor 1 102c will be turned off when the blade housing 1126 is not deployed. In other embodiments where the third blade 1320 does not have a dedicated motor, a brake and / or clutch may be used to stop the third blade 1320 from spinning when the blade housing 1126 is stowed (see FIGS. 16 and 17, for example).

[0077] As seen in FIG. 13, rotation of the first blade 1302 in a first direction 1306 causes debris to be directed to the debris collection outlet 1310 as indicated by arrow 1313. The counter-rotation of the second blade 1304 in a different, second direction 1308 causes the debris to be directed to a region 1311 where the debris moves in a direction 1309 that is aligned with movement of the first blade 1302. The rotation of the third blade 1320 in the first direction 1306 causes the debris to be directed through the debris outlet 1136 and debris inlet 1134 where the debris moves in a direction 1311 that is aligned with movement of the second blade 1304. Shrouds 1314, 1316 surround parts of the blades 1302, 1304, and together with the overhanging perimeter of the deck 1114, form airflow pathways to guide grass clippings and other debris to the debris collection outlet 1310. This arrangement allows clippings from all three blades to be sent to a single collection area, in this example collection bag 1115. Note that the blades 1302, 1304, 1320 may turn in different directions than what is shown here, e.g., reversed or all three in the same direction.

[0078] In some embodiments, the mower 1100 may include two or three electric motors. In some embodiments, the controller 1119 may be operable to selectively and independently modify rotation speeds of the first, second, and third electric motors 1102a, 1102b, 1102c (or a subset thereof) according to any scheme or scenario described elsewhere herein. In some cases, a single motor with a drive coupling as shown in FIG. 6 can be used to drive the first and second blades 1302, 1304, and a separate motor (e.g., motor 1102c) can be used to drive the third blade 1320, and rotation of these motors can be selectively and independently controlled.

[0079] In other embodiments, a single motor, either electric or ICE, may be used to drive a mower with a retractable blade. An illustrative example of such a single motor mower 1600 is shown schematically in the top views of FIGS. 16 and 17. A single motor is shown as electric motor 1102, although this embodiment may be adaptable to use an ICE motor instead. Similar to the embodiment shown in FIG. 6, drive pulleys 1602, 1603, idlerpulley 1604, and belt 1605 are shown coupling the first and second cutting blades 1302, 1304 in a way that results in the opposite rotation directions as shown in FIG. 13. Other mechanical coupling components may be used, e.g., gears, chains, instead of or in addition to the belt and pulley components shown in FIG. 16.

[0080] A second drive belt 1606 couples the drive pully 1602 on the first blade 1302 to a drive pully 1608 that drives the third blade 1320. Idler pulleys 1610, 1612 are not necessarily used in the deployed state shown in FIG. 16, although idler pulley 1612 is shown in contact with the belt 1606. Also seen in this figure is a brake arm 1614 that rotates around an axis 1616, and is biased (e.g., via a spring) such that a brake pad 1615 is pressed against the drive pulley 1608 and / or its shaft in the stowed configuration. In the deployed configuration seen in FIG. 16, a distal end of the brake arm 1614 hits a stop 1618, which moves the brake pad 1615 away from drive pulley 1608.

[0081] When the blade housing 1126 rotates a few degrees counterclockwise around its pivot 1128, the brake arm 1614 is removed from the stop 1618, and the biasing element presses the brake pad 1615 against the pulley 1608, as seen in FIG. 17. At the same time, the tension on belt 1606 is released as the blade housing 1126 begins to rotate, such that the belt 1606 can slip around one or both of drive pulleys 1602, 1608. In the stowed configuration, the idler pulleys 1610, 1612 help keep the belt 1606 from coming off of the drive pulleys 1602, 1608 without tensioning the belt 1606. By removing belt tension and application of the brake pad 1615, the third blade 1320 can be kept from moving when not in the deployed configuration.

[0082] Note that the mechanisms shown in FIGS. 16 and 17 are for illustration, and other mechanisms can be used to achieve a similar functionality in a single motor embodiment. For example, an alternate drive mechanism could instead couple the drive pulley 1604 of the second blade 1302 to the drive pulley 1608 of the third blade 1320.Such design can use appropriately-located idler pulleys to tension and de-tension the third blade drive belt in a manner similar to what is shown in FIGS. 16 and 17. In another example, a clutch could be used to stop and allow movement of the third blade 1320 instead of or in addition to a brake.

[0083] In FIG. 18, a flowchart shows a method of operating a mower according to another example embodiment. The method involves rotating 1800 first and second blades of the mower by at least one motor to create respective first and second overlapping cutting paths responsive to the mower moving along a work region. The remaining operations 1801-1809 pertain to rotating a blade housing with a third blade between a deployed configuration and a stowed configuration. These additional operations do not necessarily require or involve the machine moving along the work region, although in some cases these operations can be done while moving.

[0084] Block 1801 determines if a third blade in the blade housing is currently deployed. If so, the system checks at block 1802 if a command to deploy the blade housing is received. This command could be an electrical signal received from a user interface, although a mechanical system could receive and process equivalent commands via mechanical linkages. If the command is received, the blade housing is rotated 1803 to the deployed configuration. The third blade is started 1804, the rotation of which defines a third cutting path that overlaps at least one of the first and second cutting paths. After the third blade is running, the work region is mowed 1805 with a cutting path defined by a combination of the first through third overlapping cutting paths.

[0085] If block 1801 determines if the third blade is not currently deployed, the system checks at block 1806 if a command to stow the blade housing is received. If so, the third blade is stopped 1807, the blade housing is rotated 1808 to a stowed configuration, and the work region is mowed 1809 with a cutting path defined by a combination of just the first and second overlapping cutting paths. As indicated by reference block 1810, these operations are continued in an infinite loop.

[0086] In FIGS. 19 and 20, perspective views show additional details of a mower 1100 as in any of FIGS. 11-15. In FIG. 19, the blade housing 1126 is shown transitioning between the stowed and deployed configurations. A simplified view of the motors 1102b and 1102c is shown in FIG. 19. In FIG. 20, the blade housing 1126 is shown in the deployed configuration, and the motors are not shown in this view.

[0087] As seen in FIG. 19, a biasing member 1900 is attached between a first mounting member 1901 (e.g., post, bolt, loop) on the deck 1114 and a second mountingmember 1902 on the blade housing 1126. The biasing member 1900 in this example is a coil extension spring, in which the coils pull together in contact with one another when axial forces are removed from the spring 1900. The biasing member 1900 is mounted in an over-center geometry, in which the first and second mounting members 1901, 1902 are located closer to each other in either the stowed or deployed configuration than in any other position therebetween. This creates two states of minimal potential energy, and so the biasing member 1900 will move the blade housing 1126 to one of the stowed or deployed states, where they will remain if no other forces are acting on the blade housing 1126. In some cases, the over-center biasing-member arrangement will allow the blade housing 1126 to move to the stowed position if the blade housing 1126 makes contact with an obstacle, minimizing any damage.

[0088] In this example, a compression seal 1904 is shown mounted to the deck 1114 via fasteners 1905, although instead could be mounted to the blade housing 1126. Generally, the compression seal 1904 can provide a more complex geometry at the deck- to-housing interface rather than can be easily formed into the deck 1114 or blade housing 1126, e.g., via metal stamping. For example, a horizontal member 1904a of the compression seal 1904 can overlap a top part of the openings 1134, 1136 to provide a robust interface that substantially blocks debris from moving vertically upward beyond an upper local surface 1906 of the deck if there is a misalignment or gap between the deck 1114 and blade housing 1126.

[0089] The compression seal 1904 can be formed of a material (e.g., a soft polymer) that is conformable to tightly seal the interface, and can compensate for misalignments, entrapped debris, etc. A conformable polymer material can also help reduce noise and wear, e.g., by preventing metal-to-metal contact between the deck 1114 and the blade housing 1126. A geometry of the inlet cover (e.g., inlet cover 1132 in FIG. 11) can be adapted to fit into the compression seal 1904 in the stowed configuration. The compression seal 1904 and / or the biasing member 1900 can be used with other designs, e.g., the belt driven embodiment shown in FIGS. 16 and 17. A non-deform able seal could also be used, e.g., a hard seal, formed out of metal, plastic, ceramic, or the like.

[0090] In FIGS. 20 and 21 , perspective views show a blade housing mounting according to another example embodiment. In FIG. 20, the blade housing 1126 is shown in the deployed or unfolded configuration and in FIG. 21 the blade housing 1126 is shown in the stowed or folded configuration. In this example, the blade housing 1126 is rotatably coupled to the deck 1114 via bars 2100, in particular a four bar, vertical folding configuration. While the bars 2100 rotate between the configurations shown in FIGS. 21 and 22, the blade housing 1126 stays substantially perpendicular to the ground through its range of motion. The geometry of the bars 2100 allows the bottom edge of the deck housing 1126 to clear the top of motor 1102b when stowed.

[0091] The bars 2100 are rotatably coupled via pivoting joints 2101 to the blade housing 1126 and by pivoting joints 2102 to the deck 1114. A bottom edge of the blade housing is at a first distance 2108 above ground 2110 in the stowed configuration and a second distance 2200 above the ground in the deployed configurations. The second distance 2200 is less than the first distance 2108. A biasing member similar to biasing member 1900 in FIG. 19 may be employed to bias the blade housing 1126 to one of the deployed or stowed configurations. One or more stops 2104 may be used to provide additional support to the blade housing 1126 in the deployed configuration, as well as preventing over extension of the housing. The same or different stops may also enforce a maximum displacement / rotation in the stowed configuration.

[0092] The movement of the blade housing 1126 between positions may be performed, for example, by a push-pull cable, a motor coupled to one of the bars 2100, and / or manually by the operator. A control process such as shown in FIG. 18 is equally applicable to this embodiment. A compression seal similar to the seal 1904 shown in FIGS. 19 and 20 may be used in this configuration, with one difference being that the seal would be attached to the blade housing 1126 and not the deck 1114. As with other embodiments, the motor 1102c would be stopped as soon as the blade housing 1126 begins to move out of the deployed configuration.

[0093] In FIGS. 23, 24, and 25, perspective views show details of a removable blade housing mounting arrangement according to another example embodiment. As indicated by region 2301, the deck 2300 in this example does not have a pocket, indent,hollow, or the like for receiving a blade housing 2302 in the stowed configuration (see pocket 1201 in FIG. 12). The embodiment shown in FIGS. 21 and 22 may use a similar design as deck 2300, and the embodiment in FIGS. 23-25 may use a similar design as deck 1114.

[0094] In FIGS. 23 and 24, the blade housing 2302 is shown in a deployed or attached configuration. In this embodiment, the blade housing 2302 is removably (e.g., slidably) attached to a receiver 2305 that is attached to or part of the deck 2300 and / or the frame if the frame is separate from the deck 2300. For purpose of this example, the term “removable” implies that removal and attachment of an object can be achieved without tools, and the interface is designed to enable regularly and repeatedly attaching and removing the object during non-maintenance operations, such as changing a work configuration.

[0095] A mounting member 2306 of the blade housing 2302 interfaces with the receiver 2305 and is held in place via a securing mechanism 2308. As shown, the mounting member 2306 may be embodied as a flat bracket, tongue, tab, plate, or the like, that slides in and out of the receiver 2305, the latter being enabled with the securing mechanism 2308 is released. The securing mechanism 2308 may be embodied as a spring-loaded clip that snaps into place when the mounting member is slid into place. The securing mechanism 2308 is disengaged by pulling up a handle 2309.

[0096] As seen in FIG. 24, the mounting member 2306 can be slid in and out of the receiver 2305 in the direction of arrow 2400 to attach or remove the blade housing 2302. A seal 2304 is attached to or integrated with the mounting member 2306, The seal 2304 may be a compression seal as in previous embodiments, or a hard seal, e.g., non-deformable.

[0097] In FIG. 25, the blade housing 2302 is shown in the stowed or separated configuration. As shown, the blade housing 2303 may be attached via clips (not shown) or the like that removably secure the blade housing 2302 on or near a top surface of the deck 2300 (or frame) in the stowed position. In this example, the blade housing 2302 is located over the second motor 1102b, however could be stowed elsewhere, e.g., over region 2301, within a pocket 1201 as shown in FIG. 12, on a back or side surface of the deck 2300and / or frame, on a handle, etc. The seal 2306 is attached to the blade housing 2302 and is also separated from the deck and / or frame in the deployed position.[00981 A return-to-closed-position door 2500 (e.g., spring loaded) can be used to seal off a debris inlet of the deck 2300 near the second blade when the blade housing 2302 is removed, e.g., operating similarly to what is shown in FIGS. 11-17 except with a different hinge location. In other embodiments, a removable door may be used that fits (e.g., slides) into the receiver 2305 in place of the blade housing 2302 to block the debris inlet when the blade housing 2302 is removed. The mower may have facilities (e.g., a bracket) to store a removable door on or near a top surface of the deck 2300, or elsewhere on the mower (e.g., on or near a handle).

[0099] While not shown in the figures, the interface between the blade housing 2302 and the receiver 2305 may include an electrical interface for power and control of the third motor 1102c. The electrical interface may include a sliding electrical connector that is locked in place together with the mounting member 2306 by the securing mechanism 2308. The electrical connector may include spring loaded covers or the like to protect the contacts from dirt and debris when the blade housing 2302 is stowed.

[0100] In some embodiments, an electrical interface may also be used to ensure the debris inlet of the deck (e.g., see inlet 1134 in FIG. 11) is covered when a removable blade housing is stowed. For example, the return-to-closed-position door 2500 in FIG. 25 may have a tab (not shown) or the like that extends into an electrical connector that is normally used by the removable blade housing 2302 when it is deployed. The tab could electrically interface with existing pins (e.g., short two data lines) to indicate the door is fully closed, or could mechanically interface with an electrical component (e.g., limit switch, Hall-effect sensor) that is part of the electrical interface such that a controller can confirm the door is closed / seated. A similar setup could be used with a removable door that utilizes a connector compatible with one used by the removable blade housing 2302.

[0101] In FIGS. 23-25, the mounting member 2306 of the blade housing 2302 interfaces with a receiver 2305 that is mounted to a top surface of the deck or frame. Other mounting surfaces could be used, as shown for example in the top views of FIGS. 26 and 27. In this embodiment, a removable blade housing 2302 includes a bracket 2600 thatattaches to a side surface 2601 of the deck 2300 (or frame). A fastener 2602 (e.g., a knob bolt) secures the bracket in place, and multiple such fasteners may be used. In other embodiments, the sliding interface shown in FIGS. 23-25 could be used on a side location of the deck or frame.

[0102] In this embodiment, the interface between the deck or frame and the removable blade housing 2302 is a face-to-face interface, and can be guided by alignment features 2702 (e.g., pins, hooks) seen in FIG. 7, which align with corresponding voids (e.g., holes, slots; not shown) in the bracket 2600. The arrow 2704 in FIG. 27 indicates a direction of attachment and removal of the blade housing 2302. This embodiment may include a similar electrical interface for motor power and data as described above. Also seen in these views are door cover 1132 similar to what is shown, e.g., in FIG. 11. Other accessory attachment schemes known in the art could be used instead of those shown in FIGS. 21-27. Similarly, other locations on the deck and frame may be instead or in addition used for joining a removable blade housing. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific illustrative aspects provided below. Various modifications of the illustrative aspects, as well as additional aspects of the disclosure, will become apparent herein.

[0103] Example l is a mower comprising: at least one electric motor; a first blade that is driven by the at least one electric motor to rotate in a first direction about a first axis, the rotation of the first blade defining a first cutting circle; a second blade that is driven by the at least one electric motor to rotate about a second axis in a second direction opposite the first direction, the rotation of the second blade defining a second cutting circle smaller than the first cutting circle, the second axis being offset in a downpath or longitudinal direction from the first axis; and a deck covering the first and second blades.

[0104] Example 2 includes the mower of example 1, wherein the first cutting circle and the second cutting circle are separated such that the first and second blades do not touch during rotation. Example 3 includes the mower of example 2, wherein the first and second cutting blades define respective first and second overlapping cutting paths.Example 4 includes the mower of example 3, wherein the first and second overlapping cutting paths define a mower cutting path that is greater than 25”.[01051 Example 5 includes the mower of any previous example, wherein the second axis is located closer to a leading edge of the deck than the first axis. Example 6 includes the mower of example 5, wherein the deck comprises a debris collection outlet located at a trailing edge of the deck, rotation of the first blade in the first direction causing debris to be directed to the debris collection outlet. Example 7 includes the mower of example 6, wherein the rotation of the second blade in the second direction causes the debris to be directed to a region between the first and second cutting circles where the debris moves in a direction that is aligned with movement of the first blade.

[0106] Example 8 includes the mower of any previous example, wherein a first diameter of the first cutting circle is between 1.5 and 2.5 times than a second diameter of the second cutting circle. Example 9 includes the mower of any previous example, wherein the at least one electric motor comprises first and second electric motors respectively coupled to the first and second blades. Example 10 includes the mower of example 9, further comprising a controller operable to selectively and independently modify respective first and second rotations speeds of the first and second electric motors. Example 11 includes the mower of example 10, wherein the controller is further operable to: detect that one of the first and second rotation speeds has changed due to load at the respective one of the first and second blades; and reduce or increase another of the first and second rotation speeds in response to the changed rotation speed. Example 12 includes the mower of example 11, wherein the controller is further operable to reduce speed of a drive motor in response to the slowed rotation speed.

[0107] Example 12_1 includes the mower of any previous example, further comprising a handle, drive motor and control system to propel the mower. Example 12 2 includes the mower of any previous example, further a comprising rear discharge opening and a clipping collection receptacle. Example 12 3 includes the mower of any previous example further comprising an internal combustion engine and a generator, the at least one electric motor driven by the generator.

[0108] Example 13 is a mower comprising: at least one electric motor; a pair of interchangeable blades that are driven by the at least one electric motor to rotate about a pair of first axes, rotation of the pair of blades defining a pair of cutting circles; a cleanup blade that is driven the at least one electric motor to rotate about a second axis, rotation of the cleanup blade defining a cleanup cutting circle located between the pair of blades, the second axis being offset in a downpath direction from the pair of first axes; and a deck covering the pair of blades and the cleanup blade.

[0109] Example 14 includes the mower of example 13, wherein the pair of cutting circles and the cleanup cutting circle are separated from each such that the pair of blades and the cleanup blade do not touch during rotation. Example 15 includes the mower of example 14, wherein the pair of cutting circles defines a pair of non-overlapping cutting paths, and the cleanup cutting circle defines a cleanup path that overlaps the pair of nonoverlapping cutting paths. Example 16 includes the mower of example 15, wherein the pair of non-overlapping cutting paths defines outer bounds of a mower cutting path that is greater than 25”.

[0110] Example 17 includes the mower of any one of examples 13-16, wherein the second axis is located closer to a trailing edge of the deck than the first axes. Example 18 includes the mower of any one of examples 13-17, wherein a first diameter of each of the pair of cutting circles is between 2.5 and 3 times than a second diameter of the cleanup cutting circle. Example 19 includes the mower of example 18, wherein the at least one electric motor comprise three electric motors respectively coupled to the pair of blades and the cleanup blade. Example 20 includes the mower of example 19, further comprising a controller operable to selectively and independently modify respective rotation speeds of the three electric motors. Example 21 includes the mower of example 20, wherein the controller is further operable to: detect that one of the three rotation speeds has slowed due to load at the respective one of the pair of blades and the cleanup blade; and reduce another of the three rotation speeds to match the slowed rotation speed.

[0111] Example 21 1 includes the mower of any one of examples 13 to 21, further comprising a handle, drive motor and control system to propel the mower. Example 21_2 includes the mower of any one of examples 13 to 21 1, further a comprising rear dischargeopening and a clipping collection receptacle. Example 21 3 includes the mower of any one of examples 13 to 21 2, further comprising an internal combustion engine and a generator, the at least one electric motor driven by the generator.

[0112] Example 22 is a method, comprising: rotating a first blade of a mower by a first electric motor; rotating a second blade of the mower by a second electric motor; and determining a slowed rotation speed of one motor of the first and second electric motors and a nominal rotation of another motor of the first and second electric motors, and in response thereto, reduce a rotation speed of the other motor to match the slowed rotation.

[0113] Example 23 includes the method of example 22, wherein the slowed rotation is due to a load on one of the first and second blades being driven by the one motor. Example 24 includes the method of example 23, further comprise returning the first and second electric motor to a set speed one the load has been removed. Example 25 includes the method of any one of examples 22-24, further comprising reducing a drive speed of the mower in response to the slowed rotation speed.

[0114] Example 26 is a mower comprising: at least one motor; a first blade that is driven by the at least one motor to rotate about a first axis to define a first cutting circle; a second blade that is driven by the at least one motor to rotate about a second axis to define a second cutting circle smaller than the first cutting circle, the second axis being offset in a downpath direction from the first axis; a frame connects the first and second blades, the frame attached to or integrated with a deck; and a blade housing movably attached to one or both of the deck and the the frame to transition between a deployed configuration and a stowed configuration. The blade housing comprises a third blade that is driven by the at least one motor to rotate about a third axis. The rotation of the third blade defines a third cutting circle smaller than the first cutting circle, the third axis being offset in a crosspath or longitudinal direction from the first and second axes.

[0115] Example 27 includes the mower of example 26, wherein the blade housing comprises a debris outlet that aligns with a debris inlet of the deck when the blade housing is in the deployed configuration and allows debris to be passed from the third blade to the second blade. Example 28 includes the mower of example 27, further comprising an inlet cover that is biased to block the debris inlet of the deck in the stowed configuration,wherein movement of the blade housing from the stowed configuration to the deployed configuration moves the inlet cover away from the debris inlet. Example 29 includes the mower of any one of examples 26-28, wherein the first cutting circle and the second cutting circle are separated such that the first and second blades do not touch during rotation.

[0116] Example 30 includes the mower of any one of examples 26-29, wherein the first, second, and third cutting circles define respective first, second, and third overlapping cutting paths in the deployed configuration. Example 31 includes the mower of example30, wherein the first, second, and third overlapping cutting paths define a maximum mower cutting path that is greater than 25”. Example 32 includes the mower of example31, wherein the first and second overlapping cutting paths define a second mower cutting path that less than the maximum mower cutting path.

[0117] Example 33 includes the mower of any one of examples 29-32, wherein the second axis is located closer to the leading edge of one or both of the deck and the frame than the first axis. Example 34 includes the mower of any one of examples 29-33, wherein the second axis is located closer to a leading edge of one or both of the deck and the frame than the third axis in one or both of the deployed configuration and the stowed configuration.

[0118] Example 35 includes the mower of any one of examples 26-34, wherein the first and third blades rotate in a first direction, and the second blade rotates in a second direction opposite the first direction. Example 36 includes the mower of example 35, wherein the rotation of the second blade in the second direction causes the debris to be directed to a region between the first and second cutting circles where the debris moves in a direction that is aligned with movement of the first blade. Example 37 includes the mower of example 36, wherein the rotation of the third blade in the first direction causes the debris to be directed to a region between the second and third cutting circles where the debris moves in a direction that is aligned with movement of the second blade. Example 38 includes the mower of example 37, wherein the deck comprises a debris collection outlet located at a trailing edge of one or both of the deck and the frame, the rotation of the first blade in the first direction causing debris to be directed to the debris collection outlet.

[0119] Example 39 includes the mower of any one of examples 26-38, wherein the at least one motor comprises an electric motor. Example 40 includes the mower of example 39, wherein the at least one electric motor comprises first, second, and third electric motors respectively coupled to the first, second, and third blades. Example 41 includes the mower of example 40, further comprising a controller operable to selectively and independently modify respective first, second, and third rotations speeds of first, second, and third blades. Example 42 includes the mower of example 40 or 41, further comprising a controller operable to disable the third electric motor in the stowed configuration. Example 42 1 includes the mower of any one of examples 26 to 42, wherein the blade housing is positioned substantially within a lateral width of one or both of the deck and the frame when in the stowed configuration. Example 42 3 includes the mower of any one of examples 26 to 42_1, further wherein the deck covers the first and second blade, the blade housing being separate from the deck. Example 42 3 includes the mower of any one of examples 26 to 42 2, further comprising a handle, drive motor and control system to propel the mower. Example 42_4 includes the mower of any one of examples 26 to 42_3, further comprising a rear discharge opening and a clipping collection receptacle.

[0120] Example 42_5 includes the mower of any one of examples 27 to 42_4, further comprising a compression seal between the debris inlet and the debris outlet. Example 42_6 includes the mower of example 42_5, wherein the compression seal comprises a horizontal member that blocks debris passing between the debris inlet and the debris outlet from moving vertically upwards. Example 42_7 includes the mower of any one of examples 26 to 42 6, wherein the blade housing is pivotably attached to the frame to rotate between the deployed configuration and the stowed configuration.

[0121] Example 42_8 includes the mower of example 42_7, further comprising an over-center biasing member that holds the blade housing in the stowed and deployed configurations. Example 42_9 includes the mower of example 42_8, wherein over-center biasing member allows the blade housing to move to the stowed position if the blade housing makes contact with an obstacle. Example 42 10 includes the mower of any one of examples 42_7 to 42_9, wherein the blade housing rotates about a pivot relative to the frame, the pivot oriented normal to a ground plane such that a bottom edge of the bladehousing is at substantially a same height above ground in both the stowed and deployed configurations. Example 42_11 includes the mower of any one of examples 42_7 to 42_10, wherein the blade housing is coupled to one or both of the deck and the frame via a four bar linkage such that a bottom edge of the blade housing is at a first distance above ground in the stowed configuration and a second distance less than the first distance above the ground in the deployed configurations.

[0122] Example 42_12 includes the mower of any one of examples 26 to 42_6, wherein the blade housing is removably attached to one or both of the frame and the deck. Example 42 13 includes the mower of example 42_12, wherein the blade housing comprises a mounting member slidably attached to a receiver on one or both of the deck and the frame in the deployed configuration, and wherein the mounting member is separated from the receiver in the stowed configuration. Example 42_14 includes the mower of example 42_12 or example 42_13, wherein the blade housing is mounted to a top surface of one or both of the deck and the frame in the stowed position

[0123] Example 43 is a method of operating a mower, comprising: rotating first and second blades of the mower by at least one motor to create respective first and second overlapping cutting paths as the mower moves along a work region; and moving a blade housing between a deployed configuration and a stowed configuration, the blade housing comprising a third blade that is driven by the at least one motor to create a third cutting path in the deployed configuration, the third cutting path overlapping at least one of the first and second cutting paths as the mower moves along the work region.

[0124] Example 44 includes the method of example 43, further comprising, in the deployed configuration: directing clippings from the third blade to the second blade; directing the clippings from the second blade to the first blade; and directing the clippings from the first blade to a debris collection outlet. Example 45 includes the method of example 43 or 44, wherein in the deployed configuration, clippings are directed from the third blade to the second blade via a debris outlet in the housing and a debris inlet in a deck that covers the first and second blades, and wherein rotating the housing from the deployed configuration to the stowed configuration causes an inlet cover to block the debris inlet of the deck.

[0125] It is noted that the terms “have,” “include,” “comprises,” and variations thereof, do not have a limiting meaning, and are used in their open-ended sense to generally mean “including, but not limited to,” where the terms appear in the accompanying description and claims. Further, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably herein. Moreover, relative terms such as ’’left,” “right,” “front,” “fore,” “forward,” “rear,” “aft,” “rearward,” “top,” “bottom,” “side,” “upper,” “lower,” “above,” “below,” “horizontal,” “vertical,” and the like may be used herein and, if so, are from the perspective shown in the particular figure, or while the machine is in an operating configuration. These terms are used only to simplify the description, however, and not to limit the interpretation of any embodiment described. As used herein, the terms “determine” and “estimate" may be used interchangeably depending on the particular context of their use, for example, to determine or estimate a position or pose of a vehicle, boundary, obstacle, etc.

[0126] Further, it is understood that the description of any particular element as being connected to or coupled to another element can be directly connected or coupled, or indirectly coupled / connected via intervening elements.

[0127] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0128] The various embodiments described above may be implemented using circuitry, firmware, and / or software modules that interact to provide particular results. One of skill in the arts can readily implement such described functionality, either at a modular level or as a whole, using knowledge generally known in the art. For example, the flowcharts and control diagrams illustrated herein may be used to create computer-readable instructions / code for execution by a processor. Such instructions may be stored on a non-transitory computer-readable medium and transferred to the processor for execution as is known in the art. The structures and procedures shown above are only a representative example of embodiments that can be used to provide the functions described hereinabove.

[0129] Note that any components described herein using terms such as “processor,” “controller,” “logic circuit,” “CPU,” or the like may be implemented using a plurality of discrete units operating together. For example, a processer that performs a series of steps or operations may be construed as two or more processors operating cooperatively to perform the steps. Similarly, other processing hardware such as memory and input-output may perform the described functions with multiple discrete units operating cooperatively or being coordinated by another unit, e.g., by a central processor or processors.

[0130] The foregoing description of the example embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. Any or all features of the disclosed embodiments can be applied individually or in any combination and are not meant to be limiting, but purely illustrative. It is intended that the scope of the invention be limited not with this detailed description, but rather determined by the claims appended hereto.

Claims

CLAIMS:

1. A mower comprising: at least one electric motor; a first blade that is driven by the at least one electric motor to rotate in a first direction about a first axis, the rotation of the first blade defining a first cutting circle; a second blade that is driven by the at least one electric motor to rotate about a second axis in a second direction opposite the first direction, the rotation of the second blade defining a second cutting circle smaller than the first cutting circle, the second axis being offset in a longitudinal direction from the first axis; and a deck covering the first and second blades.

2. The mower of claim 1, wherein the first cutting circle and the second cutting circle are separated such that the first and second blades do not touch during rotation.

3. The mower of claim 2, wherein the first and second cutting blades define respective first and second overlapping cutting paths.

4. The mower of claim 3, wherein the first and second overlapping cutting paths define a mower cutting path that is greater than 25”.

5. The mower of any one of claims 1-4, wherein the second axis is located closer to a leading edge of the deck than the first axis.

6. The mower of claim 5, wherein the deck comprises a debris collection outlet located at a trailing edge of the deck, rotation of the first blade in the first direction directing debris to the debris collection outlet.

7. The mower of any one of claims 1-6, wherein the rotation of the second blade in the second direction causes the debris to be directed to a region between the first andsecond cutting circles where the debris moves in a direction that is aligned with movement of the first blade.

8. The mower of any one of claims 1-7, wherein a first diameter of the first cutting circle is between 1.5 and 2.5 times than a second diameter of the second cutting circle.

9. The mower of any one of claims 1-8, wherein the at least one electric motor comprises first and second electric motors respectively coupled to the first and second blades.

10. The mower of claim 9, further comprising a controller operable to selectively and independently modify respective first and second rotations speeds of the first and second electric motors.

11. The mower of claim 10, wherein the controller is further operable to: detect that one of the first and second rotation speeds has changed due to load at the respective one of the first and second blades; and reduce or increase another of the first and second rotation speeds in response to the changed rotation speed.

12. The mower of claim any one of claims 1-11, further comprising a third blade that forms, with the first blade, a pair of interchangeable blades, the second blade configured as a cleanup blade that defines a cleanup cutting circle located between the pair of interchangeable blades.

13. The mower of claim any one of claims 1-11, further comprising: a frame connecting the first and second blades, the frame attached to or integrated with the deck; and a blade housing movably attached to one or both of the deck and the frame to transition between a deployed configuration and a stowed configuration, the blade housingcomprising a third blade that is driven by the at least one motor to rotate about a third axis, the rotation of the third blade defining a third cutting circle smaller than the first cutting circle, the third axis being offset in a lateral direction from the first and second axes.

14. The mower of claim 13, wherein the blade housing is pivotably attached to one or both of the deck and the frame to rotate between the deployed configuration and the stowed configuration.

15. The mower of claim 13, wherein the blade housing is removably attached to one or both of the deck and the frame.

16. A method, compri sing : rotating a first blade of a mower by a first electric motor; rotating a second blade of the mower by a second electric motor; and determining a slowed rotation speed of one motor of the first and second electric motors and a nominal rotation of another motor of the first and second electric motors, and in response thereto, reducing or increasing a rotation speed of the other motor in response to the slowed rotation.

17. The method of claim 16, wherein the slowed rotation is due to a load on one of the first and second blades being driven by the one motor.

18. The method of claim 17, further comprising returning the first and second electric motor to a set speed one the load has been removed.

19. The method of claim 16, further comprising reducing a drive speed of the mower in response to the slowed rotation speed.

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