Patent Description:
Many devices make use of caster wheels to enable rolling movement. Due to their small size and simplicity, caster wheels are well suited for traditional and autonomous mower applications, where the mower frame requires support but must also be able to follow steering inputs from the tractive wheels of the lawnmower. However, the use of caster wheels in lawnmowers often leads to unsightly and undesirable wheel marks in an area of turf traversed, and can limit functionality and/or maneuverability of the mower.

For example, a traditional caster wheel can compact or lay down areas of grass, which often occurs with robotic/autonomous mowers whose cut systems do not produce enough air movement or lift to stand grass back up that has been laid over by the wheels. Most conventional caster wheels also often require a yoke-like bracket and other adjacent structure, of which freshly cut grass and other debris can become stuck or trapped against the wheel, thus clogging up and limiting the rotation of the wheel.

Further, traditional caster-type wheels can easily become stuck in small holes, ruts, and/or by other obstacles often present in an area of turf. For example, when a traditional cylindrical wheel having a flat outer face runs alongside a vertical edge surface, or a fixed face such as a sidewalk edge, it can become stuck, thus limiting the ability of a robotic/autonomous mower to maneuver properly. <CIT> discloses a castored base for an office chair. The castored base includes a plurality of radially extending legs, each leg having a socket or sleeve fixed thereto adjacent an outer end thereof. A castor is connected to each socket or sleeve, each castor having two wheel portions and an axle assembly. The axle assembly includes an axle to which the two wheel portions are rotatably mounted in spaced disposition and including a pin, wherein the pin of each castor is received in a respective socket or sleeve which extends at least in part between the two wheel portions.

The invention generally described hereinafter provides for a caster wheel assembly. According to an aspect of the invention, a caster wheel assembly is provided. In some embodiments, the caster wheel assembly comprises a double bell-shaped caster wheel comprising two bell-shaped halves; and a wheel mount.

In some embodiments, the two bell-shaped halves are identical to one another, and are brought together to form the double bell-shaped caster wheel.

In some embodiments, the caster wheel provides for a small outer diameter, and a larger outer diameter. In some embodiments, the smaller diameter is between about <NUM> and <NUM>, and the larger outer diameter is between about <NUM> to about <NUM>.

In some embodiments, the caster wheel further comprises a center tread portion. In some embodiments, the center tread portion is about <NUM> to about <NUM> in width. In some embodiments, the center tread portion further comprises a rubber tread ring, wherein the bell-shaped halves are brought together to entrap the rubber tread ring.

In some embodiments, the caster wheel further comprises a double curvature having a smooth transition provided by the two bell-shaped halves. In some embodiments, the double curvature begins at and is adjacent to the center tread ring, wherein the wheel decreases in diameter as it moves away from the center tread ring portion.

In some embodiments, the wheel mount comprises a wheel spindle and a bracket. In some embodiments, the wheel spindle comprises an elongate end, a curved portion, and an elongate horizontal portion. In some embodiments, the elongate horizontal portion passes through the center of the caster wheel.

In some embodiments, the bracket is generally curved, extending from the elongate horizontal portion, and arcs around the wheel to meet the elongate end of the wheel spindle. In some embodiments, the bracket provides a hooked end, wherein the hooked end hooks over and around the wheel spindle.

In some embodiments, the caster wheel comprises at least two magnets positioned between the two bell-shaped halves. In some embodiments, the magnets are offset from each other. In some embodiments, the caster wheel comprises four magnets positioned between the two bell-shaped halves, and arranged equidistant around the outer circumference of the bell-shaped halves. In some embodiments, each of the four magnets are orientated at <NUM>° relative to an adjacent magnet.

According to other embodiments of the invention, the caster wheel assembly comprises a wheel comprising two bell-shaped halves; and a wheel mount, wherein the mount is positioned in between the two-bell shaped halves.

In some embodiments, each bell-shaped half comprises a central hub, a smooth transition portion, an outer circumferential rim, and a planar face. In some embodiments, the smooth transition portion transitions radially outward from the central hub toward the outer circumferential rim. In some embodiments, the smooth transition portion further comprises a ground contacting portion positioned adjacent to the outer circumferential rim.

In some embodiments, the ground contacting portion is about <NUM> to about <NUM> in width. In some embodiments, the bell-shaped halves are positioned such that each planar face is directly opposed to each other.

In some embodiments, the wheel mount further comprises a spindle, a mount body, and an axle. In some embodiments, the mount body comprises an elongate aperture for receiving the spindle, and a second aperture for receiving the axle. In some embodiments, the elongate aperture and the second aperture are offset from one another. In some embodiments, the mount body comprises an elongate top portion and a rounded bottom portion.

In some embodiments, the caster wheel assembly further comprises a first magnet pair and a second magnet pair. In some embodiments, the first magnet pair and the second magnet pair are offset from each other. In some embodiments, the first magnet pair comprises two individual magnets that are positioned <NUM>° from each other. In some embodiments, the second magnet pair comprises two individual magnets that are positioned <NUM>° from each other.

These and other features of the invention, and the advantages, are illustrated specifically in embodiments now to be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:.

It should be noted that all the drawings are diagrammatic and not drawn to scale. Relative dimensions and proportions of parts of these figures have been shown exaggerated or reduced in size for the sake of clarity and convenience in the drawings. The same reference numbers are generally used to refer to corresponding or similar features in the different embodiments. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

The following terms are used throughout the description, the definitions of which are provided herein to assist in understanding various aspects of the subject disclosure.

As used herein, the terms "turf", "turf material", and "material" are used interchangeably and refer to most any type of grass or turf, soil and the grass/plant material contained therein.

The technology generally described hereinafter provides for a caster wheel assembly and a bell-shaped caster wheel for use with an autonomous mower. The specific shape of the caster wheel provides for the ability of the wheel to climb out of small holes, ruts, and/or other obstacles. With existing products, and contrast to the disclosed technology, a conventional narrow wheel (without such bell shape) can cause maneuverability issues, such as getting trapped in small holes/obstacles.

In an embodiment, with reference to <FIG>, a caster wheel assembly <NUM> is shown. The caster wheel assembly <NUM> includes a pivotable wheel mount <NUM> coupled to a caster wheel <NUM>. Wheel mount <NUM> is rotatably connected to a frame or chassis of an autonomous mower. The wheel mount <NUM> comprises a wheel spindle <NUM> and a bracket <NUM>. In an embodiment, the wheel spindle <NUM> comprises a wire form member. The wheel spindle <NUM> is shown as a single spindle which curves around the side of the caster wheel <NUM>. As illustrated in <FIG>, a portion of the wheel spindle <NUM> passes through the center axis C of the caster wheel <NUM>, and thus acts as the axle about which the wheel <NUM> rotates.

In some embodiments, the caster wheel <NUM> is a double bell-shaped wheel comprising two bell-shaped halves 110a, 110b, which are brought together to form the double-bell shaped wheel. In an embodiment, the two bell-shaped halves 110a, 110b are identical.

The caster wheel <NUM> further comprises a center tread portion <NUM>. The center tread portion <NUM> provides a limited surface area, or relatively narrow portion of the caster wheel <NUM> which contacts the ground. The center tread portion <NUM> allows for a reduced footprint, where the wheel <NUM> reduces the compaction of the grass, reduces disruption of the turf, and/or reduces the amount of grass that is being laid down in front of the cut system. This becomes particularly important for robotic/autonomous mowers whose cut systems do not generally produce significant air movement for lifting and standing the grass back up that has been laid over by the wheels.

In some embodiments, the center tread portion <NUM> is about <NUM>-<NUM> in width. It should be understood that the center tread portion <NUM> can be of most any width sufficient to support the weight of the mower and/or maintain a specific amount of pressure imposed on the grass/turf.

Referring to <FIG>, in some embodiments, the center tread portion <NUM> comprises a resilient rubber tread ring <NUM>. In some embodiments, the bell-shaped halves 110a, 110b are brought together to entrap the rubber tread ring <NUM>, such that the bell-shaped halves 110a, 110b trap the rubber tread ring <NUM> between them. It should be understood that the rubber tread ring <NUM> can be made of most any resilient, rubber material or rubber-like material, and sized to provide an installation stretch, where the rubber material serves to seal the two bell-shaped halves 110a, 110b, thus keeping water and other debris from entering an interior portion of the caster wheel <NUM>. This helps prevent the addition of weight to the wheel, and prevents corrosion and damage to the interior components of the wheel (e.g., magnets, bearings, or the like).

The rubber tread ring <NUM> provides a soft contact area and a quiet and non-skidding surface on pavement or other hard surfaces. The rubber tread ring <NUM> also provides better grip on hard surfaces so that encoding is more accurate. For example, debris build-up is present and resists rotation of the wheel, the rubber tread ring <NUM> provides substantial grip on hard surfaces to overcome the resistance.

Further, the rubber tread ring <NUM> ensures that there is not a radially exposed opening, seam, or joint that is being pressed against the ground during rotation of the caster wheel <NUM>. Traditional wheels having two halves that are joined generally have a circumferential groove in the middle through which soil is squeezed or pressed as the wheel rolls across the soil surface, and over time, the wheel can become filled or packed with mud. This phenomenon adds weight to the traditional wheel, and promotes corrosion as moisture is introduced to the interior of the wheel. The seams associated with the rubber tread ring <NUM> of the present technology are positioned such that they are not pressed against the ground during operation of the wheel thus eliminating the opportunity for dirt/soil to enter and deteriorate the interior portion of the wheel.

The caster wheel <NUM> further comprises a double curvature 116a, 116b. The double curvature 116a, 116b comprises a smooth transition provided by the two bell-shaped halves 110a, 110b.

As shown in <FIG>, the double curvature 116a, 116b begins at and is adjacent to the center tread ring <NUM>, where the wheel decreases in diameter as it gets wider (i.e. as it moves away from the center tread ring portion <NUM>). The double curvature 116a, 116b or the arc of the double bell shape can be determined by an optimization of the diameter of the center portion and the diameter of the outer portions of the caster wheel <NUM>.

The double curvature 116a, 116b allows the caster wheel <NUM> to rotate out and pivot in order to climb over an obstacle, a sidewalk edge, or otherwise free itself from a fixed vertical edge. In contrast, for example, when a traditional cylindrical wheel having flat faces runs alongside a vertical edge surface, or a fixed face such as a sidewalk edge, it can become stuck. That is, the flat face of a conventional wheel tends to become trapped and travels parallel to a vertical surface of an obstruction, and can require a significant amount of force to break free. The force required for a traditional wheel to rotate away from the obstacle is much greater since there is no moment arm between the wheel edge and the wheel swivel to axis. The moment arm determines the degree of effectiveness or influence of a force to produce rotation of the wheel around an axis, where the moment arm is the shortest distance from the line of force to the axis. Geometrically, it is the perpendicular distance from the line of force to the axis, i.e. it is perpendicular to the line of force.

Therefore, the bell shape of the present technology prevents the wheel from squaring up against a flat side wall of an obstacle or obstruction and becoming trapped. The double curvature 116a, 116b allows the wheel to contact an obstacle towards the middle of the smooth transition, thus providing a large enough moment arm so that the wheel is easily rotated engaging the outer circumference of the wheel, which can easily climb up the edge of the obstacle.

For example, if the caster wheel drops into a hole, the double curvature 116a, 116b provides a much wider footprint to prevent the wheel <NUM> from becoming stuck, or to climb out of the hole. Thus, the caster wheel is less susceptible to falling into smaller holes, and less likely to become stuck or trapped in a larger hole. In an embodiment, the height from the inner (i.e. smaller) radius of the caster wheel <NUM> to the ground surface is a function of how much drop the mower is able to sustain before another portion of the mower body, for example, the mower chassis or the mower body structure, contacts the ground.

In some embodiments, the caster wheel <NUM> provides for a relatively small diameter, d, at the outside edges of the wheel <NUM>, and a larger diameter, D (as shown in <FIG> and <FIG>) at the inner edge of the wheel halves 110a, 110b, or the middle portion of the wheel <NUM>. The diameters D and d can be tuned for various performance goals. For example, to prevent false obstructions (e.g., the autonomous mower sensor system detects a lift or bump condition when the mower encounters a small hole), a larger diameter D is desired. To detect large holes quickly, a smaller diameter d is desired to allow for a moveable body structure to detect the fall off of the caster wheel <NUM>, yet still keeping the mower chassis from making hard contact with the ground.

It should be understood that the smaller diameter d at the ends of the bell shape can be dictated by the height of the turf to remain undisturbed. In some embodiments, the smaller diameter d can be at least <NUM>, or between about <NUM> and <NUM>. In some embodiments, the larger diameter D is about <NUM> to about <NUM>.

The smaller diameter d provides a climbing "lead in" feature when trying to turn away from a vertical edge surface (e.g. a sidewalk edge, or hole) as discussed above. However, the smaller outer diameter d should not be so small that the caster wheel <NUM> could drop down into smaller holes or ruts. In an embodiment, the distance from the bottom of the small diameter portion to the ground is no larger than the height of the adjacent fixed chassis areas or frame of the mower to the ground. This is so that neither the mower chassis nor the mower body/shell bottoms out before the smaller diameter wheel portions make contact with the edges of the hole. For example, such bottoming out of the chassis could cause the mower to become stuck, and bottoming out of the mower shell/body could cause a lift event to be detected.

Turning now to <FIG>, the caster wheel assembly <NUM> further provides a wheel mount <NUM>. The wheel mount <NUM> comprises a wheel spindle <NUM> and a bracket <NUM>. The caster wheel <NUM> can be attached to the wheel mount <NUM> using the combination of the wheel spindle <NUM> and the bracket <NUM>.

The wheel spindle <NUM> acts as the swivel axis, and the rotational axis of the wheel <NUM>. As best shown in <FIG>, the wheel spindle <NUM> comprises an elongate end 118a (which extends in the vertical direction), a curved portion 118b (curving around the wheel <NUM>), and an elongate horizontal portion 118c. The elongate horizontal portion 118c passes through the center axis C of the caster wheel <NUM>, and thus acts as the axle about which the wheel rotates.

The elongate end 118a provides the swivel axis and is rotatably mounted to a movable structure, such as, but not limited to, a deck of a mower or mower chassis. The wheel spindle <NUM> may be secured by any suitable means to the mower chassis, mower frame, or its components. In an embodiment, the wheel spindle <NUM> comprises a wire form member.

The wheel spindle <NUM> is secured to the caster wheel <NUM> by the bracket <NUM>. The combination/arrangement of the wheel spindle <NUM> and the bracket <NUM> provides the benefits of a full clevis arrangement at a lower cost compared to a conventionally fabricated clevis, and eliminates the need for a metal clip when the bracket <NUM> is formed of a plastic material.

In some embodiments, the bracket <NUM> is generally curved, wherein one end is connected to and extends from the end of the elongate horizontal portion 118c, and arcs around the wheel to meet the elongate end 118a of wheel spindle <NUM>. Generally, the bracket <NUM> is fully constrained, for example, but not limited to, a cylindrical engagement with the horizontal axis and a cylindrical engagement of the vertical axis through the hook around. In some embodiments, translation of the horizontal end can optionally be restricted with the addition of a retaining ring.

In some embodiments, the bracket <NUM> provides a hooked end <NUM>, where the hooked end <NUM> hooks over and around the wheel spindle <NUM>, such that it comes down and traps the other side of the wheel. In some embodiments, the bracket <NUM> can be implemented in most any material with the strength and durability to provide support to wheel spindle <NUM> and the caster wheel <NUM> including plastic or metal.

Further, the combination of the wheel spindle <NUM> and the bracket <NUM> prevents the "spaghetti fork" effect experienced with traditional single-sided wire forms, where taller, stringy grass gets wrapped around the wire form and eventually binds up the rotation of the wheel. The hooked end <NUM> reaches around and closes off the opposing side thereby preventing any stringy material from being able to get in and wrap in that manner.

Now turning to <FIG>, in some embodiments, the caster wheel assembly <NUM> provides for magnets <NUM>, <NUM>, <NUM>, and <NUM>, located partially within and between the bell-shaped halves 110a, 110b. In some embodiments, the magnets <NUM>, <NUM>, <NUM>, and <NUM> are arranged equidistant around the outer circumference of the bell-shaped halves 110a, 110b, and oriented at <NUM> degrees relative to an adjacent magnet <NUM>, <NUM>, <NUM>, and <NUM>.

In an embodiment, a position encoder associated with the caster wheel assembly <NUM> is arranged to measure the movement, rotation, velocity or displacement of the caster wheel <NUM>. The magnetic sensing device may comprise a magnetic field sensor (e.g., Hall effect sensor), a magneto-resistive sensor or another sensor that can sense or measure movement of the caster wheel <NUM>. As described above in detail in connection with a first embodiment, the position encoder can also provide information for determining that the caster wheel <NUM> is stationary, or rotating at an unexpectedly increased or decreased speed, indicating that the mower is stuck.

In some embodiments, the magnets <NUM>, <NUM>, <NUM>, and <NUM> are securely fastened or entrapped between the bell-shaped halves 110a, 110b, and are positioned within the caster wheel <NUM>, and beneath the rubber tread ring <NUM>.

The magnets <NUM>, <NUM>, <NUM>, and <NUM> provide the autonomous mower with the ability to sense the rotation, or lack thereof, of the caster wheel <NUM>. The sensor for encoding (not shown in the figures) can be located within the chassis or mower frame, and is configured to interact with and recognize the placement of magnets <NUM>, <NUM>, <NUM>, and <NUM> during rotation of the caster wheel <NUM>.

With reference to <FIG>, an example autonomous mower <NUM> is provided with a caster wheel assembly <NUM> arranged to support the front end of the mower <NUM>. In one example, the autonomous mower <NUM> can be powered by at least one powered wheel located at the rear of the autonomous mower <NUM>, while the caster wheel assembly <NUM> is not powered and rotates freely according to the movements of the powered wheel(s).

Referring to <FIG>, a caster wheel assembly <NUM> is shown. The caster wheel assembly <NUM> comprises a caster wheel <NUM> and a wheel mount <NUM>. The wheel mount <NUM> is rotatably connected to a frame or chassis of an outdoor power equipment machine, for example, an autonomous mower.

In some embodiments, the caster wheel <NUM> comprises two bell-shaped halves 210a, 210b, thus providing a "split wheel" configuration. This "split wheel" configuration allows for the wheel to pass through grass or turf while minimizing the flattening, compressing or compacting of the grass or turf as the mower rolls across the ground.

It should be understood that the two bell-shaped halves 210a, 210b can be made of or formed from most any material sufficient to be rigid enough to provide support to the robotic mower, while also being substantially lightweight.

In some embodiments, the two bell-shaped halves 210a, 210b are made of plastic, metal, or rubber. In some embodiments, each bell-shaped half 210a, 210b has a diameter of about <NUM>. It should be understood that the outer diameter of the caster wheel is a function of the physical space available within the chassis and enclosing structure of the machine. It should generally be as large as possible in order to provide for the greatest maneuverability on rough terrain. At a minimum, its radius should be greater than the height from ground of forward bumper or guarding. This is to prevent obstructions that could pass below the bumper from contacting the wheel at is center height which would prevent it from rolling over said obstacle.

Each bell-shaped half 210a, 210b comprises, respectively, a central hub 214a, 214b, a smooth transition portion 216a, 216b, an outer circumferential rim 218a, 218b, and a planar face 220a, 220b.

In some embodiments, the central hub 214a, 214b further comprises an aperture <NUM> (as best seen in <FIG>), wherein the aperture <NUM> is configured for receiving a fastener and operatively connects each bell-shaped half 210a, 210b to the wheel mount <NUM>.

As shown in <FIG>, the smooth transition portion 216a, 216b of the bell shape smoothly transitions radially outward from the central hub 214a, 214b toward the outer circumferential rim 218a, 218b. In other words, the diameter of each bell-shaped half becomes larger as it extends inward from the hub 214a, 214b to the outer circumferential rim 218a, 218b.

With reference to <FIG>, the smooth transition portion 216a, 216b further comprises a ground contacting portion 224a, 224b positioned adjacent to the outer circumferential rim 218a, 218b. The ground contacting portion 224a, 224b together with the space <NUM> therebetween, provides a limited surface area, or narrow portion of which the caster wheel contacts the ground, which allows for the wheel to easily slip through and between the grass or turf to minimize the influence of the wheels (i.e. to prevent crushing, flattening, breakage, etc.) on the grass stems and/or area of turf. Thus, turf damage is reduced and ultimately wheel marks indicative of the traveling path of a robotic mower caused during operation are also prevented, or greatly reduced.

The reduced contact area allows the caster to slip through the grass and make contact with the soil below. This provides for a more predictable vertical height relationship of the caster wheel <NUM> with the ground, and therefore the chassis and cut system of the mower with the ground, which is important for maintaining optimum performance of the mower's cut system, in contrast to a wheel with a large contact area which may tend to "float" up on the grass in an inconsistent manner.

In some embodiments, the ground contacting portion 224a, 224b is about <NUM>-<NUM> in width. It should be understood that the ground contacting portion 224a, 224b can be of most any width sufficient to support the weight of the mower and/or maintain a specific amount of pressure imposed on the grass/turf.

In some embodiments, the bell-shaped halves 210a, 210b are positioned adjacent to each other such that the planar faces 220a, 220b are directly opposed to each other, and where the bell-shaped halves 210a, 210b are positioned along a central axis, A, wherein central axis A extends in a horizontal direction. In some embodiments, the bell-shaped halves 210a, 210b are generally hollow, thus providing an interior cavity <NUM>, (as best shown in <FIG>). In some embodiments, the interior cavity <NUM> is shaped to receive a mounting disc <NUM>.

As shown in <FIG>, the mounting disc <NUM> is shaped to be positioned within and adjacent to the interior cavity <NUM> of each bell-shaped half 210a, 210b. The mounting disc <NUM> further comprises a projection <NUM> and where the exterior portion of the mounting disc provides the planar face <NUM>. As best shown in FIG. 2C, when the mounting disc <NUM> is installed, the projection <NUM> is fully received and encompassed by the interior cavity <NUM>. The mounting disc <NUM> comprises an aperture <NUM>, which aligns with the central axis A. In some embodiments, the mounting disc <NUM> is secured to the bell-shaped half by a low friction seal, or other sealing means.

With reference to <FIG>, the caster wheel assembly <NUM> provides a wheel mount <NUM>. In some embodiments, the wheel mount <NUM> is center mounted, or positioned in between the two-bell shaped halves 210a, 210b, (best shown in <FIG>). The center mounted wheel mount <NUM> eliminates any adjacent structure that would allow for debris to become stuck or trapped against the wheel. In contrast, with conventional wheel with a yoke-style bracket, mud and other debris can easily become trapped in the yoke, which builds up and around the wheel, thus limiting wheel rotation, and eventually seizing up the wheel and preventing movement completely.

In some embodiments, the wheel mount <NUM> further comprises a spindle <NUM>, a mount body <NUM> positioned between the bell-shaped halves 210a and 210b, and an axle <NUM>. The spindle <NUM> provides for rotatably mounting the caster wheel assembly <NUM> to a movable structure, such as, but not limited to, a mower deck or chassis. In some embodiments, the spindle <NUM> defines an axis of rotation B, which extends in the vertical direction (as best seen in <FIG>). The spindle <NUM> may be secured by any suitable means to the mower chassis, mower frame, or its components. In some embodiments, the spindle <NUM> is secured to the mower by a swivel joint which allows the caster wheel <NUM> to freely rotate <NUM>°, and enabling the wheel to roll in most any direction.

The wheel mount <NUM> further provides for an axle <NUM>. The two-bell shaped halves 210a, 210b are rotatably mounted to the axle <NUM>, such that the two-bell shaped halves 210a, 210b rotate about the central axis A. In some embodiments, the axle <NUM> provides threaded ends to enable the mounting of the two-bell shaped halves 210a, 210b (best seen in <FIG>).

With reference to <FIG>, the mount body <NUM> comprises an elongate aperture <NUM> for receiving the spindle <NUM>, and an aperture <NUM> for receiving the axle <NUM>. In some embodiments, the elongate aperture <NUM> and the aperture <NUM> are offset from one another (as best seen in <FIG>). In some embodiments, the mount body <NUM> comprises a generally kidney-shaped form, having an elongate top portion which curves into a rounded bottom portion.

In some embodiments, the mount body <NUM> further comprises a projection 232a, 232b extending perpendicularly from the mount body <NUM> along axis A. In some embodiments, the mount body <NUM> and the projections 232a, 232b are one piece. In other embodiments, the mount body <NUM> is formed separately from the projections 232a, 232b, wherein the mount body <NUM> and the projections 232a, 232b are attached or fixedly-attached to each other. Each projection 232a, 232b is shaped to be received by the inner portion of the mounting disc projection <NUM>.

Now turning to <FIG>, in some embodiments, the caster wheel assembly <NUM> further provides for a position encoder including first magnet pair <NUM> and a second magnet pair <NUM>, located within each respective bell-shaped half 210a, 210b. The presence of the first magnet pair <NUM> and the second magnet pair <NUM> provide the autonomous mower with the ability to sense the rotation, or lack thereof, of the caster wheel <NUM>. The position encoder can further include a magnetic sensing device (not shown in the figures), which can be located within the chassis or frame of the autonomous mower, and is operative to detect changes in the magnetic field as each magnet of the first magnet pair <NUM> and the second magnet pair <NUM> pass over it.

In an embodiment, the position encoder associated with the caster wheel assembly <NUM> is arranged to measure the movement, rotation, velocity or displacement of the caster wheel <NUM>. The magnetic sensing device may comprise a magnetic field sensor (e.g., Hall effect sensor), a magneto-resistive sensor, or another sensor that can sense or measure movement of the caster wheel <NUM>. The position encoder can also provide information for determining that the caster wheel <NUM> is stationary, or rotating at an unexpectedly increased or decreased speed, indicating that the mower is stuck.

In further embodiments, the caster wheel assembly <NUM> can include components for sensing, measuring, and tracking wheel movement and position information, for example, components associated with incremental, absolute, magnetic, and/or optical rotary encoders.

In some embodiments, the alignment of first magnet pair <NUM> and the alignment of the second magnet pair <NUM> are offset from each other, such that each bell-shaped half 210a, 210b is in a clocked orientation at <NUM>° from the corresponding bell-shaped half 210a, 210b (as best seen in <FIG>). In an embodiment, each end of the axle <NUM> can include a D-shaped portion corresponding to a similar D-shaped portion of each wheel half 210a, 210b, and which when assembled positions the wheel halves 210a, 210b such the first magnet pair <NUM> and the second magnet pair <NUM> are offset from each other.

In some embodiments, the first magnet pair <NUM> and the second magnet pair <NUM> are securely fastened onto the mounting disc <NUM>. In some embodiments, the first magnet pair <NUM> comprises two individual magnets 234a and 234b, wherein magnet 234a is positioned directly opposite to magnet 234b (i.e. the magnets 234a and 234b are positioned <NUM>° from each other), (see <FIG>). In some embodiments, the second magnet pair <NUM> comprises two individual magnets 236a, 236b, wherein magnet 236a is positioned directly opposite to magnet 236b (i.e. the magnets 236a and 236b are positioned <NUM>° from each other).

Claim 1:
A caster wheel assembly (<NUM>, <NUM>), comprising:
a double bell-shaped caster wheel (<NUM>, <NUM>) comprising two bell-shaped halves (110a, 110b, 210a, 210b),
wherein each bell-shaped half comprises a central hub (214a, 214b), a smooth transition portion (216a, 216b), an outer circumferential rim (218a, 218b), and a planar face (220a, 220b); and
a wheel mount (<NUM>, <NUM>).