Patent Description:
Swiveling caster wheels may be used in various implements such as in zero-turn radius mowers or in various agricultural implements (see <CIT>). The caster wheels may be offset from their swivel or steering axis which allows the wheels to self-align to the direction of travel of the implement. In some applications, it is desirable to steer the caster wheel to control its swivel position.

Conventional methods for steering caster wheels may involve drive by wire systems that include caster position sensors which add to the complexity of the caster assemblies. Further, vehicles may encounter unintentional "bump-steer" in which the caster wheels pivot an amount upon encountering a change in the terrain.

A need exists for steerable caster systems that may be operated in a caster wheel steering mode and a non-caster wheel steering mode, that involve mechanical connections between the steering mechanism and the caster wheels and that reduce bump-steer during caster wheel steering modes.

<CIT> discloses an auxiliary steering device on a vehicle with left and right drive wheels and a third wheel, the steering device also has an auxiliary wheel that is lowered to alter the contact patch of the third wheel.

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below.

One aspect of the present disclosure is directed to a vehicle having a steerable suspended caster wheel according to claim <NUM>. Further preferred embodiments are provided in the dependent claims.

Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure.

Referring to <FIG>, a steered caster wheel system is referenced generally as "<NUM>". In the illustrated embodiment, the caster wheel system <NUM> includes two swivel caster assemblies <NUM> each including a caster wheel <NUM>. In other embodiments, the steered caster wheel system <NUM> may include a single caster assembly <NUM>. The term "caster wheel" includes a wheel mounted to a frame or chassis at a generally vertically oriented caster pivot B (<FIG>) so that the caster wheel is able to swivel about the caster pivot.

Each caster wheel assembly is connected to a subframe <NUM>. Generally the first and second caster assemblies <NUM> and subframes <NUM> described herein are symmetric and description herein of an assembly or subframe also applies to the second assembly or subframe (e.g., description of a hub of the assembly indicates that the first assembly has a first hub and that the second assembly has a second hub). Referring now to <FIG>, each caster wheel assembly <NUM> includes a wheel <NUM> that rotates about an axle <NUM> and about a rotational axis R<NUM> that extends through the axle <NUM>. The axle <NUM> is connected to a leg assembly <NUM>. In the embodiment illustrated in <FIG>, the leg assembly <NUM> includes a single leg that attaches to an inner side of the wheel axle. In other embodiments and as shown in <FIG>, the leg assembly <NUM> includes two legs that connect to the axle <NUM> of the caster wheel assembly <NUM> on each side of the wheel <NUM> (as with a caster fork).

In the embodiment illustrated in <FIG>, the caster wheel <NUM> is directly below its steering axis B. In this configuration, when the wheel <NUM> is aligned forward, the steering axis B intersects the rotational axis R<NUM> of the wheel <NUM>. In other embodiments and as shown in <FIG> and <FIG>, the wheel <NUM> may be offset from the steering axis B. The rotational axis R<NUM> of the wheel self-orients to be behind the steering axis B as the caster moves in a direction of travel.

Each assembly <NUM> includes a hub <NUM> (<FIG>) and a caster shaft <NUM> that rotates within the hub <NUM>. The swivel caster assemblies <NUM> may include bushings or bearings within the hub <NUM> that allow for rotation of the shaft <NUM> within the hub <NUM>. Each caster shaft <NUM> is connected to the leg assembly <NUM> that connects to the caster wheel axle <NUM>.

The first and second caster assemblies <NUM> are each connected to the subframe <NUM> by a swivel joint <NUM> formed by the hub <NUM> and shaft <NUM>. The subframes <NUM> may be suspended from a chassis by a mechanism having a suspension element <NUM>, shown as a hydraulic cylinder in the illustrated embodiment. With reference to <FIG>, each cylinder <NUM> may be connected to an accumulator <NUM> of a suspension system with the hydraulic fluid being provided from a source <NUM> by a hydraulic pump <NUM>. Other suspension elements such as shock absorbers may be used in other embodiments. The suspension system allows the wheels <NUM> to move vertically relative to the chassis to which the suspension element <NUM> is connected such as in a raised position (<FIG>) or in a lowered position (<FIG>).

The caster wheels <NUM> are connected to a steering system <NUM> which selectively controls the swivel position of the caster wheels <NUM>. The "swivel position" of the caster wheels generally refers to the angular position of the caster wheels relative to the longitudinal axis A. The steering system <NUM> may include a steering actuator <NUM> (shown as a hydraulic cylinder) connected to the caster assemblies <NUM> by tie rods <NUM> with each tie rod <NUM> being connected to an opposite side of the steering actuator <NUM>. Each tie rod <NUM> connects to a linkage <NUM> connected to the caster assembly shaft <NUM>. The steering actuator <NUM> may be connected to a chassis of the vehicle. An orbital valve <NUM> (<FIG>) regulates fluid flow to the steering cylinder <NUM> based on input from a steering mechanism such as a steering wheel <NUM>. The steering system <NUM> may include a steering pump (not shown) to provide the fluid flow.

In the illustrated embodiment, the steering actuator <NUM> is a hydraulic cylinder such as a double acting hydraulic cylinder having a through rod <NUM> that extends from each side which pushes/pulls the tie rods <NUM> to commonly align the caster wheels <NUM> during caster wheel steering. The steering cylinder <NUM> includes inlet and outlet ports <NUM>. Fluid flows through the ports <NUM> in a first direction to cause the through rod <NUM> to move to cause both caster wheels <NUM> to be steered. Fluid is caused to flow in the opposite direction to actuate the through rod <NUM> in the opposite direction and to cause the caster wheels to be steered in the opposite direction.

In some embodiments, the steering system <NUM> may be selectively disabled by a disengagement system <NUM> to allow the caster wheels <NUM> to freely pivot. The steering system <NUM> may be selectively operable in a caster wheel steering mode in which the caster wheels <NUM> are steered and a non-caster wheel steering mode in which caster wheels <NUM> are free to pivot. The caster-wheel steering mode and non-caster wheel steering mode may be selected by an operator.

With reference to <FIG>, the disengagement system <NUM> includes a disengagement cylinder <NUM> within the tie-rods <NUM> to enable selective steering of the caster wheels <NUM>. In the caster wheel steering mode, the disengagement cylinders <NUM> are in a locked position such that actuation of the steering actuator <NUM> causes pivoting movement of the caster wheels <NUM> (i.e., the tie-rods <NUM> are a fixed length). In the non-caster wheel steering mode, the disengagement cylinders <NUM> are allowed to float (i.e., fluid is allowed to freely flow with little or no pressure), thereby disengaging the movement of the steering cylinder <NUM> from the caster wheels <NUM> (i.e., the tie-rods <NUM> are variable in length). As such, actuation of the steering actuator <NUM> will not be translated through the disengagement cylinders <NUM> to the caster wheels <NUM> and the caster wheels <NUM> will be allowed to freely pivot in the non-caster wheel steering mode. Any suitable disengagement system <NUM> that operates to selectively and mechanically disengage caster wheel steering may be used unless stated otherwise.

In the illustrated embodiment, each tie-rod <NUM> includes a disengagement cylinder <NUM>, the disengagement cylinder <NUM> being a three-position cylinder. The three-position cylinder has an inner barrel <NUM>, outer barrel <NUM> and a common rod <NUM> between the inner and outer barrels. In other embodiments, the three-position cylinder may have two joined barrels in the middle of the cylinder <NUM>.

The outer barrel <NUM> is connected to the steering linkage <NUM> attached to the caster shaft <NUM>. Each inner barrel <NUM> is pivotally connected to the steering actuator <NUM> with the steering actuator being mounted to a chassis or frame of the vehicle. These pivotal connections enable the left and right portions of the steering system <NUM> to move with each respective caster wheel <NUM> as the caster wheel <NUM> moves up and down in response to uneven terrain.

The disengagement cylinders <NUM> are connected to a hydraulic system <NUM> (<FIG>) that regulates the fluid flow to the cylinders <NUM>. The hydraulic system <NUM> includes a pump <NUM>, a valve <NUM> and a hydraulic fluid tank <NUM>. In caster wheel steering mode, the valve <NUM> allows oil into the cylinders to lock-out the disengagement cylinders <NUM> with pressure created by pump <NUM>. In the drive-wheel steering mode, valve <NUM> is shifted to allow fluid to freely flow in and out of the disengagement cylinders <NUM> and back to the tank <NUM>.

The hydraulic system <NUM> is configured such that, for each disengagement cylinder <NUM>, the base end of one barrel and the rod end of the other barrel are pressurized during the float mode. This allows one barrel to be locked in an extended position and the other barrel to be locked in a retracted position during the caster-steering mode to achieve an intermediate tie-rod <NUM> length (i.e., a length that is between the maximum length at which both barrels are extended and the minimum length at which both barrels are retracted). In the float mode, the common tie-rod <NUM> may freely float in and out of each barrel as the caster wheel moves.

The disengagement system <NUM> includes a mode selector <NUM> and a control unit <NUM> that controls the valve <NUM>. The mode selector <NUM> allows an operator to select a desired mode of operation (i.e., caster wheel steering or non-caster wheel steering). The control unit <NUM> receives the signal from the mode selector <NUM> and controls the mode of the steering system <NUM> in response to the signal. The control unit <NUM> sends a signal to the valve <NUM> instructing the valve <NUM> to close when the caster wheel steering mode is selected. The control unit <NUM> transmits a signal to the valve <NUM> to open in the non-caster wheel steering mode.

In some embodiments, the steering system <NUM> is adapted to steer the caster wheels <NUM> through a steering angle that is limited, such as by the range of travel of the steering cylinder <NUM>. The operator may sense when the steering system <NUM> is in the stopped position as further movement of the steering wheel in the clockwise or counterclockwise position is prevented.

In the caster wheel steering mode, the steered caster wheel system <NUM> includes mechanical connections from the steering mechanism <NUM> to the caster wheels <NUM> for steering of the caster wheels <NUM> (i.e., includes only mechanical linkages and/or hydraulic components to translate movement of the steering mechanism into caster wheel steering). In this mode, pivoting of the caster wheels <NUM> is not a response to a control unit signal. In some embodiments, the steered caster wheel system <NUM> does not include sensors for sensing the position of the caster wheels.

In alternative embodiments, the steering system <NUM> may include other arrangements of components that enables the system to operate as described. For example, the steering system <NUM> may include any of the following components, without limitation: tie-rods, rack and pinion mechanisms, orbital valves, cylinders, motors, and bell cranks. In other embodiments, the steering system includes two steering cylinders <NUM> with a steering cylinder controlling the orientation of a single caster wheel <NUM>.

Another embodiment of a steered caster wheel system <NUM> is shown in <FIG>. The system operates similar to the system of <FIG> and <FIG> except includes a different steering actuator <NUM> (e.g., rack and pinion or steering gear with a pitman arm) connecting the caster assemblies <NUM> to the steering mechanism <NUM>.

The caster wheel system <NUM> may be part of a self-propelled vehicle such as the self-propelled vehicle <NUM> shown in <FIG>. In the illustrated embodiment, the vehicle includes a baling device <NUM> for forming a bale of crop or forage material. In other embodiments, the self-propelled vehicle <NUM> may be an agricultural vehicle such as a rake, mower or mower conditioner, merger, sprayer, windrower, broadcast spreader, nut or fruit harvester or the like. In other embodiments, the vehicle <NUM> is configured for non-agricultural use (e.g., construction, shipping or the like). Reference herein to the bale device <NUM> should not be considered limiting and any suitable device may be substituted for the baling system unless stated differently (e.g., cutting or mower head, sickle bar, spray tank and/or booms, harvesting devices (e.g., grape or nut harvesting devices), broadcast spreader or the like). In some embodiments, the vehicle <NUM> is adapted to carry a load (e.g., bale, herbicide, fertilizer, or harvested crop such as nuts or fruits).

The self-propelled vehicle <NUM> includes front caster wheels <NUM> that are part of the steered caster system <NUM>. The vehicle <NUM> also includes rear drive wheels <NUM>. The rear drive wheels <NUM> may be independently powered and controlled by motors (e.g., hydraulic motors). Independent control of the first and second rear drive wheels <NUM> allows the wheels to rotate at different rates or even in different directions. This allows the vehicle <NUM> to turn in its own footprint and consistent with a zero-turn radius profile.

The device <NUM> (e.g., bale forming system <NUM>) is supported by a chassis <NUM>. In embodiments in which the device is a baler, the vehicle also includes a pick-up device <NUM> (<FIG>) that rotates to feed crop or forage material to the bale forming system <NUM>. The vehicle <NUM> is controlled from an operator station <NUM> and is powered by an engine <NUM>. Each of the operator station <NUM>, engine <NUM> and device <NUM> are supported by the chassis <NUM> (i.e., the engine <NUM> is not part of a towed vehicle such as a tractor that releasably connects to the device by a hitch assembly attached to an implement tongue).

The first and second caster assemblies <NUM> are connected to the chassis <NUM> and the swivel positon of the caster wheels <NUM> is selectively controlled by the steering system <NUM> (<FIG>) as determined by the mode of operation of the vehicle (i.e., caster wheel steering mode or non-caster wheel steering mode such as a drive wheel steering mode).

Each of the wheels <NUM>, <NUM> is connected to the chassis <NUM> and can be rotated around a rotational axis R<NUM>, R<NUM>. In the illustrated embodiment, the drive wheels <NUM> have a common rotational axis R<NUM> and the caster wheels <NUM> have a common rotational axis R<NUM>. In other embodiments, the drive wheels <NUM> are offset from each other and have different axes of rotation and/or the caster wheels <NUM> are offset from each other and have different axes of rotation. In this embodiment, the vehicle <NUM> includes four wheels, though in other embodiments, the vehicle may include any number of drive and caster wheels.

As shown in <FIG>, the drive wheels <NUM> have a diameter that is larger than a diameter of the caster wheels <NUM>. In some embodiments, the ratio of the diameter of the drive wheels <NUM> to the diameter of the caster wheels <NUM> is at least about <NUM>:<NUM> or even at least about <NUM>:<NUM>.

The offset of the caster wheels (i.e., distance between the axis of rotation R<NUM> of the wheel and a swivel joint <NUM>) may be at least <NUM> inches, at least about <NUM> inches or from about <NUM> to about <NUM> inches. These ranges are exemplary and other ranges may be used unless stated otherwise. In some embodiments, the offset may be eliminated.

The first and second caster wheels <NUM> are pivotally connected to the chassis <NUM> (<FIG>). The caster wheels <NUM> and/or drive wheels <NUM> may be spaced to allow the chassis <NUM> to support a device (e.g., agricultural implement) such as a round baler <NUM> and pick-up device <NUM> as shown in the illustrated embodiment. In some embodiments, the vehicle <NUM> includes a single front caster wheel <NUM> (e.g., one front caster wheel centered relative to the lateral axis of the vehicle). With reference to <FIG>, the caster wheels <NUM> and subframes <NUM> are independently suspended from the chassis <NUM> to absorb forces transmitted during travel over uneven terrain.

The drive wheels <NUM> are fixed to the chassis <NUM> such that the wheels <NUM> maintain parallel alignment with a longitudinal axis A (<FIG>) of the vehicle <NUM> (i.e., do not pivot with respect to the chassis). The longitudinal axis A of the vehicle extends from a front <NUM> to a rear <NUM> of the vehicle <NUM>. As referenced herein, the "front" of the vehicle refers to a leading portion or end of the vehicle relative to the longitudinal axis during conventional operation as indicated by the arrow in <FIG>. The "rear" refers to the trailing portion or end relative to the longitudinal axis during conventional operation. Similarly, the terms "front wheels" and "rear wheels" refer to the relative position of the wheels relative to the direction of travel of the vehicle during conventional operation. The vehicle also includes a lateral axis B (<FIG>) that extends from a first side <NUM> (<FIG>) to a second side <NUM> of the vehicle <NUM> and that is transverse to the longitudinal axis A.

With reference to <FIG>, the first and second drive wheels <NUM> are each driven and controlled by separate drive systems <NUM>. Each drive system <NUM> has a drive motor <NUM> for rotating the drive wheel <NUM> forward or backward. The drive motors <NUM> may be hydraulic motors that are driven by a pump <NUM> that is powered by the engine <NUM>. Each drive wheel <NUM> may be controlled by a separate circuit (i.e., separate hydraulic pumps <NUM> with fluid lines <NUM> connected to the drive wheel motors <NUM>). The first and second pumps <NUM> may be hydrostatic, variable displacement pumps. In some embodiments, fixed displacement or variable displacement motor(s) may be used.

The vehicle <NUM> may be driven in a steering mode that corresponds to the caster wheel steering mode or non-caster wheel steering mode described above. In a drive wheel steering mode (corresponding to the non-caster wheel steering mode described above), the vehicle <NUM> is steered by creating a differential speed between the first and second rear drive wheels <NUM> (i.e., by creating a difference between the first drive wheel rotational speed and the second drive wheel rotational speed). In this mode, each drive wheel <NUM> is capable of being driven forward or in reverse independent of the speed and direction of the other wheel (i.e., the drive wheels may be operated in counter-rotation). As an operator controls a steering mechanism (e.g., steering wheel), the rear drive wheels <NUM> rotate at different speeds to steer the vehicle <NUM> through an arc or deviation in the travel pathway. The speed and direction of travel (forward or rearward) may be controlled by a separate operator control. In the drive wheel steering mode, the vehicle <NUM> may be turned within its own footprint. In this mode, the caster wheels <NUM> are not steered (e.g., the valve <NUM> (<FIG>) is open allowing the disengagement cylinders <NUM> to float). The caster wheels <NUM> self-align with the direction in which the drive wheels propel the vehicle, i.e., the caster wheels <NUM> follow the direction of travel of the rear drive wheels <NUM>.

In the caster wheel steering mode, the steering system <NUM> (<FIG>) is operable to control the swivel position of the caster wheels <NUM>. In this mode, the drive wheels <NUM> may be powered equally with differences in the rate of rotation of the drive wheels <NUM> occurring as a response to the curved path of the vehicle <NUM> (e.g., with a differential system shown as differential valves <NUM>) compensating the drive systems <NUM> of the drive wheels).

The wheels <NUM> are powered and rotated independently by the drive systems <NUM>. Accordingly, the wheels <NUM> can be rotated at different speeds by driving the motors <NUM> at different speeds. In the drive wheel steering mode (i.e., non-caster wheel steering mode), the wheels <NUM> are driven at different speeds by the drive system <NUM>. For example, in this mode, the motors <NUM> receive different amounts of fluid from the respective pumps <NUM> to differentiate the speed of the wheels <NUM>. Separate fluid lines <NUM> extend between each pump <NUM> and drive motor <NUM> to independently rotate the wheels <NUM>. The direction of fluid flow may be forward or reverse to independently rotate the wheels forward or reverse to propel the vehicle forward, reverse, through an arc (e.g., as during steering) or about a vertical axis midway between the drive wheels <NUM> (e.g., as during zero turn steering).

In the caster wheel steering mode, the pumps <NUM> provide equal amounts of fluid to the motors <NUM> but the wheels <NUM> are able to rotate at different speeds due to a differential system <NUM> (shown as differential valves in <FIG>) that transfers fluid between the drive systems. Alternatively, the drive wheels <NUM> may also be controlled for steering in the caster wheel steering mode by supplying different amounts of fluid from the respective pumps <NUM> to the motors <NUM> to differentiate the speed of the wheels <NUM> (e.g., as in a "hybrid" steering mode).

With reference to <FIG>, each subframe <NUM> may be pivotally attached to the chassis <NUM> at an outer pivot point P<NUM> and an inner pivot point P<NUM>. In this arrangement, the chassis <NUM> is supported by the subframes <NUM> and the chassis <NUM> and components carried by the chassis <NUM> (e.g., operator station and cab) may move up and down relative to the subframes <NUM> as the vehicle <NUM> travels over uneven terrain.

As shown in <FIG>, the subframe <NUM> has two arms <NUM>, <NUM> that extend from the chassis <NUM>. The swivel joint <NUM> is at the point at which the arms <NUM>, <NUM> meet and is forward of the inner and outer pivot points P<NUM>, P<NUM> relative to a longitudinal axis A (<FIG>) of the vehicle. The swivel joint <NUM> is also outward to both the inner and outer pivot points P<NUM>, P<NUM> relative to the lateral axis B (<FIG>) of the vehicle <NUM> (i.e., the outer pivot point P<NUM> of each subframe <NUM> is positioned between the inner pivot point P<NUM> and the point of attachment of the suspension element <NUM> relative to the lateral axis B).

In the embodiment illustrated in <FIG>, the first arm <NUM> is generally parallel to the longitudinal axis A (<FIG>) and the second arm <NUM> is generally parallel to the lateral axis B. In other embodiments (<FIG>), the first arm <NUM> is angled upward toward the swivel joint <NUM> with respect to the longitudinal axis A. In the embodiment illustrated in <FIG>, the second arm <NUM> is generally parallel to the lateral axis B.

In other embodiments, the subframe <NUM> has a single arm or may include any other arrangement of components that allows the caster wheels <NUM> to be positioned below the chassis <NUM> to support the vehicle <NUM>.

The vehicle <NUM> includes a control system to control the drive wheels <NUM> and the front caster wheels <NUM> based on inputs from an operator. The control system includes the control unit <NUM> (<FIG>), speed and direction control device <NUM>, the mode selector <NUM> and steering mechanism which is shown as a steering wheel <NUM>. The speed and direction control device <NUM>, mode selector <NUM> and steering wheel <NUM> may be controlled from the operator station <NUM>.

The control unit <NUM> includes a processor and a memory. The processor processes the signals received from various sensors, selectors and control devices of the system. The memory stores instructions that are executed by the processor.

Control unit <NUM> may be a computer system. Computer systems, as described herein, refer to any known computing device and computer system. As described herein, all such computer systems include a processor and a memory. However, any processor in a computer system referred to herein may also refer to one or more processors wherein the processor may be in one computing device or a plurality of computing devices acting in parallel. Additionally, any memory in a computer device referred to herein may also refer to one or more memories wherein the memories may be in one computing device or a plurality of computing devices acting in parallel.

The term processor, as used herein, refers to central processing units, microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing the functions described herein. The above are examples only, and are thus not intended to limit in any way the definition and/or meaning of the term "processor.

In one embodiment, a computer program is provided to enable control unit <NUM>, and this program is embodied on a computer readable medium. In an example embodiment, the computer system is executed on a single computer system, without requiring a connection to a server computer. In a further embodiment, the computer system is run in a Windows® environment (Windows is a registered trademark of Microsoft Corporation, Redmond, Washington). In yet another embodiment, the computer system is run on a mainframe environment and a UNIX® server environment (UNIX is a registered trademark of X/Open Company Limited located in Reading, Berkshire, United Kingdom). Alternatively, the computer system is run in any suitable operating system environment. The computer program is flexible and designed to run in various different environments without compromising any major functionality. In some embodiments, the computer system includes multiple components distributed among a plurality of computing devices. One or more components may be in the form of computer-executable instructions embodied in a computer-readable medium.

The computer systems and processes are not limited to the specific embodiments described herein. In addition, components of each computer system and each process can be practiced independent and separate from other components and processes described herein. Each component and process also can be used in combination with other assembly packages and processes.

The mode selector <NUM> may be, for example, part of a touch screen, a soft key, toggle switch, selection button or any other suitable interface for selecting the steering mode. The speed and direction control device <NUM> is typically hand-operated and may be a sliding lever that that causes an increase in forward speed as the lever is slid forward of a neutral position and an increase in reverse direction as the lever is slid rearward of the neutral position. The direction and speed control device <NUM> produces a signal in response to its position and the signal is transmitted to the control unit <NUM>. The control unit <NUM> produces an output signal transmitted to the hydraulic pumps <NUM> that drive the rear wheels <NUM>. The speed may also be controlled by a throttle that controls the engine speed. The vehicle <NUM> may be stopped by moving the direction and speed control device <NUM> to a zero-speed setting and/or by operating foot brake levers.

In the illustrated embodiment, steering may be performed by a steering mechanism shown as a steering wheel <NUM> which regulates the steering system. For example, in the drive wheel steering mode, a sensor <NUM> measures the direction and angle of the steering wheel <NUM> and sends signals to the control unit <NUM>. The control unit <NUM> produces a signal that is transmitted to the hydraulic pumps <NUM> to independently regulate the rotational speeds of the first and second drive wheels <NUM> (i.e., the rotation speed and direction of rotation of each drive wheel <NUM>).

In other embodiments, speed and/or steering may be controlled by different operator controls such as wheel levers, digital inputs, joysticks, dual sticks, and headsets.

In some embodiments, the self-propelled vehicle <NUM> is configured for autonomous operation. The vehicle may include sensors (e.g., cameras, GPS sensors and the like) that sense the position of a windrow and/or that may sense the position of the vehicle in the field. The vehicle <NUM> may also include a control unit that autonomously sends signals to control the vehicle speed and steering systems. In some embodiments, the field in which the vehicle is propelled is mapped and the field map is used to autonomously control the operation of the vehicle in the field. In such embodiments, the vehicle may include a riding station to carry an operator or the operator station may be eliminated.

With reference to <FIG>, in embodiments in which the vehicle <NUM> is used to bale forage or crop material, the vehicle also includes a bale forming system <NUM> that includes belts, rollers, belt tighteners, and a motor that drives the rollers. In this embodiment, the baler forms bales in an expandable baling chamber, though, in other embodiments, the baler may be a fixed chamber baler. In the baling chamber, multiple belts are routed around the rollers and moved as a bale is formed, though a single bale forming belt may alternatively be used. In this embodiment, tension is maintained in the bale forming belts by the one or more belt tighteners to ensure a properly compressed bale.

The baler includes a pick-up device <NUM> (<FIG>) to pick up crop or forage material. The pick-up device <NUM> is shown in a raised position. During baling, the pick-up device <NUM> is in a lowered position in which the rotating teeth of the device contact the crop or forage material and direct it toward the baling chamber. As material is picked up by the pick-up device, and deposited in the baling chamber, the material is compressed by the plurality of bale forming belts.

During operation of the baler, the baler moves across a field and along a windrow. The windrow may be formed by a mechanism, such as rakes, connected to the baler. Alternatively, the windrow may have been previously formed when the baler is driven through the field. The material transport and processing system collects material from the field and delivers the material to the baling chamber. The bale forming system forms the material into a bale within the baling chamber. Once a full bale is formed, the material transport and processing sequence ceases and a wrapping sequence is commenced by the wrapping mechanism <NUM>. Once the wrapping sequence is completed, a tailgate <NUM> is opened and the full bale is discharged from the baling chamber and guided away from the baler by a ramp. Further details relating to the baling operation within the baling chamber can be found in <CIT>.

The engine <NUM> (e.g., gas or diesel powered engine) drives one or more hydraulic pumps which in turn power the various hydraulic motors and cylinders (e.g., first and second drive wheel motors, baling chamber motor, pick-up device motor, pick-up device lift cylinder, lift-gate cylinder and/or ramp cylinder). The engine <NUM> also provides power for the electrical systems of the vehicle. The engine <NUM> is between the rotational axes R<NUM> of the rear drive wheels <NUM> and the rotational axes R<NUM> of the caster wheels <NUM>. More specifically, the engine <NUM> is between the baling chamber and the operator station <NUM>.

In some embodiments, the "operator station" comprises the seat and controls for steering and controlling the speed of the vehicle. As shown in <FIG>, the operator station <NUM> is enclosed in a cab <NUM>. The operator station <NUM> is forward of the bale forming system <NUM>, forward of the rotational axis R<NUM> of the rear drive wheels <NUM> and is also forward to the engine <NUM>. At least a portion of the operator station <NUM> and/or cab <NUM> are disposed above the caster wheels <NUM> (i.e., above the caster wheels <NUM> when generally aligned with the longitudinal axis A as the vehicle is propelled forward. ) Stated otherwise, at least a portion of the operation station <NUM> and/or cab <NUM> overlap the front caster wheels <NUM> relative to the longitudinal axis A (e.g., overlap a trailing portion of the caster wheel, overlap the caster wheel axle or overlap the entire caster wheel when the caster wheels <NUM> is generally aligned with the longitudinal axis A as the vehicle is propelled forward).

Compared to conventional systems, the steered caster wheel systems of embodiments of the present disclosure have several advantages. In the caster wheel steering mode, caster wheel steering is controlled mechanically (e.g., mechanical connections between a steering mechanism such as a steering wheel and the caster wheels). By using mechanical connections for caster wheel steering rather than a drive-by-wire system, position sensor(s) for sensing the position of the caster wheels may be eliminated which simplifies the construction and operation of the system. Mechanical connections may also be more reliable than a drive-by-wire system.

In embodiments in which the steered caster assembly includes a subframe with a first arm (i.e., longitudinal arm) that angles upward toward the swivel joint relative to the longitudinal axis, the orientation of the caster wheel along its pivot axis may be maintained relatively constant as the wheel moves through the range of travel provided by the suspension (e.g., "bump-steer" may be reduced).

As used herein, the terms "about," "substantially," "essentially" and "approximately" when used in conjunction with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.

Claim 1:
A vehicle having a steerable suspended caster wheel, the vehicle comprising:
a chassis (<NUM>);
a subframe (<NUM>) independently suspended from the chassis (<NUM>) to allow the subframe (<NUM>) to move relative to the chassis (<NUM>) as the vehicle travels over uneven terrain;
a caster wheel assembly (<NUM>) rotatably mounted to the subframe (<NUM>) at a swivel joint (<NUM>) having a steering axis (B), the caster wheel assembly (<NUM>) comprising:
a leg assembly (<NUM>); and
a caster wheel (<NUM>) rotatably mounted to the leg assembly (<NUM>) by an axle (<NUM>), the leg assembly (<NUM>) and caster wheel (<NUM>) being rotatable about the steering axis (B) through a range of swivel positions;
a steering actuator (<NUM>) connected to the caster wheel (<NUM>) to selectively control the swivel position of the caster wheel (<NUM>); and
a steering mechanism (<NUM>) connected to the steering actuator (<NUM>) to control the steering actuator (<NUM>);
characterized by:
a disengagement system (<NUM>) which selectively enables the steering actuator (<NUM>) to change the swivel position of the caster wheel (<NUM>) in response to movement of the steering mechanism (<NUM>) in a caster wheel steering mode and disables the steering actuator (<NUM>) from changing the swivel position of the caster wheel (<NUM>) in a non-caster wheel steering mode, the disengagement system (<NUM>) comprising a variable length cylinder (<NUM>) connected between the steering actuator (<NUM>) and the caster wheel (<NUM>) , the variable length cylinder (<NUM>) being in a locked position in which the variable length cylinder (<NUM>) is at a fixed length in the caster wheel steering mode, the variable length cylinder (<NUM>) being in a float mode in which the length of the variable length cylinder (<NUM>) varies in the non-caster wheel steering mode.