WO2017201445A1

WO2017201445A1 - Self-propelled vehicles

Info

Publication number: WO2017201445A1
Application number: PCT/US2017/033605
Authority: WO
Inventors: Kent L. Thompson
Original assignee: Vermeer Manufacturing Co
Current assignee: Vermeer Manufacturing Co
Priority date: 2016-05-19
Filing date: 2017-05-19
Publication date: 2017-11-23
Anticipated expiration: 2018-11-19

Abstract

Self-propelled vehicles are disclosed. The self-propelled vehicles include independently driven real wheels and front caster wheel assemblies that allow the vehicle to turn with a zero-turn radius profile. The vehicle may include a steering system that may be operated in a drive wheel steering mode in which zero turn operation is enabled or a caster wheel steering mode for operation at higher speeds such as for operation of the vehicle during transport between sites.

Description

SELF-PROPELLED VEHICLES

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 62/338,577, filed May 19, 2016; U.S. Provisional Patent

Application No. 62/338,724, filed May 19, 2016; and U.S. Provisional Patent Application No. 62/338,812, filed May 19, 2016, each of which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The field of the disclosure relates to self-propelled vehicles and, in particular, self-propelled vehicles that include independently driven rear wheels and front caster wheels that allow the vehicle to turn with a zero-turning radius.

BACKGROUND

[0003] Self-propelled vehicles are often used at various sites that are separated by large distances. To transport between sites, the vehicles may be towed, loaded on a trailer, or the vehicle may be driven over the road system (i.e., self-propelled). When driven over the road, the vehicle may be difficult to steer at high speed as the vehicle was designed for different steering characteristics during its conventional operation.

[0004] A need exists for self-propelled vehicles that are highly maneuverable during a first mode of operation and that are controllably steered during a second mode and that are configured for improved operator ride and/or improved operator positioning while providing sufficient maneuverability.

[0005] 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. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

SUMMARY

[0006] One aspect of the present disclosure is directed to a self-propelled vehicle. The vehicle has a vertical axis and a longitudinal axis. The vehicle includes a chassis and first and second rear drive wheels connected to the chassis. The system includes drive systems for independently controlling a drive speed of each of the first and second rear drive wheels so that the speed of the first drive wheel is selectively controllable relative to a speed of the second drive wheel and so that differences in the first drive wheel speed and the second drive motor speed enable vehicle steering. A front caster wheel is connected to the chassis. The front wheel is mounted on a suspension mechanism to allow the front wheel to move relative to the chassis. A cab encloses an operator station. At least a portion of the cab is above the front caster wheel relative to the vertical axis. A steering system is selectively operable in a drive wheel steering mode in which the vehicle is steered by controlling the drive speed of each of the first and second rear drive wheels and a caster wheel steering mode in which the vehicle is steered by pivoting the caster wheel.

[0007] Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may also be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a perspective view of a self-propelled vehicle; [0009] Figure 2 is a side view of a self-propelled baling vehicle;

[0010] Figure 3 is a perspective view of a self-propelled raking vehicle;

[0011] Figure 4 is a perspective view of a self-propelled mower conditioner vehicle;

[0012] Figure 5 is a perspective view of a self-propelled hay merger vehicle;

[0013] Figure 6 is a front view of the self-propelled baling vehicle;

[0014] Figure 7 is a perspective view of the self-propelled baling vehicle;

[0015] Figure 8 is a perspective view of a caster assembly of the self- propelled baling vehicle;

[0016] Figure 9 is cross-sectional side view of the self-propelled baling vehicle showing a baling chamber;

[0017] Figure 10 is a schematic view of the vehicle showing a hydraulic suspension system;

[0018] Figure 11 is perspective view of the self-propelled vehicle showing the engine mounting brackets;

[0019] Figure 12 is a perspective view of the self-propelled vehicle showing the caster assembly steering and suspension systems;

[0020] Figure 13 is a schematic view of the self-propelled vehicle showing the drive systems;

[0021] Figure 14 is a perspective view of a steering system for a self- propelled vehicle including a lockable pivoting wheel;

[0022] Figure 15 is a perspective view of a steering system for a self- propelled vehicle including a hydraulic system; [0023] Figure 16 is a side view of another embodiment of a self-propelled baling vehicle;

[0024] Figure 17 is a front view the self-propelled baling vehicle of Figure

16:

[0025] Figure 18 is a schematic top view of the self-propelled vehicle; and

[0026] Figure 19 is a schematic top view of another embodiment of a self- propelled vehicle.

[0027] Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

[0028] A self-propelled vehicle is generally referred to as "1" in Figure 1. The vehicle 1 is configured to carry a load and/or operate a device such as a baling device 5 (Fig. 2) for forming a bale of crop or forage material. While the description and Figures below may show and/or reference a baling device, it should be noted that baling device is shown as an exemplary device and the descriptions are applicable to the self-propelled vehicle itself, optionally with different devices attached thereto. While the device may, in some embodiments, be described as an agricultural device, in other embodiments the device may be suitable for use in other fields. The device 5 may be connected to the vehicle 9 in a fixed manner or may be removably connected to the vehicle 1 (e.g., modular).

[0001] The vehicle may be a self-propelled agricultural vehicle such as a rake (Fig. 3), mower or mower conditioner (Fig. 4), merger (Fig. 5), sprayer, windrower, broadcast spreader, nut or fruit harvester or the like. Other vehicles include salt and aggregate spreaders, shipping vehicles (e.g., trash, commodities, household items or other goods), construction vehicles, trenchers, and concrete cutters.

[0002] The self-propelled vehicle 1 is controlled from an operator station 13 (Fig. 2) and is powered by an engine 101. The vehicle 1 includes a device 5 such as a baling device, cutting or mower head, sickle bar, spray tank and/or booms, harvesting devices (e.g., grape or nut harvesting devices), broadcast spreader, salt and aggregate spreader, shipping container (e.g., trash, commodities, household items or other goods), construction devices or trencher, or concrete cutter. The vehicle 1 may also power the device 5. In some embodiments, the vehicle 1 is adapted to carry a load (e.g., bale, herbicide, fertilizer, or harvested crop such as nuts or fruits).

[0003] In the illustrated embodiment, the vehicle includes a baling device 5 and a pick-up device 11 (Fig. 6) that rotates to feed crop or forage material to the baling device 5 to form a bale. Each of the operator station 13, engine 101 and device 5 may be supported by a chassis 9 (i.e., the engine 101 is not part of a towing vehicle such as a tractor that releasably connects the device by a hitch assembly attached to an implement tongue).

[0004] The vehicle 1 includes first and second rear drive wheels 17 that are driven by first and second motors 23 (Fig. 13) that are disposed within the drive wheels. The rear drive wheels 17 each have a rotational axis Rn about which the drive wheels 17 rotate. In the illustrated embodiment, the wheels 17 have a common rotational axis Rn. In other embodiments, the wheels 17 are offset from each other and have different axes of rotation. The drive wheels 17 are attached to the chassis 9. In some embodiments, the drive wheels 17 have a diameter of at least about 4 feet, or even at least about 5 feet or at least about 6 feet (e.g., from about 4 feet to about 8 feet or from about 4 feet to about 6 feet).

[0005] The rear wheels 17 are fixed to the chassis 9 such that the wheels 17 maintain parallel alignment with a longitudinal axis A (Fig. 7) of the vehicle 1 (i.e., do not pivot with respect to the chassis 9). In some embodiments, the rear drive wheels 17 are not suspended from the chassis 9. In other embodiments, the rear drive wheels 17 are suspended.

[0006] The longitudinal axis A (Fig. 7) of the vehicle 1 extends from a front 55 (Fig. 2) to a rear 57 of the vehicle 1. As referenced herein, the "front" of the vehicle 1 refers to a leading portion or end of the vehicle 1 relative to the longitudinal axis during conventional use (e.g., during baling, harvesting, spraying and the like). The "rear" refers to the trailing portion or end relative to the longitudinal axis A during conventional operation. Similarly, the terms "front caster wheels" and "rear wheels" refer to the relative position of the wheels relative to the direction of travel of the vehicle 1 during conventional operation. The vehicle 1 also includes a lateral axis B (Fig. 7) that extends from a first side 58 to a second side 59 of the vehicle 1 and that is transverse to the longitudinal axis A. The vehicle 1 also includes a vertical axis C (Fig. 6).

[0007] With reference to Figure 13, the first and second drive wheels 17 are each driven and controlled by separate drive systems 15. Each drive system 15 has a drive motor 23 for rotating the drive wheel 17 forward or backward. The drive motors 23 may be hydraulic motors that are driven by a pump 20 that is powered by the engine 101. Each drive wheel 17 may be controlled by a separate circuit (i.e., separate hydraulic pumps 20 with fluid lines 22 connected to the drive wheel motors 23). The first and second pumps 20 may be hydrostatic, variable displacement pumps. In some embodiments, fixed displacement or variable displacement motor(s) may be used. In this regard, while the drive systems 15 are shown and described herein as hydraulic systems, in other embodiments an electric drive system that operates as described may be used. Exemplary electric drive systems are disclosed in U. S. Patent No. 8,657,041 which is incorporated herein by reference for all relevant and consistent purposes.

[0008] The wheels 17 are powered and rotated independently by the drive systems 15. Accordingly, the wheels 17 can be rotated at different speeds by driving the motors at different speeds. In a drive wheel steering mode, the wheels 17 are driven at different speeds by the drive system 15. For example, in this mode, the motors 23 receive different amounts of fluid from the respective pumps 20 to differentiate the speed of the wheels 17. Separate fluid lines 22 extend between each pump 20 and drive motor 23 to independently rotate the wheels 17. 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 17 (e.g., as during zero turn steering).

[0009] The vehicle 1 includes a control system to control the drive wheels 17 and front caster wheels 27 based on inputs from an operator. The control system includes a control unit 80, speed and direction control device 78, a mode selector 79 and steering mechanism which is shown as a steering wheel 67. The speed and direction control device 78, mode selector 79 and steering wheel 67 may be controlled from the operator station 13.

[0010] The control unit 80 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.

[0011] Control unit 80 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.

[0012] 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."

[0013] In one embodiment, a computer program is provided to enable control unit 80, 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.

[0014] 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.

[0015] The mode selector 79 allows the operator to select a desired mode of operation (i.e., a drive wheel steering mode or a caster wheel steering mode). The control unit 80 receives the signal from the mode selector 79 and controls the mode of the steering system in response to the signal. The mode selector 79 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.

[0016] The speed and direction control device 78 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 78 produces a signal in response to its position and the signal is transmitted to the control unit 80. The control unit 80 produces an output signal transmitted to the hydraulic pumps 20 that drive the rear wheels 17. The speed may also be controlled by a throttle that controls the engine speed. The vehicle 1 may be stopped by moving the direction and speed control device 78 to a zero-speed setting and/or by operating foot brake levers.

[0017] In the illustrated embodiment, steering may be performed by a steering mechanism shown as a steering wheel 67 which regulates the steering system. For example, in the drive wheel steering mode, a sensor 81 measures the direction and angle of the steering wheel 67 and sends signals to the control unit 80. The control unit 80 produces a signal that is transmitted to the hydraulic pumps 20 to independently regulate the rotational speeds of the first and second drive wheels 17 (i.e., the speed and direction of rotation of each drive wheel 17). [0018] 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.

[0019] In some embodiments, the self-propelled vehicle 1 is configured to optionally operate autonomously. The vehicle 1 may include sensors (e.g., cameras, GPS sensors and the like) that sense the position of a crop (e.g., windrow) and/or that may sense the position of the vehicle. The vehicle 1 may also include a controller that sends signals to the first and second rear wheel pumps or to various actuators to independently control the first and second rear drive wheels. In some embodiments, the area in which the vehicle is propelled is mapped and the area 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.

[0020] The self-propelled vehicle 1 includes first and second front caster wheels 27 that are pivotally connected to the chassis 9 about a vertical pivot axis (which may be offset from the vertical axis at a caster angle). The first and second caster wheels 27 swing below a portion of the chassis 9. The front caster wheels 27 may be spaced to allow a windrow of crop or forage material to pass between the front caster wheels 27 to, for example, engage a pickup device 11. In some embodiments, the front caster wheels 27 are separated by at least five feet or at least about seven feet. Similarly, the rear wheels 17 may be spaced to allow the device 5 (Fig. 2) to be positioned between the rear wheels. In some embodiments, the vehicle 1 includes a single front caster wheel.

[0021] Each front caster wheel 27 has a rotational axis R27 (Fig. 2) about which the front caster wheels 27 rotate. In the illustrated embodiment, the wheels 27 have a common rotational axis R27. In various embodiments, the caster wheels 27 have a diameter of at least about 20 inches or even at least about 30 inches, at least about 40 inches or even at least about 50 inches.

[0022] Description herein to the positon of the caster wheels 27 and/or their rotational axes R27 relative to other portions and components of the vehicle 1 refers to the positon of the caster wheels 27 when the vehicle is being propelled forward with the caster wheels generally aligned with the longitudinal axis A, unless stated otherwise. [0023] As shown in Figure 2, the rear wheels 17 have a diameter larger than the front caster wheels 27. In some embodiments, the ratio of the diameter of the rear wheels 17 to the diameter of the front caster wheels 27 is at least about 1.25 : 1 or at least about 1.5 : 1 or even at least about 3 : 1. In some embodiments, the vehicle 1 may have a wheelbase of at least about 80 inches, at least about 100 inches or at least about 125 inches (e.g., from about 80 inches to about 200 inches, from about 100 inches to about 180 inches or from about 110 inches to about 150 inches).

[0024] The vehicle 1 includes an engine 101 (e.g., gas or diesel powered engine) that drives one or more hydraulic pumps that in turn power the various hydraulic motors and cylinders (e.g., first and second drive wheel motors and any device motors). The engine 101 also provides power for the electrical systems of the vehicle 1. As shown in Figure 18, the engine 101 is between the rotational axes Rn of the rear drive wheels 17 and the rotational axes R27 of the front caster wheels 27. In other embodiments, such as the embodiment of Figure 19, the engine 101 is disposed to a side of the cab 121 and is above the front caster wheels 27.

[0025] The engine 101 may be arranged transverse to the longitudinal axis A of the vehicle 1. The engine 101 is supported by engine isolators and mounting brackets 11 1 (Fig. 11) that are attached to the chassis 9. The engine 101 includes a radiator 105 (Fig. 2) and a cooling fan 109 (Fig. 9) that forces air across the radiator 105. The fan 109 directs air in a direction transverse to the longitudinal axis A.

[0026] The engine 101 is disposed between the rotational axis Rn of the rear drive wheels 17 and the operator station 13 (Fig. 2) and cab 121. In some

embodiments, the "operator station" comprises the seat and controls for steering and controlling the speed of the vehicle 1. The operator station 13 is enclosed in the cab 121. As shown in Figure 2, the operator station 13 is forward of the rear drive wheels 17 and is also forward to the engine 101. At least a portion of the operator station 13 and/or cab 121 are disposed above the caster wheels 27 (i.e., above the caster wheels 27 when generally aligned with the longitudinal axis A as the vehicle is propelled forward.) Stated otherwise, at least a portion of the operation station 13 and/or cab 121 overlap the front caster wheels 27 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 27 is generally aligned with the longitudinal axis A as the vehicle is propelled forward).

Generally, the cab 121 and operation station 13 (e.g., operator seat) are not reversible.

[0027] The front caster wheels 27 are connected to the chassis independent from each other which allows the caster wheels to be independently suspended to absorb forces transmitted during travel over uneven terrain. The front caster wheels 27 may be part of first and second swivel caster assemblies 31. Generally the first and second swivel caster assemblies 31 and subframes 41 described below 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). Each assembly 31 includes a hub 35 (Fig. 8) and a caster shaft 37 (which may be referred to as a "kingpin") that rotates within the hub 35. The swivel caster assemblies 31 may include bushings or bearings within the hub 35 that allow for rotation of the shaft 37 within the hub 35. Each caster shaft 37 is connected to a leg assembly 42 that connects to the front caster wheel axle. In the illustrated embodiment, the leg assembly 42 includes a single leg that attaches to an inner side of the wheel axle. In other embodiments, the leg assembly includes two legs that connect to the axle of the front caster wheel on each side of the wheel (as with a caster fork).

[0028] The hub 35 and shaft 37 form a swivel joint 43. The first and second front caster wheels 27 of the caster assemblies 31 are each connected to a subframe 41 by the swivel joint 43. The subframes 41 are suspended from the chassis 9 by a mechanism having a suspension element 49, shown as a hydraulic cylinder in the illustrated embodiment. With reference to Figure 10, each cylinder 49 may be connected to an accumulator 50 in the suspension system with the hydraulic fluid being provided from a source 54 by a hydraulic pump 52. Other suspension elements such as shock absorbers may be used. In some embodiments, a suspension mechanism such as single pivot joint of sliding/telescoping mechanism may connect the caster assemblies to the chassis (e.g., non- shock absorbing suspension mechanisms).

[0029] Each subframe 41 is also pivotally attached to the chassis 9 at an outer pivot point Pi and an inner pivot point P₂. In this arrangement, the chassis 9 is supported by the subframes 41 and the chassis 9 and components carried by the chassis (e.g., operator station and cab) may move up and down relative to the subframes 41 as the vehicle 1 travels over uneven terrain.

[0030] As shown in Figure 8, the subframe 41 has a longitudinal arm 45 (or "first arm") and lateral arm 47 (or "second arm") that each extend from the chassis 9. The swivel joint 43 is at the point at which the arms 45, 47 meet and is forward of the inner and outer pivot points Pi, P2 relative to a longitudinal axis A (Fig. 7) of the vehicle 1. The swivel joint 43 is also outward to both the inner and outer pivot points Pi, P2 relative to the lateral axis B (Fig. 7) of the vehicle 1 (i.e., the outer pivot point Pi of each subframe 41 is positioned between the inner pivot point P2 and the point of attachment of the suspension element 49 relative to the lateral axis B).

[0031] In the illustrated embodiment, the first arm 45 is generally parallel to the longitudinal axis A (Fig. 7) and the second arm 47 is generally parallel to the lateral axis B. In other embodiments (Figs. 16-17), the first arm 145 is angled upward toward the swivel joint 143 with respect to the longitudinal axis A. In the embodiment illustrated in Figures 16-17, the second arm 147 is generally parallel to the lateral axis B.

[0032] As shown in Figure 2, the first and second front caster wheels 27 (i.e., the axes of rotation R₂7 of each wheel) are offset from the swivel joint 43 relative to the longitudinal axis A (Fig. 7) of the vehicle. The offset allows the first and second front caster wheels 27 to self-align with the direction of travel of the vehicle 1 as the vehicle is steered by differences between the speeds of the rear wheels 17. In some embodiments, the offset of the caster wheels (i.e., distance between the axis of rotation R₂7 of the wheel and the swivel joint 43) is at least about 4 inches, at least about 8 inches or from about 8 to about 20 inches. These ranges are exemplary and other ranges may be used unless stated otherwise.

[0033] In other embodiments and/or in different modes of operation the front caster wheels 27 are steered. In such embodiments, the offset may be eliminated.

[0034] In a drive wheel steering mode, the vehicle 1 is steered by creating a differential speed between the first and second rear drive wheels 17 (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 17 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 17 rotate at different speeds to steer the vehicle 1 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 1 may be turned within its own footprint. In this mode, the caster wheels 27 self-align with the direction in which the drive wheels propel the vehicle, i.e., the caster wheels 27 follow the direction of travel of the rear drive wheels 17.

[0035] In a caster wheel steering mode, the swivel position of the caster wheels 27 may be controlled to steer the vehicle. As used herein, the "swivel position" of the caster wheels generally refers to the angular position of the caster wheels relative to the longitudinal axis A (Fig. 7) of the vehicle. The caster wheels 27 are connected to a steering system 19 (Fig. 12) that selectively controls the swivel position of the caster wheels 27. As such, the vehicle 1 may travel at high speeds and the caster wheels 27 may be steered to prevent wobbling or other uncontrolled movement.

[0036] In the caster wheel steering mode, the relative speed of the drive wheels 17 may be compensated by engaging a differential system 8 (Fig. 13) that allows the relative rates of rotation of the drive wheels to match the arc defined by the swivel position of the caster wheels 27.

[0037] With reference to Figure 12, the caster steering system 19 may include a steering actuator 53 (shown as a hydraulic cylinder) connected to the caster assemblies 31 by tie rods 61 with each tie rod 61 being connected to an opposite side of the steering actuator 53. Each tie rod 61 connects to a linkage 56 connected to the caster assembly shaft 37. The steering actuator 53 may be connected to a chassis of the vehicle. An orbital valve 51 (Fig. 13) regulates fluid flow to the steering cylinder 53 based on input from a steering mechanism such as a steering wheel 67. The steering system 19 may include a steering pump (not shown) to provide the fluid flow.

[0038] In the illustrated embodiment, the steering actuator 53 is a hydraulic cylinder such as a double acting hydraulic cylinder having a through rod 65 that extends from each side which pushes/pulls the tie rods 61 to commonly align the caster wheels 27 during caster wheel steering. The steering cylinder 53 includes inlet and outlet ports 70. Fluid flows through the ports 70 in a first direction to cause the through rod 65 to move to cause both caster wheels 27 to be steered. Fluid is caused to flow in the opposite direction to actuate the through rod 65 in the opposite direction (and to cause the caster wheels to be steered in the opposite direction).

[0039] In some embodiments, the steering system 19 may be selectively disabled by a disengagement system 60 to allow the caster wheels 27 to freely pivot. The disengagement system 60 includes a disengagement cylinder 63 within the tie-rods 61 to enable selective steering of the caster wheels 27. In the caster wheel steering mode, the disengagement cylinders 63 are in a locked position such that actuation of the steering actuator 53 causes pivoting movement of the caster wheels 27 (i.e., the tie-rods 61 are a fixed length). In the drive wheel steering mode, the disengagement cylinders 63 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 53 from the caster wheels 27 (i.e., the tie-rods 61 are variable in length). As such, actuation of the steering actuator 53 will not be translated through the disengagement cylinders 63 to the caster wheels 27 and the caster wheels 27 will be allowed to freely pivot in the drive wheel steering mode. Any suitable disengagement system 60 that operates to selectively and mechanically disengage caster wheel steering may be used unless stated otherwise.

[0040] In the illustrated embodiment, each tie-rod 61 includes a disengagement cylinder 63, the disengagement cylinder 63 being a three-position cylinder. The three-position cylinder has an inner barrel 71 , outer barrel 73 and a common rod 76 between the inner and outer cylinder components. In other embodiments, the three- position cylinder may have two joined barrels in the middle of the cylinder 63.

[0041] The outer barrel 73 is connected to the steering linkage 56 attached to the caster shaft 37. Each inner barrel 71 is pivotally connected to the steering actuator 53 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 19 to move with each respective caster wheel 27 as the caster wheel 27 moves up and down in response to uneven terrain.

[0042] The disengagement cylinders 63 are connected to a hydraulic system 83 (Fig. 15) that regulates the fluid flow to the cylinders 63. The hydraulic system 83 includes a pump 85, a valve 87 and a hydraulic fluid tank 89. The valve 87 (which is electrically coupled to controller 80 shown in Figure 13) configured to selectively lock the disengagement cylinders 63 in the caster wheel steering mode and to allow fluid to freely flow in and out of the disengagement cylinder 63 in the drive wheel steering mode.

[0043] The hydraulic system 83 is configured such that, for each disengagement cylinder 63, 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 61 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 76 may freely float in and out of each barrel as the caster wheel moves.

[0044] The disengagement system 60 includes the mode selector 79 and the control unit 80 that controls the valve 87.

[0045] In alternative embodiments, the vehicle 1 may include any steering system 19 that enables the vehicle to operate as described. For example, the steering system 19 may include any of the following components, without limitation: tie-rods, rack and pinion mechanisms, orbital valves, cylinders, motors, and bell cranks. In some embodiments, the castor assemblies 31 are locked by manual and/or automatic mechanisms that prevent the castor assemblies from freely pivoting such as during the drive wheel steering mode.

[0046] The steering system 19 may also include an electrical system that may be used to control the caster wheels 27 and/or the drive wheels 17. For example, the steering system 19 may send electrical signals to the drive systems 15 to regulate the speeds of the drive wheels.

[0047] Figure 14 shows a schematic of a portion of another embodiment of a steering system 19 of a self-propelled vehicle. The self-propelled vehicle is similar to the vehicle shown in Figure 1 except the vehicle includes a different coupling between the castor assembly and the steering mechanism. A tie-rod 61 extends between the castor assembly 31 and the steering mechanism 75. The castor assembly 31 is rotatably connected to an end of the tie rod 61. In an unlocked mode, the castor assembly 31 freely pivots in relation to the tie rod 61. In a locked mode, the castor assembly 31 moves with and is pivoted by the tie rod 61. An opposite end of the tie rod 61 is connected to the steering mechanism 75 by a geared connection. Accordingly, actuation of the steering mechanism 75 is transferred through the tie rod 61 to the castor assembly 31. A pin 77 is positionable to selectively lock and unlock the castor assembly 31. The pin 77 may be controlled by automatic and/or manual mechanisms. In alternative embodiments, the castor assembly 31 may include any locking mechanism that enables the vehicle 1 to operate as described.

[0048] Figure 15 shows a schematic of a portion of another embodiment of a steering system 19 of a self-propelled vehicle. The vehicle includes a different coupling between the castor assembly and the steering mechanism. In particular, multiple floating cylinders 63 extend between the castor assembly 31 and the steering mechanism 75. In a locked mode, the cylinders 63 are locked in an extended position to allow the steering mechanism to control the castor assemblies 31. In an unlocked mode, the cylinders 63 float along tie rods 61 such that the castor assemblies 31 are free to rotate. The castor assemblies may rotate 360°.

[0049] A hydraulic system is connected to the cylinders 63 and regulates the position of the cylinders. The hydraulic system includes a pump 85, a valve 87, a hydraulic fluid tank 89, and fluid lines 91. The pump 85 generates a flow of fluid between the hydraulic fluid tank 89 and the cylinders 63 to regulate the position of the cylinders 63. In particular, hydraulic fluid is directed into the cylinders 63 to position the cylinders in the locked position. Hydraulic fluid is pumped out of the cylinders 63 and into the tank 89 to position the cylinders 63 in the unlocked or float position. The valve 87 can regulate the fluid flow between the pump 85, the tank 89, and the cylinders 63. In alternative embodiments, the vehicle 1 may include any hydraulic system that enables the vehicle to operate as described.

[0050] Compared to conventional implements, embodiments of the self- propelled vehicle have several advantages. By incorporating front caster wheel caster assemblies and hydraulic rear drive wheels that rotate independently, the vehicle is highly maneuverable and is able to turn within its own footprint (i.e., with a zero-turn radius). This allows the vehicle to be turned quickly, such as, when the vehicle include a baling device, for repositioning prior to a bale discharge to prevent bales from rolling down an incline during bale discharge. In embodiments in which the vehicle includes dual steering modes, the vehicle may be operated in a drive wheel steering mode for field operation (e.g., ground speed less than about 12 mph) in which zero turn operation is enabled. The vehicle may also operate in a caster wheel steering mode for improved steering and control at higher speeds such as travel or highway speeds (e.g., speeds of 20 mph or more).

[0051] By positioning the operator station and cab relatively forward and near the front caster wheels (e.g., at least partially overlapping the rotational axis of the front wheels), the operator has a clear field of vision of the field (e.g., windrow). In addition, the operator station is near the suspension system (e.g., at least partially disposed above) which improves the operator ride and reduces operator fatigue. In embodiments in which the front caster wheels are independently suspended, further improvement in the operator ride and reduction of operator fatigue may be achieved.

[0052] 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.

[0053] When introducing elements of the present disclosure or the embodiment(s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," "containing" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., "top", "bottom", "side", etc.) is for convenience of description and does not require any particular orientation of the item described.

[0054] As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.

Claims

WHAT IS CLAIMED IS:

1. A self-propelled vehicle, the vehicle having a vertical axis and a longitudinal axis, the vehicle comprising: a chassis; first and second rear drive wheels connected to the chassis; drive systems for independently controlling a drive speed of each of the first and second rear drive wheels so that the speed of the first drive wheel is selectively controllable relative to a speed of the second drive wheel and so that differences in the first drive wheel speed and the second drive motor speed enable vehicle steering; a front caster wheel connected to the chassis, the front wheel being mounted on a suspension mechanism to allow the front wheel to move relative to the chassis; a cab which encloses an operator station, at least a portion of the cab being above the front caster wheel relative to the vertical axis; and a steering system selectively operable in a drive wheel steering mode in which the vehicle is steered by controlling the drive speed of each of the first and second rear drive wheels and a caster wheel steering mode in which the vehicle is steered by pivoting the caster wheel.

2. The self-propelled vehicle as set forth in claim 1 wherein a portion of the operator station is above the front caster wheel relative to the vertical axis.

3. The self-propelled vehicle as set forth in claim 1 or claim 2 wherein the first and second rear drive wheels have a diameter and the front caster wheels have a diameter, the ratio of the diameter of the rear wheels to the diameter of the front caster wheels being at least 1.25: 1 or even at least about 3 : 1.

4. The self-propelled vehicle as set forth in any one of claims 1 to 3 further comprising a device selected from the group consisting of a baling device, cutting or mower head, sickle bar, spray tank and/or booms, harvesting device, broadcast spreader, salt and aggregate spreader, shipping container, construction device, trencher, and concrete cutter.

5. The self-propelled vehicle as set forth in any one of claims 1 to 4 further comprising a control system to selectively operate the steering system in the drive wheel steering mode or the caster wheel steering mode.

6. The self-propelled vehicle as set forth in claim 5 further comprising a user interface for enabling drive wheel steering mode or caster wheel steering mode.

7. The self-propelled vehicle as set forth in claim 5 wherein the control system is configured to selectively operate the steering system in the drive wheel steering mode or the caster wheel steering mode at least partially in response to a signal related to the speed of the vehicle.

8. The self-propelled vehicle as set forth in any one of claims 1 to 7 wherein the steering system comprises a steering cylinder for pivoting the caster wheel in the caster wheel steering mode.

9. The self-propelled vehicle as set forth claim 8 wherein the steering system comprises a disengagement cylinder connected to the steering actuator and connected to the caster wheel.

10. The self-propelled vehicle as set forth in any one of claims 1 to 7 wherein the steering system includes a steering gear connected to the caster wheel in the caster wheel steering mode.

11. The self-propelled vehicle as set forth in any one of claims 1 to 10 wherein the vehicle comprises an engine for propelling the vehicle, the engine being disposed between the rotational axis of the front caster wheel and rotational axes of the rear drive wheels.

12. The self-propelled vehicle as set forth in any one of claims 1 to 11 wherein the front caster wheel is a first front caster wheel, the vehicle comprising a second front caster wheel connected to the chassis, each front caster wheel being mounted on a suspension mechanism to allow the front wheels to move toward the chassis relative to the vertical axis.

13. The self-propelled vehicle as set forth in claim 12 further comprising first and second subframes, the first front caster wheel forming a first swivel joint with the first subframe, the second front caster wheel forming a second swivel joint with the second subframe, the first and second subframes being suspended from and pivotally attached to the chassis.

14. The self-propelled vehicle as set forth in claim 13 wherein each subframe is connected to the chassis at an outer pivot point and at an inner pivot point.

15. The self-propelled vehicle as set forth in claim 14 wherein the vehicle comprises first and second suspension elements, the first suspension element being attached to the chassis and to the first subframe, the second suspension element being attached to the chassis and to the second subframe.

16. The self-propelled vehicle as set forth in any one of claims 12 to 15 wherein the first front caster wheel is offset from the first swivel joint and the second front caster wheel is offset from the second swivel joint.

17. The self-propelled vehicle as set forth in any one of claims 1 to 16 further comprising: an engine for propelling the vehicle; a cab enclosing an operator station, the cab being disposed forward to the engine relative to the longitudinal axis.

18. The self-propelled vehicle as set forth in any one of claims 1 to 17 wherein the first and second rear drive wheels are fixed to the chassis to maintain alignment with the longitudinal axis.

19. The self-propelled vehicle as set forth in any one of claims 1 to 18 wherein the caster wheel has a diameter of at least about 20 inches, at least about 30 inches, at least about 40 inches or at least about 50 inches.