1. Field of the Invention
The present inventive concept relates to differential drive systems for a vehicle serving as a trailer spotter for semi-trailers or drawbar-type trailers, especially in off-highway environments such as freight terminals, ports, rail yards, warehouses, and factories.
2. Description of the Related Art
When over-the-road semi-tractors and trailers came into use, the over-the-road semi-tractors were also used to reposition the trailers in freight yards. On average, the time to reposition a trailer in the freight yard required approximately eighteen minutes. Within a few years, non-over-the-road specialized tractors were developed to reduce this time to about twelve minutes. These specialized tractors utilized two features to provide customer value compared to their predecessors—a elevating fifth wheel hitch and a smaller engine. The ability to raise the fifth wheel enabled operators to move trailers without retracting the trailer's landing gear, saving time and effort. The smaller engine reduced fuel consumption costs.
Owing to size limitations of these specialized tractors, the cabs were usually mounted on top of the vehicle frame. Ergonomically, this meant that the operator was unnecessarily climbing up and down stairs for an extra hundred feet every day. Although low forward entry cabs were known, these cabs required the vehicle to be longer in order to utilize such a cab. Due to the requirement for tight maneuverability for yard spotters, this additional length was not normally acceptable and, as a result, these specialized tractors did not benefit from a low forward entry cab.
Further, these specialized tractors included a door in the cab that facilitated an operator's ingress into and egress out of the cab via a deck on the tractor in front of the trailer hitch. However, opening and closing the door every time the operator stepped onto the deck slowed them down and gradually added to their fatigue. As a result, the operators often removed the vehicle's rear door during summer months in order to ease their workload. Accordingly, not only did the operators spend labor hours removing and reinstalling the door, but by the time they went looking for the door in the fall, the door was often damaged or lost resulting in increased maintenance costs to their employer.
The specialized tractors discussed above, commonly called trailer spotters, have existed for approximately fifty years without significant technological improvement. To date, trailer spotters have utilized a conventional truck frame, a reduced-size traditional-style cab, and a standard drive system having an engine, a transmission, a driveshaft, and a differential for relaying power to a pair of drive wheels via a set of axles. Since most trailer spotters do not require the power to achieve highway speeds, do not climb grades, and do not include the full size or sleeper cabs, they are smaller, more maneuverable, and utilize a lower horsepower engine. For example, current trailer spotters typically utilize engines having between 150-225 horsepower, as compared to fleet trucks which utilize engines having between 300-600 horsepower. As a result, the benefit of a trailer spotter is generated through the reduced time to relocate a trailer around a dock or yard while consuming less fuel than their over-the-road counterparts.
A drawback to current trailer spotters includes the standard truck drive train utilized by these trailer spotters. These standard truck drive trains include front wheels for steering the vehicle according to the Ackerman steering principle and rear wheels for driving the vehicle. As a result, the mobility of current trailer spotters is typically limited to a minimum turning radius of approximately 36 feet. This is depicted in
Further, the operation of a trailer spotter requires an unending series of sudden stops and starts, impact loads, and direction changes. This results in wear on the mechanical drive train, despite the selection of heavy duty components. As a result, even with a good maintenance program, vehicle service life seldom extends beyond fifteen years. Further, in order to keep the costs of the truck spotters down, conventional truck transmissions are typically modified to omit gear synchronization systems, thereby requiring operators to have special training. In addition, traditional drive train positioning is constrained by the size of the engine and transmission and the amount of misalignment that can be handled by universal joints at the ends of the driveshaft. Consequently, the engines and transmissions have all been located near the vehicle center line at the front of the vehicle. This positioning limits cab design options and results in little weight over the drive wheels. The lack of weight over the drive wheels is not necessarily important when towing a trailer mounted on the fifth wheel attachment, but it significantly decreases drawbar pull when attempting to tow other types of trailers.
Another instance where existing trailer spotters lack optimization is the operator interface. When moving fifth wheel trailers using existing trailer spotters, the tractor operator must rely on mirrors and/or twist their body/head to the rear to view the trailer. Reliance on mirrors restricts the operator's field of view and forces the operator to work with a flipped image, i.e., turning the opposite direction from what they see in the mirror. Also problematic, turning or twisting to see the trailer impedes the operator's ability to turn the steering wheel. As a result, both techniques slow their performance and complicate their tasks. These problems occur as a result of the typical mechanical linkages between the operator interface and the vehicle steering and transmission systems which dictate that the driver's seat and control console be fixed in one direction, the typical direction being forward. However, in some embodiments, when the work was off the back of the vehicle, as in backhoes, the seat could be rotated so that the operator may view the work directly. In these previous vehicles, though, the control console did not rotate with the seat and, as a result, an additional control console was required thereby adding cost to the vehicle.
From the above information, it is apparent that the prior art trailer spotter vehicles are far from optimized. However, although freight handling managers have been complaining about inability to keep up with demand, trailer spotter manufacturers have not envisioned the potential enhancements to their product line discussed below.
The present invention includes a trailer spotter vehicle having a seat and a control console which are relatively rotatable with respect to the vehicle frame. The trailer spotter vehicle further includes a differential drive system. The differential drive system permits the vehicle to turn within a very small turning radius while the rotatable seat and control console allow the operator's seat and control console to be positioned such that an operator may steer the vehicle without having to substantially turn their body or use mirrors to observe the path of the vehicle.
In one embodiment, the differential drive system includes an engine and first and second hydraulic pumps driven thereby. The first and second hydraulic pumps provide hydraulic fluid to first and second hydraulic motors which are mechanically engaged with first and second ground-engaging wheels, respectively, mounted to the frame of the trailer spotter vehicle. To drive the vehicle in a forward direction, the hydraulic pumps transmit pressurized hydraulic fluid to the motors to drive the wheels in a first direction. In order to drive the vehicle in reverse, the flow of hydraulic fluid to the motors is reversed to rotate the wheels in a direction opposite the first direction. To pivot the vehicle, the first wheel can be driven in the first direction and the second wheel can be driven in the opposite direction in order to substantially turn the vehicle about an axis. Advantageously, the trailer spotter vehicle can be more easily maneuvered than previous trailer spotters.
The use of differential steering enables the tractor to sharply pivot under a fifth wheel mount between the trailer spotter vehicle and a trailer mounted thereto, or pivot about a point between or near the drive wheels, wherein, as a result, the turning radius is not substantially larger than the wheel base. This design may reduce the tractor's wall-to-wall turning diameter by more than half, but, even more remarkably, as illustrated in
Further, differential steering, as described above, allows the linkages, springs, and power assists of the previous front-wheel steer systems to be replaced with two caster wheels. Eliminating these components may reduce the overall vehicle weight by approximately 2,000 pounds. Further, as the differential drivetrain can be effected by hydraulics, as described above, the engine can be relocated toward the rear of the vehicle, thereby lightening the weight of the front end of the vehicle and permitting the use of smaller tires which will swivel more easily. Accordingly, in one embodiment, the rear axle is expected to bear about 6,000 pounds of the vehicle's weight, which is approximately half again as much as existing trailer spotters, which will result in a 50% increase in draw-bar trailer towing capacity. In this embodiment, the improved draw-bar pull capacity will theoretically enable the trailer spotter to tow three loaded multi-axle trailers or doubles trailers across a flat gravel surface. This versatility is helpful in the worldwide marketplace, as fifth wheel trailers are less common outside the major industrialized countries.
In one embodiment, the use of electronic controls enables the control console to be rotated with the operator's seat to, as described above, allow the operator to directly view the work to be performed while operating the controls. The ability for the operator to directly view the work, coupled with the vehicle's enhanced mobility, may speed job completion, reduce trailer damage rates, and enhance safety. Further, electronic controls may provide for integration of vehicle speed and steering commands for nearly instantaneous responsiveness, and provide adaptable motion resistance to reduce operator fatigue. Further, as an electronic control system uses a minimal number of mechanical systems, there are less components to accumulate wear and tolerances. Further, owing to the electronically controlled hydrostatic drive, unlike trucks with mechanically geared transmission systems, the vehicle engine of the present embodiment can be set for optimum horsepower, fuel efficiency, or maximum torque as the operator deems necessary for the work performance. Advantageously, controlling the engine in this way can provide full power at lower speeds, stable engine RPM for minimum wear, and conserve energy. As a result of the improved drive train efficiency, a lower horsepower engine may be utilized to yield an approximately 20% improvement in fuel savings in one embodiment. Further, as a result of the electronic controls, the steering, brake, and accelerator controls can move independently of terrain or mechanical linkage resistance, and thus they can be designed to reduce operator effort while retaining functionality.
In one embodiment, to facilitate an operator's ingress into and egress from the trailer spotter cab, the cab can include a main entry door in the front of the cab. Manufacturers of farm tractors have previously positioned two doors in the front corners of their vehicles. However, these doors did not incorporate the vehicle windshield nor span the direct frontal area, or centerline, of the vehicle. In embodiments of the present invention utilizing a hydraulic drive train that has been placed at the rear of the vehicle, a low forward entry cab design, in combination with a lower front door, can be utilized. Ultimately, the door location, along with the rotatable seat and control console, minimizes operator fatigue and improves operator efficiency.
In one embodiment, the cab of the trailer spotter further includes a rear door for entering the cab. In this embodiment, the rear door of the cab can slide inboard on tracks to be stored along the interior sidewall of the cab. In this embodiment, the rear door is designed such that, when the rear door and sidewall are side-by-side, the rear door window substantially aligns with the window in the sidewall so as to not obstruct the operator's vision, thereby allowing the operator to maintain the same level of awareness whether the rear door is open or closed. The rear door, in this embodiment, is conveniently stowed inside of the trailer and is less susceptible to damage or being lost.
The present invention provides a dramatic enhancement in trailer spotter maneuverability, vehicle simplification, improved vehicle versatility through changes in weight distribution, enhanced safety, and reduced probability of trailer damage.
The above-mentioned and other features and objects of this invention will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate embodiments of the invention, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.
Referring to
Trailer spotter 30 further includes engine cover 59 mounted above engine 39. Engine cover 59 is rotatable about pillow block bearings 61 to provide access to engine 39. Engine cover 59, when it is in a closed position, also serves as a deck for an operator to stand on when entering and exiting cab 32. Bearings 61 also provide a pivot axis for fifth wheel lift rack 63. Fifth wheel lift rack 63 includes a mount, i.e., fifth wheel hitch 37, which can connect trailer spotter 30 to a type of trailer known as a fifth wheel trailer. Trailer spotter 30 further includes lift cylinder 65 which includes a first end mounted to lift rack 63 and a second end mounted to frame 34. In use, a cylinder rod of cylinder 65 can be extended and retracted with respect to the housing of lift cylinder 65 to raise and lower fifth wheel hitch 37. Trailer spotter 30 further includes tow pintle 71 mounted to crossmember 67 of frame 34 for towing a type of trailer known as a draw-bar type trailer. Trailer spotter 30 further includes trailer connections 69 which provide electrical, hydraulic and/or air connections for a trailer mounted thereto. In some embodiments, an additional set of trailer connections 69 are mounted to the rear of cab 32.
As briefly described above, differential drive system 36 includes engine 39, multi-pump drive 41, variable displacement hydraulic pumps 43 and 45, pressure relief valves 73, and hydraulic motors 75 and 77 which are operatively engaged with ground engaging wheels 38 and 40, respectively. Engine 39 is operably engaged with multi-pump drive 41 such that the rotational movement of the crankshaft of engine 39 is transmitted to a set of gears within pump drive 41. The gears of pump drive 41 are operably engaged with shafts mounted within hydraulic pumps 43 and 45. Each pump shaft engages an eccentric member within the hydraulic pumps which, when rotated, compress hydraulic fluid therein and discharge the hydraulic fluid into pressure relief valves 73. Pressure relief valves 73, as is known in the art, guard against the hydraulic fluid from being overpressurized by pumps 43 and 45 and thereby prevent the seals, fittings and/or hydraulic lines of differential drive system 36 from rupturing due to excessive stress. In one embodiment, the above-discussed gear ratio can be selected based on optimum engine and hydraulic pump settings. For example, in one embodiment, the RPM of a commercially-available Cummins engine, at peak horsepower, is 2300 RPM, however, in order to drive the hydraulic pumps at 3200-3300 RPM, a 1:1.4U gearbox is needed.
The hydraulic fluid then flows into hydraulic motors 75 and 77 which convert the flow of hydraulic fluid into rotational movement of motor shafts mounted therein. Motors 75 and 77 further include a pinion gear mounted to an end of each motor shaft, wherein the pinion gears are operably engaged with planetary torque hub gear reduction mechanisms 79. In this embodiment, the planetary gear reduction allows multiple gears to share the torque load and may fit into a smaller space than other direct gear drive systems while maintaining a very high efficiency for the drive train. To accommodate severe loads, gear reduction mechanisms 79 can include multiple gear sets. Owing to the difference in size between the gear set, or sets, in planetary mechanism 79, the speed of the motor shafts is reduced before the rotation of the motor shafts is transmitted to ground-engaging wheels 38 and 40. In the present embodiment, for every 26 revolutions of the motor shafts in motors 75 and 77, wheels 38 and 40 are turned through only one revolution. This particular gear ratio was selected to provide a desired balance between speed and torque for the present embodiment, however, in other embodiments, other gear ratios may be selected according to the needs of a particular application.
Pumps 45 and 47, as described in further detail below, are variable displacement pumps which pressurize hydraulic fluid in two separate circuits for independently driving left rear wheels 38 and right rear wheels 40. As a result, left rear wheels 38 and right rear wheels 40 can be driven at different speeds and/or in different directions with respect to each other. To drive the trailer spotter 30 in a forward direction, the hydraulic pumps 45 and 47 transmit a substantially equal flow rate of hydraulic fluid to rear wheels 38 and 40. As a result of the substantially equal flow rate, the shafts of motors 75 and 77 are turned at substantially the same speed and, as a result, wheels 38 and 40 are driven at substantially the same velocity. Accordingly, as wheels 38 and 40 are turned at substantially the same velocity, trailer spotter 30 is driven in a substantially linear, forward direction.
To turn trailer spotter 30 while moving in the forward direction, as described in further detail below, the rate at which hydraulic fluid is pumped to one of motors 75 and 77 is either reduced or increased with respect to the other motor to thereby turn one of wheels 38 and 40 faster than the other. For example, in this embodiment, hydraulic pumps 45 and 47 each include a swash plate that can be oriented to increase or reduce the outputs of hydraulic pumps 45 and 47. As is known in the art, the swash plates can be positioned in one of three ranges of angles. In a first range of angles, the pumps produce a flow of hydraulic fluid in a first direction and, in a second range of angles, the pumps produce a flow in the opposite direction. Alternatively, the swashplates can be placed in a flat, or neutral, position in which the hydraulic pumps are substantially incapable of pressurizing the hydraulic fluid as described above. For either of the first and second ranges of angles, the speed at which the hydraulic fluid is discharged from the pumps is determined by the orientation of the swash plates with respect to the neutral or flat position. More particularly, the greater the angle between the swashplate and the neutral position, the faster the discharge flow.
In order to turn the vehicle to the right as it is moving in the forward direction, for example, the flow rate of hydraulic fluid exiting pump 43 can be increased such that the speed of left rear wheels 38 exceed the speed of right rear wheels 40. Alternatively, the flow rate of hydraulic fluid exiting pump 45 can be reduced such that it is less than the speed of hydraulic fluid exiting pump 43. In either event, left rear wheels 38 are turned faster than right rear wheels 40 to turn the vehicle to the right. To drive the trailer spotter 30 in a rearward direction, the swashplates in pumps 45 and 47 are both positioned at an angle such that the flows of the hydraulic fluid exiting pumps 45 and 47 are reversed. Similar to the forward direction, the flow rates of hydraulic fluid entering into motors 75 and 77 are substantially equal and, as a result, wheels 38 and 40 are turned at substantially the same velocity. Also, similar to the above, to turn the trailer spotter while it is traveling in the reverse direction, the rate at which the hydraulic fluid is discharged from pumps 45 and 47 is altered such that one of rear wheels 38 and 40 is turned faster with respect to the other.
Alternatively, to pivot the trailer spotter 30 about an axis, the flow of hydraulic fluid exiting one of pumps 45 and 47 is reversed such that rear wheels 38 and 40 are turned in opposite directions. Accordingly, owing to these differentially driven wheels, trailer spotter 30 can rotate about a central axis, i.e., axis 79, which is substantially intermediate rear wheels 38 and 40. Accordingly, as trailer spotter 30 can rotate about axis 79, the speed at which the trailer spotter can be turned is substantially improved. Further, the maneuverability of the trailer spotter is greatly improved as it can be turned within a very tight turning radius. Additionally, differential drive train 36 allows the trailer spotter to swing about axis 79 and move trailers while driving perpendicular to the trailer, as illustrated in
Referring to
Ultimately, shaft member 54 is configured to rotate within apertures 56 to permit relative rotational movement between bracket 44 and frame 34 about axis 58. However, although relative rotational movement is permitted between bracket 44 and frame 34, relative translational movement is substantially limited owing to the close fit between shaft member 54 and aperture 56. To assure that bracket 44 remains mounted to frame 34, the top vertical bearing 48 is flanged to overlap the opening in frame 34. Further, the end of shaft member 54 above the top vertical bearing 48 is threaded for receiving a castellated nut. In addition, cap 62 is placed over the top end of shaft member 54 to facilitate in keeping debris from entering into vertical bearings 48. Ultimately, the permitted relative rotational movement of wheels 39 about horizontal bearings 46 and brackets 44 about vertical bearings 48 allow wheels 39 to re-positioned themselves to facilitate, or at least not substantially inhibit, the movement of trailer spotter 30. To maintain the lubricity of the vertical bearings 48, the caster assemblies may further include a plastic insert positioned within frame 34 to serve as a grease reservoir or trap.
Referring to
In an alternative embodiment, referring to
Advantageously, a rotatable chair allows an operator to turn the chair so that may directly view the work being performed. This advantage is especially helpful in embodiments of the present invention which utilize a differential drive system, as described above. More particularly, owing to the improved maneuverability and responsiveness that a differential drive system provides, an operator may adjust their seat to view the path of the trailer spotter directly instead of having to observe the trailer spotter's path through mirrors and/or twist their body to see behind them. Accordingly, this allows for safer and more efficient operation of the trailer spotter.
In an alternative embodiment, referring to
As discussed above, the trailer spotter of the present invention, in one embodiment, includes a control console, a differential drive system, and a programmable controller. As described above, the control console includes, among other things, joystick controller 96 for guiding the trailer spotter. Joystick controller 96 converts the mechanical movement of the joystick handle into electrical signals which are transmitted to the controller via, for example, a wiring harness. In other embodiments, to avoid twisting the wiring harness when seat portion 78 is turned, a rotating union between base portion 76 and seat portion 78 may be utilized to main communication between the control console and controller. In either event, in order to process these signals, the controller is programmed with a set of instructions which determine the output response to be conveyed to the differential drive system in view of the input signals. For example, if the joystick is moved to the right, the controller may be programmed to instruct the differential drive system to turn the trailer spotter to the right. In fact, referring to
Referring to
After the controller has determined values for M and Θ for the position of the joystick handle, these values are inserted into the following equations, for example, which determine the appropriate angles for the swashplates of pumps 43 and 45:
Left swashplate (pump 43) M/A×P×[cos((Θ/2−Φ)/2))]1/2
Right swashplate (pump 45) M/A×P×[sin((Θ/2−Φ)/2))]1/2
where M=(a2+b2)1/2, i.e., the magnitude of joystick deflection, A=the maximum magnitude of joystick deflection, i.e., ±A in the forward and aft directions and ±B in lateral directions, as described above, and P=the maximum swashplate angle. In effect, when M=A, i.e., when the joystick handle has been displaced its maximum value, the trailer spotter will be driven at its maximum speed in the direction determined by [cos((Θ/2−Φ)/2))]1/2 and [sin((Θ/2−Φ)/2))]1/2, where Θ=arctan(a/b), i.e., the angle of joystick deflection, and Φ=a phase shift angle for shifting the trigonometric functions so that they produce a desired value. For example, when the joystick handle is placed in the 90° position, i.e., a full right turn, Θ=90° and shift angle Φ equals a value such that cos((Θ/2−Θ)/2)) is brought to its maximum value and sin((Θ/2−Φ)/2)) is brought to zero. Accordingly, the swashplate of pump 43 is positioned at its maximum angle with respect to its neutral datum to drive left rear wheels 38 at their maximum speed while the swashplate of pump 45 is brought into its neutral position so as to not drive right rear wheels 40, thereby effecting a full right turn.
The exemplary equations described above include trigonometric functions which provide for smooth transitions between joystick control points. Further, by taking the square root of the sine and cosine functions, the response curves are smoother, thereby preventing abrupt movements in the trailer spotter. Notably, to use these trigonometric equations, the formulas may need to be modified such that the absolute values of the trigonometric functions are used when performing the square root in order to prevent the calculation of irrational numbers. Other non-trigonometric drive equations can be utilized, including linear equations. However, in one exemplary embodiment, the operator is located up to ten feet from the center of rotation of the trailer spotter and, as a result, the linear speed control inputs may result in a somewhat jerky ride.
Notably, the exemplary equations described above were simplified to describe the basic steering concept for the trailer spotter when the operator's seat is facing in the forward position (
Left swashplate (pump 43) M/A×P×D×[cos((Θ/2−Φ)/2))]1/2
Right swashplate (pump 45) M/A×P×D×[sin((Θ/2−Φ)/2))]1/2
where D is a direction correction factor that is +1 when the operator's seat is facing forward and −1 when the operator's seat is facing rearward, for example. When D=−1, each swashplate is tilted in an opposite direction than when D=+1 to drive hydraulic pumps 43 and 45 in reverse. In order for the controller to know whether the operator's chair is facing forward or rearward, the chair can include proximity sensors, for example. More particularly, referring to
The value of the D variable can also be used to determine whether the lights in the front and the rear of the vehicle are headlights or brakelights. More specifically, referring to
Referring to
Left swashplate M/A×P×D×[sin((Θ/2−Φ)/2))]1/2−SD/TS
Right swashplate M/A×P×D×[cos((Θ/2−Φ)/2))]1/2−SD/TS
where SD=the speed differential allowable between rear wheels 38 and 40 (mph), and TS=the designed vehicle top speed (mph). Notably, for the embodiment described in
Referring to
Left swashplate: SRR×D×M/A
Right swashplate: SRR×D×M/A
where SRR=the speed reduction ratio. The speed reduction ratio (SRR) represents the fraction of the maximum speed that the wheels are actually permitted to turn. More particularly, as a result of the pivoting motion, the turning speed of the trailer spotter can be much faster in this condition than in the other two conditions and, as a result, the maximum actual drive speed can be reduced via this correction factor. Reducing the turning speed may allow the operator to better and more safely control the vehicle.
Further safety controls can be implemented which cause the D variable in the drive equations to become zero, thereby forcing one or both of the swashplates into their neutral positions. For example, the operator's seat can include a sensor, such as a weight sensor, for example, for detecting the presence of the operator in the seat. When the sensor does not detect an operator in the seat, the D variable is set to zero for both the left and right swashplates causing the swashplates to be positioned in their neutral positions, thereby rendering pumps 43 and 45 incapable of driving rear wheels 38 and 40. Accordingly, rear wheels 38 and 40 cannot be driven by the hydraulic drive train when an operator is not seated in the chair. Similarly, the trailer spotter can further include an engine RPM sensor in communication with the programmable controller. When the speed of the trailer spotter engine is outside of a desirable range, the controller can set the D variable in the above equations to zero to prevent the rear wheels from being driven. Further, an emergency breaking feature can be utilized where, when a switch is activated, or deactivated, the programmable controller sets the D variable to zero.
Trailer spotter 30 includes an additional safety feature which assists in preventing a trailer from jack-knifing with respect to the trailer spotter. Referring to
Referring to
Although placing the swashplates of hydraulic pumps 43 and 45 in a neutral position, as described above, can provide a significant amount of braking for the trailer spotter, the trailer spotter can be equipped with both a parking brake and a service brake. To keep the vehicle stationary, the parking brake can be automatically engaged whenever the vehicle is turned off and/or when the operator's seat is unoccupied. More particularly, in the present embodiment, the parking brake is engaged with a brake rotor mounted to the wheel axle when the programmable controller receives a signal from the engine sensor that the engine RPM is substantially zero and/or the seat sensor indicates that an operator is not sitting in the seat. In other embodiments, the parking brake can be a traditional parking brake than is manually activated.
Further, in the present embodiment, the service brake can be integrated with the control system such that it is either engaged manually by the movement of brake joystick 100 or automatically by the turn limit system including anti-jackknifing system 120, as described above. The forces applied by the service brake can be proportional to the magnitude of the deflection of brake joystick 100 with respect to its center position, similar to joystick 96 described above. However, in the present embodiment, only the magnitude of the joystick deflection is used in determining the braking force. As a result, the operator can push or pull in any direction to apply the brake. However, in other embodiments, the direction of the brake joystick deflection can be used by the controller to apply different braking forces to the different wheels of the trailer spotter. In an alternative embodiment, an operator can twist the brake joystick to add or decrease braking forces to one side of the tractor's brakes. This would enable some differential/skid steering for the hydraulic drive system especially when the system is in an overrun condition or going downhill. In addition, by utilizing the programmable controller in the brake system, the controller can be programmed to allow the drive and brake joysticks to be swapped based on the operator's preference for having the drive joystick, for example, on their left or right side.
Once the controller has received a signal to activate the service brake, the controller can output signals to brake assemblies associated with one or more of the trailer spotter wheels. These brake assemblies can be configured to engage brake rotors, for example, mounted to the wheel axles when they are activated. In one embodiment, the output signals of the controller are communicated to a conventional hydraulic brake system which moves one or more calipers with respect to the wheel rotors, for example. In another example, the output signals of the controller can be communicated to brake calipers driven by electric motors.
In addition, when anti-jackknifing system 120 detects a jackknife condition, i.e., when grab handle 122 has been sufficiently displaced, in the present embodiment, the controller can command maximum stopping forces to all of the brakes. In order to disengage the brakes, the controller can be programmed to release the brakes when the trailer spotter vehicle is driven in the substantially opposite direction, i.e., driven out of the jackknife condition. Stated in another way, in this embodiment, if the joysticks are positioned such that the corresponding movement would worsen the hazard, the brakes will remain locked.
Additionally, to improve safety conditions, the trailer spotter can include a switch which detects whether a trailer is attached to the trailer spotter. When a trailer is attached, the sensor sends a signal to the programmable controller which, in turn, activates a back-up alarm to indicate that the trailer spotter and trailer are moving backward. Further, inputs from the trailer sensor can be used by the controller to provide outputs which are different when a trailer is not attached to the trailer spotter. For example, the magnitude of the swashplate angles can be increased to provide additional power to pull the trailer when the controller and switch perceive an attached trailer. Further, when the controller and sensor detect an absence of a trailer, the engine RPM can be set at a lower horsepower level to conserve fuel. Additional control system parameters may be used to adjust the rate of change of hydraulic fluid flow, i.e., vehicle acceleration, to prevent system damage or engine overload conditions, or to optimize performance by using system pressure measurements to effectively adjust for trailer weights.
Referring to
To enter cab 32 through rear door 162, the operator climbs rear stairs 170 or 172 onto engine cover 59 and slides rear door 162 into the interior of cab 32. As illustrated in
While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.
Number | Date | Country | |
---|---|---|---|
60647481 | Jan 2005 | US |