Guidance System for Towed Vehicles

This invention relates to a guidance system for towed vehicles and more particularly to an automatic guidance system for a towed farm implement.

The increase of the average farm size has resulted in the use of larger farm equipment. The guidance of this wider equipment while in the field can have considerable effect upon the machine's effective field capacity and thus its field efficiency. Some agricultural operations require extreme guidance accuracy due to various reasons. A common example concerns applications of herbicide. If two "passes" lap over one another possible damage to the crop may result, while if a strip is completely missed, no weed control will be present. Row crop planters also require a high degree of accurate guidance for efficient operation. The markers on a 24 row planter with a 30 inch row spacing are in the vicinity of 30 feet in length. These markers often require one joint to enable the marker to fold, and sometimes two such joints are used. Markers of such length are cumbersome and unwieldy to maneuver.

Many methods of guidance have been utilized and have been generally directed to the guidance of the tractor rather than the guidance of the towed implement. One method involved an operator at a remote location in the field and controlling the tractor by radio control. Another method comprised infrared detectors positioned at the ends of the field which would locate the machine's position by referencing to hot tractor gases. Still other methods involve an electric cable buried in a field with a magnetic follower able to follow the cable down the field, and the utilization of light, radar or infrared beams in which the machine would run between two of these sending units. All of these systems were costly and involved numerous pieces of complex mechanical and electrical sensors and mechanisms. Also to control the location of the towed implement by guidance of the tractor is cumbersome, inaccurate and not as responsive as guidance of the towed implement alone.

Previous guidance systems were not versatile to allow the farmer to use various sizes of equipment for planting, cultivating and harvesting and lacked spacing accuracy to enable exact placement of rows year after year to fully utilize any fertilizer or herbicide that may be banded.

An automatic guidance system for a towed implement is disclosed comprising a marker, a position sensor, an operational amplifier circuit, an electrical servo controlled hydraulic valve and a hydraulically controlled swinging draw bar hitch. Hydraulic force on the swinging draw bar hitch adjusts the position of the towed implement through the electrical servo controlled hydraulic valve responding to outputs of the operational amplifier circuit. The position sensor comprises a follower to follow the furrow produced by the marker on the previous pass of the implement and variable resistors on the follower to provide informational input voltages to the operational amplifier circuit relative to the displacement of the follower. The guidance system is generally located on the towed implement to guide the towed implement and allows the tractor and the towed implement to operate more or less independently. Adjustment means enable the operator to change the angular displacement necessary to actuate the solenoid valves thereby providing adjustment of the implement positioning error. Control means are also provided to allow manual operation of the solenoid valves and therefore manual control of the position of the towed implement.

It is a principal object of the invention to provide a guidance system for towed implements that guides the implement rather than the tractor pulling the implement.

A further object of the invention is to provide a guidance system for towed implements that is adaptable to various sizes of equipment for planting, cultivating and harvesting.

A still further object of the invention is to provide an improved guidance system for towed implements.

A still further object of the invention is to provide an accurate guidance system for towed vehicles to enable exact placement of rows year after year.

A still further object of the invention is to provide a guidance system for towed vehicles that operates more or less within the existing boundary of the implement.

A still further object of the invention is to provide a guidance system for towed vehicles reducing the precision of operation required by the operator to lessen fatigue upon the operator and increase the feasibility of night time operation.

A still further object of the invention is to provide a guidance system for towed implements utilizing a marker of reduced length to alleviate transportation problems due to low clearance of bridges, wire, etc. and to improve safety by reducing the number of pinch points on the marker.

A still further object of the invention is to provide a guidance system for towed vehicles that is economical to manufacture, durable in use, and refined in appearance.

This invention consists in the construction, arrangements, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings in which FIG. 1 is a top plan view of the invention mounted on a farm implement towed by a tractor.

FIG. 2 is an enlarged top plan view of the swinging draw bar hitch.

FIG. 3 is an enlarged side view of the marker and position sensor.

FIG. 4 is an enlarged side view similar to FIG. 3 seen on line 4--4 of FIG. 1.

FIG. 5 is a top plan view similar to FIG. 1 illustrating the operation of the hitch.

FIG. 6 is a schematic view of the servo controlled hydraulic valve.

FIG. 7 is an electrical schematic view of the electrical circuit.

The numeral 10 generally refers to the guidance system for a towed implement shown mounted to a planter 12 being towed by a tractor 14 as shown in FIG. 1.

Hitch 16 connects tractor 14 and planter 12. Attachment to the tractor 14 is accomplished by swinging draw bar 18 being pivotally mounted about pin 20 through clevis 21 affixed to the cross bar 22 connecting the lower links 24 of a conventional three-point hitch. Hydraulic cylinder 26 is pivotally mounted at one end to cross bar 22 with the outer end of arm 28 of hydraulic cylinder 26 pivotally mounted to brace 30 transversely extending from draw bar 18. Extension and contraction of arm 28 thereby produces pivotal movement of draw bar 18 about pin 20. Draw bar 18 is pivotally attached to tongue 32 of planter 12 by pivot pin 34. Gauge wheel 36 is rotatably mounted to fork 38 which in turn is pivotally attached to draw bar 18 by pin 40 just forward of hitch point 34. Gauge wheel 36 insulates planter 12 from the vertical tractor motion and provides a smooth consistent ride for planter 12.

A marker 42 and a position sensor 44 are located on each side of planter 12 as far forward as possible to minimize the reaction time and still not interfere with clearance for turning. Marker 42 is comprised of a standard cultivator sweep 46 mounted on a standard cultivator shank 48. Utilization of a standard cultivator sweep and shank allows the marker to trip when striking immovable objects. Position sensor 44 comprises spheroid shaped follower 50 attached to follower shaft 52 which is pivotally attached to sensing shaft 54 as shown in FIG. 3. Revolving sensing shaft 54 is bearing mounted to mounting plate 56 by bearing mounts 58. Connection bar 60 pivots on pin 62 projecting from front tool bar 64 of planter 12 and is securely connected at one end to mounting plate 56 and at the other end to shank 48. Sensing shaft 54 is mounted at approximately a 60.degree. angle to connection bar 60 so that when the mechanism is in the following mode, the revolving sensing shaft 54 will be approximately vertical (FIG. 3). When the mechanism is in the marking mode and the follower 50 is in the up position, sensing shaft 54 will be at approximately a 30.degree. angle from the vertical (FIG. 4). Stop 66 is connected at one end to sensing shaft 54 and at the other end to follower shaft 52, and allows for lift of follower shaft 52 as the mechanism shifts from a following to a marking mode. During road travel, follower shaft 52 is held in stirrup 69 as shown in FIG. 4. A marker 42 position sensor 44 combination is located on each side of planter 12 (FIG. 1) and during operation one side will be in the marking position while the other side is in the following position. At the end of a pass across the field, the planter is raised and turned around and on the return pass, follower 50 will be down to follow the furrow made by cultivator sweep 46 on the previous pass while the cultivator sweep on the side opposite the following operation is making another furrow for the next pass. Spring 68 provides a force against connection bar 60 so that when the tension in cable 70 is relaxed, marker 42 will pivot to a marking mode (FIG. 4). To raise marker 42 and lower position sensor 44 into a following mode, the tension in cable 70 is increased causing connection bar 60 to pivot about pin 62 as shown in FIG. 3. Cable 70 is attached at one end to connection bar 60 directly above shank 48 and extends over pully 72 rotatably mounted to upstanding post 74 mounted to front tool bar 64 directly above pivot pin 62. Cable 70 terminates in a control box (not shown) for controlling the amount of tension in cable 70 and for alternating the marker 42-position sensor 44 combinations as previously described.

Electronic control circuit 76 is schematically shown in FIG. 7 and controls the action of hydraulic cylinder 26 in response to an error in the position of the planter. Variable resistors 78 and 80 are mounted on the shafts 54 located on each side of the planter and provide the inputs to operational amplifiers 82 and 84. Variable resistor 78 is located on the left shaft 54 and variable resistor 80 is located on the right shaft 54.

The selection of variable resistor 80 or variable resistor 78, depending on which side of the planter is sensing position, is made by selector switch 86. In FIG. 7, selector switch 86 is shown in a "right" position activating the variable resistor on the right side of planter 12. Variable resistor 78 and 80 are operationally connected to shafts 54 such that any deviation of planter 12 from its predetermined alignment relative to the furrows is converted proportionately to voltage outputs from variable resistors 78 and 80 ranging from +12 volts to -12 volts D.C. The positive voltage is obtained from the tractor battery (not shown) and the negative voltage is obtained from an extra battery pack (not shown). Switch 88 connects and disconnects the battery power sources to electrical circuit 76. The output voltage from either resistor 78 or resistor 80 is fed into operational amplifiers 82 and 84. Operational amplifier 84 is a non-inverting amplifier while operational amplifier 82 is an inverting amplifier. A reference voltage is supplied by deadband circuit branch 90 which contains variable resistor 92 to allow variance of the reference voltage. Operational amplifiers 82 and 84 compare the voltages coming from deadband branch 90 and either variable resistor 78 or 80. Operational amplifier 84 is a non-inverting amplifier and has a positive output when its input is positive. Operational amplifier 82 is an inverting amplifier and has a positive output when its input is negative. For example, with the selector switch 86 activating variable resistor 80, the output from resistor 80 is being fed into operational amplifiers 82 and 84. When the voltage coming from variable resistor 80 to operational amplifier 84 is higher than the voltage from the deadband branch 90, the signal from operational amplifier 84 is positive. This positive signal turns on transistor 94 and current flows to solenoid 96. Since the voltage from variable resistor 80 is higher than the voltage from deadband branch 90, operational amplifier 82 converts this positive signal resulting in a negative output. Because of this negative output, transistor 98 does not conduct and therefore no current flows to solenoid 100. When the output voltage from variable resistor 80 is low, resulting in a negative input signal when compared to the deadband reference voltage across branch 90, operational amplifier 82 inverts this negative input signal into a positive output signal, thereby causing transistor 98 to conduct current to solenoid 100. At the same time, the negative input signal to operational amplifier 84 results in a negative output signal to transistor 94 since operational amplifier 84 is a non-inverting amplifier resulting in no conduction of current from transistor 94 to solenoid 96. Switch 102 provides for manual activation of solenoid 96 and switch 104 provides manual activation of solenoid 100 when electronic circuit 76 is deactivated.

Solenoids 96 and 100 are incorporated within electrical servo controlled hydraulic valve 106 as shown in FIG. 6. Hydraulic feed line 108 and return line 110 connect the remote outlet of the tractor hydraulic system and hydraulic cylinder 26 via valve 106. The position of valve 106 as shown in FIG. 6 maintains arm 28 in a stationary position. Activation of solenoid 96 as hereinbefore described will cause the direction of flow into cylinder 26 to be such as to extend arm 28 while the activation of solenoid 100 will reverse the flow so as to withdraw arm 28. Arm 28 in turn applies force through brace 30 to draw bar 18 thereby adjusting the position of planter 12 (FIG. 5). Thus, any deviation in position of planter 12 as detected by follower 50 results in a correcting force being applied to draw bar 18 thereby guiding planter 12.

Variable resistor 92 in deadband circuit branch 90 enables the operator to change the angular displacement necessary to actuate solenoid valve 106. This adjustment will be a compromise between exact control of the planter 12 and stability. If the deadband is too small, the planter will jog back and forth rapidly while traveling down the field while a wide deadband would allow large row spacing error.

In operation, during the first pass of the planter 12, one of the markers 42 is in a lowered position (FIG. 4) so that cultivator sweep 46 makes a furrow 47 in the earth. The operator then turns the planter around at the headlands, and aligns the appropriate follower 50 in furrow 47. The marker 42 on the side of the planter 12 opposite to the lowered follower 50 will thereby be positioned so as to make a furrow for the next pass. As the tractor and planter proceed down the field, the lowered follower 50 riding in the furrow, will detect any deviation of position of planter 12 and such deviation will be corrected via electronic circuit 76, servo controlled hydraulic valve 106, hydraulic cylinder 26, and swinging draw bar 18 realigning planter 12. At the end of the pass, the tractor and planter are turned around and the process is repeated with the relative operational modes on each side of the planter being reversed. Switch 86 provides activation of the variable resistor for the appropriate follower side. Switches 102 and 104 provide manual control of the system to aid the operator in getting the follower into the furrow after making the turn and going around obstacles during operation.

Thus, it can be seen that guidance system 10 accomplishes at least all of its stated objectives.