Guidance system for lateral move irrigation machines

A guidance system for a lateral move irrigation machine of the type having an elongate boom mounted on a plurality of motor driven towers which drive the boom along the field in a straight line path. A plurality of check points in the field are established by a series of magnetic and metallic elements placed in rows along the path of travel of the towers. The towers carry gradiometers or proximity switches which are sensitive to the elements and which deactivate the drive motors of the towers when the check points are reached. When all of the towers have reached the check points, the boom is properly aligned, and override circuits then activate the drive motors to resume movement of the machine.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates in general to irrigation equipment and deals more 
specificially with a system for controlling the guidance of a lateral move 
irrigation machine. 
Mobile irrigation systems having elevated booms are generally classified 
either as center pivot machines or lateral move machines which are also 
referred to as linear or in line machines. In the center pivot machine, an 
upright stand pipe at the pivot point of the system supplies water to an 
elevated boom carried on wheeled towers. The towers are driven by drive 
motors in a circular path centered at the stand pipe, and sprinklers 
spaced along the boom apply water to the field. The lateral move 
irrigation system likewise has an elevated boom carried on mobile towers. 
However, instead of moving in a circular path, the towers of the lateral 
move system are usually driven in a straight line path which is 
perpendicular to the irrigation boom. 
Although both types of irrigation system have been widely used and have 
performed well for the most part, the lateral move machine has various 
advantages over the center pivot machine which make the lateral move 
machine more desirable in many situations. With the center pivot system, 
considerable difficulty is encountered in applying adequate quantities of 
water to the corner areas of the square or rectangular fields in which the 
equipment usually operates. Also, more water must be delivered to the 
outer end of the irrigation boom than to the portions near the pivot since 
the outer portions of the boom cover more surface area. 
Lateral move irrigation systems avoid these problems but are faced with 
others which have proven difficult to overcome. Perhaps most notably, 
accurate guiding of the lateral move machine through the field has 
presented considerable difficulty. Alignment systems such as that shown in 
U.S. Pat. No. 3,608,826 have been used for both center pivot machines and 
for lateral move machines and have been generally effective in maintaining 
the irrigation boom in a straight condition. Nevertheless, such systems 
are plagued by the types of problems which arise in connection with all 
mechanical devices. For example, the reliability of mechanical alignment 
devices is lacking somewhat, particularly after the parts have become worn 
due to prolonged use and exposure to the elements. Existing alignment 
systems are also characterized by undue cost and complexity which adds 
significantly to the overall cost of the irrigation equipment. 
Additionally, existing alignment systems function only to maintain the boom 
in a straight condition. In lateral move machines, the entire boom can 
turn such that its direction of movement is angled relative to the 
intended direction of travel. Since this can occur while the boom remains 
substantially straight, conventional alignment systems are not effective 
to steer the machine back on course. If the irrigation machine departs 
appreciably from its intended course, the effectiveness of the irrigation 
suffers and in some cases the machine can move outside of the field and 
possibly cause serious damage to fences and other structures, as well as 
to the irrigation machine. 
Guidance systems which have been proposed in the past for lateral move 
machines typically operate to sense the angular relationship of a support 
tower with respect to a reference line, such as a buried wire, an above 
ground cable, a furrow in the field, or a row of stakes. Due to the great 
length of the irrigation machine, small deviations in the angle of the 
tower cause large displacements at the end of the machine. Consequently, 
for effective guidance control, these systems must be extremely sensitive 
to the tower angular displacement in order to prevent undue displacement 
at the ends of the machine, and such sensitivity is difficult to achieve 
in actual practice. 
It is the primary object of the present invention to provide an improved 
system for accurately guiding a lateral move irrigation machine along the 
intended path of travel with the irrigation boom maintained in a straight 
condition. 
Another object to the invention is to provide a guidance system of the 
character described which avoids the mechanical problems associated with 
systems that employ mechanical linkages and the like. In this respect, it 
is noteworthy that the guidance system relies on fixed check points and 
does not depend on mechanisms on the irrigation machine that can lose 
their adjustment and develop other mechanical problems. 
A further object to the invention is to provide a guidance system of the 
character described wherein the boom position is checked at regular 
intervals. In accordance with the invention, a series of spaced apart rows 
of check points are established at preselected locations in the fields, 
and the path of movement of the boom is automatically corrected when the 
irrigation machine reaches each row of check points. It is another 
important feature of the invention that the rows of check points can be 
spaced apart as desired to permit the boom position to be checked and 
corrected at various locations in the field. 
An additional object to the invention is to provide a guidance system of 
the character described in which the drive motors of the irrigation 
machine are automatically energized to resume normal movement of the 
machine each time its path of movement has been corrected. 
Yet another object of the invention is to provide a guidance system of the 
character described which is well adapted for use with various types and 
sizes of lateral move irrigation machines. 
A still further object of the invention is to provide a guidance system of 
the character described which is simple and economical to construct and 
reliable in operation. 
Other and further objects of the invention, together with the features of 
novelty appurtenant thereto, will appear in the course of the following 
description.

Referring now to the drawings in detail and initially to FIG. 1, reference 
numeral 10 generally designates an elongate elevated irrigation boom 
forming part of a lateral move irrigation machine. Boom 10 is carried on 
top of a plurality of spaced apart towers, including a central tower 12, 
an end tower 14, an opposite end tower 16, and intermediate towers 18 and 
20 located between the center tower and the end towers. Boom 10 is formed 
by a plurality of elongate pipe sections 22 which are connected end to end 
by flexible couplings 24. 
Water can be supplied to the irrigation boom 10 in any of a number of ways. 
In one type of water supply system, generally used on relatively short 
machines (up to about 1/4 mile long), a supply pipe 26 extends along the 
ground at the side of the field to be irrigated and has a plurality of 
spaced apart outlets 28 to which one end of a flexible hose 30 may be 
connected. Hose 30 connects at its opposite end with one end of boom 10 to 
deliver water thereto. The boom includes a plurality of spaced apart 
sprinklers 32 which discharge water to the field in a uniform pattern of 
distribution. Water is pumped into supply pipe 26 by a conventional pump 
(not shown). 
It should be understood that the guidance system of the present invention 
can be used on other types of linear irrigation machines such as those 
which move along the water supply pipe and automatically connect to it and 
disconnect from it at regular intervals along the length of the supply 
pipe. This type of machine is usually longer (approximately 1/2 mile) than 
the "hose drag" type of machine, and by reason of its greater length, 
conventional alignment systems and other types of guidance systems are not 
well suited for use with it. Accordingly, it is contemplated that longer 
machines can more advantageously employ the subject guidance system, 
although it can also be used with relatively short machines such as the 
"hose drag" arrangement shown in FIG. 1. 
The irrigation boom 10 and each of the mobile towers are constructed in 
substantially the same manner as described in U.S. Pat. No. 3,608,826, to 
which reference may be made for a detailed understanding of the structure 
of the boom and towers. The center tower 12 has an "A" shaped frame which 
includes a pair of downwardly diverging legs 34 carrying ground engaging 
wheels 36 at their lower ends. A conventional electric motor 38 of the 
reversing type drives wheels 36 and may be reversed in order to propel 
tower 12 in opposite directions along the field. A proximity switch 40 
extends from one of the tower legs 34 closely above the ground. As will be 
explained more fully, proximity switch 40 has normally open contacts which 
close when moved in proximity to any one of a series of metallic elements 
42. The metallic elements 42 are spaced apart from one another in a 
straight line extending along the center of the field in order to 
establish check points at which the course of the boom is checked and 
corrected if necessary. 
End tower 14 is constructed similarly, having downwardly diverging legs 43 
carrying wheels 43a which are driven by a reversing electric motor 44. 
Tower 14 is equipped with a magnetic gradiometer 48 which is carried on an 
outwardly projecting arm 49 connected with one of the tower legs 43. The 
gradiometer 48 is located closely above the ground surface and is 
sensitive to magnets such as the magnets 50 which are spaced apart in the 
field in a straight line extending along the path of movement of tower 14. 
The opposite end tower 16 similarly has a pair of downwardly diverging 
legs 52, a pair of ground engaging wheels 54, and a reversing type 
electric motor 56 which drives the wheels. A magnetic gradiometer 58 is 
carried on a projecting arm 60 closely above the ground surface The 
gradiometer 58 is sensitive to magnets such as magnets 62 which are 
arranged in the field in a straight line extending along the intended path 
of movement of tower 16 and parallel to magnets 50 and the metallic 
elements 42. 
The intermediate towers 18 and 20 are constructed in substantially the same 
manner as the remaining towers. A conventional alignment system (not 
shown) such as that shown in the above identified U.S. Pat. No. 3,608,826 
serves to prevent tower 18 from moving unduly ahead of or lagging behind 
towers 12 and 14, and to prevent tower 20 from moving ahead of or lagging 
behind towers 12 and 16. The boom 10 is thus maintained in a straight 
condition at all times by the conventional alignment system. Additional 
support towers may be provided for longer irrigation booms, and a lesser 
number of towers is also possible. It should be understood that other 
types of alignment systems can be used, and that is some cases no 
alignment system is necessary (such as when each tower is controlled by 
the check point system of this invention). 
In accordance with the present invention, the proximity switches 40 and the 
magnetic gradiometers 48 and 58 form part of a guidance system that serves 
to steer the boom such that it moves through the field in the intended 
direction of travel with the boom axis perpendicular to its direction of 
movement. Each row formed by one of the metallic elements 42, one magnet 
50 and one magnet 62 is arranged in a straight line extending 
perpendicular to the intended direction of travel of the boom. The spacing 
between each adjacent pair of metallic elements and each adjacent pair of 
magnets is preferably the same. It should be pointed out that instead of 
three rows of check points, two rows can be provided (usually for 
relatively short machines), or more than three rows can be provided 
(usually for relatively long machines). 
Referring now to FIG. 2, the guidance system includes an electrical control 
circuit having a conductor 78 to which 120 volt AC power is applied. 
Conductor 78 connects with another conductor 86 which extends between a 
pair of nodes 88 and 90. A conductor 92 extends between node 90 and 
another node 94 which connects with line 96. Line 96 extends through a set 
of gradiometer contacts 48a which are normally open but which close when 
gradiometer 48 is moved in proximity to one of the magnets 50. Line 96 
extends through gradiometer 48 to a node 100. A relay coil 102 is 
connected between node 100 and ground. A conductor 104 connects at one end 
with line 96 and at the opposite end with node 100 in order to bypass the 
gradiometer contacts 48a. Line 104 includes a set of normally closed 
contacts 44a which open when the drive motor 44 of tower 14 is energized. 
Line 104 also includes a set of relay contacts 102a which are normally 
open but which close when relay coil 102 is energized. 
Extending from node 90 in a direction opposite line 92 is a conductor 106 
which leads to a node 108. A conductor 110 extends from node 108 through 
the gradiometer 58 of tower 16. Line 110 includes a set of normally open 
contacts 58a which close when gradiometer 58 is moved in proximity to one 
of the magnets 62. Line 110 leads to a node 112, and a relay coil 114 is 
connected between node 112 and ground. A conductor 116 connects at one end 
with line 110 and at the opposite end with node 112 in order to bypass the 
gradiometer contacts 58a. Line 116 includes a set of normally closed 
contacts 56a which open when the drive motor 56 of tower 16 is energized. 
Line 116 also includes a set of normally open relay contacts 114a which 
close when coil 114 is energized. 
The proximity switch 40 controls a set of normally open contacts 40a which 
are included in a conductor 118 extending from node 90. Line 118 extends 
to ground through a relay coil 120. The normally open contacts 40a close 
when proximity switch 40 is moved adjacent one of the metallic elements 
42. 
The drive motors for towers 12, 14 and 16 are energized in normal operation 
of the irrigation machine by 120 volt power supplied to a conductor 122 
through a percentage timer 124. The percentage timer is a conventional 
device which controls the time of operation of the drive motors. For 
example, if the percentage timer has a one minute cycle, it can be set 
such that the circuit through it is completed for the first 30 seconds and 
broken for the next 30 seconds of each one minute cycle. As a result, the 
irrigation machine is driven for 30 seconds, stopped for the next 30 
seconds, driven for the next 30 seconds and so on. The cycle length can be 
varied, as can the percentage of time the machine operates during each 
cycle. 
Line 122 leads from percentage timer 124 to a node 126, and another line 
128 leads from node 126 to another node 130. Extending from node 130 is a 
condutor 132 having a set of normally closed relay contacts 134a which 
open when a relay coil 134 is energized. Line 132 has another set of 
normally closed relay contacts 102b which open when relay coil 102 is 
energized. Line 132 leads to a node 136, and another conductor 138 leads 
from node 136 and through motor 44 to ground to complete the circuit which 
activates motor 44 in normal operation of the irrigation machine. 
Motor 56 is energized in normal operation by a circuit that includes a 
conductor 140 leading from node 126 to another node 142. Node 142 is 
connected with another node 144 by a conductor 146. A conductor 148 
extends from node 144 and includes a set of normally closed relay contacts 
134b which open when relay coil 134 is energized. Line 148 extends to a 
node 150 through a set of normally closed relay contacts 114b which open 
upon energization of relay coil 114. A conductor 152 extends from node 150 
and through motor 56 to ground. 
The circuit which energizes motor 38 in normal operation includes a 
conductor 154 which extends from node 142 and includes a set of normally 
closed relay contacts 134c that open when coil 134 is energized. Line 154 
extends to a node 156 through another set of normally closed relay 
contacts 120a that open when relay coil 120 is energized. A conductor 158 
extends from node 156 to ground through the drive motor 38 of the center 
tower. Extending between nodes 142 and 156 is a conductor 160 having a set 
of normally open relay contacts 134d that close when coil 134 is 
energized. 
Energization of relay coil 134 is effected by a circuit that includes a 
conductor 162 extending from node 94. Conductor 162 includes a set of 
normally open relay contacts 102c that close when coil 102 is energized, 
another set of normally open relay contacts 120b that close when coil 120 
is energized, and a third set of normally open relay contacts 114c that 
close when coil 114 is energized. 
Coil 134 is connected with line 162 and with ground. Coil 134 also connects 
with a conductor 164 having a set of normally open relay contacts 134e 
that close when coil 134 is energized. Line 164 leads to a node 166. 
Extending between nodes 94 and 166 is a conductor 168 having a set of 
normally open relay contacts 102d that close when coil 102 is energized. 
Extending between nodes 88 and 166 is a conductor 170 having a set of 
normally open relay contacts 120c that close when coil 120 is energized. 
Another conductor 172 extends between nodes 108 and 166 and includes a set 
of normally open relay contacts 114d that close upon energization of coil 
114. 
Relay coil 134 has two additional sets of normally open contacts 134f and 
134g that close when coil 134 is energized. Contacts 134f are included in 
a conductor 174 extending between nodes 130 and 136. Contacts 134g are 
included in a conductor 176 that extends between nodes 144 and 150. 
In operation, the drive motors for the mobile towers 12, 14, and 16 are 
energized under the control the percentage timer 124 to propel the 
irrigation machine along the field in the forward direction indicated by 
the directional arrow 71 in FIG. 1. Boom 10 travels in a straight line 
path with the boom oriented perpendicular to its direction of movement 
through the field. Water is supplied to boom 10 from pipe 26 through hose 
30 (or by means of another water supply system), and the water is 
discharged to the field from the sprinklers 32 as the boom is driven 
through the field. When the circuit through the percentage timer 124 is 
completed, power is supplied to motor 44 along the circuit provided by 
line 122, line 128, line 132 through the normally closed contacts 134a and 
102b, and line 138. Power is supplied to energize motor 56 along the 
circuit formed by line 122, line 140, line 146, line 148 through the 
normally closed contacts 134b and 114b, and line 152. Power to motor 38 is 
supplied on line 122, line 140, line 154 through the normally closed 
contacts 134c and 120a, and along line 158 to motor 38. Drive motors 38, 
44, and 56 are thus energized under control of the percentage timer 124 to 
propel the irrigation machine through the field in normal operation. 
Boom 10 is stopped and its direction of movement is checked and corrected 
each time it reaches a position defined by the check points established by 
a row consisting of one metallic element 42, one magnet 50 and one magnet 
62. When the left end tower 14 reaches one of the magnets 50, gradiometer 
48 senses the magnet and closes its normally open contacts 48a. As a 
result, a circuit through relay coil 102 is completed along the path 
provided by line 78, line 86, line 92, line 96, contacts 48a, and node 100 
to coil 102. Energization of the coil opens the normally closed contacts 
102b and thus interrupts line 132 to break the circuit which normally 
energizes motor 44. Motor 44 is then deenergized to stop the movement of 
tower 14. Energization of coil 102 and deenergization of motor 44 are 
accompanied by closing of contacts 102a and 44a in order to complete a 
holding circuit from line 96 along line 104 to node 100 and coil 102. The 
holding circuit maintains coil 102 in the energized condition so long as 
motor 44 remains deenergized to hold contacts 44a in the closed position. 
Drive motor 56 of the right tower 16 is deenergized in much the same manner 
when its gradiometer 58 encounters one of the magnets 62. The gradiometer 
contacts 58a then close to energize relay coil 114 along a path defined by 
line 78, line 86, line 106, line 110, and through contacts 58a to node 112 
and coil 114. Energization of the coil causes contacts 114b to open, thus 
interrupting line 148 and breaking the circuit which normally maintains 
motor 56 in the energized condition. Coil 114 is thereafter maintained in 
the energized condition by a holding circuit which extends from line 110 
along line 116 and through contacts 56a and 114a to node 112 and coil 114. 
When the proximity switch 40 associated with the center tower 12 encounters 
one of the metallic elements 42, its contacts 40a are closed to complete a 
circuit extending along line 78, line 86, line 118, and through contacts 
40a to relay coil 120. The relay contacts 120a then open to interrupt line 
154 and thereby break the circuit which previously energized motor 38. 
In this manner, the drive motors 38, 44 and 56 are all deenergized when the 
check points established by the metallic elements and magnets are reached. 
The remaining towers 18 and 20, as well as any other towers that may be 
included in the machine, are maintained on a straight line extending from 
the center tower to the end towers by the conventional alignment system 
(not shown). Alternatively, all of the towers may be provided with sensors 
similar to the gradiometers or proximity switches, along with a line of 
magnets or metallic elements spaced along the intended path of movement of 
the tower. 
Since the check point or station defined by each row of one metallic 
element 32, one magnet 50, and one magnet 62 defines a straight line 
extending perpendicular to the intended direction of movement of the 
machine and the machine is stopped when it reaches each check point, the 
machine is positioned to travel in the intended direction of movement each 
time one of the check points is reached. 
Operation of the machine resumes automatically after all of the towers have 
reached their check point stations. Relay coil 134 is energized when this 
occurs since relay contacts 102c, 120b and 114c are all closed due to 
energization of their relay coils. This completes a circuit path extending 
from node 94 along line 162 to coil 134. Energization of coil 134 
completes an override circuit for each drive motor which activates the 
motor even though relay coils 102, 114, and 120 remain energized. The 
override circuit for motor 44 is completed along line 122, line 128, line 
174 through the closed contacts 134f, and along line 138 to motor 44. 
Motor 44 is then energized to begin driving tower 14 away from the magnet 
50. When motor 44 is energized, contacts 44a are opened to break the 
holding circuit for coil 102 which is then deenergized once the 
gradiometer 48 has moved away from the magnetic such that its contacts 48a 
open. 
The override circuit for motor 56 is completed along line 122, line 140, 
line 146, line 176 through the closed contacts 134g, and along line 152 to 
motor 56. Motor 56 is then energized to drive tower 16, and contacts 56a 
open to break the holding circuit for coil 114. Coil 114 is thus 
deenergized when gradiometer contacts 58a open due to movement of tower 16 
away from the magnet 62. 
When relay coil 134 is energized, the override circuit for motor 38 is 
completed along line 122, line 140, line 160 through the closed contacts 
134d, and along line 158 to motor 38. Motor 38 is thus energized to drive 
tower 12 even though coil 120 remains energized. Coil 120 is deenergized 
once tower 12 has moved far enough away from he metallic element 42 to 
open the contacts 40a of proximity switch 40. When coil 134 is energized, 
the circuits which activate the drive motors in normal operation of the 
machine can not be completed because contacts 134a, 134b and 134c remain 
open. 
The override circuits remain completed and the circuits which normally 
activate the drive motors remain broken so long as relay coil 134 remains 
energized. Coil 134 has a holding circuit which maintains it in the 
energized condition so long as at least one of the coils 102, 114 and 120 
remains energized. When coil 102 is energized, the circuit path to coil 
134 is completed along line 78, line 86, line 92, line 168 through the 
closed contacts 102d, and along line 164 to coil 134 through the closed 
contacts 134e. When coil 114 is energized, a holding circuit to coil 134 
is completed along line 78, line 86, line 106, line 172 through the closed 
contacts 114d, and along line 164 to coil 134 through the closed contacts 
134e. When coil 120 is energized, the holding circuit to coil 134 is 
completed along line 78, line 170 through the closed contacts 120c and 
along line 164 to coil 134 through the closed contacts 134e. It is thus 
apparent that once it is energized, relay coil 134 remains energized so 
long as any one of the coils 102, 114 and 120 remains energized. 
Consequently, the override circuits for the drive motors remain completed 
and the circuits which normally energize the drive motors remain broken 
until such time as all of the coils 102, 114, and 120 have been 
deenergized. This assures that all of the towers are moved away from the 
metallic elements 42 and magnets 50 and 62 before normal operation of the 
irrigation machines resumes. 
Once all of the coils 102, 114 and 120 have been deenergized, coil 134 is 
deenergized to interrupt the override circuits. This effects closing of 
contacts 134a, 134b and 134c to complete the circuits which energize 
motors 44, 56 and 38 in normal operation of the machine. The irrigation 
machine then operates normally until the next set of check points is 
reached, at which time the boom is again stopped and corrected in its 
course, if necessary, before further movement through the field resumes. 
The successive rows of metallic elements and magnets extend perpendicular 
to the intended direction of movement of the boom, and the rows may be 
spaced apart in any desired pattern. The metallic elements and magnets may 
be replaced by alternative members such as stakes or other fixed 
structures located in the field at positions to actuate suitable switches 
when the towers arrive at the check points. In addition to such mechanical 
trip devices, photocells and other types of sensors can be used. Other 
types of circuits can be used and the actual circuitry employed depends 
upon a number of factors such as the number of towers controlled by check 
points. 
It should be understood that only two towers controlled by check points are 
necessary for the guidance system to operate effectively. With longer 
irrigation machines, it is generally desirable to control more towers with 
check points, and all towers can be so controlled in some cases (an 
alignment system is then not needed). In contrast to guidance system which 
sense the angular deviation of a support tower relative to a reference 
line, the subject guidance system has check points at the extremes of the 
machine to eliminate significant deviations at the ends, thereby achieving 
more accuracy in guidance control, particularly with relatively long 
machines. 
From the foregoing, it will be seen that this invention is one well adapted 
to attain all the ends and objects hereinabove set forth together with 
other advantages which are obvious and which are inherent to the 
structure. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
Since many possible embodiments may be made of the invention without 
departing from the scope thereof, it is to be understood that all matter 
herein set forth or shown in the accompanying drawings is to be 
interpreted as illustrative and not in a limiting sense.