System for automatic forward bow alignment on water drive pivot

A system for automatic forward bow alignment on a water drive pivot irrigator has a valve assembly associated with each of the towers of the irrigator for regulating movement of the respective tower in a direction of rotation of the irrigator. A flexible element extends along the length of the pipe connecting together the towers of the irrigator for detecting alignment of each of the towers along a desired forward bow of the irrigator and controlling the valve assembly of each of the towers as a function of alignment and misalignment of the particular tower with respect to the desired forward bow. Each valve assembly includes a pair of valves normally held open by a weight mounted on an actuator of the valve, with a reversing lever being connected to the actuator of each of the valves for selectively closing one of the valves while assuring the other of the valves is held in an on position. The flexible cable is also connected to the valve actuators for selectively closing the one of the valve actuators which is in an on position to the closed position thereof in order to stop a tower when same is getting too far ahead of the correct forward bow, while a wind flag is advantageously also connected to the valve actuators and to the flexible element for compensating for the pressure of wind against the flexible element.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to new and useful improvements in area 
watering systems wherein a tower supported water pipe travels in a 
circular path about a central supply point, and particularly to an 
automatic forward bow alignment system for keeping the towers of such a 
watering system in proper position with respect to one another. 
2. Description of the Prior Art 
It is known in the irrigation industry that water-turbine drive pivots must 
never be operated with a reverse bow, because such reverse bow will cause 
the pipe connecting together the towers of the device to be placed in 
compression along the forward, or leading, side thereof, which compression 
will subsequently cause damage to the machine. Thus, it is desirable to 
operate the pivot with a slight forward bow, because such a bow will cause 
the main line, or pipe, to be operated while in tension along the forward, 
or leading, side thereof. Pivot irrigators have more strength in the 
tension mode than in the compression mode, and have a history of bending 
main line pipe any time that they are operated in the compression mode. If 
the pivot is reversible, the forward bow must be established immediately 
in the opposite direction when the device is reversed. 
U.S. Pat. Nos. 3,628,729, issued Dec. 21, 1971 to J. R. Thomas, and 
3,599,664, issued Aug. 17, 1971 to K. W. Hotchkiss et al, disclose pivot 
irrigators in which the towers are controlled so as not to get ahead of a 
line radiating from a pivot of the apparatus, while U.S. Pat. No. 
3,780,947, issued Dec. 25, 1973 to M. H. Ririe et al, discloses a pivot 
irrigator alignment control which includes the use of a wind vane arranged 
for compensating for the effect of wind on a control wire which 
selectively opens and closes switches regulating movement of the 
apparatus. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an automatic forward 
bow alignment system which will permit alignment of the towers of a water 
drive pivot irrigator in a simple, yet reliable manner. 
It is another object of the present invention to provide an automatic 
forward bow alignment system capable of establishing a forward bow 
immediately in either direction of rotation of a reversible pivot 
irrigator. 
It is still another object of the present invention to provide an automatic 
forward bow alignment system for use with a pivot irrigator which 
compensates for the effects of wind on the system as the irrigator rotates 
about the pivot thereof. 
These and other objects are achieved according to the present invention by 
providing an automatic forward bow alignment system for a pivot irrigator, 
which system has: a valve assembly associated with each of the towers of 
the irrigator for regulating movement of the tower in a direction of 
rotation of the irrigator; and a sensor provided on the irrigator for 
detecting alignment of each of the towers of the irrigator along a 
predetermined desired forward bow which the irrigator is to assume, and 
controlling the valve assembly of the towers as a function of alignment 
and misalignment of the towers with respect to one another. 
The valve assembly of each of the towers of the irrigator includes a pair 
of valves mounted on the irrigator at a respective one of the towers 
thereof; a reversing arrangement mounted on the irrigator and connected to 
the valves for selectively holding one of the valves closed and one of the 
valves open; and a linkage mounted on the irrigator and connected to the 
valves and to the sensor for closing the open other of the valves when the 
associated one of the towers moves ahead of the desired bow which the 
towers are to follow about their pivot. 
The reversing arrangement advantageously includes a reversing lever 
pivotally mounted for swinging movement transversely of the pipe 
connecting together the towers of the irrigator. Each of a pair of springs 
is connected to and extends between a respective one of the associated 
valves and the reversing lever, with swinging movement of the reversing 
lever alternately closing one of the valves and opening the other. The 
reversing lever is preferably a T-shaped member having a leg and a pair of 
oppositely directed arms extending from the leg perpendicularly thereto. A 
winch mounted on the irrigator adjacent the center pivot has a pair of 
cables extending therefrom for being wound on and unwound from the winch, 
with each of the cables being connected to a respective one of the arms of 
the reversing lever for selectively swinging the lever and reversing the 
direction of rotation of the irrigator. 
The valves each include a valve body mounted on the pipe of the irrigator 
at an associated one of the towers thereof, with a valve actuator being 
pivotally mounted on the valve body for opening and closing the valve and 
controlling movement of the irrigator by starting and stopping forward 
movement of the associated tower. A biasing arrangement in the form of a 
weight mounted on the valve actuator normally forces the valve actuator 
toward a valve open position in cooperation with the spring attached to 
the particular actuator and to the reversing lever when the reversing 
lever is positioned so as to open the particular valve and close the other 
of the valves. One valve is used to operate the pivot in, for example, the 
clockwise direction, while the other valve is used to operate the pivot in 
the counterclockwise direction. 
The linkage includes a crank pivotally mounted on the irrigator and 
connected to the associated valve assembly, and a second crank pivotally 
mounted on the irrigator and arranged extending toward, but having a pivot 
spaced from, the first crank. A link is pivotally connected to the cranks 
and engages the sensor, which is preferably in the form of a flexible 
element resiliently mounted to the pivot and end tower of the irrigator, 
for being moved by the sensor in a substantially straight path. By this 
arrangement, movement of the link under force applied by the flexible 
element swings the first crank in such a manner as to close the one of the 
valves of the valve assembly which is in the open position for the 
particular direction of rotation of the irrigator. 
A particularly advantageous feature of the invention has the second crank 
of the linkage formed by a first arm of a lever pivotally mounted on the 
irrigator, with the other of the arms of the lever having provided thereon 
a wind flag arranged for cancelling the effect of wind on the flexible 
element forming the sensor in either direction of rotation of the 
irrigator. 
These, together with other objects and advantages which will become 
subsequently apparent, reside in the details of construction and operation 
as more fully hereinafter described and claimed, reference being had to 
the accompanying drawings forming a part hereof, wherein like numerals 
refer to like parts throughout.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now more particularly to the Figures of the drawings, FIG. 1 
illustrates the slight forward bow of an irrigator 10 which the towers 12 
and end tower 12' are to follow in order to cause the pipe 14 connecting 
together the towers 12 and 12' to be in tension on its leading side. When 
the direction of rotation of the pivot is reversed, this same forward bow 
should be established in the opposite direction. Note how the outer towers 
12, 12' attempt to make a bigger circle when the proper bow is 
established. 
FIG. 2 illustrates an irrigator operating with a reverse bow. As can be 
seen from the Figure, such a reverse bow will cause compression of pipe 14 
as it rotates about pivot point 16, and subsequent damage to the machine 
is certain to result. Note how the outer towers 12, 12' attempt to cut in 
toward pivot point 16 and make a smaller circle as the towers 12, 12' 
rotate. 
As can be seen from FIG. 3 of the drawings, when an automatic forward bow 
alignment system according to the present invention is employed, a sensor 
arrangement in the form of a wire 18 or other suitable flexible element is 
tightly stretched between the pivot point 16 and end tower 12' as by 
springs 20 employed to maintain proper tension on wire 18. The latter is 
attached to a linkage at each of the remaining towers 12, which linkage 
will be described in detail below. The towers 12 are illustrated as 
direction arrows in FIG. 3 in order to emphasize that each of the towers 
12 pushes on wire 18 in the direction that irrigator 10 is rotating. That 
direction is counterclockwise as seen in FIG. 3. 
Referring now more particularly to FIGS. 4 and 5 of the drawings, the 
self-propelled irrigator 10 comprises the aforementioned elongated 
water-distributing pipe 14 pivotally mounted at one end 22 and in 
engagement with a water supply carried through conduit 24 which forms a 
pivot axis corresponding to pivot point 16 as seen in FIGS. 1 and 2. Pipe 
14 is supported throughout the length thereof by the aforementioned 
plurality of mobile support towers 12 and 12' selectively propelled in a 
known manner by water-powered motors (not shown), the operation of which 
motors is generally regulated by a suitable control valve. Attention is 
directed to my U.S. Pat. No. 4,080,991 issued Mar. 28, 1978. Mounted on 
pipe 14 at each tower 12, 12', not shown in FIGS. 4 and 5, is a system 26 
according to the present invention for automatic forward bow alignment of 
the irrigator 10. This system 26 includes a valve assembly 28 associated 
with each of the towers 12, 12' of irrigator 10 for regulating movement of 
the towers 12, 12' in a direction of rotation of irrigator 10 in order to 
maintain the desired forward bow. 
The valve assembly 28 includes a pair of valves mounted on pipe 14 as by 
the illustrated clamp and connected to the drive motors (not shown) of the 
respective tower 12, 12' in a suitable manner, not shown but known per se, 
for controlling the forward movement of the associated tower 12, 12'. A 
reversing arrangement 34 is mounted on pipe 14 adjacent the associated 
valve assembly 28 at a tower 12, 12' and is connected to the valves 30, 32 
for selectively holding one of the valves closed and the other of the 
valves open so as to obtain a desired direction of rotation of irrigator 
10. Mounted on irrigator 10, preferably to tower structure not shown in 
detail, and connected to valves 30 and 32 and to wire 18 is a linkage 36 
which functions to selectively close the open other of the valves 30, 32 
when the associated tower 12 moves ahead of its proper position in the 
desired forward bow. 
Reversing arrangement 34 includes a reversing lever 38 pivotally mounted as 
at pivot 40 on pipe 14 for swinging movement transversely of the pipe 14. 
A pair of coiled tension springs 42 and 44 are connected to and extend 
between a respective one of the valves 30, 32 and the reversing lever 38, 
such that swinging movement of reversing lever 38 alternately closes one 
of the valves and opens the other. Reversing lever 38 is a generally 
T-shaped member having a leg extending between pivot 40 and a point of 
attachment of springs 42 and 44, and a pair of oppositely directed arms 46 
and 48 extending perpendicularly from the leg adjacent pivot 40. 
A winch 50 is mounted on irrigator 10 adjacent the pivot axis thereof, and 
has attached thereto a pair of cables 52 and 54 arranged for being wound 
on and unwound from winch 50. Since the latter is of conventional 
construction it will not be described in detail herein. Each of the cables 
52 and 54 is connected to a length of cable on winch 50 as by the 
illustrated coiled tension springs 56 and 58, extends through guides 
provided on oppositely directed bars of a guide bracket 60 and is 
connected to a respective one of the arms 46, 48 of reversing lever 38. 
Coiled tension springs 62 and 64 connect a further extent of the cables 
52, 54 to the arms 46, 48 for connecting additional reversing arrangements 
34 to winch 50 and permitting all of the valve assemblies 28 to be 
reversed simultaneously so that all of the towers 12 and 12' of irrigator 
10 will rotate in the same direction, either clockwise or 
counterclockwise. 
Valves 30, 32 each include a valve body 66 mounted on pipe 14 as by the 
aforementioned clamp at an associated one of the towers 12, 12'. A valve 
actuator 68 is pivotally mounted on valve body 66 for opening and closing 
the associated valve 30, 32 in a known manner not described in detail 
herein and controlling movement of irrigator 10. A biasing device 
preferably in the form of the illustrated weight 70 mounted on the planar 
element forming actuator 68 is provided for cooperating with an associated 
one of the springs 42, 44 in order to hold the valve 30, 32 in an open 
position. When the associated one of the springs 42, 44 is disposed so as 
to place the valve 30, 32 in a closed position, the bias of weight 70 will 
be overcome and the actuator 68 will be permitted to swing about its 
associated hinge 72 so as to close the valve 30, 32. 
As is indicated on FIG. 5, valve 30 is open when its associated actuator 68 
is moved to the left as seen in the Figure, while valve 32 is on when its 
actuator 68 is moved to the right. Thus, in FIG. 5 valve 32 is open and 
valve 30 is closed. 
Linkage 36 includes a crank 74 pivotally mounted on irrigator 10, as to a 
portion of an associated tower 12, 12', and is connected to the valves 30, 
32 as by a rod 76 terminating at one end with a hook 78 arranged in an 
aperture provided in crank 74 and having affixed along the length thereof 
collars 80 and 82. As can be seen from FIG. 5, the collars 80, 82 are 
disposed on either side of the actuator 68 of valves 30 and 32 and pass 
through the planar members forming the actuator 68 as by suitable slots 
provided therein. Thus, reciprocating movement of rod 76, as indicated by 
the double arrow in FIG. 5, will engage the actuator 68 of the one of the 
valves 30, 32 which is open, namely 32 as shown in FIG. 5, and move that 
actuator 68 to a position closing the valve, as shown by broken lines for 
actuator 68 of valve 32. A further crank 84 is pivotally mounted on 
irrigator 10 and is arranged extending toward, but having a pivot 86 
spaced from, crank 74. A link 88 is pivotally connected to cranks 74 and 
84 and engages wire 18 for being moved thereby in a substantially straight 
path. Movement of link 88 under a force exerted thereon by wire 18 will 
swing crank 74, and thus rod 76, and cause one of the collars 80, 82 to 
close the open valve 30, 32. A guide 90 is arranged projecting from the 
longitudinal extent of link 88 so as to form an eye in which wire 18 can 
be slidably and removably disposed. 
A lever 92 pivotally mounted on irrigator 10 as at the pivot 86 and having 
a pair of oppositely directed arms preferably forms crank 84 by one of the 
arms of the lever 92, while the other arm 94 of lever 92 has a wind flag 
96 arranged thereon for cancelling the effect of wind on wire 18 in either 
direction of rotation of irrigator 10. That is, when flag 96 moves lever 
92 as shown in FIG. 5, the direction of rotation of the irrigator 10 being 
shown by the direction arrow in FIG. 5, link 88 will be shifted in the 
direction of movement of the irrigator 10 in order to compensate for the 
force of wind on the longitudinal extent of wire 18. 
OPERATION 
The appropriate valve 32, 30 which will cause the motors (not shown) 
propelling towers 12, 12' in either the counterclockwise or clockwise 
direction is biased in the on position by the associated one of the 
springs 44, 42 and by the weight 70 provided on the associated valve 
actuator 68. All the towers 12 will push with a few grams of force 
horizontally against wire 18 in the forward direction of movement of 
irrigator 10. When the wire 18 pushes back with a force equal to the bias 
on valve actuator 68, the actuator 68 will move to a position closing the 
associated valve 32, 30 and the particular tower 12 on which the valve 32 
is mounted will stop advancing. This sequence of events takes place for 
each of the towers between the pivot axis 16 and the end tower 12'. The 
result is that all the towers 12 are applying a bias to wire 18 in the 
forward direction. By proper arrangement of the various linkages 36 
associated with each of the towers 12, the wire 18 will bow ahead 
automatically as shown in FIG. 3. 
More specifically, one of the springs 42, 44 holds the associated valve 30, 
32 in the off position while the other spring 44, 42 provides a bias on 
the actuator 68 of the other valve 32, 30 which biases the valve 32, 30 
into the on position and feeds through linkage 36 to push forward on 
control wire 18. When the associated tower 12 advances far enough ahead, 
the wire 18 starts to pull back on the actuator 68 of the open valve 32, 
30 against the bias of the spring 44, 42, and the weight 70, the valve 32, 
30 will be closed, and the tower 12 will then stop. The result is that all 
the towers 12 are applying a bias to wire 18 in the forward direction and, 
thus, a forward bow is automatically established which will not be 
excessive in amount. The central towers 12 along the extent of pipe 14 
will come of course, to be set up to move at a slightly faster rate of 
speed than the end tower 12'. 
As can be readily understood from the above description and from the 
drawings, the present invention provides a system for automatic forward 
bow alignment of a pivot irrigator in a simple, yet reliable manner. The 
system can be easily installed even on existing units, and eliminates the 
necessity of an operator (not shown) having to wear a rain suit to make 
customary tower-by-tower alignment adjustments as are necessary with known 
equipment. The system is easy to maintain, and if one of the valves 30, 32 
is ever disassembled for repair or cleaning, realignment of the valve is 
not required after it is repaired. Further, immediate reversal of a water 
drive pivot from the pivot point 16 is realized by the invention. Most 
water drive pivots require the operator to make adjustments at each tower 
to reverse the system. 
Other advantages realized by the invention include inherent icing 
protection. When pivots are operated at temperatures below, for example, 
38 degrees F. (3.33 degrees celsius) evaporation cools the surrounding air 
and the resulting mist can freeze on the components of the system. This 
ice will continue to accumulate until the weight of the ice will crush the 
system. The alignment system according to the invention, however, will not 
function with ice on it, so that the pivot will be caused to go out of 
alignment and the safety system (not shown) provided on the irrigator will 
shut down the entire device. 
The foregoing is considered as illustrative only of the principles of the 
invention. Further, since numerous modifications and changes will readily 
occur to those skilled in the art, it is not desired to limit the 
invention to the exact construction and operation shown and described, and 
accordingly all suitable modifications and equivalents may be resorted to, 
falling within the scope of the invention.