WO2000032031A1

WO2000032031A1 - Centre pivot irrigator and method of operating such an irrigator

Info

Publication number: WO2000032031A1
Application number: PCT/IB1999/001791
Authority: WO
Inventors: François DE WET
Original assignee: Wet Francois De
Priority date: 1998-11-30
Filing date: 1999-11-08
Publication date: 2000-06-08
Also published as: AU6362399A

Abstract

A centre pivot irrigator comprises a boom (14) which is pivotally displaceable about a centre pivot (12) and has a series of sections (18) connected end-to-end. Each section is supported by a self-propelled tower (16) having a motor (20) for driving the tower, adjacent sections being able to flex with respect to one another. The various sections are kept in line as the boom rotates about the centre pivot by intermittently switching the various motors (other than that of the last tower) on and off. Switching of each motor is in response to a switching arrangement (24) which detects flexing of adjacent sections with respect to one another beyond a predetermined extent. To prevent damage to the irrigator in the event of malfunction of any of the switching arrangements, means including a programmed logic controller (42) is provided. This is programmed to sense if the motor of a selected tower is on or off for longer than a predetermined length of time and, in response thereto, to shut down the irrigator.

Description

CENTRE PIVOT IRRIGATOR AND METHOD OF OPERATING SUCH AN IRRIGATOR

This invention relates to a centre pivot irrigator and to a method of operating such an irrigator. More particularly the invention relates to a centre pivot irrigator of the kind comprising a boom which is pivotally displaceable about a centre pivot and has a series of sections connected end-to-end. Each section is supported by a self-propelled tower having a motor for driving the tower, adjacent sections being able to flex with respect to one another. The various sections are kept in line as the boom rotates about the centre pivot, by intermittently switching the various motors (other than that of the last or radially outermost tower) on and off. A centre pivot irrigator of this kind is herein referred to as a centre pivot irrigator of the kind described.

According to the invention there is provided a centre pivot irrigator of the kind described, which includes means for sensing if the motor of the tower of at least one of the sections other than the last section is on for longer than a first predetermined length of time or off for longer than a second predetermined length of time, and in response thereto to shut down the irrigator.

Where, in respect of the motor of the tower of said at least one of the sections, a contactor is provided for switching the motor on and off, said means may include a programmed logic controller (PLC) having an input coupled to the contactor.

Said at least one of the sections may be the first or radially innermost section of the irrigator.

The irrigator may in addition comprise means for sensing if the motor of the tower of a second one of the sections is on for longer than a third predetermined length of time or off for longer than a fourth predetermined length of time, the second section being the last but one section of the irrigator.

The irrigator may further in addition comprise means for sensing if the motor of the tower of a third one of the sections is on for longer than a fifth predetermined length of time or off for longer than a sixth predetermined length of time, the third section being the section nearest the mid-point between said first and second sections.

Further according to the invention there is provided a method of operating a centre pivot irrigator of the kind described, which method comprises sensing if the motor of the tower of at least one of the sections other than the last section is on for longer than a first predetermined length of time or off for longer than a second predetermined length of time, and in response thereto to shut down the irrigator.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings. In the drawings: Figure 1 is a diagrammatic plan view of a centre pivot irrigator in accordance with the invention;

Figure 2 is a detail of the part indicated at II in Figure 1 ; Figure 3 is a wiring diagram of a control panel forming part of the electrical system of the irrigator; and

Figure 4 is a wiring diagram of the remainder of the electrical system.

Referring first to Figures 1 and 2, reference numeral 10 generally indicates a centre pivot irrigator which comprises a pivot structure 12, a boom 14 extending radially from the pivot structure, and a series of self-propelled support towers 16 supporting the boom. The pivot structure provides the irrigator with a centre pivot about which the boom is displaced during operation. The boom 14 can move either forward, i.e. in the direction of arrow A, or in reverse, i.e. in a direction opposite the direction of arrow A.

The boom 14 comprises a series of pipe sections 18 which are connected end-to-end, there being one of the towers 16 at the end of each of the pipe sections. Each of the towers 16 comprises a pair of wheels 20 and an electric motor for driving the tower.

Adjacent pipe sections 18 are connected to one another by a short length of flexible pipe 22, which allows the pipe sections to flex with respect to one another.

For the string of pipe sections 18 to remain in a straight line as the boom rotates about the centre pivot, the various towers 16, from the centre pivot outwardly, have to travel progressively greater distances for any given period of time. To achieve this, each of the towers is provided with a switching arrangement 24 which comprises a series of links 26, a cam 28, and a microswitch 30. The switching arrangement 24 is of conventional construction and will therefore not be described in detail. It is so arranged that the contacts of the microswitch 30 change from a first state to a second state when the pipe section on the right hand side of Figure 2 (designated 18.2) moves ahead of the pipe section on the left hand side of the drawing (designated 18.1 ) to a predetermined extent, and back to the first state when the pipe section 18.1 moves ahead of the pipe section 18.2 to a predetermined extent. The microswitch 30 is connected to a contactor for switching the motor of that tower on or off. Assuming that the contacts of the microswitch 30 on the tower 16 at the right hand end of the pipe section 18.1 (which is closer to the pivot structure 12 than the pipe section 18.2) are in the first state and that, when the contacts are in this state, the motor of that tower is switched off, and assuming also that the motor of the tower at the right hand end of the pipe section 18.2 is switched on, the pipe section 18.2 will move ahead of the pipe section 18.1 , in the direction of arrow B, until eventually the contacts of the microswitch 30 change to the second state. This has the effect of switching on the motor of the tower at the right hand end of the pipe section 18.1 , allowing it to catch up with the tower at the right hand end of the pipe section 18.2, and so bringing the two pipe sections back into line. As the pipe section 18.1 moves ahead of the pipe section 18.2, the contacts of the microswitch change back to the first state, causing the motor of the tower at the right hand end of the pipe section 18.1 to switch off. The same process takes place at each of the towers, thus keeping the pipe sections of the entire boom in line. The speed of the irrigator is determined by the speed of the last tower.

A difficulty experienced with systems of this kind is that malfunction of the microswitch 30 or linkages 26 can cause serious damage to the irrigator. In some irrigators, in an attempt to overcome this difficulty, a back-up or "final" microswitch is provided, which will perform the necessary switching function should the microswitch 30 fail. This does not, however, help if the linkages 26 break or otherwise fail, or if, through some other defect, the motor does not switch on when it should switch on, or switch off when it should switch off. In accordance with the present invention the irrigator 10 is provided with a control panel 40 which includes a programmed logic controller (PLC) 42 (see Figure 4), the PLC being programmed to monitor the state of the contactor of each of a selected few of the towers. The control panel 40 is located at the pivot structure 12. As will become apparent from the description that follows, the PLC operates to detect when the motor of any of the selected towers is switched on for longer than it should be on, or is switched off for longer than it should be off, and in response thereto to shut the entire irrigator down.

Referring now to Figures 3 and 4, reference numeral 44 in Figure 4 indicates the motor of each tower, reference numeral 46 the corresponding contactor, and reference numeral 48 an outgoing 3-phase cable running from the control panel 40 and being connected to each of the motors via the corresponding contactor. As will become apparent from the description that follows, the PLC 42 is arranged to monitor the contactors 46 of three of the towers 16, namely the last but one tower (designated 1 T), the first tower (designated 3T), and a further tower (designated 2T) which is selected to be approximately midway between the towers 1T and 3T. In or on the control panel 40 there is an isolator switch

52, a circuit breaker 54, a first contactor 56 (for forward operation), a second contactor 58 (for reverse operation), a series of relays 60, 62, 64, 66, 68, 70, and 72, a 380^v to 220^v step-down transformer 74 whose output is connected to the L and N terminals of the PLC to provide the PLC with 220^v power, a number of green indicator lights 76, 78, 80, and 82, a red indicator light 84, and a number of push-button switches. 86, 88, and 90.

The control panel 40 has terminals 92 whereby an incoming 3-phase supply 93 is connected to the control panel, and terminals 94 whereby the outgoing cable 48 to the towers 16 is connected to the control panel.

The contactors 56 and 58 have normally closed auxiliary contacts 96 and 98, respectively, which serve as an interlock to prevent the contactors 56 and 58 from both being energized at the same time. When the one contactor 56 is energized the contacts 98 of the other contactor 58 will be closed, thus switching on the indicator light 80 to indicate forward operation, whereas, if the contactor 58 is energized, the contacts 96 will be closed, thus switching on the indicator light 78 to indicate reverse operation. The push-button switch 86 is connected to input terminal 0 of the PLC and is provided to enable the operator to control the start, stop, forward, and reverse functions of the irrigator. When the irrigator is off and the switch 86 is pressed and held for a short while, the irrigator switches on and automatically switches to a mode in which the irrigator runs forward at 100% speed, with all safety features being over-ridden. If no further switches are pressed within a predetermined period of time thereafter (e.g. about 2 minutes) the irrigator automatically shuts down again. When the irrigator is on and the switch 86 is pressed and released, the irrigator changes direction, i.e. from forward to reverse or from reverse back to forward. If it is pressed and held for a short while, the irrigator shuts down. All of this is achieved by suitable programming of the PLC.

The push-button switch 88 is connected to input terminal 1 of the PLC and is provided to enable the operator to change the speed of the irrigator. Each time it is pressed and released, the speed of the irrigator is reduced by a 10% decrement, until the speed has reduced to 10% of full speed, whereafter the speed changes back to 100%. When operating at 100% speed, either contactor 56 or

58 is energized continuously. When operating at reduced speed, the contractor in question is switched cyclically between the energized and de-energized conditions, the ratio of on to off times determining the speed of the irrigator. The push button switch 90 is connected to input terminal 5 of the PLC and is provided to enable the operator to select a number of other functions, as will be described in more detail hereinafter.

The control panel 40 further has a series of terminals designated PR SW, PUMP, KW, 3T, 2T, 1T, R, F, S, and N. The pair of terminals designated PR SW are, internally of the control panel, connected via a set of contacts of the relay 72 to input terminals 6 and 7 of the PLC. The irrigator is fitted with a pressure switch (not shown) which is arranged to sense the water pressure in the irrigator and is, externally of the control panel, connected across the PR SW terminals. The relay 72 is normally energized, closing its relay contacts. Should the irrigator lose pressure, the PLC will sense this via the input terminals 6 and 7 and may, for example, be programmed to shut the irrigator down in this event.

The pair of terminals designated PUMP are, internally of the control panel, connected across a set of contacts of the relay 70. The relay 70 is connected to output terminal 14 of the PLC. This will enable a remote pump whereby irrigation water is pumped to the irrigator to be switched on and off under control of the PLC. The terminal designated KW is, externally of the control panel, connected to the so-called "cat's whisker" limit switches located at the pivot structure 12. The cat's whisker switches are connected in parallel. The one switch is actuated to close when the boom 14 reaches a certain limit position when moving about the centre pivot in the forward direction, and the other switch is actuated to close when the boom reaches a certain limit position when moving in the reverse direction about the centre pivot. Actuation of either of the cat's whisker switches has the effect of energising the relay 72. The PLC will sense this and is programmed in response thereto to reverse operation of the irrigator. Operation of the push button switch 90 is as follows.

When it is pressed once and released, it brings into operation all the safety features of the irrigator. When pressed a second time and released it causes the PLC to energize the relay 70, thus switching on the remote pump. When pressed a third time and released, it causes the PLC to bring the pressure switch (connected to the terminals PR SW) into operation. When pressed a fourth time and released, it causes the PLC to bring into operation the automatic reverse feature of the irrigator, whereby the irrigator automatically reverses direction when the cat's whisker limit switches referred to above are actuated. The indicator light 76 is switched on under control of the PLC when the push button switch 86 has been operated to switch the irrigator on. The indicator light 82 is switched on under control of the PLC when the remote pump is switched on.

The terminal designated 3T is, externally of the control panel, connected to an auxiliary contact of the contactor 46 of the first tower 3T, whereby the motor 44 of that tower is switched on and off. Likewise, the terminals 2T and 1 T are connected to the auxiliary contacts of the contactors 46 of the towers 2T and 1 T respectively. The terminals designated 3T, 2T, and 1 T are, internally of the control panel, connected to the relays 68, 66, and 64 respectively. The relay contacts of the relay 68 are connected between one of the common terminals C (the one designated 100) of the PLC and the input terminal 4 of the PLC, so that the PLC can detect when the relay 68 is energized and when not. Likewise, the terminal designated 2T is connected to the relay 66, and the relay contacts of the relay 66 connected between the common terminal 100 of the PLC and input terminal 3 of the PLC, and the contact designated 1 T is connected to the relay 64, and the relay contacts of the relay 64 connected between the common terminal 100 and input terminal 2 of the PLC.

During normal operation of the irrigator, the contactor 46 of each of the towers 16 (except the last one when the irrigator is operating at full speed) should continuously switch between the on and off conditions. The PLC is programmed to sense if the contactor on the tower 3T is on for longer than a first predetermined length of time or off for longer than a second predetermined length of time and, if either of these conditions are met, to shut the irrigator down. Likewise, the PLC is programmed to detect if the contactor of the tower 1T is on for longer than a third predetermined length of time or off for longer than a fourth predetermined length of time and, if either of these conditions are met, to shut the irrigator down. Also, the PLC is programmed to detect if the contactor of the tower 2T is on for longer than a fifth predetermined length of time or on for longer than a sixth predetermined length of time and, if either of these conditions are met, to shut the irrigator down. The various predetermined times are set by suitable programming of the PLC.

The PLC 42 is therefore able to detect when there is a malfunction, regardless of the proper functioning of the switching arrangements 24. When the irrigator is shut down due to improper functioning, the red indicator light 84 is switched on under control of the PLC, via output terminal 15 of the PLC.

The terminal designated S is, internally of the control panel, connected to two bridged common terminals of the PLC (the ones designated 102 and 104). The relay 60 is connected to output terminal 10 of the PLC, and the relay 62 to output terminal 1 1 of the PLC. The terminal designated R is, internally of the control panel, connected via the relay contacts of the relay 60 to another one of the common terminals of the PLC (the one designated 106) and the terminal designated F is, internally of the control panel, connected via the relay contacts of the relay 62 also to the common terminal 106 of the PLC. Externally of the control panel, a safety wire 108 is connected to the terminal S and leads to the end of the boom 14. Likewise, wires 1 10 and 1 12 are connected to the terminals F and R respectively of the control panel and lead to the end of the boom. One side of the coil of each of the contactors 46 is connected to the safety line 108. The other side of the coil of the contactor 46 is connected via the corresponding microswitch 30 to either the line 1 10 or 1 12, depending on whether the switch is in its first or second state. Thus, when the irrigator is moving forward, the common 106 is connected to the line 1 10 via the terminal F, whereas, when the irrigator is moving in reverse, the common terminal 106 is connected to the line 1 12 via the terminal R.

The terminal N is connected to the star point of the 3- phase supply.

Claims

00/32031 _ •, -, _ PCT/IB99/01791CLAIMS:

1 . A centre pivot irrigator comprising a boom (14) which is pivotally displaceable about a centre pivot (12) and has a series of sections (18) connected end-to-end, each section being supported by a self-propelled tower (16) having a motor (44) for driving the tower, adjacent sections being able to flex with respect to one another, and the various sections being kept in line as the boom rotates about the centre pivot by intermittently switching the various motors (other than that of the last or radially outermost tower) on and off, characterized in that it includes means (40) for sensing if the motor of the tower (1 T, 2T...) of at least one of the sections other than the last section is on for longer than a first predetermined length of time or off for longer than a second predetermined length of time, and in response thereto to shut down the irrigator.

2. A centre pivot irrigator as claimed in claim 1 and comprising, in respect of the motor (44) of the tower of said at least one of the sections, a contactor (46) for switching the motor on and off, characterized in that said means includes a programmed logic controller (42) having an input coupled to the contactor.

3. A centre pivot irrigator as claimed in claim 1 or claim 2, characterized in that said at least one of the sections is the first or radially innermost section of the irrigator.

4. A centre pivot irrigator as claimed in claim 3, characterized in that it comprises means for sensing if the motor (44) of the tower of a second one of the sections is on for longer than a third predetermined length of time or off for longer than a fourth predetermined length of time, the second section being the last but one section of the irrigator.

5. A centre pivot irrigator as claimed in claim 4, characterized in that it comprises means for sensing if the motor (44) of the tower of a third one of the sections is on for longer than a fifth predetermined length of time or off for longer than a sixth predetermined length of time, the third section being the section nearest the mid-point between said first and second sections.

6. A method of operating a centre pivot irrigator comprising a boom (14) which is pivotally displaceable about a centre pivot (12) and has a series of sections (18) connected end-to- end, each section being supported by a self-propelled tower (16) having a motor (20) for driving the tower, adjacent sections being able to flex with respect to one another, and the various sections being kept in line as the boom rotates about the centre pivot by intermittently switching the various motors (other than that of the last or radially outermost tower) on and off, characterized in that it comprises sensing if the motor of the tower (1T, 2T...) of at least one of the sections other than the last section is on for longer than a first predetermined length of time or off for longer than a second predetermined length of time, and in response thereto to shut down the irrigator.

7. A method as claimed in claim 6, characterized in that said at least one of the sections is the first or radially innermost section of the irrigator.

8. A method as claimed in claim 7, characterized in that it comprises sensing if the motor of the tower of a second one of the sections is on for longer than a third predetermined length of time or off for longer than a fourth predetermined length of time, the second section being the last but one section of the irrigator.

9. A method as claimed in claim 8, characterized in that it comprises sensing if the motor of the tower of a third one of the sections is on for longer than a fifth predetermined length of time or off for longer than a sixth predetermined length of time, the third section being the section nearest the mid-point between said first and second sections.

10. A centre pivot irrigator substantially as herein described and illustrated.

1 1 . A method of operating a centre pivot irrigator, substantially as herein described with reference to the drawings.