Abstract:
The left and right truss rod assemblies of a truss that supports the span of an irrigation pipeline are bridged by a single sensor device. A movable linear connector in the sensor receives oppositely directed loads from axially spaced members of the two truss rod assemblies and provides a linear motion that can be transmitted to a control device to shut down the system if tension force in the truss becomes excessive. Movement of the linear connector is yieldably resisted by a resilient element, which resistance is overcome if and when the tension force in the truss exceeds a threshold level.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to agricultural irrigation machines and, more particularly, to a safety device for detecting untoward tension in an overhead pipeline span such as when one or more of the self-propelled towers supporting the span encounters an obstruction in the field. Such detection can be utilized to shut down the entire system, provide a warning signal, or initiate other appropriate action.  
       BACKGROUND AND SUMMARY  
       [0002]     The overhead pipelines of conventional agricultural irrigation systems are typically provided with a number of end-to-end spans or sections, each of which is supported by a self-propelled tower having ground-engaging wheels. Between each pair of towers, the pipeline span is typically maintained in a slightly upwardly arched or bowed configuration by a truss beneath the pipeline. Such truss typically includes a pair of left and right truss rods extending generally parallel to the pipeline on opposite lateral sides thereof, as well as an assemblage of other members interconnecting the truss rods and the pipeline.  
         [0003]     The present invention relates to a safety device that is incorporated into the truss of such a pipeline to detect excessive tension in the truss such as might occur in the event the machine encounters a serious obstruction during movement through the field. Such detection can then be used to actuate switching mechanism or the like to completely shut down the system or otherwise take corrective action.  
         [0004]     More particularly, the present invention contemplates an arrangement wherein both left and right truss rod assemblies of a truss are serviced by a single sensor that bridges the two assemblies and thus responds to untoward tension in the truss. In a preferred form of the invention, the sensor device includes a first component that bridges one pair of left and right truss rod members that are spaced axially from a second pair of left and right truss members. Another component bridges the second pair of truss rod members and is yieldably interconnected with the first component such that the two components can move relative to one another in an axial direction when a tension force exceeding a predetermined amount is applied to the truss. Preferably, the yieldable interconnection between the two components is established in part by a compressible element constructed of a suitable polyurethane material or the like. A draw bolt or other connector passes through a central bore of the compressible element and is anchored at one end to the first pair of truss rod members while having a suitable linkage such as a cable connected to the opposite end thereof for operating an electrical switch or the like associated with control circuitry for the motors that drive the ground wheels of the machine. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a fragmentary isometric view of an agricultural irrigation machine constructed in accordance with the principles of the present invention;  
         [0006]      FIG. 2  is an enlarged, fragmentary elevational view of a sensor device in accordance with the present invention incorporated into the truss beneath a span of the overhead pipeline of the machine;  
         [0007]      FIG. 3  is a fragmentary, bottom elevational view of the sensor device and associated truss members taken substantially along sight line  3 - 3  of  FIG. 2 ;  
         [0008]      FIG. 4  is a fragmentary isometric view of the sensor device from the bottom of the pipeline span; and  
         [0009]      FIG. 5  is an exploded isometric view of various parts of the sensor device and truss. 
     
    
     DETAILED DESCRIPTION  
       [0010]     The present invention is susceptible of embodiment in many different forms. While the drawings illustrate and the specification describes certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments.  
         [0011]      FIG. 1  illustrates an agricultural irrigation machine  10  of the “center pivot” style in which an overhead pipeline  12  is supported by a number of self-propelled towers  14  that swing the pipeline  12  about a central, stationary tower  16 . Pipeline  12  is coupled with a source of water under pressure so as to deliver the water to a plurality of sprinklers or the like (not shown) along the length of pipeline  12 . Ground wheels  18  associated with each tower  14  are driven by suitable motive means such as electric motors (not shown) but well known to those skilled in the art. U.S. Pat. No. 4,618,102 owned by the assignee of the present invention is hereby incorporated by reference into the present specification as an example of one such motor and gearbox arrangement.  
         [0012]     Although a center pivot irrigation machine has been illustrated in  FIG. 1 , it is to be understood that the principles of the present invention are not limited to that particular style of machine. Although for exemplary purposes the invention will hereinafter be described in connection with one of the trusses of rigidly interconnected spans of the pipeline  12  illustrated in  FIG. 1 , the present invention has utility in connection with any span of an irrigation machine utilizing a supporting truss. For example, a control device of the herein described type is particularly useful on a link span of a combination lateral move and center pivot unit wherein the link span has no mobile tower that directly supports the span; instead, it connects the outer end of the center pivot unit with the inner end of a lateral move unit so as to supply water to the corner or other hard-to-reach portion of a field. One such combination machine is disclosed in U.S. Pat. No. 4,674,681 owned by the assignee of the present invention and hereby incorporated by reference into the present specification.  
         [0013]     The pipeline  12  in  FIG. 1  comprises a series of pipeline spans  20  connected in end-to-end relationship. Each pipeline span  20  is provided with its own truss  22  that supports the span and maintains it in a slightly upwardly arched or bowed configuration. Among other structure, each truss  22  includes a pair of left and right truss rod assemblies  24  and  26  that extend generally parallel to pipeline span  20  below the latter and on opposite left and right sides thereof. Each of such truss rod assemblies  24 ,  26  typically utilizes rods of round cross-section or flat straps; however, wire cable or hollow tube and other members capable of being put in tension could also be used.  
         [0014]      FIGS. 2-5  afford more close-up views of the truss rod assemblies  24 ,  26 , particularly at a rigid joint between the short section  34  of pipeline at a mobile tower  14  and the next span  20 . Such a joint is denoted by the numeral  28  and includes a pair of flanges  30  and  32  on span  20  and short section  34  respectively. A suitable gasket  36  is sandwiched between flanges  30 ,  32  and compressed tightly by a series of circumferentially spaced bolts  38  between flanges  30 ,  32 .  
         [0015]     Each tension rod assembly  24 ,  26  includes a pair of truss members  40 ,  42  that are axially spaced apart. In the illustrated embodiment, the left and right truss members  40  of assemblies  24 ,  26  are connected at their remote ends to other portions of the truss  22 , while left and right truss members  42  serve as anchors for securing the proximal end of truss  22  with pipeline  12 . In the illustrated embodiment, each of the anchoring truss members  42  includes an anchoring portion  44  that is fixed as by welding to the underside of pipe section  34 , and a connecting portion  46  that extends downwardly at an angle from the outer end of anchoring portion  44 . Clearance notches  48  are provided in the flanges  30 ,  32  and gasket  36  to provide clearance for connecting portions  46 . As noted particularly in  FIG. 3 , connecting portions  46  of anchoring truss members  42  diverge as their outer and downward ends are approached, such divergence being at the same rate as the divergence of truss members  40  as also illustrated particularly well in  FIG. 3 . Each of the truss members  40 ,  42  has an enlargement  50  at its outer end.  
         [0016]     In accordance with the present invention, the truss  22  is provided with a tension sensor device  52  incorporated into and forming a part of truss  22 . Sensor  52  comprises a single sensor that is connected across both left and right truss rod assemblies  24 ,  26  for producing a linear displacement under significant load changes in truss  22 .  
         [0017]     In the illustrated embodiment, sensor  52  includes a first transverse component  54  generally in the nature of a rigid strap that interconnects the left and right truss members  40  just inboard of their enlargements  50 . Transverse component  54  may be attached to left and right members  40  by any suitable means such as, for example, by having notches  56  in the lower extremity of component  54  that are sized to receive the members  40  but prevent enlargements  50  from pulling therethrough.  
         [0018]     A second transverse component  58  of sensor  52  spans the anchoring truss members  42  just inboard of their enlargements  50  and is connected thereto by any one of a number of suitable means. In the illustrated embodiment, a pair of downwardly opening notches  60  in second component  58  are sized to receive anchoring truss members  42  but preclude passage therethrough of enlargements  50  so as to provide a means of connection of second component  58  with anchoring truss members  42 .  
         [0019]     In the illustrated embodiment, second component  58  includes a generally U-shaped piece  62  having a pair of legs  62   a  and  62   b , as well as a bight  62   c  interconnecting legs  62   a  and  62   b . Notches  60  are in bight  62   c . The ends of legs  62   a ,  62   b  remote from bight  62   c  are rigidly affixed to a cross bar  64  having a hole  66  ( FIG. 5 ) therethrough.  
         [0020]     First and second components  54 ,  58  of sensor  52  are yieldably and resiliently interconnected so as to permit relative movement therebetween. To this end, a connector in the form of a bolt  68  passes reciprocably through hole  66  in cross bar  64  and is joined at one end to first component  54  by a nut  70  and washer  72 . At its other end, connector  68  is connected to second component  58  by virtue of a compressible, resilient element  74  constructed of polyurethane material or the like. Compressible element  74  has a bore  76  therethrough ( FIG. 3 ) that receives connector  68 . One end of element  74  bears against the proximal side of cross bar  64 , while the opposite end of element  74  bears against a washer  78  beneath the head  80  of connector  68 . Movement of truss members  40  axially away from truss members  42  is thus resisted by compressible element  74  but is permitted when a predetermined tension force level tending to separate components  54  and  58  is exceeded.  
         [0021]     It will be appreciated that when truss members  40  separate axially from truss members  42  as a result of untoward tension in truss  22 , connector bolt  68  extends a corresponding amount from cross bar  64  of second component  58 . Such linear movement can be used to trigger an electronic device (not shown) that controls operation of the motors associated with ground wheels  18 . The resulting actuation of the electronic device can be used as a signal to completely shut down the motors which drive wheels  18  or to simply provide an appropriate alerting signal to some remote user that corrective action is needed. Electronic devices used to control irrigation machines are well known by those skilled in the art. One example of such a control is disclosed in U.S. Pat. No. 6,042,031 which is incorporated herein by reference.  
         [0022]     In order to transmit the linear movement of connector  68  to the electronic control device, a number of means may be utilized. In the illustrated embodiment, the head  80  of connector  68  is provided with a rigid eyebolt  82  that passes through a hole (not shown) in bight  62   c  and is connected at its distal end with a cable  84  or other link leading to the electronic device for mechanically actuating the same.  
         [0023]     Of course, although an electronic control device is the most preferred, in practice other types of control devices could be utilized. For example, various types of mechanical, hydraulic, pneumatic or water-powered devices may be acceptable.  
         [0024]     It will be appreciated that while sensor device  52  has been hereinabove described primarily in connection with sensing untoward tension in truss  22 , it could also be used to provide a linear signal in the event of untoward compression of the pipeline span  22 . Thus, instead of actuating the electronic device in response to a pulling on cable  84  due to increased extension of connector  68  from cross bar  64 , compressible element  74  could be subjected to a predetermined preload so as to produce a certain amount of extension of connector  68  from cross bar  64 . Then, in the event of untoward compression in pipeline span  20 , the axial space between truss members  40  and  42  would decrease, permitting connector  68  to be retracted within sensor  52  as compressible element  74  moves toward an uncompressed state. Such motion would be transmitted to the electronic device via the cable  84  or other link.  
         [0025]     The inventor(s) hereby state(s) his/their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his/their invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.