Abstract:
An output monitoring system and method for an air transport material delivery system that directs dry material entrained in pressurized air out of delivery tubes and against an inner surface of deflectors for even distribution. The output monitoring system has a plurality of sensors respectively affixed to the deflectors on the outer side thereof so as not to be directly contacted by the stream of air and dry material impacting the inner side. Each sensor generates a voltage which is indicative of the flowing or clogged condition of its corresponding delivery tube. This status information is dynamically provided to a display unit where it can be readily monitored by the operator of the air transport material delivery system during operation thereof to ensure that the delivery tubes are not blocked or, if a blockage occurs, that operation of the air transport material delivery system is suspended until the blockage is removed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is related to the field of application equipment for distributing dry material onto a field or the like and, more particularly, to an automatic output monitoring system for an air transport material delivery system. 
   2. Description of the Related Art 
   One method for spreading seeds or powder type fertilizers onto a field is to use a pressurized air transport material delivery system mounted to a tractor. The seed, fertilizer or other dry material is fed from a storage hopper to a manifold via a series of holes and funnels. In the manifold, the material is mixed with pressurized air from a turbine or compressor and sent down a set of horizontal delivery tubes from which the material exits at a high rate of speed. At the exit end of each tube, a metal deflector is positioned that redirects the material impinging on its inner surface downwardly, and disperses the redirected material evenly on the ground. 
   The air transport material delivery system may have up to 20 tubes, each of a different length. They are usually spaced evenly along a boom carried by the tractor in order to cover the most ground. The shortest tubes terminate immediately behind the tractor and the longest tubes generally extend out about 35 feet on either side of the tractor. In the case of a system with 20 tubes, ten tubes will extend out on each of the left and right sides. 
   A common problem encountered with machine-mounted air transport material delivery systems is that the funnels, orifices and tubes can become partially or completely blocked during operation. When this occurs, the driver of the machine may not realize there is a problem because the dust and small particle size make it very difficult for a loss in spread pattern to be visually perceived. Furthermore, the driver&#39;s position does not allow him or her to see the entire boom, but only the outermost deflectors. At a result, even if the spread pattern of the outermost deflectors could be visually monitored, blockage of the innermost deflectors would still go undetected. When blockage occurs, the driver may, without being aware of the existence of the problem, thereafter cover several acres while providing inadequate dry material distribution. 
   A system described in U.S. Pat. No. 5,831,542 for monitoring air seeder blockage uses a flexible piezoelectric element placed directly in the air/seed stream. Seed flow is detected on the basis of seeds striking the piezoelectric element, with seed flow rate being determined by counting the number of seed strikes. However, the piezoelectric element is susceptible to damage due to the continual bombardment thereof by the seed stream and may also be subject to other drawbacks and damage. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, the present invention provides a highly durable output monitoring system capable of reliably detecting a blockage in an air transport material delivery system for distributing dry material, such as seeds and fertilizer, over a geographic area. 
   In accordance with this and other objects, the present invention is directed to an output monitoring system for an air transport material delivery system having a storage hopper, a source of pressurized air and a plurality of delivery tubes which convey dry material entrained in the pressurized air from the storage hopper to respective tube exits. The air and entrained material exiting the tubes is deflected downwardly by a plurality of deflectors positioned adjacent the tube exits, thereby distributing the dry material evenly over a geographic area. 
   The output monitoring system includes a plurality of sensors, each of which is affixed to a deflector, but affixed in such a way so as not to be directly impacted by the stream of air and entrained material contacting the deflector. The sensors provide input to a respective plurality of sensor circuits which each convert the input into a voltage. The voltage inputs are provided to a concentrator circuit which monitors the inputs from each of the sensors and provides delivery tube status information to a display unit. This delivery tube status information can be readily monitored by the operator of the air transport material delivery system during operation thereof to ensure that the delivery tubes are not blocked or, if a blockage does occur, that operation of the system is suspended until the blockage is removed. 
   In a preferred form, the sensors are embodied as piezoelectric elements which are mounted on the outside of the deflectors. 
   Accordingly, it is an object of the present invention to automatically monitor and report the condition of a plurality of dry material delivery tubes during operation of an air transport material delivery system. 
   Another object of the present invention is to provide an an output monitoring system for an air transport material delivery system that detects the absence of dry material impact with at least one of a plurality of output deflectors using a sensor that detects changes in mechanical vibration to determine associated delivery tube blockage. 
   A further object of the present invention is to provide an output monitoring system for an air transport material delivery system that uses a piezoelectric sensing element to transform flexing movement in an output deflector into a voltage to determine the condition of an associated delivery tube. 
   A still further object of the present invention is to provide an output monitoring system for an air transport material delivery system that automatically notifies the operator of a clogged delivery tube. 
   Yet another object of the present invention is to provide an output monitoring system for an air transport material delivery system in which piezoelectric sensing elements are secured to the backs of output deflectors so as not to be impacted by the air and dry material output stream exiting the delivery tubes. 
   Still a further object of the present invention is to provide an output monitoring system for an air transport material delivery system in which material flow against a plurality of output deflectors is detected on the basis of sound. 
   Yet another object of the present invention to provide an output monitoring system for an air transport material delivery system that is not complex in structure and which can be manufactured at low cost while yet efficiently and dynamically monitoring and reporting delivery tube condition. 
   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. The drawings are not intended to be to scale. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an air transport material delivery system mounted at the rear of a tractor with an output monitoring system in accordance with the present invention. 
       FIG. 2  is a block diagram of the output monitoring system in accordance with the present invention. 
       FIG. 3  shows a hopper base plate with orifices therein for dry material flow within the air transport material delivery system of  FIG. 1 . 
       FIG. 4  is a perspective view of a portion of the air transport material delivery system mounted on a tractor of  FIG. 1 , showing the sensors of the output monitoring system. 
       FIG. 5  is a more detailed view of one of the sensors of  FIG. 4 . 
       FIG. 6  illustrates the display unit of the output monitoring system of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
   As broadly depicted in  FIG. 1  and summarized in the block diagram of  FIG. 2 , the present invention is directed to an output monitoring system generally designated by the reference numeral  10 , having a plurality of sensors  30  mounted to operate with an air transport material delivery system generally designated by the reference numeral  12 . The air transport material delivery system  12  is carried by a transport vehicle such as tractor  14 . Material to be delivered by the system can include, among other things, seeds and fertilizer which, for the purposes of ease in discussion, will be generally referred to hereinafter as “dry material”. 
   The air transport material delivery system  12  is of conventional design, including a hopper  16  that directs dry material to a manifold (not shown) via a series of funnels or orifices  18  in a base plate  19 , as representatively shown in  FIG. 3 . In the manifold, the dry material is mixed with pressurized air from a turbine or compressor (not shown) and sent down a set of generally horizontal delivery tubes  20  (see  FIG. 4 ) distributed along a boom  22  for distribution onto a field or other geographic area. This sort of air transport material delivery system is known in the art and therefore further details are not set forth herein. 
   As shown in more detail in  FIG. 4 , a metal deflector  24  is placed adjacent the exit  26  of each of the delivery tubes  22 . Dry material exiting the delivery tubes  22  impacts the inside surface or inner side  24   a  of the metal deflector  24  and is redirected by such impact in a downward direction so as to be evenly distributed over the ground. 
   The number of delivery tubes in the air transport material delivery system  12  can vary but for ease of explanation a system having twenty delivery tubes will be described. The exits  26  of these tubes are typically spaced evenly along the boom  22  carried by the tractor. The length of the boom  22  can also vary, but typically is on the order of 60 feet, such that the boom extends approximately 30 feet from each side of the tractor  14 . Hence, in the example being described, ten delivery tubes extend out along the 30 feet of boom length from each side of the tractor. 
   Given the span of the boom  22 , the delivery tubes  20  have different lengths depending upon the positions of their corresponding exits along the boom. The shortest tubes  20  terminate immediately behind the tractor, while the longest tubes  20  extend along the entire span of one side of the boom. 
   As previously discussed, a problem often arises when one or more of the delivery tubes  20  becomes blocked without such condition being detected by the operator of the tractor. To avoid this undetected blockage condition, the output monitoring system  10  according to the present invention includes a plurality of sensors  30 , one of which is mounted to the outside surface or outer side  24   b  of each deflector  24 . As disclosed herein, the outer side is opposite the inner side, but it is possible that a flange portion or other extension portion of the deflector, if present, could be used to support the sensor, provided that the sensor can be positioned thereon so as not to be impacted by the air stream and dry material output of the delivery tubes. 
   According to one preferred embodiment shown in detail in  FIG. 5 , the sensor  30  is a piezoelectric disk element  32  held by a mounting structure generally designated by the reference numeral  34 , which is coupled to the deflector  24 . The mounting structure  34  can be embodied as a DELRIN and PVC cup  35  or similar material, secured to the outer side  24   b  of the deflector  24  by any suitable fasteners such as bolts  37 . The piezoelectric disk  32  is held around its edges by the cup  35  so as to allow the center  39  of the disk to flex freely and thereby transform the movements of the deflector  24  into electrical voltages which are conveyed over a wired connection  36 . The voltages generated by the piezoelectric disk  32  are representative of the amplitude and frequency spectrum generated by the impacts of the dry material on the inner surface or side  24   a  of the metal deflector  24 . 
   The piezoelectric disk  32  can have a conventional sandwich construction of two metal plates on either side of a piezoelectric crystal. With this construction, the bottom plate is driven by a reference voltage RefV and the top plate is used to measure any voltages generated by the flexing of the disk. According to a preferred embodiment, the reference voltage is 2.5 volts such that the signal generated by the piezoelectric disk is an AC voltage centered on 2.5 volts. 
   The piezoelectric disk  32  will transform any flexing movement into a voltage. Mechanical vibrations, such as meshing gears, running engines or tires impacting the ground, are low frequency, generally less than 10 kHz, and generate peak-to-peak voltages on the order of hundreds of millivolts. Vibrations due to dry material impacting the metal deflector, on the other hand, tend to be above 20 kHz, generating peak-to-peak voltages on the order of only tens of millivolts or less. 
   Through experimentation it has been determined that various dry materials such as wheat, urea and ammonium sulfate, when delivered at various rates of 50, 137 and 200 lbs, all generate a peak in the energy spectrum in the ultrasonic frequency range of 40 kHz to 50 kHz. At the frequency of interest of 45 kHz, the piezoelectric disk will generate peak-to-peak voltages of approximately 12 mv to 160 mv due to the impact of the dry material against the metal deflector. This signal is in addition to the high amplitude, low frequency voltage generated due to mechanical vibrations, and is absent when no dry material is flowing, even though the air stream may still be present. 
   To detect this peak, a sensor circuit  40  is coupled to each of the sensors  30 , respectively, as shown in  FIG. 2 . Each sensor circuit is used to amplify, filter and generate a DC voltage that is representative of the amount of energy which is present at 45 kHz. The magnitude of this DC voltage is then used to indicate each delivery tube&#39;s condition, i.e., whether dry material in the tube is clogged or flowing. 
   More specifically, the sensor circuit includes an amplifier  41  that amplifies the voltage from the sensor  30 . The degree of amplification is limited to prevent clipping of the amplified signal, but is representatively a factor of four. The amplified signal is then passed through a band-pass filter  43  having a center frequency of about 45 kHz and stop band edges at about 40 kHz and 50 kHz, where it is further amplified and filtered. The overall gain of the band-pass filter  43  is representatively about 47.5. 
   The amount of energy in the signal is determined by converting the AC output from the band-pass filter  43  to a DC level using an AC/DC converter  45  which can be embodied as a half-wave rectifier. Specifically, since the AC signal from the filter  43  is centered on 2.5 volts, half-wave rectification is performed by level shifting the signal from 2.5 volts down to 0 volts. This clipped AC signal is amplified, preferably by a factor of five, and fed through a simple resistance-capacitance (RC) low-pass filter  47  to generate the DC level. The result is a DC voltage that is representative of the amount of energy present at 45 kHz. The DC voltage is amplified, preferably by a factor of six, and presented to a comparator  49  with hysteresis to determine the flow state of the delivery tube. 
   The combination of the RC low-pass filter  47  and the comparator  49  is used to prevent false indications. Because of the long time-constant of the RC filter  47 , generally about 1 second, momentary changes or disruptions in the flow of dry material will result in small changes in the DC voltage from the RC filter, but will not change the tube&#39;s flow status as indicated by the comparator  49 . Instead, a significant change in the tube flow, either from free flowing to plugged or vice versa, is required in order to effect a large enough change in voltage to alter the output state of the comparator  49 . Specifically, the signal must be above three volts before a “flow” condition is indicated and must be below two volts before a “clogged” condition is indicated. According to this preferred embodiment, the output of the comparator  49  is low for a flowing condition and high for a clogged condition but this could be reversed such that the output of the comparator  49  is high for a flowing condition and low for a clogged condition, as would be understood by persons of ordinary skill in the art. 
   In order to minimize the number of wires entering the cab of the tractor  14 , the outputs of all of the sensor circuits  40  are fed to a concentrator circuit  50  that is preferably mounted on one or more circuit boards (not shown) with the sensor circuits. A microprocessor  51  in the concentrator circuit  50 ′ monitors all of the inputs from the sensor circuits  40  and concentrates the results to produce a series of short messages that are sent over a wired connection  52  to the display unit  60 , representatively illustrated in  FIG. 6 , which is generally mounted in the tractor cab. These messages are sent continuously in order to notify the operator on a real-time basis of any changes in flow conditions. The messages are sent serially (one start bit, one stop bit, no parity) over the wired connection  52  via RS-485. Representative message format is summarized below: 
   
     
       
             
             
           
         
             
                 
             
             
               Message # 
               Data 
             
             
                 
             
           
           
             
               0 
               Status of left tubes 1-5 
             
             
               1 
               Status of left tubes 6-10 
             
             
               2 
               Status of right tubes 1-5 
             
             
               3 
               Status of right tubes 6-10 
             
             
               4 
               Number of channels being monitored 
             
             
                 
             
           
        
       
     
   
   Since not all output monitoring systems in accordance with the present invention will use all twenty of the sensors  30 , the present invention includes a switching mechanism  61  that allows the operator to select how many of the sensors  30  are to be monitored. This switching mechanism  61  may be embodied as a rotary switch that allows the operator to select a value of from between 0 and 9. For instance, selecting “6” would allow the operator to monitor six left side delivery tubes and six right side delivery tubes for a total of twelve channels. Selecting “0” would enable the operator to monitor all ten left side delivery tubes and all ten right side delivery tubes for a total of twenty channels. 
   As shown in  FIG. 6 , the display unit  60  also includes a plurality of numbered LEDs  63 ,  65  and a sound generating mechanism  67  such as a buzzer. According to the embodiment being described, the display unit includes 20 LEDs, ten left side LEDs  63  for the delivery tubes on the left side of the boom, and ten right side LEDs  65  for the delivery tubes on the right side of the boom. A microprocessor (not shown) in the display unit  60  decodes the incoming serial messages and drives the LEDs  63 ,  65  to inform the operator of the flow condition of each delivery tube. 
   According to a preferred embodiment, the LEDs  63 ,  65  are normally “off”. When a clogged tube condition is detected, the LED corresponding with the clogged tube is turned on and the buzzer  67  is activated. Alternatively, the LEDs  63 ,  65  being monitored may be illuminated at the outset to indicate flowing condition. Upon detection of a clogged condition, the corresponding LED would then be turned off. In either case, the buzzer  67  would activate upon detection of a clogged condition to provide an audible indication. 
   Message # 4  generated by the microprocessor  51  informs the display unit  60  of the number of channels being monitored, as set by the switching mechanism  61 . If not all of the channels are being monitored, and if the “off” condition of the LEDs is the indicator of proper flow status, the LEDs corresponding with the unmonitored tubes are permanently turned off. For example, if the system uses 16 delivery tubes, eight tubes on the right and eight tubes on the left, then the LEDs for the ninth and tenth delivery tubes on each side are turned off. Conversely, if the LEDs are set to be illuminated to indicate proper flow status, the LEDs corresponding with the unmonitored tubes are permanently turned on. 
   There are at least three failure conditions that the output monitoring system  10  detects and reports to the operator. First, if the wired connection  36  connecting the piezoelectric sensor  32  to the sensor circuit  40  breaks or becomes disconnected, a “clogged” condition is indicated for that particular sensor. Second, if the wire  53  connecting the sensor circuit  40  to the concentrator circuit  50  breaks or becomes disconnected, a “clogged” condition is indicated for that particular sensor. Third, if the communication wires  52  from the concentrator circuit  50  to the display unit  60  break or become disconnected, all of the LEDs  63 ,  65  will indicate a “clogged” condition. 
   The output monitoring system  10  is powered from the 12V electrical system of the tractor. 
   The present invention may further be embodied as a method of monitoring output from an air transport material delivery system that entrains dry material in pressurized air for conveyance through a plurality of delivery tubes to respective tube exits where the dry material is impacted against a plurality of deflectors positioned adjacent the tube exits for distribution over a geographic area. The method includes positioning a sensor on the outer or non-impacted side of at least one of the deflectors which is positioned adjacent a respective delivery tube and generating, by the sensor, an AC voltage in response to vibration at a frequency. The AC voltage is filtered to pass a signal with a frequency range of between about 40 kHz and 50 kHz, and then converted into a DC voltage representative of the amount of energy present at about 45 kHz. Based on this DC voltage, the flow status of dry material through the respective delivery tube can be determined. 
   The foregoing descriptions and drawings should be considered as illustrative only of the principles of the invention. The invention may be configured in a variety of shapes and sizes and is not limited by the dimensions of the preferred embodiment. Numerous applications of the present invention will readily occur to those skilled in the art. Therefore, it is not desired to limit the invention to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.