Abstract:
The monitor system for an anhydrous ammonia fertilizer injection system includes a manifold with a plurality of discharge lines connected to soil engaging knives. A temperature sensor is mounted in each discharge line. The temperature of fertilizer in each discharge line is measures and transmitted to a microprocessor in a console. The temperature in a discharge line is compared with the average temperature in the other discharge lines. This comparison is made for each discharge line connected to a manifold to determine the temperature variations. The variations are compared to a temperature variation number provided by the operator. If an excessive variation occurs a warning is provided. A console screen graph shows which discharge line needs inspection.

Description:
TECHNICAL FIELD 
       [0001]    The invention is a system for monitoring an anhydrous ammonia fertilizer applicator apparatus that includes a temperature sensor in each distribution line between a manifold and the associated injector knife, a monitoring console that receives temperature data from each distribution line, displays the temperature sensor data for the system operator to observe and provides an operator alert concerning a deviation in the temperature measured by one sensor relative to other sensors which exceeds an operator set deviation from the average of the temperatures in a number of the distribution lines at substantially the same time. 
       BACKGROUND OF THE INVENTION 
       [0002]    Growing plants need nitrogen. Plants such as maize (Indian corn) require a substantial quantity of nitrogen. The soil corn plants grow in obtains nitrogen from legumes such as soybeans, from snow and from other sources. Excess nitrogen will reduce yield of crops such as corn. Insufficient nitrogen will also reduce crop yield. Water used to irrigate plants generally contains minimal nitrogen. 
         [0003]    Anhydrous ammonia has been used for many years to provide nitrogen. The anhydrous ammonia is injected into the ground as a liquid or vapor. Injection of anhydrous ammonia into soil is subject to a number of problems. Determining the quantity of nitrogen to be added is complicated by the fact that a substantial quantity of nitrogen may be stored in the soil. Soil samples are required to determine the status of stored nitrogen that is available. The soil samples often indicate that the distribution of stored nitrogen varies from one location to another in each farm field. 
         [0004]    Anhydrous ammonia is one of the most efficient sources of nitrogen fertilizer for plant growth. Under atmospheric temperature and pressure anhydrous ammonia is a colorless gas. The gas is compressed into a liquid state for agricultural use. The liquid state can be maintained by pressure, by cooling or a combination of pressure and cooling. The equilibrium vapor pressure at sixty degrees Fahrenheit in a pressure tank is ninety three pounds per square inch (psi). 
         [0005]    The cost of anhydrous ammonia has increased overtime due in part to the increased use by farmers around the planet. Farmers have in the past applied anhydrous ammonia and other fertilizers to maximize crop yield. Farmers are forced today to consider the costs and reduce the use of anhydrous ammonia and other fertilizers, when the cost of additional fertilizers exceeds the value of a minimal increase in crop production. 
         [0006]    The loss of anhydrous ammonia needs to be limited to the extent possible. The over application in some areas of each field may also need to be limited or even eliminated. 
         [0007]    The change in some anhydrous ammonia from a liquid to a vapor makes accurate control of the application rate difficult. Vapor separated from the liquid results in the over application rate in some areas. The separation of vapor may also result in the loss of some anhydrous ammonia. 
         [0008]    Increased pressure in an anhydrous ammonia application system can keep the pressure of the liquid above the vapor pressure of the liquid at ambient temperatures. However, a pump in the supply system between a nurse tank and liquid discharge nozzle will create a pressure drop on the pump inlet side. This pressure drop will at times produce vapor. The anhydrous ammonia vapor will prevent accurate metering of a liquid and vapor mixture. Separation of the vapor generally results in a loss of some anhydrous ammonia. 
         [0009]    Reducing the temperature in an anhydrous ammonia application system can keep the temperature of the liquid below the temperature at which vapor could be formed. Temperature lowering is obtained by bleeding off some liquid, expanding the liquid into a cold vapor and passing the cold vapor through a heat exchanger. Anhydrous ammonia liquid passing through the heat exchanger is cooled. The vapor discharged from the heat exchanger is then injected into the ground. The vapor is not completely lost. However, some anhydrous ammonia vapor is added to one of several plant rows that also receives a metered quantity of liquid anhydrous ammonia. The additional anhydrous ammonia from vapor may provide excess nitrogen to one crop row and may change crop yield in that crop row. 
         [0010]    Anhydrous ammonia application systems with or without pumps as well as systems with or without cooling systems often include a flow sensor that measures the total flow rate. These systems include a servo valve that controls the total flow rate. A manifold divides the flow of anhydrous ammonia to soil cutting knives. The servo valve reduces the pressure of discharged anhydrous ammonia and may create some vapor. Vapor mixed with liquid anhydrous ammonia will result in an unequal flow from a manifold distributor downstream from a servo valve or other flow control device. 
         [0011]    A number of additional distribution problems may occur. Some of these problems are obvious to an operator without a sensor warning. A broken line between a supply tank and the distributor will generally create a visible cloud. A disconnect of an anhydrous ammonia tank would be obvious. The location of the disconnected trailer and tank would indicate where fertilizer application stopped. A plugged distribution line is however difficult to detect without a suitable monitor system. 
         [0012]    The liquid passes through various pipes and devices from the pressure tank to a manifold or distributor. The distributor divides the anhydrous ammonia liquid flow into a plurality of lines each of which is connected to a knife that opens a furrow in the ground. The furrow receives the anhydrous ammonia liquid and vapor and retains the nitrogen. The distributor divides liquid anhydrous ammonia into substantially equal flow through each line. However, if there is significant vapor mixed with the liquid, the distributor will not discharge equal quantities of fertilizer into each line. 
         [0013]    The devices between the pressure tank and the distributor varies from one fertilizer distributor system to another. The devices include off-on valves, flow measurement devices, metering valves, vapor separators, coolers, pumps, orifices, filters and other devices. Each of these devices may create a pressure drop. The pressure drops may create anhydrous ammonia vapors. 
         [0014]    Anhydrous ammonia applicators, with a large number of distribution lines and knives that open furrows, require flow splitters. The flow splitters divide the flow of liquid fertilizer into two or more equal fluid streams each of which is connected to a distributor. Distributors may be referred to as manifolds. Distributors have a limited number of discharge line ports. The number of distributors employed depend on the number of discharge ports in each distributor and the total number of furrow opening knives on the tool bar of the applicator. The flow splitters also produce pressure drops. 
         [0015]    The lines from a distributor to the knives are relatively long and extend along a tool bar or applicator frame. Tool bars and applicator frames often have wings that pivot up and down to follow the surface of a field. Each of the knives may be mounted on a shank that moves relative to the frame. The lines from the distributor to the knives or other furrow openers are subjected to the movements of the knives relative to the distributor. The discharge end of each line is also subjected to soil moved by the knives, crop material on the ground, and possible freezing or plugging. The movements of the lines may decrease the size of the inside passage, wear a hole in a line or even sever a line. 
         [0016]    The number of lines extending from each distributor to each of the knives and the small quantity of anhydrous ammonia passing through each line renders visual line monitoring difficult for an operator of an applicator. An applicator may have more than twenty four lines extending from two or more distributors. All of the lines extending from one distributor have a uniform length that is the same length as the length of the line to a knife that is the greatest distance from the distributor. The length of lines extending from one distributor are the same so that the pressure of anhydrous ammonia in the distributor forces the same quantity of fertilizer into each line. Lines with equal diameter and length have nearly the same resistance to flow, if the knives and lines are substantially identical to each other. 
         [0017]    All of the liquid and vapor exiting a manifold through a distribution line will flow to a knife unless there is a failure in the distribution line and knife assembly. The distribution lines are generally available for a visual inspection. Operators inspect the distribution lines from time to time. 
       SUMMARY OF THE INVENTION 
       [0018]    One or more anhydrous ammonia distribution manifolds are employed on each anhydrous ammonia fertilizer distributor. A distribution line is attached to a manifold discharge port and to an injector knife. The number of injector knives employed on each fertilizer applicator has increased. Multiple factors have caused the increase in the number of fertilizer distributor knives employed on each applicator. Primary factors include a reduction of soil compaction, a decrease in the availability of competent operators and the economic factors that require each acre of land to produce more food at a lower cost. 
         [0019]    Distribution lines attached to each of the manifold discharge ports have equal lengths to provide substantially equal flow through the manifold ports. Due to the variations in the distance from a manifold port to an injector knife a first distribution line extends from a manifold discharge port to the injector knife that is located the longest distance from the manifold. 
         [0020]    The first distribution line has sufficient length to accommodate movement of the injector knife relative to the manifold. The movement between the injector knife and the manifold is due to several features each of which is employed on some tool bars. These features include a spring steel shank that holds an injector knife, a knife holder attached a tool bar by links that permit the knife holder to move up and down to follow the ground surface, and a tool bar wing that is pivotally attached to a tool bar center section. 
         [0021]    The distribution lines attached to injector knives that are closer to a manifold than the first distribution line have excess line that is supported by the tool bar. These distribution lines are subjected to movements between the injector knives each distribution line is attached to, and the tool bar. All of the distribution lines are also subjected to rocks and other objects thrown up by the injector knives. The injector lines can be scraped, crimped, pulled apart or cut. 
         [0022]    Damage to one of the injector lines has been difficult to detect in an anhydrous ammonia system with a number of injector lines connected to one manifold. The quantity of fertilizer passing through each distributor line is a fraction of the fertilizer entering the manifold. Pressure sensors employed to monitor the flow of anhydrous ammonia from a storage vessel to the manifold are too slow. Most pressure sensors have a hysteresis characteristic that does not provide accurate pressure change data at times. 
         [0023]    The measurement of the temperature of liquid anhydrous ammonia flowing in each line from a distributor needs to be accurate, fast and should not produce a pressure drop. Temperature sensors that extend into the flow path of a liquid disturb the flow, can in some circumstances create some vapor and provide a lower temperature due to the heat required to change ammonia from a liquid to a gas. A temperature sensor that is in direct contact with the distributor housing or two close to the distributor housing may measure the housing temperature or be modified by the housing temperature. The housing temperature does not change significantly when there is a problem in one line. 
         [0024]    The anhydrous ammonia that pass from a distributor and into a line connected to a knife will be discharged into a furrow if the line and knife are in proper working condition. The anhydrous ammonia will be discharged if it is a mixture of vapor and liquid. The pressure, at the discharge end of the line, will be atmospheric pressure. It is therefore expected that some liquid will change to a gas by the time it is discharged at the knife. A temperature sensor in a line near the knife would indicate that freezing near the knife is likely and would subject sensor leads to failures. 
         [0025]    Under some temperature and humidity conditions, distribution knives and connected discharge ports may freeze. Thawing and unplugging a frozen knife and distribution line may be difficult. The operator is unlikely to discover the problem for sometime without a monitor. Such an occurrence would most likely result in reduced crop yield for the growing season. 
         [0026]    Temperature monitors provide accurate data several times per minute. The temperature sensors are mounted in a member such as aluminum that transfers heat rapidly. The sensor assembly is mounted in a flexible plastic tube that insulates the temperature sensor assembly from the heat of the manifold. The entire anhydrous ammonia fertilizer system is subjected to the same ambient temperature changes. The temperatures displayed for an operator of the fertilizer applicator are current temperatures within seconds and accurate within a fraction of a degree. 
         [0027]    Temperature is measured in anhydrous ammonia fertilizer distribution line monitors in combination with currently used fertilizer applicators. These applicators include systems without pumps and systems with pumps. The manifolds may be made of various materials and have various shapes. The manifold may receive fertilizer from a separate flow rate controller. A combination flow rate and flow divider may also supply fertilizer to the distribution lines. 
         [0028]    A fixed distribution cage has a cage cylindrical inside surface, a cage cylindrical outside surface, an anchor end and a free end. A plurality of axially elongated cage slots pass radially through the fixed distribution cage. The fixed distribution cage is press fit in the medium diameter bore. The anchor end of the fixed distribution cage engages the small ring shaped surface. Each of the plurality of axially elongated cage slots is aligned with one of the plurality of discharge ports. A seal is formed between the cylindrical outside surface of the fixed distribution cage and the medium diameter bore. 
         [0029]    A piston head includes a cylindrical wall with a radially outer surface and a radially inner surface. A transverse plate is integral with the cylindrical wall and divides the cylindrical wall into a head end skirt with a head end and a rod end skirt with a skirt rod end concentric with a piston head axis. A plurality of axially elongated piston slots are parallel with the piston head axis. Each of the plurality of axially elongated piston slots pass radially through the head end skirt between the transverse plate and the head end of the head end skirt. At least one bore through the transverse plate provides equal fluid pressure on the piston head. 
         [0030]    A piston shaft has a piston end. The piston end is connected to the transverse plate in the rod end skirt. The piston shaft also has a driven end. A cylindrical bearing surface of the piston shaft is between the piston end and the driven end. A first sealing ring groove in the cylindrical bearing surface and a second sealing ring groove in the cylindrical bearing surface divide the cylindrical bearing surface into a piston end bearing portion surface, a center portion bearing surface and a control end bearing portion surface. A head end resilient low friction seal is mounted in the first sealing ring groove. A control end resilient low friction seal is mounted in the second sealing ring groove. A connector rod is pivotally connected to the driven end. 
         [0031]    A control end insert has a base end received in the large diameter bore and clamped to the large ring shaped surface. A mast first cylindrical portion, of the control end insert, is received in the small diameter bore of the body. A mast second cylindrical portion has an outside diameter that is smaller than the small diameter bore and the radially inner surface of the cylindrical wall of the piston head. A mast ring shaped surface is between the mast first cylindrical portion and the mast second cylindrical portion. A mast end surface faces away from the base end. A mast central bore passes through the control end insert and is coaxial with the central axis of the body. 
         [0032]    The piston shaft extends from the transverse plate of the piston head passes through the central bore of the central end insert. The piston shaft holds the head end resilient low friction seal and the control end resilient low friction seal in the mast central bore and in sliding engagement with the mast central bore. The piston shaft holds the radially outer surface of the piston head in sliding and sealing engagement with the cage cylindrical inside surface of the fixed distribution cage. 
         [0033]    An inlet end cover is clamped to the inlet end of the cylindrical body. An inlet threaded bore in the inlet end cover is connected to the continuing supply line. 
         [0034]    An electric actuator is connected to the connector rod through a connecting rod drive assembly. The actuator moves the piston head relative to the fixed distribution cage to a position in which anhydrous ammonia flow through the plurality of axially elongated piston slots is blocked, to a position in which maximum anhydrous ammonia flow through the plurality of axially elongated piston slots and the plurality of axially elongated cage slots occurs. The actuator also moves the piston head relative to the fixed distribution cage to a position which provides a desired flow rate. 
         [0035]    Each of the plurality of axially elongated piston slots meters anhydrous ammonia fertilizer into the portion of an adjacent one of the plurality of axially elongated cage slots that is in communication with the axially elongated piston slot. 
         [0036]    The plurality of axially elongated piston slots has a piston slot length from a slot head end to a slot rod end that is substantially the same as the cage slot length from a first inside arcuate end to a second inside arcuate end. Each axially elongated piston slot has a piston slot width transverse to a piston head axis from an elongated first wall to an elongated second wall that is less than a cage slot width transverse to a cage axis from a first straight inside edge to a second inside straight edge. Each of the axially elongated cage slots in the fixed distribution cage increases in size from the cage cylindrical inside surface to the cage cylindrical outside surface. The transverse plate of the piston head includes a recess that receives a piston engaging surface of the piston shaft. 
         [0037]    The monitor and controller will work well with a variable orifice distribution assembly in which the control of the application rate of anhydrous ammonia fertilizer and the division of flow into a plurality of flow paths to each of a plurality of knives occurs in one distribution assembly. The monitor and controller will also work well with in an application system that has a flow rate controller which is adjustable to obtain a desired flow rate of anhydrous ammonia and supplies the anhydrous ammonia through a line to a separate manifold that divides the flow into a plurality of distribution lines. Each of the distribution lines supplies the fertilizer to one ground engaging knife. 
         [0038]    The cost of anhydrous ammonia fertilizer and the desire to control the quantity of fertilizer applied is mentioned above. However, the cost of fertilizer is minor compared to the decreased yield of grain in one row of plants that can occur in a short period of time when a distribution line is damaged or severed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0039]    The presently preferred embodiment of the invention is disclosed in the following description and in the following drawings, wherein: 
           [0040]      FIG. 1  is a perspective view of an anhydrous ammonia fertilizer knife, row unit and variable orifice distribution assembly, mounted on a tool bar with parts broken away; 
           [0041]      FIG. 2  is a side elevational view of the variable orifice distribution assembly; 
           [0042]      FIG. 3  is a front elevational view of the variable orifice distribution assembly; 
           [0043]      FIG. 4  is a bottom view of the variable orifice distribution assembly; 
           [0044]      FIG. 5  is a vertical sectional view of a cylindrical body of the variable orifice distribution assembly; 
           [0045]      FIG. 6  is a horizontal sectional view of the cylindrical body taken along line  5 - 5  in  FIG. 5 ; 
           [0046]      FIG. 7  is an enlarged side view of a fixed distribution cage of the variable orifice distribution assembly; 
           [0047]      FIG. 8  is a vertical sectional view of the fixed distribution cage taken along line  7 - 7  in  FIG. 7 ; 
           [0048]      FIG. 9  is a side elevational view of a piston head of the variable orifice distribution assembly; 
           [0049]      FIG. 10  is a sectional view of the piston head taken along line  9 - 9  in  FIG. 9 ; 
           [0050]      FIG. 11  is an enlarged elevational view of a piston shaft with a partial vertical section; 
           [0051]      FIG. 12  is a bottom view of a control end insert of the variable orifice distribution assembly; 
           [0052]      FIG. 13  is a sectional view of the control end insert taken along line  12 - 12  in  FIG. 12 ; 
           [0053]      FIG. 14  is an inside view of an inlet end cover of the variable orifice distribution assembly; 
           [0054]      FIG. 15  is a sectional view of the inlet end cover, through an inlet end cover axis; 
           [0055]      FIG. 16  is an enlarged elevational view of a connector rod of the variable orifice distribution assembly; 
           [0056]      FIG. 17  is a vertical sectional view through the variable orifice distribution assembly and a portion of the connector rod drive assembly; 
           [0057]      FIG. 18  is an elevational view of the variable orifice distribution assembly the attached connector rod drive assembly and a direct current actuator; 
           [0058]      FIG. 19  is an expanded view of the variable orifice distribution assembly; 
           [0059]      FIG. 20  is a schematic of the anhydrous ammonia fertilizer applicator system including the variable orifice distribution assembly; 
           [0060]      FIG. 21  is a schematic view of a control and monitoring system; 
           [0061]      FIG. 22  is a perspective view of an enlarged aluminum sensor body; 
           [0062]      FIG. 23  is a perspective view of containment tube; 
           [0063]      FIG. 24  is a perspective view of a temperature sensor assembly with a sensor, circuit board and two leads; 
           [0064]      FIG. 25  is a perspective view of a sensor potting resin; 
           [0065]      FIG. 26  is an enlarged perspective view of a temperature sensor; 
           [0066]      FIG. 27  is a graph of operation results of the temperature sensing and monitoring system of the anhydrous ammonia distribution and injecting system; and 
           [0067]      FIG. 28  is a schematic view of one distributor with a plurality of distribution lines each which is connected to one knife. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0068]    The anhydrous ammonia fertilizer distribution system  38  shown schematically in  FIG. 20  includes a pressurized supply vessel  40 , a heat exchanger  44 , flow meter  46 , an on and off valve  48  and a variable orifice distributor assembly  50 . A supply line  42  carries anhydrous ammonia from the supply vessel  40  to the heat exchanger  44 . A continuing supply line  52  carries anhydrous ammonia from the heat exchanger to the variable orifice distributor  50  through the flow meter  46  and the on and off valve  48 . The supply vessel  40  is pressurized by the vapor pressure of the anhydrous ammonia at the temperature of the liquid in the vessel. The vapor pressure in the supply vessel is generally between fifty pounds per square inch and one hundred and fifty pounds per square inch depending upon the temperature. At eighty degrees Fahrenheit the vapor pressure is one hundred and thirty eight pounds per square inch. The heat exchanger  44  cools the anhydrous ammonia to a temperature at which the vapor pressure of the anhydrous ammonia entering the variable orifice distributor assembly  50  is below the actual pressure and the liquid anhydrous ammonia is unlikely to change from a liquid to a vapor. The flow meter  46  creates no pressure drop or a very small pressure drop so that vapor is not created. The on and off valve  48  is a ball valve with a liquid passage cross section area that is substantially the same as the liquid passage cross section area of the supply line  42  and the continuing supply line  52 . A pressure drop is minimized and turbulence is minimized to reduce the pressure drop. Friction between the flowing liquid and the passage walls of the passages of the supply line  42  and the continuing supply line  52 , between the supply vessel  40  and variable orifice distributor apparatus  50  are minimized. However friction and some pressure drop will occur and increase fluid temperature. The heat exchanger  44  will reduce the creation of anhydrous ammonia vapor and may condense some vapor in the supply line  42 , to a liquid. 
         [0069]    The anhydrous ammonia entering the variable orifice distributor assembly  50  should contain very little vapor. The pressure drop between the supply vessel  40  and the variable orifice distributor  50  is minimized to reduce the production of liquid vapors. Elimination of a pump and a metering valve between the supply vessel  40  and the variable orifice distribution assembly  50  eliminates two significant vapor producers. 
         [0070]    The variable orifice distributor assembly  50  meters anhydrous ammonia and distributes the anhydrous ammonia through a plurality of discharge lines  440 . The variable orifice distributor  50  has a cylindrical body  80  with a central axis  82 . The body  80  has an inlet end  84 , a control end  86  and a cylindrical outer surface  88 . The inlet end  84  and the control end  86  are perpendicular to the central axis  82 . A central bore  90  through the cylindrical body  80  includes a small diameter bore  92  that is concentric with outer surface  88  and the central axis  82 . A large diameter bore  94  is concentric with central axis  82  and extends axially from the control end  86  to the small diameter bore  92 . A medium diameter bore  96  is concentric with the central axis  82  and extends axially from the inlet end  84  to the small diameter bore  92 . A large ring shaped surface  98 , between the small diameter bore  92  and the large diameter bore  94 , is perpendicular to the central axis  82  and faces toward the control end  86 . A small ring shaped surface  100 , between the medium diameter bore  96  and the small diameter bore  92 , is perpendicular to the central axis  82  and faces toward the inlet end  84 . 
         [0071]    A plurality of threaded bores  102 , in the body  80 , pass through the large ring shaped surface  98 . Each threaded bore  102  extends parallel to the central axis  82 . A dowel pin bore  104  passes through the large ring shaped surface  98 . A plurality of threaded bores  106  extend into the inlet end  84  of the cylindrical body  80  between the cylindrical outer surface  88  and the medium diameter bore  96 . Each of the threaded bores  106  extends parallel to the central axis  82 . 
         [0072]    A gasket recess  108  is provided in the cylindrical body  80  between the small diameter bore  92  and the large ring shaped surface  98 . An inlet end gasket recess  110  is provided in the body  80  between the inlet end  84  and the medium diameter bore  96 . A mounting groove  112  is provided in cylindrical outer surface  88  of the body  80 . The mounting groove  112  extends continuously around the body  80 . 
         [0073]    A plurality of discharge ports  114  extend radially outward from the medium diameter bore  96 . Each outlet port  114  has a radially inner portion  116  that is a cylindrical bore  118 . The radially outer portion  120  of each outlet port  114  is a threaded bore portion  122 . The threaded bore portion  122  has a diameter that is larger than the diameter of the cylindrical bore  118 . The cylindrical body  80 , as shown in  FIG. 5 , has seventeen discharge ports  114 . The number of discharge ports  114  can be changed. Seventeen ports can fertilize sixteen crop rows. Discharge ports  114  that are not required can be plugged. If more than seventeen discharge ports  114  are required for a large fertilizer applicator, additional variable orifice distributors  50  may be added. Row crop planters that plant eight, sixteen or twenty four rows per pass through a field are employed by farmers. A few large farmers employ planters that plant thirty six rows on each pass through a field. It is possible to make two or more passes through a field to apply anhydrous ammonia to an area planted during one pass by a planter and still have the desired spacing between plant rows and the fertilizer. 
         [0074]    A fixed distribution cage  130  is shown in  FIGS. 7 and 8 . The distribution cage  130  is a tubular member with a cylindrical inside surface  132  and a cylindrical outer surface  134 . The cylindrical outer surface  134  has a fixed cage diameter that is slightly larger than the diameter of the medium diameter bore  96  of the cylindrical body  80 . The fixed distribution cage  130  includes an anchor end  136  and a free end  138 . The fixed distribution cage  130  is pressed into the medium diameter bore  96 . A axis  140  of the fixed distribution cage  130  is perpendicular to the anchor end  136  and the free end  138 . The axis  140  is also coaxial with the cylindrical inside surface  132  and the cylindrical outer surface  134 . 
         [0075]    Seventeen axially elongated slots  142  pass through the fixed distribution slot from the cylindrical inside surface  132  to the cylindrical outer surface  134 . Each axially elongated slot  142  has a straight first inside edge  144  and a straight second inside edge  146 . The straight first inside edge  144  and the straight second inside edge  146  are parallel to the axis  140  of the fixed distribution cage  130 . Each elongated slot  142  has an inside arcuate end  148  positioned toward the free end  138  of the fixed distribution cage  130 . Each elongated slot  142  also has an inside arcuate end  150  positioned toward the anchor end  136  of the fixed distribution cage  130 . 
         [0076]    Walls  152  of each axially elongated slot  142  extend radially outward from the inside edges at an angle  154  of fifteen degrees thereby increasing the area of each of the elongated slot from the cylindrical inside surface  132  to the cylindrical outside surface  134 . Each axially elongated slot  142  has a straight first outside edge  156  and a straight second outside edge  158 . The straight first outside edge  156  and the straight second outside edge  158  are parallel to the axis  140  of the fixed distribution cage  130 . Each elongate slot  142  has an outside arcuate end  160  positioned toward the free end  138  of the fixed distribution cage  130 . Each elongated slot  142  also has an outside arcuate end  162  positioned toward the anchor end  136  of the fixed distribution cage  130 . 
         [0077]    The inside arcuate end  148  is spaced from inside arcuate end  150  a distance, parallel to the axis  140 , that is one third of the minimum distance from the anchor end  136  to the free end  138  of the fixed distribution cage  130 . The outside arcuate end  160  of each axially elongated slot  142  is midway between the anchor end  136  and the free end  138  of the fixed distribution cage  130 . There is no fluid passage through the cylindrical inside and outside surfaces  132  and  134  of the fixed distribution cage  130  between the axially elongated slots  142  and the free end  138  of the fixed distribution cage. All anhydrous ammonia that passes through the axially elongated slots  142  is directed out of the cylindrical body  80  through the discharge ports  114 . The cylindrical outside surface  134  of the fixed distribution cage  130  cooperates with the walls of the medium diameter bore  96  to prevent leakage between discharge ports  114 , when each axially elongated slot  142  is in radial alignment with one of the discharge ports  114 . 
         [0078]    A piston head  170  has a cylindrical wall  172 . The cylindrical wall  172  has an radially outer surface  174  with an outside piston diameter. The outside piston diameter is substantially the same as the diameter of the cylindrical inside surface  132  of the fixed distribution cage  130 . A transverse plate  176  is integral with the cylindrical wall  172 . An upper skirt  178  extends from the transverse plate  176  to a skirt head end  180 . A rod end skirt  182  extends from the transverse plate  176  to a skirt rod end  184 . a piston head axis  186 , of the piston head  170 , is coaxial with the radial outer surface  174 . The fixed distribution cage  130  is pressed into the medium diameter bore  96  until the anchor end  136  seats on the small ring shaped surface  100 . There is a slight interference fit to insure that the fixed distribution cage  130  does not move relative to the cylindrical body  80  after being clamped in place as explained below. 
         [0079]    The upper skirt  178  has seventeen slots  188 . Each slot  188  has an elongated first wall  190  and an elongated second wall  192  that are parallel with the piston head axis  186 . Each slot  188  has a head end wall  194  that is perpendicular to the piston head axis  186  and spaced from the skirt head end  180 . A rod end  196  of each slot  188  is transverse to the piston head axis  186  and in a plane that includes the head end surface  198  of the transverse plate  176 . The length of the slots  188  parallel to the piston head axis  186  is substantially the same length as the length of the axially elongated slots  142  through the fixed distribution cage  130 . The elongated first wall  190  and the elongated second wall  192  of each slot  188  in piston head  170  are closer together than the first straight inside edge  144  and the second inside edge  146  of axially elongated slot  142 . During flow of anhydrous ammonia through the variable orifice distribution assembly  50 , a slot  188  is the primary flow restrictor. Liquid and vapor that passes through one slot  188  is restricted to move through the aligned slot  142  and through a line  440  to a knife  388  in communication with the one slot. The rod end skirt portion  182  has no passages through the cylindrical wall  172  between the transverse plate  176  and the skirt rod end  184 . The rod end skirt portion  182  has a cylindrical rod end inside surface  208  that is coaxial with the piston head axis  186 . A beveled surface  200  extends from the cylindrical rod end inside surface  208  to the skirt rod end  184  and continuously about the piston head axis  186 . A cap screw bore  202  passes through the center of the transverse plate  176 . Two small diameter bores  204  pass through the transverse plate  176  to equalize pressure on the cylindrical rod end inside surface  208  and the rod side  206  of the transverse plate, with pressure on the head end surface  198  of the transverse plate. A closed end dowel pin bore  210  extends into the transverse plate  176  from the rod side  206 . 
         [0080]    A piston shaft  212 , shown in  FIG. 11 , is a cylindrical rod with a piston end  214  and a driven end  216 . The piston end  214  includes a piston engaging surface  218 , a threaded bore  220  and a dowel pin bore  222 . The piston end  214  with the piston engaging surface  218  is received in a recess  207  in the transverse plate  176 . The cylindrical wall  209  of the recess  207  engage the piston shaft  212  to center the piston head  170  on the piston shaft. The threaded bore  220  is coaxial with the piston shaft  212  and perpendicular to the piston engaging surface  218 . The dowel pin bore  222  is radially spaced from the threaded bore  220  and perpendicular to the piston engaging surface  218 . A cylindrical bearing surface  224 , on this piston shaft  212 , extends from the piston engaging surface  218  toward the driven end  216 . Two sealing ring grooves  226  and  228  divide the bearing surface  224  into a piston end bearing portion cylindrical surface  230 , a center portion bearing cylindrical surface  232  and a remote end bearing portion cylindrical surface  234 . Resilient low friction seals  236  and  238 , shown in  FIG. 17 , are mounted in the sealing ring grooves  226  and  228 . A dowel pin  240  is mounted in the dowel pin bore  222  in the piston shaft  212  and dowel pin bore  210  in the transverse plate  176  of the piston head  170 . A cap screw  242  passes through a lock washer  244 , the cap screw bore  202  through the piston head  170  and screws into the threaded bore  220 . The cap screw  242  is tightened to secure the piston head  170  to the piston shaft  212  and retain the dowel pin  240  in the dowel pin bore  222  and the dowel pin bore  210 . 
         [0081]    A control end insert  250 , of the variable orifice distributor assembly  50 , includes a base  252 , a mast  254 , and a central bore  256 . The central bore  256  has a control end insert axis  258 . A base cylindrical outer surface  260  is coaxial with insert axis  258 . The diameter of the base outer cylindrical surface  260  is substantially the same diameter as the large diameter bore  94  of the cylindrical body  80 . The axially outer surface  262  of the base  252  is transverse to the insert axis  258 . An axially inner surface  264  of the base  252  is transverse to the control end insert axis  258  and parallel to the axially outer surface  262 . The mast  254  has a mast end surface  266  that is parallel to the axially outer surface  262 . A first cylindrical portion  268  of the mast  254 , extends axially from the inner surface  264  of the base  252  to a ring shaped surface  270  that is perpendicular to the control end insert axis  258 . A second cylindrical portion  272 , of the mast  254 , extends from the ring shaped surface  270  of the first cylindrical portion  268  to mast end surface  266 . The first cylindrical portion  268  has a larger diameter than the diameter of the second cylindrical portion  272 . A plurality of space apart bores  276  pass through the base  252  from the axially outer surface  262  and through the axially inner surface  264 . Each of the plurality of spaced apart bores  276  includes a counter bore  278  that extends through the outer surface  262  of the base  252 . Two closed end threaded bores  280  are provided in the base  252  of the control end insert  250 . Both threaded bores  280  pass through the axially outer surface  262  of the base  252 . 
         [0082]    An inlet end cover  282 , of the variable orifice distribution assembly  50 , is shown in  FIGS. 14 and 15 . The inlet end cover  282  has an outside cover surface  284  and an inside cover surface  286 . The outside cover surface  284  is a flat surface that is perpendicular to an inlet end cover axis  290 . The inside cover surface  286  is parallel to and spaced from the outside cover surface  284 . An outer cylindrical surface  288  is concentric with the inlet cover axis  290 . A central inside cover surface  292  is transverse to the inlet cover axis  290 . The inside cover surface  286  is located axially between the outside cover surface  284  and the central inside cover surface  292 . A truncated conical surface  294  extends from the inside cover surface  286  to the central inside cover surface  292 . An inlet threaded bore  296  is coaxial with the inlet end cover axis  290 . The inlet threaded bore  296  has tapered pipe threads that are commonly employed in liquid fertilizer conveyor systems. A different liquid inlet bore thread could be employed if desired. Six bolt bores  298  are provided through the inlet end cover  282 . The bores  298  are spaced an equal distance from the inlet end cover axis  290  and pass through the outside cover surface  284  and the inside cover surface  286 . A threaded bore  300  is provided in the inlet end cover  282 . The threaded bore  300  is positioned to a side of the inlet threaded bore  296  and extends from the outside cover surface  284  to a bore bottom  302 . A small bore  304  passes through the bore bottom  302  and the central inside cover surface  292 . A pressure gauge (not shown) may be mounted in the threaded bore  300  if desired. The pressure gauge will indicate the pressure on anhydrous ammonia entering the variable orifice distribution assembly  10 . The pressure will let the operator know if there is a blockage to flow upstream or if the supply tank is empty. The pressure will also permit an operator to determine if there is significant gas or vapor in the anhydrous ammonia fertilizer. A plug can close the threaded bore  300  if pressure measurements are not needed. 
         [0083]    A connector rod  306 , shown in  FIGS. 16 and 18  is connected to the piston shaft  212  by a pivot pin  308 . The pivot pin  308  passes through a bore  310  through the connecting rod  306  and a bore  312  through the piston shaft  212 . An offset  314  in the connector rod  306  moves a second bore  316  to one side of a connector rod portion  318  with the bore  310 . 
         [0084]    The order of assembly of the variable orifice distribution assembly  50  can be varied somewhat from the order set forth below. However, the final position of most parts is fixed. 
         [0085]    The fixed distribution cage  130  is pressed into the medium diameter bore  96  through the inlet end  84  of the cylindrical body  80 . Each axially elongated slot  142  is centered on one of the cylindrical bores  118  of a discharge port  114 . Alignment of one elongated slot  142  with an adjacent cylindrical bores  118  will align all of the elongated slots with an adjacent cylindrical bore. The fixed distribution cage  130  is pressed into the medium diameter bore  96  until the anchor end  136  of fixed distribution cage engages the small ring shaped surface  100 . The press fit of the fixed distribution cage  130  in the cylindrical body  80  creates a seal between each axially elongated slot  142  and the adjacent cylindrical bore  118 . 
         [0086]    The control end insert  250  has a base  252  that is received in the large diameter bore  94  of the cylindrical body  80 . The mast  254 , of the control end insert  250 , includes a first cylindrical portion  268  that is received in small diameter bore  92  of the cylindrical body  80 . The engagement between first cylindrical portion  268  and the small diameter bore  92  holds the control end insert axis  258  coaxial with the central axis  82  of the cylindrical body  80 . Engagement, if any, between the base cylindrical outer surface  260  and the large diameter bore  94  may also holds the control end insert axis  258  coaxial with the central axis  82  of the cylindrical body  80 . Engagement of the large ring shaped surface  98 , of the cylindrical body  80 , and the axially inner surface  264  axially positions the control end insert  250  along the central axis  82  of the cylindrical body  80 . 
         [0087]    A dowel pin  320  received in a dowel pin bore  104  in the cylindrical body  80 , and a dowel pin bore  322  fixes the position of the control end insert  250  about the central axis  82 . A gasket  324  is received in gasket recess  108  in the cylindrical body  80 . Bolts  326  pass through bores  276  through the base  252  and screw into threaded bores  102  in the body  80  to clamp the control end insert  250  to the large ring shaped surface  98 . The gasket  324  prevents leakage of fertilizer between the cylindrical body  80  and the control end insert  250 . 
         [0088]    The piston head  170 , and attached piston shaft  212  have a resilient first seal  236  mounted in sealing ring groove  226 . A resilient second seal  238  is mounted in sealing ring groove  228 . The driven end  216  of the piston shaft  212  is inserted into the central bore  256  from the mast end surface  266 . The central bore  256 , of the control end insert  250 , cooperates with the piston end cylindrical portion bearing surface  230 , the central cylindrical portion bearing surface  232 , and the remote end cylindrical portion bearing surface  234  of the piston shaft  212  to hold the piston head axis  186  parallel to the control end insert axis  258 . All three cylindrical portion bearing surfaces  230 ,  232  and  234  remain in at least partial engagement with the central bore  256  through the control end insert  250  during operation of the variable orifice distribution assembly  50 . 
         [0089]    An inlet end gasket  340  is positioned in the inlet end gasket recess  110  in the inlet end  84  of the cylindrical body  80 . The truncated conical surface  294  on the inlet end cover  282  centers the cover relative to the medium diameter bore  96 . The inlet end gasket  340 , in the inlet end gasket recess  110 , is engaged by the conical surface  294  and the inside cover surface  286  and seals between the inlet end  84  of the cylindrical body  80  and the inlet end cover  282 . Bolts  342  pass through lock washers  344  and bolt bores  298  and screw into threaded bores  106  to clamp the inlet end cover  282  to the cylindrical body  80   
         [0090]    The connector rod  306  is inserted into a groove  346  in the driven end  216  of the piston shaft  212 . A pivot pin  308  passes through a pin bore  312  through the piston shaft  212  and the bore  310  in the connector rod  306 . 
         [0091]    A connector rod driver assembly  350  shown in  FIG. 18 , includes a housing  352  clamped to the control end insert  250  by bolts  354  that are received in closed end threaded bores  280  shown in  FIG. 12 . A crank shaft  356  is journaled in the housing  352  by bearings  358  and  360 . A bell crank  362  is fixed to the crank shaft  356 . A shoulder screw  364  passes through the second bore  316  in the connector rod  306  and screws into the bell crank  362 . Pivotal movement of the crank shaft  356  moves the connector rod  306  and slides the piston shaft  212  in the central bore  256  of the control end insert  250 . Movement of the piston shaft  212  results of movement of the piston head  170  in the fixed distribution cage  130  as described below. The connector rod  306  is held by the shoulder screw  364  for pivotal movement about a screw axis parallel to the shaft axis of crank shaft  356 . The connector rod  306  prevents pivotal movement of the piston shaft  212  bout the control end insert axis  258  and the central axis  82  of the central bore  90 . 
         [0092]    A direct current (DC) actuator  370  is connected to the housing  352  and the crank shaft  356  to control the position of the piston head  170  relative to the fixed distribution cage  130 . 
         [0093]    Linear movement of the piston head  170  to a position close to the central inside cover surface  292  of the inlet end cover  282  moves the piston slots  188 , of the piston head  170 , and the head end skirt  178  to a position in which the flow of fluid fertilizer such as anhydrous ammonia through the slots  188  is blocked by the cylindrical inside surface  132  of the fixed distribution cage  130  between the free end  138  and the axially elongated slots  142 . The cylindrical inside surface  132  of the fixed distribution cage  130  has an inside diameter that is substantially the same as the outside diameter of the head end skirt  178  of the piston head  170 . The flow of fluid between the radial outer surface  174  of the piston head  170  and the cylindrical inside surface  132  of the fixed distribution cage  130  is blocked. However, the piston head  170  is permitted to move axially relative to the fixed distribution cage  130  with a minimal force applied by the connector rod  306 . 
         [0094]    The piston head  170  is shown in a closed position in  FIG. 17 . Retraction of the piston shaft  212  from the central bore  256  in the control end insert  250  moves the slots  188  in the piston head  170  axially and into alignment with the axially elongated slots  142  and provide the maximum area flow path through each discharge port  114 . As the piston shaft  212  is retracted from the closed position adjacent to central inside cover surface  292  of the inlet end cover  282 , the rod end skirt portion  182  of the piston head  170  moves into the open space  380  between the small diameter bore  92  in the cylindrical body  80  and the second cylindrical portion  272 . A ring shaped surface  270  on the control end insert  250  closes the control end of the open space  380 . As the rod end skirt portion  182  moves into a selected position in the open space  380 , the second cylindrical portion  272  of the control end insert  250  is positioned inside the cylindrical rod end skirt portion  182 . Upon the skirt rod end  184  reaching ring shaped surface  270 , the open space  380  is nearly filled. The mast end surface  266  approaches the rod side  206  of the transverse plate  176 . The second cylindrical portion  272 , of the control end insert  250 , substantially fills the space inside the rod end skirt portion  182 . Fluid that is displaced as the piston head  170  moves to a position closest to the control end  86  of the cylindrical body  80 , passes through the small diameter bores  204  and into the head end skirt  178 . All of the anhydrous ammonia or other fluid between the transverse plate  176  and the inlet end cover  282  is moveable toward the slots  188  and out of the cylindrical body  80 . There is a minimal quantity of fluid between the rod side  206  at the transverse plate  176  and the control end insert  250 . It is desirable to minimize the quantity of fluid that is between the transverse plate  176  and the control end insert  250 . Static fluid may in some circumstances become a gas. 
         [0095]    Positioning the piston head  170  in a position in which the slots  188  in the head end skirt  178  are axially positioned along the central axis  82  to be centered on the axially elongated slots  142  in the fixed distribution cage  130  will provide the maximum flow rate of a fluid such as anhydrous ammonia through open discharge ports  114 . Maximum fluid flow rate is generally not desired. The piston head  170  and the piston shaft  212  are moved toward the inlet cover  282  to reduce the flow rate of fluid. The closer the piston head end  170  is to the inlet end cover  282  the slower the flow rate. When the rod ends  196  of the slots  188  are closer to the inlet end cover  282  than the inside arcuate ends  148  of the axially elongated slots  142  in the fixed distribution cage  130  the flow of fluid will be blocked. 
         [0096]    A tool bar  386  employed to carry knives  388  that cut a slot in soil that receives anhydrous ammonia or other liquid fertilizer can take different forms. The tool bar may be a single bar supported by ground engaging wheels and pulled by a tractor or other suitable vehicle. Such a tool bar may be moveable up or down relative to the wheels to control the depth of penetration of the knives. These tool bars may have foldable wings that reduce the total width for transport on roads. 
         [0097]    The tool bar  386  may be the tool bar disclosed in U.S. Pat. No. 5,540,290 to Peterson et al. the disclosure of which is incorporated herein by reference. The tool bar is mountable on a three point hitch of a tractor. The tool bar has a center section attached to the hitch and moveable up and down by the hitch. One or more wings are pivotally attached to each end of the center section. The center section and the wings are transverse to the direction of forward movement of the tractor. 
         [0098]    A plurality of row units  400  are clamped to the tool bar  386 . 
         [0099]    Each row unit  400  has a frame  402  clamped to a tool bar  386 . A pair of spaced apart parallel upper links  404  are pivotally attached to the frame  402  by a pivot member  406 . A pair of spaced apart parallel lower links  408  are pivotally attached to the frame  402  by a pivot member  410 . Trailing ends of the upper links  404  are pivotally attached to a mast assembly  412  by pivot member  414 . Trailing ends of the lower links  408  are pivotally attached to the mast assembly  412  by pivot member  416 . The pivot members  406 ,  410 ,  414  and  416  cooperate with the frame  402 , the upper links  404 , the lower links  408  and the mast assembly  412  to form a pantographic linkage. The linkage permits up and down movement of the mast assembly  412  relative to the tool bar  386 . A shank support bar  418  is pivotally attached to the mast  412 . A spring steel bar  420  is clamped to the shank support bar  418  by a pair of U-bolts  422 . A knife  388  is secured to the spring steel bar  420 . A pair of gauge wheels  426  and  428  are journaled on arms  430  and control the depth of penetration of the knife  388  by following the surface of the ground and moving the mast  412  up and down relative to the tool bar  386 . A disk coulter  432  is supported by the mast  412 , positioned between the gauge wheels  426  and  428  and rotates about a transverse horizontal axis. The disk coulter  432  severs old crop material forward of the knife  388 . 
         [0100]    A depth control linkage assembly  434  adjusts the position of the position of the gauge wheels  426  and  428  relative to the mast assembly  412 . An adjustable down pressure spring assembly  436  transfers weight from the tool bar  386  to the disk coulter  432  and the knife  388  when required by ground conditions. A spring adjustment assembly  442  adjust the down pressure exerted on the mast  412  by the springs  436 . A spring trip assembly  438  permits the support bar  418  and the knife  388  to pivot upward and rearward when the knife  388  contacts an obstruction. U.S. Pat. No. 5,529,128 to Peterson et al., which is incorporated herein by reference, describes the depth control linkage assembly  434 , the adjustable down pressure spring assembly, and the spring trip assembly  438  in detail. The number of row units  400  and the spacing between row units can be adjusted as desired. Each knife  388  is connected to a discharge port  114  of the variable orifice discharge assembly  50  by a fertilizer discharge line  440 . 
         [0101]    A fertilizer tank and trailer hitch assembly  450  is clamped to the tool bar  386  and extends rearward from the tool bar. The variable orifice discharge assembly  50  may be mounted on the hitch assembly  450 , of the tool bar  386 . 
         [0102]    The anhydrous ammonia fertilizer applicator monitor system shown schematically in  FIG. 21  is usable with the anhydrous ammonia applicator described above. The control system has four section manifolds  460 . Each manifold  460  may be any manifold that delivers fertilizer from one source evenly into a plurality of distribution lines  472 . The schematic shows each manifold  460  receiving anhydrous ammonia through a line  462  from a supply tank such as the supply tank  40  shown in  FIG. 20 . A master shutoff valve  464  is opened to permit flow of anhydrous ammonia from the supply line  462  through lines  466  to four section control valves  468 . Each of the control valves  468  controls the flow rate of anhydrous ammonia to one of the manifolds  460 . One of the four lines  470  connects each control valve  468  to one of the manifolds  460 . Each manifold  460  divides flow of anhydrous ammonia through six discharge lines  472 . A discharge line  472  is connected to a knife such as a knife  388  shown in  FIG. 1 . 
         [0103]    The number of manifolds  460  and flow control valves  468  is a matter of choice and the total number of knives to be mounted on one toolbar. Minimizing the total number of knives  388  connected to one manifold  460  and one control valve  468  should increase accuracy. However the cost may be increased. Increasing the number of control valves  468  makes it easier to block flow to one or more manifolds to limit the application of anhydrous ammonia to areas more than one time. 
         [0104]    A temperature sensor assembly  474  is mounted in each discharge line  472  a selected distance from each manifold  460 . The temperature sensors assembly  474  detect anhydrous ammonia temperature changes promptly. 
         [0105]    The temperature sensor  474  includes an aluminum body  476 . The body  476  has a barbed inlet fitting  478  and a barbed outlet fitting  480 . The anhydrous ammonia passage  482  extends through the entire body  476  and is coaxial with the inlet fitting  478  and the outlet fitting  480 . The diameter of the passage  482  is substantially the same as the diameter of the passage through the discharge lines  472  to minimize turbulence in the flowing anhydrous ammonia. A sensor cavity  484  extends into the aluminum body  476  in a direction perpendicular to anhydrous ammonia passage  482 . A containment tube  486  of polyvinyl chloride (PVC) is pressed into the sensor cavity  484 . 
         [0106]    A sensor unit  488  includes a printed circuit board  490 , a temperature sensor  492  in the center of the circuit board, a first lead  494  and a second lead  496 . The temperature sensor  492  is adhered to the aluminum body  476  at the bottom  502  of the sensor cavity  484 . The printed circuit board  490  is centered relative to containment tube  486  and spaced from the anhydrous ammonia passage  482  by the aluminum body  476 . The printed circuit board  490  and the containment tube  486  form a potting cavity  500 . A low viscosity potting resin  498  is poured into the potting cavity  500  and cured. The first lead  494  and the second lead  496  both extend through the potting resin  498  and out of the free end of the containment tube  486 . The second lead  496  is a ground. 
         [0107]    Each of the anhydrous ammonia temperature sensor assemblies  474  is connected to a monitor console  510  by a first lead  494 . The temperature displayed on the screen  514  for each sensor is a different color or color shade. The chart on the right side of the monitor as shown in  FIG. 27  converts the colors and color shades to a letter and numeric distribution identifier. Each monitor section  513  of an anhydrous ammonia fertilizer applicator, having a separate monitor section manifold  460 , has a separate display area on the screen  514 . The monitor system as shown in  FIG. 21  has four monitor sections  513 . Each of the four monitor sections  513  has a separate section manifold  460 . The monitoring sections  513  all send information to the monitor console  510 . The actual number of sections varies. The variations depend on the capacities of the section manifolds  460 , the number of knives  388  and discharge lines  472 , and choices made by the engineers and users of the operator. 
         [0108]    The monitoring sections  513  are identical as shown in  FIG. 21 . Only one section of the control and monitoring system is described in detail. 
         [0109]    The temperatures sensed by the temperature sensor assemblies  474  are substantially the same as the temperature of the anhydrous ammonia passing through or stopped in the anhydrous ammonia passage  482 . Aluminum transfers heat rapidly. The temperature sensor  492  is in contact with the bottom  502  of the sensor cavity  484  and close to the anhydrous ammonia passage  482 . A wire buss or lead  494  transfers a temperature signal from the monitor section  513  to the monitor console  510 . A microprocessor, in the monitor console  510 , energized by a direct current power source  512 , starts displaying the temperatures measured by the temperature sensors  492  on a screen  514 . The measured temperatures start when the master valve  464  is open, the section control valve  468  is open and flow of anhydrous ammonia starts.  FIG. 27  is a sample display of results from a test with a section manifold  460 . The test was run with twelve first leads  494  in one monitor line harness  511 . 
         [0110]    The starting temperature of anhydrous ammonia in each of a plurality of discharge lines  472  was nearly 53° F. (Fahrenheit). After the system was activated, the temperature dropped to about 3° F. At time  50  one discharge line  472  was closed to simulate a blocked line. The temperature in the blocked line  472  increased relative to the other lines. The blocked line temperature stabilized at 4° F. to 5° F. above the unblocked lines during the test. A 4° F. change is clearly observed on the screen  514 . The temperature in the unblocked discharge lines  472  raised a few degrees and then stabilized. 
         [0111]    At time  80  the flow rate was changed. The temperature of anhydrous ammonia measured by temperature sensor assemblies  474  in unblocked lines  472  increased and stabilized at about 25° F. The temperature measured by the sensor  474  in the blocked discharge line  472  rose at about the same rate as the other lines until the lines with free flowing anhydrous ammonia started to stabilize. The temperature in the blocked discharge line  472  increased at a slower rate, but continues up to almost 30° F. At time  135  the blocked discharge line  472  was opened. The temperature measured in the unblocked line dropped from 30° F. to about 23° F. The temperature in the discharge lines  472  that had not been blocked also dropped slightly. All lines were fully open and at a temperature of about 25° F. from time  130  to time  155 . At time  155  a line  472  was slightly closed. The temperature in the partially closed line  472  increased to about 25° F. At time  180  the partially closed line  472  was fully open. The temperature in all lines  472  stabilized at about 22.5° F. A two degree temperature change in one line  472  is clearly observable on the screen  514 . At time  200  the valve  468  was closed. The temperature of anhydrous ammonia in all the discharge lines  472  increased. The sample test results were with one specific manifold  460  with an unspecified ambient temperature. 
         [0112]    The microprocessor in the monitor console  510  compares the temperature of one temperature sensor assembly  474  with the calculated average temperature of all the other temperature sensor assemblies  474  connected to one manifold  460 . The measured temperature of each of the sensor assemblies  474  in the monitor section is compared with the average temperatures of the other sensor assemblies. If a sensor  474  has a temperature above or below the calculated average that varies more than a selected amount φ, a warning signal is provided for the operator. The operator can look at the screen  514  and determine which discharge line  472  is outside the selected deviation amount φ. The lines representing individual temperature sensors  474  may be in different colors to identify each sensor in a section. The lines may also be identified by a number system or other indicia. The indicia chart on the face of the monitor, as shown in  FIG. 27  converts the colors to an indicia that can be used on most fertilizer distributors. 
         [0113]    The employment of current temperatures for all monitor functions corrects for ambient temperature changes during each twenty four hour period. The deviation amount φ is set by the operator using a key pad  516  on the console  510 . The key pad  516  or there controllers may also be used to open and close the master shutoff valve  464 . Section control valves  468  used to set the application rate for anhydrous ammonia are each adjustable using the key pad  516 . All of the section control valves  468  may be set to provide a uniform application rate. The tractor and the console may be equipped with a global positioning system and provided with soil sample data automatically adjust the application rate for each section control valve  468 . 
         [0114]    The monitor console  510  is to be mounted on the tractor in a position in which the operator can see the monitor console  510 , the screen  514  and operate the control functions. 
         [0115]    The anhydrous ammonia fertilizer distribution line monitor is described above as part of a fertilizer applicator with specific components between a supply vessel  40  and the manifold  460 . A specific row unit  400  with a knife  388  is also described. The distribution line monitor with temperature sensors works well with substantially all commercially available anhydrous ammonia applicators. 
         [0116]    The applicators can rely on the vapor pressure of anhydrous ammonia in the supply vessel  40  to move the liquid and any vapor that is created to the knife  388 . The applicator can also include a pump that increases pressure to move liquid through a manifold and into distribution or discharge lines  472 . 
         [0117]    The manifold may be separate from a flow control valve that controls the rate of flow of anhydrous ammonia from the supply vessel  40 . The manifold should be capable of supplying an equal quantity of fertilizer to each distribution line  440 . Some manifolds have orifices that are changeable. These orifices should be the same size and in good working order. The orifices should be unplugged. Each distribution line  472  should receive substantially the same quantity of anhydrous ammonia at substantially the same rate of flow. The distribution lines  472  should have the same inside diameter and substantially the same length. The manifold may be made from any suitable material. The shape and size of the manifold is not important as long as flow of fertilizer is not impeded. 
         [0118]    The spring steel bar  420  and knife  388  may be attached directly to a tool bar  386 . The tool bar  386  may be supported by ground engaging wheels. The wheels may be moved relative to the tool bar to raise and lower the knives  388 . 
         [0119]    One or more anhydrous ammonia distributor manifolds  460  are employed on each fertilizer distributor. A distribution line  472  is attached to a manifold discharge port  114  and to an injector knife  388 . There are multiple manifold discharge ports  114  in use on each manifold  460 . Each distribution line  472  include a proximal line portion  560  attached to a discharge port  114  and a distal line portion  562  attached to a knife  388 . A temperature sensor  474  connects the proximal line portion  560  to the distal line portion  562 . The temperature sensor  474  includes a metal tube  566  with an inside diameter that is substantially the same inside diameter of the distribution line  472 . The metal tube has a high rate of thermal conductivity. The upstream end of the  564  of temperature sensor assembly  474  is spaced from the manifold port  114  inside the proximal line portion  560  by about three inches so that the flexible plastic proximal line portion thermally isolates the temperature sensor  492  from the manifold  460 . 
         [0120]    The combined length of the proximal line portion  540 , the metal tube  566  of the temperature sensor  474  and the distal end portion  562  is substantially the same as the length of the other discharge lines  472  connected to the same manifold  460 . 
         [0121]    A temperature sensor assembly  474  includes a temperature sensor  492  that measures the temperature of anhydrous ammonia in the metal tube  566 .