Abstract:
An apparatus and method to improve delivery of liquid anhydrous ammonia from a portable liquid NH 3  tank in cold temperatures includes an air compressor coupled to the vapor port of a portable liquid NH 3  tank used to supply liquid anhydrous ammonia to an anhydrous ammonia fertilizer applicator. The apparatus can include an actuator to relieve the tank of compressed air after the tank is empty of liquid anhydrous ammonia.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to provisional patent application 61/908,359 which was filed on Nov. 25, 2013, and is hereby expressly incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention pertains to applicators for injection of anhydrous ammonia (NH 3 ) into soil as a fertilizer. 
     In the application of anhydrous ammonia as a fertilizing agent, it is usual to utilize an applicator which includes a number of injection knives which are drawn on a tool bar with each knife making a small furrow in the soil. A conduit to carry anhydrous ammonia (NH 3 ) is carried on each knife shank and terminates at the lower end of the knife, thereby permitting a stream of NH 3  to be inserted in the furrow. The furrow is then closed, trapping the NH 3  in the soil. 
     For purposes of supplying an anhydrous ammonia applicator, a portable tank containing liquid NH 3  under pressure is drawn behind the applicator and NH 3  from the tank is permitted to escape through a liquid conduit which couples to a control/distribution unit which distributes NH 3  to the knives on the applicator. The NH 3  is forced from the tank by vapor pressure within the tank in the vapor head above the liquid level of the tank. As the tank empties or as atmospheric temperatures decline, the head pressure declines, and less pressure is available in the tank to urge liquid NH 3  into the liquid conduit. 
     In addition to having a port for intake or discharge of liquid pressurized NH 3 , portable tanks for transport of liquid NH 3  include a vapor port which communicates with the interior of the tank and is controlled by a shut off valve to prevent escape of NH 3  gas from the tank. When liquid NH 3  is being pumped into a portable tank, a vapor hose is connected to the vapor port on the tank and its shut off valve opened in order to allow movement of gaseous NH 3  from the tank while liquid NH 3  is being pumped into the tank. The vapor being allowed to exhaust from the tank is ported back to the main NH 3  supply container. 
     When NH 3  is being applied to a field, the head pressure of the NH 3  vapor in the tank forces liquid NH 3  from the tank. As the atmospheric temperature drops, the pressure of the gaseous NH 3  in the pressure head of a portable NH 3  tank drops, providing less pressure on the liquid NH 3  in the tank resulting in the slowing movement of the liquid NH 3  from the tank and into the ducts carried on the applicator knives. For example, at an outdoor temperature of 30° F., the pressure may only be forty pounds per square inch. This is a pronounced problem for application of NH 3  fertilizer because application is preferably accomplished in the fall season, after harvest of grain crops from the field. Therefore, NH 3  application on a cold day is slowed and may become erratic because insufficient pressure remains in the pressure head of the portable tank to supply a steady stream of liquid NH 3 . Additionally, as the NH 3  portable tank is emptied, the pressure of the head declines and liquid NH 3  is discharged more slowly even if atmospheric temperatures are summer like. To adjust for the problem of low head pressure, the operator of the fertilizer applicator must slow greatly to be sure adequate NH 3  is being applied to the soil. This need substantially reduces productivity of the application equipment and the operator. 
     Previous efforts to overcome the problem of reduced flow of liquid NH 3  when the atmospheric temperature is low include increasing the size of the liquid conduit from the tank, drawing from two or more tanks at the same time, and drawing liquid NH 3  from a port in the bottom of the tank instead of from the standard dip tube provided on the top of the tank. These methods provide additional shortcomings or are ineffective. Drawing a second or third tank over the soil causes increased fuel consumption of the tractor or other power unit, as well as increasing compaction of the soil from additional wheels passing over the soil. Adding a bottom port to a standard dip tube equipped tank adds expense and increases the possibility for leakage from the tank, while doing little to solve the problem. 
     Apparatus to maintain a preset pressure in the pressure head of the portable NH 3  tank would be very desirable for use by operators of NH 3  application equipment. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a solution to the problem of reduced head pressure in a portable anhydrous ammonia transport tank supplying an anhydrous ammonia fertilizer applicator. An air compressor is coupled to the vapor port of the portable NH 3  tank to cause increase of the pressure in the pressure head in the portable NH 3  tank as needed, particularly when the atmospheric temperature is low or the liquid NH 3  level is low, which results in a reduced pressure of the NH 3  vapor present above the liquid NH 3  in the tank. A regulator controls the flow of air under pressure being injected through the vapor port into the tank such that the pressure in the pressure head can be maintained at least approximately 80 psi under all conditions. As the atmospheric temperatures vary on an autumn day, the pressure regulator will control the pressure of the vapor head in the tank, causing the compressor to operate as needed to maintain a desired pressure. 
     The invention further includes apparatus to allow excess compressed air in the nurse tank to be exhausted from the tank into the fluid lines and/or the vapor lines to the knives, thereby passing any anhydrous ammonia vapor accompanying the compressed air safely into the soil. The apparatus for exhausting build up compressed air from the nurse tank includes valves and ducts which interconnect with the fluid line and an actuator to open a main valve coupled to the vapor port of the nurse tank to the fluid lines passing to the knives. 
     It is accordingly a primary object of the invention to provide a apparatus to maintain head pressure within a portable anhydrous ammonia tank used to supply a fertilizer application device so that sufficient flow of NH 3  continues regardless of the atmospheric temperature at the time the application device is used, and to allow safe release of compressed air from the nurse tank when the tank is empty and ready for refilling with anhydrous ammonia. 
     These and other objects of the invention will become apparent from examination of the detailed description of the invention which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary NH 3  applicator and supply tank according to the invention, being drawn over a field by a tractor. 
         FIG. 2  is a schematic representation of the NH 3  application system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  discloses a tractor  8  drawing an applicator  4  over soil  12 . Portable tank  10  is in turn drawn by applicator  4 . Applicator  4  comprises a tool bar  6  on which are mounted soil interrupting knives  16  which are followed by paired coulters  14 . Liquid anhydrous ammonia (NH 3 ) within tank  10  is distributed to knives  16  and the liquid NH 3  is injected into soil  12  behind each of knives  16  as knives  16  create shallow trenches by movement of knives  16  through soil  12 . The trenches are closed by the pairs of coulters  14  associated with each of the knives  16 . 
     Referring now to both  FIGS. 1 and 2 , invention  2  comprises compressor  18  which is coupled by compressed gas duct  20  to vapor port  22  of tank  10 . Compressor  18  compresses a gas, preferably air, though other gases may be used, and the compressed gas is delivered by compressed gas duct  20  to vapor port  22  where the compressed gas enters tank  10  and is joined with NH 3  vapor in the pressure head  36  above the liquid NH 3    34  present in tank  10 . 
     Head pressure within tank  10  forces liquid NH 3  to exit tank  10  through liquid port  24  and to pass through liquid pipe  26  to be distributed to knife ducts  42  leading down each of knives  16 . A pressure regulator  30  may be connected to duct  20  such that pressure in duct  20  and therefore within the pressure head  36  of tank  10  may be monitored and maintained at a preselected pressure, preferably approximately 80-150 psi and more preferably approximately 100 psi. When the vapor pressure in the pressure head  36  within tank  10  drops below the preselected pressure, flow of liquid NH 3  from tank  10  will be slowed. When pressure below the preselected pressure is detected by regulator  30 , the compressor  18  may be activated and compressed gas forced into tank  10  up to the preselected pressure. With the increased head pressure within tank  10 , liquid NH 3  will flow more quickly to knives  16  such that the tractor  8  may draw the applicator  4  over the field at a desired speed and will not be required to slow to allow for adequate NH 3  to reach soil  12 . 
       FIG. 2  schematically illustrates the structure of the invention. A liquid NH 3  storage tank  10  carried on wheels  40  contains a quantity of liquid NH 3    34  therein. Above the surface of the liquid NH 3    34 , there is a pressure head  36  of gases, including NH 3  in vapor state. The tank  10  is provided with a liquid port  24  and a vapor port  22  which may be housed under a moveable valve cover  28 . When the portable tank  10  is to be filled at a NH 3  supply facility, a liquid duct from a bulk supply reservoir (not illustrated) is coupled to the liquid port  24  and vapor pressure building in the tank  10  is vented through vapor port  22  to the bulk supply reservoir through suitable vapor duct means (also not illustrated in the drawings). 
     When the portable tank  10  is attached to fertilizer applicator  4  and both are driven over a field, liquid NH 3  is forced from the tank  10  by pressure of vapor in pressure head  36  so that liquid NH 3  will flow through liquid pipe  26  to an application control system  59 . Liquid NH 3  flows out of control system  59  via a liquid output line  64  and vapor NH 3  flows out of control system  59  via a vapor output line  62 . Eventually the liquid NH 3  is delivered to liquid port  72  and vaporous NH 3  is delivered to vapor port  70 . As the environmental temperature drops, the vapor pressure of NH 3  in the pressure head  36  of tank  10  declines, reducing the speed of transfer of liquid NH 3    34  to the applicator  4 . Therefore, compressor  18  may be operated to compress air to be injected through vapor port  22  into pressure head  36  of tank  10  which will force liquid NH 3    34  from tank  10  at a sufficient transfer rate for efficient application speed to be maintained. 
     Similarly, as the tank  10  empties of liquid NH 3 , the pressure in pressure head  36  declines and compressor  18  may be operated to compress air to be injected through vapor port  22  into pressure head  36  of tank  10  which will force liquid NH 3    34  from tank  10  fast enough for efficient application speed to be maintained. 
     A manually operated liquid valve  44  is available to stop flow of liquid NH 3  from tank  10  via liquid pipe  26 . A manually operated vapor valve  46  is provided to stop flow of vapor from tank  10 . These elements are standard on portable NH 3  tanks. 
     Compressed gas duct  20  couples vapor port  22  of tank  10  to compressor  18 . Compressor  18  compresses a fluid, preferably air, and may be driven by a hydraulic motor which may be conveniently powered from the hydraulic fluid pumping system available on a standard farm tractor. Compressor  18  may alternately be powered by a separate gas engine or from other power sources and may be substituted with a pressurized storage tank of compressed gas. Some tractors or power units provide an onboard source of compressed air which may be used to pressurize pressure head  36 . 
     The compressor  18  may be mounted to the tractor or to the applicator  4  or to the tank  10  at a convenient location which permits compressor  18  to be powered and to convey compressed air (or other gaseous fluid) to the vapor port  22  of tank  10  through compressed gas duct  20 . A pressure regulator  30  may be optionally used to monitor and regulate the pressure of compressed air in the pressure head  36  of tank  10 . The pressure regulator  30  may signal the compressor  18  to operate within a preselected range of pressures. A pressure of approximately 80-150 psi in pressure head  36  is found to be satisfactory to force liquid NH 3    34  from tank  10  via dip tube  38  to NH 3  control system  59  which in turn supplies liquid NH 3  to each liquid port  72  and vaporous NH 3  to each vapor port  70  for incorporation in the soil as knife  16  of applicator  4  is drawn through the soil. 
     The apparatus further comprises a selectively operable actuator  50  which may be electrically operated and which is coupled to the gas duct  20  coupled to the vapor port  22  of the nurse tank  10 . The actuator  50  is typically operated when the liquid anhydrous ammonia  34  in the tank is depleted or substantially depleted. However, the actuator  50  is selectively operable and can be activated at any time and is not prohibited from running in correspondence with any particular level of liquid anhydrous ammonia. First exhaust duct  52  passes compressed gasses from the pressure head  36  within the tank  10  to the actuator  50  which then sends compressed air through secondary ducts  56 . A valve then can split the compressed air to secondary ducts  56   a  and  56   b . Duct  56   a  pressurizes flow of the compressed air such that the compressed air is directed to the vapor port  70  which follow the knife shanks  17  and terminate near the toe  19  of each knife  16  which in operation is being drawn through the soil  12  below the ground surface. Therefore any anhydrous ammonia vapor mingled with the compressed air within the pressure head  36  is passed safely into the soil  12 . In the same manner, duct  56   b  pressurizes flow of the compressed air such that the compressed air is directed to the liquid port  72 . Although, both ducts  56   a  and  56   b  can be utilized, the preferred embodiment utilizes only the vapor port  70  to transport compressed air to the soil  12 . In a different embodiment, only the liquid port  72  is used to transport the compressed air to the soil  12 . 
     Single direction valve  54  is provided to prevent gases from the pressure head  36  from passing to the pressure regulator  30  and compressor  18  when actuator  50  is operated to couple vapor duct  20  to liquid duct  26 . The connectors  57  can be T-style connections used to split certain ducts or lines. Each connector can further be associated with valves to prevent flow of gas or liquid in a particular direction. 
     It can therefore be understood that once tank  10  has been effectively emptied of liquid anhydrous ammonia, the actuator  50  can be activated to allow pressurized vapor from the pressure head  36  to pass safely into the soil by way of the vapor port  70  and/or liquid port  72 . In a different embodiment the actuator  50  and associated ducts and valves can be added to an existing apparatus for applying liquid anhydrous ammonia. 
     The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations of the embodiments are possible in light of the above disclosure or such may be acquired through practice of the invention. The embodiments illustrated were chosen in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and by their equivalents.