Abstract:
An agricultural sprayer spray head is adapted for being mounted to a spray boom together with a plurality of like, equally spaced spray heads. Each spray head includes a body containing a flow control member mounted for rotation about an axis and including a fluid control passage arrangement located for effecting an intermittent connection between a fluid inlet leading to, and an outlet leading from the body as the control member is oscillated or rotated by a powered motor so as to effect a pulsing flow through said control. passage arrangement. The powered motor operates at a speed controlled by various input parameters including vehicle speed and field and crop conditions so as to maintain a desired spray application rate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to agricultural sprayers, and more specifically relates to automatically controlling the spray rate from a spray head for compensating for changes in vehicle ground speed so as to maintain a constant application rate. 
       BACKGROUND OF THE INVENTION 
       [0002]    Agricultural sprayers use nozzles for spraying a liquid which may be a fertilizer, a pesticide, a fungicide, an insecticide onto agricultural crops. Traditional nozzles consist of an orifice with geometry controlling the flow rate, droplet size and spray pattern to the target. The flow rate through the orifice is mainly a function of the orifice area and geometry as well as the fluid pressure at the orifice (i.e., pressure just prior to the orifice). Since the orifice size is fixed, i.e., the orifice geometry doesn&#39;t change, the most common way to influence the flow rate through the nozzle is by changing pressure. 
         [0003]    Changing the fluid pressure at the nozzle to influence flow rate changes has become common place on sprayers in order to allow for variable vehicle speed. Systems change the flow rate proportional to the vehicle speed in order to keep the application rate the same. 
         [0004]    However, using the traditional fixed orifice nozzle has some limitations. The pressure versus flow relationship is a squared function. To double the flow requires increasing the pressure by a factor of four times. Unfortunately, changing pressure also changes atomization dynamics resulting in an impact on spray quality. Spray quality characteristics, namely, droplet size and the spray angle, both become smaller as pressure increases. These changes can negatively impact spray deposit and spray drift. So, the need for a variable rate nozzle with uniform pressure has emerged. 
         [0005]    In recent years, pulse width modulation (PMW) has been used to control nozzle flow rate while maintaining constant pressure. The idea uses a solenoid coil and armature valve configuration to open and close flow to the nozzle. The valve is cycled between open (full pressure) and closed (no pressure) positions at a fast pulse rate. Changing the effective flow rate is done by varying the portion of open time to the portion of closed time. So, if a nozzle that sprays one gallon per minute is open only 50% of the time, the result will be an effective flow rate of only a half gallon per minute. In this arrangement, the duty cycle of open time is a linear relationship with effective flow rate. As the vehicle speed diminishes, the duty cycle decreases to match the flow rate required, while maintaining a constant pressure. U.S. Pat. No. 5,134,961 discloses a nozzle arrangement of this type which modulates nozzle flow by intermittent operation of an electrical solenoid valve attached to and located directly upstream of a spray nozzle. By cycling the valve open and closed, the flow rate through the nozzle is controlled in an analogous on/off manner. 
         [0006]    However, the PWM technology has some inherent problems. Poor coefficient of variation in the travel direction (up to 65% in one study) is caused as a result of turning the flow to the nozzle “off” and “on” during travel. It is known in the art to pulse the nozzles at 10 Hz and alternate phase 180° on every other nozzle to blend the spray. A faster pulse is recommended to help with the coefficient of variation. But, the open/close response time of the solenoid armature poses a limitation to pulsing faster. Thus, it is desired to find a way to pulse faster so as to improve the coefficient of variation. 
         [0007]    One further drawback of using a pulsing solenoid-operated valve to control flow to the nozzle is that the electrical current draw is rather high and requires a sprayer vehicle capable of handling high electrical current loads. 
       SUMMARY OF THE INVENTION 
       [0008]    According to the present invention, there is provided an improved spray head arrangement and more particularly, there is provided a spray head arrangement including a nozzle to which a supply of spray fluid may be automatically quickly switched or pulsed between “on” and “off” conditions. 
         [0009]    An object of the invention is to provide a spray head arrangement including a flow control valve arrangement which is capable of being controlled to quickly change the flow rate through the nozzle in order to compensate for changes in sprayer vehicle speed, crop and/or field conditions, while overcoming the drawbacks, noted above, associated with the prior art flow control valve arrangements. This object is accomplished by providing the spray head arrangement with a body in which a flow control member of a switching valve arrangement is mounted for rotation and includes a flow passage arrangement for intermittently routing flow between a fluid inlet and a fluid outlet provided in the body, with the outlet being coupled for routing fluid to a nozzle carried by the body. 
         [0010]    A preferred embodiment of the spray head arrangement for achieving the aforementioned object includes a flow control member defined by a disk mounted for rotation between the fluid inlet and fluid outlet leading to the spray nozzle, the disk containing one or more control openings which are constantly in fluid communication with the fluid inlet and move into and out of alignment with the fluid outlet as the disk is rotated by an electric stepper motor, with the motor being controlled to pulse flow to the outlet at a rate which compensates for changes in sprayer vehicle speed so as to maintain a desired spray application rate. 
         [0011]    The above and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic illustration of a control system for varying nozzle spray rate in accordance with spray vehicle speed by on/off pulsing of spray fluid supplied to a fixed rate nozzle so as to maintain a constant application rate. 
           [0013]      FIG. 2  is a perspective view of a pulsing spray head constructed in accordance with the principles of the present invention. 
           [0014]      FIG. 3  is a vertical sectional view taken through the spray head shown in  FIG. 2 . 
           [0015]      FIG. 4  is a top view of the flow control disk shown in  FIG. 3 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    Referring now to  FIG. 1 , there is shown a schematic of a control system  10  for maintaining the application rate of an agricultural spray to a field substantially constant at different sprayer vehicle ground speeds. The control system  10  comprises a plurality of spray heads  12  (only one shown) which would be mounted in evenly spaced relationship to each other along the length of a sprayer boom (not shown). Each of the spray heads  12  includes a manifold body  14  having an inlet  16  coupled for receiving spray fluid from a supply tube  18  carried by the spray boom and coupled to an outlet of a supply pump  20  having an inlet coupled to a source of spray fluid contained within a spray fluid tank  22  carried by the sprayer vehicle. A tubular nozzle connector  24  includes an upper end secured to a lower surface of the manifold body  14  in fluid communication with an outlet opening described below. A conventional spray nozzle  26  is coupled to a lower end of the nozzle connector  24  by a bayonet connection, for example, and includes a conventional spray tip  28  having a given flow rate for a given spray fluid supply pressure. It is to be understood that other nozzle arrangements could be used for disposing the nozzle in fluid communication with an outlet opening. 
         [0017]    A flow control valve arrangement  30  is located within the body  14  and includes a circular flow control disk  32  mounted for rotation for effecting a pulsing flow of spray fluid to the spray nozzle  26 , in a manner described below in detail. 
         [0018]    The flow control disk  32  is automatically rotated by operation of a powered motor, which may be an electrically controlled pneumatic, hydraulic or electric motor, with an electrically powered, reversible stepper motor  34  being preferred. The motor  34  is mounted to a central location of a top surface of the body  14  and having an output shaft  36  coupled, in a manner described in more detail below, to a central location of the flow control disk  32 . The motor  34  is electrically coupled, as by a motor control signal lead  38 , for receiving electrical control pulses from a motor controller  40  as commanded by an electronic controller  42  coupled to the motor controller  40  by an output signal lead  44 . The electronic controller  42  may be a microprocessor having a memory into which field mapping data, for example, relating to potential yield, soil type, soil nutrients, soil moisture content, weeds, diseases, and field topography, may be stored along with corresponding spray fluid application rates. To go along with this mapping data, a GPS receiver  46  is coupled to the controller  42  by a position input signal lead  48 . Also stored in the memory of the controller  42  is data relating an application rate of the nozzle tips  28  to ground speed of the spray vehicle. To go along with this data, a spray vehicle ground speed sensor  50  is coupled by a ground speed input signal lead  52 . The type of spraying being done and the corresponding nozzle tips being used can be keyed into the memory of the controller  42  by a manually-operable data input device  54  that is coupled to the controller  42  by a data input lead  56 . 
         [0019]    Referring now to  FIGS. 2 and 3 , there is shown the spray head  12  of  FIG. 1 , but with the nozzle  26  and spray tip  28  omitted. The spray head body  14  includes a cylindrical upper inlet section  58  and a cylindrical bottom plate  62  all clamped together by a plurality of bolt and nut assemblies  64  arranged in a circular pattern. Instead of the bolt and nut assemblies  64 , the upper and lower sections  58  and  62  could be designed to be screwed together or interlocked with each other, for example. The stepper motor  34  includes a cylindrical body  66  having a lower region joined to a horizontal flange arrangement  68  secured against a top surface of the upper inlet section  58  of the body  14  by screw fasteners  70 . 
         [0020]    As can best be seen in  FIG. 3 , a central location of the inlet section  58  of the body  14  is provided with a stepped cylindrical through bore  72 . The output shaft  36  of the stepper motor  34  is disposed along a central axis of the bore  72  and is connected to the flow control disk  32  by a shaft coupler  74  having a blind bore  76  extending axially from an upper end of the coupler and receiving the output shaft  36 , with the coupler  74  being secured for rotation with the shaft  36  by being keyed or having a splined connection (not shown) in a well known manner and being axially secured by a setscrew  78 . A lower end section  80  of the shaft coupler  74  has a non-round cross-section, here shown as being square, but which may be round with a flat, for example, received in a complementary shaped opening  82  located at the axial center of the disk  32 . The shaft coupler  74  further includes an annular flange  84  engaging a top surface of the flow control disk  32 . One or more circular annular shims  86  is (are) located on a top side of the flange  84  and takes up any space between a top surface  88  of an annular fluid chamber  90  defined by a circular recess formed in the bottom of the inlet section  58  and the top of the bottom plate  62  of the body  14 , the chamber  90  being in fluid communication with the spray fluid inlet  16  and extending over the top of the flow control disk  32 . Leakage of spray fluid from the chamber  90  along an annular flat interface established between a flat top of an outer annular region of the bottom plate  62  and a flat bottom of an outer annular region of the inlet section  58  of the manifold body  14  is prevented by an o-ring seal  92  located in an annular seal groove provided in the underside of the inlet section  58  outwardly of the chamber  90 . Leakage of fluid along an annular interface between the shaft coupler  74  and the surface of through bore  72  is prevented by a low friction, annular shaft seal  94  located in an annular seal receptacle  96  defined by the through bore  72 . An annular seal retainer plate  98  engages a top surface of the shaft seal  94  and is supported on an annular step surface  100  defined by through bore  72 . The retainer plate  98  is held in place by a snap ring  102  that is received in an annular snap ring groove provided in a surrounding wall region of the through bore  72 . 
         [0021]    Referring now also to  FIG. 4 , it can be seen that the flow control disk  32  includes a plurality of identical radial slots  104  (twenty being shown) arranged in a concentric ring about the center of rotation of the disk  32  and being spaced an equal angular amount from each other by webs  106 . As shown in  FIG. 3 , one of the radial slots  104  is shown in alignment with a fluid outlet  110  provided in centered relationship to an upper end of the tubular nozzle connector  24 . Thus, an open flow condition is established between the inlet  16  and the nozzle  26  with spray tip  28  carried at the bottom of the connector  24 , with it being noted that the webs  106  are sized so as to close off the fluid outlet  110  from receiving spray fluid when one of the webs is centered over the outlet  110 . 
         [0022]    In operation, the operator will first select the correct type and size of spray nozzle tip  28  for effectively performing the spray application at hand. The size of the nozzle tip  40  will depend upon the application rate (gallons/acre (GPA), ground speed (miles/hour (MPH), pressure in pounds/inch 2  (PSI) of the sprayed fluid at the nozzle and the planned effective width (W in inches) sprayed per nozzle). The manufacturer of the chosen spray product will normally provide a label stating the GPA recommended and, from this GPA, tables provided by a nozzle/tip manufacturer can be entered for choosing the correct nozzle tip for achieving this GPA at an appropriate maximum ground speed in MPH and nozzle pressure range. Thus, spray operation will be conducted using a standard spray nozzle tip operating at a constant spray fluid pressure for applying spray at the recommended spray application rate. 
         [0023]    Once the nozzle tip  28  is selected for each of the spray heads  12 , the operator will use the input device  54  to load the memory of the controller  42  with appropriate data correlating the desired spray application rate with the pulsing rate of the stepper motor  52  required for turning the flow to the nozzle  26  “on” and “off” for compensating for variances in spray vehicle speed from the rated speed of the nozzle tip  28 . Assuming that the appropriate nozzle spray tip  28  is rated for applying spray at a recommended 10.0 GPA at a nozzle pressure of 40 PSI (a lesser spray fluid pressure may be required if conditions are windy and droplet size has to be increased) and at an appropriate spray vehicle ground speed of 14 MPH, once spraying operation commences, the spray vehicle ground speed sensor  50  will supply the electronic controller  42  with a ground speed signal representative of the ground speed. The electronic controller  42  will compare this ground speed signal with the appropriate maximum ground speed of 14 MPH and a ratio equal to 14 MPH/sensed speed will be derived and used to generate a motor control signal for controlling the flow control disk  32  such that an appropriate decrease in spray rate occurs to compensate for the lower sprayer travel speed. For example, assuming that the motor  34  is designed to advance the flow control disk through 9° steps, it will be appreciated that, since the disk  32  has twenty slots  104  separated by twenty webs  106 , the stepper motor  34  will operate in response to receiving consecutive electrical pulses to alternately open and close the flow path to the spray nozzle tip  28 . Thus, if the sensed speed is 2 MPH, then the ratio will be 7/1 and the pulse rate of the stepper motor will be established to cause the time between consecutive control current pulses to be such that the disk  32  is located in an open position supplying spray fluid to the nozzle spray tip  28  for a period of time which is seven times the amount of time that the disk  32  is located in a closed position blocking spray fluid from the nozzle spray tip  28 . Thus, with the travel speed being 1/7 of the maximum desired speed of 14 MPH, the amount of time that the spray tip  28  is delivering spray is 7 times that when no spray is being delivered. Further, it is noted that the design of the stepper motor  34  would be chosen such that it can be easily controlled to operate so as to switch flow to the spray tip  28  at a rate which is up to 5 times the 10 hertz rate of the aforementioned solenoid control using PWM, with an attendant benefit of better spray coefficient of variation in the travel direction which means a more uniform spray deposit resulting in more effective results from spray application. Also loaded into memory are adjustments desired for different regions of a field as provided by a field map. 
         [0024]    While the stepper motor  34  is described as rotating in one rotational direction only during spraying operation, it should be understood that in a case where the flow control member is a disk containing but one opening, a pulsing flow can be caused by switching the rotational direction of the motor either every other time or at some other set algorithm. 
         [0025]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.