ELECTRICALLY ACTUATED VARIABLE PRESSURE CONTROL SYSTEM

Abstract

An electrically-actuated variable pressure control system for use with flow-controlled liquid application systems. Direct acting solenoid valves are pulsed at varying frequencies and duty cycles 0000 change the resistance to flow encountered by the flow-controlled liquid application system. This pulsing solenoid valve technique preserves a high degree of accuracy and uniformity through a wide range of pressure control. This wide range of pressure control indirectly allows the flow-controlled liquid application system to operate over a wider range of flow control, yielding indirect benefits to performance and productivity. When the solenoid valves are attached to pressure-atomization spray nozzles, control over spray pattern and droplet size is further achieved.

Claims

1-29. (canceled)

30. An agricultural spraying system comprising: a valve including a nozzle and an actuator assembly, the nozzle having an orifice defined therethrough, the actuator assembly configured to be continuously pulsed according to a duty cycle to control emission of an agrochemical from the orifice; a pipe connected to the valve and configured to deliver the agrochemical to the valve; a pressure sensor connected to the pipe for sensing a pressure in the pipe; and a pressure controller in communication with the pressure sensor, the pressure controller configured to: compare the sensed pressure to a pressure set point; and change a flow resistance through the orifice based on the comparison by adjusting the duty cycle of the actuator assembly to maintain the pressure in the pipe at the pressure set point.

31. The agricultural spraying system of claim 30, wherein the agricultural spraying system further comprises a control panel configured to receive a user input, wherein the pressure controller is further configured to determine the pressure set point based on the user input.

32. The agricultural spraying system of claim 31, wherein the user input is the pressure set point.

33. The agricultural spraying system of claim 30, wherein the pressure set point is a single pressure value.

34. The agricultural spraying system of claim 30, wherein the actuator assembly is continuously pulsed at a frequency of 10 Hz.

35. The agricultural spraying system of claim 30, wherein the nozzle is a pressure-atomization spray nozzle configured to produce a desired droplet size spectra and an agrochemical spray pattern.

36. The agricultural spraying system of claim 30, wherein the actuator assembly includes a reciprocating solenoid actuator configured to move relative to the orifice when a voltage is applied to the reciprocating solenoid actuator.

37. The agricultural spraying system of claim 30, wherein the actuator assembly includes a coil, a guide, and a plunger, wherein the coil is disposed about the guide, and wherein the plunger is interposed between the guide and the orifice and moves relative to the orifice when a voltage is applied to the coil.

38. The agricultural spraying system of claim 30 further comprising a plurality of valves, each valve of the plurality of valves including a nozzle and an actuator assembly, wherein the pressure controller adjusts the duty cycle of the actuator assembly of each valve independently of the other valves of the plurality of valves.

39. The agricultural spraying system of claim 30, wherein the pressure controller changes the flow resistance by adjusting the duty cycle of the actuator assembly to one of a plurality of duty cycles, the plurality of duty cycles including a maximum duty cycle, a minimum cycle, and at least one duty cycle between the maximum duty cycle and the minimum duty cycle.

40. The agricultural spraying system of claim 30, wherein the minimum duty cycle is 30% and the maximum duty cycle is 90%.

41. The agricultural spraying system of claim 30, wherein the actuator assembly is movable between an open position, in which the agrochemical is permitted to flow through the orifice, and a closed position, in which the actuator assembly seals the orifice.

42. The agricultural spraying system of claim 41, further comprising an actuating signal generator for controlling actuation of the actuator assembly between the open position and the closed position.

43. The agricultural spraying system of claim 42, wherein the actuating signal generator is a square wave generator configured to actuate the actuator assembly from the closed position to the open position by applying a voltage to the actuator assembly.

44. The agricultural spraying system of claim 43, wherein the square wave generator is configured to modulate a square wave frequency and the duty cycle to change the flow resistance for the emission of the agrochemical from the orifice.

45. The agricultural spraying system of claim 44, wherein the pressure controller includes the square wave generator.

46. The agricultural spraying system of claim 30, wherein the pressure controller changes the flow resistance through the orifice by increasing the duty cycle at which the actuator assembly is pulsed to decrease the flow resistance when the sensed pressure exceeds the pressure set point.

47. The agricultural spraying system of claim 30, wherein the pressure controller changes the flow resistance through the orifice by decreasing the duty cycle at which the actuator assembly is pulsed to increase the flow resistance when the sensed pressure is less than the pressure set point.

48. The agricultural spraying system of claim 30 further comprising an agrochemical tank for holding the agrochemical, the agrochemical tank connected to the pipe.

49. The agricultural spraying system of claim 30 further comprising a pump for pumping the agrochemical through the pipe.

50. The agricultural spraying system of claim 49, wherein the pump is one of a positive displacement pump and a centrifugal pump.

51. The agricultural spraying system of claim 49, wherein the pump is a positive displacement pump, the agricultural spraying system further comprising a wheel and a piston, wherein the piston is connected to the wheel and to the positive displacement pump, and wherein the piston is configured to reciprocate the positive displacement pump as the wheel turns.

52. A method for regulating pressure for application of an agrochemical from an agricultural spraying system, the method comprising: directing the agrochemical through a pipe of the agricultural spraying system to an actuating valve including a nozzle and an actuator assembly, the nozzle having an orifice defined therethrough; continuously pulsing the actuator assembly according to a duty cycle to control emission of the agrochemical from the orifice; sensing a pressure in the pipe using a pressure sensor connected to the pipe; comparing, using a pressure controller, the sensed pressure to a pressure set point; and changing a flow resistance through the orifice, using the pressure controller, based on the comparison by adjusting the duty cycle of the actuator assembly to maintain the pressure in the pipe at the pressure set point.

53. The method of claim 52 further comprising: receiving a user input at a control panel; and determining, using the pressure controller, the pressure set point based on the user input.

54. The method of claim 53, wherein the user input is the pressure set point.

55. The method of claim 52, wherein changing a flow resistance through the orifice includes transmitting control signals from the pressure controller to the actuator assembly, the control signals being associated with the duty cycle.

56. The method of claim 55, wherein the control signals are generated by a square wave generator associated with the pressure controller.

57. The method of claim 52, wherein changing a flow resistance through the orifice includes increasing the duty cycle at which the actuator assembly is pulsed in order to decrease the flow resistance when the sensed pressure exceeds the pressure set point.

58. The method of claim 52, wherein changing a flow resistance through the orifice includes decreasing the duty cycle at which the actuator assembly is pulsed in order to increase the flow resistance when the sensed pressure is less than the pressure set point.

59. The method of claim 52, wherein the actuator assembly is continuously pulsed such that the pressure in the pipe is maintained at the pressure set point independently of a predetermined flow rate of the agrochemical through the pipe.

60. The method of claim 59, further comprising regulating the predetermined flow rate of the agrochemical through the pipe using a regulating valve connected to the pipe.

61. The method of claim 52, wherein the actuator assembly is movable between an open position, in which the agrochemical is permitted to flow through the orifice, and a closed position, in which the actuator assembly seals the orifice.

62. The method of claim 52, wherein the pressure set point is a single pressure value.

63. A pressure controller for use with an agricultural spraying system including a valve including a nozzle and an actuator assembly, the nozzle having an orifice defined therethrough, the actuator assembly configured to be continuously pulsed according to a duty cycle to control emission of an agrochemical from the orifice, a pipe connected to the valve and configured to deliver the agrochemical to the valve, and a pressure sensor connected to the pipe for sensing a pressure in the pipe, wherein the pressure controller is configured to: receive a sensed pressure in the pipe from the pressure sensor; compare the sensed pressure in the pipe to a pressure set point; and change a flow resistance through the nozzle orifice based on the comparison by adjusting the duty cycle of the actuator assembly to maintain the pressure in the pipe at the pressure set point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further aspects and advantages of the invention will be apparent from the following description, or can be learned through practice of the invention, in combination with the drawings, which serve to explain the principles of the invention but by no means are intended to be exhaustive of all of possible manifestations of the invention. Thus, at least one embodiment of the invention is shown in the drawings in which:

[0046] FIG. 1 is a perspective view of a dispensing system according to an aspect of the present invention installed in an environment for which it is intended to be used;

[0047] FIG. 2 is a schematic of a flow control system that can be employed in the system of FIG. 1, particularly showing a ground-speed-compensating, positive-displacement pump and an electrically-actuated variable pressure control system according to one aspect of the invention;

[0048] FIG. 3A shows a sectional view of a solenoid valve in an open position;

[0049] FIG. 3B shows a sectional view of the solenoid valve as in FIG. 3A in a closed position;

[0050] FIG. 4 shows a puke width modulation technique for various duty cycles employed in the electrically-actuated pressure control system as in FIG. 1;

[0051] FIG. 5 is a schematic of another flow control system that can be employed in the system of FIG. 1, particularly showing a flow meter, a flow regulating valve and an electrically-actuated variable pressure control system;

[0052] FIG. 6 is a graph showing an interdependent relationship between flow control and pressure control when an electrically-actuated variable pressure control system is used in conjunction with a flow control system according to an aspect of the invention;

[0053] FIG. 7 shows a flow chart of control logic employed by the flow control system and the pressure control system as in FIG. 6; and

[0054] FIG. 8 is an elevational view of a control panel used to control the foregoing embodiments according to a further aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0055] Detailed reference will now be made to the drawings in which examples embodying the present invention are shown. The detailed description uses numerical and letter designations to refer to features of the drawings. Like or similar designations of the drawings and description have been used to refer like or similar parts of the invention.

[0056] The drawings and detailed description provide a full and written description of the invention, and of the manner and process of making and using it, so as to enable one skilled in the pertinent art to make and use it, as well as the best mode of carrying out the invention. However, the examples set forth in the drawings and detailed description are provided by way of explanation only and are not meant as limitations of the invention, The present invention thus includes any modifications and variations of the following examples as come within the scope of the appended claims and their equivalents.

[0057] As broadly embodied in FIGS. 1 and 2, an exemplary agricultural. system, designated in general by the numeral 10, broadly includes a tractor 12 having an electrically-actuated variable pressure control system 14. As shown, the tractor 12 includes a cab 16, a plurality of wheels 18A at least one boom wheel 18B for engaging a section of ground with a crop, produce, product or the like (generally, P), a tank or reservoir 22, and a spray boom 24 with a plurality of nozzles 34 attached to the spray boom 24. The tank 22 holds a liquid, a mixture of liquid and powder, or other product designated in general by the letter S. The liquid can be a quantity of water or an agrochemical such as a fertilizer or a pesticide. Likewise, the liquid-powder mixture can be the agrochemical. Thus, the product S can be sprayed from the nozzles 34 onto a crop or product or the ground. P itself as shown in FIG. 1 and described in greater detail by example operation below.

[0058] FIG. 2 more particularly shows the boom wheel 18B attached to a slider-crank or piston mechanism 26, which is connected to a ground speed compensating positive displacement pump 28. As shown, the boom wheel 18B rolls across the ground P and turns a slider-crank mechanism 26, which reciprocates the positive displacement pump 28. The positive displacement pump 28 is calibrated to apply a specific amount per acre of product S to soil of the ground P.

[0059] As briefly introduced, the product S is contained in the tank 22 and enters the positive displacement pump 28 through a suction pipe 30. The product S flows from the positive displacement pump 28, through a boom pipe 32, to the direct acting solenoid valve equipped nozzles 34, As shown in FIGS. 1 and 2, the product S flows from the nozzles 34 and is applied to the ground P in various ways; e.g., pulsed, patterned and the like as taught by Giles et al, in U.S. Pat. No. 5,134,961 and incorporated herein by reference thereto. The skilled artisan will appreciate that pipe as used herein can mean any type of conduit or tube made of any suitable material such as metal or plastic. The skilled artisan will further appreciate that other ground application devices can be added to provide varying effects of placement of the products on top or below a soil surface of the ground F, such as via pipes, knives, coulters, and the like.

[0060] FIG. 2 further shows a pressure sensor 52, which measures the pressure in the boom pipe 32. The pressure sensor 52 sends this pressure information to a pressure controller 54. In this example, the pressure controller 54 pulses the direct acting solenoid valve equipped nozzles 34 with a frequency and duty cycle that maintains a specific pressure within the boom pipe 32. An example of this operation is described below.

[0061] Turning now to FIGS. 3A and 3B, the direct acting solenoid valve equipped nozzle 34 is shown respectively in open and closed positions. The direct acting solenoid nozzle 34 pulses with a frequency and duty cycle such that an orifice 40 is active only when the valve-equipped nozzle 34 is open. The frequency is sufficiently fast to diminish any effects of pulsing on the total system, therefore creating a controlled variable resistance to flow.

[0062] More specifically, as shown in FIGS. 3A and 3B, the nozzle 34 has a body 36 including mounting means such as a bracket or screw-fitting 38 for mounting the nozzle 34 to the boom pipe 32. As shown, the orifice 40 is configured for outlet flow F1 and inlet flow F2. This aspect of the invention is described in greater detail below.

[0063] As particularly shown in FIG. 3B, the nozzle 34 also includes an actuator assembly 41, which has an actuator or coil 42 located on or around a guide 44. As shown, a plunger 46 is movably positioned between the guide 44 and the orifice 40. A square wave generator 55 is connected to the nozzle 34 and applies an electric signal or voltage 56 to the coil 42, which establishes a magnetic field. The magnetic field causes the guide 44 to become magnetized, which attracts the plunger 46. In this example, the magnetic force of the guide 44 overcomes a spring force of a spring 48 and a force of the inlet flow F2 as applied to the orifice 40. When the plunger 46 lifts a seal 50 from the orifice 40, the outlet flow F1 results.

[0064] FIG. 4 shows a pulse width modulation (PWM) signal used to actuate the direct acting solenoid nozzle 34 as in FIGS. 1 and 2. In this example, the electric signal 56 is pulsed with a fixed period length 58 of 0.1 seconds. When the signal 56 is high; i.e., when voltage is present, the pulse is shown at the ON position. As shown, the signal 56 remains high or ON for a portion of the period length 58 before switching low; i.e., no voltage is present. The relation of on-time to period length 58 is called a duty cycle 60 and is measured in percent (%). Three duty cycles of 30%, 50% and 90% are shown in FIG. 4. As described with respect to FIG. 3 above, the directing acting solenoid nozzle 34 will open and close with this on/off pulse. For example, if the duty cycle 60 is 50%, the resulting resistance to flow will be 50% of the total resistance to flow of the orifice 40. Similar respective results occur with the 30% and 90% duty cycles 60.

[0065] Turning now to FIG. 5, an agricultural spraying system 110 includes an electrically-actuated flow control system 114 including a flow meter 162 and a flow regulating valve 172. Many of the components of the agricultural spraying system 110 are similar to the components of the foregoing embodiments as described above and reference is made thereto for an enabling description of these components if not expressly described below.

[0066] As in the previously described embodiment, a product S in FIG. 5 flows from a tank 122 to a centrifugal pump 128 via a suction pipe 130. As shown, the product S flows from the centrifugal pump 128 to the flow regulating valve 172 via a pressure pipe 170. The flow regulated product S flows to the flow meter 162, to a pressure sensor 152, and to the direct acting solenoid valve equipped nozzles 134 via a boom pipe 132. Thus, the product S is delivered to a target such as the crop or ground P in FIG. 1 via spray atomization nozzles 151 of the direct acting solenoid valves 134.

[0067] More particularly, the flow meter 162 in FIG. 5 measures the flow rate and sends a signal to a flow controller 164. The flow controller 164 receives target rate information from a rate input device 168 and speed from a speed input device 166. Accordingly, the flow controller 164 controls the flow regulating valve 172 to the desired rate. Additionally, the pressure sensor 152 measures the pressure in the boom pipe 132 and sends the pressure information to a pressure controller 154. The pressure controller 154 pulses the direct acting solenoid valve equipped nozzles 134 with a frequency and duty cycle which maintains a specific pressure within the pipe 132.

[0068] The skilled artisan will appreciate that a conventional flow-control system operates by shifting a flow control system curve along a fixed pressure control curve. The intersection of the two curves is the resultant conventional application flow and pressure. As the flow changes in such a conventional system, the intersection changes accordingly such that a new system pressure is achieved as a direct result of the flow change.

[0069] FIG. 6 generally shows an interdependent relationship between flow control and pressure control when an electrically-actuated variable pressure control system is used in conjunction with a flow control system. More specifically, FIG. 6 shows a relative, pressure-versus-flow relationship for liquid flow-control systems, and an electrically-actuated variable pressure control system as described above.

[0070] As shown in FIG. 6, an electrically-actuated pressure control system according to the present invention allows a pressure control curve 190 to be shifted in various directions indicated by a double-headed arrow 194, which is an independent shift from a change in a flow indicated by a double-headed arrow 192. The result is that an intersection 196 may be navigated to any flow and pressure setting desired by an operator, within limits of the system. This ability, when controlled by flow and pressure controllers, allows the operator to set flow and pressure set points independently, and have both set points maintained throughout a range of speed. In addition, the flow set point may be changed without effecting the pressure set point, and vise versa.

[0071] With reference now to FIGS. 5, 6 and 7, a control logic is employed by the flow controller 164 and the electrically-actuated variable pressure control system 154 according to an aspect of the invention. In particular, FIG. 7 shows start-up of the flow control system 164 at step A. A flow is read at step B, and a calculation occurs to determine if the flow is too high or too low. This calculation may be simple or complex depending on the variables upon which flow is being controlled. As shown at step C, if the flow is too low, a restriction is relieved by opening the flow regulating valve 172 as in FIG. 5. Conversely, if the flow is too high at step D, a restriction can be increased by closing the flow regulating valve 172. The routine of reading and changing flow is operated continuously while the flow-control system 164 is active. Those skilled in the art will appreciate that alternate mechanisms and methods of changing flow may be employed; for instance, by using the ground driven positive pump 28 of FIG. 1, or by changing the speed of the pump 28.

[0072] Also shown in FIG. 7, the control logic of the electrically-actuated variable pressure control system 154 is similar to that of the flow control system 164 described above. Upon start-up of the pressure control system 154 at step F, a duty cycle is initiated at step C at a desired value, which is 50% in this example. This value can be set at a control panel 174 as described below with respect to FIG. 8. The initiated value is held for a predetermined or initiation time (step H) while the flow control system 164 adjusts to the target flow. When the initiation time is over, the pressure is read at step I. If the pressure is too low, the resistance to flow is increased at step J by decreasing the duty cycle 60 of the direct acting solenoid nozzle 134. Conversely, if the pressure is too high, the resistance to flow is decreased at step K by increasing the duty cycle 60 of the direct acting solenoid nozzle 134, When the pressure control system 154 is stopped, the initializing duty cycle is reset to the last known duty cycle. This delay allows the flow control system 164 to initialize and grants some priority to flow over pressure.

[0073] FIG. 8 shows an embodiment of the control panel 174, briefly introduced above, for the electrically-actuated pressure control system 154. The control panel 174 is mounted in a vehicle such as in the cab 16 of the tractor 12 at FIG. 1 within reach of the operator. In this example, a knob 176 is shown having twelve detents 180. These twelve detents 180 indicate a target pressure set point, or duty cycle, that the controller 154/164 is to maintain.

[0074] As shown in FIG. 8, a mode of operation is dictated by a switch 182. In this example, the three position switch 182 is off in a center position, in a PSI mode in an uppermost position, and in a PWM % mode in a downward position. Thus, the position of the switch 182 in FIG. 8 indicates whether the knob 176 detent is calibrated for PSI or PWM %. Making two modes of operation available reduces down-time in the event of a system failure. For instance, in PWM % mode, the system can be run from manually calculated settings until the automatic pressure control system can be repaired,

[0075] As further shown in FIG. 8, a color graphic 178 can be utilized to guide the operator to more advantageous settings of the knob 176. For instance, desirable ranges can be color coded green, less desirable ranges can be yellow and ranges that should be used sparingly or avoided can be colored orange or red.

[0076] Also shown in FIG. 8, a connector 184 is attached to a wiring harness, which connects the panel 174 to other components of the system 110. One skilled in the art will appreciate how the connector 184 connects the panel 174 and further description is not necessary to understand and practice this aspect of the invention.

[0077] These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may he interchanged either in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.