Abstract:
A device and method for dispensing precise amounts of dry particulate matter, such as agricultural chemicals, directly into a liquid carrier stream, such as a flow of water, and a method of employing such a device to distribute chemicals. The device includes a bin for holding a quantity of particulate matter, a conduit for transporting a stream of liquid carrier, and a meter at the bottom of the bin for controllably releasing a desired amount of the particulate matter from the bin into the conduit while disallowing entry of the liquid carrier to the bin. The bin, conduit and meter are all mounted upon a portable structure for transportation with particulate matter in the bin. The meter includes a multi-vaned rotor turned by a controlled motor, and defines discrete pockets of known volume. The operator simply connects the device to a flow of water and keys into the controller an amount of material to be released. The rotor releases the material into a chamber under vacuum pressure generated by a venturi, through a check valve, and into an eductor. Agricultural chemicals may be advantageously distributed to end users in particulate form, to be mixed with a liquid carrier at the work site, without possibly harmful exposure to chemical dust and fumes.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a device and method for shipping and dispensing precise amounts of dry particulate matter, such as fertilizer and pesticide products and such, into a liquid carrier stream. 
     Many useful agricultural chemicals and other such products are distributed in dry bulk form, either as powders, granules or small pellets, but are ultimately dissolved into a liquid carrier for application by spraying or irrigation equipment. Thus, a farmer will either purchase the chemicals dry, either in bags or bins, and mix them with water or other liquid carrier as needed, such as by pouring the chemicals and liquid carrier separately into a mixing tank, or will transport a tank to a chemical dealer who will dispense a pre-mixed solution into the tank. Unfortunately, environmental and safety regulations are typically more stringent regarding the transportation of chemicals in liquid form than in dry form. 
     Pneumatic systems have been developed for metering and transporting dry particulate matter in a stream of air, from a bulk storage bin to a mixing tank for subsequent mixing with a liquid. A useful example of such a system is a portable unit described in U.S. Pat. No. 5,803,673 and sold under the trade name “ACCUBIN”. The entire contents of the above-referenced patent are incorporated herein by reference as if fully set forth. 
     With many agricultural chemicals, prolonged exposure to high concentration of air-borne particulates is not desirable. 
     SUMMARY OF THE INVENTION 
     The invention features a means of transporting and storing a dry particulate material, and then dispensing controlled quantities of that material directly into a stream of liquid carrier. The invention is particularly applicable for use with agricultural chemicals, such as pesticides (e.g., herbicides), fertilizers and adjuvants. By “particulate form”, we mean to include powders, granular and pelletized materials that are not suspended in a liquid medium. 
     According to one aspect of the invention, a device is provided for dispensing precise amounts of dry particulate matter directly into a liquid carrier stream. The device includes a bin for holding a quantity of particulate matter, a conduit for transporting a stream of liquid carrier, and a meter connected to the bin for controllably releasing a desired amount of the particulate matter from the bin into the conduit while disallowing entry of the liquid carrier to the bin. The bin, conduit and meter are all mounted upon a portable structure for transportation with particulate matter in the bin. 
     In the embodiment discussed in more detail below, the meter is arranged at the bottom end of the bin, such that the particulate matter is fed into the meter by gravitational force. 
     In some embodiments, the meter includes a multi-vaned rotor constrained to rotate within a housing, with the rotor vanes defining between them discrete pockets of known volume. These pockets preferably each have a volume of less than about 30 cubic inches (500 cubic centimeters), more preferably less than about 25 cubic inches (400 cubic centimeters), and most preferably less than about 10 cubic inches (150 cubic centimeters). 
     In some cases, the meter also includes an electric drive motor for driving the rotor. 
     In presently preferred embodiments, the device includes a controller for controlling the number of revolutions of the motor, and, thereby, the volume of particulate matter released from the bin. 
     For supplying electrical power to the motor, an electrical storage battery may be mounted to the portable structure. In some instances, a battery charger may be adapted to receive power from an external source to recharge the battery. The battery may also be adapted to supply electrical power to the controller. 
     In some embodiments, an electronic programmable controller is included. The controller is adapted to operate the meter to release a desired volume of particulate matter, in accordance with operator input. This controller is preferably mounted upon the portable structure, but in other embodiments the controller may be a separable unit, with an electrical port provided on the inductor for attaching the remote electronic controller for controllably operating the meter. 
     In some instances, the controller is adapted to receive an operator input representing a desired weight of matter to be released and to calculate, based upon at least this input and a stored particulate matter density value, a corresponding volume of matter to be released. 
     When a preset amount of matter has been released, in some cases the controller is adapted to automatically stop releasing the particulate matter, while liquid carrier continues to flow along the conduit. Under such conditions, the controller is preferably adapted to alert an operator when the preset amount of particulate matter has been released. 
     In some embodiments, the conduit is adapted to apply a sub-atmospheric pressure to the released particulate matter, in the presence of an operative liquid carrier flow, to motivate the released matter into the conduit. This conduit may include an eductor, for example, which effectively forms a venturi. Such an eductor is preferably constructed to dissolve the particulate matter into the carrier liquid within the eductor, or as soon as possible thereafter. Preferably, the conduit is adapted to apply a vacuum of between about 0.5 and 6 pounds per square inch (3.4 and 41 kilo-pascals) below atmospheric pressure to the released particulate matter. 
     In some embodiments a check valve is disposed between the conduit and the meter. The check valve is adapted to be normally closed and to open when the sub-atmospheric pressure falls below a predetermined threshold, thereby applying the sub-atmospheric pressure to the downstream side of the meter. In some cases, a pressure switch responsive to this sub-atmospheric pressure is included, for enabling operation of the meter only in the presence of a desired amount of vacuum. In such cases, the pressure switch is located between the check valve and the meter. 
     Preferably, the bin comprises a hopper with sides sloped at an angle of between about 45 and 60 degrees from horizontal. It is also preferred that the hopper have an internal volume of between about 5 and 200 cubic feet (0.14 and 5.7 cubic meters. 
     In some cases, a vibrator is structurally connected to the bin and adapted to vibrate the bin during operation to assist flow of the particulate matter into the meter. 
     Preferably the portable structure has a base footprint sufficiently small to fit within a 4 foot by 8 foot (1.2 meter by 2.4 meter) rectangle. For example, one preferred embodiment has a base footprint of about 42 inches by 48 inches (1.0 meter by 1.2 meters). 
     According to another aspect of the invention, a method of dispensing precise amounts of dry particulate matter directly into a liquid carrier stream is provided. The method includes first connecting the conduit of the device of the invention, the bin of which contains particulate matter, to a source of liquid carrier; and then motivating a flow of the liquid carrier through the conduit, thereby dispensing a desired amount of the particulate matter from the bin of the device into the flow of liquid carrier. 
     In some cases, the particulate matter comprises an agricultural pesticide, fertilizer or adjuvant. 
     The liquid carrier may comprise water or a liquid fertilizer, for instance. 
     In some instances, the flow of liquid carrier is directed from the conduit of the device to a receptacle. 
     Where the device includes an electronic controller for controlling the meter of the device, the method may further include, prior to the step of motivating, entering a value into the controller representing a desired amount of particulate matter to be released. The method may also include, prior to the step of motivating, entering a value into the controller representing the density of the particulate matter to be released. 
     According to another aspect of the invention, a method of distributing agricultural chemicals in particulate form, to be mixed with a liquid carrier before use, is provided. The method includes the steps of:
         (1) providing multiple devices constructed according to the invention, as described above;   (2) distributing the devices, with corresponding quantities of agricultural chemicals, to individual end users for dispensing the agricultural chemicals into liquid carrier streams at remote locations; and then   (3) accepting the devices as returned from the end users, after the end users have dispensed at least some of the distributed chemicals.       

     In some embodiments, the method also includes, before distributing each device, filling the bin of the device with the corresponding quantity of agricultural chemical; and then, after accepting the returned devices, refilling the bins of devices with additional agricultural chemicals. 
     By using an inductor constructed according to the invention, a dry chemical substance can be properly and accurately metered directly into a liquid carrier, without possibly harmful exposure to chemical dust and fumes. Additionally, transportation of pre-mixed liquid chemicals can be avoided, with the chemicals being transported all the way to their use site in dry form. Simple, automated operation at remote sites may be provided by a control system that is adapted to run on on-board batteries, with very little operator input. Other advantages and features will also be understood from the following description of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a programmable, dry chemical inductor. 
         FIG. 2  shows the inductor being transported by truck. 
         FIGS. 3A and 3B  are schematic side views of the inductor, with transparent side panels, to illustrate its internal components and structure. 
         FIG. 4A  is a side view of the metering device, with the end caps of the meter housing transparent to show the internal rotor. 
         FIG. 4B  is a cross-sectional view taken along line  4 B— 4 B in  FIG. 4A , with the drive motor not sectioned. 
         FIG. 5  is an illustration of the control panel of the inductor. 
         FIG. 6  is an upper level functional schematic of the controller. 
         FIG. 7  illustrates a method of distributing agricultural chemicals. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring first to  FIG. 1 , a dry chemical inductor  10  is in the form of a box structure having side  12  and top  14  surfaces of sheet aluminum covering a steel frame  16 . Lifting brackets  18  at the four top corners of the frame are provided with lifting eyes  19  for hoisting the inductor by chain. Recesses  20  between the feet  22  of the frame provide clearance for fork lift tines. The feet are spaced so as to fit just inside of the lifting brackets of a lower inductor, with sufficient clearance for the lid of the lower inductor, for stable stacking. The inductor housing has an overall height “H” of 72 inches (1.83 meters), with a base footprint of about 42 by 48 inches (1.0 by 1.2 meters), the size of a standard shipping pallet, for efficient stacking on a standard flatbed truck. The height “H” of various embodiments will depend in part on the desired internal hopper volume. These dimensions provide for an internal hopper volume of 40 cubic feet (1.1 cubic meters), for example. Given the small size of the inductor, it can readily be loaded onto the bed of a standard pickup truck  24  for transportation, as illustrated in FIG.  2 . Other sizes of inductors will accommodate other hopper volumes. 
     Still referring to  FIG. 1 , the top  14  of inductor  10  has an opening which is normally covered by a removable lid  26 . The opening may be of 22.5 inches (57 centimeters) in diameter, for example, similar to the diameter of a standard drum. Lid  26  is in the form of a cover  28  and rubber gasket  30  held in place by a clamp ring  32  to form a dust-free seal to reduce the change of operator exposure to airborne chemicals. Generally, such a seal is required by some presently existing safety, environmental and regulatory standards for shipping particulate chemicals. 
     As discussed further below, and shown in subsequent drawings, inductor  10  has an internal hopper containing a quantity of bulk material which is intended to be mixed with a liquid carrier for use. To dispense a desired quantity of the bulk material into a liquid carrier, the user must first hook up the carrier inlet port  34  to a liquid carrier source, such as a water pump (not shown), that is adapted to motivate a flow of liquid carrier into the inlet port of the inductor. The mixture outlet port  36  is connected to a flexible hose for directing the liquid carrier and entrained bulk material from the inductor to a desired destination, such as a spray tank or mixing tank (also not shown). In the illustrated embodiment, ports  34  and  36  are two-inch (roughly 5 centimeter) cam and groove quick-connect couplings, sized to permit a liquid carrier flow rate of at least about 350 gallons (1350 liters) per minute. A value representing the amount of bulk material to be released (the “setpoint”) is keyed into a control panel  38 , and a flow of liquid is started through the inductor. When the inductor has sensed the presence of sufficient carrier flow, it automatically meters into the flow the desired amount of bulk material, without letting the liquid carrier flow up into the internal hopper to wet any unreleased bulk material. When the desired amount of bulk material has been released into the flow of carrier liquid, inductor  10  automatically stops dispensing the bulk material and alerts the user that the setpoint has been reached. The user can then turn off the flow of carrier liquid, or let it continue to run through the inductor, such as to complete the filling of a spray tank and further dilute the mixture. 
     Referring to  FIGS. 3A and 3B , a sealed hopper  40  is mounted within the outer structure of inductor  10 . Hopper  40  is shaped to promote gravitational feeding of bulk materials into the metering device  42  located at its lower end. We have determined that a wall slope angle “α” of between about 45 and 60 degrees will work for many particle shapes and sizes, 60 degrees being preferable for powders and other very fine particles. To assist with the flow of the bulk material into metering device  42 , an electric vibrator  44 , such as a model DC-300-24V available from Vibco, may be firmly attached to hopper  40  to vibrate the hopper and induce downward flow. Behind control panel  38  is a programmable electronic controller  46  that controls the operation of inductor  10 , including vibrator  44  and metering device  42 . Electric power is provided by a pair of 12 VDC, 17 amp-hour rechargeable batteries  48 , which provide enough power for about 4 hours of operation between charges with the vibrator running. An electrical charge port  50  is accessible from outside the inductor to recharge batteries  48  and/or power the inductor. Internal conduits hydraulically connect ports  34  and  36  through metering device  42 . 
       FIGS. 4A and 4B  better illustrate the structural detail of metering device  42 . A ⅛ horsepower, 32 RPM, 24 VDC gearmotor  52 , such as model PR990235, available from Leeson, drives the multi-vaned rotor  54  of a bulk material transfer gate  56 , such as the airlock described in U.S. Pat. No. 5,803,673. Gate  56  has a rotationally molded polycarbonate housing  58  and end caps  60 , and an injection molded “DELRIN” rotor  54  with eight integrally molded vanes  62  that define, in cooperation with housing  58  and end caps  60 , eight discrete pockets  64  that transport bulk material from upper opening  66 , open to the hopper ( 40 ,  FIG. 3A ) to a conical vacuum chamber  68  defined within housing  58  below the rotor. The rotor is supported on integrally molded axial projections  100  protruding from each end of the rotor through corresponding holes in end caps  60 . An aluminum motor shaft receiver  102 , of hexagonal outer shape, is insert molded into one of projections  100 , and defines a keyed central hole for receiving the motor shaft which drives the rotor. PTFE-encapsulated neoprene O-rings  104  provide for dynamic sealing between rotor  54  and end caps  60  during operation. A running clearance of about 0.005 inch (0.13 millimeter) is provided axially between the rotor and each end cap, and radially between the rotor and housing  58 . We have found that this clearance results in acceptably low leakage about the vanes for most intended bulk materials and at operating vacuum pressures. At the highest point of their rotation, vanes  62  of rotor  54  extend above the upper flange  106  of the gate (i.e., into the hopper) a distance “d” of about 1.0 inch (25 millimeters), helping to avoid “bridging” of packable bulk materials just above the gate. In this embodiment, rotor  54  has an overall diameter of about 7 inches (18 centimeters) and a length of about 7 inches (18 centimeters). 
     All of pockets  64  are of similar volume. In this embodiment, each pocket  64  has a volume of about 25.92 cubic inches (425 cubic centimeters), which is effectively the “resolution” of the dispensing system. Of course, gates  56  defining discrete pockets of other shapes and volumes are considered within the scope of this invention. For example, pocket volumes as low as 3 cubic inches (50 cubic centimeters) provide even finer resolution. Ideally, each pocket is completely and sequentially filled with bulk material from opening  66 , and completely empties into vacuum chamber  68 . To help ensure complete pocket filling and emptying, motor  52  may be adapted to impart a vibration to gate  56 . For embodiments having a separate vibrator ( 44 , FIG.  3 A), the gate may be structurally coupled to the vibrator to enhance pocket filling. Rotor positional feedback to the controller is provided by rare earth magnets  69  embedded in the vanes of the rotor, which are sensed by a hall effect sensor  71  in the housing end cap adjacent the motor. Alternatively, motors  52  with built-in positional feedback systems may be employed. As rotor  54  rotates, pulses from hall effect sensor  71  inform the controller of the passage of each vane, and therefore of the emptying of each pocket. The controller monitors these pulses until it has determined that the desired number of pockets of material, as determined from operator input and known pocket volume, have been dispensed. Once the controller stops applying power to motor  52 , friction and internal damping generally cause the motor to coast only a few degrees before coming to a stop, providing for an accuracy of +/−1 pocket or better in the total amount released. Better accuracies may be provided by equipping the motor with braking means (not shown) to positively stop rotation of the rotor at a desired vane increment. 
     The inner side walls of vacuum chamber  68  are sloped at an angle “β” of about 76 degrees above horizontal, to aid in directing released bulk material downward into the inlet of a vacuum check valve  70 . We prefer an angle β of at least 70 degrees to overcome the tendency of some materials to adhere to the inner walls of housing  58  which, alternatively, may be of die-cast aluminum with an anodized PTFE inner surface. 
     Check valve  70  is attached, by air-tight connections, to both gate housing  68  and eductor  72 . Valve  70  contains a wafer  74  which is urged against a seat, toward gate  56 , by a preload extension spring  76 , thereby blocking flow between the gate and eductor. When a predetermined carrier flow rate through eductor  72  has been reached or exceeded, flowing from inlet  78  to outlet  80 , a reduction in absolute pressure is achieved below wafer  74 . When the vacuum below wafer  74  is sufficient, wafer  74  moves away from its seat and transmits this vacuum to chamber  68 . It is preferred that gate  56  not be operated to dispense materials before a vacuum pressure has been established in chamber  68 . In other words, it is preferable that a threshold flow rate through eductor  72  be established before motor  52  begins to rotator rotor  54 . To that end, a pressure switch  82  is responsive to vacuum pressure within chamber  68  and signals the controller when the pressure in chamber  68  is below a predetermined threshold. The controller does not activate motor  52  until such a signal is received, thus preventing material release until a sufficient flow rate of carrier liquid has opened check valve  70 . This also helps to reduce the amount of contamination of bulk material in the hopper if the system were operated with a failed, open check valve. Should the flow of carrier liquid suddenly stop, check valve  70  will automatically and rapidly close, thus preventing any substantial flow of carrier liquid up into chamber  68 . At the same time, switch  82  will detect the loss of vacuum and the controller will stop energizing motor  52 . Of course, insubstantial amounts of carrier vapor or droplets will occasionally pass through check valve  70  and enter chamber  68 , such as when flow through eductor  72  is abruptly stopped. Of this minor amount of leakage, a small amount of vapor may be vented through gate  56  and up into the hopper. Importantly, however, the combination of check valve  70  and gate  56  avoids any significant amount of carrier liquid, any amount which would cause detrimental contamination, packing or dissolution, to enter the hopper. Commercially available eductors  72  are available as models 2083-X from Mazzei (high flow, low vacuum), and “2-inch ELL” from Penberthy (low flow, high vacuum). For more controlled air flow through vacuum chamber  68 , such as to help keep released materials flowing through check valve  70 , a vacuum check valve (not shown) may be installed through the side wall of housing  58 , below gate  56 , to let in a controlled flow of air and regulate vacuum pressure. 
     Referring to  FIG. 5 , control panel  38  has a digital display  84  for displaying textual information, and a keypad  86  for operator input. Besides a typical  10  number keys and a decimal key, keypad  84  includes a “STARTS/STOP” key  88 , an “ON/OFF” key  90 , an “ENTER” key  92  and a “RESET” key  94 . “ON/OFF” key  90  controls system power, as its name implies. Alter entering a setpoint, the operator pushes the “START/STOP” key  88  to begin automatic release of the material. During operation, pushing the “START/STOP” key  88  pauses the release of material and initiates an audible alarm and appropriate visual display indicating that release has been interrupted. “ENTER” key  92  is used for entering user input, such as data and passwords, and “RESET” key  94  is for acknowledging and resetting alarms or clearing keyed values. In addition, there are four additional functions performed by pushing various keys in combination with key “7”, sub-labelled “FUNCTION”. Holding key “7” while pushing key “1”, for example, displays the calibration factor (CF) for three seconds. This calibration factor represents the density of the bulk material, in pounds per pocket. Holding key “7” while pushing key “3”, displays current battery voltage (VDC). Holding key “7” while pushing either the “RESET” or “ENTER” keys will either raise or lower, respectively, the contrast of display  84 . If desired, a coaxial controller cable input jack  120  ( FIG. 1 ) may be provided for operation of the inductor from a pendant controller or keypad. 
     Three password levels are provided for various function authorizations. A typical user will be provided with a first level password which enables the entry of setpoints and very basic system operation. A second level password allows the user to change inventory parameters, calibration factors, or perform self-calibration. For self-calibration, the user will direct the system to dispense a given amount (e.g., weight) of material. The user then weighs the dispensed material with appropriate weighing means (not shown) and enters the weight of the material actually dispensed. The controller then adjusts its calibration factor accordingly. An example of changing inventory parameters is changing a value representing the total amount of bulk material presently contained within the hopper. For example, when filling the inductor with bulk material, a dealer may enter into the controller the total weight of material supplied. During operation, the controller continuously subtracts from this value the weight of material dispensed. When the controller determines that all of the material originally supplied has been dispersed (i.e., when the total weight register reads “0”), any further dispensing of material by the end user is disallowed. This safeguard is particularly important for enabling the dealer to reliably track the overall amount of material dispensed through the inductor, for example. A third level password authorizes more advanced adjustments, such as changing the motor speed, timer values or alarm points. 
     Referring to  FIG. 6 , a programmable microprocessor  96  is programmed to perform all data manipulations in controller  46 . CPU  96  receives input from the vacuum sensor or switch  82  (FIG.  4 B), the vane-sensing hall effect sensor  71  (FIG.  4 B), keypad  86  and, in some embodiments, a serial port (e.g., port  120  in FIG.  1 ). Based upon these inputs, CPU  96  drives motor drive circuitry  97  to pulse-width modulate high side power to gate motor  52  ( FIG. 4B ) to drive the gate rotor and dispense product. At the same time, CPU  96  triggers a power switch  98  to turn on the vibrator, if so equipped. A 5V voltage regulator  99  steps battery voltage down to power the electronic controller components. Display  84  is a two row, 16 character per row, backlit LCD display via which the controller communicates visually with the operator. In addition, a buzzer  101  gives an audible alarm when triggered by the CPU. 
     In  FIG. 7 , a method of distributing agricultural chemicals in particulate form includes distributing devices described herein, with quantities of agricultural chemicals, to individual end users  150  for dispensing the agricultural chemicals into liquid carrier streams at remote locations, and then accepting the devices as returned from the end users, after the end users have dispensed some of the distributed chemicals. 
     Other embodiments are also within the scope of the invention, although not illustrated in the drawings. For example, much smaller inductors may be produced for home gardening and landscaping applications, which are filled with dry chemicals at garden supply stores and then rented to homeowners or lawn care specialists. Such inductors may be attached to garden hoses for automatically dispensing selected rates of chemical into a monitored flow of water through the inductor. After use, the inductor may be returned to the dealer for cleaning and reuse, without the customer having ever been exposed to dry chemicals or had to either mix or transport liquid chemicals. Furthermore, inductors may be equipped with multiple, separate hoppers and metering devices, which may all feed a common eductor for instance, with a more sophisticated controller programmed to enable the operator to select chemical mix ratios, such as for customized fertilization. Such an inductor may be particularly useful to lawn care specialists, transported to each work site on the back of their equipment truck. Other embodiments will also be found to fall within the scope of the following claims.