GB2068345A - Dispensing of granular materials - Google Patents

Abstract

A granular material, e.g. a herbicide or other agricultural chemical, is applied in uniform and readily adjustable quantities using an applicator including a hopper (2) with orifices (14) in its base for discharging the granular material onto metering wheels (24) mounted on a drive shaft (15) beneath the hopper. The wheels (24) are arranged substantially to close the orifices (14) when stationary, and to feed the material to a spreader upon rotation. The shaft (15) and wheels (24) are rotated at a preset speed by a motor (21), the speed of the motor (21), and thus the rate of application of material, being maintained substantially constant by control means that constantly monitor an A.C. feedback from the motor (21) and controls motor speed by adjusting the current fed to the motor (21) to compensate for speed changes of the motor (21). <IMAGE>

Description

SPECIFICATION Dispensing of granular materials This invention relates to the dispensing of granular materials and concerns an applicator for granular material, for example granular agricultural chemicals such as herbicides, and a method of dispensing such material.

It is important for certain agricultural chemicals, e.g. herbicides to be applied in precise quantities, with a uniform distribution of the chemicals. This is particularly true of chemicals which are selective in their action. Excessive application in any given area is not only wasteful of the chemicals but may also lead to crop loss. If chemicals are applied in sufficient quantities the desired result, e.g. weed control, may not be produced, with consequent waste of the chemicals.

Further, in many cases it is desirable to apply agricultural chemicals to only selected areas of a particular crop, and for this reason, and also to avoid unnecessary loss of chemicals, it is desirable to use an applicator that is capable of being effectively retained in an off condition in which no dispensing or loss of chemicals occurs: this means that the applicator can be transported from one location to another without loss of chemicals in transit and is helpful when operating on rough terrain.

Finally, the rate of application of the applicator i.e. output per a given unit of time is desirably easily adjusted, preferably from a tractor or other machine by which the applicator is towed. Thus it is desirable for an applicator for agricultural chemicals to supply a constant, uniform and readily adjustable quantity of chemicals, and to be capable of being readily turned on or off.

Presently available applicators are designed primarily for the application of chemical fertilizer or crop dusts. Most such applicators involve a reciprocating or rocking motion, which tends to result in a cylical output of material rather than a smooth continuous flow. Granular material dispensers are disclosed in Canadian Patents Nos. 511,023; 569,598; 663,435; 707,611; 723,490 and 949,391; and U.S. Patent Nos. 2,865,536; 3,073,607; 3,190,506; 3,788,529 and 3,858,759.

Some of the devices disclosed in the aboveidentified Patents rely for feed control on changes in the weight or volume of the material being fed altering motor speed. The feed mechanisms ultilized include an auger, apertures closed by slide valves of the construction found on small, commercially available, lawn fertilizers, a feed roller with cavities for receiving and dispensing a quantity of granular material, and brushes extending into a hopper containing the granular material.

In some of the devices disclosed in the above Patents, material flows from an upper hopper through holes into a smaller, lower hopper where it forms piles. The tops of the piles are displaced into tubes leading to spreaders by a reciprocating rod that extends along the length of the lower hopper and that bears studs or washers to assist in the displacing action. The result is cyclical output. Moreover, on rough terrain, material in the piles in the lower hopper tends to escape from the applicator, with consequent wastage of the material and possible over application.

Other applicators include trap door-like devices extending the entire length of the hopper for rocking back and forth to open one side of the hopper and then the other. Such rocking action results in intermittent output which may be acceptable for certain chemical fertilizers, but is not acceptable for granular herbicides. Metering devices placed inside the main hopper of the applicator tend to pulverize the granular material, causing compaction within the hopper and reduced feed through the discharge orifices.

Thus, in spite of the large variety of granular feed devices presently available, as exemplified by the art discussed above, there is still a need for an uncomplicated applicator.

The object of the present invention is thus to provide a relatively simple applicator for granular material which is easy to render operative and inoperative, and in which the rate of application can be accurately and quickly controlled.

Accordingly, the present invention provides in one aspect an applicator for granular material, comprising a hopper for holding granular material; a plurality of orifices in a base of said hopper for discharging said material from the hopper; a respective wheel mounted for rotation beneath each of said orifices for receiving material passing through the associated orifice and feeding the material to a spreader, said wheels being arranged substantially to close said orifices when the wheels are stationary; drive means for causing rotation of said wheels at a preset speed; and control means for regulating said drive means to maintain the rotation of said wheels at said preset speed.

In a further aspect, the present invention provides a method of dispensing granular material from a hopper to a spreader, comprising discharging granular material from the hopper through a plurality ofdischarge orifices onto a plurality of rotating wheels that feed the material to the spreader; a respective wheel being mounted beneath each such orifice and being arranged substantially to close the associated orifice when the wheel is stationary; constantly monitoring the speed of drive means that cause rotation of said wheels by monitoring an alternating current feedback signal produced by an alternating current generator in said drive means and passed to a metering circuit; and adjusting the speed of said drive means in accordance with signals received from said metering circuit indicative of a variation in the speed of said drive means.

A preferred embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a top perspective view of an applicator in accordance with the present invention; Figure 2 is an end view, shown partly in section, of the apparatus of Fig. 1, with parts omitted; and Figure 3 is a circuit diagram of the control circuit for the apparatus of Fig. 1.

Referring to the drawings, the applicator illustrated in Figs. 1 and 2 comprises a casing generally indicated at 1 including an upper portion in the form of a hopper 2 and a rectangular parallelepipedic lower portion 3.

The hopper 2 is trough shaped, having rectangular front and rear walls 4 and 5, respectively, which converge towards the bottom of the hopper and end walls 6 and 7, and is divided into three compartments 10, 11 and 1 2 by means of partitions 8 and 9. The top of the hopper is open for receiving granular agricultural chemicals, and the bottom of the hopper is closed by a rectangular base 1 3.

The base 1 3 is provided with a plurality of equidistantly spaced, aligned metering orifices 14 for discharging a predetermined quantity of granular material from the interior of the hopper 2. Of course, the quantity of material discharged through the orifices 14 during any given interval of time will depend on the size of such orifices.

The lower portion 3 of the casing 1 contains a shaft 1 5 rotatably supported in a plurality of bearings 1 6 mounted in one end wall 1 7 of the bottom portion 3 and in a series of brackets 1 8 spaced apart along the width of the casing 1. One end 1 9 of the shaft 1 5 extends outwardly beyond the end wall 1 7 of the bottom portion 3 of the casing 1 and has a sprocket 20 mounted thereon.

The sprocket 20 is connected to a small electric motor 21 via a chain 22 and a sprocket 23 mounted on the shaft of the motor. The motor 21 is a variable speed, ungoverned speed regulated D.C. motor of less than 1 horsepower (745 watts) incorporating a small A.C. generator. The purpose of the generator is described in detail hereinafter.

A plurality of metering wheels 24, equal in number to the orifices 14, are mounted on the shaft 1 5 within the lower portion 3 of the casing 1. The longitudinal axis of the shaft is located directly vertically below the aligned orifices 14, and each wheel 24 is located immediately below an associated one of the orifices 14. The wheels 24 are so dimensioned and arranged that the spacing between each orifice 14 and the uppermost point on the periphery of its associated metering wheel 24 is such that granular material contained in the hopper 2 can be discharged onto the wheels 24 only when the wheels are rotating with the shaft 15; when the wheels 24 are stationary they effectively block the orifices 14 so that no granular material can pass therethrough.

During use of the applicator, when the wheels 24 are rotating, material passing through the orifices 1 4 forms a small pile on the top of the associated metering wheels 24.

The width, diameter and surface roughness of the wheels are selected such that the resulting piles of material tend not to spill over the edges or around the circumference of the wheels. The dimensions of the metering wheels 24 are thus selected appropriately depending upon the properties of the material being dispensed, the coefficient of friction between the wheel and such material, the internal coefficient of friction of the material, the diameter of the orifice and the clearance between the wheels 24 and the orifices 14. It is apparent that for any given orifice size and clearance between the orifice and associated wheel, the output of a particular material depends only on the speed of rotation of the wheel 24, i.e. the output of the applicator is dependent only on the speed of movement of the peripheries of the wheels 24.

As the wheels 24 rotate (in the direction of the arrow in Fig. 2, i.e. clockwise as seen in Figs. 1 and 2), piles of material found on the wheels as discussed above move with the wheels and the material spills into a series of funnels 25 that lead to respective collector tubes 26. The material thus passes through the tubes 26 and is discharged from bottom ends 27 thereof into a spreader (not shown).

In order to permit adjustment in a forwards and rearwards direction of the discharge ends 27 of the tubes 26, such discharge ends are mounted in a cross-bar 28 that is adjustably secured to the trough 2 via a pair of arms 29 and a pair of brackets 30. The ends of the cross-bar 28 are secured to the lower ends of the arms 29, the upper ends of these arms being pivotally mounted on the outer free ends of the brackets 30, that, in turn, extend outwardly and rearwardly from the hopper 2.

The arms 29 are connected to the brackets 30 by pins 31, and are provided with guide rollers 32 extending into slots 33 in the brackets 30.

A bracket 34 is connected on each end of the hopper 2 for mounting the applicator on the frame of a trailer, harrow or other conveying implement.

The speed of rotation of the shaft 1 5 and thus of the metering wheels 24 is capable of being varied so that the rate of application of the agricultural chemical can be correspondingly varied. Moreover, the apparatus is so arranged that it is possible to maintain such speed constant in order to ensure a uniform, constant supply of chemicals from the hopper 2 to the spreader.

The circuitry for effecting such control is illustrated in Fig. 3 and includes the A.C.

generator (not shown) in the motor 21. Signals produced by the generator are fed to a control panel located in a tractor or other towing vehicle and are used as the basis for controlling the speed of the motor 21, and consequently the speed of rotation of the rollers 24. Once a particular speed of rotation has been selected, the control circuit illustrated in Fig. 3 monitors the speed and compensates for changes in such speed. The control circuit also compensates for minor variations in torque as a result of bearing misalignment and the like. Thus, the spewed of rotation of the metering wheels 24 is maintained constant.

In general terms, the speed of the motor 21 is accurately controlled by a circuit which utilizes the A.C. output of the motor to produce a D.C. voltage which is dependent upon motor speed. The D.C. voltage level in turn controls the potential and thus the current delivered to the motor, and consequently maintains a constant motor speed under a variety of conditions.

The motor 21 is powered by a power source (e.g. the battery of the tractor towing the applicator) via leads 35 incorporating a fuse 36, an on-off switch 37 and an indicator light 38. At any control setting of a switch 39, the A.C. output (feedback) from the motor 21 is rectified by rectifier 40 to provide a D.C.

voltage level with respect to the 1 2 volt line across a capacitor 41. A net D.C. voltage level is provided at the base of a transistor 42 dependant upon the frequency of the tach generator output (feedback from the motor 21) and the setting of a speed control potentiometer 43. As the setting of the potentiometer 43 moves towards point 44, the conductivity of the transistor 42 increases, i.e. the current flow through the transistor 42 increases, providing a greater flow through further transistors 45 and 46 to increase the current to the motor 21. In the same manner, an increase in the load on the motor 21 causes an initial decrease in motor speed and a resultant drop in potential at the base of the transistor 42.Again, the transistor 42 conducts more heavily providing a greater current to transistors 45 and 46, whereby the motor torque is increased to compensate for the increased load. A rectifier 47 is provided in the control circuit to protect the transistor 46 from excessive transients (voitage variations).

The circuit described above is particularly suitable for use in apparatus of the present invention, because full potential is applied to the motor 21 initially, resulting in a rapid transition to steady state speed. As the speed of the motor 21 increases and the voltage level across capacitor 41 increases, current flow through the transistor 42 decreases to provide a smooth adjustment to the desired operating speed of the motor. A zener diode 48 protects the transistor 42 from excessive current loads by maintaining a potential of approximately 6.5 volts at the point 44.

When there is no input from the A.C. generator of the motor 21, e.g. when the motor stalls, the maximum current fed to the motor is 2 amps, at which time the current flow through the transistor 42 is limited by the zener diode 48.

The drive circuit described above is coupled to a metering circuit 49, which includes meter 50 for providing an indication of motor speed.

The meter is connected to a monostable multivibrator chip 51, which provides a D.C.

metering current dependent upon the frequency of the signal from the A.C. generator of the motor 21. The meter 50 measures the metering current, which is proportional to the motor speed. A readout calibration is provided via a variable resistor 52 as it, in conjunction with capacitor 56, changes the duration of the output pulse from the chip 51. The switch 39 permits switching so that the desired output of the A.C. generator of the motor 21, i.e.

motor speed, can be monitored. A capacitor 52 provides a ground path for high frequency potentials essentially isolating the trigger input from false signalling. Because the A.C. generator of the motor 21 provides a 6 volt A.C.

potential, resistors 54 and 55 voltage divide the input from the generator to a level which can be safely handled by the chip 51 and still provide reliable triggering.

Resistors 57 and 58 create a voltage drop from the supply to provide a voltage acceptable to the metering circuit 49. Zener diode 59 protects chip 51 by maintaining a constant potential of approximately 5.1 volts from the supply. Capacitor 60 provides added filtering of unwanted frequency signals, thus the speed of the motor 21 and consequently the speed of rotation of the wheels 24 is constantly monitored and, if necessary, adjusted.

With this arrangement, at any given setting of the switch 39, the motor 21 will operate at a constant speed to ensure accurate and uniform dispensing of granular herbicide by the rollers 24.

It will be appreciated that a control box will be provided in the tractor or other towing vehicle. The control box will contain one metering circuit 49 and from three to five drive circuits for varying the current to the motor 21 in accordance with the setting of the switch 39.

Claims (11)

1. An applicator for granular material, comprising a hopper for holding granular material; a plurality of orifices in a base of said hopper for discharging said material from the hopper; a respective wheel mounted for rotation beneath each of said orifices for receiving material passing through the associated orifice and feeding the material to a spreader, said wheels being arranged substantially ta close said orifices when the wheels are stationary; drive means for causing rotation of the wheels at a preset speed; and control means for regulating said drive means to maintain the rotation of said wheels at said preset speed.

2. An applicator according to claim 1, wherein said wheels are coaxially and fixedly mounted on a rotatable shaft the longitudinal axis of which is vertically aligned with said orifices, said drive means being arranged to cause rotation of said shaft, and thus of said wheels.

3. An applicator according to claim 1 or 2, wherein said drive means includes a motor; and said control means includes means for constantly monitoring the speed of said motor, and thus of the speed of rotation of said wheels, and adjustment means for varying the input to said motor in accordance with the signals received from said monitoring means as said motor varies from said preset speed.

4. An applicator according to claim 3, wherein said motor includes an A.C. generator adapted to generate an A.C. feedback signal that represents the speed of said motor and that is monitored by said control means.

5. An applicator according to any one of claims 1 to 4, further comprising metering means for providing to an operator a constant reading of the speed of said drive means, and thus of the speed of rotation of said wheels.

6. An applicator according to any one of claims 1 to 5, further comprising a plurality of downwardly disposed collector tubes for collecting and carrying the granular material to said spreader, each of said collector tubes having a funnel at its upper end for receiving granular material from the surface of an assaciated wheel and also having a lower discharge end positioned to discharge material into said spreader.

7. An applicator according to claim 6, wherein the forward and rearward positioning of said discharge ends is adjustable.

8. A method of dispensing granular material from a hopper to a spreader, comprising discharging granular material from the hopper through a plurality of discharge orifices onto a plurality of rotating wheels that feed the material to the spreader, a respective wheel being mounted beneath each such orifice and being arranged substantially to close the associated orifice when the wheel is stationary; constantly monitoring the speed of drive means that cause rotation of said wheels by monitoring an alternating current feedback signal produced by an alternating current generator ih said drive means and passed to a metering circuit; and adjusting the speed of said drive means in accordance with signals received from said metering circuit indicative of a varia tion in the speed of said drive means.

9. An applicator for granular material, substantially as herein described with reference to, and as shown in, the accompanying drawings.

10. A method of dispensing granular material, substantially as herein described with reference to the accompanying drawings.

11. Any novei feature or novel combination of features disclosed herein.