AU723772B2 - Improvements in metering devices - Google Patents

Description

S F Ref: 361392

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: C-Dax Systems Limited 145 Harts Road Tiritea Palmerston North NEW ZEALAND Michael Henry Aart Oosterman Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Improvements in Metering Devices The following statement Is a full description of this invention, including the best method of performing it known to me/us:- 5845 This invention relates to improvements in metering devices.

Power-operated dosing equipment has been developed for the farming industry. Such equipment includes a metering device whereby a correct dose of an animal health product or an agri-chemical or the like can be applied to an animal or plant. Normally such equipment includes a switch which starts operation of a timer or other device to meter the required dose. Flow of liquid is normally controlled with an electrically operated valve.

A disadvantage of this type of equipment, however, is the 15 reliability of the switch due to the harsh environment in which the equipment and more particularly the dosing hand piece is used. Switches, valves and the associated wiring and connectors which are able to resist moisture, mud and chemicals, and work reliably after thousands of 20 operations are very expensive.

The object of the present invention is to provide a metering device for use with power-operated dosing equipment, the metering device overcoming or at least going some way t o overcoming the aforementioned A disadvantage of with known power-operated dosingis type of equipment, however, is the reliability of the broaswitch due to the invharsh environmenthere in provwhich the equip ment and mordevice comparticularly the dosing handmeans to detect piece is used. Switches, valves and the associated wiring and connectors which are able to resist moisture, I'.":mud and chemicals, and work reliably after thousands of operations are very expensive.

The object of the present invention is to provide a metering device for use with power-operated dosing equipment, the metering device overcoming or at least going some way to overcoming the aforementioned disadvantage with known power-operated dosing equipment.

According to one broad aspect of the invention there is provided a metering device comprising means to detect operation of a motor of pump means of a dispensing arrangement, timer means to cause the dispensing arrangement to dispense for a period of time and then cease operation and means to reset the metering device ready for the detection means to again detect operation of said motor of the pump means.

In the following more detailed description of the invention according to a preferred embodiment reference will be made to the accompanying drawings in which:- Figure 1 is a circuit diagram of the metering device according to an analogue form of the invention, 15 Figure 2 is a block circuit diagram of a digital form of the invention, and Figure 3 is a logic diagram for the form of the invention shown in Figure 2.

The present invention is based on the discovery that a metering device in the form of a timer can be activated without the need for an external switch or wiring. The metering device detects an operation of dispensing equipment with which it is associated so as to initiate a timing sequence. Once the sequence is complete (ie a required dosage has been dispensed) the timer causes operation of the dispensing equipment to cease whereupon it resets ready to detect the next operation of the dosing equipment.

According to the present invention the metering device detects a voltage drop across the pump motor of the dispensing equipment at the instant that the pump motor is switched on. To achieve this the operator simply opens the valve on the dosing hand piece (eg by activating a trigger, button or the like) and a dose is automatically metered out. By detecting the voltage drop across the pump motor the metering device initiates a timing sequence and switches off the power supply to the pump once the timing sequence is complete. The operator then has a nominated time to close the valve on the S 1 5 handpiece (ie release the trigger, button or the like) before a further timing sequence is initiated to reset the pump pressure.

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Upon next detecting a voltage drop across the pump motor (ie the hand piece trigger is activated) the cycle is repeated.

5.55o5 The metering device therefore does not need to be hard wired to a switch in the hand piece or an electrically operated valve. Thus it can be incorporated with all of the electronic equipment within the pump or accessory case where it is protected from the operating environment. The reliability problems associated with known power-operated dosing equipment where switches and associated wiring are exposed to an often harsh environment are overcome.

The metering device according to one form of the invention is shown in Figure 1 of the accompanying drawing. In the circuit there is provided a series resistor 18 network 10 forming a voltage sensor, timers 11, 12 and 13 connected in series and a power transistor array 15 which is provided to turn the motor M on/off.

The motor M is connected via resistor 18 such that when the motor commences operation a voltage drop occurs across the motor. This voltage drop is sensed by the voltage sensor 10 and a signal is applied to comparator 15 14 used to commence operation of the first timer 11. To eoou provide for varying dosages the first timer 11 is adjustable such that it will operate for approximately o** 0.2 seconds to 1.5 seconds depending on the setting ee *'".chosen by the operator.

When the first timer 11 times out and turns off it commences operation of the second timer 12. In turn, when the second timer 12 turns off it commences operation of the third timer 13. Upon the third timer turning off the metering device enters an idle mode until the voltage sensor 10 detects a voltage drop across the motor whereupon a new cycle commences.

In the preferred arrangement the motor has power supplied to it at all times except when second timer 12 is operating. The reason for this is that in the preferred form the pump associated with the motor has an "on demand" pressure switch which turns off if the pressure rises above a predetermined level (eg 40 At start-up of the dispensing equipment the hand piece valve is in the off position, thus the motor drives the pump so as to build up pressure resulting in the pressure switch turning off. When the operator operates the hand piece, ie causes the hand piece valve to open, the on demand pressure switch turns on, the pump commences operation, liquid starts flowing and the voltage sensor 15 10 detects a voltage drop caused by operation of the motor and thereby starts timer 11. The pump is able to continue to operate while timer 11 is on.

When timer 11 turns off and timer 12 commences operation .0 the power transistor array 15 turns off motor M and hence S the pump ceases operation thereby preventing liquid from flowing. This is the end of the dosing operation and the operator then has nominally 1 second to release the hand piece valve before timer 12 turns off. After timer 12 turns off, timer 13 commences operation. While timer 13 operates an alarm device 17 to give an audible tone may be employed.

The motor runs for approximately 0.25 seconds when timer 13 is on because the demand pressure switch has no pressure applied to it. When pressure is built up the pressure switch turns the motor off. The alarm device 17 stops approximately 0.5 seconds later. During this sequence timers 11 and 12 are prevented from operating by reset transistor 16. When the alarm device 17 ceases operating the operator knows that the unit is ready for the next dose.

If, however, the operator keeps the hand piece valve open (after the measured dose is complete) throughout the reset sequence, the metering device will turn off for *O about one second and then the motor will run continuously Sof 15 until the valve is closed. In this way continuous oeo .dispensing can be obtained if required.

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Referring now to Figure 2 of the drawings, a digital embodiment of the invention is illustrated. This form of the invention operates, as hereinafter described, *fee.: a according to substantially the same method as the S previously described analogue form.

According to this embodiment, the metering device includes a motor start sensing unit 20, motor drive unit 21, dose adjustment potentiometer 22, microprocessor 23 and power regulator 24.

The microprocessor 23 is programmed with a two-stage programme. The first stage of the programme adjusts the speed of the pump motor to ensure that the pump head pressure is below the shut-off pressure. This ensures that the pump always runs smoothly irrespective of the nozzle size in the handpiece and the shut-off pressure.

To activate the unit the power is turned on (via switch Si). Within a nominated time span the trigger valve in the handpiece must be opened. The pump head pressure will drop and the pump motor will start in accordance with the procedure followed with the analogue version previously described.

.e 15 The voltage drop is sensed by the motor start sensing unit 20 which starts a timing sequence in the microprocessor 23. If the motor start sensing unit detects that the motor is continually starting then shutting off the motor drive voltage will be reduced by a

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predetermined amount. This process will continue until 0*505S S no further motor starts are detected. When no cycling of o o the motor is detected the motor drive voltage will then be reduced by a predetermined amount to provide a margin for variations in the power supply PS.

In the second stage of the programme when a motor start is sensed, two sub-routines take place. The first subroutine carries out an analogue to digital conversion of a dose adjustment voltage which is set via the dose adjustment potentiometer 22. The second sub-routine disables the motor start sensing unit 20 to ensure that no more motor starts are recorded. A timing sequence then commences and runs for a time determined by the setting of the dose time potentiometer 22.

When the timing sequence has concluded the motor drive is turned off via motor drive unit 21 for a predetermined period. This indicates to the operator that the dose has been dispensed. At this point the operator must close the trigger valve. After a predetermined time, however, a maximum motor drive voltage will be applied so that the pump will run at full speed for a short time and then return to the controlled speed until it reaches the shutt o 15 off pressure. After a predetermined time the motor start eee sensing unit is re-activated ready to sense another dose.

The measured dose feature can be overridden by simply to holding the trigger valve open. If this is done one dose will be dispensed then after a short pause the pump motor will run continuously until the valve is closed.

Audible tones or lamps can be activated to indicate to the operator when the device motor speed setting sequence is complete, when dosing is in progress, when the dose has been dispensed, or when the device is ready 'to dispense another dose.

The type of valve used in the hand piece is not critical thus the timer according to the present invention can be used with any type of pumping system which uses an ondemand pump. The metering device therefore permits, for example, any electrically powered dispensing equipment (eg a sprayer normally used for spraying animal health remedies or agri-chemicals) to be converted to a dosing system by the addition of an inexpensive electronic module. While the invention has particular application in the agricultural industry it can also be used in other (eg industrial) applications.

Because the metering device according to the present invention does not require external switches and *e 15 associated wiring to operate, the problems associated ee with power-operated dosing equipment having a switch or other device associated with the dosing hand piece is overcome. All of the electronic equipment can be mounted within the pump or accessory case to be protected from the operating environment. Thus the reliability problems associated with known power-operated dosing equipment do not arise.

not arise.

Claims (9)

1. A metering device comprising means to detect operation of a motor of pump means of a dispensing arrangement, timer means to cause the dispensing arrangement to dispense for a period of time and then cease operation and means to reset the metering device ready for the detection means to again detect operation of said motor of the pump means.

2. The metering device according to claim 1 wherein the detection means detects a voltage drop across the pump motor. 20

3. The metering device according to claims 1 or 2 including switching means activated after said period of time to cease operation of the pump means.

4. The metering device according to any one of claims 1 to 3 wherein said timer means is adjustable. a"

5. The metering device according to claim 3 or 4 further including second timer means for defining a second period of time during which said pump means is rendered inoperative.

6. The metering device according to claim 5 further including third timer means which is operative upon said 12 second timer means timing out, said third timer means causing the pump means to become operable.

7. The metering device according to claim 6 wherein indicator means are provided to indicate when the third timer means is operative.

8. A dispensing arrangement in combination with a metering device as claimed in any one of claims 1 to 7.

9. The metering device substantially as herein described with reference to Figure 1 or Figures 2 and 3 of the drawings. 15 DATED this Fourth day of July 2000 Spruson Ferguson S GPO Box 3898 Sydney New South Wales 2001 AUSTRALIA