GB1593993A

GB1593993A - Weightsensitive metering apparatus

Info

Publication number: GB1593993A
Application number: GB2359777A
Authority: GB
Original assignee: Whitton H W
Current assignee: Whitton H W
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-07-22

Description

(54) WEIGHT-SENSITIVE METERING APPARATUS (71) I, HERBERT WILLIAM WHITTON, a British Subject, of Primrose House, Kexby, Gainsborough, Lincolnshire, DN21 5DX, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement:- The present invention relates to weightsensitive metering apparatus and particularly to such apparatus suitable for use on motor vehicles or trailers for determining an applied load such as the weight of material charged into a hopper or other container.

It is frequently necessary to obtain an indication of an applied load, either by means of an analogue or digital readout, or by means of a simple YES/NO display which provides an indication of whether a selected or predetermined load has been applied. Weight-sensitive metering apparatus according to the present invention may be used not only on mobile systems such as are mentioned above, but also on fixed metering apparatus.

Although the present invention has a wide range of potential applications as discussed above, it will be described, for convenience, with particular reference to one of the possible applications, namely that of providing an indication of the weight of the contents of a container for the purpose of mixing batches of different ingredients.

It is frequently necessary to mix several different ingredients to provide, for example, a complete diet feed for livestock.

In agriculture and industry very large quantities are involved, and conventional weighing and measuring equipment is often inadequate for the purpose. In addition, the present invention comprehends weighing and mixing apparatus capable of accurately determining the weight of a number of different ingredients, mixing the ingredients in a container, and then discharging the mixed ingredients either entirely or in successive accurately determined portions.

According to the present invention there is provided metering apparatus selectively settable for the metered loading or unloading of material into or from a container of said apparatus, the apparatus comprising, in addition to said container, input means through which material can be loaded into the container, discharge means for unloading material from the container, sensor means operable to generate a signal which varies in dependence on the weight of material in said container, presettable means for generating a signal representing a desired target value of the weight of the material in the container, said target value being greater or less than the current weight of material in the container in dependence on whether the apparatus is set for the loading or unloading of material into or from said container, and comparison means arranged to compare the signal from the sensor means with the signal from the presettable means and operative: -when the apparatus is set for the metered loading of material into said container, to produce a characteristic warning output signal upon the current weight value rising to within a predetermined amount of said target value, and a characteristic equality output signal upon said target value and current value becoming equal, and -when the apparatus is set for the metered unloading of material from said container, to produce said characteristic warning signal upon the current weight value falling to within said predetermined amount of said target value, and said characteristic equality signal upon said target value and current value becoming equal.

The apparatus may also include means for providing an indication of the value of the current weight sensed by the sensor means, either in analogue or in digital form.

Unless compensated for, this indication will include the tare or the container.

Preferably therefore, the sensor means includes means for compensating automatically for such preliminary load so that the indicated weight value is equal to the weight of material in the container; with the signal output from the sensor means to the comparison means similarly adjusted, no further account need be taken of the tare of the container.

There are preferably provided visual indicator means energised by the warning output signal from the comparison means for providing a visual indication that the difference between the current weight of material in the container and the target value is less than the said predetermined amount. Such visual indicator means could be for example, a lamp placed on the apparatus at a position where it can clearly be seen from a distance so that, when illuminated, it provides an indication to the operator that the target weight has nearly been reached and therefore that closer supervision will soon be needed.

Thus, having set a desired target weight value on the controls, the apparatus may be left unattended with an operator merely needing to check occasionally to see whether the visual indicator means are illuminated: if so, this indicates that the weight, of material in the container is approaching the selected target value and closer supervision can be maintained if required.The equality output signal produced by the apparatus when the weight of material to change; in the example given target value may be used to operate a visual indicator means, or may be used to operate automatic control means for cutting off whatever operation was causing the weight of material to change; in the example give above, of the apparatus applied to a mixing container to which ingredients are being added, the equality output signal representing the attainment of the target weight value may be used to close a gate or to stop an auger feeding the material into the container.

The apparatus may also be provided with visual indicator means indicating that the absolute difference between the signal representing the target weight value and the signal representing the current weight is greater than the said predetermined amount; this also provides an indication that the apparatus is in operation but that the current weight is still substantially different from the target value. The three visual indicator means may be in the form of lamps of different colours, suitably green to indicate that the apparatus is in operation, amber to indicate that the current weight has approached closely the target value, and a red lamp to indicate that the current weight has reached the target value.

As well as the indicator lamps on a control unit of the apparatus, there may also be remote indicator lamps positioned at a convenient point for observation from a wide range of positions so that an operator can perform other tasks while waiting for the apparatus to complete its cycle, or can operate a plurality of systems.

In the example given above of a mixing container, the remote indicating lamps may be placed at a high point on the container so that an operator can see them from a considerable distance away. The mixing of ingredients for agricultural use, for example for livestock feeds, involves the preparation of very large quantities of material, for example up to ten thousand kilograms, and includes a requirement for the container to be discharged in portions less than the total.

For this reason, the apparatus of the present invention is arranged such that with the said target value set lower than the current weight of material in the container at the beginning of an operation, an indication will still be provided of the current weight approaching the target value, this time from above. Such an arrangement can be obtained, for example, by providing a suitable switch for selecting the polarity of a difference signal between signals representing the current weight and the target value.

There may also be provided audible indication means in place of or in addition to the visual indicators. The audible indicator could, for example, be in the form of a horn or buzzer which changes tone when the visual indicators change from green to amber and then red.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an agricultural mixing container incorporating weight-sensitive metering apparatus of the present invention; Figure 2 is a block schematic diagram of the metering apparatus applied to the container of Figure 1, which uses linear variable differential transformers (LVDT); Figure 3 is a block schematic diagram illustrating a further circuit for use with the device of Figure 1 where a plurality of batches are to be mixed again using LVDT load cells; Figure 4 is a further embodiment of the invention adapted for use with strain gauge bending movement weigh bars or strain gauge load cells mounted on mobile or static apparatus; ; Figure 5 which is an alternative embodiment of the invention for use with strain gauge transducers, useful for applications where either three or four strain gauge transducers are employed; Figure 6 is a schematic block diagram illustrating an indicator circuit with digital readout, and Figure 7 is a schematic diagram illustrating the application of the insertion to a trailer.

Referring now to the drawings, and particularly to Figures 1 and 2, there is shown an agricultural mixing container of known type, comprising a generally rectangular hopper 11 containing three parallel screw augers 12, 13, 14 driven from a drive input shaft 15 via a plurality of drive chains passing over associated sprockets on the ends of the shafts of the augers 12, 13, 14. The hopper is mounted on a trailer chassis 16 having a draw bar 17 by means of which the trailer can be attached to an agricultural tractor vehicle having a powertake-off shaft to which can be connected the input drive shaft 15 of the trailer to drive the screw augers 12, 13, 14.

Adjacent the forward end of the hopper 11 is an output chute 18 which can be closed or opened simply by pivoting an end part 19 thereof between a lowered and a raised position. In Figure 1 the end part 19 of the chute 18 is shown in the lowered position.

The container 11 is mounted on the chassis 16 by a mounting system incorporating four load cells 21, 22, 23, 24 which are connected by electrical lines to a control box 25. The control box 25 incorporates electronic circuits for detecting the load on the load cells 21-24 in accordance with signals generated by the load cells themselves. By providing four such cells any asymmetry in the loading of the container 11 can be compensated automatically in a known way without introducing errors into the operation of the circuit.Three indicator lamps 26, 27, 28, are mounted on the rear of the container 11 and connected by lines (not shown) to the control box 25 which controls operation of these lamps and which has three corresponding lamps itself as will be described in more detail below, the remote lamps 26, 27, 28 being controlled via relays, switching transistors or thyristors controlling connection of the lamps 26, 27, 28, to a twelve volt power supply (also not shown). The set of lamps 26, 27, 28 may, of course, be located at any other convenient position where it can be seen by an operator.

Figure 2 illustrates the control circuit 25 of the control box: It is suitable for use with differential transformer-type load cells and accuracy to 0.1% is obtainable with loads of up to 10,000 kilograms. On the front of the control box is a digital thumb wheel switch bank 80 by means of which the desired target value for the weight of material in the container 11 can be set on the control circuit. Indication of the target weight being reached is provided by a nullmeter 35 on the front panel which is linked to the indicator lamps 26, 27, 28 in a manner which will be described in greater detail below. An audible warning device 29 is also incorporated.The apparatus may be adjusted to select a target weight value greater or lesser than the starting weight of material in the container 11 (for loading or unloading the container 11) by means of a two-way toggle switch 37a located on the front of the panel.

The circuit comprises an oscillator 10 feeding a two-phase signal to the load cells 21-24. The output from the load cells is fed to an a.c. summing amplifier 30 which also receives a reference signal from the oscillator 10 via a line 31. A tare setting switch 32, also fed from the oscillator 10 feeds a balance signal to the input of the amplifier 30 and also feeds an initial balance control device 33 operable to adjust the balance position of the circuit to compensate for any weight to which it may initially be subject such as the tare or weight of the container itself. The output from the amplifier 30 will thus represent only the load on the load cells 21-24 due to the weight of-material in the container 11.The output from the amplifier 30 is fed to a demodulator amplifier 34 which produces a d.c. output signal fed to a null indicator 35 and to a double comparator unit 36 which latter also receives an input a signal from the switch bank 80 and an input signal from a setting device 40 which determines the threshold for the difference between the target weight value and the measured current weight at which an indication that the measured current weight is approaching the target value is given. This indication will be referred to hereinafter as the "pre alarm" signal. The output from the two comparators of the unit are 36 fed to a pre alarm remote light unit 37 and from there via switching transistor pairs to a relay circuit 38 which controls the connection between a power source 39 and the three indicator lamps 26, 27, 28.Connected in parallel with the indicator lamp 28 is an audible warning device 29. The load/unload switch 37a which sets the pre-alarm to operate when the measured weight exceeds or falls below the target value is actually part of the pre-alarm circuit 37, but has been shown externally of this to idenfity its location.

When the circuit is set in operation the pre-alarm remote light unit 37 energises the relay circuit 38 to illuminate the light 26 which is green. When the output from the demodulator 34 approaches within a predetermined amount of the target (this amount being set by the setting device 4G) one output from the comparator unit 36 changes sign and this is detected by the prealarm light unit 37 and a signal fed to the relay circuit 38 to turn off the green lamp 26 and energise the lamp 27 which is amber.

Finally, when the output from the demodulator circuit 34 reaches the target value selected, the null indicator 35 displays a null signal and the comparator unit 36 feeds an output signal to the pre-alarm light unit 37 to control the relay circuit 38 to turn off the amber lamp 27 and energise the lamp 28, which is red, and also the audible warning device 29 to draw the attention of an operator to the fact that the target weight value has been attained. The lamps 26, 27, 28 are additional to lamps provided on the control unit 25 serving the same purpose when an operator is able more closely to supervise the operation of the unit.

Referring now to Figure 3 there is shown a circuit suitable for batching purposes.

The batching circuit illustrated in Figure 3 would be provided in addition to the control circuit of Figure 2 and comprises a plurality of banks of thumb wheel switches 40, 41, 42 and 43 feeding respective four pole changeover relays 40a, 41a, 42a, 43a fed with control signals from the oscillator.

Each of the relays 40a to 43a is enabled to turn by a CMOS switching device 45 at each switching operation. A time-delay circuit 44 is provided with a range of up to eight seconds between successive switching operations. Indication of the switch bank in operation is provided by means of a panel lamp in series therewith (not shown) and further signal outputs can be provided to switch in various parts of a control system such as loading or discharging augers, or mixing augers, which may form part of the device to which the electronic scale apparatus is applied. Each switch is provided with an auto-hold facility enabling a set programme to be stopped at any point.

Indication of the approach of the measured current weight to the desired target value and attainment of the desired weight is by the circuit described and illustrated in relation to Figure 2 to which input setting information is fed from each of the setting switches 40-43 via the relays 40a ... 43a in turn (replacing the switch bank 80).

Referring now to Figure 4, the circuit for use with strain gauge transducers comprises an oscillator 45 and power unit inverter 46 fed with 12 v d.c. and supplying a.c. signals to strain gauge bridges constituting the load transducers 21, 22, 23, 24. The output from the strain gauge bridges is fed to an a.c.

summing amplifier together with the reference signal from the oscillator. Tare setting is achieved, as in the other circuits, by a plurality of digital thumb switches 44.

The output from the summing amplifier 47 is fed to a demodulator circuit 48 and thence, as a d.c. signal to a comparator unit 49 which is also fed with a reference signal from the oscillator 45 and signals from the target-value switch bank 80 and the setting device 40. The comparator unit outputs feed a pre-alarm remote light unit 50 operating relays 51 selectively to connect a power supply to one or other of the indicator lamps 26, 27 or 28 as in the circuit of Figure 2.

The remote light unit 50 also has a load/unload selector switch 50a the setting of which determines whether the pre-alarm signal is given when the measured weight approaches the target value from above or below.

The circuit of Figure 5 is similar to the strain gauge indicator of Figure 4 differing only in the provision of an encapsulated oscillator amplifier 52 and the demodulator amplifier 53. The output from the demodulator amplifier 53 is fed, as in the circuit of Figure 4, to a comparator unit 49 fed with a reference signal from the oscillator 52 and feeding a pre-alarm control circuit 50 the output from which controls respective relays of a relay circuit 51 connecting a power supply and inverter unit 39 to respective lamps 26, 27 or 28.

In Figure 6 is illustrated an indicator circuit with digital readout which is similar to the previously described load cell indicator circuit, but instead of employing a light indicator unit and thumb-wheel tare setting switches, the output is fed directly from the demodulator circuit 48 and interfaced to an analogue-to-digital converter 60 to drive a liquid crystal display or light emitting diode display 61.

Figure 7 is a general arrangement view of a system applied to a trailer and particularly illustrates the control panel 701 showing the null meter 702, balance control 703, weight setting thumb-wheel switches 704, power switch 705, load/unload switch 706 and the three indicator lamps 707 which light up green, amber and red as described above.

Connected to the control box 701 are three strain gauges 708, 709, 710, two on the axle and one of the draw bar of the trailer chassis.

Also shown on the control panel are an audible warning device 711 and two alarm setting controls 712.

WHAT I CLAIM IS: 1. Metering apparatus selectively settable for the metered loading or unloading of material into or from a container of said apparatus, the apparatus comprising, in addition to said container, input means through which material can be loaded into the container, discharge means for unloading material from the container, sensor means operable to generate a signal which varies in dependence on the weight of material in said container, presettable

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. relay circuit 38 to turn off the green lamp 26 and energise the lamp 27 which is amber. Finally, when the output from the demodulator circuit 34 reaches the target value selected, the null indicator 35 displays a null signal and the comparator unit 36 feeds an output signal to the pre-alarm light unit 37 to control the relay circuit 38 to turn off the amber lamp 27 and energise the lamp 28, which is red, and also the audible warning device 29 to draw the attention of an operator to the fact that the target weight value has been attained. The lamps 26, 27, 28 are additional to lamps provided on the control unit 25 serving the same purpose when an operator is able more closely to supervise the operation of the unit. Referring now to Figure 3 there is shown a circuit suitable for batching purposes. The batching circuit illustrated in Figure 3 would be provided in addition to the control circuit of Figure 2 and comprises a plurality of banks of thumb wheel switches 40, 41, 42 and 43 feeding respective four pole changeover relays 40a, 41a, 42a, 43a fed with control signals from the oscillator. Each of the relays 40a to 43a is enabled to turn by a CMOS switching device 45 at each switching operation. A time-delay circuit 44 is provided with a range of up to eight seconds between successive switching operations. Indication of the switch bank in operation is provided by means of a panel lamp in series therewith (not shown) and further signal outputs can be provided to switch in various parts of a control system such as loading or discharging augers, or mixing augers, which may form part of the device to which the electronic scale apparatus is applied. Each switch is provided with an auto-hold facility enabling a set programme to be stopped at any point. Indication of the approach of the measured current weight to the desired target value and attainment of the desired weight is by the circuit described and illustrated in relation to Figure 2 to which input setting information is fed from each of the setting switches 40-43 via the relays 40a ... 43a in turn (replacing the switch bank 80). Referring now to Figure 4, the circuit for use with strain gauge transducers comprises an oscillator 45 and power unit inverter 46 fed with 12 v d.c. and supplying a.c. signals to strain gauge bridges constituting the load transducers 21, 22, 23, 24. The output from the strain gauge bridges is fed to an a.c. summing amplifier together with the reference signal from the oscillator. Tare setting is achieved, as in the other circuits, by a plurality of digital thumb switches 44. The output from the summing amplifier 47 is fed to a demodulator circuit 48 and thence, as a d.c. signal to a comparator unit 49 which is also fed with a reference signal from the oscillator 45 and signals from the target-value switch bank 80 and the setting device 40. The comparator unit outputs feed a pre-alarm remote light unit 50 operating relays 51 selectively to connect a power supply to one or other of the indicator lamps 26, 27 or 28 as in the circuit of Figure 2. The remote light unit 50 also has a load/unload selector switch 50a the setting of which determines whether the pre-alarm signal is given when the measured weight approaches the target value from above or below. The circuit of Figure 5 is similar to the strain gauge indicator of Figure 4 differing only in the provision of an encapsulated oscillator amplifier 52 and the demodulator amplifier 53. The output from the demodulator amplifier 53 is fed, as in the circuit of Figure 4, to a comparator unit 49 fed with a reference signal from the oscillator 52 and feeding a pre-alarm control circuit 50 the output from which controls respective relays of a relay circuit 51 connecting a power supply and inverter unit 39 to respective lamps 26, 27 or 28. In Figure 6 is illustrated an indicator circuit with digital readout which is similar to the previously described load cell indicator circuit, but instead of employing a light indicator unit and thumb-wheel tare setting switches, the output is fed directly from the demodulator circuit 48 and interfaced to an analogue-to-digital converter 60 to drive a liquid crystal display or light emitting diode display 61. Figure 7 is a general arrangement view of a system applied to a trailer and particularly illustrates the control panel 701 showing the null meter 702, balance control 703, weight setting thumb-wheel switches 704, power switch 705, load/unload switch 706 and the three indicator lamps 707 which light up green, amber and red as described above. Connected to the control box 701 are three strain gauges 708, 709, 710, two on the axle and one of the draw bar of the trailer chassis. Also shown on the control panel are an audible warning device 711 and two alarm setting controls 712. WHAT I CLAIM IS:

1. Metering apparatus selectively settable for the metered loading or unloading of material into or from a container of said apparatus, the apparatus comprising, in addition to said container, input means through which material can be loaded into the container, discharge means for unloading material from the container, sensor means operable to generate a signal which varies in dependence on the weight of material in said container, presettable

means for generating a signal representing a desired target value of the weight of the material in the container, said target value being greater or less than the current weight of material in the container in dependence on whether the apparatus is set for the loading or unloading of material into or from said container, and comparison means arranged to compare the signal from the sensor means with the signal from the presettable means and operative:: -when the apparatus is set for the metered loading of material into said container, to produce a characteristic warning output signal upon the current weight value rising to within a predetermined amount of said target value, and a characteristic equality output signal upon said target value and current value becoming equal, and -when the apparatus is set for the metered unloading of material from said container, to produce said characteristic warning signal upon the current weight value falling to within said predetermined amount of said target value, and said characteristic equality signal upon said target value and current value becoming equal.

2. Apparatus according to Claim I, further comprising visual indicator means operative in response to said warning output signal to provide a visual indication that the current weight value is within said predetermined amount of said target value.

3. Apparatus according to Claim 2, in which instead of, or in addition to, said visual indicator means there are provided audible indicator means responsive to said warning output signal to produce an audible signal.

4. Apparatus according to any one of the preceding claims, in which the there are further provided visual indicator means operative in response to said equality output signal to provide a visual indication that the current weight value is equal to the said target value.

5. Apparatus according to Claim 4, in which instead of, or in addition to, said visual indicator means responsive to said equality output signal, there are provided audible means responsive to said equality output signal to produce an audible signal.

6. Apparatus according to any one of the preceding claims, in which said sensor means includes means for compensating for or neglecting the value of any tare in the load sensed by the sensor means.

7. Apparatus according to Claim 6 further comprising a readout instrument operable to provide a visible readout of the load sensed by the sensors.

8. Apparatus according to Claim 7, in which the said means for compensating for tare on the load on the sensors includes means for adjusting the apparatus to give a null reading on the readout instrument.

9. Apparatus according to any one of the preceding claims, in which said presettable means comprises programming means for outputting in sequence a plurality of signals representing successive target values, the apparatus including control means responsive to said first and second output signals to control the input and discharge means such that the current weight of material in the container is adjusted to correspond to successive said target values.

10. Apparatus according to Claim 7 arranged to automatically mix a plurality of different ingredients, said input means comprising a plurality of controllable inputs to said container, each input being individually controllable by said control means to load into said container a weight of a corresponding one of said ingredients equal to the difference between two successive target values output from said programming means.

II. Metering apparatus substantially as hereinbefore described with reference to, and as shown in, any of Figures 1 to 7 of the accompanying drawings.