GB2141245A - Batch weighing apparatus - Google Patents

Abstract

Particulate material or discrete articles pass from hopper 10 by way of vibratory tray feeder 14 to an oscillatory bowl feeder which supplies the articles as a succession to a conveyor 20 comprising a weigh belt 22 supported by beams 26 associated with transducers disposed within cabinet 28 and operative to provide signals corresponding to the sensed weight of the belt 22 to a digital readout 48. Upon the readout reaching a preset value set upon comparator 50 interrupter valve flap 36 is switched over so that the articles which were previously falling down chute 38 of duct 34 are now diverted to chute 40. <IMAGE>

Description

SPECIFICATION Batch weighing apparatus This invention concerns batch weighing apparatus for batch weighing and feeding particulate material or individual articles, hereinafter referred to as "material" for the sake of convenience.

In one known form of batch weighing apparatus, a material weigh box, with a hinged flap orthe like on its base, is supported on a form of weigh balance, which may comprise a load-cell, a torsion balance, a flexure balance, a force balance or the like.

On occurrence of a signal, a pre-feeder (which may be for example, an electric or mechanical vibratory tray, a belt, or an archimedian screw) feeds material into the weigh box until a pre-set stop switch on the weigh balance signals the pre-feeder to stop. The full weigh box is then discharged into a holding hopper or a following machine via the hinged flap or the like.

The main problem with current practice is inaccuracy, especially when weighing larger articles, such as biscuits, sweets, bolts and nuts.

The accuracy of the conventional machine depends on stopping the pre-feeder instantaneously when the weigh balance pre-set switch is activated.

At this time, material or articles are still falling from the pre-feeder outlet. This is so-called 'in-flight' material. If several articles should happen to fall from the pre-feeder together at the instant the stop switch is actuated, then considerable inaccuracy occurs in the amount being weighed out. Moreover, if the density of the material being weighed changes, or if the feeding rate of the pre-feeder changes, although the weigh balance cut-off signal is constant, the amount of in-flight material is not.

Attempts have been made to circumvent this problem in that recently-developed machines have several weigh-boxes, (for example fifteen), each of which weighs a respective small percentage of the total batch weight required and these weigh boxes each drop their respective smaller batches into respective holding hoppers. A computer is then used to determine which of a number of the alternative small quantities will make up the single required perfect larger batch weight and commands the selected happens to discharge. This method is extremely complex and costly.

The present invention is based upon the appreciation that the need for such a complex and expensive arrangement can be avoided and that accurate batch weighing can be achieved much more simply and inexpensively and faster if the inflight weighing error is eradicated by the material being weighed-off a conveyor device e.g. in the form of a weigh belt or weigh screw, rather than providing for it to fall into a weigh box or a number of such weigh boxes.

Pursuant hereto, the present invention provides apparatus for batch weighing and feeding material (as herein defined) comprising supply means for supplying said material to a conveyor device having sensing means for sensing the weight of material on or in said conveyor device and supplying a signal corresponding thereto, integrating means for integrating said signals against unit time, comparator means for comparing the integrated signals against a preset batch value, and actuation means for initiating a batch-determining operation upon said batch value being reached.

The conveyor device may comprise a weigh belt or weigh screw supported by one or more cantilever weigh beams, the stress in which is sensed by the sensing means which may comprise one or more strain gauges, or like transducers.

The supply means may comprise a vibratory tray feeder. In the case where the material being batched is a powder or pulverulent material, the feeder may supply the material directly to the conveyor device, batch determination being achieved by switching off the conveyor device.

On the other hand, where the material being batched is a plurality of individual articles, the supply means may comprise a vibratory tray feeder which supplies the articles to a vibratory bowl feeder which in turn forwards the articles one at a time successively to the conveyor device. The batch determination may then be achieved by actuation of an interrupting valve, the conveyor device being driven continuously. To enable the interrupting valve to operate effectively, the conveyor device is preferably driven at a speed greater than that at which the articles are supplied thereto, so as to ensure the presence of spacing between the successive articles in or on the conveyor device.

In the apparatus of the invention, the weigh-rate signal generated by the sensing means is electronically integrated against unit time; thus, an accumulating batch value can be determined and indicated digitally. This digital indication of the accumulating batch value can be compared with a pre-set digital value and the actuator means, in the form of a switch, operated (or signal given) when the two coincide.

As mentioned, on operating the switch the supply means and the conveyor device (e.g. the weigh belt) can be stopped, thus determining a batch; alternatively, the supply means and the conveyor device can be kept running and a divertervalve actuated by the actuator means to divide the flow into discrete batches.

In this way, all in-flight inaccuracies are eradicated as there is no in-flight material.

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side elevation illustrating a practical embodiment of the apparatus of the invention; and Figure 2 is a diagrammatic plan corresponding to Figure 1.

As shown in the drawing, the illustrated preferred embodiment of the apparatus of the invention, which is particularly suitable for use in the batch weighing of discrete articles 12, comprises supply means starting with a product holding hopper 10 which is filled with the articles 12 required to be batched and has an outlet to a vibratory tray feeder 14. This feeder 14, in turn, feeds the articles 12 in bulk into a vibratory bowl feeder 16 having a level switch 18 which turns the vibratory tray feeder 14 on and off so as to keep the level in the bowl feeder 16 substantially constant.

The vibratory bowl feeder 16 comprises a bowl to the inside side wall of which is secured a spiral flight 19 (shown only diagrammatically in Figure 1) the width of which corresponds to one of the articles 12 being batched. When the feeder 16 is switched on, the articles 12 are progressed in a regular file up the spiral flight 19 as can be seen from Figure 2. Thus, as can be seen in Figure 2, they are presented at high speed and in a continuous single line to a subsequent conveyor device which is indicated generally by the reference numeral 20 and which in the illustrated case comprises a weigh belt 22, but may be a weigh screw (not shown).

The weigh belt 22 is a flat belt, driven at a constant speed by a geared electric motor 24. The weigh belt 22 is supported to extend outwards from cantilever arms 26 which are fixed by their inner ends within a weigh cell cabinet 28 fixed to a base 30 of the apparatus. Sensing means comprising electromagnetic transducers in the form of strain gauges (not visible) are bonded to the fixed ends of the cantilever arms 26 within the cabinet 28. These gauges detect the strains occurring within the arms 26 as a result of supporting the weigh belt 22 and the material or articles 12 thereon. The strain gauges thus effectively form a weight sensor for the material on the belt 22. A conditioner/amplifier (within the cabinet 28 and also not visible) supplies the strain gauges with a small voltage.As a result a signal voltage is generated by the strain gauges when sensing weight, this voltage being proportional to the actual weight of the material or articles 12 on the belt 22. This signal is amplified by the amplifier within the cabinet 28.

Situated at the end of the weigh belt 22 remote from the bowl feeder 16 is a diverter arrangement 32 comprising a duct 34 in which is a diverter valve in the form of a flap 36 which, when actuated, diverts the flow of material or articles 12 to one or the other of two outlet chutes 38, 40 provided by the duct 34.

The amplifier in the cabinet 28 supplies its signal by way of a line 42 to a control cabinet 44 which accommodates the following components which have been represented very diagrammatically, namely: (A) An integrator 46 which serves to convert the weight signal from the amplifier into a series of pulses, which it integrates against time, so that for a given weight of material or articles 12 passing over the belt 22 in a given time a certain number of pulses will be generated; (B) A digital indicator 48 whose digits are advanced by pulses received from the integrator 46.This indicatorwill showthe weight of material or articles 12 which has passed over the weigh belt 22 at any instant; and (C) A pre-settable digital comparator 50 which compares the number on the digital indicator 48 with a number to which it is set to correspond to a desired batch weight. This comparator gives an output when the indication given by the indicator 48 matches the figure set in the comparator 50.

The operation of the apparatus will readily be understood from the foregoing description. The articles 12 to be batched are filled into the hopper 10 from which they pass along the vibratory tray feeder 14 to fall into the bowl feeder 16, the vibration of the feeder 14 being switched off when the level switch 18 senses too great a level of articles in the bowl feeder 16.

Oscillatory vibration of the bowl feeder 16 serves to progress the articles 12 in the bowl feeder 16 as a succession along the flight 19 as can be seen more particularly in Figure 2, and these articles 12 fall or slide successively onto the weight belt 22 as a single file. As this is occurring, the transducers connected to the cantilever beams 26 supply successive weight signals to the integrator 46so as to provide, at the digital indicator 48, a visual readout of the total weight of articles 12 which have passed along the weigh belt 22 and have fallen off the latter into the duct 32 and the chute 38.Upon the indicator 48 reaching the batch weight number which has been preset on the digital comparator 50, a signal is supplied by the latter to a valve actuator 52 which serves to change over the valve flap 36 so that the following articles 12 now fall into the chute 40, the indicator 48 resetting, of course, as this occurs. The above-described sequence is repeated, of course, to return the valve flap 36 to its illustrated position when the indicator 48 once again matches the batch weight value preset on the comparator 50.

With the weigh belt 22 driven at an appropriate speed to ensure an appropriate spacing between the successive articles 12, the changeover of the valve flap 36 can occur effectively whilst there are no in-flight articles at the end of the weigh beam above the chute 32. Thus, very accurate batch weighing is achieved in a very simple and relatively inexpensive manner, these advantages arising from the fact that the articles 12 are, in practice, "weighed off" the weigh belt 22 and the need for the provision of one or a plurality of weigh boxes is obviated.

The apparatus is not usable solely with large discrete articles 12, and it can, if desired, be employed for the batch weighing of powdered, pulverulent or particulate material, as well as small articles.

Then, the vibratory bowl feeder 16 may not be required, but of course it is still desirable to sense the presence of material passing towards the weigh belt 22 by means such as the level switch 18.

Moreover, where small articles and/or powder is being batched, use could be made of a weigh screw instead of the weigh belt 22.

Moreover, the valve arrangement 34 is not essential to the invention, especially in the case of powders and small articles, since batching can, if desired, be achieved by switching the weigh belt on and off on receipt of the switching signals from the comparator 50. The conveyor device 20 does not, of course, have to be in the form of a weigh belt but could comprise a screw feeder within a suitable tubular enclosure or any other appropriate arrangement which will progress the material being weighed and batched progressively and evenly.

Claims (12)

1. Apparatus for batch weighing and feeding material (as herein defined) comprising supply means for supplying said material to a conveyor device having sensing means for sensing the weight of material on or in said conveyor device and supplying a signal corresponding thereto, integrating means for integrating said signals against unit time, comparator means for comparing the integrated signals against a preset batch value, and actuation means for initiating a batch-determining operation upon said batch value being reached.

2. Apparatus as claimed in claim 1 wherein the conveyor device comprises a weigh belt or weigh screw supported by one or more cantilever weigh beams, the stress in which is sensed by the sensing means.

3. Apparatus as claimed in claim 2 wherein the sensing means comprises one or more strain gauges, or like transducers.

4. Apparatus as claimed in claim 1,2 or 3 wherein the supply means comprises a vibratory tray feeder.

5. Apparatus as claimed in any preceding claim in which the feeder serves to supply the material directly to the conveyor device, batch determination being achieved by switching off the conveyor device.

6. Apparatus as claimed in claim 4 in which the vibratory tray feeder supplies the articles to a vibratory bowl feeder which in turn forwards the articles one at a time successively to the conveyor device.

7. Apparatus as claimed in claim 6 in which batch determination is achieved by actuation of an interrupting valve, the conveyor device being driven continuously.

8. Apparatus as claimed in claim 7 wherein the conveyor device is adapted to be driven at a speed greater than that at which the articles are supplied thereto.

9. Apparatus as claimed in any preceding claim further including means for indicating the accumulating batch value digitally for comparison with a pre-set digital value, the actuator means being initiated or operated when the batch value and the pre-set value coincide.

10. Apparatus as claimed in claim 9 wherein operation of the actuator means serves to stop the supply means and the conveyor device thus determining a batch.

11. Apparatus as claimed in claim 9 wherein operation of the actuator means serves to actuate a diverter valve to divide the flow into discrete batches.

12. Apparatus for batch weighing and feeding material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.