GB2310729A - Material weighing method and apparatus - Google Patents

Abstract

A method of weighing out quantities of material (Fig. 1) comprises operating coarse and fine feeders (10, 11) respectively in a side-by-side relationship at the same level to supply material to respective first and second weighing pans (12, 13) disposed therebelow. A memory pan (16) is disposed below the first weighing pan (12) and receives weighed material from the first weighing pan (12) to act as a store whilst the second weighing pan (13) is supplied with a desired weight of material from the fine feeder, in accordance with the weight of material supplied by the coarse feeder. Once the first weighing pan (12) has emptied it is immediately refilled, and when the desired weight has been supplied to the second weighing pan (13), the memory pan (16) and second weighing pan are opened to release each respective weights of material which then combine, for example upon passage into a packet. The memory pan (16) may be omitted, or large enough to receive material from both of the weighing pans (12,13). The memory pan (16) and the coarse weighing pan (12) may be interchanged. In Fig 5, a slow feeder (23) discharges into a weighing pan (24).

Description

MATERIAL DOSING METHOD AND APPARATUS This invention relates to a method of and apparatus for, providing doses of material, particularly accurately weighed doses.

With conventional linear weighing machines, a single feeding mechanism, adjustable to provide a coarse (bulk) feed rate or a fine feed rate, delivers flowable material to a weighing pan supported on a weighing transducer. The material is initially fed at a high flow rate (coarse feed) until the required net weight is neared, and then at a lower rate (fine feed). When the required weight of material is present in the weighing pan, the feed is halted, and the weighing pan automatically opened to deliver the material therein into a package or the like. The sequence is then repeated. This method is disadvantageous in being low speed, in that the coarse and fine feeds are consecutive. In a variation, the linear weighing machine instead has two feeding mechanisms, namely a bulk feeder, operating during the bulk feed only, and a fine feeder operating during both the bulk feed and the fine feed.

Double-beam weighers are faster machines, these comprising a feeding mechanism delivering a coarse feed of material into a first weighing pan supported on a weighing transducer, the amount of material delivered being a large proportion of the required total material dose. A second weighing pan supported on a separate weighing transducer is positioned below the first weighing pan so as to receive its contents. The second weighing pan is fed by a feeding device which delivers material to it at a rate lower than that of the coarse feeding mechanism, to bring the total weight of material in the second weighing pan up to the required weight.

Once this occurs, the second weighing pan opens to discharge its contents into a package. This discharge takes place whilst the first weighing pan is being refilled with a further coarse feed. This method has the advantage of concurrent operations, but is disadvantageous in that material must be brought to the machine at two different levels, one above the other. This leads to difficulties when the material will not, by its flow nature, gravitate from the higher to the lower level. Cleaning and maintenance is also difficult with this two-tier construction.

An object of the invention is to provide an improved method of, and apparatus for, dosing material.

According to one aspect of the invention, a method of dosing material comprises supplying material to a first location via first feeding means having a first feed rate, determining the weight of material supplied to said first location, supplying material to a second location, via second feeding means having a second feed rate lower than said first feed rate, in accordance with said weight of material supplied to said first location, to provide a desired weight of material at said second location, and combining material having left said first and second locations respectively.

According to another aspect of the invention, apparatus for dosing material comprises first feeding means operable at a first feed rate, a first location to which material can be supplied, in use, via said first feeding means, means for determining the weight of material supplied to said first location, second feeding means operable at a second feed rate lower than that of said first feeding means, a second location to which material can be supplied, in use, via said second feeding means, means for controlling said second feeding means in accordance with said weight of material supplied to said first location to provide a desired weight of material at said second location, and the locations being arranged so that, in use, material having separately left said first and second locations respectively is thereafter combined.

Preferably the material from the first feeding means is retained at storage means during at least part of the supply of material from said second feeding means.

Desirably the storage means is a memory pan disposed either directly downstream of said first location, or between said first feeding means and said first location. Conveniently the first and second feeding means are at the same level.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of a first embodiment of material dosing apparatus of the invention, which can be operated according to a material dosing method of the invention, and Figures 2 and 5 show alternative embodiments to that of Figure 1.

A first embodiment of a method and apparatus of the invention will be described with reference to Figure 1 which diagrammatically shows a high speed automatic gravimetric weighing machine for dosing (flowable) material in accurate weighments.

The material, not shown, to be dosed arrives on a pair of feeders, disposed side-by-side at the same level. One of these is a coarse feeder 10, whilst the other is a fine feeder 11, the fine feeder 11 being intended to be run at a slower feed rate than that of the coarse feeder 10. The feeders could be vibrators, belts or similar transport devices. The feeders are separately driven and each delivers material therefrom into separate weighing pans disposed therebelow. In Figure 1 there is shown a coarse weighing pan 12, and a fine weighing pan 13. These weighing pans are supported on respective individual weighing transducers 14, 15, these being of conventional form.

Below the coarse weighing pan 12 is a memory pan 16 of similar form to the pan 12 but being merely in the form of a storage receptacle which is not connected to any transducer. All the pans are capable of being opened automatically by a control system of the machine in order to discharge their contents under gravity.

One example of a method of operation of the machine shown in Figure 1 is as follows, it being appreciated that the requirement of the machine is to provide a dose of material of a predetermined weight to a package or the like.

Firstly the coarse feeder is operated to feed a large proportion of the required total weight of material into the coarse weighing pan 12. Once this weight has been supplied, the coarse feeder is stopped by the control system. The termination of the feed can be in response to the actual weight in the coarse weighing pan, as determined by the transducer 14, or it can take place after a predetermined feeding time.

As used herein, the expression 'predetermined time' refers to a time period which is determined before the feeder starts feeding. It does not necessarily have to be a constant value, and could be adjusted automatically by the control system and vary from one feeding operation to the next in response to some historic data. For example it could be adjusted according to the average coarse weight delivered over a number of preceding coarse feed cycles.

Once the coarse feed of material is terminated, the control system then acquires the weight of material in the coarse weighing pan by using the output signal from the coarse transducer. It memorises that weight, and then causes the coarse weighing pan 12 to open, thus delivering the contents thereof into the empty memory pan 16. As will be described, the memory pan sequentially empties, and this allows the sequence of feeding material to the coarse weighting pan 12 and its transfer to the memory pan 16 to be repeated to ensure high speed operation of the apparatus, the contents of the coarse weighing pan being transferred to the memory pan as soon as it becomes empty again.

As soon as the control system has memorised the weight of the material in the coarse weighing pan 12, it causes the fine feeder 11 to commence feed of material into the fine weighing pan 13, until the weight in that pan, as determined by the signal from the transducer 15, is equal to, or greater than, the required total weight minus the memorised weight of material which is now in the memory pan 16. The control system then causes the fine feeder to stop. Optionally it then memorises the exact weight which was delivered by the fine feeder, for recording purposes.

Thereafter the control system then causes the memory pan 16 and the fine weighing pan 13 to open at the same moment, or nearly so, such that the contents of the two pans arrive in the package or equivalent disposed underneath the pans at the same, or nearly the same, moment.

This may occur immediately after the fine feed has been terminated, or it could be delayed. In either event the opening of the pans can be as a result of receipt by the control means of a command signal from a packaging machine which supplies packages to receive material from the weighing machine. The total weight delivered to the package is therefore the sum of the contents of the pans 13 and 16, the sum being equal to or greater than the required total weight The control system then operates to cause the fine filling operation to repeat.

It will be appreciated that, as described, the weighed dose of material from the coarse feeder is held in the pan 16 during at least part of the fine feed of material into the weighing pan 13, the coarse weighing pan 12 being refilled during this time, so that as soon as the memory pan 16 empties, it can be refilled immediately or almost immediately from the coarse weighing pan 12. Thus although the fine feeder supplies material at a feed rate slower than the supply of material from the coarse feeder 10, the difference in the feed rates is made use of by the provision of the memory pan 16 which means that the coarse feeder is not idle after supplying the weighed dose of material which is to be combined with the weighed dose of material supplied by the fine feeder. It will be appreciated that although the combined weights of material from the fine weighing pan 13 and the memory pan 16 would normally provide a combined amount of material which is then packaged, this is not necessarily the case in that, in another embodiment, the desired, combined weight of material could be less than the required total packaged weight, the material combined from pans 13 and 16 being transported from the weighing apparatus for further combination with additional further or different material to bring it to the final packaged weight.

As with material fed to the weighing pan 12, the supply of material to the pan 13 from the fine feeder can be terminated either in response to the actual weight recorded or in response to the expiry of a predetermined feeding time. In some instances it may be possible for feed of material to the fine weighing pan 13 to be commenced whilst feed of material with which it is to be combined is still taking place to the coarse weighing pan 12, the consideration being that the final weight of material received in the pan 13 is determined in sufficient time to stop feed to the pan 13 before the weight of material received therein is unacceptably greater than that required, together with a coarse fed material, to be discharged from the pans 13 and 16. Whilst an underweight condition is unacceptable, in this embodiment, a limited amount of overweight is acceptable, though this must be strictly controlled for example so as not to supply more material than the package can hold.

It will also be appreciated that it might be possible to omit the memory pan 16, and, in effect, replace it by an empty package below the pans 12 and 13, so that a weighed dose of material would be supplied to the package from the pan 12, the pan 12 then being refilled whilst the fine feeder supplies material to the pan 13, this material then being supplied to the package to combine with the coarse fed material and the package removed from under the pans, whereupon as the next empty package moves under the pans, it can immediately be supplied with coarse fed material from the pan 12 which was refilling whilst the pan 13 was being fed with material from the fine feeder. Thus in this instance the package acts as the memory pan to store one part of the combination of material which makes up the final total weight from the pans 12 and 13.

Figure 2 shows a further embodiment of the invention, this being very similar to that shown in Figure 1, the difference being that the memory pan, now denoted by the numeral 17, is arranged to receive material from both of the weighing pans 12 and 13. This would not substantially change the method of operation of the dosing machine. A difference would be that the contents of the fine weighing pan would either pass through the memory pan 17 whilst it was still open, or said contents might arrive in the memory pan before it were to open, should the fine weighing pan 13 have completed its feed before the memory pan received a command signal from the control system, and/or packaging machine, to open. Figure 3 shows a slightly different form of this embodiment, where the memory pan 18, equivalent to the memory pan 17 of Figure 2, could take the physical form of a simple gate having doors 19 at the outlet of a collecting funnel/chute arranged to concentrate the output of the weighing pans 12 and 13 to a common discharge area.

Figure 4 shows a further embodiment of the invention, this being similar to that shown in Figure 1, but with the positions of the memory pan 20 and the coarse weighing pan 21 reversed so that the memory pan is directly downstream of the coarse feeder and directly upstream of the coarse weighing pan 21, and its associated transducer 22.

With this arrangement the weight of the material supplied via the coarse feeder 10 would be acquired by the control system after that material is transferred from the memory pan to the coarse weighing pan.

Accordingly the sequence of method operations would be the same as described with the machine of Figure 1, but with the phrases 'coarse weighing pan' and 'memory pan' reversed. In this instance the coarse feeder would be stopped as a result of the expiry of a predetermined time period. The material collected in the memory pan 20 would then be discharged into the coarse weighing pan 21, whereupon via the transducer 22 its weight would be determined and a control system would cause the fine feeder 11 to operate to commence supply of material to the weighing pan 13. During this time, the memory pan 20 would again be supplied with material from the coarse feeder 10, so that once material is fed to the package from the weighing pan 21, and simultaneously from the weighing pan 13, the then empty weighing pan 21 is again supplied with material from the replenished memory pan, with the process repeating as described in reverse with the Figure 1 embodiment.

With this embodiment, it may be convenient to deliver the first coarse feed directly through the memory pan into the coarse weighing pan 21 in order to expedite the first cycle of the machine, in the event of the coarse weighing pan not being refilled immediately after its contents are discharged. This would occur, for example, if the coarse feeder became starved of material for some reason.

Figure 5 shows how the invention can be extended to provide three different feeders arranged side-by-side at a common level. The part of this embodiment identical with that shown in Figure 1 has been numbered identically thereto, with the third feeder being a slow-fine feeder denoted by the numeral 23 and disposed at the side of the fine feeder 11 remote from the coarse feeder 10. This feeder 23 would have an even slower feed rate than the fine feeder 11 previously described.

This fine feeder 23 discharges, in use, into a slow-fine weighing pan 24.

As can also be seen from Figure 5, the material discharged from the fine weighing pan 13 and memory pan 16 are combined in a further memory pan 25 disposed beneath said pans 13 and 16, but arranged not to receive discharge from pan 24. The amount of material fed into the weighing pan 24 by the feeder 23, which is regulated in accordance with the combined weight in pan 25, would further correct the weight held in the further memory pan 25, said weight being arranged to be slightly less than the required dosed weight. Instead of the pans 12 and 16 being as in Figure 1, they would more likely be as in Figure 4, with the upper pan being a memory pan and the pan below it being a weighing pan.

The advantage of this arrangement would be to improve accuracy by allowing the slow-fine feeder 23 to have as much time, and therefore as lower feed rate as possible, as the fine feeder 11.

It is clear that this concept could be extended to n levels by adding a still slower feeder, a slower-feeder weighing pan, and a further memory pan at each level. Although not shown for ease of illustration, all weighing pans shown in Figure 5 would be supported on individual weighing transducers of a form of transducers 14 and 15 in Figure 1, or of any other convenient form.

Accordingly it can be seen that with the Figure 5 arrangement, the dose received in a package at the bottom of the machine would be a combination of the material discharged from the further memory pan 25, and the material discharged from the weighing pan 24.

In any embodiment of the invention, any of the feeders could be equipped with shut-off flaps/gates near their discharge ends to prevent fall-off of material, and to minimise the amount of produce which is inflight when the corresponding feeder stops.

Accordingly the arrangements described and illustrated are advantageous in that at least the coarse feeder can operate more efficiently than with the described prior art linear weighing machines, as a result of the storage of the dosed weight previously discharged from the coarse feeder whilst a finer feeder operates. Accordingly the coarse feeder can be discharging the next dose of material whilst the finer feeder operates. As the respective weighing pans of the coarse and finer feeders respectively are not one above the other as with the described prior art double-beam weighers, the disadvantages thereof are overcome, with the described arrangements having the feeders at a common level and in a side-by-side relationship. This enables separate doses of material to be combined by being dropped side-by-side into a common memory pan for storage, or directly into a package to be filled. It will be appreciated that the materials supplied by the different feeders need not be the same.

Claims (31)

1. A method of dosing material comprising supplying material to a first location via first feeding means having a first feed rate, determining the weight of material supplied to said first location, supplying material to a second location, via second feeding means having a second feed rate lower than said first feed rate, in accordance with said weight of material supplied to said first location, to provide a desired weight of material at said second location, and combining material having left said first and second locations respectively.

2. A method as claimed in Claim 1, wherein a first storage location receives material from said first location, and retains such material therein during at least part of the supply of material to said second location.

3. A method as claimed in Claim 2, wherein once material from said first location is received at said first storage location, material is immediately or substantially immediately again supplied to said first location.

4. A method as claimed in Claim 2 or Claim 3, wherein material leaves said first storage location at the same or substantially the same time as material leaves said second location.

5. A method as claimed in any one of Claims 2 to 4, wherein after termination of supply of material to said first location the weight of material at said first location is determined.

6. A method as claimed in any one of Claims 2 to 4, wherein after termination of reception of material at said first storage location the weight of the received material is determined.

7. A method as claimed in Claim 5 or Claim 6, wherein supply of material to said second location commences after the determination of said weight.

8. A method as claimed in Claim 5 or Claim 6, wherein supply of material to said second location commences before the determination of said weight.

9. A method as claimed in any one of Claims 2 to 8, wherein said first storage location receives material from both said first and second locations.

10. A method as claimed in Claim 9, wherein material from both said first and second locations is held in combination at said first storage location.

11. A method as claimed in Claim 9, wherein material from said second location received at said first storage location passes directly therefrom without being held thereat.

12. A method as claimed in Claim 9 or Claim 10, including supplying material to a third location, via third feeding means having a third feed rate lower than second feed rate, and combining material leaving said first storage location and said third location, the supply of material to said third location being in accordance with the weight of said combined material at said first storage location.

13. A method as claimed in any one of the preceding claims, wherein the supply of material to said second location is terminated when the weight of material supplied at said second location is equal to or greater than a required total weight minus the weight of material supplied to the first location, such a weight being said desired weight.

14. A method as claimed in any one of Claims 2 to 13, wherein supply of material to the locations, and the reception of material at the first storage location is by means of gravity.

15. Apparatus for dosing material comprising first feeding means operable at a first feed rate, a first location to which material can be supplied, in use, via said first feeding means, means for determining the weight of material supplied to said first location, second feeding means operable at a second feed rate lower than that of said first feeding means, a second location to which material can be supplied, in use, via said second feeding means, means for controlling said second feeding means in accordance with said weight of material supplied to said first location to provide a desired weight of material at said second location, and the locations being arranged so that, in use, material having separately left said first and second locations respectively is thereafter combined.

16. Apparatus as claimed in Claim 15, including a first storage location arranged to receive material from said first location.

17. Apparatus as claimed in Claim 15 or Claim 16, wherein said first location is a first weighing pan.

18. Apparatus as claimed in Claim 17, wherein the first weighing pan is arranged below the first feeding means and the first storage location is a receptacle arranged below the first weighing pan.

19. Apparatus as claimed in any one of Claims 16 to 18, wherein said second location is a second weighing pan.

20. Apparatus as claimed in Claim 19, wherein the second weighing pan is arranged below the second feeding means.

21. Apparatus as claimed in any one of Claims 16 to 20, wherein the first storage location is arranged to receive material from both the first and second locations.

22. Apparatus as claimed in Claim 16, wherein the first storage location is a first weighing pan.

23. Apparatus as claimed in Claim 22, wherein the first weighing pan is arranged below the first location, which itself is arranged below the first feeding means.

24. Apparatus as claimed in Claim 22 or Claim 23, wherein said second location is a second weighing pan.

25. Apparatus as claimed in Claim 24, wherein said second weighing pan is arranged below the second feeding means.

26. Apparatus as claimed in any one of Claims 1 5 to 25, including a third location to which material can be supplied, in use, via a third feeding means operable at a third feeding rate lower than that of the second feeding means, means for determining the weight of the material supplied to said second location, the locations being arranged so that, in use, material having separately left the first, second and third locations respectively is thereafter combined, and means for controlling said third feeding means in accordance with the weight of combined material having left the first and second locations.

27. Apparatus as claimed in Claim 26, wherein the third location is a third weighing pan.

28. Apparatus as claimed in any one of Claims 15 to 27, wherein all the feeding means are arranged at the same level.

29. Apparatus as claimed in any one of Claims 15 to 28, wherein the feeding means are disposed side-by-side.

30. A method of dosing material, substantially as hereinbefore described, with reference to, Figure 1 or Figure 2 or Figure 3 or Figure 4 or Figure 5 of the accompanying drawings.

31. Apparatus for dosing material, substantially as hereinbefore described, with reference to, and as shown in Figure 1 or Figure 2 or Figure 3 or Figure 4 or Figure 5 of the accompanying drawings.