Method for switching between product types on a sorting system for sorting products such as vegetables and fruit and sorting system therefor

Abstract

The invention relates to a method for switching between different products such as vegetables and fruit on a sorting system, a computer-readable medium and sorting system suitable therefor, the method comprising of:receiving a switching signal during sorting of products of the first product type that products of the second product type have to be sorted;the controller selecting sorting channels which are free of products of the first product type;assigning at least some selected sorting channels to the second product type;assigning sorting classes of the second product type to one or more of the assigned sorting channels; andsorting products of the second product type in sorting channels assigned thereto during the emptying of sorting channels of the first product type. Preparatory emptying of some of the sorting channels optionally takes place prior to the switch-over.

Claims

1. A method for switching from a first product type to a second product type on a sorting system for sorting products provided with a sorting device comprising a number of sorting channels, the method comprising: supplying products via a feed system; singulating the supplied products using a singulator; measuring the products; classifying each of the products into a sorting class based on measured product characteristics; receiving by a switch-over module from a controller of the sorting system during sorting of singulated products of the first product type a switching signal indicating that singulated products of the second product type have to be sorted; selecting by the controller part of the sorting channels of the sorting system which are free of products of the first product type, wherein the selected part of the number of sorting channels is smaller than a total number of the sorting channels; assigning at least some of the selected part of the sorting channels to the second product type; assigning sorting classes of the second product type to one or more of the sorting channels of the selected part of the sorting channels assigned to the second product type; and during emptying of a non-selected part of the number of sorting channels of the sorting device in respect of the first product type, sorting products of the second product type in the sorting channels assigned to the second product type in the selected part of the number of sorting channels to which a sorting class of the second product type has been assigned.

2. The method of claim 1, wherein selecting by the controller sorting channels which are free of products of the first product type and the switch-over module assigning selected sorting channels to the second product type are performed repetitively in respect of at least additional sorting channels of the sorting system which become available over time and which are clear of products of the first product type as a result of emptying sorting channels in respect of the first product type.

3. The method of claim 2, wherein assigning a sorting class of the second product type to sorting channels selected for the second product type in the selected part of the sorting channels is performed repetitively.

4. The method of claim 1, wherein the assigning by the switch-over module of sorting classes of the second product type to one or more of the sorting channels assigned to the second product type in the selected part of the sorting channels is performed on the basis of a prioritization of sorting classes.

5. The method of claim 4, wherein the prioritization comprises a quantity of product in a class per unit time.

6. The method of claim 4, wherein the prioritization is carried out based on information obtained by a measuring and classification system about the second product type which is gathered by measuring a first group of products of the second product type.

7. The method of claim 1, wherein one of the sorting classes assigned to the selected part of the sorting channels comprises a residual category of the second product type.

8. The method of claim 1, further comprising preparatory emptying of a part of the number of sorting channels in respect of the first product type prior to the switch from the first product type to the second product type.

9. The method of claim 8, wherein some product classes of the first product type are combined in a residual category of the first product type on the basis of a prioritization.

10. The method of claim 9, wherein the residual category of the first product type is assigned to one or more available sorting channels.

11. The method of claim 9, wherein the prioritization comprises a quantity of product of the first product type in a class per unit time.

12. The method of claim 9, wherein the prioritization is carried out based on information obtained by a measuring and classification system about the first product type which is gathered by measuring products of the first product type.

13. The method of claim 9, wherein the prioritization is carried out based on a quantity of the first product type still to be expected per class.

14. The method of claim 7, further comprising sorting the products from the respective residual category again at a later stage.

15. The method of claim 7, wherein the products from the respective residual category are fed back via a return channel.

16. The method of claim 1, wherein preparatory emptying of at least a part of the number of sorting channels takes place in respect of the first product type prior to the switch from the first product type to the second product type.

17. A non-transitory computer-readable medium comprising a computer program configured, when executed on a computer, to perform a method for switching from a first product type to a second product type on a sorting system for sorting products provided with a sorting device comprising a number of sorting channels, the method comprising: supplying products via a feed system; singulating the supplied products using a singulator; measuring the products; classifying each of the products into a sorting class based on measured product characteristics; receiving by a switch-over module from a controller of the sorting system during sorting of products of the first product type a switching signal indicating that products of the second product type have to be sorted; selecting by the controller part of the sorting channels of the sorting system which are free of products of the first product type, wherein the selected part of the number of sorting channels is smaller than a total number of sorting channels; assigning at least some of the selected part of the sorting channels to the second product type; assigning sorting classes of the second product type to one or more of the sorting channels of the selected part of the sorting channels assigned to the second product type; and during emptying of a non-selected part of the number of sorting channels of the sorting device in respect of the first product type, sorting products of the second product type in the sorting channels assigned to the second product type in the selected part of the number of sorting channels to which a sorting class of the second product type has been assigned.

18. A sorting system for sorting products, comprising: a feed system; a sorting device connected operatively to the feed system and provided with sorting channels; a measuring and classification system connected operatively to the sorting device and provided with a sorting mechanism for sorting products over the sorting channels on the basis of product classification obtained with the measuring and classification system; a controller configured to control at least the measuring and classification system and the sorting device; and a switch-over module configured to receive from the controller a switching signal indicating that products of a second product type have to be sorted, wherein the controller is configured to select part of the sorting channels of the sorting system which are free of products of a first product type, wherein the selected part of the number of sorting channels is smaller than a total number of the sorting channels, wherein the controller is configured to assign at least some of the selected part of the sorting channels to the second product type, wherein the controller is configured to assign sorting classes of the second product type to one or more of the sorting channels of the selected part of the sorting channels assigned to the second product type, and wherein the controller is configured to sort, during emptying of a non-selected part of the number of sorting channels of the sorting device in respect of the first product type, products of the second product type in the sorting channels assigned to the second product type in the selected part of the number of sorting channels to which a sorting class of the second product type has been assigned.

19. The sorting system of claim 18, wherein the sorting channels comprise water channels and/or accumulating buffer lanes.

20. The sorting system of claim 18, further comprising a return channel for re-sorting of products.

Description

(1) Further advantages, features and details of the invention are further elucidated hereinbelow on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

(2) FIG. 1 is a top view of a (pre-)sorting system on which the method according to the invention can be applied;

(3) FIG. 2 shows a view of results with a conventional product switch;

(4) FIG. 3 shows results of the effect of proactive emptying of sorting channels;

(5) FIG. 4 shows results of the effect of optimized proactive emptying;

(6) FIG. 5 shows results wherein products of the second type are sorted while products of the first type are being emptied;

(7) FIG. 6 shows results of the effect of optimized starting of the new sorting;

(8) FIG. 7 shows results of the effect of both optimal proactive emptying and optimal starting; and

(9) FIGS. 8-11 show results of an example of a product switch according to the invention.

(10) Sorting system 2 (FIG. 1) comprises sorting device 4 and feed system 6 provided with singulating means 8. Sorting system 2 is further provided in the shown embodiment with measuring system or measuring or classification system 10, a transfer device 12 with which products P are laid in a bed of transport holders 14. Sorting device 4 also comprises a large number of sorting channels 16. The outlet of sorting channels 16 is operatively connected to discharge system 18. In the shown embodiment of discharge system 18 a group of sorting channels 20 is guided to a transverse channel 22 of sub-discharge system 24 which is provided with empty crate feed 26 and crate filler 28, for instance of the underwater filler type. In the shown embodiment there are four crate fillers 28 which are each connected using transverse channel 22 to about 15-20 sorting channels 20. It will be apparent that other configurations are likewise possible according to the invention. Filled crates 52 are placed on stacks 34 for discharge, preferably using automated system 30. These stacks 34 are then transported further for further treatment or storage.

(11) In the shown embodiment sorting system 2 is also provided with return channel 36. In the shown embodiment return channel 36 is embodied, just as sorting channels 16, as water channel.

(12) Sorting system 2 is provided in the shown embodiment with controller 38 with switch-over module and comprising a user interface 40. Controller 38 is preferably connected to control system 42 with which information is obtained using detector 44 in upstream feed part 46 with dumper 47. This is for instance information about the products of the first product type which are yet to be sorted and/or a notification of a product switch to the second product type. It will be apparent that this information can also be obtained in other automatic and/or manual manner Controller 38 makes use of sorting channel control 48. It will be apparent that such a module, as well as other modules, can be integrated into controller 38 and/or can be arranged as separate controllers. Measuring system 10 is likewise connected operatively to controller 38. In the shown embodiment controller 38 is also connected operatively to position controller 50 and flow controller 52. It will be apparent that diverse variants of sorting system 2 are possible. It is thus possible for instance to dispense with return channel 36, to vary the number of sorting channels 16, configure discharge system 18 differently and configure feed system 6 differently, to give controller 38 a central and/or local form, and the like.

(13) Natural products in particular, such as vegetables and fruit, display a natural variation in product characteristics. The probability density function of for instance product diameter or product weight of unsorted products usually has a normal distribution in practice. More products will hereby fall into the one sorting class than into another sorting class. By combining these product characteristics with additional product characteristics such as colour, bloom, external quality and so on, the distribution of products over sorting classes usually becomes even more uneven. A typical ratio here is that 20% of the sorting classes comprises about 80% of the products. The distribution of products over the sorting classes and sorting channels is tracked in sorting system 2 so that the probability of a product falling into a specific channel and the probability of a product falling within a determined sorting class are known.

(14) In the shown embodiment according to sorting system 2 unsorted product P is for instance dumped in water in feed system 46 with dumper 47 in the feed part and subsequently carried by feed system 6 to singulating means 8. Here product P leaves the feed bath, subsequently comes to lie behind other products P and is preferably transported further while being rotated. Measuring system or measuring and classification system 10 measures characteristics of product P, after which it is classified. Product P is then placed by transfer device 12 into a transport holder of bed 14, wherein product P is preferably also weighed. After product P has been assigned to a sorting class, and when the sorting class has been assigned to a specific sorting channel 16, product P is then transported on bed 14 to the respective sorting channel 16 and there released. Sorting channel 16, preferably a water channel and/or accumulating buffer lane, comprises a number of products P and thereby fulfils a buffer function. Controller 48 tracks how many products P lie in the channels and will if desired select another sorting channel for this sorting channel when sorting channel 16 is fully filled. When discharge system 18 is ready to fill sorting channel 16 and sorting channel 16 comprises enough products to fill for instance a crate, sorting channel 16 is emptied and the products are carried into crate 32, for instance using crate filler 28, which is subsequently placed on a stack 34 for discharge, for instance with a crate stacker 30.

(15) Depending on the embodiment of sorting system 2, the embodiment of discharge system 18 is taken into account so that it is for instance possible to take into account during proactive emptying of sorting channels 16 that crate fillers 28 are utilized as effectively as possible. During the proactive emptying of a sorting channel 16 use is optionally made of an adjustable percentage of sorting channels which have to be empty prior to the product switch. The time to start proactive action can also be determined on the basis of the crates still to be sorted and the related sorting time. It is also possible to take into account the quantity of product to be expected per sorting class between the moment that the sorting class of a sorting channel must change because the channel is full and the end of the sorting of the products of the first product type. If this remaining quantity is for instance less than 30% of the crate volume, this sorting class can then be linked to the residual category so that products can be sorted again at a later stage.

(16) In a conventional application with a capacity of for instance 100 crates per hour for crate stacker 30 about thirty minutes is required to empty fifty channels 16. The results of such a conventional method for the purpose of a switch-over are shown in FIG. 2. At a time 30 minutes the processing of products of the first product type stops, after which outlets 16 are emptied in about 30 minutes. From a time 60 minutes the new product of product type 2 can be sorted. The total switch-over time in a conventional process therefore amounts to about 30 minutes.

(17) FIGS. 2-7 show, A, scaling down of the sorting of the first product type, B, scaling up of the sorting of the second product type and, C, the production time loss represented by the area below the curve/line. The broken line in the figures relates to the production/sorting and the full line relates to the percentage of channels in use for the respective product type.

(18) Several steps according to embodiments of the method according to the invention are then applied in the situation which is otherwise the same as above in the conventional process. For the sake of clarity in the graphs the maximum number of outputs is defined at 95%. This does not affect the comparison of a conventional process and embodiments according to the present invention. The productivity loss relates to the decrease in products processed by discharge system 18. The effective switch-over time can be determined by relating this productivity loss to the theoretically realizable capacity of sorting system 2.

(19) In the case a first proactive action is performed after a coming product switch has been signalled, a number of outlets are emptied at time twenty minutes. The results hereof are shown in FIG. 3. The emptied outlets are for instance outlets which it is estimated on the basis of production data will no longer become sufficiently full and/or of which the sorting classes assigned to the sorting channels will make only a limited contribution to the total production. The relevant sorting classes are combined on one or several sorting channels and usually sorted again later. This is visible as productivity loss with a gradual increase between the times twenty and thirty minutes. In the shown example 30% of the sorting outlets are emptied in this period of time and thereby made available to products of the second product type. By making use of prioritization on the basis of the above criteria the sorting channels for proactive emptying can be intelligently chosen, whereby the number of channels which are cleared increases more quickly than the decrease in the properly sorted product. This is shown in FIG. 4 wherein it can be seen that the productivity loss is smaller and the total switch-over time is further reduced from about twenty minutes to about eighteen and a half minutes. In both cases the sorting of products of the first product type is stopped at the time thirty minutes. In a non-optimized embodiment sorting of products of the second product type starts at the time fifty minutes, while in an optimized proactive step it is already possible after eighteen and a half minutes to start with sorting of products of the second product type.

(20) In a further example proactive use is made of clearing sorting channels without optimization, and sorting classes are assigned to sorting outlets without prioritization when starting the sorting of products of the second product type. This achieves a significant reduction in switch-over time from thirty minutes to about six and three-quarter minutes. This is shown in the results of FIG. 5, wherein a significant reduction in the productivity loss is realized.

(21) In the case of prioritization during assigning of sorting classes of the second product type to sorting channels 16 which have become available it is possible in the first instance to assign all sorting classes to one sorting channel which is defined as residual category. By measuring products for several seconds or a minute for instance, the expected distribution function of the products over the sorting classes can be determined. Use can additionally or alternatively be made here if desired of a distribution function on the basis of historical data which are retrievable from a database or which is already available in controller 38. By starting with sorting of products of the second product type from time thirty minutes and guiding products in the first instance to the residual outlet until a reliable estimate of the distribution of the products over the sorting classes is available, and subsequently assigning sorting classes to sorting channels with prioritization on the basis of the expected specific distribution determined for the relevant batch, a sorting class in which many products are expected can be assigned first to the sorting channel which has become available. The percentage of properly sorted product of the second product type can hereby be much higher from the start than the percentage of available sorting channels (FIG. 6). Only the products which come together in the residual category contribute toward the undesirable productivity loss of the lower graph and have to be sorted again. The switch-over time amounts in this example to about six minutes. It is possible according to the invention if desired to limit the number of products to be re-sorted, and thereby further reduce the risk of damage to products, by only beginning with sorting of the product of the second product type when a determined percentage of sorting outlets is available, for instance 20%.

(22) An optimal effect and maximum reduction in the switch-over time for sorting products of the first product type to products of the second product type is realized by applying a combination of the above effects. By carrying out repetitively and on the basis of quality the emptying of sorting channels and the assigning of sorting classes of the second product type over sorting channels which have become available, a further reduction in the switch-over time is obtained to about two minutes (FIG. 7). Between times twenty and thirty minutes the sorting of products of the first product type is scaled down. At time thirty minutes a start is made with sorting of products of the second product type. All sorting channels with the old product are empty at time fifty minutes and at that moment all sorting classes of the product of the second product type also have their own sorting channel. Productivity loss and the effective switch-over time hereby remain limited.

(23) The above examples have been obtained with sorting system 2 on which the different effects are applied individually as far as possible. The results in FIG. 7 relate to a combination of the individual steps which results in the greatest reduction in effective switch-over time and productivity loss.

(24) A further example is described below on the basis of a practical simulation wherein a product switch is carried out from apples of the Golden Delicious variety as first product type to apples of the Elstar variety as second product type. Both varieties have 50 sorting groups. The sorting system used has 60 sorting channels and a capacity of about 30 ton/hour. The total feed capacity is hereby about 100 crates/hour. The discharge for sorted products is formed by the sorting channels (16), four underwater fillers (28) and a so-called binmatic (30) which stacks the crates filled by underwater filler (28). These underwater fillers and binmatic can process about 140 crates/hour.

(25) A typical distribution of the production per sorting group for Golden Delicious is shown in FIG. 8A. Several sorting groups deliver 5-6 tons per hour, a large part is well below this and several sorting groups deliver very little fruit, for instance only 300 kg per eight hours. The distribution for Elstar as shown in FIG. 8B is roughly the same.

(26) In a conventional product switch all sorting channels (16) are emptied. A minimum of 21 minutes is necessary for this purpose. Of the 50 sorting channels used, about 30% will usually be filled for less than 30% with products. In order to limit storage space these products are usually placed in a crate combined with residual product. At a typical channel content of about 300 kg this results in about 675 kg of residual product. This amount can of course vary. After emptying of the system a start is made with the second product, the Elstar, on the desired 50 sorting channels.

(27) For an optimized product switch according to the invention a signal is given upstream in the process to initiate the switch about 30 minutes before the intended switch. At that moment 50 crates with a total of about 15,000 kg of apples of the first variety still have to be sorted. Two ways of making sorting channels available to the second variety are applied according to the invention.

(28) The first way is to end the least productive sorting groups during the final phase of the sorting of the Golden Delicious variety and to empty the channels by making use of the overcapacity of the underwater fillers. In addition to the normal full notification for outlets because of the current sorting process for Golden Delicious, those outlets linked to the least productive sorting groups, for instance the 15 least productive sorting groups, are also notified as being full. These sorting groups are unlinked from the associated outlets and assigned to a residual outlet. The associated outlet is notified to the underwater filler for filling of a crate. This is possible for instance by unlinking all 15 least productive sorting groups at the same moment and notifying them to the underwater filler for the purpose of being emptied. The underwater fillers have overcapacity of a total of 40 crates per hour, so the 15 notified outlets will be empty again after about 23 minutes. Another way is to distribute the unlinking of these slow running sorting groups over the available time until the switch in variety. This is possible for instance by looking every two minutes at which remaining sorting group is the least productive and subsequently unlinking it and notifying the associated channel as being full, or, for instance as soon as an underwater filler no longer has any channels notified as full, unlinking the slowest running sorting group connected via a channel to this underwater filler. An additional advantage of the latter two variants of unlinking less productive sorting groups is that the quantity of product which is placed in the residual group is much less than in the first variant.

(29) The second way is to check during the final phase of the sorting process of the Golden Delicious variety at each channel which becomes full whether sufficient fruits are still expected for the sorting group associated with this channel. If on the basis of the production statistics this is then less than for instance 30% crate filling, a new sorting channel is not selected for the respective sorting group, and it is added to the residual outlet. About 30% of the sorting groups are hereby eventually terminated and combined in the residual outlet.

(30) All outlets notified as being full at an underwater filler are processed individually. If multiple outlets are notified simultaneously as being full, it will then therefore take some time before they are all emptied. In FIG. 9 (full line represents the number of empty channels, broken line represents the number of terminated sortings and the dotted line the number of channels waiting) the relation is shown between the number of channels notified as full and the number of emptied channels. As shown in FIG. 9, there is a slight lag in empty channels becoming available when the sorting group is terminated. The momentary number of channels which have to be emptied by the underwater fillers is shown on the dotted line, this including the number of channels notified as full by the current sorting process. When a channel is notified as being full without the sorting group being terminated, an empty channel is again immediately selected for further sorting. This is the reason that the line for the empty channels has an irregular progression. At the moment of the switch in variety, at time t=1800 seconds, all other channels are notified as full and the number of waiting channels peaks at 25. The full line, which represents the number of empty channels, shows that this has risen from 10 free channels at t=0 to 32 free channels at t=1800 seconds.

(31) As described above, two ways of terminating sorting groups are applied. First of all the least productive groups are terminated one by one, distributed over the remaining time. Secondly, each time a channel is full a check is made as to whether the associated sorting group can be terminated because the anticipated quantity of residual product up to the switch in variety is less than 30% channel filling. The result is shown in FIG. 10 (full line represents the number of kilograms as a result of terminating less productive groups, broken line represents the number of kilograms residual product as a result of a small remainder following full notification and the dotted line the percentage of correctly sorted products over time). The quantity of residual product which occurs in the variety switch-over process is indicated separately for termination of less productive groups and for termination for the purpose of preventing a channel with a small residual quantity. In this example the total quantity of residual product resulting from premature ending of sorting groups amounts to 250+375=625 kg. It should be noted here that some of the 15 less productive sorting groups which are terminated also have a channel filling which is less than 30%. This results in an estimated additional quantity of residual product of *0.3*15*0.3*300=203 kg. In this specific simulation this is 88 kg. These channels can be efficiently cleared by for instance having them together fill one crate (to the extent they are connected to the same underwater filler) and/or by employing them as an outlet for the residual group. In this latter case the number of extra outlets and crates for filling necessary for the residual group is very limited.

(32) At time t=1800 s the sorting of the Golden Delicious variety is ended. Owing to the proactive emptying of channels, 32 outlets are at that moment available (see FIG. 9). The other 28 outlets still comprise fruits and still have to be emptied. As of t=1800 s fruits of the Elstar variety are guided over the machine. For the first 20-40 seconds the fruits are measured in order to make an assessment of the distribution of the fruits over the sorting groups. During this time the fruits are assigned to a residual outlet. The sorting groups are assigned their own sorting channel in order of productivity. Each time a sorting channel becomes available it is assigned to the sorting group with the highest priority which is then not yet linked. The effect on productivity of linking sorting groups to channels is shown in FIG. 11 (full line represents percentage of linked sorting groups, small dotted line the net number of free channels, large dotted line the number of channels waiting and the broken line the percentage of effective production). In the figure the number of channels waiting and the net free channels for 0<t<=1800 are equal to the corresponding numbers in FIG. 9. Further shown is that at the start more than 60% of the sorting groups are already linked to their own outlet. With the correct choice of these sorting groups more than 90% of the production will then already arrive at the correct outlet. The other sorting groups remain linked to a residual outlet until a sorting outlet becomes available.

(33) At t=2294 the final sorting group is linked to its own sorting channel. In the simulation the quantity of residual product is 194 kg. An approximation of the quantity of residual product can be given on the basis of the graph by measuring the area between the 100% line and the effective production line between times t=1800 and t=2294. An estimate hereof amounts to 206 kg.

(34) A further optimization can be realized when starting the new sorting by an optimal assignment. As stated, fruits of a sorting group are assigned to a residual outlet as long as an outlet of its own is not available for a sorting group. This residual outlet can in principle be any random outlet of the machine. The assignment of the fruits to outlets takes place as soon as the fruits come from the singulating means and have been weighed. In the case the residual outlet lies further toward the end of the machine, this means that a considerable quantity of fruit is in transit on the cup bed. As soon as a sorting group is linked to an outlet, fruits of the same sorting group are possibly still in transit to the residual outlet. It is in that case worthwhile, for all fruits of this sorting group which are still lying on the cup bed and which have not yet passed the outlet that has just been linked, to implement a mutation by nevertheless unlinking them from the residual outlet and linking them to the outlet of the sorting group which has just been assigned, to unload the fruit there, and to also update the registrations of the sorting group, the sorting outlet and the residual outlet on the basis of the implemented mutation. This will result, certainly at the beginning of sorting of the new product, in a saving on the quantity of residual product. Sorting of several hundred fruits, or for several tens of seconds, then takes place solely in order to determine the distribution of the sorting groups. Since the transit time over the cup bed to the final (60.sup.th) outlet lasts for about 45 seconds, it is in this way possible at the beginning of the new sorting to ensure that many fruits used to determine the distribution of the sorting groups will nevertheless arrive at the outlet linked to the sorting group instead of at the residual outlet. This can be optimized still further by selecting the residual outlet at the end of the machine at the beginning of the new sorting, and by then allocating the sorting groups which are most represented to the free outlets likewise located at the end of the machine. The greatest possible part of the fruits will hereby still arrive directly at the correct outlet of the sorting group.

(35) The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.