Fivez, Christiaan (Romeinsestraat 20, Heverlee, B-3001, BE)
Berghmans, Paul (Romeinsestraat 20, Heverlee, B-3001, BE)
Fivez, Christiaan (Romeinsestraat 20, Heverlee, B-3001, BE)
| CLAIMS 1. Method for sorting products which move in a product flow so as to remove undesired products from the product flow, whereby the products of this product flow are moved downward with a thickness of about a single product (2,10,11) over a slanting distributing surface (3) to a detection zone where the products are scanned by a beam of light which moves over the product flow according to a scan line in a direction crosswise to the direction of movement of the products, whereby this product flow leaves the distributing surface and, downstream of the distributing surface, undesired products are blown out of the product flow, characterised in that an air flow is generated to this end which is directed to this product flow on the side of the product flow where said distributing surface is situated, whereby this air flow is generated at a blow nozzle which is directed to said product flow, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzle is smaller than the double of the largest diameter (Pmax) of the products to be sorted, increased with 100 mm.. 2. Method according to claim 1, whereby said air flow is generated at a blow nozzle whose centre is situated at a distance (X) from the product flow at the height of said blow nozzle which is smaller than the largest diameter (Dmax) of the products to be sorted. 3. Method according to claim 1 or 2, whereby each of said products, while moving over the distributing surface (3), hits the latter in a contact point (13) of the product (2,10,11) concerned, whereby said air flow is generated at a blow nozzle whose centre is situated at a distance (X) from the contact point (13) of a product (2,10,11), when this product, during its free fall, as it leaves the distributing surface, is situated opposite said blow nozzle, which distance (X) is smaller than the largest diameter (Dmax) of the products to be sorted. 4. Method according to any one of claims 1 to 3, whereby undesired products are removed from the product flow by generating an air flow at corresponding blow nozzles whose horizontal component of velocity has the same orientation as the horizontal component of velocity of the products. 5. Method according to any one of claims 1 to 4, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzles is selected such that it is larger than the distance which the products (2,10,11) travel during the time that is required to process the data that are generated by the detection device (12) for the products (2,10,11) concerned, and to generate said air flow, in particular this distance is selected larger than 3 mm. 6. Method according to any one of claims 1 to 5, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzle of each of said blow nozzles is larger than the largest diameter (Dmax) of the products to be sorted. 7. Method according to any one of claims 1 to 6, whereby an air flow is generated which is directed to the product flow on the side of the product flow where said distributing surface is situated, whereby this air flow is generated at a second blow nozzle which is directed to said product flow, whereby the distance (S) between said scan line (15) and the centre of the second blow nozzle is smaller than the quadruple of the largest diameter (Dmax) of the products to be sorted, increased with 200 mm. 8. Method according to claim 7, whereby the distance between the centre of said second blow nozzle and each of the products in the product flow is selected smaller than the largest diameter (Dmax) of the products to be sorted. 9. Method according to any one of claims 1 to 8, whereby said detection zone (4) extends under the lower edge (14) of the distributing surface (3) and whereby the products move in free fall through the detection zone (4). 10. Method according to any one of claims 1 to 9, whereby said products are moved in free fall along said blow nozzles, whereby said air flow is generated at these blow nozzles under the lower edge (14) of the distributing surface (3) and under said scan line (15). 11. Method according to any one of claims 1 to 10, whereby said beam of light is formed of a laser beam. 12. Method according to any one of claims 1 to 11, whereby the length of the blow nozzles according to a direction running parallel to the scan line (15) is selected smaller than the diameter (dmjn) of the smallest products from the product flow and in particular smaller than half of or than one third of this diameter. 13. Method for positioning a row of compressed air valves with blow nozzles for sorting granular products, whereby a slanting distributing surface (3), a detection device (12) and a removal device (7) are provided, whereby the products to be sorted (2,10,11) are supplied onto the distributing surface (3) and move over this surface (3) in a wide product flow, and whereby this product flow with a thickness of about a single product (2,10,11) is guided through a detection zone (4) of said detection device (12), whereby the products (2,10,11) are scanned with a beam of light of the detection device (12) according to a scan line (15) in said detection zone (4) in a direction crosswise to the direction of movement of the product flow in order to characterise these products as suitable products (10) or as undesired products (11), whereby a row of compressed air valves (8) is provided under the lower far end (14) of the distributing surface (3) on the same side of the product flow as said distributing surface (3), such that this row of compressed air valves (8) extends almost crosswise to the direction of movement of the product flow and practically parallel to the latter, whereby each of the compressed air valves (8) contains a blow nozzle which is directed to said product flow, characterised in that the position of the compressed air valves (8) is selected such that the distance (Y) between said scan line (15) and the centre of the blow nozzle of each one of said compressed air valves (8) is smaller than the double of the largest diameter (Dmax) of the products to be sorted, increased with 100 mm. 14. Method according to claim 13, whereby the distance (X) between said centre of the blow nozzles and the product flow at the blow nozzles height is selected smaller than the largest diameter (Dmax) of the products to be sorted. 15. Method according to claim 13 or 14, whereby each of said products, while moving over the distributing surface (3), hits the latter in a contact point (13) of the product (2,10,11) concerned, whereby said row of compressed air valves (8) is positioned such that the distance (X) between said centre of each blow nozzle and the contact point (13) of a product (2,10,11), when the product is situated opposite said blow nozzle during its free fall, is smaller than the largest diameter (Dmax) of the products to be sorted. 16. Method according to any one of claims 13 to 15, whereby said compressed air valves (8) are oriented such in relation to the product flow that the horizontal component of velocity of the products has the same orientation as the horizontal component of velocity of the air flow generated by the compressed air valves (8). 17. Method according to any one of claims 13 to 16, whereby a distance (Y) is selected between said scan line (15) and the centre of the blow nozzle of each of said compressed air valves which is larger than the distance travelled by the products (2,10,11) during the time which is required to process the data that are generated by the detection device (12) for the product (2,10,11) concerned, in particular larger than 3 mm. 18. Method according to any one of claims 13 to 17, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzle of each of said compressed air valves (8) is set such that it is larger than the largest diameter (Dmax) of the products to be sorted. 19. Sorting machine for sorting granular products which comprises a slanting distributing surface (3), a detection device (12) and a removal device (7), whereby the products to be sorted (2,10,11) are supplied onto the distributing surface (3) and move over this surface (3) hi a wide product flow, and whereby this product flow with a thickness of about a single product (2,10,11) is guided through a detection zone (4) of said detection device (12), which detection device (12) makes it possible to scan the products (2,10,11) according to a scan line (15) in said detection zone (4) following a direction crosswise to the direction of movement of the product flow hi order to characterise these products as suitable product (10) or as undesired product (11), whereby said removal device (7) comprises a row of compressed air valves (8) extending almost crosswise to the direction of movement of the product flow and almost parallel to the latter under the lower far end (14) of the distributing surface (3) on the same side of the product flow as said distributing surface (3), whereby each of the compressed air valves (8) contains a blow nozzle which is directed to said product flow, characterised in that the distance (Y) between said scan line (15) and the centre of the blow nozzle of each of said compressed air valves (8) is smaller than the double of the largest diameter (Dmax) of the products to be sorted, increased with 100 mm. 20. Sorting machine according to claim 19, whereby the distance (X) between said centre of the blow nozzles and the product flow at blow nozzle height is smaller than the largest diameter (Dmax) of the products to be sorted. 21. Sorting machine according to claim 19 or 20, whereby each of said products, during the movement of the distributing surface (3), hits the latter in a contact point (13) of the product (2,10,11) concerned, whereby said row of compressed air valves (8) is positioned such that the distance (X) between said centre of each blow nozzle and the contact point (13) of a product (2,10,11), when this product is situated opposite said blow nozzle during its free fall, is smaller than the largest diameter (D1Hax) of the products to be sorted. 22. Sorting machine according to any one of claims 19 to 21, whereby said compressed air valves (8) are oriented such in relation to the product flow that the horizontal component of velocity of the products follows the same orientation as the horizontal component of velocity of the air flow generated by the compressed air valves (8). 23. Sorting machine according to any one of claims 19 to 22, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzle of each of said compressed air valves is larger than the distance travelled by the products (2,10,11) during the time which is required to process the data which are generated by the detection device (12) for the product concerned (2,10,11), in particular is larger than 3 mm. 24. Sorting machine according to any one of claims 19 to 23, whereby the distance (Y) between said scan line (15) and the centre of the blow nozzle of each of said compressed air valves (8) is larger than the largest diameter (Dmax) ofthe products to be sorted. 25. Sorting machine according to any one of claims 19 to 24, whereby it comprises a second removal device (19) which is positioned such that the distance (S) between said scan line (15) and the centre of the blow nozzle of each of the compressed air valves (8) of this second removal device (19) is smaller than the quadruple of the largest diameter (Dmax) of the products to be sorted, increased with 200 mm. 26. Sorting machine according to claim 25, whereby the distance between the centre of the blow nozzles of said second removal device (19) and each of the products in the product flow is smaller than the largest diameter (Dmax) of the products to be sorted. 27. Sorting machine according to any one of claims 19 to 26, whereby it has a contact zone where the products (2,10,11) move over the distributing surface (3) and hit the latter in a contact point (13) during their movement, whereby this machine has a sorting zone which extends as of said scan line (15) up to a sorting zone boundary line which is parallel to said scan line (15) and whereby for this boundary line applies that the sum of the squares of the distance of the products' contact points (13) up to this line, when these products are situated at the line height, is minimal and whereby the contact points (13) of the products at the line height are situated at a distance thereof which is smaller than the diameter (dmjn) of the smallest products to be sorted, and whereby said row with compressed air valves (8) is provided in this sorting zone. 28. Sorting machine according to claim 27, whereby the distance between the contact point (13) of a product from the product flow situated opposite a blow nozzle in said sorting zone and the centre of the blow nozzle concerned is smaller than the largest diameter (Dmax) of the products to be sorted. 29. Sorting machine according to any one of claims 19 to 28, whereby said detection zone (4) extends under the lower edge (14) of the distributing surface (3), such that the products move in free fall through this detection zone (4). 30. Sorting machine according to any one of claims 19 to 29, whereby said removal device (7) extends under the lower edge (14) of the distributing surface (3) and under said scan line (15), such that the products move in free fall along said blow nozzles. 31. Sorting machine according to any one of claims 19 to 30, whereby said detection device (12) comprises at least a laser source for generating a laser beam and means for moving this laser beam according to said scan line (15) over said product flow. 32. Sorting machine according to any one of claims 19 to 31, whereby the length of the blow nozzles of the compressed air valves (8) according to a direction which is parallel to the scan line (15) is smaller than the diameter (dmin) of the smallest products from the product flow, and in particular is smaller than half or a third of said diameter. |
The invention concerns a sorting machine for sorting granular products comprising a slanting distributing surface, a detection device and a removal device. The products to be sorted are hereby supplied onto the distributing surface and move over said surface in a wide product flow. Said product flow is guided through a detection zone of the detection device with a thickness of about a single product, whereby the detection device makes it possible to scan the products according to a scan line in the detection zone in a direction crosswise to the direction of movement of the product flow. Further, the removal device comprises a row of compressed air valves extending almost crosswise to the direction of movement of the product flow and almost parallel to the latter under the lower far end of the distributing surface on the same side of the product flow as the distributing surface. Each of the compressed air valves has a blow nozzle which is directed to said product flow and which makes it possible to blow undesired products out of the product flow.
In order to obtain an optimal sorting of the products to be sorted, it is necessary for the detection device to detect the presence of undesired products in the product flow in a correct manner on the one hand, whereby it is avoided that suitable products are characterised as undesired or vice versa. On the other hand, it is important for all the products that have been characterised as undesired by the detection device to be separated from the product flow by the removal device without thereby removing suitable products from the product flow. With the existing sorting machines, it is found that when removing an undesired product by opening a compressed air valve situated opposite said product, it frequently happens that a suitable product situated near the undesired product is removed from the product flow as well due to the air flow which is generated by the compressed air valve. This loss of suitable products is even considerable from time to time, but at present it is accepted as a side effect in the existing sorting machines.
Such a situation occurs in particular when products having different diameters need to be sorted. The characteristics of the compressed air valves are hereby selected such that they make it possible to remove products with a large diameter as well as a products with a small diameter from the product flow should they represent any flaws. If, for example, undesired components must be separated from a product flow containing predominantly broccoli florets having a diameter of up to some 6 cm and peas having a diameter of up to maximally 1 cm, a pea which is situated in the immediate vicinity of the broccoli floret concerned will sometimes be removed together with a broccoli floret representing a flaw.
Document EP 0952895 describes for example a sorting machine according to the present state of the art, whereby a removal device is provided on the front side of the product flow, whereas said distributing surface is situated on the back side of the product flow.
In US 4 723 659 is described a sorting machine in which the products to be sorted are cast from a conveyer belt and move in a coasting flight along a removal device. The problem of undesired products being removed from the product flow together with suitable products or of undesired products being not removed at all occurs in this sorting machine as well.
A remedy to this problem at present consists in making use of what are called channel sorting machines. In such sorting machines, the products are guided one by one through one or several parallel ducts or channels to a detection device and a removal device. In these channel sorting machines, the products move at a sufficient distance from one another, thus avoiding that suitable products are removed from the product flow. The output of products that can be sorted with these machines is much smaller than with sorting machines where the products are supplied in a wide product flow via a slanting distributing surface, however. Also, the invention concerns such sorting machines with a slanting distributing surface.
The invention aims to remedy said disadvantages by providing a sorting machine which makes it possible to remove undesired products from the product flow in a very accurate manner without simultaneously separating suitable products from the product flow. Moreover, the invention prevents that the path of the products which have been qualified as undesired by the detection device, is insufficiently influenced by the air flow generated by the compressed air valves, such that these undesired products might nevertheless remain in the product flow with the desired products.
Moreover it is possible in a sorting machine according to the invention to remove products from the product flow by means of compressed air valves having for example a smaller blow nozzle than those that are provided in sorting machines according to the present state of the art, or to use a smaller air pressure for generating an air flow at the blow nozzle of the compressed air valves.
To this aim, the distance between said scan line and the centre of the blow nozzle of each of said compressed air valves is smaller than the double of the largest diameter of the products to be sorted, increased with 100 mm.
Practically, the distance between said centre of the blow nozzles and the product flow at said blow nozzle height is smaller than the largest diameter of the products to be sorted.
Advantageously, said row of compressed air valves is placed such that the distance between the centre of each blow nozzle and the contact point of a product, when this product is situated opposite said blow nozzle during its free fall, is smaller than the largest diameter of the products to be sorted, whereby said contact point is the point where said product, while being moved over the distributing surface, touches the latter. Said compressed air valves are preferably directed such in relation to the product flow that the horizontal component of velocity of the products follows the same direction as the horizontal component of velocity of the air flow generated by the compressed air valves.
According to a preferred embodiment of the machine according to the invention, the distance between said scan line and the centre of the blow nozzle of each of said compressed air valves is larger than the distance which is travelled by the products during the time required to process the data which are generated by the detection device for the product concerned, in particular it is larger than 3 mm.
According to an interesting embodiment of the invention, the sorting machine has a contact zone where the products move over the distributing surface and touch the latter in a contact point during their movement, whereby this machine has a sorting zone extending as of said scan line up to a sorting zone boundary line which is parallel to said scan line and whereby for this boundary line applies that the sum of the squares of the distance of the products' contact points in relation to said line, when the products are at the line height, is minimal and whereby the contact points of the products at said line height are situated at a distance thereof which is smaller than the diameter of the smallest products to be sorted, and whereby said row is provided with compressed air valves in said sorting zone.
In an additional embodiment of the sorting machine according to the invention, it comprises a second removal device which is provided such that the distance between said scan line and the centre of the blow nozzle of each of the compressed air valves of this second removal device is smaller than the fourfold of the largest diameter of the products to be sorted, increased with 200 mm.
The invention also concerns a method for sorting products which move in a product flow so as to remove undesired products from the product flow, whereby the products of this product flow are moved downward with a thickness of about a single product over a slanting distributing surface to a detection zone where the products are scanned by a beam of light which moves over the product flow according to a scan line in a direction crosswise to the direction of movement of the products. This product flow leaves the distributing surface, and downstream of the distributing surface undesired products are blown out of the product flow. This method is characterised in that, to this end, an air flow is generated which is directed to the product flow on the side of the product flow where said distributing surface is situated, whereby this air flow is generated at a blow nozzle which is directed to said product flow, and whereby the distance (Y) between said scan line and the centre of the blow nozzle is smaller than the double of the largest diameter (Dmax) of the products to be sorted, increased with 100 mm.
The invention also concerns a method for positioning a row of compressed air valves with blow nozzles for sorting granular products, in particular for positioning the blow nozzles in the sorting machine according to the invention. Other particularities and advantages of the invention will become clear from the following description of a few specific embodiments of the method and the sorting machine according to the invention. This description is given as an example only and does not limit the scope of the claimed protection in any way; the figures of reference used hereafter refer to the accompanying drawings. Figure 1 is a schematic view in perspective of a sorting machine according to the present state of the art.
Figure 2 is a schematic cross section of the distributing surface of a sorting machine and a product flow according to the present state of the art. Figure 3 is a schematic cross section of the distributing surface of a sorting machine and a product flow in a sorting machine according to the invention.
Figure 4 is a schematic cross section of the distributing surface of a sorting machine and a product flow in a sorting machine according to the invention, whereby two removal devices are provided.
In the different figures, the same figures of reference refer to identical or analogous elements.
A sorting machine according to the present state of the art, which is fit for sorting granular products and which is described for example in document EP 0952 895, is represented in figure 1. This sorting machine is provided with a vibrating table 1 onto which the products to be sorted 2 are supplied. These products comprise suitable products 10 as well as undesired products 11. As a result of the vibrations of said vibrating table 1, the products 2 are guided to a distributing surface, in particular a drop plate 3. As a result of the forces of gravity, the products 2 move over the surface of the drop plate 3 in a wide product flow with a thickness of about one product over practically its entire width, whereby they leave the drop plate 3 at its lower edge.
Next, the products 2 move in free fall in a product flow through a detection zone 4 where they are scanned by a beam of light 5 moving crosswise over the product flow. This beam of light 5 thus moves according to a scan line over the product flow.
In the detection zone 4, the product flow moves over a background element 6 extending over the entire width of the product flow. The background element 6 is placed such that the beam of light 5 scanning the product flow will hit said background element 6 whenever there is no product 2 in the path of the beam of light 5.
Downstream of the detection zone 4, the products 2 from the product flow move along a removal device 7 which makes it possible to remove anomalous products from the product flow. The removal device 7 consists of a row of compressed air valves 8 situated next to one another which extends parallel to the product flow and crosswise to the direction of movement 9 of the latter. Each of the compressed air valves 8 is provided with a blow nozzle which is directed to the product flow. When a product 2 is thus qualified as an undesired product 11, a compressed air valve 8 will be opened in a position corresponding to that of the anomalous product 11, such that the latter, under the influence of the thus generated compressed air flow, will be blown out of the product flow. Thus are generated a product flow with mainly suitable products 10 and a flow with mainly undesired products 11 , separated from the latter.
Further, the sorting machine comprises a detection device 12 which makes it possible to generate said beam of light 5 and to detect the light reflected by the products 2 in said detection zone 4. If the presence of an undesired product is discovered by the detection device 12, a detection signal will be generated which activates the compressed air valve situated opposite the path of the product concerned.
In this sorting machine according to the present state of the art, said row of compressed air valves 8 of the removal device 7 is provided on the front side of the product flow, whereas the distributing surface 3 is situated on the back side of the product flow. This is represented in greater detail in figure 2.
The product flow to be sorted which is represented in this figure 2 contains products of various sizes. The maximal diameter of the products hereby amounts to D max , whereas the smallest diameter of the products amounts to
Under the influence of the forces of gravity, the products slide down along the distributing surface 3 which is formed of a bent plate with a smooth surface. During their movement, the products 2 hit the distributing surface 3 in a contact point 13. While the products 2 move over the distributing surface 3, the latter thus forms a contact zone for the products.
After they have left the distributing surface 3 at its lower edge 14, the products move in free fall along said detection zone 4 where they will be scanned by the beam of light 5 according to said scan line 15.
After the products have been scanned by the beam of light 5, they move along said compressed air valves 8 of the removal device 7. These compressed air valves 8 are situated at a distance A which is larger than the maximal product diameter D max of the path 16 being followed by said contact points 13 after the products have left the distributing surface 3 in order to prevent the compressed air valves 8 from making contact with the products 2 while they fall. This distance A must be among others larger than D max , since the product flow, after having left the distributing surface, will fan out somewhat, whereby the average distance of the products, due to the air resistance among others, gradually increases as is schematically represented by the dashed lines 17.
Line 16 represents the ideal path of said contact point 13 under fπctionless circumstances.
If in such a sorting machine, a suitable product 10 is situated at a short distance from an undesired product 11, when the latter is situated opposite a compressed air valve 8 which is activated so as to remove the undesired product 11 from the product flow, the suitable product will be blown out of the product flow together with the undesired product 11 , as is represented by the arrows 18.
For the compressed air which is released at the blow nozzle of the compressed air valve 8 concerned generates a conical air flow which not only moves the undesired product 11 out of the product flow, but also the suitable product 10. Further, the compressed air must be under a considerably high pressure, since during the removal of a product with a small diameter, i.e. d m ,,,, this product will be at a distance in the order of magnitude of D ma χ - d m i n from the blow nozzle of the compressed air valve 8.
The invention thus particularly concerns sorting machines for sorting a product flow formed of products having different diameters. Thus, the diameter of the largest products will be for example larger than the double, the triple or more of the diameter of the smallest products.
A cross section of the distributing surface 3, the detection zone 4 and the compressed air valves 8 of the removal device 7 of a sorting machine according to the invention is represented in figure 3. hi this sorting machine, said compressed air valves 8 are provided on the same side of the product flow as said distributing surface 3.
The distance Y, according to the ideal path 16 of said contact points 13, between said scan line 15 and the centre of the blow nozzle of each ol said compressed air valves 8 is hereby smaller than the double of the largest diameter D max of the products to be sorted, increased with 100 mm.
Furthermore, the distance X between the centre of the blow nozzles and the product flow at the blow nozzle height is smaller than the largest diameter D max of the products to be sorted. In particular, the distance X between the path 16 followed by said contact points 13 under ideal circumstances, in particular without any friction of air, after the products have left the distributing surface 3, is smaller than D max .
For it appears that when the distance Y is selected smaller than 2 x D ma x + 100 mm, and the distance X is smaller than D max , this will result in a considerable improvement in relation to the present state of the art, and practically no suitable products whatsoever will be removed from the product flow together with any undesired products.
However, if the distance Y is larger than 2 x D max + 100 mm or if the distance X is larger than D max , the percentage of suitable products which is removed together with any undesired products will be similar to that of sorting machines according to the present state of the art.
For the sake of completeness, it should be mentioned that the diameters d m i n and D max may also concern identical products. If the products to be sorted are elongated, for example, D max will correspond to the largest length of the product, whereas dmi n will then refer to the shortest diagonal distance of a product.
The compressed air valves 8 are preferably oriented such in relation to the product flow that the horizontal component of velocity of the products has the same orientation as the horizontal component of velocity of the air flow generated by the compressed air valves. In this way, a positive acceleration is enforced on the undesired products 11 so as to remove them from the product flow. If said components of velocity were oriented in opposite directions, a stronger flow of air would be required to remove the undesired products from the product flow.
The length of the blow nozzles of the compressed air valves 8 according to a direction which is parallel to the scan line or which is parallel to the product flow and perpendicular to the direction of movement of the products, is advantageously smaller than the diameter d mm of the smallest products from the product flow. This length is for example smaller than d m i n /2 or even smaller than d min /3.
Further, the products are preferably not removed from the product flow until they have been completely scanned and after the data generated thereby have been entirely processed in the detection device. Thus, the distance between said scan line and the centre of the blow nozzle of each of said compressed air valves is preferably larger than the distance travelled by the products during the time which is required to process the data generated by the detection device for the product concerned, in particular larger than 3 mm. Consequently, the distance between said scan line and the centre of the blow nozzle of each of said compressed air valves is advantageously larger than the largest diameter of the products to be sorted.
According to a variant of the preceding embodiment of the sorting machine according to the invention, it has a sorting zone which extends as of said scan line up to a sorting zone boundary line running parallel to said scan line.
This boundary line is determined by the line where the sum of the squares of the distance of the products' contact points up to this line is minimal at the time these products are situated at said line height. The contact points of the products at this line height are hereby situated at a distance from the latter which is smaller than the diameter D max of the largest products to be sorted or, preferably, smaller than the diameter d m i n of the smallest products to be sorted.
According to the invention, said row of compressed air valves 8 is provided in the sorting zone between the scan line and the sorting zone boundary line. Since, in the sorting machine according to the invention, the removal device 7 is situated at a very short distance from the scan line 15, it is possible to provide a second removal device 19, as is shown in figure 4.
This second removal device 19 is positioned such that the distance S between said scan line 15 and the centre of the blow nozzle of each of the compressed air valves 8 of this second removal device 19 is smaller than the quadruple of the largest diameter D max of the products to be sorted, increase with
200 mm. The distance X between the centre of the blow nozzles of said second removal device 19 and each of the products in the product flow is hereby smaller than the largest diameter D max of the products to be sorted.
Consequently, in such a sorting machine with two removal devices 7 and 19, it is possible to split a product flow in three fractions. A first fraction consists then for example of undesired products 11, whereas a second and a third fraction contain desired products 10. The desired products in this second and third fraction may then be sorted for example on colour, ripeness, moisture content, etc. Naturally, in a sorting machine according to the invention, it is also possible to scan the product flow with several beams of light, such that it may have two or more scan lines. In that case, said distance Y or S is determined as of the lower scan line on the basis of which the products are scanned so as to remove them from the product flow with the removal device concerned. Further, said detection device 12 preferably contains at least one laser source for generating a laser beam which forms said beam of light 5. Thus, the detection device 12 also contains means for moving the laser beam according to said scan line over the product flow.
Although the detection zone 4, and consequently said scan line 15, preferably extends under the lower edge 14 of the distributing surface 3 such that the products move in free fall through the detection zone, it is also possible for the products to be scanned by said beam of light while they are still on the distributing surface. In that case, said distance Y and said distance S are measured as of the lower edge 14 of the distributing surface 3.