阅读说明：本技术 用于从产品流中剔除劣质产品的装置 (Device for eliminating inferior products from product flow ) 是由 马蒂亚斯·杰因德 于 2019-01-04 设计创作，主要内容包括：一种用于从产品流(3)中剔除劣质产品(2a、2b)的装置(1、5、17),包括：识别单元(5、5a、5b),其被设计用于检测所述产品流(3)；和计算机单元(6),其被设计用于由所述识别单元(5、5a、5b)得到所述产品流(3)的特性数据,并由特性数据识别出在所述产品流(3)中的劣质产品(2a、2b)。所述装置(1、5、17)具有由所述计算机单元(6)控制的压缩空气-剔除单元(7)且具有偏转部件-剔除单元(8),这些剔除单元被设计用来被动地从所述产品流(3)中剔除劣质产品(2a、2b)。所述计算机单元(6)被设计用于把识别出来的劣质产品(2a、2b)分成第一等级和第二等级的劣质产品(2a、2b),并控制所述压缩空气-剔除单元(7)主动地剔除所述第一等级的劣质产品(2a),以及控制所述偏转部件-剔除单元(8)被动地剔除所述第二等级的劣质产品(2b)。(An apparatus (1, 5, 17) for rejecting inferior products (2a, 2b) from a stream (3) of products, comprising: an identification unit (5, 5a, 5b) designed to detect the product flow (3); and a computer unit (6) which is designed to obtain the characteristic data of the product stream (3) from the identification unit (5, 5a, 5b) and to identify from the characteristic data an inferior product (2a, 2b) in the product stream (3). The device (1, 5, 17) has a compressed air-rejection unit (7) controlled by the computer unit (6) and has deflection means-rejection units (8) designed to passively reject inferior products (2a, 2b) from the product stream (3). The computer unit (6) is designed to classify the identified inferior products (2a, 2b) into a first and a second grade of inferior products (2a, 2b) and to control the compressed air-rejection unit (7) to actively reject the first grade of inferior products (2a) and to control the deflection means-rejection unit (8) to passively reject the second grade of inferior products (2 b).)

1. An apparatus (1, 5, 17) for rejecting inferior products (2a, 2b) from a product flow (3) consisting of superior products (4) and inferior products (2a, 2b) moving in a conveying direction (T), comprising:

an identification unit (5, 5a, 5b) designed to detect the product flow (3);

a computer unit (6) which is connected to the recognition unit (5, 5a, 5b) and is designed to obtain characteristic data of the product stream (3) from the recognition unit (5, 5a, 5b) and to recognize from the characteristic data in real time poor products (2a, 2b) in the product stream (3) detected by the recognition unit (5, 5a, 5 b); and

a rejection unit (7) controlled by the computer unit (6), arranged after the identification unit (5, 5a, 5b) at the product stream (3), viewed in the conveying direction (T), and designed to reject the inferior products (2a, 2b) from the product stream (3) by means of at least one pulse of compressed air, wherein,

the device (1, 5, 17) has at least one further rejection unit (8) controlled by the computer unit (6), wherein the further rejection unit, viewed in the conveying direction (T), is arranged after the identification unit (5, 5a, 5b) at the product flow (3) on the side of the product flow (3) opposite the compressed air rejection unit (7) and is designed to reject inferior products (2a, 2b) by locally deflecting the product flow (3) by means of at least one deflection member (13),

-the computer unit (6) is designed to separate the identified inferior products (2a, 2b) into a first level of inferior products (2a) and a second level of inferior products (2b), wherein the compressed air-rejection unit (7) is designed to reject the first level of inferior products (2a) under the control of the computer unit (6), and a deflection member-rejection unit (8) is designed to reject the second level of inferior products (2b) under the control of the computer unit (6), wherein the deflection member-rejection unit (7) has at least one actuator (12) that causes the at least one deflection member (13) to be shifted between a first position and a second position, characterized in that the deflection member (13) protrudes into the product stream (3) in the first position, and is arranged outside the product flow (3) in the second position, wherein the quality product (4) is deflected in the first position.

2. Device (1, 5, 17) according to claim 1, characterized in that the deflection means-rejection unit (8) is arranged after the compressed air-rejection unit (7) in the conveying direction (T).

3. The device according to claim 1, characterized in that the deflection unit-rejection unit is arranged before the compressed air-rejection unit in the conveying direction.

4. Device (1, 5, 17) according to any of claims 1 to 3, characterized in that the identification unit (5, 5a, 5b) is designed to detect at least one partial region of the reflection spectrum or transmission spectrum when the product is illuminated with electromagnetic waves and to output corresponding characteristic data.

5. Device (1, 5, 17) according to claim 4, characterized in that the identification unit (5, 5a, 5b) is designed as an optical identification unit for detecting light within the visible wavelength range and/or outside the visible wavelength range.

6. Device (1, 5, 17) according to claim 5, characterized in that the optical recognition unit comprises a hyperspectral camera, wherein preferably the hyperspectral camera resolves frequencies in the near infrared-wavelength range, preferably frequencies in the near infrared-wavelength range and the visible wavelength range.

7. Device (1, 5, 17) according to claim 5 or 6, characterized in that the optical recognition unit comprises an RGB-camera or a laser system.

8. Device (1, 5, 17) according to any of claims 4 to 7, characterized in that the identification means (5, 5a, 5b) comprise identification means for detecting electromagnetic waves outside the light wavelength range, in particular for detecting X-rays or terahertz radiation.

9. Device (1, 5, 17) according to any one of claims 1 to 8, characterized in that the compressed air-rejection unit (7) has a regulating valve which is designed to regulate the intensity of at least one compressed air pulse.

10. The apparatus of any one of claims 1 to 9, wherein the deflection member deflects the stream of product to a first reject path in the first position and deflects the stream of product to a second reject path in the second position.

11. The apparatus of claim 10, wherein the deflection member is movable to other positions for forming other rejection paths.

12. The device (1, 5, 17) according to any one of claims 1 to 11, wherein the computer unit (6) is designed to learn from the characteristic data of the product stream (3) the color of the products contained in the product stream (3) and to distinguish between a good-quality product (4), a bad-quality product of a first grade (2a) and a bad-quality product of a second grade (2b) by means of the color of the products.

13. The apparatus (1, 5, 17) according to any one of claims 1 to 12, wherein the computer unit (6) is designed to learn from characteristic data of the product stream (3) an outline or a configuration of a product contained in the product stream (3) and to distinguish between a good-quality product (4), a bad-quality product (2a) of a first grade and a bad-quality product (2b) of a second grade by means of the outline or configuration of the product.

14. The apparatus (1, 5, 17) according to any one of claims 1 to 13, wherein the computer unit (6) is designed to learn from the characteristic data of the product stream (3) the spectral composition of the products contained in the product stream (3) and to distinguish between a good-quality product (4), a first grade of a poor-quality product (2a) and a second grade of a poor-quality product (2b) by means of the spectral composition of the products.

15. The device (1, 5, 17) according to any one of claims 1 to 12, wherein the computer unit (6) is designed to ascertain from the characteristic data of the product flow (3) the contours or contours of the products contained in the product flow (3) and the spectral composition of the products contained in the product flow (3) and to infer the material of the products from the spectral composition of the products contained in the product flow (3), to infer the volume of the products from the contours or contours of the products, to estimate the mass of the products from the material and the volume of the products, and to distinguish between a premium product (4), a first grade of a poor product (2a) and a second grade of a poor product (2b) by means of the mass of the products.

16. The device (15, 17) as claimed in any of claims 1 to 15, characterized in that the device (15, 17) has at least one further detection unit (16a, 16 b).

Technical Field

The invention relates to a device for rejecting inferior products from a product flow consisting of good products and inferior products moving in a conveying direction according to the preamble of claim 1.

Background

From the patent US 9,452,450B 2, a device is known for rejecting defective products from a product flow consisting of good and defective products moving in a conveying direction, which device comprises an optical recognition unit, a computer unit, a first rejection unit consisting of a compressed air unit and a second rejection unit consisting of a controllable mechanical lever. The optical recognition unit, the computer unit, the first and second culling units are connected to each other for exchanging data. The first and second reject units are arranged downstream of the optical recognition unit in the conveying direction at the product stream. The first and second reject units are arranged adjacent to each other on the same side of the product stream, wherein the first reject unit is arranged before the second reject unit in the conveying direction. The optical recognition unit detects the product stream and continuously transmits the optical data generated in this case to the computer unit. The computer unit processes the optical data, identifies in real time poor products in the product stream, and controls the compressed air unit and/or the mechanical lever to reject the poor products from the product stream. Such devices are used, for example, for picking up fruits or vegetables. Patent US 9,452,450B 2 is also disclosed as EP 2396124B 1.

However, this known device has proved to be disadvantageous: since the first and second reject units are arranged directly next to one another on the same side of the product flow and thus lead to narrow space conditions, these reject units must have only small installation dimensions. However, due to the small possible installation dimensions of these rejection units, the following disadvantages arise: in particular for very small products and very large, heavy products, the performance of these rejection units, both in terms of the quality that can be rejected and in terms of the speed, is too low to reject inferior products from the product stream. Although there is the possibility that the spacing between these rejection units can be increased, this results in an undesirably long device that cannot be used in superior systems such as washing, sorting and packaging equipment due to limitations in installation requirements. In addition, since the reject units are close together, it is difficult to maintain the reject units because they are difficult to reach.

Another problem with sorting mechanisms is that each inferior product can have very different shapes, sizes and weights, so it is difficult, often not even possible, to design rejection units suitable for rejecting all the inferior products that are actually present in the product stream.

Disclosure of Invention

The object of the present invention is therefore to propose a device for rejecting inferior products from a stream of products which eliminates the drawbacks of the prior art and improves the quality of rejection.

According to the invention, this object is achieved by a device having the features of claim 1. Preferred designs of the invention are the subject of the dependent claims.

With the device according to the invention, the compressed air-rejection unit and the deflection member-rejection unit are arranged on opposite sides of the product flow. This results in the following advantages: there is a larger installation space for the rejection units, without however lengthening the length of the device. These rejection units can therefore be designed to be more powerful, whereby small products and large, heavy products can also be reliably rejected from the product stream. In addition, by arranging the reject units on opposite sides of the product stream, accessibility to the reject units is improved, whereby they can be maintained better and more easily. An important advantage of the invention is that a higher rejection accuracy is achieved. That is, the closer the reject unit is installed to the observation line of the recognition unit, the higher the reject accuracy because the reliability of hit against inferior products in the material flow is improved and the over-sorting, which is an undesirable reject of good products together with inferior products, is reduced. By arranging the reject units on opposite sides of the material flow it is achieved that the reject units can be arranged close enough to the viewing line, thereby achieving an improved reject accuracy.

By combining the compressed air removal unit and the deflection unit, the system-related disadvantages of the respective removal method can be eliminated and the respective system-related advantages can be used synergistically and optimally. Relatedly, the compressed air-rejection unit is advantageously applied to inferior products of small dimensions, which can be accurately deflected with the air flow. Such inferior products are characterized by a low mass, especially in the case of a relatively small surface area, or a small surface area in the case of a relatively small mass.

Poor products which do not meet these criteria have a large mass in the case of a relatively small surface area or a large surface area in the case of a relatively small mass and are rejected by means of a deflection unit rejection unit, wherein, according to the invention, the deflection unit rejection unit has at least one actuator which displaces at least one deflection member between a first position in which the deflection member projects into the product stream and a second position in which it is arranged outside the product stream, wherein in the first position a good product is deflected. This device is called a passive system because it allows the good product to be deflected away from the product stream, while the trajectory of the bad product in the product stream is not affected by the deflecting member. The passive system has the following advantages: the rejection unit and associated controls can be optimized for quality products of generally known shape and weight. Whereas a poor product may consist of a very different product, which makes optimization of the deflection unit considerably more difficult, such optimization is not required according to the invention, since the poor product does not come into contact with the deflection unit. Therefore, inferior products that cannot be rejected by the compressed air-rejection unit are passively rejected by the deflection unit-rejection unit. The quality of rejection is thereby improved, since inferior products are left in the product stream less than in conventional sorting equipment, and over-sorting is kept small.

From document US 2010/236994 a1 a sorting device is known which is based on active removal of impurity products from the product stream, as opposed to passive removal of impurity products from the product stream according to the invention. Active rejection refers to the following system: the inferior products are deflected away from their flight trajectory by the rejection unit so that the inferior products are kept away from the product stream and are transported on a separate path. And the flight track of the high-quality product is not influenced by the rejection unit. Active reject of contaminant products has been common practice in industry prior to the present invention, as one skilled in the art would recognize that over-sorting can be largely avoided. The contribution of the inventors of the present application is that, contrary to previous general opinion in the art, it has been found that by implementing passive rejection, advantages can be achieved in terms of product reliability, namely reliable rejection of impurities and inferior products, which far outweigh the disadvantages of possible over-sorting. For example, the following risks are reduced by the device according to the invention: impurities cannot be removed from the product stream and are left behind at the consumer, which results in expensive returns.

In a preferred embodiment of the invention, the deflection means-the rejection unit-viewed in the conveying direction-are arranged downstream of the recognition unit at the product stream and are designed for rejecting inferior products by locally deflecting the product stream by means of at least one deflection means. In an alternative embodiment, the order of the rejection units is reversed, i.e., the deflecting unit rejection unit is arranged upstream of the compressed air rejection unit in the conveying direction.

In rejecting inferior products, the deflection member-rejection unit provides high rejection reliability, since the inferior products are simply deflected away from the product stream, also independently of the size, material and shape of the inferior products, but has the following drawbacks: products which are not required to be removed, namely high-quality products, are also removed together every time poor-quality products are removed, so that excessive separation occurs.

The inferior products are classified by the computer unit, wherein the computer unit classifies the inferior products into a first grade of inferior products which can be rejected well by means of an air stream and a second grade of inferior products which are the remaining inferior products. The inferior products of the first grade are rejected by a compressed air-rejection unit under the control of a computer unit, and the inferior products of the second grade are rejected by a deflection component-rejection unit under the control of the computer unit.

Advantageously, the computer unit distinguishes between a good product, a poor product of the first grade and a poor product of the second grade by means of at least one of the following features:

-the colour of the product contained in the product stream;

-the contours and the shapes, in particular the size and shape, of the products contained in the product flow;

-differences in reflection spectrum or transmission spectrum when illuminated with electromagnetic waves, preferably X-rays, infrared rays, terahertz radiation, from the whole electromagnetic spectrum or parts thereof;

differences in the conductivity or magnetisability of the product stream.

The at least one identification unit is preferably correspondingly designed to detect the above-mentioned features and to output corresponding characteristic data. In particular, in a preferred embodiment, the identification unit is designed to detect at least one partial region of the reflection spectrum or transmission spectrum when the product is illuminated with electromagnetic waves. The partial regions of the reflection spectrum or transmission spectrum can be, on the one hand, light in or outside the visible wavelength range, but also other electromagnetic waves, such as X-rays, terahertz radiation (microwave radiation).

If the computer unit is designed to know both the contour and the configuration of the product contained in the product stream and the spectral composition of the product contained in the product stream from the characteristic data of the product stream, the computer unit advantageously knows the product material from the spectral composition of the product contained in the product stream and the product volume from the contour and the configuration of the product, in order to estimate the mass of the product from the material and the volume of the product, and to distinguish between a good-quality product, a first-grade bad product and a second-grade bad product by means of the mass of the product.

If the identification unit is designed as an optical identification unit for detecting light in the visible wavelength range and/or outside the visible wavelength range, the optical identification unit preferably comprises a hyperspectral camera and/or an RGB camera and/or a laser system. By using a combination of a hyper-spectral camera, an RGB-camera and a laser system as an optical recognition system, a high degree of discrimination accuracy for high quality products, first grade inferior products and second grade inferior products can be achieved, since with the optical system various properties of the products in the product stream can be detected. The use of a hyperspectral camera is preferred because it resolves the spectrum into individual narrow frequency bands with high accuracy, whereby a very fine differentiation of the various materials can be achieved. Further improved material discrimination can be achieved if a hyperspectral camera is used which (also) operates in the near infrared range, since a plurality of materials have unique frequency bands in the near infrared range. The distinctiveness of the various materials can again be improved by the optional combined use of a hyperspectral camera with an RGB-camera and/or a laser system.

Advantageously, the device according to the invention comprises at least one further identification unit, wherein the further identification unit is arranged on the opposite side of the product flow to the first detection unit. This has the following advantages: the product flow can be better detected, whereby the computer unit can better distinguish between good-quality products, poor-quality products of the first grade and poor-quality products of the second grade, whereby the rejection quality can be even further improved. The cameras can also be arranged three-dimensionally, that is to say, viewing the material flow from different spatial directions.

Drawings

The advantageous design of the device according to the invention is described in detail below, by way of example, with the aid of the accompanying drawings.

Fig. 1 to 3 show schematically an embodiment of a device for rejecting inferior products from a stream of products moving in a conveying direction according to the invention.

Detailed Description

Fig. 1 shows a schematic view of an embodiment of a device 1 according to the invention for removing inferior products 2a and 2b from a product flow 3 moving in a conveying direction T, wherein the product flow 3 is composed of a good product 4 and the inferior products 2a and 2 b. Fig. 1 shows a partial section of the product flow 3, wherein the product flow 3 moves along a path 14 through the device 1 and is divided into two sections by guide plates 9 and 10.

The apparatus 1 comprises an identification unit 5, a computer unit 6, a first culling unit 7 and a second culling unit 8, which are interconnected for data exchange. In the embodiment shown in fig. 1, the second reject unit 8 is arranged after the first reject unit 7 in the conveying direction T at the product stream 3, and the first and second reject units 7, 8 are arranged opposite to each other at the product stream 3. However, the following possibilities exist: the second reject unit 8 is arranged before the first reject unit 7 in the conveying direction T at the product stream 3. Advantageously, the arrangement of the first and second rejection units 7, 8 is such as to satisfy the installation requirements of the device 1 in the superordinate system and/or of the direction of transport T of the stream 3 and of the path 14 resulting therefrom.

The first rejection unit 7 is designed to reject the inferior products 2a of the first grade. The first rejection unit 7 is constituted by a compressed air unit having a nozzle 11 with a valve that can be electrically controlled by a computer unit. The compressed air unit is connected to a compressed air supply by a supply line, not shown. The first rejection unit 7 thus forms a compressed air-rejection unit. In the design variant of the device 1 according to the invention shown in fig. 1, only one first rejection unit 7 is shown, but the device 1 can also have a plurality of first rejection units 7, which can be arranged one after the other, side by side or offset from one another. The following possibilities also exist: the compressed air unit has a regulating valve which is designed to regulate the intensity of the compressed air pulse discharged from the nozzle 11. The intensity regulation can be carried out manually or by means of the computer unit 6. When the intensity is regulated by the computer unit 6, the intensity is advantageously adjusted according to the first grade of inferior products 2a to be rejected. Therefore, for example, the strength is larger in the case of the first-grade inferior product 2a having a large mass and a small extension degree than in the case of the first-grade inferior product 2a having a small mass and a small extension degree.

The second rejection unit 8 is designed to reject the inferior products 2b of the second grade. The second rejecting unit 8 is formed by an actuator, for example in the form of an electrically controllable pneumatic cylinder 12, and a deflection element 13, wherein the pneumatic cylinder 12 acts on the deflection element 13, which is displaceable between a first position and a second position. The second rejection unit 8 thus forms a deflecting member-rejection unit. The pneumatic cylinder 12 is connected to a compressed air supply via a supply line, not shown. In the first position, the deflection member 13 projects into the product flow 3 and deflects it; in the second position, the deflection member 13 is arranged outside the product flow 3. For the design variant shown in fig. 1, the pneumatic cylinders 12 are controlled by the computer unit 6 so as to deflect the good-quality product 4 in the first position and reject the poor-quality product 2b of the second grade in the second position. The rejection of the inferior products 2b of the second grade without contact is therefore also called passive rejection.

Active rejection refers to the following system: the inferior products are deflected away from their flight trajectory by the rejection unit so that the inferior products are kept away from the product stream and are transported on a separate path. And the flight track of the high-quality product is not influenced by the rejection unit. This active rejection takes place only in the first rejection unit 7 by means of compressed air.

Under the passive rejection condition realized in the second rejection unit 8, the high-quality product is deflected, but the flight path of the low-quality product is not affected. Such passive systems have the following advantages: the rejection unit and associated controls can be optimized for quality products of generally known shape and weight. Poor quality products may consist of very different products, which makes optimization significantly more difficult. By not affecting the flight trajectory of the inferior product, impurities such as rubber balls are also reliably discharged, because upon deflection in an active system, uncontrolled movements of the elastic product, for example uncontrolled jumps of the rubber ball, can easily occur within the device, so that said ball eventually falls back into the superior product. The same is true for very light or floating inferior products such as films or papers. The system also provides other advantages for glass, for example, because glass can be culled without breakage.

Instead of an electrically controllable pneumatic cylinder, other actuators may be used. Those skilled in the art are aware of such actuators and understand that these actuators are selected according to the purpose of use. The requirement for these actuators is that they can be used in the system sufficiently quickly, with sufficient accuracy and high reliability. Such alternative actuators are, for example, hydraulic cylinders, solenoids, electric drives, in particular rotary or linear drives.

For some applications, in particular when the shape, size and weight of the inferior product are within narrow tolerances, the following possibilities also exist: the second rejection unit 8 is configured according to the characteristics of the products like a switch which actively deflects the good products 4 to a first rejection path and actively deflects the poor products 2b of the second grade to a second rejection path to be rejected. Furthermore, the following possibilities exist: the second reject unit has more than two positions and is therefore only used for multi-channel sorting (e.g. by deflecting to different reject paths and passively rejecting the inferior product, separating the superior product into multiple categories).

In this embodiment, the recognition unit 5 is designed as an optical recognition unit and has a hyperspectral camera and optionally an RGB camera or a laser system. Instead of an optical identification unit, however, alternative identification units as mentioned above can also be used.

In use of the device 1 according to the invention, the product flow 3 is guided through the device 1 along the path 14 in the conveying direction T. The product flow 3 is detected by means of an optical detection unit 5, the optical characteristic data thus generated being continuously transmitted to a computer unit 6.

The optical properties comprise the spectral composition, size, shape and color of the products contained in the product stream 3, wherein the computer unit 6 is designed to divide the products according to their different chemical composition by means of their spectral composition. With the aid of the detected size, shape and color, the computer unit can optimize the division, for example, to distinguish wood residues from shell residues. Based on this division, the computer unit 6 identifies in real time the good-quality products 4 and the bad products 2a and 2b in the product stream 3, wherein the computer unit 6 divides the bad products 2a and 2b into a first level of bad products 2a and a second level of bad products 2b according to a better culling method.

With the knowledge of the good product 4, the first level of inferior products 2a and the second level of inferior products 2b, the computer unit 6 controls in a further step the first rejection unit 7 to actively reject the first level of inferior products 2a and the second rejection unit 8 to passively reject the second level of inferior products 2b, whereby only good products 4 remain at the end of the path 14.

Fig. 2 shows in a schematic view another embodiment of the device 15 according to the invention for rejecting inferior products 2a and 2b from a stream 3 of products moving in a transport direction T. In contrast to the device 1 according to fig. 1, the recognition unit 5 of the device 15 is divided into two housings, wherein, for example, a hyperspectral camera and an RGB camera are arranged in the housing 5a, and a laser system is arranged in the housing 5 b. In contrast to the device 1 according to fig. 1, the device 15 furthermore has an additional detection unit 16 which is arranged on the opposite side of the product stream 3 from the detection unit 5 and is also divided into two housings, wherein, for example, a hyperspectral camera and an RGB camera are arranged in the housing 16a and a laser system is arranged in the housing 5 b. It should be noted that, instead of or in addition to optical sensors, the detection units 5, 16 may also have other sensors, in particular sensors for detecting electromagnetic waves outside the wavelength range of light, for example for detecting X-rays or terahertz radiation. With the additional detection unit 16, the following advantages are obtained: the product stream 3 can be detected more accurately, whereby the computer unit 6 can better distinguish between the good-quality products 4, the inferior products 2a of the first grade and the inferior products 2b of the second grade, thus improving the quality of rejection even further. The same components as in the case of the device 1 according to fig. 1 are denoted by the same reference numerals. It is further noted that in other embodiments of the invention, the above-described arrangement of the detection units 5, 16 may be varied in different housings on different sides of the product flow. For example, a side-by-side arrangement or an arrangement around the product stream can also be selected, or more than two streams of inferior products can also be selected without restriction.

It should be noted that, for the device 15, the rejection of the inferior products 2b of the second grade by means of the second rejection unit 8 is a passive rejection. That is, the quality product 4 is deflected in a first position of the deflection member 13, and the second grade of inferior product 2b is removed from the product stream 3 in a second position of the deflection member 13.

Fig. 3 shows in a schematic view another embodiment of the device 17 according to the invention for rejecting inferior products 2a and 2b from a stream 3 of products moving in a transport direction T. Unlike the device 15 according to fig. 2, the positions of the rejection units 7 and 8 with respect to the product stream 3 are exchanged for the device 17.

The same parts of the device 17 as in the case of the device 15 according to fig. 2 are denoted by the same reference numerals.