Device and method for removing metal object from conveyance flow

Abstract

To provide a device for removing metal objects from a conveyance flow.SOLUTION: A device 10 for removing metal objects from a conveyance flow 12 of a bulk material has: a metal detector 20 which is arranged in a conveyance pipe 14; and a removal device 22 which discharges metal objects from the conveyance pipe. The removal device has: a housing 24 including a discharge pipe 28; a revolving flap 26 which can revolve in a conveyance flow during a removal process in order to bypass the conveyance flow in the discharge pipe; and a motor-driven type excitation unit 42. The excitation unit is located in the housing, and vibrates the housing of the removal device when the excitation unit operates. The excitation unit operates when the metal objects are detected in the conveyance flow. When the revolving flap revolves in the conveyance flow, the conveyance flow is discharged through the discharge pipe, and thereafter, the revolving flap returns to revolve, and operation of the excitation unit is canceled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for removing metal objects from a transport stream.

[0002] For example, in food manufacturing transport stream systems, metal detectors are used to detect unwanted metallic foreign bodies in the transport stream of bulk material, where the continuous transport stream is inspected for metallic contaminants, particularly metal chips or particles, wires, screws or nuts, tools, or other foreign bodies, and if detected, the metallic foreign bodies are then removed from the transport stream by a removal device during continuous operation of the transport stream system.

[0003] In so-called free-fall systems, in at least one free-fall section of the conveying tube, the conveying flow is guided vertically, i.e., approximately parallel to the direction of gravitational acceleration, with the bulk material falling by gravity from a higher potential energy level to a lower potential energy level.

[0004] In free fall systems, the metal detector is, as is known, arranged in the area of ​​the free fall section, with the removal device for removing foreign bodies from the transport stream immediately following the metal detector in the flow direction of the transport stream.

[0005] A conventional removal device is a flap distributor, in which a flap pivots into the free-fall section and diverts the transport flow into a discharge pipe that leaves the transport pipe at the side. The discharge pipe is inclined, but not vertical, which can lead to undesirable material deposits, especially at the transition from the transport pipe to the discharge pipe.

[0006] The object of the present invention is to reduce material deposits in the area of ​​the removal device with high reliability and low cost.

[0007] This problem is solved by an apparatus for removing metal objects from a conveying stream of bulk material, the apparatus comprising a conveying pipe, a metal detector arranged in the conveying pipe, and a removal device for discharging the metal objects from the conveying pipe, the bulk material flowing through the conveying pipe, the metal detector being arranged along the conveying section upstream of the removal device in the flow direction of the conveying stream. The removal device has a housing with a discharge pipe and a pivoting flap that can be pivoted into the conveying stream during the removal process to divert the conveying stream into the discharge pipe, the removal device having a motor-driven excitation unit arranged in the housing and vibrating the housing of the removal device when the excitation unit is activated.

[0008] The vibrations caused by the excitation unit shake the housing, moving the walls of the housing and, in particular, the walls of the discharge pipe. This movement, on the one hand, shakes off the bulk material adhering to the inside of the housing. On the other hand, the detached bulk material does not remain inside the housing, but is moved through the housing by the vibration of the housing walls, and does not collect and adhere to the inside of the housing. In this process, the bulk material sweeps away the removed metal objects, so that these metal objects are carried together with the bulk material into the discharge pipe and are discharged from the device.

[0009] Furthermore, in this way, the adhering bulk material is peeled off from the inside of the housing, in particular from the inside of the discharge pipe and the swiveling flap, during each removal process and carried away through the discharge pipe, thereby preventing the accumulation of bulk material inside the housing.

[0010] The pivot flap can pivot between an initial position and a discharge position. During normal operation of the system and the device, the pivot flap is in the initial position, in which it closes the discharge pipe, while the entire transport flow falls past the pivot flap without being hindered by the pivot flap. During the removal process, the pivot flap enters the transport flow and pivots to the discharge position, closing the transport pipe, so that the entire transport flow is diverted into the discharge pipe.

[0011] Here, the removal process includes the time span from when the rotating flap starts moving from the initial position to the discharge position until the rotating flap returns to the starting position after the metal object has been successfully discharged.

[0012] Preferably, the metal detector and the removal device are connected to a control unit, which is designed to activate the excitation unit during the removal process. In this way, the excitation unit can be synchronized with the detection of contaminants and only operate when necessary. Otherwise, the excitation unit can be deactivated (with possible exceptions, as described below), which saves electricity and reduces noise emissions. Typically, when the metal detector is activated, the removal process is carried out, during which the excitation unit is also activated as a rule.

[0013] Typically, the excitation unit comprises a moving element acting on the outside of the housing of the removal device and a drive for moving this moving element. The drive of the excitation unit is in particular controlled by a control unit. For example, the drive of the excitation unit is an electric motor or a pneumatic drive. The task of this drive is to move the moving element in such a way that vibrations of the housing wall occur, the amplitude of the vibrations being large enough to shake off the bulk material adhering to the inside of the housing.

[0014] The drive of the excitation unit is a separate component from the actuator of the pivoting flap and is arranged in the housing spatially separated from this actuator.

[0015] To reduce noise generation and minimize wear, the moving element is preferably prevented from directly impacting the housing wall, and a damping element is arranged between the outside of the housing and the moving element, which may be, for example, a rubber buffer or other suitable elastic component.

[0016] The excitation unit may include, for example, a hammer mechanism, a percussion mechanism, or a vibrator. In the case of a hammer mechanism, the moving element is in particular a pivotally supported striking rod, while in the case of a percussion mechanism, it is realized by a linearly moving plunger. In both cases, the moving element delivers individual blows to the housing wall. In this case, the moving element moves at a relatively low frequency. In the case of a vibrator, the moving element is, for example, an unbalanced eccentric drive, which generates continuous vibrations of the housing wall at a higher frequency.

[0017] Typically, the frequency at which the housing wall is excited is in the range of about 0.5 Hz to 50 Hz, with a frequency of about 20 Hz being particularly preferred.

[0018] It is conceivable to select the frequency so that the natural vibrations of the housing wall are excited, i.e. the excitation frequency is selected according to the resonant frequency of the housing, thereby obtaining a higher vibration amplitude with a lower energy requirement.

[0019] In a preferred variation, the excitation unit is placed on the housing of the removal device and fixed there. The excitation unit may need to be mounted so that it does not come into contact with the interior of the housing, and the movable elements do not come into contact with the bulk material. For example, the excitation unit is fixed by fixing bolts welded to the housing from the outside. In this way, the excitation unit can be easily accessed for replacement or maintenance, while the inside of the housing is preferably designed flat and smooth in the area of ​​the excitation unit, thereby making it difficult for bulk material to adhere.

[0020] The excitation unit is preferably located outside the discharge pipe, for example in the region of the housing through which the transport stream passes, in the confluence region of the discharge pipe.

[0021] In particular, the excitation unit may be arranged above the discharge pipe, in which area the well-known flap-type distributor usually provides sufficient and easily accessible mounting space.

[0022] The control unit is optionally designed to preset an after-run time for the pumping unit after the removal process is completed. In this case, the pumping unit continues to operate for a while after the pivot flap has reached its initial position again. This after-run time varies depending on the type of bulk material and is determined so that most of the deposits are shaken off from the pivot flap and the inside of the housing, including the inside of the discharge pipe. The after-run time is selected to be, for example, approximately 1 to 10 times the length of the removal process.

[0023] The control unit may be designed to activate the excitation unit before or simultaneously with the pivoting flap pivoting into the conveying stream. In particular, activation of the excitation unit by the control unit may occur as soon as the metal detector responds to the presence of a metal object and the control unit receives a detection signal from the metal detector. Activation of the excitation unit may occur, for example, approximately 100 milliseconds before the pivoting flap fully pivots to the discharge position.

[0024] Preferably, the removal device is located within the free-fall section of the transport pipe, so that in normal operation the bulk material passes through the housing in free fall without being fed through the inside of the housing. When the pivoting flap pivots to the discharge position, the entire transport flow is diverted diagonally downward into the discharge pipe. The length of the free-fall section can be up to several meters, as in known systems.

[0025] The above-mentioned problem is also solved by a method for removing metal objects from a conveying stream of bulk material in the above-mentioned device, which comprises the following steps: - detecting metal objects in the transport stream; -activating the excitation unit; - swirling the swirl flap into the conveying flow; - discharging the carrier stream from a discharge pipe; - a step of returning the rotating flap to its original position; - deactivating the excitation unit; is executed.

[0026] The excitation unit is preferably activated before or at the same time as the swirl flap swivels into the conveying flow and / or is deactivated after the swirl flap swivels back out of the conveying flow. The excitation unit is thus kept moving for as long as possible during the removal process, while deposits of bulk material on the inside of the housing are avoided by the vibrational movement of the housing, or any deposits that do form are quickly shaken off again. However, the excitation unit only needs to be moving for a relatively short time during each removal process, and the excitation unit can remain deactivated during most system operations.

[0027] Preferably, the excitation unit is activated immediately after the metal detector responds, which, as mentioned above, allows the excitation unit to be activated already about 100 milliseconds before the pivoting flap reaches its ejection position.

[0028] If necessary, the excitation unit is deactivated after a preset after-runtime after the removal process has finished, as already explained above.

[0029] In addition to its operation during each removal process, the excitation unit can also be activated at pre-set times, independently of the metal detector's response, to clean the removal device. The duration of the excitation unit's operation in this case is, for example, a few seconds each and varies depending on the type of bulk material. Furthermore, such cleaning processes can be started and stopped automatically, as they are monitored by the control unit.

[0030] In such a cleaning process, the excitation unit is preferably switched on while the discharge pipe is closed, i.e., while the swivel flap is in its initial position and the conveying flow is flowing normally. During this time, bulk material that has accumulated on the conveying flow side of the swivel flap and on the inside of the housing during operation is shaken off and carried away with the conveying flow. Any deposits that may have not been removed from the conveying flow side of the swivel flap and on the inside of the housing during the removal process are also loosened and are carried away through the discharge pipe.

[0031] For example, the excitation unit may be activated at periodic time intervals and / or after a preset amount of bulk material has passed.

[0032] The invention will now be described in more detail on the basis of examples with reference to the accompanying drawings. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is an exploded view of an apparatus for removing metal objects according to the present invention; [Figure 2] 1 is a flow chart of a method for removing metal objects according to the present invention.

[0034] 1 shows an apparatus 10 for removing metal objects from a conveying stream 12 of bulk material in a conveying pipe 14, here a free fall system.

[0035] During operation, bulk material, such as granular or powdery dry products (such as plastic granules, flour or coffee grounds), flows through the conveying pipe 14 in a predetermined conveying section 16 along the free fall section 18, where the bulk material moves through the free fall section 18 mainly based on the conversion of potential energy into kinetic energy, which results in a flow direction that mainly follows the vertical direction V of the gravitational acceleration.

[0036] A metal detector 20 is located in the free fall section 18, here at least partially surrounding the transport tube 14. The metal detector 20 is used to detect metal contaminants, i.e., metallic foreign objects, in the transport stream 12.

[0037] The apparatus 10 includes a removal device 22 below the metal detector 20 in the flow direction of the transport stream 12 and in the vertical direction V.

[0038] In this case, the removal device 22 is a flap-type distributor and includes a housing 24 in which a pivotable flap 26 is arranged. The housing 24 is formed with a discharge pipe 28 which is spaced apart from the conveying direction and the conveying pipe 14 downwards at an acute angle.

[0039] The pivot flap 26 can be adjusted about a pivot axis 30 between an initial position in which the pivot flap 26 completely closes the discharge pipe 28 and a discharge position in which the pivot flap projects into the conveying flow 12 and completely closes the conveying pipe 14. The initial position of the pivot flap 26 is shown in dashed lines in Figure 1, and the discharge position is shown in solid lines.

[0040] An actuator 32 is provided which is connected to the pivot flap 26 to enable pivoting of the pivot flap 26 into and out of the conveying flow 12. The actuator 32 is specifically designed to prevent excessive vibrations from being transmitted to the housing 24, so that the pivot flap 26 moves as quickly and evenly as possible.

[0041] When the swivel flap 26 is in the discharge position, all of the transport flow 12 is diverted into the discharge pipe 28. In this way, the swivel flap 26 can briefly direct the transport flow 12 from the transport pipe 14 through the discharge pipe 28, for example into a collection container (not shown).

[0042] The housing 24, including the discharge pipe 28, is a rigid component manufactured from stainless steel or the like. Further along, the discharge pipe 28 leaves the housing 24 and optionally transitions into a flexible hose.

[0043] The removal device 22 is inserted into the conveying pipe 14 with an upstream inlet side 34 and a downstream outlet side 36, so that when the swirl flap 26 is in its initial position, the conveying flow 12 passes through the removal device 22 without resistance and without contact with the swirl flap 26 and the discharge pipe 28.

[0044] The metal detector 20 and the removal device 22 are connected to a control unit 38 .

[0045] The control unit 38 evaluates the signal sent from the metal detector 20 and, if any contaminants are detected in the conveying stream 12, activates the actuator 32 of the pivoting flap 26 to pivot the pivoting flap 26 into the conveying stream 12 to the discharge position, so that the detected metal objects are sent together with the conveying stream 12 into the discharge pipe 28.

[0046] Within the discharge tube 28, the bulk material undergoes sliding motion, with some contacting the interior surface 40 of the discharge tube 28.

[0047] As soon as it is determined that the metal object has bypassed into the discharge pipe 28, for example after a predetermined dead time, the pivoting flap 26 again exits the conveying flow 12 and pivots back to its initial position, so that the conveying flow 12 again flows exclusively within the conveying pipe 14 and completely passes through the discharge pipe 28. This procedure is referred to herein as the removal process.

[0048] The removal device 22 further includes a motor-driven excitation unit 42 designed to vibrate the housing 24 , thereby preventing bulk material from accumulating inside the housing 24 .

[0049] The vibratory motion of the walls of the housing 24 shakes off any adhering bulk material from the interior 40 and carries the moving bulk material downward into the discharge pipe 28. Metallic objects contained in this type of accumulated bulk material are moved into the discharge pipe 28 along with the bulk material due to the shaking caused by the vibrations.

[0050] The excitation unit 42 includes a movable element 44 which is moved by a suitable drive 45 and which in its movement acts on the outside 46 of the housing 24 .

[0051] The drive 45 of the excitation unit 42 can be, for example, an electric motor, but can also be pneumatically driven. In any case, the drive 45 of the excitation unit 42 is structurally distinct from the actuator 32 that moves the pivoting flap 26 and is spatially separated from the actuator 32.

[0052] The moving element 44 is, for example, part of a hammer mechanism, a percussion mechanism or a vibrator. Depending on the type of moving element 44 and the drive 45, the excitation unit 42 applies individual percussions or pulses occurring in succession at regular time intervals to the housing 24. For example, excitation can occur at frequencies from about 0.5 Hz up to 50 Hz, in particular up to 20 Hz.

[0053] Optionally, the frequency is selected so that the resonant frequency of the housing 24 is excited.

[0054] In general, the frequency and type of excitation unit 42 are selected depending on the bulk material and its properties contained in the conveying stream 12. For example, for highly adhesive bulk materials such as cocoa or coffee grounds, it has proven advantageous to use a hammer or percussion mechanism, which uses individual strong pulses to loosen the deposits, while for less adhesive bulk materials, such as plastic granules, it has proven advantageous to use a vibrator, which uses periodic vibrations, for example at about 20 Hz, to move the bulk material from the housing 24 into the discharge pipe 28.

[0055] A damping element (not shown), such as a rubber buffer, is preferably disposed between the moving element 44 and the exterior 46 of the housing 24 to prevent direct contact between the moving element 44 and the exterior 46 of the housing 24. However, the pulse transmitted by the moving element 44 must always be of such magnitude that it causes the wall of the housing 24 to vibrate with sufficient amplitude.

[0056] Similarly, the excitation unit 42 is also connected to the control unit 38 and its driver 45 is controlled by the control unit 38 so that the control unit 38 can activate and deactivate the excitation unit 42 .

[0057] In this example, the excitation unit 42 is manufactured as a separate component from the housing 24. The excitation unit 42 is arranged on the outside 46 of the housing 24. For this purpose, here, a number of fixing bolts 48, e.g., stud bolts, are welded to the outside 46, and the excitation unit 42 is attached to these stud bolts 48. Since the fixing bolts 48 do not penetrate the wall of the housing 24, the inside 40 of the housing 24 is flat and smooth, even in the area of ​​the excitation unit 42.

[0058] In the illustrated variant, the excitation unit 42 is arranged on the upper side 49 of the housing 24 of the discharge pipe 28 , near the junction 50 of the discharge pipe 28 into the transport section 16 inside the housing 24 .

[0059] FIG. 2 shows a possible sequence of steps for removing metal objects from a transport stream 12 in the described apparatus 10.

[0060] The method begins with a first step 100 when the metal detector 20 detects a metal object and transmits a corresponding detection signal to the control unit 38 .

[0061] In step 102, the control unit 38 activates the excitation unit 42, i.e., turns on the driver 45 of the excitation unit 42, which moves the movable element 44. At this point, the excitation unit 42 begins to vibrate the wall of the housing 24, with the type and frequency of excitation being determined by the type of excitation unit 42 and the preset frequency.

[0062] Furthermore, the control unit 38 initiates the removal process by actuating the actuator 32 of the oscillating flap 26, which causes the oscillating flap 26 to begin moving from the initial position to the ejection position (step 104).

[0063] Here, the control unit 38 activates the excitation unit 42 immediately after the metal detector 20 reacts, or more precisely, immediately after receiving a detection signal from the metal detector 20 .

[0064] In one variation, activation of the excitation unit 42 occurs before the pivoting flap 26 begins to pivot. In another variation, activation of the excitation unit 42 occurs at least before the pivoting flap 26 reaches its ejection position, for example, approximately 100 milliseconds before reaching the ejection position. This is particularly possible when the free-fall section is several meters long. A short free-fall section reduces this time span, since it takes less time for the bulk material to travel from the metal detector 20 to the removal device 22.

[0065] When the pivoting flap 26 is in the discharge position, all of the transport flow 12 is diverted away from the transport section 16 into the discharge pipe 28. At this time, any detected metal objects are also discharged from the discharge pipe 28 (step 106).

[0066] Once the appropriate amount of bulk material containing metal objects has been diverted to the discharge pipe 28, the pivoting flap 26 is pivoted back to its initial position in step 108 and the excitation unit 42 is turned off (step 110).

[0067] In this example, the excitation unit 42 is activated for at least the entire removal process, i.e., from just before or after the pivoting flap 26 pivots from its initial position until at least the pivoting flap 26 pivots back to its initial position.

[0068] Furthermore, the excitation unit 42 now also operates during the after-run time beyond the point after the pivoting flap 26 has again reached its initial position. After the bypassed amount of bulk material has been discharged by the pivoting flap 26, any deposits remaining on the removal device 22, in particular on the pivoting flap 26 and on the discharge pipe 28, are now directly peeled off and carried away from the discharge pipe 28.

[0069] Typically, the after run time is determined based on the bulk material being used as well as the apparatus 10 as a whole, and can be, for example, 1 to 10 times the duration of the removal process.

[0070] Here, the excitation unit 42 is activated every time during the removal process.

[0071] After the removal process is completed, possibly taking into account after-runtime, the control unit again deactivates the excitation unit 42. Thus, vibration excitation of the housing 24 is performed as needed. The excitation unit 42 is deactivated for the majority of the operating time of the device 10.

[0072] Here, in addition to operating during the removal process, the excitation unit 42 is activated at a preset time during operation, i.e., when the transport flow 12 is flowing, regardless of the reaction of the metal detector 20, and at this time the cleaning process of the removal device 22 is carried out.

[0073] In this case, the swirl flap 26 remains in its initial position, so that the discharge pipe 28 is completely disconnected from the conveying flow 12. The excitation unit 42 is activated by the control unit 38 for a preset time, for example a few seconds. During this time, any bulk material deposits on the inside 40 of the housing 24 are removed. The bulk material removed from the inside of the discharge pipe 28 and from the discharge-pipe-facing side of the swirl flap 26 is carried away through the discharge pipe 28 by the vibration of the housing 24. The bulk material removed from the conveying-flow-facing side of the swirl flap 26 and from the inside 40 of the housing 24 in the area of ​​the conveying flow 12 is carried away together with the conveying flow 12.

[0074] Such a cleaning process may be carried out automatically by the control unit 38 periodically, for example after a preset time interval or after a preset amount of bulk material has passed, respectively.

[0075] Furthermore, the transport tube 14 may also be provided with a test part inlet 51, through which test parts can be introduced into the transport flow 12 and the function of the metal detector 20 can be checked. The test part inlet 51 consists of an insert piece 52, through which test parts can be introduced into the transport flow 12 from outside the transport tube 14. In this case, the insert piece 52 is provided with a closure element 53, which can be opened and closed by rotating it. In this case, the closure element 53 is designed to reach the inside 40 of the transport tube 14, thereby providing the insert piece 52 with no dead spaces into which sediment from the transport flow 12 cannot enter. Preferably, the closure element 53 may have at least one seal that compensates for tolerances and seals the insert piece 52.

[0076] Preferably, the guiding and positioning of the test component can be achieved solely by the thread of the insertion piece 52 and the corresponding thread of the closure element 53. To this end, an insertion aid for the test component can be fitted in the closure element 53 or a further closure element 53 with an insertion aid for the test component can be used to hold the test component. As soon as the closure element 53 is inserted into the insertion piece 52 and the closure element 53 is turned from the open position to the closed position, the test component is placed into the transport flow 12. [Explanation of symbols]

[0077] 10 equipment 12 Transport flow 14 Conveyor pipe 16 Transport Section 18 Free Fall Section 20 Metal Detector 22 Removal device 24 Housing 26 Rotating flaps 28 Discharge pipe 30 Swivel Axis 32 Actuator 34 Entrance side 36 Exit side 38 Control Unit 40 Inside 42 Excitation Unit 44 moving elements 45 Drive unit 46 Outside 48 Fixing bolt 49 Upper 50 Junction 51 Test part inlet 52 Insert Piece 53 Closure elements 100 processes 102 processes 104 Process 106 Process 108 processes 110 processes

Claims

1. The present invention relates to an apparatus (10) for removing metal objects from a conveying flow (12) of bulk material, the apparatus (10) comprising a conveying pipe (14), a metal detector (20) arranged in the conveying pipe (14), and a removal device (22) for discharging the metal objects from the conveying pipe (14), the bulk material flows through the conveying pipe (14), the metal detector (20) is arranged along a conveying section (16) upstream of the removal device (22) in the flow direction of the conveying flow (12), the removal device (22) comprising a housing (24) with a discharge pipe (28), and a pivot flap (26) that is pivotable into the conveying flow (12) during the removal process to divert the conveying flow (12) into the discharge pipe (28), wherein the removal device (22) comprises, apart from an actuator (32) that moves the pivot flap (26), a motor-driven excitation unit (42) that is arranged in the housing (24) and that vibrates the housing (24) of the removal device (22) when the excitation unit (42) is activated.

2. 2. The apparatus (10) of claim 1, wherein the metal detector (20) and the removal device (22) are connected to a control unit (38), the control unit (38) being designed to activate the excitation unit (42) during the removal process.

3. The device (10) according to claim 1 or 2, wherein the excitation unit (42) includes a movable element (44) acting on the outside (46) of the housing (24) of the removal device (22) and a drive device (45) for moving the movable element (44).

4. The apparatus (10) of any one of claims 1 to 3, wherein the excitation unit (42) comprises a hammer mechanism, a striking mechanism or a vibrator.

5. 5. The device (10) according to any one of claims 1 to 4, wherein the excitation unit (42) acts on the housing (24) with a frequency in the range of 0.5 Hz to a maximum of 50 Hz, in particular a maximum of 20 Hz.

6. The apparatus (10) according to any one of claims 1 to 5, wherein the excitation unit (42) is placed on the housing (24) of the removal device (22) and fixed therein.

7. The apparatus (10) of claim 6, wherein the excitation unit (42) is located outside the exhaust pipe (28).

8. The apparatus (10) of claim 7, wherein the excitation unit (42) is disposed above the exhaust pipe (28).

9. 9. The device (10) according to any one of the preceding claims, wherein the control unit (38) is designed to pre-set an after-run time for the excitation unit (42) after the end of the removal process.

10. 10. The apparatus (10) according to any one of claims 1 to 9, wherein the control unit (38) is designed to activate the excitation unit (42) before or simultaneously with the pivoting flap (26) pivoting into the conveying flow (12).

11. The apparatus (10) according to any one of the preceding claims, wherein the conveying section (16) is within a free-fall section (18) of the conveying tube (14).

12. A method for removing metal objects from a conveying stream (12) of bulk material in an apparatus (10) according to any one of claims 1 to 11, comprising the steps of: - detecting metal objects in said transport stream (12); - activating said excitation unit (42); - pivoting said pivot flap (26) into said conveying flow (12); - Discharging said carrier stream (12) through said discharge pipe (28); - pivoting the pivoting flap (26) back; - deactivating said excitation unit (42); The method according to claim 1,

13. 13. The method of claim 12, wherein the excitation unit (42) is activated before or simultaneously with the swirl flap (26) pivoting into the conveying flow (12) and / or is deactivated after the swirl flap (26) pivots back out of the conveying flow (12).

14. 14. The method of claim 13, wherein the excitation unit (42) is activated immediately after the metal detector (20) responds.

15. 15. The method according to claim 13 or 14, wherein the excitation unit (42) is deactivated after a preset after runtime after the end of the removal process.

16. 16. The method according to any one of claims 12 to 15, wherein the excitation unit (42) is activated at a preset time point, independent of the reaction of the metal detector (20), in order to clean the removal device (22).

17. 17. The method according to any one of claims 12 to 16, characterized in that the excitation unit (42) is switched on briefly, in particular at periodic time intervals, while the outlet pipe (28) is closed and the transport flow (12) is flowing.

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