Abstract:
A packaging device including a filling unit for transporting a filling material, a filling tube connected to said filling unit, for introducing the filling material supplied by the filling unit into a tubular casing and for ejecting the filling material located in the casing, a clipping unit disposed in the direction of transport of the filling unit, for constricting the casing at a predetermined position and for closing the casing with at least one closure element, a sensor unit disposed between the filling unit and the filling tube, for detecting impurities in the filling material and for emitting a detection signal to a control unit, wherein the control unit has a control connection to the clipping unit. The invention also relates to a method for controlling a packaging device.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a packaging device, and in particular to a packaging device in which a filling material is introduced into a tubular casing, and to a method for controlling a packaging device. 
     A packaging device known from practice, in which a filling material is introduced into a tubular casing, is shown in  FIG. 3 . Such a packaging device can be used to produce sausages, for example. 
     The packaging device in  FIG. 3  comprises a mostly funnel-shaped filling container or storage container for the liquid, pasty and/or granular filling material, which may, for example, be sausage meat for producing sausages. The filling material  2  is supplied to a filling unit  4 . Filling unit  4 , also referred to as a filler, causes filling material  2  to be ejected via a connecting pipe  5  to a valve unit  6 . A filling tube  7 , on which a tubular casing  8  closed at one end by means of a closure element is arranged, is connected to valve unit  6 . Casing  8  is pulled in folded form from a respective supply onto at least one part of filling tube  7 , and the casing end with the closure is pulled over the end of filling tube  7 . 
     If, during operation of the packaging device, filling material  2  is transported under a predetermined pressure from storage container  1  in the direction of filling tube  7  by means of filling unit  4 , then the filling material  2  is introduced into casing  8 . That part of casing  8  which is filled with the filling material  2  is transported to a clipping unit  9  disposed in the direction of flow of the filling material. 
     Portioning is carried out in clipping unit  9  according to a predetermined filling capacity (portion size, product size) in casing  8 , by the filling material being displaced in a predetermined region of casing  8  by displacement devices (not shown in  FIG. 3 ), and by the clipping unit  9  placing two spaced-apart closure elements (not shown), such as clips, in the resultant displacement region which is in the form of an unstuffed tress, such that casing  8  is closed and the constricted part of casing  8  can be severed between the closure elements. 
     The individual sausage products are removed after they leave clipping unit  9 , and are transported for further processing to the respective processing positions. 
     The packaging device further comprises a sensor unit  10 , which is provided in the form of a detector for detecting impurities in filling material  2 . In particular, any pieces of metal that have been undesirably introduced into filling material  2  are detected. Sensor unit  10  emits a corresponding detection signal, which is supplied to a central control unit  11  for further processing and evaluation. 
     When filling material  2  is being processed, and particularly during mixing and comminution of components of filling material  2 , it is possible, for example, that parts of the metal tools for comminuting the components of filling material  2  can be damaged and break off. The pieces of metal which have broken off, for example parts made of light metal such as aluminum, or made of steel, are transported in the volumetric flow of filling material  2 , the direction of volumetric flow in  FIG. 3  being indicated by respective arrows  12  in connecting pipe  5 . 
     If, during operation of the packaging device, filling material  2  is contaminated by such metal parts, then these metal parts may end up in the finished product (for example in a sausage), which means that the product may be hazardous for the final consumer eating the product. Such metal parts are likewise hazardous in view of the fact that the product packaged in portions in casing  8 , for example, is further processed in another processing operation. In that case, apparatus and machinery provided for further processing may be damaged. 
     The pre-processed filling material  2  stored in container  1  is fed past the sensor unit  10  into the connecting pipe  5  under a pressure produced by filling unit  4 , such that a metal part can be detected by means of the relevant known measurement methods. 
     If a metallic impurity in filling material  2  is detected by sensor unit  10 , control unit  11  emits a corresponding alarm for the operator of the packaging device and induces shut-down of filling unit  4 , so that no further filling material  2  is transported in an uncontrolled manner in the direction of valve unit  6  and filling tube  7 , and hence to prevent the impurity from entering the finished product. 
     After a metallic impurity has been detected in filling material  2 , it is necessary for measures to be carried out manually by an operator. After detection of the metal impurity by sensor unit  10  and shut-down of the filling unit  4  by operating personnel, or automatically, valve unit  6  may be switched such that any filling material  2  transported to valve unit  6  is not fed to filling tube  7  but to a discharge pipe  13  and that filling unit  4  is manually operated for a predetermined duration, and that the part of filling material  2  which contains the metal impurity is ejected via discharge pipe  13  into an appropriate container  14 . The amount of filling material  2  to be ejected, i.e. the amount of filling material  2  that is not fed to filling tube  7  and hence for processing into the final product, but instead is discharged into container  14 , depends on the stuffing speed resulting from the volumetric flow generated by filling unit  4 . In general, a relatively large amount of filling material  2  is ejected, in order to be certain that the metal impurity is ejected. 
     The filling material  2  thought to contain the metallic impurity is thus ejected in a time-dependent manner according to an adjustable time associated with the predefined volumetric flow rate of filling unit  4 , on the one hand, or ejection can be carried out in such a way that the ejected amount corresponds to a number of portions set on filling unit  4  (pre-adjusted amount of product). 
     It is also possible that direct ejection is not carried out after a metallic impurity is detected by sensor unit  10 , but that connecting pipe  5  and valve unit  6  are manually cleaned instead. To do this, the device must be partially disassembled manually and re-assembled. After operation of the entire portioning and packaging device is temporarily discontinued, it is also necessary to put the device back into operation. 
     However, such handling is very laborious and time-consuming and leads to the undesirable and protracted stoppage of the device. Manual intervention is also required, wherein disassembly and re-assembly of the device or at least parts thereof can be dangerous for the operating personnel. 
     Ejecting part of filling material  2  after detection of a metallic impurity means increased loss of filling material, since a larger amount of filling material must be ejected to ensure that the contaminated filling material is definitely ejected. Hence, in addition to the extended period that operation of the device is discontinued, substantial amounts of filling material  2  are also lost. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is therefore to design a packaging device of the kind initially specified in such a way that a metallic impurity is reliably detected, while preventing any major loss of filling material and extended periods in which operation of the device is discontinued. 
     The invention thus relates to a packaging device comprising a filling unit for transporting a filling material, a filling tube connected to said filling unit, for introducing the filling material supplied by the filling unit into a tubular casing and for dispensing the product thus formed, a clipping unit disposed in the direction of transport of the filling unit, for constricting the casing at a predetermined position and for closing the casing with at least one closure element, a sensor unit disposed between the filling unit and the filling tube, for detecting impurities in the filling material and for emitting a detection signal to a control unit, wherein the control unit has a control connection to the clipping unit. 
     This ensures that a metallic impurity, in particular, can be reliably detected in the filling material. The volumetric flow of the filling material passes the sensor unit, and a corresponding detection signal is supplied to the control unit. The control unit likewise controls the operation of the clipping unit. According to the invention, a data and/or control connection is provided for this purpose between the control unit and the clipping unit, such that the clipping unit can be controlled by means of the controller, and more particularly in an operationally dependent manner. 
     The control unit can also actuate the clipping unit such that a product with a predetermined product size is formed when the detection signal is no longer received, and actuate the clipping unit when the detection signal is present, such that a product size is generated which is larger or smaller than the predetermined product size. 
     Depending on the detection signal being outputted from the sensor unit, a signal can thus be supplied to the clipping unit such that the clipping unit adopts a predetermined operating mode with a correspondingly defined operating behavior. The special operating mode of the clipping unit, which is set by the control unit depending on detection of the impurity, serves to designate a specific amount of product in a special manner such that said amount of product differs reliably in its arrangement and appearance from the product resulting from normal troublefree operation. The product modified by the changed operating behavior resulting from actuation by the control unit can be identified as the product in which the impurity is definitely located, so the contaminated region of the filling material is not ejected with substantial losses and production stoppages in the course of normal further processing of the product, and particularly during normal and troublefree product throughput, but instead is passed through the device in a predetermined, precisely defined manner. In this way, controlled, detection-based actuation of the clipping unit such that it enters a particular operating state or operating mode causes a change in the shape and arrangement of the product, with the result that a region of the product containing the metallic impurity can be distinguished with a very high level of probability from the uncontaminated products. 
     With the device according to the invention, it is therefore possible to detect a metallic impurity reliably, and, without interrupting the production process, i.e., the operation of the device as a whole, to mark a part of the product in such a way that the impurity can be unambiguously associated with this marked part of the product. There is no necessity to use other devices or methods in order to apply a special marking. 
     During operation of the filling unit, the control unit is able to actuate the clipping unit in a predetermined manner when the detection signal from the sensor unit is present, such that the clipping unit discontinues operation. 
     Discontinuing the operation of the clipping unit includes discontinuing at least one of the functions of portioning, closing using a closure element and performing a separating cut in order to form the predetermined product size. 
     The control unit is able to actuate the clipping unit to discontinue its operation for a predetermined duration that is greater than the duration required to form the predetermined product size. 
     The control unit is able to actuate the clipping unit to discontinue its operation during operation of the filling unit, in order to form a predetermined number of products with the predetermined product size. 
     The device may also have a valve unit disposed between the sensor unit and the filling tube and provided to channel the filling material provided by the filling unit either to a filling tube for forming the product, or to a discharge pipe, disposed on the valve unit, for discharging the filling material, depending on the control exercised by the control unit. 
     The device may also have a closable opening disposed between the filling unit and the sensor unit, for supplying predetermined test elements for testing the functioning of the sensor unit. 
     The present invention also relates to a method for controlling a packaging device, said method comprising the steps: transporting a filling material in a volumetric flow through a filling tube into a tubular casing and outputting the filling material located in the casing, constricting the filled casing at a predetermined position and closing the casing with at least one closure element to form a product having a predetermined product size, detecting an impurity in the filling material and outputting a detection signal to a control unit, and forming a control connection between the control unit and the clipping unit for actuating the clipping unit. 
     The method may also include the step of actuating the clipping unit in response to emission of the detection signal, in a predetermined manner to form a product size that is larger or smaller than the predetermined product size. 
     The method may also include the step of actuating the clipping unit during operation of the filling unit when the detection signal is present, such that the clipping unit discontinues operation. 
     Discontinuing operation of the clipping unit may include discontinuing at least one of the functions of portioning, closing using the closure element and performing a separating cut in order to form the predetermined product size. 
     The method may also include the step of actuating the clipping unit to discontinue its operation for a predetermined duration that is greater than the duration required to form the predetermined product size. 
     The method may also include the step of actuating the clipping unit to discontinue its operation during operation of the filling unit in order to form a predetermined number of products having the predetermined product size. 
     The method may also include the step of suppressing filling unit operation, emitting an alarm signal and shutting down the device. 
     The method may also include the step of ending operation of the filling unit, when the detection signal is present, with an adjustable delay until filling unit operation actually ends. 
     The method may also include the step of inserting test elements into the volumetric flow and testing the detection of the test element by means of the sensor unit. 
     The present invention shall now be described in detail on the basis of embodiments and with reference to the Figures, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an overall view of the packaging device according to one embodiment of the present invention, 
         FIG. 2  shows a part of the packaging device shown in  FIG. 1 , according to a second embodiment of the present invention, and 
         FIG. 3  shows a schematic view of a prior art packaging device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a schematic view of the arrangement of a packaging device according to the present invention. 
     According to  FIG. 1 , a filling material  20  located in a container  10  is fed to a filling unit  40 , which for its part generates, with a predetermined pressure, a volumetric flow that feeds filling material  20  to a valve unit  60  via a connecting pipe  50 . By means of a filling pipe  70  disposed on valve unit  60 , onto which filling pipe a predetermined amount of a casing  80  for packaging filling material  20  is arranged, the casing  80  closed on one side at a particular place is stuffed with filling material  20 . Stuffed casing  80  is fed to a clipping unit  90  disposed in the direction of movement of stuffed casing  80 , in which clipping unit the portioning is carried out by respective displacement devices in the manner described above with reference to  FIG. 3 , wherein a predetermined amount of the filling material  20  is disposed in casing  80  and is portioned by the displacement devices in such a way that a constriction or an unstuffed tress of casing  80  is formed between the portions. In the region of the unstuffed tress of casing  80 , the amount of filling material  20  portioned in casing  80  is closed on both side by clipping unit  90 , in that closure elements or clips are fixed to casing  80 , after which the individual product parts located in the constricted region between the closure elements are severed by clipping unit  90 . A predetermined product size corresponding to the set portion size (amount of filling material) is achieved. 
     In the same way as was described with reference to  FIG. 1 , filling material  20  is monitored by means of a sensor unit  100 , by which any metallic objects (metal parts) undesirably contained in filling material  20  can be detected. 
     Respective output signals from sensor unit  100  or from the metal detector are supplied to a central control unit  110  so that the respective operations can be triggered on the basis of the detection signals received from sensor unit  100  and after said signals have been processed accordingly by control unit  110 . Control unit  110  may also be an integral component of clipping unit  90 . 
     If an impurity in filling material  20  is detected in connecting pipe  50  after the volumetric flow has passed in the stated direction (arrows  120 ), then a corresponding amount of filling material can be ejected, in the same manner as in the prior art, by switching valve unit  60  accordingly. The volume of filling material  20  to be ejected is guided by means of a discharge pipe  130  into a container  140 . 
     To control predetermined measures and in particular the packaging device as a whole, control unit  110  is connected to a display and operating panel  150 . On said display and operating panel  150 , operation modes and set operating conditions can be displayed for the user of the device, and by pressing the relevant input keys or by means of a menu the user can also control the device manually, semi-automatically or automatically and can specify the respective operating parameters. Operating parameters can also be stored in a memory device in control unit  110 , particularly with regard to detection by sensor unit  100 . 
     In comparison to the arrangement according to  FIG. 3 , the arrangement of the inventive device according to  FIG. 1  includes a data connection or control connection  160  between control unit  110  and clipping unit  90 . By means of said control connection  160 , which can be wired or wireless, commands for a particular form of operation can be supplied by control unit  110  to clipping unit  90 , and data can be transferred from clipping unit  90  to control unit  110  that describe the operation of clipping unit  90  as well as set parameters and operating conditions, in particular. Thus, clipping unit  90  has an interface to control unit  110 . 
     The inventive device according to  FIG. 1  is thus able to perform the functions and to adopt the operating states that were described for the prior art with reference to  FIG. 3 . This relates, in particular, to the ejection of an amount of filling material  20  in the event that a metallic impurity is detected by means of sensor unit  100 . Control unit  110  can therefore eject an amount of material into container  140 , depending on the current set operating conditions, by switching valve unit  60 . 
     The device according to the invention is therefore able to adopt additional operating modes, in addition to ejection as a function of time, wherein after detection of a metallic impurity the product is ejected by means of valve unit  60  during an adjustable time period, and ejection as a function of portion size, wherein a number of portions of the product adjustable at filling unit  40  is ejected after detection of a metallic impurity. In detail, control unit  110  controls the entire device in order to provide the additional operating modes. 
     In  FIG. 1 , control unit  110  is shown as being separate from any of the components of the device. As already stated in the foregoing, control unit  110  is preferably disposed in clipping unit  90 , so that, when operating clipping unit  90 , the entire device can also be controlled via control unit  110 . In particular, valve unit  60  for ejecting filling material can be controlled by clipping unit  90  (or by control unit  110  disposed therein). 
     In detail, after a metallic impurity has been detected in filling material  20  by sensor unit  100 , a signal is given to control unit  110 , at which control unit  110  actuates clipping unit  90 , in particular, in a predetermined manner corresponding to at least one of the additional operating modes, in response to emission of said detection signal. 
     The possibilities of ejecting on a time basis or a portion basis defines a first operating mode. 
     In a second operating mode, ejection is not carried out by adjusting valve unit  60 , but the filling material  20  containing a metallic impurity is likewise passed through the device. According to a first option of the second operating mode, pass-through is carried out as a function of time, wherein stuffing of filling material  20  is continued for an adjustable time period. In this context, filling unit  40  is actuated in such a way that a corresponding amount of filling material  20 , as a function of time, can be stuffed into casing  80  by means of filling tube  70 . During this period of passing the filling material through the device, clipping unit  90  is actuated in such a manner by control unit  110  that generation of an unstuffed tress, closure of the product by means of respective closure elements and severing of the product in the constricted region of casing  80  between the closure elements disposed there is suppressed. During this predetermined period, clipping unit  90  does not receive any clip signal, which means that its functions are suppressed. 
     Due to the suppression of these functions of clipping unit  90  and the continued operation of filling unit  40 , a product ensues which has a larger volume than the preset portion volume, with the result that a longer sausage, for example, is produced in which the filling material  20  containing the detected metal part is located, wherein this longer and hence clearly identifiable product can easily be removed. An alternative option is to form a product which has a smaller volume than the preset portion volume, with the result that a shorter sausage, for example, is produced in which the filling material  20  containing the detected metal part is located, wherein this shorter and hence clearly identifiable product can easily be removed. 
     The product to be removed is therefore characterized by its having a greater or smaller length, and by the greater or smaller portion volume resulting from the temporarily discontinued operation of clipping machine  90 . The product size is therefore larger or smaller than a predetermined product size corresponding to a product with the preset portion size. 
     As another option within the second operating mode, the filling material can be passed through the device on a portion basis, and no filling material  20  is ejected via valve unit  60  and discharge pipe  130 . Instead, the filling material  20  contaminated with the detected metal part is passed through the device, wherein a preset (predetermined) number of portions of the product is formed which correspond to the preset portion size (portion volume, predetermined product size). In this way, stuffing of casing  80  continues in the preset manner after detection of the metallic impurity. 
     However, during this portion-based passing of the filling material through the device, and after the detection signal is supplied by sensor unit  10 , clipping unit  90  is actuated by control unit  110  in a predetermined manner in order to reach a product size that is larger than the predetermined product size (single portion). This actuation has the effect that the product is portioned by clipping unit  90  in the normal manner and hence that constrictions are formed in casing  80 . However, clipping unit  90  is actuated in such a way that both attachment of the closure elements in the constricted region and severing of the product in the constricted region (applying separating cuts) is suppressed. 
     A longer product (which is longer than the predetermined product size) thus ensues, for example a sausage longer than the length of the predetermined number of portions, but in which no closure elements and no separating cut are provided. In this way, the filling material  20  containing the metallic impurity is likewise stuffed into casing  80  in the usual way, but the predetermined number of portions (single portions), of which one contains the impurity, is distinguished from defect-free product by the suppression of closure and severing. 
     In both of the cases of second operating mode described in the foregoing, the predetermined period can determine the time-based pass-through, or the number of portions can be determined according to the volumetric flow generated by filling unit  40  in the case of portion-based passing of the filling material through the device. These additional parameters for pass-through may be set according to the dimensions and operating parameters of the device. In either case, closure and severing of the longer product is carried out at the beginning and at the end of temporary suppression of operation of clipping unit  90 , with the result that said product can be recognized and separated from the other, uncontaminated products. 
     In this way, it is possible for the contaminated product to be passed through the device without discontinuing operation of the entire device, and for product parts containing the contamination to be marked by actuating the clipping unit  90  accordingly, so that they can be removed easily. 
     Operation of the packaging device includes a third operating mode, in which filling material is passed through with suppression of stuffing and emission of an alarm signal. After a metallic impurity has been detected by means of sensor unit  100 , the packaging device is stopped by means of control unit  110 , wherein filling unit  40  and clipping unit  90  are stopped. An alarm signal for the operating personnel is emitted. The operating personnel then operates clipping unit  90  manually and sets a first closure element (clip) at a predetermined place in casing  80 . After that, filling unit  40  is restarted, and a volumetric flow in the direction of arrows  120  in  FIG. 1  is again formed by filling unit  40  (Auto-On). During a predetermined (adjustable) period, a portion is stuffed into casing  80 , and filling unit  40  is then stopped again. The operating personnel places the first closure element by manually operating clipping unit  90 , so that a marked product is formed in a predetermined manner by manual intervention by the operating personnel, which product can be removed after clipping device  90  has applied a corresponding separating cut. Due to the device being stopped immediately after detection of the metallic impurity, said product contains said metal part. After the product which has been marked in this way has been removed, the operating personnel can switch on the packaging device and put it into operation for further automatic production (Auto-On). 
     In this way, it is possible to pass through a very small loss amount of filling material  20  and to remove it subsequently. Hence, with this manual intervention by the operating personnel, a predetermined portion is stuffed into casing  80 , wherein clipping unit  90  is manually operated to apply the closure elements and the separating cuts. 
     In the fourth operating mode of the packaging device, portion-based passing of the filling material through the device is carried out after detection of a metallic impurity, wherein stuffing is suppressed, an alarm signal is emitted and the device is stopped. An operator applies a first closure element (clip) to casing  80  at filling tube  70  by manually operating clipping unit  90 , after which filling unit  40  is started (Auto-On). A normal stuffing operation is carried out by operating filling unit  40 , wherein a predetermined adjustable number of portions is stuffed until the filling unit  40  is once again stopped. A first closure element (clip) is thus applied, and after the product (for example the sausage) has been removed according to the predetermined number of portions, continued production is reset by the usual automatic method (Auto-On). 
     In a fifth operating mode, beginning with automatic troublefree operation of the packaging device, filling unit  40  is stopped when a metallic impurity is detected in filling material  20  by means of sensor unit  100 , with an adjustable delay in combination with a known path and a known speed. This results in a situation in which filling unit  40  is not stopped immediately, but in which the filling operation is continued during the adjustable delay, so that the place with the impurity (the place where the metallic impurity is located in filling material  20 ), combined with the continued volumetric flow, can be passed through the device and brought near the ejection point in valve unit  60  or at the end of filling tube  70 . In this way, the amount of filling material lost can be reduced, because when the impurity is ejected it is located in the immediate vicinity of valve unit  60  and preferably inside valve unit  60 , and hence a smaller ejection volume is required in order to eject the impurity. Furthermore, when the filling material is passed through the device, the impurity is already located at the end of filling tube  70 , with the result that with the next portion an amount of filling material  20  corresponding to one portion can be put into casing  80  in the normal manner. 
     The fifth operating mode described in the foregoing can be combined with the operating modes described in the foregoing, since both ejection and pass-through can be carried out on a time basis as well as on the basis of a predetermined number of portions. 
     According to a sixth operating mode of the packaging device according to the invention, the filling unit is briefly stopped after an ejection of material (filler stop), so that valve unit  60  can be switched under normal pressure. This relates, in particular, to the preferential configuration of valve unit  60  with a ball valve, so that it can be adjusted under normal pressure. This also prevents further stuffing from being carried out against the closed displacement devices of clipping unit  90 , in certain situations after the packaging device has been restarted. By this means, the device is started more slowly, thus preventing damage to filling material  20  and casing  80 . 
     A second embodiment of the present invention shall now be described with reference to  FIG. 2 . 
       FIG. 2  shows, in a schematic view, a part of the arrangement in  FIG. 1 , showing filling unit  40 , connecting pipe  50 , valve unit  60  with filling tube  70  disposed thereon and with discharge pipe  130  and with sensor  100  disposed in connecting pipe  50 . Arrows  120  designate the controlled direction of the volumetric flow of filling material  20  ( FIG. 1 ) that is transported by means of filling unit  40 . The data connections between the components specified above and control unit  110  are not shown in order to simplify depiction. 
     Sensor unit  100  in  FIG. 2  is used in the same manner as sensor unit  100  in  FIG. 1  to detect impurities, and metal impurities in particular. In the event that a metallic impurity is detected, sensor unit  100  emits a corresponding detection signal to control unit  110 . 
     Hence, reliable detection of an impurity in filling material  20  is only assured when sensor unit  100  functions without disruption. To ensure the operability of sensor unit  100 , a functional test of sensor unit  100  must therefore be carried out. In one known method, test rods containing metallic or metal parts are used, but all that can be measured is purely the detection function of sensor unit  100 . However, confirmation that sensor unit  100  can reliably detect metallic impurities does not permit any reliable conclusions to be drawn as to whether a detected metallic impurity has also been removed (for example by ejection). One problem, and a safety disadvantage, in particular, consists in the fact that the power supply to the entire device is not disconnected when sensor unit  100  has been dismounted from the device. 
     For this purpose, connecting pipe  50  is provided with an opening between filling unit  40  and sensor unit  100  that is closed by means of a closing lid  170  during normal troublefree operation. When closing lid  170  is open, the interior of connecting pipe  50  is then accessible. It is possible thereby to insert predetermined test elements (test bodies)  180  into connecting pipe  50 , such that these are carried along in the volumetric flow of filling material  20  in the direction indicated by arrows  120 . In particular, test element  180  is guided with the volumetric flow past sensor unit  100 , and the metal part of test element  180  is recognized by means of sensor unit  100  when the latter is working faultlessly, and a corresponding detection signal is emitted to control unit  110 . In such a case, it is possible to carry out an operation according to the second operating mode, so that filling material is passed through the device in a time-based or portion-based manner, and wherein test element  180  must be contained in the correspondingly marked product (larger than the predetermined product size). This can likewise be checked, more specifically, by means of an additional testing device, not shown, with which it is possible to determine whether the times for time-based pass-through, or the number of portions for the portion-based pass-through, are correctly and adequately adjusted so that the impurity (test element  180  in this case) is detected reliably and with certainty. 
     In the same way, it can be determined by means of a test element  180  or a plurality of test elements whether test element  180  (the simulated impurity) has also been actually ejected, in the ejection case. 
     By opening closing lid  170 , inserting one or several test elements  180  and reclosing closing lid  170 , it is thus possible, in a simple manner, to carry out a test that includes not only the operability of sensor unit  100  as such, but also the correct adjustment of the operating parameters (stipulated period and stipulated number of portions to be ejected or passed through the device). By carrying out such checks using test elements  180  and with simple insertion of test elements  180  using the opening in connecting pipe  50 , it is therefore possible, as a safety precaution for operation of the inventive device, to simulate an impurity and to reliably check the separation of a contaminated product or the ejection of product containing the impurity. 
     Test elements  180  preferably consist of a plastic ball with an enclosed metal core. 
     In the packaging device according to the invention, valve unit  60  is actuated with compressed air in order to switch it. A ball valve preferably contained in valve unit  60  is actuated directly by compressed air, wherein the packaging device comprises a safety connection for compressed air. The compressed air for actuating valve unit  60  and especially the ball valve contained therein can only be connected when sensor unit  100  is connected to clipping unit  90 . This avoids the problem that it is possible to reach into the ball valve and to switch it when no sensor device  100  is installed, since the electric control has not yet been connected. The entire sensor unit  100  can be taken out of the device. In that case, the compressed air is inevitably disconnected, with the result that even unintentional starting of the device is not possible. 
     In the prior art, clipping unit  90  operates without an electrical interface to the other components of the device, and more particularly to central control unit  110 . Instead, clipping unit  90  operates autonomously. 
     Sensor unit  100  according to  FIGS. 1 and 2  has been described in the foregoing in connection with the detection of metallic impurities. Depending on the type of detection and the configuration of sensor unit  100 , it is possible to detect other impurities, so the invention is not limited to the detection of metallic impurities. 
     The present invention has been described in the foregoing with reference to preferred embodiments and to the associated Figures. However, it is self-evident that the configuration of the present invention according to the Figures described in the foregoing, and the reference signs used for the respective parts and components in the Figures, the description and the claims, and the details provided by way of example are not to be interpreted in a restrictive sense. Rather, all embodiments and variants which come under the enclosed claims are considered to belong to the invention.