Abstract:
The invention relates to a method of, and to a device for, checking cigarettes ( 12 ) during the production or packaging of the cigarettes ( 12 ), a push rod ( 35 ) being displaced axially in the direction of a cigarette end, with the result that, in the event of the incorrect formation or absence of a cigarette ( 12 ), the push rod ( 35 ) assumes a position other than an ideal position. The invention is based on the problem of improving the operation of checking cigarettes and of configuring this operation such that it is less susceptible to malfunctioning. 
     This problem is solved by a method according to the invention in that an electric, magnetic or electromagnetic field assigned to a sensor ( 32, 53 ) is influenced in dependence on the position of the push rod ( 35 ), a signal which corresponds to the push-rod position being generated as a result of said field being influenced. The invention also relates to a device for implementing said method.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method of checking cigarettes during the production or packaging of these cigarettes, a push rod being displaced axially in the direction of a cigarette end, with the result that, in the event of the incorrect formation or absence of a cigarette, the push rod assumes a position other than an ideal position. The invention also relates to a device for checking cigarettes for cigarette-packaging and/or cigarette-production machines, having at least one axially displaceably mounted push rod which has a head for penetrating into a cigarette end. 
     Methods and devices are known for checking cigarette ends using push rods, which are arranged in three layers and correspond to the geometry of a cigarette formation, said push rods being advanced up to a cigarette formation in order to check the cigarette ends. In the event of the correct formation of the cigarettes, in this checking operation, all the push rods are pushed into a rear position. However, if a cigarette is absent or if a cigarette is only loosely filled, the push rod remains in its starting position or is only pushed in to a slight extent. This operation of pushing in the push rods is usually checked by means of a light barrier provided for each layer. It is thus possible to infer from the pushing-in depth whether cigarettes are absent or defective. This checking method has the disadvantage that the light-barrier components become dirty over time. This may result in operational malfunctioning and thus in production being interrupted. Frequent maintenance of these installations is thus necessary. 
     SUMMARY OF THE INVENTION 
     The invention is thus based on the problem of improving the operation of checking cigarettes and of configuring this operation, in particular, such that it is less susceptible to malfunctioning. 
     In order to solve this problem, the method according to the invention is characterized in that an electric, magnetic or electromagnetic field assigned to a sensor is influenced in dependence on the position of the push rod, a signal which corresponds to the push-rod position being generated as a result of said field being influenced. The problem is also solved by a checking device according to the invention, which is characterized in that the push rod has a region for influencing an electric, magnetic or electromagnetic field assigned to a sensor, the sensor being designed such that it generates a signal which corresponds to the push-rod position as a result of said field being influenced. An advantage of the invention is that the checking method according to the invention or the checking device according to the invention is no longer susceptible to dust, since it is not based on an optical principle. 
     The position of the push rod is preferably determined by way of a depth to which a ferromagnetic and/or ferrimagnetic region of the push rod penetrates into the interior of a sensor-forming, in particular annular, coil. In this case, the coil is connected electrically to a measuring arrangement which emits a signal in dependence on the depth, representing the push-rod position, to which the ferromagnetic and/or ferrimagnetic region penetrates into the coil. 
     It is also preferred for the position of the push rod to be determined by way of a sensor-forming Hall element being magnetized by a magnetic field generated by a magnetic region of the push rod, it being the case that the Hall element is subjected to an electric voltage on two opposite sides and the signal is generated in dependence on the magnetic field, which magnetizes the Hall element and represents the push-rod position. Here too, the Hall element is preferably connected to an electric measuring arrangement which emits a signal in dependence on the magnetic field, which magnetizes the Hall element and represents the push-rod position. 
     The advantage of these preferred solutions is that they are small enough in order to be able to sense each cigarette of a relatively large cigarette formation at the same time. By virtue of the invention, it is then no longer necessary for cigarettes to be checked at different locations or times. This is because the devices according to the invention may be small enough for the necessary measuring arrangements, namely Hall elements or coils, not to be larger than the thickness of a cigarette. In particular, the coils thus have an external diameter which is smaller than a cigarette diameter. 
     It is preferable, during a checking operation, for all the cigarettes of a cigarette formation fed to a cigarette pack to be checked at the same time, the individual push-rod positions being evaluated individually, with the result that systematic faults can be detected. The latter include, in particular, such faults as occur in the case of adjacent cigarettes or cigarette positions which are located in different layers one above the other. It is thus possible to detect, for example, a defective cigarette shaft. In the event of such a fault, finally, an alarm or control signal is generated in order to reduce the rotational speed of a packaging and/or production machine, or in order to stop the same. 
     The push rods are preferably interrogated individually. For this purpose, each push rod is assigned an element which can be interrogated individually, namely a Hall element or an, in particular, annular coil. The signals emitted by these elements are evaluated by means of an evaluation unit. This evaluation unit is small enough to be accommodated in the housing of the checking device, with the result that it is advantageously possible to dispense with high-outlay wiring of all the individual elements to a central machine-control means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the invention can be gathered from the subclaims and with reference to the exemplary embodiments illustrated in the drawing, in which: 
     FIG. 1 shows part of a cigarette-packaging machine with checking devices arranged on both sides of the cigarettes which are to be checked; 
     FIG. 2 shows a section of the packaging machine from FIG. 1 along line II—II; 
     FIG. 3 shows a checking device along section line III/V—III/V according to FIG. 2; 
     FIG. 4 shows a checking device along section line IV—IV according to FIG. 3; 
     FIG. 5 shows a checking device along section line III/V—III/V according to FIG. 2; and 
     FIG. 6 shows a checking device along section line VI—VI according to FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a cigarette-packaging machine  10  with a cigarette magazine  11 , in which cigarettes  12  are located and which move downwards, as the packaging process is in operation, in the direction of the arrow  13  illustrated in FIG.  2 . The magazine  11  opens out into a plurality of, namely  4 , shaft groups  14 , which are illustrated in FIG.  2  and each comprise a plurality of, namely seven, shafts  15 . 
     Formed at the bottom end of the shafts  15  is in each case one cigarette formation  16 , that is to say a total of four cigarette formations  16 . Each cigarette formation  16  comprises three layers, the outer layers each comprising seven cigarettes and the inner layer comprising six cigarettes. However, other formations with a different number of layers and/or cigarettes per layer are also possible. A rotating cigarette turret  17  transports the cigarette formations  16  for further packaging. During the rotation of the formations  16  in the turret  17 , the cigarettes are at rest relative to one another. The cigarettes turret is thus preferable for carrying out a cigarette-checking operation, in particular for checking that cigarette formations are complete. 
     As can be gathered from FIG. 1, four checking devices  18  are located on the right and left of the cigarette turret  17 . These checking devices  18  are arranged on both sides of the cigarette turret  17  such that two devices serve for checking the filter-side cigarette ends and two further devices  18  serve for checking the tobacco-side cigarette ends. The checking devices  18  are accommodated in a housing  19  which can be displaced in a longitudinal direction of the cigarettes. The respective housings  19  can be displaced in the direction of the double arrow  20  illustrated in FIGS. 1,  3  and  5 , to be precise by means of an adjustment arrangement (not illustrated). The adjustment arrangement displaces a checking device  18  in the direction of a cigarette formation  16  in order to carry out a checking operation, which is described in more detail hereinbelow. 
     Following checking of the cigarettes as the formations  16  run through the cigarette turret  17 , a conveyor  21  guides the formations  16  in the direction of the arrows  22 , to be precise in the direction of a subassembly  23  for winding the formations in tin foil. Tin-foil reels  24  store the tin foil in a state in which it is wound up in web form and discharge it in the direction of the arrows  25 , namely in the direction of the subassembly  23 . On the way to the subassembly  23 , the tin-foil web passes a stamping device  26 . The subassembly  23  also serves for cutting the tin-foil web into blanks, which are wound around cigarette formations. Collar reels  27  store material webs which are wound up in web form and are intended for collars which are to be cut to size and are positioned on the cigarette formations  16  wrapped in tin foil. 
     FIG. 2 shows a section along line II—II according to FIG.  1  through the packaging machine  10 , for the detailed illustration of the arrangement of the checking devices  18 . Two checking devices  18  illustrated by solid lines are located on the front side of the cigarette turret  17  and are mounted on a common carrier  28 . Two further checking devices  18  are located on the rear side of the cigarette turret  17  and are illustrated by dashed lines. These rear-side checking devices  18  are also mounted on a common carrier (not illustrated). The checking devices  18  are connected to a machine-control means (not illustrated) in each case via connections  29  and connection cables  30 . Once they have passed the checking devices  18 , the cigarette formations  16  pass, by way of the cigarette turret  17 , into a discharge position, in which they are carried along on two parallel conveying sections  31   a ,  31   b  by a conveyor  21 . 
     FIGS. 3 and 4 show a checking device with annular coils  32 , which have an interior cavity  33 . A ferromagnetic or ferrimagnetic region  34  of a push rod  35  (in the manner of a coil core) can pass into said cavity  33 . This means that the push rod is produced either just partially or else completely from ferromagnetic or ferrimagnetic material. The push rod  35  is mounted in the housing  19  such that it can be displaced axially counter to a spring force. In this case, a spring  37 , which is supported on an inner housing wall  36 , causes the push rod  35  to be pushed out of the housing, to be precise until a stop  38 , against which the spring  37  pushes, reaches an outer housing wall  39 . In order to carry out a checking operation, the housing  19  together with the push rod  35  and coils  32 , is displaced in the direction of cigarettes  40 ,  41 ,  42  which are to be checked. 
     In the presence of a correctly filled cigarette  41 ,  42 , a head  43 ,  44  of a push rod  35  comes to rest on the cigarette end, with the result that the end with the ferromagnetic/ferrimagnetic region  34 , said end being located opposite this push-rod head  44 ,  45 , penetrates into the cavity  33  of the coil  32 . If, however, a cigarette  40  is of defective formation or if a cigarette is absent from this position, the push rod remains in its starting position, with the result that the ferromagnetic/ferrimagnetic region  34  of the push rod  35  does not pass into the cavity  33  of the coil  32 . It is thus only in the presence of a correctly filled cigarette that the push rod  35  reaches a first push-rod position, as is shown in FIG. 3 for the two top push rods  35 . In contrast, the bottom push rod  35  is located in a second position, in which the ferromagnetic/ferrimagnetic region  34  of this push rod  35  does not penetrate into the coil interior. 
     The second position is generally characterized in that the ferromagnetic/ferrimagnetic region does not fully reach the coil interior, for example also when the ferromagnetic/ferrimagnetic region  34  only partially fills the coil interior or the cavity  33 . 
     The penetration of the ferromagnetic/ferrimagnetic region  34  of the push rod  35  into the cavity  33  of the coil  32  changes the inductance of the coil  32 . This change can be measured. According to a first variant, for this purpose, the coil is subjected to alternating current or alternating voltage. The electrical behavior of the coil changes as a result. For example, it is possible to determine the changed damping behavior of an oscillator which is formed by means of the Coil—and is likewise subjected to alternating current or alternating voltage. For example, the change in impedance is also obtained by determining a different resonant frequency of an oscillating circuit formed from said coil and a capacitor or if the oscillation of the oscillating circuit breaks off. 
     In a further variant, the coil is subjected to direct voltage or direct current. The action of pushing in the ferromagnetic/ferrimagnetic region then likewise results in a change in inductance. With a constant current through the coil, the energy content of the coil thus changes. Conversely, with a constant energy content of the coil, the current through the coil changes with a change in the inductance. Such changes may be measured, and it is possible to draw therefrom information about the push-rod movement and thus the depth by which the push rod penetrates into the cigarette end. 
     In this arrangement, the push rod  35  is mounted such that the ferromagnetic and/or ferrimagnetic region  34  of the push rod  35  can penetrate concentrically into the interior of the coil  32 . This allows such a device for interrogating each individual push rod  35  to be of very small construction. It is easily possible in this way for the sensor which has the coils  32  to be configured such that it is smaller than a cigarette diameter of approximately 5.3 to 7.9 mm. The coils  32  are likewise arranged at a distance corresponding to this diameter. The coils  32  thus have a smaller external diameter than the cigarette diameter, to be precise preferably not more than 5 mm. The push rods  35  then preferably have a maximum external diameter of approximately 2 mm. 
     The construction described has the advantage that all the coils and/or sensors can be accommodated within the housing  19 . The space-serving construction additionally makes it possible to accommodate within the housing  19  an evaluation arrangement which may have a microprocessor and also has an evaluation board  46  in addition to electrical and electronic components  47 . It is thus possible for the evaluation arrangement to be accommodated in the vicinity of the actual sensors and/or coils, with the result that it is possible to dispense with high-outlay wiring of all the sensors to a remote evaluation unit, for example the machine-control means. The connection to the machine-control means  29  therefore need only have a small number of lines, rather than a number of lines which corresponds to the number of sensors. As a result, the packaging machine, as a whole, is less susceptible to malfunctioning and, furthermore, can also be produced more cost-effectively. 
     The coils  32  are arranged in a carrier element  48  which is connected to the housing  19  and has bores for receiving the annular coils  32  and bores which are arranged concentrically with the above and are intended for receiving the push rods  35 . The carrier element  48  also provides the mechanical stability of the arrangement of the coils  32 . The electrical connection of the coils  32  to the evaluation electronics located on the evaluation board  46  takes place by means of traces arranged on a printed circuit board  49 . The printed circuit board  49  is connected to the evaluation board  46  via a plug-in connection  50 . The printed circuit board  49  has bores  51  which are located opposite the push rods  35  and avoid damage to the printed circuit board  49  if the push rods  35  are pushed too far into the interior of the housing  19 . 
     A further checking device  18  is illustrated in FIGS. 5 and 6. This checking device  18  differs from the checking device according to FIGS. 3 and 4 in that, instead of ferromagnetic/ferrimagnetic regions on the push rods, a magnetic region  52  is provided on each push rod. This magnetic region  52  is a bar magnet which generates a constant magnetic field. However, coils which generate a magnetic field are also possible. By virtue of a push rod being displaced, this magnetic field can then magnetize a Hall element  53  in a first position, namely one which applies to the two top push rods  35 . In a second position, however, the magnetic field magnetizes the Hall element  53  merely to a lesser extent or not at all. This second position corresponds to the position illustrated in FIG. 5 for the bottom push rod  35 . The Hall element  53  is connected to an electric reference voltage or power source on two mutually opposite sides. As a result of the magnetic lines of force passing vertically through the Hall element, charge carriers are deflected perpendicularly to the reference-source-induced movement direction thereof. This produces a potential difference, referred to as Hall voltage, on two sides of the Hall element which are offset in relation to the connections of the reference source. This Hall voltage is measured by means of an electric measuring arrangement. This voltage generates a signal in dependence on the magnetic field, which magnetizes the Hall element  53  and represents the push-rod position. 
     The measuring arrangement for determining the push-rod position with Hall element  53  and magnetic push-rod region  52  also allows the device to have a small formation, with the result that it is also possible in this case for the necessary electronics to be accommodated within the housing  19 . There is thus also provided in this checking device an evaluation board  46  for accommodating electrical and/or electronic components  47 , in particular a microprocessor for evaluating the sensor signals or signals of the Hall elements  53 , within the housing  19 . The evaluation board  46  is connected to a printed circuit board  55  via a plug-in connection  50 . This printed circuit board  55  has the Hall elements  53 , which are arranged in the region of bores  56 . These bores  56  are arranged opposite the push rods  35  and serve for guiding the magnetic regions  52  of the push rods  35 . The electrical connection of the Hall elements  53  to the evaluation board  46  takes place via traces arranged on the printed circuit board  55  and via the plug-in connection  50 . A carrier element  57  connected to the housing  19  serves for securing said printed circuit board  55 . 
     The two checking devices  18  according to FIGS. 3 and 4 and according to FIGS. 5 and 6 are connected, via a connecting element  55 , to an adjustment arrangement for advancing the checking device  18 , together with push rod  35 , up to the cigarettes in order for a checking operation to be carried out. Said adjustment arrangement can be actuated mechanically, electrically, pneumatically and/or hydraulically. 
     Either the evaluation unit already provided on each checking device or the machine-control means determines data on possible malfunctioning by way of the signals supplied by the coils or Hall elements. Since preferably an entire cigarette formation is sensed in each checking operation, it is possible, for example, for three adjacent coils or Hall elements which are located one above the other and each display a fault to indicate a blocked cigarette shaft. By way of the signals generated by the evaluation unit and/or machine-control means, it is possible for an alarm or fault signal to be generated or else also for a control signal to be generated in order to stop the machine or to change certain machine parameters, for example the rotational speed of the machine. Furthermore, in order to eject a defective cigarette formation, it is possible to emit a control signal which causes an ejector to separate the defective cigarette formation out of the packaging process. 
     Overall, the reduced construction of the measuring arrangements sensing the individual push rods provides a compact checking device which, on account of the absence of optical components, is less susceptible to malfunctioning on account of dust. This means that the devices and methods according to the invention can configure the operation of checking cigarette ends in a considerably more reliable and meaningful manner. The invention also allows evaluation via the production data acquisition, with the result that it is possible to ascertain the filling of an individual cigarette position. This makes it possible to detect any possible unreliability of individual cigarette shafts in the cigarette magazine. The cigarette checking and/or head monitoring is advantageously already carried out using a microprocessor accommodated in the checking device, with the result that it is possible for the sensor signals to be evaluated already in the checking device. 
     The devices explained also have the advantage that cleaning of the mechanical components is possible without the device as a whole and electronic components being dismantled or detached since it is possible to remove lateral covers (not illustrated) for cleaning, for example, using a compressed-air gun. Furthermore, the arrangement described has the advantage that a push rod  35  which is pushed in too far cannot damage the coils  32  or Hall element  53  and the associated printed circuit boards  49 ,  55 , as may be the case, for example, in other arrangements with axially arranged initiators and/or proximity switches. The invention thus makes it possible to achieve a considerable improvement in cigarette checking as a whole.