Abstract:
A method is provided to regulate a conveying stream composed of articles of the tobacco-processing industry between at least one tray discharger and connected to at least one feed device by a conveying element that conveys a mass flow of the articles. The feed device has at least one chamber designed to receive the articles, and each chamber has at least two feed units running independently of each other to feed the articles to subsequent apparatuses. Each feed unit has an individual feed rate (P 1 , P 2 , . . . P n ). The method includes monitoring a level within the feed device using monitoring elements; sending a signal to each of the at least one tray dischargers for regulating the speed of transport of the conveying element and the feed rate (in articles/min) as a function of a current level within the feed device, and adapting the speed of transport to a desired level. The speed of transport of each conveying element is additionally regulated as a function of the feed rate (P total ) formed from the sum of the individual feed rates (P 1 , P 2 , . . . P n ) of all feed units assigned to a respective chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Application No. 102007030049.4, filed on Jun. 26, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a method for regulating a conveying stream composed of articles of the tobacco-processing industry between at least one tray discharger and at least one feed device connected to the or each tray discharger by a conveying element for conveying a mass flow consisting of articles, wherein the feed device has at least one chamber designed to receive the articles, and each chamber has at least two feed units running independently of each other for feeding the articles to subsequent apparatuses, wherein each feed unit has an individual feed rate (P 1 , P 2 , . . . P n ), with the steps of: monitoring the level within the feed device using monitoring elements, sending a signal to each tray discharger for regulating the speed of transport of the conveying element and hence the feed rate (in articles/min) dependent on the current level within the feed device, and adapting the speed of transport to the desired level. Furthermore the invention concerns an arrangement for transferring rod-shaped articles of the tobacco-processing industry to subsequent apparatuses, comprising at least one tray discharger, at least one feed device, wherein the feed device has at least one chamber designed to receive the articles and each chamber being assigned at least two feed units, each tray discharger and the feed device being connected to each other by a conveying element and each comprising a control system for regulating the conveying element. 
     Such methods and apparatuses are used in particular in the tobacco-processing industry. Here, preferably rod-shaped articles such as e.g. filter rods or the like are processed. In particular, these articles are frequently stocked or temporarily stored in containers, the so-called trays, or otherwise. The articles delivered to the feed device are then sent from the latter preferably pneumatically to subsequent apparatuses. For this purpose the feed device has at least two, but preferably more feed units, by means of which the articles are sent dependent on the individual feed rate. In order now to supply this feed device with articles, the articles are transferred from the trays or the like to the tray discharger, and from the tray discharger via the conveying element the mass flow composed of the articles is transported to the feed device. The mass flow flows in the region of an inlet into the magazine of the feed device. The monitoring elements, which are preferably arranged within the magazine, detect the current level within the magazine. With the aid of the information picked up by the monitoring elements, the speed of transport of the conveying element and hence the feed rate of articles are regulated. 
     In practice, this means that the signal exchange is usually effected via two signals by means of which only three different states for the conveying element can be shown, namely e.g. a) transport no articles, b) transport 100% articles and c) transport more than 100% articles. This method, however, has the drawback that only uneven supply of the magazine of the feed device with a varying level within the magazine can be achieved. In other words, the magazine of the feed device is supplied with articles cyclically only, wherein filling of the magazine depends exclusively on the level of the magazine. Switching the conveying element on and off alternately, accompanied by interruption of the stream of articles into the receiving device, leads to so-called stop-and-go operation. Document DE 33 33 859 A1 from the applicant&#39;s firm shows a storage arrangement and a corresponding method having the features of the preambles of independent claims  1  and  19 . The arrangement shown there has a receiving chamber within the feed device, the level of which is monitored by sensing means. Depending on the information of the sensing means, the input conveyor for the delivery of articles is switched on or off. A comparable arrangement can be found in DE 36 11 707 A1, which also comes from the applicant&#39;s firm, wherein the storage container of the feed device has two chambers. An input conveying means leads into each chamber. The articles conducted into the chamber by the respective input conveying means are carried away via outlet shafts assigned to each chamber. From DE 35 38 660 C2 is known a signal transmission system in which delivery of the articles to a receiving device is regulated dependent on the level of the latter device. The feed amount is regulated by interrupting the conveying stream for an interval of time, in order then to be switched on again for an interval of time. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to propose a method which ensures uniform supply of the magazine with a substantially constant level. Furthermore it is the object of the invention to propose an arrangement for carrying out the method. 
     This object is firstly achieved by a method with the steps mentioned hereinbefore by the fact that the speed of transport of each conveying element assigned to a tray discharger, in addition to dependence on the current level within a chamber, is also regulated dependent on the feed rate (P total ) formed from the sum of the individual feed rates (P 1 , P 2 , . . . P n ) of all feed units assigned to a chamber. Thus in a surprisingly simple and exact manner the current and individual feed rates of the feed units are known, so that in combination with the level within the magazine of the feed device a constant level is obtained. As the current quantity removed by the feed units at any time is taken into consideration when regulating the conveying stream, the conveying element can be regulated in such a way that the level of the articles in the magazine or in the individual chambers remains constant at any given time. 
     An appropriate development of the invention provides that the speed of transport of the conveying element is regulated continuously. “Continuously” means that the cycles of scanning the respective demand are shorter than the reaction time of the conveying element. In other words, scanning of the respective demand is carried out cyclically, but the conveying element continuously transports the articles from the tray discharger to the feed device. Thus the current demand for articles at any given time can be determined more or less online and adjusted accordingly. 
     Advantageously, signal transmission takes place by pulse-width modulation which is particularly insensitive to interference and also allows stable transmission over longer distances. 
     A preferred method is characterised by the fact that the pulse width is a function of the feed rate. In other words, the length of the signals gives information about an actual value of the articles to be conveyed. Specifically, this can mean for example that a signal of length 100-299 ms corresponds to a quantity of 5000 articles/min. In other words, the signals not only contain the information that articles are needed, but concurrently deliver the information as to what specific quantity is needed. As a result it is possible to keep the level within the magazine almost constant. 
     Preferably, the pulse width behaves in inverse proportion to the feed rate. A short signal corresponds to a large quantity (many articles/min) and a long signal corresponds to a small quantity (few articles/min). This ensures that, in case of a high demand for articles, very quick information (short signal) is delivered, whereas, if the demand is lower, slower information (long signal) is sufficient. 
     Secondly, the object is also achieved by an arrangement having the features mentioned hereinbefore by the fact that the control system of the feed device includes an adder for forming a feed rate P total  from the individual feed rates of all feed units assigned to a chamber. The resulting advantages have already been named in connection with the method described above, so that reference is made to the corresponding passages to avoid repetition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further preferred or appropriate developments and features of the invention are apparent from the subsidiary claims and the description. The method and the arrangement are described in more detail with the aid of the attached drawings. The drawings show: 
         FIG. 1  a schematic view of the arrangement with a tray discharger and a feed device connected to the tray discharger by a conveying element, and 
         FIG. 2  a schematic circuit diagram of the control systems of the tray discharger on the one hand and the feed device on the other hand, which are linked to each other. 
     
    
    
     DETAILED DESCRIPTION 
     The method described below with the corresponding arrangement serves to regulate a conveying stream composed of filter rods from a tray discharger to a feed device. Naturally, conveying streams of other articles and between other apparatuses, devices, machines, etc. can be regulated using the method as well. 
     In  FIG. 1  is shown schematically a part of a first arrangement  10 . The arrangement  10  comprises in full a feed device  11  which is supplied with articles  13  by two tray dischargers  12 . For this arrangement  10 , the principle of the method described below is particularly effective and efficient. For the sake of simplicity, only one of the tray dischargers  12  is shown. The feed device  11  has a magazine  14  which is divided e.g. by a partition  34  or the like and which on both sides has an inlet  15  for the mass flow composed of the articles  13 . Naturally, the arrangement  10  can also consist of only one feed device  11  and one tray discharger  12 . Other embodiments have a single tray discharger  12  which supplies two or more feed devices  11 . Also the feed device  11  can have an undivided magazine  14 . The or each feed device  11  is connected to the or each tray discharger  12  by a conveying element  17 . The conveying element  17 , which is preferably designed as a belt conveyor, serves to convey/transport the mass flow  16  into the magazine  14  of the or each feed device  11 . 
     Within the magazine  14  are arranged several monitoring elements. In each chamber  18 ,  19  of the magazine  14  are preferably arranged three monitoring elements B 1 , B 2  and B 3 . The number of monitoring elements B 1 , B 2 , B 3  can of course vary as well as their position. Preferably, two monitoring elements B 1  and B 2  are constructed and designed to monitor the level of the articles  13  within the magazine  14  or in each chamber  18 ,  19  of the magazine  14 . In other words, the elements B 1  and B 2  monitor the level within the magazine  14 . The monitoring elements B 1 , B 2  can e.g. be designed as proximity switches which are activated via a lever  20  which senses the level. Naturally, the monitoring elements B 1  and B 2  can also be designed as optical elements or in some other usual way. The same applies to the monitoring element B 3  which monitors the level in the region of the inlet  15 . 
     The feed device  11  has several feed units  21  which are usually arranged below the magazine  14 . The number of feed units  21  is at least two, preferably ten. But the number of feed units  21  can also be any other quantity. In particular, with a so-called divided magazine  14  there is provision for variable assignment of the feed units  21  to the chambers  18 ,  19 . In the case of an undivided magazine  14 , all the feed units  21  are assigned to the single chamber. In the example shown, each chamber  18 ,  19  is assigned feed units  21 . Purely as an example, chamber  18  is assigned three feed units  21  and chamber  19  seven feed units  21 . By means of the feed units  21 , the articles are taken out of the magazine  14  and preferably sent pneumatically to a subsequent receiving station. The feed units  21  also each work independently of each other within a chamber  18 ,  19 . This also means that each feed unit  21  can have an individual feed rate which is usually between 0 and 1500 articles/min. However, other feed rates are possible as well. The respective feed rate is optionally predetermined by an operator or via a signal wire by the corresponding receiving station. A preferred method for predetermining the feed rate is described in DE 35 38 660 C2 mentioned hereinbefore. 
     The tray discharger  12  is constructed in the usual manner, so that a detailed description is dispensed with. The conveying element  17  assigned to each tray discharger  12  is driven in rotation by a motor  22 . The tray discharger  12  is assigned a control system  23  by means of which in particular the motor  22  can be regulated. To put it another way, the control system  23  preferably serves to regulate the speed of transport of the conveying element  17 . The feed device  11  is also assigned a control system  24  which is functionally connected to or communicates with the control system  23  by wires  25  or by radio. Apart from the monitoring elements B 1 , B 2 , B 3 , the feed units  21  are also connected to the control system  24  of the feed device  11 . 
     For the sake of simplicity, the control part of the control system  24  for signal processing of chamber  19  is shown below. The control part for chamber  18  is, if it exists, constructed accordingly. The control system  24  of the feed device  11  includes an adder  26  which adds up the individual feed rates P 1  to P n  of the feed modules  21  of chamber  19  to form the total feed rate P total , that is, the current quantity to be picked up by the feed device  11 . Specifically, in the example shown the feed rates P 4  to P 10  are added up. Furthermore the control system  24  has several, preferably two change-over switches  27 ,  28  by means of which it is possible to switch back and forth between different signal wires, depending on the monitoring elements B 1 , B 2 , B 3 . A further adder  29  for forming a difference (by adding or subtracting, depending on the preceding sign) as well as a converter  30  for converting a quantity (e.g. articles/min=A/min) to a signal also form part of the control system  24 . The control system  23  of the tray discharger  12  includes a converter  31  for converting a signal to a quantity (e.g. articles/min), an adder  32  for forming a difference (by adding or subtracting, depending on the preceding sign) as well as a further converter  33  for converting a quantity (e.g. articles/min) to another quantity (e.g. revolutions per minute=rpm). 
     Below, the method is described in more detail with the aid of  FIG. 2 . During production of the apparatuses subsequent to the arrangement  10 , feed drums of the feed units  21  take from the magazine  14  a quantity of articles  13  which changes constantly and differs from one feed unit  21  to the next. The adder  26  adds up the individual feed rates P 1  to P n , in the present case P 1  to P 3  for chamber  18  and P 4  to P 10  for chamber  19 , to a total feed rate P total  (e.g. in articles/min) for each chamber  18 ,  19 . In the event that the feed device  11  has only one chamber, the feed rates of all feed units  21  are added up. In the present case with a feed device  11  comprising two chambers  18 ,  19 , chamber-related total feed rates are produced for each chamber  18 ,  19  independently of each other. This quantity/sum which is determined for each chamber  18 ,  19  is corrected according to the state of the monitoring elements B 2  and B 3  dependent on the level. The correction is preferably made by the fact that the total feed rate P total  is multiplied by a correction factor K 2  or K 3  in dependence of the monitoring elements B 2  and B 3  which permanently monitor the level within the magazine  14 . Here, monitoring element B 2  monitors a defined level which is below the maximum level which is monitored by monitoring element B 1 . Monitoring element B 3  monitors the level in the region of the inlet  15 . Alternatively, a sum can be added to or subtracted from the quantity/sum determined by the adder  26 . The sum resulting from multiplication or addition/subtraction is the sum S 2 . 
     Specifically, this means that the feed rate P total  is increased by a defined value. To put it another way, the sum S 2  is basically greater than the feed rate P total . But if one of the two monitoring elements B 2  or B 3  indicates that the level monitored is reached, the change-over switch  27  is thrown so that subsequently the feed rate P total  is reduced by a defined correction value, so that then the sum S 2  is lower than the feed rate P total . The sum S 2  is then passed to the adder  29 . In the event that the monitoring element B 1  indicates that the maximum level within the magazine  14  is reached, the switch  28  is thrown so that the sum S 2  is optionally replaced by a sum S 3  which is much lower than the sum S 2 , or multiplied by a reduction factor R 1 , multiplication also yielding the sum S 3 . 
     Depending on the position of the switch  28 , the sum S 2  or S 3  is processed by the adder  29 , including the feed rate N 1  calculated immediately before. In other words, the adder  29  calculates by addition or subtraction the difference between the last calculated feed rate N 1  (in articles/min) and the current new feed rate which is expressed by the sum S 2  or S 3  (also in articles/min). The resulting difference value (A/min) is converted by the converter  30  to a signal on a first signal wire  25 . On a further signal wire  25  is transmitted a signal which indicates whether the difference value or the corresponding signal has a positive or negative preceding sign, that is, whether the new feed rate is to be increased or decreased. The length of the signal formed from the difference value indicates how great the difference value is, that is, how great is to be the quantity to be conveyed. In other words, signal transmission takes place by pulse-width modulation, the pulse width being a function of the feed rate. As already mentioned above, the pulse width behaves in inverse proportion. This means that a short signal indicates a high feed rate, while a longer signal indicates a lower feed rate. 
     The signal wires  25  form the transition from the control system  24  of the feed device  11  to the control system  23  of the tray discharger  12 . By the control system  23  the signals transmitted by the signal wires  25  are evaluated. This evaluation contains first of all conversion of the signals to a quantity (A/min) as a sum S 4 . From this sum S 4  on the one hand and a feed rate N 2  which was calculated two or more calculation cycles before, that is, at least before the feed rate N 1 , the adder  32  calculates by addition or subtraction a difference which is represented by the sum S 5 . The sum S 5  then represents the currently needed feed rate. The sum S 5  in turn is converted by the converter  33  to a reference variable F (e.g. in revolutions per minute=rpm). This reference variable F then regulates the motor  22 . By regulation of the motor  22 , the speed of transport of the conveying element  17  is regulated. A high speed of transport means a high feed rate or conveying capacity. A low speed of transport means a low feed rate or conveying capacity. In other words, the conveying element  17  is regulated in its speed in such a way that it delivers only the quantity of articles  13  actually required, ensuring continuous delivery of the articles  13  to the feed device  11 .