Patent Publication Number: US-2005126127-A1

Title: Method for controlling a packaging machine

Description:
The invention concerns a method for controlling a packaging machine comprising a product conveyor for a product and a package conveyor for a package which partially extend parallel and synchronously with respect to each other such that the product can be inserted into a package at a transfer station, and with a conveyor for an additional part to be added to the product, e.g. a leaflet or a dosing spoon, and having a data storage in the form of a shift register which contains various state and control data of packaging units which include the product, the package and an additional part, wherein the data is displaced in a clocked manner in the shift register at a point in time t o , and with at least one point in time t p  given by an initiator at which a control or processing action on the additional part is started, wherein the point in time t p  can be adjusted relative to the point in time t o  in dependence on the product and/or the package and/or the additional part.  
      For packaging products in a transfer device of a packaging machine, the motions of a first circulating package conveyor for the package, e.g. a so-called folding box chain, and of a second circulating product conveyor for the products, e.g. a so-called product chain, are conventionally synchronized such that the product can be inserted laterally into the folding box transversely to the direction of motion of the chains. To change the format, the two chains can be adjusted relative to each other.  
      For certain products, e.g. medication, an additional part which may e.g. be a leaflet, a side note or a dosing spoon may have to be inserted into the package. A leaflet is taken below as an example of this additional part. The packaging machine has a further circulating additional part conveyor, e.g. a so-called leaflet tong chain which carries several tong-like holders which each receive and clamp one leaflet. A leaflet to be inserted into the package is moved between the product and the folding box by the leaflet tong chain, and carried along by the product through the lateral inserting motion thereof to be introduced into the folding box, wherein the tong-like holder opens as soon as the product abuts the leaflet.  
      The packaging machine stores a data set for each packaging unit which comprises the product, the folding box and the leaflet, and which contains all essential state and control data of the packaging unit. Since a plurality of packaging units are simultaneously processed in and run through the packaging machine, the data sets are conventionally filed in a common data storage. The data storage is designed as a shift register, wherein the data sets are displaced, i.e. shifted, within the shift register in a clocked manner in accordance with the working cycle of the machine, i.e. the changing position of the associated packaging unit in the packaging machine up to the ejecting station. The shift register is clocked via a shift cycle which is usually tapped by the drive of the product chain.  
      To provide the folded leaflet, it must usually undergo several examination and processing steps. The leaflet must be received by a so-called leaflet apparatus from a leaflet pile of unfolded leaflets at a certain point in time (request time t p ) and subsequently be folded. The leaflet must then be transferred to a tong-like holder of the leaflet tong chain at a predetermined point in time. Additionally, the correctness of the leaflet type must be checked through detection and evaluation of a code provided on the leaflet at a certain point in time within the leaflet apparatus. The point in time of introduction or initiation of the respective action is predetermined either via rotating mechanical cams which trigger an initiation signal at a certain rotation or via an electronic reproduction of a corresponding cam. The initiation signals are thereby only triggered if a previous examination of some data of the data set in the shift register indicates that the packaging unit is properly combined, i.e. that a product and a packaging are present.  
      A packaging machine must be able to process products and also packagings of various formats as well as various leaflet formats. Depending on the product sizes, the packaging sizes and the leaflet sizes, the individual components of the transfer station of the packaging machine must be adjusted relative to each other. For format change, the leaflet apparatus and/or the leaflet tong chain are usually adjusted relative to the product chain and/or the folding box chain. This causes the points in time which are predetermined by one or more initiators or cams, to also be adjusted relative to the shift time t o  of the shift register which defines the start of a processing cycle of the packaging machine. The request time t p  for the leaflet from the leaflet pile is used as an example below, however, similar problems also occur at other times when a control or processing action on an additional part, e.g. a leaflet, is started.  
      Due to adjustment of the request time t p  for the leaflet relative to the shift time t o  of the shift register, a situation may occur wherein the two points in time coincide or are at least sufficiently close to each other that the controller does not recognize and process them as two independent signals. This can result in incompatible control runs and inadmissible operating states which cause the packaging machine to switch off, signalling an error. To eliminate the error, the mechanical and electronic settings of the packaging machine and, in particular, of the leaflet appartatus relative to the product chain must be changed until a safe operating state is provided. Such an adjustment is possible, since there is a certain time tolerance during transfer of the leaflet to the tong-like holder of the leaflet tong chain. However, elimination of the error is demanding and has a disadvantageous effect on the efficiency of the packaging machine.  
      It is the underlying purpose of the invention to produce a method for controlling a packaging machine of the above-mentioned kind which reliably eliminates any error due to coinciding or unacceptably close points in time, as mentioned above.  
      This object is achieved in accordance with the invention in that the relative position of the request time t p  for the leaflet relative to the shift time t o  of the shift register is examined and the time t p  is shifted if it is within a tolerance period T about the point in time t o .  
      After adjustment of the packaging machine through format change and associated adjustment of the request time t p  for the leaflet relative to the shift time t o  of the shift register, a controller checks whether the point in time t p  of the leaflet request coincides with the shift time t o  of the shift register or is at least sufficiently close that a conflict can be expected. This is the case if the request time t p  of the leaflet is within a predetermined tolerance period or interval T which is disposed about the shift time t o  of the shift register. If the examination shows that the request time t p  of the leaflet is within the tolerance period T, the request time t p  for the leaflet is automatically shifted by the controller. This shift is possible without influencing the operation of the packaging machine, since, during transfer of the leaflet to the tong-like holder of the leaflet tong chain, there is a certain time tolerance which is utilized in accordance with the invention. A switching off of the packaging machine after format change due to incompatible operating states or control runs is thereby reliably prevented.  
      A quickly operating packaging machine performs approximately 450 working cycles per minute such that the cycle time is approximately 133.33 ms. The cycle time is the time interval which the control program requires for working. The cycle time may e.g. be 5 ms. The tolerance period T around the shift time t o  of the shift register should therefore be at least 3% of the cycle time of.the packaging machine, i.e. the request time t p  of the leaflet should not coincide with the last 3% of the previous working cycle before the shift time t o  or the first 3% of the next working cycle after the shift time t o . A value of ±10% of the cycle time of the packaging machine has proven to be reasonable as an upper limit for the tolerance period T. The tolerance period is preferably ±5% of the cycle time of the packaging machine.  
      If the controller determines that the request time t p  is within the tolerance time T, the request time t p  is shifted until it is outside of the tolerance time T. This shift is possible in both directions on the time axis, i.e. in the direction of an earlier or later point in time. In a preferred embodiment of the invention, the controller determines the two shifts Δt 1  and Δt 2  of the request time t p  which are required to obtain a position outside of the tolerance time period T in both directions (earlier, later). The request time t p  is subsequently shifted into the direction with less shift to obtain a position outside of the tolerance time T. 
    
    
      Further details and features of the invention can be extracted from the following description of an embodiment with reference to the drawing.  
       FIG. 1  shows the points in time t o  and t p  on the time axis t in an uncritical arrangement before format adjustment;  
       FIG. 2  shows the points in time t o  and t p  on the time axis t in a critical arrangement after format adjustment; and  
       FIG. 3  shows the points in time t o  and t p  on the time axis t in an uncritical arrangement after correction. 
    
    
       FIG. 1  shows a time axis t which shows a shift time t o  of the shift register which simultaneously also defines the start of a working cycle of the packaging machine. The time interval between a request time t p  for a leaflet in a leaflet apparatus and the shift time t o  is sufficient, such that no critical operating states are generated in the packaging machine.  
      After format adjustment, wherein the temporal processes of the leaflet apparatus relative to the product chain are adjusted, the position of the request time t p  of the leaflet relative to the shift time t o  of the shift register has also changed. The request time t p  for the leaflet is now much closer to the shift time t o  of the shift register than before format adjustment ( FIG. 2 ). When the format has been changed, a controller of the packaging machine checks whether the request time t p  for the leaflet is within a tolerance period or interval T about the shift time t o  of the shift register which is ±5% of the cycle time of the packaging machine. The embodiment of  FIG. 2  shows that the request time for the leaflet is within the tolerance period T. The controller subsequently determines a first time shift Δt 1  which is required to shift the request time t p  to an earlier position such that it is directly before the tolerance period T. A second time shift Δt 2  is correspondingly determined which is required to shift the request time t p  to a later time, such that it is just outside of the tolerance period T. The two time shifts Δt 1  and Δt 2  are compared and the leaflet apparatus is subsequently adjusted such that the request time t p  is adjusted by the smaller value (absolute value) of the two determined time shifts Δt 1  and Δt 2  in the associated direction. In the embodiment shown Δt 2 &lt;Δt 1 , which is why the request time t p  is delayed by the time period Δt 2  to a later time as shown in  FIG. 3 . In this state, in which the request time t p  is now outside of the tolerance period T about the shift time t o  of the shift register after displacement, incompatible runs and operating states in the packaging machine due to excessively close initiation points or signals are reliably eliminated.