Abstract:
Method for filling containers with liquids, wherein the containers are filled using a plurality of controllable filling elements and the liquid is fed to these filling elements starting from a reservoir, common to the filling elements, for storing the liquid, wherein during the filling the containers are transported at least in sections along a circular track and wherein the filling of the containers by at least one filling element is controlled as a function of at least one first parameter characteristic of the liquid in the reservoir and this parameter is determined repeatedly at given intervals of time during the filling operation.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device and a method for filling containers with liquids. Such devices and methods have been known from the prior art for a long time. Thus, for example, filling devices are known which have a plurality of filling elements which are arranged, for example, on a filling wheel and which each fill the containers arranged on them with liquid. In this context, methods for controlling the particular filling elements are also known from the prior art. Thus, for example, it is known that the individual filling elements perform time-controlled dosing of the liquid products. A weight-dependent, for example, control as a function of a filling weight already reached would also be possible. 
     In filling processes it is not possible to keep the influencing variables of the filling operation constant. During the filling operation variations in the tank level, temperature variations in the products, drops in the working pressure and different filler speeds of rotation arise. 
     WO 97/00224 discloses a method for filling containers with a liquid which is under pressure. In this method, the pressure of a liquid is measured and passed on to a control device which, from the liquid pressure measured and the notional filling amount to be filled, controls the filling valve by means of a control signal. The control device furthermore calculates the filling amount actually filled from a totalling of part volumes which are obtained taking into account the particular liquid pressure measured, the intervals of time between the individual pressure measurements and a pressure/flow characteristic curve of the filling valve. 
     WO 2005/080202 A1 describes a filling machine with time-controlled dosing valves. In this, at least one master valve is provided, which has a flow meter device which is connected to a computer unit which calculates the time for the filling. The further filling valves of the unit are controlled on the basis of this flow meter device and the output data from this. 
     In this procedure it has proved problematic that the individual filling valves often deviate from one another and the control methods known from the prior art therefore do not take into account such a deviation of the valves with respect to one another. 
     The present invention is therefore based on the object of providing a method for time-controlled dosing of liquid products which also takes into account variabilities in the individual filling elements or valves. 
     SUMMARY OF THE INVENTION 
     In a method according to the invention for filling containers with liquids, the containers are filled by means of a plurality of controllable filling elements and the liquid is fed to these filling elements starting from a reservoir, common to the filling elements, for storing the liquid. In this context, during the filling the containers are transported at least in sections along a circular track and the filling of the containers by at least one filling element is controlled as a function of at least one first parameter characteristic of the liquid in the reservoir. In this context, this parameter is determined repeatedly at given intervals of time during the filling operation. 
     According to the invention, the filling of the containers by at least a second filling element is likewise controlled as a function of the parameter characteristic of the liquid in the reservoir, wherein for the control of at least one filling element at least one parameter characteristic of this filling element is additionally taken into account. Overall, a time-related filling method is therefore preferably carried out. 
     It is therefore initially proposed that during transfer of the liquid products an incremental polling of the influencing variables of the filling operation is carried out. However, since the individual filling elements are not completely identical to one another and also do not display completely identical filling properties, it is proposed according to the invention that this variability of the individual filling elements is also taken into account. In this manner it is possible, but not absolutely necessary, for a master valve to be used for the control, but for the remaining valves and their differences likewise to be taken into account. 
     Advantageously, the reservoir for the liquid also rotates with the individual filling elements. 
     In a further advantageous method, the filling element has and preferably all the filling elements have in each case controllable filling valves which control the filling operation of the liquid into the containers. 
     In order to be able to react constantly to the influencing variables of the filling operation, for example variables which depend on the liquid in the reservoir, a control which calculates the course of the filling operation incrementally and in this way controls the filling time is advantageously used. 
     Advantageously, for control of a plurality of filling elements at least one parameter in each case characteristic of these filling elements is taken into account. Advantageously, for control of all the filling elements at least one parameter is in each case characteristic of these filling elements is taken into account. In this context, this particular characteristic parameter can be determined, for example, in the context of a calibrating operation for each individual filling element. 
     In a further advantageous method, the tilling of the containers is controlled as a function of a plurality of parameters characteristic of the liquid in the reservoir. In this context it is possible for the said parameters to be recorded regularly. 
     In a further advantageous method, the parameter is chosen from a group of parameters which contains a temperature of the liquid in the reservoir, a geodetic height of the liquid in the reservoir, a circular frequency of a rotation of the reservoir, a level of the liquid in the reservoir, a density of the liquid in the reservoir, a pneumatic working pressure, combinations of these and the like. 
     Advantageously, in each time increment the pneumatic working pressure, the filler speed of rotation, the product temperature and the current level in the tank are polled and the filling amount of this time interval is calculated from these. The individual filling amounts of the time increments are added up in the course of the filling and compared with the cut-off filling amount. Advantageously, when the cut-off filling amount is reached, a cut-off signal is issued and the filling valve in question is thus closed. 
     In a further advantageous method, the parameter characteristic of the filling element is determined as a function of a flow-through amount of the liquid passing through this filling element. In particular, in this context the said filling element is kept in an opened position and the flow passing through this opened valve is determined. 
     In a further advantageous method a height of the level of the liquid in the reservoir is determined as a function of a distance from a geometric axis of rotation of the reservoir. It is to be taken into account here that the level, in particular in the event of relatively fast revolutions, is not constant as a function of this distance, but, for example, funnel-like formations may result, which have the effect that closer to axis of rotation the level is lower and further outwards the level is higher. 
     In a further advantageous method, at least one characteristic parameter is determined in a calibration operation of the unit and is stored in a memory device. In this case, for example, the particular filling amounts or also the flow amounts through the individual opened filling valves can be measured and actual deviations of the filling elements with respect to one another or also with respect to a reference value can be determined with the aid of these filling amounts and/or flow amounts. 
     Advantageously, the parameter characteristic of the filling element is determined by filling containers with at least two different filling amounts. The individual filling elements deviate from one another in particular during the opening operation of the valves and during the closing operation of the valves, but also during the filling operation with a constant flow rate. By calibration with two different filling amounts, those differences which arise in particular during the opening and the closing of the particular valve can be determined very accurately in this manner. 
     The present invention is furthermore reported to a device for filling containers with liquids. This device here has a carrier which can be rotated about a given axis of rotation and on which a plurality of controllable filling elements for filling the containers are arranged. The device furthermore has a reservoir for storing the liquid to be transferred and for supplying the filling elements with the liquid. In this context, this reservoir can also be rotated about the given axis of rotation and is equipped with at least one first sensor device which records at least one first parameter characteristic of the liquid in the reservoir. 
     A control device which controls the tilling of the containers by the individual filling elements on the basis of the first parameter is furthermore provided. 
     According to the invention, the filling courses by the individual filling elements can be controlled independently of one another, and for the control of at least one filling element the control device additionally takes into account at least one parameter characteristic of this second filling element or a filling operation by means of this filling element. 
     It is therefore also proposed with respect to the device that the variability of the individual filling elements or the specific characteristics of the individual filling elements are taken into account during the control thereof. 
     In a preferred embodiment, the device has a memory device in which parameters characteristic of each individual filling element are stored. 
     Further advantages and embodiments can be seen from the attached drawings: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These show: 
         FIG. 1  a schematic diagram of a device for filling containers; 
         FIG. 2  a diagram of a filling course for a filling element; and 
         FIG. 3  a further diagram of the division of the filling course. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a schematic diagram of a device  1  for filling containers. This device here has a reservoir  4  in which a liquid  5  is arranged. This reservoir rotates here about an axis of rotation D. Reference symbol  8  identifies in rough outline a carrier—such as, for example, a filling wheel—on which a plurality of filling elements  2  is arranged, each of which serves to fill the containers  10 . For this purpose, the filling elements  2  have filling valves, these filling valves here having filling cones  22  which can be moved along the double arrow P. Reference symbol  24  identifies a carrier for the container and reference symbol  26  identifies a so-called CIP cap which can be mounted on the delivery opening  28  of the filling element  2  for cleaning the filling element. Reference symbol  36  refers to a return line for returning a cleaning medium. The carrier is likewise arranged such that it can be rotated about the axis of rotation D, rotating synchronously with the reservoir  4  with the same circular frequency. 
     Reference symbol  30  identifies in its entirety a drive for the filling element  2 , i.e. the drive which controls the filling of the containers  10 . Reference symbol  34  identifies the product line which leads from the reservoir  4  to the individual filling elements  2 . Filling speeds can be controlled by means of a membrane valve  16 , more precisely the changeover to a second filling speed can be effected here. Reference symbol  32  identifies a choke arranged on the outflow of the reservoir  4 . 
     Reference symbol  12  identifies in rough outline a sensor device which measures at least one characteristic property of the liquid  5  in the reservoir  4 . As mentioned above, this can be, for example, a temperature or also a level of this liquid. However, several sensor devices can also be provided. 
     A control device  20  controls the filling of the containers  10  with the filling material as a function of the parameters measured. 
       FIG. 2  shows a flow curve K which illustrates the filling of the containers with a particular filling valve. In this figure, the time in seconds is plotted on the ordinate and the flow Q in ml/s is plotted on the coordinate. It can be seen that in a starting section A the flow Q initially increases sharply, it then remains essentially constant over a certain period of time (section B) and finally returns to zero again in a section C. In this context, the black line K identifies the actual flow and the line K 1  identifies an approximation of the flow. 
     It can be seen that the filling operation is divided into a plurality of time increments Z, during which the individual measurement parameters are measured. 
     An important component in the calculation of this flow curve K 1  is the maximum flow rate Q max . This is recalculated in each time increment Z and depends, for example, on the geodetic height z of the product to be transferred (this geodetic height resulting from the base height of the reservoir plus the level in the tank). A further parameter for determining the flow rate is the centrifugal acceleration a, (at a circular frequency ω) and the product temperature T. Taking into account these parameters, the flow rate Q max  is calculated according to the following formula: 
     
       
         
           
             
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     Needless to say, the individual filling elements are mechanical components which bring with them different dead times and flow resistances because of their production tolerances. According to the invention, a correction method for the other filling valves is therefore proposed. 
       FIG. 3  shows a diagram which illustrates this method. In this, the flow operation is divided into five time sections t 1 , t 2 , t 3 , t 4  and t 5 . Time t 1  is the dead time of the valve, which depends on the working pressure of the pneumatic controlling of the valve. The period of time t 2  identifies the increasing region of the flow curve, this period of time depending on the level in the reservoir, the speed of rotation thereof and the product temperature. The period of time t 3  identifies the constant filling region up to the cut-off point in time, which can be calculated as a function of the filling amount to be introduced. 
     The periods of time t 4  and t 5  designate the after-running time from the cut-off point in time, this after-running time in turn depending on the level, the speed of rotation and the product temperature. 
     The calibration of the individual filling elements is described in detail in the following. If two different filling amounts are transferred, exclusively the length of the time span t 3  changes. A filling with a first filling amount of, for example, 500 ml and a filling with a second filling amount of, for example, 1,000 ml are taken as the basis. The ratio of the calculated time spans t 3  for the filling amounts here is for example, as has been confirmed by experiment, 1:2.24. The notional volume is set on the device  1  initially at 500 ml and then at 1,000 ml and a filling operation is then performed in each case. The actual filling amounts are weighed in order to deter mine the volume actually transferred. The deviation of the actual from the notional volume is designated ΔV 500  for the 500 ml filling and ΔV 1000  for the 1,000 ml filling. These values ΔV 500  and ΔV 1000  are then each divided into a deviation in the constant filling region X 1  and into a deviation in the increasing region X 2 . The ratio of the running times of the constant filling region of a 1,000 ml and a 500 ml filling is 2.24. In this manner, the following relationships result for the two filling amounts: 
     For the filling amount deviation of the 500 ml filling:
 
Δ V   500   =X   1   +X   2  
 
     For the filling amount deviation of the 1,000 ml filling:
 
Δ V   1000 =2.24 ·X   1   +X   2 .
 
     In this manner, the following relationships result for the deviations 
     
       
         
           
             
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                     · 
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                     500 
                   
                 
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                     1000 
                   
                 
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     In this manner, the precise deviations of the filling amount in the particular regions can be determined. For determining the flow corrections ΔQ 1  and ΔQ 2 , the tilling amount in the increasing region is divided by the increasing time and the filling amount in the constant filling region is divided by the time span of this filling region: 
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
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                 Q 
                 1 
               
             
             = 
             
               
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                 2 
               
               
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                 2 
               
             
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                 3 
               
             
           
         
       
     
     The parallel shift of the flow course by ΔQ 1  and ΔQ 2  in the region of t 2  and t 3  is represented in  FIG. 3  by the lines V 1  and V 2 . 
     In this manner, overall it is possible to determine, on the basis of the actual filling amounts filled by the individual filling elements, correction factors or flow corrections ΔQ 1  and ΔQ 2  which are characteristic of the individual filling elements. In this context, these corrections ΔQ 1  and ΔQ 2  can be stored for each individual valve in a memory device and can be taken into account for each of the filling elements in question in the actual working operation. 
     In this context, it is advisable to carry out this calibration envisaged here again at certain intervals of time, for example once a month, in order to determine the particular flow corrections ΔQ 1  and ΔQ 2  for the individual filling elements. 
     The applicant reserves the right to claim as essential to the invention all the features disclosed in the application text where, individually or in combination, they are novel with respect to the prior art. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Device 
           2  Filling elements 
           4  Reservoir 
           5  Liquid 
           8  Carrier 
           10  Containers 
           12  Sensor device 
           16  Membrane valve 
           20  Control device 
           22  Filling cone 
           24  Carrier 
           26  CIP cap 
           30  Drive 
           32  Choke 
           34  Product line 
           36  Return line 
         A Starting section 
         a z  Centrifugal acceleration 
         B Section 
         C Section 
         D Axis of rotation 
         K Flow curve, actual flow 
         K 1  Approximation of the flow 
         P Double arrow 
         Q Flow 
         Q max  Flow rate 
         T Product temperature 
         Z Time increment 
         t 1  Dead time of the valve 
         t 2  Increasing region of the flow curve 
         t 3  Constant filling region 
         t 4 , t 5  After-running time from the cut-off point in time 
         X 1  Constant filling region 
         X 2  Increasing region 
         ΔQ 1 , ΔQ 2  Flow corrections 
         ω Circular frequency