Patent Publication Number: US-2013251917-A1

Title: Device for Plasma Coating Product Containers, Such as Bottles

Description:
FIELD OF THE INVENTION 
     The disclosure relates to a device for plasma coating product containers, such as bottles. 
     BACKGROUND 
     There are some devices for plasma coating in prior art. For example, a method and a device for treating substrates in a rotary plant are known from DE 10 2004 028 369. This device can be in particular used for coating plastic containers in a rotary plant. Here, several treatment devices are provided on the rotary machine and carry out several process phases depending on their angular position on the rotary machine. It is possible to variably adjust the angular position for at least one of the different process phases depending on the predetermined rotational speed of the rotary machine. The advantage of this device is that the process duration for each process phase can be kept constant, even if the rotational speed of the rotary machine changes. 
     Moreover, WO 03/100120 shows a device and a method for treating workpieces. The advantage of this method is that a plurality of treatment devices with at least one workpiece to be treated each is provided. 
     Furthermore, DE 10 2005 015 063 shows a device and a method for automatically creating control instructions for rotary machines. This disclosure provides a system which permits the user to create a program code for controlling a rotary machine via a structured menu navigation. This is done at two menu levels, at the first one, a segment on the rotary machine being defined, and at the second one, the function of the rotary machine or the processing stations being determined. This permits a logic partition of the circulating periphery into individual segments within which certain functions can be controlled. 
     It is therefore an object of the present disclosure to develop a device for plasma coating product containers, such as bottles, which permits high flexibility and a minimization of rejects. 
     According to some aspects of the present disclosure, this object is achieved by the device characterized in claim  1  and the method described in claim  11 . The dependent claims contain functional embodiments of the invention. 
     The present disclosure is characterized in that each of the electrode segments can receive at least one product container and the control unit can automatically control the plasma coating in one or in each one of the electrode segments or in selectable electrode segments depending on process parameters. It is therefore on the one hand possible to coat several product containers in one single process step in an electrode segment, and it is furthermore possible to adapt the course of the process to changing external process parameters. This is in particular advantageous if accidental changes of process parameters occur, such as the missing of single product containers or jams upstream or downstream of the device. 
     In one embodiment, the control unit can adjust the power of high-frequency radiation to values between 0 watts and a value L which is employed at a maximum product container population number n and normal operating speed b which normally is the maximally provided operating speed. Thereby, a preferably ideal adaptation of the power of high-frequency radiation to changed process parameters can be achieved. 
     In another embodiment, a speed sensor is provided which can measure a current transport speed v of the product containers and forward the value to the control unit, or a current transport speed v can be predetermined in the control unit and the control unit can correspondingly control a drive for the product containers. This can assist in adapting the plasma coating process, in particular in case of jams of product containers upstream or downstream of the device, such that an aggravation of the jam after the containers have passed the device is prevented, and/or a device is prevented from remaining empty in case of a jam of product containers upstream of the device. 
     In another embodiment, the control unit controls the power of high-frequency radiation in one or in each one of the electrode segments depending on the current transport speed v of the product containers, such as the rotational speed in the rotary machine. This permits to always deposit the same amount of energy in the respective product container in each plasma coating process of each product container via the high-frequency radiation coupled in via the electrodes. 
     In another embodiment, the control unit adjusts the power L 1  of high-frequency radiation to 
     
       
         
           
             
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     according to or based on the ratio 
     
       
         
           
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     of the current transport speed v and the normal operating speed b. This permits, in particular at a lower current transport speed b compared to b and thereby an extended exposure time of the product containers in the device for plasma coating, to nevertheless deposit the same amount of energy in the product containers compared to normal operating speed. 
     In another embodiment, a detection device for product containers, such as a light barrier, is provided and can transmit signals relating to the entry of product containers into one or into each electrode segment to the control unit which can, based on these signals, determine a number m of the product containers in one or each electrode segment. This permits a continuous control of the number of product containers in one or in each one of the electrode segments and permits the determination of the energy deposited in the product containers depending on the power of high-frequency radiation which is coupled out through the electrodes. 
     In another embodiment, the control unit controls the power of the electrodes in one or in each one of the electrode segments depending on the number m of product containers. This permits an adaptation of the power of high-frequency radiation which is coupled out by the electrodes and thus permits, for example, a reduction of the electrode power in the presence of only a few product containers as the maximum product container population number in one or each one of the electrode segments. 
     In another embodiment, the control unit adjusts the power  4  of high-frequency radiation in one or in each one of the electrode segments to 
     
       
         
           
             
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     of the number of product containers m in one or each electrode segment and the maximum product container population number N in one or each electrode segment. Even with a low number of product containers in one or each one of the electrode segments, this also permits to deposit the same amount of energy in each of the product containers over the duration of the complete plasma coating process, compared to the maximum product container population number during the plasma coating process. 
     In another embodiment, the control unit adjusts the power  L  of high-frequency radiation in one or each electrode segment according to or based on 
     
       
         
           
             
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     Despite a reduced transport speed v, compared to the normal operating speed b, and/or a reduced number of product containers m compared to the maximum product container population number N, this permits to nevertheless deposit the same amount of energy in the product containers to be coated over the complete duration of the plasma coating process. 
     In another embodiment, the control unit can terminate the coupling out of high-frequency radiation from the electrodes of the electrode segment or each electrode segment if either the current transport speed of product containers is 0 ms −1 , where at least one product container, but preferably the maximum product container population number, is located in one or each one of the electrode segments; or if no product container is located in one or each one of the electrode segments. This on the one hand contributes to it being possible to stop the plasma coating operation in case of a standstill of the device with product containers simultaneously remaining in the electrode segments to prevent the total amount of energy which is deposited in the product containers from exceeding the maximally provided amount of energy, thereby minimizing rejections. Thus, the device does not have to be run empty after a standstill and the number of rejects is reduced. In case of an empty electrode segment, it can moreover be avoided that mechanical components are damaged by electric arcing due to coupled-in high-frequency radiation. 
     For example, by using this device, a method can be realized in which, with the aid of a control unit and one or several electrode segments, product containers, as in particular bottles, can be coated during a plasma coating process, where each one of the electrode segments receives at least one product container and comprises electrodes for coupling out high-frequency radiation. The method is characterized in that the plasma coating is automatically controlled by the control unit in one or each one of the electrode segments depending on process parameters. This permits a precise adaptation of the plasma coating process to changing process parameters and thus a reduced quality variance in the plasma coating of product containers, thereby reducing rejects. 
     In one embodiment, the method is characterized in that it can be optionally realized with one or several ones of the following features: a speed sensor determines the current speed of the product containers to be coated; or the control unit predetermines a current transport speed v and controls a drive for the product containers; a detection device for product containers, such as a light barrier, transmits signals relating to the entry of product containers into one or each electrode segment to the control unit which determines a number m of the product containers in one electrode segment. These features permit, by suited combination, high flexibility of the method with respect to changing process parameters. For example, at a lower transport speed and/or with a lower number of product containers in one or each electrode segment, the power can be reduced such that the energy deposited in the product containers always remains the same while they are passing the complete plasma coating process. Furthermore, the formation of secondary plasmas and the damage of mechanical components due to arcing can be reduced. Moreover, a melting of product containers due to excessive deposited energy during the plasma coating process can be avoided. 
     In another embodiment, the method is characterized in that the control unit terminates the coupling out of high-frequency radiation from the electrodes of the or of each electrode segment when either the transport speed of the product containers is 0 ms −1 , wherein at least one product container, but preferably the maximum product container population number, is located in one or each one of the electrode segments; or if no product container is located in one or each one of the electrode segments. It is just in case of a standstill of the machine that this permits the termination of the plasma coating operation to prevent the amount of energy deposited in the product containers from exceeding the intended amount of energy. On the other hand, in case of not existing product containers, it permits to prevent damages of components due to the nevertheless coupled-in high-frequency radiation. 
     Additional aspects and/or advantages of the devices and methods disclosed herein will be apparent upon review of the following detailed description and the attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a complete plan view of a preferred embodiment of the device. 
         FIG. 2  is a representation of the feeding of high-frequency radiation with different numbers of product containers in one electrode segment. 
         FIGS. 3A and 3B  are representations of the coupling out of high-frequency radiation with different transport speeds of the product containers. 
         FIG. 4  shows a further preferred embodiment. 
         FIG. 5  shows a further preferred embodiment. 
         FIGS. 6A and 6B  are representations of the plasma coating operation 
         FIG. 7  shows a further preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The plasma coating of products, in particular product containers, such as bottles, is achieved by means of a device for plasma coating with one or several electrode segments and a control unit. Identical or functionally similar components are indicated with reference numbers having the same last two digits but increased or decreased by hundreds corresponding to the figure number (e.g. mountings  180 ,  280 ,  380 ,  480 ,  580 ,  680 ,  780 ). 
       FIG. 1  schematically shows the assembly of a preferred embodiment of a device  101  according to the disclosure for plasma coating product containers. Here, the uncoated product containers  110  are located on a conveying belt  115  leading to the device  101 . The uncoated product containers  110  can be relocated, for example by means of a guide starwheel  190 , onto the coating line  117  which leads through the device for plasma coating  101 . If the product containers  111  to be coated are located in the coating line  117  which leads through the device for plasma coating  101 , the progression of the product containers  111  to be coated is preferably effected by transporting them suspended in respective mountings  180  through the coating line. Here, the mountings  180  are preferably designed such that they hold the product containers at their necks. The mountings  180  are only schematically indicated in  FIG. 1 .  FIG. 6  refers to a preferred assembly. The product containers  111  to be coated pass, with the mountings  180 , through one or several electrode segments  102  where electrodes  103  are located which are preferably mounted in parallel to the moving direction of the product containers. In these electrode segments  102 , the plasma coating process of the product containers  111  to be coated takes place. After the product containers have passed through the device for plasma coating  101 , the now coated product containers  120  reach, for example, a further guide starwheel  190  which can relocate the now coated product containers  120  from the coating line  117  onto a conveying belt  116  leading away from the device for plasma coating  101 , the connection of the coated product containers  120  to the mountings  180  being released beforehand. The conveying belts  115  and  116  are driven by drives  106 . The mountings  180  in the coating line  117  can also be driven by such a motor  106 , as can be seen in  FIG. 1 . The speed of the product containers  111  to be coated in the device for plasma coating  101  is measured by means of a speed sensor  104 . The entry of an uncoated product container  110  into the device for plasma coating  101  is preferably detected by means of a detection device for product containers, such as a light barrier  108 . A control unit  105  can evaluate the data of the speed sensor  104  and the detection device  108  and control the electrodes  103  of the electrode segments  102  and the drives  106  of the conveying belts  115  and  116  as well as of the mountings  180  in the coating line  117 . 
       FIG. 2  shows the course of the plasma coating process depending on the number of product containers  211  to be coated which are located, during the plasma coating process, within one or each one of the electrode segments  202 . The uncoated product containers  210  deviated, for example by the guide starwheel  290 , from the transport line  215  into the coating line  217  are detected by the detection device  208 . If there is a gap in the line of uncoated product containers  210 , this gap will also be present in the region of the device for plasma coating  201 . The corresponding mounting  280  which is located at the place of the not present product container to be coated is now vacant. This means that the coupled-in high-frequency radiation with its total power L deposits energy in a lower number than the provided maximum product container population number N. Thus, more energy than intended falls onto each of the other product containers  211  to be coated in the corresponding electrode segment  202  with an unchanged power of high-frequency radiation. To prevent this, the control unit  205  controls, upon evaluation of the signals of the detection device  208  of the electrode segment  202  which contains a number m of product containers  211  to be coated which is smaller than the maximum product container population number N, the coupled-in power so that the coupled-in power  4  is smaller by the factor 
     
       
         
           
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     than the power coupled in with the maximum product container population number. If, however, the control unit  205  detects, upon evaluation of the signals of the light barrier  208 , that the maximum product container population number is present in one electrode segment  202 ′, meaning that for each available mounting  280 , one product container  211  to be coated is present, the power  4  provided for normal operation is used in the coupling out of high-frequency radiation. 
       FIGS. 3A and 3B  show the plasma coating process depending on the current speed v of the product containers  311  to be coated. To simplify things, the gapless availability of uncoated product containers  310  in the transport line  315  leading to the device for plasma coating  301  is assumed for this representation. The uncoated product containers  310  are again guided onto the coating line  317  leading through the device for plasma coating  301 , possibly by the guide starwheel  390 , and supplied to a mounting  380 , the conveying belt  315  and the mountings in the coating line  317  preferably having the same speeds v. Reference is now made to  FIG. 3A  where the uncoated product containers  310  and the product containers  311  to be coated move at the normal operating speed b on the conveying belt  315  and in the coating line  317 . The control unit  305  either determines by means of the speed sensor  304  that the uncoated product containers  310  and the product containers  311  to be coated move on the conveying belt  315  and in the coating line  317  at normal transport speed b, or it determines, by controlling the drive  306 , the speed at which the uncoated product containers  310  and the product containers  311  to be coated move on the conveying belt  315  and in the coating line  317 . In either case, the speed of the product containers is equal to the normal transport speed b ( FIG. 3A ). If the product containers  311  to be coated are located within the device for plasma coating  301  in one of the or in the electrode segment(s)  302 , the control unit  305  controls the coupling-out of high-frequency radiation from the electrodes  303  in the electrode segment  302 , such that the power L 1   1  corresponding to normal transport speed b is coupled out, whereby, within the exposure time of the product containers  311  to be coated in the electrode segment  302  determined by the normal transport speed b, a predetermined amount of energy is coupled into the plasma which is ignited in the product containers  311  to be coated by coupling in high-frequency radiation. 
     Reference is made now to  FIG. 3B . Here, the current transport speed v of the uncoated product containers  310  on the conveying belt  315  and the product container  311  to be coated in the coating line  317  is lower than the normal transport speed b. The control unit  305  obtains corresponding information either by the speed sensor  304  which measures the speed of the product containers  311  to be coated in the coating line  317 , or by the control unit  305  directly controlling the drive  306  of the conveying belt  315  and the mountings  380  in the coating line  317  and thus adjusting the speed v&lt;b. To prevent excessive energy from being deposited, during the exposure time of the product containers  311  to be coated in the electrode segment or segments  302  caused to be longer by the lower speed v, in the plasma located in the product containers  311  to be coated and thus in the product containers  311  to be coated, the control unit  305  can control the electrodes  303  of the electrode segment or of each electrode segment  302  such that the power of high-frequency radiation L 1   2  coupled out from them is lower by the factor 
     
       
         
           
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     than that in the plasma coating process of  FIG. 3A . Thereby, despite the longer exposure time of the product containers  311  to be coated in the electrode segment  302 , the total amount of energy deposited in the product containers  311  to be coated is as high as that in a normal operation case. 
     The processes described in  FIG. 2  and  FIGS. 3A and 3B  can be combined by suited programming of the control unit  205  or  305 , respectively, to obtain a resulting power  L . Due to technical limits, the above-described adjustment of the powers L i   j  cannot be effected with any desired precision on the basis of the prefactors by the control unit  205  or  305 , respectively. Preferably, the power can therefore be controlled step by step. This is preferably mainly true for the prefactor 
     
       
         
           
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     defined by the number of product containers as here the possible prefactors and thus the steps to be adjusted with a given maximum product container population number N are known and can be already present, for example, as stored data record. The adaptation of the power to the current transport speed v is preferably possible with a finer graduation, where here it is also obvious to a person skilled in the art that this graduation cannot be arbitrarily precise. It can be predetermined, for example, that the power actually predetermined by the control deviates from the calculated powers L 1 , L 2 ,  L  within a range of, for example, up to 5% or 10%. 
       FIG. 4  is another possible embodiment which represents a device for plasma coating  401  product containers  411  to be coated. Here, the electrode segments  402  and in particular the electrodes  403  are arranged in parallel to a straight coating line  417 . This can render superfluous the guidance of uncoated product containers  410  and product containers  420  to be coated in the respective conveying belts  415  and  416  with the aid of, for example, guide starwheels. 
     In another possible embodiment which is shown in  FIG. 5 , the device for plasma coating  501  includes a rotary rail which is divided into several, at least, however, two electrode segments  502 . The conveying belt  515  which guides the uncoated product containers  510  to the device for plasma coating  501  and the conveying belt  516  which guides the coated product containers  520  away from the device for plasma coating  501  are preferably arranged such that the current electrode segment  502 ″ which transfers the coated product containers  520  to the conveying belt  516  is adjacent to the electrode segment  502 ′ which receives the uncoated product containers  510  from the transport line  515 . This ensures that the product containers  511  to be coated have a preferably long exposure time in the rotary machine. The arrangement of the electrodes  503 , the product containers  511  to be coated and the mountings  580  is here chosen for illustration purposes. It would be obvious to a person skilled in the art that there are other, possibly better suited possibilities of arranging the electrodes  503 , the mountings  580  and the product containers  511  to be coated within one or each electrode segment  502 . The positioning of the conveying belts  515  and  516  relative to the device for plasma coating  501  is here also only given for illustration purposes. It would be also conceivable, for example, that the conveying belts  515  and  516  run perpendicularly to the plane of projection and the rotary machine and that the bottles are introduced into the electrode segments  502  by possible guide starwheels. 
       FIGS. 6A and 6B  show a possible embodiment of the operation of plasma coating a product container  611  to be coated in one of the electrode segments  602 . In  FIG. 6A , a product container  611  to be coated is represented in which a lance  612  located in each mounting  680  is introduced. Furthermore, the mounting  680  grips around the neck of the product container  611  to be coated. Within the mounting  680 , a process gas unit  670 , which can be coupled, for example, by means of a valve to the opening of the product container  611  to be coated, can take care of the supply of the process gas  640  for plasma coating and of an evacuation for a density of the process gas  640  to be low compared to the exterior of the product container  611  to be coated. In  FIG. 6B , an electric field is applied between the lance  612  and the electrodes  603 , so that high-frequency radiation of a predetermined power L can be coupled out. Here, the lance  612  functions as a further electrode. The high-frequency radiation can be either coupled out from the electrodes  603 , the lance  612  being connected to ground, or the high-frequency radiation can be coupled out from the lance  612 , where then the electrodes  603  are connected to ground. 
     Due to the low particle number density of the process gas  640 ′ within the product container  611  to be coated, the power L of the high-frequency radiation is converted by igniting a plasma of the process gas  640 ′. As the conditions necessary for the ignition of a plasma of the process gas  640 ′ are preferably given only within the product container  611  to be coated, the total power L of high-frequency radiation is only converted within the product container. 
       FIG. 7  shows another possible embodiment of the device for plasma coating  701 . Here, the device  701  consists of only one electrode segment  702  in which mountings  780  for product containers  711  to be coated are guided. Here, too, the determination of the entry of an uncoated product container  710  from the transport line  715  into the coating line  717  within the device for plasma coating  701  is preferably effected by means of a detection device for product containers, for example a light barrier  708 . The transport speed of the product containers can be measured by means of a speed sensor  704 . Furthermore, conveying belts  715  and  716  are driven, like the mountings  780 , by means of a drive  706 . The control of the electrodes  703 , the evaluation of the signals of the detection device  708  and the speed sensor  704 , and the control of the drive  706  are effected by means of a control unit  705 .