Abstract:
A container treatment machine has treatment positions provided on a circumferential transport element rotating about a vertical machine axis. Each has a container carrier, a centering element, an aggregate, a control valve, and an actuation element. The treatment position clamps empty containers with a clamping force between the carrier and the cone. The actuation element generates the container clamping force. The control valve controls flow through the channel. Containers lying in a sealed position against the centering cone are loaded with pressure medium that travels through the channel to generate a container-stabilizing internal pressure. The control valve, which is in the centering element, causes container pre-tensioning by being opened by a container clamping force that acts between the centering cone and the container to pretension the container.

Description:
RELATED APPLICATIONS 
       [0001]    This application is the national stage entry of international application PCT/EP2013/002734, filed on Sep. 12, 2013, which claims the benefit of the Dec. 21, 2012 priority date of German application DE 102012025149.1, the contents of which are herein incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention related to container processing, and in particular to application of equipment characteristics to thin-walled bottles or similar containers that are empty of liquid. 
       BACKGROUND 
       [0003]    When applying equipment characteristics to a container, it is preferable to securely hold the container. Typically, one holds the container between a container support and either a centering element or a centering cone that lies against the container opening. The container support then causes a controlled rotation of the container about a vertical container axis. 
         [0004]    In many cases it is necessary to label or print on thin-walled empty containers. Examples include thin-walled plastic or PET containers, including bottles. Such containers are often made by blow molding. Because these containers have low inherent stability, it is useful to pre-tension them with gas. The high pressure gas supports the walls so that the bottles are neither deformed nor destroyed by the container clamping force needed to apply the equipment characteristics. 
         [0005]    Known pre-tensioning methods feature having a centering cone form a tight seal against the container mouth and having the centering element opening a control valve to let in high pressure gas. The pressure is usually generated by cam control with in each case an actuation element or linkage interacting with a control cam. The element or linkage acts on the centering element via a pressure spring. As a result, the pressure or container clamping force acting between the centering element and the container rises suddenly immediately after lowering the centering element onto the container. Since this occurs before high-pressure gas has stabilized the container, container damage can result. 
         [0006]    In known labeling machines, a control disk opens the control valve for the pressure medium depending on the rotary position of the rotor. This makes it possible to dispense support medium even when there is no container at the relevant treatment position. 
         [0007]    In labeling machines, it is also known to make the centering elements so that actuating the control valve to release the pressure medium takes place by the particular container and by raising the centering cone of the centering element. The force needed for this is, however, determined by the pressure of the support medium. As container walls become ever thinner, they become increasingly unstable when empty. This results in a considerable disadvantage. Loading the containers with an elevated internal pressure that stabilizes them means that a high force is needed between the container and the centering cone when the container is still not sufficiently stabilized. 
       SUMMARY 
       [0008]    The invention provides a method that avoids the above drawbacks of the prior art and allows the application of equipment characteristics onto empty thin-walled containers with improved operating reliability and with gentle treatment of the containers. 
         [0009]    In one aspect, the invention features a method for applying equipment characteristics to empty thin-walled bottles using a container treatment machine. The container treatment machine has treatment positions on a circumferential transport element that rotates about a vertical machine axis. The containers on the treatment positions are clamped between a container support and a centering cone of a centering element by a container clamping force that acts between the container and the centering cone. The transport element moves the containers past an aggregate that applies an equipment characteristic. Gas pressure stabilizes the containers by pre-tensioning them. A control valve controls this gas pressure. The centering cone, in turn, controls the control valve. The container has an opening that is sealed against the centering cone. The method includes executing a first container-clamping phase, opening a control valve prior to the end of the first container-clamping phase, and executing a second container-clamping phase. Executing the first container-clamping phase includes causing a container to sustain a clamping force that increases from a first value to a second value. Executing the second container-clamping phase includes causing a container to sustain a clamping force that increases from the second value to a third value. Opening the control valve comprises causing the container clamping force to open the control valve, thus allowing pre-tensioning of the container. 
         [0010]    Practices of the invention include those in which the container clamping force increases continuously during the first and second phases, those in which it increases in stages, and those in which it increases only in the first phase. 
         [0011]    In other practices, the container-clamping force is a dependent variable that varies in response to a change in an independent variable to define a force function. The force function is piecewise linear with a slope in the first phase that has a greater absolute value than the slope in the second phase. 
         [0012]    Other practices include causing an actuation element to generate the clamping force. These include embodiments in which the actuation element is under path control and embodiments in which it is under power control. 
         [0013]    In other practices, the actuation element interacts with a control cam that acts on a structure selected from the group consisting of the container support and the centering cone. Among these are practices in which the control cam acts with the aid of a spring element. Also among these embodiments are those in which the clamping force during the first phase is generated at least in part by the spring element. In these practices, the spring element pretensions the control valve when the control valve is in a closed state. 
         [0014]    In yet other practices, the control valve opens as a result of relative movement between the centering cone and a housing of the centering element. 
         [0015]    Further practices include those in which, after the first phase, a label is applied to the container, and those in which, after the first phase, the container is printed upon. 
         [0016]    In another aspect, the invention features an apparatus comprising a container treatment machine. Such an apparatus includes treatment positions provided on a circumferential transport element rotating about a vertical machine axis. Each treatment position comprises a container carrier, a centering element, an aggregate, a control valve, and an actuation element. The centering element comprises a centering cone with one or more walls that forms channel. The treatment position clamps empty containers with a container clamping force between the container carrier and the centering cone. The transport element moves the containers past the aggregate, which then applies an equipment characteristic. The actuation element generates the container clamping force. A control valve controls flow through the channel so that containers lying in a sealed position against the centering cone are loaded with pressure medium that travels through the channel. This pressure medium generates an internal pressure within the container to stabilize the container. The control valve, which is provided in the centering element, causes pre-tensioning of the container when a container clamping force that acts between the centering cone and the container is opened. This pre-tensions the container. 
         [0017]    Some embodiments includes a spring, a valve element, and a housing that houses the centering element. The valve element extends along an axis of the housing. The centering cone is held on the valve element. The spring pre-tensions the valve element into a first position. When the valve element, which in some embodiments is a piston, is in the first position, the control valve is closed. When the valve element is moved into a second position against action of the spring element, the control valve is opened. 
         [0018]    In some embodiments, the spring causes generation of pressure in the first phase. 
         [0019]    As used herein, equipment characteristics include elements that are applied onto the containers for providing information, advertising, notice, proof of originality, and to create a desired visual appearance of the containers. Equipment elements include labels, bands, foil wrappings, and printed images applied onto the containers, as well as printing aggregates. 
         [0020]    As used herein, terms such as “substantially,” or “approximately” are intended to mean deviations from the exact value in each case by +/−10%, and preferably by +/−5% and/or deviations in the form of changes that are not significant for function. 
         [0021]    Further developments, benefits and application possibilities of the invention arise also from the following description of examples of embodiments and from the figures. In this regard, all characteristics described and/or illustrated individually or in any combination are categorically the subject of the invention, regardless of their inclusion in the claims or reference to them. The content of the claims is also an integral part of the description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]    These and other features of the invention will be apparent from the following detailed description and the accompanying figures, in which: 
           [0023]      FIGS. 1 and 2  show a simplified representation of a labeling machine from above and from side; 
           [0024]      FIG. 3  is a graph of container clamping force as a function of time in the labeling machine shown in  FIGS. 1 and 2 ; 
           [0025]      FIG. 4  is a magnified representation, of a centering element of the labeling machine shown in  FIGS. 1 and 2  together with a partial representation of a bottle in the area of its bottle mouth; 
           [0026]      FIG. 5  is a side view of another embodiment of the invention; and 
           [0027]      FIG. 6  shows the container clamping force as a function of rotary position of a rotor of the labeling machine shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  shows a labeling machine  1  for labeling empty thin-walled containers  2  such as blow-molded bottles made of plastic or PET. The labeling machine  1  has a rotor  3  that rotates continuously about a vertical machine axis MA. The rotor  3  forms a plurality of treatment positions  4  on its circumference. 
         [0029]    Through a container inlet  6 , an external conveyor  5  supplies these treatment positions  4  with empty containers  2  that are to be labeled. The treatment positions  4  move containers  2  that are to be labeled past a labeling aggregate  8  that does not move with the rotor  3 . 
         [0030]    Each container  2  stands upright on its treatment position  4  with its container axis parallel to the machine axis MA. As shown in  FIG. 2 , the container  2  is clamped between a lower rotary plate  9 , on which it stands on its base, and a top centering element  10 , which extends by a centering and sealing cone  11 , best seem in  FIG. 4 , into the container mouth  2 . 1 , thereby sealing it. The labeled empty containers  2  are removed from the treatment positions  4  on a container outlet  6 . 1  and supplied by an external conveyor  5 . 1  to a further use, for example to a filling machine for filling the containers  2 . 
         [0031]    Referring to  FIG. 2 , a linkage  12  connects the centering element  10  to an actuation device  13 . Following the transfer of a container  2  to a treatment position  4 , the centering element  10  for clamping that container is lowered from a raised position to receive the container  2 . The labeling of the containers  2  takes place by rolling the labels  7 . This is carried out by clamping the container between the rotary plate  9  and the centering element  10  and driving the rotary plate  9  to rotate the container about its container axis. The centering element  10  is later lifted to release the container  2  on the container outlet  6 . 1 . 
         [0032]    To achieve an adequate stability of the empty thin-walled containers  2  during labeling, the containers  2  are each loaded internally with high-pressure gas. The gas is preferably sterile gaseous and/or vaporous pressure medium, for example, sterile compressed air. The gas-loading is carried out by the centering cone  11  when it is sealed against a container mouth  21 . A control valve  14  provided in the centering element  10  controls the loading of the container interior with pressure medium. Lowering the centering element  20  or the centering cone  10  onto a container  2  controls the control valve  14 . In particular, lowering the centering element  20  or the centering cone  10  opens the control valve  14  and allows entry of pressure medium into the container&#39;s interior while the centering cone  11  lies pressed into sealing position at the container&#39;s opening  2 . 1 . 
         [0033]    The actuation element  13  controls the force with which the centering cone  11  lies against the container mouth  2 . 1 , i.e. the container clamping force K. It does so in a way that causes it to follow curve I in  FIG. 3 . A first phase of the container-clamping procedure extends between times t 0  and t 1  in  FIG. 3 . During this first phase, a low container-clamping force K rises over time. Eventually, and in particular, at time t 3 , the container-clamping force K grows large enough to open the control valve  14  and to seal the centering body  11  against the container  2 . Meanwhile, the gradually increasing internal pressure p 1  becomes sufficient to stabilize the container. This occurs by the end of the first phase and sometimes even before the end of the first phase, for example by the time t 4 . 
         [0034]    The second phase of the clamping extends between t 1  and t 2 . During this second phase, the internal pressure of the container is p 1 . The container has thus become stable enough to sustain a gradual increase in the container clamping force K. The actuation element  13  thus gradually increases the clamping force from an intermediate clamping force K 1  to a final clamping force K 2 . This transition is carried out by linearly increasing pressure, though with a slope steeper than that used during the first phase. The final clamping force K 2  is then maintained at least until the end of the labeling process. 
         [0035]    For comparison,  FIG. 3  also includes a curve II showing the evolution of the container clamping force K in a conventional cam-controlled centering element acting that acts on a containers using pressure springs. As can be seen in curve II, in these conventional centering elements, the container clamping force acting on the particular container  2  is higher by the amount ΔK at t 3  when the valve opens, before the container has achieved adequate stability. This creates the risk of damage to the containers  2  due to application of higher container clamping force than the container can sustain. Force-controlled actuation of the centering element  13  as described herein effectively avoids such damage to the containers  2 . 
         [0036]    Referring to  FIG. 4 , the centering element  10  has a centering element housing  15  with an opening  16  that receives a lower end of the linkage  12 . A clamping screw  17  provides a way to detachably secure the centering element  10  on the linkage  12 . 
         [0037]    On its underside, the housing  15  forms a piston space  18  that is connected to the environment by a ventilation channel  19  A cover  21  seals the piston space  18  on the underside of the housing  15 . Screws  20  hold the cover  21  on the housing  15 . 
         [0038]    Within the cover  21  is a centering or valve piston  22  that forms part of the control valve  14 . The valve piston  22  moves axially relative to a vertical centering element axis ZA against the effect of a first pressure spring  23  between a lower position and an upper position. The lower position, which is shown in  FIG. 4 , corresponds to a closed control valve  14 . As the valve piston  22  proceeds toward its upper position, it reaches a point at which the control valve  14  opens. 
         [0039]    The first pressure spring  23  acts between the valve piston  22  and the base of the piston space  18 . Within the valve piston  22 , there lies a first channel  24  that is arranged on the same axis as the centering element axis ZA. At the lower end of the valve piston  22 , the first channel  24  opens. The first channel  24  protrudes past the underside of the cover  21  and connects, at its top end, to an annular channel  25  that concentrically encloses the centering element axis ZA. The annular channel  25  is open at the lateral surface of the valve piston  22 . 
         [0040]    Within the cover  21 , a second channel  26  connects to a pressure source via a connecting pipe, only a connecting piece  27  of which is illustrated. The second channel  26  has a control window  28 . When the control valve  14  is closed, as shown in  FIG. 4 , the valve piston  22  reaches its lower position. In the lower position, the lateral surface of the valve piston  22  seals the control window  28 . As the control valve  14  opens, the valve piston  22  reaches its upper position. In the upper position, the valve piston  22  is arranged congruently with the circumferential groove  25  and thus unseals the control window  28 . 
         [0041]    The first pressure spring  23  moves the valve piston  22  out of its lower position and into its upper position. It does so as the centering cone  11  comes to rest against the mouth  2 . 1  of the container  2  and seals the container  2  adequately. As shown in  FIG. 3 , the valve piston  22  reaches the upper position long before the end of the first phase, i.e. at time t 3 . Only at the end of the first phase does the valve piston  22  lie against the base of the piston space  18  so that the further rise in the container clamping force K is transferred from the housing  15  directly to the centering cone  11 . 
         [0042]    A ball-bearing  22  mounts the centering cone  11  on the valve piston  22 . As a result, the centering cone  11  rotates freely about the centering element axis ZA. This means that, while labeling a container  2 , it is possible to rotate the container  2  about the centering element axis ZA without also moving the valve piston  22 . A seal  30  seals the gap between the valve piston  22  and the centering cone  11 . 
         [0043]      FIG. 5  shows a further embodiment of the labeling machine  1  that differs from the previously described embodiment only in that the lowering and pressing movement of the centering element  10  is path-controlled instead of power-controlled. This is implemented by having a lifting-and-control cam  31  that does not rotate with the rotor  3 . A cam follower  32  provided on the linkage  12  interacts with the lifting-and-control cam  31 . In this embodiment, a second pressure spring  33  contributes to the container clamping force K of the centering element  10  by acting acts between the part of the linkage comprising the cam follower  32  and the centering element  10 . The second pressure spring  33 , the lifting-and-control cam  31 , and the cam follower  31  together form an actuation element  13   a.    
         [0044]    In operation, the embodiment illustrated in  FIG. 5  causes two phases in the clamping of the container  2  at the treatment position. The two phases are shown in the curve I in  FIG. 6 , which shows the container clamping force K as a function of rotation angle w of the rotor  3 . As shown in curve I, during a first phase between w 0  and w 1  the container clamping force K rises slowly until it reaches the intermediate clamping force K 1 . During a second phase between w 1  and w 2 , the container clamping force K rises more rapidly until it reaches the final clamping force K 2 . In other words, the function that relates clamping force K to rotation angle w has a discontinuous first derivative, with the greater first derivative corresponding to higher rotation angles. The point of discontinuity occurs at w=w 1 . 
         [0045]    During the first phase, the container clamping force K is sufficient to open the control valve  14  at w 3  and to produce the sealed position between the centering body  11  and the container  2 . In addition, at some point during the first phase, for example at w 4 , enough pressure medium will have entered the container to stabilize it. The container clamping force K during the first phase allows the container  2  to be adequately stable at the end, and preferably before the end of the first phase at w 4  by a sufficiently high internal pressure of the container p 1  generated by the support medium. The final clamping force K 2  is again maintained at least until the end of the particular labeling process. 
         [0046]    Curve II in  FIG. 6  shows the evolution of the container clamping force K in conventional cam-controlled centering elements acting on container with pressure springs. It can be seen from the course of curve II that with these conventional centering elements, the container clamping force K acting on the particular container  2  is higher by the amount ΔK at the time at which the particular container is still not adequately stable. This raises the risk of container-damage due to excess container clamping force. A clamping system that uses the principles of the invention thus avoids damage to containers  2  resulting from a force by force-controlled actuation of a centering element  10  with an actuation element  13  upon a container  2  that has not been pre-tensioned sufficiently to withstand that force. 
         [0047]    Curve III in  FIG. 6  shows the evolution of force applied by the control cam  31 . The reduced rise in the container clamping force K is determined by the first pressure spring  23  which is designed so that in the event of clamping it deforms before the second pressure spring  33  or deforms by a greater amount for a given applied force than the second pressure spring  33 . As a result, the valve piston  22  reaches the base of the piston space  18  only at the end of the first phase, at w 2 . 
         [0048]    The first pressure spring  23  is also designed so that the valve piston  22  moves from its sealing position into its opening as soon as the centering cone  11  adequately seals the container mouth  2 . 1 . This occurs long before the end of the first phase, i.e. at w 3 . Only at the end of the first phase does the valve piston  22  lie against the base of the piston space  18  so that the further rise in the container clamping force K is generated by the second pressure spring  33 . In this embodiment, the first and second pressure springs  23 ,  33  operate in series. 
         [0049]    Common to all the embodiments described is that at the end of the first phase, i.e. at t 1  and w 1 , the intermediate clamping force K 1  is below the final clamping force K 2  at the end of the second phase, i.e. at t 2  and w 2 . In the illustrated examples, the intermediate clamping force K 1  at the end of the first phase is no more than 50% of the final clamping force K 2 . In some embodiments, the intermediate clamping force K 1  is around 25%-30% of the final clamping force K 2 . In either case, the intermediate clamping force K 1  is selected such that the container  2  has gained sufficient stability, at least at the end of the first phase, t 1 , w 1 . This stability arises from the pressure medium that has already been introduced into the interior of the container  2 , either by the open control valve  14  or by internal pressure p 1  generated by the pressure medium. This internal pressure p 1  is at most equal to or slightly less than the ratio of the intermediate clamping force K 1  to the square measure F of the opening cross-section of the container  2  in the area of their container mouth  2 . 1 , i.e. p 1 ≦K 1 /F. 
         [0050]    In some embodiments, during the second phase, i.e. between t 1  and t 2  or w 1  and w 2 , further influx of pressure medium into the interior of the container causes the internal pressure p of the container  2  to continue rising to the value p 2 . In other embodiments, the internal pressure of the container remains constant or substantially constant at the value p 1 . 
         [0051]    The invention has been described above using examples of embodiments. It is clear that numerous modifications or variations are possible without thereby departing from the inventive idea underlying the invention.